The Aquia Formation is a Paleocene-Eocene glauconitic marine sand. It forms part of the Pamunkey Group of the Atlantic coastal plain. The geochemistry of the water in the Aquia aquifer, as shown by computer analysis, is controlled by the hydrologic flow regime and the mineralogy of the sediments. The ionic exchange of Na for Ca in glauconite and the dissolution of the sedimentary minerals are believed to be major sources of the cations in the aquifer waters. A model equation for the dissolution of glauconite has been developed and found to be thermodynamically feasible. The value for Gibbs free energy of formation for glauconite was estimated by a known method for layered silicates and found to be -1425 Kcal/mol. this produced a log Kiap/Keq ratio of -197 and shows glauco ite undersaturated with respect to the formation water.

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