Chalk

Cretaceous

By 95 million years ago sea level was the highest it had ever been, more than 20m above present sea-level. The result was the very pure limestone we call the Chalk. There are hundreds of metres of chalk, but only a couple of beds are suitable for exploiting as building material, for instance, the Totternhoe Stone or ‘Clunch’.

Flint is also found within the Chalk, but it is not a limestone: it is pure silica (quartz). It is very durable and resistant to weathering. In fact it is so strong that it always lasts longer than the structure around it - the mortar, bricks or other building stone always crumble first, leaving re-usable flints behind. Flints can be collected directly from the Chalk where they commonly form in bands. This may be easy when Chalk is being quarried for other purposes. Flints are also found in coarse river deposits, or in the ‘Clay-with-Flints’ where natural weathering of chalk leaves a residue of flints and clay.

Totternhoe Stone is a bed 2.4m thick of hard cream or greyish-cream rock within the Lower Chalk. During the deposition of the Chalk there were pauses in sedimentation that encouraged a greater amount of cement to form on the sea floor. These thinner beds are often called ‘hardgrounds’ because of this property. The Totternhoe Stone is a bed that has acquired more cement than the usual Lower Chalk (it can also be slightly gritty). Despite being very prone to damage by frost and acid rain, it has been a popular building stone since Roman times - where there are few other building materials! It's popularity for use in buildings near its outcrop lies in the fact that it is easy to locate, easy to quarry, soft enough to make decorative carvings, and cheap.

The main quarries are along the slopes between Totternhoe and Sewell, including underground workings of the late 1700s to late 1800s. Where used inside buildings Totternhoe Stone survives the ravages of time very well. It has often been used inside Church porches and even in the alter back of Westminster Abbey. However, when used in the outside building structure on older buildings, this rock is often badly weathered. Woburn Abbey is probably the most famous building in Bedfordshire made from Totternhoe Stone.