Melissa V. Connely

Academic paper

Tate Geological Museum, Tate �96, Paleonenvironments of the Jurassic

30-37

The Sundance Formation of Central and South Central Wyoming records a unique marine environment worthy of further study. Located below the familiar �Dinosaur Beds� of the Upper Jurassic Morrison Formation, the Sundance throughout Wyoming has variations in both thickness and lithology. One biological characteristic is outstanding: Fossils of plesiosaur and ichthyosaur species are highly abundant within the boundaries of the Redwater Shale member of the Sundance Formation. The Redwater Shale fossils of Wyoming are coompared to the Oxford Clay fauna, and found to be lacking in diversity. By using stratigraphic techniques, each fossil locality in the test area was charted and individual envionments recorded and compared. Through these comparisons, a closer look has been taken at the unique fauna otthe Sundance Sea. The results indicate that the Sundance Sea was perhaps a hostlle environment, allowing the fauna to survive only for brief intervals. This would explain the absence of the varieties normally associated with marine environments, yet allow population explosions of non-predated species. With this information and further study, a better understanding of the paleoecology of marine reptiles in North America can be obtained.

English