3 2 4 



EDWARD STEIDTMANN 



Has Sedimentation Increased the Ratio or Calcium to Magnesium of 



the Lands during Geologic Time ? 



The geologic record of the continental interiors. 



The geologic record of the continental margins. 



Deposition within the ioo-fathom line. 



Deposition beyond the ioo-fathom line. 



Significance of the deposition of muds in the ocean basins. 



Does the ratio of calcium to magnesium in the sea show a selective loss 



of magnesium from the lands with geologic time ? 



Resume of the results of sedimentation and their effect on the ratio of 



calcium to magnesium of the lands. 

 Has the Ratio oe Calcium to Magnesium in the River Waters Increased 



with Geologic Time? 



Influence of the terranes on the calcium-magnesium ratio of underground 



waters and streams. 



The influence of climate on the calcium-magnesium ratio of streams. 



Influence of the belt of cementation on the calcium-magnesium ratio of 



underground waters. 



Average calcium-magnesium ratio of the solutions contributed to the sea. 



Conclusion: Increase of the ratio of calcium to magnesium in rivers with 



geologic time. 

 Statement of Hypothesis 

 Summary 



INTRODUCTION 



Many writers 1 have called attention to the decrease in the 

 percentage of dolomite in going up the geologic time scale, and 



1 Daly has shown the decrease in dolomite with age in the following compilation 

 of analyses (Table I, from Bull. Geol. Soc. Am., XX, 165): 



table I 



Average Ratio of Calcium to Magnesium in Limestones of Different Periods 



Period 



Number of 

 Analyses 



Ratio of CaC0 3 

 to MgCOj 



Ratio of Ca to 

 Mg 



Pre-Cambrian: 



a) From North America, except those 

 in b) 



b) From Ontario (Miller) 



c) Average of a) and b) 



d) Best general average 



Cambrian (including 17 of the Shenan- 

 doah limestone) 



Ordovician 



Silurian 



All pre-Devonian 



Devonian 



Carboniferous 



Cretaceous 



Tertiary 



Quaternary and Recent 



Total 



28 

 33 

 61 

 49 



3° 

 93 

 208 



106 



238 



77 



26 



26 



1 . 64 : 1 



4.02:1 

 2:93:1 



2.58:1 



2.96:1 



2.72:1 

 2.09:1 



2.39:1 



4 • 49 : 1 



8.89:1 



40.23:1 



37-92:1 



25.00:1 



2.30:1 

 6.89:1 

 4.10:1 

 3.61:1 



4.14:1 

 3-8i:i 

 2.93:1 



3-3S:i 



6.29:1 

 12.45:1 

 56.32:1 

 53-°9:i 



3S-oo:i 



865 



