Topography of the floor of the sea bordering the Catskill Delta (referred to here as the Catskill Sea) differed markedly from modern continental-margin configurations. Data from exposures in New York and Pennsylvania indicate that the Catskill Sea floor was a subdued surface with three topographic subdivisions. Nearest the shore was the basin margin, a low-gradient, shelf-like surface. Seaward, this gave way to the clinoform, the gradient of which was not much greater. The clinoform merged seaward into the basin floor.
A sandstone and shale sequence with abundant fauna developed on the basin margin; thin turbidites and gray, silty shales with both transported and pelagic fauna were deposited on the clinoform and silt-stones and black shales with pelagic fauna formed on the basin floor. Boundaries between facies and between the inferred topographic subdivisions on which they formed reflect the different sedimentary processes active on the sea floor and not geophysical discontinuities. The basin margin was affected mainly by deltaic processes, waves, tides, and, perhaps, internal waves. Turbidity currents deposited the majority of clinoform sediments with a lesser contribution from pelagic sedimentation. Pelagic deposits dominate on the basin floor.