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!

The Hut of the Discovery expedition 1902-1903

Yesterday one of my New Zealand colleagues, Greg Browne, gave a presentation about the early expeditions in the Ross Sea area. The first one with a ship called the Discovery went as far South as the sea ice would let it and laid anchor at what is now Hut Point peninsula. It is about 0.5 mile outside McMurdo Station and last week our janitor invited us to accompany him to the hut to take a look inside (he has access to a key). The Discovery expedition in 1902-1903 was lead by british navy captain Robert Falcon Scott. Their accomplishment was that the team made it to 82 degrees South, a place no man had gone before. Later the Nimrod expedition, led by Shackleton, in 1907-1908, made it to within 180 miles of the South Pole. You probably know about the tragic story of 1911, when the Norwegian Roald Amundson, beat Scott and his men in the race for the South Pole. None of the 1911 team members made it home alive. Here they are at South Pole after they discovered the Norwegian flag was already there.

The Discovery Hut was built in 1902 on what is now Hut Point peninsula. It is a prefab Australian outback hut, and it is actually not very suitable for Antarctic conditions. The field party stayed here for 2 winters. In the hut you can still find the fur mittens and the wool sweaters they wore and there is still food on the stove in the kitchen. The clothes are lying near the stove, presumably left there to dry. Boxes of food are scattered through the hut. It is interesting to see that Cocoa is in one of them; it is still a favorite drink here today! Besides a kitchen area, there is a food storage area, a meat storage area and there are stables for the ponies they used. Some seal carcases are lying near the entrance.

Several other expeditions have used this hut after the Scott party, but it is now off limits, unless you are accompanied by a hut guide (there are several on station, such as our dorm janitor). The huts are valuable part of the Antarctic exploration history and we are all trying to keep it that way. I have been in the Discovery hut twice now (the first time 10 years ago), but the second time was as good as the first.

Skies are clearing and more core

The skies are clearing and the weather is improving. Two planes came in in the past 24 hours. One brought our Italian co-chief scientist and a large supply of drilling mud. The decision has been made that we will continue drilling now that it is going so well and skip geophysical logging of the hole until later: that is when logging scientists send instrumentation and a camera down the borehole to make measurements and images of the formations. We are working 12 hours a night now and are describing 30-40 meters of core per shift. We are still about 100 meters behind the drill bit which is currently sitting at 635 mbsf. Today we saw mudstones with hundreds of Serpulid worm tubes and another possible piece of plant debris. We also encountered a beautiful dropstone: a rock which fell out of an iceberg into te ocean and depressed the laminated (or layered) sediments. It is a Ferrar Dolerite clast, which is a group of igneous rocks cropping out in the Transantarctic Mountains. They form hundreds of meters thick sills (the chocolat brown layers in the photo), which are eroded by outlet glaciers feeding from the ice sheet behind the mountains. We are finding many clasts of this type in the core lately. Overall we can see the ice sheets come and go and they leave their signature in the rocks we log. It is a pretty nice job we have!

More than 500 meters below sea floor!

Drilling is proceeding very well at the moment. We are already at 600 meters below seafloor, before we had time to celebrate that we have passed the landmark depth of 500 meters below sea floor. We don't know exactly where we are in time, because the paleontologists are behind in analyzing their samples due to the speed of drilling and the flow of samples coming in. We sedimentologists have seen some very interesting changes in the core over the past 2 days. We encountered several meter thick intervals of what we call mudstones. These are rocks made of very small rock particles. They often appear laminated with distinct layering. The rocks are now also more cemented and they dry out quickly, so we spray water on the surfaces to observe the textures. Also important is the absence of large rock fragments or clasts in the mudstones: it indicates there was not much ice around during the time of deposition. Interestingly, between the mudstones are beds with very large clasts: the record clast so far we found today is at least 42 cm in diameter, which means I am out of the competition .... my entry was 38 cm for the biggest clast contest.

While drilling is going well, the weather is not entirely cooperating. We haven't seen a plane come in from Chrischurch for the past 5 days as a large depression has the Ross Sea area in its grip. We have had a couple of snow storms and travel is permitted only in the very short pauzes between storms. The helo with core has come in from the drillsite, but the windows of fair weather are too short for trips further away, or trips that require sea ice travel. We haven't gotten any fresh fruit or vegetables for a while now and people and cargo are backed-up in Christchurch. Ha: the new weather forecast just got posted and it says inprovement will come in the next two days. Despite the snow and wind, it is actually quite warm. The -12C/+10F minimum windchill is nothing compared to what we had previously and it feels extremely pleasant now that we can expose our faces to the wind. Also: the first Skuas have arrived (Photo: C.B. Gunn). They typically arrive in early November. Skuas are scavenger birds that feed on anything from penguin eggs, dead penguin chicks, afterbirths of seals, and unfortunately the trash cans at McMurdo Station. They are also known to snatch food from peoples hands if they carry it outside. Still: it is quite nice to see some birds flying around. It is a sign of spring after all!
Another great experience was that the janitor in our dorm took us to the Discovery Hut and let us take a look inside yesterday. He is part of a select group of people with access to the keys of the huts. I have no time to post pictures now, but I promise to do that later. The Discovery Hut is in the picture posted previously here.. Check back in a few days for photos from inside the hut.

Another snow storm and more to come

The weather forecast that was just posted reads: "The region continues to be under the influence of a large low pressure system to the east-northeast. Intermittent gusty winds, snow and blowing snow will impact the station until the full brunt of the system moves in." We had a "Condition 1" situation last night, which was lifted just before Midrats. Condition 1 means you cannot leave the building you are in. It is more severe than Condition 2, which means you have to stay on station, or Condition 3, which means that all travel is permitted. Our Midrats meal was in another building, so we were glad to hear that Condition 1 was lifted just before midnight. Here in the picture are some people walking to Midrats, like us. It was still pretty gusty with a lot of blowing snow. It is looking fine now (see picture to the right), but there is more to come. Snow is plastered on the walls of the buildings and the windows. There is a large cloud on Minna Bluf in the distance, which is a bad sign. Luckily a helicopter was able to make a trip to the drillsite before the storm to get us some core, so we can work. Another perhaps comicle fact is that Ann Curry of the Today Show is now stuck here with us. Her Live broadcast was yesterday in front of the Chalet with the flags. Last night at Midrats she was in the lobby and was talking very loudly and came obviously out of one of the bars. She seems to have a good time here. We have not seen the show, so we can only hope that the science we do here was featured to some extent. She called off a trip to our drillsite...

So, yes what about the science? It is becoming increasingly more interesting. We are finding fossils every day now: yesterday a possible plant fossil, today a couple of shell beds with what look like large clam shells. There is still the intermittent presence of glaciers, so it looks like ice ages came and went, but there were some intervals of time with balmier climate conditions than today.

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.

More than 300 mbsf and in uncharted territory?

We are now describing core from below 300 meters below the seafloor. If we have interpreted the seismic data correctly, we are now in uncharted territory, never drilled in Antarctica before. (We are still waiting for confirmation from the paleontologists). The core is providing surprises every day. Last night we logged sections that were composed of layered (stratified) diamictites with rock clasts (stones), but also very delicately laminated rocks without clasts (see photos). Yesterday we found a diatomite (diatom-ite = rock made of diatoms) and the paleontologists are busy investigating samples. Brad Field is the sedimentologist currently responsible for making smear slides to investigate the rock composition under the microscope. A smear slide is made from rock scrapings and it is used for a quick and dirty initial investigation.
After we describe it, samples are taken from the half core for further study. Scientists on the day shift have a "flagging" party where they put little flags in the core at the locations where they would like to have a small piece of the core. The curatorial team then later cuts the samples out of the core.

The ANDRILL website is now also Live. Science reports are updated weekly and the next one will give an overview of the findings of the whole team. Check it out at http://www.andrill.org/