Summerville Formation Stop
Immediately west of Hanksville. Summerville Formation outcrop on the north side of Highway 24.
38o 22.263' N
110o 45.064' W
Late Jurassic, deposited during early to late Oxfordian time (161 - 155 Ma) (Wilcox, 2007)
Tidal. The Summerville Formation is mud-dominated intertidal to supratidal deposits of the Jurassic epicontinental sea. The lower boundary of Summerville is gradational with upper facies of the marine Curtis Formation and indicates a gradual shallowing of sea through time. Caputo and Pryor (1991) describe the deposition of Summerville as mud rich, restricted, evaporative, hypersaline conditions. Upper Summerville, with its desiccation mud cracks and ever present evaporite stringers, represents the supratidal stage of the upward shallowing cycle in the last vestiges of the receding Jurassic seaway.
Figure 1: Summerville Formation outcrop on Highway 24, grain size and bed thickness tend to increase up section.
Figure 2: Gypsum stringers cut across ripple forms.
Figure 3: Vertical mudcracks filled with sand, representing polygonal desiccation cracks in the clay bed.
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Disclaimer: The information is property of the University of Utah. Unless cited, images and files found on this site have been taken or created by the Geology and Geophysics Department at the University of Utah. Any use of these images should be cited appropriately. The stratigraphic column is from: Mathis, A. C. 2000. Capitol Reef National Park and Vicinity Geologic Road Logs, Utah, in: P.B. Anderson and D.A. Sprinkel (eds.) Geologic Road, Trail, and Lake Guides to Utah’s Parks and Monuments Utah Geological Association Publication 29. http://www.utahgeology.org/uga29Titles.htm
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