PETROLOGICAL ABSTRACTS AND REVIEWS 407 



Most of the rocks of the trondhjemite character are laccoUths or laccolithic. 

 They all appear to be post-Ordovician; they may be described in general as of 

 Caledonian (Upper Silurian) age. 



Many rocks do not definitely fit into any of the foregoing three groups. 

 These include pyroxenites, gabbroid types, basic and normal diorites, tonahte, 

 granites, and their aschistic and diaschistic differentiates. This group may, 

 if the sequence be as given above, indicate progressive differentiation. They 

 occur south of the Trondhjemfjord. Granites are found on the west coast, too, 

 and here are definitely assignable to Caledonian age, but cannot be readily 

 placed in a magmatic province. Some augengneisses are also assigned to the 

 same period. 



As to the consanguinity of the three main groups recognized above, nothing 

 definite can as yet be stated; surely the relationship is not as close between the 

 separate groups as within each group. Each group, however, illustrates beauti- 

 fully the differentiation-parallelism of separate magmas. Whether or not they 

 are related might perhaps be answered by calculating the general composition 

 of each group from a study of the rock-components. Data for such a calcula- 

 tion is, in the opinion of Doctor Goldschmidt, not yet sufficiently complete to 

 undertake any generalizations. This is unfortunate, for here is a large geo- 

 graphic province which might furnish the best of examples for a study of 

 magma-relationships and petrographic provinces in time if not in space. 



Rocks similar to the green lavas occur in Scotland, and others like the 

 Bergen-Jotun-granites (Group 2, above) are recognized from Sweden. The 

 third group (called by Goldschmidt the opdalite-trondhjemite group) is 

 undoubtedly represented in southern Scotland by the Galloway granite of 

 Peach, Home, and Teall, the age of which is less than the Ludlow and greater 

 than the Old Red. 



The writer seeks to draw analogies between the petrographic character of 

 the rocks in the Stavanger-Trondhjem district and those elsewhere, especially 

 in the Alps. 



Twenty-two analyses of typical representatives of the several groups are 

 appended, and many more, sometimes recalculated, are incorporated in the 

 text. 



Goldschmidt, V. M. Geologish-Petrographische Studien im Hoch- 

 gehirge des Siidlichen Norwegens: V, Die Injektionsmetamor- 

 phose im Stavanger-Gehiete. Christiania, 192 1. Pp. 142, pis. 

 15, map (with separate legend) i, with numerous tabulated 

 analyses. 



The rocks in this district are of several periods. At the base of the section 

 are pre-Cambrian rocks, unconformable below Cambro-Silurian deposits. The 

 latter consist of phyllites of Cambrian and lower Ordovician age and of green 

 slates of the upper Ordovician and Silurian. These are followed by eruptives 



