Timing and mechanisms of basement uplift and exhumation in the Colorado Plateau-Basin and Range transition zone, Virgin Mountain anticline, Nevada- Arizona

Abstract

Structural, stratigraphic, and thermochronologic studies provide insight into the formation of basement-cored uplifts within the Colorado Plateau-Basin and Range transition zone in the Lake Mead region. Basement lithologic contacts, foliations, and ductile shear zones preserved in the core of the Virgin Mountain anticline parallel the trend of the anticline and are commonly reactivated by brittle fault zones, implying that basement anisotropy exerted a strong influence on the uplift geometry of the anticline. Potassium feldspar 40 Ar/ 39 Ar thermochronology indicates that basement rocks cooled from ≥250-325 °C to ≤150 °C in the Mesoproterozoic and remained at shallow crustal levels (<5-7 km)..