No helo trip, but core with calcite veins

The weather turned bad with snow across the sound so we did not get out on our helo trip. Instead, we logged more core (we still have 111 m to go to complete the 1011 m that were drilled). The core had multiple fractures and faults last night, evidence of brittle deformation associated with tectonics. The Earth's crust is spreading apart in this area: we call this a rift and that causes the fracturing and faulting in the rock, as well as the volcanism in this area. One calcite vein fill was truely spectacular: so here is the photograph. Calcite precipitates from the fluids that circulate through the rock.

Helo trip to the Dry Valleys scheduled

This is 08H or zero-eight-hotel. We received the helo schedule last night and a few of the night shift scientists are signed up for a trip with 08H to Taylor Valley in the Transantarctic Mountains this evening. The purpose of the trip is to survey the regional geology so we get a better understanding of the composition of the sediments in the core we are investigating. The plan is to be dropped off at a high point in the Dry Valleys and then walk down the valley walls of Taylor Valley to the valley floor. We will then pass through several rock units, which were eroded by outlet glaciers of the East Antarctic ice sheet. It is likely that some of that eroded rock material is what makes up the sediments in the ANDRILL SMS core. All is scheduled, of course as always weather permitting. Right now it is not looking great with more snow in the forecast.....we will have to wait and see if they let us go out.

A 1000 meters below the sea floor on the night shift!

Last night the night shift at the drill site reached 1000 meters below sea floor, our target depth. We, the core loggers in McMurdo are also on night shift and we celebrated a little bit with them. It is quite hard work, from 10 pm until 10 am every night, 12 hours a day, 7 days a week, but now with the celebrations of the project and the end in sight we are getting new energy. Last night was amazing because we logged meters and meters of core without any evidence for large ice sheets at all. There were a few rocks (clasts) that probably fell out of icebergs, but really only few. That was quite unexpected, but I like surprises better than getting what is predicted: it is the exploring that makes doing this type of research so enjoyable. We also found some fossil scallops, such as these here in the photo: the original fossil is still there, but also a mold, an imprint of the shell. These discoveries make the work worthwhile and interesting. What you see here is the half core: so the drill bit drilled partially through the scallop and then the drill core was split in half.Drilling at the drillsite has stopped and now a new team will step into action. After the drillstring has been removed from the hole, the down-hole logging team will bring their tools to the bottom of the hole and then pull them up slowly. While the tools are pulled up, they will measure the physical properties of the layers of rock and also take images of the walls of the borehole. In the mean time we will continue to describe the core until we have gone through all 1011 meters of it. There will be another phase of drilling with a narrower drillbit after the down-hole logging is completed, but we will describe that core on the dayshift towards the end of the season. The plan is that we will also take a helo trip to the Transantarctic Mountains to survey the geology there, because many of the sediments in the core are eroded by glaciers from that region. Stay tuned for a report of that trip.

Back in time and almost where we would like to be: 1000 meters below the sea floor!

This is an interesting phase of our project. The drill bit is more than 940 meters below the seafloor. The rock is getting really hard and the sediment is impregnated with hard, sometimes black, cement. So deep below the surface the pressure and the temperature are much higher than at the surface and that turns sediment (like beach sand) into rock. We are drilling such a deep hole because we would like to take a journey back in time and observe what Antarctica looked like in the past. We are also trying to find out when and how Antarctica got so cold and whether it is likely to stay that way in times of future global warming. Today, Antarctica is a frigid place, as you may have seen on this blog , but we know from previous drilling that it was not always like that. The arrow points to where I am on the image made by NASA. More than 90% of the continent is covered in ice, with only some mountain ranges sticking out above the ice surface. The photo to the right is of a biodiversity study here close to the station, but as you can see there are no plants growing here now. Previous drillholes have indicated that plants were once present in Antarctica. We are finding coaly plant debris in the core for some time now. We have been sending samples to scientists off the ice in New Zealand and the U.S. who are trying to find out what type of plant the material represents. Today we found some more coaly bits in the dark grey rock to the right. The question now is whether this material represents the vegetation on the Antarctic coast at the time of the deposition of the sediments or some older coal material. We will find out later! We know that aprox. 35 million years ago Antarctica looked very much like the coast of New Zealand (see image by I. Woodward), but when did it change? That is what we are trying to find out.

On the sea ice of the Southern McMurdo

The drill rig is situated on multi-year ice (shore-fast ice) adjacent to the Transantarctic Mountains. In the image you can just make out the drill rig in the distance. Those blue ice areas in the front are frozen meltwater pools, which developed during the last summer season and froze again during the winter (remember that the seasons are opposite here to those of the Northern Hemisphere). The surface of the sea ice can be dirty from dust and rock particles blown onto it by storms or material carried by small meltwater streams. Fresh snow gives the surface a bright and white color, but the sea ice surface is never smooth: the wind sculpts and erodes the snow into sastrugi. Most of the sea ice travel is on flagged routes, where the sastrugi have been plained off.

The sea ice is the habitat of penguins and seals. I didn't see any penguins this year, only footprints so far. I did see a seal flapping around in the distance. Most of the seals we see here are Weddell seals, who are endemic to the Antarctic region. Weddell seals primarily feed on fish. There is also a predatory seal here: the Leopard seal. Divers and biologists studying the seal and fish populations are always on the lookout for Leopard seals. They are solitary hunters and can follow their prey for a long distance without being noticed. Some close encounters have occurred, but no major injuries have been reported.

A visit to the drill site out on the sea ice

Last night we had a day off and we had a chance to visit the drill site. We were picked up by the staff scientist and he drove us per Mattrack vehicle out on the sea ice. We followed the procedures for sea ice travel: checked out with Macops by radio and delivered our estimated time of arrival at drill camp, picked up an extra survival bag, because we had one person more in the vehicle than normally, and off we went. After about two hours we arrived at the drillsite. The drillrig is covered in a white fabric to keep the rig and the people on it away from the wind. The rig is situated on 7-8 m thick multi-year sea ice (frozen ocean) and there are around 380 meters of water below it until the drill pipe reaches the sea floor. The small blue building attached to the rig is the mud room. In the mud room the drilling fluid is prepared and recovered. Drilling fluid keeps the drill hole open and lubricates the drill string. The drillers on the rig floor keep and eye on the pressure of the drill bit on the formation it is drillling. Once a core section of 6 meters is completed, the core comes up from the drill hole and is further processed and cut into one-meter long sections at the drillsite lab. The fractures and physical properties of the cores are studied and measured there too. The whole-round core sections are transported to McMurdo Station by helicopter. There the core sections get split and imaged, before we get to describe the core. Check back later for a blog on the core process here in McMurdo. Lastly: some penguin feet we discovered out on the sea ice, but unfortunately the penguins had left. There was a group of them at the drillsite not long ago and the people there enjoyed the entertainment. They have very little entertainment there so I am glad they had a chance to enjoy themselves.

A busy week for the science team and 800 meters down!

The current depth of drilling is at more than 800 meters below the sea floor. The sedimentology team has logged and decribed more than 700 meters of core and we are starting to feel a bit worn down. We are getting beautiful rocks though, like the ones in the photos below. We still see diamictites but the last few days they alternate with mudstones that are laminated or layered. In the photo the layers are at an angle, tilting, which is a sign of disturbance of the original beds. Sediments are always laid down horizontally, so if we see these tilted layers, we know that something happened to the layers after deposition. Details like these are recorded by us, the sedimentologists, in the core descriptions. We also found very flat-laminated rocks. You can see us at work in the photo above (photo by Tracy Frank). These mudstones are important to the science team because they potentially indicate conditions away from an ice sheet, although some mudstones may accumulate very close to a glacier. We will find out by analyzing their composition and the microfossils they enclose. For example: if there was vegetation on land with formation of soils, we would find pollen of plants and clay particles indicative of chemical weathering in soils in the mudstones. The pollen and soil materials were washed into the ocean from land and the particles accumulated as mudstones. So: we can analyze the composition of the mudstones and reconstruct what the environment was like on land in the past.

Yesterday I took some time to take a walk around the peninsula. The weather was very calm and I enjoyed the view across the sound and the presence of Mount Erebus, the active volcano. I also encountered two skuas, who totally ignored me so I decided to take a picture of one of them.