THE GEOLOGY OF HENGISTBURY HEAD - The beds of sedimentary rocks found at Hengistbury Head were deposited about 60 million years ago beneath a warm sub-tropical sea. At this time the Alps were forming and the Dinosaurs were in serious decline. The Boscombe sands form the lowest visible layer or bed at Hengistbury Head. Their colour varies from buff to purplish brown. There are bands of rolled black flint pebbles here which suggests that there were tidal currents strong enough to move and deposit them. There are plant remains but no animal fossils here. Above the Boscombe Sands is a layer of black pebbles which separates them from the Lower Hengistbury Beds. This layer consists of olive-green sandy clays with plant remains typical of a once great sub-tropical bog.

The Upper Hengistbury Beds 'sit' above the Lower Hengistbury Beds and these sediments contain the easily recognisable ironstone or 'doggers'. The doggers were formed in stagnant water of a very large river estuary and were later embedded in the Upper Hengistbury Beds. The sea retreated after the Hengistbury Head beds were formed depositing white and yellow sands which we now call the Highcliffe Sands. About 2 million years ago the climate changed with the arrival of an Ice Age. Sea levels dropped causing rivers to cut down through their valleys - leaving terraces on either side. Three river terraces which consist of river gravels and sand can be seen at Hengistbury Head, the most obvious of which is on the top of Warren Hill