A new ammonite from the Penarth Group, South Wales and the base of the Jurassic System in SW Britain

Two ammonites have been found in porcelaneous limestones of the White Lias Formation traditionally considered to be of Rhaetian (Late Triassic) age at Lavernock Point, south Wales (ST 181 681). These ammonites, named here Neophyllites lavernockensis. sp. nov, are the earliest recorded from the UK. This horizon is located directly above a major negative δ 13 C isotope anomaly (CIE1) in the Upper Cotham Member that marks the top of the Triassic System and below another negative δ 13 C isotope anomaly (CIE3). Both correlate with negative δ 13 C isotope anomalies in the Triassic–Jurassic global boundary stratotype section and point (GSSP) at Kuhjoch, Austria. This establishes the base of the tilmanni Chronozone, Hettangian Stage and Jurassic System in SW Britain within the White Lias Formation at Lavernock Point.