Archaeology & Geology



The main rock-building period for north Buckinghamshire was about 200 million years ago when a large shallow sea slowly laid down layer upon layer of limestone sediment. This eventually formed a hard durable rock which made an excellent building material. During the Ice Age, north Buckinghamshire was covered by glaciers which not only helped to form the rolling characteristic of the landscape, but also covered it in a thick layer of boulder clay. This very dense clay was produced by the moving ice, using its weight to grind solid rock down into microscopic fragments. Boulder clay makes a heavy soil with strong water retention. It is difficult to work at first, but once the topsoil is broken down it makes a fertile basis for cultivation. This boulder clay is evident all over Thornborough parish and the surrounding district. It is interspersed with sandy deposits, often quite large, such as Shelspit, which were left by the outwash from retreating glaciers. There are also areas of stoney ground, such as Stoneylands and the Stonepit Field by Coombs Quarry, where limestone and cornbrash deposits are close to the surface and are very apparent when working the topsoil.

Copied from Thornborough: Past and Present by kind permission of Betty Bunce

The Estate