On the Pre-Cambrian Rocks of Bangor

Open Access
Publisher Website
Google Scholar
Abstract
I n a paper entitled “Outline of the Geological Structure of North Wales,” read before the Geological Society, June 21, 1843, and published in abstract in the Proc. Geol. Soc. vol. iv. pp. 212–224, Prof. Sedgwick gives a general sketch of the Cambrian rocks from the Bangor and Caernarvon series to the Bala beds. The general character he describes as follows:—“The rocks occupying the region are chiefly composed of felstone (compact felspar) and felstone porphyry, trappean conglomerates, plutonic silt (exactly like the chloritic varieties of German Schaalstein ), and other erupted or recomposed igneous products; and the above-named rocks alternate indefinitely with fine masses of roofing-slate, and with great masses of greywacke—and with greywacke slate, often calcareous, but rarely containing beds and masses of limestone” (p. 215). Further on he states that “the group of chlorite, slate, &c. contains no organic remains, and forms no passage into the rocks of the other division; it therefore offers no sure means of classification; but it seems to be inferior to the other slate-rocks in the southern promontory of Carnarvonshire” (p. 219). Passing over these, and “commencing with the line of the Nant Francon and Llanberis slate-quarries, the author (Prof. Sedgwick) describes a series of regular ascending sections, continued through a horizontal distance of three miles,” i. e. up into the Bala beds. In a subsequent paper, read before the Geological Society, Dec. 16, 1846, and published in the Quart. Journ. Geol. Soc. vol. iii. p. 133, though it is clear he has not yet

This publication has 0 references indexed in Scilit: