Re: paleonet 'Exceptional' preservation?

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And what counts as "Exceptional Preservation" in the Ediacaran System then? Since it's basically all the same? Khatyspyt and Spaniard's Bay would probably be the answer in the context of the Ediacaran System but in the context of the general fossil record, it's all exceptional.

I think Joe is right, that the specialisation of most researchers slows things down in some cases. One of the things I'm currently working on is "exceptional" Ordovician material that was in a dusty museum drawer, uncatalogued and forgotten for thirteen years because the guys who collected it didn't know what is was, and didn't care. They wanted the brachiopods and corals, and soft-bodied material didn't concern them. It was only pure chance that someone remembered it having heard me talking about my work. I'm sure there are many more such cases the world over, waiting to be remembered. 

Breandán

----- Original Message -----
From: joseph00@esc.cam.ac.uk
To: paleonet@nhm.ac.uk
Subject: paleonet 'Exceptional' preservation?
Date: Thu, 7 Apr 2005 10:05:53 GB

> 
> Something different.
> 
> Having just come back from a few days' fieldwork in Wales, and returned
> with yet another site with 'exceptional preservation' that has been
> unnoticed in previous decades of study, a few questions arise. In this
> case, the fossils include fragile hexactinellid sponges, palaeoscolecid
> material, and a holothurian, from the Middle Ordovician. None of these are
> definitely preserving truly soft tissues, but they do rank as something
> very unusual. Over the past few years, we (Lucy Muir & I) have found five
> sites of this type, in different lithologies, and in a very small area,
> two of them with extremely labile tissues preserved.
>     In the latest site, and the most spectacular of the others, the fossils
> are from a classic locality which has been heavily studied, and where
> fieldtrips have been going repeatedly for decades. The fossils aren't
> obvious, true - most of them are small, and could easily be overlooked -
> but because we're working on ecosystems rather than a specific group, we
> still try to collect anything that looks interesting. It can always be
> discarded back at the office, after all. The fossils are also rather
> uncommon at the new place - we got five or six really interesting
> specimens in a day, plus loads of trilobites, brachiopods etc. But we were
> working on a small, weathered exposure in non-ideal conditions, and went
> through a very small amount of rock. Compare the abundance with somewhere
> like the Soom, or even Chengjiang, and it's very rich indeed.
> 
> So, the question is, just how exceptional is 'exceptional' preservation?
>  From what we've seen (particularly with the sponges, which need to be
> effectively buried alive to be preserved), these deposits are actually
> almost the norm - we just need to have patience, and look at the fine
> details, the small fragments, and out they pop. Part of the problem seems
> to be the 'search image.' In general we look for one group, trilobites,
> graptolites or whatever, and tend to ignore the small, 'difficult' fossils
> in the field. A lot of our finds are not even visible in the field - it's
> only bulk sampling or chance that reveals them under a microscope. Sponges
> in particular can look like stains on the surface, until the spicules leap
> out at higher magnification.
>    I don't doubt that the Burgess Shales of the world are truly
> exceptional, but how many fall into the gap between those and 'normal'
> deposits? There are a number of papers on single extraordinary fossils (an
> ostracode with soft tissue, and the favositid zooids from Canada spring to
> mind), with apparently no sign of any other soft tissue. Is it the case
> that most deposits contain the odd freak of preservation, but most are
> almost barren of such things, or are a large number of deposits actually
> rich in inconspicuous, perhaps small or easily weathered, soft tissue
> fossils?
> 
> There's a major emphasis on the celebrated sites, with 'complete'
> ecosystems, which is all very well. But each of these deposits is only one
> environment, and for some times, we have very few such sites. If there are
> many more smaller occurrences of exceptional fossils, it could open a
> major new angle for looking at the evolution of ecosystems. So, does
> anyone else have these experiences of finding unusually preserved things
> on a regular basis, or is it just that we happen to work in a remarkable
> area?
> 
> Hoping for some interesting responses,
> 
> Joe
> Botting
> 
> ---------------------------------------------
> Department of Earth Sciences
> University of Cambridge
> Downing Street
> Cambridge CB2 3EQ
> Phone: ( +44 ) 1223 333400
> Fax: ( +44 ) 1223 333450

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