Ji^. ^:i^ IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I 1.25 1^ 1^ 1 2.2 1.8 U il.6 V] vQ (?5 # V O 7 '^ > / / /A % «!• CIHM/ICMH Microfiche CIHM/ICMH Collection de microfiches. Canadian Institute for Historical Microreproductions Institut Canadian de microraproductions historiques 1980 Technical Notes / Notes techniques The Institute has attempted to obtain the best original copy available for filming. Physical features of this copy which may alter any of the images in the reproduction are checked below. L'Institut a microfilm^ le meilleur exemplaire qu'il lui a 6t6 possible de se procurer. Certains ddfauts susceptibles de nuire d la quality de la reproduction sont notds ci-dessous. D D D D Coloured covers/ Couvertures de couleur Coloured maps/ Cartes gdographiques en couleur Pages discoloured, stained or foxed/ Pages ddcolordes, tachetdes ou piqudes Tight binding (may cause shadows or distortion along interior margin)/ Reliure serri (peut causer de I'ombre ou de la distortion le long de la marge intdrieure) n n Coloured pages/ Pages de couleur Coloured plates/ Planches en couleur Show through/ Transparence Pages damaged/ Pages endommagdes D Additional comments/ Commentaires suppl^mentaires Bibliographic Notes / Notes bibliographiques n D D D Only edition available/ Seule Edition disponible Bound with other material/ Re\\6 avec d'autrrts documents Cover title missing/ Le titre de couverture manque Plates missing/ Des planches manquent D D D Pagination incorrect/ Erreurs de pagination Pages missing/ Des pages manquent Maps missing/ Des cartes gdographiques manquent D Additional comments/ Commentaires suppldmentaires The images appearing here are the best quality possibie considering the condition and legibility of the original copy and in keeping with the filming contract specifications. Les images suivantes ont 6t6 reproduites avec le plus grand soin, compte tenu de ia condition et de la nettet6 de I'exemplaire film6, et en conformity avec les conditions du contrat de filmage. The last recorded frame on each microfiche shall contain the symbol ^^> (meaning CONTINUED"), or the symbol V (meaning "END"), whichever applies. Un des symboles suivants apparaTtra sur la der- niAre image de cheque microfiche, selon le cas: le symbols — ► signifie "A SUIVRE". le symbols V signifie "FIN". The original copy was borrowed from, and filmed with, the kind consent of the following institution: National Library of Canada L'exemplaire film6 fut reproduit grAce it la g6n6rosit6 de I'dtablissement prdteur suivant : Bibliothdque nationale du Canada Maps or plates too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes ou les planches trop grandes pour dtre reproduites en un seul clichd sont filmdes d partir de I'angle supdrieure gauche, de gauche d droite et de haut en bas, en prenant le nombre d'images ndcessaire. La diagramme suivant illustre la m6thode : 1 2 3 1 2 3 4 • • BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA Vol. 6, pp. 297-304, pls. 13-15 HONEYCOMBED LIMESTONES IN LAKE lUIRON BY ROBERT BELL ^ \ .-?■--■' ROC ULSTER PUnLISIIEI) BY THE SOCIETY Makch, 1895 BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA Vol. 6, pp. 297-304, PIS. 13-16 MARCH 25, 1896 IIONEYCOMREI) LIMESTONES IN LAKE HURON BY IWnKKT niCLL (Read before ihe Society December 20, ISOJf) CONTKNTS Area of oocui ronop and conditions 2!)7 Pliywical characteriKtics of {\w orodt'd rocks 2!>S As^c and attitude of the eroded rockH . . 21M) Jlronion forms in relation to variety of rock 2^X) Possible oriijins of the erosion .'100 Itorinjis of niolhisks .">ther until oidy thin walls remain between tliem. while others coalesce, and ultimately the whole mass becomes separated into a highly erodell>-l']\M. l''ii;i i;i J— N'litt m - \ mi Spi ■ nil \ \\ \\ .\\i.m ^i 1..'i,i im:. Hi I' ii vni-:. HDNtVCOMBtD DiiLOMITE. l-'rom ."iollth r,;iy Mnulll. M:ilKltimllll l-l.-llhl. I llllirin, (■.■ill;iil:l I BULL. GEOL. SOC. AM. VOL. 6, 1894. PL. t4. a^ ■■ ^ 'Hi^--?^U' sS '^^"^ BP^mB ^^^^£SiP ■ \> W^ ,.^^^Kw'j ^8K ' ''* ^itKfj^ \ • w" > *-*^^i^^ I'i'.i HI-, 1. \'ii;\\ iT I M>n: ~mumi \i v i.'I'.iii .\\..ii. iw iiii. l>ih-ri»M;. '"I'.i III 1. -\irw "I' -iMi ■~1T'LMIN \\ \\ As'.i.t. ni I') II. IIII r>i ii-ri \\r.. PiTTCtJ LIMESTONE OF THE BLACK RIVER FORMATION. [■'I'l'in l.ittlr (liHlir l«;;iii,l, I iiii:iri,,. (^ihaiJM. CIIAUACTEUISTICS, MiK AND ATTIirDK. 21)5) Tlii.H variety of deeply pitted surfaec rcHemltkw limestone wlii(;li has been tlioniiijilily riiMled liy the l>urn»\v.s itf Sdrirani. In a well marked ease, to lie airain noticed, where a suhmerj.'ed shelf or hani,dn^ ledj^e was ero(led on the und''r side, the pittinji look the form hero deseril>ed. It is well shown in (ignres 1 and 2, plate 14. A(ih: ANM ArnTrDK ok rnK i:Koni:i) Rocks. The rocks of (irand Manitoulin and the adjacent islands end)race eij.dit dill'erent formations, from theChazy, in the nortliern partofthe La Cloche island, to the (lUelph, on Fitzwilliam island and on the southeastern part of the main island, wiille dolomites of the Huronian systen) are met with on many of the islands of the channel hetwecn the Manitoulin chain and the nnvin north shore of lake Huron. TlKiChazy is rci)resented l»y iirownish red and green marls and line grained white sandstone; the Black River consists of pure limestone and yellow weathering dolomites ; the Trenton priiicMpally of hluish gray limestone, with earthy beds; the litica of Mack hituminous shale; the Hudson Iviver of marls, with thin iteds of limestone and sandstone; the Clinton of dolomite, with bright red and green marls at tlie base, while tlu; Niagara and (iuelph forma- tions are couiposed almost entirely of dolomites. The dip is 'uiiforndy to the south, at a very low angle, and the nakeil beds of the higher forma- tions al»ove en>imerated slope gently undisr the lake along the southern sides of all the islands of the Manitoulin group. Euosiox Forms iv Rki.atio.n to Vahiktv ok Rock. The largest and most irregular cavities are in the magnesian lime- stones of the (lUelph formation. Their appearance //; ailn is shown in l)late 1"), w'lich is from a photograj)!!. The globular and pear-shaped varieties, shown in figures 1 and 2, i)late 13, are excavated in somewhat argillaceous dolomites of the Niagara and Clinton formations. The cup- shaped hollows are conunonest in the pure limestones (jf the Hudson River. Trenton and Black River and in tin,' dolomites of the last men- tioned tbrmation. The finger-shaped honeycombed structure was found principally in the pure limestone of the Jilack River formation, while the smoother and rather larger excavations are characteristic; of the Huronian dolomites. Tlu; shallower varieties of this form >if pitting resemble that of a well eroded aerolite. Tlie occurrence of these various forms of hone3'combing and pitting in such a variety of limestones and dolomites in this portion of lake Huron proves that the phenomenon is not due to anything unusual in the general composition or to any ch''mi(>al pecu- liarity of a particular variety of rock, but to some outside cause. The various forms which the erosion takes, however, show a slightly une(|ual solubility connected in some way with the internal structure of the rock; i 300 IJ. I!i:i,[, — IIONKYCOMnKI) LIMKSTON'KS FN I.AKK HURON'. otherwise it would he of a mon; uniforiu chivnicter, .since it is tliie to some coinmon extoniiil cause operatiujr alike upon them all. The (lissolviuff of the unaltered limestones or dolomites e rocks are practically horizontal, never at an ohli(piu an;j;le nor horizontally, which, in the ahscnco of some inhihitinj; cause, mi made in rocks hy horing mollusks, such as Saxlatra, Phobti^, Pdricntd, Vallisin^ Tapex^ Vnicnipix and I .'lUiodnmnx. The case of tht; zones on the niarhle pillars of the temple of Jupiter Serapis, at I'uzzuoli, eroded hy lithodomi, > o D > D I C n -< o o iS CD Fl O O H m I n (T, c c z CD C Q m O p en O O < o 00 to yi I'OSSinLK ORIGINS OF TIIK EROSION. 301 whicli has been remlercd clasnic by Lyell in his " Principles of Geol- ogy," will occur to every geologist. The cavities formed by boring nioUusks are, however, burrows which are of pretty uniform calibre, or increase in diameter with the depth, owing to the growth of the animal as it proceeds. They are generally many times deeper than wide, whereas those under consideration are either globular or short by comparison, and they contract instead of enlarge toward the bottom. ACTION OF SroyOES AND ALOJE. A small sponge, Cliona cclatn, makes burrows in the shells of oysters, and this fact led to the supposition that possibly some species of fresh- water sponge might have aided in deepening or enlarging the cavities under discussion, or in determining their form by the production of small quantities of an organic acid, either during life or upon decompo- sition, but no evidence could be found in support of this idea. The re- mains of branching fresh-water alga? may be seen in some of the cavities, but they do not appear to have exercised the least influence in their l)roduction. The lower or jelh'-like algai of fresh water do, however, possess the power of dissolving limestone. The journal of the Royal Microseo})ical Society for October, 1894, says, on page 597, that — " ProfoHHor F. Cohn i)oint8 out tlie important part i)laye(l by very lowly organ- ized aljiii' — PhycochroinaooiC and Cyanophycoje — in the formation of calcareous and KiliciouH rocks. Many beds of marl)lo and travertine liave heen formed in this way. He furtlier enumerates the algje that are known to de.stroy calcareous rocks by erosion. In all fixed liV^ve there appears to ))e this contrast between the basal cells and the rest of the Hlament; that the former excrete an acid which dissolves lime, while the laiter has the power of depositing a soluble lime-salt be- tween the iilaments, but within the mucilage which is e.\creted from the sheath." WEARING ACTION OF PEDDLES. A i)opular notion current among many of the residents of the localities where the pitted surfaces occur is that the cavities have been worn by the whirling of itebbles and sand in a maimer analogous to the forma- tion of potholes at rapids and falls. That they have not been thus formed is obvious from the following reasons, selected from among others: Their sha])es do not corresi)ond with this mode of formation. They occupy the whole surface of the rock, whereas iwtholes occur at irregular int(;rvals. The walls of the cavities are generally uneven or rough, and delicate silicified fossils often project from them or stretch completely across the cavities, whereas the wearing action of rotating pebbl(\s and sand would have produced smooth and cylindrical walls. No pebl)les are ever found in tluMn except such as can be shown to have been placed there subsetiuent to their excavation. If these cavities 302 R. 15KLL — HONEYCOMIJliD LIMKHTONKS IN LAKK III'IIOX. had ])een due to tliis rauso, tluiir occurronco would uotbo coufincMl to tlie liiuestont's of lake Huron, l>ut would l>o a rob- able that the cause will be found in the dillcrcntial solubility of t\u) rock in the water of the lake itself. The slight difference in the solubility of those parts of the rock which give rise to the cavities is likely due to its internal structure, which originated, in the first place, at the time of the formation of the limestones or dolomites themselves. The eroded beds are not generally those which are largely made uj) of organic remains, but oftener those which have been due to chemical precipitation. Then^ are, however, excei)tions to this general rule which add to the difiiculty o*' accounting for this singular i)henonu'n()n. In the process of consoli- dation of chemically formed beds in which Hiik;, magnesia and argilla- ceous matters were present, there would naturally be more or less tend- ency to concretionary action around certain points or centers, thus giving ris(! to slight differences in composition. Kvcn if such cotKtretionarv structure were too obscure to be readily noticed, the probability of its existence in the rocks of the al»ove composition will be readily admitted ; but in some cases, especially where oxide of iron is present, this structure may be detected in the form of obscure concentric lines. The globular shape of the cavities is a fact which points to this origin. Hut, if this bo true, it may be asked, why are similar linu!stones not always eroded in this maimei when they are covered by fresh water? The ijxplanation of the difference is probably to be found in a sufficiently acid condition of the water of this part of the lake to slowly dissolve the limestones. ACID WATKR AND ITS KFFECTS. 303 The solvent action of tlie sliurposes. A new tin pail, if kept filled with the lake-water, will in a few days show rusty excrescences in the bottom, which increase rapidly and soon per- forate the vessel. Tlie water of the portion of the lake where honeycoml)- ing of limestones is most obvious is distinctly harder than elsewluire, probably owing to the ])ressure of sulphate of lime. 'i'he source of the sulphuric acid may be looked for in the Huronian rocks lying to the nortlnvard of the lake. It is nMuarkable that tlie por- tion of the lake in whicli this form of erosion of limestt)ne takes place lies directly in front of that part of the north shore occupied by the Huronian rocks, and receives several consideral»le rivers which drain an immense area of rocks of the same age. They are mostly of volcanic origin and arc rich in sul[)hi(les, whereas all the other rocks around the lake are comparativel}' free from them. Sulphides of several metals, but especially of iron, are disseminated through most of the Huronian rocks. Pyrites and pyrrhotite are par- ticularly al»undant in the greenstones, and these form a considerable j)roportion of the series. The two suli)hides referred to occur both as disseminated grains and in the form of numerous masses, some (juite large, such as those around Sudbury, a few of which are being worked for nickel. The decomposition of these sulphitles upon the surface of the rocks and along their fissures and joints produces iron-sulphate, which is carried away by the streams, where its ])resence is fre(]Uently shown by the i)recipitation of a part of the iron. In the swamp at the Murray mine near Sudbury, where a large mass of pyrrhotite and dial- 1 304 K. BKLL — HONICYCOMBED LIMESTONES IN LAKE HURON. copyrito comes to the surface, the i)resence of acid sulphate could be detected by the taste of the water, and when the latter, containiufi; as it does vegetable matter also, was used experimentally for the boilers, it gave off a most offensive smell and had a very corrosive eff'ect. The streams of the whole of this Huronian region no doubt receive many contribu- tions of acidulated water from similar sources. As the decomposition of the greenstones and other pyritiferous rocks, and also the oxidation of the drift materials derived from tliena, j)roceeds, the quantity of acid derived from them and carried into the northern part of lake Huron will increase. At The Narrows between Cloche peninsula and Little Cloche island, as already mentioned, the pits in the soft argillaceous grey limestone are surrounded by a zone stained by iron oxide. This is just what might be expected to result if such a rock were being slowly dissolved by iron-sulphate and, therefore, this fact helps to support the present hypothesis. Tiie fresh rock-surfaces and uuoxidized drift left at the close of the Glacial epoch would produce a much smaller proportion of sulphuric acid in a given time;, and we therefore supi)ose that the erosion of the limestones in the bottom of the northern part of lake Huron went on even more slowly then than now. Another example may be cited here of water containing sulphuric acid which has been derived api)arently from volcanic rocks. A sample from the shallow fresh-water in the estuary of the Nelson river, Hudson bay, was taken by the writer to the late Professor William Dittmar, the well known authority on water analyses, and he found it to contain no less than 4.73 grains of sul()huric acid to the imperial galhju.* The source of this acid appeared to be the drift-material which had come from the volcanic rocks of the central or eastern part of the bay. Conclusions. The conditions which have contril)uted to the production of the pecu- liar forms of erosion al)Ove described ai)pear to have been : 1. The internal structure of the limestone itself. 2. A small {^upjitity of acid in the water acting for a great length cf time. 3. A considerable depth of water, the hydrostatic pressure seeming to promote the dissolving of the rock. 4. Freedom from sediment during the long time required. 5. The rock must be exposed to the open or free action of the water. 6. Shifting currents in the water would also appear to assist the process. •See Appendix V, Report C, of the Cniuuliiin Geological Survey for 1879-80, p. 78.