606 GEOLOGY 



Other continents. In other continents, where geological work 

 is less advanced, the Lower and Upper Carboniferous have not 

 always been carefully separated, but the system is known in all of 

 them. In Australia and New Zealand, the Lower Carboniferous 

 is much disturbed and metamorphosed, and associated with more 

 or less igneous rock. In Western Australia, as in some parts of 

 North America, gypsum and salt are found in the system. 



Climate and Duration 



Most of the data at hand indicate the absence of great diversity 

 of climate during the Mississippian (Lower Carboniferous) period, 

 and suggest at the same time that it was genial. The salt and 

 gypsum of the Mississippian series in Montana, Michigan, Nova 

 Scotia, and western Australia, suggest aridity, but it is not now 

 clear that this aridity was general. Certain conglomerate forma- 

 tions (the Culm) of western Europe have been thought to suggest 

 glaciation, but the evidence does not seem to warrant this conclu- 

 sion. Recently, phenomena which have been interpreted to imply 

 floating ice, have been found in Oklahoma. 1 



The period was probably somewhat longer than most of the 

 Paleozoic periods which had preceded it. 



THE LIFE OP THE MISSISSIPPIAN (SUBCARBONIFEROUS) 

 1. The Marine Faunas 



Just as there was no great stratigraphic break between the 

 Devonian and Mississippian systems in the American continent, 

 so there was no radical break in the succession of life. It will be 

 recalled that the life history of the Devonian in North America 

 included a series of great invasions from different quarter-, ami 

 that the invaders and the invaded mingled with one another until 

 at the close there was an approach to a single continental fauna. 

 The life of the Great Basin, however, was still partly isolated, and 

 there were dependencies of the main fauna that still retained 

 provincial features. 



1 Taff. Geol. Soc. Am. Dec. 1908. 



