288 



arriving at the base of the mountains, where, in places, it may yet be 

 demonstrated that these comparatively modern deposits have been sud- 

 denly tilted and more or less changed by metamorphism in the upheaval 

 of the great lateral spurs, as instanced in the eastern flank of Great Baldy. 

 In the shallow recesses between t'he outbursts of igneous activity, which 

 threw up the gigantic masses domineering the range, these beds may 

 extend up to the old metamorphic ridge, upon the flank of which they 

 may rest in comparative undisturbed condition. 



The following profile-section (Plate 43, Fig. 2) is introduced to show 

 approximately the superposition of the Tertiary and Cretaceous forma- 

 tions as they appear in the eastern border of the Eaton plateau between 

 the Purgatory near Trinidad, and Urac Mountain south of the Cimarron, 

 and the relation of the plateau to the Spanish range. 



The heavy line indicates the watershed, the dotted line showing the 

 position of the lofty spurs diverging into the basin of the Eio Grande, 

 the broken line the Baldy range, the lower dotted line showing the 

 ui^raised western border of the Tertiary at the base of the mountains. 



Eespecting the mineral wealth entombed in this formation, its de- 

 posits of coal and iron have already become famous. Besides the 

 sections alluded to by Dr. Hayden in 1869, and those observed by Dr. 

 LeConte and other gentlemen in different parts of the extensive region 

 occupied by these deposits, we are especially indebted to Mr. Morley, 

 and later to the distinguished Dutch engineer Herr Cornelius De 

 Groot, who has prosecuted special examinations in this direction with 

 the view of developing these resources, and upon whose observations 

 I have mainly relied for the facts relative to the occurrence and aggre- 

 gate thickness of the coals here met with. 



The base of the formation is sharply defined from the immediately 

 subjacent dark-gray shales of the Cretaceous by the sudden introduction 

 of arenaceous material. This primary deposit consists of 20 to 25 feet of 

 thin-b^edded dark-brown or rusty ferruginous sandstone, uj)ou which 

 rests a massive bed of light-yellowish sandstone, which latter often 

 forms precipices of 20 to 40 feet vertical. Above this occur alterna- 

 tions of more or less micaceous sandy shales and coarser sandstones, 

 which, in the vicinity of the Cimarron, reach, all told, a thickness upward 

 of 400 feet to the topmost ledges in the neighboring hills. 



The same association and succession of strata again appear in the 

 valleys of the Poiiil and Yermejo, the latter of which was visited by 

 Dr. Hayden. These sections all indicate the lower portion of the for- 

 mation as the productive coal-bearing measures. The heaviest bed, 

 which ranges from 4 to 7 feet in thickness, occurs early, though probably 

 preceded by one or two minor carbonaceous horizons. Thus, near Mr. 

 John Dawson's estate, at the mouth of the Vermejo Valley, the section 

 exhibits seven beds of coal, of an aggregate thickness of 22 feet, included 

 in about 160 feet vertical thickness of strata. At the base of this section 

 occurs a heavy deposit of excellent coal, which is little more than 7 feet 

 in thickness ; 13 feet above this occurs a bed about 4.} feet thick, sepa- 

 rated by thin partings ; and 40 and 20 feet respectively still higher a 

 couple of 3-foot beds of coal are met with, the intervening strata consist- 

 ing of slightly arenaceous shales, above which three 18-inch beds are 

 found in a vertical thickness of about 65 feet. 



The fine under- and roof-clays associated with some of these coals often 

 contain vegetable remains, but which generally so readily crumble on 

 coming in contact with the air as to render it exceedingly difficult to 

 secure specimens. Higher in the series, the sandstones afford the usual 

 vegetable representatives peculiar to the formation, amongst which nota- 



