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Salt-dissolution faults versus tectonic faults from the case study of salt collapse in Spanish Valley, SE Utah (USA)

Jesus Guerrero, Ronald L. Bruhn, James P. McCalpin, Francisco J. Gutierrez, Grant Willis and Morteza Mozafari
Salt-dissolution faults versus tectonic faults from the case study of salt collapse in Spanish Valley, SE Utah (USA)
Lithosphere (December 2014) 7 (1): 46-58

Abstract

A paleoseismological investigation in Spanish Valley, SE Utah, reveals that faults related to interstratal karstification of salt may show episodic displacement and significantly different parameters than tectonic faults. Spanish Valley is a 25-km-long, 3-km-wide, NW-SE-trending graben formed by the collapse of the crest of a salt anticline. This collapse is related to the karstification of Paleozoic salts, which are several kilometers thick and form the core of the anticline. Differential passive bending of the supra-evaporitic Mesozoic strata produced smaller-scale, NW-SE-trending anticlines and synclines parallel to the axis of the graben on both margins of the collapse valley. Mapping reveals that swarms of synthetic and antithetic normal faults associated with these folds accommodate most of the vertical displacement. A 27-m-long, 4.5-m-deep, trench-like artificial excavation was dug into the hanging wall of the master normal fault of the NE flank with 30-40 m of throw. The excavation exposed a complex structure consisting of a half graben and an asymmetric upper graben separated by a horst. Nine displacement events have been inferred and constrained by consistent AMS (Accelerator mass spectrometry) radiocarbon dates, indicating an anomalously high mean vertical slip rate of 3.07 mm/yr and a very low average recurrence of approximately 316 yr. The most recent recorded faulting event took place after 2330 cal. yr B.P. Data derived from detailed maps indicate that the faults have aspect ratios (maximum displacement to fault length) comparable to those reported for tectonic faults. However, they show greater aperiodicity, with coefficient of variation values greater than 1, long-term slip rates between 2 and 25 times greater, and displacement per event values up to 30 times higher than those expected for tectonic faults of the same length.


ISSN: 1941-8264
EISSN: 1947-4253
Serial Title: Lithosphere
Serial Volume: 7
Serial Issue: 1
Title: Salt-dissolution faults versus tectonic faults from the case study of salt collapse in Spanish Valley, SE Utah (USA)
Affiliation: University of Zaragoza, Earth Sciences Department, Saragossa, Spain
Pages: 46-58
Published: 20141211
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 100
Accession Number: 2015-007632
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 1 table, geol. sketch map
N38°32'20" - N38°32'20", W109°29'43" - W109°29'43"
Secondary Affiliation: University of Utah, USA, United StatesGEO-HAZ Consulting, USA, United StatesShiraz University, IRN, Iran
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201504
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