Monday, November 5, 2007

Fossils in the core

The drill bit is now more than 400 meters below sea floor and we are logging core from deeper and deeper layers. It has also been confirmed by the diatom paleontologists that we are currently in middle Miocene rocks. The middle Miocene is the geological period around 15 million years ago, when Antarctica may have experienced extensive ice expansion and cooling, and may have progressed into its current deep freeze state. That hypothesis is debated, however, because of evidence that certain plants and animals survived in Antarctica through this transition. The middle Miocene is also the time of a climate optimum with balmier conditions than today. We are trying to understand what big changes were taking place in Antarctica around 15 million years ago. Before the present drilling program we had no complete rock record of these changes in Antarctica, but we did see the effects on the climate in the rest of the world.
The siginificant find of the last couple of days is that we are encountering more fossil beds in the core. The fossils represent the remains of worms, snails and barnacles that were living on the ancient sea floor at the site where we are drilling. The macropaleontologists are busy to uncover exactly what these fossils can tell us about the water depth and the temperatures of the sea water. Some organisms prefer a certain set of conditions, so when we find them we can use them to reconstruct the environment during that time. In the photo you can see some light-colored circular rings, which are cross-sections of worm tubes and a nice conical shell of a snail. Notice also that there are some rock fragments in the sediment. We can only explain the latter with the presence of icebergs or sea ice. So apparently these snails and worms were living in relatively cold conditions, but perhaps not as cold as today: we will find that out through further research, which will continue when we get back to our home institutions.

2 comments:

Jet (Anat) said...

Love your blog, Sandra!

Thomas de Groot said...

This is really exciting! It looks like you are gradually reaching beyond the icehouse conditions that prevailed till today, and approaching the earlier greenhouse ones, aren't you?

Keep us posted!