P. A. Daly —Timeless Ocean of Pre- Cambrian Time. 93 



Art. X. — The Limeless Ocean of Pre- Cambrian Time / by 

 Reginald A. Daly, Ottawa, Canada. 



[Published by permission of the Canadian Commissioner, International 

 Boundary Surveys.] 



Introduction. 

 Unfossiliferous pre-Carnbrian and Cambrian formations. 

 Explanations of the unfossiliferous character of pre-Cambrian 

 sediments. 



1. Hypothesis of the metamorphic destruction of fossil 



remains. 



2. The Brooks hypothesis. 



3. A suggested hypothesis. 



Precipitation of lime salts through the decomposition of dead 



organisms. 

 Duration of the limeless sea. 



The oldest calcareous fossils in the stratified rocks. 

 Tests of the suggested hypothesis. 



1. Corroborative experiments. 



2. Observations on the Black Sea. 



3. Pre-Cambrian sedimentary deposits. 



Origin of dolomite and other magnesian sediments. 

 Origin of the Lake Superior iron ores. 

 Origin of certain pre-Cambrian cherts and jaspers. 

 Origin of petroleum and natural gas emanations from 

 pre-Cambrian sediments. 



Summary. 



Premises. 

 Conclusions. 



Introduction. 



Unfossiliferous pre- Cambrian and Cambrian formations. 

 — In comparatively recent years a new stratigraphic province 

 has been discovered in the mountain-tracts of British Colum- 

 bia, Alberta, Montana and Idaho. A dozen workers in Canada 

 and the United States have now established that the region is 

 underlain by an exceptionally thick series of sedimentary rocks, 

 sandstones, argillites, conglomerates, limestones and dolomites. 

 These rocks are proved to be of Cambrian and pre-Cambrian 

 age. Along the international boundary the series is conform- 

 able throughout. In the southern Selkirk range its base is 

 exposed and nearly 27,000 feet of these sedimentaries, besides 

 6,500 feet of contemporaneous basic lavas, are seen resting, in 

 strong unconformity, upon an older, Archean, series of schists, 

 quartzites and impure dolomites. In the Purcell range some 

 20,000 feet of the rocks are exposed, and, in the Rocky Moun- 

 tains proper, about 14,000 feet are exposed, but in neither case 

 is the base there seen. 



This stratigraphic province is notable for furnishing the 

 characteristic "Algonkian" fossil, Beltina da?iai, one of the 

 most ancient organisms yet found. At the international boun- 



Am. Jour. Sci. — Fourth Series, Vol. XXIII, No. 134. — February, 1907. 



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