Field Guide to Plutons, Volcanoes, Faults, Reefs, Dinosaurs, and Possible Glaciation in Selected Areas of Arizona, California, and Nevada
This guidebook, prepared in conjunction with the 2008 joint meeting of the GSA Cordilleran and Rocky Mountain Sections, contains background information and road logs for eleven field trips in Nevada, Arizona, and California. Southern Nevada and adjoining areas contain a rich geologic history spanning the interval from the Paleoproterozoic to the present. Las Vegas lies at or near several critical geological junctures and localities including the structural boundary between the Colorado Plateau and Basin and Range, the physiographic boundary between the Great Basin and the southern Basin and Range, the eastern margin of the Sevier fold-and-thrust belt, the tectonically active Death Valley area, tilted and faulted volcanic-plutonic systems exposing the upper part of the crust, and the enigmatic “amagmatic zone.” With guides in this volume spanning the geologic record from the Ediacaran (late Neoproterozoic) to the Holocene, covering ground from the middle crust to the surface, and looking at topics from tectonics to paleontology, volcanism to glaciation, this volume offers something for everyone.
Devonian carbonate platform of eastern Nevada: Facies, surfaces, cycles, sequences, reefs, and cataclysmic Alamo Impact Breccia
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Published:January 01, 2008
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CiteCitation
John E. Warme, Jared R. Morrow, Charles A. Sandberg, 2008. "Devonian carbonate platform of eastern Nevada: Facies, surfaces, cycles, sequences, reefs, and cataclysmic Alamo Impact Breccia", Field Guide to Plutons, Volcanoes, Faults, Reefs, Dinosaurs, and Possible Glaciation in Selected Areas of Arizona, California, and Nevada, Ernest M. Duebendorfer, Eugene I. Smith
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Abstract
Devonian limestone and dolostone formations are superbly exposed in numerous mountain ranges of southeastern Nevada. The Devonian is as thick as 1500 m there and reveals continuous exposures of a classic, long-lived, shallow-water carbonate platform. This field guide provides excursions to Devonian outcrops easily reached from the settlement of Alamo, Nevada, ~100 mi (~160 km) north of Las Vegas. Emphasis is on carbonate-platform lithostratigraphy, but includes overviews of the conodont biochronology that is crucial for regional and global correlations. Field stops include traverses in several local ranges to study these formations and some of their equivalents, in ascending order: Lower Devonian Sevy Dolostone and cherty argillaceous unit, Lower and Middle Devonian Oxyoke Canyon Sandstone, Middle Devonian Simonson Dolostone and Fox Mountain Formation, Middle and Upper Devonian Guilmette Formation, and Upper Devonian West Range Limestone. Together, these formations are mainly composed of hundreds of partial to complete shallowing-upward Milankovitch-scale cycles and are grouped into sequences bounded by regionally significant surfaces. Dolomitization in the Sevy and Simonson appears to be linked to exposure surfaces and related underlying karst intervals. The less-altered Guilmette exhibits characteristic shallowing-upward limestone-to-dolostone cycles that contain typical carbonate-platform fossil- and ichnofossil-assemblages, displays stacked biostromes and bioherms of flourishing stromatoporoids and sparse corals, and is punctuated by channeled quartzose sandstones. The Guilmette also contains a completely exposed ~50-m-thick buildup that is constructed mainly of stromatoporoids, with an exposed and karstified crest. This buildup exemplifies such Devonian structures known from surface and hydrocarbon-bearing subsurface locations worldwide. Of special interest is the stratigraphically anomalous Alamo Breccia that represents the middle member of the Guilmette. This spectacular cataclysmic megabreccia, produced by the Alamo Impact Event, is as thick as 100 m and may be the best exposed proven bolide impact breccia on Earth. It contains widespread intervals generated by the seismic shock, ejecta curtain, tsunami surge, and runoff generated by a major marine impact. Newly interpreted crater-rim impact stratigraphy at Tempiute Mountain contains an even thicker stack of impact breccias that are interpreted as parautochthonous, injected, fallback, partial melt, resurge, and possibly post-Event crater fill.
- Basin and Range Province
- biochronology
- biogenic structures
- bioherms
- biostratigraphy
- biozones
- breccia
- carbonate platforms
- carbonate rocks
- Conodonta
- cyclostratigraphy
- Devonian
- dolostone
- field trips
- guidebook
- Guilmette Formation
- impacts
- limestone
- Lincoln County Nevada
- lithofacies
- lithostratigraphy
- megabreccia
- microfossils
- Milankovitch theory
- Nevada
- North America
- outcrops
- Paleozoic
- reef environment
- road log
- sea-level changes
- sedimentary rocks
- sedimentary structures
- sequence stratigraphy
- United States
- eastern Nevada
- Alamo Breccia
- Alamo Nevada