Lower Carboniferous ostracods from the Ballagan Formation, Midland Valley, Scotland: analysis of the Spilmersford Borehole; improved analysis of the Glenrothes Borehole; and a review of stratigraphical and palaeoecological ostracod data from key sections

This report details ostracod distribution in the Ballagan Formation (Lower Carboniferous) of the Spilmersford Borehole [NGR NT 4570 6902], provides an improved biostratigraphical and biofacies analysis of the Glenrothes Borehole [NGR NO 25615 03142] ostracod faunas and summarises knowledge about ostracod biofacies and biostratigraphy in the Lower Carboniferous of the Midland Valley. A summary ostracod biostratigraphical range chart for the Ballagan Formation is presented, calibrating the total ranges of key individual species with the palynomorph biozones. Several species emerge as potential proxies for the palynomorph biozones: Shemonaella cf. scotoburdigalensis may indicate the PC Biozone; the widespread Cavellina coela and C. incurvescens indicate the CM Biozone; and Sulcella cf. afiliata indicates the uppermost CM Biozone and succeeding Pu Biozone. In terms of palaeoecology, the ostracod assemblages suggest as many as four recurrent biofacies for the Ballagan Formation, indicative of quasimarine, brackish and freshwater habitats. The Ballagan Formation may yield some of the earliest freshwater ostracods.