BIOSTRATIGRAPHIC CONSTRAINTS ON UPPER PALEOZOIC TECTONIC EVENTS IN EDNA MOUNTAIN AND SURROUNDING AREAS, WESTERN NEVADA

The Mississippian to Permian sedimentary section in Nevada includes several angular unconformities constraining timing of deformation (Snyder et al., 1997). The unconformities represent genetically important breaks in the stratigraphic record. Our studies to date reveal several intriguing features about late Paleozoic deformation in Nevada and southeastern California. First, the very precise age control and the fortuitous combination of exposure and preservation at Carlin Canyon demonstrate unequivocally that deformation there occurred at several distinct times. At a minimum, we document folding, uplift and erosion in mid-Mississippian (C2) (Trexler et al., 2003), mid-Pennsylvanian (C6), and earliest Permian (P1) time (Trexler et al., 2004). It is critical to map these deformations over a larger area, to attempt to recognize a pattern in age, orientation, geographic position or structural style of these events. In our recent studies at Edna Mountain and surrounding areas near Winnemucca, several unconformities were recognized and biostratigraphically constrained. C3 unconformity, of early Morrowan (Millerrella marblensis foraminiferal zone) age, coincides with the base of Highway Fm at Edna Mountain. C6 unconformity, characterized by primitive Triticites of early Missourian age, occurs at the base of Antler Peak Formation and is widespread throughout the area. P2 unconformity (Schwagerina elkoensis etc.) is recognized locally at Elephant Head area, near Battle Mountain. This unconformity may correspond to the widespread unconformity at the base of the Edna Mountain Fm. Chronostratigraphic constraint of the latter is poor due to limited biostratigraphic control.