(in San Rafael Group)
Figure 1: Paleogeographic map of the Middle Jurassic, Page Sandstone, Carmel Formation, Entrada Sandstone, Curtis Formation, and Summerville Formation. (Blakey, 2008)
Middle Jurassic, 160 Ma
Sabkha (and supratidal) to marine
Frequent, but short-lived sea level fluctuations during the Middle to Late Jurassic caused periodically flooding from shallow extensions of the ocean. Flooding deposited gypsum, sand, and limey silt in depressed blocks of land that were bordered by parallel faults (grabens), and were periodically covered by sea water. Evaporites were deposited from repeated flooding during this time.
Stable, some volcanism with subduction to the west.
The Carmel Formation is composed of 200 to 1,000 feet (60 to 300 m) of reddish-brown siltstone, mudstone and sandstone that alternates with whitish-gray gypsum and fossil-rich limestone in a banded pattern. Fossils include marine bivalves and ammonites. The Carmel formation contains massive limestone beds in varying shades of gray, but also contains brittle limestone beds that weather into hard angular chips. The limestone beds can also be sandy and some contain ripple marks. Various types of soft sediment deformation also characterize the Carmel Formation. Typical Carmel exposures occurs as a series of low cliffs and steep slopes. In some areas, the Carmel Formation forms a resistant cap and slows the erosion of the underlying Navajo Sandstone.
Sites Best to See it:
Stop 2-2: Carmel Formation
Figures 2-3: Soft Sediment Deformation features in the Carmel Formation on Hwy 24 heading east between the visitorís center and the east park boundary. Soft sediment deformation forms shifting, and displacement of sediments, possibly from escape of water from below, and/or from sediment loading (denser bed sinking into a less dense bed). Soft sediment deformation is an important process because it records rapid deposition, fluid movement, or tectonism prior to lithification. Various styles of soft sediment deformation are commonly associated with evaporite minerals.
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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 Utahís Parks and Monuments Utah Geological Association Publication 29. http://www.utahgeology.org/uga29Titles.htm
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