Keyes — Dakotan Series of Northern New Mexico. 127 



of the i$ew Mexican region belongs to the Dakotan series, or 

 below. The discussion is quite remarkable and, in the light 

 of recent investigations, is strangely incongruent. Marcou and 

 Newberry traversed very different routes ; that of the first 

 named explorer being up the Canadian river valley a hundred 

 miles south of the old Santa Fe trail which the last mentioned 

 observer followed. While Newberry was discrediting Mar- 

 cou's recognition of Jurassic rocks, he himself passed over 

 country where they were not present except at one point — at 

 the Cimarron crossing ; and years afterward,* with no refer- 

 ence whatever to his former contention, he assigned certain 

 beds in this vicinity to a Jurassic age. Recently Stantonf 

 finds that these and the Tucumcari beds of Marcou are con- 

 tinuous and form part of the Morrisonian series. 



Newberry;}; in his later report subdivided the Cretaceous into 

 three sections, the " Lower " division embracing only the 

 Dakota sandstone. 



Although Hayden,§ who with Meek originally defined the 

 Dakota division of the Cretaceous, recognized his formation 

 within the limits of New Mexico in traveling from Raton to 

 Santa Fe, it is not possible to determine from his meager de- 

 scriptions just how much of the general section of the region 

 he intended to include under the title. However, it is known 

 from the route which he followed that he had at no time any 

 other than the main massive sandstone in view. At no point 

 which he visited are any of the lower, or Morrisonian, beds 

 exposed. 



As originally described, the " Lower Cretaceous " of Steven- 

 son,] of northeastern New Mexico, appears to embrace only 

 what is now called the Dakotan series. In a later publica- 

 tion^ this writer uses the terms " Dakota Group " to cover 

 not only the Dakotan series, as at present understood, but also 

 the Jurassic section, and a part of the underlying Triassic beds 

 of previous writers. This group was subdivided by him into 

 three sections called the Lower Dakota, the Middle Dakota 

 and the Upper Dakota. The last mentioned alone can now 

 be considered as the equivalent of Meek and Hayden's original 

 Dakotan series. This author** says : " The grouping to be 

 proposed is merely provisional ; dependence has been placed 



* Macornb's Expl. Exp. June. Grand and Green Kivers, p. 28, 1876. 



f Journal of Geology, vol. xiii, pp. 657-669, 1905. 



% Macomb's Expl. Exp. Geol. Kept., 121, 1877. 



§U. S. Geol. Surv. Terr., Third Ann. Kept., 2d ed., p. 162, 1873. 



■{[Ibid., Supp., p. 90, 1881. 



|| U. S. Geol. Surv. W. 100 Merid., vol. iii, p. 400, 1975. 



**Loc. cit., p. 88. 



Am. Jour. Sci. — Fourth Series, Vol. XXII, No. 128.— August, 1906. 

 9 



