Site Summaries (continued) | Table of Contents

SITE SUMMARIES (continued)

Site: SEPAC-10A

Priority: 3 (alternate to SEPAC-9A)
Position: 40°28.98´S, 75°54.96´W
Water Depth: 3858 m
Sediment Thickness:
300 m
Target Drilling Depth: 300 mbsf
Approved Maximum Penetration: 350 mbsf
Seismic Coverage: Sediment Cover TWTT = 0.40 s (300 m).
Primary Line: 970309 (Revelle), Line CBA-3A-7, 0430z, SP126
Crossing Line: 970309 (Revelle), Line CBA-3A-6, 0308z, SP276

Trackline map | Seismic Line 6 | Seismic Line 7 | Bathymetry map

Objectives: The objectives at Site SEPAC-10A are to provide a continuous sedimentary sequence to:

1. Assess variations in the character of Antarctic CPDW, which enters the Chile Basin from the south as bottom water, over the past 19 Ma (estimated crust age south of Valdivia Fracture Zone).

2. Assess variations in the southernmost reaches of the northward flowing Humboldt Current, based on planktonic fauna and flora, including responses of the southern subtropical South Pacific. Crustal age suggests that this site may be suitable for examining climatic response to Miocene growth of ice in Antarctica.

3. Assess biostratigraphic and paleomagnetic stratigraphies in the southeast Pacific, for comparison to similar data in the subtropical and tropical regions.

Drilling Program: Triple APC to refusal. Tensor orientation on APC cores. Single XCB to basement or refusal (expected penetration ~300 mbsf).

Logging and Downhole: Triple Combo, third-party Lamont MGT, FMS/sonic, GHMT

Nature of Rock Anticipated: Upper section is expected to be fossiliferous pelagic clay. Site SEPAC-10A is in an area of rough basement topography, filled by sediment that drapes the bathymetry. The bathymetric highs appear to have shielded the area from turbidites. Average (0-19 Ma) sediment accumulation rate is near 15 m/m.y. Rates are likely higher in the Pleistocene, and lower in older intervals when the site was far to the west of South America. Lower section likely to contain more carbonates, gradually lithifying with greater meters below seafloor depth. Basement is likely oceanic basalt.

Site Summaries (continued) | Table of Contents