. "Upward change to darker mudstone of the Kimmeridge Clay Formation; commonly an erosive non-sequence marked by phosphatic pebbles; generally a marked colour change and break of slope at outcrop; change comonly well-marked on borehole geophysical (particularly gamma-ray) logs. Top of unit AmC42 in Fenland (Cox and Gallois, 1979), but incomplete and succeeded unconformably by Cretaceous rocks in the vicinity of the type section."@en . . . . "161.5"^^ . . "Base of mudstones (as described under Lithology), resting on darker more silty mudstone of the West Walton Formation or on limestone/sandstone of that formation's members (Upware Limestone, Elsworth Rock) or of the Corallian Group; generally a marked colour change and break of slope at outcrop; change commonly well-marked on borehole geophysical (particularly gamma-ray) logs. Base of unit AmC1 in Fenland (Cox and Gallois, 1979)."@en . "Ampthill Clay Formation"@en . . "Ampthill Clay [Obsolete: use AMC]"@en . . "Gamlingay Clay [Obsolete: use AMC]"@en . "Mudstone, mainly smooth or slightly silty, pale to medium grey with argillaceous limestone (cementstone) nodules; some rhythmic alternations of dark grey mudstone in the lower part; topmost beds are typically pale grey marls with cementstone."@en . "Tetworth Clay [Obsolete: use AMC]"@en . "Bluntisham Clay [Obsolete: use AMC]"@en . "Corallian [Obsolete: use AMC, WWB]"@en . "0 to c.90m; typically c.25m in Oxon-Bucks., c.10m in the Bedfordshire type section; c.50m in Fenland, c.90m in north Lincolnshire."@en . "West Walton Formation and Ampthill Clay Formation (Undifferentiated)"@en . "154.8"^^ . . . . "stable"@en . . . . "Mudstone with subsidiary calcareous mudstone and limestone. Stratified bedrock. Occurs onshore. Deposited during the Oxfordian Age (Jurassic Period) (161.5-154.8 Ma BP)."@en . . . "Ampthill Clay Formation"@en . "AMC"@en .