﻿Vol. 6 1.] 



THE DOLOMITES OF SOUTKEKN TYROL. 



103 



decimal place. For purposes of comparison, it will be most con- 

 venient to bring together the results of analyses of rocks from the 

 same horizon, and see how the results vary when the deposit is 

 followed from one area to another. Since the Schlern Dolomite is 

 the principal deposit the formation of which has been attributed to 

 coral-reefs, it is perhaps best to consider the results of analyses 

 from that horizon first, and subsequently to compare with them 

 analyses of the rocks, both higher and lower, in the stratigraphical 

 succession. 



The Schlern Dolomite. 



Area of the Schlern. 



A good section of the whole of the Triassic deposits is exposed 

 from the summit of the mountain (8400 feet) along the marked 

 path which is traversed during the descent to Bad Ratzes, and 

 nearly 3000 feet of this consists of massive imbedded Schlern 

 Dolomite. The rock, however, immediately below the plateau near 

 the summit consists of bedded dolomite, and the first specimen 

 analysed (No. 7) came from this upper bedded part. The succeeding 

 specimens were taken at intervals of approximately 300 to 400 feet 

 during the descent towards Bad Ratzes. The last specimen (No. i3) 

 was from just above the junction of the dolomite with the augite- 

 porphyrite : — 



No. 



7 



8 



9 



10 



11 



13 



CaC0 3 . 



MgOO s . 



Per cent. 



Per cent. 



51*50 



4345 



52-70 



44-80 



55-30 



40-80 



54-61 



43-75 



52-80 



43-40 



67*00 



32-80 



Fe 2 3 & A1 2 3 . , Insoluble residue. 



er cent. 



Per cent. 



060 



440 





247 





393 



102 



055 



trace 



3-73 





0-20 



Three other specimens may be considered here. No. 31 was 

 collected near the summit of the Rosszahne, the eastern prolon- 

 gation of the Schlern massif, near the point where it meets the 

 fragment al volcanic deposits of the Seiser Alp : — 





CaC0 3 . 



MgC0 3 . 



Fe.,0 3 & A1 2 3 . 



Insoluble residue 



No. 



Per cent. 



Per cent. 





Per cent. 



31 



55-3 



43-8 





0-86 



(3 



56-9 



41-6 



trace 



1-53 



27 



60-1 



39-1 





0-73 



Specimen (3 was from a rolled fragment, probably Schlern Dolo- 

 mite, taken from the bed of the stream at Bad Ratzes. No. 27 was 

 from a block of ' Cipit '-dolomite from the Seiser Alp. 



In 1875 Prof. C. Doelter & Prof. R. Hcernes wrote a paper on 

 the composition of the Dolomites of the Tyrol, and published the 

 results of a number of analyses. 1 They recorded two analyses 

 from the dolomite of the Schlern Mountain : the first one from a 



1 Jahrb. d. k.-k. geol. Reichsanst. vol. xxv (1875) pp. 293-332. 



