Spatial variation in provenance signal: identifying complex sand sourcing within a Carboniferous basin using multiproxy provenance analysis.

Multiple factors (e.g. source rock composition, climate, nature/scale of sedimentary system) influence the volume and composition of sediment delivered to basins. Fluctuations in these parameters produce cryptic source signals which can vary within the same sedimentary system. Bespoke multi-proxy provenance approaches, targeted at minerals of variable stability, allow for an assessment of natural biasing (recycling) and intra-basinal spatial variations. Provenance of fluvial/deltaic sandstones (Mullaghmore Sandstone Formation) in the NW Carboniferous Basin, Ireland, has been constrained using zircon and apatite U–Pb geochronology, trace elements in apatite and Pb-in-K-feldspar analysis. Zircon U–Pb grain populations are consistent with feldspar data, suggesting Proterozoic basement highs offshore Ireland and Scotland were the main contributor with minor supply from Archean-Palaeoproterozoic rocks of Greenland/NW Scotland and Caledonian-aged rocks. However, apatite data shows a much larger proportion of Caledonian-aged grains of metamorphic origin, suggesting significant sediment was recycled from Neopropterozoic metasedimentary rocks. The spatial variation in provenance indicates that, at onset of clastic input, sediment was being routed to the basin through a complex drainage system, comprising of several discrete hinterland catchments, rather than supply from a single, large interconnected sedimentary system. Such complexities can only be identified with the careful application of a bespoke multi-proxy provenance approach.