Date of Award
Master of Science in Biological and Environmental Sciences (MSBES)
David E. Fastovsky
A detailed lithostratigraphic, geochronological, and paleomagnetic framework at Corral Bluffs, CO, USA, captures key mammalian evolutionary steps during the terrestrial Paleocene radiation and provides high-resolution insights into the post Cretaceous-Paleogene extinction recovery. Here I examine earliest Paleocene paleoenvironments preserved at a vertebrate microsite locality at Corral Bluffs, leading to a deeper understanding of the context of the earliest Cenozoic mammalian radiation.
I carried out a detailed sedimentological analysis including field as well as laboratory petrographic analyses to reconstruct the paleoenvironments preserved at a microsite locality in Corral Bluffs. I utilized a limited microfossil collection from this locality for an additional test of the paleoenvironmental hypothesis. My analysis affirms an earlier operational hypothesis that the Corral Bluffs microsite locality was part of a low-sinuosity river system. The river system exhibited high flow intensities and the presence of soft-sediment deformation suggests very rapid sediment deposition, from which I infer episodic deposition in an active landscape. Paleocurrents suggest an average northeast flow direction of 37° ± 41°. The presence of root casts, small, isolated layers of coal, and dense deposits of macerated plant matter as well as whole leaves indicate that the region was vegetated and organically productive.
The general direction of flow suggests a source area approximately 60 km to the southwest of the Corral Bluffs area. During the Laramide Orogeny, the source was uplifted and low-sinuosity rivers drained the early Rocky Mountains, transporting sediment to Corral Bluffs. The spatial relationship between the Rocky Mountain Front and the Corral Bluffs outcrops, as well as crystalline units preserved at Corral Bluffs, suggest that the former is the source area for the latter. Given that, the deposits at Corral Bluffs likely represent the distal part of an alluvial fan, built by low-sinuosity rivers draining the Laramide Rocky Mountains.
The taphonomy and sedimentology of the sedimentary deposits indicate that transport of the microfossils occurred before deposition. Because of this, the assemblage of organisms found at the microsite locality might not have lived in association with the low-sinuosity, distal fan environment of the Corral Bluffs area.
Naprstek, Rebecca, "DAWN OF THE CENOZOIC: VERTEBRATE-BEARING POST-DINOSAUREXTINCTION PALEOENVIRONMENTS OF CORRAL BLUFFS, CO, USA" (2023). Open Access Master's Theses. Paper 2401.