PALEOHYDROLOGIC IMPLICATIONS OF O-18 ENRICHED LAKE AGASSIZ WATER

Lake Agassiz water oxygen isotopic compositions inferred from sediment core organics and pore waters provide some additional insight into th e paleohydrology of the Great Lakes and their drainage into the North Atlantic during the late glacial and early Holocene. Isotopically enri ched Lake Agassiz water supports the hypothesis that high Huron Basin lake (Mattawa) phases, during the early Holocene (9600-9300 and 9100-8 100 years BP) resulted from an influx of Lake Agassiz water and sugges ts that low lake (Stanley) phases (9800-9600, 9300-9100, 8100-7400 yea rs BP) were influenced more by regional influxes of isotopically deple ted glacial melt water. Eastward drainage of enriched early Lake Agass iz water supports an active Port Huron outlet between 11 000 and 10 50 0 years BP and also helps to explain the absence of an O-18 depleted i nterval in North Atlantic foram records. This may be the result of a b alance between the opposing isotopic effects of depleted Lake Agassiz water and lower sea surface temperatures on carbonate precipitation be tween 11 000 and 10 000 years BP.