Chitinozoan biostratigraphy of the regional Arenig Series in Wales and correlation with the global Lower–Middle Ordovician series and stages

Abstract The Arenig Fawr area of North Wales constitutes the type for British Lower to Middle Ordovician Series and is complemented by sections in Carmarthen Whitland areas South Wales. We describe chitinozoan assemblages from both order aid correlation its region with global series stages. Chitinozoans recorded provide permissive rather than conclusive evidence but suggest that Henllan Ash Member correlates upper Floian Stage Slice Fl3 or lower Dapingian Dp1. Better results were obtained where six are distinguished, ranging age late Tremadocian middle Darriwilian (early Llanvirn). Most species known China, Gondwana and/or Baltica there controls on ranges. They show much (Moridunian) succession (Fl3). Correlatives (Fl1, Fl2), if present, must be represented Ogof Hên Formation lowest Formation. Chitinozoan (Fennian Stage) more readily correlated Gondwanan biozones indicate Fennian (Dw1) Whitlandian constrained an interval uppermost basal Stage, resulting inferred increased rate sediment accumulation.