Earth Sciences Commons^™

Geomorphic History Of The Grand Staircase Region Of The Colorado Plateau: Understanding Arroyo Cut-Fill Dynamics, Erosion Rates, And Wildfire, Kerry E. Riley

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Most streams in the southwestern United States do not flow all year, and given their delicate balance of sediment and water flow, they are sensitive to climate change. At the turn of the 20th century, many streams in the Southwest rapidly incised into their floodplains, forming arroyos with a channel entrenched into near-vertical channel banks mostly composed of sand and mud. This dissertation investigates past changes in watersheds draining the Grand Staircase region in southern Utah with the goal of understanding how changes in climate and sediment influence these types of streams. Results show sediment supply is highly variable across …

Quaternary Evolution Of The Colorado River At Lees Ferry, Arizona, William Scott Cragun

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A well-exposed suite of Colorado River fill terraces preserved at Lees Ferry records the oscillating history of this major river superimposed on its overall downcutting of the Colorado Plateau. Detailed mapping, sedimentology, cross-sectional surveys, and the use of two geochronometers have been used in order to establish a detailed chronostratigraphy for the area. Eight distinct deposits have been identified along the Colorado River (Ml -M7, and S3), and four deposits have been identified along the Paria River (Pl -P4).

Geochronology of six of these deposits using optically stimulated luminescence and cosmogenic ¹⁰Be exposure techniques indicates a long-term average bedrock …

Effects Of Quaternary Climate Change On Tributary Sedimentation And Geomorphology In Eastern Grand Canyon, Benjamin D. Dejong

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Climate variability has had a dramatic impact on eastern Grand Canyon tributaries over the past ~100 ky. This is readily observed in the Lava Chuar and Comanche catchments, which host well preserved colluvial remnants and river terraces that resulted from several climate-induced cycles of aggradation and incision. This study investigates these climate responses using surveying, sedimentology, and luminescence geochronology methods to investigate the mechanisms and timing of their deposition.

The survey data demonstrate that the concavity of terrace treads is lower than modern drainages. The sedimentology suggests the prevalence of stream-flow reworking of debris flow deposits and portrays an expected …

The Quaternary Tectonic And Structural Evolution Of The San Felipe Hills, California, Stefan M. Kirby

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

We examine the transition between extension and strike-s lip in the San Felipe Hills, western Salton Trough, southern California using new and compiled geologic mapping, measured stratigraphic sections, magnetostratigraphy, and structural analysis. A 625 m measured section describes the Borrego, Ocotillo , and Brawley formations in the SE San Felipe Hills and constrains a regional disconformity and correlative angular unconformity at ~ 1 Ma. Sedimentation rates for the Brawley Formation above the disconformity range from 1.0 to 1.2 mm/yr, palcoflow was to the ENE. The Brawley Formation consists of three interbeddcd lithofac ics; (I) fluvial and fluvio-d eltaic, (2) lacustrinc, …

Quaternary Geology And Landscape Evolution Of Eastern Grand Canyon, Arizona, Matt D. Anders

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Tectonics and drainage evolution are controlling overall landscape incision in eastern Grand Canyon. Superimposed on downcutting are dynamic responses of hillslopes, tributary streams, and the Colorado River to glacial-interglacial climate cycles. Five tributary stream fill terraces have been identified, and luminescence dating indicates aggradation was occurring 50- 34 ka {S3), 12-7 ka (S2), and 5-3.5 ka (S1). Seven Colorado River fill terraces have been identified, and luminescence and U-series dating indicate deposition was occurring 343-322 ka (M5), 151-118 ka (M4), and 71-64 ka (M3).

Aggradation by the Colorado River in eastern Grand Canyon begins during glacial advances and continues into …

Quaternary Bear River Paleohydrogeography Reconstructed From The 87sr/86sr Composition Of Lacustrine Fossils, David P. Bouchard

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Diverted from its former course to the Pacific Ocean by basalt flows in Gem Valley, Idaho, the Bear River presently flows south into the Bonneville Basin. Constraining the timing of the river's diversion is pivotal to understanding the hydrologic budgets, and thus the climatological implications of the Bonneville Basin lakes. This study employs strontium (Sr) isotopes in mollusc fossils as a tracer of the Bear River water that entered Lake Thatcher, a small, closed-basin lake into which the redirected river flowed en route to the Bonneville Basin. The Sr ratios, combined with the temporal control afforded by amino acid geochronology …

Late Quaternary Glacial Geology, Shoreline Morphology, And Tephrochronology Of The Lliamna/Naknek/Brooks Lake Area, Southwestern Alaska, Karen B. Stilwell

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This study focuses on the late-Wisconsin Brooks Lake glaciation, lake-level fluctuations, and volcanic deposits in the lliamna/Naknek/Brooks Lake area on the northern Alaska Peninsula, southwestern Alaska. The Brooks Lake glaciation consists of five stades, from youngest to oldest: Kvichak, Iliamna, Newhalen, Iliuk, and Ukak. This thesis reassigns the type Mak Hill moraine to a pre-late-Wisconsin glaciation, and considers the moraine enclosing Naknek Lake an early-late-Wisconsin deposit correlative to either the Kvichak stade, lliamna stade, or both. The presence in the Iliamna Lake valley, and the absence in the Naknek Lake valley of a two-fold earliest-late-Wisconsin Kvichak/Iliamna glacial sequence suggest that …

Petrology And Mineralogy Of Tertiary(?) Volcanic Rocks West And Southwest Of Kelton (Box Elder Co.), Utah, R. L. Voit

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Kelton, Utah, area has numerous, isolated basaltic outcrops of probable Tertiary age mostly in the form of cuestas with steep faces displaying columnar joints. One ash-flow tuff is located in the southeastern part of the study area. Basaltic fragments in the tuff indicate that pyroclastic activity was preceded by extrusion of basalt.

Effects of Lake Bonneville on the basaltic outcrops include wave­cut terraces, scarps, and other wave-built forms in low lying areas. Massive carbonate deposits formed at levels of former shorelines of Lake Bonneville. Tertiary and Quaternary deposits cover the low- lying areas between basaltic flows, and consist of …