^^^' 55-] TOKSION-STRUCTUKE OF THE DOLOMITES. 629 



appearance in the Dolomites of northwardly-inclined normal flexures 

 passing into faults with downthrow on the north ; whereas Suess, 

 Bittner, and other geologists had traced overfolds and thrusts 

 towards the south and south-east in the area south of Cima d'Asta, 

 and in the Judicarian district. 



The present author and Dr. Salomon (see p, 565) showed the 

 existence of overfolds and overthrusts within the Dolomites whose 

 direction agreed with that demonstrated in the Judicarian and Asta 

 areas. Now this paper shows that a characteristic feature of the 

 Dolomites is the repeated combination of flexures and 

 flexure-faults, towards the north and north-west, in 

 the sense demonstrated by Mojsisovics, with overfolds 

 and overthrust-faults towards the south and south- 

 east: that is, in the Judicarian-Asta sense. The inclina- 

 tion of the planes is in both cases precisely the same, but the actual 

 combined result is so far neutral. 



The neutralizing action of similarly-inclined normal 

 and reversed faults whose direction is curved, explains 

 the recurrence of Dolomite-massives with the same strata and the 

 same tectonic features over a wide area. 



A further fact brought out in this paper is equally significant 

 for the structure of the Dolomites, namely, the relation of return- 

 folds and overthrusting to the original fold-system. The strike- 

 faults on the southern and inner portion of the Dolomites mostly 

 produce overthrust southward ; the strike-faults along the northern 

 rim (as, for example, Diirrenstein) are overthrust northward. 



This want of uniformity is paralleled by the researches of 

 Bittner and Yacek in the Adige Basin. There the chief fault is the 

 Judicarian Fault, ranging north-north-east and south-south-west, 

 and with it the occurrences of eruptive rock are associated. Along 

 this western limit and throughout the mountains, the overcasting 

 and overthrusting are eastward ; whereas along the eastern limit of 

 the same area the quartz-porphyrj has been overthrust westward 

 over the rocks of the Adige Basin. The occurrence of fold and 

 back-fold, the frequent obliquity in the shape of folds, the variation 

 of the same lines of disturbance from gentle flexures into sharp 

 faults, and the relations between strike and diagonal faults are 

 identical. 



The Judicarian Faults, north-north-east and south-south-west, 

 are said to be crossed by Asta Faults, which come from the Lom- 

 bardy Plain, both in an east-south-easterly and east-north-easterly 

 direction, or are likewise associated with dykes. Certain sharp 

 north-and-south faults, sometimes more north-north-west and south- 

 south-east, cut the others. The virgation of faults is still another 

 feature common to the Dolomites and to the Judicarian-Asta region ; 

 while the latter area also confirms the observation, made with 

 respect to the eruptive rocks in Fassa, Fleims Yalley, Buchenstein, 

 and Enneberg, that the bosses and dykes are present 

 pre-eminently in twisted anticlines and along diagonal 

 lines of fault where torsion has been greatest (fig. 22, 

 p. 630). 



