Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-2018 Quaternary Incision, Salt Tectonism, and Landscape Evolution of Moab-Spanish Valley, Utah James P. Mauch Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Geology Commons Recommended Citation Mauch, James P., "Quaternary Incision, Salt Tectonism, and Landscape Evolution of Moab-Spanish Valley, Utah" (2018). All Graduate Theses and Dissertations. 7068. https://digitalcommons.usu.edu/etd/7068 This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. QUATERNARY INCISION, SALT TECTONISM, AND LANDSCAPE EVOLUTION OF MOAB-SPANISH VALLEY, UTAH by James P. Mauch A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Geology Approved: ______________________ ______________________ Joel L. Pederson, Ph.D. Tammy M. Rittenour, Ph.D. Major Professor Committee Member ______________________ ______________________ Susanne U. Jänecke, Ph.D. Mark R. McLellan, Ph.D. Committee Member Vice President for Research and Dean of the School of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2018 Copyright © James P. Mauch 2018 All Rights Reserved ABSTRACT Quaternary Incision, Salt Tectonism, and Landscape Evolution of Moab-Spanish Valley, Utah by James P. Mauch, Master of Science Utah State University, 2018 Major Professor: Dr. Joel L. Pederson Department: Geology Modern topography and fluvial terraces can be used to understand deformation and incision. These approaches are applied to the Moab-Spanish Valley salt graben in the central Colorado Plateau. Here, localized salt deformation is superimposed on regional incision, yet the co-evolution of these processes is not understood. Using mapping, luminescence and cosmogenic dating, surveying, and geographic information system (GIS) terrain analyses, this work seeks to understand the rates, patterns, controls, and geomorphic signatures of the fluvial and salt-tectonic processes that have sculpted this landscape. Deposits of Colorado River tributaries Mill and Pack creeks are offset along fault zones and down-warped along the Moab-Spanish Valley graben axis. Luminescence dating and surveying constrains displacement rates over the last 100,000 years to approximately 440 meters per million years (m/my) at the northeast graben margin across discontinuous, steeply-dipping faults with atypical geometries. Over the same time, total iv subsidence has occurred at about 450 m/my in Spanish Valley and up to 1000-1350 m/my in Moab Valley. Late Pleistocene incision of Mill Creek has kept pace with northeast graben-margin fault slip, though chronostratigraphy indicates incision prior to 200,000 years ago was much slower. Meanwhile, digital projection of cosmogenically-dated upland gravels indicates that subsidence likewise must have accelerated in the middle- late Pleistocene and that graben collapse is essentially a Quaternary process. Graben subsidence accelerating in conjunction with fluvial incision supports the conceptual model for deformation, where salt-dissolution and transport by groundwater drives subsidence. GIS-derived indices of normalized steepness and concavity demonstrate that longitudinal profiles of regional tributaries are primarily controlled by heterogeneous bedrock. Yet common baselevel signals are also evident in the distribution of major knickzones in tributaries both crossing and independent of the graben recorded by the Chi parameter. This suggests drainages are responding to regional transient incision of the Colorado River system and that local subsidence is largely compensated by depositional filling of the graben. This study adds to the growing number to document late Pleistocene transient incision across the central Colorado Plateau. Such results require a baselevel fall downstream, either much-delayed from the integration of the Colorado River or from a more recent, unknown source. (253 pages) v PUBLIC ABSTRACT Quaternary Incision, Salt Tectonism, and Landscape Evolution of Moab-Spanish Valley, Utah James P. Mauch To study the history of processes that shape the Earth’s surface, geologists look for markers in the landscape that they can date and use to measure change. Rivers leave such markers in their deposits and terrace landforms and in the overall shape of their elevation profile from head to toe. This thesis uses luminescence and cosmogenic methods to date the sediment in terraces to determine when the river deposited it. Field mapping and global positioning system (GPS) surveying are also used to measure the distance between terrace levels to quantify how much change has occurred. This study seeks to answer questions about when, how quickly, and why streams near Moab in Utah’s Canyonlands region have incised into bedrock. It seeks also to determine the history, rates, and patterns of the active and incremental sinking of Moab and Spanish valleys. The results from this work show that the incision of canyons along Mill and Pack creeks upstream from Moab accelerated around 200,000 years ago to between 0.44 and 0.62 millimeters per year (mm/yr). The sinking of Moab and Spanish valleys also appears to have quickened around the same time and has occurred at up to 1.35 mm/yr in Moab Valley and around 0.45 mm/yr in Spanish Valley over the last 100,000 years. The Kayenta Heights fault zone (KHFZ) accommodates part of the sinking of Moab Valley and has slipped at an average rate of 0.44 mm/yr in the last 100,000 years. This study’s vi mapping of the length and width of individual fault strands supports prior interpretations that the KHFZ does not pose an earthquake hazard, though it can still be expected to produce active rock fall and rupture the ground surface locally. That the sinking of Moab and Spanish valleys and the down-cutting of the upstream canyons has occurred at similar rates, and may indeed have sped up at a similar time in the past, indicates a linkage of the two processes. This is consistent with an existing hypothesis that Moab and Spanish valleys are sinking because groundwater is dissolving the buried salt deposits and transporting them out through the Colorado River. This process is able to continue because as the Colorado River and its tributaries incise lower into the landscape, groundwater follows and can reach greater depths in the salt deposits. The results of this study paint a picture of the recent and accelerated sinking of Moab and Spanish valleys, which has occurred jointly with incision of the regional drainage network. This acceleration of incision, which has been documented throughout the Canyonlands region, may relate to the Colorado River’s carving of Grand Canyon around 6 million years ago or may have come from a more recent and unknown downstream source. vii ACKNOWLEDGMENTS I am grateful for the generosity of the organizations that provided financial support for this work. These include the National Science Foundation Graduate Research Fellowship Program, the U.S. Geological Survey EDMAP Program, EarthScope, the Geological Society of America, the Society for Sedimentary Geology, the Utah State University (USU) Office of Research and Graduate Studies, and the USU Geology Department. This work has been a joint effort that received important contributions from many people who have been generous with their time and went above and beyond to help me succeed. I was lucky to be accompanied and assisted during dawn-to-dusk days in the field by Jon Harvey, Sherm Young, Zac Williams, Rob McDermott, Mike Turley, and Tim Garvey. Carlie Ideker and Michelle Nelson at the USU Luminescence Lab were timely and helpful in the processing and analysis of luminescence samples. Alan Hidy and Susan Zimmerman at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Lab provided abundant hospitality, mentorship, and teaching during my 10-day visit to process and analyze cosmogenic burial samples. Rob McDermott deserves another acknowledgement for helping overcome hurdles in the longitudinal profile analysis workflow at a critical juncture, as well as for his efforts to bring the USU Geology Department’s Vr workstation up to speed. Grant Willis and Kent Brown at the Utah Geological Survey (UGS) provided abundant mentorship and technical support throughout my mapping project (Chapter 4). I would not have been able to produce a viii complete map product without their tireless assistance. Jessica Castleton and Ben Erickson at the UGS shared fruitful conversations and insight about geologic hazards around Moab. Thank you to committee members Dr. Susanne Jänecke and Dr. Tammy Rittenour for being patent when I missed deadlines, responsive when I needed feedback, and supportive throughout the entire research and writing process. Their collective input has made my thesis much stronger than it would otherwise be. I owe a sincere and special gratitude to my advisor Dr. Joel Pederson, who has been an unwavering advocate since I first stepped foot in Logan. His patience, guidance, expertise, and friendship have been exactly what I’ve needed through these years, and I am lucky to have been his student. I walk away from my time under his mentorship as a better geologist and person, with a renewed commitment to remain rooted in the landscapes