Structure And Stratigraphy Of The Ordovician Vinini Formation Tyrone Creek Area Eureka County Nevada

Author : Jill M. Bird
Publisher :
ISBN 13 :
Total Pages : 286 pages
Book Rating : 4.:/5 (241 download)

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Download or read book Stratigraphy and Structure of the Northern Part of the Fish Creek Range, Eureka County, Nevada written by Jill M. Bird and published by . This book was released on 1989 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Upper Cambrian through Middle Devonian carbonate and clastic sequences of the northern part of the Fish Creek Range represent shallow-shelf sedimentation in the Cordilleran miogeosyncline. The lower and middle Paleozoic section exposed in the northern Fish Creek Range fits well within regional facies patterns and paleogeographic reconstructions. The Upper Cambrian Dunderberg Shale was deposited in a muddy outer shelf embayment which extended eastward into the Eureka area. The embayment was eliminated as seas regressed in late Dresbachian time and marine carbonate sedimentation (represented by the Catlin Member o-f the Wind-fall Formation) was established. The argillaceous Bullwhacker Member of the Windfall was deposited in deeper shelf waters as the sea transgressed briefly during Trempeleauian time. Shallow-shelf carbonates of the Lower Ordovician Goodwin Limestone are succeeded by Ninemile Formation strata representing deposition in a muddy embayment, similar to the Late Cambrian embayment in the Eureka area. Regression followed, and a shallow-water Girvanella-rich carbonate bank prograded westward during Whiterockian (early Middle Ordovician) time, represented by the lower part of the Antelope Valley Limestone. Mudstone and wackestone of the upper part of the Antelope Valley Limestone was deposited in quieter, deeper, or more protected environments shoreward of the bank margin. Basal sands of the Eureka Quartzite prograded westward across the carbonate shelf during the Middle Ordovician. Carbonate sedimentation persisted in some areas in silty embayments, and is represented by the Copenhagen Formation. Transgression began during Eureka deposition, and shelf-lagoon carbonates of the Hanson Creek Formation were deposited as transgression continued during Late Ordovician and earliest Silurian time . The lower part of the Silurian-Lower Devonian Lone Mountain Dolomite in the Fish Creek Range is transitional to outer platform carbonate-bank deposits at the type section to the northwest, and to restricted, inner-platform deposits of the partly correlative Laketown Dolomite to the east. Rhythmically alternating, shallow subtidal and restricted peritidal deposits form the upper part of the Lone Mountain in the study area, and reflect progradation of peritidal environments as the earliest Devonian sea regressed. Younger Devonian rocks in the Fish Creek Range lie within a north-trending transitional belt in which shallow, eastern lithofacies (predominantly dolomite) and deeper-water, limestone lithofacies intertongue. Peritidal deposits of the Beacon Peak Dolomite prograded westward during the mid-Early Devonian. Subtidal, fossiliferous limestone of the Bartine Member of the McColley Canyon Formation was deposited as transgression began during Emsian time (qronberoi to inversus conodont Zones). Lime mudstone, wackestone, and packstone of the Coils Creek Member of the McColley Canyon Formation was deposited in quieter, slightly deeper, shelf waters during late Emsian time (inversus Zone). Regression followed during latest Emsian time (serotinus Zone). Dolomite and crinoidal dolomite of the Sadler Ranch Formation (latest Emsian to Eifelian) was deposited in shallow waters of the outer shelf. The overlying Coarse Crystalline Member of the Oxyoke Canyon Sandstone is a regressive sequence of quartzose dolomite and dolomite-cemented sandstone deposited on the inner platform, where beach and intertidal environments were separated by a low-relief coastline. Thick-bedded, peritidal dolomite of the lower part of the Sentinel Mountain-Bay State interval represents progradation of peritidal facies across the shallow platform during early Middle Devonian time. The upper part of the Sentinel Mountain-Bay State interval was deposited in more circulated, shallow-marine carbonate-bank environments. The lower part of the Devils Gate Limestone in the study area reflects deposition in shallow, agitated shelf waters and quieter, deeper, shelf lagoons and embayments. Inundation of the carbonate platform followed and is reflected by a shift to deeper water facies during Frasnian (early Late Devonian) time. The Fish Creek Range was affected by Sevier hinterland deformation during the Late Mesozoic; N to N15E-trending folds reflect overall east-west compression. Upper Cretaceous granitic rocks were emplaced at depth beneath the southwest side of the study area, where conodont alteration indices from Paleozoic collections indicate paleotemperatures of 500-600 C. Two-mica granitic dikes, exposed at McCulloughs Butte, intrude Ordovician rocks. Thermal effects may have promoted initial gravity sliding of the Silurian-Devonian section off of the Ordovician section at the Hanson Creek level (Upper Ordovician-Lower Silurian). Low-angle normal faulting within this stratigraphic level is pervasive in the northern part of the Fish Creek Range. It is interpreted that faulting at the Hanson Creek level was initiated at about the same time that the Upper Cretaceous intrusion was emplaced. Movement along the faults may have continued or been renewed during Oligocene extension. Low-angle normal faulting at the Silurian and Lower Devonian levels post-dates faulting at the Upper Ordovician level. It is interpreted that these faults developed during Oligocene uplift and extension. Volcanism and shallow intrusive activity affected the northern Fish Creek Range during earliest Oligocene time, and is represented by the Ratto Springs Rhyodacite. High-angle normal faults typical of basin-and-range extension are common through out the area and represent the most recent phase of deformation.