Principal Investigator: David Wenner (University of Georgia)
Sponsor: GWRI
Start Date: 1993-04-01; Completion Date: 1993-04-01;
Keywords: oxygen isotopes, groundwaters, confined aquifer,unconfined aquifer, phreatic aquifer
Description:
A total of 127 groundwater samples were analyzed to date for their oxygen isotopic composition from 50 counties throughout the Coastal Plain of Georgia during the period from June 24, 1992 to September 17, 1992. Samples from shallow wells (<200 ft.) have measurable north to south isotopic variations, coincident with yearly mean rainfall. In general, groundwaters from the Upper Coastal Plain are about 1‰ more negative than those from the Lower Coastal Plain. Groundwaters from varying depths also have differing δ180 values, although inland and coastal areas appear to have contrasting isotopic patterns. For example, samples from cluster wells varying from 180 feet to >1200 feet deep from coastal Glynn County show oxygen isotopic enrichment with increasing depth, probably due to sea water encroachment. In contrast, samples from wells ranging from 35 feet to 900 feet deep from Worth County in south central Georgia do not have isotopic variations that correlate with depth. At both sites, however, groundwaters taken from different hydrostratigraphic levels have small isotopic variations (0.6 ‰). The present stable isotopic data set is not sufficient to be able to quantify the amount of leakage between aquifers at different hydrostratigraphic zones within the Coastal Plain.