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VI.—Some New Points in the Pre-Cambrian Geology of Anglesey

Published online by Cambridge University Press:  01 May 2009

C. Callaway
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Extract

1. The granitoid (Dimetian) rocks of Anglesey pass down into an anticlinal of dark gneiss (above) and grey gneiss (below). The gneiss is also seen in the Menai anticlinal.

2. Low down in the granitoid series are bands of felsite, hälleflinta, and felspathic breccia, which can lay no claim to the rank of a distinct group (Arvonian).

3. The schistose series at Ty Croes is brought into contact with the principal quartz-felsite and hälleflinta band by a fault, and there is, therefore, no proof, from this section, that the schists are of Pebidian age.

Type
Original Articles
Information
Geological Magazine , Volume 7 , Issue 3 , March 1880 , pp. 117 - 125
Copyright
Copyright © Cambridge University Press 1880

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References

page 117 note 1 Quart. Journ. Geol. Soc. vol. xxxv. pp. 302 and 307.Google Scholar

page 118 note 1 Quart. Journ. Geol. Soc. vol. xxxv. p. 322.Google Scholar

page 118 note 2 I have adopted Mr. Lapworth's name (Geol. Mag. Jan. 1879) for the rocks called “Lower Silurian,” that is, the groups from the Arenig to the Caradoc inclusive.

page 118 note 3 Quart. Journ. Geol. Soc. vol. xxxv. p. 316.Google Scholar

page 118 note 4 Geology of North Wales, p. 195.

page 119 note 1 Quart. Journ. Geol. Soc. vol. xxxv. p. 302.Google Scholar

page 120 note 1 The numbers within brackets refer to Prof. Bonney's appendix (pp. 125–126). This rock looks like a hornblende-gneiss, but Prof. Bonney considers the dark mineral a mica. A great part of the upper gneiss seems hornblendic, but I have generally used the term “dark” throughout this·paper, in deference to his opinion.

page 122 note 1 It will be seen that Prof. Bonney considers this a diorite, though his determination is not very positive. There is apparent foliation in the rock, and I have left my observation to stand for what it is worth.

page 123 note 1 Quart. Journ. Geol. Soc. Vol. xxxv. p. 302.Google Scholar