Collaborative Research: High-resolution Basin Analysis of a Large-offset Extensional System, Lake Mead Domain, East-Central Basin and Range Province

University Of St. Thomas, Saint Paul MN

Investigators

Abstract

This project aims to determine the tectonic and paleogeographic development of the central Basin and Range in the Lake Mead area near Las Vegas, Nevada, through a high-resolution analysis of syn-extensional basins. This region includes low-angle detachment faults, normal faults, transtensional fault systems, areas of complex three-dimensional strain with extensional and contractional structures, and locally voluminous magmatism. This study will focus on three major questions that are important for extensional tectonics globally: (1) Is there a predictable series of processes in the evolution of a major extensional episode in wide, magmatic rifts built on thick crust such as in the Basin and Range? (2) Are extensional processes in the internal part of wide continental plate boundaries controlled by far-field or internal forces? (3) How does climate change and evolving topography affect sedimentation in a major extensional orogen? The main hypotheses the research team is testing are that: (1) the Lake Mead domain developed from east to west in discrete stages from detachment faulting to transtensional faulting, to tectonic escape accompanied by shortening; (2) extension, detachment faulting, and exhumation were initially driven by over thickened crust, but the temporal evolution was controlled by far-field plate boundary changes; (3) changes in patterns and rates of faulting exert a first-order control on basin geometry and stratal thickness, but climate controls significant details of the stratal architecture that have heretofore been attributed to tectonic processes. Basin analysis techniques - including characterization of stratigraphic architecture, facies analysis, geochronology, structural mapping, and stable isotope geochemistry - are being utilized to address these hypotheses. This research will examine Miocene age basins in Lake Mead to determine the detailed development of faulting and the changing landscape between 6 and 10 million years ago during an episode of crustal extension. This is the geologic episode that fundamentally formed the low landscape of the region and made the Basin and Range a distinct province from the adjacent Colorado Plateau. Despite decades of research, there remain fundamental unanswered questions about the mechanism and evolution of deformation in the central Basin and Range that this project aims to address. The research has wide application because extensional regions are common hosts of oil and gas globally and the Basin and Range is considered a well exposed example of these processes.