CONCLUSIONS

We summarize the principal aspects of our analytical work as follows (see [N1]):

  1. In the five seismic sections analyzed, we found a generally very steep vertical velocity gradient. The steepest average gradient is found at the continental shelf edge (see Figure F6A at southeast end of the section, including the Site 1102 location) where a velocity of 3 km/s is found at less than 200 m sub-bottom depth. Anomalously high seismic velocity is a common feature in continental shelf sediments of Cenozoic glacial margins, as a consequence of ice load and/or glacial erosion (i.e., Solheim et al., 1991).
  2. However, we have not found anomalously high velocity at the seafloor, as may have been expected. For comparison, Cochrane and Cooper (1991) report a velocity of 2.08 m/s at the seafloor at Site 472 (ODP Leg 119 in Prydz Bay), a location geometrically analogous to our Site 1100, and a velocity of 2.4 m/s at the seafloor at other locations on the outer and inner shelf.
  3. The sharpest velocity increase downwards is found at the boundary between topsets (above) and foresets (below). One partial exception to this is the Site 1103 location, where such an increase does exist, although it is less than another increase found deeper, between Units S3 and S4.
  4. The only sharp velocity inversion occurs at the near-conformable boundary between Units S2 and S3 at proposed Site APSHE-04A.
  5. We encountered difficulty in picking coherent reflections in foresets of Unit S1 at Site 1102 and in foresets of Unit S2 at Site 1100. This is due to the poor lateral continuity of reflectors with respect to the topset units, as a consequence of the difference in depositional environments between continental slope and continental shelf, respectively.
  6. The comparison between the tomographic and stacking velocity profiles shows that the tomographic velocity is generally lower than the stacking velocity in the upper few hundreds of meters, while significant but variable differences occur below. As expected, the tomographic velocities provide a higher-resolution, smoother profile than the stacking velocities.

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