Daily Science Report 27 -- Friday, 7 January 2011
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Drilling in Hole U1374A progresses slowly (today’s average penetration rate= 1.1 m/hr) because the hole is not yet deep enough to apply effective weight on the drill bit. In return, Cores U1374A-5R (25.1-29.4 mbsf), U1374A-6R (29.4-34.2 mbsf), U1374A-7R (34.2-39.0 mbsf), and U1374A-8R (39.0-43.8 mbsf) were retrieved with an exceptional average recovery rate of 98%. A large variety of different lithologies were recovered starting with aphyric, massive basalt in Core U1374A-5R. The horizontal magmatic foliation (preferred orientation of crystal grains and/or flattened vesicles) supports the interpretation that this unit represents a lava flow. At the bottom of the core, the flow transitions into a calcite-cemented, volcaniclastic breccia with pillow fragments containing slightly altered glass, which continues across Core U1374A-6R. Aphyric lava is encountered again in Core U1374A-7R underlain by volcanic sandstone containing bioclasts and small (mm-size) yellow particles of pumice (?) but the description of this core is not completed yet. The shipboard paleontologists found a possible ammonite fragment in the conglomerate of Core U1374A-3R that was recovered the day before. Since this conglomerate is overlying the igneous basement it would confirm that the volcanism at this site ceased in the Mesozoic. However, further paleontological investigations (including the attempt to identify foraminifers in a small limestone interval within the conglomerate) are pending. At noon, the series of site summary meetings for previous Site U1373 was opened with presentations by the Sedimentology, Paleontology and Microbiology lab groups.
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