AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
The Sedimentary Influences of Hurricanes Hannah and Ike (September 2008) on the Caicos Platform, B.W.I.: Do High-Energy Storms Impact Sedimentation on Carbonate Platforms?
(1) Chevron Energy Technology Company, Houston, TX.
(2) The University of Texas at Austin, Austin, TX.
(3) ExxonMobil Upstream Research Co., Houston, TX.
Two high energy storms impacted the Caicos Platform during September 2008. Tropical storm/Hurricane Hannah passed N-to-S just west of the Caicos Platform, then, after turning eastward, reversed course to S-N, and passed directly across the platform interior. Winds from Hannah ranged from 70 knots (80.6 mph) on its southward journey, and 50 knots (57.6 mph) as it passed over the platform. One week later, the eye of Hurricane Ike made an E-W pass just 10 miles south of the southern margin (Ambergris Shoal) and had sustained winds of 115 knots (132 mph).
Ground observations, collected during February 2009, are combined with remote sensing data from both pre- and post-storm satellite imagery. Foreshore and back beach erosion occurred at Long Beach, “Donna Cut”, and Little Ambergris Island. Erosion of tidal flat levees and sedimentation on the proximal tidal flat was observed at North Caicos. A complete redistribution of submarine bedforms on the wind-dominated Ambergris Shoal was observed on satellite imagery. Significant erosion of the algal flat in the interior of Little Ambergris Island as well as the deposition of ooid sand washover fans of up to 4 cm thickness in the island interior were also observed. Imbricated blocks of beach rock were seen above the foreshore on the island and a meter-scale “racetrack playa” block was found 300 m inland. The large block is interpreted to have been transported during maximum wind gusts.
Comparisons of hurricane effects presented here with those of other authors suggest that the role of individual storms on sedimentation is highly variable. Factors including direction of approach, platform physiography, and magnitude of key physical processes (wind strength, swell, ground speed, and timing versus tides) directly impacts net sedimentation and erosion. Reworking of sediment by normal daily processes also limits the time in which the effects of hurricanes can be studied, as these processes may quickly mask the storm-generated sedimentary features.