STABLE-ISOTOPE ENRICHMENT IN PALEOWATERS OF THE SOUTHEAST ATLANTIC COASTAL-PLAIN, UNITED-STATES

Paleowaters from the Floridan aquifer system in the southeastern Atlantic coastal plain have higher D/H and O-18/O-16 ratios than local Holocene ground water. Maximum deltaO-18 enrichments in ground water having adjusted radiocarbon ages of 20,000 to 26,000 years are 0.7 to 2.3 per mil. The trend in isotopic enrichment in paleowaters is the reverse of that normally observed in continental glacial age ground water. Dissolved nitrogen and argon concentrations indicate, however, that the average recharge temperature was 5.3-degrees-C cooler than that today. The data indicate cool conditions in the southeast Atlantic coastal plain during the last glacial maximum, with recharge limited primarily to late summer tropical cyclones and hurricanes.