Stratigraphy And Patterns Of Sedimentation Of The Garden Valley Formation In Eureka County Nevada

Author : Joseph T. Lipka
Publisher :
ISBN 13 :
Total Pages : 188 pages
Book Rating : 4.:/5 (171 download)

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Download or read book Stratigraphy and Structure of the Southern Sulphur Spring Range, Eureka County, Nevada written by Joseph T. Lipka and published by . This book was released on 1987 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Early Paleozoic limestones and dolomites of the shallow shelf transitional facies belt were mapped in the southern Sulphur Spring Range, Eureka County, Nevada. The four youngest units in the map area are in fault contact with the Lower Devonian rocks and were probably transported westward, along a low-angle normal fault. The crinoidal dolomites of the Hanson Creek Formation, dated as latest Ordovician in the map area, were deposited in a low-energy lagoon. Overlying the Hanson Creek Formation, with a gradational contact, is the lower member of the Lone Mountain Dolomite, a probable reef complex. The exposed thickness of the lower Lone Mountain Dolomite is estimated to be 250 feet. The Lower Devonian Old Whalen Member of the Lone Mountain Dolomite is composed of well-bedded, alternating brown and gray dolomites. The repetition of rock types in the Old Whalen Member indicates recurring shallow marine environments on a broad carbonate platform. The Old Whalen is estimated to be 1400 feet thick. Directly overlying the Old Whalen Member, is the Kobeh Member of the McColley Canyon Formation. Rocks of the McColley Canyon Formation were deposited on a shallow shelf under normal marine conditions. The mid-Lower Devonian Kobeh Member is sparsely to abundantly fossiliferous and varies from a peloidal wackestone to a peloidal sandy wackestone to a sandy peloidal packstone. The thickness is 276 feet. Overlying the Kobeh Member are the abundantly fossiliferous beds of the lower part of the Bartine Member. The lower part, of the Bartine ranges from a wackestone to a packstone and weathers to a chacteristic yellowish tan. The upper part of the Bartine varies from wackestone to packstone, is darker in color, and is sparsely to moderately fossiliferous. The thickness of the Bartine Member is 189 feet, and it is late Early Devonian in age. The Sadler Ranch Formation is a dolomitic wackestone containing conoids with or without brachiopods, and it is latest Early Devonian in age. The Sadler Ranch Formation was deposited on a shallow shelf under normal marine conditions. Above the Sadler Ranch Formation is the lower member of the Oxyoke Canyon Sandstone. The lower member of the Oxyoke varies from a peloidal packstone to sandy peloidal wackestone to quartzite. The upper member of the Oxyoke Canyon Sandstone is a structureless dolomitic mudstone. The Oxyoke Canyon Sandstone was probably deposited in a high to moderate energy lagoon with a subsequent decrease in depositional energy. The Middle Devonian Sentinel Mountain Dolomite overlies the Oxyoke Canyon Sandstone. The Sentinel Mountain is a structureless to finely laminated dolomite that was deposited in a lagoon that initially had open circulation, but which was later cut off. The youngest formation in the map area is the Permian Garden Valley Formation which is a reddish brown silicified conglomerate. The Sadler Ranch Formation, Oxyoke Canyon Sandstone, Sentinel Mountain Dolomite, and Garden Valley Formation are all present as allochthonous blocks, which were transported from the east as a result of movement along low-angle normal faults. The blocks were juxtaposed on top of the autochthonous Old Whalen Member of the Lone Mountain Dolomite and on the McColley Canyon Formation. Denudation of the Kobeh and Bartine Members of the McColley Canyon Formation occurred as a result of the movement on the faults. The timing of the movement on the low-angle normal faults is estimated to be Cretaceous because of the eastern source and the pre-Cretaceous age of the allochthonous rocks. The age is still problematical as a consequence of the lack of any cross-cutting dikes or other age-determinable units.