522 



J. F. BLAKE ON" THE TOPER 



Ammonites marantianus &c. must have taken the place of the upper- 

 most portion. 



On account, however, of the many questions which have heen 

 raised about the Haute Marne, taken by the French geologists as 

 their typical area of Corallian rocks, it is needful not only to make 

 out the succession from the rocks themselves, bub also to discuss the 

 evidence brought forward in support of a different and more complex 

 reading. The peculiar changes supposed to be here effected in the 

 relations of the recognized Corallian rocks and those hitherto con- 

 sidered Oxfordian, and the generalizations founded on this, have been 

 developed by degrees in numerous papers by M. Tombeck (45, 48, 50, 

 55,57,58,64,65,66). 



The " Marls without fossils," stated by M. Eoyer to underlie the 

 Corallian, were first made to be their lateral equivalents (55), and 

 afterwards (64) were divided into two parts ; and the whole Corallian 

 mass, when that occurred, was inserted between the two, which unite 

 into one in its absence. Hence the fossils of these barren marls, espe- 

 cially Amm. marantianus, were considered Corallian ; and wherever 

 that species is found we are to look for the Coral-beds and Pisolites 

 beneath it. Hence, too, the beds with Amm. tenuilobatus, which are 

 said to come above those with Amm. marantianus, are to be placed in 

 the Astartian instead of the Oxfordian. Now, whatever evidence 

 there may be elsewhere to show the true position of these zones, the 

 only evidence obtainable from the Haute Marne shows that the first 

 zone lies below the Corallian. 



The idea that the Corallian rocks change into marls depends on a 

 comparison of the series in the valley of the Marne with that in the 

 neighbouring valley of the Aube, and will be discussed later. The 

 newer idea that they are to be intercalated is supposed to be proved 

 in the valley of the Marne itself. 



The river- cliff before mentioned, which skirts the right bank of 

 the Marne from Les Lavieres to Buxieres, forms a semicircle of rocks 

 having a fairly constant dip to the north. The radius of this semi- 

 circle is 1500 yards ; and near the centre is a low hill, through which 

 the railway passes in a cutting at a distance of only 1000 yards 

 from the cliff. In this cutting it is said that the Diceras-beds, 300 

 feet thick at 1000 yards distance, have died out to a thin wedge, 

 and may be seen lying in the midst of the marls (65) and the under- 

 lying rubbly limestones at the base. Neither of these statements 

 can be accepted. The marls at the cutting are the continuation of 

 those of Les Lavieres, with exactly the same character : there are hard 

 bands in them ; but these are not Corallian ; and the top of the cut- 

 ting on either side is covered by the shelly limestones of the cliff 

 and their fragments, with corals and Pecten articulatus <fec. Here, 

 therefore, the Oxfordian marls are seen to underlie the Corallian 

 limestones. The Corallian limestones lie very slightly unconform- 

 ably on the marls ; so there may be something wanting here. 



Another locality supposed to prove the same is at Youecourt, 

 two miles to the south (62). Above this village is a ravine leading 

 east (Ravin du Heu), and a road sloping up the hillside to Yieville 



