Mid-Dinantian brachiopod biofacies from western Ireland

Abstract

Abstract New silicified brachiopod faunas from lower and middle Viséan horizons have been retrieved from the vicinity of Loughs Carra, Corrib and Mask in west Connaught. In addition, carbonate shell beds dominated by Linoprotonia are recorded from mid County Galway. At present over 40 species of brachiopod are known, from current sampling programmes and the literature, variably associated with bryozoan, coral, echinoderm, mollusc and trilobite faunas; microvertebrates such as sharks teeth are locally common. Four main assemblages are recognized; in ascending order, Arundian strata at Ardnasillagh, Lough Carra, Kibeg Wood and Ballintober in a northern belt are variably dominated by Rhipidomella, Schizophoria, Leptagonia, Rugosochonetes, Krotovia, Echinoconchus, Tylothyris, Punctospirifer and Spiriferellina . In addition to genera recorded from Arundian strata elsewhere, Streptorhynchus, Plicochonetes, Dictyoclostus, Pleuropugnoides and ‘ Spirifer ’ also occur in the diverse Kiltiernan fauna assembled last century. In a southern belt, possible Holkerian horizons at Dunsandle are less diverse, with faunas dominated by Composita , whereas limestones of Holkerian-early Asbian age at Kiltullagh Bridge have quite different faunas with Schizophoria, Brochocarina, Minythyra and Cleiothyridina ; these faunas are more similar to the diverse Asbian assemblages described from County Fermanagh in the north of Ireland. In a central belt, in the Bunoghanaun area, Holkerian to early Asbian horizons are dominated by relatively thick shell beds in pure limestones with mainly opportunist large linoproductids; this fauna is not silicified.