DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR 352 GEOLOGIC EECONNAISSANCE OF A PART OF WESTERN ARIZONA BY WILLIS T. LEE WITH NOTES ON THE IGNEOUS ROCKS OF WESTERN ARIZONA BY ALBERT JOHANNSEN WASHINGTON GOVERNMENT PRINTING OFFICE 1908 CONTENTS. Page. Introduction.............................................................. 9 Purpose of the investigation.............:.............................. 9 Extent and character of the investigation................................ 9 Summary of previous knowledge....................................... 10 General geography........................................................: 11 Relation to surrounding regions......................................... 11 Topography........................................................... 12 General character................................................. 12 Mountains........................................................ 13 Valleys and plains.................................................. 14 Descriptive geology........................................................ 14 Rock formations........................................................ .1.4 Pre-Cambrian..................................................... 14 Cambrian.......................................................... 15 Carboniferous..................................................... 15 Tertiary... ^...................................................... 16 Eruptive rocks................................................ 16 Greggs breccia................................................ 17 Quaternary........................................................ 17 Temple Bar conglomerate....................................... 17 Chemehuevis gravel............................................ 18 Basalt flows......................;............................. 18 Geographic and geologic details of highlands................................. 18 Grand AYash Cliffs..................................................... 18 Location........:................................................. 18 Topographic features.............................................. 19 Rock masses...................................................... 19 Cottoiiwood and Aquarius cliffs.......................................... 19 Location.......................................................... 19 Topographic features............................................... 20 Rock masses...................................................... 20 Yampai Cliffs.......................................................... 20 Location.......................................................... 20 Topographic features..............................;....,.......-... 20 Rock masses...................................................... 21 Truxton Plateau..................................................'.... 21 Location.......................................................... 21 Topographic features.............................................. 21 Rock masses...................................................... 21 Aquarius Mountains.................................................... 22 Location.......................................................... 22 Topographic features.............................................. 22 Rock masses...................................................... 22 ' 3 4 CONTENTS. Geographic and geologic details of highlands Continued. Page. Artillery Mountains.".................................................. 22 Location.......................................................... 22 Topographic features.............................................. 22 Rock masses. ..................................................... 22 White Hills.......................................................... 23 Location........................................................... 23 Topographic features.............................................. 23 Rock masses...................................................... 23 Cerbat Mountains..................................................... 23 Location.......................................................... 23 Topographic features.......................................'....... 23 Rock masses...................................................... 23 Structure.......................................................... 24 Hualpai Mountains.................................................... 24 Location.......................................................... 24 Topographic features.............................................. 24 Rock masses...................................................... 25 Structure.......................................................... 25 Aubrey Hills........................................................... 25 Location.......................................................... 25 Topographic features.............................................. 25 Rock masses...................................................... 25 Black Mountains................................:...................... 25 Location.......................................................... 25 Topographic features..........:................................... 25 Rock masses...................................................... 26 Black Mesa............................................................ 26 Location.......................................................... 26 Topographic features.............................................. 26 Rock masses...................................................... 27 Mohave Mountains..................................................... 27 Location.......................................................... 27 Topographic features.............................................. 27 Rock masses...................................................... 28 Harcuvar and Harquahala Mountains.................................... 28 Location.......................................................... 28 Topographic features............................................... 28 Rock masses...................................................... 28 Buckskin Mountains.................................................... 28 Location.......................................................... 28 Topographic features...............:.............................. 28 Rock masses...................................................... 29 Palomas and Dome Rock ranges........................................ 29 Geographic and geologic details of valleys................................... 29 Colorado Valley........................................................ 29 General statement.................................................. 29 Mouth of Grand Canyon........................................... 30 Grand Wash Trough................................................ 30 Haulpai Wash...................................................... 33 Virgin Canyon..................................................... 34 Temple Bar....................................................... 35 Virgin Valley..................................................... 36 Boulder Canyon............ r ............... r ...................... 36 CONTENTS. 5 Geographic and geologic details of valleys Continued. Page. Colorado Valley Continued. ' ' Las Vegas Wash................................................... 37 Black Canyon..................................................... 37 Cottonwood Valley................................................ 37 Pyramid Canyon................................................... 38 Mohave Valley..................................................... 41 The Needles...................................................... 42 ^_ Chemehuevis Valley................................................ 43 Aubrey Canyon. .......^.......................................... 44 Great Colorado Valley.............................................. 45 Chocolate Mountains............................................... ' 46 J Hualpai Valley........................................................ 48 Location and character............................................ 48 Structure.......................................................... 50 Big Sandy Valley...................................................... 50 Location and character............................................ 50 Rock formations.................................................... 51 Structure.......................................................... 51 / Signal Canyon........................................................ 52 Detrital-Sacramento A^alley............................................. 52 Location and character............................................ 52 Detrital filling.................................................... 53 Williams Valley.....................!.................................. 53 Location and character............................................ 53 Rock formations.................................................... 54 Other valleys........................................................... 55 Location and character... ^......................................... 55 Detrital filling........:........................................... 55 Geologic history............................................................ 56 Introductory statements................................................ 56 Pre-Cambrian conditions............................................... 56 Crystalline rocks................................................... 56 Sedimentation....................................................