Northeastern Section - 48th Annual Meeting (18–20 March 2013)

41
A PROBABLE LATE WISCONSINAN GLACIAL READVANCE SITE, HONEY BROOK, CENTRAL VERMONT

Paper No. 41-2
Presentation Time: 8:00 AM-12:00 PM

A PROBABLE LATE WISCONSINAN GLACIAL READVANCE SITE, HONEY BROOK, CENTRAL VERMONT


HERMANSON, T.M., Geology & Environmental Science, Norwich University, 158 Harmon Drive, Northfield, VT 05663, thermans@student.norwich.edu and DUNN, R.K., Geology and Environmental Science, Norwich University, 158 Harmon Drive, Northfield, VT 05663
Exposures in Honey Brook valley, East Barre, Vermont, reveal glacial outwash and lacustrine deposits, which are within Glacial Lake Winooski elevation, that are overlain by a dense, very hard diamict. In this study, stratigraphic, grain size, and fabric analyses were undertaken to determine if the diamicts are tills or debris flows, and if till, then the logical glacial history.

At the base of the sequence and resting on bedrock is a dark gray, very hard, silty diamict with SSE clast fabric, which we interpret as lodgement till. Above this, stratified gravels and sands are interpreted as glacial outwash and are overlain by laminated and thinly bedded silt and clay that contains isolated clasts with deformed and draped laminations, revealing a quiet lake depositional environment with icebergs producing dropstones. These deposits are found below the Glacial Lake Winooski level of 938 ft asl. Within the laminated sands and silt-clay are several 20-50 cm thick on average, firm silty-clay diamicts whose origin is unclear. Units exhibiting intense folding of beds may represent subaqueous mass failures. All units exhibit some over-compaction or are firmer than expected. The top of the section consists of a thick (15-25 m), blue gray, very hard and compacted silt-clay diamict with SSW clast fabric. Given its aerial extent, texture, compaction and fabric, we interpret this as a readvance till, probably correlative with the Middlesex and Bethlehem-Littleton readvance.

Radiometric ages from other studies suggest this readvance occurred during the Older Dryas. We do not know the exact age of the till in Honey Brook but the field evidence suggests it may represent one of a growing number of likely readvance sites discovered throughout central Vermont. The event seems to have been short lived and its southern extent limited to central Vermont.