Calcareous microplankton and polarity reversal stratigraphies of the upper Eocene browns creek clay in the Otway Basin, southeast Australia: Matching the evidence

We attempt to correlate the Browns Creek Clay type section—one of the most important Palaeogene marine reference sections in southern Australia—with the geomagnetic polarity time scale. The correlation depends on the choice of bioevent ties between the Browns Creek Clay and other sections with well‐defined polarity reversals at similar mid to high southern latitudes. Of the various possible ties, we discuss two that best fit the available evidence, nominating our preference. The first correlation is a one‐to‐one match of reversals between the Browns Creek Clay record and the Geomagnetic Polarity Time Scale interval Chron 18n.1 to Chron 16n.2. This is achieved via the Weddell Sea record (ODP Leg 133 Site 689), using as the baseline tie the disappearance event of the foraminiferid Acarinina collactea. Inherent in this correlation are misfits with other more reliable bioevents and the utilisation of two short normal polarity events in the Browns Creek record, each based on a single stratigraphic sampling lev...