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doi:10.2204/iodp.sp.327.2010

Expedition objectives

Primary scientific objectives

The primary scientific objectives of Expedition 327 are listed below, in a rough order of priority, although changes in the detailed operational plan are expected based on weather, hole conditions, actual time requirements for individual operations, and other factors (Table T1). The maximum lateral distance between primary work sites is 2.4 km, so we expect to move frequently between sites to take advantage of favorable weather conditions and time savings that may be afforded by avoiding unnecessary pipe trips.

The primary work area for Expedition 327, including Sites 1027 and U1301 and proposed Site SR-2, is referred to as the Second Ridge (SR) area (Fig. F1) because these sites are located on or adjacent to the second major buried basement ridge east of the JFR. All of the highest priority objectives for Expedition 327 are to be achieved through work in the SR area. Secondary objectives may be achieved during Expedition 327 at the sedimented regions adjacent to Grizzly Bare (GRB) outcrop, above the first buried basement ridge (FR) east of the JFR, and above a series of more deeply buried ridges (DR) to the east of the SR area (Fig. F1).

1. Proposed Site SR-2

We will drill two new basement holes at Site SR-2, ~200 m south-southwest of Hole 1026B and ~800 m north-northwest of Hole U1301B, where sediment thickness is ~255 m. Seismic coverage in this area is detailed (Fig. F2), and holes will be located along the peak of the buried basement ridge (Fig. F3), much like Holes U1301A and U1301B (Fig. F4) and Hole 1026B (Fig. F5). Hole SR-2A will be the deepest of the two new holes, but this hole can be used as the shallowest completion if poor hole conditions or other operational problems necessitate it. The sedimentary section and the uppermost 100 m of basement will be drilled and cased in this hole but not cored. Coring will occur only within the interval of ~100–260 msb, with the final hole depth determined by hole conditions and time remaining during the expedition. The open basement interval in this hole will be wireline logged with a single string (see "Logging/downhole measurements strategy"), tested for permeability using the drill string packer, and instrumented with a multilevel CORK. This and other CORKs deployed during Expedition 327 will include instruments to monitor formation fluid pressure and temperature, sample fluids (using downhole and wellhead OsmoSamplers), and provide growth substrate for microbes inhabiting the basement aquifer.

Hole SR-2B will be the shallowest of the new basement holes. The sedimentary section and the uppermost ~30 m of basement will be drilled and cased in this hole, and additional drilling below casing will open the hole to ~70 msb. There will be no coring or wireline logging in Hole SR-2B. A 24 h pumping and tracer injection experiment will occur in Hole SR-2B, and then this hole will be instrumented with a CORK. This CORK will be similar to that installed in Hole SR-2A, except that it will monitor a single basement interval.

2. Hole 1027C

We will recover an existing CORK in Hole 1027C, core and deepen the hole by ~40 m, extending it to ~60 msb, and deploy a multilevel CORK to monitor and sample basement fluids. If there is sufficient time we may complete hydrologic (packer) tests within the new basement interval in this hole before setting the CORK in place, but no wireline logging or other downhole experiments are planned.

3. Hole U1301B

We will recover the CORK instrument string deployed in Hole U1301B, which researchers were unable to recover during submersible operations in summer 2009, and deploy a replacement instrument string, including thermal sensors, fluid samplers, and microbial growth substrate.

4. Hole U1301A

We will complete remedial cementing operations in Hole U1301A with the goal of sealing this system at the seafloor, isolating the open hole at depth from the overlying ocean.

Primary education and outreach objectives

The primary scientific objectives of Expedition 327 will be achieved concurrently with an extensive education and science communication program involving 6–7 shipboard science educators, communicators, writers, and media developers and hundreds of additional personnel on shore (classroom students, teachers, museum visitors, families, etc.). Working alongside the science party, shipboard educators will advance the scientific goals of the expedition and of IODP in general by communicating its importance to a broad external audience and engendering understanding and enthusiasm for scientific exploration, ocean drilling, and subseafloor observatories.

Earlier full-length scientific ocean drilling expeditions included a single teacher at sea, who focused on a subset of similar objectives, whereas shorter expeditions or transits included a larger number of educators, who participated in shipboard activities while limited, if any, science operations were performed. In contrast, Expedition 327 will be the first full-length ocean drilling expedition to include a broader education, outreach, and communication program. While on board, participants will complete an intensive short course on marine geology and hydrogeology, take part in a seminar series from the scientists about their research, and offer a seminar series on science communications to assist shipboard scientists in sharing their research and creating effective broader impacts for nonscientific audiences. This on-board education team will also produce podcasts and videos, articles for mainstream media outlets and Web sites, a regular schedule of live video conferences to audiences on shore, daily blogs, Facebook and Twitter updates, photo-based documentary journals to be published during or after the cruise, graphic novel–style books, classroom curricula, journal articles, and videos for YouTube, among other products. Because of the nature of collaborative research in education circles, sailing multiple educators as a team provides a unique opportunity for creating innovative science communication products.

Secondary scientific objectives

If the primary scientific objectives are completed or we cannot complete some of these objectives and time still remains during the expedition, we may attempt to achieve secondary scientific objectives. These objectives involve mainly sediment coring, sampling, and measurements, prioritized in this order:

5. Proposed Sites GRB-1, GRB-2, and GRB-3

Sedimentary (advanced piston corer [APC]/extended core barrel [XCB]) coring and heat flow measurements at proposed Sites GRB-1A, GRB-2A, or GRB-3A (Fig. F6) may take place with the goal of documenting evidence for hydrothermal recharge adjacent to Grizzly Bare outcrop, as hypothesized from pore water and formation fluid compositions from the north and heat flow and modeling studies of the corridor that extends ~50 km north from Grizzly Bare outcrop.

6. Proposed Site FR-1

Sedimentary (APC/XCB) coring and heat flow measurements at proposed Site FR-1 (Fig. F7) may take place to evaluate the nature of sedimentary properties and basement fluid compositions along a short transect of holes, including locations where there is known hydrothermal seepage.

7. Proposed Sites DR-1 and DR-2

Sedimentary and basement (rotary core barrel [RCB]) coring and heat flow measurements at proposed Sites DR-1 or DR-2 (Fig. F8) may take place to extend the Leg 168 transect to the east and assess the nature of crustal evolution at greater temperatures, basement ages, and depths of basement burial.

Work at GRB and FR sites could occupy ≤3–4 days, whereas coring at the DR sites would require at least 11 days to reach basement because of greater sediment thickness.

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