1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 1/5 



The chief natural feature which influenced me in relation to this 

 question was, that wherever I turned my steps in the Savoy Alps, 

 whether into the Maurienne or the Tarentaise, or towards the en- 

 virons of Mont Blanc, I uniformly ohserved that heneath a zone di- 

 stinguishable as lias by its fossils as well as by its intimate relations 

 with overlying Jura deposits, there was (with the exception of a certain 

 conglomerate and sandstone, often associated closely with such lias) 

 no sufficient development to represent any of the inferior formations 

 from the trias inclusive downwards ; all the lower strata being in a 

 metamorphosed and crystalline condition. In other words, it seemed 

 to me that between the inferior crystalline rocks and the stratum with 

 belemnites (often itself much altered), there was no adequate repre- 

 sentative in space or time for the carboniferous rocks ; w hich if ever 

 they existed, must, therefore, I inferred, have been merged in the 

 great metamorphosis which all the central portion had undergone. 

 Nor could I avoid the query, if the schistose deposits in which true 

 and beautifully preserved coal species occurred, were of the old car- 

 boniferous date, why no vestige of any palaeozoic animal had been 

 ever detected in the Western Alps, whilst in the Eastern Alps there 

 are, as has been stated, animal remams of the triassic, carboniferous, 

 Devonian and Silurian ages ? 



Let us now appeal to the facts of the section of Petit Coeur. On 

 inspecting the map of Savoy, it will be seen that at Conflans or 

 Albertville, the river Isere having hitherto flowed tranversely by 

 IMoutiers in a deep valley across the ridges of the Tarentaise, or from 

 S.W. to N.E., makes a sudden bend and thence trends south-west- 

 ward to Montmelian and Grenoble. This latter part of its course is, 

 in fact, determined by mountains of Jurassic limestone, which have 

 the same general direction, and which constituting the outer zone of 

 the Alps, are composed of the equivalents of the Oxfordian and upper 

 oolites, together with the overlying cretaceous deposits hereafter to 

 be alluded to. In ascending the transverse gorge of the Isere from 

 Albertville to Moutiers, the geologist has no sooner quitted that outer 

 calcareous zone and passed to the opposite side of the valley, than he 

 finds himself immersed in talcose crystalline schists, in parts highly 

 quartzose, and in parts having somewhat of a gneissose aspect. I do 

 not pretend to describe every variety of these rocks, but it is worthy 

 of remark, that in this narrow transverse gorge, whether they be 

 talcose, micaceous, felspathic or quartzose, the strata in their central 

 part appear to wrap over an ellipsoid of granite and granitic gneiss, 

 which is in parts porphyritic*. As far as dip can be marked, these 

 crystalline rocks between Albertville and the zone of granite are ver- 

 tical ; whilst to the S.E. or higher up they incline away from the 

 granite. At all events, when the gorge wddens and you approach 

 to Petit Coeur, a village on the right bank of that river, the dip of 

 the crystalline mass is decisively to the S.E. A coarse quartzose 



* See the clear and copious account of all these phaenomena in the narrative of 

 the excursion of the geologists assembled at the meeting of Cliambery in 1841, 

 by the Abbe (now Canon) Chamousset, as well as M. Virlet's note on the porphy- 

 ritic granite of La Batie (Bull. Soc. Geol. Fr. vol. i. New Series, pp. 166 et seq.), 



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