8. Site 11401

Shipboard Scientific Party2

BACKGROUND AND OBJECTIVES

Site 1140 lies on the northernmost part of the Kerguelen Plateau, ~270 km north of the Kerguelen Archipelago (Fig. F1). Flanked to the north and east by Eocene and younger oceanic crust of the Australian-Antarctic Basin, and to the west by Cretaceous oceanic crust of the Crozet and Enderby basins, the northern Kerguelen Plateau (NKP) is believed to have formed since 40 Ma via Kerguelen hot spot magmatism (Royer and Sandwell, 1989; Royer and Coffin, 1992). The Kerguelen Archipelago is part of the NKP; its igneous rocks yield dates from 39 Ma to the Holocene (Nicolaysen et al., 1996, in press). However, submarine igneous basement of the NKP has never been sampled, so its age and composition, as well as its relationship to the central and southern plateau sectors and to Skiff and Elan Banks, are unknown. We located Site 1140 on Marion Dufresne multichannel seismic (MCS) line MD109-06 (Fig. F2). Site 1140 lies at a depth of 2394 m on the northern flank of the NKP. We chose this location as representative of the NKP on the basis of its relatively simple structural setting and thin sedimentary section (Fig. F3). The top of acoustic basement is flat lying, and overlying basement is a sediment sequence ~350 m thick. The boundary between the NKP and the Australia-Antarctic Basin lies ~5 km north of Site 1140 and offsets basement by ~400 m.

Summary of Objectives

The main objectives at this site were to

  1. Characterize the petrography and compositions of the lavas;
  2. Determine the age of the lavas, testing the hypothesis that the uppermost igneous basement of the NKP is ~40 Ma, the age of the oldest known igneous rock from the Kerguelen Archipelago (Giret and Lameyre, 1983; Giret and Beaux, 1984), or younger;
  3. Determine the physical characteristics of the lava flows;
  4. Identify the environment of eruption (subaerial or submarine);
  5. Obtain minimum estimates for the age of basement from overlying sediment;
  6. Estimate the duration of possible subaerial and shallow marine environments from the sedimentary and igneous record;
  7. Determine the facies of the seismic stratigraphic sequences;
  8. Define the ages of seismic sequence boundaries; and
  9. Determine the paleoceanographic history of this mid-latitude site.

1Examples of how to reference the whole or part of this volume can be found under "Citations" in the preliminary pages of the volume.
2Shipboard Scientific Party addresses can be found under "Shipboard Scientific Party" in the preliminary pages of the volume.

Ms 183IR-108

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