Abstract The Eocene Castle Hayne Limestone crops out on the southeastern part of the North Carolina Coastal Plain. The major concentration of surface exposures, where the formation is covered only with surficial Pliocene to Pleistocene sediments, is found along a 16-32 km wide zone that extends from Brunswick and New Hanover counties northeastward through the east central part of Pender County, western Onslow County (west of Jacksonville), western Jones County, western Craven County (west of New Bern) and into the southeastern corner of Pitt County (Fig. 1). The Castle Hayne Limestone dips seaward and goes deeper into the subsurface east of this outcrop belt, and is covered with Oligocene to Recent sediments, only to crop out again on the Continental Shelf (Dubuisson, 1982). Outliers of the Castle Hayne Limestone, west of the major outcrop belt, are clustered in Duplin and Wayne counties, but also occur in Lenoir and Sampson counties (Fig. 1). Additional strata of Eocene age are found in the subsurface from the Neuse River northward. The exact stratigraphic relationship of these northern strata to the Castle Hayne Limestone has yet to be resolved. Strata of definite Eocene age in North Carolina were first recognized by Lyell (1845) when he visited an exposed section of carbonate sediment near Wilmington, in New Hanover County. Over the past 140 years more than 60 exposures of the Castle Hayne Limestone, including large quarries, small agricultural lime pits, exposures made during highway and bridge construction and canal dredging, and such natural outcrops as stream