The Lower Lias of Robin Hood's Bay, Yorkshire, and the work of Leslie Bairstow

Abstract

Introduction 82Leslie Bairstow 82Biography 82Bairstow's unpublished work 84Geological maps 84Geological structure of Robin Hood's Bay 93Stratigraphical succession 93Bed numbers 95Detailed succession in Robin Hood's Bay 96Lithostratigraphy 111Staithes Sandstone Formation 111Redcar Mudstone Formation 111Exposures in Robin Hood's Bay now 114Correlation with previous descriptions 114Bairstow's ammonite collection 115Systematic description of the ammonites and nautiloids 118Family Juraphyllitidae 118Family Lytoceratidae 118Family Psiloceratidae 119Family Schlotheimidae 119Family Arietitidae 119Subfamily Arietitinae 119Subfamily Agassiceratinae 123Subfamily Asteroceratinae 123Family Echioceratidae 125Family Oxynoticeratidae 129Family Cymbitidae 132Family Eoderoceratidae 132Family Coeloceratidae 136Family Phricodoceratidae 137Family Polymorphitidae 137Family Liparoceratidae 141Family Nautilidae 144Biostratigraphy 144Acknowledgements 150References 150Rocks of Lower Liassic (Sinemurian and Lower Pliensbachian) age exposed in Robin Hood's Bay, near Whitby, north Yorkshire, are described from the mapping, stratigraphical descriptions and ammonite collections made by Mr Leslie Bairstow in the years 1927–1970, and preserved in the Palaeontology Department, The Natural History Museum, London. His large-scale map of the geology of the foreshore is published on five sheets at a scale of approximately 1:5000. The stratigraphical sequence from bed 418 at the base up to bed 600.5 at the top of the Lower Pliensbachian is 163.74 m thick, and consists of the Redcar Mudstone Formation, for which four members are formally defined – the Calcareous Shale (at the base), Siliceous Shale, Pyritous Shale and Ironstone Shale Members – overlain by the lower part of the Staithes Sandstone Formation. The lowest beds exposed by the lowest spring tides are Sauzeanum Subzone, Semicostatum Zone, in age; ammonites occur in all subzones, and the only uncertain boundary is that between the Masseanum and Valdani Subzones (Ibex Zone), where there are few characteristic ammonites. Bairstow's ammonite collection consists of more than 2360 specimens, all from recorded horizons, and is notably rich in Promicroceras, Asteroceras, Eparietites and Oxynoticeras from the Obtusum and Oxynotum Zones, Echioceratids, Eoderoceras and Apoderoceras from the Oxynotum, Raricostatum and Jamesoni Zones, and Liparoceratids from the Davoei Zone, making it a primary source for Sinemurian and Lower Pliensbachian ammonite biostratigraphy. The recently proposed selection of Wine Haven at the south-eastern end of the bay as the Global Stratotype Section and Point (GSSP) for the base of the Pliensbachian Stage (ie. the world standard definition), is supported by the sequence of ammonites across the Sinemurian/Pliensbachian boundary. All previously figured ammonites from Robin Hood's Bay are listed in a systematic section that includes the evidence on which the ammonite identifications in the paper are based, and 56 of the best preserved ammonites are figured. Eparietites bairstowi sp. nov. is proposed for an early species of Eparietites and a Sowerby Collection ammonite from the Aplanatum Subzone, Raricostatum Zone, in the bay, is designated neotype of Eoderoceras armatum (J. Sowerby).