4 A. G. LEONARD 



THE CRETACEOUS SYSTEM 



Dakota sandstone. — The oldest Cretaceous formation in North 

 Dakota is the Dakota sandstone which is reached in many wells but 

 does not appear at the surface anywhere in the state. In the 

 southeastern counties, as well as in South Dakota and elsewhere, 

 the sandstone is the chief source of artesian water. It is a non- 

 marine formation and was deposited either in a large lake or was 

 spread by rivers over their broad flood plains. The Dakota sand- 

 stone underHes the entire state, except a considerable portion of 

 the Red River Valley, where it has been removed by erosion 

 (Fig. i). 



A rather fine-grained white sandstone, which is doubtless the 

 Dakota, is found in a number of wells in the Red River Valley at 

 depths ranging from 250 to 400 feet, and in several wells the sand- 

 stone was penetrated 100 feet. In southeastern North Dakota 

 outside the valley, the Dakota sandstone is encountered at depths 

 varying from about 500 feet near the western edge of the Red River 

 Valley to 1,800 feet and over not far west of the James River and 

 near the edge of the Missouri Plateau. The increasing depth of 

 the formation is due both to the westward dip of the Dakota and 

 the rise of the land surface in that direction. The depth of the 

 sandstone at Enderlin is 640 feet; Valley City, about 800 feet; 

 Oakes, 880 feet; Ellendale, 1,035 feet; and Jamestown, 1,450 feet. 

 The deep well at Devils Lake, in the northeastern part of the state, 

 struck the sandstone at 1,431 feet, while at Leeds, 30 miles north- 

 west of Devils Lake, it Kes at a depth of 2,110 feet. The Harvey 

 well, near the center of the state, reached the Dakota at 2,235 feet, 

 and a deep boring a few miles from Westhope, Bottineau County, 

 entered the sandstone at about 2,100 feet. Though the well at 

 Mandan reached a depth of 2,000 feet it failed to strike the Dakota, 

 probably by several hundred feet. 



As disclosed by the wells which penetrate it, the Dakota forma- 

 tion is a soft white or gray sandstone in beds 10 to 50 feet thick, 

 separated by shale. In the regions where it occurs at the surface the 

 sandstone has yielded an abundance of fossil leaves, the Dakota 

 flora including no less than 450 species of trees and other plants. 



