Abstract

The first geochronological data from the Minister Basin (SW Ireland) contradict the accepted biostratigraphical maximum age (late Givetian-early Frasnian) of the oldest alluvium in the basin depocentre. Magmatic zircons from the Enagh Tuff Bed, a sub-plinian air-fall tuff within fluviatile Old Red Sandstone of NW Iveragh, give a Pb/Pb isotope age of 384.9 ± 0.7 Ma. This confirms Middle Devonian (probably Eifelian) sedimentation and allows possible Early Devonian basin initiation. Associated second-cycle gravels suggest a pre-385 Ma minimum age for the Caherbla Group of the Dingle Basin. Correlation with alluvium containing tetrapod trackways indicates a pre-385 Ma age for the trace maker.

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