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Tom Holtz referred the person who asked about fossilization processes
to any elementary textbook on geology or paleontology to answer this question.
I have found, however, that these books have one glaring error: the speed
at which they assume these processes occur. My research has shown that
secondary mineralization, remineralization, leaching of bone mineral,
and biologically-induced mineralization begin very rapidly after the bone
is exposed to the environment. If the bone is not buried or underwater
within 1-2 years of defleshing, it will literally become dust in the wind.
The bone fragments may persist for several more years, but they are
as to species. If the bone is buried or underwater, diagenetic processes
begin rapidly. A bone can be completely remineralized within 5-10 years.
Secondary mineralization can fill all the porosity elements within
a few months in some environments. These are the environments which preserve
bone the best.
Hypersaline environments in which carbonates are precipitating favour
bone remineralization and secondary mineralization. Saline environments
also are good, but there the processes are slower. Caves may offer excellent
preservation over the short term, but karst processes may attack the bone
later destroying it along with the cave.
Soil is not a favourable environment generally because the bone mineral
will tend to dissolve in the acidic conditions that occur in many soils,
carbonate-rich soils of arid zones being the exceptions.
It is the requirement of rapid burial/submergence that ensures that
few vertebrates become fossilized.
Bonnie Blackwell, email@example.com
Dept of Geology, (718) 997-3332
Queens College, City University of New York, fax: 997-3349
Flushing, NY 11367-1597