1848.] MURCHISON ON THE STRUCTURE OF THE ALPS. 183 



Cretaceous System, composed of Neocomian Lirnestones=^ Lower 

 Greensand ; Gault; Upper Greensand, and Inoceramus Limestone or 

 Chalk. — In noting some features of the Jurassic or oolitic rocks, as 

 traceable through the Alps, I have already pointed out several natural 

 sections which show, that the rocks which in the ascending order are 

 the equivalents of our oolitic series are conformably surmounted by 

 other limestones, the " Neocomian " of foreign geologists*. In 

 England, as I anticipated it would prove to be, and as we now know 

 through the labours of Dr. Fitton and others, our lower greensand, 

 if not the exact equivalent, represents a large portion, at least, of the 

 neocomian. In the Alps this formation is so linked on to the alpine 

 limestone, that before it was distinguished by fossils. Professor Sedg- 

 wick and myself, considering it simply the uppermost member of 

 the great calcareous mass of the Alps, referred it with the geologists 

 of that day to the upper oolite. Our stratigraphical view is, indeed, 

 even now quite correct ; for, with a few local exceptions cited by other 

 authors, it seems that in the Alps, as in the Jura, there has been 

 a continuous series of marine deposits in which no general dissever- 

 ment took place, until after the completion of the supracreta- 

 ceous nummulitic group (see figs. 12 and 14 in subsequent pages). 

 M. Favre has, it is true, endeavoured recently to show, that in the 

 Alpine tracts around Mont Blanc, the cretaceous system (i. e. from 

 the neocomian up to the nummulitic zone inclusive) occurs in more 

 or less horizontal bands, which rest on the convoluted strata of the 

 Jurassic agef . It is not in my power to controvert the specific 

 cases which that geologist has cited ; but other evidences will pre- 

 sently demonstrate, that even in the same region there are many 

 proofs of the uninterrupted and conformable succession I have 

 spoken of, and which is so clearly seen in the Venetian Alps. No 

 one who has examined the mountains near Chambery in Savoy, or 

 the flexures and contortions to which the whole of the secondary 

 series has been subjected in the little Cantons of Switzerland, and 

 who has seen the manner in which even the supracretaceous as well 

 as the cretaceous beds fold over and conform to the convolutions 

 of the Jurassic rocks beneath them, could, I think, hesitate in adopt- 

 ing the conclusion at which I have arrived. 



Not, however, to anticipate what I wish to demonstrate by evidence, 

 I may in the mean time say a few words on the general structure 

 and characteristic features of the Alpine cretaceous system properly 

 so called. Its lower member, the neocomian limestone, is by far 

 the thickest and most important cretaceous formation. This deposit 

 has already been adverted to in the Venetian Alps as a hard white 

 limestone with many bands and geodes of flint, and numerous cha- 

 racteristic fossils ; and it there dips under the grey, red and white 

 scaglia or chalk. In the Austrian Alps it is the hippuritic lime- 



* See my observations on the equivalents of the neocomian at the Meeting of 

 the French Geological Society at Boulogne, anno 1839 (Bull. Soc. Geol. Fr. vol. x. 

 p. 392), and my Address to the Geological Society of London, anno 1843 (Pro- 

 ceedings Geol. Soc. Lond. vol. iv. p. 112). I was not aware, at that time, that 

 Captain Ibbetson had expressed the same opinion at Neufchatel. 



t See Bull. Geol. Soc. Fr. vol. iv. p. 996. 



