PRELIMINARY ASSESSMENT OF STRUCTURAL CONTROLS ON THE SPATIAL RELATIONSHIPS AMONG FLUVIAL SYSTEMS IN THE CARBONIFEROUS WESTERN IRISH NAMURIAN BASIN, COUNTY CLARE, IRELAND

The preliminary results of geologic mapping of exposures of the Carboniferous Western Irish Namurian Basin (WINB; 310-316 Ma) along the Loop Head Peninsula are used to resolve the spatiotemporal relationships among marine to fluvial sedimentary successions in a series of world-class cyclothem deposits. WINB cyclothem sequences are easily correlatable at the kilometer scale in coastal exposures and record environments of deposition ranging from prodelta to amalgamated fluvial channel deposits. However, the spatiotemporal relationships among these deposits are obscured by fold-thrust belt related deformation associated with the Variscan (Hercynian) orogeny and rift-related deformation associated with the breakup of Pangea. Our analysis has developed a detailed evaluation of the interconnectedness of the sedimentary deposits and the physical processes that shaped the internal stratigraphy of the cyclothem deposits in the WINB by accounting for the nature and magnitude of the tectonic deformation affecting these strata.

Reconnaissance geologic mapping on 1:2500 and 1:5000 scales of coastal exposures between Loop Head Lighthouse to Fisher Street was used to identify three key study areas (listed from south to north): Trusklieve, Doonbeg-Killard, and Liscannor-Lahinch. Mapping provides a basis for constructing geologically admissible structural cross sections which are used to interpret the original spatial configuration of the sedimentary environments. A pre-deformational framework will provide a new perspective on the stratigraphic spatial variability in the WINB, including the size and distribution of fluvial-deltaic distributary channels within the Tullig and Kilkee Cyclothems. Channel characteristics (e.g. channel height and width, grain size, etc.) will be used to calculate avulsion nodal points, constrain the physical processes that shaped the sedimentology of the fluvial dispersal system, and evaluate the spatiotemporal variability between the cyclothems.