Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geological Sciences

First Advisor

Karl J. Mueller

Second Advisor

Roger Bilham

Third Advisor

Kristy Tiampo

Fourth Advisor

Gregory Tucker

Fifth Advisor

Phaedra Upton

Abstract

Gravity-driven salt systems occur worldwide and their prevalence and unique, ultraweak mechanical properties create complex structures where brittle and ductile processes are closely linked and sensitive to external processes (e.g.\ climate, and surface processes). Many questions remain as to exactly how stresses combine to drive large scale mass movements of salt, which has implications for the timing of deformation, rate limiting factors, and variations in stresses through space and time. Terrestrial salt systems provide a unique opportunity to study the temporal evolution of these complex structures and explore the spatial scales of deformation in a highly coupled system. The Needles District within Canyonlands National Park, Utah, is a well-exposed gravity-driven salt system that I have utilized to constrain the rates and styles of rapidly developing strain in the uppermost crust. Three-dimensional numerical modeling of the Needles demonstrates the spatial complexity of salt mechanics in an actively eroding and deforming system, indicating that salt flow is sensitive to pressure gradients on the scale of 10s to 100s of meters. Surface displacements measured using differential interferometric synthetic aperture radar (DInSAR) provide high resolution velocity fields of surface deformation that are used to validate three-dimensional mechanical models. DInSAR results reveal the spatial variation of the regional displacement field, providing insight into the conditions that enhance or inhibit brittle deformation. Analysis of the displacement rates within individual grabens reveals evidence for fault segment linkage that is highly complex, patterns of which cannot be defined by structural observations of linkage maturity alone. Displacement rate measurements obtained along an active fault in the region using an extensometer and line leveling reveal continuous, steady state creep over a five-year period that can be attributed to the mechanics of the system and strength of the overburden. These studies form an ensemble of measurements and tests that allow determination of the various stress drivers that collectively combine to enhance or inhibit the growth of salt structures including extensional faults, diapirs, and elongate river anticlines.

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