Aug
07
2010

The role of bacteria in fossilization examined

Close-up of fossilized dinosaur bone: Notice the amazing level of preservation displayed by the vascular system inside the bone.
Close-up of fossilized dinosaur bone: Notice the amazing level of preservation displayed by the vascular system inside the bone.Courtesy Mark Ryan
A recent study published in the journal Palaios raises new questions about the role of bacteria in the process of fossilization of bone material. In tests simulating rapid burial and groundwater percolation, researchers Joseph Daniel and Karen Chin set up four different groundwater environments where chunks of bone were placed in river sand and water, laden with calcium carbonate, was allowed to flow through it for three months. In one test the environment was left untreated allowing for bacteria in the sediment to grow naturally. In two other tests the simulated environment was sterilized using antiseptics that either reduced or eliminated completely the naturally growing bacteria. For the fourth test, Chin and Daniel washed and treated the sediment with bleach then reseeded it with the natural bacteria.

The samples were monitored closely, and after just one week, the scientists noticed mineral precipitants had already begun to attach sand grains to the bone fragments in both the nonsterile tests, but saw no change in the sterile environment samples.

After three months, the results showed that the cubes of bone soaked in the natural, untreated environment had begun to show signs of permineralization, and some of the bacteria even showed early signs of lithification. As before, the fragments in the sterile environment were unchanged and appeared as fresh as new bone.

This is pretty amazing, because I was always under the impression that in order to become a fossil, the remains of an animal had to be buried rather quickly so as to remove them from the destructive elements of nature. But it looks like some of nature’s tiniest elements are necessary to the process.

This study could also help explain how, after 68 million years, organic material managed to remain essentially unchanged (or actually less-permineralized) deep inside the fossilized femur of a Tyrannosaurus rex, such as that discovered a few years back by paleontologist Mary Schweitzer (Read about it here).

Karen Chin, by the way, specializes in the study of fossil feces (coprolites), and participated in a 2001 study also published in Palaios documenting the role of bacteria in the fossilization of herbivore dinosaur droppings.

SOURCES
Abstract of Chin and Daniel study in PALAIOS
Story at Smithsonian.com

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