Thermopolis Shale

The Thermopolis Shale is a geologic formation which formed in west-central North America in the Albian age of the Late Cretaceous period.

The rock formation was laid down over about 7 million years by sediment flowing into the Western Interior Seaway.

[3] A foreland basin existed just to the east of the Sevier orogenic belt, which was inundated by the Western Interior Seaway.

He described the Thermopolis Shale as Late Cretaceous in age,[19][18] generally dark in color, from 710 feet (220 m) thick, and with sandstone lenses common.

No type locality was identified, but the formation was named for the town of Thermopolis in Hot Springs County, Wyoming—where, nearby, outcroppings of the shale were well exposed.

[19] Lupton's division of the Thermopolis Shale was adopted by the United States Geological Survey and used for the next 50 years.

[23] Both historically[24] and currently,[25][23] the stratigraphic units in these groups, and in the Thermopolis Shale, have been unclear, and the nomenclature used by geologists is not standardized.

Eicher has argued that the "rusty beds" division is clearly distinguishable in many ways from the Cloverly Formation, and thus belongs to the Thermopolis Shale.

[30] On the Wind River Indian Reservation of Wyoming, using the inclusive definition, it was reported to be a more robust 320 to 450 feet (98 to 137 m) thick.

[26] For the purposes of this article, the definition of the Thermopolis Shale used by Porter et al. [12][35] and Lash[41] will be used, recognizing (as Condon does) that there is scientific disagreement about this issue.

[10] The Thermopolis Shale is unusually rich in marine vertebrate fossils, consisting primarily of skeletal material, teeth, and coprolites.

[4] A particularly rich marine vertebrate fossil zone exists in the lower beds of the Upper Thermopolis Member.