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A new terrane in the Old Red Sandstone of the Dingle Peninsula, SW Ireland

2000; Geological Society of London; Volume: 180; Issue: 1 Linguagem: Inglês

10.1144/gsl.sp.2000.180.01.09

2041-4927

Lorna Kathleen Richmond, Brian P. Williams,

Geological and Geochemical Analysis

Abstract We propose the name Northwest Dingle Domain for the enigmatic Old Red Sandstone terrane whose tectono-sedimentary evolution has perplexed generations of geologists. The Domain remained largely misinterpreted, unappraised or simply disregarded, and its fundamental impact on regional basin dynamics was grossly overlooked. 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 Upper Devonian Carrigduff and Ballyroe Groups. Their fluvial-aeolian, and locally tidal, sedimentation patterns profile Late Caledonian transpression to Mid-Late Devonian extension. The inherent primary structural control on basin location, development, geometry, sedimentary-fill and preservation is manifest in the Northwest Dingle Domain. The Acadian emplacement of the Smerwick Group set the foundations of the Northwest Dingle Domain. The Smerwick Group documents sandy and gravelliferous ephemeral-fluvial and erg-margin aeolian processes on an ancient terminal fan(s). 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.