PETROLOGY AND PETROFABRICS OF THE JACOBSVILLE SANDSTONE IN THE vzcmmor THE ’ ’ KEWEENAW FAULT ' Thesis for the Degree of M, S. MICHEGAN STATE UNIVERSHY ANN E. CASCADDAN 1969 ichig '13: ate Umversity f WW » I: I ABSTRACT PETROLOGY AND PETROFABRICS OF THE JACOBSVILLE SANDSTONE IN THE VICINITY OF THE KEWEENAW FAULT By Ann E. Cascaddan The Jacobsville sandstone has been brougnt into contact with the Portage Lake lava series by displacement along the Keweenaw fault. At many locations the originally horizontal sandstone has been thrust into a vertical position or even overturned by forces associated with the faulting. Sandstone outcrOps were sampled at varying distances from the actual fault contact and petrographic and petrofabric studies were made on thin sections prepared from the samples. The results showed that there is: I) a sedimentary fabric which is represented, in most cases, by a girdle in the bedding plane, 2) a weak BC girdle, 3) an AB girdle, often quite well defined, and 4) the suggestion, in a few diagrams, of an AC girdle. It is postulated that the sedimentary fabric is an original depositional fabric and the remaining fabrics are the result of forces associated with the faulting. PETROLOGY AND PETROFABRICS OF THE JACOBSVILLE SANDSTONE IN THE VICINITY OF THE KEWEENAW FAULT BY ‘~ Ir :1). ." Ann E. Cascaddan A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology I969 ACKNOWLEDGMENTS The author wishes to express her sincere appreciation to Dr. James Trow for his cooperation and assistance during the preparation of this paper; also to Drs. (3. E. Prouty and H. B. Stonehouse for their helpful suggestions and criticisms. ii TABLE ACKNOWLEDGEMENTS . . LIST OF FIGURES . . . LIST OF PHOTOS . . . LIST OF APPENDICES . . INTRODUCTION . . . Geography . . . Previous Investigations GENERAL GEOLOGY . . . Lithologic Setting . Structural Setting . PROCEDURE . . . . PETROLOGY . . . . PETROFABRICS . . . Wall Ravine . . Wall Ravine Area . Saint Louis Ravine . OF CONTENTS Page . . . . . . ii . . . . . . iv . . . . . . x . . . . . . x1 . . . . . . l . . . . . . l . . . . . 2 . . . . . . 5 . . . . . . 5 . . . . . . 9 . . . . . . IO I O O O O O 27 Douglass Houghton Ravine . . . . . 34 Hungarian Falls . Vicinity of Torch Lake Torch Lake Quarry . a c o o o o 38 Quarry . . . . 4| C C O C O C 43 M 26 Near the Town of Mason . . . . 43 Jacobsville . . Algomah Mine . . Tobacco River . . CONCLUSION . . . . BIBLIOGRAPHY . . . APPENDIX A . . . iii l2. LIST OF FIGURES Location of the Area. . . . Generalized Geological Map of a Part of the Keweenaw Peninsula . Sample Locations, Houghton County . . . . . . . . Modal Analyses of Jacobsville Sandstone . . . . . . . Sample il, Vertical Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size<.3mm . Sample ll, Vertical Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size .l-.3mm Sample ll, Horizontal Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size‘<.3mm . Sample ll, Horizontal Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size .l-.3mm Sample ll, Combined Diagram. Wall Ravine, Conglomeratic Facies. 400 Quartz C-Axes; Grain Size«<.3mm . Sample Ii, Combined Diagram. Wall Ravine, Conglomeratic Facies. 400 Quartz C-Axes; Grain Size .l-.3mm Sample IO, Horizontal Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size (.Bmm . Sample IO, Horizontal Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size .i-.3mm WV Page 20 2O Figures IE. 20. 2|. 22. 23. Sample I5, Vertical Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size <.3mm . . Sample l5, Vertical Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size .|-.3mm . Sample l5, Horizontal Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size <.3mm . . Sample l5, Horizontal Cut. Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size .l-.3mm . Sample l5, Combined Diagram. Wall Ravine, Conglomeratic Facies. 400 Quartz C-Axes; Grain Size«<.3mm . . Sample l5, Combined Diagram. Wall Ravine, Conglomeratic Facies. 400 Quartz C-Axes; Grain Size .l-.3mm . Sample l5, Vertical Cut. Wall Ravine. 200 Quartz C-Axes; Grain Size (.Bmm. Bedding Rotated Parallel to Natural Wall . . . . . . Sample I5, Vertical Cut. Wall Ravine. 200 Quartz C-Axes; Grain Size .l-.3mm. Bedding Rotated Parallel to Natural Wall . . . . . . Sample l5, Horizontal Cut. Wall Ravine. 200 Quartz C-Axes; Grain Size (.Bmm. Bedding Rotated Parallel to Natural Wall . . . . . . Sample l5, Horizontal Cut. Wall Ravine. 200 Quartz C—Axes; Grain Size .l-.3mm. Bedding Rotated Parallel to Natural Wall . . . . . . Sample l5, Combined Diagram. Wall Ravine. 400 Quartz C-Axes; Grain Size (.Bmm. Bedding Rotated Parallel to Natural Wall. . . . . . . Page 2| 2| 22 22 23 23 24 24 25 25 26 Figures 24. 25. 26. 27. 28. 29. 30. 3|. 32. 33- 34. Sample l5, Combined Diagram. Wall Ravine. 400 Quartz C-Axes; Grain Size .l-.3mm. Bedding Rotated Parallel to Natural Wall . . . . . . Sample l7, Vicinity of Wall Ravine, Conglomeratic Facies. 2OO Quartz C-Axes; Grain Size (.3mm . . . . Sample l7, Vertical Cut. Vicinity of Wall Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size ol‘oSmm o o o a o o 0 Sample l8, Vertical Cut. Saint Louis Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size (.Bmm . . . . . . Sample l8, Vertical Cut. Saint Louis Ravine, Conglomeratic Facies. 2OO Quartz C-Axes; Grain Size .l-.3mm . . . . . Sample l8, Horizontal Cut. Saint Louis Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain SiZe (.3mm 0 o o o o 0 Sample l8, Horizontal Cut. Saint Louis Ravine, Conglomeratic Facies. 2OO Quartz C-Axes; Grain Size .l-.3mm . . . . . Sample l8, Combined Diagram. Saint Louis Ravine. 400 Quartz C-Axes; Grain Size (.3mm . . . . Sample l8, Combined Diagram. Saint Louis Ravine. 400 Quartz C-Axes; Grain Size .l-.3mm . . . Sample l9, Vertical Cut. Saint Louis Ravine, Conglomeratic Facies. 200 Quartz C-Axes; Grain Size <.3mm . . . . . . Sample l9, Vertical Cut. Saint Louis Ravine, Conglomeratic Facies. 2OO Quartz C-Axes; Grain Size .l-.3mm . . . . . vi Page 26 28 28 3O 30 3| 32 32 33 33 Figures 35. 36. 37. 38. 39. 40. 4|. 42. 43. 44. 45. Sample l, Vertical Cut. Douglass Houghton Ravine. 200 Quartz C—Axes; Grain Size (.3mm . . . . Sample l, Vertical Cut. Douglass Houghton Ravine. 200 Quartz C-Axes; Grain Size CIT-03mm o o o 0 Sample I, Horizontal Cut. Douglass Houghton Ravine. 200 Quartz C-Axes; Grain Size (.3mm . . . . Sample I, Horizontal Cut. Douglass Houghton Ravine. 2OO Quartz C-Axes; Grain Size Ol-O3mm o o o 0 Sample I, Combined Diagram. Douglass Houghton Ravine. 4OO Quartz C- Axes; Grain Size <03mm o c o 0 Sample I, Combined Diagram. Douglass Houghton Ravine. 400 Quartz C- Axes; Grain SIZE .|-.3mm o o. o 0 Sample 4, Vertical Cut. Hungarian Falls. 200 Quartz C—Axes; Grain Size (.3mm . Sample 4, Vertical Cut. Hungarian Falls. 200 Quartz C—Axes; Grain Size .l—.3mm Sample 22, Vertical Cut. Vicinity of Torch Lake Quarry. 200 Quartz C—Axes; Grain Size (.3mm . Sample 22, Vertical Cut. Vicinity of Torch Lake Quarry. 2OO Quartz C-Axes;Grain Size .l-.3mm Sample 3, Horizontal Cut. Torch Lake Quarry. 200 Quartz C-Axes; Grain Size (.Bmm . . . vii Page 35 35 36 36 37 37 4O 4O 42 42 44 Figures 46. 47. 48. 49. 50. 5|. 52. 53. 54c 55. 56. 57. Sample 3, Horizontal Cut. Torch Lake Quarry. 200 Quartz C-Axes; GraIn SIZE .|-.3mm o o 0 Sample 7, Horizontal Cut. Highway M 26 Near Mason. 200 Quartz C-Axes; Grain Size (.3mm . . . Sample 7, Horizontal Cut. Highway M 26 Near Mason. 2OO Quartz C-Axes; Grain Size .|-.3mm o c 0 Sample 2|, Vertical Cut. Jacobsville. 200 Quartz C—Axes; Grain Size < .3mm . . . Sample 2i, Vertical Cut. Jacobsville. 2OO Quartz C-Axes; Grain Size .l-.3mm . . . Sample 2|, Horizontal Cut. Jacobsville. 2OO Quartz C-Axes; Grain Size (.3mm . . . Sample 2|, Horizontal Cut. Jacobsville. 200 Quartz C-Axes; Grain SIZE .|-.3mm . o 0 Sample 2|, Combined Diagram. Jacobsville. 4OO Quartz C-Axes; Grain Size (.3mm . . . Sample 2|, Combined Diagram. Jacobsville. 400 Quartz C-Axes; Grain SIZE .|-.3mm a o 0 Sample 6, Vertical Cut. Algomah Mine Area. 200 Quartz C-Axes; Grain Size (.Bmm . Sample 6, Vertical Cut. Algomah Mine Area. 200 Quartz C-Axes; Grain Size .l-.3mm . Sample 20, Horizontal Cut. Tobacco River. 200 Quartz C-Axes; Grain Size Approximately .2mm viii Page 44 46 46 47 47 48 48 49 49 5| 5| 53 Figure Page 58. Combined Maxima From Highly Deformed Areas Within 600 Feet of Fault Contact; Grain Size (.3mm . . . . . . . . 57 59. Combined Maxima From Highly Deformed Areas Within 600 Feet of Fault Contact; Grain Size Il-Ijmm c o o o o o o o 57 60. Combined Maxima For Areas Showing Some Deformation; Grain Size (.3mm . . . . . . . 58 6|. Combined Maxima For Areas Showing Some Deformation; Grain SIZE .|-.3mm a o o o o o 58 62. Combined Maxima For Horizontal Strata . . . . . . 59 Photo "LIST OF PHOTOS Page Thin Section Showing Cross Bedding Upside Down Relative to the Top of the Outcrop, Which is Indicated by the Barb of the Arrow . . . . . . . . 39 LIST OF APPENDICES Appendix Page A. Key to Petrofabric Diagrams . . . . 6| xi INTRODUCTION The Jacobsville sandstone has been studied extensively by several investigators in an effort to determine its age and stratigraphic position. Its relationship to the Keweenaw fault has also been noted and theories have been advanced as to how the faulting caused the disturbance of the sandstone. Although several petrofabric analyses have been made on quartzites adjacent to major and/or minor faults in order to determine the nature of the stresses associated with the faulting, there have been no similar studies on non-recrystallized materials associated with faults. It is the purpose of this thesis to make a petrofabric study of samples of the Jacobsville sandstone taken at various distances from the Keweenaw fault in an effort to determine what effect, if any, the forces associated with this major fault had on the fabric of the sandstone. Even if the study did not reveal much about the nature of the faulting, or forces associated with the faulting, it was hoped by the author that it would be possible to determine whether or not a fabric, either sedimentary or tectonic, would devel0p in material which had not been recrystallized. Geography The studied areas are located in the Keweenaw Peninsula and, for the most part, in Houghton County along the Keweenaw fault. Samples were also taken near the Algomah mine, which is located I% miles east of Mass, Michigan, and from the Tobacco River in Keweenaw County (Figure l). The general area is extensively covered by glacial deposits, and the best sandstone outcrops are found in deep ravines which have been cut by streams flowing over the Keweenaw fault. Previous Investigations Although the Natural Wall (page l5) has attracted the attention of geologists for years, there have been very few detailed studies of the structural features of the Jacobsville sandstone and their relationship to the Keweenaw fault. Irving and Chamberlin (l885) wrote the first definitive descriptive work of areas along the fault contact, incorporating into their paper the observations of earlier investigators. From their observations of the actual Junction of the Jacobsville (Eastern) sandstone and the Keweenaw fault, and of the nature of the disturbances in the sandstone adjacent to the fault, Irving and Chamberlin concluded that: "The Keweenaw Series is much older than the Eastern (Potsdam) Sandstone; that it was upturned, faulted along the escarpment, and much eroded before the deposition of the Eastern Sandstone; that the sandstone was laid down unconformably against and upon the keweenaw Series which stood as a sea cliff in the Potsdam Seas; and that subsequently minor faulting along the old line ensued, disturbing the contact edge of the sandstone." (l) I) Irving, R. D., and Chamberlin, T. C., "Observations on the Junction Between the Eastern Sandstone and the Keweenaw Series on Keweenaw Point, Lake Superior”, United States Geological Survey, Bulletin 22, l885, page 480. [all 1. fan» nnnnnnnn ILIS 4 Hamblin (l958) made a detailed study of the Jacobsville formation, including the structure, petrology, and heavy minerals in an effort to determine the geologic history of the area. He found, as previous investigators, that the sandstone is relatively undisturbed except near the Keweenaw fault. Hamblin, however, dates the fault as post-Jacobsviile partially on the basis of the predominant structural trends of the formation at Limestone Mountain. Here the Jacobsville sandstone and the Limestone Mountain sediments are folded into an anticline and syncline, the trends of which parallel the Keweenaw fault and suggest, to Hamblin, that the folding in the area is related to the compressional forces which caused the faulting. If this is true, then the Keweenaw fault is probably post-Devonian, since Devonian rocks are involved in the folding. GENERAL GEOLOGY Lithologic Setting The stratigraphic sequence of the Keweenaw Peninsula is, from oldest to youngest; the Portage Lake lava series, which has been locally intruded by small rhyolite bodies, the C0pper Harbor conglomerate, the Nonesuch shale, the Freda sandstone, and the Jacobsville sandstone. A generalized map of the Keweenawan geology is included as Figure 2. The Portage Lake lava series is a thick sequence of flows ranging in composition from olivine basalt to andesite. Individual flows vary in thickness from a few feet to over lBOO feet, and may extend from a few hundred feet to over forty miles in length along the strike. The flow t0ps are amygdaloidal, averaging five to ten feet in thickness. Many of the amygdules have been filled with calcite, epidote, and quartz. Interbedded with the flows are conglomerates with rhyolitic pebbles. The COpper Harbor conglomerate overlies the Portage Lake lava series. This formation consists mainly of rounded to sub-angular rhyolitic pebbles and boulders, with minor quantities of basalt fragments. Matrix material is of similar composition. Sandstone lenses and fine-grained andesltic lava flows are interstratifled with the conglomerate. The thin amygdaloidal t0ps of the lava flows have calcite, chlorite, and zeolite mineral fillings. EAGLE RIVER LAKE SUPERIOR ONTONAGON Q ‘~:\ ‘ E ‘\ §\\\\:\ \ ‘\\ \~:‘ ________ 1 KEWEENAW \ ‘\ ’’’’’’’ “~\\\ — ’—____ POINT GEOLOGIC MAP . OF THE (9 VICTORIA FALLS ' V JACOBSV'LLE KEWEENAW PENINSULA 0 KEY I\ Q JACOBSVILLE SANDSTONE 0 FREDA SANDSTONE i\\ ‘2 \ ,, \ - \\\ NONESUCH SHALE , 5’; \. i7 la COPPER HARBOR CONGLOMERATE P l PORTAGE LAKE LAVA SERIES PRE" KEWEENAWAN ROCKS iua BNAJ '”h muo‘l'flc - ‘ I r\ “OL- #I/ u — ' ' .v’ a n ‘P" a I n ,v _ r y a a- , ,r v ‘ I I / o a I O O . ‘--‘~ q a”’ I I -~ .. .. ~.~ ‘9’ r ” '7 ‘ nihiin-“fl I‘F ’ .fi ” - I ~r~‘ ’ ’ afiIr-cd‘.--——-" gafl- 1: _ -3 *8 .—~ ‘1 7 " " 1 Ext?! 3941;? mama”. 6?. «r: 5“, 5W 7 .r“. 7 The Nonesuch shale is mainly slltstone. The upper part is a gray to reddish-gray siltstone with minor quantities of gray silty shale. The lower part is a dark gray siltstone with a few coarse-grained arkose beds near the base. Total thickness of this formation is about 600 feet. The Freda is a light gray to red, fine to medium- grained sandstone with occasional lnterbedded red shale and conglomerate layers. The contact between the Nonesuch and the Freda ls transitional. Total thickness of the Freda is approximately 500 feet. The Jacobsville sandstone is primarily a buff or salmon colored, fine to medium-grained, well sorted sand- stone with minor amounts of reddish-brown pebble conglomerate, red shale, and silty shale. Well rounded quartz grains averaging & to § millimeter in diameter are the main mineral consitiuent. Four facies of this formation have been defined by Hamblin (l958). l. Conglomerate facies. This facies is confined to the base of the formation. Well rounded and highly spherical felsite and granite porphyry clasts ranging from granules to boulder size are the main constituents. Minor quantities of diabase and amygdaloidal basAIt pebbles are also included. Matrix material is a poorly cemented sandstone. Channel structures Indicate that this is a fluvial deposit. This facies is well exposed in the Wall Ravine, where it was definitely shown, through heavy mineral studies, by Hamblin, to be Jacobsville. 2. Lenticular sandstone facies. This facies is dominant in lateral and vertical extent. It is a red- brown, medium-grained, well sorted sandstone. Prominent sedimentary features include channel-and-fiil structures and fluvial trough cross-stratification. 3. Massive sandstone facies. The massive sandstone facies is well exposed in many areas of the Keweenaw such as Victoria Falls, Hungarian Falls, and Keweenaw Bay Cliffs. Massive beds averaging five feet or more in thickness characterize this facies. The light red to white color of the sandstone may be related to its higher permeability and resultant greater leaching. Trough cross-stratification and oscillation ripple marks indicate that this facies formed in an environment changing from fluvial to lacustrine. 4. Red siltstone facies. The red siltstone facies is local in extent, with its best exposure north of Jacobsville. Sandstone lnterbedded with it indicates that this facies formed in an alternating fluvial and lacustrine environment. Structural Setting The Keweenaw Peninsula is on the southern side of the Lake Superior synciine of Keweenawan age. In a vertical cross-section, perpendicular to the strike, early Keweenawan rocks dip steeply (60°) and later ones progressively less steeply (down to 250) northwestward to the center of the basin. Transverse to the general strike of the Lake Superior synciine are broad (up to IOO miles across), Open cross folds that plunge down the dip of the larger fold. Superimposed on these large folds are small ( five to ten miles across) open folds of a similar nature and trend, although some are sub-parallel to the Keweenaw fault. The Jacobsville sandstone is almost flat lying with a slight regional dip of one to six degrees to the northwest. This formation is relatively undeformed except in the vicinity of the Keweenaw fault and near limestone Mountain where some folds have developed, possibly as a result of stresses associated with the faulting. The greatest fault in the region is the Keweenaw fault. This is a reverse fault with a northeast strike and a variable dip of 20 to 70 degrees northwest, along which the lava flows have been thrust over the younger Jacobsville formation. In general, the northwestward dipping lava flows on the hanging-wall side of the fault are bent downward so that in places the dip is reversed. The flat lying sandstone on the footwall is turned up abruptly in a number of locations such as the Saint Louis Ravine and the Wall Ravine (Figure 3). In other locations the sandstone near the fault is relatively undisturbed with only minor warping evident. PROCEDURE The field work for this study was accomplished in the summer of i967. The Jacobsville sandstone was sampled at several locations along the Keweenaw fault, at varying distances from the actual fault contact (Figure 3). The strike and dip of each sample was measured in the outcrOp. The specimen was marked with a north arrow and horizontal lines and then detached from the outcrop. Two perpendicular thin sections were cut from each sample. In each, the c-axis orientations of 200 small and 200 large quartz grains were measured using a Leitz microsc0pe and a 4-axis universal stage. The orientations were plotted on a Schmidt equal area net and the concentrations of c-axes were determined uéing a counter of l cm radius and a counting grid measuring l cm between intersections. The large and small quartz grains were plotted separately. IO .Sample 7 JQAOG Sample 4 C) 1 TORCH L A K E Sample 22 LEWO'WO 11 S -- —---—- a Sample I FA U LT g coPPER c 9 a m m ’5' o (’9 9L o 9 SAMPLE LOCATION SanTpIe l8 ° . Sample l9 MINE MAP 3O . Sample I? l. ..\~ - —"‘ V Sample l5 Sample l0 Sample HE S a = ’ ' I-” PETROGRAPHY Microscopjc analyses of the samples from the studied areas indicatethat the sandstone is definitely Jacobsville at all of the localities. The thin sections compare almost identically in composition and percent of constituents to the samples taken from the type section at Jacobsville. There are, however, slight variations from area to area in the amount of quartz present, and the amount and composition of the matrix material. The Jacobsville sandstone is composed mainly of subangular to rounded detrital quartz grains which are present in amounts ranging from 53 to 80 percent of the total constituents. Many of the quartz grains contain strings of gas bubbles and brownish, glassy inclusions. Many also show undulatory extinction. A high percentage of the quartz grains were fractured in the sample from the Algomah mine area, which was taken only a few feet from the fault contact. In all sections a few grains of polycrystalline ouartz were recognized. Some of the quartz grains have secondary overgrowths and in the area of the Tobacco River the sandstone has a siliceous matrix. The feldSpars occur as subangular to rounded grains. Microcline occurs as fresh grains in amounts ranging from one to five percent of the total constituents. The orthoclase and plagioclase present is usually altered to sericite which is stained with iron oxide. The feldspar is present in amounts less than l5 percent in all sections. l2 I3 The matrix in most sections consists of fine particles of quartz and feldspar along with sericite, hematite, and leucoxene. It is the hematite cement that gives the red color to the sandstone. Notable exceptions in the composition of the matrix occur in the Tobacco River area where the matrix is siliceous, and the sandstone is almost a quartzite; at Algomah where most of the matrix material has been removed; and at Jacobsville where most of the cementing material is carbonate. The accessory minerals present are ilmenite, hematite, leucoxene, zircon, apatite, garnet, and tourmaline. Augite, biotite, chlorite, epidote, and lithic fragments also occur in minor amounts. (Figure 4). There is nothing in the petrography of the samples that gives any clue to the nature of the faulting. There is no orientation of the long axes of the quartz grains in the thin sections. The occurrence of crushed grains at Algomah is probably due to the faulting. However, this same abundance of crushed grains is not present in sections from other localities where the sandstone has been thrust into a vertical position. The percentage of grains with undulatory extinction does not seem to be dependent on the sample location with respect to the fault. There is some variation in the size of the grains from sample to sample. The average range in size is .l millimeter to .5 millimeter, with an occasional grain measuring as large as 2 millimeters. __ _0 _m _a _m .0 _ mm u s a m. 0 m0 mmwmm_ooam: Mm“ 0AN. mu.~ 00.u 00.0 m0.¢ m0.0 00.0 m#.. mm.~ am.» ma.s 0¢.~ m0.~ a_.a mm. nm_a. 0.. 0.0 0.0 _u.m 0.w I a._ 0.u I «.0 a._ s.a m.s I. g_n10. m.a m.m m.s U._ m.m u.u .0 m.0 I _._ .0 _.m _._ _h ouayo. I I I I I u.s I I w.q I I I I Iaw 0.00. I I I I I «m I I I I I I I m“ emu. .0 .p .m am am I am .0 I w.a .u I I am n00 I I I _.m I I I I I I I I I IHI :30» am I I I I I I an I .e I .u I I. mmwsmfi I I am I I I I I I I I I I IHL 03.04. am I I am I I I I I I I I I I. 01Nzam _.a .a I am I _.0 m.a m.m m.u .0 m.» I I a“ N24. I I am am I I I I I am am an I “I 40:1. am I am am I I I I I I ._ am I an gmaw.x m_.o _m.0 I I _w.m m_.m _m._ _m.0 m.m _m.s _s.o mm.e _m.m an 1.3. a.a m.m _._ I «.0 I s.u m.m s.0 __._ a.~ .0 am I. m am” I I m0.¢ I I I I I a.¢ I I I I ma“ .HMwn. .0 .0 I I I I .a an _.m _.u .w I I I. >cn‘am Hm .u I I I I I I I I am I I I <0ma I I I I I I I I I I I I m.o IHI now I I I I I I I I I I I I I m“ >uma. I I I I I I I I I I I I I . __3. I I I I I I I I I I I I I m f3 (0 n) fl) PETROFABRICS The Wall Ravine The Wall Ravine is located approximately l.5 miles east of the town of Laurium in the north half of Sec. 20, T. 56, R. 33 W. (Figure 3). Here the Jacobsville sandstone has been thrust into an almost vertical position along the Keweenaw fault. Horizontal joints give the sandstone the appearance of artificial masonary, thus the name Natural Wall. The dip of the sandstone decreases eastward until, within a few hundred yards from the fault the formation is almost horizontal. Toward the fault from the Natural Wall a block of sandstone is observed that has been rotated into a position perpendicular to the Wall, presumably by the Mayflower cross fault which intersects the Keweenaw fault in this area. Sample II was taken from the Natural Wall where it outcrops on the north side of the Wall Ravine, approximately 600 feet from the fault contact. The orientation of the sample is N2OE, 868E. The fabric diagrams of both large and small grains (Figures 5,6,7, and 8) show a weak concentration parallel to the bedding plane which probably represents a sedimentary imbrication. There is the suggestion of a concentration in the form of a broken AB girdle with low maxima, parallel to the fault plane. It is also possible to define a weak BC girdle, probably parallel to real and/or incipient joint planes which are related to l5 l6 the thrusting. The combined diagrams (Figures 9 and lO) show these same general trends, but in a less well defined manner. About 72 feet upstream from the Natural Wall itself, the sandstone forms a waterfall approximately four feet high. The orientation of the sample (IO) taken from this outcrop is N4W, 6ONE. The fabric diagrams for this sample (Figures ii and l2) show a well devel0ped girdle with maxima of two to three percent in the plane of the bedding, which is also nearly the BC plane. The clearly defined girdle may be a result of the combination of a weak BC girdle and a weak bedding plane girdle, which act to reinforce each other. There is also the suggestion of an AB girdle, that is, a concentration parallel to the plane of the fault. A third sample (l5) was taken 2|5 feet upstream from the Natural Wall from an outcrOp in the stream bed which is nearly perpendicular to the Wall. The bedding bows slightly northwest-northeast, the sample orientation being N7OW, 668W. Joints perpendicular to the bedding are displayed, as in the Natural Wall. The orientation of this outcrop can be explained by its proximity to the Mayflower cross fault. Forces responsible for the cross fault probably rotated the bed from an original position nearly parallel to the Natural Wall. The fact that the present orientation of the bed was not caused by the major faulting is illustrated by the fabric diagrams. Figures l3, l4, l5, l6, l7, and l8 show the present orientation of the bedding. It is clear that there is no good relationship 0f the fabric elements It .2227: azaMERflr/c five/£5. was 3-2-/ °o. 9‘17“ MRPMRZ 3. ENHAR -- _' ~. 3'9:le 7715565 OLE 'h3‘gl‘k‘q 00:“ . ;,- ‘ oi“. .3: was ‘ awn ax I: _. , I, I - ,._.- .- . arias. 5 2‘1 °/o p c/écx s. I . 0 r0 54-34 (flan/E. [/15 rag/2c! 01.5 I?” wxvg, Cozvczo Miner; mm C N UR ". 3 E £304 £4055. 3mmPCbA/TOURS 4-3‘2—l °/o 04f Lfi/VE, [/7/5 rye/245F045 K4; V/lVIE} [aw/64 avg/«fine 5 >. 5 [79 -2-/ % . ' a 7'0 0R5 4'3 104 8N5. F1015 7/9’5 Face- 1004: 1.‘ Rn VINE; (bx/64 ONERfif/c five/55'. 3mm C N ‘ 5; GRfi/N 5125 ./ - . 77 N01. Bannvé/QA/VE 52" 15 77/5 59047 ONTHL CU IQ /v/ozz/z C— AXE £77055. O >.3mm.CONVOURS3 E / /o r. WHLL flaw/we; (oNGLOMERHr/c 1 av 57/25 — - fl 5N5: 52 15 was/2047' flan/E. F.” 1.5 THE FECE ~ XES' GRH ca our .41.; ,qw E, NGLO sear/c wows. IGURE /4-. LE /5, VERrICHL cur: NfiLL Hill , E firm: 3c 5. fixes/- RHIN 6725 >.3m . CENroa/es 5-433—2-1 ”/0 20 QUHRTZ C—fixss; I Gaza/N 512.5 ./ —..3mm, QNTOURS 4~3-Z-/ 7° E /5 77/5 .904 HALE. P15 7.95 fficg x0045 5; my; 6 flan/E. 52:15 r35 fiazrflnlve. WM 77/5 Fives 9\ /¢ A2. ., .sVN ., 197% .,. _,.-._/_ "— ” « z .a E}; 1/, HGURE L9. 5,1"ng /5j [/ERf/cx-fl. cur. N541. flaw/v5, C‘o NGLOMERflr/C five/55, FIGURE 20. 5,9”sz /5, V5,? 71654 cur. NH“ 269 VINE, C 01v azoflfflfir/c £79055. 2000a»: 72: CLfixz—‘s; Gflfi/N S/zé' >. 3mm.Co~rou/25 5- 41-3-27 %_ 200 00.9er C—flxEs; 6R3!N5}z5,/—.3mm. CONTOURS 4—3-2—/ 7, 5, /5 7/45 Eon/N6 2’74”.sz WHICH m3; 555” flo ”a 7‘50 fi/(flLLEL 5 15' 7/45 Become/QHNE WHICH mas age-w 40mm» ”maze-4 70 7'19! ”fifU/QHL NfiLL.5 IS 7H5 %HULffl/9NE, Ffl/S VHF/47765 7:0 ffié‘ ”firyRfiL fi4¢_5 [5 7H5 [fig/47 LHNE [lg/s- 7395/5ch P045 0” 77"! flag: 2 1701.5 0; 7H5 [£70477 2 . flexes. 3 ‘ a-/ '70. 17.6.91. 54 27/5 fies / -. 3mm. 6‘ NI'OURS 355M flame/£7350 Hen/é: Plo- flvx/I/é; QNGLOMEMr/c Hal/.7 ”I? [S 7.95 AIM/E WHICH .5 fl 4. .441. r nan/£9 _ 7‘ [2414. . z goo/No , /Uoz.E or HE ma rz C-HXES; GM/N IS} 25 . / /5, /7/0RI ZON 7.41. car: 00 5' AS 7H5 7' #5 flex/R5 22. Samoa; 200 a—/ %.' L K»? wva, (EA/64 OMERfif/C 59055 7.5 >. 3 mmgoxvroa/fas 3 - arena—’0 fiflfiLLefi—‘L file/v6. F/g 1.3 ff/E F205 cur. IA/nz. m/ S/ 7H5 F5047" R N L rz. C—flXEs; GR)? E 6500x~a FLA/w; WHICH was @9ng .SZ/s M44. 1904.77 PPPPP ”Ge/RE 23. SHHPA E /5, COMB/N50 i/fiGk/VN- WWI-I- flfiwxvé; (5M6LOMERRr16/j96/ES. AG URE E4. gnu/74 E /5, Cone/NED flag/23M. H.944 flfi VINE, (BA/64 ONEkflr/C [kc/5,5. 400 0"”ng 0,4:ng GR’V’” 5:25 >- 3mm-G’N’OURS 3‘24 7°» 5, ’5 400 0019/372- GFXES'; Gflfi/NIfiszn 3mm. (fauna/R5 Zv/ 70.5, IS I 7.95 55.00/NG fizz/v5 wave/4 M95 EEE/v flo 779750 fixes/.454 70 77/5 7H5 5500/N6 flan/5 wH/C‘H #195 6’5ng fa r9750 ’49.?54454 70 27/5 ' Aden/.071. Nfiéé. 52' IS 7H5 A301. TfifiA/Ef [10/5 rag/2c; xpazg or fix; //l/_.firc/Rflz_ A/fizz, 5?: 15- 77/5 15304.7 flame; yew/5 7,955,635 ,0045 a; ”I: Ffiuz. 7‘.’ flux. 72‘ e.\ am 2.\ '3 mmE .< 33.x \ .EIMRSN 3» . \A\\l W O . Z\ vans aavm'b ‘ sane \A {~\ an“ {E a s\‘:m F E/7, V50 C G /\/ I. flaw/2‘56 F 6.2%” O C WAC/f. N640” . E , 3mm. 0 I m. 0N - S... a”; ,0 F 2 Ms. 50,. F x7 57?. 5 P if 50,. :255/7 5 62"” 0': r F 29 examined lie in the vicinity of the old Saint Louis mine, approximately one mile east of Laurium. The sandstone is overturned near the fault contact, the northwesterly dip being an overturned dip, as indicated by cut-and-fill cross bedding, rather than one indicative of the sandstone passing beneath or being overridden by the basalt. Eastward, the dips pass through the vertical position, seen also in the Wall Ravine, to a southeasterly direction and then decrease until the formation is nearly horizontal a few hundred feet from the fault. The sandstone at this location is very thin bedded, almost shaly, and lnterbedded with conglomerate. Sample l8 was taken approximately |5O feet from the fault contact and no sandstone was seen outcropping above this point. Cut-and-fill cross bedding indicates that this outcrOp has been overturned, the orientation being N5OE, 64NJ. The fault at this location has an orientation N25E, 3ONW. The fabric diagrams (Figures 27, 28, 29, 30, 3|, and 32) show the presence of a BC girdle, especially well defined I in Figures 27 and 28. There is also the suggestion of an AB girdle and a fairly well defined bedding plane girdle. A broken AC girdle is suggested, however, in most cases there is a very well defined central minimum which disrupts the girdle. The combined diagrams (Figures 3| and 32) show the tendencies mentioned above, but in a somewhat less well defined manner. Miazontfinnc 16¢“; 2&sz ©\ 31“““EBSESIUBA‘ _. "323'\:3V: «roux: I- J-aa/ 733:3 . we) svstroS - , , : i _ - . 3.“ , (S gsr/rgflc‘g‘g a, s am;i?§\:~n I I ,- , _ - ,. . ,. mums“: - \-\\ _ AMP) 5 l8, yé—erfiu cw; 639m r/guzsflnvmz—j (“ax/oz onERfir/c [fie/ES. Fwy/«5‘28. Spry/OLE /8, [/z-ver/cfiz cw; Samar-Zeal: flaw/v5, (EA/040M fine/:40 s EOOOUHRTZ GFXES; 6,9,91ng >_ 3mm. CED/VTOU/{S 3-2—/ 0/0. 5: /5 THE EOOQz/fi/Qf‘z C‘fiXES'; GRfi/N 5725. /-. 3mm.(5~7ouks 3 a-/ 9/43 ,5 EEOC/N6 Pay/v5. 3 /S was ,9qu fizz/v.5. Fig/s 7095 Flea—r xgozé af THE THE 6500/NG law/v.2: 67: 15 773/5 fluzrxpzmvé. F2015 77/5 on? 01.5 ’ F5047: z 7H5 504—73 a A s .1 _ 1N7 7.46 4‘ I“ is 101%. (A4» ,0 .l, a N v,” x, , Q A. /\ ............. se a 147/" gCa/I/Gzongkfir/c/flczés, , Rs‘s-Z- ‘a. V i 41mg, [PM 71/5 #7435 Pass * ,: Loo/5 Hill I? IV 1Z5. / fmrn/gozvroc/ fat/E 1704-7 ”ms/eggs: N 5 l.5/8, (Elva/NED z C‘fiXES' Glam ING- PLEA/E, z 15 P 0a»? 47' 15 rare/.5500 p.94. 77 E .3. 73x 3\\\9AMQS€SV\63§V\N?§\txucfij“IQ, 1w) SWAW'AEN \QA'aAfihAZIE‘é E‘ABBR \ \-.S ~E-§ zfivoxvmbgumf, .< BSI \A>P\9\t) paw-G) 3'! 9.an ODS - - ' , asakswn z®\\ 3ms§\mmv1\ as“ zxsbbmhamxacsfizmx 2.x 2, -- ;. . . , Rst an“ no 34 Downstream, approximately I66 feet from sample l8, or 3|O feet from the fault, the sandstone is not overturned and has an orientation N45E, l6SE. Sample l9 was taken from this outcrop. The fabric diagrams (Figures 33 and 34) show a fairly well defined sedimentary, bedding plane girdle and the suggestion of an AB girdle. A BC girdle, if present is broken and very faintly developed. Figure 33 shows a slight development of an AC girdle. Douglass Houghton Ravine The Douglass Houghton Ravine runs east and southeast through Sec. 3|, T. 56, R. 32 W. (Figure 3). The sandstone at this location is not highly deformed as in the Saint Louis and Wall Ravines. The northwesterly dip indicates that the sandstone has been forced beneath or overridden by the basalt. It is possible, however, that this is an overturned dip similar to that observed in the Saint Louis Ravine, but no criteria for judging this were seen. The sandstone at this location is well indurated, quartzose, and interbedded with conglomerate. Sample I was taken near the Douglass Houghton Falls. The first sandstone outcrop was seen approximately IOO feet from the fault contact. The sandstone is not highly deformed at this location (N2OE, 23NW), the strike and dip of the bedding being nearly parallel to the fault. The fabric diagrams (Figures 35, 36, 37, and 38) for the large and small grains show a well defined girdle in the plane of the bedding, which nearly corresponds to the . / I I ‘l-IIIIIII .I. I w H «a. I n L WV! / V —/% 3 "2 flea/0045 /’ 0 K5!" we; (gave; awe/2577 c .6 Alma [figs 72/5 shire/wee w m m ;GM/N SIZE ./—.3 65x55 fig”. f/MA/E. flouo azrz oxNGflnNE. .5“; 15 777/5 36, 5.4/9sz /, Malena/94 cw: Fa c155. Zoo 0w: 5 IS THE 50 r . fisuRE 0/0. R53‘Z‘/ IVA/5: [/45 THE [5'66 /Ooz.£ >. 3m m. @NTOU 6‘ 5' 5 417/” IZE 7/2 xflouozpss cue/470 a C—fixES ING flfi/véf 57: /5 7/95 flu; /, VIE/37071. c u t 15 THE 55.00 (147: fiUL d; 27%; —a-/% F 3 fires @245 o 0R5 ./—-.3mm. Comm [10/5 7195 Hoary/r0” Kn VIII/El CdNGLO/‘fl-‘Rfi we, 7/”; ”M5 fl/N 5125 £504 r flame-1.525 0 flan/272: C'HXES; 61¢ 62' IS 7H K932 77an ca 7H5 5500M/G flame: Mei .3 8. Sfiflfiéé‘ /, 14796155. 20 5’ IS fHE 59:14.7: ,46 4 3-2~/ “A p 5_ _ I965 @z E o HMS. 50/5 77/5 F HOUGHI’ON 169 V/A/E/ GflNGLOME/Qfif/C ,> 3mm-Cozvroufls N 5726 . 5041/01. z flouc—LA 55 05/27er Gfixgs; Gram ING firm/5, 5;“; rm; hem—’5. éOO HE 6500 I! 159047: AGO/a" 37. SHMPLE / VERr/CHL CU 5, /S7' J 560/25 33. SnmpLgl, COMB/NED amok/WV, oueuzs /—/oueH roxv Rn xxx/mg, flea/25 40. SflanEA Game/NED fl/fieRfi/v; flat/64195 /—/o'uo,q 701v fig Wye: ON 64 OMERflflc flC/E 5, 400 (#9er C'HXES; GRfi/N $25 CONGLOMERfif/C #6155’6400 flan/<77, 63,7155)- G/gfiuv 5,15 >. 3mm. CENrouxzs Z-/ 70. \5, IS THE BEDDING/ULfi/VE 5 IS ,/«_ 3mm. CBNrouRS 2‘ / [3. 8 IS fHEBEfiolNG Lfl/Vé‘. S; ,5 7/715 f204r/va5. 50/5 771/5 flag 10045 a: rm; [Zn/u: 2 1 A V A. ‘ ~ (7 r > --V _wr _ __... -,--,;,. . _ fl-lé‘ [ya/.7 flaw/E. F1” I; 77/! Fine Pow: or Ms flan? n '3 \ NAB BE Baum? a M 5v") ' ' -' mmtifi C» ' ~ F953 zm- " " 1.2 - L__— .p; .r‘ oknqaemfiqimxa c ‘3.“ QQQQ§.ZE\'JR om 9‘3 0: o ' Bum—'3 xx 9A a\ 3, (X \—s iavofimé) '- zvzx m‘y .ByxguR a h m“ as 2;.me 2.2% emu“ amen ‘3“ AR mow“ m ESQ, vwaaB 3, ‘\ «4R ommus aw: 3.3““ 2.\ 3,3“ 5. 38 AB plane. The tectonic and sedimentary fabrics probably act to reinforce each other, accounting for the well developed girdle. A fairly well defined BC girdle can be seen in Figures 35, 36, and 37. The author also believes that there is a faint suggestion of a girdle in the AC plane. This is especially noticable in Figures 37 and 38. The combined diagrams (Figures 39 and 40) show the AB-bedding plane girdle well and also the suggestion of a BC girdle. Hungarian Falls The Hungarian Falls are located on the Dover Creek, approximately l/2 mile northwest of the town of Hubble. (Figure 3). The river makes three falls, the first two over Keweenawan rocks, and the third, and main one, over the sandstone. The sandstone at this location is massive. The dips are low, ranging from lOo to horizontal, and vary in direction. The most common direction is northwest, however, dips to the northeast, southeast, and southwest are also observed. An interesting feature noted in one thin section from this area is an example of cross bedding, which is visible megascopically on the slide, and defined by a concentration of Opaque minerals. (Photo i). This cross bedding is upside down relative to the tap of the slide, or the direction the author called the t0p of the outcrOp. Although the sandstone in this area has never been considered Photo l. 39 Thin Section Showing Cross Bedding Upside Down Relative to the Top of the Outcrop Which is Indicated by the Barb on the Arrow. CE ‘ ' /‘»’/,‘ anE 00/94/27. R5 3- 2 — 7/04 mus-j F,” I: 77-15 A? 75/3CH w 5725 ./—.3r»m.C2wroa fiA/E 5; 15 rm:— [[904 Gan on. Car. VIC/N177 a; , PL E 22, 17er C-fixglg; L OO , IS 7H5 EDD/MG E OF 77/5 Fiat/(.7: flame/2 7’. Iva/3a. CD/vfouks 3 ~2-l ‘2. new A321. 7 ale/v5. [7/5 7145 £705 75/66}! A HKE X9~9~9A>Q Ems-A HaauT no wauzN Kc?) mamas.“ :SS BARMZIEJ§ asuaR \° \-S-E2,sx\so~w\© .mma .< axx'e, \MwAB ;z‘txv\~f) 5..“ >_\P~\>.Q DDS _.:.', - ‘ 232*“ z\“\\ ammeauSA as“ ax 5:2, .BvxaRam§QQ'a am at B, "zuffn wawzfi 3w< no 34o 4| to be highly deformed it is conceivable that the observed dips are overturned dips and that the sandstone, rather than being horizontal has been pushed into a recumbant fold by forces associated with the faulting. Sample 4 was taken from the base of the Hungarian Falls. This area is located approximately l,300 feet from the fault, which trends N35E, and dips 25NW. The orientation of the sample is N35W, 4NE. The fabric diagram (Figure 41) for the small grains shows a rather pronounced AB girdle, and also a tendency for a BC girdle, the main concentration (6%) being nearly perpendicular to the plane of the fault. There is no girdle in the bedding plane and,therefore, no indication of a sedimentary fabric. The evidence of a sedimentary imbrication is also lacking in the diagram of the large grains (Figure 42). The large grains also show the deveIOpment of a weak AB girdle, although the highest maxima do not lie exactly in the fault plane. One could imagine a weak BC gridle and also, perhaps, a tendency for a girdle in the AC plane. Vicinity of Torch Lake Quarry Sample 22 was taken very close to the fault contact, which is not exposed at this location. The outcrop, undulating and massive, is located approximately l/4 mile southwest of Douglass Houghton Falls. (Figure 3). The sandstone does not appear to be deformed, Other than its 33 mauC; 00$ 3'stqu nun-A Rosita aw; 4‘1“§x\9\5\3 ‘6 nausea» “03R .g\° \-S-E.§,9\uoxvm. umMB‘, Rm?) ““6st "t —. ESSNNMA Eva mQF-x Amfifixauclxnwl- .r‘ ' . amen“; ovxxuoafiixn m :8, . x .mm ‘emx \o 43 crinkled or undulatory appearence. Although it is difficult to determine, due to its massive nature, the outcrOp appears to be essentially horizontal. There is no well developed pattern in the fabric diagrams (Figures 43 and 44). There does seem to be an indication of an AB girdle, and also a suggestion of a girdle in the BC plane. The remainder of the fabric elements probably represent a slightly disturbed sedimentary girdle in the plane of the bedding. Torch Lake Quarry The Torch Lake Quarry lies about one mile south from Douglass Houghton Falls. (Figure 3). The sandstone in this area is massive and undulating with the dip ranging between 0 - ID0 to the northwest. The orientation of the sampled outcrop being N355, lONW. No definate preferred orientation is present in the fabric diagrams (Figures 45 and 46). There is, however, an indication of a bedding plane girdle and an AB girdle, perhaps reinforcing each other. There is also a faint BC girdle which is broken and of low intensity. In Figure 46 however, the three percent maxima could be assumed to lie parallel to the BC plane. M 26 Near the Town of Mason The outcrOp sampled lies along Highway M 26, west of the town of Mason. (Figure 3). Here the sandstone is essentially horizontal and lies approximately l.5 miles F 1/572 rm f/ F /7 E 540/ F VERf/CHL c H F M F 5. 6‘. m C - - 0 J 5 mm " 1’0. Q 6;:0/N: ,0 G 6‘ F P [)0 figs/5,2; 0 ,6 gal/(1,6326)? S F lg)? [/0 F 25// , fl 5 Eu; P [EULZ‘ ' ‘ ‘ s Exact 3 : , EVA 3.0 34% .zg’tS‘xmwQQQSa ‘- . ' BE \BQ ,- 3.x»; 8 .< 53:2, \mwAQ ;33XR~ an: EA 3; Emma e , “5A _xxcR “mama vm\-\ K03 am: give.“ {(1 amnefi .\\- 35w. .3. R V\ 3 ZSvBTMD .mm 3 Run 3533 .3VW~§\\ 2,2.va 3u\2.zm\‘\ 3 RE A o\°\— - 3 45 from the fault contact. The fabric diagrams (Figures 47 and 48) show a tendency toward a BC girdle and a concentration parallel to the plane of the fault (AB girdle). The AB girdle could be partially sedimentary and perhaps there has again been a reinforcment of the sedimentary fabric by forces associated with the faulting. Jacobsville Sample 2| was taken near the town of Jacobsville (Figure 2). Here the sandstone forms an outcrop which rises approximately 35 feet above the lake. The bedding is horizontal and massive. The sample was taken for use as a standard in determining the effect of the faulting on the orientation of the quartz grains. It was assumed by the author that since the sandstone in this area is undeformed, if a fabric is present it would be the original sedimentary fabric and not one caused by the faulting. The results of cross-stratification studies in the Jacobsville by Hamblin (l958) indicate that the direction of sediment transport in this area was west-northwest. If this direction is assumed, then a maximum or girdle t plunging northwest, or downstream, would be expected on the petrofabric diagram due to the orientation of the long axes of quartz grains in the direction of stream flow. The fabric diagrams (Figures 49 and 50) seem to indicate a rather poorly defined girdle dipping northwestward "f \) e¢ s. é/VEFR ”no-om ‘3 Emma'l, .8} aaugA / .- . x3: .awowas 3-2-/% saw. 003 _ - . ' .- ‘ m 5N5. P15 7H5 b.3m--¢\ 3 . ~ 346\ in.“ F 5 ZONffiL w Y/‘f-E‘é f7 7 // z. c 7:/ w é/vg R ”as N 0 6‘ x55; 6’ 5 mmfom 1/2 f 5 ,4ng N Rig/N mfb ray/as 3 / GPO?” 5 F 47 4’9” fl 6500 x7 E. 5 /s F ”NE. [/15 779 x” as 5 A30 ,c- 1.5 or f 7: z % 5 r0 RS 4—3-2-l Ffé/s rag/9c 7670/VE [136/561 Fur/v5. 5; £50 5/4 7.95 59qu rjécoxss wu. , Glee/N 812.5. /-. IDLHNS. % 15 C H EDO/NG 0F THE flau- 0. varpz E El, VER 77an Car. 200 vagrz - XES' F/GURE 5 a-/ % 3 IS THE xfioLE NE file/£5, f? 6725 >.3rr’»m. (Zn/vrouks 4-3‘ F flflNE.F/p/5 ff/E flea I ” ms five/ES. ' "/ cg . (K 5 oxvrouxzs 4-3-2~/ o 7' 10 M/VE. Fla/s 77/5/79 WEaU/flekfimrchoeswug, .527 ersro S; GRfi/N5725 .7-. 3mm. 8 7/5 747907. I, (29173 C‘HXE E 5£DDING laLH/VE. z 7.5 r F 7-7/5 [:7qu Aim K /(,1->\ 2, RR amtfi'cx 3.x?) as? \asswaswfij \wasemQx travuano'} 3‘2; 3 nun—e. .L‘c‘. flauaC-‘x «32,? (55—8 zsxuowmo .mma .5 am?) an?) ream-‘5.) 3T9~RsuQ cg». . - 1' S;‘~3‘=~\ BM HER EARS: .‘..\)%\ :«mx ‘m SL1 .vaxi amuse. 7mm 2, A“ A . \ / . .. IRAQ“ 3\'\'\ \Q BAOR 50 between 20 — 500 and defined by three, four, and five percent maxima. Figures 5| and 52 also show this girdle tendency, however, there seems to be two quite well defined highs in Figure 52 situated Opposite each other. Figure 5| shows a concentration of grains plunging at a low angle to the east-southeast. The combined diagrams (Figures 53 and 54) again exhibit a tendency for a dipping girdle with the main concentration in Figure 54 in the eastern portion of the diagram. It is the authors Opinion that the diagrams do suggest a girdle dipping in a west-northwesterly direction. The other concentrations could be explained as common sedimentary fabric patterns in which there is a tendency for a single or double maximum in the plane of the bedding, situated either parallel or transverse to the prevailing current direction (Figures 5| and 52). Another common sedimentary fabric is a girdle in the plane of the bedding. These fabric diagrams probably show a combination of sedimentary fabric patterns. It is also possible that these patterns have been disrupted somewhat by forces associated with the faulting even at this distance from the fault contact. Algomah Mine The Algomah mine area is located l.5 miles east of Mass, Michigan in Sec. 3, T. 50, R. 38 w. (Figure 2). Sample 6 was taken from massive and very friable sandstone 00/9er C-fiXES' o. 5, Is “7/; 6600/NG ' ' 57%“: a; 77/5 7534/47: ‘ 3-2-/ 7’ fi/VE. .FF/s ”IE/57c cnz. car/71.607187]! MNE/qREfi. Zoo .60 rooms 4- ' afi- fiMPLEé, 5/277 N 125, 1—.3mm s 7W5 flu 1) sxgmsgoss .exem‘k 3mm \ARMQE).\\ Ru‘) no“ wail "5 awe/‘63 BB 315“: E>\_‘\ “QQBBBRK a\ 3 A? \-S-8-¥_‘¢9\\>o~< m6) out-«EX ESQ, \Amsxa '- \ an“ \0 3x3 33% m“ s\"\\\ ,3va tsueR and 2,\- ~53 .‘amaf‘v , '- .- 52 outcropping near the Algomah mine and only a few feet from the fault contact. Although massive, the sandstone appears to weather along a plane that has the orientation N50W, BONW. The fabric diagrams (Figures 55 and 56) show a fairly well defined girdle in the bedding plane and a somewhat less apparent AB girdle. Maxima of one to two percent define a girdle parallel to the BC plane. There is, perhaps, also the suggestion of an AC girdle, especially noticable in Figure 56. Petrographic studies by the author indicate that this sandstone is almost identical in composition to known Jacobsville outcropping in the type section, and also to that outcropping at Victoria Falls, as described by Hamblin (l958). Tobacco River Sample 20 was taken from an outcrOp in the Tobacco River, which runs east across Keweenaw County (Figure 2). This location is approximately seven miles from the fault contact. The outcrOp has a slight northwesterly dip. It is composed of white sandstone and has a siliceous cement. The fabric diagram (Figure 57) shows a tendency for a bedding plane and AB girdle. A weak BC girdle can also be defined. Axfb ERNEMQ QQS .anvx‘k OSSRba xv) A“‘\AOS\9\Q‘\A\ ‘05 Rafiww, . an m 2,, \—s~‘e‘,-§ B's-\QCR‘ykéb 'm‘C‘S Ngsxmmxxomquxaxx m9. 2.x“ 5.0 3;§\33Q\3w< 2,\ 5R BAR ;\\ A\>?~:\ 3‘“- 2,\ E .EMafA amxoas S CONCLUSION Three, and possible four patterns of preferred orientation are found in the sampled area. One is a sedimentary pattern defined by a girdle lying nearly in the plane of the bedding. It is probably a combination of sedimentary fabrics which may have been slightly disturbed by forces associated with the faulting or.with tilting prior to the major faulting. The second fabric is the suggestion of an AB girdle. This girdle would be expected as the long or c-axes of the quartz grains would tend to align themselves parallel to the direction of movement or perpendicular to the direction of greatest stress. In many cases where the bedding and fault planes are nearly parallel this girdle is very well defined. Probably the sedimentary and tectonic fabrics tend to reinforce each other. The third pattern is that of a BC girdle. In many cases this girdle is of low intensity but the trend is visible. Balk (l952) found the deveIOpment of a BC girdle in the Poughquag quartzite, Dutchess County, New York, in a similar situation of thrust faulting. This girdle would be expected as the result of dilation on a direction parallel to the fault, resulting in recrystallization along Joint or incipient joint planes formed perpendicular to the fault plane. A possible fourth pattern can be distinguished in 54 55 some diagrams. This is an AC girdle, perhaps similar to that found by Higgins (i947) in the Sturgeon quartzite, Dickenson County, Michigan. Higgins feels that this orientation is related to rotational shear about a vertical axis related to the faulting. He correlates the shear with differential movement of adjacent fault blocks. It is also possible that tension resulting from a rapid change in the plunge of the fold axis would cause tension joints to devel0p parallel to the AC plane. There would be a tendency for recrystallization on this plane in response to reduced pressure. The maximum concentration on diagrams for horizontal, slightly deformed, and highly deformed outcrOps were combined and plotted. The resulting patterns for large and small grains in the highly deformed areas lying within approximately 600 feet of the fault contact (Figures 58 and 59) show fairly well defined AB and BC girdles. The orientation of the fault is about the same for all of the areas, the average orientation being N25E, BONW. The fault plane and face pole are shown on the diagrams. In the diagrams for the less deformed appearing areas (Figures 60 and 6|), at distances greater than 600 feet from the fault contact, the AB and BC girdles are not as well defined. There is, however, the suggestion of a weak girdle in the AC plane. The combined horizontal maxima (Figure 62) lie in a fairly well defined girdle nearly parallel to the bedding plane. 56 The study shows that there is an original depositional fabric present in the sandstone. This fabric has been disturbed by forces asscoiated with the faulting, and a tectonic fabric has been overprinted on the sedimentary fabric in the form of fairly well defined AB and BC girdles. The presence of this tectonic fabric indicates that the major movement along the Keweenaw fault was definately post-Jacobsville, and that the contact between the basalt and the sandstone does not represent an unconformity with the sandstone being deposited against the fault scarp sometime after the major thrusting. Although there is the development of a tectonic fabric, the exact nature of the deformation of the sandstone is not indicated by the petrofabric study. Ripple marks from the Natural Wall, collected by Dr. Harold Stonehouse (2), indicate that the top of the formation is to the southeast. This means that the Wall was formed by the thrusting of originally horizontal beds upward into a vertical position, and is not a situation of reverse drag. There is also evidence, in the form of overturned cross bedding, that the sandstone at the Hungarian Falls has been thrust into a recumbant fold by the faulting, instead of being relatively undeformed as was previously believed. Detailed field work, which was beyond the sc0pe of this thesis, is needed to interpret fully the exact nature and extent of the deformation of the Jacobsville sandstone by forces associated with the faulting. 25 Stonehouse, Dr. Harold, Personal Communication, l969. image 5 8 Cone/NED ”RX/Mg FROM HIGHLY 05/04/750 meg/v.5; w; mmv 600 F567 fiGURE 59, Cane/NED ”mum-7 FRONH/GHLY OEFORNEO meg/95, wzrxmv 600 figgr 0.6/27qu (bx/racy? Gknzfl$z£ ./ -. 3m m. .5; IS 7745 fluzr fin/vs, 0.: 15,3047 (Ex/ram: 64/9/14 545 >. 3m m. 3 15 77725 fivULr/azn/VE, 2- 1‘?” IS 7H5 AIME $45 a; 7.95 5:14.77 FF ,5 77/5 flog $4.5 at 77/5 15794147: l l l I l i i l i 03 LA FIG was 40, Cong/~55 Max/rm FOR fiREfis SHOWING SOME 05/60/1149 ng/N J/zg >, 3mm. 5‘: IS n45 fioazrflmve: f/als 77/5/ch or fl-IE Fin/47’. 770M. PoLE '____— —-.._—_ HGURE él. Cons/NED ”fix/N17 FOR mums 5H0 WING 50/75 OEFORNH r/oM RMN 5,25 >. 3mm. ,5 ,5 ”/5 Favuzr/ULHNE.FPI5 7w; IEkC'E/aoLE OF THE FPULT. ‘ z FIGURE 62. COMBINED Nflxxnfl 143R /-/0R/ZON rm. ,5ar n7, m m P: (be. \ é: 6 )rl *4 .1 *MM l i -~ .. ~. A . ~° ' - I"-.“"’- ~~ . f \ “ 9-- A -“ .V.\$\S\‘\B A‘A‘u‘v’x‘x‘: um... ‘r‘\ PUEN Wes. ,. ‘4‘ :1 3\'\ IEMCIB .52: ‘2.>‘x“4~.4\'\ BIBLIOGRAPHY Balk, Robert, l952, Fabric of quartzites near thrust faults: Jour. Geology, v. 60, p. 4l5-435. Billings, M. P., l954, Structural geology, 2d Edition: New Jersey, Prentice-Hall, Inc., 490 p. Dennlng, R. M., l949, The petrology of the Jacobsviiie sandstone, Lake Superior: unpublished M.S. thesis, Michigan College of Mining and Technology. Fairbairn, H. W., l939, Hypothesis of quartz orientation in tectonites: Geol. Soc. America Bull., v. 50, p0 '475‘l4920 Griggs, David, and Bell, James F., I938, Experiments bearing on the orientation of quartz in deformed rozgs: Geol. Soc. America Bull., v. 49, p. l723- l7 . Hamblin, W. K., l958, The Cambrian sandstones of northern Michigan: Michigan Geol. Survey, pub. 5i, l46 p. Higgs, D. V., and Tuneli, C., l966, Angular relations of lines and planes: San Francisco, w. H. Freeman and Co., 43 p. Higgins, James W., l949, Structural petrology of the Pine Creek area, Dickenson County, Michigan: Jour. Geology, V. 55, p. 476-496. Irving, R. D., and Chamberlin, T. C., l885, Observations on the junction between the Eastern sandstone and the Keweenaw series on Keweenaw Point, Lake Superior: U. S. Geol. Survey Bull. 23, I24 p. Pettijohn, F. J., l957, Sedimentary rocks, 2d Edition: New York, Harper and Bros., 7l8 p. Stonehouse, Dr. Harold B., l969, Personal Communication. Turner, F. J., and Weiss, L. E., l963, Structural analysis of metamorphic tectonites: New York, McGraw-Hill, 620 p. Visteilus, Andrew B., l966, Structural diagrams: New York, Pergamon Press, l78 p. 60 APPENDIX A Key to Petrofabric Diagrams 6i // /