The Cretaceous sequence begins with the Wealden Group limestones, mudstones, sandstones and siltstones which occur from Gibraltar Point in a band which narrows northwestwards to the Caistor area. To their east, and stratigraphically above them, are the sandstones of the Lower Greensand Group and beyond them the Chalk which gives rise to the Lincolnshire Wolds and extends to the North Sea coast but is obscured along the coastal margin.