RT Journal Article T1 A potential global chronostratigraphic boundary for the base of the middle Viséan A1 Cózar Maldonado, Pedro A1 Somerville, Ian D. A1 Hounslow, Mark W. AB High-resolution foraminiferal biostratigraphy of carbonates immediately below and near the base of the Holkerian Substage in three sections of the South Cumbria Shelf allows the recognition of the Cf5α and Cf5β subzones. The most complete section at Grubbins Wood is almost free of dolomitisation. At the White Scar Quarry and Barker Scar sections, minor faunal gaps are inferred at the base of one or both subzones, respectively. The Grubbins Wood section has the most limited exposure, whereas White Scar Quarry has extensive exposure of this interval, especially the basal horizons of the subzones, compared to Barker Scar. The Grubbins Wood section, because of its exceptional foraminiferal record is more suitable for the establishment of a coincident boundary stratotype for the mid Viséan and Holkerian boundary at the base of the Cf5β subzone. However, the Barker Scar section should be retained as the Holkerian unit stratotype for Britain, with the base of the Holkerian repositioned lower in the section, at the base of the Cf5β subzone. White Scar is a suitable unit-parastratotype, filling data gaps due to possible faunal gaps and dolomitisation at Barker Scar. The rich foraminiferal assemblages allow good global correlation with other regional zonations, which if refined in other countries, would allow a more affirmative global chronostratigraphic basal boundary for the middle Viséan. PB Schweizerbart SN 0078-0421, ESSN: 2363-6122 YR 2023 FD 2023 LK https://hdl.handle.net/20.500.14352/73080 UL https://hdl.handle.net/20.500.14352/73080 LA eng NO NERC DS Docta Complutense RD 13 abr 2025