All Leg 177 sites, with the exception of Site 1088, yielded magnetic polarity stratigraphies to augment other chronostratigraphic information. Of the high-sedimentation-rate sites, the primary magnetization was most clearly recorded at Sites 1089 and 1094. At the two other sites (1091 and 1093) with expanded sections, the magnetization is affected by secondary components that were not entirely removed by shipboard demagnetization treatments. Nonetheless, all four high-resolution sites along the latitudinal transect have high potential for detailed (u-channel) studies of directional and bulk magnetic properties (Fig. 11). The objectives of these studies will be (1) to generate the first geomagnetic paleointensity records from the Southern Ocean for long-distance millennial-scale stratigraphic correlation; (2) to generate proxies for magnetic grain size and mineralogy that can be used for paleoenvironmental interpretation and to monitor detrital fluxes; and (3) to obtain detailed polarity transition records from the high-latitude Southern Hemisphere.
Sites 1090 and 1092, which are marked by lower sedimentation rates, both yielded well defined magnetic stratigraphies, although the upper part of the section at both sites was severely compromised by drilling-related core deformation. Below about 60 mcd at both sites, the shipboard magnetic polarity stratigraphies are well defined; however, correlation of polarity zones to the geomagnetic polarity time scale is ambiguous in the absence of detailed biostratigraphic analyses. Even in the XCB section of Site 1090, magnetic stratigraphies were well defined mainly because of the exceptional quality (lack of drilling deformation) of these cores. The middle Miocene to early Pliocene magnetostratigraphic record at Site 1092 and the exceptional Eocene to early Miocene record at Site 1090 will provide important new biomagnetostratigraphic correlations, and may allow orbital tuning of this part of the time scale.
To 177 Summary - Whole-Core, Split-Core, and Downhole Logging Data
To 177 Table of Contents