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The Upper Greensand Formation is a Cretaceous formation of Albian to Cenomanian in age, found within the Wessex Basin and parts of the Weald Basin in southern England. [1] It overlies the Gault Clay and underlies the Chalk Group. It varies in thickness from zero to 75 m. It is predominantly a glauconitic fine-grained sandstone, locally becoming ...
This sandy bank has been exposed by the River Wey as it cuts through the Upper Greensand stratum (mid Cretaceous) near Shalford. During the Early Cretaceous epoch (from about 145 to about 100 million years ago) Surrey alternated between a fresh-to-brackish water embayment depositing Hastings Beds and Weald Clay, comprising shales and mudstones that are often finely banded.
Chalk is an important aquifer and continues to provide the larger part of West Sussex's water supply. Sandstone for use as a building stone has been worked in the Upper Greensand, Hythe and Weald Clay formations. In the Weald, the Horsham Stone, Cuckfield Stone and Ardingly Sandstone have all been quarried for building purposes.
The formation is lithologically similar to the Ashdown Formation and comprises complex cyclic sequences of siltstones with sandstones and clays, typically fining upwards. In the western parts of the county the Tunbridge Wells Sands can be divided into three; the Lower Tunbridge Wells Sand, the Grinstead Clay, and the Upper Tunbridge Wells Sand.
the Vale of Holmesdale formed from Gault Clay overlaid in the north with the upper layer greensand; the Greensand Ridge, formed from the lower layer of greensand, containing the source of the River Medway and its tributaries; the Low Weald, a Weald Clay valley; the sandstone High Weald. [3] [4] [5]
Overlying the Lower Greensand are the two formations which comprise the Selborne Group; the Albian age Gault Formation and the Upper Greensand Formation which extends from the Albian into the Cenomanian (c.100.5-94 Ma) thereby straddling the boundary with the Late Cretaceous epoch.
This water is also responsible for the many landslips throughout Dorset's history from the prehistoric to modern times. [52] Above the Gault is the Upper Greensand, which varies from the golden sands that crown the West Dorset heights, such as Pilsdon Pen and Golden Cap, to the rubbly sandstones found in the centre of the county. [52]
The Cretaceous Upper Greensand is about 120 million years old and was deposited in brackish, oxygen depleted, water when Bowerchalke was located at around 35 degrees north of the equator, roughly equivalent to southern Spain and Portugal. At that time it was still part of the supercontinent Pangea which was just starting to split and form the ...