Vol. 55.] TOESIOK-STEUCTUEE OF THE DOLOMITES. 621 



Dachstein strata lie in the hollow of this flexure at the Eisenofen 

 huts. Immediately north of the huts and of Lake Valparola, Cassian 

 strata are dislocated bj a steeji fault and brought, along with Schlern 

 Dolomite, into complex stratigraphical relations with the Raibl strata 

 and Dachstein rock in the Sett-^ass basin. 



This Eisenofen -Valparola Eault with southerly downthrow was 

 previously demonstrated by the writer to be a curved continuation 

 of the east-and-west Falzarego Eault which runs from the Tra-i-Sassi 

 Pass to the Ampezzo Valley. In its portion north of Sett Sass this 

 fault may be regarded as a reversed one limiting the northern 

 side of the basin, and neutralizing the steep flexure-fault of Monte 

 Sief which limits the Sett-Sass basin on the south. The Monte- 

 Sief and Sett-Sass Faults give expression to a general overcasting of 

 earlier east-and-west anticlines towards the south during the later 

 torsion-movements. At the same time we have seen how com- 

 pensating overcasts took -place towards the north in the Langs-da-Elir 

 Anticline north of Siadu. 



The northern fold-arc of Pralongia and Sett Sass. — 

 A northern fold-arc is presented in the curved form of the Langs- 

 da-Eiir Anticline, but the anticline is cut oif from the basin of 

 Siadu by the intrusion of porphyrite continuous with that of the 

 Pescosta centre (p. 583). The Siadu basin is cut ofi" from a corre- 

 sponding basin on the opposite side of the Sore stream by the 

 diagonal arch of Pralongia continued northward between Eu and 

 the Centurinus Dolomite-group. The downthrow from this arch 

 towards the Centurinus group is part of the long downthrow from 

 the north-north-west and south-south-east fault-shears between 

 Abtey and the Dolomite-group of Kreuz Kofl and La Varella. 



Cross-arches. — The anticlines of the earlier epoch of com- 

 pression are the easterly continuation of the arches demonstrated in 

 the Sella area, and will now be briefly mentioned in the same order, 

 to facilitate comparison (p. 609) : — 



1 (a) Langs-da-Fur limiting antichiie; (b) Siadu trough. 



2 (a) Ruones-Piccol-Tra-i-Sassi arch ; (b) Stuores and Sett-Sass trough 



(Fondo di Valparola). 



3 (a) and (b) [wanting]. 



4 (a) Southern arch of Pralongia and Sett Sass ; (b) southern trough 



(underlay of southern overthrusts). 



5 (a) Monte-Sief and Col-di-Lana limiting anticline. 



The diagonal series of cross-buckles, and the torsion-curves and 

 torsion-radii associated with them, indicate two later diagonal 

 arches across the middle of the area — the Pralongia-Soraruaz arch 

 and the Eisenofen-Sett Sass arch (2434 metres). 



The main diagonal anticline is that of Campolungo, limiting the 

 area on the west, and the eastern limit is the diagonal arch crossing 

 Tra i Sassi, and forming a natural boundary between the two 

 distinct torsion-systems of Enneberg and Ampezzo. 



If we consider now the position of the strata in the Sett-Sass 

 area previous to the torsion-movements, clearly the Cassian strata 

 occupied a relatively high position in the arches north and south of 



