During Integrated Ocean Drilling Program (IODP) Expedition 336 to North Pond on the western flank of the Mid-Atlantic Ridge (8 Ma crust) in the late fall of 2011, borehole observatories were installed in IODP Holes U1382A and U1383C and Deep Sea Drilling Project Hole 395A. These borehole observatories are designed for long-term (multiyear) coordinated hydrogeological, geochemical, and microbiological monitoring and experimentation to understand the nature of life, fluid flow, and fluid-rock interactions in young and cool oceanic crust. Additional related activities during Expedition 336 included recovery of an instrument string that was deployed within an earlier generation of a circulation obviation retrofit kit (CORK) observatory in Hole 395A and preparation of IODP Hole U1383B, which was drilled, cased, and left open during Expedition 336, for a future deployment of a borehole observatory. A streamlined CORK observatory was deployed in Hole U1383B during a remotely operated vehicle–supported cruise in April 2012. An additional CORK servicing cruise is scheduled for 2013. Here, we summarize the observatory project goals and provide an overview of the design, construction, and deployment of these CORKs and related instrumentation during Expedition 336. We also summarize the project goals, design, and construction for the CORK-lite installation in Hole U1383B and discuss plans for its deployment. CORK servicing plans for 2012 and 2013 also are presented.
Integrated Ocean Drilling Program (IODP) Expedition 327 installed two new subseafloor borehole observatory systems (“CORKs”) in 3.5 m.y. old upper ocean crust on the eastern flank of Juan de Fuca Ridge in Holes U1362A and U1362B. Expedition 327 participants also recovered part of an instrument string previously deployed in a CORK in Hole U1301B and deployed a short replacement string. These observatories are part of a network of six CORKs that was designed to monitor, sample, and complete multidisciplinary cross-hole experiments. We present an overview of project goals and describe the design, construction, and deployment of new CORK systems. We also provide an update on the status of preexisting CORK systems as of the start of Expedition 327. Additional CORK servicing and sampling are scheduled for summer 2011 and 2012, including a long-term free-flow perturbation experiment that will test the large-scale directional properties of the upper ocean crust around the observatories.