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III.—The Crystalline Rock Areas of the Piémontese Alps
Published online by Cambridge University Press: 01 May 2009
Extract
In continuation of the preceding paper (Geol. Mag., April, p. 156) which, as a preliminary to the present one, outlined the new classification of the crystalline rock formations and the nomenclature of the pietre verdi of the Piémontese Alps, I now propose to briefly describe the principal pietre verdi areas with which I became familiar during a long stay on repeated occasions in Turin. This city, apart from its rich collections of the rocks and minerals of the Piémontese Alps, is a most central and convenient starting-point for examining the different valleys debouching into the plain of the Po from the magnificent crescent formed by the Maritime, Cottian, Grajan, and Penniue Alps, which, as seen from Turin, afford by far the most extensive and fascinating Alpine panorama in Italy.
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References
page 200 note 1 “The Permian Formation in Piémont, Dauphiné, and Savoy”: Geol. Mag., 01, 1916, p. 7 et seq.Google Scholar
page 200 note 2 Zaccagna, D., “Alpi Marittime”: Boll. R. Com. geol., 1889, p. 395 et seq.Google Scholar
page 200 note 3 Franchi, S., “Zona Pietre Verdi fra I'Ellero e la Bormida, Alpi Marittime”:Google Scholaribid., 1906, p. 89 et seq.
page 200 note 4 The nomenclature used throughout this paper is that given in the preceding one, Geol. Mag., 04, 1916, pp. 156–63.Google Scholar
page 201 note 1 Franchi, S., “Alcuni Metamorfisi di eufotidi e diabasi Alpi Occid.”: Boll. R. Com. geol., 1895, p. 181 et seq. The transformation described in this important memoir applies equally to similar phenomena in all the other pietre verdi areas of the Piémontese Alps. In the massive and schistose amphibolites of the Grana and Maira Valleys, as also in Val Chisone, at Pegli, Liguria, and in the Tuscan archipelago, Franchi found the equivalent of the Californian mineral lawsonite, a secondary pseudomorphic plagioclase corresponding to the formula of hydro-anorthite felspar (Boll. R. Com. geol., 1898, p. 308).Google Scholar
page 201 note 2 The term ‘eruptive’ is used in this paper in preference to ‘igneous’ as better corresponding to the non-intrusive character of the Piémontese rocks.
page 202 note 1 The term ‘primitive’ gneiss is used throughout this paper in its strictly stratigraphical sense as the ‘fundamental’ substratum of all the more recent formations.
page 202 note 2 Sacco, F., “L'Age du massif de l'Argentère”: Bull. Soc. géol. France, 1907, vi, p. 484 et seq. Also “Gruppo dell' Argentera”: Mem. R. Acc. Scienze, Torino, 1911, lxi, p. 457 et seq.Google Scholar
page 202 note 3 Franchi, S., “Osservazioni lavori geol. Alpi Marittime”: Boll. R. Com. geol., 1907, p. 145 et seq. Among the excellent reports in the Boll. R. Com. geol., besides those already quoted in this and the preceding paper, are the following relating to the Cottian Alps:—Google Scholar
Franchi, S., “Tettonica della zona pietre verdi del Piemonte,” 1906, p. 118 et seq.; “Appunti geol. e petrogr. Monti di Bussoleno,” 1895, p. 3 et seq.Google Scholar
Franchi, S. and Novarese, V., “Appunti geol. e petrogr. dintorni di Pinerolo,” 1895, p. 385 et seq.Google Scholar
Novarese, V., “Rilevamento geol. Valle Germanasca,” 1895, p. 253 et seq.; “Rilevamento geol. Valle Pellice,” 1896, p. 231 et seq.Google Scholar
Stella, A., “Rilevamento geol. Valle Varaita,” 1895, p. 283 et seq.; “Rilevamento geol. Valle Po,” 1896, p. 268 et seq.Google Scholar
page 202 note 4 Figs. 2–4 will appear in the next part of this paper in June.
page 203 note 1 This section is founded on Zaccagna's great transverse section west to east of 70 kilom. from St. Paul in Dauphiné through the calc-schist formation, Monte Viso, and the Dora-Maira massif to Rocca Cavour in the Po Valley (Boll. R. Com. geol., 1887, p. 416, tav. ix). Franchi gives a similar section of the Monte Viso group at a lower level further south (ibid., 1898, p. 482, tav. ix; also Stella, ibid., 1896, p. 288). (For Fig. 2 see June Number.)