SURFICIAL GEOLOGY & WATER RESOURCES OF MANCHESTER, VT

An objective of this investigation was to provide a modern inventory of surficial and hydrological data illustrated through a series of 11 GIS formatted maps. A technical report and accompanying maps serve as a baseline for our current knowledge of the surficial geology and hydrogeology. Appendices make the data useful to the average land use planner or developer. The surficial geologic mapping units are explained in the context of their encompassing soils, slope stabilities, permeabilities, drainage, and gravel/sand resource potential.

Mapping results enabled me to decipher details of the deglaciation unrecognized by previous workers. Three ice margins – Skinner Hollow, Manchester and South Dorset - were delineated on the basis of prominent kame moraines and moraines. A retreat of largely active valley glaciers is envisioned and stagnation zones may have existed along the margins. Asynchronous retreat is revealed by the moraines formed by the Dorset glacier perhaps due to a localized re-advance while the Danby glacier apparently stagnated. Deposition of ground moraine occurred throughout the valley but especially along the western margin of the Manchester glacier and this suggests the presence of a stagnation zone. No significant quiet water lacustrine sediments were observed and coupled with a similar paucity of lacustrine sediments to the south (De Simone, 2001) strongly indicates that Glacial Lake Batten did not exist.

Both an overburden aquifer developed in glacial gravels and bedrock aquifers developed in carbonate rock exist and represent extremely valuable sources of potable water. The data hint that these two aquifers may be hydraulically connected. Gravel is often recorded by drillers immediately atop limestone; any overlying impermeable overburden unit appears to be thin and discontinuous. The overburden water table and the carbonate aquifer piezometric surface maps are very similar. The extensive areas of permeable kame moraine, ground moraine, kame and outwash at the surface indicate that considerable recharge of the overburden and carbonate aquifers is occurring through direct infiltration.