DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY , ' ' ' *< ! !-" GEORGE OTIS SMITH, DIRECTOB BULLETIN 549 THE SHINUMO QUADRANGLE GRAND CANYON DISTRICT ARIZONA BY L. F. NOBLE WASHINGTON GOVERNMENT PRINTING OFFICE 1914 CONTENTS. Preface, by F. L. Kansome................................................. Introduction.............................................................. Location and geography................................................ Field work............................................................ Literature............................................................ Acknowledgments.........................................."............ Physiography of the Grand Canyon district................................. 15 Topography of the Shinumo quadrangle...................................... 2l Climate. .........=...................................................... 25 Vegetation............................................................... 27 Indian ruins.............................................................. 28 Geology.................................................................. 29 Age and character of the rocks.......................................... 29 . Series of rocks discriminated........................................... 31 Proterozoic rocks..................................................... I 32 Archean system.................................................... 32 Vishnu schist.................................................. 32 Name.................................................... 32 Distribution in the Grand Canyon........................... 32 Occurrence and distribution in the Shinumo quadrangle..... 32 Types of the schist......................................... 33 Lithology of the types..................................... 33 Origin of the schist............................:............ 34 Age and correlation....................................... 35 Intrusive quartz diorite and dikes of pegmatite associated with the Vishnu schist............................................ 35 Quartz diorite............................................. 35 Pegmatite................................................ 36 Algonkian system.................................................. 37 Grand Canyon series........................................... 37 Name.................................................... 37 Distribution in the Grand Canyon........................... 37 Structure and distribution in Shinumo quadrangle.......... 39 Unkargroup............................................... 40 Character and subdivisions............................. 40 Hotauta conglomerate................................... 42 Bass limestone........................................ 43 Hakatai shale.......................................... 48 Shinumo quartzite.................................... 51 Dox sandstone......................................... 53 Comparison with type section in Unkar Valley........... 53 Age and correlation of the Grand Canyon series......... 54 4 CONTENTS. Geology Continued. ' page. Proterozoic rocks Continued. ' Algonkian system Continued. Grand Canyon series Continued. Intrusive diabase associated with the Unkar group.......... 55 Occurrence............................................ 55 Petrography.......................................... 56 Variations in character................................ 56 Contact metamorphism................................. 57 Asbestos.............................................. 58 Age of diabase........................................ 60 Paleozoic rocks........................................................ 60 Results of previous work in the region............................... 60 General succession of the Paleozoic rocks........................... 61 Cambrian system................................................... 61 Tonto group................................................... 61 Tapeats sandstone........................................ 61 Bright Angel shale........................................ 62 Muav limestone....... i.................................... 64 Correlation of Tonto group. ................................. 65 Unconformity.................................................... 65 Carboniferous system.............................................. 66 Redwall limestone............................................. 66 Aubrey group................................................. 68 Supaiformation........................................... 68 Coconino sandstone........................................ 69 Kaibab limestone......................................... 70 Variations in thickness of the Paleozoic strata........................ 71 Effect of the variation in thickness of the Paleozoic strata upon topog­ raphy of the canyon wall......................................... ' 73 Structural geology........................................................ 75 West Kaibab fault..................................................... 75 Faults of the Unkar wedge. .................................... ^....... 77 Displacements of the Paleozoic strata.................. i ............... 78 Geologic history.......................................................... 80 The sedimentary and erosional record................................... 80 The plateau problem................................................... 88 Scenic interest of the Shinumo quadrangle................................. 91 Copper deposits of the Shinumo quadrangle.................................. 93 Index.................................................................... 97 ILLUSTRATIONS. Pago. PLATE I. Geologic map of Shinumo quadrangle, Ariz., with structure sec­ tions. .................................................... In pocket. II. A, Traveling on trail in Grand Canyon with pack train; 5, At Bedrock tank, Bass Canyon.................................... 12 III. A and B, Views up Colorado River near Cable Crossing............ 16 IV. A, Panoramic view of Po.well Plateau across Muav Saddle from the Kaibab Plateau; B, Panoramic view of Unkar wedge from Tonto platform................................................... 18 V. Tonto platform: View eastward up Kaibab division of Grand Canyon from level of the Esplanade directly under Havasupai Point..... 20 VI. The Esplanade: View northwestward from Havasupai Point........ 21 VII. A, View northward from Bass Camp; B, View eastward from the summit of Mount Huethawali.................................. 22 VIII. A, East wall of canyon of Shinumo Creek near Shinumo garden; B, View eastward up Colorado River from a point near the mouth of Bass Canyon..................... ; ............................ 28. I.. Generalized columnar section of the rocks of Shinumo quadrangle.., 30 X. A, Bass limestone, in Hotauta Canyon; B, Strata of Unkar group near mouth of Bright Angel Creek.................................. 38 XL View northward across the Grand Canyon from the end of Grand Scenic Divide................................................. 39 XII. Shinumo quartzite: A, North of Cable Crossing; B, In canyon of Shinumo Creek, showing garden................................ 52 XIII. A, View near Cable Crossing, looking down Colorado River; B, Dox sandstone in canyon of Shinumo Creek.......................... 54 XIV. Lower contact of diabase sill: A, On Shinumo Creek; B, At Bedrock tank, Bass Canyon ............................................ 55 XV. A, Muav limestone in Muav Canyon; B, Faults in Unkar wedge in canyon of Shinumo Creek...................................... 64 XVI. A, Pinnacles of erosion (hoodoos) in Kaibab limestone along rim of Kaibab Plateau; B, Wheeler fold in Bass Canyon............... 78 XVII. A, Wheeler fold from bed of Bass Canyon; B, Faulting in strata of the Unkar wedge in Burro Canyon.............................. 79 XVIII. Geologic history of the Shinumo quadrangle as revealed in the canyon wall................................................... 86 FIGURE 1. Index map showing location of Shinumo quadrangle............... 12 6 PREFACE. By F. L. RANSOME. Ever since Powell's daring boat trip down the Colorado in 1869 geologists have known that the walls of the Grand Canyon display one of the most remarkable and instructive geologic sections in the world. At first glance the impressive feature of that section is the great thickness of nearly horizontal strata through which the river has sunk its bed strata ranging in age from Carboniferous (Pennsyl- vanian) at the top, on the brink of the chasm, to Cambrian at the base. Powell found, however, that unconformably below the Cam­ brian in certain portions of the canyon there are extensive remnants of an older and much thicker series of sediments in beds which had been upturned into mountains and truncated by prolonged erosion before the sands of the Cambrian sea covered them. These beds he called the Grand Canyon group and described as resting with pro­ found unconformity on the vastly more ancient crystalline rocks into which the river has also cut deeply in the so-called Granite Gorge. In 1882 appeared Button's well-known "Tertiary history of the Grand Canyon district," which dealt mainly with the erosional development of the canyon and barely touched upon the earlier chapters of the geologic history recorded in its walls. Between 1883 and 1895 Dr. Charles D. Walcott, in a number of papers, described in greater detail the Grand Canyon group of PoweU, dividing it into an upper or Chuar terrane, 5,120 feet thick, and a lower or Unkar terrane, 6,830 feet thick. He assigned