— — — — — — — — — — — 7—.- — — fl {9—} N—i _.| I (f)_.\_x A HELD ANE‘} PETROGRAF‘HEC SYUEY OF SOME EX'FRUSEE’E AfiD SE’WMENTARY RGCKS ALONG THE CARP AWE: LZTYLE CAR? RW’ERS ié‘i ONYOE'égfiGGN AND fiéS-GEEEC GUN'E’HES, NJCE‘IEGAN Tisssis 5‘0:- i‘iw Dagcee of M. S. MECE‘flGM‘J 3?:iTE CGLLEGE OW’QH Maria Hurzisfi‘ain 19% Trants This is to certifg that the thesis entitled V\\\ I! r >-‘ /7’I//’//7 Al” //,'~/-"’5//‘/)U_4/L’ \_--rJ"/7 "K’Iw? 4.. ,.,L”/‘,/__’ 1/], Ur,-/. . ' Ia 4/4f'4r‘ ”VL— Ll}r/J IJWI/ / / -L/O(£v ,I/p y / fl - . Ahf‘f/c. (4’) sz‘,»t 4 C(4V-344/a4 /‘ (/7 6-971/k’9 (30 I w v‘lfdl /’7/v -’- [fly] I./ presented hg C:W/_:/y M HfA/NO/JE/N has been accepted towards fulfillment of the requirements for r0 7‘, @_ degree in we ‘/ \ (bfou‘ Ma ' r prufes. Date 31/71/‘9‘0 O~169 :3. FIELD 111:1; P31111041“?1111.3 STLJZ CF 5’31“; EZRT?‘ '13 VII. ILLD SEZLudel-nitf‘: 117‘ 3&3 :;LOS.G TEE {7111 -11.: LITTLE.- uzIftT’ fir/EINJ II‘I OJ\J,..‘JJ- £10013 I'TL) COLL: ‘iv C-CU-..LIL3D, ‘IICT’IC-J by Owen Herle Hornstein A Thesis 'Submitted to the Graduate School of Kichigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of i? OF SCIENCE Department of Geology and Geography 1950 THESIS ACKNOWLEDGEXENTS The writer wishes to express his sincere apprecia- tion to Dr. i. T. Sandefur, under whose direction this thesis was written. Dr. Sandefur Cave freely of his time and knowledge to assist in the laboratory and in the writ- ing. Dr. n. A. Kelly's assistance in providing a base map and briefing the writer about the area is deeply appreciated. The writer also wishes to express his thanks to Dr. S. G. Bergquist for checking the manuscript and offering sug- gestions used in this thesis. Eu? :0 " (”fl '3 nd i w Table of Contents Acknowledgments................. List of Illustrations..... IntrOduCtionOOOO...0.0.0.0000... .istory and Previous Investigation. .0 O. O .0. O. .0 I kethod of Approach......... Purpose of Study................ Objectives of This Thesis. Geography....................... Location................... TopographV................. Lakes and Streams.......... Climate“.................. Timber..................... OccupationS................ Seclog:y00000000000000000.0.0.... General...OOOOOOOOOOOOOOOOO Stratigraphy. Thickness and Structure.... PetrOlogy-OOOOOOOOOOOIOO0....O... IgneouSOOOOOOOOIOOO0.0.0... Sedilnentaryvoooooooooooooooo Preparing the Samples. Houndness and Sphericity Page iv o\c\U'I.+—“ \O 10 10 11 ll Table of Contents (Cont.) rage Sorting. . O O O O O O O. I O. O I O O. O. O O O O O O O O O O. C. O 50 COIICluSlonSo O O O O O O O O O O O 0 O O O O O O O O O O O O O O 0 O O 0 O O O C O O O O C 52 Bibliog‘raphBTOOOOO0.0...OOOOOOOOIOOOOOOOOOOOOOO.O... 51;- LIST OF ILLUSTRATIONS Page Tap I, Index Map (inset)........................... 8 Map I, Showing Topography of the Porcupine Mountains............. ....... ...£............. 8 Nap II, Showing Location of Traverses and Position of Samples....................... 5h Stratigraphic Column.......................... 1? Diagram I, Structural Diagram.......................25 Cumulative Curves of the Weight Percentages of Samples Along the Little Carp River............................. 55-58 Cumulative Curves of the Weight Percentages of Samples Along the Carp River.................................... 59-h0 PLATES Plate I Fig. 1, Little Carp River Flowing into Lake Superior................................. h8 Fig. 2, Carp River Flowing into Lake Superior...................................... h8 Plate II Figs. 1 & 2, Waterfalls in Carp River at Location B-Bl........................ A9 Plate III Fig. l, Outcrop of Coarse Conglomerate Lens... 50 iv LIST or ILLU TRATICNS (coxr.) \J Plate III F g. 2, Thin-bedded Sandstone Along Carp River at Location 3-17....................... 50 Plate IV Fig. 1, Dip of Sandstone Beds in Little Carp 31V811000000000000000.0.0.000000000000... 51 Fig. 2, Strike of Sanistone Lads in Little C) m ‘3 ’3 .JJ iveroooooooooooooooooooooo000.000.00.00 J1 INTRODUCTION history and Previous Investigation For the past 155 years, a number of geologists have written on different portions of the Lake Superior basin. Probably the first report of significance was written by John J. Bigsby, titled, "Notes on the Geography and Geology of Lake Superior", published in the, Quarterly Journal 2: Science and Arts, l82h-25. Between 1825 and 1883, many geologists wrote copiously upon this subject. Consult R. D. Riving, "The Cop- per Bearing Rocks of Lake Superior", U.S.G.S. Honograph V, 1885, pages lh-25, for a complete, chronologic list of works from 1825 through 1881, that refer to the Keweenawan rocks. Tntil Irving began his field investigations in the summer of 1880, there was little or no knowledge available concerning the structure of the Porcupine Mountains. Irving's work in this area ranks high among the classics, for never before had so much detailed work been done on the lithology, stratigraphy, and structure bf the Porcupine iountain area. The next important work was done by W. C. Gordon,* *Gordon, w. 0., A Geological Section from hessemer Down Black River, Published by the Board of Geological Survey as a part of the reportibr 1906. when he studied the section down Black River from Bessemer ,to the Lake Superior shore. He made a detailed study of all l‘.) outcrops and wrote an excellent description of the lithology, structure, and thickness of the several formations encountered. Three years later, A. C. Lanea *Lane, A. C., The Keweenawan Series of hichigan, Michigan Geological and Biological Survey, Vols. I and II, 1909. published a two volume report on the Keweenawan Series of Michigan. In this report, he gave complete descriptions of all rock types in the Porcupine Lountain area and also ex- pressed his ideas as to-the structure, age, and correlations that can be determined. Finally, Van Hise and Leith* *Van Hise, C. R. and Leith, C. K., The Geology of the Lake Superior Region, U.S.G.S. Monograph LII, 1911. presented their ideas of the stratigraphy and conditions of} formation of the rocks in the Porcupine Mountain area in their classic report of 1911. Method of Approach Since there are no roads traversing the Porcupine Mountain area, the writer was forced to hire a boat at Black River Harbor, about thirteen miles southwest of the mouth of the Little Carp River, to carry in the supplies needed. The boat followed the shore of Lake Superior while enroute to the mouth of the Little Carp River. At this time, arrangements were made for the writer to be picked up at the mouth of the Carp River, three weeks later, and taken back to black River Harbor. Base camp was set up at the mouth of the Little Carp River and each day's work was started from that point. The Little Carp River is about to feet wide at its mouth and carries very little sediment by normal flow. The water is clear and suitable for drinking. The bed of the stream is covered with large, well rounded pebbles of solidi- fied lava, conglomerate, granite, felsite, and quartz. The Little Carp River was followed upstream and at each outcrop, a representative sample was taken and labeled. When the Little Carp River traverse was completed, the camp site was moved one mile northeast, to the mouth of the Carp River. The procedure used along the Little Carp River was followed in collecting samples along the Carp River. Samples were taken from outcrops along both rivers as long as the direction of flow was across the strike of the formations. The last day in the field was used to collect samples of extrusive felsite rock, which is abundant near Mirror Lake. V In the past, little detailed, geological work has been done between the Carp and Little Carp Rivers in the Porcupine mountains. This presented a good opportunity for the writer to search the area in hopes of collecting some data that would help broaden the knowledge of the geology there. The formation sampled and studied by the writer has been named the, Outer Conglomerate formation, by Irving.* *Irving, R. D., The Copper Bearing Rocks of Lake Superior, U.S.G.3. Monograph V, 1885. Since 1885, the name Outer Conglomerate has been used by other authors, and the name is well established in the litera— ture. This name, however, does not conform with the usual rules set up by the United States Geological Survey, in that a for- mation should be named after a locality. Also, the name Outer Conglomerate is a poorly selected one for the formation is I nearly all fine grained sandstone with a few lenses of coarse conglomerate. For the above reasons, the writer feels that this formation should be called the Porcupine mountain for- mation. The name Porcupine Hountain sandstone will be used in place of the name Outer Conglomerate in this thesis. OBJE"TIVES OP TLIS TLESIS To collect samples of outcrooning bedrock along the Carp and Little Carp Rivers. To obtain information pertaining to the age of the Porcupine Iountain sandstone. To determine, through sphericity, roundness, sorting, and composition of the particles, the source of the sediments and the direction from which they were derived. To observe the general structure and thickness of the Porcupine Uountain formation. To correlate the Stratigrapny, through lithologic characteristics, in the Carp River area with that of the Little Carp River. To observe the general geology of the area. GEOGRAPHY Location The area described in this thesis is situated in the southwestern part of the Porcupine Mountains State Park. This park includes the extreme northern part of Gogebic and the northeastern part of Ontonagon counties, in the weStern portion of the upper Peninsula of Michigan. See index map, insert, Map I. The Little Carp River has its source in the small streams that feed into Kirror Lake, which is located in Sec. 2., T. 50 N., R. hh H., Ontonagon county. The Little Carp River flows S.-SW. from Mirror Lake until it enters Lily Pond, which is much smaller and more shallow than Mirror Lake. Upon leaving Lily Pond, it makes a large loop to the south and flows northwest until it empties into Lake Superior. The mouth of the Little Carp River is located in the see, Nag, sw: of Section 1, T. 50 N., 3. A5 w. in Gogebic county. The Carp River has its origin in the small streams which flow into Carp Lake (Lake of the Clouds).* The water of these small streams, flows from northeast to southwest through Carp Lake. The Carp River follows the strike of the rocks until it crosses into Gogebic county, where it swings to the % The U.S.G.S. has never changed the name ofTCarp Lake to Lake of the Clouds. Personal communication with F. G. Pardee. northwest and empties into Lake Superior. The mouth of the Carp River is located in the 82%, NW4, SE: of Section 55, T. 51 N., R. Eh W. in Ontonagon county. zonh 2.0? z_m m¢:m old; ,I a g [with as: >§o| 38 .133 nnnnn 32. and)... s: 0d 3.3 53.80 l\J\I :3»... {III -d¢ ozwowq IIIIIIIIII K \ \ \ \ [0.50al80 lbs—s .ZOnh c o .c u dggn \ \ \ \ \ \ I’ll \ L . .. A . ‘. .3ntc \fiv u. A \ \ \ \ . .- I’d u I t 4 t( I .‘QQI mp1 \D Topography The Porcupine flountains, a prominent landmark of rugged and rocky terrain rising from Lake Superior about fif- teen miles west of Ontonagon, have received wide recognition for their scenic beauty and virgin forest stand. The moun- tains are made up of a series of broken ridges, roughly par- allel and concentric to the shore of Lake Superior. The Michigan Department of Conservation lists the highest ele- vation as Government Peak, which is 2,025 feet above sea level, or l,h2l feet above Lake Superior. More recent sur- veys of the area indicate that these figures are too high and in error, another peak to the southwest being denoted as the highest. This is the highest range of hills between the Black Hills of South Dakota and the Applachians in the east. From a distance the slopes seem to be gentle, however, when actually traversing the mountains, one finds very rugged slopes leading to the tops of the ridges. The ridges in the Carp and Little Carp River area have slight surface depressions which trap the meteoric water, and because of lack of drainage, large swamps persist. The swamps are a constant menace to the hiker, in that he has to secure his way across them and they breed millions of mosquitoes. Since the rainfall is heavy and the vegetation thick, there is little evaporation of water in these areas. See Nap I, for a contour map of the Porcupine Mountains. lO Lakes and Streams Draining the east side of the Porcupine hountains are five rivers of importance; the Presque Isle, the Black, the Iron, the Carp, and the Little Carp. The Carp and Little Carp Rivers are of present interest. hhile they are not exception- ally large or long rivers, they are quite different in that they flow rapidly down deepcut valleys through virgin wilder- ness, over a series of spectacular waterfalls and foaming rapids. Carp Lake is really a part of the Carp River because the headwaters of the Carp flow into the northeast end of Carp Lake and out the southwest end. Likewise, the Little Carp River has two lakes through which it flows. The water from the headwaters of the Little Carp River pass through Hirror Lake and again through Lily Pond before reaching Lake Super- ior. These relationships of drainage are shown on Map I. Climate The Upper Peninsula of Michigan, along the coast of Lake Superior, has an entirely different type of climate from the rest of the state. In Cntonagon County, the average annual rainfall is about 51 inches. This is a surplus of water because the average annual growing season is only between 80 and 90 days. Temperatures, however, do not go to extremes because of the proximity to Lake Superior. The average tem- perature for January is between 10 and 11 degrees Fahrenheit, ‘- J r‘ . F. ,‘1' I while the aver? e suly te:“‘r‘11;3 is Ln to u) ht_3ees am. as .-; I ;4;L11§3f.-3.3 J... b . “ . M . A ‘1 ° . , .. ,. “ .--. -, 2‘ "~ , ' wU. S. Department of ;¢ricult;re, olimate and ”:2, Tear as: ‘h m ! I , ! -.. .',,. '10. _. A . C\.. of A_ricultu:e, i,wl, pp. ylh-,a4. m .7 A y, : 'q -- ‘ +~LJ’V.. m Most of the area is thickly covered with virgin stand q of the hardwood-hemlock forest, interspersed with scattered colonies of white pine and Lirch. The three major occupations, in order of their importance d are minixg, lumbering, anc iishing. The largest open pi iion Ho (9 I...’ DJ M C J. 53’ U} C 1‘ C 'an is located in the town of nakef few miles to the southwest of the Porcupine Lountains. Timber ebic Counties and out into is taken from both Cntonaron and so m \u L1 in of Con orville, Lichifian. The main fishin ,4 k‘ ‘1 q" r: :u— ‘f‘lfl J— lul..0 I” 4.; tie to 5 port is locate; at Llack hiver harbor. The rock strata exposed along the shore of Lake Superior, in the area of the Carp and Little Carp Rivers, were laid down in the Upper Keweenawan period of the Proterozoic era and re- present the youngest formations in this area. This area is in the Lake Superior region, a part of the southern margin of the great pre-Cambrian shield of North I America. The pre-Cambrian outcrops are bordered on C“ he east and south by younger Paleozoics and on the west and north by the basin of Lake Superior. The area under discussion has a complex geologic history which C. s...= .eologists are now atte«pting to interpret. briefly, the area was blanketed by hot lavas, folded by diastrophic movements, eroded, intruded by maemas, again eroded, and finally glaciated. The formations of this area may be separated into several different lithologic units, each originating under different circumstances. It is the geologist's task today to determine these circumstances. The central core of the Porcupine lountains, comprises a rhyolite mass.* The beds of sandstone, conglomerate and shale dip away on all sides except where the rhyolite connects on the south with the Main Trap flange. This Range consists of * Thaden, R., Personal Communication. basaltic lava flows with amygdaloidal tops, extending south from Eagle Harbor and paralleling the coast of Lake Superior. The Main Trap Range is believed to be younger than the rhyolite core. Irving* *Irving, R. D., 23. cit., 1835, pp. 150-151. compares the structure here to the structure in southern Utah. He states, "The structure of the Porcupine Kountains has so much in common with that of the lacco- litic mountains of Southern Utah, described by G. K. Gilbert, that they might be supposed to owe their existence to an eruption of acid rocks at a time quite subsequent to that of the formation of the latest of the basic flows. But, as shown subsequently, these mountains owe their existence in all probability to a fold, the porphyry of the central portions being one of the usual embedded masses laid bare by subsequent denudation." Stratigraphy The age of the Porcupine Mountain formation (Outer Con- glomerate) has been classified by Irving% "n‘Ir'Ving, R. D., ibido’ 18850 as heweenawan, belonging to the upper series of the Algonkian system. The Keweenawan period in this area was a time of regional volcanic activity. One-third to one-half the rocks have been classified as extrusive. The formations have been identified as Keweenawan in age, by Irving. Some of the more recent geologists have doubted the validity of Irving's classification and prefer to place the formations in the Cambrian period. Van Hise and Leith* *Van hise, c. 3., and Leith, c. K., 93. 933., 1911, pp. LL15- '416. give their reasons for calling it Keweenawan, in the following statements. 1. The absence of middle and lower Cambrian sediments in the region, leaving an unconformity between the Keweenawan and the Cambrian. 2. The lack of fossils of any kind in the so-called Keweenawan, 5. The sedimentary formation is composed of many volcanic fragments which is not typical of other known Cambrian sediments. h. The Cambrian is largely subaqueous while the Keweena- wan is subaerial. 5. The Cambrian lacks volcanism, whereas in Keweenawan time, volcanos were abundant in this area. 6. The Cambrian formations are horizontal in attitude, while the Keweenawan are tilted. 15 Alfred C. Lane* *Lane, A. C., op. cit., Vol. II, 1909, pp. 9hO-9hl. believes that the so-called Keweenawan may be Cambrian in are. In answer to some of the above statements made by Van Rise and Leith, Lane says, "That the Cambrian contrasts with the Keweena- wan in lacking volcanism, is certainly not true of the Upper Keweenawan...." In answer to the horizontal attitude of the Cambrian beds, Lane states, "Though the 'Upper Cambrian is flat lying,‘ so in the Lake Superior sandstone of the apostle Islands, which Thwaites recognizes as conform- ably above and part of the Upper Keweenawan." Lane also remarks that any subaerial deposit would be non- fossiliferous, and therefore cannot be used as a criterion for determining age. C. Leith, R. Lund, and A. Leithw wLeith, 3., Lund, R., and Leith. A., Pre-Cambrian Rocks of the Lake Superior Region, U.S.G.S. Professional Paoer 183, 1955’ p0 8- take the same view as Lane and explain it thus, "Although the Keweenawan is pre-Cambrian in the sense of preceding the Upper Cambrian transgression, having structural and igneous affiliations with the Pre—Cambrian and being nonfossiliferous, it may in part be Cambrian 16 in the sense that its deposition pro- bably continued into the time when Middle and Lower Cambrian sediments were being laid down in approaching Cambrian seas." The writer, after spending three weeks in the field, found no information which would contradict the statements made by either Lane or Van Hise. However, clay galls are very numerous in some places, which, the writer believes, supports the statement that the Porcupine hountain forma- tion is largely a subaerial deposit. R. D. Irving* states; *Irving, R. D., op. cit., 1833, p. 151. "The most prominent fact in regard to the stratigraphy of the Keweenaw Series is its separation into two divisions; an Upper member, made up chiefly of a succession of flows of basic rocks, but including layers of conglomerate and sandstones nearly to the base, and more or less of original acid rocks." The situation is far from being proven, but under any hypothesis, the Keweenawan beds constitute a marked local variation from preceding conditions. Legend The stratigraphic column below, was taken from the Centennial Geologic Map of the Northern Peninsula of Wichi- gan, compiled by Helen M. Kartin, Publication 59, Geological Series 55, which is a part of the annual report for 1956, by the hichigan Geological Survey. The writer has added to this column, the Porcupine Mountain formation, which does not appear in the report. The possibility that the Procu- pine Fountain formation is a facies equivalent of the Freda sandstone must not be neglected. Proterozoic Era Algonkian System Keweenawan Series Upper Group Freda sandstone Nonesuch shale Porcupine Mountain sandstone Lower Group Lake Shore Traps Description 2: Formations Freda sandstone The geologically highest rock in the Keweenawan Series is the Freda sandstone. Irving considered this, "the main body of sandstone", but it does not outcrop in the area between the Carp and Little Carp Rivers, along Lake Superior. This formation is composed of red sandstone, arkose, and shale, with a composite thickness of some hOO feet. Nonesuch Shale This shale lies beneath the Freda sandstone, but does not outcrop along Lake Superior in the Carp and Little Carp Rivers area. This formation has a thickness of 550 feet ‘ orcuuine fountain fiandstone 'H The youngest rock which outcrops in this area is the Porcupine Jountain sandstone. It is composed of a section of sandstone overlying a conglomerate base, which consti- tutes about 23 percent of the total formation. in this section, the measured thickness is more than 5,000 feet. Lore detailed descriptions of this formation are éiven in the section on Sedimentary Petrqlojy. Lake Qhore Traps Lying conformably beneath the Porcupine Lountain sani- stone, and in contact w 1.1. -th it, is a formation made up of a series of flows of eruptive rocks. These eruptives were divided into five separate flows by Gordon and assi ned a F“ C; thickness of h00 feet. This formation can be describet briefly as thin basaltic lava flows, amygdaloidal on top, and intercalated with amygdaloids and felsitic conglomerates. Descriptions will not be given to the remaining Lower Keweenawan rocks, as the writer did not encounter them in the sections taken along the Carp and Little Carp Rivers. A detailed account of these can be lound in, "The Keweenawan Series of Nichigan", hichigan Ceolopical and Eiolonical Survey, Vol. II, 1909, bv A. 0. Lane. Thickness and Structure Overlying the Lake Shore Traps is a sedimentary forma- tion, grading from conglomerate at the base to sandstone at the top. This formation is not uniform in texture through- out, the upper beds are fine grained sandstone, while the lower portion is a true conglomerate. A. C. Lane* aLane, A. C., pp. cit. Vol. I, 1909, p. 59. ‘- calculated the thickness of the writer's Porcupine Mountain formation, Lane's Outer Conglomerate, to be 1,000 feet at Keweenaw Point, near COpper Harbor. W. C. Gordon% *Gordon, w. C., 92. cit., 1907. p. A29- measured the thickness to be 5,000 feet along the Black River, about 12 miles southwest of the Little Carp River. R. D. Irving* *Irving, W. D., 32. cit., 1885, p. 151. determined a thickness of 5,000 feet in the Porcupine Mountains. The writer, however, calculated the thickness of the Por- cupine Mountain sandstone to exceed the figures of Irving and Lane. The section*of rock outcrop along the Little Carp River was followed very carefully and the horizontal distance per- pendicular to the strike, actually exposed was found to be 10,800 feet. Allowing for an average din of 27.5 degrees, this results in a minim*u thickness of about 5,000 feet, because neither the tOp nor the bottom of the formation was actually observed. «C’s/9" The possibility of repitition by faulting is notfipossible- here, however, the writer saw no indication of faulting in either the Carp or Little Carp River sections. The rocks between the two rivers are completely concealed by soil and thick veget.tion. At the lake shore, the beds may be seen outcronninc above the lake level for a distance of some fifty yards. The contact between the Porcupine Nountain sandstone and the Lake Shore Traps is not exposed along the Little Carp section. Because of the above reasoning, the thickness will have to be over 5,000 feet, and may have a much greater thickness in places. *Qordon, h. 3., 22- cit., 1907: 09° M25'L26° ,- "Descending through the formation we get in succession sandstone, sandstone with conglomerate phases, mixed sandstone and conglomerate, conglo- merate with sandstone phases, and pure conglomerate. The change from sandstone above to coarse conglo— merate below is a fradual one, and there is no sharp dividing line, but in a general way, it may be said that the upper one-quarter is sandstone, and the remaininf three-quarters is conglomerate." ‘l -* . v . ,... a ,. 3 A ,.H 7-.- . ; ,- H-” in the seetion nth; ,ne Little uarp giver, the to er 1, .‘ _ ‘ “4.. m , ., o. ~~ ,, be. r- - . 0, ~.‘ {- eighty percent of the EQECdJlflm ”ouhtaln ioruatuon is sani- _. r. .. - A .L... a , ,. - °, ,. ..,,.,. - r. f-fi; ‘ DtOho, on, he if .r t they percent is conglonerate. ,dis is just the reverse of xvi-tat Gordon found in the black River . "' . “ .1 .n 7‘ "'1'.“ 'i" A n“"‘ ' ‘V ’\ 1 ‘ 080131011. The writer LPlls-i/b‘s tin-t tier“: are “Boutiques-j f l _ ‘ ‘l 4 H tie con\lg .rate WL‘SS, t‘lch c.nhot oc traced l terilly In A ”r '1 g _‘ —~ _ o w o A ' a 4*. . _o 1‘ 10“ a“; rest ist1Lce. l is believed irOn fi,lc obser- vations, that these lens-shaped beds tji‘ tions.. All the lenses observed by the writer are probably less than 100 feet thick and have very sharp contacts with the surrounding beds on either side. The largest lens noted was at the mouth of the Carp River where the hard, resistant conglomerate causes a sharp bend in the rive . See Plate III, Fig. 1. The actual dimensions of the outcrop are, 75 feet by 25 feet. This conglomerate cannot be traced laterally, since it enters the side of a hill and is covered completely. There is no indication of such a conglomerate along the strike, in the ‘anks of the Little Carp River, merely a mile away. Well defined jointing is prevalent in the lower portion of the Porcupine Lountain formation. Fracture planes cut through the large pebbles, while there is very little break— ing in the cement, around the pebbles. R) I J k. P. billings% states, *Billings, I. P., Structure Geology, Prentice-Hall, Inc., New York, New York, 19h2, p. 125. "It is often supposed that tension frac- tures break around the pebbles of conglomerates, and that only shear fractures cut indiscrimin- ately across pebbles and matrix. Although this may be true for loosely-consolidated conglomer- ates, apparently it is not a reliable criterion in well-cemented conglomerates." The joints trend in several directions, but generally strike K. 20 N. to I. 25 a. and S. 50 1. These icints are sidni- ficant in that the force which caused them was directed along a line which bisects the angle made by any two inter- secting joint planes.% *Billings, a. P., ibid., p. 126. They also assist the geologist to realize the great forces exerted during diastrophism. The strike of the Porcupine Mountain formation changes from N. 20 E. to N. 50 E. as it extends northwarC1y. The average dip is 27.5 degrees northwest. See Lap II. 1’\-‘ -A—LVLG (IO—LC . L 1 ' h the texture is uniloru .W — ‘\ I“ '/~ ' +‘ .- 7' ‘ ‘ fl 1 " 1. PT '. ‘ ‘flul the quSU a..>un<:_z--.nt nn_1eral_ is FA 0. quartz, most of which is uuite angular. The feldspars present 3 are ortnoclase, andusine, an: uicrocline. The calcite cement and particles of felsite are abundant and scattered throughout the slide. Opaque magnetite and hematite cover the slide and the iron oxide stain gives a dirty annearance to the iarticles. Sample A-lS This specimen w~s collected from an outcron in the Little Caro giver sectio.. The rock is deep red and anoears almost colitis The J .i.u.1-u. ,llu cementing material 18 gray calcite, which reacts with dilut hydrochloric acid. Quartz 9nd feldspar can be recognized y ' , .0 ' .. .z with the aid of a hand lens. The speCimen is stained eith w 0 . l I“ 0“ . D - ‘ ‘ '5. .1 0 iron oxice, which masks the CmuPflCtef oi the Lrains. Licroscopic: The texture is fine and uniform. The most abundant mineral is quartz, some of which show undulatory extinction and are quite angular. There is evidence of secondary quartz growing about the urinary quartz grains. The feldspars are microcline, L J. in oligoclase and ancesihe, however, not all the feldspars are altered, a few being very fresh in appearance. There are frag- ments of felsite and trap rock, the latter showing small amygdules. Occasional particles of chlorite are present. The opaque minerals are magnetite and hematite. The whole slide is colored with red iron oxide. Specimen A-23 This specimen was collected from an outcrop in the Little Carp giver section. Henasconic: 'The specimen is reddish-brown and has a uniform texture. Clay galls are numerous and reach the size of two by two by one-tenth centimeters. These clay galls have a darker color than the sandstone and are orientated parallel to the bedding planes of the sandstone. The weathered surface penetrates about three-tenths centimeter into the exposed portion, and is quite porous. The sandstone is made up of angular particles, all . probably under one gillimeter in diameter. The calcite cement VLA reacts with dilute hydrochloric acid, while the clay galls do not. Particles of quartz and feldspar can be recognized, but the coloring caused by iron oxide masks the nature of the grains. Licroscopic: The texture is uniform and the particles are not well rounded. The most abundant mineral is quartz, most grains of which contain gas bubble inclusions. Some grains are of cryptocrystalline quartz, which appear exactly like the quartz an. in the rhyolite, found near lirror Lake, Some felsite particles are present. The feldspars are oligo-andesine and microcline, the latter being in minor amounts. All the plagioclase has a dirty appearance due to its alteration into sericite and kaolin. Calcite, the cementing scent, displays abundant parallel lines due to repeated lamellar twinning. Chlorite is present in minor amounts and opaque magnetite and hematite dot the thin section. The whole slide is covered with iron oxide, masking the characteristics of most minerals. One very fine—grained clay gall runs the length of the slide. Specimen A-BO This sample was collected from n outcrop in the Little Carp River section. Hejascopic: The specimen is reddish-brown with some gray calcite cement showing on the freshly broken surface. The texture is coarser than in the other specimens already described, and all the grains are quite angular. Some of tne particles have diameters up to three millimeters. The weathered surface is darker and more porous tnan the fresh surface. Kicroscopic: The larger particles are more rounded than the smaller ones. The most abundant mineral is quartz. The feldspars are microcline, orthoclase, and andesine, which are generally dirty in appearance because of alteration into sericite and kaolin. Throughout the slide are particles of felsite and grains of magnetite. An occasional small piece of augite can be seen. The whole slide is covered with iron oxide, which obscures portions and gives a reddish color to the thin- section. The calcite cement is not too apparent. Specimen B-5 This specimen was collected from an outcrop near the mouth of the Carp River. Megascopic: The sample is reddish-brown and has a uniform texture. Bedding planes range from one to three inches in thickness. The particles are of all diameters, up to about one milli- meter, The most abundant mineral is quartz, although feld- spar can be seen. The calcite cement reacts with dilute hydrochloric acid and l (.0 present in sufficient amount to give a gray tinge to the freshly broken surface. kicroscopic: The particles are not well rounded and the most abundant 4:- C\ mineral is quartz, some grains of which are quite angular. A few quartz grains contain gas bubbles, which seem to be arran;ed in definite rows. Some felsite particles are pre- sent. The plagioclases are andesine and oligoclase, most of which has begun to weather. There are occasional particles of microcline and hornblende. hagnetite and hematite are present in large quantities. The slide is covered with iron oxide, giving a reddish appearance to, and obscuring portions of, the thin-section. Specimen B-lé This specimen was collected from an outcrop in the Carp River section. hegascopic: The rock is reddish-brown and has two distinct types of texture, fine and very fine. The part composed of very fine grains is much lighter in color than the part composed of fine grains, the latter being a small lens. The liphter, iner sediments react slightly, while the darker, coarser sedi- ments react readily with dilute hydrochloric acid. The few clay galls present are in random orientation. The weathered surface displays a darker color and more porosity because the calcite cement has been dissolved. Cuartz and feldspar can be recognized with aid of the hand lens. Kicroscopic: Most of the grains are angular, but vary somewhat in size. The most abundant mineral is quartz. The feldspars are ortho- clase, microcline, and andesine, all of which are quite fresh. A small amount of hornblende is present. The opaque minerals are magnetite and hematite. The whole slide has a reddish appearance due to iron oxide. Specimen 3-50 This specimen was collected from an outcrop in the Carp River section. Heiascopic: The rock is reddish-brown and has a fine, uniform texture. Bedding planes in the hand specimen are about two centimeters apart. The particles are of variable diameters up to one millimeter. The freshly broken surface shows a tinye of gray due to the calcite cement. The cement reacts with dilute hydrochloric acid. Parallel to the bedding planes are streaks, up to two millimeters in width, which have a darker color due £4 to slightly more clay material. Quartz and felcspar can be determined with aid of the hand lens. Iicrosconic: The slide shows a very fine texture, the rock beino com- posed of small, angular particles. The most abundant mineral is quartz, some of which contain gas bubble inclusiors. Some felsite particles are present. The alagioclase is andesine, of which some is slithly weathered. One grain of microcline and a few slivers of mica were noticed. The slide is covered with iron oxide, giving a reddish appearance to, and obscuring portions of, the thin-section. #8 PLATE I { Fig. 1, Little Carp River Floring into Lake Superior. \ i '\ i l\ \ \ Fig. 2, Flooded Carp River Flowing into Lake Superior. #9 PLATE II 1 i. f \. x { k 3 5. Fig. 1, waterfalls in Porcupine Mountain formation at location B-31, in Carn River. I i 7 1 fi 3' z 1 l \ l L i- _ ‘, "“‘““““‘“ “‘v‘- ~~W-m alls as above, after a heavy rain. Fig. 2, Same f 50 PLATE III -~. \_-__/" , __ ‘ .«x *v’." ‘~ ' - \-._/‘./~o-’\v-/"p-JMA.‘/ I , l C i i \..--. M» —/\~‘ My— A’“ “W" . —’\r“ q. ~ «k —~\ —\_I’\‘ \AK —-\ ~~ \v—V\‘\_l-l-—\A ~. . Fig. 1, Large outcrop of coarse conglomerate lens, near mouth of the Carp River. 0- f.-/ /.J..-\ .’— v‘J-fl J‘~-. ’I—W _ , « '\‘~l~—J\r_‘_fi NwMVXxI-‘rM ~a\ _\/k\.’_’\\_’-~\'~ f\_‘-\ s , W~\.__ \‘ ~ Fig. 2, Thin-bedded sandstone at location B-l7, along Carp River. 51 PLATE IV % ‘~. ;, I 2 l \ E Fig. 1, Location A-S, in Little Carp River. *— The din of the sandstone beds is noticeable. l (. ix E L I '1 I i l 7‘ \‘v ‘ _~ A 1 _ - ‘ \ A ‘ “ \\__ ‘> _ \ \4’< Fig. 2, Between locations A¥l9 and -2h, in \w the Little Carn River. Note how the strike of the beds can be easily recognized. 1T ‘TT‘ "T 73*"1 CCnCLd iOAD The conclusions reached, in detailed gtuhy of the For- cupine Lountain formation, are not exactly vhat the writer expected before he b gen the field work. \0 Since this sedimentary formation is composed essentially of fine-grained sandstone with a few conglomerate lenses, the . 1 «— '. “ '9 »‘ j 0 name Outer Conglomerate, given by irvin; in lo35, is not (‘3 (a (U appropriate. The writer refers to this sandston the, Porcupine lountain formation, which is in keeping with naming formations after localities, and does not give a false impres- sion as to the lithology of the formation. The sandstone and conglomerate beds lie conform'bly on the older, Lake Shore Traps. both formations strike essentially l. 20 2. and dip to the northwest, with the din increasing as the Lake Shore Trans are arproached. The average dip is 27.5 degrees. 3e (D U H. "J Poundness and sphericity measurements taken on samples from both the Carp and Little Carp River sections, do not conform to the idea, advanced by many students of sediments, that sand grains become more rounded and less spherical as they are carried away from their source. These roundness and sphericity measurem nts do not conform to the above idea be- cause the lateral distance in which outcrops occurred is too short, and this is a probable subaerial deposit. also, these measurements give no clue as to the direction from which the sediments were derived and could not be used to determine, or \fl \N correlate, different members of the Porcupine Mountain form- ation. Poor sorting is typical of a non—marine formation, however, exceptions do occur, such as Winfi -blown sand. It was found that the Larshall formation of western Licnigan is 2.5 times better sorted than the Porcupine fountain formation. iecause the Porcupine fountain formation is poorly sorted and because numerous clay galls are imbedded in the sandstone, the writer feels certain that this formation is of su aerial ori in. Clay galls are dried and flakes which have been blown into the sedi- ments 1 Miately prior to diagenesis. The writer fails to visualize how clay galls could be blown out to sea and pre- served. They would be destroyed in the process. From th study of thin-sections of the Porcupine fiourtain formation, it can be said t-at the se di ents were derived, in part, from the weathering of the rhyolite wnich outcrops near mirror Lake. Thus, the Med nts must have come fron the south- east. The occurrence of two plagioclases, andesine and 01130- clase, suggest an orig gin from two different igneous masses. The writer was unable to subdivide the Porcupine iountain formation on the basis of lithology, roundness, or sphericity. KL dons sequentl., no beds or members were correlated betw en the ( Carp and Little Carp Rivers. BIBLIOGRAPHY Billings, K. P., Structural Geology, Prentice-Hall, Inc., New York, I. Y. l9h2. Gordon, 7. C., A Geological Section From Bessemer Down Black River, Published by the Board of Geological Survey as a part of the report for 1906. Hobbs, R. A., The Application of Roundness and Sphericity f‘ asuremcnts to Subsurface samples of the Iarshall G) M Formation of aestern hich-gan, Unpublished Taster's Thesis, Lepartnent of Geology and Geography, Michigan State College, l9h9. Irving, 8. D., The COpper Bearing Rocks of Lake Superior, U.S.G.S. Honograth V, 1885. Johannsen, 5., A Descriptive Petrcgraphy of the Igneous Rocks, Vol. I, The University of Chicago Press, 1931. Lane, A. C., The Keweenawan Series of Richigan, Michigan Geological and biological Survey, Vols. 1 and II, 1909. Leith, C., Lund, R., and Leith, A., Pre—Cambrian Rocks of the Lake Superior Region, U.S.G.S. Professional Paper 383, 1955. Pardee, F. C., Personal Communication. '1 Riley,lN. A., Projection Sphericity, Journal of Seoimentary L. Petrology, Vol. II, l9hl. , Thaden, H., Personal COMmunication. Trask, P. D., Origin and Enviornment of Source Sediments of Petroleum, (Houston, Texas, 1952), pp. 67 ff. 4 .55 Van Hise, C. R., and Leith, C. K., The Geology of the Lake Superior Region, U.3.€.S. Konograph LII, 1911. Wadell, H., Volume, Shape, and Roundness of Quartz Particles, Journal Of GeOlOCY: V010 £33 1955. U. S. Department of agriculture, Climate and nan, Yearbook of Agriculture, 19u1. ' . M g; wig-Y . ' at“... E H. I\E.VE.E,.v-I8 I. LII [.hyiv .llwflllu h.» ‘c I... w I