Date of Award:
5-1992
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Geosciences
Department name when degree awarded
Geology
Committee Chair(s)
James P. McCalpin
Committee
James P. McCalpin
Committee
Robert Q. Oaks, Jr.
Abstract
Southern Star Valley is a structural and physiographic basin bounded on the east by the southern Star Valley fault, an active normal fault associated with Basin and Range extension. The southern Star Valley fault separates southern Star Valley from the Salt River Range and forms a dramatic north-south trending topographic escarpment. Statistical analysis of relative-age dating (RD) parameters taken from glacial deposits in the Salt River Range defined distinctive age groups for the deposits, and comparison of RD data allowed correlations with late Pleistocene and Holocene glacial deposits elsewhere in the Rocky Mountains. However, the sedimentary lithologies in the glacial deposits in the study area and inherent variability of RD data limited definitive regional correlations.
The southern Star Valley fault (SSVF) lies in a parabola-shaped zone of large, seismogenic normal faults. The zone trails to the west of the eastward-migrating Yellowstone hot spot. Basin-facing fault scarps up to 11 meters high created by recurrent late Quaternary faulting along the southern Star Valley fault are preserved in late-Pleistocene and Holocene alluvial fans along the Salt River Range front. Radiocarbon ages from faulted deposits exposed in a trench provide age estimates of ca. 8,090 ± 80 and 5,540 ± 70 yrs. B. P. for the two most recent paleoearthquakes. The magnitudes of the paleoearthquakes, based on surface rupture height and length and estimates, were between Ms6.9 and Ms7.1. The tectonic geomorphology of river alluvium and alluvial fans near the SSVF suggests that recurrent faulting has down-dropped the northern end of southern Star Valley more in relationship to the southern part of the valley and created a deep depocenter in the northern part.
Checksum
29cd1ba45db7ad82c63b53bea9ed5913
Recommended Citation
Warren, Gregory A., "Quaternary Geology and Neotectonics of Southern Star Valley and the Southwest Flank of the Salt River Range, Western Wyoming" (1992). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 6699.
https://digitalcommons.usu.edu/etd/6699
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