Geography, Geology, and Mineral Resources of the Ammon and Paradise Valley Quadrangles, Idaho GEOLOGICAL SURVEY PROFESSIONAL PAPER 238 Geography, Geology, and Mineral Resources of the Ammon and Paradise Valley Quadrangles, Idaho By GEORGE R. MANSFIELD GEOLOGICAL SURVEY PROFESSIONAL PAPER 238 A supplement to earlier studies^ supplying new geologic information and additional data on phosphate reserves UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1952 UNITED STATES DEPARTMENT OF THE INTERIOR Oscar L. Chapman, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price $2.00 (paper cover) CONTENTS Page Page A bstract___________________________________________ 1 Stratigraphy—Continued Introduction _______________________________________ 1 Jurassic system_________________________________ 35 Purpose and scope of work_______________________ 1 Lower Jurassic series: Nugget sandstone_______ 35 Location and extent of area. ___________ __________ 2 Middle and Upper Jurassic series: Twin Creek Historical notes_____. ___________________________ 2 limestone._______________________________ 36 Hayden Surveys._______________________________ 2 Upper Jurassic series._______________________ 38 Later geologic work.____________________________ 4 Preuss sandstone-___ ___________________ 38 Field work leading to present report_____________ 4 Stump sandstone.______________________ 38 Geography.________________________________________ 5 Jurassic and Cretaceous systems: Upper Jurassic Summary of physiographic development.__________ 5 and Lower Cretaceous series___________________ 39 Principal topographic features.___________________ 7 Basis for age assignment_____________________ 39 Willow Creek valley_______________________ 7 Gannett group._______ ______________________ 39 Blackfoot Mountains._______________________ 8 General description.____________________ 39 Paradise Valley ________________ _____________ 9 Ephraim conglomerate._________________ 41 Blackfoot River valley ______________________ 10 Cretaceous system._____________________________ 42 Chesterfield Range._________________________ 11 Lower Cretaceous series: Gannett group (con­ Portneuf Mountains.________________________ 11 tinued) __________________________________ 42 Portneuf River valley.______________________ 12 Peterson limestone._____________________ 42 Snake River valley____ ______________________ 12 Bechler conglomerate.___________________ 43 Drainage ______________________________________ 13 Lower (?) and Upper Cretaceous series: Wayan Rivers_-______________________ _____________ 13 formation ________________________________ 43 Springs. _ __________________________________ 13 Tertiary system: Pliocene (?) series (Salt Lake Sinkholes __________________________________ 14 formation)___________________________________ 44 Climate. ______________________________________ 15 Quaternary system____________ __________________ 46 Vegetation._ ___________________________________ 15 Pleistocene series ___________________________ 46 Animal life.___________________________ ________ 16 Travertine,____________________________ 46 Water supply and mineral resources_______________ 16 Hill wash and older alluvium. ____________ 47 Settlements and industries.______________________ 16 Sand dunes and wind-blown dust _______ 47 Transportation facilities_________________________ 16 Recent series: Alluvium.____________________ 48 Stratigraphy_______________________________________ 17 Igneous rocks_____________---_----________-____-___ 48 General features._______________________________ 17 General occurrence. _______ ______________________ 48 Earlier Paleozoic formations____________________ 18 Andesitic breccia and tuff________________________ 48 Carboniferous system.__________________________ 18 Distribution, _______________________________ 48 Mississippian series _________________________ 18 Character- _______.___-__--____________----_ 48 Madison limestone._____________________ 19 Structure._________________________________ 49 Brazer limestone._______________________ 19 Source. ____________________________________ 49 Pennsylvanian series: Wells formation_________ 21 49 Relation of Carboniferous to Permian _________ 22 Thickness _______________________ 50 Permian system. __________________--_-_-_-_-_- . 23 Rhyolitic rocks._____________________ 50 Phosphoria formation _______________________ 23 Mode of occurrence. ___________ 50 Distribution. ___________________________ 23 Distribution. _ __________________ 50 Phosphate shale member.______________ 23 Welded tuff _____________________ 50 Rex chert member-____________---_--.__ 25 Character. __________________ 50 Broader relations of Phosphoria formation. 27 Sequence._ _________________ 52 Age_ __________________________________ 27 Relation to underlying rocks__. 53 Relation of Permian to Triassic_______________ 28 Successive falls of welded tuff__ 53 Triassic system.________________________________ 28 Thickness ___________________ 54 Lower Triassic series____________-_-__------_ 28 Volcanic ash and tuff (not welded) _____ 54 Woodside shale-_____________-_-_------_ 28 Basaltic tuff_____________________ 54 Thaynes group.________________-__----_ 30 Rhyolitic ash and tuff (not welded). 54 Subdivisions and general distribution__ 30 Basalts. ____________--_-_-----._-___- 56 Ross Fork limestone._______________ 30 Distribution. ____________________ 56 Fort Hall formation._______________ 31 Character, ______________________ 56 Portneuf limestone_________________ 31 Older basalts__________________ 56 Upper Triassic series: Timothy sandstone____ 33 Younger basalts. -__-__-_--______ 57 Triassic (?) system.__ ___________________________ 34 Successive flows _________________ 57 Higham grit______________________________ 34 Columnar jointing.______________ 57 Deadman limestone.________________________ 34 Thickness, _______________________ 57 Wood shale_______________________------_-- 35 Volcanic plug.___________________ 57 ni IV CONTENTS Page Page Igneous rocks—Continued Mineral resources.________________-_-____--------__ 77 Relation of igneous to sedimentary rocks__________ 57 Phosphate rock__._____________________________ 77 Relation of igneous rocks to one another.__________ 58 General character......____________________ 77 Age of igneous rocks_ ___________________________ 59 Iron and alumina content.__________________ 78 Structural geology._________________________________ 59 Vanadium content._________________-_---_- 78 Earlier geologic work____________________________ 59 Distribution of phosphate.__________________ 78 General features- _____________________________ 61 Description of townships containing phosphate _ 78 Principal folds____ ___________________________ 61 T. 1 S., R. 38 E_ ______________________ 78 Snowdrift anticline__-._______________________ 61 Location_________________________ 78 Folds between Blackfoot River and Paradise Accessibility ______________________ 78 Valley__________________________________ 61 Surface features ___________________ 78 Folds of Portneuf Mountains ______ ___________ 62 Geology __-_________-__.-_-_----__ 78 Seventy Creek syncline,_____________________ 62 Phosphate deposits_________________ 80 Mount Taylor anticline______.._______________ 62 T. 4 S., R. 38 E_______________________ 80 Williams Creek syncline____________________ 63 T. 5 S., R. 38 E_ ______________________ 80 Sellers Creek anticline.______________________ 63 T. 1 S., R. 39 E_ ______________________ 81 Buck Creek syncline__ ___________________ 63 Location________________________ 81 Wolverine anticlinorium_____________________ 63 Accessibility- _____________________ 81 Birch Creek synclinorium____________________ 63 Surface features, __________________ 81 Otherfolds_. ______________________________ 64 Geology __________________________ 81 Principal faults ________________________________ 6-4 Phosphate deposits.. _______________ 81 Bannock overthrust.________________________ 64 T. 2 S., R. 39 E_ _____________________ 83 Paradise Valley window_ _ _______________ 65 Location, _________________________ 83 Bannock overthrust zone ____________ ___ 67 Accessibility. _____________________ 83 West branch. ___________ ________ 67 Surface features ___________________ 83 Middle branch.___________________ 67 Geology __________________________ 83 East branch________,______________ 68 Phosphate deposits-________________ 83 Other thrust faults_____________________ __ 69 T. 3 S., R. 40 E_ ______________________ 84 Faults of Mount Taylor anticline _________ 69 Geology __________________________ 84 Faults of Williams Creek syncline_________ 69 Phosphate deposits.____________ ___ 85 Faults of Buck Creek syncline____________ 69 T. 4 S., R. 40 E_ ______________________ 85 Faults of Wolverine anticlinorium, _______ 69 Location. _________________________ 85 85 Faults of Birch Creek synclinorium_______ 70 Accessibility ______________________ Surface features. __________________ 85 Faults of Portneuf Mountains.___________ 70 Geology.___ ______________________ 85 Horst and graben structure._________________ 70 Phosphate deposits. ________________ 85 Horse Creek fault__-______-____-____-___.___ 72 Limestone ____________________________________ 86 Other normal faults-________________________ 72 Carboniferous limestones ____________________ 87 Paradise Valley quadrangle ______________ 72 Triassic limestones.________ ________________ 87 Ammon quadrangle _____________________ 72 Jurassic limestones.._______________________