IMPLICATIONS FOR HURON-ERIE LOBE DEGLACIATION FROM UNIQUE SUBGLACIAL MELTWATER FEATURES IN INDIANA AND OHIO

Several linear glacial features have been discovered spanning northeastern Indiana and northwestern Ohio in the area glaciated by the Huron-Erie Lobe of the Laurentide Ice Sheet. Known as “two-tracks”, they consist of pairs of discontinuous troughs separated by a central ridge and are oriented roughly east to west, subparallel with the reconstructed flow direction of the Huron-Erie Lobe. There are two groups, one consisting of narrower and longer “two-tracks” north of Fort Wayne and east of the Interlobate area between the Saginaw and Huron-Erie Lobes, and another that has much wider “two-tracks” located south of Fort Wayne. The former group contains several “two-tracks” each ~1 km across with the troughs and central ridge individually measuring ~300 m wide, and up to 80 km long, ending at the Interlobate area. The latter group contains two distinct “two-tracks”, one 11 km long and 1.5 km wide, and one 50 km long and 3 km wide, both ending at the Mississinawa Moraine. Across both groups, the troughs are 20 m deep on average, and have a consistent width throughout. Interestingly, all “two-tracks” truncate the recessional moraines of the Huron-Erie Lobe, but they are truncated by current drainage.

Vertical electrical soundings and IDNR water well logs have revealed the stratigraphy underneath the “two-tracks” beginning with a basal lower sand and gravel aquifer overlain by a lower till (Trafalgar Fm.), a discontinuous upper sand and gravel aquifer (Huntertown Fm.) and an upper till cap (Lagro Fm.). The “two-tracks” are only cut into the Lagro Fm. but always over the thickest portions of the Huntertown fm. This geometric relationship implies hydrologic connection between the subglacial meltwater and the Huntertown Fm. Deep portions of the Huntertown Fm. may be buried valleys oriented parallel with the flow of Huron-Erie Lobe. The 50 km “two-track” located south of Fort Wayne reinforces this idea as it directly overlies the Teays River valley, but only when the valley is oriented parallel with the ice flow direction. Understanding the formation of these “two-tracks” may have broad implications for reconstructing and predicting subglacial meltwater transport overtop complex unconsolidated sediment packages and the final deglaciation stage of the Huron-Erie Lobe.