The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.
Road cut into the lower Dakota Group at crest of Dinosaur Ridge, near Golden, Colorado
Dakota Formation in Central Kansas
Schematic reconstruction of the eastern side of the Cretaceous seaway during deposition of the sediments that eventually became the Dakota Formation. Erosional highlands occur in South Dakota and Minnesota.
Lignite coal seam and mine, Wilson, Kansas, 1873
A fossil track or ichnite is a fossilized footprint. This is a type of trace fossil. A fossil trackway is a sequence of fossil tracks left by a single organism. Over the years, many ichnites have been found, around the world, giving important clues about the behaviour of the animals that made them. For instance, multiple ichnites of a single species, close together, suggest 'herd' or 'pack' behaviour of that species.
A reverse ichnite of the impression of Jialingpus yuechiensis, on display at the Paleozoological Museum of China.
Fossil trackway Protichnites in sedimentary stone.
Specialized marine trace trackway, Yorgia, from the Ediacaran of northern Russia.
Laetoli Site, February 2006