622 MISS M. M. OGILVIE [mKS. GORDOn] ON THE [Aug. 1 899, 



that area, while the Upper Triassic limestones were well depressed 

 in the Sett-Sass trough. It was therefore natural that, during 

 oblique compression and overcasting in the later period of folding, 

 reversed faults should carry to a certain extent lower horizons in 

 the arches above higher horizons in the troughs. 



Compensating torsion - movements in companion 

 basins. — The chief diagonal anticline is that of the Campolungo 

 Pass, and the predominating torsion-phenomena have distinct 

 reference to the torsion -buckles formed at its superposition upon 

 the Groden-Pass and Buchenstein Anticlines. 



The leading torsion-curves of Sella are determined by the oblique 

 and divergent faults which pass south-eastward from the Groden 

 Pass to the Campolungo arch, and by the oblique faults which pass 

 north-eastward, from the Cima-di-Rossi and Col-di-Luc portions of 

 the southern anticline, towards the Campolungo arch. 



The leading torsion-curves of Pralongia and Sett Sass are deter- 

 mined by the oblique faults which pass south-westward from the 

 Langs-da-Fiir Anticline to the Campolungo arch, and by the north- 

 western faults which pass from the Buchenstein Valley to the 

 Campolungo arch. Both the basins east and west of the arch are 

 elliptical, but the long axis of the Sella basin is directed north- 

 north-east and south-south-west; while the long axis of the 

 Pralongia and Sett-Sass basin is directed north-north-west and 

 south-south-east, parallel with the leading torsion -curves (Corvara- 

 Contrin, Euones-Castello, Piccol-Lake Yalparola). 



Whereas the torsion of the strike in the anticlines has only 

 been through a small angle of about 20°, here, as at Sella, the strike- 

 torsion is greater in the higher horizons occupying the syncline, 

 where it is north-east and south-west and north-north-east to south- 

 south-west, in the immediate neighbourhood of the diagonal arches 

 west of Sett Sass, veering to north-west and south-east in the 

 Castello meadow. 



Conclusions. 



(1) The area of Sett Sass and Pralongia originally formed part of a main 

 east-and-west syncline situated between a Groden-Enneberg anticline on the 

 north and a Belvedere-Buchenstein anticline on the south, and dating from an 

 early period of crust-movement so far begun in Middle Triassic time (see ' Coral 

 in the Dolomites,' Geol. Mag. 1894). 



(2) During the great Middle Tertiary epoch of crust-compression this syncline 

 was thrown into a series of cross-arches and troughs oblique to the former 

 synclinal axis ; the chief diagonal arch was that of the Campolungo Pass, which 

 subdivided the original syncline into two adjacent basins, Sella on the west and 

 Pralongia and Sett Sass on the east, and whose superposition on the Groden- 

 Pass Anticline has been accompanied by igneous intrusions. 



(3) During the continuance of crust-compression neutralizing flexure and 

 overthrust-faults took place in the combined sense of the earlier and the later 

 movements ; thus torsion fault-curves were formed and were associated with 

 fault-radii across the curves. The fault-curves of Pralongia and Sett Sass 

 describe an arc round the south-west, while the fault-radii diverge from a 

 northern area of convergence towards westerly, west-south-westerly, south- 

 westerly, south-soutb- westerly, and southerly directions. 



