Late Ordovician deep-water brachiopod fauna from Raheen, Waterford Harbour, Ireland.

Abstract

The Raheen Formation at Newtown Head in Waterford Harbour is a small isolated section of Ordovician rocks, dominated by volcanics of the Duncannon Group, but with interbedded fossiliferous shales. Although a brachiopod and trilobite dominated fauna has been known since the mid-nineteenth century, only the trilobites and cystoids have been assessed in modern terms. This paper describes the brachiopod fauna for the first time. The assemblage from Raheen is overwhelmingly dominated by the dalmanelloid Onniella, with the small plectambonitoid Sericoidea comprising the second most numerous species; both are represented by new species. This revision has also identified a wide range of other genera, but all in very small numbers. These include an obolid, a paterulid, Paracraniops and Orthisocrania divaricata (M'Coy) amongst the non-articulated brachiopods. Articulated genera present include the orthoids Nicolella, Ptychopleurella, Sulevorthis, Skenidioides and the plectambonitoid Leptestiina. Very rare forms include Idiospira? and Palaeostrophomena, together with possibly Biscuspina and Sowerbyella. The brachiopod revision supports the late Caradoc (early Katian) age indicated by the trilobite fauna. The trilobite fauna generally indicates a probable deeper-water environment and the brachiopod assemblage confirms an outer-shelf environment. Although elements of the assemblage indicate affinity with the well-defined Late Ordovician Foliomena fauna, it probably occupied a more shoreward position.