BULLETIN I OK THE '' MUSEUM OF COMPARATIVE ZOOLOGY HARVARD COLLEGE, VOL IN CAIMBRIDGE VII (Geological Series, CAMBRIDGE, MASS., 1880-1884 I.) U S A University Press: John Wilson and Son, Cambridge +.7 ^^^" CONTENTS No — Notes on the Geology of the Iron and Copper Districts of Lake SupeBy M rior No E "Wads WORTH — The Felsites and their (6 Plates) By Associated Rocks, North of Boston J S DiLLER No No No — Observations G C E By M E Wadsworth By M E Wajjsworth (2 Plates) 189 the Museum Col- 225 Great Dike at Hough's Neck, Quincy, Mass By Joiix Eliot Wolff No — On 231 some Specimens of Permian Fossil Plants from Colorado By Leo Lesquereux No 243 — On the Relations of the Triassic Traps and Sandstones of the Eastern United States No 10 — The By "William Morris Davis 11 — The (3 Plates) Folded Helderberg Limestones, East of the "William Morris Davis No 183 upon the Physical Geography and Geology of Mount Hamlin By Leo Lesquereux — The 181 the Iron Ore, or Peridotite of Iron-Mine — Report on the Recent Additions of Fossil Plants to lections No By Maine in Cumberland, Rhode Island Ktaadn No 165 — On an Occurrence of Gold — A Microscopical Study of Hill, Page Azoic Catskills .249 By 811 (2 Plates) System and its "Whitnet and M E "Wadsworth Proposed Subdivisions By J D, 331 CONTENTS Page INTRODUCTION THE IRON DISTRICT 1-76 Historical 1-26 Historical Summary 26, 27 ]\Iethods of Observation 27, 28 The Jasper and Iron Ore The Basic Intrusive Rocks, 28-36 Schists, and Felsite 36-49 " Soft Hematites " 49-52 Granite, Gneiss, and Quartzite 52-60 Potsdam Sandstone 60 Peridotite and Serpentine 60-66 General Discussion and Results 66-76 THE COPPER DISTRICT Historical Summary The Traps 76-132 76-107 Historical 107-109 , 109-113 The Sandstones and Conglomerates 113-122 The Veins and Copper DntosiTS 123-127 Conclusions 127-132 BIBLIOGRAPHY 133-157 DESCRIPTION OF THE PLATES 159-164 (^i^^ No — Notes on the Geology of the Lake Superior There By M Iron and Copper Districts of E Wadsworth are probably no regions of like extent in the United States that have attracted greater interest or attention than the Copper and Iron districts of The most discordant views have been held Lake Superior concerning their geology, and the origin of their ore deposits are also probably no districts in this conntry which have been There more accu- rately studied, taking all of the conditions into consideration, than these The were some thirty years ago geolog}-, including the origin of their ore deposits, was then, for the time and methods of study, stated with a remarkable degree of accuracy, so far as observe or judge would It these districts, wei'e is has been our province to duty to write concerning not that the almost universal belief of geologists it at the present time regarding one, and in trict, it not, then, be our some respects the other diswe interpret them so entirely at variance with the facts as Before giving the facts it is necessary to present to the reader some of the various ideas held regarding the geology of both districts We shall, however, in the main confine ourselves to those parts which we have visited, except so far as observations elsewhere have a bearing upon our work, or upon the questions which we wish to discuss It seems best to take up these views in chronological order, even does impart a dictionary flavor to this paper if it Fii'st in order, then, we propose to discuss The Iron The earliest writer that it is District necessary to quote Schoolcraft, whose Narrative Journal of Travels, etc here is Henry R was published at Albany in 1821 He speaks of the granite at Granite Point (p 158), and of its being traversed by veins of greenstone trap He gives the composition of the former rock, and advances his reasons for considering that it occupied lying sandstone present position before the deposition of the over- its He although he thinks " * old red sandstone.' VOL VII — NO does not attempt to give the age of the sandstone, its position would indicate a near alliance to the " BULLETIN OF THE Dr Douglas Houghton, in his Report on the Geology of Michi- first gan, remarks upon the " appearance of primary and trap rocks forming mountahi chains, and the great disturbance which has taken place since the deposition of the red sandstone," and says that this sandstone in the vicinity of Granite Point is "scarcely disturbed, resting upon nobs of primary rocks." * In Dr Houghton's Fourth Annual Keport, primary ones, con- for 1841, t the rocks of this region are described as and greenstone with sisting chiefly of granite, sienite, sienitic granites, metamorphic rocks on their forming a flanks, stratified series consist- ing of " talcose, mica and clay slates, slaty hornblende rock, and quartz rock ; the latter rock He the whole group." by constituting far the proportion of largest considered that the granite passed "almost sensibly into a serpentine rock." (/ c, p in- In like manner, he 482.) thought that the granites on the southeasterly side of the district changed going northwesterly into a greenstone, and that the dikes traversing these granites were identical with the greenstone, having been His serpentine bears a close resemblance to injected into the granite greenstone, and he states that " possibly a more close examination show it age of the slate rocks." (/ " This point of land has its Regarding Presque c, p 494.) The trap to sixty feet in height it Isle he says origin from the simple elevation of a trap rock, which rises on the north in abrupt of may to be a simple series of dikes, lying parallel to the line of cleav- is cliffs, : mass of varying from twenty mostly greenstone, though portions are so largely impregnated with a dark-colored, almost black ser- pentine, as to deserve the luider consideration is name The knob of serpentine rock possessed of additional interest, of trap from the un- manner in which these The cliff's of trap occupy the very extremity of the point, while the neck and central portions are made up of conThese glomerate or trap tuff" and sand-rock, resting uiwn the trap upper rocks also appear upon the immediate coast, in cliffs of from equivocal evidence of uplift, as also from the evidences are exhibited twenty to sixty directly feet in height, upon the has been very trap much The disturl)ed, and line of junction, is many The character * History t Joint is, sedimentary rocks dip, at a high angle, of both rocks, at the lost, and the evidences But the most curious feature almost completely of change most unequivocally marked of the wdiole places they are seen resting and they invarialdy in all directions from the trap itself immediate in stratification of these that the sedimentary rocks, for a distance of several of Michigan, by J H Lannian, (New York, Documents, Michigan, 1841, pp 471-607 18-39,) pp 348, 352 MUSEUM OF COMPARATIVE ZOOLOGY hundred feet, have been completely shattered or broken into minute fragments, which, having retained their original position, were again This injection has cemented by the injection of calcareons matter the most minute fissures, and so perfect is it, that, in looking the face of a mural may be filled many a distance of the and cliff, contains so forming, as i-ods, minute is it, many hundreds In this Report He have seen of Rocks," latter of these rocks, the veins cliff ** is the of these veins." first {I all is it does not appear in any one point that has been examined, to be of (/ c, p 504.) Report some remarks were In Dr Houghton's Fifth this district Regarding the abundantly disseminated the rocks of the metamorphic group, and upon the copper importance w^as added.* district, River, made both but nothing of special Mr George N Sanders, in a report to the Office,t speaks of collecting " rich Menomonee specimens of iron ore In the same documents for 1845 - 46 ;}: " on are given reports for the year 1845, by William A Burt and Bela Hubbard § Hubbard we in this district that scaly red oxide of iron" and " hscmatite." practical importance." Ordnance c, p 492.) mention of iron ore gives amongst the minerals of the " Metamorphic group sufficient quantity, at the were, a complete net-work over that a single hand specimen frequently he says: "Although the htematite through upon it upon easily seen at Mi\ evidently considered that the ridges in the Marquette Iron District were composed in the centre of eruptive rocks, but not outcrop- "capped as well as flanked by the metamorphosed rocks.' in regard to the metamorphic rocks that "these rocks are ping, being He states throughout pervaded by the argillaceous red and micaceous oxydes of iron, sometimes intimately disseminated, and sometimes in beds or veins These are frequently of so great extent as almost to entitle them to be considered as rocks The largest extent of iron ore noticed is in township 47 north, range 26 west, near the corners of sections 29, 30, 31, 32 There are here, too, large beds or hills of ore, made, up almost entirely of granulated, magnetic^ and specular iron, with small quantities of spa- those and micaceous iron The more northerly of these hills extends in a direction nearly east and west, for at least one fourth of a mile, and * Joint Documents, Michigan, IS 42, t Senate Documents, 28th Cong } pp 436-441 2(1 Sess., 1844-45, XI., Doc 175, p 11 29th Cong 1st Sess., VII., Doc 357 § See also Senate Documents, The Mineral Region 1846,) pp 3-39 of 1849-50, 31st Cong 1st Sess., III 802-842, and Lake Superior, by J Houghton and T W Bristol, (Detroit, BULLETIN OF THE has a breadth less little than 1,000 feet, the whole of which forms a single mass of ore, with occasional thin strata of imperfect chert and dips north 10 degrees, east about 30 degrees At its southerly outcrop, the ore is exposed in a low cliff, above which the hill rises to the height of 20 or 30 feet above the country on the and jasper, ore here exhibits a stratified or laminated structure, The south and manner as will greatly facilitate the operation of quarrying or mining the ore This breaks readily into sub-rhomboidal fragments, in such a bed of iron any known will in compare favorably, both our country." for extent The sandstone (p 22.) and is quality, with said to be found frequently "surrounding, and in contact with, the uplifted masses of igneous rocks, and and textiu'es, is then invariably much altered both in appearance and may, under such circumstances, metamorphic." (p fairly be considered as 23.) In the report of Mr A B Gray to the Ordnance Bureau,* galena and copper pyrites were said to exist quite abundantly, and that Mr Samuel Peck able that rich tin ores would be found having first is it was prob- credited with explored the iron region, and called attention to the exist- ence of that mineral {I c, pp 15, IG) in the vicinity of the Chocolate and Carp Rivers (Hvironian of Brooks) were " the equivalents Prof H D Rogers t stated that the rocks undoubtedly of the Primal sandstone and Primal sandstone of the New York slate," or the Potsdam survey Mr William A Burt, in his report " with reference to mines and minerals for 1846,":}: (pp 849-852,) described "fourteen beds of magMr Bela Hubbard in his report for the netic iron ore " in this district 901 - 905) advances some views upon the passage of one rock into another, as follows " A feature peculiar to all the rocks of same year {I c, pp : the country alluded to as granitic, and the rare occurrence of mica is their occasional trappose character, The which vary extremely sienite, stone, ; the proportions of Thus, while the general character that of true while frequently the last-mentioned mineral predominates almost which a crystalline structure, and usually has a slaty cleavage * Executive Documents, Am 29tli is generally of Again, quartz Cong 1st Sess.,.Vol VII., No 211, 1845-46, pp Jour Sci., (2,) Vol V., 1848, p 151 t Proc Bost See X is the absence of quartz in a distinct form often produces a green- exclusively, constituting a true hornblende rock, 2-23 make up the constituents which greater part are quartz, felspar, and hornblende Nat Hist., April 1st, 1846, II 125 Senate Documents, 31st Cong 1st Sess., 1849-50, III 371-935 BULLETIN OF THE 320 places so nearly in contact, and unconformable, as to leave scarcely a and they are so (p 374) doubt that they were really unconformable" shown in his section on Esopus Creek (PI ; 7, fig here 9, may have been author suggests that the Hudson series fig 9) disturbed the ; first only to the east of the " anticlinal axis," and, later, to the west with the overlying formations (p But 374) his section (PI 38, fig 14, here 10) at Catskill shows conformity fig Second Annual Report on the Geological Exploration H D, Rogers Harrisburg, 1838 The sandstone and conglomerate of IV (Oneida and Medina) are " displayed near Rondout, of the State of Pennsylvania resting unconformahlij and with a gentle inclination upon the steeply uptilted, contorted, slates" and disrupted strata of the immediately subjacent In Pennsylvania, the conglomerate at the base of IV (p 37) contains fragments of the three earlier formations, showing a violent physical change The same but no unconformity was noted there ; (p 36) the Correlation of the North American and British On Palaeozoic Strata Brit Rep., Assoc "Undulated 1856 (178-180) Matinal rocks support horizontal Niagara or Scalent strata, with a lapse of two intermediate formations for some distance from the Hudson, westward along the base of the Helderberg range." (p 178.) In the Mohawk valley, these formations approach conformity South westward to Alabama there a violent change strata ; is neither lapse of formations nor unconformity, but in the rocks in passing from Hudson River to Medina the latter contain fragments of earlier formed layers The same Geology of Pennsylvania, 1858, Gaspe on the Gulf of St Lawrence, S W 11 (784-787) to the River "From Hudson, wherever the Matinal rocks appear in contact with any of the superposed formations, the former are either highly inclined and folded, or give evidence of disturbance and partial metamorphism, display much less w^hile displacement and alteration." the overlying strata (p 785.) Becraft's Mountain and Rondout (fig 11, here copied from Vol II p 785) are mentioned as points where the unconformity is distinct It is said to exist E "from Rondout Emmons to Schoharie" (p 785) Agriculture of New York Albany, 1846, I The sec- and at Becraft's of Waterlime on sequence Mountain are drawn showing, a conformable here figs 12, and PI XX 136, p Hudson River layers (his sections 5, unconformable by faultas represented is relation at Rondout, the 13) tions in the gorge of the Catskill at Austin's Mill ; ing (fig 17, p 134, here JaiBes HalL fig 14) Paleontology of New York, Vol II Albany, 1852 ; MUSEUM OF COMPAEATIVE ZOOLOGY 321 " Along the base of the Helderberg, where the Clinton, Niagara, and Onondaga salt groups are very thin, the Oneida conglomerate and the shales and sandstones of the Hudson River group few feet of the Tentaculite limestone or Waterlime group." The same New Palaeontology of York, Vol absent, within a (p 1, note.) The author 1859 111 is rise to repeats a doubt previously expressed as to the truth of the unconformity at Becraft's Mountain, and states that the Upper and Lower are conformable on the northern front of the (p Farther on, he writes 33, note) " : Siluriana Helderberg ^lountains The Hudson River group, which constitutes a few feet of their [Catskill Mountains] elevation at the base, " is disturbed, and the succeeding beds lie upon this unconformably 69); and again, "the unconformability of the Lower Helderberg (p " group upon the Hudson River group old sea bottom was periodical {p 70 ; shows that the subsidence of the see also p 88) These are the older observations on the subject The following ref- erences show the recent work, as well as the lack of agreement on the question in the two text-books in more general use J (p New Elements of Geology Lecoute York, 1878 " In the United the rocks of the whole [Paleozoic] system are conformable." States, 277.) J D Dana Manual New of Geology York, 1880 The making of the Green Mountains came at the end of the Lower Silurian (211, 212) the disturbance extended to the Hudson (214) formity mentioned are Mountain (216,* 241) southwestward of J G Lindsey Proc, II., Localities of uncon- near Gaspe, near Montreal, and at Becraft's The distm-bance New Jersey (217) A Study of the Rocks is thought not to extend Poughkeepsie Soc Nat Sol 1879, 44-48, giving a careful description of the rocks at the Rondout cement quaiTies, and regarding the junction of the Upper and Lower Silurian rocks as unconformable T N Dale The Fault at Rondout 1879, 293-295, from which figure 15 is Amer Joum Sci., XVIIL, here copied, showing the Lower Helderbergs, with a thin layer of Niagara (Encrinal) limestoue at the bottom, lying squai-ely across the tilted Hudson River strata It would seem from this review that Mather and Rogers regarded the Upper and Lower Silurians as unconformable on both contact of the sides of the Hudson ; Emmons figures a conformable relation, siders the apparent unconformity at Rondout the at first admitted the general unconformity, but later doubts * Here Becraft's Mountain VOL vii — KG 10 is wrongly said 21 to and con- result of a fault it ; Hall even be west of the Hudson for ; 322 BULLETIN OF THE Becraft's Mountain (but not for Rondout T) Leconte, on I know not what authority, takes a view opposite from the generally accepted one given by Dana Lindsay and Dale both represent the junction at Kondout as an unconformity am "West of Catskill, I evidence for this conclusion persuaded that no unconformity exists is given below : Mountain and Becraft's the its smaller neighbor I have not seen, except from the railroad in passing : the opinions concerning this important point are contradictory, Mather and Rogers being opposed disagreement is to Emmons and directly expressed except Hall About Rondout no by Emmons and yet none of ; the observations or figures of the hill-sections in that district are conclusive the ; none enable the reader completely to exclude the possibility of apparent unconformity being really a junction by faulting would seem, It therefore, that all this subject needs reviewing The observations on which I rely to prove the conformable sequence of the strata in the district here mapped are as follows : — At the north end of French's Quarry Hill, by a good spring on middle one of the three roads that run around the slope, there is a the contact of sandstone and an impure limestone clearly shown for some ten feet The rocks here lie horizontal in the axis of a synclinal fold First their strata are closely parallel, hill several outcrops of sandstone and evenly superimposed may be found ; ; going down ascending to the south, the several limestones of the Lower Helderberg group are easily recognized in proper order rise ; going east or west, the Hudson River strata soon from the synclinal axis, becoming steeper and steeper by gradual change In the road and railroad cuts just east of Austin's Mill on Second the Catskill, the absolute contact is hidden by about ten feet of detritus, but the strata show only parallel arcs of the eastern half of a synclinal The apparent unconformity (see fig 3) is due in the limestones here to horizontal faulting in the trough of the fold, as is shown described farther on Third Along the front bluff of the Kalk Berg, generally marked by vertical strata of also vertical belt, and Waterlime and Lower Pentamerus, the sandstones are parallel in strike the sandstone stones, but We ; in the anticlinal valleys within the perfectly conformable to the curves of the lime- no absolute contacts were found therefore this district, sections is must conclude that the entire series is conformable in is folded together; and so it is represented on our and MUSEUM OF COMPARATIVE ZOOLOGY When the attempt is the several strata were formity is difficult made made 323 to restore the geographic changes to vary, The sands to understand by which cannot be denied that this con- it of the Hudson River group indicate a return of the shore line on the east after the open ocean conditions of the Trenton formation ;* the shallowing of the waters and the westward advance of the shore continued certainly as far as the present If the unconformity at Becraft's Mountain be acline of the Hudson cepted, then we may follow the generally allowed belief in the folding of by their elevation and erosion and the these sandstones accompanied ; veiy variable composition of the Niagara group as a whole, and the probable changes of level during the Onondaga most (Salina) period are likely to be explained by the oscillations of the adjoining land on the east dur- ing the Green Mountain growth Excepting the few feet of beds found at the northern end of the Quarry Hill, which were not definitely referred to any group, there is nothing to be seen sent this vast lapse of time ; for directly in the Catskill section to repre- and conformably above the Hud- mark son River sandstones come the Lower Helderberg limestones, which the second and greater eastward advance of the sea in the Upper Silurian, the first district being that of the Xiagara limestones cannot then have been dry land, for it The present beneath the Lower Helderbergs so far as we could discover hardly have been far under water, for then it Catskill shows no eroded surface It could should have received some share of the various sediments so plentifully supplied to the ocean ther west and southwest It district lay just off shore, or received very little almost between wind and water, and either detritus, or else was alternately covered and swept bare again by shoal water currents, so that in the end scarcely it had gained any rock material The change that followed next was not ocean far- may, therefore, be best to suppose that our floor as a distant so much a depression of the eastward retreat of the shore line ; for the Lower Helderberg limestones show shallow waters, with freedom from shore sediments such as the Green Mountain rocks could have furnished Catskill shaly limestone probably marks a slight open ocean, and the presence of a neighboring shore, much more low The departure from this for it contains non-calcareous material than the limestones above and be- it This second oceanic cycle ends with the Oriskany sandstone, marking a return of the shore, though perhaps not a very near approach * See Professor Newberry's "Circles of Deposition," &c ' XXII., 1873, (2,) 185-196 Airier ; and Assoc Proc., BULLETIN OF THE 324 a third cycle culminates in the Corniferous limestone, with deeper water The Marcellus shale, which follows abruptly, here than the second seems too fine-grained and even-bedded over large areas to mark either a change to shallow water or a neighboring shore the limestone below the disappearance of ; was more probably connected with a further it deepening of the water, or with a change But temperature in its shal- low water and near shore conditions came very clearly in the cross-bedded Hamilton and higher sandstones, and even more skill distinctly in the Cat- conglomerates what It is difficult to say know too little here meant by "shallow water," for we is of the winds and currents of these old times meaning of "near shore" can be estimated from the But the Catskill conglom- from the Hudson River erates, the coarsest of the entire series here seen upwards, and therefore probably nearer their source than any of the other fragmental strata ; and yet the crystalline rocks fr6m which their pebbles have been chiefly derived cannot be less distant than the Highlands of the Hudson (forty miles), the same series of rocks in Connecti- cut and Massachusetts (forty), or the Adirondacks (sixty miles), for all the intervening areas, even if then exposed to erosion, were of non" Near shore " does not, therefore, necessarily imply a crystalline rocks very close neighborhood to land and the carrying power of the paleozoic ; The currents must have been very considerable source of the Catskill conglomerate pebbles tant piece of work is identification of the an interesting and impor- — The folds of small radius and varying form into Folds and Faults which the above-described strata have been pressed, and the strong influence of the rocks' attitude on the surface form, combine to render this district an excellent training ground for Appalachian work I know of no other where so many structural problems are as well shown within so limited a space Two w^ell-known features are clearly seen become more pronounced in going eastward, and their steeper dips on the west all : the folds the anticlinals have Points of special interest may be named as follows The Catskill gorge from Austin's Mill series of natural sections The up to Leeds gives a very fine railroad cutting and the lane leading up from the mill to the turnpike give good evidence of the conformity of the Hudson River strata under the limestones, presents two interesting forms of distortion ity by horizontal faulting (fig another on an oblique crack 3) ; and the Waterlime here The first is an unconform- the layers have been shoved past one It is worth noting that a similar style of 325 MUSEUM OF COMPARATIVE ZOOLOGY dislocation would probably be called true unconformity had taken if it place and been laid bare just at the junction of this formation with the Hudson strata below it; but happening twenty feet higher, it can be referred to its may Secondly, we true cause note the effect of internal disturbance in the limestone, shown by the breaking up of some of its this must be referred to the epoch of general foldtine layers (fig IG) in