Lower Jurassic foraminifera from the Llanbedr (Mochras Farm) Borehole, North Wales, UK

The complete, fully cored Lower Jurassic (Hettangian, Sinemurian, Pliensbachian, Toarcian) succession from the Llanbedr (Mochras Farm) Borehole, North Wales, the thickest known British section, has yielded a diverse and well preserved foraminiferal fauna, comprising 270 species and subspecies which are described and illustrated. An additional nine taxa, not encountered at Mochras, are also described. This typical European Boreal Atlantic foraminiferal fauna is dominated by members of the Lagenida, with the Ceratobuliminoidea, Miliolida, Spirillinina, Involutinina, Buliminida and Textulariida as important accessory groups. The Ceratobuliminoidea and Miliolida are unusually diverse, with Reinholdella and Ophthalmidium being notably abundant. The presence of the family Oberhauserellidae is significant. A benthonic foraminiferal biozonation scheme for the Lower Jurassic, comprising 16 biozones and tied to the standard ammonite-based chronostratigraphy, is described in detail. It is reco...