Story posted May 04, 2011
"Analysis of subglacial meltwater erosion in the Hudson Valley, NY"
The Hudson Valley of New York is an important throughway from the Great Lakes and the St. Lawrence Valley to the Atlantic Ocean, known to have had large subaerial meltwater discharges. The role of subglacial meltwater flows, however, has not been previously investigated. This study approached Hudson Valley subglacial flows through GIS-based modeling of subglacial hydraulic heads using a DEM base (uncorrected for postglacial changes or bathymetry below lakes and rivers) and superimposing planar ice sheets with systematically varying slopes and flow directions. Results show that subglacial meltwater flow was substantially constrained by major topographic features including the Catskill and Taconic Mountains and largely restricted to the Hudson trough. Local field evidence for subglacial meltwater erosion exists as a boulder-strewn channel within the uplands of Harriman State Park. Large crescentic erosional forms, up to several km across and hundreds of meters high, in subhorizontal sandstone and shale of the Devonian Hamilton Group near Alcove Reservoir are similar to ‘mega-sichelwannen’ described from other glaciated areas and interpreted by some to be formed by meltwater erosion in subglacial megafloods. Associated evidence for large-scale subglacial meltwater erosion is lacking, however, and the origin of these features remains unclear. Overall, the subglacial landscape of the Hudson Valley is strongly controlled by bedrock structure and lithology, as eroded both directly by ice and by meltwater.