Introduction. ______________________________________ Location and geography_____-___--______________ Purpose and scope of the investigation.___________ Climate, vegetation, and wildlife._________________ Fieldwork and acknowledgments._________________ Previous work__________________________________ Stratigraphy.______________________________________ Precambrian_ __________________________________ Lower Precambrian gneiss and schist of Trappman Hills area___________________________ Upper Precambrian Stirling Quartzite_ _______ Precambrian and Cambrian Wood Canyon Formation-_____________________________________ Cambrian_ _ __________________________________ Zabriskie Quartzite_________________________ Carrara(?) Formation.______________________ Limestone, silty limestone, and shale of Middle Cambrian age____________________________ Bonanza King Formation.___________________ Nopah Formation.__________________________ Ordovician_ _ ___________________________________ Pogonip Group.____________________________ Goodwin Limestone,____________________ Ninemile Formation.___________________ Antelope Valley Limestone-______________ Eureka Quartzite._________________________ Ely Springs Dolomite.______________________ Ordovician and Silurian dolomite_________________ Silurian and Devonian dolomite of the Spotted Range_ ____________________________________ Devonian._____________________________________ Nevada Formation._________________________ Limestone and dolomite-_-___--___--________ Devonian and Mississippian-____________________ Eleana Formation._________________________ Eleana(?) Formation in the Cactus Range____ Mesozoic(?) granite..___________________________ Tertiary-______________________________________ Fan glomerate. _____________________________ Monotony Tuff___________________________ Sedimentary rocks of Cedar Pass area.________ Tuffs of Antelope Springs.-__ ________ ________ Shingle Pass Tuff________ ___________________ Lacustrine sedimentary rocks of the Cactus Range_ __________________________________ Tuff and rhyolite of Gold Flat________________ Tuff of White Blotch Spring_________________ Rocks between the tuff of White Blotch Spring and Fraction Tuff _ ___________________ Zeolitized bedded tuff and sedimentary rocks______________ __________________ Lavas and intrusive rocks of intermediate composition. _ ________________________

Two normal fault systems are present in Nevada Test Site and Nellis Air Force Range. The earlier system consists of two sets that strike northeast and northwest, and the later system., a single set, strikes north. In the southern Kawich and Belted Ranges the Belted Range Tuff, dated at 13 to 14 m.y. and faulted only by the north-trending faults, laps onto older volcanic rocks that are broken by both fault systems. The older faults probably started to form during or shortly after the extrusion of the oldest welded tuff dated at 26.5 m.y. (age dates by R. W. Kistler, written commun., 1964), as is evidenced by essentially the same fault densities and displacements in preTertiary rocks as in Tertiary rocks.The north-trending faults first began to appear after the deposition of the Fraction Breccia, dated at 17.8 m.y., and the present mountain ranges were well defined prior to extrusion of the Thirsty Canyon Tuff dated at 7 m.y.In the southern part of the Bombing and Gunnery Range near the Las Vegas Valley shear zone, north-trending faults that are inferred to be the same age as those to the north change strike gradually from north to northeast as the valley is approached from the north. This rotation, interpreted as being caused by drag during later right-lateral movement rather than a change in the stress field, suggests that much of the displacement along the shear zone has taken place within the last 17 m.y. 247 on July 1, 2015 memoirs.gsapubs.org Downloaded from

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