TWO DISTINCT SHORELINES OF PLEISTOCENE LAKE TIGHT IN SOUTH-CENTRAL OHIO

During the Pleistocene, glacial ice dammed the northwest-directed Teays River drainage in southern Ohio, creating proglacial Lake Tight in the incipient Upper Ohio River Basin (UORB). The true extent and depth of Lake Tight is poorly constrained due to a scarcity of published studies; even the long-held assumption that lake levels had reached the 900 ft. contour appears to be based primarily on botanical, rather than geological data (Transeau, 1941; Wolfe, 1942). Erosional features in the Lower Scioto and abandoned Teays Valleys (LS-ATV) of south-central Ohio provide geomorphic evidence for the 900 ft. contour shoreline. Additional features at 825 ft. indicate a second long-lived shoreline, suggesting an episodic filling model for Lake Tight. Evidence observed in the LS-ATV consists of wave cut notches, bluffs, and elongated stacks along ridge tops developed on outcrops of resistant Mississippian sandstone, which are consistent with features found on modern rocky shorelines. These features were mapped using altimetric and GPS data to correlate the Pleistocene shorelines across the LS-ATV. Correlation of these features reveals the existence of two large islands within the basin of Lake Tight. Data for these two shorelines can be extrapolated from the large islands to delineate the outer boundaries of this large body of water (see Erjavec, this conference). A correct understanding of the extent of Lake Tight allows further elaboration of the history of drainage modification and origin of geomorphological features in UORB. The persistence of these erosional features at high elevations, over long distances, outlining a continuous shoreline, supports the presence of Lake Tight in UORB for an extended length of time during the Pleistocene, and may provide alternative explanations for other geologic features in UORB.