Academy of Sciences] 

 No. 11 



ALPINE AND ATLAS MOUNTAINS. 



27 



I 



ozoic rocks form deep synclines in the wonderful folded 

 packet of recumbent folds in the Simplon complex. 

 The fundamental gneissic rocks are followed by Triassic 

 quartzites and dolomite and Jurassic calc-phyllites in 

 which the green-rocks occur — lying so placed that it 

 seems difficult to conceive that they could be other 

 than the product of Jurassic submarine eruptions. 

 They are now prasinites, picrites, serpentines, etc., 

 but originally were diabases, "gabbros," picrites, and 

 peridotites, appearing in some cases very like the 

 coarser members of the English Devonian spilitic suite 

 of rocks. 5 The rocks of the series have sometimes a 

 notable amount of albite as revealed by chemical 

 analyses, of which certain are like those of kerato- 

 phyres, while albitic products of contact alteration 

 have been formed in the invaded calc-phyllites. It 

 may thus be suggested that these rocks have some 

 features of those of the spilitic suite, and were formed 

 during Jurassic subsidence prior to the great alpine 

 folding. Dunite and wehrlite, though also present in 

 the calc-schists near Visp (Preiswerk '03) , are found 

 chiefly in the gneisses of a higher recumbent sheet in 

 the Geisspfad and Upper Tessin areas (Preiswerk 

 '01, '18). Another lenticular mass of peridotite in 

 gneiss occurs near Andermatt (Schneider '12). 



We now pass to eastern Switzerland whereon 

 Steinmann based his discussion of ophiolitic rocks 

 ('05) . These basic intrusive rocks are associated with 

 radiolarian rocks as well as calc-phyllites (the East 

 Alpine f acies of the Biindnerschief er) , and lie entirely 

 within the Rhaetic sheet overlain by the largely 

 gneissic East Alpine sheet. Lorenz ('02) held that the Vs 



diabase-porphyrites were intrusive into the Jurassic 

 radiolarite and Cretaceous marls along lines of thrust 

 during the period of great overthrusting, von Seidlitz W/0< /' /,? 7#Yl/ 

 ('06) considered that in the absence of Tertiary rocks 

 there was no evidence that they were younger than 

 Cretaceous, while Hoek ('03, '06) showed that they 

 invaded all rocks up to the Jurassic radiolarite and the 

 Cennomanian breccia, but did not enter the Cretaceous 

 flysch. The petrographic description of these rocks 

 has been given by Ball ('97) and Bodmer-Beder ('97). 



The green-rocks of the Julier Pass at the south- 

 western end of the Engadine have recently been 

 investigated by Cornelius ('12).' The stratigraphy is 

 intensely disturbed. The Rhaetic sheet consists of 



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> The writer examined specimens of these rocks in Basel and Zurich through 

 the courtesy of Drs. Preiswerk and Woyno. They are very diflerent from the rocks 

 of the Ivrea zone studied by Schaefer ( '98) and those forming the gneissic gabbros 

 and allalinites of Zermatt and the Saasthal (Schaefer '95, Bonney '92) of which 

 representative collections were examined by the writer in Heidelberg and Cam- 

 bridge. 



8 The writer is indebted to Dr. Cornelius for the opportunity of examining his 

 collections in Zurich and discussing the same. The extreme complexity of the 

 crushing in the areaexamined may be gathered from the following remark (op. cit. 

 p. 3S2):" The Triassic dolomite is tornapart into isolatedlenses, between which wind 

 in and out dark Liassic limestones and phyllites, while gneiss is gripped in between 

 them in bands sometimes a kilometer in length, but only a few yards in width." 

 81795°— 26 3 



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