Structure of the Eastern Alps. 401 



Conclusion. 



1. The slight inclination of the tertiary system at Eibesvvald, Hartber"-, 

 Marburg, and other places on the confines of the Styrian basin, naturally leads 

 to the conclusion, that the extremity of the Eastern Alps had undero-one its 

 chief movements of elevation before the existence of the several "-roups 

 described in this chapter. 



!2. The formation of the lowest group probably commenced soon after tliese 

 movements of elevation had ceased ; and it is, at ail events, newer than any 

 of the inclined strata on which it rests, or against which it abuts. This con- 

 sideration proves it to be younger than the secondary green sand and fucoid 

 shale, and proves nothing more : for there is nothing in the accompanying 

 details, which positively limits the great movements of elevation, and proves 

 them not to have extended to a period newer than that of the secondary green 

 sand, 



3. The age of the lowest tertiary groups of Styria can, therefore, only be 

 determined by their structure and their fossils ; and on this evidence (as 

 above stated, p. 387, 388.) we are rather disposed to compare them with the 

 calcairc grossier and the London-clay, than with the newer Sub-Apennine 

 formations, 



4. Although, as before stated, our subdivisions were in some measure arbi- 

 trary, and were adopted chiefly for the convenience of description ; yet the 

 tertiary system may be separated into, at least, tliree natural groups, each of 

 which seems to have been tranquilly deposited during a long period of time — 

 a conclusion justified by the condition of the beds and the distribution and 

 preservation of the fossils. If the lowest group be compared with the calcaire 

 grassier, the middle group may, with perhaps more certainty, be compared 

 with a portion of the great Sub-Apennine deposits, or with those of the Bor- 

 deaux basin. The highest group seems to be on a parallel with the higher 

 Sub-Apennine strata; but its limits are ill defined ; and we may pass it over for 

 the present, as its relations are perhaps better exhibited in the Vienna basin, 

 which we are about to notice. 



5. The volcanic forces appear to have been called into action, chiefly during 

 the formation of the most recent group, and were probably continued, with 

 more or less interruption, during a long succession of ages. The varied struc- 

 ture of the different volcanic masses seems to have originated in mere local 

 causes, and we saw no reason for referring the great masses of breccia, of 

 lava, of scoria, and of trachytic porphyry, to distinct epochs of eruption. 



6. Respecting the age when the igneous causes ceased, we can offer no 

 conjecture. We find no traces of their action since the sea retired from the 



VOL. III. SECOND SERIES. 3 F 



