Bucks Earth Heritage Group

Brill Hill

Grid reference: SP 650 140.

Location: NW of Thame and south of the A41, off the B4011.

Interest: an open area with geology, landscape and building stones.

The geological interest in the form of local building materials, can be seen in the building stones of the village, which incorporate a large collection of locally sourced stone including Whitchurch Sandstone and Portland Limestone. Geologically, Brill is one of several villages in the area which are situated directly on the Whitchurch Sandstone. Other hills capped by this sandstone include Whitchurch, Stone, Chilton, Waddesdon and Ashendon (see geology sketch below). The hills are only present because of the resistant capping provided by this hard bed, and also the bed of equally hard Portland Stone underlying the Whitchurch Sandstone. Together they produce a hard layer which is resistant to erosion. The surrounding clays around these hills have been eroded down to form the lower clay vales which are so distinctive a feature of Bucks. The geomorphological aspect of this combination of rock type and erosion has produced a highly aesthetic landscape.

The Whitchurch Sandstone (above) is lowermost Cretaceous (Valanginian in age, that is 138-131 million years old). The distinct red, iron-rich sandstones can be seen in numerous walls and buildings of Brill.

As well as the Whitchurch sandstones there are other local building materials identifiable in the village - for instance the Portland Stone (the pale blocks in building below), including ammonites, and locally produced bricks. The latter was often very local - the open land all around the windmill area is pock-marked with small pits and traces of kilns. There are also good records of brick-making at Brill from the 13th century. The clay this industry was exploiting for bricks is the Kimmeridge Clay.

The windmill at Brill within the pockmarked area where clays have been extracted for local kilns.