Wednesday, 4 August 2010

A week off

Last week we went up to Scotland, visiting relatives, picking up some fossils the University has bought from a professional collector we know and finally actually collecting some fossils ourselves just north of Berwick on Tweed.  Very pleasant, very relaxing and totally knackering!

Berwick is weird in one respect; I don't think they drink much wine there.  We tried several eateries, but only the last had any half-way decent wine, and even their 'wine list' consisted of four reds and four whites.   Unimpressed!

The fossicking went well, however.  The pro mentioned above and another guy we know have been collecting at this particular locality for years and some of the material will form the basis of a project Jenny wants to start next year, so going there ourselves was kind of essential.

Well the other two guys reckon to have found fossils in about 5 places in the bay, but we could only find one spot that yielded anything, despite spending a long time wandering around.  So eventually we just focussed on this one place.

Based on a paper Jenny had brought with us, and the fossils in the rock, we reckoned this was a shallow, marine deposit, laid down close to a shoreline.  There was a lot of charcoal in it, which you only get near the shore, but the fish fossils were marine.  Mostly they were Gyracanthus fin spines, but there were also a lot of scales, a few teeth and lots of small, unidentifiable bits.  And we also found three large (up to about 20 cm long) bones which we have tentatively identified as rhizodont fish shoulder girdle components.

The picture here shows a fin spine, somewhat eroded away.  It's in a massive block of stone and it's not practical to try to extract it, but you get the idea of what they look like.  The spines formed the edge of the pectoral fin, I think, but Jenny said the preservation of intact fish is very rare and often hard to interpret, so the picture I've linked to might not be accurate.

I've just learned something as I put in the link to the Wikipedia page on rhizodont fishes, and it might contradict what I put about the supposed marine environment, because Wikipedia says rhizodonts were freshwater fish.  It's not impossible that a dead rhizodont was washed out to sea from a river, but it makes me more cautious about claiming it was a marine facies.

I tried to find some rhizodont information to link to, but that seems a bit thin on the ground, too!

The site itself is interesting, too.  As you can see, the strata are vertical, whereas they were obviously horizontal when originally laid down 300 and odd million years ago. We do know that two tectonic plates were colliding at that time and the ocean between them was disappearing, so the forces involved were obviously enormous, but I've not seen strata like this before.

The actual rock containing the fossils was very wet from water percolating down from above and had become soft and friable, which made it possible to extract stuff from the cliff, but at the same time, meant that anything you did pull out, broke into pieces as you did so.

A Gyracanthus spine I extracted came out in over a dozen pieces, and the rhizodont bones were all in many bits.  In fact, the last rhizodont bone is incomplete because when I tried to extract the last, thin piece, it just crumbled away into hundreds of tiny fragments, impossible to reassemble.

Then when it came time to pack everything up, we found we'd used all our boxes.  We'd brought some plastic food storage boxes but had collected too much!  Even a ruthless cull of the less interesting material didn't meet the demand and we had to improvise.

On the beach, Jenny found a 5-litre plastic container which had obviously been used as a buffer on the side of a boat, judging by the rope tied to the handle.  We cut that off, (in my handbag I carry a Leatherman with a saw blade) rinsed out the dregs of whatever the container had held originally (hope it wasn't too toxic to marine life!) and then cut it in half lengthways to make two shallow trays.   That finally allowed us to pack everything away and come home!

Anyhow, we dropped all the material off at the museum and I'm hoping to get a chance to go in on Friday to take a look at it.

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