GEOPHYSICAL EVIDENCE AND IMPLICATIONS OF AN EARLY PLEISTOCENE GLACIATION OFFSHORE MASSACHUSETTS, USA

With a new, high-resolution, multi-channel seismic survey, we present evidence for the extent of an Early Pleistocene glaciation offshore Massachusetts (USA). The seismic data contain several glacial geomorphic features we use to infer the maximum extent of the glaciation nearly 125 km offshore. These features include (1) a large, regionally distributed erosion surface up to 250 m below the seafloor; (2) steeply eroded sediments with nearly 100 m of relief; (3) a network of sub-ice sheet meltwater channels; and (4) a transparent, glacifluvial seismic unit. We present a conceptual model to illustrate the influence of the Early Pleistocene glaciation on the observed stratigraphy. The features we observe are similar to Early Pleistocene glacial geomorphic features observed offshore Maine, USA. Assuming these features are contemporaneous, we present a regional extent for the Early Pleistocene glaciation offshore New England. Our new interpretations provide valuable geophysical constraints on the maximum extent of an Early Pleistocene glaciation offshore New England and are consistent with shore based studies of Early Pleistocene glacial extent. This new information will be used as an additional model constraint in a basin scale hydrogeologic model to understand the influence of Pleistocene glaciations on the distribution and flux of sub-surface freshwater offshore New England throughout the Pleistocene.