Fluvial-Aeolian interactions and Old Red Sandstone basin evolution, Northwest Dingle Peninsula, County Kerry, southwest Ireland
The tectono-sedimentary evolution of the enigmatic Old Red Sandstone terrane of the Northwest Dingle Domain perplexed generations of geologists. The Domain remained largely misinterpreted, unappraised or simply disregarded. Its fundamental impact on regional basin dynamics was grossly overlooked. This integrated sedimentological, stratigraphical and structural research unravels the complexities of this unique red-bed collage. The Northwest Dingle Domain is largely structurally-constrained between two ENE-trending Caledonian structures: the North Kerry Lineament and the Fohernamanagh Fault. It comprises four unconformity-bounded Groups: the Lower Devonian Smerwick Group; the Middle Devonian Pointagare Group; and the Late Devonian Carrigduff and Ballyroe Groups. Their fluvial-aeolian, and locally tidal, sedimentation patterns profile Late Caledonian transpression to Middle-Late Devonian extension. The inherent primary structural control on basin location, development, geometry, sedimentary-fill and preservation is manifest in the Northwest Domain. A hierarchical cyclicity to fluvial-aeolian basin-fill architecture is established in order to differentiate between climatic, tectonic and eustatically-controlled 'sequence stratigraphy' in active strike-slip and extensional syn-rift basin settings. The Acadian emplacement of the Smerwick Group Terrane set the foundations of the Northwest Dingle Domain. The Smerwick Group documents sandy and gravelliferous ephermeral-fluvial and erg-margin aeolian processes on an ancient terminal fan. The Pointagare Group is cogenetic with the Caherbla Group of south Dingle. Together they record the renewed influx of coarse-grained sediment in the form of transverse alluvial fans and axial braidplains in response to increased tectonism followed by overstep of an erg complex. The Pointagare-Caherbla basin model highlights the fundamental structural control on basin topography, palaeodrainage patterns, provenance, palaeowind directions and sedimentation style in tectonically-active extensional basins. The Ballyroe and Carrigduff Groups record syn-rift basin-margin fluvial and precursive tidally-influenced sedimentation on the active northern margin of the Munster Basin half-graben.