Structure of the Eastern Alps. 303 



Chap. I. 



* On the general Structure of the Eastern Alps. 

 Having, in a paper already publislied_, explained our views respecting- the 

 general structure of the Eastern Alps, we shall here avoid all details, except- 

 ing such as are necessary to make our local descriptions understood, and to 

 supply the deficiencies in some portions of our former transverse sections*. We 

 stated — that the chain, when considered only in a general point of view, was of 

 very simple structure, having an axis of primary or transition rocks, chiefly of 

 slaty texture, flanked and surmounted to the north and the south by two great 

 secondary calcareous zones, which are in their turn surmounted by tertiary 

 sandstones, conglomerates, and clays, descending on one side into high plains 

 of the Upper Danube, and on the other into the Subalpine plains of Italy — 

 that the primary and secondary portions of the chain gradually diminish in 

 elevation in their range towards the east — and finally, that they seem to pass 

 under the recent deposits of the Vienna basin and of Lower Styriaf. 



The moment, however, we enter on a detailed examination of any portion of 

 this great chain, the apparent simplicity of its structure vanishes ; for it has 

 undergone movements of elevation at several successive epochs, probably 

 from some of the oldest down to the newest geological periods. By these 

 movements the relative position of all its subordinate parts has been greatly 

 deranged : the northern and southern calcareous zones are in many places 

 completely rent asunder ; and their component groups of strata are not merely 

 thrown into most violent contortions, but are placed in such positions that it 

 is impossible to determine their relative age by any single section. In proof of 

 this we need only state, tliat in many places on the northern flank of the Alps, 

 the newest secondary deposits, generally considered of the age of the green- 

 sand, are broken off" by enormous faults, from the calcareous zone, under 

 which they appear to dip towards the centre of the chain ; and that, deceived 

 by this appearance, a geologist of great experience was induced, only a few 

 years since, to place the older Alpine limestone on the same parallel with the 

 chalk. 



To the east of that part of the valley of the Inn which traverses the great 

 secondary zone, the derangements are, however, we believe, in no instance 

 so great as to produce an entire inversion of the calcareous groups: the trans- 

 ition rocks and red sandstone on the flanks of the central axis are uniformly 

 surmounted by the oldest portion of the system of Alpine limestone; and the 



* See Phil. Mag. and Annals of Philosophy, N. S. vol. viii. August 1830. 

 ■ t^See Plate XXXVI, fig. 1. 



