^^^' 55-] TORSION-STEUCTURE OF THE DOLOMITES. 583 



occurrence of the fault permitted the strata on the one side to be twisted and 

 faulted with different degrees of complexity, and sometimes in a different sense 

 from the strata on the other. Therefore I regard these faults as a simul- 

 taneously developed system of complex torsion-curves, due to the inertia of the 

 rock-masses while undergoing torsion-deformation. 



At the same time, it is noteworthy that the fundamental form of an anticline 

 everywhere underlies the torsion-phenomena. Disregarding for the moment the 

 diagonal buckles, one anticline can be followed west and east from the Groden 

 Valley to the Euneberg Valley. It has been cut by cross-faults at several points, 

 and its axial line has been disjointed and displaced at such points, hence the 

 anticlinal form would seem to be older than the cross-faults. The Grroden Pass 

 area represents only one of the anticlinal segments, displaced laterally fi'om its 

 neighbours west and east by the Wolkensteiu and Pescosta diagonal faults. 

 Intrusive rocks are present in both of these faults, and are associated with the 

 ramifying series ol' dykes which mark the system of torsion-faults in the anticline. 



These data lead me to infer that torsion-deformation took place subsequently 

 to the determination of a meridional anticlinal buckle. The probability is 

 that the torsion-phenomena represent a later and more com- 

 plex phase of crust-movements, superinduced upon a simpler 

 phase characterized chiefly by lateral compression. The evidence 

 is that the simpler folds in the Grroden -Enneberg area had their axes in almost 

 meridional direction ; whereas the more complex folds of the torsion-epoch 

 have no straight axes. The torsion-folds are curved, and the torsion-faults lie 

 in all possible oblique directions, displaying complicated phenomena of inter- 

 section and reversal. 



The disposition of anticlinal buckles in curves circling round separate massives 

 in the detached synclines is entirely a result of crust-torsion. 



III. The Ai;rTicLiNE oe the Buchenstein Valley. 



:N'orthern slopes of the Buchenstein Valley.— Buchen- 

 stein Valley is the name given to the upper part of the Cordevole 

 Valley (see PI. XL). The Cordevole stream flows east-north- 

 eastward from the Pordoi Pass to Arabba, then bends east-south-east 

 towards Pieve, and there curves sharply south-eastward. The curve 

 described by the river is much the same as the curve described by the 

 Groden Pass round the northern base of the Sella Massive, and it 

 will be shown to be due to the same structural feature of torsion. 



The steep crags of Cherz Hill rise on the north of the valley. 

 An old river-terrace occurs about 500 feet above the present river- 

 level, where two groups of cottars' houses are perched, called 

 respectively Varda and Cherz. Dark precipices rise 1400 feet 

 higher to the summit (about 7000 feet), and it is chiefly among these 

 precipices behind Varda and Cherz that instructive rock-exposures 

 are to be found. 



Southern slopes of the Buchenstein Valley. — The ridge 

 of Belvedere and Sasso di Mezzodi shuts in the valley on the south. 

 This is the ridge which has been already recognized on palaeonto- 

 logical grounds (see p. 562) as corresponding generally in position 

 with the geographical limit of the difl'erent facies in Enneberg and 

 Passa during the Wengen-Cassian time. Enneberg then, in my 

 opinion, represented the submarine terrace, which was at once 

 the upthrow side of a contemporaneous Middle Triassic fault or 

 flexure, and part of the area over which Middle Triassic lavas and 

 tuffs spread inward from the active zone of crust-movement. We 



