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V.—Observations on the Sequence of the Glacial Beds

Published online by Cambridge University Press:  01 May 2009

S. V. Wood Jun.
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Extract

The Article in this Magazine by Prof. Harkness, “On the Middle Pleistocene Deposits of Britain,” will, I trust, call the attention of geologists more prominently to the fact that a break occurred in the Glacial period, wherein the formation of Boulder-clay was arrested for a considerable interval, and an extensive formation of sands and gravels spread out, accompanied, apparently, by some amelioration of the temperature of the sea. Nevertheless, there are several things pressed by Prof. Harkness into his case as to which a word of caution, and even of dissent, seems necessary.

Type
Original Articles
Information
Geological Magazine , Volume 7 , Issue 67 , January 1870 , pp. 17 - 22
Copyright
Copyright © Cambridge University Press 1870

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References

page 17 note 1 Vol. vi., p. 543.

page 17 note 2 As this shell has so long, but erroneously, been included in lists of Crag shells, it may be useful if I add that it is not given as a shell of the Belgian Crag by M. Nyst.

page 17 note 3 Subject, however, to the doubt expressed further on in this paper.

page 18 note 1 The list of Mr. Maw's Severn Gravel shells, identified by Mr. Jeffreys, contains thirty-five forms of Mollusca, all of them living. Eight of these (inclusive of Tellina Balthica) are unknown to the Crag, and of such eight two only range into the Arctic seas. As to the East Anglian shells, see post.

page 18 note 2 For this, see principally the following papers, viz.:—S. V. Wood, jun. and J. L. Rome, Quart. Journ. Geol. Soc, vol. xxiv. p. 146. S. V. Wood, jun. and F. W. Harmer (Brit. Assoc., 1868), GEOL. MAG., Vol. V. p. 452. S. V. Wood, jun., in a paper read before the Geol. Soc. on Dec. 8,1869.

page 19 note 1 Different altogether to the enveloping Glacier, or ice sheet of the Glacial, or subsidence period referred to in the latter part of this paper.

page 20 note 1 How far it may have extended into Scotland I know not; but, while the central parts of England do not appear to have participated in this partial re-submergence, it is important to observe that the evidence seems to me clear that all the South of England, as far as the Northern limit of the Thames gravel formation, except the higher parts of the Wealden dome, had not, at the time of which I am speaking, emerged from the original Glacial depression, but was being denuded under the influence of those submarine disturbances which began by breaking up the Thames gravel formation, and terminated with the elevation and complete denudation of the Weald valley. It seems reasonable to suppose that the partial re-submergence of the North-East of England was the result of this elevatory activity in the South, by way of counterpoise, and that during it the Cyrena fluminalis occurring in the Thames gravel formation, and in the bed c, and not known as a Glacial shell, died out in this country.

page 20 note 2 This term, “Lower Boulder-clay,” is very objectionable and illusory; for not only are there several Boulder-clays, but the so-called Lower Boulder-clay of Cromer (part of h) is not the bed called Lower Boulder-clay at Norwich, which is the contorted drift, g, that overlies h on the Cromer coast. On the other hand, if I am right in my deductions, the bed, e˝, which is the uppermost in East Anglia, is the lowest Boulder-clay in Yorkshire; the bed b, which I regard as no part of the Glacial series at all, being the uppermost Boulder-clay of this county.

page 22 note 1 Geol. Mag., Vol. II., p. 298.

page 22 note 2 Quart. Journ. Geol. Soc, vol. xvii, p. 448.