ORIGIN AND EVOLUTION OF WATERFALLS IN OHIO'S HOCKING HILLS: FROM PRO-GLACIAL LAKE SPILLOVER TO PRESENT

Slot canyons, polished potholes, and amphitheater-headed waterfalls are likely not landforms that leap to mind when you envision Ohio’s landscapes. However, these fluvial features are abundant in the Hocking Hills region of southeastern Ohio. During the Illinoian Glacial Stage (ending 130,000 years ago), an ice sheet impounded pro-glacial lakes along its margin in southern, central, and eastern Ohio. At the ice sheet’s maximum extent, a lobe of ice dammed Pine and Queer Creeks near their junction at present-day Haynes, OH, forming a pro-glacial lake just west of Hocking Hills State Park. At some point prior to 130,000 years ago, this lake spilled over a southern drainage divide carving a 100-meter-deep, steep-walled valley that is now occupied by Salt Creek. This spillover and drainage integration event lowered baselevel for Pine and Queer Creeks and a wave of incision propagated upstream from the spillover point. These drainage systems incised through the gently dipping Mississippian strata that underlie the Hocking Hills with prominent knickpoints forming on the resistant Blackhand Sandstone Member of the Cuyahoga Formation. The modern-day elevation of waterfalls is largely a function of the local thickness and dip of the Blackhand Sandstone within the Hocking Hills, but the dynamics of how far upstream waterfalls propagated and, in some cases, how waterfalls are still moving upstream are more puzzling problems.

We combine field mapping, surveying, and digital terrain analyses in GIS to investigate the origin and evolution of the Hocking Hills’ waterfalls. We use longitudinal profiles extracted from 1-meter resolution LiDAR to identify knickpoint elevations and reconstruct baselevel for Pine and Queer Creeks prior to incision. We use drainage areas both above and below waterfalls to quantify a relationship between potential stream power and the upstream propagation distance for each tributary’s waterfalls. Field observations of erosion via sapping beneath waterfalls “hung up” on the Blackhand Sandstone and the presence, or absence, of recent block fall downstream from amphitheater-headed waterfalls guide our investigation of current waterfall propagation. We will present the results of this ongoing work in the Hocking Hills and the early stages of a broader look at similar spillover-incision events along the Illinoian and Wisconsinan ice margins in Ohio.