[meteorite-list] Fossil, Relict, or Paleo- was "Fossil" NWA 2828

From: Mr EMan <mstreman53_at_meteoritecentral.com>
Date: Sat, 6 Jan 2007 21:46:37 -0800 (PST)
Message-ID: <725671.56995.qm_at_web51012.mail.yahoo.com>

Under this NomCom guideline NWA2828 isn't "relict" as
it is hardly altered and should be referred to as a
paleo meteorite. (Note:If this gets too drawn out all
meteoritic material is paleo as most is 4.5 billion
years old). However, paleo is a best choice of the
three proposed terms.

My take on the three options:

Relict: in petrology and geology is used to describe
the occurrence of traces of original material after
alteration. e.g. Serpentine is the hydrated
alteration product of olivine and the presence of
olivine or peridot within serpentine would be referred
to as "relict olivine" etc. Lignite within a coal seam
is relict lignite. NWA2828 is hardly relict under this
definition and the NomCom guidelines. However, Relict
is a valid incorporation of the concept into
meteorites. Note that Relict is consistent with the
almost complete alteration to secondary minerals.
Where "Fossil" may include replacement of the original
mineral. This is a subtle but important distinction.

Fossil: (Greek Dug or to Dig) Obviously evolved this
term is in wide use but rarely specified. It is
usually descriptive of any ancient "organically"
produced artifact; Trace, imprint, hard or soft
tissue, premineralized, mineralized segment,
mummified-- in some fashion altered from its original
composition or state. By convention and to which
source one subscribes,a fossil must be older than
20,000 OR 2 million years, cannot be derived from a
living species, nor produced artificially .
(AFAIRecall). Charcoal from the wildfire caused by
Canyon Diablo can't be fossil but is paleo. Omitting
the organically derived stipulation "Fossil" has
been applied for example, to describe meteorites which
were found in Ordovician aged sediments where the
meteorites had been completely altered. It is also
loosely used to describe ancient geological processes
NWA2828 doesn't meet the criteria for being fossil.

Paleo: denotes "ancient" and is used to describe
events or things that are prehistoric--prehistory as
in what that was not recorded: also to describe a
process, condition or state occurring before the
present Paleosoil, paleoatmosphere, paleoclimate, etc.
The Winona Meteorite has been called paleo and was
associated with a paleo settlement. Under strict
reference Wolf Creek, Canyon Diablo, Winona, Lake
Murray -- all would be paleo meteorites, as would
anything derived from a prehistoric event as would
tektites however that distinction need not always be
applied.

By elimination and like it or not PALEO is a best fit
for NWA2828. As with any science, this represents the
discovery of yet another distinction that we need a
new category for. Both "fossilized" and "relict" seem
to be subsets of the term "paleo".

Eman


--- David Weir <dgweir at earthlink.net> wrote:

>
> Yea, "fossil" may be accurate or maybe not, but why
> not use the broader
> terminology as designated by NomCom in their latest
> revision in which
> this new category is proposed?
>
> Read it here in section 1.2(c) Relict meteorites:
>
>
http://www.meteoriticalsociety.org/bulletin/nc-guidelines.htm#s12c
>
> This section is copied here for your convenience:
>
> c) Special provisions are made in these Guidelines
> for highly altered
> materials that may have a meteoritic origin,
> designated relict
> meteorites, which are dominantly (>95%) composed of
> secondary minerals
> formed on the body on which the object was found.
> Examples of such
> material may include some types of "meteorite
> shale," "fossil
> meteorites," and fusion crust.
>
> David
Received on Sun 07 Jan 2007 12:46:37 AM PST