1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 1/7 



the sandstone being repeated. In fact, T cannot imagine how any 

 geologist can look at this section and not declare that the whole of 

 these strata form one natural group of very small dimensions. In 

 tracing these beds up the hill-side I further convinced myself, that 

 the belemnite flags (the belemnites most abound in the upper quarries) 

 have there exactly the same relations to overlying and underlying 

 grits, the whole resting, as m the lower quarries, on the white talc 

 slates and also in perfect conformity. In these sections there can 

 be no ambiguity, for you can absolutely follow the line of strike of each 

 bed nearly a mile up the mountain-side. No traces of folding or 

 contortion are observable ; and as belemnites have been found within a 

 foot of the coal-plant bed, it appears, that however w^e may endeavour 

 to explain them, the physical facts are clear and decisive. 



It is true, that in ascending the hill the anthracite thins out from 

 four feet to a few inches, whilst the black belemnite flags are more 

 expanded in the higher than in the lower quarries ; but this phseno- 

 menon, so well known to every working geologist, is not worth men- 

 tioning, were it not necessary to allude to the minutest circumstance 

 in this singular collocation. The whole group is afl'ected by the same 

 lines of joint or division, and all the beds exfoliate parallel to the laminae 

 of deposit, the more calcareous portions showing a tendency to assume 

 flat concretionary forms, which produce small undulations in the upper 

 quarries. 



Above Petit Coeur the dip to the S.S.E. is continuous for a short 

 distance, and there is therefore a certain amount of ascending order ; 

 but in the parallel of Moutiers the succession is checked by one of those 

 grand transverse dislocations so frequent in the Alps, accompanied by 

 the evolution of hot springs. 



According to M. de Beaumont and M. Sismonda, the belemnites, 

 shales and flagstones of Petit Cceur are a portion of certain adjacent 

 Jurassic groups in which many ammonites and other fossils occur. 

 These fossils are found in strata of dark shale and schist, which ap- 

 pear on the strike of these beds as they range across the valley of the 

 Isere and appear in the passes which traverse the mountains that 

 separate the Tarentaise from the Maurienne. It is probable that the 

 same strata are several times repeated by fractures if not by undula- 

 tions ; for it seemed clear to me that the whole of the series exposed 

 between St. Michel and St. Jean de Maurienne, i.e. the dark shale and 

 patches of coaly matter underlying or associated with Jurassic rocks, 

 represents the succession seen between Petit Coeur and Moutiers in 

 the Tarentaise. The ammonites and other fossils I now present 

 were taken from the broken slopes of the Col de la Madeleine, or 

 rather from the elevated depression immediately to the S.S.W. of 

 Aigues blanches, where they were collected by M. Ansenet. They 

 appear to be in great part the same as those already collected in the 

 tract at the Encombres by M. A. Sismonda, among which that author 

 enumerates the Ammonites Jimbriatus, Sow., A. planicostatus, Sow., 

 Aviciila inceqidvalvis, Sow., A. costata, Sow., Terebratula incequi- 

 valvis. Sow., T. variabilis, with a multitude of belemnites*. 



* See a more complete list of these fossils, with specimens from other places in 



