March 20, 2009
All,
News of today:
- Soon after the report of yesterday, i.e. close to 70 m, we finally had to change to to the Extended Nose (EXN), since the mud became too stiff for sufficient penetration with the HPC. Simultaneously, the graded sand layers (most likely turbidites) increased in thickness and partly contained gravel at the bases, so that the recovery (when gravel and sand was washed out at the core bases) became significantly reduced. In between the graded layers, however, fine-grained muds of potentially "pelagic" origin still occur and were hopefully retrieved in most cases. The gravel and sand layers have slowed down the coring progress, so that we were at "only" at 118 m below lake floor (blf) at the end of today´s day shift. This actually is not too bad, taking into account that we are in all likelyhood dealing with sediments of more than 1 Mio years age and that the depth is already beyond that reached on the last ICDP lake drilling campaign at Lake Potrok Eike in Argentina. Anyway, it´s still more than 200 m of lake sediments to go, before we will reach the impact breccia. Then we are planning to move to another hole at the same side (just a few meters apart) to replicate the sequence thus filling at least some of the gabs that exist from incomplete recoveries after the first hole.
- Shift operations have meanwhile reached much routine. Everybody knows what to do to, and people experienced with public traffic in western cities would be impressed about the timing of the shuttle bus leaving/returning to/from the drill site. The latter is supported by lasting good weather, sunny without any significant wind.
Cheers for now
Martin
