GEOLOGICAL INVESTIGATIONS ON NORTHERN GREAT BAHAMA BANK

I recieved my doctorate in Marine Sciences from the University of North Carolina in 1994, where I conducted research on northern Great Bahama Bank.

Great Bahama Bank is a platform located in the western Atlantic Ocean which was inundated by rising sea-level as the great continental glaciers of the last ice age melted. The platform (as seen above in this mosaic of Landsat images) varies in depth from 25 m to areas which are barely awash and provides a unique opportunity to examine the effects of rising sea-level on relatively short geologic time scales (several thousand years). As such, information gleaned from the study of this platform may help to mitigate effects of rising sea-level in other low-lying coastal areas such as those which comprise much of the S.E. United States.
Because the platform is presently submerged, research on Great Bahama Bank requires the use of oceanographic research vessels and the capability for scientists to work underwater using SCUBA equipment. The two vessels pictured here are the Research Vessel Calanus (left) operated by the University of Miami and the Research Vessel Bellows (right) operated by the Florida Institute of Oceanography. These ships both have very shallow draft (about 2 m), which makes them ideal for work across the shallow waters of Great Bahama Bank.

The first step toward understanding the sea-level and depositional history of Great Bahama Bank was to conduct geophysical surveys across the bank-top. The instrument of choice for this work is a high-resolution seismic profiler (above, left) which is towed behind the ship and uses acoustic impulses to image geologic features on the seafloor and interior of the platform. The image on the right is an example of the record produced by the profiler. It has been enhanced to show geologic features of interest to my investigation. The lighter shaded material at the top of the profiles is sediment deposited across the platform since the time it was flooded. The darker shaded portions of the image represent acoustic reflections from within the platform and show what the surface of the platform looked like before sea-level flooded it.

The geophysical survey helps to identify specific sites across the platform for more detailed investigation. Then the work really begins! All of the work needs to be conducted underwater by SCUBA divers making detailed observations and collections to piece together the story of Great Bahama Bank. Sometimes, we just make detailed notes and observations.
Sometimes we need more substantial forms of data such as can be derived from cores collected on the platform. We can obtain cores in both unconsolidated sediments (left) or drill into solid rock (right). Drilling is one of the most arduous underwater tasks, requiring rotating teams of divers to work continuously for long hours. The coring operation illustrated on the right required 3 teams of divers and 15 hours to obtain a single core approximately 10 m long.

We also excavate large holes which provide us with a "window" into the sediments of the platform. By digging these holes and logging the sedimentary features exposed in the walls, we are able to recognize distinctive events in the flooding history of the platform. We are also able to collect material from the walls of these excavations for carbon-14 dating, which permits us to determine the absolute timing of events in the history of the platform. As you might expect, excavating a hole large enough for a person with SCUBA equipment to work in is also an arduous and time-consuming task.

We investigate the growth history of coral reefs developed across the platform because these yield information related to varying environmental conditions during platform flooding.
While the underwater work is exhausting, occasionally we experience the sublime - in this case, we were visited by a school of dolphins who were intensely curious of our activity. This group of adults circled us closely for nearly 20 minutes as we conducted our work. I have been diving since 1973, and have logged 100's of dives. During those 24 years, dolphins have visited me while underwater once.
Great Bahama Bank held many other surprises during the period of my investigations there. In 1992, Hurricane Andrew passed directly over the study area and afforded an opportunity to examine the effects of this storm on the shallow marine environments across the bank top. At left is a radar image of the hurricane on Great Bahama Bank which I received from WSI, Inc. WSI is a company which provides weather products for such outlets as The Weather Channel. By examining a series of radar images of the storm, I was able to process the composite image at right. In this image, only radar reflections from the eye of the storm are shown. The increasing brightness and continuity of the eye from right to left shows the hurricane intensifying as it exited Great Bahama Bank and crossed the Straits of Florida prior to landfall south of Miami.
After a long day of underwater exploration, I like to kick back, relax, and blow a few air rings! (Yes, they are air rings and no, I will not tell you how I make them!)
Would you like to see the Bahamas? You can at the University of Arkansas! The Department of Geosciences conducts a field trip to the Bahamian Field Station on San Salvador Island, Bahamas every few years. Students paticipating in this field trip get to experience first hand how we conduct research in the Bahamas.

SEE THE LATEST RESULTS OF MY RESEARCH HERE

Students interested in majoring in Geology are encouraged to contact Dr. Boss by e-mail or stop by my office in 202 Ozark Hall to find out more.

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