Ammonites and belemnites from the Early Cretaceous Claxby Ironstone formation of Nettleton Hill

John P Green (UK) The Early Cretaceous succession in Lincolnshire consists of a series of shallow water marine sandstones, ironstones, clays and limestones, not unlike those deposited elsewhere in the UK during early Jurassic times. In the north of the county, at Nettleton Hill, near the village of Nettleton, minor exposures of the Claxby Ironstone Formation are present. Fig. 1. Nettleton Hill, showing former site of workings for Spilsby Sandstone and the overlying Claxby Ironstone, now restored. This deposit, approximately 5.7m thick, rests unconformably on the eroded Late Jurassic Spilsby Sandstone Formation of Volgian age. The age of the ironstone ranges from the Lower Valanginian to the Lower Hauterivian stage, and is of particular interest due to the ammonite and belemnite faunas it contains. My studies over a number of years have brought to light a series of cephalopod faunas that are also prevalent in Speeton, East Yorkshire, as well as northern and southern Europe. Prominent contributors to the study of the cephalopod faunas of this formation include Lamplugh (1918), Swinnerton (1935), Casey (1973), Wright (1975) and Kemper et al (1981). The ironstone is divided into two members: the Lower and Upper Claxby Ironstone Formations. Both these formations are characterised by a brown to purple clay matrix, rich in prominent iron ooliths, and which is highly fossiliferous. Excellent exposures were formerly present in opencast and deep mines around Nettleton (TF 1140 9868, TF 1164 9870). However, these sections are now unfortunately filled in. The current exposures at Nettleton Hill, while … Read More