SEDIMENT DISTRIBUTION ON A STORM-DOMINATED INSULAR SHELF, LUQUILLO, PUERTO-RICO, USA

A sea-floor mapping investigation designed to assess the sediment dist ribution, the movement of the nearshore sand supply, and the fate of s ediment eroded from the shoreline was conducted using high-resolution sidescan-sonar, seismic reflection, and sediment sampling techniques o n the northern insular shelf of Puerto Rico, off the town of Luquillo. sea-Boor structures and the distribution of sediment texture and comp osition suggest that regional oceanographic processes result in a net offshore direction for cross-shelf sediment transport on the middle an d outer shelf during storms. If these same processes are active on the inner shelf, mapping results indicate that this sediment is not trans ported seaward of a series of east-west trending Pleistocene-age eolia nite ridges that outcrop on the middle shelf. The eolianite ridges may act as natural dams, preventing the removal of sediment from the near shore area. sand deposits behind the ''dams'' are up to 20 m thick on the shoreward flank of the ridges.