Stratigraphy And Depositional Environments Of The Ordovician Through Devonian Mountain Springs Formation Southern Nevada

Author : Linda Jane Jarvis
Publisher :
ISBN 13 :
Total Pages : 166 pages
Book Rating : 4.:/5 (822 download)

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Download or read book Lower and Middle Devonian stratigraphy and depositional environments of the Sheep, Desert, Pintwater, and Spotted Ranges, Northern Clark County, Nevada written by Linda Jane Jarvis and published by . This book was released on 1981 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: During much of the Early and Middle Devonian, shallow normal marine and peritidal sediments were deposited in northwestern Clark County, Nevada. Lack of a standard stratigraphic nomenclature for the area necessitates utilizing terminology from central Nevada and western Utah. The Sevy Dolomite represents Early Devonian deposition in a tidal flat environment. A Zlichovian transgression initiated deposition of the normal marine McColley Canyon Formation in the area. Continuation of that transgression was responsible for the deposition of the lower part of the Pintwater Formation, a new formation which consists of silty, argillaceous dolomite with abundant secondary chert. A Dalejan regression occurred during deposition of the upper part of the Pintwater Formation; it was during the later phases of this regression that the Oxyoke Canyon Sandstone was deposited in a complex barrier bar system which paralleled the coastline. Three Middle Devonian transgressions of varying magnitude have been recognized in southern Nevada. The first transgression, during the early Eifelian, was responsible for the widespread deposition of the Coarse Crystalline Member of the Simonson Dolomite. The Coarse Crystalline Member represents an entire transgressive-regressive cycle. The second Middle Devonian transgression, which occurred later in the Eifelian, initiated deposition of the restricted, shallow subtidal to supratidal Alternating Member of the Simonson Dolomite. Deposition of this unit was marked by periodic minor rises in sea level. Each dark-light dolomite couplet represents a single transgressive pulse followed by upward-shallowing sedimentation. Peritidal sedimentation was 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 into the area. The tectonic setting in southern Nevada during the Early Devonian was significantly different than that in central Nevada; southern Nevada facies are different than central Nevada facies, and a relatively condensed conodont sequence indicates a slower rate of subsidence. During the Middle Devonian, however, facies throughout southern and east-central Nevada are markedly similar, as is the timing of depositional events. This indicates that the tectonic setting along the southern Cordilleran margin was more uniform by Middle Devonian time.