U. C D. L1B7.ARY CALIFORNIA STATE MINING BUREAU. A. S. COOPER, State Mineralogist. Bulletin No. 16. San Francisco, December, 1899. ^ The Genesis of Petroleum and Asphaltum in California. By A. S. OOOPBR, State Mineralogist. SACRAMENTO: A. J. JOHNSTON : : : superintendent state printing. 1899. U J^^lijB&ITI^e..xl j:j|i'« •>. €ENESIS OF PETROLEUM AND ASPHALTUM IN CALIFORNIA. By a. S. cooper, State Mineralogist. It can be tentatively stated that fossil bitumens are princi- pally derived from terrestrial and marine vegetation, deposited in sedimentary strata, then changed to carbonaceous matter, and afterwards distilled by the heat of metamorphism. In other words, the bitumens are Nature's coal oils and tars distilled in Nature's still, generally with infinite slowness when compared with a modern tar still or retort. Although some of the hydrocarbons can be produced syn- thetically in the laboratory, still it is to be believed that nearly all, if not all, of the accumulations of fossil hydrocarbons owe their existence to the vital principle that they are derived directly or indirectly from organized beings — animal or vege- table, probably the latter, for reasons given hereafter. In the decomposition of vegetable tissue, when air is wholly or partially excluded from it, as, for example, when buried in the ground, the constituent elements of the vegetable tissue re-arrange themselves mutually into new products, either with or without the co-operation of the elements of water, the oxygen gradually uniting with the carbon to form carbonic acid, which separates and leaves as a residue substances rich in carbon and hydrogen. It is in this way that bituminous coal, peat, and brown coal (lignite) have been formed from vegetable matter. With carbonaceous material in the same deposit, the same series of strata, or in the same stratum, there are differences of composition. The varieties of carbonaceous materials may have been produced from different kinds of plant form, from which coal has been derived, and the peculiar conditions of the districts where the plants flourished before their downfall and inhumation or submersion. The changes that have taken place c. H. 0. 52.65 5.25 42.10 60.44 5.96 33.60 66.96 5.27 27.76 74.20 5.89 19.90 76.18 5.64 18.07 90.50 5.05 4.40 92.85 3.96 3.19 4 CALIFORNIA STATE MINING BUREAU. in the original plants, during their passage from woody fiber into coal, are ascribed to evolution of a part of their hydrogen and oxygen, as there are less of these elements in coal than in wood. This will be observed by viewing the following table: Organic. Formation. Wood Recent Peat Recent Lignite Cretaceous and Tertiary -.. Brown Coal Cretaceous and Tertiary... Coal _:Secondary Coal ..Older Anthracite Crystalline Graphite Crystalline and Archaean... 100.00 There is no strict line of demarcation between the above- named organic matter; the one below gradually merges into the one above. The older the formation, the greater the amount of carbon contained in the coal, the amount of hydrogen and oxygen having been diminished. This fact may be ascribed chiefly or in part to the degree of heat and pressure to which the lower and older coal strata have been, and still are, subjected. Graphitic and anthracitic varieties of coal are metamorphic coal produced by heat, the volatile matter being vaporized, which, probably, afterwards condensed in fissures and porous rock above, as bitumen, petroleum, etc. Graphite occurs in the Archaean, but none of the other coals are found in these rocks; neither is bitumen or petroleum oil found in the Archaean formation, but thej^ are found in all the other formations lying above the Archaean. From this it would seem that the bitumens originated in or above the Laurentian rocks, and not below them. The absence of the bitumens and petroleums in the Archaean formation is evidence against the theory that petroleums are produced by the action of water upon red-hot carbonized iron in the interior of the earth. It is at least conclusive evidence that this process is not at present in operation. Graphite is, in all probability, the ultimate stage in the series of changes which vegetable matter undergoes, passing through the conditions of heat, lignite, and mineral coal, to end in graphite. Several modifications of graphite may be produced artificially. When cast-iron is melted with an excess of char- coal, it dissolves a portion of the carbon. This carbon, when THE GENESIS OF PETROLEUM AND ASPHALTUM. 5 the iron is allowed to cool, slowly crystallizes out in the form of large and beautiful leaflets of graphite. Anthracitic varieties of coal are associated with folded and metamorphic rocks. Anthracitic condition of coal may some- times be traced to local effect of igneous rocks. As rocks grow less and less metamorphic, the more bituminous is the coal contained in them. Graphite is disseminated in strings, veins, and beds through hundreds of feet of the lower Laurentian strata, and its amount is calculated to be equal in quantity to the coal seams of an equal area of the carboniferous rocks. In Central Scotland, where the coal fields have been so abun- dantly pierced by igneous masses, petroleum and asphaltum are of frequent occurrence, sometimes in chinks and veins of sand- stone and other sedimentary strata, sometimes in the cavities of the igneous rocks themselves. In West Lothian, intrusive sheets, traversing a group of strata containing seams of coal and oil shale, have a distinct bituminous odor when freshly broken, and little globules of petroleum may be detected in their cavities. In the same district, the joints and fissures of a massive sandstone are filled with solid, brown asphalt, which the quarry-men manufacture into candles. Graphite has probably the same vegetable origin as mineral coal. It is now generally conceded to be of organic origin, the result of metamorphism of some of the products of destructive distillation of vegetable tissues. In general arrangement and microscopic structure, the layers of graphite correspond fre- quently with coal and some bituminous deposits. The majority of coal mines in California are in the cretaceous rocks and the lower tertiary. The rocks underlying the tertiary formation and in the lower parts of the tertiary formation are in many instances metamorphic, the cretaceous and tertiary rocks having been changed to metamorphic rock by hydrothermal action, and, if they contained carbonaceous material, petroleum was distilled, which ascended in a vaporous condition and was condensed in the unaltered rocks. After condensation, it was carried upwards by gas and hydrostatic pressure, and, in some instances, by rock pressure. The presence of nitrogen in the California petroleum oils has been adduced as a proof that they are of animal origin; this proof is not conclusive, as most all of the coals and carbon- 6 CALIFORNIA STATE MINING BUREAU. aceous shales yield nitrogenous products when subjected to destructive distillation. As a proof of the animal origin of petroleum, it has been stated that pools of petroleum have been found which were filled with live maggots. Many hundreds of pools of petroleum in California have been examined without discovering any maggots or other forms of life in them, although there have been swarms of flies and other insect life in their neighborhood. In the vicinity of pools of petroleum, flies quickly discover and lay their eggs on spoiled or moist foodstuffs, meat, decaying meat, meat broths, dead animals, in manure heaps, etc. Taking into consideration the persistency of flies to deposit their eggs upon anything capable of sustaining the life of their young, it is to be believed that all pools of petroleum would be filled with maggots if flies were present and petroleum was a suitable food for their larvae. Maggots feed upon animal and vegetable tissues and liquids, and not upon their fats and oils. When animal hydrocarbons are deprived of all animal tissues and liquids, they are not molested by flies. Petroleum is also found to be an excellent maggot-killer. There are only four ways of preserving animal remains from decay and putrefaction: first, in a case from which the air has been completely removed and excluded; second, by antiseptic agents; third, subjected to a heat exceeding 100° C; fourth, subjected to a cold under 0° C. To secure and preserve any quantity of animal remains by any of these four ways, cataclysms of nature must occur. Geology does not show that any large quantity of animals have been inhumed in the earth by cataclysms; even provided animals were buried in this manner, there is sufficient oxygen present to start decay, and, after this has commenced, putre- faction ensues. It is also claimed that the decay of organic matter is not due simply to oxidation, but to the action of organisms, ferments, or enzymes, which attack the organic substances and decompose them into their original elements or into simpler compounds. The ordinary rate at which sedimentary rocks are deposited is too slow to effect the inhumation of animal substances so that they will be excluded from the air and preserved. But few animal remains are found incased in ice, and these THE GENESIS OF PETROLEUM AND ASPHALTUM. 7 are not buried beneath the earth; there is no other way in which they can be preserved by cold. There is no way in nature that animal remains can be maintained at a temperature of 100° C. from the time of their death until changed to bitumen. Very seldom are animal remains preserved by antiseptics in nature, and, if so preserved, their aggregate amount is small. All the ways that can be employed to preserve animal sub- stances are destructive to animal life. The presence of life and the conditions and way necessary for the preservation of animal substances cannot exist in the same place at the same time. In order that petroleum oil may be derived from animal remains, it is first necessary that such remains be placed and preserved in a condition for such change. In the present age, the inevitable end of animals after life is to furnish nutriment to the scavengers of the earth and sea, or their decomposition by putrefaction. There is no reason why, in former ages, this was not the ultimate fate of animals. The products of the decomposition of nitrogenized animal substances are as follows: The oxygen of the substance unites with the carbon to form carbonic acid, while the hydrogen divides itself between the nitrogen, the sulphur, and the phosphorus, and forms ammonia with sulphuretted and phosphoretted hydrogen. The surroundings would indicate that the fossils in the petroliferous formations of California lived and died, and were embedded in the same manner as the mollusca of the present day; in fact, a large number of the fossils in these formations are the prototypes of existing mollusca, and must have lived and died in the same manner. There is nothing showing that after death the mollusca existing at the present day are preserved for the future manufacture of petroleum. This is also true of the infusoria. The fossil animals do not show any stage of transition between animal matter and petroleum oil. Large quantities of fossil shells exist in the shales and sand- stones of California; these are usually filled with silt, or the shells have been changed to silica, and the interior filled with silica, or molds and casts exist, the carbonate of lime having 8 CALIPORNIA STATE MINING BUREAU. been leached away. They only contain bitumen when the interspaces and cracks in the adjoining rocks are filled with bitumen. There is no carbon in these fossils, except in some instances the carbonate of lime constituting their shells. There is no carbonaceous matter from which bitumens could be derived by any known process. There are no more fossils in the rocks which are impregnated with bitumen than in those which are destitute of bitumen. Bitumens are found in the unaltered sedimentary rocks of California sandstones, shales, limestones, etc. There is no bitumen in the metamorphic rocks. The only substances originally contained in these rocks, that could and can be con- verted into bitumen, are organic vegetable remains in the form of coal, lignite, and carbonaceous shales. These carbonaceous substances are not changed to bituminous unless distilled by heat. Most all of the known beds of coal, lignite, and carbonaceous shale belong to the cretaceous or tertiary formation. If bitumens exist in them at all, the surrounding and accom- panying phenomena show that these accumulations of bitumen are secondary. . A primary deposit of petroleum is in the rocks in which it was formed. A secondary deposit is where it has migrated from the rocks in which it was formed and accumulated in other rocks. If petroleum is produced by destructive distillation, it cannot remain in the rocks in which it is formed. The petroleum of California is not confined to any particular geological horizon in the Coast Range, but may exist in any of the sedimentary rocks lying above the altered rocks; there- fore, palaeontology is of but little value in determining its location. The chief guide to the discovery of bituminous accumula- tions is the character of the rocks constituting the formation, and their structure and position. There is no evidence tending to show that these accumula- tions or deposits are primary; and, if secondary, they may occur in any porous or seamed sedimentary strata of any age lying above the altered rocks. The age of a formation may assist in the discovery of pri- mary mineral deposits; but migratory fluids and gases will ^-... ^ ^^^^ THE GENESIS OF PETROLEUM AND ASPHALTUM. ^<^yl 9 circulate through any porous or seamed strata, and accumulate in such places as are rendered suitable through structure and position, irrespective of the age of the rocks. The accumulations of bitumens in the domes and summits of the anticlines, and the existence of tar and gas springs, prove that they were, and are at the present time, migratory, and that the principal direction of their migrations was, and is, upwards. In California, the upper cretaceous and the eocene, miocene, pliocene, and quaternary formations, when not metamor- phosed or otherwise changed, consist of soft shales, sandstones, conglomerates, and limestone. The large majority of these rocks are soft shales and sandstones. The rocks of one age resemble those of another. In California, the miocene seems to contain the largest amount of petroleum ; this is owing to the fact that, in ascend- ing from its place of origin below, it had not reached the pliocene in the same quantity as it did in the miocene; the pliocene, being the farthest away from the place of its origin and the eocene, does not have the same amount of exposures as the other formations, and, when visible, the formation is so broken, and tilted to such high angles, that the oil has escaped. The fossil shells are vastly more numerous in the tertiary rocks of California than the remains of all other kinds of animals put together. Mollusca, similar to those of California, abound to an extraordinary degree in the tertiary in other places besides California, but usually they contain no petroleum. In none of these ages are animal remains found in a state fit for the future manufacture of petroleum. Neither can there be found any substance that would suggest a state of transition between the fauna of these ages and bitumen. But suppose, for argument's sake, that it is admitted that petroleum oil is derived from animal remains. There is no reason why the fauna of one of these ages should not be the origin of petroleum as well as the fauna of another of these ages. Oil which can be claimed as being indigenous is not found in the quaternary. In California there are large areas of fine sand containing many fossil shells which contain no bitumen; if they had at 10 CALIFORNIA STATE MINING BUREAU. any time contained bitumen, there would still be some bitumen remaining in them, as there are many shells lying in such a position that the bitumen could not escape by draining from, or being floated out of them. If the petroleum originated in these shells, each shell would contain a modicum of oil, and would not be completely filled with petroleum or entirely destitute of the same, these being the conditions in which they are usually found. If these fossil shells are full, these deposits must be partly or wholly a secondary one, as no mollusk could produce a quantity of oil equal to the size of its body; and if they were destitute of oil, it would tend to prove that they are not the source of oil. It certainly cannot be claimed that animal remains in anticlines produce oil, while similar remains in the synclines are unproductive. The presence of nitrogen in the bitumen does not prove that petroleum containing nitrogen is of animal origin, as nearly all plant remains contain nitrogen in greater or less quantity, and yield nitrogenous compounds by distillation. How can the different kinds of bitumen be accounted for if they are derived from animal remains? Is the oil that originates from one species of mollusca different from that which is derived from another? In Russia, the petroleum consists principally of the naph- tene series; in Pennsylvania, of the paraffine series and a paraffine base; in California, of the define series with an asphalt base. Adjoining fossil shells, when bituminized, contain similar bitumens; for instance, if one shell is found inclosing a bitumen containing six per cent of sulphur, the adjoining shells all contain bitumen containing six per cent of sulphur. This large amount of sulphur was not originally present in the body of the mollusca, consequently it must have been derived from some other source, and if derived from some extraneous source, the percentage of sulphur in the bitumen in each shell would not have been so constant — some would contain more sulphur than the other. This would lead to the belief that the bitumen was sulphurized before entering the shells, and is, therefore, a secondary deposit. THE GENESIS OF PETROLEUM AND ASPHALTUM. 11 Then there are varieties of asphaltites, uinteite, albertite^ grahamite, and elaterite. It does not seem possible that the bodies of the mollusca^ which so closely resemble each other in composition, should produce so many dissimilar bitumens. When petroleum is found in fossil shells, it is also found in the porous or seamed strata in which the shells are embedded. The character of the bitumen in the shells is the same as that which is in the porous strata, excepting that it is some- times in a more liquid condition, owing to the fact that a greater opportunity is offered for the evaporation of the bitumen in porous strata than in closed shells. Owing to the buoyancy of the bitumens in fresh or mineral water, their migrations are usually upwards until checked by impervious strata, or until they have reached the highest point to which water will float them, or until they reach the surface of the earth. Very seldom do they descend, and then descent only occurs when the strata to which they have ascended are uplifted above permanent water by orogenic movements. They may migrate for a thousand feet, and, as stated above, generally upwards. In the Ojai Valley is an accumulation of asphalt, lying like a huge black tear upon a hillside, which has slowly issued from the small springs at its upper end. Scattered throughout the Coast Range are similar deposits. Distillation. — The maximum quantity of liquid hydrocar- bons is obtained from the solids by a process of distillation under high pressure and low temperature, combined with rapid condensation. Temperature and pressure exercise a considerable influence on the nature of the products of distillation. The method of cooling also exercises great influence in the re-arranging of the molecules and upon the nature of the product of distillation. Slow cooling or quick cooling makes no difference on some substances, but the difierence between slow and rapid cooling has a marked effect on others. If we reduce the heat of water from a high to a low tem- perature, it will not affect the constitution of the water; whether we lower the temperature slowly or quickly, the result will be the same. Water that is slowly cooled from the boiling 12 CALIFORNIA STATE MINING BUREAU. point down to the freezing point will have the same properties as water that is rapidly cooled down from 212° to 32° F.; but that does not hold good with all substances. For example, if we take three bars of steel of equal dimensions and make them all- red-hot; then, if we slowly cool one bar down to say 50° in the air, and if we cool the second bar by slipping it slowly into cold water, and if the third bar be suddenly cooled by plunging it into cold water, the time of cooling these three bars of steel will produce a different effect in each bar. The bar that is slowly cooled in the air will remain comparatively soft and be of fibrous texture, malleable, and ductile, capable of being bent double without breaking. The second bar will be harder and more elastic, and can only be. bent a small degree without breaking. The third bar will be very hard and brittle and cannot be bent, and if struck with a hammer will fly to pieces, the fracture showing crystalline structure. Now, these three bars were simply deprived of the same number of degrees of heat. They were reduced from an equally high degree of heat to an equally low temperature, but we find that the difference in time occupied in cooling makes a vast differ- ence in the molecular structure and properties of the metal. These facts are well known to all workers in metal; but it is not so well known that in cooling mixed gases, especially the hydrocarbons, from a high to a low temperature, the effect on the constitution of the gases varies with the time occupied in cooling, and that difference between quiescence and agitation during cooling has different effects on the molecular constitu- tion of mixed gases, especially with mixed hydrocarbons. Place two retorts, of the kind used for making illuminating gas from coal, in one oven, so that they will get equally heated up to a bright, red heat, and let us charge each retort with one hundred-weight of good coal, which will make five hundred feet of gas. Now, let us cool the gas from retort number one slowly by passing the gas slowly through a number of pipes placed vertically in the open air, in the manner usually done in gas works; let us cool the gas from number two retort rapidly by passing the gas through a multitubular condenser surrounded with a freezing mixture, and we will find the result to be that five hundred feet of permanent gas and five pounds of tar will be delivered by number one retort, and we shall get about eight hundred feet of permanent gas and thirteen pounds THE GENESIS OF PETROLEUM AND ASPHALTUM. 13 of tar from number two retort. There we find that rapid con- densation reduces two fifths of the gas to a liquid state; and if we w^ere to distill under high pressure and low temperature, we should, with rapid condensation accompanied with agitation, reduce nine tenths of the gas to a liquid state. To produce permanent gas from coal, we should distill under low pressure and high temperature, and cool the vapors rapidly under agitation. When gas is violently agitated during the cooling process, a greater quantity is condensed into the liquid state than when kept in a quiescent state during the cooling process. When gas, much cooled, is passed through a coke tower down which heavy oil is trickling, this oil will absorb the light hydrocarbons of the gas. t The boiling points of the hydrocarbons of petroleum are altered very considerably by foreign, or even by the traces of foreign, substances being present. The presence of difi'erent substances during distillation has an influence on the distillate. It has been found that, when a mixture of chlorine with hydric chloric is passed through an ordinary charged gas retort, it acts as a hydrogenating or dissociating agent, producing a tar very rich in benzol. On the other hand, zinc chloride in the presence of hydric chloride greatly increases the yield of heavy hydrocarbides from coal, and can convert some of the lighter constituents of the tar when distilled therewith into heavy ones. The nature of the product also depends on the material of the retort. A rough surface will facilitate chemical changes. By repeated distillations solid paraffine can be gradually changed into liquid kinds of paraffines and olefines. Mineral tar, by repeated distillation in the presence of superheated steam, will be converted into gas if the united vapors of the steam and tar are decomposed by heat after each distillation. Sulphur, when present in a still with paraffine, retards its ebullition. The introduction of sulphur into a paraffine boiling at 140°-156° C. may retard its boiling point as far as 180°-200° C, according as it may exist in a greater or less quantity. In consequence of the presence of the sulphur in the still retarding the ebullition, the vapors of the paraffine are heated to a point far above their boiling points; therefore, 14 CALIFORNIA STATE MINING BUREAU. they are decomposed to hydrogen and carbon. The liberated hydrogen combines with the sulphur vapors, forming sulphu- retted hydrogen. Shales containing y% per cent of sulphur yield scarcely any paraffine on distillation. Yield of Gas, Oil, Etc., feom Shales and Coals at High AND Lo-^ N Heat. Good Shales. Boghead Coal. Gas ( 30AL. fGas High. 13.65 3.65 11.04 .99 2.82 Low. 2.54 6.47 17.65 High. 37.32 2.43 20.65 .18 .80 Low. 4.83 3.23 50.29 High. 20.49 3.09 17.08 .29 4.15 Low. 6.49 Volatile . Am'onia water. Tar or oil Sulphur Water at 212° E, Fixed carbons. Sulphur Ash 7.24 26.45 <3oke — - 32.15 4.16 1.05 62.64 26.66 10.81 62.53 61.38 9.01 .06 29.55 58.35 12.40 29.25 45.10 45.00 .34 9.56 40.18 49.93 9.89 100.00 100.00 100.00 100.00 100.00 100.00 What is known under the general name of petroleum includes a series of hydrocarbon oils varying widely in physical properties. Some are limpid fluids with many intermediate :grades; others are found viscid and tar-like. Hydrocarbons generally exist in three different conditions: first, the gaseous condition, wherein the equivalents of hydro- gen are equal to, or greater than, the number of equivalents -of carbon; second, in the liquid state, where the equivalents of carbon exceed the equivalents of hydrogen; third, in the solid state, where the carbon exceeds the hydrogen in still greater ratio than in the liquid state. Their color by transmitted light ranges from a light yellow through orange and red to a reddish brown, so dense as to be translucent only in thin films; while by reflected light it passes from a light dusky color to a dark green and to a black. They differ as markedly in odor, and also in other properties, some having a very disagreeable smell, while others are considered even pleasant. There is a wide range in their gravity. The greater the quantity of carbon in proportion to the hydrogen any one of them contains, the greater is its specific gravity, and the higher THE GENESIS OF PETROLEUM AND ASPHALTUM. 15 its boiling point and density of vapor. In the same oil field, in the same series of strata, and in the same stratum there are differences of composition. The following are the commercial names of the products of distillation of crude petroleum: cymogene, rigolene, gasoline, naphtha, benzine, kerosene, maltha, and paraffine. There is no well-marked division line between any of the above named products, but they gradually merge one into the other. Their division is simply one of caprice. These hydrocarbons are extremely complex and different in composition. The pro- portion of carbon and hydrogen is extremely variable. There seems to be no end to the different combinations of hydrogen and carbon. The great diversity in the physical and chemical conditions of the bitumen can be attributed: first, to the organic remains from which it was distilled — different kinds of terrestrial vegetation and marine vegetation — by natural process these organic remains may have been changed into peat, lignite, or coal before distillation; second, to the degree of temperature to which organic remains are subjected during distillation; third, to the pressure to which it is subjected during distillation; fourth, to the time consumed in effecting distillation; fifth, to the presence of different substances during distillation — sulphur, lime, water, oxygen, nitrogen, etc., which render their properties very different; sixth, to the condensation of the bitumen after distillation, whether rapid or slow, agitated or quiescent; sev- enth, to the material of the still; eighth, to repeated distillations; ninth, to evaporation; tenth, to sulphuration, oxygenation, etc. Electricity may also play an important part. Maltha, asphalt, jew pitch, mineral pitch, and brea are hydrocarbons which contain either sulphur, oxygen, or nitro- gen. They may contain one or more or all three of these elements in varying proportions. They can be produced synthetically by sulphurizing, oxidizing, or nitrogenizing petroleum oils. Oxygen, sulphur, or nitrogen, when chemically united with a hydrocarbon, such as some of the petroleum oils, produces a resin-like substance, to wit: asphaltum. One of the solid asphaltums, when taken from the ground, is brown, owing to its porous condition, caused by the evapo- ration of the petrolene. It melts at 245° Fahr. When it is 16 CALIFORNIA STATE MINING BUREAU. melted, it becomes black or blackish green. Another asphal- tum, when taken from the ground, is black in color, shaded with brown, or red and dark green when sulphur is present. When purified it assumes an indigo-blue reflection. It is opaque, scentless, tasteless, and fragile, breaking with a con- choidal fracture, which has a glassy brilliancy. By rubbing, it acquires a resinous electricity. Its specific gravity varies from 1.100 to 1.247. At ordinary temperature it is readily reduced to a powder. In a condition of extreme subdivision it takes a brownish tinge. It melts at about 105° to 108° C. Immediately above its melting point asphaltum is volatile, and, if the temperature is carefully raised, it disengages in abundance white vapors which belong to oils, which become thicker in proportion as the operation is prolonged little by little; but slowly the volume of vapors diminishes, gas ceases to form, and a deposit of carbon, slightly bituminous, is reached, which is solid and has the appearance and often the hardness of jet. When subjected to quick distillation in passing on towards the dark red, it sets free at the same time a mixture of brown oils, sometimes sulphuretted hydrogen and sometimes ammonia, while the retort retains about one third of its weight of loosely compacted carbon. It is entirely insoluble in water; it gives up to absolute alcohol a small quantity of a yellow substance which exhales the odor, and has the appearance, of resin. Ether extracts from it a brownish-black substance called petrolene. The portion left by the alcohol and the ether is asphaltene. The yellow substances, petrolene and asphaltene, do not exist in asphaltum in defined proportions. Sometimes the petrolene will represent two thirds or more of the asphaltum. On the other hand, asphaltene composes almost exclusively other asphaltums. The properties of the asphaltums vary according to different proportions of these three principles. Yellow Resin. — Absolute alcohol dissolves yellow resin with- out dissolving petrolene or asphaltene; it is also readily soluble in the solvents of petrolene and asphaltene. It has the appear- ance of a resin. When the solution in alcohol of the yellow resin-like principle is treated with liquid ammonia, it produces an abundant white precipitate, while small globules of petrolene spring up from the bosom of the liquid and come floating in greenish-yellow lentils to the surface. THE GENESIS OF PETROLEUM AND ASPHALTUM. 17 Petrolene. — This is brownish black in color and has a soft and glutinous consistency. It is insoluble in absolute alcohol. Ether, benzine, benzene, acetone, and the fat oils dissolve it and the yellow resin, but leave the asphaltene intact. Petrolene is also soluble in the solvents of asphaltene. The specific gravity of petrolene at 21° C. is 0.891. It burns with a very sooty flame. It has but very little taste. A highly concentrated solution of caustic soda or caustic potash, when hot, dissolves petrolene; if some diluted sulphuric acid is poured into the liquid, a brown gelatinous substance is precipitated. A current of chlorine precipitates the . petrolene from its solution in benzine or in turpentine in brown and viscous flakes. These precipitates contain chlorine, and do not give anything further to alcohol or ether. Hydrochloric acid precipitates petrolene from its solution in benzine in thick flakes; sulphuric acid, in a solid and viscous deposit, which is transformed in time into a brownish red. In making the experiment with sulphuric acid, the acid must be carefully and slowly added. If asphaltum be kept at a temperature of about 250° C. by means of an oil bath, until it no longer loses by weight, the petrolene is evaporated from the asphaltene. Asphaltene. — Heavy petroleum oil, carbolic acid, turpentine, chloroform, and bisulphide of carbon dissolve asphaltene with- out residue. It burns like resin, leaving coke. It is black, brilliant, and breaks with a conchoidal fracture. In the fire it only becomes soft near 300° C, and decomposes before com- pletely melting. When torrified upon a platinum plate, it diffuses an odor of burned fat, afterwards of a sharp taste, which reveals an acid. It is solid, hard, and fragile. When pulverized, it presents a mass of purple color, oftener of a brownish red. It develops, by friction, resinous electricity. In some of the asphaltums, analysis has disclosed a large proportion of oxygen; in others, a large proportion of sulphur. A current of chlorine precipitates the asphaltene from its solution in petroleum oils and turpentine. Asphaltene is not sensibly affected by caustic potash or caustic soda in a concentrated solution in water. 2— Bl6 18 california state mining bureau. The Formation of Asphaltum by the Resinification of Petroleum Oils. — When petroleum oils are left for a long time in the presence of oxygen gas, or the atmosphere which contains oxygen, and in the light, they absorb oxygen; some carbonic acid is set free, water is formed, their odor becomes weakened, and they likewise become viscous while they assume a darker and darker color. When petroleum oil is heated in a current of oxygen, it undergoes a quick change and turns into petrolene. If a current of sulphuretted hydrogen is conducted into boiling petroleum, a very mobile sulphurized liquid is distilled, having an unbearable odor of onions. If this treatment is repeated with the new compound, a second portion of the sulphuretted hydrogen comes to reinforce the former, and the odor of the liquid becomes that of garlic. When this sulphurized oil is evaporated, a resin is formed. If petroleum oil is changed by the compression of sulphuretted hydrogen, and then the sulphuretted hydrogen be decomposed to sulphur and water, the oil will be sulphurized and resinified. If petroleum oil is distilled in the presence of sulphur, the oils will be decomposed and sulphur compounds formed in. the shape of a resin. Petroleum oil treated with nitrous gas absorbs it with a slight development of heat; the petroleum becomes thicker and is partly converted into resin. All the petroleum upon which azotic acid is caused to act, furnishes yellow resins. If petroleum is boiled in a concentrated solution of nitrate of potash or of soda, the nitrate converts the bitumen into resin, and the liquid becomes a brownish red. Polymerism of Asphaltum.— By exposure to daylight, as- phaltum polymerizes; that is, it acquires a higher molecular weight, retaining the same atomic proportions. The stronger the daylight the more rapid polymerization takes place. When polymerized, its molecule consists of two or more simple molecules united to form a complex molecule. It can be changed from a state of polymerization to its original or simple state by heat. Polymerization is much more rapid and conspicuous with asphaltene than with petrolene; the part of asphaltum soluble in alcohol does not polymerize. Polymerization is more rapid and greater in asphaltum THE GENESIS OF PETROLEUM AND ASPHALTUM. 19 containing sulphur than in asphaltum containing oxygen. When polymerized, the physical properties of the asphaltum are changed; it has a greater specific gravity, it is harder and more brittle; but the most marked change is that of becoming insoluble, or, to speak more exactly, of being dissolved with greater difficulty in its solvents than when not polymerized. Asphaltum, on account of this photochemical action, is used in photography. If a moderately concentrated solution of asphaltum, in spirits of turpentine or chloroform, be placed in a transparent bottle and securely corked, and then exposed for some time to the light of the sun, resinous substances separate and gradually appear, which dissolve with greater difficulty in these solvents. If heated, they dissolve; the greater portion of these separated substances adheres firmly to the sides of the bottle; a smaller portion remains in suspension in the solution. Colored resinous substances will form in the California petroleums of commerce, if exposed to light, in the manner described above. *^ulter Ij/^ 2d ,, Solutions of asphaltum, which are to be employed in pho- ^^^l6 tography, must be kept in the dark. Asphaltum is employed in photography in the following manner: When the solution of asphaltum with turpentine or chloroform is spread over a plate, and left in a dark room until it becomes nearly dry, which will require a few days, and the plate exposed in a camera, or placed under an object in contact with it, the time necessary to make the print varies very much, and can only be ascertained by experiment. When printed, the development is effected by quickly flooding with spirits of turpentine, which will at once dissolve the asphaltum which has been protected from light, and partly dissolve that portion which has been exposed to the light. As soon as the subject is seen to be fully developed, a gentle stream of water from a tap is allowed to flow over it to wash off the turpentine. If all operations have been conducted rightly, a very delicate and perfect picture in asphaltum is the result. Anticlines, synclines, monoclines, centroclines, and quaqua- versals, and also faults, exert a great influence in the accumu- lations of gas, petroleum oil, and water. Especially is this true in California, where the dips and undulations along the strike of the anticline are exposed and well defined. 20 CALIFORNIA STATE MINING BUREAU. Although a description of the different inclinations and curvatures of strata would seem elemental, a thorough knowl- edge of the effect of these inclinations is necessary for an understanding of the laws governing the accumulations of bitumen in California. In the Eastern States the slopes of the domes frequently do not exceed twenty feet to a mile, whereas in California the strata stand at a very steep angle with the horizon, frequently being overturned. Fig. 1.— Plano-Section Showing Inclinations. When a group of strata is bent into a curve like a saddle, with its convexity turned towards the earth, it is called an anticlinal curve. Such a condition of strata is shown in Fig. 1 above the word " anticline." A synclinal curve is exactly the opposite of an anticlinal curve. When the strata are folded or curved, so as to form a trough, the concave side of which is turned from the earth, this is called a synclinal curve. This is shown in Fig. 1 above the word ^'syncline." In both anticlines and synclines, the line in each bed, along which the change in the direction of the dip takes place, is called the anticlinal or synclinal axis of that bed, and the planes containing all the axes of an anticlinal ridge, or a synclinal trough, are called axis planes. The axis plane usually approaches verticality. Anticlines and synclines frequently nose out, or coalesce. When an anticline undulates along the line of its axis, dome-like elevations occur, from the summits of which the beds dip away in every direction. In this case the strata are said to have a quaquaversal dip. An anticline is an elongated dome. THE GENESIS OF PETROLEUM AND ASPHALTUM. 21 A quaquaversal, or dome, is a nest, usually of a great number, of different strata composing numerous overlying, gigantic, inverted funnels, the strata of the formation forming the sides of these rock funnels, all of which tend to guide and convey the ascending gas and oil to the apex of the dome. When a syncline undulates along the line of its axis, basin- shaped depressions occur, towards the bottom of which the beds dip from all sides. This is called a centroclinal dip. A syncline is an elongated basin. A fault, or dislocation, is a fissure or crack in the crust of the earth, accompanied by the elevation of the mass upon one side of the fault, while the other side remains stationary, or sinks down. Anticlines and synclines are often truncated by faults, and may be so faulted as to form the segments of a sphere or cone. If an oil-bearing bed, ascending to the north, be interrupted by an east and west fault, the further ascent of the oil northwards will be arrested, and then an abundant supply of oil may be obtained by boring on the south side of the fault; while for a considerable distance to the north, water will occupy the formation, to the exclusion of the oil. This is more apt to be the case where the throw of the fault is sufiicient so that the edges of the porous strata are covered by impervious strata. Selvage frequently occupies the line of faults, gener- ally caused by the movement of the two sides of the fault on each other, which have ground up the materials of the rock, forming a sheet of matter impervious to the flow of oil or water, or the faults may be filled up with mineral matter of various kinds, which are also impervious to oil or water. When a formation contains permanent water, the accumula- tion of petroleum oil will be found near the upper part of the dome, as is shown in the piano-section. Fig. 1. The oil floats on the surface of the water, and if natural gas is present, it will be found above the oil. These three substances arrange themselves according to their specific gravity, the lightest on top. Fig. 2 (see page 22) is a view of an anticline. The camera was pointed in the direction of its strike. The black line represents the plane of bedding, which was once horizontal, but is now curved in the form of an arch. The unaltered rocks of California cover an area of forty thousand square miles. 22 CALIFORNIA STATE MINING BUREAU. The bitumens are found, in greater or less quantities, in all of the unaltered rocks of California of the cretaceous and tertiary periods, and sometimes in the quaternary rocks, in the form of natural gas, petroleum oil, and solid and liquid asphaltum. The difficulty is the discovery of accumulations at particular places large enough to justify developments. The unaltered rocks consist principally of alternating beds of shale, sandstone, and conglomerate, varying in thickness Fig. 2.— Mesa Deposit, Sisquoc, Santa Barbara County. and resting upon metamorphic rock. The sandstones and con- glomerates act as reservoirs for the accumulations of bitumen, and the shales as incasements for these reservoirs. Some of these sandstone beds are more than three hundred feet in thickness, as will be described hereafter. Anticlines exercise great influence upon the accumulation of natural petroleum oil and other bitumens. The main anticlines of California oil regions bear north- westerly and southeasterly. The summits of these anticlines have been denuded, exposing metamorphic rock. Numerous THE GENESIS OP PETROLEUM AND ASPHALTUM. 23 smaller anticlines branch in all directions from these main anticlines, and generally nose out in the valleys. Smaller and lower anticlines also run rudely parallel with the main anticlines. When the uplifts, by orogenic movements, have been great, the apexes of the anticlines are frequently denuded, the bitumens either being washed away or, as more often hap- pens, drained into the dips of the anticlines. The petroleum-bearing strata are exposed to a greater geo- logical depth in the outcrops of the strata of the main anticlines that show a metamorphic core, than in the lower anticlines that are but slightly denuded; consequently, there are visible many seepages of oil and flows of gas from the outcrops of oil strata on the sides of the main anticlines, while in the lower anticlines the same oil strata lie far below the surface of the earth. In the valleys in which bituminous strata are overlaid by quaternary rocks, the bituminous deposits may exist at such great depths that they cannot be reached by drilling. In the northern part of the State a large amount of tertiary rocks have been washed away ; these rocks grow thicker and thicker to the southward, until in the southern part of the State they are of great thickness. The unaltered rocks in the northern part of the State are geographically higher and more broken than in the southern part. Owing to these diflerent conditions, there is more and better storage room for the bitumens in the southern part of the State than in the northern. The unaltered rocks of the Coast Range are more broken and contorted, and have a much larger outcrop than those forming the foothills of the Sierra Nevada on the east side of the San Joaquin Valley. Therefore, there are more visible evidences of bitumen on the west side than on the east side of valley. There can be no question but that the cretaceous and tertiary rocks, which are the oil-bearing rocks, of California, underlie the quaternary deposits of the San Joaquin and Sac- ramento valleys. Gas wells exist in these valleys ; this shows that the lighter and more volatile parts of the petroleum oil have been preserved; consequently, the heavier parts of the oil exist. 24 california state mining bureau. Red Shales as Connected with the Genesis of Bitumen in California. — Shales were, and are, deposited in still and salt water. The iron contained in these waters and organic remains, both animal and vegetable, and other materials constituting the shales, were deposited contemporaneously. If the iron was the peroxide of iron, ferric oxide (FcaOg), by contact with organic remains, it was deoxidized and reduced to a protoxide, ferrous oxide (FeO), by the absorption of one equivalent of its oxygen ; when the peroxide was reduced to a protoxide, carbonic acid, produced by the decom- position of organic matter, then united with the protoxide, forming carbonate of iron (FeCOa). The carbonate of iron imparts a bluish or greenish color to the deposit. The accumulation of iron, in the presence of an excess of organic matter, retains the form of ferrous carbonate. In all coal measures, of all periods, whether carboniferous, Jurassic, cretaceous, or tertiary, or in all cases where there is organic matter in excess in a state of change — in all strata, whether older or newer, in which there is organic matter in excess in a state of change (not graphite) — the iron is in the form of carbonate protoxide, or ferrous carbonate (FeCOg). Sulphide of iron, ferric sulphide (FeSg), is subsequently formed and deposited instead of carbonate of iron. The sulphates of lime (CaOSOg) and magnesia (MgOSOg-f-^HO), and other sulphates which exist in sea water, when subjected to the action of decaying organic matter, out of contact with air, are deoxidized and converted into solubles, from which sulphuretted hydrogen gas is set free by the carbonic acid gas produced by the decomposition of organic matter. Sulphu- retted hydrogen converts the soluble compounds of iron into sulphide of iron. The color of pyrites is brass yellow. The presence of protoxide of iron, and of iron pyrites, in these shale beds, arises from the considerable amount of organic substances exercising a reducing action. The water flowing from the mountain heights, where there are no organic substances, exercises at first an oxidizing influence, by virtue of which the rocks over which it flows are decomposed. The suspended substances carried down by these rivers, and the detritus swept along their beds, come, after a time, in contact with organic substances, by means of which the per- THE GENESIS OF PETROLEUM AND ASPHALTUM. 25 oxidized iron compounds are again reduced. Consequently, the iron thus carried into the sea is, for the most part, in the state of protoxide, either combined with silica or with carbonic acid, the silicate being suspended, and the carbonate dis- solved in the water. When unaltered by oxidation, the carbonate of iron, with varying amounts of lime, clay, or sand, is dark grayish-blue or green, or even white, in color. When unaltered by oxidation, the sulphide of iron is brassy yellow in color. From the preceding explanation, it is safe to say that, at the time of their deposition, the carbonaceous shales were not red; and as long as they are not submitted to oxidizing influences, they will not become red. When carbonate of iron is exposed to the oxidation of the air, it forms limonite (hydrous ferric oxide), which is usually of a brownish yellow, or brownish red color. These iron ores are found in all stages of transformation. On the outcrop, they are limonite; under dense cover, carbonate. While going from the outcrop inward, the limonite constantly decreases in proportion to the carbonate. In the alteration of the compact carbonate, the line of chemical change and color is usually very sharply defined, and the limonite covering can often be entirely removed from the inclosed core of carbonate by a blow with a hammer, the limonite covering preventing the carbonate core from being oxidized by the air. In shales charged with gray carbonates of iron, the following reaction takes place by the action of the air: the carbonic acid is released, and part of its oxygen oxidizes the iron. Gray shales containing finely divided pyrites, or bisulphide of iron, are converted by heat into bright red, the sulphur being released, leaving the shales charged with red oxide. The color of burnt ferruginous shale is entirely due to the amount of iron present. Gray shales containing less than one per cent, or one and one half per cent of iron, change by heat to various shades of cream color, or buff; while those contain- ing two per cent to ten per cent, or twelve per cent of iron, produce, by heat, pink and bright red bodies. The depth of the color depends merely on the amount of iron present, the buff shades gradating into the deeper shades of red. A group of stratified rocks usually consists of various species, 26 CALIFORNIA STATE MINING BUREAU. arranged in alternating beds, a series of beds of many hundreds, or even thousands, of feet in thickness, containing strata of shale, limestone, or sandstone. Some strata are seamed or porous, and easily penetrated by fluids, serving as conduits and reservoirs for fluids. Some strata are nearly impervious to fluids, while others are practi- cally so, frequently serving as incasements for the conduits and reservoirs formed in, and by, porous and seamed strata. All stratified beds have been originally deposited in a horizontal position, or approximately so. While these beds were in the horizontality of their deposition, and incased by impervious strata, there was little or no circulation of fluids within their porous or seamed strata. When they were tilted and inclined to the horizon, at angles varying from the hori- zontal to nearly absolute perpendicularity, and their porous and seamed strata exposed to the entrance of fluids, by denuda- tion, fracture, or otherwise, and an exit for the fluids was supplied, or produced, at a lower level than the place of its entrance, the circulation of fluids commenced, slowly at first, gradually increasing as the inclination and exposure of the different strata became greater. The course of the circulating fluids was complex and anfractuous. Water, supplied by the rainfall of the region, enters at the outcrop of the porous and seamed strata. If the porous and seamed strata are incased in impervious strata, the greater the depth to which the strata extend from the place of entrance of the water, the greater the pressure will become. In some instances this pressure will be very great, forcing the water into comparatively impenetrable rocks. The water, percolating and circulating through the porous and seamed strata, by its solvent action, accumulates mineral ingredients. These waters, saturated with minerals, coming in contact with other minerals existing in the shales, by chemical reaction produce heat. This heat contracts and fractures the shales, permitting a freer circulation of water. This chemical heat distills petroleum from carbonaceous shales, and oxidizes the carbonate and sulphide of iron, produc- ing the red colors of the shales, and water of different temper- atures, charged with mineral ingredients, will frequently rise, by hydrostatic pressure, through fissures and faults, etc., to the THE GENESIS OF PETROLEUM AND ASPHALTUM. 27 surface of the earth, forming mineral springs. These springs are often accompanied by bitumen. But very few fossils exist in these red pyrogenous shales, as they have been obliterated by the solvent action of hot water, or by the chemicals held in solution by the circulating waters; or, if the molds or casts of their external forms existed, they have disappeared from the same causes, or they have been crushed and distorted beyond recognition. Red Shales in California. — Red shales in California are the effects of chemical heat. Strata which have been more or less altered by the action of heat emanating in the strata from chemical reaction, consist of burnt shale, porcelain jasper, earth clinkers, slag, and white shale. Burnt Shale. — Its color is usually red, sometimes gray, yel- low, or brown, and gradating from cream color to brilliant red. It is clay, or shale burnt, but not so much changed as to form a porcelaneous mass. Porcelain Jasper. — It is shale, or changed into a kind of porcelain by the action of heat. It is dark red, yellow, or striped yellow and red. Earth Clinker or Slag. — This is a shale, converted into a kind of clinker slag. It is black brownish or reddish, and it has occasionally a tempered steel tarnish. Sometimes it shows iridescent colors. It is vesicular, usually amorphous, but occasionally possessing the prismatic form of artificial coke. White Shale. — During these chemical fires, carbonic acid, sulphuretted hydrogen, and aqueous vapors are formed; these exhalations, in passing through the shale, bleach and decom- pose it. The silicates are decomposed by the continuous action of aqueous vapors, at 212° Fahr., sulphuretted hydrogen, air, and the alkalies, magnesia and lime, are nearly removed, and metallic oxides are carried away. The vapors convert the shale into a white clay, or nearly white, when a small quantity of iron still remains. By the removal of the alkalies (mag- nesia and lime) and metallic oxides, the quantity of alumina and silica increases. The absence of the bases, such as lime and iron, in these bleached shales, gives growth to a different 28 CALIFORNIA STATE MINING BUREAU. vegetation from that which grows where these bases exist. This difference in vegetation is a good index to deposits of petroleum and bitumen. The removal of these substances makes the shale incapable of sustaining vegetable life; the absence of, or scarcity of, vegetation is indicative of this action. Immense beds of these white and altered shales frequently occur in the vicinity of bituminous deposits, generally running in the direction of the anticlines. "Not infrequently the marine shales, through which hot silicated waters have percolated, and from which the bases, such as lime, magnesia, iron, etc., have been carried away by the solvent action of these waters, contain diatoms in large numbers, whereas the adjoining shales, which have not been leached, do not contain diatoms in any notable quantities. Diatoms abound in the hot springs of California and Yellow- stone Park. In the hot springs of the Yellowstone Park, deposits of this kind are now forming over many square miles, and are five or six feet thick. Why should they not originate and abound in percolating hot silicated saline waters, and be deposited in the interspaces and joints of the shales through which the water percolates ? Isolated bodies of diatomaceous earth in California would indicate that they originated and were deposited from springs. At the Buena Vista Oil Springs, in Kern County, quaternary deposits of infusorial earth exist, the stratification of which is horizontal; it has either been denuded from the leached and adjoining formation, and deposited in still water, or else it originated in quaternary waters, and then deposited; probably the latter is the case, as these strata do not show the presence of other material from the adjoining formation. From the immense amount of mineral matter which has been carried away by the solvent action of water — thousands of tons of fossil shells, silica, magnesia, iron, etc. — and the large area now occupied by the whitened shales, the flow of mineral water, at some former time, must have been very copious as compared to the flow at the present time. The illustration (Fig. 3) shows an outcrop of red shales and porcelanite near Mount Solomon, Santa Barbara County. Phenomena Attending Red Shales. — The red shales are discovered by their bright colors, by the heat of the earth in THE GENESIS OF PETROLEUM AND ASPHALTUM. 29 their vicinity, and sometimes by smoke. Sulphurous and other vapors frequently occur. These vapors, in their course upward, are condensed, and incrust the fissures of the rocks, and even the surface of the ground. Mineral springs, hot and cold, issue from the ground in their vicinity. The earth is charged with salts and minerals Fig. 3.— Outcrop of Red Shales akd Porcelanite. occasioned by the percolation and evaporation of these mineral waters. Shales, through the joints of which these mineral waters have flowed, have become impregnated with salts, and the salts, subsequent to the flow, have become vitrified by heat. They are further known by the issuance of warm or cold natural hydrocarbon gas, by seepages of bitumen in their 30. CALIFORNIA STATE MINING BUREAU. neighborhood, by fissures, joints, and porous rock filled with asphalt, and by the almost total absence of fossils in the burnt shale porcelanite and clinkers, which have been obliterated by hot water and heat. Before chemical heat commenced, these shales did not contain over two per cent of carbonaceous matter — not sufiicient for them to be set on fire at the surface. Physical Characteristics.— When unburnt, these shales are easily split along their lines of lamination, but when burnt to a tile red, or to a greater degree, their fissility is partly destroyed. When unburnt, their lines of lamination are plainly visible; but when burnt, their lines of lamination are obscured or obliterated. When unburnt, they have a clayey -like smell when breathed upon ; but this physical characteristic is partly, if not altogether, lost when they are burnt. When unburnt and suspended so as to freely vibrate, they' have a dull sound when struck; but when burnt, they become resonant. In this characteristic they resemble brick. Chemical fires destroy, or partly destroy, their lines of lamination, their fissility, and their argillaceous smell when breathed upon, but increase their resonance. These characteristics do not occur when these shales are discolored by the oxidation of the iron naturally contained in them, through the agency of water without heat. Serpentine cups filled with a pigment made from these bright shales are dug from the graves of the aborigines. About thirteen miles east of Santa Barbara City, an excava- tion was made on the blufi" of the ocean for the road-bed of the Southern Pacific Railroad, and the gray shale, charged with chemical substances and carbonaceous matter, taken from the excavation, was thrown over the blufi", forming a conical -shaped pile, composed of pieces of shale containing from one to eight cubic inches. Water could easily penetrate the broken shale, and air could easily circulate through the mass. When the winter rains fell upon this pile, chemical action commenced, producing sufficient heat to vitrify and weld the pieces of shale together. A large part of this shale was burned to a red porcelanite, and the remainder was colored a buff shade, gradating into the deeper shades of red. Above the railroad track, the face of the shale bluff has been cut off to the angle of repose by the railroad company. This smooth surface is a good place to observe the action of chemical heat and attending phenomena. THE GENESIS OF PETROLEUM AND ASPHALTUM. 31 La Patera Mine. — La Patera Mine lies nine miles west of the City of Santa Barbara. Its relation with a lake and the ocean is shown in Fig. 4. The lake contains about sixty acres. Along the periphery of the lake, the stratification of the shale dips towards the lake at an angle varying from 30° to 40°. The composition and the arrangement of the component parts of the soil are the same upon the island as upon the mainland. The shale must have existed at a level shown by the dotted lines in Fig. 4, and subsided after the deposition of the soil, otherwise the soil would not have been deposited upon the island in a manner similar to that of the mainland. This subsidence was probably occasioned by the contraction of the underlying shale, Fig. 4.— La. Patera Mine, Santa Barbara, California. produced by chemical heat. Some idea of the contraction of the shale by burning may be learned from the contraction of brick through burning. Before burning and when in a dry condition, a brick is 8 inches long; when burned — not vitrified — it is 7J inches long, and when vitrified it is 7| inches long. If the basin of the lake near the La Patera Mine had been formed by erosion of the land by sea or surface water, the shale would have been squarely cut off and not contorted so as to dip towards the lake. In the excavation at the mine at the depth of 100 feet, a temperature of 105° Fahr. is generated in the shales by chemical heat. Circumjacent to the lake are fissures filled with hard asphalt, through which comminuted shale and mineral water are disseminated. 32 CALIFORNIA STATE MINING BUREAU. Off the shore, petroleum rises from submarine springs, cover- ing a large surface of the ocean with a thin film of iridescent oil, the odor of which can be detected at a long distance. Ledges of hard asphalt exist in the ocean, below high tide, which run nearly parallel with the shore. Surface wells show the existence of water highly charged with mineral substances, in which petroleum is discovered. So far, no potable water has been found near this mine. Six miles west of Santa Barbara, on the Calera Rancho, and on the ocean shore, an area of twenty acres has subsided some Fig. 5.— Lake Formed by Subsidence of Land. twenty-five feet; of this subsidence, four feet occurred in five years. This subsidence has occurred through the contraction of the shale. The surface of the subsidence is rifted and seamed, and from these rifts and seams sulphurous and other vapors ascend. The ground is hot. The bluff is composed of burnt shales, showing tints from a cream color to a brilliant red. Water containing salt seeps from the base of the bluff. Shales with carbonaceous material, shales saturated with bitumen, and smoky-looking shales surround the hot places. THE GENESIS OF PETROLEUM AND ASPHALTUM. 33 Near the hot places, heavy petroleum oils ooze through the shales. To the eastward and westward heavy and thick petroleum tars ascend through the cracks and seams and joints of the shale. Some of the seams of shales, containing a small proportion of bitumen, have hardened to such an extent that they resemble dark flint, and will cut glass. Lyell gives the following: " Captain Mallett quotes Guinillar, as stating in his description of the Orinoco, that about seventy years ago a spot of land on the western coast of Trinidad, near half-way between the capital and an Indian village, sunk suddenly, and was immediately replaced by a small lake of pitch, to the great terror of the inhabitants." A similar subsidence at an earlier period may probably have given rise to the great Pitch Lake of Trinidad, the cavity having become gradually filled with asphalt. There are a number of places in California near these red shales from which natural gas issues. Some are hot, showing that they are formed at a high temperature. Fig. 5 is a view of a small lake formed by the subsidence of the land near Mount Solomon, in Santa Barbara County. It may not be out of place to mention in this connection the occurrences of red shale in other parts of the world in which bituminous deposits are known to exist. Red Shales in the Island of Trinidad. — The formation of the island of Trinidad consists of clay, loose sands, shales, limestones, calcareous sandstones, indurated clays, porcelanites of brilliant red colors, with pitch deposits and lignite here and there. The only substances containing sufficient carbon and hydrogen for the formation of asphalt, and likely to be inclosed in the strata, are vegetable remains. They are particularly abundant at La Brea, where most of the asphaltic beds have been originally carbonaceous and lignitic shales. Mineral springs abound throughout the island. In a series of loose sands, clay, and shale, lies Pitch Lake, seemingly occupying a depres- sion in the strata. (See Fig. 6, page 34.) To the southward of the lake the shore is made up of bold cliffs, the strata of which consist of indurated clays. They also present thick veins of por- celain jasper. Strata of loosely coherent sandstone also abound, some of which are impregnated with bitumen. Rounded 3— Bl6 34 CALIFORNIA STATE MINING BUREAU. pebbles of pitch and porcelain jasper form a beach at the foot of the cliffs. A species of coke is occasionally observed along the shore with a porous structure and the prismatic form of the artificial product, but, of course, much denser, on account of the large proportion of earth. Near the lake is a red, yellowish substance, semi-baked, evidencing that a considerable degree of heat attended its formation. Part of the impurities in the Trinidad asphalt consist of comminuted red clays or shales, with some sand. It is evidently not adventitious at the surface, but must have been thoroughly incorporated, and brought up from the depths with the bitumen, judging from the constant amount, dissem- FiG. G— Pi < E AT Trinidad, W. I— From an old print. ination, and character in all parts of the deposit. Water, con- taining all the mineral ingredients of strong thermal water, is found in the Trinidad asphalt. The presence of borates, iodides, and so man}^ forms of sulphur compounds, and other charac- teristics, show that the water must be of the same origin as that of many thermal springs. This water, in all unaltered pitch, shows that the formation of the pitch and water must have been simultaneous, and cannot be considered adven- titious. It would be impossible for water, in any adventitious way, to become intimately mixed with the bitumen, so as to form, practically, an emulsion. Near the center of the lake is a body of pitch, softer, blacker, and newer than that of the THE GENESIS OF PETROLEUM AND ASPHALTUM. 36 remainder of the lake. Gas constantly issues from the cracks in the bitumen. These phenomena show that asphalt is being distilled at the present time. The porcelanite and red shales must have been formed by heat created in the strata themselves, as these shales are burned uniformly, in no place showing a greater degree of heat than in another. They are, probably, formed in the same manner as similar rocks in Cali- fornia. The depression in which Pitch Lake lies, was, probably, made by the subsidence of the surface of the earth, caused by the heat contracting the underlying shale. There was no focus to this heat, no central point. If there was, in the material next to the central point the evidences of heat would be great, gradually decreasing as you went from the focus;, this is not shown. To illustrate, bricks of very different qualities are to be found in the same kiln, for as the fire is applied below in arches, the lower bricks in their immediate vicinity will be burnt to great hardness, or, perhaps, vitrified; those in the middle will be well burned; and those on the top will be too little burned. Even then the bricks the farthest from the fire would not have been burned to this extent, if it were not for the numerous flues left between the bricks in the construction of the kiln. The intense heat of a furnace is confined by a foot- wall of firebrick. Three feet of lava will confine the heat of melted rock underneath. From the uniform burning of these shales, the heat must have originated in the shales themselves. A good, clean red heat is required for the burning of brick; it is fair to suppose that this temperature is required to produce red shales. Porcelanites and vesicular clinkers are scattered throughout these red shales; they are not centralized. No fumaroles connect these porcelanites with a central fire. Moisture was concerned, as is evidenced by their even burning. Moisture was the vehicle of heat, as the burning would not have been so uniform in its effect if disseminated by conduction or radiation. The parts of the shale burned to porcelain resemble earthenware and stoneware; to burn earthenware and stoneware, a clean, white heat is required. Arborescent forms, of huge scale, of these hydrothermal shales extend their ramifications throughout the earth in the vicinity of bituminous deposits. This form also goes to show that their burning was accomplished by chemical action, with 36 CALIFORNIA STATE MINING BUREAU. the presence of moisture, and not from radiation or conduction from a focalized fire. Nearly all readily solvent substances, and all volatile substances, have been removed from these red shales, or, where solvent substances now exist in them, they are different from those that were in them at the time of their formation. The noticeable bright red colors of these shales could not have been produced by the oxidation of the iron in the shales by water alone; heat must have been present to produce them. This heat would be sufficient to distill any carbonaceous substance contained in them. In the metamorphic rocks of the San Rafael range of mountains of Santa Barbara County, it can be plainly seen that these porcelanized shales were converted into serpentine. All gradations from shale to serpentine can be found: shales reddened by heat, porcelaneous masses still retaining the structure of shales, and porcelain partly converted into serpen- tine. There are no visible signs of metamorphic action now in operation where the serpentine is exposed to view, but in the tertiary shales and sandstones to the west, especially in the hills lying north and south of the Los Alamos Valley, this metamorphic action is going on at the present time. These red shales lie above and precede greater metamorphism, such as is exhibited by serpentine and quartzite, and, probably, metamorphic granite. This can be seen where erosion has been great enough to expose the contact between metamorphic rock and red and unaltered shales. When burnt, the cracks and seams in the shale are large, showing the extent to which they have contracted. Near the surface, the red shales are vesicu- lar, and look as if they had faulted. These red shales are very much distorted and contorted; many of the contortions have a radius of but a few feet. No carbonaceous matter exists in these red shales. No bituminous substances exist in these red shales, unless they have entered subsequent to their burning. There is also an absence of sulphur. Carbonaceous and bitu- minous substances, and sulphur, are disseminated throughout the strata adjoining the red shales. At the time of their deposition in sea water, and before any alteration had taken place, the red shales should contain chloride of calcium, carbonate of calcium, carbonate of iron, carbonate of magnesia, sulphate of calcium, etc., vegetable matter in a fine state of subdivision, and, in some places, large THE GENESIS OF PETROLEUM AND ASPHALTUM. 37 deposits of vegetable matter; this organic matter, in time, becoming carbonaceous shales and seams of coal. When these shales are heated with a chemical heat, the following described vapors and gases are given off: sulphur dioxide, carbonic acid, sulphuretted hydrogen, carburetted hydrogen, distilled from the carbonaceous substances, nitrogen derived from the same source, etc. These vapors are forced into the circumjacent formation, which is highly charged with mineral matter origi- nally present in the shale, and which had been deposited from hot water. Chemical actions arise when these vapors, or their condensations, come in contact with the minerals existing in the shales, causing heat. There remain in the shales, after the vapors and gases are eliminated by heat, oxide of calcium, oxide of iron, etc. Mineral waters and gases coming in contact with these substances produce heat. These chemical actions and reactions are complex and numerous. By these chemical actions and reactions, distillations and condensations, the alteration of the shale by heat becomes progressive and cyclic. This heat, under great pressure, and through subsidences and orogenic movements, is intensified. Chemical reactions are augmented through pressure and hydrothermal action. The hydrocarbons and other substances are distilled and condensed, dissociated and united, a multiplicity of times. Mineral springs, ranging in temperature from that of the earth, from which they issue, to the boiling point, are frequent in the neighborhood of these burnt shales. They contain, in notable quantities, sul- phate of sodium, magnesium, and calcium, aluminum, carbon- ate of sodium, calcium, and magnesium, chloride of sodium, potassium, and calcium, silica, and, in excess, carbonic acid, sulphuretted hydrogen, carburetted hydrogen, and traces of arsenic, sulphuric acid, and iron. Besides the visible phenomena, the warmth of these springs shows that this metamorphic action is still in progress. Deposits of bitumen, in California, are found in sedimentary rocks of all ages, and principally in three different ways: 1. In superficial detritus; 2. In veins; 3. In porous or seamed strata. The bitumen may be of any consistency — gaseous, fluid, viscous, or solid. Bitumen often occurs in superficial detritus or alluvium. This character of deposit is usually the overflow of tar springs, into which the detritus from the surrounding country has CALIFORNIA STATE MINING BUREAU. been washed or blown, and, where mineral tar is sufficiently liquid, it has percolated into the underlying earth. The detritus, when saturated with mineral tar, most always has been repeatedly burned, leaving black, vesicular clinkers, which are frequently refilled, where there has been a flow of tar after the fire. Cooking utensils of the Indians are found in the vicinity of these tar springs, showing that they were used for pur- poses of fuel. After this they were set on fire by shepherds, so that the fleeces of their sheep would not be injured, or lambs suffocated by going into the sticky mass. Where the bituminized detritus has escaped the fires, and exists below the clinkers, it contains about five per cent of brown and friable bitumen, having a specific gravity less than that of water. It consists of seventy per cent of asphal- tene and thirty per cent of petrolene. The accompanying map section and view show the Buena Vista Oil Spring, at Asphalto, Kern County, California. (Fig. 7.) The mineral tar reaches the surface at the place marked " tar spring." At the place marked *Har springs," a number of trenches have been cut, and a tank erected, so as to intercept and save the tar. These trenches are cut in clinkers and comminuted shale, which is often saturated with tar. Thin layers of detritus, impregnated with mineral tar, lying nearly Fig. 7.— Buena Vista Oil Spring, Asphalto, Kern County, California. THE GENESIS OF PETROLEUM AND ASPHALTUM. 39 horizontal, are intercalated with thicker layers of detritus, which contain no bitumen. These beds are formed by flows from the tar springs and deposition of detritus denuded from the adjoining hills. Before this deposit was worked, mineral tar had flowed from the springs over the surface of the clinkers, until it had reached a thickness of from one to six inches; it had evaporated and oxidized, becoming stiff. It was of different degrees of purity, sometimes absolutely pure; at other times, it contained as high as eighty per cent of detritus. In 1891 and 1892 this concreted tar was being mined and refined. At the present time there are but a few tons, which are scattered over the ground, in small pieces. It has been estimated that, in recent years, these springs afforded about one hundred and sixty barrels annually. There are a large number of other tar springs in California, nearly all of which have been burned in the manner described above. In the shaft sunk at the Hancock deposit, lying northwest of the City of Los Angeles, in the center of what appeared to be an old tar spring, on the surface were found the bones of domestic animals — horses, cattle, sheep, etc.; at a greater depth the bones of the bear, elk, and other wild animals; and, resting on the shale beneath the bituminized sand, at a depth of about thirty feet, were the bones of the Elephas Americanus. During the latter part of the summer season, in California, the natural grasses dry up, but, owing to the slight amount of water which ascends with the bitumen, as it does at the present time, many years ago, during the dry season, there grew, surrounding these asphalt springs, green and succulent herbage. This herbage was the bait of the trap which tempted these herbiv- orous animals to their death. With everything else dry, these green herbs were an irresistible temptation. In struggling to get to them, the animals became mired in the tar lake and suffocated, their bones gradually sinking to the bottom. The Elephas Americanus seemed to be the first one that met this fate, as his bones rest upon the underlying shale, below the remainder of the fossils. These springs must be very old, as it is many years since the American elephant fed upon the plains adjacent to the spring. Veins of asphaltum, being rents, seams, and fissures filled with asphaltum, occur, usually vertical, or not far from vertical. An innumerable number of small faults, contortions, and 40 CALIFORNIA STATE MINING BUREAU. breaks occur in the formation in which these veins of asphal- tum exist. These veins of asphaltum occur in the vicinity of red shales, or shales that have been burned and contracted by chemical heat; the contraction of the shales opened, and open cracks and seams in the adjoining formation permitted the ascent of the asphaltum. These cracks and seams extend to such depths as to reach deposits of petroleum oil. From observations made at Asphalto, Mount Solomon, La Patera, and other places, it would appear that these fissures and rents and faults are filled with bitumen in the following manner: Heavy petroleum oil at various depths below the surface of the earth, in porous or seamed strata, is urged upwards, principally by rock pressure. The subsidence of the formation in which the asphalt veins occur, is caused by the contraction of the shales by heat. In consequence of the subsidence, the shales and sandstones are very much broken and contorted. Around the edges of these subsidences these veins of asphaltum are found. The specific gravity of the asphaltum is too great for it to be buoyed up by water, and the formation in which the veins exist is too broken for gas to exert a pressure, but hydrostatic and gas pressure do, in some instances, urge the bitumen upwards. When ascending in porous or seamed strata, the petroleum oil is partly evaporated, the evaporated portion forming gas, which reaches the surface through passages which are closed to the viscous oil. The oil is readily oxidized on account of its divided state, and, if sulphuretted hydrogen or sulphur dioxide is present, the oil is resinified, forming asphaltum. By sulphuration, oxidation, and evaporation the petroleum oil is finally hardened. When nearing the surface it is indurated to such an extent that it rarely ever shows itself. Polymerization of the bitumen by photochemical action of the light also assists in the induration of the bitumen when nearing the surface. Adjoining the selvage of the veins, when near the surface of the earth, the asphaltum is brown and friable, fully two thirds of which is asphaltene. In the interior of the vein it is black and shining, and, when cold, breaking with a conchoidal fracture, fully two thirds of which is petrolene. The propor- tional amount of petrolene and asphaltene existing in the asphaltum is very variable. When at a sufficient depth, THE GENESIS OF PETROLEUM AND ASPHALTUM. 41 SO as to be removed to a considerable degree from atmos- pheric influences, the brown margin of asphaltum does not exist. As a general rule, the farther from atmospheric influ- ences, the more liquid the asphaltum will be. Bivalvular shells, filled with petroleum, are frequently found in these asphalt veins, the bitumen on the shells being much more liquid than the surrounding asphalt, and of a lighter color. The asphalt veins are rudely parallel to the periphery of the red shale deposits, and exist along the margin of the subsidences, Fig. -Asphalt Veins, Santa Maria, California. the seams for the reception of the asphalt having been opened by the movement of the formation towards the contracting shales, permitting the ascent of the asphalt, forced up by rock pressure. The parallelism of the veins to the periphery of the burnt shales is frequently changed by the varying hardness of difi'erent strata, or by orogenic contortions. When the hanging wall consists of hard and close-grained strata, the bitumen will accumulate below the same, which, on account of its being conformable with the plane of bedding of the adjoining strata, gives it the appearance of having been deposited at the same time as the other strata. When these 42 CALIFORNIA STATE MINING BUREAU. shales are burning, large amounts of sulphur vapors are disengaged. It is reasonable to believe that these vapors sulphurized the bitumen in their neighborhood, forming asphaltum. Mineral waters, containing sulphuretted hydrogen in large quantities, usually accompany the ascent of the asphaltum. The earth adjoining the veins is usually charged with mineral matter, deposited from infiltrated mineral water. If these openings and sulphur vapors had not been made and generated, through the contraction and burning of the shales by chemical heat, the asphaltum would not have been formed, nor could it have reached the surface of the earth. ' The physical characteristics of the asphaltum filling these veins are extremely variable. In consistency, it gradates from a hard rock to a viscous condition. The asphaltum contains, intimately mixed, from one per cent to seventy per cent of impurities. The impurities hardly ever exceed seventy-five per cent. The presence of more than seventy-five per cent of impurities makes the bitumen so stiff that it cannot be forced through the cracks and seams. In the vicinity of the injected veins there are beds of shales containing from ten per cent to fifteen per cent of bitumen, but existing rock pressure is unable to move them. The impurity in some of these asphalts is infusorial earth, in others, sand, while in others, finely ground shales and angular fragments of shales and fossil shells, or all of these impurities may be present in the same deposit. Shale preponderates as an impurity; in fact, the impurities are derived from the rock which the asphaltum encountered during its ascent. Most of the time the impurities are very fine and light, making the refining of the asphalt, by any known process, difficult. The thickness of these veins of asphaltum is variable; some- times they are twenty feet in thickness, decreasing until they become the thickness of a knife blade. In exploring for asphalts, these small seams are followed, and often lead to thicker parts. The asphaltum breaks with a conchoidal fracture, some of these conchiform pieces being ten feet in diameter. The viscous asphaltum cannot enter the interstices or pores of the rocks of the formation; especially is this true where the pores or interstices of the rocks are filled with quarry water; consequently, when it is urged upward and forward by THE GENESIS OF PETROLEUM AND ASPHALTUM. 43 rock, hydrostatic, or gas pressure, it exerts a pressure in all directions (similar in action to a hydraulic press), and through this pressure pushes the rocks asunder, making room for itself. The pressure required is not great when the shale is contracted on one or both sides, the asphaltum being constantly alert to take advantage of any movement of the earth. Next to these bituminous veins, the formation is of a bluish color, owing to the presence of a slight amount of bitumen. These veins entered the formation subsequent to its subsidence, as the veins are not faulted; although frequently very tortuous, they are continuous. These veins sometimes bisect the brown bituminized sand, showing that they were injected subsequent to the filling of these sands with bitumen, and even after they had become brown and indurated through long exposure. These veins of asphaltum frequently contain fossil shells and shark's teeth, which must have been brought up from lower strata, as no similar fossils occur in the adjoining walls of the vein. These fossil shells are filled with bitumen, mixed with the silt and sand that entered them when they died. The bitumen in the shells must have been much more liquid when it entered them than at the present time. At the present time the bitumen is too stiff to enter the shells. Sometimes the bitumen in the shells is much softer than that in the veins, and sometimes it is of a yellow color. Slickensides, on both sides of these bituminous veins, show that the material has moved upwards. Fossil shells, embedded in the hanging wall of these veins, have plowed grooves in the asphaltum as it ascended. At the Waldorf Mine a groove was formed in this manner, ten feet in length. These veins of asphaltum, in several instances, are found injected into the detritus which has descended from the adjoining hills. Tunnels and shafts, excavated in the formation con- taining these veins, have been partly filled with the ascending bitumen. At the La Patera Mine, in sinking upon some asphaltum, it was discovered that the excavation was being made in an old shaft, which, outside of the earth that had fallen into it, was filled with asphaltum. At a depth of fifteen feet, an old-fashioned pick and sledge-hammer were found, which must have been buried for a long number of years. Inquiries were made, but it could not be ascertained who sunk the shaft. At the La Patera, limpid sea water is inclosed in cavities in 44 CALIFORNIA STATE MINING BUREAU. the asphaltum. its limpidity showing that sea water has no effect upon the asphaltum. In the Santa Barbara Channel, below high-water mark, near the La Patera Mine, veins of this mineral occur. Owing to the plastic nature of this character of asphalt, and the broken condition of the formation in which it usually occurs, it is very difficult to mine. When inclines, tunnels, shafts, and other excavations are made in asphalt, or near it, they are hard to maintain, as the asphaltum lying above or near the excavations, even below them, commences to move through rock pressure, so that the excavations are soon destroyed. Deposits near excavations give evidence of their existence by the earth bulging into the excavation. Wedges, picks, and other tools, used in mining the asphaltum, become sharp, instead of dulling. When mined and relieved from pressure, occluded gas expands in the asphaltum, making it very vesicular. In Fig. 9, A A portrays unaltered shale, greatly distorted by subsidence, caused by the contraction of the red shale, D D. B B B B, veins of asphaltum squeezed and forced up by rock pressure exerted by the shale A A, owing to their broken and contorted condition. C C, shales filled with condensed hydro- carbonSj which were vaporized by hydrothermal heat in the red shales. Near or adjoining the red shales, the shales are filled with liquid asphaltum; in some places the shales and the liquid asphaltum have formed a mud, which is forced outwards and upwards by the weight of the superincumbent shale, through cracks and seams, to the surface of the earth. Farther away from the periphery of the red shale, the shale has a smoky appearance, owing to the condensation of different vapors, generated by hydrothermal heat in the red shales, D D. D D, red shales which have contracted through the action of hydrothermal heat, such contraction causing subsidences in the overlying shales, A A — such subsidences opening fissures and cracks, B B B B, permitting the ascent of the bituminous mud, urged upwards by rock pressure, and, maybe, by gas and hydrostatic pressure. Underlying the red shales is serpentine, being shales metamorphosed to a greater extent than the red shales. Engraving Fig. 9 on the following page gives a view of a formation into which veins of asphaltum have been injected. THE GENESIS OF PETROLEUM AND ASPHALTUM. 45 Reservoirs for oil and aspbaltum are created as follows: The porosity of limestone is created by chemical action, the changing of limestone into dolomite; the porosity of sandstone, Fig. 9.— Plano-Section Showing Asphalt Veins, by the solvent action of water leaching out the cementing material, such as lime, silica, iron, etc.; the capacity of shale for holding oil, or bitumen, by the mechanical bending and cracking of the strata, the cracks afifording storage room. 46 CALIFORNIA STATE MINING BUREAU. Limestone. — The Trenton limestone is very productive under certain circumstances. In its normal condition it is a compact rock, and then it contains neither gas nor oil; but, over large areas, limestone has been dolomitized, and so transformed into a porous and cavernous rock, in which the gas and oil are contained. The dolomitization of the Trenton limestone is probably occasioned by the removal of carbonate of lime by the solvent action of water charged with certain minerals, and as the Trenton limestone contains originally a small percentage of magnesia, it gradually becomes dolomitic in character, and, on account of its reduced bulk and crystallization, porous and cavernous. When water has taken possession of shale in the shape of quarry water, or the shale is saturated with water, it is nearly impossible for oil to eject the water and enter the shale; the reverse is also true, for, when oil has taken possession of the shale, it * is nearly impossible for water to enter the shale. This is undoubtedly owing to capillary attraction of the fluids in the shale. When the surface of a capillary tube is greased, it exerts but little capillary attraction upon water, and when a capillary tube is moistened, it exerts but little capillary attraction upon oil. Other rocks act the same as shale; the finer the grain of the rock the greater the capillary attraction, and the more difficult it will be for oil to replace water, or for water to replace oil. Shale, occupied by water, makes a good incasement for oil and asphaltum. The retention of petroleum and pissasphalt, in the porous and seamed rocks, cannot be effected without the accumulations or reservoirs having a cover or impervious incasement. This impervious incasement usually consists of unfractured shale or other close-textured rocks, or porous and fractured rocks cemented and sealed with indurated bitumen or other minerals. When the outcrop of bituminized sand is exposed to the atmosphere for a long time, the bitumen contained in it loses its volatile parts by evaporation and oxidation, turns brown, and is easily pulverized between the fingers. The sand sepa- rates from the bitumen, and the bitumen is easily ground to an impalpable powder. This brown asphaltum extends to but a short distance below the surface of the stratum. Beneath the THE GENESIS OF PETROLEUM AND ASPHALTUM. 47 brown coating of bituminized sand the deposits receive a coating of hard asphaltum, made hard by evaporation and oxidation. The condition of the bitumen in the seamed and cracked shale resembles that which is in the sand. This con- creted surface is impervious to the flow of pissasphalt and petroleum oil, and frequently sufficiently tight as to inclose natural gas. In fact, all porous or seamed rocks, when the base of the saturating petroleum is asphaltum, become water and petroleum tight, by reason of the petroleum becoming concreted by oxidation and evaporation; the same as when a tree is wounded by a cut or puncture, the impissated sap soon closes the pores, so that little sap escapes. The surface of the bituminized sands and shales is hard, increasing in fluidity as the bitumen enters the deposit, or is removed from atmospheric influences. In some deposits, a short distance from the surface will show a petroleum oil of 10° Baume, decreasing at 1,000 feet to 32° Baume. If rather stiff maltha is melted and poured into a hole in a sheet of iron one sixteenth of an inch in diameter, so that it will form a thickness one sixteenth of an inch on each side of the sheet, the sheet being one sixteenth of an inch thick, it cannot be removed with a pressure of water equal to fifty pounds to the square inch. The prodigious pressure necessary to force maltha through the interspaces of sand, or irregular seams of shales, for a distance of several hundred feet, can hardly be imagined. In fact, the salvation of most of the accumulations of petroleum oil in California is owing to this induration of petroleum by oxidation and evaporation. This impervious coating also protects the oil reservoirs from the entrance of surface water. The petroleum oil, in passing through the sand or shale, collects the silt and carries it forward. This, also, assists in forming a cover, filling up the places through which the liquid hydrocarbons attempt to escape. Under great pressure, the petroleum oils are constantly alert to take possession of any space created by the uplifting, or other movements, of the earth; and if these oils are con- creted into asphaltum, by oxidation and evaporation, they retain possession. The oil occupying the surface of the water in a formation has an advantageous position to perform this 48 CALIFORNIA STATE MINING BUREAU. work, as the formation is more fractured in these parts than in the synclines and the dips of the anticlines. The cut (Fig. 10) shows strata of bituminized sand on a ridge running north and south, between the Coja Creek and a branch of the Baldwin Creek, seven miles west of Santa Cruz, California. The bituminized sand lies nearly horizontal, and extends from canon to canon, through the ridge. The dip of the shales and sandstones of the surrounding country shows that this is the apex of a large dome covering an area of some twelve square miles. Overlying these strata of bituminized sand is a close-textured shale, forty feet thick, and underlying the same is a porous and incoherent sand. Fig. 10.— C. S. I. Co.'s Mine, Santa Cruz County, California. The Coja Creek, lying immediately west of this deposit, is 200 feet deep, and must have taken many thousands of years to form. Redwood trees, proving by their concentric circles to be several hundred years of age, are growing in the bottom of the creek. The impregnation of the sand with bitumen must have occurred before the gulch on either side of the deposit commenced to form through denudation, otherwise the liquid bitumen would have run out of the porous sand. From the horizontality of the surface of the porous sand which underlies the bituminous strata, it must have been filled with water, forming a horizontal plane, upon which the bitumen floated. This, also, must have occurred before the denudation of the gulch on either side. The petroleum must have been under considerable pressure, as it has thoroughly saturated the sand between the porous sand and the overlying shale, THE GENESIS OF PETROLEUM AND ASPHALTUM. 49 and, where porous places have existed in the shale, petroleum has been forced into them. Notwithstanding the thousands of years which this bitumin- ized stratum has been exposed to the elements, the bitumen in the interior parts of the deposit is at present liquid, its liquidity being preserved by the concretion of the bitumen on the top, bottom, and sides of the deposit, stopping evaporation, oxidation, and leakage. These strata of sand, when bitumin- ized, contain gold in considerable quantity: whereas, in those portions which are not bituminized, but little gold exists. It would seem that the gold in the bituminized sand was protected from the solvent action of mineral water, the presence of the bitumen in the sand stopping the percolation of mineral water; whereas, in the sands not bituminized, this percolation is permitted, and the gold is dissolved and carried away. But further examination will be required to be positive that such is the case. Sand rock, sand, and sandstone are composed mainly of rounded or broken grains of quartz of varying form, color, and fineness. The material cementing the grains is either argillaceous, bituminous, silicious, or calcareous, or a mixture of any of these four substances. Some of these sands contain cementing material, some in such a small quantity that they are friable. When found beneath the earth's surface, it is seldom in an incoherent state. When they are porous, they are occupied by either natural gas, petroleum oil, or water (generally of a mineral character), or both of these fluids and gas. The buoyancy of the oil in associated water is the force which impels the oil upwards. The oil is carried so far upwards that it sometimes escapes at the surface in the form of tar springs, or seepages, and is lost, or it accumulates in porous or seamed strata beneath the surface of the earth. For the reception of the petroleum oil or gas, the sandstone strata are at first made porous by the solvent power of water, which removes the calcareous and silicious cementing material. Frequently these bituminized sands are jointed, and, although this adhesive and plastic material, when excavated and thrown into a pile, will stick together so that it has to be again mined, it will separate readily at these joints when 4— Bl6 60 CALIFORNIA STATE MINING BUREAU. being taken from the deposit. The joints are often filled with mineral matter, such as carbonate of lime, deposited by circulation of waters subsequent to the bituminization of the sands. (Fig. 11.) Fig. U.— Bituminized Sand Showing Joints. Fro. 12.— Bituminized Sand Show- ing CONTOBTKD JOINTS. These joints are probably partly due to pressure, as they seem to have a trend which appears to be at right angles with the line of the steepest inclination upon which bituminous deposits rest, but always nearly per- pendicular to the plane of bedding. Some deposits, when jointed in this manner, appear like a row of books upon a shelf. Fig. 12 shows bituminous strata on the Sisquoc River, in Santa Bar- THE GENESIS OF PETROLEUM AND ASPHALTUM. 51 bara County. By the movement of the formation, the joints, filled with lime, have been distorted so as to nearly form the letter '*S," showing that there has been a considerable move- ment since the bituminization and jointing of the sand. Thes trata are often faulted a few inches at these joints. In the folding of a formation, the shales will be contorted, and the bituminized sand faulted at its joints. The bendings of the bituminized sand are never very small and acute, whereas in shale they are small and acute. This makes a formation often appear unconformable, but it is the nonconformity made by bending and faulting, and not of deposition. The argillaceous material cannot be removed like the calcareous and silicious cementing matter; consequently, sands cemented with argillaceous material seldom contain bitumin- ous accumulations to any great extent. When the calcareous and silicious cementing material is removed by circulating water, the oil, if present, occupies the sand. This leaching generally occurs along the line of faults and on the summits of anticlines, as they more readily offer avenues for the egress of water, but may occur along anticlinal dips and in synclines; in fact, in any place where the intricate subterranean course of percolating water reaches the sandstone. When the circulating water has been copious, the calcareous and silicious cementing material has bepn carried away to the surface of the earth, sometimes forming deposits of sinter, tufa, limestone, or dolomite. When the flow of these waters, charged with carbonate of lime and silica, has been feeble, and the sandstone has again been cemented and made impervious to water, then the flow of water ceases, or finds some other path of escape. Deposits of petroleum oil, resembling pools, occur in the sandstone stratum in which the circumjacent sandstone is cemented with calcareous and silicious material. The portion of the stratum now occupied by the bitumen was formerly occupied by the carbonate of lime or silica, the lime or silica having been removed by the solvent action of percolating and circulating waters. If the gas and oil are ever removed from these porous strata, they will, in all probability, be again cemented by lime or silica, if water again takes possession and its flow is feeble. 52 CALIFORNIA STATE MINING BUREAU. Shale is laminated clay, more or less indurated, splitting into thin sheets along the original laminae of deposition. In California, the majority of shales are quite soft, being easily cut with a knife. A large proportion of the oil obtained in California is taken from the cracks and recesses in shale. The strata are arranged around the axis of the anticline in concentric circles. During distortion, occasioned by the uplifting of the strata, there would be an elongation of these concentric strata. If they consisted of non-elastic shale, they would be cracked and seamed trans- versely to the seams of their bedding. This would occur to a greater extent in the strata farthest from the axis of the anticline. If there was a great weight of superincumbent earth, the cracks and seams would not be so large along the planes of bedding of the shale. Being more acutely bent, the strata on the steep side of an unsymmetrical flexure would be more broken than on the other side. During their uplifting, the strata on the slopes the farthest away from the axis of the anticline would move slower than those nearer the axis; consequently, one stratum would move upon the other, grinding the shale into plastic mud, and luting seams and cracks, which would assist in forming an incasement of water and oil. This grinding movement also keeps cracks and seams from occurring parallel with and along the planes of bedding of the shale. When the shales are bituminized in their cracks and seams, one tenth of the bitumen is in the seams that occur parallel with the planes of bedding, and nine tenths in the cracks and seams that occur transverse to these planes. Where the shales, the cracks and seams of which are filled with bitumen, which resist the action of denudation better than the shales that do not contain it, are side by side, the latter are worn away more largely than the former, and a valley results, owing to denudation acting unequally. Many blutis, and prominent peaks and ridges, owe their existence and stability to the bitumen in the cracks and seams of their shales. When water takes possession of shale, the capillary attraction ofiers so great a resistance that oil, even under enormous pressure, is incapable of forcing an entrance and ejecting the water. When oil is in possession of the shale, the same resistance is ofiered to the entrance of water. Shale saturated THE GENESIS OF PETROLEUM AND ASPHALTUM. 53 with water is a far better covering for petroleum than dry shale. Where the distortion of the strata has been acute, the multiplicity of these cracks and seams makes the storing capacity of these fractured shales very large — in fact, many will be equal in this respect to porous sands. For reasons stated heretofore, the cracks and seams will be wider on the summits of anticlines than on their slopes or in synclines. Owing to the broken condition of the shale, the petroleum has ascended from strata to strata, and not for any great distance through any particular stratum or strata, until the concretion of the bitumen, by exposure to atmospheric actions, assisted by silicious waters, sealed strata from each other. Silica and Lime. — The hot waters created by chemical heat, held in solution large quantities of silica. When the hot silicious water approached the surface of the earth, it was cooled; the cooler the water became, the less capable it was to hold in solution this large amount of silica. Cooling of the water eliminated the silica, which was deposited in the interstices of the shales, increasing their solidity and impervi- ousness. There may also be an interchange between the silica dissolved in the water and certain constituents in the sandstone and shale — for instance, carbonate of lime — the silica, having a greater degree of hardness than the substance removed, would be deposited. This silicification is a very frequent phenomenon in these rocks. If the silicious water circulated through particular strata, the silica eliminated by the cooling of the silicious water, owing to its superior gravity, sank to the bottom of the strata and cemented the same. Strata adjoining the hot, silicious water may be cooler than those in which the silicious water circulates; in that case the cooler strata act as condensers. This action created the strata known as "shells"; the shells often occur on the top and bottom of the sands, and throughout the shales. This silicification, together with the concreting of the bitumen, creates impervious strata, which are capable of holding petro- leum oil and natural gas. These silicifications, when formed in ' strata in which bitumen occurs, are colored black. Their color is destroyed by burning, proving that it is owing to organic material. Silica, in a very fine condition, is frequently attracted to 54 CALIFORNIA STATE MINING BUREAU. some organic or inorganic nucleus which has grown in suc- cessive layers or bands, often of different colors. In a similar manner the small silicious particles, separated from hot, silicious solutions, are attracted by the incasements of porous, or partly porous, and seamed strata. Lime is controlled usually by the same conditions and laws as silica. Large masses of shale and sandstones have been calcified and salicified near the bituminous deposits in California. Deposits of bitumen and petroleum oil are controlled by the line of permanent water. Below the level of the ocean, all cracks, seams, fissures, and interspaces are permanently filled with water. Above the level of the ocean, and below the beds of streams, the supply of water in these spaces is fairly-perma- nent. Above the beds of streams the supply of water is dependent upon the rainfall, and the degree of freedom with which it leaves the formation. Pervious and impervious strata modify the above conditions. Permanent water may be replaced or occupied by a deposit or column of bitumen, petroleum oil, or natural gas. When the underlying water, which supports the oil, is released by the uplifting of a formation above the permanent water by erogenic movements, the water leaves the formation, and the oil drains into the voids formerly occupied by the water, and, possibly, reaches the surface by the same avenues taken by the water, and is lost or resinified to asphaltum. Frequently the porous strata accumulations of bitumen have resulted through the drainage of oil from a higher and large area of porous rock into a lower porous stratum. The bituminized sands on the mesa deposit, on the Sisquoc Rancho (Fig. 13), show the drainage action. They are drained into a centrocline, the sides of the centrocline afterwards having been carried away by denundation; the water which buoyed up the oil escaped, and the oil slowly sought the bottom of the centrocline. The sands forming the uppermost edge of the centrocline have, to a great extent, lost their bitumen ; as soon as the bitumen leaves the sand, it falls into an incoherent mass, and is rapidly washed away by rains. The existing bitumen, in consequence of the long distance traveled, has become viscous, principally through oxidation and evaporation. This drainage is still slowly progressing, as in hot weather THE GENESIS OP PETROLEUM AND ASPHALTUM. 55 balls of nearly pure bitumen form on the surface of the sands in the lower part of the deposit. South of Asphalto, in Kern County, the bitumen has reached the bottom of the syncline by drainage, and is now gradually descending through the syncline, as through a ditch. Although this occurred ages ago, this drainage is still in process. What evidence is there that water circulates and circulat- ed through these formations ? B The presence of calcareous i tufa at the outcrops of the ^ strata; the presence of bitu- ^ men in the cracks and seams 2 of the shales, and in the inter spaces of the sands floated up ^ by associated waters — if the bitumen was forced up exclu- | sively by gas, it would not | have been so evenly and gen- | erally disseminated through- out the shales and sands; springs of water accompanied by natural gas and oil, issuing from the outcrop of strata which dip towards the source of the water, and the absence of these springs from the out- crop of strata which dip away from the source of the water; the seams of hard shale, called "shells," silicated by infiltrat- ing silicious waters; nothing but molds and casts of fossil shells, the carbonate of lime 5ft' CALIFORNIA STATE MINING BUREAU. having been removed in solution in water. Near the outcrops of these strata, in the creek and river beds, the sands and gravels are cemented together with carbonate of lime, forming conglomerates. What is the efi'ect on deposits and accumulations of bitumen by circulating waters, fresh and mineral ? Petroleum oil, when exposed for a long time to water containing sulphuretted hydrogen, is resinified by being sulphurized; especially is this true where the sulphur is liberated by decrease of pressure, or by the oxidation of the hydrogen. The sulphurizing of petroleum oils by sulphuretted hydrogen is a chemical combination, but,, if only a mechanical combination, it is so intimate as to resemble a chemical combination. Petroleum oil will be oxidized when exposed for a long time to water containing oxygen, or atmospheric air. Oxidation converts the oil into petrolene, and greatly increases its gravity. As slight quantities of petroleum oil are dissolved in fresh water, the lighter parts are dissolved; consequently, the effect of circulating fresh water is to carry away the lighter parts of the oil, leaving the heavier parts behind. Water saturated with salts has but little e£fect on petroleum oil. Sometimes the salts, through the agency of water, are mechanically and intimately mixed with the bitumen, so as to render their separation difficult. Besides these chemical effects of water on the bitumen, water exerts the following described hydrostatic and hydraulic effects : In cases where strata are rendered leaky by denudation, and water is ascending to the surface through the same, the petroleum oil is floated out on the surface of the water and lost. Meteoric water, which falls on higher ground, penetrates the earth, sometimes to great depths, through inclined and porous strata, or through fissures, cracks, seams, and joints of rocks; and, after flowing a distance, sometimes the distance being very great, it must ascend through permeable strata to the surface, or, hidden, flnd its subterraneous way to the sea. The course of water flowing underground is not strictly analogous to that of a river on the surface, there being, in one case, a constant descent from a higher to a lower level, from the source of the stream to the sea; whereas, in the other, the water may at one time sink below the level of the ocean, and afterwards rise high above it, by hydrostatic pressure, due to the superior level at THE GENESIS OF PETROLEUM AND ASPHALTUM. which the ram-water was re- ceived, and the incasement of permeable strata by impervious strata. It must be borne in mind that the circulation of water through the rocks can be ex- tremely slow. On account of the broken condition of the rock on the anticlines, caused by the acute curvature of the anticlinal arch, and its greater exposure to denuding agents, far greater quantities of rock have yielded to erosion than in the synclines, where the rocks have been hardened by lateral pressure and cemented by infiltration of minera waters. This broken condition of the rocks of the anticlines permits water to enter them more freely than the synclines or the slopes of the anti- clines, and also permits more readily the escape of petroleum oil and nat- ural gas. The accumulation of petro- leum oil must have commenced when these rocks were but slight- ly undulated. The former and 4/ ancient features and state of a formation should be taken into consideration, as well as those existing at the present time, in the examination of an oil field. If there is no opposing force or intervening obstacle, gas, petro- leum oil, and water distribute themselves in porous or seamed strata in accordance with the difference of their gravity. The gas lies above the petroleum oil, and the oil floats upon the water. It must be remembered that, under ordinary pressure, oil and 57 5/ 68 CALIFORNIA STATE MINING BUREAU. water do not mix, and that the gravity of petroleum oil is less than that of water, but for which little would have been seen on the face of the earth. If petroleum oil is introduced into the bottom of a vessel filled with water, it will rise to the top of the water; and if water is placed on the surface of the oil, it will sink to the bottom of the oil. The pressure of water is exerted below the petroleum oil, and the pressure of natural gas above. Porous strata, incased in nearly impervious strata, must be considered as conduits for the fluids, petroleum oil and water. When petroleum oil and water flow in the same direction, the porous and seamed strata are liable to be barren of oil. Where the oil and water flow in opposite directions, the porous or seamed strata are liable to be fruitful with oil. Many years ago, before the denudation occurred, these strata were incased in an impervious cover; the right-hand dip of the anticline was towards the mountains; meteoric water, falling on the mountains, entered the porous strata at A (Fig. 14, page 57), and finally flowed up the right-hand dip of the anticline, B, as shown by the arrows, being impelled forward by hydro- static pressure in the higher levels of the mountains; and the associated oil which entered these strata, by its inferior gravity when compared with water, flowed in the same direction as the water; therefore, this dip of the anticline is barren of bitumen. In the left-hand dip of the anticline, B, the water flowed downward, impelled by gravity, and, probably, hydro- static pressure, seeking an exit as springs in the valleys, or, unseen, found its way to the sea; the oil, by its inferior gravity, was buoyed up by the water, or ascended in a contrary way to the flow of the water; consequently, the pores and seams in this dip are filled with bitumen. These same conditions exist in the Zaca anticline, Las Pozitas anticline, lying west of Santa Barbara, and at Summerland, and many other places. The following is an exception to the accumulation of oil in the dip remote from the source of circulating water: Petro- leum oil is nearly always accompanied by natural gas. If the porous or seamed strata, serving for conduits for water or oil, have vertical curves or summits, and such summits are sufficiently tight to hold the gas, in time the gas will accumulate in such summits and occupy a considerable part of the sectional area, and it will continue to accumulate until THE GENESIS OF PETROLEUM AND ASPHALTUIki?^;^ 69 the velocity of the water or oil is sufficient to carry the gas forward, and down the incline. If the pressure never reaches such a point as to effect the removal of the gas, the flow of the water or oil will be more or less obstructed; and, finally, if the gas is not removed, or does not escape, the flow of the water or oil ceases. In this case, oil will be found in the dip of the anticline which is towards the head, from which the water emanates. Fig. 15 shows alternating beds of different sands, all of which are bituminized. Fig. 15.— Altebnating Beds of Different Sandstones. Strata C C C are formed of coarse quartz sand, containing round pebbles of hard rocks, such as quartz. They do not contain many fossils. Strata B B B are formed of fine, muddy sand, containing lenticular pebbles of shale. These pebbles have been silicated, forming chert, but their surfaces still retain the appearance of shale, and they have the lamination of shale. This silicification must have occurred before these sands were bituminized. This silicification was, probably, effected by the 60 CALIFORNIA STATE MINING BUREAU. infiltration of hot silicious water. The creation of this water was, probably, through the agency of metamorphism, which preceded the distillation of petroleum from carbonaceous matter by the heat of metamorphism. In the figure, A represents fine shale with few fossil shells; in places it contains fossil fish-bones. The cracks and joints at right angles with the planes of bedding are frequently filled with bitumen. No cracks at right angles with the plane of bedding could have existed in these shales until they were contorted; there- fore, these cracks were bituminized after the folding of the formation had commenced. Neither could bitumen have ascended through these shales before they were cracked or jointed, for when these fine shales contain quarry water, they are impervious to oil. These different strata, B B B and C C C, are conformable, and do not pass into one another by gradation; the lines between them are clearly marked. The muddy, fine sand does not weather as rapidly as the coarse sands; consequently, their faces of exposure are nearer verticality than those of the coarse sand. The different strata must have been derived from two forma- tions, one being composed of altered rocks, and the other of unaltered rocks, and the changes in the derivation of the sediments composing this formation, from the altered to the unaltered rocks, were quickly made, either by a change in ocean currents or by the sudden uplifting of the land. These strata of sand, described above, are situated on the Tinaquaic Rancho, in Santa Barbara County. The character of the bituminized sands near Santa Cruz is very difierent. They contain few round pebbles of hard rock, and no lenticular pebbles of shale. They are clean quartz sands, of varying fineness, and were, probably, formed by the disintegration of granite. They do not contain many fossils, and contain gold in notable quantities. That sudden upliftings did occur, is shown by the terraced structure at the Santa Cruz bituminous deposits, there being three terraces clearly defined. The uprise, or face, of the first and second terraces was partly cut from the bituminous sands, showing that the sands were contorted and bituminized before these terraces were made by the sea. THE GENESIS OF PETROLEUM AND ASPHALTUM. 61 When these bituminized strata rose above the line of per- manent water, the flow of the bitumen was, and is at the present time, down the dip of the strata towards the sea, and the sands in the upper part of the dome, which were vacated by the bitumen, are calcified, the lime probably being derived from overlying calcareous beds which have been removed at this place, but which exist farther towards the east. The following is a description of the only explored submarine oil fields in the world: Fig. 16.— Bituminous Sand Dipping Towards the Sea. In Santa Barbara County, California, the Summerland oil- bearing strata consist of a fine-grained sand, incased in strata of clay or clay slate. When near the oil-bearing strata, the clay, or slate, is of a bluish color, owing to its being slightly impregnated with bitumen. The sands and shales form an elongated dome, the longest axis of the dome being from east to west, running nearly parallel with the coast and parallel with the trend of the Santa Ynez Mountains. Near the eastern end of the dome the formation dips about S. 20° E., at an angle of about 50°, whereas, on the western end, the sand dips 62 CALIFORNIA STATE MINING BUREAU. about S. 10° W., at an angle of about 60°. The general dip of the sand is southerly, at an angle of about 40° or 50°. The first discovery of the hydrocarbons in this field was made on the south slope of the anticline. At this place there was a fumarole, some twenty feet in diameter, from which warm carburetted and sulphuretted hydrogen gas escaped. No vegetation grew on this place, owing to the sulphur fumes. The Spaniards had a legend that a man was killed there, which, according to them, accounted for the fact that nothing grew upon it. A pipe was sunk in the fumarole, and capped, and a two-inch pipe inserted in the cap, when the gas was permitted to flow through the pipe. It did so with con- siderable pressure, and, when lighted, gave a flame ten feet in length. On a line nearly east and west with this fumarole, other wells have been bored, which have yielded gas. The gas has been employed for domestic purposes. South of the gas wells, on a nearly east and west line, are a line of oil wells; they are from 130 to 260 feet deep. The flrst oil obtained in the field was from a well dug 90 feet in depth, which produced three or four barrels daily. The oil is black or dark green, and is of a very heavy gravity, being 1 1° to 16° Baume. Judging from other oil fields, the northern dip of the sands of this anticline will be barren. Meteoric water, falling on the higher ground of the Santa Ynez Mountains, which at places reach an altitude of 3,600 feet, penetrates the earth through inclined and porous strata, or through fissures, cracks, seams, and joints. After flowing through subterranean passages, it must ascend through permeable strata to the surface, or, hidden, find its way to the sea. As the Summer- land anticline forms a barrier between the Santa Ynez Mountains and the sea to the passage of the water, it is forced by hydrostatic pressure to ascend through the north dip of the sand of this anticline. Owing to its inferior gravity, the petroleum oil is floated upwards by the water, and is lost on the surface of the earth, or is carried over to the south dip of this anticline. With the southern dip of this anticline it is different; the flow of the water is downwards, the oil remaining on top of the water by its buoyancy. Owing to the large amount of organic matter in the shales underlying the Summerland oil field, if any iron was present Fig. 17. 64 CALIFORNIA STATE MINING BUREAU. during their deposition, it must have been in the form of ferrous carbonate. The carbonate of iron imparts a bluish or greenish color to the deposit. When the shales, in which carbonate of iron exist, are turned red, it is caused by chemical heat. The presence of red shales below the Summerland oil strata, as revealed by a well drilled to the depth of 1,000 feet, and the high temperature of the natural gas, show that chemical changes are in active operation at present beneath this field. It is probable that sulphur compounds, liberated by chemical heat in the shales, have resinified the petroleum oils of Summerland, which will account for their great gravity. A wharf has been extended into the sea towards the south, and at nearly right angles with the trend of the shore. From this, productive wells are drilled in the bottom of the ocean, yielding a petroleum oil somewhat lighter than the numerous wells upon the shore. Fig. 17 (page 63) is a profile made by J. B. Treadwell, M.E., showing the character and structure of the rocks encountered, and the number of wells which have been drilled. The illustration Fig. 18 shows a formation lying east of Zaca Creek, in the county of Santa Barbara, California. A A A is bituminized sand, forming the south dip of an anticline; under- lying the bituminous sand are bleached shales, B B B, and below the shales are metamorphic rocks, quartzite, and serpentine. At one point the metamorphic rock has closely approached the bituminized sand. At this point the bitumen has been removed from the sand, and the sand is calcified and silicified. From the attending phenomena, it would seem that these sands were bituminized before metamorphism reached them. This sandstone, when not reduced by erosion, is xiearly 300 feet in thickness, and, like a mantle, covers a large part of the territory lying between the Santa Maria and Santa Ynez rivers, the Pacific Ocean and the Alamo Pintado Creek, in Santa Barbara County, some 600 square miles. In the summit of the domes, and in the dip of the anticlines which are farthest away from the mountains which are higher than the summits of these anticlines, the sands are sometimes bituminized. Extending towards the northwest, from the place shown in the illustration, are sands containing millions of tons of bitumen. These bituminized sands are very prominent, forming high THE GENESIS OF PETROLEUM AND ASPHALTUM. 65 bluffs. Throughout the area which this upper sand covers, there are places where these sands are silicified, in others cal- cified. On the south slope of the Santa Maria Valley, and in some other places, these sands are uncement- ed, and have been formed into sand hills through the shifting of the sands by water and the winds. Also, scattered throughout this area, there are a num- ber of sulphur blows, min- eral springs, and places where natural gas escapes in large quantities. On the slopes of Mount Solo- mon, asphaltum is in- jected into the formation surrounding subsidences. Veins of asphaltum also occur on the Jonata Rancho. White leached shales, and shales burned to various tints of red, occur in large masses. The shales and sandstones in this area are fairly con- formable. On the Sisquoc River there is another exposed sand which is bituminized, and which is, geologically, about 1,000 feet lower than this upper sand, and is separated from it by a bed of shale. How thick 5— b16 66 CALIFORNIA STATE MINING BUREAU. this lower sand is cannot be positively determined, but, judging from its exposures, it must be over 300 feet thick. If this sand covers the same area as the upper sand, which it is reasonable to suppose it does, there is no reason why it should not contain, in its domes and the dips of its anticlines, millions of tons of bitumen, which, on account of being excluded from the atmos- phere, should be in the form of petroleum oil, and which could be obtained by the sinking of wells. If it be true that the bitumens are derived from terrestrial and marine vegetation, deposited in sedimentary strata, and then changed to carbonaceous matter, which was afterwards distilled by the heat of metamorphism, then we may expect to find petroleum oil or other bitumens in unaltered rocks lying above the metamorphic rocks, irrespective of the age of the unaltered rocks. A number of facts that have been presented in the preceding pages tend to prove that this is the origin of bituminous accumulations in California. A conclusive determination of the origin of the bitumens is of great importance, for if the origin is as set forth in this monograph, explorations can be continued to such depths as to reach the metamorphic rock, and these explorations may be successful, especially so if the bitumens are found near the surface; but if the bitumens are indigenous to the rocks in which they are found, the depth to which they may extend is uncertain. PHENOMENA ATTENDING THE ACCUMULATIONS OF BITUMEN. The phenomena described in the succeeding pages are con- nected with the accumulations of bitumen as observed in Cali- fornia. All of these phenomena are generally found in one formation, and so frequently together and in conjunction with bituminous deposits that it must be considered that one is the result of or is closely connected with the other, especially when it is known that one can produce or is the direct effect of the other. These phenomena would not be important in prospecting for a primary or stationary mineral deposit, but will be of great assistance in the discovery of a derived and migratory fluid such as petroleum oil. THE GENESIS OF PETROLEUM AND ASPHALTUM. 67 When their influence, relation, and position in regard to bitumens or* bituminous deposits are determined and more generally understood, they will materially assist in the dis- covery and development of such deposits. Red shales, earth subsidences, mineral and hot springs, leached shales and sandstones, silicified shales and sandstones, and accumulations of bitumen accompany one another and are traceable to metamorphic action. Normal Shale. — This is an impure hydrous silicate of alumina. It contains about twenty per cent of alumina, about seventy per cent of silica, and, in variable and small amount, protoxide and carbonate of iron, lime, soda, magnesia, potash, and other minerals, and organic substances. It contains fossils in greater or less number. Color of the shale is usually dirty white to brown, but sometimes of other colors. It gives out an earthy odor when breathed upon, and is readily scratched wdth the finger nail. When wet with water it can be kneaded into a plastic mass. It is clay consolidated by pressure, and is capable of being split into thin layers along the original laminae of deposition. When exposed to atmospheric influences it rapidly disintegrates. Normal Sandstones. — When first deposited by water, these consist of incoherent grains of silica of different fineness. The grains are more or less rounded by attrition, the result of their transportation by water. They may contain fragments of other rocks, and they may contain in small quantities lime, magnesia, potash, soda, a number of other minerals, and organic sub- stances. After deposition, the cohesion of the grains may be effected by pressure alone. They may contain fossils in greater or less number. Sandstones are of many colors. Both shale and sandstone at the time of their deposition may be cemented by ferric, calcareous, silicious, or other material ; but this cementation usually occurs subsequent to their deposi- tion, when fresh or mineral waters commence to circulate through them. Alterations in the shale and sandstone, effected by fresh and mineral waters, heat, and in other ways, will be described hereafter. The accompanying sketch and sections (Figs. 19 and 20) show a portion of the San Rafael Mountains, situated in the northern end of Santa Barbara County, State of California. 68 CALIFORNIA STATE MINING BUREAU. The territory shown on the map includes an anticline with a northwest and southeast strike and having a metamorphic core. The unaltered rocks of the anticline consist of alternat- ing beds of sandstones and shales, and the metamorphic rocks principally of cherts, jaspers, and serpentines. The metamorphic rocks shown in the diagram and sections once formed a portion of the unaltered shales and sandstones r L£G£r/\fO ^^ SH»L£ PORTION OF THE SAN RA FAEL^, MOUNTA 1 NS SANTA BARBARA CO. FfG. 19. now forming these mountains. The unaltered strata have afforded casts of marine shells, considered by Dr. Merriam as pliocene. The broken, bent, distorted, and warped condition of these metamorphic rocks has been attributed to the movement of the mass after metamorphism has taken place. The broken condition and intricate jumble of these altered shales and sandstones could not have occurred subsequent to THE GENESIS OF PETROLEUM AND ASPHALTUM. 69 their metamorphism. The chief cause of the disturbance of these rocks occurred before they were metamorphosed, owing to the contraction of the sandstone and shale. When burned to a jasper, the overlying rocks of Nature's kiln were continu- ally falling and subsiding. The face of a bluff of shale or sandstone in which subsidence Fig. 20.— Cross-Section San Rafael Mountains, Santa Barbara County, California. is taking place is much different in appearance from the face of a bluff composed of these rocks which are being thrust upwards, or which are subjected to lateral pressure. In subsidences of shale and sandstone numerous cavities are formed which are arched above, the rock having fallen from beneath the arch. When these arches break, the cavities are filled with loose material. These arched cavities do not occur in formations which are 70 CALIFORNIA STATE MINING BUREAU. being uplifted. In subsidences, cracks in the rocks which approach horizontality are widened and the rocks fault on these cracks. These cracks are not widened in an upward thrust. Subsidences are not faults; they usually form a centrocline, and the depression is always greater at the center than at the periphery; many of the depressions are bowl-shaped, and are called "ollas" by the Spaniards. Many of these depressions now form the beds of lakes. In the same area these subsi- dences are repeated many times. The entire area does not subside at the same time, and it is, therefore, greatly broken and crushed; nor does the movement take place at one time, but may continue for years. By the time these shales and sandstones come in contact with metamorphic heat they are badly broken and contorted, owing to the action of subsidence, and they are further warped and twisted by the heat of metamorphism. At a depth of 500 to 1,000 feet the subsidence due to coal workings amounts to about fifty per cent of the thickness exca- vated; sometimes these subsidences continue during as much as four years. The contraction in a formation composed of equal volumes of shales and sandstones when burned to a por- celanite, is about one tenth of its original volume. A forma- tion burned to a depth of 1,000 feet would give a subsidence on the surface of 100 feet in depth, or, taking the amount of subsi- dence as is shown in coal workings, would give a subsidence of 50 feet in depth. The red shales and porcelanites previously described nearly always accompany these subsidences. If the interspaces exist- ing in these red shales were filled with soluble silica, they would become jaspers of many colors. The presence of comminuted red shale in the oils at Summer- land, Santa Barbara County, California, and the striking of red shales at the same place at a depth of 1,000 feet, show that these shales exist at great depths. Scattered throughout Santa Barbara* County are over one thousand acres which have undergone subsidence, and some of which are still subsiding. The amount of depression is from 20 to 60 feet, with an average of 40 feet, and there may be many more acres which have undergone subsidence that have escaped observation, or which are or were not visible on the THE GENESIS OF PETROLEUM AND ASPHALTUM. 71 surface, or, if visible, all signs of the subsidence have been obliterated. Near the north line of the Sisquoc Rancho, on La Brea Creek, Santa Barbara County, the blufl' on the west side of the creek is over 300 feet high, and over a mile long, and covers an area exceeding three hundred acres. The entire bluff is badly broken and contorted, and shows evidences of subsidence, even now going on. Fig. 21.— Subsidence, La Brea Creek. Chemical heat reddens and bakes and vitrifies the shales at the bottom of the bluff. The surrounding shales are blackened with carbonaceous matter. Fig. 21 shows the southern end of the bluff. Surrounding this subsidence are hundreds of acres of shales which have been silicified. In the vicinity of nearly all these subsidences, burned and leached shales and sandstones are found. The breaking and contortion of the metamorphic rocks have 72 CALIFORNIA STATE MINING BUREAU. been attributed to the dynamic force exerted in the uplifting and plication of the mountains. While this force is responsi- ble for this broken and contorted state in part, the greater part must have been effected by subsidence and the warping of the rocks by the heat of metamorphism. The curvature in the altered rocks is too acute and in the wrong direction, and the fragments of the rocks bent too small, to have been made by the uplifting of the rocks. Attending the uplifting and the metamorphism of mountains there must have been subsidences of the superincumbent unal- tered rocks to fill the space caused by the contraction of the rocks through the action of heat. The breaking and division of the unaltered rocks lying above and adjoining the places where metamorphic action is in progress facilitate metamorphic changes. It is like the placing of broken coals upon a fire: the interspaces between the pieces permitting the circulation of gases, minerals, and heat. Water. — Through its inferior gravity, petroleum oil ascends through water from the depths of the earth, and either forms bituminous springs upon the surface of the earth, or, by its buoyancy, floats upon the water and is stored in the upper parts of porous or seamed strata. The movement of subter- ranean water is indicative of the movement of oil. Besides these offices, the influence which thermal waters holding silica and other minerals in solution have exerted in many rocks is a question closely connected with the accumulations of the bitumens. All deposits precipitated from water — lime, silica, etc. — may become the cementing substance of shale or sand- stone; and, again, all substances cementing or composing rocks which are soluble in water are liable to be leached from the rocks by percolating water. There may be mineral springs without the presence of bitumen, but there are no springs of bitumen that are not accompanied by mineral waters. Southwest of the metamorphic rock shown in Fig. 19 are sandstone strata, and farther to the west is shale. The sand- stone, where it adjoins the serpentine, is snow white. Hot alkaline and acid waters entered these shales and sandstones and dissolved the bases contained in them, also dissolving a quantity of silica. These waters cooled as they neared the surface. The silica would have been deposited had these THE GENESIS OF PETROLEUM AND ASPHALTUM. 73 waters not encountered a flow of meteoric water, which greatly- diluted the hot solution. This increased volume of water made it possible for the silica and bases to be held in solution and be carried away to the sea. The shales become darker as they go from the altered rocks, until they finally assume the color of normal shale. In places these leached shales have a width exceeding one mile. The arrows in the sectional views indicate the direction in Fig. 22.— Contact of Leached Sandstones and Serpentine. which the water flowed and the general direction in which it now flows. The geographical configuration of the country shows that the waters flowed in this direction, as higher moun- tains lie to the north of the formation shown in the sectional views. The finding of bitumen in the southern dip and the absence of the same from the northern dip of the anticline shown in section C D is additional proof that waters flowed in the direction shown by the arrows. (See Fig. 20.) Near the serpentine all fossil shells are removed from the shales and sandstones by the solvent action of mineral waters, 74 CALIFORNIA STATE MINING BUREAU. and the casts and molds are obliterated through the incoher- ency of said sandstones and shales, and also by the removal of the coloring from the darker material that usually replaces the part formerly occupied by the shell. At a distance of a thou- sand feet or more from the serpentine, the same stratum that adjoins the metamorphic rocks contains casts and molds of fossil shells, while still farther away fossil shells exist. The whitened shales have a porous structure, and are very light compared with normal shales. They can be easily ground between the fingers, owing to the removal of soluble material which once occupied the pores. Shales and sandstones leached of all bases, such as lime, magnesia, metals, etc., are but slightly coherent and are easily eroded. Jaspers. — The metamorphic rocks shown in the sketch con- sist principally of jaspers, or shales, and sandstones partly converted to jaspers. They have a hardness of 7 and a specific gravity of 2.55, and break with a conchoidal fracture. Their prevalent colors are yellow and brownish red of various shades, sometimes nearly black in the seams, and sometimes a greenish white. The darker jaspers often have a resinous luster, but are generally dull. The transition from shale to jasper is plainly visible; all gradations from unaltered shale to jasper will occur within a distance of a few feet. A portion of the jaspers retains the form of shales, with the exception that they are contracted and distorted by heat. Sometimes they are burned so as to form a solid mass. After burning, they have been silicified with amor- phous silica, filling minute cracks and spaces in the jaspers. The brownish-red jaspers show unmistakable signs of having been burned. They are warped, contracted, broken, and vesicu- lar, showing all the structural conditions that shale does when artificially burned in large masses. The whitish-green jaspers do not show all these signs of burning, even when in immediate contact with the brownish- red jaspers; but the shales, between which and the brownish- red jaspers these whitish-green jaspers lie, are contorted by heat, and next to the whitish-green jaspers are discolored by oxide of iron. The vesicular condition only occurs when the brownish-red shales are apparently greatly burned. THE GENESIS OF PETROLEUM AND ASPHALTUM. 75 In places these brownish-red jaspers closely resemble the jaspers that are the most burned and which are produced by chemical heat near the surface of the earth, and probably are produced by the same metamorphic actions, but on a greater scale. Pockets containing burned shales not exceeding eight inches in diameter are found in unaltered shales near the surface, which closely resemble some of the jaspers that are in the large mass of metamorphic rocks shown in the sketch (Fig. 19). It might be expected that, through metamorphic agencies, jaspers might be formed in a large space, but it is remarkable that they can be formed in a space six inches in diameter. Fig. 23.— Open Seams at Right Angles to Planes of Bcdding. Overlying the serpentine and jaspers at J (see Fig. 20) are chemically burned shales; these burned and red shales are previously described. In Santa Barbara County these red shales cover a large area. Frequently, in the jaspers, seams and cracks approaching horizontality are closed, while those approaching verticality are open to the extent of the contraction of the rocks during burning. (See Figs. 23 and 24.) The closing of the hori- zontal cracks and seams may be due to the weight of the metamorphosed rocks, but it must have been augmented by other superincumbent strata. The opening of the vertical seams and cracks must have occurred at the time they were 76 CALIFORNIA STATE MINING BUREAU. metamorphosed, showing that there was no great lateral pressure on the rocks during or since their change. The open cracks and seams are either with, or at right angles with, the plane of bedding of the rocks. When the plane of bedding is nearly horizontal, the open cracks are nearly verti- cal; when the plane, of bedding is nearly vertical, the open cracks are along the plane of bedding. There are three important changes during the production of jasper, or chert, from shale, viz: leaching, baking or burning, and silicification, and these changes occur in the order given above. Fig. 24.— Open Seams with Planes of Bedding. The leaching of lime, magnesia, and other bases by perco- lating hot waters leaves a light and porous rock, consisting principally of insoluble silica and alumina. The porous condition of the rock permits the circulation of heat and hot gases; this circulation of heat and gases is also aided by the breaking of the formation through subsidence. When burnt by chemical fires these shales are of many shades of pink, red, reddish brown, white and yellowish white, and are sometimes black, this color being caused by the presence of carbonaceous matter. Some of these shales are fused and are of a brownish red to black; by fusion they THE GENESIS OF PETROLEUM AND ASPHALTUM. 77 became impervious to fluids, while the remainder of the shales remain more or less porous. Besides the cracks caused by earth movements there are numerous small cracks caused by the burning and breaking. One layer of jasper is a bad misfit with the adjoining layer. Sometimes a piece of a layer of jasper a few inches in length will be warped in one direction, whereas an adjoining piece of a layer will be warped in a contrary direction; some are acutely bent, but the layers of jasper seldom fit perfectly with one another. Nothing but baking and burning could create this almost universal misfit in the layers. After the jaspers are hardened they cannot be contorted and bent. They would break before bending, and if they were contorted and twisted when in a plastic condition they would probably exhibit slickensides and would have but few wide seams and seams of irregular width and would not be vesicular. No slickensides are to be seen between the layers, the surface of these layers being nearly always rough. The greatly con- torted, bent, and roughly seamed condition of the jaspers must have been occasioned by heat which baked, burned, fused, con- torted, cracked, warped, and hardened them and made them vesicular. Subsequent to their burning the small vesicles and cracks in them were filled with chalcedonic silica. On account of their burning and silicification they greatly resist weathering. Subsequent to their leaching, burning, and baking, in some of these burned shales the vesicles produced by fusion, and the small cracks and pores and numerous minute round and oval areas, have been filled with soluble silica deposited from circu- lating silicious waters, forming jaspers and cherts. These spaces are usually filled with silica, which has a difierent color from the ground mass of the rock, the colors usually being white and of various shades of red or brownish red. Sometimes these interspaces have been filled with bands of different colored soluble silica, the bands running parallel "ivith the walls of the spaces. The interstices in the strata of sandstone shown in section E F (Fig. 20) have been filled with soluble silica, making a hard, compact rock; whereas, the same strata a short distance to the east and west consist of sand cemented with bitumen. 78 CALIFORNIA STATE MINING BUREAU. Serpentine Rocks. — On the periphery of the jaspers, and between the jaspers and unaltered rocks, are serpentine rocks; also resting upon the jaspers are isolated bodies of serpentine rocks. All gradations from shale to serpentine rocks can be seen. Shales having a slight bluish-green tint can be obtained; also pieces of the shale partly converted into serpentine rock, one part being serpentinous and the other shale. The serpentine rock lying on the surface of the jaspers would have a tendency to prove that the said serpentine is not eruptive, but metamorphic. Serpentine is seen in every stage of passage from argillaceous sandstone, shale, and jasper to perfect serpentine itself. Fig. 25. The spaces between the irregular but somewhat cubical frag- ments of jasper, which are arranged in rows after being con- verted to jasper from shales, are filled with serpentine rock, and these fragments are frequently partly rounded by the alteration of the jaspers to serpentine rock. The lined portion of the cut (Fig. 25) indicates unaltered jasper, and the remainder is serpentine rock. The rounding of the cubiform fragments of jasper represents an incipient decomposition of the same. The serpentine rock being next to the unaltered rocks, which at one time were saturated with mineral water, the said unaltered rocks would permit the circulation of water bearing these minerals. The decomposition of jasper and shale to serpentine rocks seems to be more the action of hydrothermal than dry heat. In places the spaces between the fragments of shales and ser- pentine rocks are filled with quartz carrying a notable amount of copper pyrites and a small amount of gold and silver. By an examination of the sectional views and sketch it will be seen that the northern side of the metamorphic rocks cuts the THE GENESIS OF PETROLEUM AND ASPHALTUM. 79 strike of the unaltered rocks diagonally, and that on the south side they run parallel with the strata of the unaltered rocks, sandstone being in contact with the serpentinic rocks. A sectional view shows that the unaltered rocks on the south are part of the same strata as the unaltered rocks lying on the north of the metamorphic rocks. The unconformity of the metamorphic rocks with the sandstones and shales on the north, and their conformity with the sandstones and shales on the south, taken with other phenomena described in this arti- cle, clearly demonstrate the fact that these unaltered rocks were not deposited on the altered rocks after they were meta- morphosed. The unaltered shale underlying a sandstone is of great thickness, whereas at a point half a mile east of this sectional view the metamorphic rock is nearly in contact with the same sand stratum. Northeast of the metamorphic rocks are alternating beds of shale and sandstone. The shales are highly silicated. Silica dissolved in hot waters slowly ascended through the unaltered rocks lying north of the metamorphic rocks. The metamorphic rocks acted as a dam for its retention, and as these hot waters cooled they were incapable of holding the same amount of silica in solution as when hot; therefore, silica was deposited in the interspaces of the porous rocks. When silicious waters flow upward through a formation the rocks are silicated, and when the water flowed or flows downward through a formation the rocks are leached. There are several reasons why this occurs. When waters flow upward their flow is generally very slow; when coming from the depths of the earth the waters are generally hot, grad- ually cooling as they approach the surface, and as they cool silica is deposited. Silica is soluble in cold water. Under pressure and heat the solvent power of water is greatly increased. Upon the relief of the pressure or the cooling of the hot silicated water, silica is deposited. A solution of silicate of soda, when undis- turbed for a year or more, will deposit silica; if frequently disturbed, no such deposition takes place. The deposition of silica from such a solution is quickened by the presence of carbonic acid. Petrified wood is often found in rocks that are not silicated. This is owing to the fact that the capillary tubes in the wood are much smaller than the interspaces in 80 CALIFORNIA STATE MINING BUREAU. the circumjacent rock. Water filters through the wood and these rocks more . or less quickly in proportion to their permeability; consequently, circulation of fluids is slower in the wood than in the adjoining rocks. Rapid percolation of silicious waters through a rock prevents the deposition of silica. Shales and other substances contain- ing small pores are very frequently silicated, whereas the adjoining sandstones or coarse substances are still porous. The greater porosity of the sandstones and other coarse-grained substances permit a too rapid flow of the silicious water, and silica is not deposited; whereas, since the percolation of silicious water in the fine shale or other fine-grained sub- stances is extremely slow, silica is deposited. When these cherty shales are black it shows that bitumen was ascending with the silicious waters at the time they were silicated. After being silicated they do not split along the plane of original deposition. Their hardness is 7. Their black color is destroyed by fire, showing that their color is due either to a bituminous or a carbonaceous substance. It is in all probability the former, as carbonaceous matter does not, whereas bituminous matter does, accompany the flow of silicious waters. In many places these blackened and silicated shales adjoin cracks and seams, through which mineral water accompanying bitumen is ascending. Zaca Peak owes its prominence to the protection of a crown of cherty shale; in fact, the preservation of this mountain range is owing to its silicification, which must have occurred before it rose above permanent water; whereas, several thousand feet of sediments lying to the southwest of the same have been denuded in consequence of being leached and broken. Silicated shales and sandstones are not easily eroded, and suffer but slight decomposition through the action of the weather. The sandstone is not indurated to the same extent as the shale. The face of the shales is flatter than the face of the sandstones; the sandstones are nearly vertical. Frequently these cherty shales contain many small faults and cracks, the character of which shows that they were made while the shale was in a semi plastic condition. They have been silicated subsequent to their faulting and cracking, clearly showing that shales were silicated after the formation had been greatly disturbed. The alteration of these white shales has been partly GENESIS OF PETROLEUM AND ASPHALTUM. 81 caused by baking, through the heat of adjacent metamorphic rocks. Joints and seams in the shales and spaces in the sand- stones are colored red with the oxide of iron. In part of the bituminized sands lenticular pieces of shale are found converted into chert, and fossil shells have been removed. These silicated lenticular pieces of shale were sili- cated after being water-worn, as their exteriors have all the appearances of shale. If they had been changed to chert before being water-worn, they would have had a polished sur- face. They show the laminae of deposition, but do not split along them. The insoluble silica in the pieces of shale consists of fine quartz sand which composed the original shale, whereas the soluble silica was deposited in the pores of the shale from infil- trating water. These fragments of shale were silicified before the interspaces of the sand were filled with bitumen, as the circulation of water ceased after the appearance of the bitumen. For the same reason fossil shells must also have been leached from the sands before they were filled with bitumen. Therefore, these sands were bituminized after their deposition, and must have been bituminized before they were tilted to the high angles which they now occupy, and before the metamorphic rocks came in contact with them. The bituminized sand near Zaca Creek contains at least ten million barrels of maltha. Eight barrels of ordinary petro- leum are required to make one barrel of maltha. As the inter- spaces of the bituminous sand are filled with maltha, a space ten times as large as the present bituminous deposit was required to accommodate eighty million barrels of petroleum before it was changed to maltha. The apex of the anticline lying above the metamorphic rock, when the curvature of the rocks was slight, must have been the storage room for this vast amount of petroleum. When the strata of this anti- cline containing the petroleum slowly rose above permanent water, and owing to the fact that the anticline rose to a higher altitude in the east than in the west, the oil flowed down the porous strata towards the west, and during the flow was evapo- rated, forming maltha, which finally reached its present resting place. During this migration of the oil, besides the amount dissipated by evaporation, a vast amount must have been 6— Bl6 82 CALIFORNIA STATE MINING BUREAU. carried away b}^ percolating waters or drained from the porous strata and was lost. In 1864 a multitude of fish were asphyxiated in the Pacific Ocean and came ashore between Monterey and Ven- tura in large quantities. Many were dead and others were barely alive. This was probably occasioned by the ocean waters being charged with sulphuretted hydrogen or carbonic acid. These mephitic gases emanated from metamorphic action beneath the ocean, ocean currents and migratory habits of the fish submerging them in the deadly waters. In 1899 the fish were killed in Zaca Lake by sulphuretted hydrogen, the presence of sulphuretted hydrogen being evidenced by the whitish state of the water, caused by the liberated sulphur. The Indians had a number of superstitions regarding this lake, which were probably occasioned by former phenomena which appeared supernatural to them. Conclusions. — Black or dark-colored cherty shales and sand- stones show that bitumen accompanied the silicious waters while these rocks were being silicated. Light-colored cherty shales and sandstones show the absence of bitumen during their silicification. These cherty shales and sandstones indicate either that silicious waters have cooled while ascending towards the surface, or that the circulation of the silicious water, gen- erally upwards through them, has been very slow. Both these flows of water would have a tendency to remove petroleum from a formation if any had existed therein. If bitumen deposits exist in a formation the leached shales and sandstones usually overlie them, although white leached shales and sand- stones may exist where there is no bitumen. PROSPECTING FOR PETROLEUM. Surface indications of the presence of petroleum consist of unaltered rocks, white-leached shales and sandstones, shales burnt to redness, fumaroles, mineral springs and the residue from mineral springs, such as selenite, etc., subsidences, natural gas, springs of petroleum oil and maltha, porous rocks saturated with bitumen, cracks in shale and other rocks filled or partly filled with bitumen, black silicified shales. It would seem like supererogation to say that petroleum oil is not found in any notable quantity in metamorphic rocks, and GENESIS OP PETROLEUM AND ASPHALTUM. 83 if found at all that it is a secondary deposit. One may as well expect to find accumulations of petroleum in a limekiln as in metamorphic rocks, yet notwithstanding this fact, which one would think would be patent to every person, wells for oil have been drilled in granite. The prospector should confine his attention to unaltered rocks. The color of the bitumens, when they exist near the surface of the earth, is black, bluish black, and brown and dirty brown. The bitumen can be determined from coal, vegetable deposits, iron, manganese, and other minerals that closely resemble them, by the following tests: By its bituminous odor and taste; by melting in the flame of a match or candle with a bituminous odor (iron and manganese do not fuse, and coal and vegetable matter burn without fusion) ; by dissolving in bisulphide of carbon, chloroform, and turpentine. It would be well, in prospecting for oil, to carry a small bottle of one of these solvents and another small bottle in which the substance to be determined is placed in a com- minuted form and agitated. If a brown or black solution is formed, the substance under examination is bitumen. Iron, manganese, coal, and vegetable matter do not dissolve in these solvents. All streams, pools, and other bodies of water should be care- fully inspected. If oil is present it will float on the surface, showing prismatic colors. Compounds of iron floating on the surface of water frequently show these iridescent colors. Whether this scum is oil or an iron compound can be deter- mined by stirring the surface of the water with a circular motion. If iron, the scum will break into irregular fragments, and if oil it will form bands of color. In other words, the iron compound seems to act and break like a solid, whereas the oily scum acts like a liquid. Frequently gases are seen to ascend from the bottom of streams and pools of water. In the bed of La Brea Creek, upon the Sisquoc Rancho, Santa Barbara County, gases rise from the bottom of the creek for a distance exceeding one mile, which can be lit upon the surface of the water and burn with a luminous flame. This occurs in many other places in California. Carburetted hydrogen, or natural gas, is a far greater indi- cation of the presence of the bitumens than is sulphuretted 84 CALIFORNIA STATE MINING BUREAU. hydrogen or carbonic acid gas; consequently, it is frequently important to determine between these gases. Carburetted hydrogen burns with a yellow, luminous flame, whereas sulphuretted hydrogen burns with a bluish flame. A familiar example of the color of these flames is shown in the burning of an ordinary match. Light the match, and while the sulphured end is burning a bluish flame is shown. When the sulphur is consumed and the wood alone burns, a luminous flame is shown. Sulphuretted hydrogen has a strong odor of sulphur, and when a brightened piece of silver is held in it the silver becomes blackened. Carbonic acid gas does not burn. The test papers described below should be obtained and kept dry and well protected both from air and light, which can be done by keeping them in a small, wide-mouthed bot- tle of dark glass. First — Acetate of lead paper, which, when exposed to gas con- taining sulphuretted hydrogen, becomes darkened and eventually brown; if, after an exposure of ten minutes, the paper does not become discolored, the gas may be consid- ered free from sulphuretted hydro- gen. Second — Blue litmus paper, when used, should be moistened with pure water; when exposed to carbonic acid gas, or water highly charged with carbonic acid gas, it turns red. The tests with the papers can be made as follows, this explana- tion referring to Fig. 26: Procure an ordinary beer bottle of clear glass; run a red-hot poker several times around and near the bottom of the bottle; dip the bottle into cold water, and the bottle will break at the line where the hot poker has been applied. Stop the bottle with a cork, through which the small hole A has been made. The test paper B is suspended in the bottle by a wire fastened in the cork. Leave the hole A open and hold the lower and open Pig. 26. GENESIS OF PETROLEUM AND ASPHALTUM. 85 end of the bottle partly submerged in the water and over the bubbles of gas which are ascending through the water. If sul- phuretted hydrogen or carbonic acid is present they will act in the manner described above on the respective test papers which are used to detect their presence. These papers will show the absence of sulphuretted hydrogen and carbonic acid gas, but where they are mixed with carburetted hydrogen the other tests will have to be employed, such as the color of the flame when burning to determine whether carburetted hydrogen is present. To make the test by the color of the flame: Open the hole A and submerge the entire bottle in the water; after the bottle is filled with water, close the hole A and lift the bottle nearly out of the water; the bottle will remain full of water, on account of atmospheric pressure; hold the open end of the bottle over the ascending gas. When the water in the bottle is replaced by gas, sink the bottle nearly to its head in the water; the water will then press upon the gas. Open the hole A and light the issuing gas. If sulphuretted hydrogen is present a green flame is seen; if carburetted hydrogen, a yellow lumin- ous flame; if carbonic acid gas, the gas will not ignite; if these gases are mixed, the flame will be more or less yellow and luminous in proportion to the amount of carburetted hydrogen present. If carburetted hydrogen is found it is nearly a certain sign that somewhere in the formation liquid bitumens exist, although they may be distant from the place where the gas issues. All outcrops of the stratified rocks should be examined. There are generally better exposures of these rocks on the sides of streams, canons, and gulches than elsewhere. The surface of the ground should also be examined. If any brown or black material is seen in the seams of the rocks or saturated porous strata, the test for bitumens with solvents as described herein should be made. If natural gas or bitumen is found upon the surface of shale there is a strong probability that the bitumen has ascended vertically through these rocks from porous strata below, as the avenues for the migration of the bitumen are usually seams and cracks in the shale, the shale itself being impervious to the flow of the bitumens, especially the liquid ones. But when 86 CALIFORNIA STATE MINING BUREAU. porous sand is reached, or when the outcrop is porous sand, it can be presumed that the bitumens reached the surface through the sand. Especially is this liable to be true if the sandstones stand at a high angle with the horizon. Subsidences are indicative of the presence of petroleum, but if any oil is found in them it will be viscous and heavy, the fractured condition of the earth in the subsidence permitting the escape of the volatile parts of the oil. This is also true of burned shales, and if any petroleum exists in these shales it would be a secondary deposit, having entered the shales after they were burned. Petroleum vapor in all probability assisted in the burning of these shales. As mineral waters always accompany the bitumens, mineral springs and the evi- dences of former mineral springs are to a limited extent evidence of the accumulations of the bitumens. Selenite, travertine, infusorial earth, and a number of other mineral deposits are evidences of for- mer mineral springs. When bitumens exist in a formation they are more often than otherwise overlaid with white leached shales and sandstones; therefore, these rocks are an indication of the bitumens to a certain extent, and, owing to their conspicuous color, can be seen from a long distance. In Fig. 27 there is represented a horizontal plane showing outcrop of a sand-bearing petroleum. The strike of an anti- cline should not be confused with the strike of the strata or outcrop. The strike of an anticline is its axis plane, shown by C D on this diagram. The strike of the strata or outcrop is shown by the lines G B and G A. The outcrop may be followed in the directions shown by the arrows A and B, and in some instances for a long distance, with a liability of discovering oil in the depths of the dip of the oil strata, even when bitumens are not seen upon the surface. Fig. 27. GENESIS OF PETROLEUM AND ASPHALTUM. 87 So can the apex of the anticline D C be followed in the direction of the arrow C, and in some instances for many miles, with a reasonable expectancy of getting oil by drilling wells, even if no bitumens are to be seen upon the surface; but it would be an absurdity to follow the direction of the outcrop G B and G A in the direction of E or F, for the farther one goes in these directions the farther he will be getting away from the petroliferous strata. Therefore, outcrops and anticlines can be followed from out- side property into the property being examined, and the struc- ture be considered sufficiently well demonstrated so as to justify a person in drilling a well for oil, even if bitumens were absent from the surface of the land upon which the well is to be drilled and the exposures of the strata are but slight. The strike of the anticlines and outcrops can be determined by a pocket ; ompass. 5^5^ o--m '■ Fig. 28. Fig. 28 shows a clinometer, to be employed for the determi- nation of the dip of rock strata or the slopes of hillsides. It can be readily made out of stiff cardboard. B is a piece of stiff cardboard upon which is traced the squares and numbers in the manner shown in the figure. A is a piece of cardboard cut in the shape as shown in diagram. These two pieces are hinged together with the rivet C, this hinge permitting one piece of cardboard to move upon the other. Care should be taken to see that the upper edge of the cardboard A passes through the center of the rivet, and also that the center of the rivet C is on the upper and right-hand corner of the squares B. 88 CALIFORNIA STATE MINING BUREAU. A plumbob D is suspended from the rivet C, which helps the observer to keep the vertical lines of the clinometer vertical. When an observation is made the clinometer is held in the manner shown in Fig. 28, and while the cardboard B is held vertical, which is determined by the plumbob C, A is moved upon B until its dip agrees with the strata E E (in Figs. 28 and 29), or other strata under examination. Considering that each square represents ten feet square, the readings of the cli- nometer would be as follows: First, with the upper edge of A on line G; second, with the upper edge of A as represented; third, with the upper edge of A on line F. Vertical. Horizontal. 1 - 20 feet 100 feet 2 - 56 " 100 " 3 100 " 45 " Fig. 29. After the observations are taken in the field the clinometer can be used to draught the sectional views. One use of the clinometer is shown in Fig. 29. With the clinometer the bituminous sand stratum E E is determined at its outcrop A, and found to be equal to 1,000 feet horizontal and 560 feet vertical, and the slope of the land is found to be 1,000 feet horizontal to 150 feet vertical. The vertical depth of the slope being deducted from the vertical depth of the bitu- minous * stratum below B, shows that a well to reach the bituminous stratum at B, 1,000 feet from A, would have to be drilled to a depth of 410 feet. When grown familiar with the operation of this clinometer, it can be u6ed for many purposes and different examinations. 4fi GENESIS OF PETROLEUM AND ASPHALTUM\ *=^