Site Summaries (continued) | Table of Contents
SITE SUMMARIES (continued)
Site: COC-4A
Priority: 2 (Alternate to COC-3A)
Position: 7°51.352´N 83°36.402´W
Water Depth: 1370 m
Sediment Thickness: 461 m
Target Drilling Depth: 250 mbsf
Approved Maximum Penetration: 250 mbsf
Seismic Coverage: Sediment thickness: 0.559 s (461 m at 1650 m/s velocity)
Primary Line: 2000 NEMO-3 (Melville), COC-4 Line 5, JD158 09:09:05z (SP3295)
Crossing Line: 2000 NEMO-3 (Melville), COC-4 Line 7
Seismic Line 5 | Seismic Line 7 | Bathymetry map
Objectives: The objectives at Site COC-4A are to provide a continuous sedimentary sequence to:
1. Monitor the composition of basal intermediate waters and upper deep waters at the northern edge of the Panama Basin.
2. Monitor the Costa Rica Current and the movement of the intertropical convergence zone.
3. Monitor upwelling along the Costa Rica Margin.
4. Examine a middle Miocene shallow pelagic section from the Galapagos region.
Drilling Program: Triple APC to refusal. Tensor orientation on APC cores. Single XCB if
needed to extend one hole to maximum approved penetration ~250 mbsf.
Logging and Downhole: Triple combo, third-party Lamont MGT, FMS/sonic, GHMT.
Nature of Rock Anticipated: Site COC-4 is located in a graben on the crest of the Cocos Ridge,
within the region of strong hemipelagic sedimentation from Costa Rica. Site survey core is
composed of dark olive gray clay. The hemipelagic sediment-filled modern graben is of uncertain
age, but if it is Pleistocene in origin, the sedimentation rate is on the order of 150 m/m.y. (the
graben sediments are ~300 m thick).
