Yol. 55.] THE TOKSION-STRrCTTJRE OP THE DOLOMITES. 587 



main body of the fault-network, the Pieve, or eastern part, is 

 characterized by wonderful exposures of highly-folded and strongly- 

 sheared Werfen rocks and Muschelkalk (including the uppermost 

 horizons representing true Buchenstein strata), arranged as a fan of 

 fault-blocks virgating eastward. 



The overthrusts in the Pieve area. — The uppermost of the 

 Cherz Hill overthrusts is twisted eastward by the Soraruaz Fault 

 into Col di Lana : the lower descends the Gliera slopes in a west- 

 north-westerly and east-north-easterly direction, but it is twisted 

 into a westerly and easterly direction near St. Johann by intersection 

 with a subordinate oblique fault, and continues through the Federa 

 fields into Col di Lana. The divergence of these overthrusts towards 

 Col di Lana is in remarkable contrast with their overlapping position 

 in the Varda area. 



Another strike-fault runs south of these from Soraruaz, in a west- 

 north-westerly and east-south-easterly direction, to the slopes of Col 

 di Lana, immediately above Pieve. The throw of this fault is 

 different on the east and west of its intersection with the St. Johann 

 oblique fault. 



It has thus been demonstrated that the crushed buckle of older 

 Trias at Soraruaz and St. Johann is flanked on the northern wing 

 by S-folds, with southerly overthrusts. Although the accompanying 

 map (PL XL) ^ does not include a survey of the Belvedere ridge, 

 the general northerly dip of the Muschelkalk rock in the middle and 

 higher exposures of that range, as contrasted with the inward dip of 

 the Muschelkalk in the lower hill-horizons, would seem to indicate 

 the presence of a back-fold in the southern wing of the anticline. 



The curved normal fault between the northern 

 wing of the anticline and its correlated syncline. — 

 Once more we find a steep flexure broken by a normal fault as the 

 means by which a series of reversed faults has been neutralized. 

 The flexure is best seen on the northern slopes of Monte Sief 

 (fig. 10, p. 586). The Wengen strata strike north 40° east and dip 35° 

 westward on the mountain, while the Wengen-Cassian Series of Pra- 

 longia, with a nearly east-and-west strike, and northerly dip, comes 

 into contact with the bent series of Monte Sief along a flexure-fault 

 with downthrow to the north. The fault describes a torsion-curve 

 from west-north-west at Campolungo, round a southern arc 

 through Monte Sief to east-north-east, where it is cut by the Yal- 

 parola diagonal fault. This curved normal fault bounds the 

 syncline of Pralongia and Sett Sass. 



The Buchenstein torsion-system. — The Pordoi-Pass area 

 of this region represents a portion of the northern wing, very deeply 

 sunk in comparison with the Yarda portion of the same wing. It 

 will be dealt with more conveniently on a subsequent page (p. 599). 

 Sufiicient data have been already given to afford a clue to the com- 

 plete system of torsion in the Buchenstein region (see fig. 13, p. 588). 



^ The stratigraphical details of the Buchenstein virgating faults can be seen 

 in the map ; the paths marked on the map are old footpaths, now in great 

 measure obliterated, owing to the building of fortifications and the laying-out 

 of strategical roads at present going on in the valley. 



