The stratigraphy and palaeobotany of the Late-glacial and Post-glacial deposits in the Gordano valley, North Somerset, have been investigated. At the west end of the valley there is a lake basin which is cut off from the east end by a transverse sand bar. This bar appears to have prevented the sea from penetrating to the head of the valley during the main eustatic rise in sea level. The local conditions have allowed peat formation from Late-glacial times in the basin which contains a record of vegetational history not hitherto recorded in Somerset. In the Somerset Levels the pre-Atlantic peat deposits are either out of reach beneath estuarine clays or have been eroded away.
During the Late-glacial period the vegetation present in the Gordano valley was the same type of open herbaceous calcicolous vegetation recorded elsewhere in southern Britain. The pollen record from the profiles further shows that the Middle and Late Boreal stages of forest development are also similar to those in other parts of southern Britain. The main phase of peat formation in the Gordano valley dates from the onset of the Atlantic period. The upper peat layers are indicative of the establishment of fen communities and not raised bog as occurred in parts of the Somerset Levels. Peat which is representative of Zone VIII is missing, partly on account of human activities but also because the sea entered the east end of the valley during the Romano-British marine transgression.