The British Geological Survey and the Rijks Geologische Dienst are jointly publishing a series of 1:250.000 maps of amongst others Quaternary sediments of the North Sea along the median line between the British and Dutch sectors. The Early Pleistocene deposits show an upward transition from marine to deltaic and fluviatile sediments. The succession is clearly subdivided by unconformities on seismic profiles, defining the boundaries between the largely seismo-stratigraphic units (formations). Each has characteristic seismic facies. The uncorformities are interpreted as indicating significant periods of non deposition. The sedimentary record from the Middle Pleistocene onwards comprises a number of lithostratigraphic units ranging from marine transgressive sediments to tidal flat deposits, lacustrine clays and various non-marine, including glacial deposits. Also the sediments of the Holocene marine transgression have been subdivided into a few formations each with a characteristic lithology.