: BON-8A

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Priority: 1
Position: 31°18.5ŽN, 142°57.5ŽE
Water Depth: 6000 m
Sediment Thickness: 600 m
Target Drilling Depth: 900 mbsf
Approved Maximum Penetration: 900 mbsf
Seismic Coverage: Conrad 2005, Line 39, shotpoint #2936 at 1613Z on 10/13/76

Objectives: The objectives of BON-8A are the following

  1. Provide estimates of the sediment inputs and altered basalt inputs (geochemical fluxes) into the Izu-Bonin subduction zone.
  2. Contrast crustal budgets here with those for the Marianas to test whether along-strike differences in the volcanics can be explained by along-strike variations in the crustal inputs.
  3. Compare basement alteration characteristics with those in Hole 801C (also in old Pacific crust).
  4. Provide constraints on the Early Cretaceous paleomagnetic time scale.
  5. Provide constraints on mid-Cretaceous carbonate compensation depth (CCD) and equatorial circulation fluctuations.

Drilling Program: APC, XCB, MDCB, RCB

Logging and Downhole Operations: Triple combo, GLT, FMS/Sonic, GHMT, ARI, Permeability

Nature of Rock Anticipated: Pelagic clay with volcanic arc ash (150 m); cherty porcellanites and chalks (450 m); basaltic pillows, flows, breccia, and possibly dikes (>300 m)

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