12 A. G. LEONARD 



they reach from 1,300 to about 2,235 f^et. At Jamestown they are 

 1,330 feet thick, at Devils Lake, 1,403 feet, Leeds, over 2,000 feet, 

 and at Harvey they are not far from 2,235 f^^t thick. The deepest 

 well in the state, at Max, 30 miles south of Minot, has a depth of 

 about 2,400 feet, but it passed through drift, some Fort Union, 

 and probably the Lance before entering the Cretaceous shales, and 

 it did not reach the Dakota sandstone. The Deloraine well not 

 far north of the international boundary went through 1,800 feet of 

 shales, including some Fort Union strata, without reaching the 

 Dakota. 



Fox Hills sandstone. — This upper member of the Montana group 

 is known to outcrop in three separate areas in North Dakota. The 

 largest of these is along the Missouri River, where the formation is 

 exposed for over 40 miles north of the South Dakota line and 

 extending 5 to 10 miles on either side of the river. A narrow belt 

 of Fox Hills sandstone surrounds the Pierre area in the southwestern 

 corner of the state, and there is a small outcrop near the center 

 of the state. ^ 



The Fox Hills is particularly well shown along the Cannonball 

 River for a distance of over 12 miles above its mouth, where the 

 sandstone forms vertical cliffs rising from 80 to 90 feet above the 

 river and is overlain by banded shale. The sandy portion of the 

 formation is a yellow, rusty brown or gray, rather soft sandstone. 

 Cross-bedding is very common, and the formation contains great 

 numbers of large and small ferruginous sandstone concretions and 

 indurated masses and layers, these also exhibiting cross-bedding. 

 The concretions are apparently due to the segregation of the iron 

 in certain portions of the rock, cementing the sand into firm, hard 

 masses, considerably harder than the sandstone in which they are 

 imbedded. These concretionary masses vary in size from an inch 

 and less to 6 and 8 feet. Small, irregular, twisted or stemlike 

 forms are abundant in places. Some portions of the rock are so 

 completely filled with these rusty brown concretions that they 

 constitute the main bulk of the formation, and the gray, loosely 

 cemented sandstone forms a kind of matrix, in which the harder 

 concretions are imbedded. In the process of weathering these 



^ Described by Dr. T. W. Stanton in a letter to the writer. 



