Sedimentology and Paleontology of the Upper Cretaceous Wahweap Formation sag ponds adjacent to syndepositional normal faults, Grand Staircase-Escalante National Monument, Utah

Simpson, E.L., Koch, R., Heness, E.A., Wizevich, M.C., Tindall, S.E., Hilbert-Wolf, H.L., Golder, K., and Steullet, A.K. (2014) Sedimentology and Paleontology of the Upper Cretaceous Wahweap Formation sag ponds adjacent to syndepositional normal faults, Grand Staircase-Escalante National Monument, Utah. Cretaceous Research, 50. pp. 332-343.

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Abstract

During the development of the East Kaibab monocline, listric normal faulting related to outer arc influenced the sedimentation style of the Upper Cretaceous Wahweap Formation. The initiation of the Laramide Orogeny was therefore recorded in the sedimentary record of south-central Utah. Evidence for this includes the preservation of sag ponds adjacent to two of the normal faults in our study area, which developed when fault movement created topographic features. Ancient sag-pond deposits are likely under-identified in the rock record. This study demonstrates their significance and potential for unraveling fault histories.

The northern, younger, sag-pond deposit is located at the boundary between the upper and capping sandstone members of the Wahweap Formation, and consists of sandstone dikes and sills hosted in gray mudstones and siltstones with no discernable invertebrate fauna, but some small macerated flora. The second southern sag-pond fill, is located at the base of the upper member. The sag pond is older, larger in area, and contains a thicker deposit. In contrast to the northern sag-pond deposit siltstones and mudstones are gray and visiblity structureless. Within the southern sag pond there are a series of fossil horizons consisting mainly of juvenile unionid bivalves, a lesser number of gastropods, and macerated plants. Comparison of the two preserved Upper Cretaceous sag-pond deposits suggests two distinct responses to fault movement, perhaps governed by fault kinematics, manifested in sedimentation style and type; the impact of faunal invertebrate invasion; and post-sedimentation deformation.

Item ID: 38764
Item Type: Article (Research - C1)
ISSN: 1095-998X
Keywords: Cretaceous; sag pond; normal fault; Utah; paleoseismology
Funders: Donors of the American Chemical Society Petroleum Research Fund, Kutztown University Research Committee, Pennsylvania State System of Higher Education Professional Development Committee, CSU/AAUP University Research Grants, Grand Staircase-Escalante National Monument
Date Deposited: 14 May 2015 02:59
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040310 Sedimentology @ 50%
04 EARTH SCIENCES > 0403 Geology > 040308 Palaeontology (incl Palynology) @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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