Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/181

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Mr. Webster on the Strata lying over the Chalk.

in Dorsetshire, is horizontal, differing in this respect from their position in Alum bay. There must, therefore, have been some twist in the chalk stratum, a remarkable instance of which I discovered at the other end of the chalk range beyond Lulworth.[1]

Since I shall have a future opportunity of making some remarks on the very singular stratification of these places, I shall only at present observe, that the highly inclined chalk from the Culver cliffs at the east end of the Isle of Wight to White Nose, in Dorsetshire, 5 miles west of Lulworth, formed the southern side of this depression in the chalk stratum. The north side of it may be traced in that range of hills called the South Downs, extending from Beechy Head, in Sussex, to Dorchester, in Dorsetshire. The strata of which these hills are composed, dip generally from 15° to 5° to the south; the inclination varying in different places. The south side of the basin therefore must have been extremely steep, while the slope of the north side was very gentle. The closing of this basin at the west is obscure, and cannot be distinctly traced; but the east is now entirely open, the sea passing through it.

III. Extent of the London Basin.

Transactions of the Geological Society, 1st series, vol. 2 figure page 0600.png

This extensive basin, like that of the Isle of Wight, is probably owing to a depression in the chalk stratum.

Its south side is formed by a long line of chalk hills, including those of Kent, Surrey, and Hampshire, called the North Downs, extending through Basingstoke to some distance beyond Highclere

  1. The drawings and description of this, as well as of many other parts of this remarkable coast, will be found in the above-mentioned work now preparing for publication, by Sir H. Englefield.