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1 University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Papers in the Earth and Atmospheric Sciences Earth and Atmospheric Sciences, Department of 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. Edward S. Belt Amherst College, [email protected] Neil E. Tibert Mary Washington College H. Allen Curran Smith College John A. Diemer University ofnorth Carolina Joseph H. Hartman University of North Dakota Belt, Edward S.; Tibert, Neil E.; Curran, H. Allen; Diemer, John A.; Hartman, Joseph H.; Kroeger, Timothy J.; and Harwood, D 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). Papers in the Earth and Atmospheric Sciences. Paper This Article is brought to you for free and open access by the Earth and Atmospheric Sciences, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Papers in the Earth and Atmospheric Sciences by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.

Edward S. Belt Amherst College, esbelt@amherst.edu Neil E. Tibert Mary Washington College H. Allen Curran Smith College John A. Diemer University ofnorth Carolina Joseph H.

2 See next page for additional authors Follow this and additional works at: Part of the Earth Sciences Commons

3 Authors Edward S. Belt, Neil E. Tibert, H. Allen Curran, John A. Diemer, Joseph H. Hartman, Timothy J. Kroeger, and D M. Harwood This article is available at DigitalCommons@University of Nebraska - Lincoln: 199

Harwood This article is available at DigitalCommons@University

4 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. Edward S. Belt 1 *, Neil E. Tibert 2, H. Allen Curran 3, John A. Diemer\ Joseph H. Hartman 5, Timothy J. Kroeger 6, and David M. Harwood 7 1 Department of Geology, Amherst College, Amherst, MA 01002, U. S.A. 2 Department ofenvironmental Science & Geology, Mary Washington College, 1301 College Avenue, Fredericksburg, VA , U.S.A. 3 Department ofgeology, Smith College, Northampton, MA 01063, U.S.A. 4Department ofgeography and Earth Sciences, University ofnorth Carolina, Charlotte, NC 28223, U.S.A. 5 Department of Geology and Geological Engineering, and Energy & Environmental Research Center, University of North Dakota, Grand Forks, ND 58202, U.S.A. 6 Department of Biology and Geology, Bemidji State University, Bemidji, MN 56660, U. S.A. 7 Department of Geosciences, University of Nebraska, Lincoln, NE 68588, U. S.A. *Correspondence should be addressed to: [email protected] 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. T wo 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. T wo 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-iacustrine, 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. KEY WORDS: bivalves, diatoms, estuarine environment, Fort Union Formation, Tongue River Member, Ostracoda, trace fossils, Paleocene, Williston Basin. Rocky Mountain Geology, v. 40, no. 1, p. 1-24, 12 figs., 1 table, 1 appendix,july,

Harwood 7 1 Department of Geology, Amherst College, Amherst, MA 01002, U. S.A. 2 Department ofenvironmental Science & Geology, Mary Washington College, 1301 College Avenue, Fredericksburg, VA 22401-5308, U.

TEXAS A&M UNIVERSITY CORPUS CHRISTI COLLEGE OF SCIENCE AND TECHNOLOGY PROPOSAL FOR NEW COURSE/ELECTIVE. Credit Hours: 6 Semester: Summer Year: 2009

TEXAS A&M UNIVERSITY CORPUS CHRISTI COLLEGE OF SCIENCE AND TECHNOLOGY PROPOSAL FOR NEW COURSE/ELECTIVE Course Number: GEOL 46xx Instructor: James R. Garrison, Jr. Credit Hours: 6 Semester: Summer Year: