THE CANNONBALL MARINE MEMBER OF THE LANCE 

 FORMATION OF NORTH AND SOUTH DAKOTA AND 

 ITS BEARING ON THE LANCE-LARAMIE PROBLEM^ 



E. RUSSELL LLOYD and C. J. HARES 

 U.S. Geological Survey, Washington, D.C. 



Field examination by the writers and the paleontological 

 determinations by Drs. Stanton and Knowlton during the years 

 1912 and 1913 show that in a large region west of Missouri 

 River in North and South Dakota the Lance formation consists 

 of two distinct parts, a lower non-marine part containing a flora 

 very similar to, if not identical with, that of the Fort Union and 

 an upper marine member containing a fauna closely resembling, 

 but not identical with, that of the Fox Hills sandstone. This 

 upper part, on account of its peculiar fauna, has been mapped 

 separately and named the Cannonball marine member of the 

 Lance formation. Farther west non-marine beds bearing lignite 

 and occupying a similar stratigraphic position have been named the 

 Ludlow lignitic member of the Lance. 



The area examined by the writers embraces a territory of over 

 5,000 square miles, extending from Mandan, North Dakota, west 

 to Montana, a distance of about 175 miles (Fig. i), and south 

 beyond the boundary line of South Dakota. The marine member 

 of the Lance has been mapped from Mandan to a point 4 miles 

 west of Haley, North Dakota, a total distance of about 130 miles. 

 A large part of the area examined by the writers has been described 

 already from an economic standpoint.^ 



The Lance formation had previously been mapped in two adjoin- 

 ing regions, the Bismark Quadrangle^ and the Standing Rock 



' Published by permission of the Director of the U.S. Geological Survey. 



^ E. Russell Lloyd, "The Cannonball River Lignite Field, Morton, Adams, and 

 Hettinger Counties, North Dakota," U.S. Geol. Survey Bull. 541-g; D. E. Winchester, 

 C. J. Hares, E. M. Parks, and E. Russell Lloyd, "The Lignite Field of Northwestern 

 South Dakota," U.S. Geol. Survey Bull, (in course of preparation); C. J. Hares,. 

 "Lignite in Southwest North Dakota," U.S. Geol. Survey Bull, (in course of prepara- 

 tion). 



3 A. G. Leonard, U.S. Geol. Survey Geol. Atlas, Bismarck Folio (No. 181), 1912. 



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