On the Age of some Sands and Iron-Sandstones on the North Downs

Open Access
Publisher Website
Google Scholar
Abstract
T he lower and central tracts of the valley of the Thames, from Reading to the sea, consist of Eocene strata, with a limited covering of Crag on the sea-board of Essex and Suffolk. This mass of Tertiaries is skirted on the south of the Thames by a belt of chalk, which rises by a gradual and continuous slope, broken by numerous small transverse valleys, until it attains an average height of from 500 to 600 feet: it is then abruptly escarped, forming a cliff-like declivity stretching east and west, and at the base of which extend the Lower Cretaceous and Wealden series. This elevated chalk-tract is about ten miles broad at Dover and Canterbury, and ranges westward, with a variable width of six or eight miles, to Guildford, where it contracts to a narrow ridge not half a mile broad. These Downs form a distinct and marked division between the Tertiary strata of the synclinal Thames Valley, and the anticlinal dome-plain of the Weald: they exhibit throughout a chalk-surface, either quite bare or covered on the hill-tops by a thin capping of reddish clay, sand, and flints, with, here and there, an outlier of the Lower Tertiary strata rising above the general level of the chalk-plateau, and forming slightly detached and more conspicuous hills. These outliers are continued at a few places to the very edge of the chalk-escarpment. Besides the more general drift, and the few local Tertiary outliers, there are, however, scattered commonly on the very summit of

This publication has 0 references indexed in Scilit: