Site summaries (continued)

Proposed Site PEAT-3C (middle Eocene Equator)

Primary for Expedition 320, alternate for Expedition 321
10°30.997’N, 138°25.175’W (WGS-84)
Water depth (m):
4874 (6.498 s TWT)
Target drilling depth (mbsf):
174 then tag basement
Approved maximum penetration (mbsf):
250 (approved by TAMU safety panel based on EPSP June 2006 recommendation)
Survey coverage
(track map; seismic profile):
Roger Revelle (4–5 April 2006; 6 kt):
• Simrad EM-120 multibeam system
• Knudsen 320B subbottom profiler
• Dual 150 c.i. GI seismic sources
• Scripps 48-channel Geometrics GeoEel
Piston core: 11.3 m (RR0603-09JC)
Primary seismic line: PEAT-3 Line 3
Crossline: PEAT-3 Line 8 (Figs. F17, F18, F19) (see also report to the EPSP panel, available at
Site PEAT-3C was sited on ~46 Ma crust to target the middle Eocene. Recent results from Leg 199 show a factor of up to 2–3 times increase in accumulation rates of siliceous ooze in the middle Eocene (41–45 Ma) and several notable periods of highly fluctuating CCD, associated with intervals in which carbonate is preserved to 4000 m, or ~700 m deeper than the average Eocene CCD. Such fluctuations in the CCD are similar in magnitude to those at the Eocene/Oligocene boundary.
Site PEAT-3C aims to provide good carbonate recovery from this interval in order to apply the substantial array of carbonate-based proxies to this interval to evaluate the temperature and structure of the near-surface ocean.
Drilling program:
• Holes A, B, and C: APC with core orientation to refusal; XCB to basement; logging in Hole A
• Hole A: APC/XCB to basement
• Holes B and C: wash to 100 m; APC/XCB to basement
Downhole measurement program (low priority at this site):
• Wireline logging: triple combo, FMS-sonic, possibly check shot
• Temperature measurements: 3 APCT-3, 2 DVTP
Nature of rock anticipated:
Clay, radiolarian ooze, nannofossil ooze/chalk, possibility of chert strings, hydrothermically altered ridge basalt