The provenance of the Mississipian Ballyvergin Shale an integrated palynological and lithostratigraphic investigation

Abstract

The Ballyvergin Shale Formation (BSF) is a unique and enigmatic formation within the Irish Toumaisian lithostratigraphy. While a definite provenance for the formation has not been identified speculation of a north, north-west origin has been proven using a variety of analytical techniques. Analysis of core has shown a general coarsening up sequence with the coarsest silts seen in localities to the north, north-west. Spore and organic particle, abundance and size have shown that the coarsest material is seen to the north, north-west and decreases to the south. Geochemical discriminant analyses have shown that the BSF has a different provenance to underlying and overlying formations. BSF sediment is derived from a quartzose sedimentary and felsic igneous provenance and the original sediment was in part derived from oceanic arc material. Underlying and overlying formations are derived fi'om felsic and intermediate igneous provinces and the original sediment was derived from passive to active continental margin material. Palynological analysis is in agreement with previous research that the BSF belongs to the mid-Toumaisian, Spelaeotriletes pretiosus - Raistrickia clavata (PC) Biozone. Climate change is not considered a factor in BSF deposition owing to the continuation of spore assemblages, through the BSF without major change. The reworked acritarchs are restricted mainly to the Ordovician and Silurian. The occurrence of acritarch species commonly restricted to the Devonian is discussed.