Figure 2. Bathymetric map of the Antarctic Peninsula margin, showing primary sites APRIS 01A to 02A, APSHE-01A to 05A, and APSHE-13A as circles, and alternate and lower priority sites as squares (R3 and R4 are Sites APRIS-03A and 04A, respectively; S6 to S12 are Sites APSHE-06A to 12A, respectively; and T1 and T2 are Sites APSST-01A and 02A, respectively).
Figure 3. Pacific margin of the Antarctic Peninsula (revised from Barker, 1995) showing sedimentary features of the continental shelf, slope, and rise, including drifts D1-8 and Lobes L1 4, with proposed sites for ODP Leg 178. Large spots mark primary sites (APRIS-01A, 02A; APSHE-01A to 05A and APSHE-013A); smaller spots mark alternate and lower priority sites (labelled as in Figure 2).
Figure 4. Graph and maps of ice-sheet growth, showing ice-sheet size and location at mean sea level temperatures 5, 9, 10, 15, 19, and 20 Kelvin (K) above present. The maps indicate where margin sedimentation might be sensitive to particular stages of ice-sheet growth. Antarctic Peninsula glaciation appears to have developed during the last 5-9 K of cooling (from Huybrechts, 1993).
Figure 5. Seismic sequence model of a single glacial cycle (Larter and Barker, 1989, 1991b). Unsorted diamicton is deposited on the upper slope during glacial (GS) maxima, and on the shelf during retreat. Pelagic and hemipelagic deposition takes place on shelf and slope during interglacials (IGS). With re-advance, some or all shelf topsets may be eroded.
Figure 6. Cartoon of processes leading to construction and maintenance of a hemipelagic drift deposit along the Antarctic Peninsula margin (from Rebesco et al, in press), showing a section through a shelf progradational lobe and adjacent continental rise during a glacial maximum when an ice sheet grounded to the shelf edge is transporting unsorted basal till to the upper slope. Small scale slumps on the uppermost slope become debris flows. Farther downslope, these become turbidity currents which flow via tributaries on the uppermost rise into the main channel running between the drifts towards the abyssal plain. Suspended fines are entrained in ambient bottom currents and deposited down-current. Subsequent turbidity-current flow in the channels, and slope instability on the steeper drift slopes sweep those recent deposits away, leaving a permanent sediment increment only on the gentle slope of the drifts.
Figure 7. Schematic dip section of Lobe 1 (revised from Barker, 1995), showing (long arrows)
primary Sites APSHE-01A to 04A and sequence groups S1-4 (from Larter and Barker, 1989,
1991b) on the outer shelf. Shorter arrow shows lower priority Site APSHE-10A on the flank of
the mid-shelf high.
Figure 8. Locations of all available multichannel seismic (MCS) and single-channel seismic (SCS) profiles on the Antarctic Peninsula margin (from UK, Italian, U.S.A., Brazilian, and German cruises and from Spanish, Chinese, Polish, and Japanese data in S. Shetlands/Bransfield Strait area). Boxes (Figs. 9, 10, and 11) are areas where almost all primary and alternate sites are located.
Figure 9. Track chart in Drifts D7 and D6 area (Fig. 3) showing primary (large circles) and alternate (small circles) sites. Each drift has a proximal and distal site, with Drift D7 as the prime target.
Figure 10. Track chart in Lobe 1 area (Fig. 3) showing primary (large circles), alternate (small circles) sites, and lower priority sites (squares).
Figure 11. Track chart in Lobe 3 area (Fig. 3) showing primary (large circles), alternate (small circles) sites, and lower priority sites (squares).
Figure 12. Track chart showing MCS profiles in the South Shetland Trench area (Figs. 2 and 3),
where alternate Sites APSST-01A (large triangle) and APSST-02A (small triangle) are located.
To 178 Primary Site Time Estimates
To 178 Alternate Site Time Estimates
To 178 Table of Contents