MORPHOLOGICAL CONNECTION BETWEEN PAIRED TUNNEL CHANNELS, BURIED TUNNEL CHANNELS, AND SUBAERIAL CHANNELS OF THE HURON-ERIE LOBE, ACROSS THE INDIANA, MICHIGAN AND OHIO TRISTATE AREA

LiDAR data has revealed previously unidentified subglacial landforms across the tristate region of Indiana, Michigan, and Ohio covered by the Huron-Erie Lobe (HEL) of the Laurentide Ice Sheet. Paired tunnel channels and buried tunnel channels obliquely cross recessional moraines in the study area and transition to subaerial channels at ice margins. Further supporting a subglacial origin for the paired and buried tunnel channels is their upslope gradient leading to ice margins that are often marked by small moraines. The paired tunnel channels are identified by a distinctive morphology consisting of two parallel depressions separated by a medial ridge. For most paired tunnel channels, the depressions are ~100 m wide and 5–10 m deep, and the medial ridge is ~200–300 m wide. Paired tunnel channels are discontinuous across the landscape with depressions a few hundred meters to several kilometers long. The tunnel channels are partially buried by till, creating a hummocky topography that masks lateral margins making it difficult to map channel boundaries. Some tunnel channels contain small eskers about 0.5 km long. The buried tunnel channels commonly are many kilometers long and 500–1000 m wide. At the ice margins, the buried tunnel channels transition into well-defined subaerial channels a few hundred meters to a few kilometers wide and tens of kilometers long. The small ice marginal moraines are generally parallel with the large recessional moraines (Fort Wayne, Salamonie, Wabash) of the HEL. The conclusion of this study is that the paired and buried tunnel channels that connect to subaerial channels at ice margins are evidence of a readvance over the large Fort Wayne, Wabash, and Salamonie moraines of the Huron-Erie Lobe.