WD-EVENT DISTURBENCES IN THE CHAMPLAIN VALLEY

In 2002 we extracted a 14.87 m core from Crown Point, New York, 2 km north of the Bridport Readvance type locality. The core site is a flat featureless surface 10 m above and immediately adjacent to Lake Champlain. The nearest uplands are Bulwagga Mt., 3 km west at the edge of the Adirondacks, and The Great Ledge, 11 km east in Vermont.

The core was spudded in 300 cm of marine clay deposited in the Champlain Sea, exhibiting ghosts of calcareous shells and horizontal stratification. Beneath the marine clays is a 47 cm disturbed interval designated WD1, then 13 cm of varves and another disturbed zone 85 cm thick designated WD2. Beneath WD2 is a sequence of 322 cm of 88 thinly laminated to thin bedded varves underlain by 124 cm of disturbed sediment designated WD3. Beneath WD3 are 35 cm of varves, 180 cm of disturbed sediment designated WD4, and then 138 cm of alternating varves and disturbed zones representing WD5, WD6, and WD7. Next is 11 cm of disturbed WD8, 113 cm of varves, 19 cm of till, and then 99 cm of varves at the base.

The varved sediments were deposited on the proglacial lake-bottom while the surface dropped from Lake Albany, to Lakes Coveville, Fort Ann, and Greens Corners. Each disturbed zone is here attributed to a drainage event that removed an unknown thickness of previously deposited varves, prior to its deposition.

Lake Albany began at the Harbor Hill Moraine and expanded northward in contact with the retreating Woodfordian ice margin. Shortly after the Bridport Readvance, the southern threshold was lowered ±12 m to Lake Coveville, sending a slug of cold fresh water into the northern Atlantic Ocean as event WD8. Events WD7, 6 and 5 represent slugs of water draining into Lake Coveville from minor tributary lakes. WD4 represents the addition of Lake Iroquois waters from the west. When the Coveville dam was breached, another slug of freshwater issued down the Hudson Valley (WD3) creating Lake Fort Ann. When the Fort Ann dam was breached a final slug of freshwater issued southward (WD2) creating Lake Greens Corners. When the ice retreated north of the Champlain Valley, Greens Corners waters drained northward (WD1) into the St. Lawrence River Valley. WD8, WD3, WD2, and WD1 are correlated with events R6, R5, R4, and R3 in the north Atlantic Ocean.