270 



THE CLIMATIC FACTOR AS ILLUSTRATED IN ARID AMERICA. 



and the marine Cambric is always a sharp one, leading to the inference that the sea of this 

 time transgressed over an old flat land. Under these circumstances, deposition was not 

 continuous, for the geologic section is here broken between the tillite and the Cambric 

 deposits, indicating that the age of the former is rather late Proterozoic than early Paleozoic. 

 From the evidence of the Lower Cambric life, to be presented later, we shall see that the 

 waters of this time, the world over, were of tropical or subtropical temperature, conditions 

 not at all in harmony with the supposed glacial climates of earliest Cambric time. (For 

 further detail see pp. 291-93.) 



Fig. 89. — M.ap of Proterozoic Gl.aciation. 



The Norwegian occurronee shown by an empty circle on this map ia supposed to be late Proterozoic, but there is doubt as to the exact 

 date. The occurrence in Great Britain and also the occurrences indicated by diagonal lines are undated Proterozoic. 



Arctic Noncay. — As long ago as 1891, Doctor Reusch described unmistakable tillites 

 in the Gaisa formation in latitude 70° N. along the Varanger Fiord of Arctic Norway. 

 Similar deposits are also known farther east on Kildin Island, and on Kanin Peninsula 

 at Pae (Ramsay, 1910). At first the age of these deposits was thought to be late Paleozoic 

 and even Triassic, but the Swedish geologists now correlate the Gaisa with the Sparagmite 

 formation, one of the members of the Seve series. As the latter is overlain by the Lower 

 Cambric fauna it appears best to refer the Gaisa formation to the top of the Proterozoic 

 series. The tillite occurs at the very base of the Gaisa formation and overlies the ancient 

 and eroded granites. Strahan reinvestigated the area originally studied by Reusch and 

 his description of the geologic phenomena must convince anyone, not only that here are 

 intercalated thin zones of sandstone and tillite in a series of red shales (these may indicate 

 warmer and arid interglacial climates), but as well that the tillite rests upon a striated 

 sandstone, the very ground over which the glacier moved. Strahan further states that 



