Thus references to "greensand marl" sometimes refer specifically to glauconite. The abbey was built from a mix of chalk, flint, ragstone, greensand, and Caen stone. Glauconite particles are one of the main components of greensand, glauconitic silstone and glauconitic sandstone. The soil of the greensand is quite varied, ranging from fertile to fairly sterile. The fossils are from the Paleocene Waipara Greensand formation. A distinction is made between the Upper Greensand and Lower Greensand. The Gault Formation represents a marine transgression following erosion of the Lower Greensand. This is called the Greensand Ridge Walk. The Upper Greensand is of Albian age. It forms an impermeable layer beneath the Greensand and Upper Coralline Limestone formations. The modern village lies on top of a greensand ridge at approximately above sea level. The Knole estate is located on well-drained soils of the Lower Greensand. Some greensand from the Selandian is also present. The practical value of his article on greensand caught the eye of the Virginia legislature. The Chalk Group, like the underlying Gault Clay and Upper Greensand, is diachronous.