No CrossRef data available.
Article contents
IV.—On the Age of the Crystalline Schists in the Piedmontese and other parts of the Alpine Chain
Published online by Cambridge University Press: 01 May 2009
Extract
Dr. preller's recent contributions to this Magazine on the geology of the Piedmontese Alps prove that (1) Italian authorities have expressed widely different opinions on this subject, and (2) some of them have maintained sundry Alpine gneisses and crystalline schists to be Palæozoic or Mesozoic (often Permian or Trias) in age. I infer from these contributions that he is well acquainted with the physical geography of this region, but fail to find in them any signs of either microscopic study or independent petrological work. As these have led me in several cases to very different results, I shall venture to put them on record as briefly as possible. In the course of thirty-five visits I have wandered over the peaks and valleys of the Alps from the southern border of the Cottians to the Salzkammergut, paying at first much more attention to physical than petrological questions. But in 1869, when beginning to lecture on geology, I found not only (as I was already aware) that my knowledge of rocks was scanty, but also that on this subject very little trust could be given to much that had been written. So I tried, as best I could, to teach myself. With this intention I visited many places of petrological interest in our own country and on the Continent, forming (partly by purchase) a considerable collection of rock specimens and slices. Circumstances soon directed my attention to the gneisses and crystalline schists, and from 1872 I paid more and more attention to them in my Alpine journeys, of which this was the thirteenth. In 1885 (my twenty-first journey) I began endeavouring to obtain clearer ideas about their succession, history, and relation to the ordinary stratified rocks, by running sections, sometimes up to, sometimes across the watershed of the chain, going in that year from the Lake of Lucerne to the Lago Maggiore and returning across the Great St. Bernard.
- Type
- Original Articles
- Information
- Copyright
- Copyright © Cambridge University Press 1916
References
page 505 note 1 Sorby, the “Father of Microscopic Petrography”, had not published much on that subject before this date, David Forbes still less, and Samuel Allport was only beginning. The ordinary textbooks of geology were either of no value or misleading.
page 506 note 1 Both these collections have been given to the University of Cambridge, and are in the Sedgwick Museum.
page 506 note 2 As, of course, certain apparently older gneisses and schists may be.
page 506 note 3 As this term, proposed by Delesse, has for long been familiar to English geologists, I do not see why Dr. Preller should call it euphodite (p. 161).
page 507 note 1 Q.J.G.S., 1889, pp. 87, 88, 108.Google Scholar.
page 507 note 2 Id., 1893, pp. 94–103; 1894, pp. 279–84; 1903, pp. 55–6.Google Scholar.
page 507 note 3 Gabbro intrusive into serpentine is, of course, a very common thing. I may add that locally the schistes vertes are cut by eclogites.
page 507 note 4 See p. 307.
page 508 note 1 Q.J.G.S., 1884, pp. 4, 5, 21 ; 1889, p. 92, and remarks on rocks of the pietre verdi type at p. 98.Google Scholar.
page 509 note 1 The stock instance of gneisses and Jurassic limestones on the northern erags of the Jungfrau is now abandoned, so it needs no discussion.
page 509 note 2 Geol. Mag., 1883, p. 507.Google Scholar.
page 509 note 3 See Q.J.G.S., 1890, pp. 199–211 ; 1894, pp. 297–300. There are four marked varieties of these schists, three of which I have found in the rauchwacké and the fourth at the base of the Lias near the Lukmanier Pass, where this rock rests directly on that particular schist.Google Scholar.
page 509 note 4 Q.J.G.S., 1893, pp. 90–1.Google Scholar.
page 509 note 5 Q.J.G.S., 1890, pp. 213–21; 1893, pp. 90–1.Google Scholar.
page 510 note 1 Geol. Mag., 1901, p. 161.Google Scholar.
page 510 note 2 For instance, the schistes lustrèes have been for long a “waiting-room” where rocks in very different states of metamorphism are left till called for.
page 510 note 3 Q.J.G.S., 1886, Proc., p. 79. A generally similar succession of crystalline schists (originally sediments) occurs in the Highland zone between Dunkeld and Braemar, and hornblende schists (grüner schiefer of the coarser type) in the North-West Highlands. Id., pp. 91, 92.Google Scholar.
page 510 note 4 Papers dealing with different points in the nature and succession of these rocks will be found in Min. Mag., 1887, pp. 1, 191 ; Geol. Mag., 1887, p. 573 ;Google Scholar 1889, p. 483 ; 1890, p. 533; 1893, p. 204; 1894, p. 114; 1896, p. 400 ; 1897, p. 110 ; Phil. Mag., 1892, p. 237; and Q.J.G.S., 1889, p. 67; 1890, p. 187; 1893, pp. 89, 94, 104 ; 1894, pp. 279, 285 ; 1897, p. 16; 1898, p. 357; 1903, p. 55; 1905, p. 690; 1908, p. 152.