The stratigraphy of the Chalk Group in Yorkshire and Lincolnshire

The Chalk Group, mainly of Late Cretaceous age, forms the bedrock beneath much of East Yorkshire and Lincolnshire (Figure 1). In the western part of this region, it crops out at the surface to form the downland scenery of the Yorkshire and Lincolnshire Wolds, and spectacular cliffs up to 120 m in height where the Wolds meet the coast between Speeton and Bridlington. Farther south in Yorkshire and Lincolnshire, there are no corresponding chalk cliffs because the Chalk is buried beneath drift deposits. These deposits, mainly Late Pleistocene (Devensian) tills, sands and gravels of glacial origin, and post-glacial (Holocene) coastal and marsh sediments, are typically some 20 to 30 m in thickness along the coast, and locally exceed 50 m. They blanket the eastern and southern part of the region, forming the lowland areas of Holderness and Lincoln Marsh. A former sea-cliff, of pre-Devensian age, can be traced beneath this drift cover some kilometres inshore of the present coast; it meets the modern coast at Sewerby, near Bridlington, and can be recognised on the banks of the Humber at Hessle and Barton (Figure 1). Across the Wash, to the south of the region, the Chalk is present in Norfolk. Again, much of the outcrop is concealed beneath drift, but it emerges to form the coastal cliffs at Hunstanton.