Re: what is a fossil

[Andrea Spreafico <sprea@linknet.it>]

At 15.27 18/06/97 EDT, you wrote:
>you have asked the 64 k$ question there.   there are currently two
>working definition as to what constitutes a fossil:
>1.  remains from an animal or plant that have been remineralized.
>2.  any dead animal or plant
>
>obviously, these are two ends of a very long very complex spectrum of
>processes that turn fossils type 2 into type 1 (you might think of
>them as sensu stricto and sensu lato).  I have personally found
>remains that fully qualify as #1 that are less than 5 YEARS OLD!!
>SOME AS YOUNG AS 3 MONTHS!!! so age plays little role.  the speed
>at which fossilization (sensu stricto i.e. remineralization occurs)
>can be very rapid in some environments, such as saline lakes.
>if you examine the fossil record, preservation is enhanced in areas
>where the fossilization is very rapid. 
>
>conversely, there are 200,000 year old fossils in which the 
>bone mineral and its organic component are 98% pristine.  
>so again age is not a guideline.  
>
>no should remineralization alone be a factor.  there are some
>40 different processes that affect animal bones and teeth (the stuff
>i am most familiar with) during their fossilization.  remineralization
>may be the first step, the last, anywhere in between, or not occurring
>in many remains that most geologists and archaeologists would
>recognize as being fossils.  in molluscs for example, few molluscs
>younger than 1 Ma show any remineralization, and many as old as
>10 Ma still have little remineralization. 
>
>i personally like definition #2. 
>b
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Bonnie A.B. Blackwell,                         bonn@qcvaxa.acc.qc.edu
>Dept of Geology,                                off: (718) 997-3332
>Queens College, City University of New York,    fax: (718) 997-3299
>Dept of Earth \& Environmental Sciences,        messages: (718) 997-3300
>The Graduate Center, CUNY,                      
>Flushing, NY, 11367-1597, USA                         
>

I think that a dead fish on the beach is a fossil only in a too much wide
sense. I do prefer the following definition: everything remains of animal
and vegetal organisms that lived in the past geological times, included
tracks of their activity, mantained up today because of physical-chemical
processes called "fossilization".

Eugenio Spreafico