3 April 2009 Logging day out on the Rig

Journal

Today was a day for scientific logging of the borehole. Because of the earlier problems we want to continue the scientific study with extra care. We have retrieved sediment cores to a depth of approximately 150 meters below the lake bottom (320 meters below the ice). Since the drilling has once again encountered sandy sediments, which are difficult to drill, the science team decided yesterday to log the drill hole to be sure and acquire a complete record of the sediments we have already extracted. What does it mean to log the hole? The whole reason for drilling the sediments in Lake E is to learn about the past climate history of the Arctic regions. We can learn about the climate by studying different physical properties of the sediments. Some of the properties that we measure include: magnetic properties, radioactivity, sonic properties and electrical resistance. The initial measurements are completed in the on-site core laboratory, however, many of the more precise measurements will be taken when the cores are shipped to Germany or the United States. Unfortunately, drilling is a bit of a messy process and it is difficult to retrieve a continuous core. By carefully measuring the distance drilled and the cores removed, we know that some parts of the sediment record are not recovered. This is why we need the down-hole logging team.

The team members from GFZ in Potsdam Germany, are representatives from the Operational Support Group of the International Continental Drilling Program (ICDP) and they are logging experts. Martin Topfler and Jochem Kuck have many different scientific probes that are designed to be lowered down the borehole to measure the sediments that are still in the lake. They will get a continuous measurement of the entire borehole. These down-hole measurements can then be compared to the measurements of the cores in the laboratory and used to fill in gaps in the sediment record.