Bucks Earth Heritage Group

Buckinghamshire Geology Map

Buckinghamshire’s oldest rocks and fossils, that are present at the surface, are 190 million years old. These are the rocks of the Lias which form part of the Jurassic sequence of marine rocks making up the northern part of the county (Figure 1 below) The British Isles were much further south 190 million years ago – far enough to be enjoying a tropical climate. During this time, in fact to the end of the Jurassic 145 million years ago, Britain was covered by sea for all but the very last part of this period. How do geologists know this? The evidence is in the rocks and fossils and this website aims to help you discover what the evidence is, how to interpret it, and where to see it for yourselves.

The rocks of Buckinghamshire, unlike other parts of the British Isles, are all sedimentary rocks. This means they were laid down as particles that have been weathered and eroded from somewhere else. Sometimes geologists can tell where the 'somewhere else' was, and sometimes it is impossible. But the interesting part of the story for Bucks is - what were the different environments for these sediments? - where has Bucks been in the past? - and where to visit in order to see these rocks and fossils for yourselves.

Geological sketch of the main solid geology of Bucks.

(Remember, these layers are often overlain by the so-called 'drift' deposits - ice age and other sediments.)

If you want to know the detailed geology you can always order the geological maps from the British Geological Survey ( www.bgs.ac.uk ). You will want the 1:50 000 Geological sheet for one of the following, depending what area you are interested in:

Thame, Aylesbury, Henley-on-Thames, Beaconsfield, Buckingham. Leighton Buzzard, Milton Keynes.