The highly seasonal runoff from badlands and other treeless landscapes along the Little Missouri carries heavy loads of eroded sediment downstream.[9] The sedimentary layers, which extend from the headwaters in Wyoming all the way to the mouth in North Dakota, vary in age, but most of the beds along the river belong to the Bullion Creek and Sentinel Butte formations, both deposited during the Paleocene (about 66 to 56 million years ago).[10] The deposits include siltstone, claystone, sandstone, and lignite coal laid down in a coastal plain during the Laramide orogeny.[10]
^ abPersonius, Robert Giles; Eddy, Samuel (February 18, 1955). "Fishes of the Little Missouri River". Copeia. 1955 (1). American Society of Ichthyologists and Herpetologists: 41. doi:10.2307/1439450. JSTOR1439450.
^"USGS 06337000 Little Missouri River near Watford City, ND". November 2010. Retrieved April 27, 2011. This is only a close approximation of the entire basin. It does not include a small fraction of the basin below the river gauge, located about 25 mi (40 km) upstream of the river mouth.