The Interpretation of Pleistocene Glacial Deposits in the Lower Clay Brook Basin

The Laurentide ice sheet retreated through central Vermont about 14,000 years ago. In the process, meltwater was temporarily dammed in north-flowing valleys, like the Mad River valley. This study investigated glacial-era deposits in the lower Clay Brook valley, a tributary to the Mad. Field mapping and the measurement and description of stratigraphic sections were used to characterize glacial outwash deposits. The sedimentology and stratigraphy were determined at four locations that were then correlated along the valley axis. From these data, the depositional mechanics, energy conditions, and environment of deposition were determined for each unit. Units were combined into depositional lithofacies, which are associated with various glacial depositional environments, including in this case: distal lacustrine deposits of rhythmically laminated silt-clay, proximal lacustrine and subaqueous outwash deposits that are generally coarse-grained and indicative of high energy conditions, and post-glacial fluvial deposits that are characteristically coarse-grained and poorly sorted. Earlier studies in this area suggested a late-glacial readvance episode which is not supported here, but rather the interpretation of either a subglacial tunnel or subaqueous fan depositing ice-proximal or ice-contact deposits in the Clay Brook valley during Glacial Lake Granville.