REPORT OF THE CHIEF ASTRONOMER 

 SESSIONAL PAPER No. 25a 



675 



Life. 



Oceanic 

 Composition. 



River influence on 



Oceanic 



Composition. 



Carbonate 

 Deposits. 



Time Place of the Great Unconformity.* 

 Cambrian Period. 



Diversified animal types ; 

 beginning of lime secre- 

 tion. 



Chief Fossils. — Calcareo- 

 chitinous and calcare- 



Lime salts sufficient for 

 lime secretion by an- 

 imals. 



Land areas probably 

 diminished but still 

 large in absolute mea- 

 sure. 



Both chemically preci- 

 pitated and directly 

 organic calcium car- 

 bonate ; magnesium 

 carbonate in dimin- 

 ished proportion. 



From Cambrian to Epoch of Colonization of General Sea floor. 



Limey structures of an- 

 imals fully developed. 



Chief Fossils. — Calcare- 

 ous. 



Same as last period. 



Land areas, and areas 

 of weathering lime- 

 stone, slowly though 

 not steadily increas- 

 ing. 



Same as last period. 



Period following Colonization of General Sea floor. 



Same as last period. 



Gradual increase of cal-jLand areas approach- 

 cium sulphate in solu- ing maximum extent. 

 tion. Rivers drain maxi- 



mum area of lime- 

 stone. 



Directly organic cal- 

 cium carbonate dom- 

 inant ; magnesium 

 carbonate at its min- 

 imum. 



* It may be noted that in British Columbia there is local conformity between the Beltina bed 

 and the beds corresponding to the Olenellus zone. This is, of course, an exceptional relations 

 between Cambrian and pre-Cambrian rocks as exposed on the, continental plateaus. 



25a — vol. iii — 44 



