EVIDENCE FOR CONNECTION BETWEEN A UNIQUE SUBGLACIAL LANDFORM AND A BURIED TUNNEL CHANNEL OF THE HURON-ERIE LOBE, NE INDIANA

During the LGM, the Huron-Erie Lobe of the Laurentide Ice Sheet covered a significant portion of Indiana. Recent advances in LiDAR have revealed previously unidentified landforms across the region of northeastern Indiana which have been dubbed two-tracks due to their distinctive morphology of two parallel linear troughs. Two-tracks have been found crossing recessional moraines in NE Indiana and are stratigraphically above buried river valleys. Their formation is assumed to be subglacial and may be the result of a readvance overtop of recessional moraines in the area. This study focuses on a two-track near Waterloo, IN, and its potential connection to an implied tunnel channel. Morphological, stratigraphic, and geophysical results from this study imply that the buried aquifer under the two-track is directly connected to the tunnel channel. LiDAR data was used to observe the morphology of the features while electrical resistivity surveys in dipole-dipole arrays across the two-track and the tunnel channel were used to establish a further connection between the two features. Morphologically, the two-track was observed to pass laterally into a tunnel channel, showing a direct surface connection between the features. IDNR water wells were used to construct fence diagrams which show a valley like feature below the two-track, as well as a distinct hydrologic disconnection between the surrounding aquifers and the aquifer directly beneath the two-track. In addition, there was a connection between the span of a confined aquifer beneath the two-track and the tunnel channel. While a sharp contact between till and sand/gravel in a U-shape was found in the tunnel channel, characteristic of a channel feature, the two-track showed a more chaotic stratigraphy. This has been seen beneath other two-tracks as well and is likely a result of the formation of the two-track itself. The conclusions of this study are that two-track formation in NE Indiana are likely linked to the presence of underlying aquifers, as seen in buried channel features, and that their formation can change the stratigraphy beneath the feature. This has implications for how the formation of these two-tracks may impact conditions at the bed of the ice, where their formation may lead to changes in sediment supply, bed morphology, or response to pressure from overlying ice.