Reflections on three-dimensional (3-D) seismic line 278 can be correlated with lithostratigraphic boundaries at Site 1178 (Fig. F34). Specific correlations should be considered preliminary at this time because the velocity structure at this site is not well known. Any inaccuracies in velocity will produce errors in depth conversion. Additional velocity work will be carried out postcruise to improve depth conversions and stratigraphic correlations.
Lithostratigraphic Unit I is recognized on the seismic line as a sequence bounded at the top by the seafloor and at the bottom by an angular unconformity (Fig. F34) at ~200 mbsf. The upper part of the unit has a thin seismic stratigraphic sequence that onlaps to the northwest. The lower part of the unit is characterized by discontinuous low-amplitude reflections that dip to the southeast. The strong unconformity at the base of the unit dips to the southeast.
Lithostratigraphic Unit II underlies the strong unconformity at 200 mbsf. The top of the unit is truncated by the unconformity. Reflections within the unit are moderate-amplitude and generally dip to the northwest, although dips are shallow downsection.
A strong bottom-simulating reflection crosses Unit II at ~400 mbsf at Site 1178. It dips southeast and cuts across the northwest-dipping reflections of Unit II.