I 
4 PALEONTOLOGY: R. RUEDEMANN 
continues through Greenland with some variation to NNW along the coast 
of Labrador through Tertiary crustal movements (Adams) and it is even 
recognizable in the western edge of Scotland. It is further observed in sev- 
eral ways, as in the interlocking NE-SW bands of different gneisses, showing 
ancient folding (Keith) in the southern extension of the Pre-Cambrian base- 
ment complex in the Appalachian and Piedmont systems. In the western 
part of the Canadian shield, north of Lake Superior, the Pre-Cambrian folds 
have assumed an E-W direction. Likewise the outcrops of Pre-Cambrian 
rocks south of Lake Superior in Wisconsin etc. show a predominant E-W 
direction. In the Ozark Mountain Pre-Cambrian nucleus however, a NW 
direction (strike N 50°W) is already recognizable; likewise in the Black Hills 
and farther south in the Arbuckle uplift in Indian territory (strike WNW) 
and in Texas, in Burnet county; where a monadnock of the ancient Lauren- 
tian land projects with a NW strike of the major folds in the Pre-Cambrian 
rocks. In the southern Rocky Mountains the Pre-Cambrian masses strike 
from S to N but exhibit a tendency to turn NNW to NW. 
It thus appears that there can be recognized in the Pre-Cambrian base of 
North America a uniform structure consisting of a NE system of folds in the 
east, that however does not abut, as in Asia, against a NW system, but grad- 
ually swings into it. 
In Africa large areas of the Pre-Cambrian basement complex are exposed in 
the Sahara Desert and south, throughout Central Africa to the Red Sea and 
across it into Arabia. In the Sahara and. western Africa as far as the Kal- 
ahari Desert, the strike of the folds is reported to be uniformly N-S, as far 
as known today, with variations in the east to NNW etc. Likewise in West 
Australia the direction of the folded areas of metamorphosed Pre-Cambrian 
rocks is N-S with a shght trend to W; and, as far as we could find, the north- 
erly direction is also present in Madagascar with variations to NE. It thus 
appears that there was a third immense tract of uniform Pre-Cambrian 
folding extending from West Africa to Australia. 
There are a number of smaller areas of Pre-Cambrian rocks known that 
have not been folded since Pre-Cambrian time. These are in Asia, found 
in Cambodia, Borneo and India. The latter shows in the Arvali Mountains 
Pre-Cambrian folds striking NNE (N 36°E) and extending within 65 Km. 
of the Himalaya Mountains which frora the north have overridden the Pre- 
Cambrian Mountain system. Farther south there is also a younger group 
(Algonkian?) of folds with E-W direction. These Indian Pre-Cambrian 
folds, especially as seen in the Arvali Mountains, are entirely distinct from 
the Asiatic system and probably referable to the African system. There is 
likewise in Bohemia a Pre-Cambrian complex, striking NE for the most 
part, that is independent of the Russian plate and the Baikal direction. In 
America the Colorado mass, exposed in the Grand Canyon and south, repre- 
sents a body of Archean and Algonkian folds with a NE direction and dis- 
tinctly outside of the Laurentian system of North America. 
