Timing of Cenozoic volcanism and Basin and Range extension innorthwestern Nevada; new constraints from the northern Pine ForestRange

Abstract

Eocene-middle Miocene volcanic rocks in the northern Pine ForestRange, Nevada, are ideally situated for reconstructing the timing andstyle of volcanism and extensional faulting in the northwesternmostpart of the Basin and Range province. A conformable sequence ofCenozoic volcanic and sedimentary strata in the northern Pine ForestRange dips approximately 30 degrees W, and 11 new (super 40) Ar/(super 39) Ar ages from this sequence define 3 major episodes ofvolcanic activity. Pre-Tertiary basement and older (ca. 38 Ma)Tertiary intrusive rocks are overlain unconformably by Oligocene (ca.30-23 Ma) basalt flows and dacitic to rhyolitic ash-flow tuffsinterbedded with fine-grained tuffaceous sedimentary rocks. Oligocenerocks are overlain by approximately 550 m of ca. 17-16 Ma basalt flowsequivalent to the Steens Basalt in southern Oregon, and basalt flowsare capped by a thin 16.3 Ma ignimbrite that likely is correlativewith either the Idaho Canyon Tuff or the Tuff of Oregon Cany!

37 samples from this reference