Lithostratigraphy of the Great Estuarine Group (Middle Jurassic), Inner Hebrides

Abstract

Synopsis Revised lithostratigraphical terminology for the Great Estuarine Group in Skye, Raasay, Eigg and Muck is proposed. The group comprises the Cullaidh Shale Formation, Elgol Sandstone Formation with Kildonnan Member and Lonfearn Member, Valtos Sandstone Formation, Duntulm Formation, Kilmaluag Formation and Skudiburgh Formation. The type sections of these formations are defined, new measured sections of 5 of them are illustrated and their lateral variations described. The Group is predominantly Bathonian in age, having its base in the Garantiana Zone (Upper Bajocian) and its top in the Macrocephalus Zone (Lower Callovian). The mainly argillaceous formations show wide lateral continuity indicating that a single depositional basin must have occupied the Inner Hebrides—Minch area during the Bathonian.