Kurt Jendrek
Bedrock Controls on Submarine Groundwater Discharge in Easter Casco Bay
Advisor: Edward Laine
In the summer of 2002, it was discovered that submarine groundwater discharge was pervasive beneath Quahog Bay, but rare beneath adjacent Harpswell Sound. Examinations of published studies of the bedrock geology of the region (Hussey, 1971) showed that Quahog Bay is surrounded and underlain by gneisses of the Harpswell Group while Harpswell Sound is surrounded and underlain by the schists of the Cape Elizabeth Formation. Because of the hard, brittle nature of gneiss, the bedrock fracture in the gneisses of the Harpswell Group have remained open in the hundreds of millions of years since their creation and thus able to conduct groundwater. Similar fractures in the schists of Cape Elizabeth Formation of the Harpswell Sound (if they ever existed) have closed by "flow" of the more plastic schists, thereby providing no conduits for groundwater. This summer ('03) Mr. Jendrek will create a composite geological map of the eastern Casco Bay region, and then conduct a CTD survey supplemented with water sampling in several of these locations to test whether bedrock lithology controls submarine groundwater discharge.
Sources
Hussey, A.M.,II (1971) Geologic map and cross sections of the Orrs Island 7.5' Quadrangle and adjacent areas. Maine Geological Survey, Department of Conservation, Augusta, Maine.