Deltaic sedimentation and transgressive/regressive cycles in Green River Formation, southern Uinta basin, Utah
Study of outcrop exposures shows that the lower Green River Formation in the south-central Uinta basin consists of 1650 ft (500 m) of sandstone and subordinate mudstone and limestone deposited in a large deltaic complex along the southern shore of Eocene Lake Uinta. The southern half of the lake consisted of a broad, shallow, low-gradient platform fringing a much deeper open-lacustrine oil-shale depocenter to the north. Relatively minor fluctuations in lake depth caused broad fluctuations in shoreline position, producing a complex interfingering of transgressive shallow-water carbonates and regressive fluvial/deltaic deposits. During periods of lake level rise, the fluvial systems deposited most of their sediment upstream, permitting development of extensive thin lake-margin carbonate-flat oolite and ostracod grainstones and stromatolites. Shallow-water siliciclastic bars are rare, suggesting that regressive fluvial/deltaic deposits were not extensively reworked during transgressions. Regressions of Lake Uinta are recorded by fluvial/deltaic sandstones and associated interdeltaic sandstones and mudstones deposited in a fluvially dominated shallow-water delta. Migration of distributary channels on the delta plain caused them to stack in places, producing tabular sand bodies up to 50 ft (15 m) thick and 5000 ft (1.5 km) long. Delta distributary channels cannibalized deltaic deposits during delta progradation. Deltaic deposits consist mainly of lenticular distributary-mouth bars which are stacked in places, producing lenticular composite sand bodies over 50 ft (15 m) thick. Shallow lacustrine prodelta/delta-front deposits consist of thin sandstones, green mudstones, and shallow-water limestones.
- Research Organization:
- Louisiana State Univ., Baton Rouge (USA)
- OSTI ID:
- 6132566
- Report Number(s):
- CONF-890404-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Vol. 73:3; Conference: AAPG annual convention with DPA/EMD Divisions and SEPM, San Antonio, TX, USA, 23-26 Apr 1989
- Country of Publication:
- United States
- Language:
- English
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