Bartonian Working Group Field Meeting

There is a field trip scheduled to visit the sea-cliffs of Dorset, Hampshire and the Isle of Wight to study the Bartonian strata at Barton (unit stratotype), Alum Bay (parastratotype) and Hengistbury Head in October 2015. Eexact dates will be communicated after we complete risk assessments because of requirements of the landowners. The field trip will be attended by Jerry Hooker (leader), Laia Alegret, Jaume Dinarès-Turell, Rick Fluegeman and Simonetta Monechi, members of the Bartonian Working Group. The aim of the visit is to sample for microfossils at the different sites and to carry out pilot sampling for magnetostratigraphy at Barton.

Base Bartonian at the stratotype and the other sites is defined at a bed containing abundant tests of the larger benthic foram Nummulites prestwichianus, which nearly coincides with the first appearance of the dinocyst Rhombodinium draco. Both taxa are important for correlation within the Hampshire Basin, but are problematic for wider correlation. Magnetochrons C18n, 18r and possibly 19n have been recognized in the Barton Clay of Alum Bay, through calibration to calcareous nannoplankton and dinocyst zones, placing base unit Bartonian within Chron C18r. However, there are problems with interpreting the succession and magnetostratigraphy in Alum Bay, probably related to tectonic disturbance. We therefore hope to improve the microfossil correlation and, by sampling at Barton where the strata are gently dipping, test and extend the existing magnetostratigraphy. This will lead the way to ensuring that any GSSP that is subsequently chosen for the Bartonian will not truncate the unit stratotype.