continuation from March 25, 2009
Science
- Waiting for the replacement parts that will allow for a continuation of the drilling operation we found some more time to reflect what we have recovered so far. Catalina has already completed the susceptibility measurements on the cores from both holes. Based on these data, both cores match almost perfect, reflecting that the core quality is very high and that the sediments represent not only local events but the lake history.
- Down to 107 m both cores built up a composite without any gaps,reflecting the depositional history continuously. Below that depth,the record is discontinuous (two larger gaps of ca. 3 m, respectively) and thus should become completed by the next core.
- First interpretations of the sediments recovered (confidential, please), based on observations through the liner and of the sediments accessible at the cuttings, are very preliminary but manifold. In short: whilst most of the core seems to reflect glacial/interglacial and stadial/interstadial fluctuations as those already known from the 16 m long core recovered in 2003, the lower part of the core (below ca. 80 m) shows a different composition. These sediments may reflect repeated glaciations of the area to the west of the crater. According to the subrecent sedimentation rates these glaciations might date into the Early Pleistocene (ca. 1.6-2 Ma ago?). The ice has inundated the crater but likely (fortunately, if true) did not fill the lake. This hypothesis seems to explain many of our observations: the sediment composition (including clastic varves? in parts), the much higher sedimentation rate compared to that of today needed to have occurred some time in the Quaternary to explain the total lake sediment thickness, the asymmetry of the sediment fill in the crater, the thickness of the coarse-grained permafrost deposits cored at site D3, etc. Such glaciations are unexpected and as far as we know never were described before. If they become confirmed by our lab analyses, they might be traced back to higher precipitation rates, due to missing ice sheets further to the west, at potentially warmer temperatures -- this could become the FIRST scientific highlight of the El’gygytgn Drilling Project!
Cheers for now, Martin
