Palynomorph and ostracod biostratigraphy of the Ballagan Formation, Midland Valley of Scotland, and elucidation of intra-Dinantian unconformaties

SUMMARY An interdisciplinary biostratigraphical study of Tournaisian–early Viséan sedimentary rocks from six sections in central Scotland has established the ranges of important palynomorph and ostracod taxa that can be used to refine the existing palynomorph-based biozonation scheme. The work highlights the value of joint ostracod-palynomorph studies in correlating sequences where a single biostratigraphical discipline alone cannot provide the resolution needed. To this end, a new joint palynomorph/ostracod stratigraphical assemblage, the Acanthotriletes cf. macrogaleatus – Sulcella affiliata Assemblage, has been established. This assemblage correlates with the upper part of the CM Biozone and allows the CM–Pu biozonal boundary to be positioned more reliably in the Midland Valley of Scotland (MVS) than previously. The distribution of the assemblage, and the palaeontological characteristics of the Ballagan Formation and stratigraphically higher formations in the Dinantian of the MVS, show that significant but localized hiatuses, correlating with the Pu, TS and TC biozones, occur in parts of the western MVS, while generally smaller hiatuses, correlating with the TS Biozone and possibly part of the Pu Biozone, exist in the east of the MVS and in parts of the Cockburnspath Outlier (Dunbar-Oldhamstocks Basin).