Lower Mesozoic sedimentary and volcanic rocks of the Yerington region, Nevada, and their regional context

Abstract

Metamorphosed Triassic and Jurassic volcanic and sedimentary rocks have been mapped, described, and measured in the Singatse, Buckskin, and northern Wassuk Ranges near Yerington, west-central Nevada. Herein, we establish new formation names for these rocks and correlate them regionally with other Triassic-Jurassic rocks, in part by use of fossil and radiometric ages. From oldest to youngest, rocks in the Singatse Range consist of a Middle Triassic or older volcanic sequence (McConnell Canyon volcanics), an Upper Triassic sequence of interbedded fine-grained clastic sedimentary rocks, carbonate rocks, tuffaceous sedimentary rocks, and tuffs (Malachite Mine Formation and tuff of Western Nevada Mine), a thick Upper Triassic limestone (Mason Valley Limestone), an uppermost Triassic and Lower Jurassic siltstone sequence (Gardnerville Formation), an Early and/or Middle Jurassic limestone-gypsum-quartzite sequence (Ludwig Mine Formation), and Middle Jurassic volcanic rocks. The sequence is exposed in septa between two Middle Jurassic batholiths and was folded and metamorphosed during emplacement of the batholiths. The Middle Jurassic volcanic rocks are best exposed in the Buckskin Range to the west, where they consist of a lower andesitic sequence (Artesia Lake volcanics) and an upper sequence of more felsic, porphyritic rocks (Fulstone Spring volcanics). The Triassic and Early Jurassic rocks are also exposed in the Wassuk Range to the east and include a thick section of andesitic and silicic volcanics, which may be in part equivalent to the McConnell Canyon volcanics, the lower part of which is intruded by the possibly cogenetic Middle Triassic Wassuk diorite and associated quartz monzonite and quartz porphyry.