230 



ME. T. ROBERTS ON THE UPPER JURASSIC ROCKS 



Since the publication of Oppel's work 'Die Jura Formation' in 

 1856-58, but little has been done towards the correlation of the Ju- 

 rassic beds of the Jura with those of England, and since that time 

 many new discoveries have been made both in England and in the 

 Jura, which tend to make the task of correlation somewhat more easy. 



The district visited is included in the cantons Berne, Neuchatel, 

 and Vaud ; and as the rocks in the north part of the Jura differ 

 considerably from their equivalents in the central Jura, we ma}^ 

 conveniently divide the area into two parts, a northern and a 

 southern. The northern district contains the greater part of the 

 Jura Bernois, its southern boundary being a line running east and 

 west through St. Imier. The southern district includes the re- 

 maining portion of the Jura Bernois, together with the whole of 

 the Neuchatelois and Vaudois. 



Before commencing the description of the geology of the above 

 districts, it is necessary to state that much valuable assistance was 

 received from the following geologists, who accompanied us on most 

 of the excursions made in their respective districts, and to whom 

 the success of our expedition was in great measure due : — 



M. Mathey, at Delemont ; Prof. Xoby, at Porrentruy ; Prof. 

 Eollier, at St. Imier ; Prof. Jaccard, at Locle and Neuchatel ; Prof. 

 Golliez, at Ste. Croix. 



I have also to thank Prof. Renevier of Lausanne for a letter of 

 introduction to the above-named gentlemen ; and to Prof. Hughes I 

 am indebted for much help and advice. 



1. The Northern or Bernois District. 



The geology of the Jura Bernois has been fully described by 

 Greppin in the works already referred to (1 and 2), and there is a 

 geological map of the district by the same author. He gives (' Jura 

 Bernois,' &c. p. 210) the following classification of the upper series 

 of the Jurassic Rocks : — 



I. Purbeckien. 

 II. Portlandien. 



III. Virgulien. 



IV. Kirameridgien (or Pterocerien). 

 V. Sequanien (or Astartien). 



VI. Eauracien (or Corallien). 



I. Oxfordien. 

 II. Callovien. 

 JurajBrun Bathonien, &c. 



As already stated, the group of rocks with which it is proposed 

 to deal is included in the above " Jura Superieur " and " Moyen." 



The " Callovien," the lowermost division of the upper Jurassics, 

 is subdivided into : — 



2. Le fer sous-oxfordien. 



1. La zone k Ammonites macrocephalus. 



The opinion of the Swiss geologists is not unanimous as to the 

 true position of these beds. Greppin states (op. at.) that in the 



Jura blanc ou 

 Superieur 



Jura Moyen | 



