126 Keyes — Dakotan Series of Northern New Mexico. 



fully applicable to certain sandstones widely distributed in the 

 south. 



Many different titles have been given to the sandstones 

 belonging to the Dakotan series ; and the term itself has been 

 used in many different senses by the various writers who have 

 passed through the New Mexican field. Among the first to 

 call attention to the formation in question was Jules Marcou,* 

 who, as early as the year 1853, traversed this region in connec- 

 tion with an expedition sent out by the Federal government 

 to survey a railroad route to the Pacific coast along the thirty- 

 fifth parallel of latitude. 



Capping Pyramid Mountain, Cerro Tucumcari and the cliffs 

 of the Canadian river near the eastern border of New Mexico, 

 Marcou noted about 50 feet of massive yellow sandstones 

 which, with other underlying beds, he regarded as Jurassic in 

 age. The massive yellow sandstone of these sections subse- 

 quently proved to be the attenuated eastern edge of what is 

 now denominated the Dakotan series ; while lately the age of 

 the beds beneath was finally adjudged in accordance with 

 Marcou's original designation. 



During the year 1858 Newberryf crossed northern New 

 Mexico and recognized an extensive development of rocks 

 which he regarded as of Cretaceous age and which he divided 

 into a lower group and an upper group. These divisions are 

 not regarded as representing the similarly named subdivisions 

 of the general Cretaceous section. In the "Lower" division, 

 as thus understood, the Dakotan sandstones were included; 

 and the terms so far as they apply to northeastern New Mexico 

 may be considered as practically co-extensive. In northwest- 

 ern New Mexico he embraced in this Lower division also the 

 Jurassic Zunian beds. His "Lower Cretaceous" does not, as 

 has been widely believed, correspond to Meek and Hayden's 

 subdivision of the " Early Cretaceous." This is very clearly 

 shown in his descriptions of the region around Las Yegas.J 

 In the year following Newberry's return from the Colorado 

 Piver of the West, and two years before the publication of his 

 official report just referred to, this author published a criti- 

 cism! on Marcou's Jurassic system of New Mexico, in which 

 he attempted to show that all of the so-called Jurassic rocks are 

 really Cretaceous in age, and correspond to Meek and Hay- 

 den's Fort Benton and Niobrara groups, or the Coloradan series 

 of present nomenclature. This, however, is not strictly cor- 

 rect. The larger part of Marcou's Jurassic system of rocks 



*Exp. and Sur. Pacific R. R. Route, vol. iii, p. 137, 1856. 

 f Ives Rept. Colorado River of West, pt. iii, p. 107, 1861. 

 |Loc. cit., p. 106. 

 §This Journal (2), vol. xxviii, pp. 298-299, 1859. 



