460 THE JURASSIC PERIOD 



have already seen that marked changes were in progress during 

 the upper Malm. The result of the diastrophic movements in the 

 interior during the latter part, and at the close of the Jurassic 

 period, was to drain the inland seas and the great northern gulf, 

 converting nearly the whole region into land. 



Foreign. — The greater part of South America was above the sea 

 during the Jurassic period, as it had been in the Trias. Marine 

 deposits of the former period are found only along the western 

 border of the continent, where they extend from 5 to 35 S. lat. 

 Throughout the Jurassic the sea which covered this western coast 

 retained its faunal connection with the central European region, 

 and even the minuter divisions, the substages and zones of the 

 European Jura, are applicable to the classification of the South 

 American beds. In what manner this southern area became 

 separated from the Pacific border of North America in the upper 

 Malm, it is difficult to conjecture. 



In Europe the Jurassic rocks are magnificently displayed, but 

 they differ much both in thickness and in character as they are 

 traced from one country to another, which results from more 

 frequent and more localized changes of level than had occurred 

 during the Palaeozoic. 



The Lias has a much more restricted extension than the later 

 Jurassic stages. At the end of the Triassic had begun a trans- 

 gression of the sea, which flooded many of the inland basins and 

 salt lakes, and the same transgression continued into the Lias, 

 proceeding northward from the Mediterranean, and covering large 

 areas in central and southern Europe, as well as a belt across 

 England, but not extending to Russia. By far the greater part of 

 the Eurasian land mass was above the sea, and fresh-water lakes 

 extended across Siberia, while in China wide-spread deposits of 

 Liassic coal were accumulated. 



In the latter part of the middle Jura the transgression of the 

 ocean was renewed, and this time on a vastly larger scale, cutting 

 the continents by seas and straits, invading great areas that had 

 long been land, and covering the larger part of Europe and Asia. 

 This is one of the greatest transgressions of the sea in all recorded 



