Thursday, November 5, 2009

Once more with the splendour of the historical sciences!

Last week or the week before I went to the niftiest seminar I have been to for a long time. It was by Prof Ian Metcalfe, who is a master of conodont lore- conodonts being the premier biostratigraphic animal. If you know enough about conodonts, and you are lucky enough to find enough conodonts, you can tell when a stratum of rock was laid down and what biogeographic province it belonged to, over a vast range of space and time. And the degree of detail that is possible with these little guys was enough for Prof Metcalfe to deconvolute the whole extraordinarily complex geological history of Southeast Asia, which is basically a matter of bits breaking of of Gondwanaland and different times and sailing away north and mashing into the ancient subcontinents of Siberia and Kazakhstan.

I remember one thing that struck me forcefully, long ago, in the writings of Stephen Jay Gould, was all the ancient oceans that we would never know anything about, because they were subducted away completely- all those primordial analogues of the Hawaiian islands, with their unique fauna and flora, irrevocably lost.

But not always! That was the most impressive bit of Prof Metcalfe's talk for me. I have pinched one of his figures so I can show you, as like me you are probably too lazy to follow the link.

In between the dark orange Sibumasu block that used to be part of the Cimmerian Continent and the pink bit that is the mashed remains of the ancient archipelago of Cathaysialand, there runs an ancient biogeographic divide: at the same time in prehistory, the fauna on one side was quite different from the fauna on the other side. And mashed up in between those two blocks are sediments that are the remains of the Palaeo-Tethys ocean. Not all subducted away! Some of it is still there, enough of the ocean for us to tell a lot about its history and the sort of things that lived there, in a kind of Reader's Digest condensed version squashed into a discontinuous squiggle across central Thailand. I think that is so cool...

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