Bathymetric LiDAR Offers Insights into Sizes, Shapes and Distribution of Patch Reefs, Northern Florida Keys, U.S.A.

Eugene C. Rankey¹, John Brock², and C. Wayne Wright^3
1 Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL
² USGS, St. Petersburg, FL
³ NASA/GSFC, Wallops Island, VA

Reefs form important components of many carbonate reservoir systems. Nonetheless, the distribution of reefs is notoriously difficult to predict in subsurface reservoirs. The purpose of this talk is to outline preliminary results of size, shape, and spatial patterns in some South Florida patch reefs.

To explore patterns in patch reef systems, this study utilized IKONOS optical remote sensing data (4m2 pixels) and altimetry data from NASA's Experimental Advanced Airborne Research LiDAR (EAARL) (1m2 pixels), with data analyzed in a GIS. The study focused on an area of 8 km2 located offshore of northern Key Largo in Biscayne National Park of south Florida.

Patch reefs in this area range in area from <100 to >75,000 m2, with a general lognormal distribution. Reefs range in relief (measured from the highest point to the lowest point within 50 m of each reef) from 0.6 m to 9.3 m, with mean 3.27 m. Reef area is weakly correlated (R2 = 0.43) with relief on the reef by a power-law relationship. The aspect ratio of reefs (long axis width/height) ranges from ~3 to 187, with a mean value of 12.7. The most common orientation of the long axes of reefs is between 30-50°, parallel to the shelf break. Quadrat analysis suggests that patch reefs are more spatially clustered than would be expected in a random (Poisson) distribution.

These results illustrate how advanced technology facilitates quantification of spatial patterns in Modern carbonate systems, providing information that could be used as input to geologic models.