Geology of the Lower Permian Dry Mountain Trough, Buck Mountain, Limestone Peak, and Secret Canyon Areas, East-Central Nevada

Publication Date

1987

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Geology

Department

Geosciences

Supervisory Committee Chair

Claude Spinoza

Supervisory Committee Member

Paul Karl Link

Abstract

The Lower Permian Dry Mountain Trough, east-central Nevada, is one of several basins that developed during the late Paleozoic along the western edge of the North American continent. The Dry Mountain Trough records marked subsidence with the appearance during the Early Permian of carbonate slope and basinal facies. The basinal facies in the central Dry Mountain Trough at Buck Mountain and Limestone Peak consist of 600-1000m of thin-bedded silty micrites and micritic siltstones. These lithologies were deposited by a combination of fine-grained, dilute turbidity currents and hemipelagic sedimentation during a maximum time span of 5my. The western margin of the Dry Mountain Trough at Secret Canyon consists of a euxinic basinal facies overlain by carbonate apron toe-of-slope deposits.

Ammonoid-bearing concretions from near the base of the stratigraphic sections at Limestone Peak, Buck Mountain, and Portuguese Springs yielded up to 84 conodont elements per kilogram of rock. Recovered taxa from these lower intervals include Neogondolella bisselli, Sweetognathus whitei, and the Diplognathodus stevensi multi-element assemblage. These elements indicate an Aktastinian (latest Wolfcampian) age. The units above the concretionary ammonoid horizon of the Buck Mountain and Limestone Peak sections yielded 4 elements from a total of over 100 kg of rock, including one representative of Neostreptognathodus peguopensis from the top unit of the Buck Mountain section. N. peguopensis is restricted to the Baigendzhinian. Six fragmentary elements were recovered from the Secret Canyon section, three of which were identified as N. bisselli.

The Aktastinian (latest Wolfcampian) age provided by conodonts for the western margin of the Dry Mountain Trough is in conflict with previously published data. Fusulinids occurring above the Aktastinian datum at Secret Canyon and Portuguese springs indicate a middle to late Wolfcampian age. The conflicting data may be due to unrecognized paleogeographic provincialism between West Texas and eastern Nevada fusulinid faunas which may be more severe than previously documented.

Preliminary basin analysis indicates a tectonic drive for basin subsidence. Subsidence rates for the Dry Mountain Trough were a minimum of 6-14 cm per 1000 years. The mechanism which initiated subsidence is inferred to be the Pennsylvanian -Permian Ancestral Rocky Mountain orogeny.

Comments

This thesis was issued by Idaho State University in collaboration with Boise State University.

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