PART II. CHAPTER XXIV. 



287 



Trap Rocks coeval with Oolite and Coal. 



As some Cretaceous rocks, however, have been raised to the 

 height of more than 9000 feet in the Pyrenees, we must not 

 assume that plutonic formations of the same age may not have 

 been brought up and exposed by denudation, at the heigut of 

 2000 or 3000 feet on the flanks of that chain. 



Period of Oolite and Lias. In the department of the Hautes 

 Alpes, in France, near Vizille, M. Elie de Beaumont traced a 

 black argillaceous limestone, charged with belemnites, to within 



a few yards of a mass 

 Fig. 290. of granite. Here the 



limestone begins to put 

 on a granular texture, 

 but is extremely fine- 

 grained. When nearer 

 the junction, it becomes 

 grey, and has a saccha- 

 roid structure. In ano- 

 ther locality, near Cham- 

 poleon, a granite com- 

 posed of quartz, black 

 mica, and rose-coloured 

 felspar, is observed partly 

 to overlie the secondary 

 rocks, producing an al- 

 teration which extends 

 for about thirty feet down- 

 wards, diminishing in the 

 beds which lie farthest 

 from the granite. (See Fig. 290.) In the altered mass the argil- 

 laceous beds are hardened, the limestone is saccharoid, the grits 

 quartzose, and in the midst of them is a thin layer of an imper- 

 fect granite. It is also an important circumstance, that near the 

 point of contact, both the granite and the secondary rocks 

 become metalliferous, and contain nests and small veins of 

 blende, galena, iron, and copper pyrites. The stratified rocks 

 become harder and more crystalline, but the granite, on the con- 

 trary, softer and less perfectly crystallized-near the junction.* 



Although the granite is incumbent in the above section, (Fig. 

 290.) we cannot assume that it overflowed the strata, for the dis- 

 turbances of the rocks are so great in this part of the Alps that 

 they seldom retain the position which they must originally have 

 occupied. 



Junction of granite with Jurassic or Oolite strata 

 in the Jllps, near Champoleon. 



* Elie de Beaumont, sur les Montagnes de i'Oisans, &c., Mem. de la Soc. 

 d'Hist. Nat. de Paris, tome v. 



