Magnetostratigraphy of marine sediments from Jane Basin, southeast of the South Orkney microcontinent, Antarctica

O'Brien, Paul Desmond (1989) Magnetostratigraphy of marine sediments from Jane Basin, southeast of the South Orkney microcontinent, Antarctica. University of Southampton, Doctoral Thesis.

Abstract

A detailed magnetostratigraphic study has been undertaken on a sequence of Early Palaeogene and Neogene sediments from an area to the east of the South Orkney Microcontinent, Antarctica. The specimens for this study were obtained from three sites (Site 695, Site 696 and Site 697) drilled during Ocean Drilling Project (ODP) Leg 113 (Weddell Sea), together with a suite of eight piston and gravity cores recovered during Royal Research Ship (R.R.S.) Discovery Cruise 172. Stepwise Alternating Field (A.F.) demagnetization has enabled a detailed magnetostratigraphy for the three ODP sites to be constructed. This magnetostratigraphy, in conjunction with available biostratigraphical controls, has been correlated with the absolute Geomagnetic Polarity Time Scale (GPTS) of Berggren et al., (1985). Gaps in core recovery have resulted in a tentative rather than an unequivocal chron assignment for the three sites. However, a general increase in sedimentation rates from the present day back to Early Pliocene times (Chrons C1N through C3N4) is indicated. The basal section of Site 696 has little useful biostratigraphic control which compounds the problems caused by the lack of core recovery at this Site. A tentative chron assignment of C12 through C16N1 (Late Eocene age) is suggested. These assignments can be used to determine sediment accumulation rate variations which are relevant to assessments of proposed models for the palaeoceanographic history of the Southern Oceans. Detailed magnetostratigraphic studies on the R.R.S. Discovery 172 cores from this area have identified short period excursions in several cores. These excursions have been tentatively identified as the Mono Lake Event and the Blake Event. Correlation of these events leads to a reappraisal of the identification in one core of the Blake Event by Pudsey et al., (1988). Declination measurements of the R.R.S. Discovery specimens indicate that the specimens have been subject to a deformation process during sampling. The inclination directions appear to be relatively unaffected.

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