Dinosaur biostratigraphy of the Nonmarine Cretaceous of Utah

Abstract

Over the past thirty years, exploration of the terrestrial Mesozoic section in Utah has resulted in a more than fivefold increase in the known species of dinosaurs. A highly resolved temporal and sequence stratigraphic framework for these strata is facilitating the utility of these newly discovered dinosaur assemblages in geologic, evolutionary, paleoecologic, and paleogeographic research. Local subsidence due to salt tectonics in the northern Paradox Basin is responsible for this region of eastern Utah preserving basal Cretaceous dinosaur faunas, known nowhere else in North America, that document paleobiogeographic connections across the proto-North Atlantic with Europe. The more medial Cretaceous strata west of the San Rafael Swell, in central Utah, preserve a unique dinosaur assemblage on an isolated North America. These strata also record the first immigration of Asian dinosaurs into North America and the last occurrences of a number of endemic North American dinosaur lineages. Through the Late Cretaceous, extensive, fossiliferous floodplain deposits are exposed in the high plateaus of southern Utah within the Grand Canyon Bight on the western side of the Late Cretaceous Western Interior Seaway. Research on microvertebrate sites has resulted in a diverse record of vertebrate life substage by substage through most of the Upper Cretaceous sequence. Particularly, rich dinosaur-bearing beds through the Campanian have resulted in the discovery of many new dinosaur species distinct from the coeval dinosaur-bearing beds farther north along the western coast of the Western Interior Seaway in Montana and Alberta. The further development of these numerous rich dinosaur assemblages will provide the basis for considerable research in the future.