Lithostratigraphic units: The Sinemurian-Pliensbachian boundary succession lies within the Pyritous Shale Member of the Redcar Mudstone Formation and comprises pale grey and buff-coloured sandy mudstones, which pass upwards into silty dark grey shales.
Locality: The GSSP section at Wine Haven is located about 3 km SSE of the town of Robin Hood's Bay, Yorkshire, at a location 54°24'25" N and a longitude of 0°29'51" W. National Grid reference: NZ 9762 0230.
Lithology and sequence stratigraphy
The Sinemurian–Pliensbachian boundary at Wine Haven lies within a succession that generally progresses upwards from relatively pale and thoroughly bioturbated sandy mudstone into dark shales, with this change taking place over ~20 m. Superimposed on this change are smaller-scale (0.5–5m) alternations of coarser and finer sediment.
The lithologies of the Raricostatum and Jamesoni zones are fairly uniform, with ammonites in almost every bed and the upward transition from pale grey to dark grey shale is gradational. In the field, two of the most noticeable features of this interval are the 10-cm-thick beds of concretionary siderite (e.g. in bed 72). Above the upper concretionary level, macrofossils are abundant, and are concentrated into several discrete shell-beds. The whole succession was deposited in a shallow-marine environment, but the succession from the upper part of the Sinemurian (Aplanatum Subzone) to the lower part of the Pliensbachian (Taylori Subzone) represents a long-term relative sea-level rise of at least regional extent, possibly global.
The GSSP level is primarily correlated by the first occurrence of the ammonite association of Bifericeras donovani and Apoderoceras sp. and associated also with Gleviceras juv. aff. iridescens. This level defines the base of the Phricodoceras taylori Subzone of the Uptonia jamesoni Zone. This boundary is placed at the base of Bed 73b, 6 cm above the mid-line of nodules forming Bed 72 in the section.
Biostratigraphy
Across the boundary the following ammonite intervals can be defined:
UPPER SINEMURIAN
Upper Raricostatum Zone
1) Aplanatum Subzone (4,60 m, levels 69 to 73a) is characterized by the Paltechioceras gr. aplanatum -tardecrescens and allied species. Two horizons are recognized in the subzone.
1a) P. aureolum horizon (level 69 partim): Paltechioceras aureolum, Eoderoceras gr. armatum-miles.
1b) P. tardecrescens horizon (level 69 partim – 71 partim): Paltechioceras tardecrescens, Paltechioceras aff. romanicum, Eoderoceras gr. armatum, Leptonotoceras sp., Gleviceras sp.
2) The last Gleviceras sp. and Eoderoceras gr. armatum are recorded from the upper part of bed 71.
LOWER PLIENSBACHIAN
Lower Jamesoni Zone
3) Taylori Subzone: (partim, more than 5 m, levels 73b to 76). Two horizons are recognized:
3a) B. donovani horizon (level 73b): Bifericeras donovani, Apoderoceras sp. juv., Gleviceras juv. aff. iridescens
3b) A. gr. aculeatum horizon (level 74 to 76): Apoderoceras gr. aculeatum, Apoderoceras sp. juv., Phricodoceras gr. Taylori, Leptonotoceras sp., Eoderoceratidae sp. juv.
This lower fossil assemblage overlies the last Upper Sinemurian Echioceratidae and precedes the first classic Lower Pliensbachian Apoderoceras and Phricodocerastaylori zones.
Bivalves, foraminiferans, ostracods, dinoflagellates and pollen and spores do not provide much in the way of additional level of detail for the boundary. Dinoflagellates appear to provide the best potential with the range top of Liasidium variabile in the Late Sinemurian Oxynotum Zone as a useful reliable stratigraphical marker.
Isotope stratigraphy
A good secondary global marker includes strontium isotopes with a 87Sr/86Sr ratio of 0. 707425 at the boundary. Oxygen isotope data (δ18O) from belemnites show a marked rise of about 1 per mil over the 10 m interval sampled in detail, equivalent to a water temperature drop of about 5 ºC, which is likely of local significance only (Korte & Hesselbo, 2011).
Recent more extensive stable carbon isotope data suggest a major negative excursion of ~2‰ at the Sinemurian–Pliensbachian boundary. This Sinemurian–Pliensbachian boundary event is similar to the slightly younger Toarcian Oceanic Anoxic Event and is characterized by deposition of relatively deep-water organic-rich shale.
Osmium isotope data become increasing unradiogenic (0.40 to 0.20) across the Sinemurian–Pliensbachian boundary, suggesting evidence for a continual flux of unradiogenic Os into the oceans during the latest Sinemurian, possibly associated with the formation of the ‘Hispanic Corridor’ during the breakup of Pangaea (Porter et al., 2013).
Magnetostratigraphy
A preliminary magnetostratigraphy, based on fairly wide sample spacing indicates termination of a reverse magnetozone < 0.5m below the Sinemurian–Pliensbachian boundary (probably the reverse couplet of Si-Pl-N magnetochron). This reversal pattern allows some global correlation to other datasets, and has potential to be refined further.
Text and figures taken from Meister et al. (2006), Korte & Hesselbo (2011) & Porter et al. (2013)
(MWH,DATH, SPH)
Meister, C., Aberhan, M., Blau, J., Dommergues, J. L., Feist-Burkhardt, S., Hailwood, E. A., Hart, M., Hesselbo, S.P., Hounslow, M.W. Hylton, M. , Morton, N., Page, K., & Price, G.D. (2006). The Global Boundary Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (Lower Jurassic), Wine Haven, Yorkshire, UK. Episodes, 29, 93.
Korte, C. & Hesselbo, S. P. (2011). Shallow marine carbon and oxygen isotope and elemental records indicate icehouse‐greenhouse cycles during the Early Jurassic. Paleoceanography and Paleoclimatology, 26, doi:10.1029/2011PA002160.
Porter, S. J., Selby, D., Suzuki, K. & Gröcke, D. (2013). Opening of a trans-Pangaean marine corridor during the Early Jurassic: Insights from osmium isotopes across the Sinemurian–Pliensbachian GSSP, Robin Hood's Bay, UK. Palaeogeography, Palaeoclimatology, Palaeoecology, 375, 50-58.