156 Scientific Intelligence. 



study of the Zufii plateau in 1884, by Capt. Dutton, was essen- 

 tially a continuation of his investigations of the plateau region of 

 Utah and Colorado, the subjects of former memoirs. We take 

 the following facts from the report. The plateau is situated in 

 western New Mexico, between the parallels of 35° and 36° N., 

 and the meridian of 108° and 109° W., near the Atlantic and 

 Pacific railroad, having on the west side the Rio Puerco of the 

 west, a branch of the Little Colorado, a southeastern tributary of 

 the Colorado river, and to the eastward, the eastern Rio Puerco, 

 a tributary of the Rio Grande. The prevailing formation about 

 the region is Cretaceous — the most universal of Rocky mountain 

 strata. Going westward from the eastern Puerco, the country 

 becomes almost immediately that of the plateau region, which 

 stretches west for 400 miles, with great uniformity in its geology 

 and in the grandeur of its scenery. South of Fort Wingate rises 

 the highest part of the Zufii plateau. In the ascent the rocks 

 change from the Cretaceous to the Jura-Trias. These Mesozoic 

 rocks dip away from the interior of the plateau at a small angle, 

 while the surrounding Cretaceous beds are horizontal. Over the 

 plateau the rocks, after leaving the brightly colored Jura-Trias 

 of the border, are the Permian, the Upper Carboniferous, and 

 crystalline rocks, which are referred to the Archaean, these being 

 brought to view by extensive denudation over the top of the 

 swell. 



The region differs strikingly from the plateau region of Utah, 

 in the absence of all formations between the Upper Carbonifer- 

 ous and Archaean. A generalized section of the plateau (p. 137) 

 includes Upper Carboniferous, 1200 ft. (of which 800 ft. are 

 Lower Aubrey, and 400 ft. Upper) ; Permian, 450 ft. ; Trias, 

 2050 ft. (1600 ft. of Luwer Trias and 450 ft. of Wingate Sand- 

 stone) ; Jurassic? (the Zufii sandstone), 1100 ft.; the Cretaceous, 

 2900 ft. (embracing 250 ft. of Dakota sandstone, 1200 ft, of Col- 

 orado, shales, 900 ft. of Lower Fox Hill, 550 ft. of Upper Fox 

 Hill); Laramie group, 800 ft,; Wasatch sandstone, 1600 ft. 

 The whole, the Wahsatch included, is believed to have covered 

 the Zufii region in the early Tertiary. A monoclinal uplift is 

 described as occurring at Nutria, where the Cretaceous stands at 

 an angle of 73°. 



The high plateau northeast of the Zufii mountains, north of the 

 San Jose, has at top a broad area of igneous rocks, with Mount 

 Taylor, a conical pile, toward its southern side, 11,3S9 feet high, 

 as the great volcanic cone, standing 8,200 feet above the level of 

 the plateau or mesa. Many small cones occur over the volcanic 

 area marking the sites of former eruptions. The rock is mainly 

 andesyte. The eruptions are referred to the Tertiary, probably 

 the Middle Tertiary, the earliest " not much, if any older than the 

 Miocene." More recent lavas, with cinder cones, occur around 

 the eastern base of the Zufii Plateau, the rocks of which are 

 normal basalts. 



In the statement of his general conclusions Captain Dutton 



