RED SANDSTONE OF THE VOSGES. 



16S 



Where the red marl and sandstone formation is fully developed, 

 It may be arranged, as before stated, under three divisions : the low- 

 er, which corresponds with the rothe-todte-liegende, consisting of frag- 

 ments of different rocks cemented by sand or marl, and of beds of 

 imperfect porphyry ; this occurs below magnesian limestone : the 

 middle beds, consisting chiefly of sandstone, called by the French 

 gres rouge and gres des Vosges : and the upper, consisting of marl 

 and variegated sandstone, in which beds of rock-salt and gypsum oc- 

 cur ; this corresponds with the gres bigarre and marnes irrisees of 

 the French. In England the three divisions of this formation rarely 

 if ever, occur together, accompanied with magnesian limestone ; but 

 it should appear, from the situation of these different beds on the 

 Continent, that the place of magnesian limestone is between the low- 

 er and the middle division ; for the magnesian limestone or zechstein, 

 rests on the conglomerate beds of red sandstone. 



In the third number of the Annales des Mines, 1827, there is a 

 very full account by M. Elie de Beaumont, of the different arenace- 

 ous strata that separate the coal strata from lias limestone, along the 

 feet of the Vosges mountains on the eastern side of France. This 

 account throws considerable light on a part of geology hitherto ob- 

 scured by the conflicting opinions of former observers, and assimi- 

 lates the red sandstone of France and Germany with the different 

 divisions of the same formation in England. The Vosges mountains 

 are composed of granite and transition rocks, and at their feet, there 

 are several coal-fields : the coal strata, and also the lower declivities 

 of the granite, are in part, covered unconformably, by nearly hori- 

 zontal strata of red sandstone ; and this is covered by lias limestone. 

 We have here, on a larger scale, an exact correspondence with the 

 geology of the Charnwood Forest district, where the granite and slate 

 rocks are bordered by coal strata, and are both partly covered by 

 horizontal strata of red marl and sandstone ; and this again is cov- 

 ered by lias limestone. The red sandstone of the Vosges is, however 

 more developed ; the lowest part consists of conglomerate and por- 

 phyroidal beds : these cover the coal strata; they agree in their min- 

 eral characters, precisely, with the conglomerates in the English red 

 sandstone, particularly those of Devonshire, and are described by M. 

 Beaumont as being the true rothe-todte-liegende. Above this occurs 

 a considerable thickness of strata of red sandstone, which passes by 

 gradation into the conglomerate ; this is the proper gres rovge : it is 

 designated by M. Beaumont gres des Vosges ; it approaches in its 

 character nearer to the gres bigarre than to the lower beds. The 

 variegated sandstone, or gres bigarre, covers the gres des Vosges; 

 but there appears to have been a considerable degradation of the 

 surface of the gres des Vosges, and also a disturbance of the beds by 

 subsidence or faults, before it was covered by the gres bigarre, or 

 variegated sandstone : nevertheless they are evidently members of the 

 same formation. 



