Early Carboniferous (Late Tournaisian-Early Visean) ostracods from the Ballagan Formation, central Scotland, UK

The Ballagan Formation (Late Tournaisian-Early Visean) of central Scotland yields an ostracod fauna of 14 species in ten genera, namely Beyrichiopsis, Cavellina, Glyptolichvinella, Glyptopleura, Knoxiella, Paraparchites, Sansabella, Shemonaella, Silenites and Sulcella. The ostracods, in combination with palynomorphs, are important biostratigraphical indices for correlating the rock sequences, where other means of correlation, especially goniatites, conodonts, foraminifera, brachiopods or corals are absent. Stratigraphical distribution of the ostracods, calibrated with well-established palynomorph biozones, identifies three informally defined intervals: a sub-CM palynomorph Biozone interval with poor ostracod assemblages including Shemonaella scotoburdigalensis; a succeeding interval within the CM palynomorph Biozone where Cavellina coela, Cavellina incurvescens, Sansabella amplectans and the new species Knoxiella monarchella and Paraparehites discus first appear; and, an upper interval, in the upper CM Biozone, marked by the appearance of Sulcella affilata. At least locally in central Scotland, S. affiliata permits a level of resolution equivalent to a sub-zonal upper division of the CM Biozone. The fauna, flora, sedimentology and stable isotope composition (delta C-13 and delta O-18) of carbonate minerals in the Ballagan Formation suggest the ostracods inhabited brackish, hypersaline and ephemeral aquatic ecologies in a coastal floodplain setting.