Skip to Main Content
Book Chapter

Integration of tectonic, sedimentary, and geohydrologic processes leading to a small-scale extension model for the Mormon Mountains area north of Lake Mead, Lincoln County, Nevada

By
R. Ernest Anderson
R. Ernest Anderson
U.S. Geological Survey, P.O. Box 347, Kernville, California 93238, USA
Search for other works by this author on:
Tracey J. Felger
Tracey J. Felger
U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, Arizona 86001, USA
Search for other works by this author on:
S.F. Diehl
S.F. Diehl
U.S. Geological Survey, Box 25046, MS 966, Federal Center, Denver, Colorado 80225, USA
Search for other works by this author on:
W.R. Page
W.R. Page
U.S. Geological Survey, Box 25046, MS 966, Federal Center, Denver, Colorado 80225, USA
Search for other works by this author on:
J.B. Workman
J.B. Workman
U.S. Geological Survey, Box 25046, MS 966, Federal Center, Denver, Colorado 80225, USA
Search for other works by this author on:
Published:
June 01, 2010

Scattered remnants of highly diverse stratigraphic sections of Tertiary lacustrine limestone, andesite flows, and 23.8–18.2 Ma regional ash-flow tuffs on the north flank of the Mormon Mountains record previously unrecognized deformation, which we interpret as pre–17 Ma uplift and possibly weak extension on the north flank of a growing dome. Directly to the north of the Mormon dome, 17–14 Ma ash-flow tuffs and rhyolite are interstratified with landslides, debris avalanches, debris flows, and alluvial-fan deposits that accumulated to a thickness of more than 2 km in an extension-parallel basin. The source for the landslides and debris avalanche deposits is unknown, but it was probably an adjacent scarp along a transverse fault bounding an early part of the Mormon dome. An average 45° of easterly tilt of the entire Tertiary basin-fill succession represents the major post–14 Ma deformation event in the region. We question the basis for the published estimate of 22 km of westerly displacement on the Mormon Peak detachment fault and, on the basis of landslides in the upper plate having a probable source in the adjacent Mormon dome, constrain the heave to ~4 km. We interpret the dome and basin as coupled strains similar to others in the region and suggest that these strains reflect a waveform pattern of extension-normal lateral midcrustal ductile flow. Previously, doming was interpreted as an isostatic response to tectonic unloading by large-displacement detachment faults or as pseudo-structural highs stranded by removal of middle crust from adjacent areas. Moreover, we argue that the strong thinning of upper-plate rock successions throughout the Mormon Mountains and Tule Springs Hills resulted from a loss of rock volume by protracted fluid flow, dissolution, and collapse, seriously limiting the usefulness of upper-plate strain in evaluating extension magnitude. We present a geohydrologic model that couples uplift driven by ductile inflow with dissolution driven by fluid infiltration, possibly augmented by mantle-derived CO2-rich fluids. Karsting in the uplands led to carbonate sedimentation in adjacent lowlands. Whether or not our downward revision of extension in the Mormon Mountains is valid, extension at that latitude is isolated from extension in the Lake Mead area by a low-strain corridor between the two areas. Recognition of the isolated and potentially diminished strain impacts estimates of maximum finite elongation of the Basin and Range Province because one of three vector paths used in those estimates passes through the Mormon Mountains.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Special Papers

Miocene Tectonics of the Lake Mead Region, Central Basin and Range

Paul J. Umhoefer
Paul J. Umhoefer
Department of Geology, Northern Arizona University, Flagstaff, Arizona, USA
Search for other works by this author on:
L. Sue Beard
L. Sue Beard
U.S. Geological Survey, Flagstaff, Arizona, USA
Search for other works by this author on:
Melissa A. Lamb
Melissa A. Lamb
Geology Department, University of St. Thomas, St. Paul, Minnesota, USA
Search for other works by this author on:
Geological Society of America
Volume
463
ISBN print:
9780813724638
Publication date:
June 01, 2010

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal