1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 1/9 



glomerate of Valorsine, and it is fair to state that a very clear and 

 instructive recent section of M. Favre indicates, that this band there 

 forms (Col de Bahne) the conformable base of all the liassic and 

 Jurassic deposits, whether altered or unaltered, of that highly dis- 

 turbed tract*. 



I do not wish, with my present knowledge, to press the question 

 more closely. Those who have not examined the sections might 

 theorize that the thin anthracitic zone of Petit Coeur was a mere 

 shred, which had been left among the gorges of the pre-existing 

 and crystalline rocks, but it is impossible to apply such a hypothesis 

 to the case ; for if the crystalline rocks on the Isere be of anterior 

 date, then we see that the belemnites lie between them and the coal 

 plants ; and if they be altered lias and Jura, then it is almost in- 

 credible that a few feet of old carboniferous rocks should be so con- 

 formably interlaced with these younger deposits. It is just barely 

 possible, that instead of the vertical truncated cone theoretically sug- 

 gested byM. Favre to explain the anomaly f, the older carboniferous 

 rocks may have here been thrown into a very rapid inverted anticlinal 

 flexure, leaving a few feet only at their apex, and that Jurassic or 

 liassic strata have been conformably folded around this point,^ the 

 whole having been since altered and denuded. But if so, it is cer- 

 tainly a section more deceptive than any I ever examined ; and until 

 I meet with other sites affording a different explanation, I can only 

 repeat my belief, that the relations of the strata sustain the conclu- 

 sions of M. E. de Beaumont I . 



Upper Alpine Limestone {Oxfordian, ^c). — I may remind English 

 geologists, that the parallelism with their oolitic deposits which has 

 been so elaborately worked out by M. P. Merian and other Swiss au- 

 thorities in the Jura mountains, has, despite of change of mineral cha- 

 racter and the much rarer occurrence of fossils, been successfully ap- 

 plied to the French and Savoy Alps by M. Sismonda, and to the Swiss 

 Alps by Prof. Studer and M. Escher. But notwithstanding the former 

 publications of Pasini and Catullo, the clear definition of an equiva- 

 lent of the Oxfordian group, as established in the Savoy and Swiss 

 Alps, had not been defined in the Southern Alps until M. von Buch 

 demonstrated to the Italian geologists at the Milan meeting that their 

 " Ammonitico rosso" was of Oxfordian age§. This view has since 

 been much extended in respect to the Venetian Alps by M. de Zigno 

 of Padua. In the excursion of the geologists of the Venetian meet- 

 ing before alluded to, in the mountains of the Setti Com muni, my 

 friends and myself were convinced of the accuracy of the fossiliferous 

 distinctions hy which that geologist had separated the red ammonite 

 limestone from the lower Jurassic rocks on the one hand, and 



* Bull. Soc. Geol. Fr. vol. v. p. 263. 



t Remarques sur les Anthracites des Alpes, par Alphonse Favre. Tom. ix. Mem. 

 Soc. Phys. et Hist. Nat. de Geneve. 



X The able Memoir of M. Scipion Gras, on the association of the carbonaceous 

 deposits of the Isere, and on their passage into crystalline rocks beneath, and their 

 being clearly separated from all liassic strata above them, is to be taken into con- 

 sideration in settUng this question. See Aiinales des Mines, vol. xvi. p. 361. 



§ See Bull. Soc. Geol. Fr. vol. i. pp. 132 et passim. 



