THE EVOLUTION OF LIMESTONE AND DOLOMITE. I 



EDWARD STEIDTMANN 



University of Wisconsin 



T CONTENTS 



Introduction 



Part I. The Evidence on the Origin of Dolomite 



A. The evidence for the origin of dolomite in the sea. 

 Interstratification of limestones, magnesian limestones, and dolomites, 

 the result of primary conditions of sedimentation, or of the differential 

 metamorphism of limestones after their emergence from the sea. 

 Fineness of grain peculiar to some dolomites, probably indicative of 

 very little metamorphism since deposition. 



Many dolomite formations lack fossils. 



Association of certain dolomites with gypsum and salt deposits. 

 Chemical precipitation of dolomites in the sea. 

 Experimental evidence for the chemical precipitation of dolomite. 

 Daly's hypothesis of direct precipitation of dolomite in primitive ocean. 

 Deposition of magnesian limestones by marine organisms. 

 Development of magnesium limestones and dolomites by marine 

 leaching. 



The origin of dolomite by the secondary replacement of calcium by 

 magnesium in the sea. 



Experimental evidence on the origin of dolomite by secondary replace- 

 ment of calcium chloride. 



B. The evidences for the origin of dolomite by the metamorphism of 

 limestones after their emergence from the sea. 



Direct chemical precipitation of dolomite. 



Origin of dolomite by leaching limestones after their emergence 



from the sea. 



Origin of dolomite by secondary replacement of limestone. 



C. Evolution versus the metamorphism of limestones after their emer- 

 gence from the sea as explanation for the increase in the ratio of 

 calcium to magnesium of limestones and dolomites with geologic time. 



What Factors Controlling the Deposition of Calcareous Marine 



Deposits Have Undergone a Gradual Evolution Resulting in the 



Evolution of the Limestones and Dolomites? 

 Part II. Calcium and Magnesium in the Products of Metamorphism 



Materials lost by the weathering of acid igneous rocks. 



Materials lost by the weathering of basic igneous rocks. 



Materials lost by the weathering of limestones. 



Resume of the materials lost by weathering. 



Materials lost by dynamic metamorphism 



Materials lost by contact metamorphism. 



Materials lost by hot solution. 



Resume of calcium and magnesium in the products of metamorphism. 



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