172 Scientific Prospectus


Site: BBOR-4B

Priority: 1
Position: 29°58.5'N, 73°36.0'W
Water Depth: 3975 m
Sediment Thickness: 1000 m
Approved Maximum Penetration: 350 m
Seismic Coverage: Conrad 2102 (LDGO line 87), conrad 1601, Conrad 2012, KNR 140 3.5kHz

Objectives: The objectives of BBOR-4B are to:

1.Determine the history of circulation change in the deep western North Atlantic near the boundary between AABW and NADW.

2.Provide reference section for Pliocene circulation change associated with onset of northern hemisphere glaciation

3.Determine a high-resolution history of paleomagnetic change

Drilling program:
Triple APC to 200 m, extending one hole to 350 m by XCB coring if recovery and degree of disturbance are satisfactory. If time permits, double or triple XCB coring to 350 m will be attempted.

Logging and Downhole: FMS-sonic and Triple combo, possibly in a dedicated logging hole, if time permits.

Nature of Rock Anticipated: Foraminifer-bearing silty clay and nannofossil marl

To Site BBOR-5
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