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GEOREF RECORD

Taphonomy and paleoecology of nonmarine Mollusca; indicators of alluvial plain lacustrine sedimentation, upper part of the Tongue River Member, Fort Union Formation (Paleocene), northern Powder River basin, Wyoming and Montana

John H. Hanley and Romeo M. Flores
Taphonomy and paleoecology of nonmarine Mollusca; indicators of alluvial plain lacustrine sedimentation, upper part of the Tongue River Member, Fort Union Formation (Paleocene), northern Powder River basin, Wyoming and Montana (in Paleo-lacustrine theme issue, Leo Laporte (editor))
Palaios (1987) 2 (5): 479-496

Abstract

Paleoenvironments are interpreted from the taphonomy of freshwater mollusc assemblages in the Tongue River Member of the Fort Union Formation (Paleocene) in the northern Powder River Basin, Wyoming and Montana. The composition, species abundances, and spatial and temporal distributions of these assemblages were controlled by the environments in which the molluscs lived and the depositional processes that affected the molluscs after death and before final burial. Post-mortem transport, reworking and concentration of shells, and mixing of faunal elements from discrete habitats produced a taphonomic "overprint" on assemblage characteristics that directly reflects the processes of alluvial plain and floodbasin lacustrine sedimentation. The "overprint" can be interpreted from outcrop analysis of molluscan biofabric, which consists of: 1) orientation, fragmentation, size-sorting, abrasion, density, and dispersion of shells, 2) the nature and extent of shell-infilling, and 3) ratio of articulated to disarticulated bivalves. In this study, taphonomic characteristics were used with sedimentological properties to differentiate in-place, reworked, transported, and ecologically mixed mollusc assemblages. This study also defines the paleoecology of habitat preferences of mollusc species as a basis for recognition of the environments in which these assemblages were deposited: 1) large floodbasin lakes (on- and off-shore), 2) small floodbasin lakes, and 3) crevasse deltas and splays. Integration of sedimentology and paleoecology provides an interdisciplinary approach to the interpretation of alluvial environments through time in the Tongue River Member.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 2
Serial Issue: 5
Title: Taphonomy and paleoecology of nonmarine Mollusca; indicators of alluvial plain lacustrine sedimentation, upper part of the Tongue River Member, Fort Union Formation (Paleocene), northern Powder River basin, Wyoming and Montana
Title: Paleo-lacustrine theme issue
Author(s): Hanley, John H.Flores, Romeo M.
Author(s): Laporte, Leoeditor
Affiliation: U. S. Geol. Surv., Denver, CO, United States
Affiliation: Univ. Calif., Earth Sci., Santa Cruz, CA, United States
Pages: 479-496
Published: 1987
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 30
Accession Number: 1988-029681
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, block diags., sketch maps
N43°00'00" - N45°19'60", W107°15'00" - W105°00'00"
N45°00'00" - N45°47'60", W106°19'60" - W104°57'00"
N41°00'00" - N45°00'00", W111°04'60" - W104°04'60"
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
Program Name: USGSOPNon-USGS publications with USGS authors
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