Biostratigraphical dating of the Ingleton Group, northern England

Palynological slides from rocks assigned to the Ingleton Group in the Beckermonds Scar Borehole and from the Ingleton Group at outcrop have been examined in an attempt to replicate the Arenig date assigned to the borehole section. No microfossils have been seen in slides from borehole samples, apart from those originally used to date the section in 1982, from a sample at 396.20 m. However, acritarchs have been observed in slides from three outcrop samples, one from the vicinity of Thornton Force and the other two from the River Doe section above Ingleton. The acritarchs are similar in preservation to those from the borehole. Most specimens recorded are simple acanthomorph acritarchs that are not especially diagnostic of age, but two specimens of Veryhachium trispinosum were recorded from one of the samples from the River Doe. The species has its first appearance in the latest Tremadoc (Early Ordovician) and is also present in the Beckermonds Scar assemblage. The acritarchs provide the first biostratigraphical evidence for the age of the Ingleton Group at outcrop, and strengthen the case for the Beckermonds Scar specimens being in situ. Together, the outcrop and borehole material provide consistent evidence that the Ingleton Group is no older than Early Ordovician.