A University of Rochester paleontologist has taken to the deep in a miniature submarine to settle a question about how fossils are formed.
Carl Brett, professor of geology, has been dropping bags filled with wood, walnuts, sea urchins, and clam, snail, and crab shells on the sea floor to watch what happens to these animal and plant remains. Brett was part of two research projects designed by Eric Powell, professor of oceanography at Texas A&M University, to study marine environments.
While fossils take thousands or even millions of years to form, many paleontologists, including Brett, believe the first few years -- perhaps even the first few hours -- are key in determining whether an object will become a fossil.
Brett and many other paleontologists from the "rapid burial" school believe that an object must be buried very rapidly -- almost instantaneously -- in order to become a fossil. They also believe the conditions of fossil preservation may provide clues about the environments where they form.
To test these ideas, the researchers dropped mesh bags at different depths in various sea environments. This fall they took several trips hundreds of feet below the surface of the Atlantic Ocean in the Bahamas, and this summer they went down more than 1,800 feet in the Gulf of Mexico.
"When we started out, the water was well-lit from the sun," says Brett, "but as we dove deeper -- around 200 feet -- the light began to fade. Around 800 feet it was pitch black except for some light twinkling like stars -- the twinkles were coming from phosphorescent plankton. The only other sight was the occasional squid emitting a phosphorescent stream of ink."
The miniature craft used in the Bahamas had just enough room for two people per trip. A pilot guided the craft and operated a mechanical arm placing the bags on the sea floor. At each site the researchers set down four rods, with four one-foot bags tethered to each. They also set out loose shells, though those will be harder to find and will probably be gathered by suction dredging. Environments ranged from well-oxygenated coral reefs to steep ocean cliffs to deeper, non-oxygenated waters where big scavengers don't rummage.
"Three hours after we placed the bags at 1870 feet, some of them were already being attacked by giant spider crabs," says Brett. "That's how fast scavengers can move in. I think we'll see a lot of changes after just one year. In fact, I'll be amazed if there is much left after a few years." Nevertheless, the researchers intend to recover bags after one, three, five and ten years to check the evidence.
The research could also change the way paleontologists identify different ancient environments based on the fossil record. Currently one environment is distinguished from another based on sediments and the types of animals that once lived there. But Brett proposes that the way fossils are preserved -- regardless of the species found in a given area -- may provide a great deal more information.
"There is a whole set of clues which people ignored in the past. These include the ways in which fossils are preserved," he says. "The extent of breakage or corrosion, the orientation of fossils -- basically, what happens to shells after organisms die."
The experiments brought together biologists, oceanographers, ecologists, and paleobiologists. While Brett and Powell are concentrating on the preservational features of the shells, others are studying such things as the destruction of woods, the geochemistry of the water, and oxygen uptake by organisms. The team included scientists from Texas A&M University, Pennsylvania State University, Old Dominion University, the University of Georgia, the Texas Wake Commission, and the National Oceanic and Atmospheric Administration (NOAA).
This work is funded through Texas A&M by a grant to Powell from the National Undersea Research Program of the Division of NOAA. The Harbor Branch Research vessel R.V. Seward Johnson hosted the experiments in the Gulf of Mexico, while the Caribbean Marine Research Institute in the Exuma Island chain of the Bahamas hosted the September trip. tr