part 2] OF SOUTHERN EYEE PENINSULA. 129 



than one way, both from igneous rocks and from sedunents, parti- 

 cularly from impure carbonate-rocks. In the Flinders Series there 

 are no amphibolites that can be recognized as arising in the 

 second wsiy, nor in the associated Hutchison Series is such a 

 process of development met with. They appear to be essentially 

 of the first class. 



The development of the older Hutchison Series in Southern 

 Eyre Peninsula is in a more f]-agmentary state of preservation 

 than the corresponding Grenville Series of Ontario. That series is 

 penetrated by basic dykes and sills, now highl}'- metamorphosed, 

 and the igneous amphibolite-inclusions of the granite-gneisses are 

 regarded as due to the shattering and rifting-off of these rocks 

 from the invaded sedimentary series. 



In the absence of any extended exposures of the Hutchison 

 Series such processes cannot be observed in general in the Flinders 

 area. We have, however, already noted the presence of definite 

 inclusions of sedimentary rock of dolomitic origin, in the diopside- 

 bands developed in the gneisses of Sleaford. 



The field-evidence encourages the interpretation of the amphi- 

 bolites as pre-existing igneous rocks which have become involved 

 in the later gneisses, these igneous rocks in all probability having 

 been intruded into — and there consolidated — a portion of the 

 crust corresponding to an extension of the present fragmentary 

 Hutchison Series, or some earlier formation, at a period preceding 

 the irruption of the granite-gneisses. 



(3) The Lewisian area of the North-West Highlands of Scot- 

 land. — In the Lewisian tract, with its great development of basic 

 bands alternating with more acid and granitic types, a parallel 

 with the Eja-ian region is again revealed. There appear, however, 

 to be certain distinctions forbidding that close comparison which I 

 have instituted with the Ontarian region. 



The relations of the gneisses and their intercalated basic bands 

 in the Lewisian tract (as described in the Survey memoirs) are of 

 a much more complex and involved nature than in the relatively 

 simple Laurentian and Eyrian areas. It would appear that 

 hybridism has played a much more important part, and the 

 distinction between basic and acid members is less sharply 

 demarcated. 



The vivid analogy which Sir Jethro Teall ^ has drawn between 

 the relations of these basic and acid portions of the complex, and 

 the forms and dispositions of the foam-Hecks on the pools of com- 

 paratively still water below falls and rapids, also the intensive 

 disruption with concomitant hybridism of the earlier basic members, 

 have — with the exceptions of highly-localized areas — no parallel in 

 the Eyrian region. 



^ ' The Geological Structure of the North-West Highlands ' Mem. Geol. 

 Sury. 1907, p. 71. 



