HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Smith, J. J. Articles by Kraus, M. J. Search for Related Content GeoRef GeoRef Citation

Paleoclimatic Implications of Crayfish-Mediated Prismatic Structures in Paleosols of the Paleogene Willwood Formation, Bighorn Basin, Wyoming, U.S.A.

¹ The University of Kansas, Department of Geology, Lawrence, Kansas 66045-7613, U.S.A.
² The University of Kansas, Department of Geology, Lawrence, Kansas 66045-7613, U.S.A.; Natural History Museum and Biodiversity Research Center, Lawrence, Kansas 66045-7613, U.S.A.
³ University of Colorado, Department of Geological Sciences, Boulder, Colorado 80309, U.S.A.
⁴ University of Colorado, Department of Geological Sciences, Boulder, Colorado 80309, U.S.A.

Paleosols at Polecat Bench, northern Bighorn Basin, Wyoming, show prismatic structures not previously described in the Paleogene Willwood Formation. Prisms are densely spaced 15–50 mm diameter cylinders with vertical to slightly sinuous paths up to 400 mm long, subangular to rounded vertical faces, and slightly concave to convex tops. Prism exteriors are coated commonly by < 1-mm-thick clay films; exteriors also commonly show knobby and striated surficial morphologies. Prismatic structures are nearly exclusive to thin-bedded (< 1 m thick) compound paleosols composed of red to red-purple sandy mudrock overlying gray to green-gray heterolithic units composed chiefly of fine-grained sandstone. In addition to prismatic structures, these paleosols are characterized by large gray mottles, slickensides, and calcareous rhizocretions which crosscut or more typically follow prism exteriors. The architectural and surficial morphology of the soil prisms suggest strongly that these are pedogenically modified freshwater crayfish burrows of the ichnospecies Camborygma litonomos.

At Polecat Bench, an ~ 40 m interval of the Willwood Formation records a transient episode of global warming known as the Paleocene–Eocene Thermal Maximum (PETM). The PETM interval is characterized by a series of predominantly red, cumulative paleosol profiles and increased soil carbonates. Prismatic soil structures and crayfish burrows are rare or absent in cumulic paleosols typical of the PETM, whereas they are locally abundant in red compound paleosols outside the PETM interval. The changes in paleosol morphology and a sharp decrease in crayfish burrows within the PETM interval suggest significantly improved soil-drainage conditions and lower water tables on the Willwood floodplain during the global warming event.

This article has been cited by other articles:

				J. J. Smith, S. T. Hasiotis, M. J. Kraus, and D. T. Woody Relationship of Floodplain Ichnocoenoses to Paleopedology, Paleohydrology, and Paleoclimate in the Willwood Formation, Wyoming, During the Paleocene-eocene Thermal Maximum Palaios, October 1, 2008; 23(10): 683 - 699. [Abstract] [Full Text] [PDF]