This crushed stone quarry, operated by Martin-Marietta, is developed in hard, gray middle Eocene limestone.  Occurring as overburden is lower Pliocene calcareous sand.  Both units are fossiliferous.  Above the Pliocene lies a blanket of Pleistocene sand, generally ignored by collectors.

During quarrying operations, the Pliocene and Pleistocene formations are stripped off and heaped into steep spoil piles, forming lines of hills.  Then, the limestone beneath is blasted and quarried, leaving long galleries or "streets" lined by 20-foot vertical limestone cliffs.  Most collectors do not work Cliff walls or gallery floors, but rather collect from spoil piles, or loose limestone boulders.

SANTEE FORMATION (middle Eocene, 45 million years).  This is the massive, hard, gray limestone which forms highwalls and the floor of the quarry.  Most of it is referred to the Moultrie Member, about 20 feet thick, in which fossil shells occur mostly as molds of bivalves and snails.  Aragonitic shells have been dissolved away; only calcitic shells remain.  However, the calcitic fossils can be collected, and include oysters and scallops.  A common index fossil (although ugly) is the large squarish oyster Cubitostrea sellaeformis.  Whale bones and crabs are also found, but rarely.  Shark teeth are uncommon.

The uppermost three feet of the Santee is the Cross Member, a rather poorly indurated limestone which weathers to a friable sand.  It contains the brachiopod Terebratulina lachrymal many echinoid fragments, and small oysters and scallops.  Shark teeth are uncommon.  The Cross member is the chief limestone at the Giant Cement Quarry in Harleyville; it is about 30 feet thick there.

RAYSOR or DUPLIN FORMATION (lower Pliocene, 3 to 5 million years).  This occurs as piles of sand, containing many loose chalky white shells.  You may find clams, scallops, snails, olives, barnacles, sand dollars, tusk shells, and Ecphoras.  Shark teeth are uncommon.  This formation is time-equivalent to the Yorktown Formation in North Carolina.

WICOMICO FORMATION (Pleistocene, younger than 2 million years).  It is mostly unfossiliferous sand and peat.  Little is known about it, but it may contain bones, leaf impressions, etc.  Pleistocene insects have been found in the peat.

Hard blocky limestone: Moultrie member of Santee Formation
Cliff walls: Moultrie member of Santee Formation
Hollow molds: Moultrie member of Santee Formation
Oysters: Moultrie or Cross members of Santee
Cubitostrea sellaeformis: Moultrie member of Santee Formation
Brachiopods: Cross member of Santee Formation
many Echinoid fragments & sea urchin spines: Cross member of Santee Formation
Chalky white clams: Raysor/Duplin Formation
Ecphora: Raysor/Duplin Formation 
Chione, Lucina, Oliva,Glycymeris, Mulinia: Raysor/Duplin Formation
Barnacles: Raysor/Duplin Formation
Quartz pebbles: Wicomico or Raysor/Duplin
Loose sand: any but Moultrie
Shark teeth: any but Wicomico
Scallops: any but Wicomico
Modern roots and peat: Wicomico