Article: The Hampen Marly and White Limestone formations: Florida-type carbonate lagoons in the Jurassic of central England

The Hampen Marly Formation of central England was laid down on a shallow shelf fringing the shore of the London Landmass to the east. Three principal environments can be recognized: (i) a nearshore lagoonal region, dominated by clastic sediments, with faunal and floral evidence of periodic brackish and freshwater influence; (ii) a shallow marine, more offshore region dominated by oyster reefs, where clastic and carbonate sediments intermix; (iii) a deeper, more fully marine area further offshore, where the carbonate sediments and their marine fauna are identical to those of the overlying White Limestone Formation. The White Limestone Formation of the area studied can be divided lithostratigraphically into three members. These are, in ascending order, the Shipton Member, the Ardley Member, and the Bladon Member. Each member represents a shallowing of the sea by sediment accumulation after an initial deepening that was probably under tectonic control. Eight recurrent assemblages of invertebrates, which are strongly correlated with the nature of the substrate, can be recognized. Close similarities exist between these assemblages, and those found today in comparable habitats, such as those in Florida. A picture of the region's palaeogeography and the distribution of the main habitats is built up from the facies analysis. Some ideas on the tectonic control of the sedimentation are put forward.