for National Geographic News
A unique "blue hole" is giving expert divers and scientists a chance to travel back in time for a rare glimpse of life in the pre-human Bahamas.
The deep underwater cave, known as Sawmill Sink, is filled with a treasure trove of well-preserved fossils, including the remains of tortoises and crocodiles previously unknown to exist in the West Indies.
The sinkhole also holds the ancient remains of globally or locally extinct species of lizards, snakes, bats, birds, and plants.
In addition, the cave has yielded human bones that may be the first-known Bahamian—a young person who lived some 1,050 years ago.
"On almost every dive we find more fossils," said Nancy Albury, project coordinator and scientist with the National Museum of the Bahamas, the Antiquities Monuments and Museums Corporation.
"Having so many species coming out of one particular site [shows] that there was a lot more going on than we formerly thought in the Bahamas."
Albury co-authored a paper on the fossils of Sawmill Sink that appeared online last week in the Proceedings of the National Academy of Sciences.
Into the Deep
A blue hole is a sinkhole in which deep saltwater layers are covered by surface fresh water. The underwater caves can be found across the islands of the Bahamas and elsewhere in the Caribbean.
(Related news: "World's Longest Underground River Discovered in Mexico, Divers Say" [March 5, 2007].)
The environment in a blue hole is ideal for preservation, because the salty, oxygen-free waters keep bacteria and fungi from decomposing organic remains. Artifacts are also often covered with layers of protective sediment.
But exploring the sinkholes is risky. Depth, tight spaces, vision-clouding particles, and toxic layers of hydrogen sulfide can make blue holes dark and dangerous places to dive.
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