Exploring the Science and Beauty of Sand
Joulter Cays, off Andros Island, Bahamas
Joulters Cays is located on the NE margin of the Great Bahamas Bank, about 10 miles north of Andros Island in the Bahamas.
Joulters Cay is unique as the cay is made nearly entirely of ooids or oolites. These coated grains form around a nucleus; on Joulters, the nucleus is tiny grain of shrimp feces, elsewhere, the nucleus might be a grain of sand or a shell fragment. As the grains are constantly agitated by the tides and the currents in the shallow carbonate-rich waters, concentric layers of calcium carbonate (in the form of aragonite) accretes and the grains “grow.”
Oolites range between .5 and 1 mm in diameter. Larger than 2 mm, they are called pisolites. Their size is controlled by rates of precipitation and abrasion. Oolites are also being formed in Great Salt Lake, Utah, at Shark’s Bay, Australia and in the Persian Gulf in the vicinity of Qatar. Oolites and Oolitic rock are also found in the fossil record.
Joulter Cays, north of Andros Island.
Shallow water on Joulter Cays’ ooid shoal extends as far as the eye can see.
The ripple marks reflect the ebb and flow of the tides plus the ocean currents.
Ooids vary in size on Joulter Cays.
Moon Snails live on Joulter Cays and build their egg cases from ooids.