Structure of the Eastern Alps. 377 



mining their age. Notwithstanding- this, from the general position of the 

 group, as well as from the analogy of other sections, we think it undoubtedly 

 a part of the tertiary system. 



After quitting the group last described, the river again winds among low 

 round-topped elevations, undeserving of notice, till it passes near the base of 

 Weibach, Peissenberg, and other hills in the neighbourhood of Schongau, 

 where it exposes a considerable succession of beds, dipping still toward the 

 north, but at a small angle of inclination. The strata, indeed, in this latitude 

 seem to have been comparatively little affected by any elevatory movements 

 of the Alps. The following section, in the ascending order, derived from the 

 escarpments south-east of Schongau, will give a general notion of the struc- 

 ture of these upper tertiary groups. 



Feet. 



1. Yellow and blue, unctuous marls, with hands of greenish grey, micaceous sand. 



stone containing a few rolled pebbles Thickness exposed 28 



2. Conglomerate, with a cement of sandstone 3 



3. Unctuous marls throwing out springs 20 



4. Bluish grey marls, with obscure traces of shells 12 



5. A system of blue and yellowish marls ; in some parts unctuous, in others sandy 



and micaceous: containing bands of coarse, brown sandstone, of greenish blue, 

 micaceous flagstone, of calc.grit passing into conglomerate, and, near (he top, 

 of indurated marl, assuming, here and there, a septarian form 100 



6. Yellow, ferruginous sand, with bands of ferruginous and micaceous sandstone. , 30 



7. Great masses of conglomerate, obscurely stratified, containing some large, an- 



gular masses both of secondary and tertiary rocks, here and there mixed with, 

 and seeming to pass into, coarse sand and greenish, micaceous sandstone, ... 80 



We have little doubt that the conglomerates (No. 7.) belong to the old, 

 horizontal formation above alluded to. They cannot, however, be so readily 

 separated from these slightly inclined groups, as they were from the highly 

 inclined strata of the Arzt and Untersberg sections*. The marl beds of 



* Plate XXXVI. figs. 6 and 9. We before stated, that the horizontal overlying conglomerates 

 were probably formed immediately after one of the most recent elevations of the chain ; and that 

 they are not only spread over the edges of the strata descending to the northern plains, but also 

 penetrate within the lateral valleys of the Alps. As a remarkable, additional instance of this 

 kind, we may here mention a horizontal deposit, two or three hundred feet thick, which appears 

 on the left bank of the Isar, below Mittenwald, twenty or thirty miles from the place where the 

 river emerges into the tertiary plains. It consists of a coarse conglomerate of rounded calcareous 

 pebbles irregularly mixed with sand, sometimes cemented into a solid rock, and of strong beds of 

 yellow sand, here and there, containing subordinate, irregular beds of yellowish white, semi- 

 indurated marl, called chalk (kreiile), which is worked and exported to Munich and Vienna. 

 The regularity and great thickness of many of these deposits make them very unlike the diluvial 

 formations in our island. 



VOL. III. SECOND SERIES. 3 C 



