PALEOHYDROLOGY OF THE CHAUTAUQUA TUNNEL VALLEY NETWORK, NW PENNSYLVANIA

This study examines the paleohydrology of the Chautauqua Tunnel Valley Network in northwestern Pennsylvania. A broad suite of tunnel valleys dissects the Chautauqua Drumlin Field that extends from the Ohio – Pennsylvania border into upstate New York. These valleys have received little attention from researchers and were initially interpreted as proglacial meltwater channels. They have since been reinterpreted as subglacial in origin based on their anabranching pattern, uphill longitudinal profiles and their association with other known subglacial landforms, such as eskers that sit inside some of the valleys. These valleys contain extensive sedimentary deposits, that with the help of ground penetrating radar (GPR) analysis, will provide information necessary to address several key questions about tunnel valley genesis, including the hydrological conditions under which the sediments in the valleys were deposited (e.g. catastrophic vs. steady state flow conditions).

Using parameters derived from digital elevation models, sedimentary analysis and GPR, preliminary data are presented on the potential rates of flow. Several scenarios are presented based on interpretations of bedforms present in the tunnel valleys, as well as boulder sizes and the hydraulic head(s) required to drive the water up and over the tunnel valley thalweg “crests”. This study will aid in reconstructing the paleohydrology of the Erie Lobe of the Laurentide Ice Sheet. It will also help to determine the role that the Lake Erie Basin, that exists directly to the north of the study area, played in the formation of the tunnel valley network.