SD Scientific Drilling SD Sci. Dril. 1816-3459 ICDP-IODP Göttingen, Germany 10.2204/iodp.sd.15.04.2013 IODP Expedition 340T: Borehole Logging at Atlantis Massif Oceanic Core Complex Blackman D. 1 Slagle A. 2 Harding A. 1 Guerin G. 2 McCaig A. 3 Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA Lamont Doherty Earth Observatory, Columbia University, 61 Route 9W, P.O. Box 1000, Palisades, NY 10964-8000, USA School of Earth and Environment, Maths/ Earth and Environment Building, The University of Leeds, Leeds LS2 9JT, UK 01 03 2013 15 31 35 Copyright: © 2013 D. Blackman et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://sd.copernicus.org/articles/15/31/2013/sd-15-31-2013.html The full text article is available as a PDF file from https://sd.copernicus.org/articles/15/31/2013/sd-15-31-2013.pdf

Integrated Ocean Drilling Program (IODP) Expedition 340T returned to the 1.4-km-deep Hole U1309D at Atlantis Massif to carry out borehole logging including vertical seismic profiling (VSP). Seismic, resistivity, and temperature logs were obtained throughout the geologic section in the footwall of this oceanic core complex. Reliable downhole temperature measurements throughout and the first seismic coverage of the 800–1400 meters below seafloor (mbsf) portion of the section were obtained. Distinct changes in velocity, resistivity, and magnetic susceptibility characterize the boundaries of altered, olivine-rich troctolite intervals within the otherwise dominantly gabbroic se-quence. Some narrow fault zones also are associated with downhole resistivity or velocity excursions. Small deviations in temperature were measured in borehole fluid adjacent to known faults at 750 mbsf and 1100 mbsf. This suggests that flow of seawater remains active along these zones of faulting and rock alteration. Vertical seismic profile station coverage at zero offset now extends the full length of the hole, including the uppermost 150 mbsf, where detachment processes are expected to have left their strongest imprint. Analysis of wallrock properties, together with alteration and structural characteristics of the cores from Site U1309, highlights the likely interplay between lithology, structure, lithospheric hydration, and core complex evolution. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.15.04.2013" target="_blank">10.2204/iodp.sd.15.04.2013</a>