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III.—On the Structure of the Valleys of the Blackwater and the Crough, and of the East Essex Gravel, and on the Relation of this Gravel to the Denudation of the Weald 1

Published online by Cambridge University Press:  01 May 2009

Searles V. Wood Jun
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Extract

In a paper in this Magazine, upon the structure of the Thames Valley, I endeavoured to show that instead of being, as had been asserted, a valley of similar structure to those of the Somme and Seine, and containing deposits of nearly similar order and age, the valley in which the Thames gravel was deposited possessed no outlet to what is now the North Sea, being divided from it by a range of high gravelless country; and that, in lieu of such an outlet, the valley opened, in more than one part, over what is now the bare Chalk country forming the northern boundary of the Valley of the Weald. I also endeavoured to show that all the deposits of the Thames Valley, except the peat and marsh clay, belonged to several successive stages, marking the gradual denudation of the Boulderclay, the lower Bagshot, the London Clay, and the subjacent Tertiaries, which had, at the end of the Glacial period, spread over the south-east of England in a complete order of succession: the sea into which this valley discharged occupying, what is now, the Chalk country of the Counties of Kent, Surrey, Sussex, and Hampshire, inclusive of the interval subsequently scooped out to form the Valley of the Weald: so that, not only was the latter valley newer than that of the Thames, and of the most recent of the Thames Valley deposits, except the peat and marsh clay, but that these deposits in themselves marked a long descent in time from that comparatively remote period of the Boulder-clay.

Type
Original Articles
Information
Geological Magazine , Volume 3 , Issue 26 , August 1866 , pp. 348 - 354
Copyright
Copyright © Cambridge University Press 1866

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Footnotes

1

This paper is intended as a continuation of that “On the Structure of the Thames Valley, and its contained Deposits,” at pages 57 and 99, of Vol. III. of this Magazine, and the direction of sections 1, 3, 4, 5, and 6, given in that paper, have been shown by lines with corresponding numbers on the Map accompanying this paper.

References

page 349 note 1 This patch is of limited extent, and occurs about 1500 yards south-west of Tower Hill and 500 of Holland Gap (its longitudinal dimensions are unavoidably exaggerated in section 8). About a mile and a half from the north-eastern termination of section 8, small patches of the Middle Drift sand occur on the summit of the much loftier (London clay) Cliff of Frinton. The patches are but a few feet deep, and are best exposed under Frinton Old Church, and their distinctive character from the Clacton gravel is very apparent.

page 350 note 1 Phil. Magazine for 03, 1864.Google Scholar

page 351 note 1 The line of section has been chosen in order to show the Middle Drift continuous over the crest of the ridge. If, however, the line of section were drawn a little more to the north-east, all the crest of the ridge would appear denuded of the Middle Drift and exclusively occupied by the London clay; e.g. if the section were drawn from Inworth to Bradwell-on-sea this would be the feature of the section, and the London clay on the crest of the ridge would be capped by summit gravel (x1).

page 353 note 1 Except that of the Hamford Water surrounding the Naze point of Walton, which has participated in the same re-excavation and redenudation as the valleys of the Crouch and Blackwater Estuary, and like them, has on the crown of the slopes forming its valley, patches of denudation gravel, analogous to those described in the former paper under the symbol x 2.