HISTOEICAL REVIEW OF THE LARAMIE PROBLEM. 



41 



of the Cannonball member and argued for its 

 probable Cretaceous age. They wrote: 



Field examinations by the writers and the paleonto- 

 logical determinations by Drs. Stanton and Knowlton 

 during the years 1912 and 1913 show that in a large area 

 west of Missouri River in North and South Dakota the 

 Ijance formation consists of two distinct parts — a lower 

 nonmarine part containing a flora very similar to if not 

 identical with tliat 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 nonmarine 

 beds bearing lignite and occupying a similar stratigraphic 

 position have been named the Ludlow lignitic member 

 of the Lance. 



After describing the areal distribution and 

 giving a number of sections of tlie strata, they 

 proceeded to a discussion of interrelationships. 

 The fauna of the Cannonball was studied by 

 T. W. Stanton, who wrote concerning it as 

 follows : 



The fauna of the Cannonball member of the Lance may 

 now be characterized as a modified Fox Hills fauna. It 

 contains a considerable proportion of undescrilied species 

 of Cretaceous affinities, and it is noteworthy that a number 

 of the most common Fox Hills species have not been dis- 

 covered in this fauna. * * * In this list of about 40 

 forms there are 21 named species and varieties, of which 

 15 occur in the Fox Hills, 4 occur in the Pierre, and 5 were 

 originally described from rocks now known to belong 

 to the marine member of the Lance. One species, Cor- 

 hicula cytherifunnis, was described from the Judith River 

 formation and is known in the Mesaverde formation and 

 the Lance of other areas. 



After presenting and weighing the several 

 lines of evidence that may be used in fixing 

 the age of the Cannonball, these authors con- 

 cluded as follows: 



A recent detailed consideration of all the evidence has 

 led to a decision by the United States Geological Survey 

 that the Denver and Arapahoe, Dawson, and Raton forma- 

 tions in Colorado and New Mexico all be placed in the 

 Tertiary system. This decision was based primarily on 

 the correlation of these formations with the Wilcox forma- 

 tion of the Gulf region on the evidence of their fossil floras 

 and also on the consequent correlation of the unconformi- 

 ties in the two regions. Although the Lance formation is 

 believed to beof the same age as the Denver, Raton, and 

 "Upper Laramie," it is classified by the United States 

 Geological Survey as Tertiary (?), the doubt being thus 

 expressed on account of the Cretaceous character of the 

 Cannonball marine fauna. The writers believe that 

 greater weight should be given to the evidence of the 

 marine faunas and the dinosaurs, and that, in view of the 

 strong evidence presented by these faunas, the correla- 

 tions made on the basis of fossil floras should not be 

 considered as conclusive. 



In a final footnote they added that "further 

 studies on the Lance problem have strength- 

 ened the conviction of the writers that the 

 Lance is Cretaceous." 



FORT UNION FORMATION. 



The early history of the Fort Union forma- 

 tion, or"Great Lignitic," as it was at first called, 

 has been sufficiently set forth in the preceding 

 pages. In fact, it was not until the Laramie 

 was established that the element of discord was 

 introduced which gave rise to so much subse- 

 quent discussion and difference of opinion. 

 Most of the geologists and paleontologists who 

 had studied the Fort Union contended for its 

 Tertiary age, and Newberry, who investigated 

 the flora, was at first inclined to refer it to the 

 Miocene. It appears that Hayden was in the 

 end more or less responsible for promulgating 

 what has since been accepted as an erroneous 

 view regarding the relation of the Fort Union 

 to the Laramie. When the Laramie was 

 adopted by Hayden, he made it include or at 

 least be equivalent to the Fort Union, as the 

 following statement shows :'^ 



If objection is made to the use of the term "Lignitic" 

 group, I would say that in this work it is restricted to a 

 series of coal-bearing strata lying above the Fox Hills 

 group, or Upper Cretaceous, and these are embraced in the 

 divisions Laramie and Fort Union. 



On the same page Hayden continued: 



As far back as 1859 it was my belief, founded on what 

 appeared sufficient evidence, that the sequence between 

 the well-characterized Cretaceous strata and those of the 

 Lignite group, as defined at that time, was continuous, 

 and that the chasm that was supposed to exist between the 

 Cretaceous and the Tertiary epoch would be found to be 

 bridged over. 



He then proceeeded to quote Dr. C. A. Wlaite, 

 who, he said, 



had made a critical examination of these formations during 

 the past season, and he says that his investigations have 

 freely confirmed the views expressed by me some years ago 

 and indicated by the paleontological studies of Mr. Meek, 

 that the Fort Union beds of the upper Missouri River are 

 the equivalent of the Lignitic formation as it exists along 

 the base of the Rocky Mountains in Colorado. 



Inasmuch as the Fort Union was regarded 

 as equivalent to the lignite-bearing beds east 

 of the mountains in Colorado, which fell 

 within the typical areas included by King in 

 the Laramie, it of course followed that the 



86 Hayden, F. V., letter of transmittal for Lesquereux's " Tertiary 

 flora": U. S. Geol. Survey Terr. Rept., vol. 7, p. iv, 187S. 



