Skip to Main Content

Paleoenvironments and age of the Wasatch Formation (Eocene), Powder River basin, Wyoming

David T. Pocknall
Paleoenvironments and age of the Wasatch Formation (Eocene), Powder River basin, Wyoming
Palaios (1987) 2 (4): 368-376


A well-exposed section of the lower Eocene Wasatch Formation near Arvada, Wyoming, was examined palynologically. The 60-70 m section includes a 2.5 m thick coal tentatively correlated with the Felix coal and a series of coarsening-upward sequences representing standing-water environments. In the lower part of the section wetland forests of Glyptostrobus were widespread as indicated by pollen percentages of 40-75%. During accumulation of the coal swamp, Glyptostrobus dominated the initial phases of swamp vegetation, but due to subsequent changes in basin subsidence and drainage it was eventually replaced by a vegetation in which Ulmaceae and Sphagnum were dominant. Platanus, Tilia, Gentianaceae, and Alnus maintained a consistent presence throughout development of the coal swamp. In samples from above the coal several palynomorphs were recorded that provide evidence of the sedimentological conditions which followed coal swamp inundation. Under standing-water environments, plants flourished that were adapted to growth on lake margins or within lakes; Platycarya became more prominent as a lake- and stream-margin plant, and in the lakes' freshwater zygnemataceous algae, the aquatic fern Azolla, and Sparganium were common. The OK Creek section is of early Eocene age based both on the presence of Platycarya, Tilia, and Eucommia, and on the low abundance of juglandaceous pollen--especially Carya and the Engelhardia-Alfaroa group--when compared to their abundance in late Paleocene sediments from the same geographic region. The almost synchronous appearance of Platycarya in North America is a useful datum. Evolution within the family Juglandaceae, climatic warming in the early Eocene, and availability of early successional habitats may have all acted to produce this biostratigraphically important event.

ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 2
Serial Issue: 4
Title: Paleoenvironments and age of the Wasatch Formation (Eocene), Powder River basin, Wyoming
Author(s): Pocknall, David T.
Affiliation: N.Z. Geol. Surv., Lower Hutt, New Zealand
Pages: 368-376
Published: 1987
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 31
Accession Number: 1988-020369
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sect., sketch map
N44°40'00" - N44°45'00", W106°00'00" - W16°15'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 1988
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal