GSSP for Pliensbachian Stage
Definition:
The Base of the Pliensbachian Stage (lower Jurassic) is defined at the base of Bed 73b at Wine Haven, Robin Hood's Bay, Yorkshire Coast, UK. This level coincides with the ammonite association ofBifericeras donovani andApoderoceras sp., which define the base of thePhricodoceras taylori Subzone of theUptonia jamesoni ammonite Zone. Secondary global markers include a87Sr/86Sr ratio of 0.707425 and a brief reversed-polarity magnetic zone within the uppermost Sinemurian.
Location:
The GSSP section at Wine Haven is located about 3km S-SE of Bay Town in the Robin Hood's Bay, Yorkshire, UK at a latitude of 54°24'25" N and a longitude of 0°29'51" W.
The Sinemurian-Pliensbachian boundary succession lies within the 'Pyritous Shales Member' and comprises pale grey and buff-colored sandy mudstones which pass upwards into silty dark grey shales. The boundary is placed at the base of Bed 73b, 6cm above the mid-line of nodules forming Bed 72.
Primary Markers:
The GSSP is marked by the ammonite association ofBifericeras donovani andApoderoceras sp.. This association also includesGleviceras juv. aff.iridescens.
Secondary Markers:
Strontium Isotopes:
Analysis of belemnites yields a calcite87Sr/86Sr ratio for the boundary level of 0.707425.
Magnetostratigraphy:
The Upper Sinemurian to lowermost Pliensbachian at Wine Haven section has predominantly normal polarity, but two discrete reversed polarity magnetozones are present. One spans much of theaplanatum zone of the latest Sinemurian and terminates < 0.5m below the boundary. The second reversed interval extends from the latestoxynotum subzone probably through the lower part of theraricostatum subzone.
Correlation Events:
Ammonite association ofBifericeras donovani andApoderoceras sp.
Notes on Derivation of Age:
Cycle-scaled linear Sr trend