Ocean Drilling Program (ODP) Leg 183 Site 1140 provided a lower Oligocene to middle Miocene record of diatom assemblages from the northern Kerguelen Plateau. Samples were examined to improve the resolution of shipboard diatom biostratigraphy. The material is complementary to that recovered during ODP Legs 119 and 120, and the diatom zonation of Harwood and Maruyama could be readily applied. A standard succession of biostratigraphic zones from the middle Miocene and lower Oligocene was delineated, although some zones were unrecognizable because of poor core recovery. The detailed diatom biostratigraphy presented here agrees well with shipboard calcareous nannofossil biostratigraphy. Sediment accumulation rates based on diatom bioevents average 1.26 cm/k.y.
The magnetic record of sediments of Sites 1138 and 1140 established by shipboard measurements is extended and corrected. About 600 sediment cubes were stepwise demagnetized with alternating fields to determine their characteristic remanence. For some samples from Site 1138, standard shipboard demagnetization at 20 mT turned out to be insufficient to obtain the characteristic remanence. Selected samples were examined by laboratory-induced magnetization analysis, hysteresis measurements, and thermomagnetic measurements. Titanomagnetites with varying Ti content are the main magnetic minerals in the sediments of Sites 1138 and 1140.
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