98 NEW YORK STATE MUSEUM 



proving that this ancient body of Precambrian rocks remained free 

 from the Caledonian orogenic diastrophism, and possibly is the 

 terminus of the Laurentian continent. 



Another ancient Precambrian nucleus appears to be present in 

 the gneissose mass of the Cyclades, which, according to Philippson, 

 has determined to some extent the position and trend of the arc 

 now observable in the later folds (Dinarids) (see Suess, v. 3, pt 1, 

 p. 417 ; English trans., v. 3, p. 331). A further remarkable fact is that 

 in another region, on the island of Cerigo, between Greece and Crete, 

 ancient phyllite strikes east-northeast and is unconformably over- 

 lain by the Mesozoic limestones which strike southeast (see Suess, 

 ibid., p. 418). 



There are apparently no independent Precambrian blocks known 

 from the Spanish and Apennine peninsulas. 



The combined facts of the prevailing northeast to east trends of 

 the Bohemian massif, the remnants of the Variscan fold system 

 which probably followed the older Precambrian folds and the small 

 patches in the Greek islands, seem to' suggest the possibility of a 

 larger Precambrian platform in southwestern Europe with a north- 

 east or east trend. The Armorican folds, if also posthumous in 

 nature, would add, however, a different northwest element to the 

 Precambrian basement complex. 



c Precambrian Fold System of Africa 



While the old continent of Africa has long been known to be 

 composed over vast areas of granite, gneiss and other metamorphic 

 rocks of Precambrian aspect and in most cases also Precambrian 

 age, it is difficult to find conclusive evidence of the dominant trend 

 lines of these regions. 



In the broad belt of Precambrian rocks that extends across the 

 Sahara desert south of Morocco the north-south direction of the 

 lines has been found as a remarkably persistent feature by the 

 expeditions that have crossed this belt. Suess (see Suess-Sollas, 

 p. 94) says of this belt: " The Archean zone, formed of gneiss, 

 crystalline schists, phyllite, cipolin and granite, is steeply folded; 

 its prevalent north and south strike is a noteworthy feature. . . . 

 The north and south strike, interrupted at most by local deflections, 

 which is observed in the Archean basement and the beds folded 

 in with it, dominates all the central part of the Sahara from the 

 Tidikelt (lat. 27 N) onwards, and neither to east, south nor west 

 are its boundaries to be found." This north-south strike has been 



