Geophysics in the fog and an exciting sediment core

Thanks to the good weather and ice condition forecast, as well as the predictive and safe ship navigation any collision of our dragged 3 km streamer and drifting ice flows or smaller ice bergs (growler) could be avoided. Besides seismics, other geophysical methods like gravimetry and magnetics could be deployed, giving us further insight to the sub-seafloor structures of the only 150 - 300 meters deep shelf area. With the collected data we aim to image the over 11 kilometers of sediment in the Danmarkshavn Basin to define the 300 million years that shaped the deep, coast parallel sedimentary basin. Observed upwards propagation of older salt diapirs into stratigraphically younger layers hint on passed deformation processes and explain zones of weakness, which can be brought in coherence with the opening of the North Atlantic over 55 million years ago.

Our goal is not only the reconstruction of the basin’s geological evolution, but also to determine the extent of transformation of organic material to hydrocarbons since its deposition. After having collected seismic profiles with a total length of nearly 1000 kilometers, the continuous geophysical work came to a scheduled hold and geological sampling was recommenced in the night of Wednesday to Thursday.

So far, dense fog has been our companion, making helicopter missions impossible. However a forecasted, short good weather period with clear skies had us expecting good flying conditions on Friday. Whilst the station work on board of Polarstern continued outside of the 12-miles-zone, one of the two helicopters repeatedly took teams of geologists to the coastal area for sampling. The gathered sediment- and bedrock samples are to contribute the same, already discussed, objective as the marine sediments.

For the GEOMAR colleagues, who are working on reconstructing the environmental and climatic evolution of the last 150.000 years, long sediment cores are essential. Therefor the extraction of a 9.09 meters long - and thereby possibly record-breaking - sediment core on Saturday was a huge success. This together with the so far highly successful first half of the cruise provided a good reason to celebrate the cruise summit together with the ship’s crew.

Everyone on board is doing fine.

On behalf of all colleagues

Volkmar Damm                                                                                 

Position 83°42‘N, 24°30‘W