Early environments at Denge Marsh

In 1990 Dr. Andrew Plater of the Department of Geography, Liverpool University, began a geological study of the early environments at Brickwall Farm, Dengemarsh (between Lydd and Dungeness). The following is an extract from the conclusion to his report.

Dengemarsh developed in the shelter of the evolving shingle barrier beach of Dungeness. The Ness grew out, eastward and northward, as one ridge was built up after another, as a result of the massive input of shingle along the shore from the south-east. Some of the ridges were "re-curved" (bent round in an elbow-shape), and so provided the necessary protection behind which the finer-grained sect iments of Dengemarsh could accumulate.

The evidence from Brickwall Farm shows that the water in this area was initially quite deep, and tidal, and then became progressively shallow as the area was filled with sediments. At first, after the shingle ridges arrived, sedimentation took place on tidal flats where the open sea had a strong influence. This tidal flat sedimentation is indicated by the types of diatoms (marine algae) contained in the sediments, and the laminated character of the lowermost sediments themselves. Upwards in the sequence the particle size decreases, laminations decrease, and brackish- and fresh-water diatom species appear, showing that the open sea was becoming increasingly remote.

Brickwall Farm itself is built on a major SE/NW shingle ridge, and this study has shown that the area on the north-east side of that ridge remained open to the sea for a longer time, and was open more recently, than the area to the south-west of the ridge. The Brickwall Farm ridge therefore seems to have acted for some time as a barrier to the incoming flood tide on the north. The whole sequence indicates that sedimentation began suddenly, either as a result of a rather rapid rise in sea level or a catastrophic breaching of the shingle barrier. The sea then became more shallow and then increasingly remote.

So far, it has proved impossible to determine the timing of this sequence. It is hoped that in the course of this year some vegetation may be found preserved in the elbows between the shingle ridges, and that it will be possible to date this by carbon-14 methods and so provide a more precise date for the sequence of events. The opportunity will also be taken to carry out experiments in an attempt to date some of the inorganic sediments.

Taken in association with similar findings of previous studies on other parts of the Marsh, the results of this investigation suggest that deposition of the sands and clays of the whole Marsh took place in a sheltered back-barrier environment, rather 1 ike that seen today at Scolt Head Island on the north Norfolk coast. Progressive sedimentation occurred in a relatively low-energy, marine to brackish tidal environment which formed and evolved in the lee of the vast complex shingle barrier beach wh i eh extended from Fairlight across the great bay to Hythe.