Stratigraphy and depositional environments of Jurassic Gypsum Spring and Sundance Formations, Sheep Mountain anticline area, Big Horn County, Wyoming

Conference · Fri Aug 01 00:00:00 EDT 1986 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:7230430

Doyle, A B

The Sheep Mountain anticlinal complex between Lovell and Greybull, Wyoming, in the Bighorn basin provides exposure suitable for three-dimensional stratigraphic studies of Mesozoic rocks. The lower unit of the Gypsum Spring Formation is interbedded shale and gypsum. The middle unit is a cyclic sequence of variegated shales, mudstones, and wackestones. The upper unit is red shale. The contact between the underlying Upper Triassic Chugwater Group and the Gypsum Spring Formation is unconformable, as evidenced by an erosional surface. The Sundance Formation is divided into Sundance A and Sundance B, based on fossil data. Sundance A is predominantly green shale with some limestone-shale interbeds. Sundance B lithology is similar to Sundance A with belemnoid guards. Toward the top of Sundance B are beds of glauconitic sandstones that grade upward into fossiliferous limestone. The contact between the Gypsum Spring, Sundance, and Morrison Formations appears to be gradational. The Western Interior sedimentary basin experienced four major transgressions during the Jurassic, resulting in the deposition of the Gypsum Spring and Sundance. Gypsum Spring deposition was influenced by paleohighs, specifically the Belt Island and Sheridan arch, and a warm, arid climate with rare storms. The lower Gypsum Spring unit was deposited in a restricted basin, with the middle and upper units reflecting subsequent deepening and freshening of the Jurassic sea. Most of the Sundance Formation was deposited in a relatively quiet, open-marine environment. Individual units represent shoaling conditions during minor regressions. Storms cut channels into sand bars, which were filled with coquinoid deposits.

• Research Organization: Hotline Energy Reports, Casper, WY
• OSTI ID: 7230430
• Report Number(s): CONF-8609129-
• Journal Information: Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 70:8; Conference: AAPG Rocky Mountain Section meeting, Casper, WY, USA, 7 Sep 1986
• Country of Publication: United States
• Language: English

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03 NATURAL GAS
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STRATIGRAPHY
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GEOLOGIC FORMATIONS
JURASSIC PERIOD
FEDERAL REGION VIII
GEOLOGIC AGES
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