REPORT OF THE DIRECTOR I92O-2I 97 



not now be established. In the south it plunges under the Car- 

 pathian folds and the other- more recent fold systems. 



The outstanding feature of this immense Precambrian segment 

 extending through the greater part of Asia and Europe is the grand 

 uniformity of the Precambrian fold directions which remained rather 

 uninfluenced by all later folding. This immense block has thus 

 remained utterly independent from and immobile against the orogenic 

 movements that have involved the rest of Asia and Europe. 



That part of Europe which is outside of the Eurasian Precambrian 

 platform just described, namely, southwestern and southern Europe, 

 is involved in later folding to such an extent that the original Pre- 

 cambrian trend of folds can no longer be recognized, with the 

 important exception of the Bohemian block, the Hebrides and 

 perhaps certain small Precambrian massifs in Greece. The Pre- 

 cambrian nuclei of the Vogesian mountains, the Black forest, 

 Spessart and Taunus, possess a northeast strike, those of the Hartz 

 mountains, Frankenwald, Thuringian forest, Erzgebirge, Riesenge- 

 birge a northeast to east-northeast strike. These strikes, which 

 are entirely independent from the present strikes of these mountain 

 ranges, prove that they are relics of an ancient mountain system, 

 the Variscan system, that arose toward the end of Carboniferous 

 time through tangential pressure exerted from south-southeast. 

 This system meets and combines in a syntaxis (Schaarung) with 

 the equally old Armorican system in the central plateau of France. 

 The Armorican system of mountain folds with its northwest and 

 west-northwest direction, dominates the Precambrian massifs of 

 the Bretagne in France and of Cornwall in England. As is well 

 known, this mighty fold system has been found to reappear in 

 eastern North America. 



The Bohemian Precambrian body did not become involved in 

 the Variscan folding, but in its turn profoundly affected the latter 

 (see Suess, v. 3, pt 2, p. 25; v. 4, p. 26 of English translation). Its 

 boundaries toward the Variscan Fichtelgebirge and Sudets are 

 marked by sudden changes of strikes; the principal trend lines of 

 the body are northeast and east (see Katzer, 1892, p. 56). 



Another foreign body is represented by the Precambrian of the 

 Hebrides and some promontories of western Scotland. This is described 

 by Suess (v. 3, pt 1, p. 484; English trans., v. 3, p. 386) as an ancient 

 foreland of Archeozoic (Levisian gneiss) and older Proterozoic rocks, 

 that were folded and eroded before the deposition of the late Protero- 

 zoic Torridon sandstone. The latter has remained unfolded, thus 

 occupying a similar position as the Jotnian series in Finland, and 



