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IV.—Note on the Pollurian–Trewavas Coast Section, Cornwall

Published online by Cambridge University Press:  01 May 2009

Upfield Green  and
C. Davies Sherborn
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Extract

Assuming that the Lizard Peninsula is a pre-Cambrian complex (Fiett), and that the Hornblende Schists of Pollurian have nothing to do with the northern sediments, it will be well to call attention at first to the extensive folding of the rocks at Pollurian, which, gradually loses itself as we pass northward in a series of lengthening S.E.–N.W. folds, finally dying away at Porthleven into more or less horizontal beds as we approach Trewavas. Minor contortion is ignored.

Type
Original Articles
Information
Geological Magazine , Volume 9 , Issue 12 , December 1912 , pp. 558 - 560
Copyright
Copyright © Cambridge University Press 1912

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References

page 558 note 1 Lacaze-Duthiers, op. cit., pl. xiii, fig. 9.

page 558 note 2 These alternating periods were fully appreciated by Duerden, “The Morphology of the Madreporaria.—V. Septal Sequence”: Biol. Bull., vol. vii, pp. 99–101, 1904.Google Scholar

3 Lang, , “Growth-stages in the British species of the Coral genus Parasmilia”: Proc. Zool. Soc. Lond., 1909, pp. 287–90.Google Scholar

page 558 note 4 This paper was written in 05, 1910.Google Scholar In the previous month the Director of the Geological Survey kindly allowed us to look at the npublished map, for which favour we undertook to give priority to the Survey. The Survey Memoir having now appeared, we print our views as then written.

page 559 note 1 The “Mylor-Veryan” of Green (95 Ann. Bep. Eoy. Cornwall Geol. Soc, 1908, p. 7).Google Scholar We now recognize the “Mylor” Beds of the Survey to be the upper part of the Porthscatho Series, which, if needing a special name, can be called “Mylor”.

2 Portions of this specimen are now preserved in the Brit. Mus. (Nat. Hist.) and in Jermyn Street Museum. In Pollurian Cove we found a thin band in the Veryan containing discs of limonite after iron pyrites about 12 mm. in diameter; these are comparable to the ‘coal-money’ found in the North of England (L. J. Spencer). Specimens of this rock also have been given to the above-mentioned museums.

page 560 note 1 That the Ordovician Quartzites of the Gorran-Veryan-Manaccan anticline once existed in this area is evident from the abundance of the rock in the walls at White Cross and elsewhere. As it is continually being broken up for roadmetal, the dotted lines on the old one inch map (Sheet 13, 1839 and 1866) of De la Beche will soon be the main record of its existence in the area.