The carbon isotope and sequence stratigraphic record of the Sheinwoodian and lower Homerian stages (Silurian) of the Midland Platform, UK
Abstract New high resolution δ 13 C carb isotope data are presented through the Sheinwoodian and lower Homerian stages of the Wenlock Series (Silurian) from sections in Shropshire, Herefordshire and the West Midlands (UK). This data identifies the well-known Early Sheinwoodian positive Carbon Isotope Excursion (ESCIE), the minor mid-ESCIE negative shift, and an Early Homerian positive Carbon Isotope Excursion (EHCIE) in the region of 1.4‰, as developed upon the Midland Platform and in close proximity to the Sheinwoodian and Homerian GSSPs. These carbon isotope excursions have been correlated against graptolite, conodont and chitinozoan frameworks from across the Midland Platform, and alongside details of sedimentology and faunas, have allowed for the establishment of a sequence stratigraphic framework. These integrated data sets reveal that the shallow-water Barr–Buildwas–Woolhope limestones reflect approximately synchronous deposition across the Midland Platform; in that they all contain the ESCIE and five widely traceable depositional cycles. Moreover, biostratigraphic and sequence stratigraphic frameworks from across the Midland Platform (Avalonia) confirm that both the ESCIE and the five cycles are synchronous with records from other palaeocontinents (Baltica and Laurentia) and indicate that the early Sheinwoodian graptolite zones as established in the type area are in need of review.