VOLUME XXVII NUMBER i 



THE 



JOURNAL OF GEOLOGY 



JANUARY-FEBRUARY igig 



THE GEOLOGY OF NORTH DAKOTA 



A. G. LEONARD 



University of North Dakota, Grand Forks 



INTRODUCTION 



The geology of North Dakota is comparatively simple. The 

 geological formations are not as numerous or of such great variety 

 as in many states, and the strata have undergone but little deforma- 

 tion since they were deposited. They are for the most part prac- 

 tically horizontal or have only a gentle dip. Metamorphism has 

 produced Httle or no change in the rocks, and, except for the deeply 

 buried granite near the eastern borders of the state, there have been 

 no intrusions or extrusions of igneous material. The rocks are 

 chiefly clays, shales, and sandstones belonging to the Cretaceous 

 and Tertiary periods, overlain in most places by the drift deposits 

 of the Pleistocene. The surface features of about two-thirds of the 

 state are therefore those of a gently rolling to rough drift plain. 

 The flat lacustrine plain of the Red River Valley occupies a strip 

 25 to 35 miles wide along the eastern border, while west and south 

 of the Missouri River the drift mantle is too thin to affect the topog- 

 raphy to any great extent. This large area beyond the Missouri 

 everywhere shows evidence of long-continued erosion, with its 

 numerous stream valleys, buttes, mesas, and badlands. 



