LAKE ALBANY REDUX

Four named freshwater bodies occupied the Hudson-Champlain trough during deglaciation; in descending order Glacial Lakes Albany, Coveville, Fort Ann, and Greens Corners. The lake levels were essentially parallel. A longitudinal plot of the Hudson-Champlain deltas illustrates the named lake levels, suggests possible unnamed lakes, and documents post-lacustrine tectonics. Lakes Albany and Coveville extended south to the Harbor Hill Moraine. Lake Fort Ann’s southern dam was north of Albany, and Lake Greens Corners was restricted to the Champlain basin.

Lake Albany began at the Harbor Hill Moraine ca23,900 cal yrsBP, expanding northward in contact with the retreating Woodfordian ice margin. About 20,000 cal yrsBP the ice withdrew up the Hudson Valley, north of the Mohawk Valley confluence, releasing a slug of cold freshwater from the Great Lakes. This caused the Shed Brook Discontinuity in the Mohawk Valley and probably correlates with event R8 in the northern Atlantic Ocean. Then, during the Rosendale Readvance, ice readvanced up the Mohawk and down the Hudson. While withdrawing to the Champlain Valley, cold freshwater again flowed into Lake Albany from the Mohawk Valley on the west and the Kinderhook and Hoosic valleys on the east, perhaps correlating with R7 in the northern Atlantic.

About 13,850 cal yrsBP, shortly after the Bridport Readvance, the southern threshold lowered about 40 ft sending a third slug of cold freshwater into the northern Atlantic Ocean, perhaps augmented by Glacial Lake Iroquois drainage, initiating Lake Coveville. When the Coveville dam was breached, creating Lake Fort Ann, a fourth slug of freshwater issued down the Hudson Valley. The two flood events probably correlate with events R6 and R5 in the Atlantic Ocean. Varve cores from the Champlain Valley straddle this interval and tentatively correlate with the varve record from the Connecticut Valley.