Vol. 55.] TOKSION-STEFCTIJKE OF THE DOLOMITES. 575 



thinning out into contemporaneous earthy deposits of Wengen 

 age around the steep outer slopes of the ' reef.' 



Cleavage- phenomena of the Pass. — The phenomena of 

 cleavage are similar in the dolomite-cliffs on both sides of the Groden 

 Pass. Great cleavage-slabs of iSchlern- Dolomite rock face west- 

 north-westward with high inclination, the direction of strongest 

 cleavage being north-north-easterlj' and south -south-westerly in 

 the areas adjoining the Pass. In the north-eastern corner of the 

 Sella Massive, however, the cleavage-planes are vertical and run 

 almost due north and south. 



A second set of cleavage-planes, also well developed although less 

 assertive to the eye, cut the first set obli(]uely in a north -north- 

 westerly and south-south-easterly direction, and are more constant in 

 direction throughout the massives than the north-north-easterly and 

 south-south-westerly planes (see fig. 21, p. 614). 



These two series of cleavage-planes are also clearly developed in 

 many of the harder stratified rocks comprised within the Groden 

 Pass anticline, but are scarcely decipherable as such in the softer, 

 strongh'-crumpled rocks. In the twisted wedges of Muschelkalk, 

 I frequently distinguished east-and-west and east-north-east and 

 west-south-west planes of cleavage. 



The intercrossing in the directions of cleavages is an observation 

 which I value as one in complete harmony with the intercrossing in 

 the direction of the main faults over the Pass. 



Diagonal disposition of the Dolomite Massives with 

 respect to the Groden Pass Anticline. — The imposing 

 mountain-block of the Lang Kofl. Massive rises west of the Sella 

 Massive, separated from it only by the Sella Pass, and may be said 

 to face the Groden Pass on the south-west. The present author's 

 familiarity with Pitzculatsch HiU (see p. 567) and the Sella Pass 

 enable her to give some indication of the probable connexion 

 between Lang Xofl and the Dolomite-mountains facing the Groden 

 Pass on the north-east. 



The neighbouring areas are separated by the Wolkenstem cross- 

 fault (see p. 570). The structural details differ on the two sides 

 of the cross-fault, although the main directions of folding are 

 retained. The Pitzculatsch strike-fault can be traced quite well across 

 the Sella Pass slopes to the north or Groden side of Lang Kofl. There 

 it limits the now widened anticline, exposed on the Mont de Sora 

 slopes, against the younger strata that compose the cliffs of Lang Kofl, 

 the fault being accompanied throughout by intrusive porphyrite and 

 an altered contact-zone of Muschelkalk and Wengen fault-rock. 



The chief general feature to be observed is that the downthrow 

 to the south of the fault is distinctly greater at Lang Kofl than at 

 Sella ; the fault is, just as at Pitzculatsch, a normal fault, inclined 

 southward towards the mountain. Reversed faults, likewise hading 

 southward, occur on the Mont de Sora slopes and in the Groden 

 Valley, so far neutralizing the effect of the Lang Kofl normal fault. 



