Continued studies of the buried St. Davids gorge, an ancient valley of the Niagara River, have indicated that the upper part of this gorge was filled in mid-Wisconsinan time and later. Lacustrine sediments dated at 23 000 years B.P. were deposited in the gorge when the late Wisconsinan ice caused the water level to rise in the Lake Ontario basin by blocking the eastern outlet, prior to over riding the Niagara area. Palynological studies support the correlation of the dated lacustrine deposits in the gorge with the Plum Point Interstade of southern Ontario.

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