GIFT OF 
 
v ''-"*> 
 
THE AUTHOR 
 
Geological Notes 
 
 on Oil Structures 
 
 Edward Allison Hill 
 
 Consulting Geologist 
 
 cAuthor of 
 "Geological Story of the Mid-Continent Oil Fields" 
 
 Hall-Gutstadt Company, Publishers 
 San Francisco, 1922 
 
CONTENTS 
 
 Page 
 
 CHAPTER I A Glance at Early Oil Fields in Cali- 
 fornia, and Mention of Other Regions 9 
 
 CHAPTER II The Organic Shales of California 14 
 
 CHAPTER III Remarks about Identification of De- 
 posits and Determination of Age, and 
 
 the Use of That Knowledge 21 
 
 CHAPTER IV Relating to Oil Structures and the 
 
 Methods of Determining Them 30 
 
 CHAPTER V Some Types of Oil Structure and Re- 
 marks About Their Character in Some 
 
 Weil-Known Fields 34 
 
 CHAPTER VI Oil Accumulation Areas, How De- 
 termined 45 
 
 CHAPTER VII Summary, Probable New Fields 55 
 
 CHAPTER VIII Notes on Oil Company Promotion and 
 
 Related Subjects 64 
 
 Personal Letter to the Author from 
 
 George H. Hook, Geologist 75 
 
 CHAPTER IX Tarrant County Geological History 
 
 Revealed by Drill 76 
 
 LIST OF ILLUSTRATIONS 
 
 Page 
 
 Cuts Nos. 1 and 2 16' 
 
 The Illustration Explained 17 
 
 Cut No. 3 28 
 
 Explanation 29 
 
 Cut No. 4. 38 
 
 Explanation 39 
 
 Cut No. 5 50 
 
 Explanation 51 
 
 Cut No. 6 56 
 
 Explanation 57 
 
 Cut No. 7 62 
 
 Explanation 63 
 
INTRODUCTORY 
 
 object of this booklet is to review some of the relative 
 1 facts incident to the oil-producing industry of California and 
 other States; to suggest some of the conditions existing in 
 formations; the character and methods of determining the bet- 
 ter known types of oil structures; afnd the possibilities of dis- 
 covering additional areas where oil in commercially profitable 
 quantity may be found. 
 
 As viewed from the standpoint of the technical geologist, it 
 is not altogether easy to put the matter in a form to be quickly 
 and fully visualized by the lay reader. The difficulty is not 
 found to be present in the substance to be embraced, but in 
 accurately knowing what to leave out and still maintain com- 
 plete and understandable text regarding the subjects treated. 
 If it seems that some aspects of certain of the items chosen by 
 the writer for inclusion herein are scantily discussed, or upon 
 the other hand if too much space appears to have been devoted 
 to some other thing, it will be remembered that there are many 
 sources of data of extremely various kinds of an historical, com- 
 mercial, geological and economic character, which are drawn 
 upon. The mass of information which has developed regard- 
 ing petroleum, drilling, producing, marketing and other 
 branches of the industry, and the literature covering the cog- 
 nate subjects is so vast that the difficulty in treating any 
 department of the oil business briefly is in knowing what to 
 omit, not what to retain. 
 
 Since the Geological Departments of various of the States, 
 the United States Geological Survey, and other public and pri- 
 vate interests, publish many able and trustworthy bulletins, 
 reports and other papers fully setting forth the statistics of the 
 fields, as to barrels of production, value in money, analyses of 
 the different grades of petroleum and other detailed and reli- 
 able information of that general type, it appears needless to 
 t repeat that matter here. Referring particularly to California, 
 it is and has been for many years one of the chief oil-producing 
 regions of the United States. The names of its principal fields 
 are almost as well known to the general public as are the loca- 
 tions and names of its leading cities: Kern, Taft, McKittrick, 
 
 7 
 
 500561 
 
Sunset, Coalinga, Westside, Eastside, Oil City, Lost Hills, 
 Whittier, Ventura every one of these and others are names 
 almost as common as the terms employed to designate the 
 articles in our living rooms. To the people of California the 
 names of these fields are familiar not only, they are known to 
 millions of men that have never even been in the State. Their 
 oil output has a cash value which is measured in hundreds of 
 thousands of dollars every week and a potential economic worth 
 doubtless almost wholly beyond estimation. Kern County 
 alone produces over one-tenth of the total petroleum output 
 of the United States, though oil of higher gravity and in great 
 quantities is annually produced in the Coalinga and other 
 districts. 
 
 THE AUTHOR. 
 
 Copyrighted by EDWARD ALLISON HILL 
 February, 1922. All rights reserved 
 
CHAPTER I 
 
 A GLANCE AT EARLY OIL FIELDS IN CALIFOR- 
 NIA AND MENTION OF OTHER REGIONS 
 
 AS LONG ago as 1896 it appeared probable that the 
 State would develop great oil-producing areas. Dur- 
 ing that year drilling in the Coalinga district opened a 
 flowing well. The known productive areas in the southern part 
 of the State which had shown profitable output before that time 
 were a considerable distance from the "Blue Goose" well near 
 Coalinga, and the new discovery fanned the torch of activity 
 into a blaze of excitement, which carried new drilling like a 
 wave of heat throughout every favorable and many unfavor- 
 able portions of California. It was known that many locali- 
 ties appeared geologically similar to the areas in which oil had 
 been found. That inference led to the formation of many 
 exploitation companies, which did a lot of drilling throughout 
 the State. 
 
CALIFORNIA AND OTHER FIELDS 
 
 That early period of activity brought into existence many 
 successful companies; some new fields were discovered and 
 the known fields were widened and extended. Referring to the 
 epoch, a publication of the California State Mining Bureau 
 known as Bulletin No. 32, "Production and Use of Petroleum 
 in California, page 1 1 , says : 
 
 when the excitement had passed away the pro- 
 duction of the State had increased from two and one-half mil- 
 lion to nearly seven and three-quarter million barrels per annum, 
 and an enormous amount of well-invested capital remained in 
 the business, and it had been shown that, under rational man- 
 agement, the production of and the prospecting for petroleum 
 in California formed a legitimate employment for capital." 
 
 Relative to the results that followed drilling, a table of field 
 activities tabulated on page 19 of the Bulletin shows: 
 "RECORD OF FIELD OPERATIONS TO 
 DECEMBER 31, 1903 
 
 "Producing wells, 2998. Abandoned wells, 1271 . Wells 
 drilling, 1 59. Wells of doubtful value, 322." The record 
 includes a total of 4750 actual drill holes put down in the 
 State to that date, of which 2998 were productive, a proportion 
 of successes which represents better than 60%, without taking 
 account of any part of the 322 holes set down as doubtful. 
 
 The record of petroleum output for the year 1919 will give 
 a clear idea of the tremendous growth of the industry during 
 the 15-year period from 1903 to 1919. Bulletin No. 88, 
 California State Mining Bureau. "California Mineral Produc- 
 tion for 1919," page 23: 
 
 " . . . sworn statement from the producers of 8932 
 wells . . . 101,073,517 barrels valued at $142,610,- 
 563 the total is inclusive of some small output of the Los 
 
 10 
 
OIL FIELD STATISTICS 
 
 Angeles City field." (Page 24) "from the Coalinga field 
 16,091,037 barrels ... the average daily production 
 from California wells decreases about two barrels each year. 
 In order to maintain a given total output, new wells must be 
 continually drilled." (P. 26) "The total production of 
 petroleum since the date of discovery in 1875, inclusive of the 
 production for 1919, is recorded as 1,240,198,740 bbls." 
 
 The actual cash value of this enormous production of one of 
 the world's most vital mineral resources has not been far from 
 a billion dollars. Again it may be repeated, the economic 
 worth of that great addition to the State's vested riches is almost 
 beyond possible calculation. 
 
 Bulletin 32, page 1 7, regarding the values of land in the 
 various fields, reports: "Land values run from $3,500 to 
 $5,000 per acre in the better parts of Kern River; from $500 
 to $1,000 at Sunset; in Midway, as high as $1,000; at 
 Coalinga, from $250 to $4,000 or $5,000. At Kern it is 
 customary to allow from one to two acres for each well; at 
 Sunset, about the same; at Coalinga, from one to four acres." 
 
 It will be seen that the identical processes were operative in 
 California which had theretofore been prevalent in all oil fields 
 the country over. Indeed, the results of discovering oil in 
 profitable commercial quantities in any new locality are today 
 parallel in every respect as regards vastly enhanced prices of 
 lands and leases. The striking of oil almost in the twinkling 
 of an eye sends land values to unbelievably high levels. Such 
 vast increase of value brought about in so short a period of time 
 is^ the underlying cause of the compelling allurement which 
 urges the pioneer to never weary of searching for new pools of 
 oil. It is the magnet which attracts capital from every imagin- 
 able source to assist in pioneer drilling. Were it not for the 
 
 11 
 
OIL MAKING FORMATIONS 
 
 tremendous returns which flow to the successful operators in 
 new regions when a profitable well is brought in, it seems likely 
 that what is known as wildcat drilling would not often be under- 
 taken. It is that kind of pioneering work, however, which has 
 kept the United States in the lead of all the countries of the 
 earth in petroleum output. It is the character of venturing 
 which of necessity must be kept up if the petroleum output of 
 the country is to equal the requirements of the increased and 
 increasing demands. 
 
 Not less potent were the Pennsylvania formations of the early 
 Appalachian fields in firmly establishing the oil production of 
 America upon a solid foundation, than are formations of later 
 periods in other regions effective in keeping the industry upon 
 such basis. The Trenton limestone of Ohio, Indiana and 
 Illinois has done and is doing its part in oil output; though it is 
 a formation belonging in the Ordovician era, deposited during 
 the Silurian period, which was many ages before the Pennsyl- 
 vania. The great fields of the mid-western States, Kansas, 
 Oklahoma and Texas, the most profitable regions of oil output 
 of high gravity refining quality ever drilled in any country, 
 deliver their values from the Pennsylvania formations. The 
 remarkable fields of south Texas, known as the Gulf Coastal 
 fields, in which classification Louisiana largely belongs, release 
 their production from formations of the Upper Cretaceous and 
 Tertiary periods; and it is in the Upper Cretaceous that the 
 notable wells of the Mexia, Texas, field are being drilled. 
 The Colorado shales of the last named period are the source 
 of the Wyoming and Montana petroleum in great part. 
 
 But it should be remembered that the mere presence of the 
 organic shales of the thick formations of the periods named is 
 not within itself sufficient to an area to guarantee the finding of 
 
 12 
 
oil in profitable amount by drilling at random. There must 
 exist also what are called Oi7 Structures to render practicable 
 drilling at once feasible and successful. These considerations 
 will be discussed in later sections of this booklet, and it will be 
 seen that they apply to all California areas with equal force to 
 their application in other oil-producing regions, though the shales 
 of the State are among the richest oil-bearing formations known. 
 
 13 
 
CHAPTER II 
 THE ORGANIC SHALES OF CALIFORNIA 
 
 IT appears to have been quite definitely established that the 
 probable sources of the petroleum of California are in the 
 organic shales deposited during Upper Cretaceous and Ter- 
 tiary periods, though some higher gravity oils of amber and very 
 light greenish color are thought by the present writer to come 
 from the Ordovician probably Silurian strata. While it may 
 be set down as being likely that accumulations of the last men- 
 tioned grades of oil will be found in profitable quantity in 
 properly enclosed catchment reservoirs in certain districts in and 
 adjacent to Sacramento Valley, and in the foothills of the Coast 
 Range in that portion of the State, no large commercial output 
 of the peculiar oil described has yet been developed in the re- 
 gions named or elsewhere in California. The chief output of 
 the State has been and is being delivered from Tertiary shales, 
 though millions of dollars of petroleum values have been and 
 are being taken from strata which were saturated by the oil 
 from rich shales of Upper Cretaceous epochs. 
 
 14 
 
CALIFORNIA PHYSIOGRAPHY 
 
 Examination of a topographic map of the State will be of 
 service in giving a good idea of the regions where organic shales 
 in great quantity may be expected. It will be noted that the 
 land area is definitely divided into two major physiographic 
 features: the section which occupies the extensive basin area, 
 and the sections where uplifted strata are now represented by 
 mountain ranges. The former was covered throughout long 
 geological ages by the waters of an inland sea or embayment, 
 and upon its floor there were deposited the great thicknesses of 
 shales and sands now found to be oil bearing. That old sea 
 was somewhat near 300 miles long north and south, and about 
 50 miles wide. Upon the eastward side it was enclosed by 
 the mountain system known as the Sierra Nevadas; upon the 
 western side its boundary was the Coast Range. For parts of 
 successive ages the last named boundary appears to have been 
 a discontinuous land surface made up of the summits of higher 
 peaks, forming a chain of islands. Throughout later epochs 
 more or less extensive earth movements closed up the gaps 
 between the islands by erogenic (mountain-making) and tec- 
 tonic (structural) actions, and by the breaking down and 
 erosion of the existing summits, to the effectual building of a 
 coastal mass of relatively high elevation. 
 
 Though it should not be overlooked that there are other 
 areas in the State where profitable oil output comes from 
 organic shales which are not an integral part of the defined 
 geological province described, such formations are known to 
 have been deposited during identical epochs and under condi- 
 tions largely parallel with conditions obtaining in the province 
 of the great embayment, now known as San Joaquin and 
 Sacramento Valleys. 
 
 15 
 

It will be seen that cut No. 1 is a view of the topography 
 of a very definitely disclosed anticline, while cut No. 2 is a 
 diagram of the topography shown. To obtain a correct idea 
 of the underlying strata it is necessary that surface exposures 
 of such formations be present in the region. These surface 
 pictures of the relative position of the formations are best seen 
 and most likely to be found in the localities where erosion has 
 carried away adjacent and overlying strata, leaving the edges 
 of the deeper formations showing in the side of creek banks, 
 cliffs and other natural excavations and elevations. 
 
 As pictured in cut No. 2, it will be noted that the formation 
 marked "Lower Cretaceous," which underlies the stratum 
 marked "Dakota Sandstone," and overlies the formation 
 marked "Morrison Formation," is determined along the slope 
 of the highest elevation of the landscape, and that the other 
 formations lying with it are depicted in their relative position. 
 That place of the Lower Cretaceous member would be main- 
 tained underground in its precise relation to the other formations, 
 and could be so mapped. 
 
 If there were conditions present which would contradict the 
 conclusion stated with reference to the relative position of the 
 formations underground, such facts would be plainly marked 
 in some manner on the surface and could be taken account of 
 in the investigation. 
 
 17 
 
EARLY PLANT LIFE 
 
 Within the shale formations, which were deposited in a 
 horizontal position, as all other sedimentary formations were 
 deposited, there were embedded vast quantities of marine plant 
 and animal organisms. What we know as the Diatomaceous 
 earths of California offer examples of the character of shales in 
 which much of the petroleum of the State had origin. Shales 
 of the late Upper Cretaceous are also of similar organic char- 
 acter and provide a substantial portion of the oil production 
 which has placed California in the lead of petroleum-producing 
 States. 
 
 In the comparatively shallow, warm waters mentioned, tre- 
 mendous growths of algae, fungi, lycopods, equisetas, filices 
 and other forms of early plant life falling within the kingdom 
 known as Cryptogams, choked the sea and clothed the waters 
 throughout vast epochs. As these plants spread and multiplied 
 and flourished, and as their decaying portions sunk to the bot- 
 tom with the myriads of minute animal organisms which 
 swarmed about and clung to their tendrils, the ooze and slime 
 on the sea-floor gathered inch by inch, foot by foot, into hun- 
 dreds and thousands of feet in thickness ; for their numbers were 
 almost infinite, their aggregate quantity almost beyond imagina- 
 tion, and the factor of time was so long that the mind fails to 
 comprehend and the fancy halts before picturing its immensity. 
 If we omit a tabular summary of the plant and animal life of 
 the Paleozoic, which ended with the beginning of the Mesozoic 
 era, and which tabulation and descriptions make up an extensive 
 literature, and mention only the fact that the latter era passed 
 with the beginning of the Cenozoic, and state that the remains 
 of its plant and animal life provided organic sediments in quan- 
 tities entirely beyond our imagination, we have not even then 
 entered the maze of life which existed in the last named era, 
 
 18 
 
PETROLEUM MAKING PROCESS 
 
 in which is included the Tertiary period. Nor should it be 
 thought that the varied forms of life were less numerous, or 
 that the multitude of individuals of the countless species was 
 not so great, or that the vast stretch of time was more shortened 
 for the later than for the earlier epochs. The stupendous total 
 of organic creatures, animals and plants of land and sea, the 
 embedded remains of vestiges of which are preserved to our 
 examination in the shales of the Upper Cretaceous epoch and 
 the Tertiary period, we may understand were quite abundant 
 in quantity for the provision of the antecedents for the natural 
 making of more petroleum than oil drillers have yet had time 
 to find. 
 
 So, this section ends as it started with the statement that the 
 organic shales appear to have been sufficiently determined as 
 the source of California petroleum. Since scientists have quite 
 fully achieved in laboratory experimentation a copy of natural 
 processes in the genesis of petroleum, it transpires that much is 
 accurately known about what methods were followed by Nature 
 in making the oil we find in the ground. The learned chem- 
 ists of the world engaged in such studies compound a meager 
 quantity of ingredients and generate an ounce or more of petro- 
 leum therefrom within a few hours or a few days, while Nature 
 used the forces and exhaustless ingredients of a world as a 
 laboratory in which to generate billions of barrels of petroleum 
 during multiplied millions of years of working time ; and in each 
 case similar ingredients, like forces and parallel methods are 
 called into use. Hence, it occurs now that the origin of petro- 
 leum is in a manner quite well known, to an appreciable extent 
 what conditions surround its making, and in a more or less 
 definite way the methods and laws involved in the process. It 
 is largely because of that knowledge that we understand rea- 
 
 19 
 
OIL MAKING PROCESS 
 
 sonably well in what formations to expect it, and have acquired 
 information about how to locate such formations, estimate their 
 probable petroleum content and decide whether possible accum- 
 ulation reservoirs have been provided by earth movement for the 
 gathering and impounding of the petroleum in such formations 
 or in contact beds. 
 
 The foregoing considerations have carried us to the point of 
 directing some attention to the interesting methods employed in 
 determining the age of various formations, learning under what 
 conditions the sedimentation took place and what possible 
 economic value such knowledge may embody. 
 
 20 
 
CHAPTER III 
 
 REMARKS ABOUT IDENTIFICATION OF DE- 
 POSITS AND DETERMINATION OF AGE, 
 AND THE USE OF THAT KNOWLEDGE 
 
 THE profound study which has been given to every 
 variety of rock formations throughout the world over 
 a long period of time by men of such learning that we 
 delight to honor them has extended our fund of knowledge to 
 a point of actual certainty with respect to nearly all rocks. It 
 should be said that geologists call all formations "rocks'* ; even 
 the dirt in the streets and the soil in the fields are known to 
 scientists as rocks. It was said that nearly all rocks are known 
 which is intended to mean that it is known somewhat definitely 
 what constitutes their material and when they were deposited 
 in the time scale, as related to other deposits. 
 
 The remains of minute insects, equally with those of the 
 largest serpents and biggest creatures of every kind, such as 
 lived upon the land and in the waters; the stems and leaves of 
 plants, marine and terrestrial alike; the shells and skeletons of 
 every kind of land and water infesting thing of life, would most 
 
 21 
 
IDENTIFYING FORMATIONS 
 
 naturally be embedded in some quantity in the formations which 
 were constantly being put down throughout every past age under 
 bodies of water everywhere. As time passed, some of these 
 formations would be exposed at some place upon the surface; 
 indeed, every one of them would be uncovered somewhere upon 
 the earth, some at one place, others somewhere else, many of 
 them again at another place; until here and there in almost 
 countless localities there would appear every sedimentary deposit 
 ever put down. Embedded in them would be the impressions, 
 moulds, casts, or rock-encrusted or fossilized remains of the 
 varied and various species of plant and animal life which had 
 during any period grown in the earth or the oceans, crawled 
 upon the dry land, flown through the air, or swarmed in the 
 water of the seas. Such fossils have enabled many of the 
 world's most learned men, working and studying in every coun- 
 try upon the earth, to classify and distinguish the species and 
 individuals of one age from like and unlike species, and in- 
 dividuals of another. It has been found that the plants and 
 animals of any given epoch during the vast stretch of time that 
 has silently passed in almost infinite measure down through the 
 dim corridors of the ages, have maintained that character of 
 progression and so fit into the mosaic of evolving forms, as 
 adapts them to methods of intelligible interpretation. 
 
 The beautiful shells and other fossils often seen in rocks are 
 the actual records left along the shores of time as an ineffaceable 
 literature of the plants and animals of past ages. If one gave 
 a lifetime to the study of these records and to comparison of 
 them as to similarities and differences, and extend the search to 
 all lands upon the earth, studying them in canyons, gorges, 
 cliffs, shores and mountainsides, and carry with him specimens 
 of every varying kind he finds, he will be surprised and de- 
 
 22 
 
CLASSIFYING LIFE FORMS 
 
 lighted in the end to see how many of them will be similar in, 
 some main essential, how many will be alike in some other par- 
 ticular, and how many will be wholly unlike in almost every 
 respect. Also, he will be amazed to learn at last into how 
 many classes he shall be compelled to divide them, and how few 
 individual specimens there will actually remain in each class. 
 The investigations mentioned have been pursued for many years 
 throughout all parts of the world by thousands of learned men 
 in a most earnest manner, and the results have been set down 
 in careful descriptions and photographs, so that the vast amount 
 of accurate knowledge gathered is open to the study of every 
 one. A great architect might not have the time or means to 
 visit every country on earth and examine the form of every style 
 of architecture, but with photographs and exact specifications 
 of every character of building before him, he would not mistake 
 one style for another. That is true of the geologist regarding 
 different formations; he must know if the exposed strata upon 
 one side of a hill is a part of the identical strata exposed on 
 another slope. Information of formations must be so full that 
 two elevations taken upon what is thought to be the same for- 
 mation in nearby areas will not in fact be the levels of different 
 deposits put down during epochs separated by a time interval 
 of possibly millions of years. Indeed, the Molluscoid forms 
 or any other forms of the animal kingdom of the Cambrian 
 period must not be confounded with the descendants of such 
 marine creatures of the Permian period separated in the time 
 sc/ile and rock stage by many millions of years. Such confu- 
 sion would render futile the results of an examination of any 
 region, and perilous indeed would be the employment of funds 
 based upon such inaccurate conclusions; yet the writer has re- 
 ported upon many locations of drilling wells where it was 
 
 23 
 
SOURCES OF PETROLEUM 
 
 apparent mistakes of equally glaring character had been made, 
 though not by an authority who could scientifically determine 
 where a drill should be located. 
 
 During Upper Cretaceous times, not to search into deeper 
 past epochs than such as are suitable to the illustration, it has 
 been found that certain species of very minute marine plants, 
 known as algae, were similar in the waters of equable tempera- 
 ture in every sea of the world. Such plant life and others of 
 similar and unlike character, together with the diminutive animal 
 life of the seas, have been found to be the source of much of the 
 petroleum coming from formations of that age. The fossils 
 preserved in the strata render them not difficult of determination. 
 
 Later, during the Tertiary period, there seems to have been a 
 marked development and increase of one branch of algae, known 
 as diatoms, so that their growth filled the waters which sub- 
 merged a part of what is now the great valley area of Califor- 
 nia. Our diatomaceous shales are so named because the greater 
 proportionate part of such shales are often almost entirely com- 
 posed of the limey portion of that marine plant. 
 
 Since other forms of plant and animal life were embedded in 
 the shales and other formations of the periods named, it be- 
 comes apparent that there is no uncertainty as to what relative 
 time must be referred these minute specimens of organic life. 
 
 The accuracy to which age correlation and identification of 
 strata have been carried by science will bear one full illustra- 
 tion: It is possible to trace with unerring assurance the physical 
 history of the horse from his embedded remains in formations 
 of the Eocene epoch of the Tertiary period to the present time. 
 Similar methods are employed in the identification of the devel- 
 oping and changing forms of every species of plant and animal 
 life, as such alterations were brought about by the adaptations 
 
 24 
 
THE PASSING OF SPECIES 
 
 enforced by survival. But it is especially interesting to follow 
 the skeletons of the horse backward from his present proud and 
 beautiful form into the inhospitable conditions of the early Ter- 
 tiary, a long period of volcanic eruptions, and of widespread 
 and almost continuous earth movements. The atmosphere was 
 laden with noxious gases, the waters contained acids, were 
 saline, sulphurous and choked with ashes and volcanic dust; 
 and when such perplexities were joined to the perils of a quak- 
 ing earth, avalanches, lava flows, the opening of extensive fis- 
 sures where the solid strata were broken and uplifted by faulting, 
 buckling and folding, combining to the enforcement of constant 
 and rapid shifting of places of habitat, it is indeed marvelous 
 that the creature survived not only, but with the multiplying 
 stages of growth and improvement became the fleet and comely 
 animal of our prize shows. Not less strange is it that of all 
 the animal and plant life which has ever inhabited and clothed 
 the planet, the myriad wonderful representatives which have de- 
 scended into our day are but a scant fraction. The vast pano- 
 rama of life which has in every age been spread out over the 
 lands and in the seas has in every species changed, some falling 
 backward and dying out, others improving and multiplying ; but 
 we know that all were of Nature and exist within the horizon 
 of Divine provision. In that ancient system of rocks where the 
 earliest remains of the horse have been preserved in skeletons 
 which do not change, we learn that he was about the size of the 
 fox squirrels of today. In the formations of every succeeding 
 eppch from the first remains found there have been unearthed 
 and identified hundreds of skeletons which are unmistakably the 
 remains of horses. The writer has examined parts of skeletons 
 of horses of the Pleistocene epoch embedded in formations of 
 that sedimentation in Florida. In Wyoming he has seen the 
 
 25 
 
GEOLOGY AND PALEONTOLOGY 
 
 bones of such skeletons embedded in rocks of the early Miocene 
 epoch. There may be seen in museums many almost wholly 
 complete skeletons of the horse of every epoch from the first 
 identifiable structures of his beginning to the present time. It 
 will be remembered that the character of the herbiage changed 
 as epoch grew into epoch with the passing of ages, and that as 
 age followed age grasses came and flourished and developed, 
 and that climatic and atmospheric conditions evolved environ- 
 ments and influences which provided better food and more 
 favorable surroundings, hence the animal's additions of size and 
 strength. 
 
 In the formations filling some of the hollows of such old 
 bones, where marrow had been in the living animal, there have 
 often been found many bony structures of insects and other 
 animal organisms, impressions of plant leaves and stems and 
 other remains of the living things of the earth belonging to the 
 particular epoch of the bones when a part of the living animal. 
 Hence, we come to the knowledge of many verifying and cor- 
 roborative facts relative to the contemporary life and many of 
 the happenings of every epoch. 
 
 The science of rocks is called Geology. The science of fos- 
 sils is called Paleontology. These sciences are as essential to 
 the successful oil driller as the science of chemistry is necessary 
 to the steel manufacturer. The major oil-producing companies 
 and all successful oil operators employ men learned and experi- 
 enced in these professions to examine possible oil-bearing lands 
 and select locations for drilling, as the steel maker employs 
 chemists to advise proper alloys in right quantities for the mixing 
 and fusing of iron ores in the blast furnace. The railway 
 companies and others demand steel of a specified chemical 
 composition, hence the steel maker must employ scientific 
 
 26 
 
SCIENTIFIC KNOWLEDGE NECESSARY 
 
 advisers of learning and experience in order to deliver such 
 grades. 
 
 The oil producer is very rarely a competent, experienced 
 scientist, but if he wishes to locate new fields he employs capable 
 geologists to that end. The steel manufacturer is rarely if ever 
 a learned and experienced chemist, but he is not without the 
 advice of men learned and experienced in that profession. 
 
 27 
 
28 
 
In cut No. 3 a dome is shown. The hills of light-colored 
 material in the central part of the picture are made up of rocks 
 of much greater age than the formations in the crests of the 
 ridges lying about them. If by reason of vertical action there 
 is a body of formations pushed upward in a local area, it will 
 be obvious that such formations as lie over that body will be 
 elevated, and by that movement will upturn the edges of the 
 strata which were broken by the upthrust. 
 
 It usually develops that in cases like the foregoing the domal 
 part of the structure, the top of the dome, is subject to greater 
 erosional activities than the surrounding material. It also 
 follows that the disintegrated mass of formations which most 
 definitely express the character of the action are the ends and 
 edges of strata which were lying more deeply buried, hence 
 are more compact, denser and harder than the formations pushed 
 up in the central portion of the dome; therefore their upturned 
 portions do not erode away so rapidly. The top of the dome 
 carries greater or less thicknesses of the material which was upon 
 and near the surface, hence surrenders more readily to the ele- 
 ments, leaving a depression wherein there is left upon the sur- 
 face the hard formations which belong to rock stages much 
 earlier than the surrounding rim of rocks which bound the 
 dome. 
 
 For the reason stated, though other causes also enter into 
 the fact, domes and anticlines will often express their highest 
 understructure along creek and river beds and sometimes in 
 lakes. Much of the Cherokee Shallow Oil Fields of Okla- 
 homa are illustrative of the first; and Caddo Lake, Louisiana, 
 of the latter. 
 
 29 
 
CHAPTER IV 
 
 RELATING TO OIL STRUCTURES AND THE 
 METHODS OF DETERMINING THEM 
 
 The dependable results gained by drilling experience 
 throughout the world have established a vast assembly of facts 
 relative to oil-bearing formations, and the laws and conditions 
 which govern oil accumulation in certain areas. 
 
 The fact will not be lost sight of that there are certain im- 
 perative essentials which are antecedent to the discovery of new 
 oil fields. Though it would be manifestly impossible to stay 
 within the boundaries of a brief plan if we enter fully into 
 discussion of the almost countless minor details and aspects of 
 the less important conditions which must be considered by the 
 geologist in locating a new field, it is possible to set down in a 
 few short paragraphs the main factors which are of first 
 moment. 
 
 30 
 
LAWS OF OIL STRUCTURES 
 
 1. The presence of petroleum-making formations must be 
 known to exist in the sub-surface strata either directly or in 
 contact in the inclined beds. 
 
 2. Permeable formations, such as sand, porous limestone, 
 or other sediments in which oil could find lodgment, must be 
 accessible to the oil-making formations. 
 
 3. The oil-making strata and the formations acting as a 
 reservoir into which the oil has passed must occupy such rela- 
 tive positions as provide or have provided for the oil to move 
 from the former into the latter. 
 
 4. The permeable formation in which the oil has had 
 natural provision for accumulation must be enclosed by imper- 
 meable strata, or otherwise be definitely surrounded by rock 
 formations, so that the oil draining into it could not have been 
 lost by escape to the surface. 
 
 The foregoing conditions are interpreted as oil structures, 
 such as the Anticline, Dome, etc., etc., of which there will be 
 something said later. Disregard or ignorance of the absence 
 of facts similar to such as are mentioned above has been re- 
 sponsible for the drilling of a very large number of holes in 
 attempts to find oil in regions and at locations where no effort 
 of the character should ever have been made. The shales 
 from which oil is generated and the limestones from which it is 
 distilled by natural processes are fairly well known throughout 
 all of the oil-producing regions of the world. Also, the various 
 kinds of oil structures which may be expected to contain oil 
 accumulations, if present in a region where oil-bearing forma- 
 tions are believed to occupy sub-surface levels, are not usually 
 difficult of discovery and location. 
 
 There are areas adjacent to nearly all productive oil fields 
 which contain the shales and limestones in which the oil is 
 
 31 
 
LOCATING OIL AREAS 
 
 found in the nearby producing area, though such formations 
 may not lie in a favorable position or be of adequate thickness 
 to warrant drilling. Often because of some other ascertainable 
 reason oil should not be expected in them, such as lack of poros- 
 ity in the oil-bearing members, the presence of water because 
 of low sub-surface elevation, or some prime essential which is 
 found to be lacking there must be nothing of direct bearing 
 on possible oil presence absent in any area where drilling is 
 to be done. 
 
 In a great many areas throughout the large number of oil- 
 producing regions of the United States, and the same facts are 
 found to exist in fields elsewhere in the world, it has been noted 
 that new fields have been opened in nearby or related areas 
 after the development near the discovery well had progressed 
 to the drilling of every feasible location in the producing field. 
 It is often possible to follow the oil-producing and oil-bearing 
 formations from the producing districts into related areas either 
 near to or more distantly removed from present production. In 
 event we are able to trace from a productive area into a nearby 
 region the upturned edges of alternating sandstone and shale 
 members which quite definitely express the conditions of such 
 strata as to sequence of deposit, character and position occupied 
 under the new region, we are enabled without much doubt to 
 reckon upon the presence of oil in profitable amount in any 
 structure found in the latter region. 
 
 The great fields which came at last to show almost a con- 
 tinuous succession of profitable wells from Robinson to Casey, 
 Illinois, is a case in point. An untested area in that region, 
 known to the writer, may be another case. Also, the trend of 
 productive strata from Caney, Kansas, to Chelsea, Oklahoma, 
 in the great Mid-Continent fields, a distance of upward of 
 
 32 
 
LOCATING OIL AREAS 
 
 seventy miles, was traced out very well by geologists following 
 the exposures of formations along the bases of the hills and in 
 the cut-out channel of Verdigris River upon the western bound- 
 ary of the region. The California fields located in southern 
 San Joaquin Valley and at Coalinga offer marginal boundaries 
 along the foothills of the Sierras and the Coast Range which 
 are almost ideal for the tracing out of the possible oil-making 
 and oil-bearing strata, as the upturned edges of these are ex- 
 posed with their related members along the foothills mentioned. 
 
 33 
 
CHAPTER V 
 
 SOME TYPES OF OIL STRUCTURES AND RE- 
 MARKS ABOUT THEIR CHARACTER IN 
 SOME WELL-KNOWN FIELDS 
 
 THOUGH all formations of a sedimentary character 
 were deposited in a horizontal position, but rarely are 
 they now found lying in that position in any region of 
 considerable areal extent. The crust of the earth, though 
 stable enough in the present epoch, has been subject to almost 
 endless disturbances, which have had the effect of displacing 
 the strata, and tilting, upending, breaking and rearranging the 
 sequence of rock formations. 
 
 The planet we live upon has gradually contracted in size, 
 causing rock strata which were deposited long ago to lie exposed 
 upon the surface, or to thrust out their edges where erosion has 
 carried away the disintegrated and loosened material. Many 
 great mountain chains, peaks and summits, and many hills and 
 ridges, with their related or corresponding depressions of valley, 
 plain, gorge and canyon, are displayed all over the world as 
 results of the buckling, warping, faulting and other earth move- 
 ments occasioned largely by that contraction. Of course the 
 shrinkage of the planet has been entirely too slight to be meas- 
 
 34 
 
OIL ACCUMULATION FACTS 
 
 ured by any instruments of even the most delicate exactitude, 
 but the inequalities of the surface of the earth everywhere bear 
 legible records of the fact. These erogenic and tectonic move- 
 ments, mountain-making and structural, respectively, have been 
 taking place in the more or less solid crust of the earth through- 
 out much the greater part of its physical history, though very 
 surely quite more prevalent in some ages than in others. They 
 have occurred with diminished frequency during the period in 
 which men have lived than at any previous time, and it seems 
 that our habitation is growing more nearly secure and is not so 
 much beset by disturbances as period is added to period in 
 its age. 
 
 Such movements have been of determining effect in the dis- 
 placements which have provided the natural rock structures 
 which appear to exist in all areas where oil in commercially 
 profitable amount has been found. There are several well- 
 known types of these so-called oil structures, though the anti- 
 cline and dome are the most common and appear to be the types 
 present in many of the areas of greatest productivity. The 
 various forms of structure have been so definitely determined by 
 drilling in hundreds of areas in all oil-producing regions through- 
 out the world, and scientific measurements and mapping of the 
 surface demarcations of such structures have been carried to 
 such a high degree of accuracy, that it appears there has been 
 established a series of related natural laws regarding the gath- 
 ering of petroleum into catchment reservoirs. This will not be 
 understood that the oil is contained in basins in the ground like 
 pools, lakes or rivers upon the surface, but in sand and other 
 porous formations, as water is contained in gravel. 
 
 It has been said that if the oil found in any great oil structure 
 were disseminated back into the formations from which it 
 
 35 
 
TYPES OF OIL STRUCTURES 
 
 drained it would be impossible to drill a profitable oil well at 
 any location upon the earth. This reflection brings us to a more 
 detailed examination of what is meant by an Oil Structure, and 
 what we must search for in order to locate that peculiar em- 
 placement of the rock strata. 
 
 The most commonly known types of oil structures are named 
 after the specific architectural build of the formations, as the 
 anticlinal, meaning roof-like; the domal, like a dome; the 
 terrace, a level area of the formations interrupting or ending a 
 dip plane; etc., etc. 
 
 ANTICLINE OR ANTICLINAL FOLD: This type of structure 
 is more common than any other. It is that displacement of the 
 strata which forms an arch of the formations, and disposes dips 
 upon two opposing sides from an extended apex. The inclined 
 beds are in the place of the sides of a roof over a building and 
 the apex is in the position of the ridge-pole. 
 
 In the section where earth disturbances were mentioned it 
 was said that mountains, hills, valleys and other inequalities of 
 the earth's surface were apparent everywhere. Referring to 
 such elevations and depressions, of course it will be seen that if 
 an upward movement developed from the buckling, folding or 
 warping of underlying formations, there would be a more or less 
 definite elevation of all overlying strata. Such condition would 
 be called anticlinal, and would be inclusive as to the alternating 
 formations and their arching similar to a layer cake bent upward 
 across the middle every layer would bend equally. (See 
 Cuts 1 and 2, page 1 6. 
 
 It will be remembered that the formations were put down in 
 a more or less regular position horizontally under water. They 
 are not all sand, or all clay, or shale, or limestone, or of any 
 one sedimentary material. In drilling wells for oil, sinking 
 
 36 
 
33 
 
The character of the topography shown in cut No. 4 is not 
 unlike that of Devil's Den and the general region of that oil 
 field in California. It requires no technical examination to 
 determine that the light-colored sandstone ledge, shown in the 
 left-center foreground in the cut, passes under the rocks which 
 define the escarpment, shown upon the right and middle back- 
 ground of the picture. 
 
 However, it does require a very critical examination and the 
 exercise of constructive logic in reasoning from the facts to 
 determine positively if there be an unconformity between the 
 former and the latter, and if a catchment area for oil accumu- 
 lation in the former material might have been provided by the 
 overlapping upper formation. 
 
 The picture in fact sets out graphically one-half of a domal 
 structure, which in this case is a sealed fault. The facts deter- 
 mined by drilling disclosed an upthrust of the strata shown in 
 the picture, leaving the formations in place towards the left, 
 though not shown. The test well was located in this instance 
 about five-eighths of a mile from the breakage line of the fault, 
 just back of the highest terrace in the extreme right-hand side of 
 the cut. Oil in good commercial quantity was found in the 
 lighfr-colored sandstone at a depth of 1800 feet, though there 
 were some little seepages of it along the sandstone wall shown 
 with the trees of evergreen variety near the center of the picture. 
 
 39 
 
DEFINING OIL STRUCTURES 
 
 shafts for mining, or digging wells for our domestic water sup- 
 ply, we see that there is usually on top a given thickness of shale 
 (shale was mud at first), then possibly clay, afterward lime- 
 stone and then sand or gravel. The succession of these and 
 other formations known in the ground vary with every locality; 
 almost no two sections of any depth will be identical. Any 
 elevation of the successive strata will of course lift all of them, 
 and in most cases it will be found that upon one side or the other 
 of the apex of an arched or folded area there will be a longer 
 slope than upon the other side; and in one of the two sides 
 (limbs of the anticline, as they are called) there will be a steeper 
 dip than in the other. Also, in many such types it will be seen 
 that the inclination of the beds as they dip away from the apex 
 maintains about the same degree of pitch and will extend to a 
 distance of several miles upon one limb of the anticline, but will 
 be dipping at a very steep angle upon the other limb; the effect 
 being that of a very long roof on one side and a very short, 
 steep one on the other. The direction from which we will 
 expect the oil to have migrated into the anticline will usually 
 be from the long side of the roof, and in making a location for 
 the drilling of the test well upon the structure we will select a 
 site near the apex but somewhat upon the side of the less steeply 
 dipping beds. There are local conditions present sometimes 
 which would vary that logic, but they are the exceptions. 
 Sometimes the anticline will be very regular, the limbs upon 
 either side of approximately uniform inclination, and the apex 
 maintain a more or less equal elevation. The selection of a 
 location for test drilling will in such cases be approximately 
 upon the apex. It will often be seen that the fold did not pass 
 through the area in a straight line ; indeed, such uniform straight 
 folding is not common. The apex will be sinuous, or curved, 
 
 40 
 
DESCRIPTION OF STRUCTURES 
 
 or present a turn or various turns at sharp or more rounded 
 angles in nearly all areas where folding has developed in very 
 thick limestones which occupy the sub-surface levels throughout 
 an extensive region, or in a region of prominent folding which 
 results from vertical thrusts of deeper lying massive formations 
 or igneous material. 
 
 In many regions where the folding has been pronounced, and 
 the action has been in great measure common to a considerable 
 area, the other types of structure will also be very likely found. 
 Domes will exist, or Terraces, or Faultings or Faulted Zones, 
 though any of the last named may be present in an area and 
 no other form of structure be near. 
 
 A DOME OR DOMAL STRUCTURE : A structure of this type 
 is found to have a central elevated area from which the strata 
 slope in every direction. (See cut No. 3, page 28.) Such 
 condition is sometimes called a Quaquaversal structure. The 
 description which applies to an anticlinal fold covers also the 
 disposal of the rocks over a dome, though the inclined beds 
 will but rarely define a perfect mathematical dome, as the limbs 
 of the anticline will not often be uniform and regular. Some 
 of the greatest oil fields known are upon domes. The related 
 earth forms are similar in all such structures, though the causes 
 underlying the existence of the dome are greatly different in 
 various of them. An uplift of the igneous or other deep-lying 
 rocks forms a structural build of the overlying beds which has 
 all the appearances of the similar condition caused by the ex- 
 pansion which is developed by certain minerals upon crystalli- 
 zation, such as rock salt or gypsum; the latter occupies about 
 one-third more space when in a crystallized than when in a 
 massive state. The enlargement would have the effect of 
 
 41 
 
DESCRIPTION OF STRUCTURES 
 
 pushing up a body of overlying material, as an upward move- 
 ment of the underlying mass would do. Some of the great 
 fields of the southern Texas and Louisiana regions, known as 
 the Gulf Coastal Fields, owe their existence to what are known 
 as salt domes. Oil accumulation in the porous beds of a domal 
 structure is a result of similar conditions and in obedience to the 
 same laws which prevail in governing its accumulation in the 
 anticline. 
 
 TERRACE AND DIP-PLANE STRUCTURES: The terrace 
 structure is defined as that area which embraces a leveling of 
 the strata. What is meant by the description may be briefly 
 made plain by noting that there are many areas where the gen- 
 eral inclination of the beds has all been tilted in one direction 
 over a very wide region. Where the formations are similar and 
 were deposited under identical conditions, and where the suc- 
 cessive disturbances occurred contemporaneously throughout the 
 region, and where there does not exist evidences of divergent 
 and extraneous earth movements, the region is called a geo- 
 logical province. Now, upon investigation of many geological 
 provinces it is found that the degree of inclination of the beds 
 is changed and there are localized areas where the strata lie 
 flat. That is a terrace such as is known to oil fields. While 
 it may be true that after passing upward along the inclination 
 of the beds falling away from the terraced area, and across the 
 latter area also, the beds will again disclose the inclination noted 
 further down the dip, and that such inclination will continue to 
 rise until the point of action or the apex of the dip-plane is 
 found. The fact remains that the terrace is present, and that 
 oil will not continue to pass along under a level stratum or move 
 through one, though it may accumulate in it after it is driven 
 from lower levels in the dip-plane because of the greater specific 
 gravity of water. 
 
DESCRIPTION OF STRUCTURES 
 
 The Dip-plane Structure is that area of change of degree of 
 inclination of the dipping beds, and may be present at any point 
 along the dip of the strata. Oil will move upward through a 
 porous stratum as water passes to the low levels, but will not 
 have the freedom of action at places where the pitch exhibits 
 any considerable change of degree. This type of structure is 
 not as favorable as the terrace, though it differs from it only in 
 the fact of being somewhat removed from an actual horizontal 
 position of the permeable material in which the oil may be 
 contained. 
 
 THE FAULT STRUCTURE: Properly speaking, we do not 
 refer to the faulted conditions found in nearly every region 
 where the evidences of disturbances are present as a structure; 
 though a sealed fault into one or the other plane of which oil 
 may have found access and be impounded, is a form of struc- 
 ture. Since some of the very important producing areas are 
 delivering their values from structures of this type, it will be 
 well to explain the condition under which the petroleum may 
 gather and remain in them. (See cut No. 4, page 38.) 
 
 In the first place, a fault is a breaking of the formations in 
 a more or less nearly vertical manner, and a lifting of the strata 
 on one or the other side, possibly upon both sides, but usually 
 with one plane lifted higher than the other. The plane of 
 higher elevation is called the up-throw side, in event it is known 
 that the lower side was not in fact an actual down-throw, leav- 
 ing the other side in place at the time of movement. Now, 
 observe that if the up-throw plane of a fault were to lift with 
 its movement a porous stratum of material containing oil so that 
 its edge rested against the broken edge of a massive body of 
 limestone, or a clay stratum, or some other impervious material, 
 the oil content of the porous body would be sealed in and would 
 
 43 
 
DESCRIPTION OF STRUCTURES 
 
 stay in that higher portion of the formation. If there were 
 water on top and oil on the bottom of the formation so uplifted, 
 the position the bed would occupy after being elevated would 
 drain the oil to the higher part of the formation as the water 
 settled to the lower part. The present disclosures upon the 
 'surface in some of the fields now producing from sealed fault 
 planes indicate that the oil-bearing member was uplifted from 
 a position in the earth so deep that it could not have been 
 reached by the drill; possibly also leaving the other portion of 
 the elevated formation at the original great depth from which 
 recovery would be impracticable if not impossible. 
 
 It may be said that there are other forms of structure known 
 which are uncommon, and doubtless yet others exist the type or 
 form of which we do not know ; but the foregoing gives a fairly 
 good idea of the most prevalent types met with in various of the 
 great producing fields. Something about the natural processes 
 of oil movement in the ground so that it gathers into catchment 
 reservoirs will be of interest. 
 
 44 
 
CHAPTER VI 
 
 OIL ACCUMULATION AREAS, HOW 
 DETERMINED 
 
 SOME INSTANCES 
 
 Petroleum as it is found in the ground in local accumulations 
 represents the results of gathering processes which are operative 
 by reason of certain laws of Nature which are pretty well 
 understood. It is believed that the great amount found in the 
 many fields of the world were at first in very small particles or 
 drops in the formations which bore the antecedent possibilities of 
 oil making; also that such formations may or may not have 
 occupied a level position then, and that water was also in the 
 formations at that time or was later admitted to them. It is 
 known that petroleum migrates to elevated positions above 
 water whether it be on the surface of the ground or in sub- 
 surface levels. It is also true that nearly all strata have been 
 shifted and tilted out of a horizontal position, and that such 
 position offers the condition which provides for separation of 
 water and oil by natural activities known to have been present 
 in the earth throughout its past, and not absent in this age. 
 
 45 
 
LOCATIONS IN NEW REGIONS 
 
 Upon the foregoing knowledge and its .application to the 
 earth picture of an area every location for a drill in a new 
 region should be based. It is needless to say that a great many 
 test wells are drilled without regard to the existence of such 
 information, and that possibly one out of every two or three 
 hundred of them find oil in profitable quantity. The percentage 
 of successful wells drilled in new areas selected by experienced 
 and capable geologists after they have determined that petro- 
 leum-bearing formations are present in the area is relatively 
 very large ; probably out of every one hundred such wells drilled, 
 ninety of them find oil in commercially profitable amount. 
 Statistics of oil discoveries of late years appear to fully bear 
 out that statement. During 1920 it is reported that 21 new 
 oil fields were discovered in the United States, and that 20 of 
 them were drilled in areas and at locations selected by geol- 
 ogists. It may be well to make a brief statement of some of 
 the more important considerations which must be remembered 
 if one would safely locate areas in which petroleum may exist 
 in commercial quantities, and would properly select the site for 
 the drilling of the first wells in that area. 
 
 1 . Determine if the area is underlain with oil-making for- 
 mations, and if so, if such formations are in contact with or so 
 located in the sub-surface area as to allow the migration of any 
 petroleum content to porous formations which may act as reser- 
 voirs for the accumulation and retention of it. 
 
 Develop a knowledge of the foregoing conditions by a careful 
 examination of all exposures of the formations which indicate 
 that they are present under the area. Learn if such formations 
 are actually productive of oil in any area in the geological prov- 
 ince which includes it. Examine the identities, similarities and 
 differences of the formations exposed as to their lime, sand or 
 
 46 
 
HOW TO FIND STRUCTURES 
 
 shale character, their looseness, porosity, density, etc., as com- 
 pared to the same formations from which oil is being taken out 
 of profitable wells in all related areas. 
 
 2. Determine as far as possible if any area in the province 
 shows arching, doming or terracing of the strata which include 
 the petroleum-making and the petroleum-bearing formations 
 which the investigation outlined above has identified. 
 
 3. Measure the degree of dip, the direction of the inclina- 
 tion, the thickness of the various sandstone, lime and shale for- 
 mations, and determine definitely if there actually be a folding 
 of the rocks, or a possible elevated condition of the sub-surface 
 strata indicated; and if so, if there be adequate thickness of the 
 oil-producing and porosity of the oil-bearing members to war- 
 rant the conclusion that the possible output may be in profitable 
 amount. 
 
 4. Note on a map of the area the corners of sections and 
 other sub-divisions of the land, and with relation thereto mark 
 the places of outcrop, what rocks are exposed, what their incli- 
 nation may be as to degree of dip and direction and to what 
 extent disclosed. Use pencils of different colored lead for the 
 different formations. 
 
 5. Proper use of the Aneroid Barometer will give eleva- 
 tions, which should be noted on the map as the formations are 
 spotted, so that the level of any given formation will be seen 
 at a glance throughout an area the size of a small ranch or as 
 extensive as a county. 
 
 6. One must be assured by sufficient examination to decide 
 if any possible arch or dome might have been caused by the 
 presence of some mineral in the sub-surface levels, such as beds 
 of salt or gypsum, which increase in size while crystallizing and 
 
 47 
 
HOW TO FIND STRUCTURES 
 
 produce effects in overlying formations similar to such effects 
 caused by folding and buckling of the deeper formations. Also, 
 the possibility of ancient landslides having left effects which 
 may be similar to the change of pitch found in terrace and dip- 
 plane structures, or the reversal of dip as found in anticlinal or 
 domal structures must be carefully noted. But such superficial 
 displacements of the strata are usually easy and certain of 
 determination, though they must not be neglected. 
 
 7. Examine the area along the apex of the anticline and 
 at either extremity of it to determine if it is closed, so that any 
 accumulation which may ever have drained into it is still present. 
 
 This may usually be definitely ascertained by noting if the 
 inclined beds again resume their normal dip after the uplifted 
 areas have been passed; or by a fault zone which has forma- 
 tions exposed in one or the other of its planes which are of an 
 impermeable character ; or if the inclination of the rocks is away 
 from the apex of the fold at the ends ; or if sealed non-conform- 
 able contacts are present, thus cutting off the possibility of 
 escape of the oil. 
 
 Terrace and dip-plane structures will in almost all cases be 
 naturally closed to prevent the wastage of the oil content to the 
 surface by reason of the peculiar forms of such structures. To 
 learn if a fault be sealed so that the one or the other plane of 
 it will hold oil if any were in it or has drained into it, is a matter 
 of the most careful field investigation, and the methods are so 
 complex and the usual earth forms are so broken up and dis- 
 torted that it is impracticable to undertake to describe condi- 
 tions upon which a conclusion might be based as to whether 
 the fault actually does seal the structure or leave it open. Upon 
 that point, however, the field examination must proceed to a 
 degree of definite satisfaction. 
 
 48 
 
RULES TO OBSERVE 
 
 The type of structure will be determined in most cases at 
 the first glance over a region, if any be present ; but its character 
 and exact form, and the various disclosures shown on the surface 
 denoting the extent of the inequalities and displacements of the 
 underground picture, must be examined with the utmost care, 
 and exactly mapped. 
 
 It is now seen that every type of oil structure confirms the 
 following assumptions and appears to provide for the operation 
 of the laws of gravity, though with respect to the latter there 
 will be found many qualifying conditions and determining 
 factors involved. 
 
 Let us state the matter in short sentences : 
 
 1 . The beds must incline from a horizontal position. 
 
 2. There must be beds present in which petroleum 
 originates. 
 
 3. The possible gathering area must be extensive. 
 
 4. The generating formations must be in some manner in 
 contact with the porous formations which act as catch- 
 ment reservoirs. 
 
 5. Impermeable formations must in some manner enclose 
 the latter. 
 
 6. Adequate thickness must exist in the oil-making forma- 
 tions. 
 
 7. Matters of feasibility and practicability of access to the 
 world are important. 
 
 8. Petroleum in many instances is found impounded by 
 water in a syncline (a relatively low area with reference 
 to adjacent strata). 
 
 9. Oil may be driven by water into a trap formed by a 
 fault wall or a non-conformable deposit which is im- 
 pervious. 
 
 49 
 
50 
 
In cut No. 5 one limb of an anticline is shown. In the bank 
 of the stream at the right of the horse the inclination of the beds 
 is well developed. In the extreme background at the left of 
 the horse, in the side of the hill, the level-lying formations are 
 well pictured. Evidently the tilting strata of the anticline pass 
 under the latter formations, but the level strata do not dip con- 
 formably with the formations in the limb of the fold at the 
 right. 
 
 In nearly all cases similar to the earth picture shown in the 
 cut it will be found that there is an unconformity in the top 
 formations. That is to say, after the forces were expended 
 and the anticline was formed, later sedimentation occurred and 
 beds were put down in a horizontal position, the ends of which 
 lie in that level manner against the formations which define the 
 tilting beds of the anticline. In all such cases it is of moment 
 to determine to what depth such non-conformable formations 
 reach, and what rock stages are embraced in the unconformity. 
 Usually the line of unconformity may be readily determined, 
 and from the facts it will not be difficult to decide if accumu- 
 lation a*reas for oil might have been provided along such line. 
 
 51 
 
DIASTROPHIC ACTION 
 
 10. Like all other fluidic substances in or upon the ground, 
 oil will seek the lowest accessible level, and if water be 
 absent, it will settle in time into any trough (syncline) 
 formed by the strata. 
 
 With respect to paragraph 4, it may be explained that the 
 originating formation may lie very distant indeed from the for- 
 mation in which we find the oil when we drill; but the fact of 
 accessibility is not thereby absent. The travel or migration of 
 oil through a formation may have covered a short or a very 
 great distance before being impounded in some character of 
 natural trap in the earth. (See cut No. 6). 
 
 There is a very interesting theory to account for the presence 
 of petroleum accumulations which has lately been advanced by 
 Marcel Daly. It is known as the "Diastrophic" theory, and 
 may be presented with some clearness by illustration. If we 
 squeeze a mass of sugar saturated with water, the latter will 
 be forced out; as when we wring a water-soaked cloth, the 
 water leaves it. 
 
 As has been said, the earth is not solid, but is made up as 
 to its crust by alternating harder and softer formations of vary- 
 ing characteristics; some are very thin and massive, others are 
 thick and porous, and still others are modifications of the 
 qualities of one or the other. When the tremendous forces are 
 exerted in Nature's vast power stations which are adequate to 
 the disturbance of extensive areas of the surface and sub-surface 
 strata, it appears possible that any petroleum in the formations 
 affected might be squeezed or wrung out. It would not follow 
 that it would be forced to the surface or wasted, but it might 
 well be driven into areas of the formations adjacent, over, at 
 one side, or upon the sides, or possibly under the formations, 
 which felt the force of the action. Even so, the petroleum 
 
 52 
 
HOW TO KNOW OIL STRUCTURES 
 
 could conceivably be retained in formations within the axis of 
 action, but in less space as compared to its scattered condition 
 before the earth movement. 
 
 Examination of the illustrations throughout the book will 
 convey a good idea of the appearance of a large number of 
 areas near oil fields and elsewhere throughout the United 
 States. In the first picture, on page 1 6, the topography is well 
 shown. In the second the diagram indicates the place occupied 
 by each formation with relation to underlying and overlying 
 strata. Also, in the second the outcropping beds could be 
 examined as to character, thickness and relative position, as to 
 inclination and direction of dip, as we walked up the side of 
 the elevation shown in the middle of the top of the picture, if 
 we were going toward the east. If we were going toward the 
 west from the base of the hill shown at the right-hand side of 
 the picture, we would walk upon the Mancos shale to the sum- 
 mit of the hill unaware as to what beds might lie under it, or 
 indeed as to what position they might occupy, and could not 
 have knowledge as to their character. Oil accumulation in 
 an area like this could have been caused by Diastrophic action. 
 
 Now, assume that the Dakota sandstone outcrop near the 
 summit of the hill shown in the middle of the top of the picture 
 could be followed along the surface for ten or a hundred miles 
 as the case might be, somewhat as its upturned edges have been 
 traced by the writer about the slopes of the Black Hills of 
 South Dakota and Wyoming for a greater distance than the 
 maximum stated; suppose also that in a nearby area oil was 
 being taken in profitable quantities from wells which found the 
 saturated horizons in the Dakota sandstone, and that it had 
 been found that the productive area occupied a place where 
 the sandstone had been uplifted above its normal position, and 
 
 53 
 
HOW TO KNOW OIL STRUCTURES 
 
 that the overlying strata was of an impervious character, and 
 that the last named formation was exposed lying over the sand- 
 stone farther up the hill; it would be known that the sandstone 
 with the massive material overlying it would occupy relative 
 positions throughout the general region; now, suppose that we 
 are at position A, and the imaginary oil field mentioned is 
 40 miles southeast of us at position B, and that 30 miles north- 
 west of us at C, or some 60 miles north of B, there is a defined 
 anticline or dome, the inference would be strong that an oil 
 field could also be opened at C. Then the examination would 
 proceed to the determination of every factor involved in the 
 strata and their character and relative position in the entire 
 region, before decision could be made as to the probabilities of 
 finding oil in paying quantity in the new area. However, new 
 oil fields are located with much greater assurance in the manner 
 stated than in any other way. It will be found that nearly all 
 of the problems which will be involved in arriving at depend- 
 able conclusions with reference to the probabilities of profitable 
 oil accumulation in new areas have now been touched upon. 
 
 54 
 
CHAPTER VII 
 SUMMARY, PROBABLE NEW FIELDS. 
 
 In the illustration shown in cut No. 5, the inclina- 
 tions of the beds are plainly seen in the hillside in the right 
 background from the horse. When following such strata 
 throughout an extensive region it is always well to select certain 
 beds as horizon markers. By that we mean to say, certain 
 members which are distinctive by reason of color, size of grains 
 and all other features which render them certain of identifica- 
 tion, in order that we may be assured that the same formation 
 and an identical part of that formation is being followed. It is 
 possible to secure the exact levels above or below some selected 
 datum line of any part of a designated formation throughout 
 every part of a region if the formation is exposed at intervals, 
 even if covered in places by hills or removed at other places by 
 erosional processes. 
 
 55 
 
The diagram showing an excellent vertical section of non- 
 conformable strata, pictured in cut No. 6, is selected from 
 U. S. Geol. Sur. Bulletin 647, and represents one of the best 
 illustrations of that form of earth picture available to the writer. 
 Indeed, all of the pictures reproduced in this booklet, except 
 cut No. 7, first appeared in Government publications. 
 
 It will be seen that the position of the beds lying against the 
 andesite of the Livingston formation could not be known except 
 by drilling at many places, or because of their exposures at 
 many localities in the related geological areas. 
 
 Various local areas in Texas, such as the productive district 
 adjacent to Desdamona, in the Electra area, in the developing 
 areas along the Marathon Fold in the west-central portion of 
 the State, Mitchell County, etc., first investigated and mapped 
 by the present writer in 1919, are expressive of many uncon- 
 formities. It has been essential to such knowledge to compare 
 drill cuttings from many wells, though the general fact was 
 determined by geological investigation. In and around the 
 great Healdton oil field in Oklahoma the drills have provided 
 accurate information of lines of unconformity, though at the 
 time of the first examination of the area, when the writer made 
 the location upon which the discovery well was drilled about 
 twelve years ago, many lines of unconformity were indicated in 
 the report upon the region. 
 
 Formations lying upon rocks of older or younger stages ex- 
 press such interrupted age position to good advantage where 
 several *beds are exposed in deep depressions, and along hill- 
 sides which embrace considerable areas in their slopes. 
 
 57 
 
FORMATION EXPOSURES 
 
 The diagram shown in cut No. 6, clearly sets out 
 the position of the beds underground in an area familiar to the 
 writer. At points many miles distant in different directions 
 some of these strata are exposed. At other places others of 
 them are exposed, and at still other places others are upturned 
 to the surface. It is by noting such conditions with relation to 
 other stratigraphic and lithologic facts that we are able to 
 determine with a reasonable degree of certainty what beds were 
 to some extent wasted away before later beds were put down 
 over them, causing what is termed an unconformity. That 
 determination is in some regions impossible, though there are 
 yet other methods involving many complex and baffling prob- 
 lems which may be employed in arriving at working conclusions. 
 They are too intricate to admit of treatment here. 
 
 The diagram shown in cut No. 7, is a vertical chart 
 of the formations embraced in a structure of the anti- 
 clinal type investigated by the writer recently for a California 
 oil company. The area lies in the geological province which 
 includes the productive district of Coalinga, and in the main 
 embodies identical formations with the last named oil fields. 
 
 Disclosed by the exposures of the uplifted Tejon sandstone 
 formation of the Eocene deposits, the first sedimentation of the 
 Tertiary period, the anticline passes southeastward from near 
 the middle of Section 3, Township 6 South, Range 7 East, in 
 the foothills west of Patterson, Stanislaus County, California, 
 in a definite arc to a final southwesterly direction, ending in 
 the southward tilting beds along the south line of Sections 35 
 and 36 of the township and range named. It underlies ap- 
 proximately 9,000 to 1 1 ,000 acres. The Moreno shales, the 
 last deposit of the Upper Cretaceous formations in that region, 
 underlie the sandstone mentioned. It is known to be a petro- 
 
 58 
 
SALADO ANTICLINE DESCRIBED 
 
 leum-making formation and to be delivering oil in profitable 
 amount from wells in the Coalinga district. 
 
 The last named formation is principally shale, though sand 
 lenses exist in it. The first formation named is principally a 
 sandstone body, though shale members of varying thickness are 
 found in it 
 
 It is noted that these formations lie in proper relative position 
 for the gathering of petroleum into the upper out of the lower 
 strata. The Moreno is known to be organic and is equally 
 known to produce oil. The Tejon is of a porous character, as 
 all sands are to a greater or less degree. The beds lie in a 
 series of inclined strata which dip towards the east away from 
 the apex of the Coast Range, it being possible to follow their 
 upturned edges from the Coalinga district to the area of the 
 structure west of Patterson as described. 
 
 Lying towards the east is the San Joaquin Valley, under 
 which the beds lie, as has been determined by reason of their 
 exposed edges on the east side of the valley where they have 
 been uplifted along the slopes of the Sierra Nevada Mountains. 
 
 The extent of the formations throughout the region from 
 which petroleum may have been gathered by drainage into the 
 structure is very great, being possibly as much as 150 square 
 miles in areal dimension at their sub-surface level. The thick- 
 ness of the Moreno, which is the oil-making member, is some- 
 what near a possible average of 800 feet ; hence the possibilities 
 of the anticline containing oil in profitable amount appear very 
 well founded indeed. 
 
 In San Joaquin Valley towards its eastern border, a con- 
 siderabfe distance from Bakersfield, the writer has investigated 
 a structure which it is thought contains an accumulation of oil, 
 and which will in time no doubt be exploited by test drilling. 
 
 59 
 
PROBABLE NEW OIL FIELDS 
 
 South of Devil's Den, west of the Lost Hills field, another 
 structure has been examined which should contain oil in profit- 
 able amount. It now has a drill located upon it at a point 
 which it is thought will prove its possible value. A consider- 
 able distance southeast of the anticline described west of Pat- 
 terson, in Township 6 South, Range 7 West, which was called 
 the Salado Anticline by members of the United States Geolog- 
 ical Survey in Bulletin No. 603, there are evidences pointing to 
 a very extensive anticlinal fold, which, if actually present, is 
 ideally located to have gathered an accumulation of oil of large 
 proportions. % 
 
 The writer believes that there are oil fields in California, as 
 well as in the mid-western States, which have not been opened, 
 basing that opinion upon many more or less critical investigations 
 made during the past 20 years. As to California, it appears that 
 there might be profit resulting from more detailed and careful 
 investigation of various areas in and along the borders of Sac- 
 ramento Valley, where the formations are in many places similar 
 and in some places identical with formations in the south valley. 
 There are areas where structural conditions warrant the opinion 
 that oil accumulations exist, and such regions constitute an 
 integral portion of the varied and wonderfully rich domain 
 known and loved by us as California. In Texas, Louisiana, 
 Oklahoma, Kansas and New Mexico, including areas in Illinois 
 where critical examinations have been made, the writer knows 
 of localities where new fields will probably be opened. 
 
 With the constantly increasing number of avenues into which 
 the refined products of crude petroleum are poured, and the 
 ever-widening and extending necessities of expanding industries 
 essential to the prosperity of the race, there appears to be an 
 equal broadening of the opportunities for great wealth held 
 ready for the intelligent, capable and straightforward oil field 
 promoter. ^ 
 
MUCH FUTURE OIL OUTPUT 
 
 Falling within the experiences of the present writer through- 
 out an active professional life extending to all of the oil- 
 producing regions of the United States, he has seen very 
 few men indeed who failed of success in the oil fields if 
 their purposes were clean and logical, if their good names 
 were kept good, if they were counseled by scientific advisers 
 of experience and ability, and if they followed with deter- 
 mination the rapidly opening fields of this great industry. 
 
 While it appears true that the known sources of great oil 
 production are being rapidly depleted throughout the country, 
 it is equally true that there are a very large number of regions 
 in many of the States where the present writer has in times past 
 made critical and extensive investigations, some of which will 
 quite surely be opened to production and which will deliver 
 quantities of oil for the enlarging needs of the world, and will 
 in equal measure make and break promoters in about the estab- 
 lished ratio of the past. He that drills at random will in many 
 cases lose, while he that drills upon proper counsel will in most 
 cases win. 
 
 The United States may be kept at the fore for many years 
 in oil production among the nations of the world. California 
 may be kept in the lead for many years in oil production among 
 the States of the Union. 
 
 Pacific shore lands will be the most active portion of the 
 world throughout the next century or longer. California is on 
 Pacific waters. 
 
 61 
 
l^l^Hp^'Hlf ^, 
 
 62 
 
The diagram shown by cut No. 7 was prepared by the 
 present writer for a California oil company, and is representa- 
 tive of a general vertical section of San Joaquin Valley and the 
 foothills of the Coast Range along the western border of the 
 valley. 
 
 It will be understood that no possible knowledge available 
 in advance of drilling would be adequate to the exact determi- 
 nation of the precise line where any given underlying formation 
 is cut out, though sufficiently dependable information of such 
 probable line would be obtainable by examination of the whole 
 area lying along the western border of the valley. 
 
 Referring to the diagram, it may be said that the formations 
 grouped near the surface, beginning with the bottom of the 
 Kreyenhagen shale and inclusive of the overlying Vaqueros, 
 Santa Margarita and Etchegoin (horizon), are unmistakably 
 absent at a point in the picture which may be pointed out as 
 the top of the oval hill shown under the word "East.'* The 
 diagram was intended to predicate the general position of the 
 formations along the western border of the valley, but with 
 direct reference to the location and character of Salado Anti- 
 cline west of Patterson. The Tejon formation is known to 
 be disposed on the surface in some places along the apex of 
 the anticline, though in many places it is hidden by a thin 
 covering of the San Pablo. Exposures of the edges of the 
 inclined beds immediately west of the anticline are proof of 
 the absence or presence of certain of the otherwise sequent 
 deposits embraced in the fold. Such upturned edges when 
 followed southward to the productive fields indicate with equal 
 assurance the recurrent lines of unconformity indicated in 
 the cut 
 
 63 
 
CHAPTER VIII 
 
 NOTES ON OIL COMPANY PROMOTION AND 
 RELATED SUBJECTS 
 
 THE lure of quick returns and great riches appears to be 
 the compelling attraction which turns the efforts of 
 many promoters in the direction of oil company promo- 
 tions. The drilling of oil wells throughout the United States 
 and elsewhere in the world has been made into a history of 
 spectacular delight to the shrewd men whose energies are given 
 to the enterprise. 
 
 The Bulletins of the United States Survey, and the Profes- 
 sional Papers, Reports and Statistical Reviews published by 
 the Department, together with the annals of the oil fields every- 
 where, have supplied documentary evidence in quantities 
 amounting to actual proof of the tremendous riches hidden in 
 the oil industry when such documents are subjected to the 
 
 64 
 
PAYING WELLS AND LOSING WELLS 
 
 winnowing processes employed by men whose wish is to uncover 
 the promises and neglect the snares that inhabit the business. 
 
 It will be admitted that if a statistician is actuated by a desire 
 to establish the very high percentage of paying wells to the 
 whole number of wells drilled in any good paying field, the 
 facts extant upon the subject provide the necessary material to 
 amass the proofs needed. If such array of established facts 
 relative to some special field be applied to the fields in general 
 throughout the country it will be found that the ratio of paying 
 wells is rated entirely too high. If, again, such ascertained 
 facts be applied to the possible fields throughout the country 
 and to regions where oil is possible of occurrence in profitable 
 quantity but has not yet been discovered, the hypothetical infer- 
 ence will bear no relation to the real facts. 
 
 This is equivalent to saying: If we assume that there were 
 a total of 5,657 wells drilled in the old Glenn Pool in Creek 
 County, Oklahoma, and of that number it is found that 95 per 
 cent of them were paying wells, and that by reason of that 
 established fact we may expect 95 per cent of the wells to be 
 drilled within the area of any oil-producing State will be paying 
 wells, it will be found that our estimates are very much awry. 
 
 If we further assume that a vast lot of wildcat drilling is 
 being done in a region, say for illustration, in the State of Texas, 
 and we are possessed of the knowledge that that State has about 
 40 fields where oil in commercially profitable amount is being 
 produced, and is generally known to be a region favorable for 
 oil, it does not of necessity follow that the same percentage of 
 paying wells will be found in the wildcat areas to the whole 
 number; of wells drilled that will be found in the more nearly 
 proved districts. 
 
 Suppose that there are 4,000 wells actually under the drill 
 
 65 
 
PERCENTAGES OF SUCCESS 
 
 at any given time in the entire country, but that of the whole 
 number stated four-fifths of the,m are drilling in partially proved 
 and proved areas, the others are drilling in unproved regions. 
 This would mean that about 3,200 of the drills are at work 
 in areas where oil should be found, while 800 of them are in 
 areas where the possible oil-bearing formations are so far un- 
 tested. Actual facts heretofore proved by drilling in a vast 
 number of districts throughout the United States appear to 
 have shown that of the 3,200 wells somewhat near 90 per cent 
 of them may expect oil in paying quantity ; the 800 in unknown 
 regions may expect a possible 8 wells out of the entire lot. 
 Now, it will be noted that the percentages of dry holes to 
 paying wells out of the whole number drilling would be but 
 little changed, though nearly all of the profitable wells would 
 actually be found in the areas where oil is a most reasonable 
 expectation because of its known presence in the geological 
 complex. 
 
 The tremendous excitement which attends the bringing in of 
 a big field in a new area has the effect of immediately setting 
 the promoters busy in acquiring leases and starting the drill in 
 many impossible regions, of some relation in some cases to the 
 known facts of the productive area, and in other cases of no 
 known relation to them whatsoever. It is admitted that some- 
 times new fields are really opened by such indiscriminate drill- 
 ing, but in proportion to the whole number of such untoward 
 attempts the successes are very rare. 
 
 In arriving at a dependable opinion relative to the ratio of 
 profitable wells to the whole number of wells drilling in any 
 given State it is essential to ascertain how many such tests are 
 being put down in regions where oil has not yet been proven, 
 
 66 
 
EARLY OIL FIELD SCIENCE 
 
 usually distant from present oil production, as distinct from the 
 tests that may be drilling in proved and partially proved areas. 
 
 An experienced scientist will usually be equipped with the 
 knowledge necessary to determine if good opportunity to dis- 
 cover oil exists in an untried region though it may be distant 
 from present oil output; but such information would be too 
 much to expect of any man whose training and information 
 do not include expert knowledge of geological formations and 
 structures which are adequate to the making and impounding of 
 oil. 
 
 Wholly aside from the aspect of the geologist's profession as 
 an economic asset to the oil-producing industry, there exists an 
 ethical side to the matter. Such subjects are often treated by 
 learned men in the journals and other publications of a scientific 
 character devoted to the professions, but it is not often that we 
 see the matter mentioned in mediums of general circulation. 
 
 Except by a few world-renowned geologists it was not 
 thought that the science of geology could have any relation to 
 the knowledge of oil well drilling and oil production, until long 
 after the output of oil in America became very great. The 
 first well drilled for oil in the United States was at Titusville, 
 Pennsylvania, in 1859. Thereafter during a period of 15 to 
 20 years the industry was feeble, undergoing the formative 
 stages through which nearly all new things of an economic char- 
 acter pass. Extensive fault planes partly determined the direc- 
 tion and width of the oil accumulation areas in the first great 
 Pennsylvanian fields, and as the drilling progressed along the 
 plane in which the oil was impounded it was found that profit- 
 able wells were opened. If the drilling diverged from that line 
 there were dry holes. That fact gave rise to what the drillers 
 called "Oil Lines." Wells were located in new areas by the 
 
 67 
 
GEOLOGY AND OIL LOCATING 
 
 simple process of placing a ruler upon the map of a region so 
 that its edge passed through the productive areas, the proposed 
 wells being spotted on ahead of known production along the 
 line mentioned. Geologists were derided the old Pennsyl- 
 vania driller had small use for the profession; his father found 
 oil without science and what his father did was good enough 
 for the son. 
 
 During the early years of the Kansas fields many locations 
 were made with the rule and map. Drilling near Indepen- 
 dence, Coffeyville and Caney had to some noticeable extent 
 developed along a given line, indicating that even in the West 
 as in the East the "oil lines" held good. An operator of note 
 in the pioneer days of Kansas, a man by the name of Bloom, 
 of Pennsylvanian experience, electrified his credulous auditors 
 by announcing that he would ship an outfit over to Cleveland, 
 Oklahoma, and drill a well. He proved to all listeners that 
 the oil line passed near Cleveland as it plunged its way south- 
 ward out of Kansas. He did move over to the new location 
 some fifty miles southward, and did actually get a producing 
 well. Time and drilling have long since developed the knowl- 
 edge that it was by the merest good luck that the new location 
 happened to be on a good anticline, and that it was local to 
 the Cleveland area, though embracing oil-making and oil- 
 bearing formations of great regional extent. 
 
 Little by little throughout the years, developing in the many 
 oil-producing regions throughout the world, information ac- 
 cumulated and experiences multiplied to the point of convincing 
 oil operators that a scientific knowledge of the character of 
 rocks and their relative position in the earth bear a most inti- 
 mate relation to the possible presence or absence of oil in a 
 locality. The great oil-producing companies first employed 
 
 68 
 
GEOLOGICAL INFORMATION ESSENTIAL 
 
 geologists to determine favorable regions where test drilling 
 should be done. Later such advice was sought also in making 
 new locations in a known productive field, since it soon became 
 known that not all locations upon a well-defined oil structure 
 possessed equal opportunity of returning large quantity oil 
 output. 
 
 Since about the year 1900 no serious undertaking in the 
 control of men of noteworthy achievement in the oil business 
 has been launched without the counsel of geologists. At this 
 time if one were to institute measures looking to the drilling for 
 oil in an unknown region, and did not include an exhaustive 
 examination of the ground to determine its oil-bearing possi- 
 bilities, the men of successful experience in the industry would 
 refuse to impute intelligence or honesty to the undertaking. 
 
 Even with the facts stated being constantly before us, it 
 appears of statistical record in the documents of the United 
 States Geological Survey, the Geological Surveys and Mining 
 Bureaus of various of the States, and in the private reports of 
 various of the great oil-producing companies, that in excess of 
 400 test wells are drilled every year throughout the country 
 at locations which have not had the benefit of intelligent inves- 
 tigation by scientists whose opinions are worthy of confidence. 
 It follows quite naturally that an excessively small percentage 
 of such tests result in discovering oil. 
 
 It is facts of the character stated which have to no inappre- 
 ciable extent surrounded the oil-producing industry with a gen- 
 eral mental complex which embraces every conceivable hazard. 
 It is generally thought that nothing can represent a danger of 
 loss equal to the peril of oil drilling. The records mentioned 
 bear out the opinion, though in the main it is wrong. 
 
 After a region has been critically examined by scientific 
 
 69 
 
RECENT CONSTRUCTIVE LAWS 
 
 investigators, and its oil-bearing possibilites passed upon favor- 
 ably, test drilling carried on at the indicated locations under 
 the direction of competent managers and experienced oil drill- 
 ers, has been found to result in discovering oil in upward of 
 90 per cent of the tests. When such test drilling is done at 
 random, without the benefit of a favorable report from com- 
 petent advisers, the percentage of failures is probably greater 
 than 90 per cent. 
 
 Oil promotions which have been rife throughout the country 
 for a period of twenty years induced the enactment here and 
 there, and with commendable rapidity in logically located legis- 
 lative bodies, of various statutes looking to the protection of 
 the legitimate and the discouragement of the irresponsible 
 company promoter. While it appears that there are heard from 
 time to time certain criticisms directed at laws of the character 
 mentioned, it is the experience of the writer that almost in- 
 estimable good has been achieved by the efforts to curb useless 
 and unwarranted promotions, especially as applied to the oil 
 industry. 
 
 It will be seen that there would grow up around the condi- 
 tions which would evolve from the laws referred to, commonly 
 called "Blue-Sky Laws"; the industry of oil drilling; and the 
 province of the geologist as an economic factor in the business; 
 a situation which would include the State Department charged 
 with the administration of the law, the driller, promoter, and 
 the geologist, as parties to any new oil promotion. These con- 
 ditions have enforced a further necessity which has been taken 
 in hand by various organizations of professional geologists, 
 notably in the direction of formulating certain categorical 
 requirements antecedent to accepted professional standing. The 
 American Association of Petroleum Geologists is one of the 
 
 70 
 
GEOLOGISTS' ORGANIZATIONS 
 
 organizations of national standing; the International Geological 
 Society is another; the Southwestern Association of Petroleum 
 Geologists, largely devoted to interests lying within the Mid- 
 Coniinent, Gulf Coastal and Louisiana-Arkansas fields, is 
 another of local note. At this time a movement is under way 
 to organize the International Pacific Geological Society in 
 California, which should quite fully provide for adequate rep- 
 resentation of professional men of standing in the lands of all 
 Pacific Ocean shores. 
 
 Many of the State Universities have added teachers to their 
 Geological departments, and have greatly widened and ex- 
 tended the scope of the scholastic work, making special pro- 
 vision for classes in oil field examination. 
 
 It is by such processes that enterprise joins with learning in 
 developing sanely the leading economic resources of the coun- 
 try, and in doing so conforms to a liberal and intelligent appli- 
 cation of the laws governing the identification of funds for the 
 purpose. The results which have been accomplished by the 
 administrators of the restrictive statutes defining honest and 
 practicable promotions are as excellent as could be rightly ex- 
 pected from efforts undertaken during the formative stages of 
 such activities. Millions of dollars have been saved to specu- 
 lators by reason of such laws; and millions in addition have 
 been saved and will be saved to them when it is generally 
 known that geologists of standing and reputation work in 
 harmony with such State officers. 
 
 It appears practicable to suggest that amendments to the 
 laws mentioned in many of the States might be enacted to 
 include a 'complete and readily verifiable statement of the entire 
 purposes of the promoters, not only, but a copy also of a geo- 
 logical report upon the area proposed for drilling made by a 
 
 71 
 
OIL COMPANY PROMOTION 
 
 geologist of standing, all to be supplied to the administrative 
 department having charge of the province of the law. This 
 simple addition to the laws would in many cases operate to 
 prohibit drilling in new and untried regions where competent 
 knowledge of the formations and structure would perforce 
 advise against it. In addition, it would have the beneficial 
 effect of serving favorably the proper interests of legitimate and 
 honest efforts in opening new fields. 
 
 Quite often the very interesting question recurs that geolo- 
 gists might refuse to make investigations in regions known to 
 them to be wholly unfavorable for oil. Also, that they might 
 well withhold their professional services from men or companies 
 that cannot make a proper showing of intention and record. 
 Neither would be practicable or in good practice. The sur- 
 geon asks no questions with respect to the causes of injury 
 before operating, unless he knows that penal laws have been 
 violated; even then he operates and discloses the facts to the 
 authorities afterward. The lawyer asks no questions relative 
 to the standing of his client if the proper fee and a right issue 
 are offered, except that he really has knowledge of law viola- 
 tion. The subject is one of an ethical character, and must be 
 answered by the geologist as it is answered by men of other 
 professions; that is, Is the thing offered honorable and of good 
 report? The surgeon's knife has at times uncovered the seat 
 of trouble where it was not suspected, as the geologist has found 
 adequate evidences of oil accumulation in areas which he had 
 previously supposed to be unfavorable. 
 
 However, the fact must not be lost sight of that there is no 
 man of greater value to a community than a capable, conscien- 
 tious promoter. It is during the period only before success 
 has followed his efforts that his methods are questioned, or his 
 
 72 
 
CONDITIONS GROWING BETTER 
 
 objects and purposes are adversely scrutinized. After the in- 
 itial success, and after there develops from his activities profit- 
 paying, stable enterprises resulting in general good, is he 
 admitted to the inner circles of solid business. One should not 
 quarrel with that fact; it is a situation no amount of discussion 
 will change. There may be cases where the restrictions of the 
 laws and the regulations of commissions appear to render more 
 difficult the speedy accomplishment of a worthy promotion; but 
 it should be borne in mind that such conditions also operate to 
 remove from the field many who would take advantage of the 
 absence of such restrictions and such regulations. 
 
 During the past few years the writer has observed that there 
 is a rapidly growing sentiment among promoters everywhere to 
 more fully and definitely trim their activities to the strict ethics 
 of speculation, and to so order their promotions as to actually 
 give the people who supply the funds a square deal and a 
 clean run for their money. It has been noted further that few 
 will complain of having lost their money if they realize that 
 they have been treated fairly, and have had to contend only 
 with the hazards nearly always present in any enterprise which 
 offers the possibilities of very big profits in a comparatively short 
 time. It is when a stockholder believes he has not had an 
 honest chance that he will complain, and very justly so. 
 
 The blue-sky laws are day by day making it safer and 
 better for the honest promoter to successfully launch and com- 
 plete his enterprise, and day by day more difficult for the 
 unscrupulous promoter. 
 
 73 
 
LETTER FROM DR. GEORGE H. HOOK, GEOLO- 
 GIST, REQUESTING THE AUTHOR TO INCLUDE 
 CHAPTER IX IN THE BOOK 
 
 SAN FRANCISCO, CALIFORNIA, 
 
 FEBRUARY, 1922. 
 Dr. Edward Allison Hill, 
 San Francisco, California. 
 DEAR DOCTOR HILL: 
 
 The writer has been afforded great pleasure by availing him- 
 self of the privilege extended by you to read the proof sheets 
 of the entertaining and instructive matter in GEOLOGICAL 
 NOTES ON OIL STRUCTURES. 
 
 While the epitome of geologic history gathered into the brief 
 compass of an article written for the Fort Worth Star-Telegram, 
 which treats in a masterly fashion the fascinating subject of suc- 
 cessive formations for millions of years as they are found under- 
 lying Tarrant County, Texas, might not be thought cognate to 
 the matter of the book, it would be a real loss not to incorporate 
 that profound study as a part of your delightful analyses of earth 
 forms and oil structures. It deserves a place in a work of per- 
 manent value, and in that form it will add to the interest of the 
 reader while it impresses him with the knowledge that you are 
 in full possession of the abstruse as well as the simple elements 
 of your profession. 
 
 The writer adopts this opportunity of again expressing to 
 you his appreciation of the honor of reading your book before its 
 publication, and wishes to suggest that the layman will find in 
 your work a most pleasing, direct and forceful exposition of the 
 subjects treated. Interesting and instructive books are rarely 
 found which cover so fully and in such every-day language any 
 of the deeper and more technical aspects of the many departments 
 of any economic science; your book achieves such objects in a 
 very happy manner. 
 
 I have the honor to remain 
 
 Fraternally and sincerely, 
 
 GEORGE H. HOOK, 
 
 GHH-S Geologist. 
 
 75 
 
CHAPTER IX 
 
 (Requests of many friends of the author to include the fol- 
 lowing article is complied with. It first appeared in the Fort 
 Worth Star-Telegram, of Fort Worth, Texas, Sunday, May 8, 
 1921. Ed.) 
 
 TARRANT COUNTY GEOLOGICAL HISTORY 
 REVEALED BY DRILL 
 
 IN PERIOD OF 1 0,000,000 YEARS BOTH LAND AND SEA 
 EXISTED HERE SOME QUEER ANIMALS 
 
 By EDWARD A. HILL 
 
 DEEP well drilling in Tarrant County has revealed the geo- 
 logical structures upon which Fort Worth's skyscrapers 
 have been built as well as the prehistoric record of this section. 
 Cuttings through the various formations take us back ten 
 million years or more. 
 
 The sands, limes and shales that have been uncovered by the 
 drill in the Burchill well in Polytechnic recount eras of hot 
 deserts, the submerging of waters of cold and warm seas and 
 alternating ages of arctic, tropic and temperate climates. 
 
 Cuttings from the Aledo well and from other deep borings 
 in counties west of Tarrant supply evidence that monstrous 
 creatures roamed or waddled awkwardly over the land or slid 
 slimily into seas of an ancient world. These wells also tell of 
 profuse and entangled verdure. 
 
 76 
 
SEA LIFE CAME FIRST 
 
 No species of plant or animal ever has returned after once 
 it passed. Nature cleared the page as one erases figures from 
 a slate when once the infinite object of life was achieved. 
 
 First were the Azoic rocks, void of organism, lying doubtless 
 7,000 to 1 0,000 feet under the pavements of the city. No 
 drill near Tarrant has penetrated to their great depth. But 
 we believe they are there because in other places we find them 
 lying under formations which are here. Over Azoic are rocks 
 called the Proterozoic formations, which contain traces of 
 organic life. 
 
 SEA LIFE FIRST 
 
 After that are other series called Paleozoic rocks, meaning 
 ancient life formations. No hint of any land life has been 
 found in them. Evidently living organism passed all or nearly 
 all of its life in the waters that formed the seas of those ages. 
 
 The succeeding era was the Mesozoic, the last one before the 
 era in which we live, the Cenozoic. Some have liked to say 
 we live in the Quaternary. We live in the early part of the 
 Cenozoic probably the spring season of it. 
 
 At the opening of the Paleozoic we find the oldest known 
 normal fossils, and we know that they are at very great depth 
 under Fort Worth. Before that time billions of varied genera 
 and species lived in the waters. Throughout the last named 
 period, and in the Ordovician and Silurian, the two next suc- 
 ceeding periods, what we call Cystoids (stone lilies) grew in 
 the seas and upon their bottoms in immense profusion. Their 
 remains have in some places made great bodies of limestone. 
 Also there were marine scorpions not unlike their stinging pos- 
 terity of today, some of them attaining nine feet in length. 
 Fossils of the latter have been found in the limestones of Travis 
 County. In early Cambrian times nearly all of Texas was dry 
 
 77 
 
STRANGE ANIMAL LIFE 
 
 land. In late epochs of that period a sea covered the State 
 and adjoining regions. 
 
 ARMOUR BEARING ANIMALS 
 
 In sea life the mollusks and arthropods were legion. Trilo- 
 bites rolled up, unrolled and scuttled away from the bigger and 
 more active Cephalopods, other armour-bearing marine ani- 
 mals. Famous slate quarries in Wales and in New York and 
 other places are in rocks of Cambrian age. 
 
 Then came the Ordovician age (Lower Silurian), during 
 which the nearest land surfaces to what is now Tarrant County 
 were islands extending chainlike from Wyoming to Arizona, 
 and in what we know as the Ozark region in Missouri and 
 Oklahoma. A great authority has said that upward of 1 ,600 
 classified species of animals are known from the Middle Ordo- 
 vician alone. 
 
 In the Upper Silurian limestones we find that Crinoids be- 
 came so prolific that they formed veritable flower gardens in 
 the seas. Horned crawfish-looking fish, some with hook-shaped 
 beaks, were in the waters. Probably sharks of primitive type, 
 among the first vertebrates, were also in the waters. 
 
 STRATA HERE UNTAPPED 
 
 But none of the drills near Tarrant have penetrated to the 
 depths of the foregoing forms; nor have they reached the for- 
 mations made under a later and much more extensive sea, the 
 Devonian. Yet it is probable that in the midst of that period 
 the seas withdrew from a considerable of the land area of 
 Texas, and that Tarrant County and large adjacent regions 
 were dry land. 
 
 The seas of the Mesozoic era possibly came nearly to North 
 Fort Worth. Great fishes like sea cows ground their food with 
 
 78 
 
EARLY LAND AND SEA 
 
 a side wise motion of the jaws, gyratory, somewhat as cud- 
 chewing animals do now. 
 
 In the earlier period, the Mississippian, nearly all of North 
 America was submerged by waters. Drill holes not far from 
 Tarrant have penetrated to rocks of that age, hard, crystalline, 
 massive. 
 
 About 140 miles northward an island was formed then by 
 an upthrust of the strata, the upheaval releasing to the flood 
 vast quantities of sulphurous, iron-bearing waters. The Ar- 
 buckle mountains were made at that time. But before the end 
 of the period the waters withdrew from many localities and the 
 exposed rocks were denuded by erosion. We know that there 
 are hills, ridges, valleys and great tilted sub-surface areas that 
 were the result of the wastage wrought by the elements and the 
 buckling strata. The drills have shown this in many places. 
 
 MINERALS OF MISSISSIPPIAN 
 
 Many animals survived from the Devonian to the Missis- 
 sippian, and flourished throughout the latter, multiplying and 
 developing. Many and varied values of an economic kind are 
 taken from rocks of that age. Much of the oil in the Eastern 
 States and some of it in Kansas and Oklahoma come from for- 
 mations of that series. Vast quantities of salt are pumped 
 from them, and zinc and lead are found in their later members 
 in Missouri, Kansas and Oklahoma. Great cup-like, flower- 
 appearing corals of that age were in abundance. Ivory-like, 
 bead-shaped embedded heads of Crinoids, beautiful sea 
 growths of lime, are. nearly the entire component of many beds 
 of limestone of that period. Their growth must have been 
 widespread and excessive. 
 
 Of the vertebrates, the shark shows the greatest development 
 
 79 
 
COAL FORMING PLANTS 
 
 from Devonian times; it grew very big and was very fierce and 
 bloodthirsty, but without anything like a living man to eat. 
 
 In the Pennsylvanian period, the great middle series of the 
 Carboniferous age, we are nearer home as to depth, but long 
 ages removed in time. 
 
 It is near us in depth under our streets. If we were to dig 
 a hole fifteen times deeper than our tallest skyscraper is high, 
 the bottom might be upon the formations of Pennsylvanian age. 
 The waters over this region then formed great bodies of lime- 
 stone, shale and sand rock, beating for hundreds of thousands 
 of years against the walls of the Arbuckles, which were formed 
 in an earlier age 1 40 miles north of Tarrant County. 
 
 Plant life was far more prolific then than in any previous 
 period. Our present ground pines are direct lineal descendants 
 of plants of that age. Their ancestors we call Lycopods. 
 What are known as Equisetas, our present horsetails, growing 
 along creeks and ditches, were also representative of Lycopodian 
 vegetation. 
 
 SWAMP OF FORESTS 
 
 Over in the region of Bridgeport and in Palo Pinto County 
 and Jack, and in the numerous places where we now mine coal, 
 vegetable growth of the character mentioned must have been in 
 bewildering swamp forests. Our coal measures are made of 
 them and kindred plant life. What we call Cordaites grew 
 in swamp and marsh lands in impenetrable profusion, for we 
 find their remains in our coal bodies in vast amount. Some- 
 times they were 50 to 100 feet high, their diameters from two 
 to five feet, their leaves from five to six feet long and as many 
 inches wide. Certain of their species are called Sigillarians, 
 meaning seal-trees, so called because their trunks bore seal-like 
 impressions running spirally around them. 
 
 80 
 
MONSTROUS BEASTS 
 
 Now, at about the time of the ending of the period a vast 
 sea of blood-red waters came to the shores where Weather- 
 ford now is. We know its place in geological history as the 
 Permian period. The great ranch country of Texas is upon 
 earth deposited during that period. It was made throughout 
 a transition stage between the Paleozoic and Mesozoic eras. 
 Plant life was more scant, which means that animal life was 
 not so varied or so extensive as during the Pennsylvania!!. 
 
 True reptiles of monstrous size and great beasts which de- 
 veloped out of the lesser species of earlier times, were to be 
 seen along the shores of the red seas. The waters spread north- 
 ward as far as Idaho, southward into what is now Mexico and 
 westward to New Mexico. But it is not quite true to speak 
 of this widespread water as a sea, as it consisted of great lakes, 
 rivers, shallow and deeper bodies of water in its later epochs. 
 HEAVY, AWKWARD BEASTS 
 
 Where we now live, snake-like beasts with sharp teeth, long, 
 cumbrous tails and short, heavy legs, waddled in the soft muds 
 of the shore and over the semi-arid lands. Upon the bottoms 
 of the water bodies, as well as during the following periods, the 
 Triassic and Jurassic, great deposits of gypsum and salt and 
 dolomite were made. We are plastering and whitening the 
 walls of our homes with the first, sometimes building them of 
 the last and seasoning our food and feeding our cattle with the 
 other. 
 
 The Permian period ended with a great physical disturbance. 
 What is called the Appalachian Revolution occurred then. By 
 its action there were bofn the mountains of that name in Eastern 
 United States, and the Ouchita Mountains of Oklahoma and 
 Arkansas were then strung in zigzag along the horizon to define 
 Homer and Caddo and other oil fields. The region of Tarrant 
 County remained dry land. . 
 
THE FIRST BIRDS 
 
 ANIMALS OF PERMIAN AGE 
 
 Though the animals of the Permian were often clumsy, 
 clinging to and bending down the branches of trees to eat the 
 foliage ; in the Triassic and Jurassic, they were huge and fierce. 
 The nearest shores of the Triassic sea were about the vicinity 
 of Bluffdale, and some of the blundering creatures with arm- 
 like, nimble front legs, doubtless had habitat where now flows 
 the Paluxi River. Mostly the land surfaces in the southwestern 
 regions of the United States were desertlike during that period, 
 the climatic conditions arid. Yet in Arizona, in what we call 
 the Petrified Forests, there are tree trunks 100 feet long and 
 ten feet in diameter, dating back to the Triassic. Such trees 
 grew near water or during a less dry epoch. In Erath County 
 not more than forty miles from Forth Worth there are great 
 tree trunks, silicified, heavy, solid rock, that are part Cretaceous, 
 but probably also part Triassic. What we know as Cycad 
 trees grew then as they now grow in Mexico. 
 
 FIRST FEATHERED BIRDS 
 
 The first feathered birds known to the earth came then. 
 There had been great flesh-eating, ravenous, smooth-skinned, 
 birdlike reptiles, reptilian-birds, in the world for long periods, 
 but no feathered songsters. Moisture increased during the latter 
 'part of the period and the balmy air and greater dampness 
 clothed the vast Western and Northwestern plains with verdure. 
 
 In excavations for our tall buildings, in the railway cuts, 
 along the deep channels made here and there by Trinity River, 
 are to be seen the layers of rocks of Cretaceous age. Towards 
 the Gulf of Mexico these rocks are covered by formations of 
 later periods. At Galveston, drills have shown that there are 
 later deposits of 3,000 feet in thickness. Though our homes 
 
 82 
 
SOME TEXAS FORMATIONS 
 
 are built upon the solid foundation of the Cretaceous period, 
 we are surely removed from it by something like a million years. 
 
 Throughout the period there was an extensive sea connecting 
 what are now Gulf waters with the oceanic basins of the Arctic 
 region. Tarrant County is about 1 40 miles south of its north- 
 eastern shores, which bent northwesterly and then northward 
 toward the pole. Under that water in this area thick sand 
 deposits were put down. We know these deposits as the Trinity, 
 Woodbine and other sands. Afterward were earth movements 
 which depressed the bottom of the sea and limestones of great 
 thickness were deposited. We call that the Fredericksburg 
 lime. Later, what we know as the Austin chalk was put down, 
 far from shore. Its purity and freedom from wastage carried 
 away from land masses prove that. 
 
 CRETACEOUS OIL 
 
 In the Cretaceous much oil and gas have been found, and 
 without question vastly greater quantities will yet be developed. 
 The fields at Beaumont and Corsicana, and later at Mexia, are 
 producing from rocks of that age. Some have thought that 
 there are very good reasons for believing that profitable fields 
 will be found in formations of that age near Fort Worth. 
 
 What is called the Rocky Mountain Revolution occurred 
 during the ending epochs of the Cretaceous period. The fold- 
 ing and the buckling of the rocks of western North America, 
 the Isthmus and South America happened then. The turmoil 
 traveled from Alaska to Cape Horn, in some places upturning 
 strata 20,000 feet in thickness. Mountain chains were made 
 with peaks sometimes as' much as fifteen miles high. 
 VOLCANIC ERUPTIONS 
 
 Far towards the northwest was a red flare of light reflected 
 by the dust-filled air near where are now Rabbit Ear Mount- 
 
 83 
 
GREAT ANCIENT SEAS 
 
 ains in northern New Mexico. There were volcanic eruptions 
 near there then. The Black Mesa is there today, a lava flow 
 formation. 
 
 At that time Tarrant County was covered with sea water, 
 but it was not very distant from the northerly shore. The 
 whole firmament was filled with fine, suffocating dust, blown 
 about thousands of miles by the contrary and shifting winds. 
 The logs of wells have disclosed such conditions. 
 
 The eruptions continued throughout the succeeding period, 
 the Tertiary. The infusion of volcano waters and gases into 
 the seas, and the breaking up of the solid foundations of the 
 earth in so many places and at such widely separated localities, 
 resulted in great changes in the existing forms of animal and 
 vegetable life. 
 
 At first Tarrant County was some 300 miles north of the 
 more northerly shores of the Tertiary waters. Later it was 
 about midway between a great epicontinental sea toward the 
 northwest some 250 to 300 miles, and another southeasterly 
 nearly an equal distance, but the area of Fort Worth was land. 
 To be sure it was a land of many lakes and rivers, marsh and 
 swamp and slough and embayment, a soggy land. Also, it 
 was a warm country. Fossils are in abundance and are satis- 
 fyingly accurate in denoting a warm climate even to the north- 
 ern boundaries of the United States. Figs, palms and magnolias 
 grew over the Great Plains. 
 
 LIFE FORMS CHANGE 
 
 But all life forms had undergone bewildering changes. 
 Many forms took on grotesque shapes, struggling with the sul- 
 phurous waters and the gaseous air to adapt themselves to 
 swiftly altering conditions. 
 
 What we now know as the Glacial periods fell athwart the 
 
 84 
 
PAST AGES OF ICE 
 
 hemispheres during the times named. During a part of the ice 
 epochs we know that the ice sheets extended as far south as 
 Texas, and irregularly to about that latitude across the con- 
 tinent. Across Northern Kansas and in Illinois and Indiana, 
 where the debris is accumulated in most pronounced dunes, 
 terraines, ridges and mounds, we easily and certainly trace the 
 approximate southern margin of the vast ice sheets. Their 
 melting dropped down boulders and gravels carried in the ice 
 from Labrador and Greenland and from other far northern 
 Laurentian rock lands. 
 
 The last glaciation was something like 35,000 years ago. 
 It had a relaxing effect upon the meteorological conditions of 
 Tarrant County. The climate was temperate and every variety 
 of vegetation multiplied and increased. Probably it was earlier 
 than the last epoch that Mastodonic tribes of great beasts, called 
 proboscidians, roamed about in the thick wooded bottoms of 
 the Trinity, the Brazos and the Colorado Rivers. In the 
 Carnegie Library at Fort Worth are a pair of ivory tusks that 
 were found in a gravel pit southwest of the city a few miles. 
 These are but a specimen among many that are like, and very 
 many that are different, which represent other parts of the 
 skeleton build of these and other great animals making their 
 homes in Texas then. 
 
 85 
 
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 UNIVERSITY OF CALIFORNIA LIBRARY