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IODP Expedition 330 Louisville Seamount Trail

Daily Report 24 -- Tuesday, 4 January 2011 -- Site U1373 on 28.6°S Guyot



Site U1373 on 28.6°S Guyot 28° 33' 55.8" S, 173° 16' 46.8012" W
Louisville Seamount Trail
0 m above sea level

After the abrupt ending of the first drill site, we weren't in for a guyot covered by boulders and a surface of outcropping lava flows, but that is exactly what we encountered when lowering the VIT camera at Site U1373. The co-chiefs were now huddling over a small black-and-white monitor in the dynamical positioning (DP) room to use this vibration-isolated television camera to find ourselves a spot with a decent soft sediment cover. Using GPS and its abundant thrusters, the JOIDES Resolution and its DP officers are absolute heroes in DP movements. We first moved 30 m south, then 150 m west, another 300 m north, south again and another east-west segment. This was no sweat for the JR and it almost seemed "child-play" when it brought us back to a potential soft sediment patch that we found earlier during this survey. Of course we had to move slowly, because the 2 km long drill string needs to settle after every movement down there on the ocean floor and that easily took up to five minutes. After almost three hours, we met with the expedition manager and drilling superintendent (who we had to wake up unfortunately) to discuss the situation. Finally, we made the decision to try and spud in.

The seafloor was tagged at 1458 meter below rig floor and Hole 1373A was successfully spud at 07:00 hr. However, as feared the rocks were hard and it took quite some time to drill the first core, simply because not a lot of weight could be put on the drill bit without the possibility of snapping off the drill string. So the first core was not received until 20:10 and it consisted of carbonate-cemented poorly-sorted conglomerate with a ~75 cm large highly olivine-phyric bolder. Amazingly the olivine phenocrysts were up to ~0.5 cm in diameter and relatively fresh in some cases.

The transition from this conglomorate and other clastic sediment to “igneous basement” was identified at 33.9 mbsf when we encountered a distinct highly olivine-pyroxene-phyric basaltic lava flow. The lava flows that followed often had tops with peperitic textures meaning that the lava flows erupted into an environment with soft and wet sediment. We happily kept drilling until 65.7 mbsf. At that time the drill bit had accumulated at least 65 hours of rotation in the seamount formation and it was time to exchange it for a new bit. Of course this required the deployment of a free-fall funnel, but we didn't have any soft sediment for an easy deployment. Indeed it turned out to be impossible and we were to be unlucky again over the next 24 hours.