A reassessment of the Southern Ocean biochronology. Geological Society Memoir No. 18 Book uri icon

abstract

  • Numerous biochronological models have been developed for the Southern Ocean based on coring results from the various Deep Sea Drilling Project and Ocean Drilling Program expeditions to this region. These models are based on combining micropalaeontological datums, including the first and last occurrences of individual species with the record of magnetic polarity reversals. Previous biostratigraphical age models represent an amalgamation of cruise-specific micropalaeontological datums derived from specific geographical sectors of the Southern Ocean and from other ocean basins. In the development of these models previous workers were constrained by limited sedimentary sequences containing an integrated biostratigraphical (siliceous and calcareous microfossils) and magnetostratigraphical events. The results presented here integrate data sets generated through previous studies into a Southern ocean-wide perspective. The biostratigraphical (diatoms, radiolarians, and calcareous nannofossils) and magnetostratigraphical data sets are reviewed, integrated, calibrated, and reinterpreted to the Geopolarity Timescale of Cande and Kent (1995) providing a comprehensive Southern Ocean data base. In doing so, this study identifies inconsistent chronostratigraphical ranges of many previously used biostratigraphical markers thereby questioning the usefulness of these events within the Southern Ocean. The reassessment of previous data sets results in the recognition of 13 primary events which are chronostratigraphically useful throughout the Southern Ocean for the Late Eocene to Recent. Twenty additional events are identified as potentially stratigraphically useful; however further refinement of their spatial and/or temporal distribution is required. The limited number of primary events suggests that the biostratigraphy in the Southern Ocean is less sophisticated than currently assumed. The integrated approach applied in this study provides a reassessment of the stratigraphy previously established for the 18 holes re-examined. The revised stratigraphy indicates typically more complete sequences compared to previous interpretations.

author list (cited authors)

  • Ramsay, A., & Baldauf, J. G

complete list of authors

  • Ramsay, ATS||Baldauf, JG

publication date

  • January 1999