The northern shelf of Puerto Rico is a mixed-sediment (carbonate/siliciclastic), high-energy, storm-dominated, steep, narrow shelf. Muddy, allochthonous siliciclastic sediments are introduced directly onto the shelf from small rivers during floods. Clean, autochthonous carbonate sediments accumulate away from river mouths. Shelf-sediment cover is in equilibrium with shelf processes compositionally and texturally. Sedimentation is controlled by two processes acting at different time scales: storms and river-mouth migration.

Storms introduce, rework, transport, and mix sediment on the shelf. Degree of river influence (not always simple distance from river mouth) and water depth are the most important controls on storm stratification in the study area. Water depth controls flux of wave energy to the sea bottom (potential for physical reworking of sediments). Degree of river influence controls distribution of cohesive versus noncohesive sediments.

River-mouth location controls which portion of the shelf is actively receiving siliciclastic sediment at a given time. Changes in location influence mixing of sediment between river systems and between shelf- and river-sediment sources. River-mouth location switching may also help explain the great number of submarine canyons found indenting the shelf.