Page:Early Man in Britain and His Place in the Tertiary Period.djvu/277

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CHAP. VIII.]
SUBMERGED FORESTS.
249

angular detritus," and to be covered by deposits in the following order:—

1. A blue freshwater-mud deposit, resulting probably from the depression of the land.

2. A surface of plant growth (Iris).

3. A marine silt with Scrobicularia piperata.

4. Shingle that forms a ridge, which is at the present time encroaching on the level water meadows behind.

The physical changes in the district implied by this section are considered by Mr. Godwin-Austen to be as follows:—The angular detritus in which the trees are rooted was an old surface soil, formed at a time when the climate was more severe than it is at present, and probably while the boulder clays north of the lower valley of the Severn were falling from melting icebergs. This was followed by the epoch of the growth of the forest and of the accumulation of vegetable matter. The overlying blue clay (No. 1) marks the time during which the trees were killed; the surface of marsh- growth (No. 2) covered with iris marks the epoch when the trees fell; the silt (No. 3) indicates a depression below the sea-level; and, lastly, the silt was elevated, and the shingle (No. 4) thrown up on its surface, to form the barrier at high-water mark.

Mr. Godwin-Austen's valuable essay recalled to mind a worked flint which I had found in the angular detritus in 1861, and the Rev. H. H. Winwood and myself resolved to re-examine the forest-bed and the associated deposits.

On digging through the layer of undisturbed vegetable matter, we met with ample traces of man's handiwork in flint and chert chippings, as well as a well-formed