T378 Insights from Microfossils, from Traditional to Novel Approaches (Posters)

Wednesday, 25 October 2017
9:00 AM - 6:30 PM
Halls 4EF

REASSESSING THE BARTONIAN UNIT STRATOTYPES: AN INTEGRATED APPROACH

Paper number: T378-4
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Global boundary Stratotype Section and Point (GSSP) for the base of the Bartonian, currently remains undefined. The Bartonian unit stratotype is located at the Barton coastal section in the Hampshire Basin, on the South Coast of the UK. However the bases of the chronostratigraphic and lithostratigraphic units do not coincide. The parastratotype section is located at Alum Bay, 7 km away, on the Isle of Wight. Despite a number of studies carried out in 1970s and ‘80s on both sections, global correlation remains problematic.

The base of the Bartonian Stage in the type area is defined by the Nummulites prestwichianus bed, which provides a locally distinctive level, however is not widely correlatable outside of the Hampshire basin. Only a single, long-ranged, planktonic foraminifera has been identified, Dipsidripella danvillensis, and so correlation of this bed with planktonic foraminiferal biostratigraphy has not been possible. The dinoflagellates do show a taxonomic turnover with Rhombodinium draco occurring a few centemeters above the level of the N. prestwichianus bed at several localities in the Hampshire basin, however, this is not consistant outside of this region. Calcareous nannofossils from the site were relatively impoverished, with NP zones being largely recognized by secondary markers. However, Aubry (1983, 1986) recognized Reticulofenestra umbilica, which is a primary marker within the CP zonation, and suggests further correlation potential for calcareous nannoplankton. Palaeomagnetic studies have also been carried out at the Alum bay section; Dawber et al., (2011) identified C18n with the NP16-17 boundary and the Nummulites prestwichianus bed as being within the underlying reversed interval, but there are problems with their interpretation with the nannofossil record.Improvement in the stratigraphy is essential to better define this interval and provide a globally useful datum. In order to resolve this issue, we present a new assessment of the Alum Bay section using integrated smaller and larger benthic foraminiferal, dinoflagellate and nannofossil stratigraphy.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-305810

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