REVIEWS. 853 



The second division or green schists include foliated gabbro, diabase, 

 variolite, serpentine and various pyroclastic deposits now filled with 

 new epidote, uralite, chlorite, saussurite and other secondary products. 

 They show many points of analogy with the greenstone schist areas of 

 the Marquette and Menominee districts on Lake Superior. Of more 

 than usual interest are Schmidt's descriptions of the chloritic ferru- 

 ginous oolite of Callovien. This was once a glauconitic oolite of 

 Jurassic age, whose spherical particles have, by dynamometamorphism, 

 been flattened, while their iron has crystallized as magnetite and hema- 

 tite, and their glauconite changed to chlorite. The process of meta- 

 morphism in the Biindnerschists is summed up by Schmidt as follows : 

 "The first stage of the metamorphism of the sediments always con- 

 sists in the development of rutile microliths, as well as isolated and 

 usually skeleton crystals whose nature depends on the composition of 

 the metamorphosed material. These new phenocrysts gradually 

 increase both in number and size ; they are always filled with 

 abundant inclusions of the groundmass whose sedimentary arrange- 

 ment is not destroyed within the newly formed phenocryst. Finally, 

 the clastic groundmass is transformed into an aggregate of crystal- 

 line minerals ; and, where the metamorphism is most intense, the 

 contrast between new phenocrysts and groundmass is least distinct." 

 (1. c, p. 71.) 



As a result of both his own and Schmidt's work, Heim concludes 

 (1. c. p. 488) : 1) that all the demonstrable orographic disturbance, 

 and hence all the dynamometamorphism within his area, is post- 

 Eocene, and much of it post-Miocene ; 2) that two sorts of meta- 

 morphism must be distinguished. The recent dynamic metamorphism 

 which was caused by, and hence was synchronous with orographic 

 movement ; and the much more ancient and probably still continuous 

 metamorphism due to heat, moisture, and simple pressure without 

 motion, which he calls diagenetic metamorphism (statical metamorphism 

 of Judd). He contrasts the effects of mechanical metamorphism upon 

 highly crystalline and sedimentary rocks, in that the same cause 

 crushes the former into a finely granular schistose series, and recrys- 

 tallizes the latter by developing large phenocrysts within them. He 

 attributes these results in his particular Alpine region entirely to 

 dynamic action, since he can find no trace of' eruptive material 

 which could have produced contact metamorphism in rocks of tertiary 

 age. 



