Evidence for Marine Influence on a Low-Gradient Coastal Plain: Ichnology and Invertebrate Paleontology of the Lower Tongue River Member (Fort Union Formation, Middle Paleocene), Western Williston Basin, U.S.A.

Authors

Edward S. Belt, Amherst College
Neil E. Tibert, Mary Washington College
H. Allen Curran, Smith CollegeFollow
John A. Diemer, University of North Carolina at Charlotte
Joseph H. Hartman, University of North Dakota
Timothy J. Kroeger, Bemidji State University
David M. Harwood, University of Nebraska - Lincoln

Document Type

Article

Publication Date

7-2005

Publication Title

Rocky Mountain Geology

Abstract

The Paleocene Tongue River Member of the Fort Union Formation contains trace-fossil associations indicative of marine influence in otherwise freshwater facies. The identified ichnogenera include: Arenicolites, Diplocraterion, Monocraterion, Ophiomorpha, Rhizocorallium, Skolithos linearis, Teichichnus, Thalassinoides, and one form of uncertain affinity. Two species of the marine diatom Coscinodiscus occur a few meters above the base of the member. The burrows occur in at least five discrete, thin, rippled, fine-grained sandstone beds within the lower 85 m of the member west of the Cedar Creek anticline (CCA) in the Signal Butte, Terry Badlands, and Pine Hills areas. Two discrete burrowed beds are found in the lower 10 m of the member east of the CCA in the little Missouri River area.

Abundant freshwater ostracodes include Bisulcocypridea arvadensis, Candona, and Cypridopsis. Freshwater bivalves include Plesielliptio and Pachydon mactriformis. We recognize four fossil assemblages that represent fluvio-lacustrine, proximal estuarine, central estuarine, and distal estuarine environments. Biostratal alternations between fresh- and brackish-water assemblages indicate that the Tongue River Member was deposited along a low-gradient coastal plain that was repeatedly inundated from the east by the Cannonball Sea.

The existence of marine-influenced beds in the Tongue River Member invalidates the basis for the Slope Formation.

Keywords

bivalves, diatoms, estuarine environment, Fort Union Formation, Tongue River Member, Ostracoda, trace fossils, Paleocene, Williston Basin

Volume

40

Issue

1

First Page

1

Last Page

24

DOI

doi.org/10.2113/40.1.1

Creative Commons License

This work is licensed under a Creative Commons Attribution 3.0 License.

Comments

Archived as published.

Recommended Citation

Belt, Edward S.; Tibert, Neil E.; Curran, H. Allen; Diemer, John A.; Hartman, Joseph H.; Kroeger, Timothy J.; and Harwood, David M., "Evidence for Marine Influence on a Low-Gradient Coastal Plain: Ichnology and Invertebrate Paleontology of the Lower Tongue River Member (Fort Union Formation, Middle Paleocene), Western Williston Basin, U.S.A." (2005). Geosciences: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/geo_facpubs/38