Studies in the Post-glacial history of British vegetation. VIII Swamping surfaces in peats of the Somerset Levels IX. Prehistoric trackways in the Somerset Levels

Abstract
A preliminary account has already been given of peat stratigraphy, pollen analysis, archaeological and climatic circumstances in the Wedmore-Polden basin of the Somerset Levels (Godwin 1941). It was there pointed out that the deep valleys between the Mendips, Poldens and Quantocks had been subject to marine transgression at the close of the Boreal period, and had thereby been filled with clay to about present sea-level. Upon this flat surface there grew up, at least in the region between the Polden Hills and the Wedmore Ridge, a complex of large ombrogenous raised bogs (figure 1). It was shown that the stratigraphic sequence in these structures exhibited a general consistency, and further investigation has confirmed this. Upon the clay surface is a layer 1 or 2 m. thick of greyblack Phragmites peat passing upwards into Cladium peat: this represents a phase of widespread reed-swamp and sedge-fen, probably brackish in its earliest stages. Succeeding this layer is a bed of wood-peat, containing abundant remains of Betula , and doubtless representing the normal transition from eutrophic fen to the oligotrophic stages of raised bog. These are represented in the main by peats derived from Sphagnum, Calluna, Eriophorum and their usual associates, and they may achieve thicknesses of as much as 3 or 4 m.