240 



LYELL'S ELEMENTS OF GEOLOGY. 



Lower New Red and Magnesian Limestone. 



south-west, previously to the origin of the New Red sandstone, 

 did not extend towards Durham and the more northern counties. 



Near Bristol, in Somersetshire, and in other counties border- 

 ing the Severn, the unc<9nformable beds of the Lower New Red, 

 resting immediately upon the Coal, consist of a conglomerate 

 called " dolomitic," because the pebbles of older rocks are ce- 

 mented together by a base of magnesian limestone. Among the 

 imbedded pebbles are many derived from the Coal, particularly 

 from the carboniferous limestone, the peculiar fossils of which 

 are still seen in many large rounded fragments. In the north- 

 east of England the dolomitic conglomerate is represented by a 

 yellow limestone, generally called the Magnesian Limestone; 

 which passes upwards into marl slate, and downwards into red 

 marl and gypsum. In the intermediate counties of Worcester- 

 shire, Staffordshire, and Shropshire, are conglomerates referred 

 to the same age, but which are calcareous, with scarcely any 

 magnesia. Between these conglomerates and the Coal is a great 

 formation, called the Lower New Red sandstone (see Table, p. 

 236.), composed of sandstones, red shales, and marls, occasion- 

 ally spotted green.* 



The country of Mansfeld, in Thuringia, may be called the 

 classic ground of the Lower New Red, or Magnesian Lime- 

 stone formation on the continent. It has there been long cele- 

 brated, because one of its members, a slaty marlstone, is richly 

 impregnated with copper pyrites, for which it is extensively 

 worked. The formation in that country is composed of an upper 

 calcareous division, called the Zechstein, and a lower red quart- 

 zose formation of sandstone and conglomerate, called the Roth- 

 liegendes. The upper of these systems is very complex, 

 consisting of marl, Hmestone, copper-slate, magnesian limestone, 

 gypsum, and rock-salt, in which numerous fossils occur, bearing 

 a striking generic resemblance to those of our English Magne- 

 sian Limestone. The Lower system, or Rothliegendes, is inter- 

 posed between the Zechstein and the Coal ; and is supposed to 

 correspond with the Lower New Red sandstone, above mentioned, 

 as occupying a similar place in England between our Magnesian 

 Limestone and Coal. Its local name of Rothliegendes, red-Iyer, 

 or " Roth-todt-liegendes," red-dead-lyer, was given by the work- 

 men in the German mines from its red colour, and because the 

 copper has died out when they reach this rock which is not 

 metalliferous. It is, in fact, a great deposit of red sandstone 

 and conglomerate, with associated porphyry, basaltic trap, and 

 amygdaloid. 



* MnrchiRon, Silurian System, p. 54. 



