PALEOZOIC STRATIGRAPHY OF ROCKY MOUNTAINS 113 



The Middle and Upper Ordovician Dolomites 

 Extent of the Bighorn Dolomite 

 The Bighorn Dolomite in Montana 

 Members 2-4 



Members 5-7 ; the Leigh Formation 

 Members 8 and 9 



PART III 

 Stratigraphy — Continued 

 The Silurian System 



In Utah 



In Nevada 



Is the Laketown Dolomite in Part Devonian ? 



Pre-Laketown and Pre-Devonian Emergence 

 The Devonian System: The Jefferson Dolomite 



Basal Division of the Jefferson Dolomite 



Main Division of the Jefferson Dolomite 



Upper Division of the Jefferson Dolomite 



Misuse of the Name "Jefferson" in Yellowstone Park and Vicinity 



Correlation of the Jefferson Dolomite with the Nevada Limestone 

 The Devonian System: The Three Forks Formation 



Type Sections 



Members 19 and 20 



Beds of Doubtful Age in the Bighorn Range and near Cody 



Member 2 1 



The Three Forks Formation in Northern Utah; Correlation with the 

 Benson and Ouray Limestones 

 Disconformities 

 Summary of Results on Special Problems of Investigation 



Historical Sketch 



Upper Cambrian and Lower Ordovician 



Extent of Submergence 



Paucity of Clastic Sediments 



Evidence That the Sea Was Shallow 



The Chazyan( ?) Sands 



Emergence and Peneplanation 

 Middle and Upper Ordovician 



The Trenton Submergence 



The Post-Trenton Emergence 



The Richmond Submergence 

 Silurian 



Emergence 



The Niagaran( ?) Invasion 



