||Preferred Map Code:
||Aptian Age (KP)
— Albian Age (KA)
|| Mainly sands and sandstones (varying from well-sorted fine-grained to poorly sorted medium- to coarse-grained) with silts and clays in some intervals.
|Definition of Lower Boundary:
|| In southern England, erosional unconformity or disconformity at base of Atherfield Clay Formation: in most of area overlies Wealden Clay Formation, elsewhere Lower Greensand Group oversteps onto Jurassic rocks.
|Definition of Upper Boundary:
|| Base of Gault; specifically in the Wealden area, base of a short interval of condensed facies beds at the base of the silty clays of the Gault above the sands of the Folkestone Formation.
|| c.250m in south-western Weald
|| As described, circum-Weald. Also developed in the Isle of Wight, and less well in Wiltshire to Bedfordshire, Norfolk, Dorset, Lincolnshire and Yorkshire.
Not Applicable (-)
|| Lower Greensand
none recorded or not applicable
||Wealden area: see type sections for component parts: Atherfield Clay Formation, Hythe Formation, Sandgate Formation and Folkestone Formation.
|Rawson, P F. 1992. Cretaceous, 355-388 in Duff, P McL D and Smith, A J (editors), Geology of England and Wales. (London: Geological Society.)
|Casey, R, 1961. The stratigraphical palaeontology of the Lower Greensand. Palaeontology, Vol.3, 487-621.
|1:50K maps on which the lithostratigraphical unit is found, and map code used: