616 MISS M. M. OGILVIE [mRS, GORDOn] ON THE [Aug. 1 899, 



Hill. The three faults across the Priilongia ridge diverge at almost 

 equal distances one from another within the triangle, and demon- 

 strate alternate cross-buckliug and depression of the strata entirely 

 analogous to that observed on the east side of Sella ; but here the 

 general downthrow is eastward, while at Sella it is westward. The 

 base of the triangle is an anticlinal curve round the south-west, 

 towards which direction the diagonal faults of Pralongia diverge. 



Strike - torsion round Pralongia and Sett Sass. — The 

 wide triangular exposure of Cassian strata at Pralongia is cha- 

 racterized on the south side by a torsion of the strata from a 

 north-easterly and south-westerly strike at Monte Sief, an easterly 

 and westerly direction of strike on the Selvaza slopes, to a northerly 

 and southerly direction of strike on the Euones slopes ; on the 

 north side, by a torsion of the strata from a west-north-westerly 

 and east-south-easterly direction at Eisenofen, and an east-north- 

 easterly and west-south-westerly direction in the lower slopes 

 between the Piccol and Stuores streams, to a northerly and southerly 

 direction in the upper Piccol slopes. 



Thus two torsion-arcs limit the shallow syncline of the Pralongia 

 meadows — a northern arc from Ruones to the lower Piccol district, 

 and a southern arc from Corvara round Cherz Hill to Monte Sief. 

 As in the case of the Sella syncline, D & C spiral movements have 

 been followed in the northern arc, and A & B spiral movements 

 through the southern arc. But whereas the northern arc and the 

 associated torsion-movements form the greater part of Sella, it is 

 "the southern arc which is the larger round Pralongia and Sett Sass, 

 so that torsion-curves corresponding with the A & B spiral move- 

 ments predominate in this area (see fig. 8, p. 581). 



jN'orthward continuation of the diagonal Campo- 

 lungo Anticline. — Although the Langs-da-Fiir Anticline crosses 

 the Pralongia system between Corvara and St. Cassian, it is evident 

 that the north-north-easterly and south-south-westerly strike con- 

 tinues down the Abtey Valley, and that Campolungo and Abtey 

 form a main diagonal anticlinal buckle between two opposite 

 synclinal areas occupied by Dolomite-massives. ^ Pralongia was 

 part of a long syncline limited north and south by two earlier 

 east-and-west anticlines (Langs-da-Piir and Buchenstein) and after- 

 wards crossed obliquely by the superposed anticline of the Campo- 

 lungo Pass. Torsion-curves pass from the east-and-west anticlines 

 towards the north-north-east and south-south-west anticlines. 



Relation of the Sett-Sass Syncline to Pralongia. — 

 Minor complications within the Pralongia Syncline have arisen, 

 owing to the presence of another diagonal anticline, namely that of 

 Pralongia, parallel with the Campolungo Anticline. This cross-arch 

 has broken up the original syncline into two troughs, of which that 

 occupied by Sett Sass is the deeper. Again, in the Sett-Sass 

 Syncline another cross-arch is apparent, parallel with those of 

 Pralongia and Campolungo. It forms that part of Sett Sass which 



1 Quart. Journ. Geol. Soc. vol. xlix (1893) p. 27 & fig. 4. 



