User:MeanStreets/Geology of County Clare, Ireland

Regional Context

During the Carboniferous, County Clare was one of several interconnected basins. Clare forms part of the ‘The Western Irish Namurian Basin’ (WINB) - laterally linked from Nova Scotia to Belgium (Maynard et al, 1997; Calder, 1998), and similar to the Bude Formations, Cornwall (Higgs, 2004).

Carboniferous

In the Early Carboniferous, sea levels (that had fallen in the Devonian) begin to rise, creating warm, shallow shelf seas around the equator. Flourishing coral and crinoids caused limestone build-up in these low latitudes. The majority of northern County Clare is formed of this Variscan Limestone (See The Burren). Sea levels fluctuated in the Carboniferous, most noticeable in the Mid-Carboniferous as sea levels fell and marine life became extinct. A combination of isostatic and eustatic sea deeping associated with the opening of the Iapetus suture caused deeping.

Research in County Clare

The Western Irish Namurian Basin has been heavily studied in recent years mostly on the southern sections of County Clare. Namurian geology is well exposed along the whole of County Clare’s coast. Martinsen & Collinson (2002, pp 523) comment that the WINB has a “…wider significance [due to its] …close analogy to hydrocarbon-bearing successions offshore Europe, North America and West Africa”. The direction of sediment infill and the basin’s palaeogeography especially the existence or not of a central trough has been hotly debated in a recent paper (see Martinsen & Collinson/Wignall & Best 2002), which compared the models of Collinson et al (1991) and Wignall & Best (2000). Collinson et al (1991) concentrate and expand on the model of Hodson (1954a,b) and Hodson & Lewarne (1961) that refers to a central trough model. They present an argument for a more complicated relationship between delta shifting, downslope transfers of sediment sometimes oblique to strike of the slope and along the axis of the central trough and concentrate on palaeoslope data (slope to the SE). However, Wignall & Best (2000) provided evidence for basin infill that is inferred on their own and previous palaeocurrent data (majority to the NE in all post-Clare Shale sediments), the assumption that northern County Clare was distal to land mass supplying sediment and that a model explaining the deposition needs no central trough aligned along the present-day Shannon Estuary.