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IODP Expedition 330 Louisville Seamount Trail

Daily Science Report 16 -- Monday, 27 December 2010


Site U1372 on 26.5°S Guyot 26° 29' 35.9988" S, 174° 43' 45.0012" W
Louisville Seamount Trail
0 m above sea level

Cores U1372A-21R (145.0-149.2 mbsf), -22R (149.2-156.2), -23R (156.2-161.0), -24R (161.0-165.8), and -25R (165.8-170.6) were retrieved with and average recovery of only 28%. The low recovery rate is most likely caused by the heterogeneous nature of the rocks containing both soft and hard intervals. The core catcher (device at the end of the core barrel that prevents the core from falling out) got jammed several times by individual hard clasts thereby preventing further material to enter. Cores U1372A-21R to -25R are composed of a volcanic breccia with larger, boulder-size and very fresh, plagioclase-phyric clasts and a greenish, sand-size matrix that appears to be sedimentary (a 2 cm-size interval shows apparently cross-bedding structures). Some clasts exhibit thin altered glass margins. Meanwhile the investigation of the carbonate-cemented clastic conglomerate/breccia succession between Core U1372A-4R and -8R continues. This interval (13.5- 45.6 mbsf), located between the uppermost thin layer of pelagic Pliocene to recent sediments and the igneous basement (lava flows) of the seamount, obviously contains material from the late stage of volcanism at this site. The paleontologist are trying hard to further constrain a more specific age for the micritic limestone matrix which is currently only identified as “mid to late Cretaceous”. However, doing this by investigating thin sections that arbitrarily cut through the foraminifer fossils and reveal no sight of the smaller nannofossils (much smaller than the thickness of a thin section) proved to be a difficult or even impossible task.