DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR 353 GEOLOGY OF THE TAYLORSVILLE REGION, CALIFORNIA BY J. S. DILLER WASHINGTON GOVERNMENT PRINTING OFFICE 1908 t f CONTENTS. Page Introduction.............................................................. 7 Location and extent................................................... 7 Outline of geography and geology of region.............................. 7 Topography............................................................... 9 Relief. ............................................................... 9 Diamond Mountain block.......................................... 9 The escarpment. .............................................. 10 The plateau slope.............................................. 10 Valleys on southwest border.................................... 10 Genesee Valley............................................. 10 Indian Valley............................................. 10 Mountain Meadows........................................ 11 Jura Valley................................................ 11 Grizzly Mountain block........................................... 11 Crest line and escarpment..................................... 11 Southwest slope............................................... .12 Drainage.............................................................. 12 Descriptive geology........................................................ 13 General statement........'............................................... 13 Sedimentary rocks..................................................... 13 General account................................................... 13 Silurian.......................................................... 14 Grizzly formation............................................. 14 Montgomery limestone......................................... ' 16 Devonian.......................................................... 17 Taylorsville formation......................................... 17 Carboniferous..................................................... 20 Calaveras group....................'........................... 20 Arlington formation....................................... 20 Shoo Fly formation......................................... 23 Peale formation........................................... 24 Robinson formation............................................ 26 Triassic........................................................... 30 Hosselkus limestone...............:............................ 30 Swearinger slate............................................... 32 Jurassic............................................................ 34 General account............................................... 34 Trail formation................................................ 35 Hardgrave sandstone.......................................... 37 Thompson limestone............................................ 41 Mormon sandstone............................................ 44 Bicknell sandstone............................................ 48 Hinchman sandstone.................................:........... 51 Foreman formation............................................. 53 4 CONTENTS. Descriptive geology Continued. Sedimentary rocks Continued. Page. Southern extension of Triassic and Jurassic rocks of the Taylorsville region........................................................... 57 Sailor Canyon formation........................................ 57 Milton formation.............................................. 58 Relation of the Taylorsville Jurassic to the Mariposa................. 59 Supposed Mariposa in Nevada...................................... 60 Tertiary.......................................................... 60 Auriferous gravels...... j....................................... 60 General statement.......................................... 60 Jura River channel......................................... 61 Mount Jura divide..................................... 61 Taylor diggings........................................ 61 Hull diggings.......................................... 61 Peale diggings......................................... 62 Cascade mine to Mohawk Valley........................ 62 Along Haskell Peak escarpment......................... 63 Chips diggings, reversed drainage....................... 63 Question as to head of Jura River...................... 63 Drainage suggested by rhyolite flow..................... 65 Suggestion of double crest............................. 65 Fan-shaped drainage of Milton region.................... 65 Present divide........................................ 65 Main mass of auriferous gravel.............................. 66 Moonlight region...................................... 66 South end of Mountain Meadows....................... 67 North end of Mountain Meadows....................... 67 Willards Creek district................................. 68 Head of Gold Run.................................... 68 Diamond Mountain gravel............................. 69 Diamond Mountain shore terraces....................... 69 Lone Rock and Kettle Rock regions.................... 70 Isolated masses of gravel northeast of Mohawk Valley........ 71 Classification of the auriferous gravels........................... 72 Earlier deposits............................................ 72 Arkose sands........................................... 72 Prevolcanic gravels.................................... 72 Later deposits............................................. 72 Rhyolitic tuff......................................... 72 Intervolcanic gravels.................................. 72 Volcanic flows, chiefly andesitic breccia................. 74 Shore gravel........................................... 74 lone formation............................................. 74 Flora of the prevolcanic gravels................................ 74 Age of the prevolcanic auriferous gravels........................ 76 General statement.......................................... 76 Eocene flora of southwest Oregon............................ 77 Topography of the auriferous-gravel period....................... 78 The two divides........................................... 78 Altitude of the region..................................... '78 Jura River Valley......................................... 78 Drainage of Sierra Valley................................... 78 Uplift in gravel period.............................'........" 79 CONTENTS. 5 Descriptive geology Continued. ,""*) Sedimentary rocks Continued. - Page. .// Quaternary........................................................ 79 Gravels of Keddie Ridge....................................... 79 Gravels near Greenville........................................ 79 North Arm pot-hole........................................... 79 Shoo Fly gravel terraces........................................ 80 Glacial moraines.............................................. 80 \ Valley alluvium............................................ 80 Igneous rocks......................................................... 80 n General account................................................... 80 ; Pre-Silurian............................. ......................... 81 Metarhyolite.................................................. 81 Carboniferous..................................................... 82 Taylor meta-andesite.......................................... 82 Kettle meta-andesite........................................... 84 Reeve meta-andesite.......................................... 86 * Jurassic.......................................................... 87 r Fant meta-andesite............................................. 87 Hull meta-andesite............................................ ' 88 Late Jurassic or early Cretaceous................................... 88 Serpentine.................................................... 88 Granodiorite.................................................. 89 Various dike rocks............................................ 90 Miocene.......................................................... 92 Rhyolite..................................................... 92 Pliocene........................................................... 93 Andesite..................................................... 93 Quaternary........................................................ 95 Basalt......................................................... 95 Structure.............................................................. 97 / General statement............................................ T..... 97 Mount Jura belt.................................................... 97 r Grizzly Mountains belt............................................. 98 Grizzly Mountains anticline........................................ 98 Mount Jura syncline................................................. 98 Taylorsville fault.................................................. 99 Hull fault......................................................... 100 Honey Lake fault.................................................. 101 Mohawk Valley fault............................................... 102 Indian Valley fault................................................ 103 Geologic history of Taylorsville region ...................................... 104 Pre-Silurian........................................................... 104 Silurian.............................................................. 105 Devonian..............................................................