In a slightly acidic situation, calcite is less susceptible to dissolution than aragonite. Oysters have thick shells in order to resist being bored into. However, oyster drills can penetrate their shells. At Hempstead Harbor, oyster drills are not found as fossils, but the oysters have drill holes in them. The oyster drills have been dissolved away.
Oysters are filter feeders that create pseudofeces which is silt bound by mucus.
Thus, they trap and bind sediment. According to Sirkin's dates, a glacier aoocupied this area 60000 years ago during the early Wisconsinan. It reatreated and seawater filled Long Island Sound, wit a maximum concentration of oysters in the fossil record occurring at about 33000 years ago. During the late Wisconsinan, ice occupied the area again. Sediment that experienced a force applied by the glacier while it was frozen exhibits crenulated chevron folds.