Generalized geologic framework of the National Reactor Testing Station, Idaho

______________________________ Bl Introduction __________________________ 2 Summary of late geologic events, by R. L. Nace___________ 4 Geologic structure, by R. L. Nace _________________ 7 Geologic materials and their surface distribution _______ 8 Paleozoic rocks, by Morris Deutsch and P. T. Voegeli __ 8 Cenozoic volcanic rocks, by Morris Deutsch and P. T. Voegeli 10 Silicic volcanic rocks ____________________ 10 Welded tuff _____ ________________ 11 Rhyolite ________________________ 11 Volcanic ash _____________________ 11 Basalt _____________________________ 11 Quaternary volcanic rocks, by R. L. Nace and P. T. Voegeli 11 Snake River Group ____________________ 12 Basalt province of the Snake River Plain _____ 12 Petrography of the basalt _ __ _ _ _ _ _ ___ 13 Black Basalt _________________________ 14 Petrography of the basalt _______________ 14 Chemical composition of the volcanic rocks _________ 15 Rock structures in basalt _________________ 15 Layering___________________________ 15 Partings ___________________________ 15 Joints and other fractures _________________ 16 Miscellaneous natural voids _________________ 16 Quaternary sediments __________________ 17 Terreton Lake beds _____________________ 17 Mechanical composition._______________ 18 Chemical composition._____________ 18 Alluvial-fan gravel __________________ 18 Mechanical composition ______________ 18 Gravel of Birch Creek___________________ 19 Mechanical composition ______________ 19 Alluvium of the Big Lost River ___ ______ _ __ 19 Depositional phases of the gravel _____ ___ 25 Mechanical composition _________________ 26 Chemical composition of secondary cement ____ 26 Playa sediments _____________________ 27 Mechanical composition _________________ 27 Slopewash sediments _________________ 27 Windblown sediments___________________ 27 Loess ________________________ 27 Drifted sand and silt _________________ 28 Mechanical composition ________________ 28 Page Geologic materials and their surface distribution Con. Quaternary sediments Continued Mineral composition of sediments _____ ____ _ _ B28 Geologic materials and their subsurface distribution 30 Subsurface exploration, by R. L. Nace, J. R. Jones, and P. T. Voegeli _______________ _ 30 Test drilling _____________________ ___ 30 Electrical-resistivity and seismic surveying ______ 30 Radioactivity logging ____________ __ 31 Subsurface geology, by R. L. Nace _ _ ______ __ 31 Snake River Group _____________ ___ 31 Alluvium of Big Lost River ________ _______ 31 Underlying silty clay __________ 32 Alluvium of Birch Creek ___ ______ __ 32 Terreton Lake beds ______ ______ ___________ 32 Interflow sediments ________________ ___ 33 Special geologic factors in earth materials _________ 35 Ion exchange, by R. L. Nace _________________ 35 Ion-exchange capacity of sediments in the NRTS __ 35 Ion-exchange capacity of basalt ___________ 36 Desiccation and earth cracks, by R.L. Nace and R. O. Smith 36 Distribution of the earth cracks _____________ 37 Characteristics of the earth cracks ___________ 38 Cause of the earth cracks ________________ 40 Geology in relation to construction, by R. L. Nace and J. R. Jones 41 Test-hole and well drilling ____ ___ __________ 41 Methods of drilling _______________________ 41 Raw materials __________________ _____ 42 Ease of excavation ______________ ____ 42 Stability of materials in excavations _____________ 42 Stability of materials under load__________ __ 42 Basalt _____________ -_______________ 43 Lake and playa beds ______ ___ ____ 44 Gravel ___________________________ 45 Loessial soil __________________ ___ 45 Drainage, weather, and accessibility _____ _____ 46 Dust and drifting sand ____ ____ ____ __ 46 Control of drifting sand _____________ _ 47 Earthquake hazard _________ ___ _ 47 Volcanic activity hazard _________________ _ 48 References cited __________________________ 49