324 ROLLIN T. CHAM BERLIN 



vertical Cambrian and Ordovician strata.^ It is evident, therefore, 

 that in this region considerable disturbance and extensive denuda- 

 tion followed the Ordovician and preceded the commencement of 

 the Silurian sedimentation.^ 



Of the events in Asia at this time much less is known. But it is 

 known that in the eastern portion of that continent the Ordovician 

 seas withdrew late in the period, leaving large areas emerged in 

 Mongolia and Manchuria^ and probably also in northern China 

 where the Ordovician is terminated by unfossiHferous dolomites 

 which were probably lagoon deposits. The Silurian has not yet 

 been recognized above them and very likely was never laid down 

 there.'* But we have as yet no good evidence of any pronounced 

 mountain-making movements in Asia at this time. 



In the Andine region of South America there is a suggestion of 

 diastrophic movements following the Ordovician, for the Silurian 

 is often lacking there, the Devonian resting directly upon the 

 Ordovician. 5 



The eastern portion of the Australian continent was the locus of 

 mountain-making movements at several periods during the Paleo- 

 zoic. In New South Wales, the close of the Ordovician was at- 

 tended by both volcanic and diastrophic disturbances. Siissmilch 

 states that at Tallong, the one place where a junction between the 

 Ordovician sediments and those of the next period has been observed^ 

 a well-marked unconformity occurs. The evidences of this region 

 are interpreted by Siissmilch as showing that at the close of the 

 Ordovician period there occurred extensive earth movements by 

 which the marine sediments and volcanic ash, which had accumu- 

 lated to a thickness of many thousands of feet, were pressed into a 

 series of folds trending approximately north and south, and that 

 these suffered denudation so that when the sea readvanced upon 

 these land areas in Silurian time, the new sediments were deposited 

 unconformably upon the trunkated edges of the Ordovician strata.^ 



' A. C. Ramsay, op. ciL, p. 77. 



2 Sir Archibald Geikie, Textbook of Geology, 4th ed., II (1903), 953. 



3 A. de Lapparent, Traite de geologic, 5th ed., II (1906), 807. 

 ■i Emile Haug, Traite de geologic, II (191 1), 653. 



^ Ibid., p. 657. 



^ C. A. Siissmilch, Geology of New South Wales (1911), p. 18. 



