IODP

doi:10.2204/iodp.sp.315.2007

Contingency

There are two levels of contingency: internal and global. The internal contingency is an alternative operation/science plan inside proposed Site NT2-03. Global contingency refers to a more general alternative plan among all Stage 1 sites. In case we cannot proceed with operations at the primary site (proposed Site NT2-03B), we will first try the internal contingency. If this also turns out to be impossible, we will then follow the global contingency plan.

Internal contingency

If the primary site cannot be drilled because of seafloor conditions or other local problems, we will move to the alternate proposed Site NT2-03C. Proposed Site NT2-03C is ~1.5 km southwest of proposed Site NT2-03B along the same 3-D crossline and on the same inline as proposed Site NT2-01B (Fig. F12). All objectives and geologic characteristics are the same as for proposed Site NT2-03B.

Global contingency

If major hole problems are found for both proposed Sites NT2-03B and NT2-03C during the LWD expedition (Expedition 314), or if a strong Kuroshio Current crosses the sites, the alternative sites listed below will be prepared. This contingency plan is based upon our current state of knowledge at the time of writing this Scientific Prospectus and may be modified based on continuing NanTroSEIZE Project Management Team (NT- PMT) discussions and actual NanTroSEIZE Stage 1 operations. This contingency plan also reflects the linkage among multiple NanTroSEIZE Stage 1 expeditions to achieve the following overarching NanTroSEIZE and Stage 1 scientific goals:

  • Coring at proposed Site NT2-04. This site will penetrate 1400 m of the Kumano Basin sequences to clarify its stratigraphic evolution in correlation with the activities of the megasplay fault.
  • Drilling and coring at proposed Site NT1-04. This site will provide additional information about physical properties, pore water geochemistry, and hydrogeology of turbidites within the Shikoku Basin beneath rapidly deposited trench-wedge turbidites at a site between proposed Sites NT1-03 and NT1-07.
  • Drilling and coring at proposed Site NT1-02. This site will document subduction inputs at a site along strike from proposed Site NT1-01 to document along-strike variability.