Site Summaries (continued) | Table of Contents

SITE SUMMARIES (continued)

Priority: 1
Position: 36°10.32´S, 73°34.32´W
Water Depth: 509 m
Sediment Thickness: >300 m
Target Drilling Depth: 200 mbsf (or APC refusal)
Approved Maximum Penetration: 200 mbsf
Seismic Coverage: Primary Line: 970313 (Revelle), Line CBA-3D-06, 0536z, SP930.
Crossing Line: 970314 (Revelle), Line CBA-3D-15, 1040z, SP317. Although the site is approved for drilling as is, a short seismic survey will be done prior to drilling this site (crossing both Sites SEPAC-13B and SEPAC-14A) using the JOIDES Resolution 80 in³ airgun.

Trackline map (same as SEPAC-13B) | Seismic Line 6 | Seismic Line 15 | Bathymetry map (same as SEPAC-13B)

Objectives: The objectives at Site SEPAC-14A are to provide a continuous sedimentary sequence to:

1. Assess Pleistocene history of a biological production in a coastal upwelling center near Concepción, Chile, which is sensitive to regional winds, with millennial-scale resolution.

2. Assess Pleistocene history of terrigenous sedimentation off central Chile to assess climate variability on land, with millennial-scale resolution

3. Assess variations in the boundary between oxygen-rich AAIW (which is strongly developed near 700 m depth) and the oxygen-poor GU (which is strongly developed near 300 m depth), using tracers of paleo-oxygen and paleonutrients. Site SEPAC-14A, which monitors the upper boundary of AAIW, complements Site SEPAC-13B, which monitors the lower boundary of AAIW. Because the two sites are very close to each other, histories of changing paleoproduction should be quite similar, whereas seafloor oxygen histories may be quite different.

4. If time is available, provide a dedicated hole for pore water measurements in the upper 100 m of the sediment column.

Drilling Program: Triple APC to refusal or maximum approved penetration. Tensor orientation on APC cores. On a time-available basis, provide a fourth APC hole for purposes of sampling pore waters and other ephemeral properties, and for reconnaissance-level sampling at the discretion of the SAC.

Logging and Downhole: None.

Nature of Rock Anticipated: Site SEPAC-14A is in a small slope basin in an active margin setting. It appears to be sheltered from downslope turbidite flows by phosphate-rich reefs on the continental shelf. A sediment core recovered organic-rich muds and clayey silts, including some fragments of mollusk shells, suggesting some downslope transport. Sedimentation rates are probably high, expected to be >200 m/m.y.

Note: Some H₂S may be present, and appropriate shipboard precautions should be taken.

Site Summaries (continued) | Table of Contents