MILLER BROOK INCISION HISTORY, NORTHERN VERMONT

The Miller Brook Valley in northwestern Vermont is an eastward trending valley containing ice contact and lacustrine sediments deposited during and after the retreat of the Laurentide ice sheet. Previous research suggests ridges in this area are esker deposits and that lacustrine deposits are from Glacial Lake Winooski. This study documents the complex incision history of Miller Brook following the retreat of the ice sheet and draining of Glacial Lake Winooski using a detailed geomorphic map of terraces in a 0.3 km² area. The map was created with latitude, longitude, and elevation data collected by a GPS unit of approximately 5 meter accuracy. Ground penetrating radar (GPR) was also used along accessible terraces in order to image the underlying stratigraphy but in many cases the profiles suggested that the fluvial terraces do not consist of alluvium and are set directly on till. This study argues that the Miller Brook Valley was an arm of Glacial Lake Winooski and the draining of this glacial lake provided base level fall and subsequent formation of fluvial terraces over time. Minimum thickness of surficial materials excavated by the stream is on the order of 20 meters and includes lacustrine, esker tunnel, and esker mouth sediments. The esker appears to have played a part in determining where the stream channel flowed. Miller Brook loops around the large esker on its south side and it may have been dammed by the esker before breaking through and eroding sediment to create gaps between the ridges.