Carbon Isotope Stratigraphy Across the Tournaisian–viséan Boundary in Ireland

The Earth System experienced major climatic upheaval during the Early Carboniferous as it transitioned from the Devonian Greenhouse to the Carboniferous–Permian Icehouse. The mode and timing of the onset of the Late Palaeozoic Glaciation remain poorly constrained. Significant organic carbon burial has been suggested as the dominant pCO2-lowering mechanism and subsequent instigator of the cooling. A major ~4–6‰ positive δ13Ccarb excursion has been observed on carbonate archives from North America, Belgium and Russia within the Tournaisian stage (359–347 Ma), recognised as the Tournaisian Carbon Isotope Excursion (TICE). Yet, the reconstruction of carbon cycle evolution across the Mississippian has rarely been attempted on sedimentary organic carbon. Both offshore and onshore Ireland has an extensive Carboniferous sedimentary archive, which is biostratigraphically well constrained, but has been underutilized chemostratigraphically. Here, we present the organic carbon isotope record of two sections from the Dublin Basin (Ireland), the Rush outcrop and the new Grangegorman core, across the Tournaisian–Viséan transition. This study evaluates whether the organic carbon isotope (δ13Corg) record of the Irish Carboniferous is a reliable stratigraphic correlation tool within the Dublin Basin and assesses the regional Tournaisian–Viséan carbon cycle evolution relative to the global Mississippian carbon isotope record.