'fol- 55-] 



TOESIOIJ'-STKUCTUEE OF THE DOLOMITES. 



581 



intencrossing torsion-strikes, a principal strike west-south-west and east-north- 

 east, and a subsidiary strike west-north-west and east-south-east. 



Such contending whirls of the forces seem to me to explain all the observed 

 data — not only the phe- 

 nomenon of an inner j^- S.— Diagram illustrating the torsion- 

 or median area of m- ° ^, ^ ^i /^ ■■ j t> 



tertwining, correlated movements at the Groden Pass. 



with lateral (east-and- 

 west) outer areas of 

 virgation, but also the 

 phenomenon of asso- 

 ciated longitudinal 

 and diagonal buckling : 

 since the resultants of 

 the inner force-compo- 

 nents pushing obliquely 

 one towards another 

 are the stronger result- 

 ants, and are those 

 which would form 

 curved longitudinal 

 buckles ; while the re- 

 sultants of the outer 

 force-components push- 

 ing obliquely away one 



from anotlier are the weaker, and are those which would form curved diagonal 

 buckles. The latter are, in this area, distinctly subordinate to the longitudinal 

 anticlinal buckles in size, but are almost equally important in determining the 

 general configuration of the crust. 



The Pass structure thus affords an admirable example of cross-folding and 

 buckling due to the conflicting action of force-components, forming two unequal 

 sets of force-couples, directed obliquely one against the other. 



6. Tors ion -ellipsoid. — The axis of the anticline, which extends from 

 Plon to Pescosta in a slightly west-south-wosterly and east-north-easterly 

 direction, is cut west of Plon by the Wolkenstein cross-fault, and east of 

 Pescosta by the Pescosta (or Corvara) cross-fault. The two opposite centres of 

 intrusive rock occur on the axial line, the western centre above the waterfall, the 

 eastern centre above Ruon hamlet. With these two centres as foci and the 

 anticlinal axis as a main axis, an elliptical figure may be drawn, which will 

 embrace the torsion-phenomena of the Groden Pass. For convenience I 

 propose to term this figure a torsion-ellipsoid. 



A straight line drawn at right angles to the major axis through the centre 

 represents the minor axis of the ellipse, and, at the same time, the direction 

 of the resultant forces acting inward on the anticlinal buckle, namely, 

 in a direction slightly north-north-west and south-south-east. 



The maximum ' interference '" in the fold-formatioii has taken place between 

 the foci, where the northern and southern fold-arcs have cut each other and 

 interlocked. 



7. Characteristic furcation of diagonal faults. — Furcation 

 takes place in what may be called a dichotomous fashion. The main throw 

 of a fault is taken up by the branch or branches in the new direction, while 

 the throw either may be sensibly diminished in the continuation of the original 

 direction, may die out. or may be replaced by a steep flexure or a series of con- 

 tortions, according to the petrographical nature of the strata. 



Two diagonal faults in a ncrth-north-easterly and south-south-westerly 

 direction, and a tliird in a northerly and southerly direction, cut the focal area 

 in the western slope of the Pass. A main diagonal fault crosses between the 

 Groden Pass and the Wolkenstein, and passes south-south-westward over the 

 Sella Pass, sending off a branch due south. 



Upon the east side of the Pass, one diagonal fault crosses the focal area in 

 a north-north-westerly and south-south-easterly direction, a branch passing 

 due south into the Sella Massive. The Pescosta Fault is a njain diagonal fault 



