552 SECTIONAL TRANSACTIONS.— C. 



for the view that the bedded succession of the complex rests unconformably upon 

 its Gneisses ; and as it is certain that there are schists of sedimentary origin which 

 are older than the deposition of the bedded succession, corresponding relations may 

 be looked for in Scotland. 



I once put forward the view that the dominant anamorphism of the complex is 

 not a product of the recumbent but of the later foldings. I now find this to be an 

 error. The dominant anamorphism is certainly older than the major secondary 

 folding, so the same is likely to be the case in Scotland. Many more stages in the 

 metamorphic process have been disentangled, so many may be expected in Scotland. 



The existence of the Bodorgan anamorphic minimum in Anglesey is a warning 

 against assuming that the boundary of the Scottish anamorphism is approached at 

 the Highland boundary fault. 



With due caution correlation of beds does not seem to be impossible between the 

 two regions. 



In Anglesey coincidence between the directions of the Palaeozoic and the pre- 

 Cambrian movements turns out to be no more than a simulation. May not the 

 coincidence in the Highlands be likewise a simulation ? 



Thus Anglesey seems to create at least presumptions in regard to Highland 

 problems. 



But in view of the probability of deceptive structures let us, in both regions, hold 

 our theories ' with a loose hand.' I have advocated the theory of recumbent folding 

 for the Mona Complex, and I still do so. In regions such as these, however, may 

 there not be some hidden principle whereof we have no more idea at present than 

 our predecessors had of recumbent folding ? 



Afternoon. 



Excursion to Victoria Park, Fossil Grove, Bowling, and Dumbarton. 

 Leaders : Dr. G. W. Tyrrell and Mr. P. Macnair.) 



Tuesday, September 1 1 . 



Discussion on The Tectonics of Asia. (Prof. F. E. Suess ; Dr. D. J. 

 MusHKETOV ; Prof. J. W. Gregory, F.R.S. ; Prof, de Bockh ; 

 Prof. G. P. Barbour ; Prof. H. A. Brouwer ; Mr. F. West.) 



Prof. F. E. Suess. — The horsts of middle and western Europe which Suess has 

 considered as fragments of a branch of the Asiatic Altaids, are composed of different 

 elements. To the north they contain the remnants of a fold zone with far-reaching 

 thrustfolds of Alpine dimensions, the Variscan-Armorican arc proper. The broad 

 middle region that comprises the bulk of the Bohemian massif, the Black Forest, the 

 Vosges and the French Central Plateau, shows a peculiar structure which is called the 

 ' Intrusion tectonics ' ; it is characterised by the great extension of granitic intrusions, 

 by the lack of general strike and by the post-tectonic crystallisation of the schists with 

 the mineralogical constituents of the katametamorphism. Other folded structures 

 of Alpine type with the corresponding crj^stalline fades of the schists are attached to 

 the Bohemian massif on the east and to the French Central Plateau on the west. 



The field of intrusion tectonics in the European horsts represents one gigantic 

 chip splintered from the roof above the ' Sal ' and pushed forward by great tangental 

 forces. The folded range in front of this large block is an effect of this movement. 



We may learn from the data of these and similar regions that in any crystalline 

 complex to work out trendlines of geological structure the careful study of the type 

 of metamorphism is indispensable, and we may expect that also the pre-Permian 

 basement complex of Central Asia will contain a great variety of structures and a 

 considerable portion of them will have to be attributed to the intrusion tectonics. 



It is hardly possible to establish definite connecting lines between the pre-Permian 

 structures that have been distinguished as European and Asiatic Altaids. 



In Europe, as in Asia, the old structures have been overwhelmed by the younger 

 tangential movement, and in the European horst-region, as in many parts of Central 

 Asia, the actual morphology is related to transverse disturbances sometimes of great 



