68 HISTORICAL GEOLOGY 



sandstones, and shales. In western Europe, for example in Wales 

 and southern Scandinavia, the Cambrian strata are thoroughly 

 indurated and usually highly folded, but in eastern and central 

 Europe, for example in Russia, the strata are mostly practically 

 horizontal, and even unconsolidated beds of sand and clay have 

 been found. Unconsolidated beds of so great age are truly 

 remarkable. 



The Cambrian period closed in Europe without any important 

 physical disturbance. 



Other Continents. — The Cambrian of other continents has 

 generally not been well studied, but rocks of this age are known in 

 Australia, Tasmania, India, China, Korea, Siberia, and Argentina. 

 Only slightly folded or tilted strata of Cambrian age up to 20,000 

 feet thick are known in northern China. Glacial deposits in China, 

 Norway, and Australia will be described under the next heading. 



Climate 



Very distinct evidences of glaciation are known in the earliest 

 Cambrian or possibly late Algonkian of China, Norway, Australia, 

 and perhaps also South Africa. At the base of the thick section of 

 Cambrian strata in China "on the Yangtse River, 31° Lat., i.e. 

 as far south as New Orleans, not high above sea level, a large body 

 of glacial material (170 feet thick) was discovered. ... It demon- 

 strates the existence of glacial conditions in a very low latitude in 

 the early Paleozoic. " 1 



At Lat. 70° N. in Norway, glacial deposits containing clearly 

 striated pebbles have been found resting upon a distinctly smoothed 

 and striated surface of hard rock. 



In southern Australia glacial beds of similar age and consider- 

 able thickness are distinctly folded along with the enclosing strata. 



The significance of these earliest Paleozoic glacial deposits is 

 difficult to exaggerate in considering the climate of the time. The 

 old idea, based upon the Laplacian Nebular hypothesis, that early 

 Paleozoic climate was notably warmer, moister, and richer in 

 carbon dioxide than now, is directly refuted by the evidence of 

 glaciation. Such evidences of glaciation, combined with the char- 

 acter and distribution of the organisms, indicate that Cambrian 



1 B. Willis: Researches in China (Vol. 2), Published by Carnegie Insti- 

 tution of Washington. 



