Ketner K.B. The Inskip Formation, the Harmony Formation, and the Havallah sequence of northwestern Nevada: an interrelated Paleozoic assemblage in the home of the Sonoma orogeny. - Reston: U.S. Geological Survey, 2008. - v, 20 p.: ill. (some col.), maps (some col.). - (U.S. Geological Survey professional paper; 1757). - Ref.: p.18-20. - ISBN 978-14-1132266-0  Место хранения:   018 | Институт нефтегазовой геологии и геофизики им. А.А.Трофимука | Новосибирск | Библиотека

Оглавление / Contents

Abstract ........................................................ 1 Introduction .................................................... 1 Geologic Setting ............................................. 1 Early Work ................................................... 2 Purpose and Method ........................................... 3 East Range ...................................................... 3 Preble Formation ............................................. 3 Valmy Formation .............................................. 3 Chert Couplet of Table Mountain ........................... 4 Inskip Formation ............................................. 4 Lower Unit ................................................ 4 Upper Unit ................................................ 4 Base of the Inskip ........................................ 4 Triassic Rocks ............................................... 5 Nomenclatural Problems in the East Range ..................... 5 Northern Exposures ........................................ 5 Southern Exposures ........................................ 5 Metamorphism ................................................. 5 Megastructures of the East Range ............................. 5 Petrologic Features of the Inskip Formation ..................... 7 Source of Data ............................................... 7 Metasedimentary Rocks ........................................ 7 Metaigneous Rocks ............................................ 9 Metabasalt ................................................ 9 Metafelsite .............................................. 10 The Felsite Problem ...................................... 10 Depositional Conditions of the Inskip ....................... 11 Hot Springs Range .............................................. 11 Source of Data .............................................. 11 Strata in the Hot Springs Range Underlying the Inskip- Equivalent Rocks ............................................ 13 Stratigraphic Units Equivalent to the Inskip in Age and General Aspect .............................................. 13 Harmony Formation ........................................ 13 Home Ranch Subterrane .................................... 13 Lower Poverty Peak Sequence .............................. 13 Upper Poverty Peak Sequence .............................. 13 Poverty Peak-Golconda Melange ............................ 14 Phyllite and Shale Sequence .............................. 14 Triassic and Jurassic Rocks ................................. 14 Megastructures of the Hot Springs Range ..................... 14 Osgood Mountains ............................................... 14 Sonoma Range ................................................... 14 Stratigraphic and Structural Issues ......................... 14 Havallah Sequence ........................................... 15 Triassic Rocks .............................................. 15 Battle Mountain ................................................ 15 North Slope ................................................. 15 South Slope ................................................. 15 The Havallah Sequence ....................................... 16 Unconformities .............................................. 16 Relation of the Inskip and the Harmony Formations to the Havallah Sequence in the Arkosic Triangle ...................... 16 Sonoma Orogeny and Golconda Thrust ............................. 16 Conclusions .................................................... 17 Acknowledgments ................................................ 18 References Cited ............................................... 18 Figures 1 Map showing northwestern Nevada the locations of figures 2 and 11. Also shown, in the inset outline of Nevada, are the locations of the arkosic triangle and the area shown in figure ................................................... 12 2 Map showing the central part of the East Range modified from Whitebread (1994), Whitebread and Sorensen (1983), and Johnson (1977) ........................................... 6 3-10. Photographs showing: 3 Sheared arkosic sandstone from the lower Inskip Formation. Clasts are quartz, quartzite, K-feldspar, and plagioclase .... 7 4 Unpolarized view of figure .................................. 37 5 Coarse arkosic sandstone from a massive bed in the lower Inskip Formation. This specimen shows no evidence of shear. Crossed polarizers .................................... 7 6 Chert from the uppermost part of the Inskip Formation. The carbon-rich stylolites are preserved in this specimen, and radiolarians are sporadically preserved in others. The only effect of the relatively slight metamorphism was to slightly increase the grain size. Unpolarized ......... 8 7 Metabasalt from the upper member of the Inskip Formation. Megacrysts are magnesian hornblende, groundmass is albite and ilmenite. This specimen shows slight evidence of shear. Crossed polarizers ........................................... 8 8 Relatively unsheared porphyritic felsite from the upper part of the Inskip Formation. Megacrysts are albite, groundmass is quartz and biotite. Crossed polarizers ......... 8 9 Sheared felsite from the lower part of the Inskip Formation. Light bands are albite and quartz, medium bands are muscovite, dark bands are biotite. Uncrossed polarizers ................................................... 8 10 Sheared porphyritic felsite from the Rochester Rhyolite at the base of the Triassic sequence immediately overlying the Inskip Formation. Megacrysts are albite, groundmass is albite, quartz, and muscovite. Crossed polarizers ............ 9 11 Generalized and simplified map showing part of the Hot Springs Range modified from Jones (1997a, b) showing the Hot Springs Range syncline and the northern Hot Springs Range anticline ............................................. 12 Tables 1 Chemical composition of metabasalt of the Inskip Formation, East Range, Nevada .......................................... 10 2 Chemical composition of metafelsites of the Inskip Formation and the Triassic Rochester Rhyolite, East Range ... 11