Field Update: Dec. 11, 2010

The gravity coring is continuing today and I’m taking more pictures of what’s going on in the MECC. Later today we’ll see the shot hole drilling, but right now we’re waiting to see what length of core is recovered.

Mike Williams has gotten some rest after many long hours of instrument deployments yesterday. Sanne Maas climbs into the safety harness and hooks herself to the line suspended above the hole in the floor. J.R. and Sanne watch as the core barrel comes up out of the ice and through the hatch and then they evaluate what has been recovered – about 15 cm of sediment.

Sanne puts the end cap on the core liner and J.R. starts to cut the plastic tube above the level of the sediment to drain the water and then cut the tube to the size of the sediment collected so it can also be capped.

Richard steps in to lend a hand, and Bob Detrick offers his observations about the coring process and takes a look at the core material.

Once the core sample has been removed, J.R. guides the weighted end of the gravity corer to the deck as the line from the winch provides more slack. Then it’s time to prepare for the next run and do it all over again, perhaps with more penetration into the seafloor this time.

The longer the core is, the further back in time we are able to reach. These are probably all Holocene sediments that have been deposited since after the Last Glacial Maximum when the grounding line of the ice sheet retreated southward from the edge of the continental shelf to a position that is today about 700 to 800 km south of our camp at Coulman High. Below this veneer of fine-grained soft sediment that has rained out of the ice shelf bottom or been transported around by ocean currents there are older, glacial sediments that are coarse-grained and hard. We would like to get a long core that penetrates into these deeper horizons, but so far we haven’t been able to accomplish this goal using the gravity corer and plastic tube. We may try coring with a metal barrel later in the season if we can get one sent to us from Christchurch in time. Nevertheless, we’re doing well and have as many 1 m-long cores as these small ones. Sanne will be describing these cores and analyzing the sedimentary components as part of her thesis work at Victoria University of Wellington. There’s more work to be done off-ice.

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