STATE OF IDAHO, .· C. BEN Ross, Governor IDAHO BUREAU OF MINES AND GEOLOGY Moscow, Idaho JOHN w. FINCH, Secretary IDAHO BUREAU OF MINES AND GEOLOGY BULLETIN PRICE 50 CENTS No.14 September, 1931 GEOLOGY AND MINERAL RESOURCES OF EASTERN CASSIA COUNTY, IDAHO by ALFRED L. ANDERSON UNIVERSITY OF IDAHO MOSCOW, IDAHO Entered as second class matter Aug. 11, 1924, at the postoffice at Moscow, Idaho, under the Act of March 3, 1879 STATE OF IDAHO C. BEN Ross, Governor IDAHO BUREAU OF MINES AND GEOLOGY Moscow, Idaho JOHN w. FINCH, Secretary IDAHO BUREAU OF MINES AND GEOLOGY BULLETIN PRICE 50 CENTS No.14 September, 1931 GEOLOGY AND MINERAL RESOURCES OF EASTERN CASSIA COUNTY, IDAHO by ALFRED L. ANDERSON UNIVERSITY OF IDAHO MOSCOW, IDAHO Entered as second class matter Aug. 11, 1924, at the postoffice at Moscow, Idaho, under the Act of March 3, 1879 CONTENTS Page Abstract. vii Introduction ........................................................ 1 Purpose and scope of the investigation .............................. 1 Fieldwork ....................................................... 3 Acknowledgments ................................................ 4 Previous geologic work ............................................ 4 Geography ............................................... ·.......... 7 Location ........................................................ 7 Topography ..................................................... 7 Physiographic setting .......................................... 7 Mountains .................................................... 7 South Mountain ................. ·........................... 8 Albion Range ............................................... 8 Malta Range .............................................. 11 Black Pine Range .......................................... 12 Sublett Range .............................................. 13 Raft River Range ......................... : ................ 14 Basins and plains .............................................. 14 Raft River Valley .......................................... 14 Goose Creek Valley .......................... , .............. 15 Snake River Plains ..................· ....................... 15 Drainage ..................................................... 16 Cassia City of Rocks ........................................... 18 Climate ...................................... : .................. 19 Vegetation· ........................................................ 20 Culture .......................................................... 20 Transportation ................................................... 21 General geology . .............................· ................... 23 Stratigraphic geology ............................................. 23 General outline .•......................................... : .... 23 24 Preif:rri~~~a~~ie~~s- .. ·. ·. : : : : : : : : : : : : : : : : : : : : : : : : : : :·: : : : : : : : : : : : : : 24 Character and distribution ................................ 24 Lower division ........................................ 2~ Middle division ...................................... 25 Upper division ........................................ 27 Correlation and age ......................................... 27 Cambrian system .............................................. 29 Carbo.nifer?us. systel!l .......................................... 30 M1ss1ss1pp1an series ......................................... 30 Brazer formation ........................................ 30 Pennsylvanian series ........................................ 33 Wells formation ......................................... 33 Permian series . ........................................... 35 Phosphoria formation .................................... 35 Tertiary system ............................................... 37 General features ............................................ 37 Distribution and character ................................... 38 Correlation and age ......................................... 41 Correlation with the Payette formation .................... 41 Correlation with the Salt Lake formation ................... 43 Quaternary system ............................................ 44 Pleistocene series ........................................... 45 Hillwash and older alluvium .............................. 45 Older· glacial deposits .................................... 46 Younger glacial deposits .................................. 47 Aeolian deposits ........................................ 47 iv CONTENTS General geology (continued) Page Stratigraphic geology (continued) Quaternary system (continued) Recent series ............................................... 48 Alluvium ............................................... 48 Igneous geology .................................................. 49 General outline ................................................ 49 Intrusive rocks ................................................ 49 Distribution and extent ..................................... 49 Structural features .......................................... 50 Petrography ............................................... 51 Granitic rocks ........................................... 51 Pegmatites ............................................. 54 Age of the intrusives ........................................ 55 Weathering of granite ....................................... 56 Extrusive rocks ............................................... 60 Tertiary series ............................................. 60 Quartz latite ....................................... ; ..... 61 Distribution ......................................... 61 Description .......................................... 62 Basalt ................................................. 65 Distribution ......................................... 65 Description .......................................... 65 Correlation and age ...................................... 65 Quaternary series ........................................... 66 Snake River basalt ...................................... 66 Distribution ......................................... 66 66 r:=~~~~t~:~: :: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 67 Structural geology ................................................ 67 General features ........................................ ' .. ·..... 67 Folds ............................. : .......................... 69 Albion anticline . · ........................................... 70 Black Pine folds ............................................ 71 Sublett folds ............................................... 73 Faults ....................................................... 75 Overthrust faults ......................... ,.................. 75 Albion overthrust ....................................... 75 Black Pine overthrusts ................................... 76 Sublett overthrusts ...................................... 77 Early transverse and normal faults ........................... 78 Kelsaw fault ............................................ 78 Other faults ............................................ 79 Younger normal faults ...................................... 80 Malta Range fault ....................................... 80 Oakley fa ult ............................................ 81 South Mountain fault .................................... 82 Other faults ............................................ 83 Landslide faults .........................................• 84 Snake River downwarp ......................................... 85 Age of the folding. 85 Age of the faulting ............................................ 86 Age of the Snake River downwarp ............................... 88 Cause of diastrophism ......................................... 88 Laramide deformation ....................................... 88 Basin-Range faulting ....................................... 90 Snake River downwarp ...................................... 92 Geologic history .................................................. 92 ti Proterozoic era. ............................. ·............... 92 Paleozoic era. : ............ 94 Mesozoic era .................................................. 96 Cenozoic era .................................................. 97 CONTENTS V Page Mineral resources ..................................................... 101 Ore deposits. 102 Historical sketch . 102 Geographic and geologic distribution. 103 General character of the deposits ..................... ; . 103 Mineralization in the Stokes district . 104 Geographic features .......................................... 104 Geologic features. 104 Character of the deposits ..................................... 105 Mineralogy. 105 General summary . 105 Primary minerals. 105 Secondary minerals ............. :- ......................... 107 Mineral paragenesis. 109 Deposits .................................................... 109 Structural features. 109 Vein structure ........................................... 111 Secondary enrichment. 111 Genetic classification. 112 Age and genesis . 112 Comparison with deposits in other regions. 113 Outlook for the district.... 114 Properties. 114 Melcher mine ............................................ 114 Big Bertha group . 117 Albion group. 117 Golden Eagle property ....................... : . 118 Harris and Hume property ................................ 119 Old Dominion mine ....................................... 119 Last Chance group. 120 Prospects on Fairchild Creek