Submarine Geomorphology of the Continental Shelf off Southeast Florida Based on Interpretation of Airborne Laser Bathymetry

Abstract

Airborne laser bathymetry (ALB) is a new laser bathymetric survey tool that has applicability in clear coastal (Case II) waters to depths of −70 m. The new sounding technique features rapid acquisition of large, high-quality data sets via variable swath widths that are independent of water depth. This advanced ALB system was deployed along the continental shelf of southeast Florida (Palm Beach, Broward, and Miami-Dade Counties), providing a contiguous data set for 160 km of coast from onshore to 6 km offshore. Image enhancement of the ALB digital data facilitates recognition of numerous seafloor features and bathymetric patterns. Bathymetric analysis of the 600-km2 survey area on the continental shelf shows inherited lithologic features that are partly covered by surficial sediments. Primary parabathic (shore-parallel) provinces include: (1) nearshore rocky zones dominated by the Anastasia Formation, (2) coral-algal reef systems (Florida Reef Tract [FRT]), and (3) marine platforms (terraces). Sedimentary subprovinces include shoreface sands, interreefal sedimentary infills (coral rubble in basal sequences and near reef gaps), and finer-grained materials seaward of coral reefs. Tertiary topographic features include: (1) longshore bar and trough systems, shoals, sand sheets (flats), and diabathic (cross-shore) channels; (2) reef crests and ledges, forereef spur-and-groove topography, sediment ramps in large reef gaps, and incised paleo-river channels; and (3) drowned karst topography. Hierarchical organization (classification and mapping) of these bathymetric features is now possible for the first time because of the increased accuracy and density of ALB data. These data and related maps allow, for the first time, assessment of links between the influence of seabed morphology on wave transformation patterns and beach morphodynamics in southeast Florida.