Vol. 50.] THE GEOLOGY OF MONTE CHABERTON. 303 



20. The Geology of Monte Chaberton. By A. M. Davies, Esq., 

 B.Sc, F.G.S., and J. W. Gregory, D.Sc, F.G.S. (Road May 

 9th, 1894.) 



In the study of the geology of the Cottian Alps the problem that 

 has given rise to most difference of opinion is the age of the beds of 

 serpentine and ' pietre verdi ' which occur so abundantly among 

 the schists of this district. Most geologists now admit them to be 

 altered igneous rocks, though the theory of their being bedded 

 sediments still lingers in Italy. As to their age, however, there is 

 much greater uncertainty, so that in spite of all the work that had 

 been done in the Cottians, when the subject was considered in 1890 

 in the description of the Variolitic Rocks of Mont Genevre, it was 

 only possible to conclude that " we must iu fairness merely style them 

 Post-Carboniferous until further evidence is forthcoming." 1 The 

 locality that offered the best prospect of the solution of this question 

 seemed to be on the flanks of Monte Chaberton, the great dolomite 

 mass on the north side of the well-known pass of Mont Genevre. 

 Here a typical series of the intrusive rocks is associated with stratified 

 beds containing three distinct sets of fossils, namely, those of the 

 radiolarian phthanites of Cesana, the Gyroporella and other Triassic 

 organisms of Clavieres, 2 and those hitherto known only from some 

 fallen boulders on the eastern talus-slopes of Chaberton. The age of 

 the first and last of these was uncertain, and it was necessary to 

 determine that of the last before any great advance could be made. 

 The fossils in the boulders had been found on two occasions ; a 

 few were collected by the members of the Societe geologique de 

 Prance, during its excursion to the mountain in 1861 3 ; a larger 

 and better series was obtained by Michelotti and is now in the 

 Pisa Museum. These were described by him in 1877, and deter- 

 mined as of Silurian age 4 ; the schists of the district were therefore 

 assigned to the pre-Palseozoic. Neumayr re-examined Michelotti's 

 specimens and identified them as Cretaceous. 5 The fossils, however, 

 had never been found in situ, and the bearing of this change of view 

 on the age of the main dolomite series was therefore very uncertain, 

 nor could any positive objection be urged against either the views of 

 Lory, 6 who included all the dolomite in his Liassic ' Calcaire du 



1 Cole & Gregory, Quart, Journ. Geol. Soe. vol. xlvi. (1890) p. 323. 



2 K. Diener, ' Der Gebirgsbau der Westalpen,' 1891, p. 18. 



3 ' Keunion extraordinaire a St. Jean de Maurienne,' Bull. Soc. geol. France 

 ser. 2, vol. xviii. (1861) p. 779. 



4 B. Gastaldi, ' Sui fossili del caleare dolomitico del Cbaberton (Alpi Cozie) 

 studiati da G. Michelotti,' Atti E. Accad. Line. ser. 2, vol. iii. Mem. (1876) 

 pp. 114-121, pis. i.-ii. 



3 A. Bittner, M. Neumayr, & Fr. Teller, ' Ueberblick iiber die geologischen 

 Verhaltnisse eines Tbeiles der agaischen Xiistenlander,' pt. iii. Denkschr. d. k. 

 Akad. Wissensch. Wien, vol. xl. (1880) pp. 404-405. 



6 ' Stratigraphie des Alpes Graies et Cottiennes,' Bull. Soc. geol. France, 

 ser. 3, vol. i. (1873) p. 278 ; and ' Description geologique du Dauphine,' §§ 256 

 & 286, Bull. Soc. Stat. Isere, ser. 2, vol. vii. (1864) pp. 14 & 72. 



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