Regional stratigraphic units and structural features of the Lake Mead region are presented as a 1:250,000 scale map, and as a Geographic Information System database. The map, which was compiled from existing geologic maps of various scales, depicts geologic units, bedding and foliation attitudes, faults and folds. Units and structural features were generalized to highlight the regional stratigraphic and tectonic aspects of the geology of the Lake Mead region. This map was prepared in support of the papers presented in this volume, Special Paper 463, as well as to facilitate future investigations in the region. Stratigraphic units exposed within the area record 1800 million years of geologic history and include Proterozoic crystalline rocks, Paleozoic and Mesozoic sedimentary rocks, Mesozoic plutonic rocks, Cenozoic volcanic and intrusive rocks, sedimentary rocks and surficial deposits. Following passive margin sedimentation in the Paleozoic and Mesozoic, late Mesozoic (Sevier) thrusting and Late Cretaceous and early Tertiary compression produced major folding, reverse faulting, and thrust faulting in the Basin and Range, and resulted in regional uplift and monoclinal folding in the Colorado Plateau. Cenozoic extensional deformation, accompanied by sedimentation and volcanism, resulted in large-magnitude high- and low-angle normal faulting and strike-slip faulting in the Basin and Range; on the Colorado Plateau, extension produced north-trending high-angle normal faults. The latest history includes integration of the Colorado River system, dissection, development of alluvial fans, extensive pediment surfaces, and young faulting.

Abstract The Hurricane Fault is one of the longest and most active late Cenozoic normal faults in southwestern Utah and northwestern Arizona. This fault shows evidence of tectonic activity during the late Tertiary and Quaternary, neotectonism involving the Hurricane Fault as well as the Toroweap Fault imply encroaching Basin and Range extension onto the Colorado Plateau. Paleoseismology investigations suggest that the Hurricane Fault poses a seismic hazard to the southwestern Utah area. During the trip, we will examine evidence of late Pleistocene and earliest Holocene(?) surface-rupturing faulting along the Shivwits and Whitmore Canyon sections of the fault. The Hurricane Fault separates the Uinkaret and Shivwits plateaus and displacement along the fault produced the spectacular Hurricane Escarpment. We will see late Quaternary land-forms related to back-wasting and mass movement along the Hurricane Escarpment and look at evidence of the style and age estimates of late Pleistocene fan deposition.