This is a critical stage in the development of the Champlain Sea, Because it results in a lower lake phase in the Lake Ontario basin. This is significant in explaining the fresh water conditions in Lake Ontario, while marine conditions existed in the St. Lawrence lowlands. (This will be discussed at a later time)
    As the ice sheet continued it's northern retreat, an outlet was developed at the northern tip of the Adirondack mountains, in the Covey Hill region.  This caused a large amount of water to be displaced into the Champlain valley (Vermont/New York), creating lower water levels in the Lake Ontario basin.