14 C. R. VAN HISE THE PROBLEM OF THE PRE-CAMBKIAN 



was objected that while the nature of the life is now unknown, in the 

 future it is likely to become known. 



In my correlation bulletin upon the Archean and Algonkian,® while I 

 did not exclude Agnotozoic from the classiiication of the pre-Cambrian, 

 I inserted Proterozoie opposite to Agnotozoic as the name of the era and 

 expressed my preference for the former. In a later paper I dropped the 

 latter term altogether.'^ Of the two terms, Proterozoie has increased in 

 favor and Eparchean has disappeared from current usage. 



It is my own belief that Irving did not care particularly what term was 

 used for the pre-Cambrian sedimentary series. That was a matter of 

 small consequence. The idea was the thing for which he strove. 



Shortly after Irving had shown to most of the thinking geologists that 

 the pre-Cambrian group of sedimentary rocks must be recognized and 

 discriminated from the basement group, his unfortunate death occurred, 

 and I was asked to continue the direction of the work of which he had 

 had charge in the Lake Superior region. In 1889 a conference was called 

 at Washington to consider the nomenclature to be placed on the proposed 

 geologic atlas of the United States. It was decided at this conference 

 that zoic terms should not appear on the maps, although they might be 

 used in the text. The largest divisions on the map were to be systemic. 

 Thus the terms Silurian, Cretaceous, etcetera, but not Paleozoic and 

 Mesozoic, were to be placed on the maps. This decision raised the ques- 

 tion what should be done in reference to the Agnotozoic or Proterozoie. 



The fossiliferous groups of rocks are divided into periods and cor- 

 related on the basis of fossil evidence. In the Lake Superior region is a 

 fauna called Silurian, similar to faunae in the Silurian rocks of ISTew 

 York and of "Wales, but no way has been found to tell whether a pre- 

 Cambrian sedimentary series of the Lake Superior region is equivalent 

 to one which occurs in the Grand Canyon district, in Scotland, or in 

 China. What, then, should be done? In the Lake Superior region we 

 have not one, but four series of sedimentary rocks separated by uncon- 

 formities, all separated by another unconformity from the basement group 

 below, and by still another unconformity from the Cambrian above. 

 Which of these series should be correlated with the Grand Canyon series 

 of the Colorado? And may not the Grand Canyon series be equivalent 

 to one of the imconformities in the Lake Superior region? To these 

 questions there were no answers. The science of geology had not sufiB- 

 ciently advanced to correlate on a physical basis from province to province, 

 nor has it to the present time. When the physical history of the conti- 



« Bulletin no. 86 of the U. S. Geological Survey, p. 493. 



' Principles of North American pre-Camhrian Geology. Sixteenth Annual Report of 

 the U. S. Geological Survey, p. 762. 



