(and the Grease, and the Salt Water)
The past week has been a busy one. We have secured 3 full kasten cores, 1 jumbo gravity core and 1 jumbo piston core (with 1 accompanying trigger core). A kasten core has a rectangular barrel that is deployed via gravity. It penetrates 2-3 meters into the sediment and can be opened on the ship so we can describe the stratigraphy, take photos, and collect samples. Each kasten core takes about 12 hours to process, depending on the length. First Gene has to describe the core (color, layers, sediment composition), then Tasha will take pictures. After that, someone on shift puts on the lab coat and nitrile gloves and takes samples for DNA/RNA.
The next round of sampling includes taking sediment for organic geochemical analysis and foraminifer microfossils (fossils of calcareous single-celled animals). These samples will be used for a suite of geochemical analyses to determine past temperature, productivity, and oxygen content, among other things. While geochem and foram sampling are happening on one side of the core, another person is sampling for physical properties on the other side. If there is enough mud left, we will also take pea-size samples for diatom analysis and 5-cm interval samples for radiocarbon. Believe it or not, the first layer of sampling on a 2-3 m core takes 7-8 hours with planning, putting together the core barrel, sampling, cleaning sponges and utensils, labeling bags, and sample storage/inventory. These are the days when the marine geology group spends 12 hours on their feet.
Once the initial sampling is done we scrape the sampled surface clean, taking care to smooth out the sediment across the core and not down the core. This way, all sediment stays at the level it’s supposed to and sediment down-core isn’t mixed with sediment up-core. At this second level, we insert archive channels and U-channels. Archive channels are rectangular PVC channels that will hold the archive sediment that will ultimately be sent to the Antarctic core repository at Florida State University. The U-channels are skinny, rectangular channels approximately 1 inch wide that are placed along the archive channels and capture the exact same sediment intervals. These are used as records of magnetic susceptibility- the measure of magnetization of sediment grains in the core.
In addition to the sampling we do on the ship, there is still the sampling we do off the ship on the jumbo gravity and jumbo piston cores. As much work as we do with the cores on the ship, it is still just a fraction of the work that will continue to be done on the cores once we return to the States. The samples taken from this cruise will very likely serve as a senior capstone or graduate thesis any time from next year to 10 years down the line. For me, that fact is pretty cool because it means that there are still more questions to ask/answer and much more to learn about a glacier system that we are just beginning to understand.