Palynological evidence for an early Namurian age of the Cornbrook Sandstone Formation, Clee Hill, Shropshire

Abstract

SUMMARY The formational name Cornbrook Sandstone has been applied to a variable succession of conglomerates and coarse-grained sandstones, with thin mudstone and coal intercalations, which occurs between the Carboniferous Limestone (Dinantian) and Coal Measures (Westphalian) in the Clee Hills area of Shropshire. Previous biostratigraphical investigations have proved inconclusive, suggested ages ranging from Tournaisian to Westphalian B. Palynological investigations on material from surface exposures and from three cored shallow boreholes, which penetrated most of the Cornbrook Sandstone sequence together with part of the underlying Carboniferous Limestone, provide new evidence for the age of the formation. Well preserved miospore assemblages indicate an early Namurian (Pendleian-Arnsbergian) age. The palynological evidence suggests that the base of the Cornbrook Sandstone is younger than the base of the Drybrook Sandstone of Gloucestershire, which exhibits broad similarities in tectonic and depositional settings. The two sandstones may, therefore, represent unrelated sand bodies, located north and south of St George’s Land. Alternatively, if they represent remnants of a more extensive deposit, its base may have been diachronous, becoming younger to the north.