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Upper slope Site U14131

R.N. Harris, A. Sakaguchi, K. Petronotis, A.T. Baxter, R. Berg, A. Burkett, D. Charpentier, J. Choi, P. Diz Ferreiro, M. Hamahashi, Y. Hashimoto, K. Heydolph, L. Jovane, M. Kastner, W. Kurz, S.O. Kutterolf, Y. Li, A. Malinverno, K.M. Martin, C. Millan, D.B. Nascimento, S. Saito, M.I. Sandoval Gutierrez, E.J. Screaton, C.E. Smith-Duque, E.A. Solomon, S.M. Straub, W. Tanikawa, M.E. Torres, H. Uchimura, P. Vannucchi, Y. Yamamoto, Q. Yan, and X. Zhao2

Background and objectives

Integrated Ocean Drilling Program (IODP) Site U1413 (proposed Site CRIS-13B) targeted the upper slope of the Costa Rica margin, 30 km from the trench. This site is within the 3-D seismic data set along Line 2466 and crossing Line 4882 (Figs. F1, F2). Interplate earthquake relocations and interpretation of geodetic measurements show that this site is located above the seismogenic zone (S.L. Bilek, pers. comm., 2003; LaFemina et al., 2009).

The margin consists of slope sediment with a minimum thickness >1425 m. The primary purpose of drilling Site U1413 was to determine the nature, composition, and physical properties of the slope sediments. This site is also designed as a “pilot hole” in preparation for a proposed deeper CRISP Program B drilling. The location of this site represents a trade-off between being in the >500 m of water depth necessary for D/V Chikyu riser drilling and being over the seaward edge of the seismogenic zone so that drilling depths are a minimum. Additionally, it was important to locate the site within the 3-D seismic data volume.

In preparation for riser operations, engineering objectives included obtaining (1) shallow formation strength data for top hole design, (2) shear strength data to 100 meters below seafloor (mbsf), and (3) material for onshore geotechnical analysis.

Science objectives at Site U1413 included (1) documenting lithology and physical properties, (2) determining the stress orientation of the margin above the seismogenic zone, and (3) estimating the fluid-flow regime and role of slope sediment in fluid flow. Documenting periods of subsidence and uplift provides important information about the process of tectonic erosion that characterizes the Costa Rica margin. Stratigraphic correlation of multiple sites allows for estimating the relative motion of the margin.

1 Harris, R.N., Sakaguchi, A., Petronotis, K., Baxter, A.T., Berg, R., Burkett, A., Charpentier, D., Choi, J., Diz Ferreiro, P., Hamahashi, M., Hashimoto, Y., Heydolph, K., Jovane, L., Kastner, M., Kurz, W., Kutterolf, S.O., Li, Y., Malinverno, A., Martin, K.M., Millan, C., Nascimento, D.B., Saito, S., Sandoval Gutierrez, M.I., Screaton, E.J., Smith-Duque, C.E., Solomon, E.A., Straub, S.M., Tanikawa, W., Torres, M.E., Uchimura, H., Vannucchi, P., Yamamoto, Y., Yan, Q., and Zhao, X., 2013. Upper slope Site U1413. In Harris, R.N., Sakaguchi, A., Petronotis, K., and the Expedition 344 Scientists, Proc. IODP, 344: College Station, TX (Integrated Ocean Drilling Program). doi:10.2204/​iodp.proc.344.107.2013

2Expedition 344 Scientists’ addresses.

Publication: 11 December 2013
MS 344-107