Graduate Thesis Or Dissertation
 

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4f16c7786

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  • During much of the Early and Middle Devonian, shallow normalmarine and peritidal sediments were deposited in northwestern ClarkCounty, Nevada. Lack of a standard stratigraphic nomenclature for thearea necessitates utilizing terminology from central Nevada andwestern Utah.The Sevy Dolomite represents Early Devonian deposition in a tidalflat environment. A Zlichovian transgression initiated deposition ofthe normal marine McColley Canyon Formation in the area. Continuationof that transgression was responsible for the deposition of the lowerpart of the Pintwater Formation, a new formation which consists ofsilty, argillaceous dolomite with abundant secondary chert. A Dalejanregression occurred during deposition of the upper part of the PintwaterFormation; it was during the later phases of this regressionthat the Oxyoke Canyon Sandstone was deposited in a complex barrierbar system which paralleled the coastline.Three Middle Devonian transgressions of varying magnitude have beenrecognized in southern Nevada. The first transgression, during theearly Eifelian, was responsible for the widespread deposition of theCoarse Crystalline Member of the Simonson Dolomite. The CoarseCrystalline Member represents an entire transgressive-regressive cycle.The second Middle Devonian transgression, which occurred later in theEifelian, initiated deposition of the restricted, shallow subtidal tosupratidal Alternating Member of the Simonson Dolomite. Deposition ofthis unit was marked by periodic minor rises in sea level. Eachdark-light dolomite couplet represents a single transgressive pulsefollowed by upward-shallowing sedimentation. Peritidal sedimentationwas brought to an end by the third Middle Devonian transgression.This transgression, which occurred during the middle to late Givetian,brought the deeper water lithotope of the Guilmette Formation intothe area.The tectonic setting in southern Nevada during the Early Devonianwas significantly different than that in central Nevada; southernNevada facies are different than central Nevada facies, and a relativelycondensed conodont sequence indicates a slower rate of subsidence.During the Middle Devonian, however, facies throughout southern andeast-central Nevada are markedly similar, as is the timing of depositionalevents. This indicates that the tectonic setting along the southernCordilleran margin was more uniform by Middle Devonian time.
  • During much of the Early and Middle Devonian
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file details Plate_6.jpg 2017-11-06 Pubblico Scaricare