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Re: fossils



Basically, to second the below, we have been "researching" "fossils" for
two purposes: (1) to come up with a useful educational definition so
that the term is standardized throughout our editorial material, (2) to
clarify just what folks are getting "emotional" about when they want
regulations to protect "fossils"

A number of straw polls which we've taken have done very little to
clarify anything:

What is mostly in contention is:

a) type of fossil eg. vertebrate, invertebrate, plant, etc.
b) age -- in the loosest definitions, there is no useful criteria for
distinguishing between "ancient" and "modern" material, regardless of
the specific chemical process that is involved in "transforming" the
original material.

>From the point of view of our publication (DIG), we are extremely
interested in clarity: our readers are not only highly educated paleo
types, but also K-12 educators and their students, as well as the
general public with their varying degrees of comprehension.

Anecdotally, we find that certain terms are simply too generalized and
vague, and "fossil" is becoming one of them.  

Perhaps as Ms. Blackwell suggests, it's time for a new term or set of
terms.

ES


Bonnie Blackwell, x 3332 wrote:
> 
> clearly we have a problem with the terms fossil and fossilization.
> probably, these have resulted from the fact that we use this extremely
> general term to categorize the many products from some 20-odd different
> geological processes that can affect animals, plants, and their traces.
> those processes include:
> - death
> - defleshing
> - burial
> - reexposure
> - inundation
> - weathering, including cracking, drying (dehydration), rehydration,
>         frost, heating, exfoliation, what for rocks is called `spheroidal
>         weathering', etc.
> - transport
> - chemical weathering, hydrolysis, dehydrolysis, acid dissolution, aqueous
>         dissolution, precipitation, etc.
> - organic chemical weathering, including hydrolysis, dehydrolysis, organic
>         degradation, formation of new organic compounds, leaching, etc.
> - cast formation (which includes many processes noted above)
> - mould formation (ditto)
> - remineralization, including bacterially mediated precipitation of new
>         minerals, simple precipitation in porosity elements, dissolution &
>         reprecipitation on a molecular level, etc.
> - ingestion by other organisms
> - biological weathering (including acid dissolution by roots, insect boring,
>         fungal boring, algal boring, sponge boring, bacterial boring, (i
>         know bo-o-o-ring), ingestion by insect larvae, mechanical degradation
>         such as by echinoderm spines, etc.)
> - crushing due to trampling
> - gnawing (i.e. bones by dogs, wolves, etc.)
> - dispersal of the various parts of the animal by mechanical or biological
>         means
> - carbonization
> - pyritization (again a combination of many processes noted above)
> - encasement in amber, calcite, aragonite, dolomite, various salts
>         (of which amber and sometimes calcite are the only ones that
>         really have any hope of long term perservation)
> - opalization
> - impregnation by silica, calcite, ferromanganese minerals
> - impregnation by clays (or in situ formation of clays in porosity elements
> 
> I suspect that I have forgotten several here, but you get the idea.
> The point is that the basket term "fossil" and "fossilization"
> have been used to cover all these processes.
> 
> Some occur very rapidly, producing very noticeable changes in the fossil
> within a few days to weeks.  Some ensure preservation, such as amber 
> encasement,but only require hours to days to complete.  Should we not 
> consider an
> insect encased in amber that is only 5 ka to be not a fossil, but consider
> a Tr coral with its original aragonite to be a fossil, PURELY ON THE BASIS
> OF THEIR AGES?  Clearly, this is not good science.  In fossilization,
> age confers no special characters.  Most fossils that are going to be
> preserved have been preferentially affected within their first few
> days to months in the geological environment.  Taphonomic studies have
> clearly demonstrated that bones that are not buried within 3 months
> to 5 years in 99% of environments will not be preserved for perpetuity.
> Similarly, carbonate shells not buried or inundated in near-neutral waters
> within 3-10 years become dust in the wind.  Plants we all know must
> be perserved within days to weeks (except pollen which is designed to
> be impervious to almost every known agent of destruction).
> Tracks, feeding traces, burrows, etc., all must be covered by
> more sediment in appropriate manners within days to perhaps as long as
> a few years in some very quiet environments.
> 
> Ergo, anything potentially able to become a fossil (sensu quasi stricto),
> namely surviving for more than 10 ka remineralized or not, has actually
> had the necessary geochemical or sedimentological conditions occur
> LONG before that, usually within 1 year.  Hence, the insistence on
> 10 ka, is meaningless, as would an insistence on 1 Ma, or 1 Ga, as
> a 'prerequisite age'.
> 
> Maybe it is time to abandon the term fossil and use more rigorous
> definitions for such geological phenomena that more precisely describe
> their potential for preservation for long times, or that more carefully
> detail their experienced geochemical and sedimentological histories leading
> to/resulting in what we now loosely call 'fossilization'.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 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

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