Priority:
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Alternate for both expeditions
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Position:
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02°36.327’N, 117°59.412’W (WGS-84)
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Water depth (m):
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4330 (5.773 s TWT)
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Target drilling depth (mbsf):
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455 then tag basement
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Approved maximum penetration (mbsf):
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480 (approved by TAMU safety panel based on EPSP June 2006 recommendation)
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Survey coverage
(track map; seismic profile):
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Roger Revelle (21 March 2006):
• Simrad EM-120 multibeam system
• Knudsen 320B subbottom profiler
• Dual 150 c.i. GI seismic sources
• Scripps 48-channel Geometrics GeoEel
Piston core: 10.87 m (RR0603-03JC)
Primary seismic line: PEAT-8 Line 1
Crossline: PEAT-8 Line 6 (Figs. F33, F34, F35) (see also report to the EPSP panel, available at eprints.soton.ac.uk/45921)
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Objective:
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Site PEAT-8C focuses on paleoceanographic events following a middle Miocene maximum in deposition along with large changes in the glaciation state and frequency in the interval following ~14 Ma. There is a wide latitude range of CaCO3 deposition during the earliest Neogene, with a relatively sharp transition to a narrower CaCO3 belt after 20 Ma. CaCO3 MARs in the central equatorial Pacific recovered from the 18–19 Ma "famine" and at 14–16 Ma reached a second maximum in carbonate deposition, which is also evident in the seismic stratigraphy of the equatorial sediment bulge. We designed Site PEAT-8C to recover an equatorial record at the early middle Miocene sedimentation maximum on 18 Ma crust.
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Drilling program:
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Preferred:
• Holes A, B, and C: APC with core orientation to refusal; XCB to basement; logging in Hole A
Minimum:
• Hole A: APC/XCB to basement
• Holes B and C: wash to 200 m; APC/XCB to basement
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Downhole measurement program:
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• Wireline logging: triple combo, FMS-sonic, possibly check shot
• Temperature measurements: 3 APCT-3, 2 DVTP
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Nature of rock anticipated:
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Clay, nannofossil ooze, nannofossil ooze/chalk, possibility of thin diatom layers, hydrothermically altered ridge basalt; low possibility of chert strings
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