114 R. A. Daly — Limeless Ocean of Pre- Cambrian Time. 



sedimentary beds. It is also suggested that possibly the silica 

 of the cherts and jaspers characteristically associated with 

 these carbonates, were likewise thrown out of solution by 

 ammonium carbonate of organic origin. The petroleum and 

 natural gas emanations from Eozoic sedimentary rocks receive 

 explanation if the fundamental postulate of abundant Eozoic 

 marine life be accepted. 



5. The hypothesis seems to explain the greater development 

 of magnesian rocks in the earlier geological formations, espec- 

 ially those belonging to the Eozoic system. The hypothesis 

 throws light on the formation of dolomitic rocks of all ages. 



6. The hypothesis suggests that, in general, secular varia- 

 tions in the oceanic composition may be found to explain some 

 features of biological history, including certain accelerations 

 and retardations in life development, especially as regards the 

 elaboration of the hard parts of animals and the rise and fall 

 of lime-secreting organisms. 



According to the hypothesis the outlines of developments 

 may be tabulated as follows : 



Life. 



Oceanic 

 Composition. 



River Influence 



on Oceanic 



Composition. 



Carbonate 

 Deposits. 



Azoic Period. 





? ? ? 





Early Eozoic Period. 



Pelagic, soft-bod- 'Beginning of pre- Minimum ; land- 

 ied, low types! cipitation of areas small 

 of animals., and lime-salts 

 plants. 



Gradual evolution 

 of higber types of 

 animals, all soft- 

 bodied. 



Chief Fossils. — 

 Siliceous; impres- 

 sions of soft-bod- 

 ied animals ; pos- 

 sibly tests of pure 

 cbitin ; plants ? 



Followed by a long 

 limeless stage. 



minimum area 

 of limestone ex- 

 posed to weatb 

 ering. 



Calcium carbonate 

 followed by 

 mixed deposits 

 of calcium car- 

 bonate and mag- 

 nesium carbon- 

 ate ; iron car- 

 bonate. 



Late Eozoic Period. 



Relatively b i g b 

 types of animals, 

 soft-bodied. 



Chief Fossils. — As 

 in former period ; 

 also some cal- 

 careo-cbitinous. 



Great and rela- 

 tively rapid in- 

 crease of river- 

 borne carbonates 

 of calcium and 

 magnesium. 



Orogenic revolu- 

 tion ; land-areas 

 enlarged ; spec- 

 ial increase of 

 areas of weatb- 

 ering lime- 

 stones ; base- 

 leveling. 



Renewed abund- 

 ance of calcium 

 carbonate ; con- 

 tinued deposit of 

 magnesium and 

 iron carbonate. 



