The Sandgate Formation of the M20 Motorway near Ashford, Kent, and their correlation

Sections in the Lower Greensand showing the top of the Hythe Formation, its junction with the Sandgate Formation of East Kent clay facies, incomplete sections in the Sandgate Formation and its junction with the Folkestone Formation, were exposed at two sites on the Maidstone-Ashford section of the M20 motorway 9–15 km to the NW of Ashford, Kent. At the type locality of the Sandgate Formation, between Sandgate and Folkestone, similar sediments have yielded a Parahoplites nutfieldiensis Subzone fauna in the lower part, with a Nolaniceras nolani Subzone fauna at the top. Ammonites from the upper part of the Sandgate Formation at the M20 exposures, however, are younger still and correspond in age to the basal Hypacanthoplites jacobi Subzone sequence formerly exposed near Sandling Junction, Saltwood. A revision of the latest Aptian ammonite zonal scheme is discussed together with a short commentary on the ammonite family Parahoplitidae.