Stratigraphic and sedimentologic analysis of the (Upper Mississippian) lower Newark Valley sequence, Diamond Range, Eureka and White Pine Counties, Nevada

Abstract

The Newark Valley sequence is the upper of two Mississippian tectonostratigraphic units recognized within the Diamond Mountains of east- central Nevada. These rocks comprise part of the (Upper Mississippian) Diamond Peak Formation and (Pennsylvanian) Ely Limestone. Seven depositional facies are recognized from the lower siliciclastic portion of the Newark Valley sequence. These include the braided fluvial, meandering fluvial, delta plain, delta front, prodelta, shallow-marine carbonate and shallow-marine siliciclastic facies. Facies trends within a north-south cross- section of the lower Newark Valley sequence exhibit a thinning of alluvial deposits toward the south complemented by a decrease in thickness of shallow marine carbonate deposits toward the north. Paleocurrent trends indicate a dominant southeast flow direction accompanied by a subordinate northeast direction. Provenance studies reveal a marked shift in plagioclase content between the Newark Valley sequence and the underlying Diamond Range sequence. The evolution of this sequence is marked by six depositional stages including two siliclastic progradations and three carbonate transgressions. These stages indicate that Late Mississippian tectonism played a significant role in the formation of the basin in which the Newark Valley sequence was deposited.