Site Summaries (continued) | Table of Contents

SITE SUMMARIES (continued)

Site: NAZCA-17A

Priority: 1
Position: 16°00.42´S, 76°22.68´W
Water Depth: 3228 m
Sediment Thickness: 280 m
Target Drilling Depth: 280 mbsf
Approved Maximum Penetration: 300 mbsf
Seismic Coverage: Sediment cover TWTT = 0.37 s (280 m)
Primary Line: 970329 (Revelle), Line NAZ-3B-4, 1412z, SP589
Crossing Line: 970330 (Revelle, Line NAZ-3B-5, 0217z, SP103

Trackline map | Seismic Line 4 | Seismic Line 5 | Bathymetry map

Objectives: The objectives at Site NAZCA-17A are to provide a continuous sedimentary sequence to:

1. Monitor variations in deep water masses and carbonate dissolution in Neogene.

2. Monitor the Pleistocene core of the Humboldt Current at low latitudes with well-preserved fauna.

3. Monitor surface water properties of the subtropical South Pacific during Neogene time, and perhaps as old as late Eocene time (with lower resolution in older intervals).

Drilling Program: Triple APC to refusal. Tensor orientation on APC cores. Single XCB to extend one hole to basement or refusal (expected penetration ~280 mbsf).

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

Nature of Rock Anticipated: Site survey cores recovered clay-rich foram-nannofossil ooze, with abundant diatoms and radiolarians. By analogy to modern sediment patterns, older sediments are likely nannofossil or foram oozes. Nazca Ridge basement ages are likely near 40 Ma in this region. Acoustic basement is likely hotspot volcanics, although subaerial erosion surface or drowned reefs are possible (younger than 40 Ma). Sediment thickness of ~280 m suggests average sediment accumulation of ~7 m/m.y., although based on sediment cores in the region late Pleistocene sedimentation rates are probably 20-30 m/m.y. A rhythmic sequence of >50 reflectors through the section suggests that this area will record significant changes in climate in the local lithology.

Site Summaries (continued) | Table of Contents