As the ice margin retreated northward through the Champlain Basin, Glacial Lake Vermont filled the valley with cold fresh meltwater. The basin initially drained southward across the Champlain/Hudson drainage divide, but unstable outlet conditions caused the lake to lower abruptly three times, including the final large (7.8 x 10⁴ - 1.6 x 10⁵ m ³s^-1) discharge event through the St. Lawrence River Valley at the onset of the Champlain Sea sometime before 11.0 ¹⁴C ka BP. Each abrupt lowering caused the lake to form a new shoreline. A short (60 cm) core was taken along the Salmon River near Plattsburgh, New York, through the uppermost glaciolacustrine and lowermost marine sediments of the Lake Vermont/Champlain Sea transition. The stratigraphy consists of gray rhythmically laminated lacustrine clays at the bottom and gray rhythmically laminated marine silts and clays at the top. The transition between the two includes massive clay with clast inclusions, soft sediment deformation, and a single bed of red clay. Pollen analysis from this core indicates very low pollen abundance (1863-9274 grains/cm³) and a coniferous-deciduous tree assemblage that suggests long-distance transport. However, an increase in abundance and better preservation of spruce pollen in the marine sediments may indicate the arrival of spruce forests to this area. A musk-ox bone, dated at 11.3 ¹⁴C ka BP found near Elizabethtown, New York, indicates that the large mammals were not far behind the vegetation advance.