Vol. 55.] THE TORSIO]Sr-SIE,UCIURE OF THE DOLOMITES. 595 



the Schlern Dolomite (which is not less than 500 feet thick below the 

 Griiner Fleck) has been gradually cut away by the thrust-plane, 

 so that it thins out to mere streaks of sheared and smashed rock. 



Opposite the highest point of the Groden Pass the Cassian strata 



above and below the shear-plane almost meet ; but the difference in 



their dip-and-strike relations is perfectly distinct, since the Cassian 



strata above the shear-plane incline outward, and those below 



dip from 25° to 40° inward. The shear-plane descends from about 



the 2300-metre contour-line at the Griiner Eleck to 2200 opposite 



the Pass height, and to 2150 at its exposure in the Pissadoi Ravine. 



In the direction of the ravine the dolomite again thickens below 



the shear-plane, a circumstance which is associated with the general 



west-south-westerly and east-north-easterly strike of the conformable 



succession of Wengen, Cassian, and Schlern-Dolomite strata on the 



Pass. The course of the shear-plane through the cliffs is marked by 



patches of vegetation, wherever the Cassian strata have been 



weathered out along the exposure of the plane. 



While the Schlern Dolomite below the shear-plane is a variable 

 factor with regard to thickness, that above the shear-plane is 

 practically constant in this respect, and represents the complete 

 thickness, where it has Cassian strata at its base and Haibl strata 

 on the top of the Meisules terrace. This thickness may be estimated 

 as 1100 feet at the most. 



Immediately west of the Griiner Fleck the relations of the shear- 

 plane are disturbed bj a scree-slip, which seems, from the strati- 

 graphical features on either side, to coincide with a small transverse 

 fault. Beyond it, the precipitous walls of dolomite correspond to 

 the similar precipices next the Griiner Fleck on the Groden-Pass side,. 

 The position of the shear-plane, however, can be still determined 

 by differential strike and dip, and is also indicated by a well-marked 

 horizontal fissure through the rock. 



The dolomite below the shear-plane forms an outjutting crag, 

 named Buscatins on the local map. Together with the Cassian 

 strata below it, the Schlern Dolomite of Buscatins strikes towards 

 the Ciavatzes Alp, and is gradually cut out in that direction. On 

 the top of Buscatins indications of Cassian limestone are present, 

 but scree (and what is probably shear-breccia) cover the terrace 

 between Buscatins and the western face of the Meisules cliffs. 

 The line of scree continues southward into the midst of the Cassian 

 strata exposed on the Sella Pass. These occupy the Pass-ridge 

 from about the 2275-metre contour up to 2400 metres. The dip 

 changes in this group of Cassian strata. The strata below the 

 Sella Spitze have the almost horizontal position of the younger rocks 

 forming these summits, whereas the Cassian strata on the Sella- 

 Pass ridge have a steep and variable north-north-easterly dip. The 

 Wengen strata, so widely exposed over the Sella Pass, are here 

 highly contorted. 



In the ravine of Yal la Stries the Cassian strata are slightly 

 inchned, as at the SeUa Spitze. They correspond to the Meisules over- 

 thrust series, and are succeeded by Schlern Dolomite in its normal 



2q,2 



