Tuesday, November 13, 2007

A forest of wormtubes and the UNDRILL 500

Last night we logged another 30 m of core and a large proportion of it consisted of mudstones with abundant fossil worm tubes made of carbonate. We are having a unique view here on an Antarctic seafloor more than 15 million years back in time. Between the worm tubes we found fragments of moss animals (bryozoa), and foraminifera, microscopic single-celled organisms that live either at the surface or at the bottom of the ocean. Serpulate worms and bryozoa make up part of the present Antarctic benthic community and were recently discovered to be living underneath a floating glacier or ice shelf (see link here). Paleontologists will now investigate the specific species and try to determine in what type of an environment these organisms were living: in open water without ice or near the ice.
The presence of foraminifera, these microscopic creatures, is good news. Diatoms (see a few blogs earlier) are apparently not really flourishing in this environment, so instead of the diatoms, the foraminifera may help us to obtain an age for these rocks. Different species of foraminifera are characterized by different shell or test morphologies and through evolution one species followed another in the past. In other words: different shell morphologies are characteristic of different times in the past. So, these microfossils can help us to find out how old these rocks are.
Yesterday we celebrated the fact that we reached 500 meters below sea floor with the UNDRILL 500. The drillbit is currently already more than 700 meters below seafloor, but we didn't have time to celebrate earlier. The traditional Antarctic way of celebration (going back to Scott's and Shackleton's times) is that you dress up with elements of underwear (or sometimes men wear womens clothes and make-up, yeah really!). We were marching around the station dressed up, with the national flags of the team, a tuba and a trombone, good fun!

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