38 GEOLOGICAL MEMOIRS. 



of the Cretaceous formation : — Lower Quader sandstone, — the Planer, 

 with its characteristic species of Inoceramus, Exogyra, Ostrcea, &c. 

 (not above 48 feet thick), — and the Upper Quader, in steep chifs 

 more than 100 feet high, are all well developed. This system is 

 terminated to the north somewhat abruptly by a valley-like depres- 

 sion, probably connected with the basaltic eruption, and running 

 through Graber, Auscha, and Libeschitz, and along the Egra Valley. 

 Northward of this depression, the Cretaceous beds, depressed under 

 basaltic tuffs of various kinds, are only visible in the deeper parts of 

 the valleys. 



These tuffs are more or less of an arenaceous or argillaceous com- 

 position, and alternate with genuine basaltic tuffs, basaltic conglo- 

 merates, and solid basalt. Here and there they contain beds of 

 brown-coal, nowhere more than 3 feet thick. The argillaceous tuff- 

 beds include numerous remains of land-plants and freshwater mol- 

 luscs. One of them, resembling bituminous slate, is full of remains 

 of Batrachians. These strata are more recent than the sandy ones 

 of Saatz, but older than the upper lignitiferous beds of the Saatz, 

 Falkenau, Ellbogen, and Egra basins*. 



The brown-coal strata are frequently disturbed by masses and 

 veins of basalt. Phonolite appears in several localities amidst basalt, 

 traversing it in large veins, without, however, having caused any no- 

 table disturbance. Trachyte is spread over isolated areas. It appears 

 as a completely closed crater of elevation, of about 200 feet diameter, 

 on the Ratzk Mountain, near Lewis. A similar crater, closed north- 

 ward by a wall of phonolitic slag, occurs near Algersdorf. 



The basalt appears to have been erupted in several large currents 

 or beds, continuing without interruption for several miles. In the 

 central region they are disposed in horizontal or slightly inclined 

 layers, alternating with tuffs and conglomerates of the same origin. 

 Nearer to the circumference, their remains appear in the form of 

 isolated hills or flat ridges. This basalt is generally porphyroid, 

 containing olivine ; occasionally it is amygdaloidal, porose, or scori- 

 form. The older basaltic strata are frequently cut through by veins 

 or funnel-shaped masses of more recent basalt. The same variety 

 appears, in the shape of hills, with columnar structure ; while the 

 more ancient affects a tabular or spheroidal structure. The beds of 

 tuff and stratified basalt contiguous to the younger eruptive basalt 

 are generally inclined inwards in the hills. 



Tenacious Diluvial loam occurs even on the higher zones of the 

 valley-slopes. Diluvial gravel is scarce. 



The highest central portion of these mountains, around Warnstadt 

 and Tribsch, is impressed with a still more decided volcanic type. 

 The only visible sedimentary rock is sandstone with brown-coal, 

 cropping out in deep valleys or in the vicinity of phonolites and ba- 

 salts which have upheaved it. Trachyte is seen in many places cut- 

 ting through basalt and phonolite ; and here and there it rises into 

 hills of striking outlines, or breaks, without intermediate tuffs and 



* See above, p. II. 



