Background Reading
The following papers will help you to understand the different geological interpretations that have been applied to the Little Badlands.  As you read these papers, you might want to construct a table in which you list the expected differences between faults and landslides.  Some criteria might be: morphology of the surface trace of the structure, curvature of the slip plane, features on the slip plane such as slickensides or lineations, competence of the strata, angular relationships of the strata, etc.
 
Caldwell, J.W., 1954, Surface Structure of Western Stark County and Adjacent Areas of North Dakota, NDGS Report of Investigations #14, 1 pl (1:125,000) with text. (A geologic and structural map of the Little Badlands)
Denson, N. M. and Gill, J. R. 1965. Uranium-bearing lignite and carbonaceous shale in the southwestern part of the Williston Basin - a regional study. Geological Survey Professional Paper 463, 75 p. with maps, US Government printing Office, Washington, D. C. (Provides a structural interpretation for the geology of the Little Badlands)
Alternative Link to Denson, N. M. and Gill, J. R. 1965. Uranium-bearing lignite and carbonaceous shale in the southwestern part of the Williston Basin - a regional study. Geological Survey Professional Paper 463, 75 p. with maps, US Government printing Office, Washington, D. C. (Provides a structural interpretation for the geology of the Little Badlands)
Gill, J.R., 1962, Tertiary landslides, northwestern South dakota and southeastern Montana. Geological Society of America Bulletin, 73: 725-736.   (Provides a model for the origin of pre-Miocene structures in the Slim Buttes, South Dakota - NDSU Library 550.5 G29)
Hickey, L. J. 1977. Stratigraphy and paleobotany of the Golden Valley Formation (Early Tertiary) of western North Dakota. Memoir 150, Geological Society of America (Provides useful information on the stratigraphy and sedimentology of the Golden Valley Formation).
Hoganson, J. W., Murphy, E.C. and Forsman, N.F., 1998, Lithostratigraphy, paleontology, and biochronology of the Chadron, Brule, and Arikaree Formations in North Dakota, in Terry, D.O., Jr., LaGarry, H.E., and Hunt, R.M., Jr., eds: Depositional Environments, Lithostratigraphy, and Biostratigraphy of the White River and Arikaree Groups (Late Eocene to Early Miocene, North America). Geological Society of America Special Paper 325, p. 185-196. (a version of Murphy et al 1993)
Murphy, E.C., Hoganson, J.W., and Forsman, N.F. 1993. The Chadron, Brule, and Arikaree Formations in North Dakota. Report of Investigation No. 96, North Dakota Geological Survey (Good overview of the geology of the Little Badlands, especially stratigraphic units)
Seeland, D. 1985. Oligocene paleogeography of the northern Great Plains and adjacent mountains, In ( Flores, R.M. and Kaplan, S.S., eds.) Cenozoic Paleogeography of west central United States. pp. 187- 205. SEPM, Rocky Mountain section (Sedimentological -tectonic interpretation of the White River Group).
Stone, W. J. Stratigraphy and Sedimentology of middle cenozoic (Oligocene and Miocene) deposits of North Dakota. 1973. Ph.D. Thesis, University of North Dakota (Provides a sedimentological and structural interpretation for the deposits of the Little Badlands that conflicts with the Denson and Gill hypothesis).
Trapp, H., Jr., and M.G. Croft, 1975, Geology and Ground-Water Resources of Hettinger and Stark Counties, North Dakota, County Ground-Water Studies 16 - Part I, North Dakota State Water Commission, 51p + plates (Background geologic description, geologic map, and groundwater information)
 
The following maps, book chapters and papers provide useful background information
Field methods, symbols and notations
Compton, R.R. 1985. Geology in the Field. Wiley, 398p. (Use of the compass pp.16-20; basic procedures at outcrops, taking notes, measuring strike and dip, etc, pp. 22-40;finding and tracing contacts between rock units, pp. 80-83; Measuring and describing stratigraphic sections, pp. 222-241; Illustrations for reports, cross-sections, etc.pp. 348-353).
 
Sedimentology - Read about facies and sedimentary structures of  fluvial and deltaic systems. Several potential sources including:
Boggs, S., Jr., 1995.  Principles of Sedimentology and Stratigraphy.  Prentice-Hall. (Chapter 5, Bedding pp. 108-131; Chapter 10, Continental Environments, pp. 299-318).
Davis, R. A., Jr., 1992.  Depositional Systems. Prentice-Hall. (Chapter 3, Sedimentary Structures, pp. 60-75); Chapter 7, The Fluvial System, pp. 204-237).
Prothero, D. R. and Schwab, F.  1996. Sedimentary Geology.  Freeman (Chapter 4 - Sedimentary Structures, pp. 43-52); Chapter 8 - Terrestrial Sedimentary Environments, pp. 137-157)
Walker, R. G. 1984. Facies Models. Geoscience Canada Reprint Series 1, 317 p. ( Consult sections on alluvial fans, sandy fluvial deposits , and deltas). Especially important to know how the facies of a meandering system differ from those of a braided system).
Structure - Read about methods for analyzing and plotting structures, especially normal faulting.  There are several potential sources, including:
Davis, G. H. and Reynolds, S.J., 1996.  Structural Geology of Rocks and Regions. John Wiley &  Sons, Inc. (Measuring structural orientations with a compass (pp. 662-669); Preparing Geologic Cross Sections (pp. 669-674); Stereographic Projection (pp. 691-720); Methods in Joint Analysis (720 - 730); Normal Faulting (340-352).
Paleontology
Jepsen, G. L., 1963.  Eocene vertebrates, coprolites, and plants in the Golden Valley Formation of western North Dakota. Geological Society of America Bulletin 74.6 (1963): 673-684.
 
General references for field geology useful for the descriptions of various types of surveys, standard map and lithological symbols, and useful in production of geological maps and sections:
AGI Data Sheets Fourth Edition, revised. (Compiled by J. D. Walker and H. A. Cohen, 2009 printing). ISBN 978-0-922152-84-1. spiral bound, 5.00"x8.00" 310 pp.
Assaad, F. A.,  P. E. LaMoreaux, and T. H. Hughes (eds.). 2004. Field methods for geologists and hydrogeologists. Berlin ; New York : Springer-Verlag. Library Call # QE45 .F527 2004.
Barnes, J.W. 1981. Basic Geological Mapping: 1-112. Geological Society of London Handbook, The Open University Press and Halsted Press.
Compton, R. R. 1962. Manual of Field Geology: 1-378. John Wiley and Sons, Inc.
Freeman, T. 1999. Procedures in field geology. Maiden, Mass. : Blackwell Science. Library Call # QE45 .F733 1999.
Gardiner, V. and Dackombe, R. 1983. Geomorphological Field Manual: 1-254. Allen and Unwin.
Kottlowski, F.E. 1965. Measuring Stratigraphic Sections: 1-253. Holt, Rhinehart, and Winston.
Lisle, R. J., P. J. Brabham and J. W. Barnes. 2011. Basic geological mapping. 5th ed. Wiley-Blackwell. Call No. QE36 .B33 2011.
Tucker, M. E. 2011. Sedimentary rocks in the field : a practical guide. 4th ed. Wiley-Blackwell. Call No.   QE471 .T84 2011
General Literature Resources (Courtesy of Lura Joseph, Librarian, University of Illinois at Urbana-Champaign): https://sites.google.com/site/lurascollections/bibliographies/littlebad