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IODP Expedition 330 Louisville Seamount Trail

Daily Science Report 21 -- Saturday, 1 January 2011


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 drillstring was deployed, the VIT camera revealed that the seafloor at the summit of this guyot is covered by boulders and outcrops of hard rock (lava flows?). Eventually a clear location was found and seafloor was tagged at 1458 meter below rig floor. Hole 1373A was spud at 07:00 hr but due to the hard formation the first core was not received until 20:10. Core U1373A-1R (0-9.6 mbsf) recovered a 2.86 m succession of carbonate-cemented, poorly sorted conglomerate, which contains abundant volcanic clasts of all sizes and rare small bioclasts. Of particular interested is a ~75 cm large highly olivine-phyric bolder. The individual olivine phenocrysts reach up to ~0.5 cm in diameter and appear, except for the outer 4 cm at the bolder rim, surprisingly fresh. Geochemical analyses will reveal if this rock can be called “picritic” (a volcanic rock characterized by high magnesia and low silica content). To everyone’s surprise, the core catcher contained some unconsolidated sediment (about 3 table-spoons full) that most likely came from the top of the core. The sand- to pebble-size sediment is composed of abundant volcanic rock fragments and planktonic foraminifers and rare benthic foraminifers, nannofossils and Mn-crust fragments. Preliminary assessments of the fossil assemblage and the fact that the foraminifer shells are not filled also suggest that the sediment represents a sample of the present-day seafloor cover.