PALEOHYDROLOGY OF EARLY PLEISTOCENE DRAINAGE SYSTEMS: A STUDY OF THE ANCESTRAL MONONGAHELA RIVER

The modern-day North American drainage is the result of major rerouting caused by continental glaciation. During a pre-Illinoian glaciation, the ancestral Monongahela River, also known as the Pittsburgh River, was dammed by an advancing ice sheet and its drainage was rerouted from its previous path into the Erie Basin toward the Ohio River and Gulf of Mexico. This study aims to reconstruct several aspects of the pre-glaciation Monongahela River, including unit stream power and tractive force, through the use of gradient reconstruction and cobble and boulder measurements collected on ancient river terrace deposits. These data indicate that the flow of the Monongahela River prior to the formation of the glacial lake likely differed from its modern counterpart.

Rounded clasts, measured along the intermediate axis and ranging in size from 3 mm to 680 mm, have been found on terraces at an elevation of around 287 m (940 ft), which may be indicative of the bed elevation of the river in the Morgantown-New Geneva area. D95 (290 mm) will be used in the calculations, as it represents the larger boulders that were transported and the true power of the river.

Collected data will be compared to the dynamics of the modern system in order to better understand how the river has changed through time. Insight into the details of this river could assist in paleoclimatic reconstruction of the Appalachian region and better understanding of how continental glaciers reshape drainage divides. A general understanding of how fluvial systems have evolved through time can give us an image of how they will continue to evolve in the future; specifically, this study will attempt to deepen the understanding of the overall dynamics of the Monongahela River system.