Scientific and technical design and deployment of long-term subseafloor observatories for hydrogeologic and related experiments, IODP Expedition 301, eastern flank of Juan de Fuca Ridge

Abstract

Integrated Ocean Drilling Program (IODP) Expedition 301, on the eastern flank of the Juan de Fuca Ridge, established part of a three-dimensional network of borehole observatories (Circulation Obviation Retrofit Kits [CORKs]) in the oceanic crust. These observatories are to be used to conduct active, multidisciplinary experiments over timescales of minutes to years and length scales of meters to kilometers. The complete experimental program will comprise two IODP expeditions (the first having been Expedition 301, the second to be scheduled), an offset seismic experiment, and long-term monitoring and crosshole testing carried out by submersible and remotely operated vehicle. During Expedition 301, we replaced a preexisting CORK observatory in Hole 1026B and created and instrumented new Holes U1301A and U1301B, which penetrate 108 and 320 m into basement, respectively. The borehole observatories deployed during Expedition 301 share some characteristics with systems deployed during the Ocean Drilling Program but also include many improved components and novel features.

Methods

“…These studies expand on previous work in this region at nearby Site U1301 during IODP Expedition 301 and postexpedition in Holes 1026B, U1301A, and U1301B (Cowen et al, 2003;Engelen et al, 2008;Fisher et al, 2005;Lever et al, 2006;Nakagawa et al, 2006;Orcutt et al, 2011;Wheat et al, 2010). The secondary microbiology objective of this expedition was to collect sediment from Grizzly Bare outcrop (Site U1363) to examine the influence of presumed seawater recharge on sediment microbiology and to compare these findings with microbiological results obtained from sediments drilled during Expedition 301 (Engelen et al, 2008;Lever et al, 2010).…”

Design, deployment, and status of borehole observatory systems used for single-hole and cross-hole experiments, IODP Expedition 327, eastern flank of Juan de Fuca Ridge

“…In this section we report on the status of CORKs installed before Expedition 327, as of the end of Expedition AT15-66. Operations involved in creating these CORKs, as well as details of hole completion, servicing operations, and CORK configuration through 2004 are described elsewhere Davis and Becker, 2004;Expedition 301 Scientists, 2005a, 2005bFisher et al, 2005;Shipboard Scientific Party, 1997).…”

Site U1382

“…These probes were purchased from Antares and Onset, and they fit within holes drilled into the plastic couplers in the OsmoSampler packages. Both probes provide a dynamic range that covers the expected temperatures (2°-30°C), but the Antares probes have greater sensitivity (see Fisher et al, 2005).…”