FLATTER WATERSHEDS HAVE STRONGER RESPONSES TO PLEISTOCENE GLACIERS IN NORTHERN NEW ENGLAND

The Appalachian Mountains of eastern North America have long been considered the type-locality for old, slowly eroding landscapes from which models of landscape evolution have been conceived. However, in the last decade, a growing number of studies utilizing new techniques from mantle convection modeling to fluvial geomorphology and geochronology have illustrated that there is evidence for recent disequilibrium and relief generation in the Appalachians, even though the last major tectonic event was the opening of the Atlantic Ocean. In this study we take advantage of the predictable behavior of river long-profiles to investigate the landscape history of the northern Appalachians of Vermont, New Hampshire, and Maine. This region is characterized by locally mountainous terrain with considerable relief, but also by large areas of low-relief rolling topography, suggesting a complicated relationship between (and long memory of) tectonics, bedrock geology and response to repeated glacial-interglacial cycles during the Pleistocene. River and stream networks were derived from this region using SRTM- and LiDAR-derived elevation data, and show a wide range of range of behaviors, from the smoothly decreasing slope of a well equilibrated river channel to a staircase of knickpoints climbing to a relict portion of the landscape. Curiously, we find evidence for the greatest disequilibrium in stream networks to lie in low relief settings, suggesting that the greatest imprint of Pleistocene glaciation on the modern landscape is not found in the high-relief notches, but rather the flatlands away from the rugged topography. Continued research will examine how disequilibrium in the modern stream networks correlates with channel bed materials (bedrock type vs. glacial deposits), local relief, and regional-scale drivers related to variations in crustal thickness and dynamic mantle processes.