The significance of Tournaisian tectonism in the Dublin basin: Implications for basin evolution and zinc-lead mineralization in the Irish Midlands

Recently acquired seismic reflection data, combined with detailed subsurface stratigraphic analysis (core analysis and gamma ray logs) reveal a new view of Lower Carboniferous stratigraphy and tectonism in Ireland. Seismic stratigraphic relationships and stratal thickness variations within Tournaisian units indicates that the Ballinalack High (and associated faulting) was produced by tectonism during the mid to late Tournaisian (Moathill Event, similar to 348 Ma). A second major tectonic event, dominated by regional subsidence (rather than faulting), occurred during the Lower Visean (Tober Colleen Event, similar to 345 Ma). Each of these tectonic events was associated with major subsidence in the basin, producing strong transgressions within the stratigraphy. We suggest that the Late Tournaisian Moathill Event was responsible for producing the structural setting of the Ballinalack and other Zn-Pb deposits in the Irish Midlands. The suggested earlier timing of fault movement in the basin has implications for arguments about the origin of Irish-type Zn-Pb deposits and the necessity (or not) for having active faulting during mineralization. (C) 2015 Elsevier B.V. All rights reserved.