MESOZOIC TIME — TRIASSIC AND JURASSIC. 747 



by Gabb from fossils discovered during the Whitney Geological Survey 

 (1864), and later studied over the Taylorville region by Diller and Hyatt 

 (1892). The thickness of the Triassic in this region is about 4800 feet, and 

 of the overlying Jurassic sandstones, limestones, and tufa about 2000 feet. 

 The formation is continued northwestward into the Klamath Mountains. 

 Whether it exists in the Cascade Eange still farther north is unknown, as 

 these mountains are mostly under recent volcanic rocks. 



The Island belt in British Columbia contains areas of Upper Triassic on 

 Vancouver Island, Queen Charlotte Islands, in the Straits of Georgia j and 

 beyond they occur at Wrangel Bay, Alaska. 



Upper Triassic beds occur also in Mexico, in the states of Sonora (New- 

 berry, 1876), Puebla and Oasaca (Aguilera and Ordonez, 1893). They are 

 found also in Honduras (Newberry, 1888). 



In the Black Hills, the Triassic beds, or the "Red Beds" supposed to be Triassic, 

 come to the sui'face, along with the Jurassic, from beneath the Cretaceous beds of the 

 Continental Interior, as first shown by Meek (1858, 1860). They are mainly arenaceous 

 clays, unfossiliferous, 300' to 400' thick, with 15' to 30' of impure limestone below the 

 middle, and with gypsum in the upper half. In the foot hills east of the Front Range in 

 Colorado, the Triassic and Jurassic often appear overlying the Archaean, or the Paleozoic* 

 600' to 1000' of the former, to 200' or 300' of the latter. In these foot hills, to the west- 

 ward, within 30 miles of the line of New Mexico, and for 50 miles beyond, as stated by 

 Stevenson, the Cretaceous rests on the Carboniferous over Archsean, the Triassic not 

 extending so far west. 



Bordering the Laramie Plains, in Wyoming, these formations may be seen over 

 Archsean ; the gypsum beds of the Triassic are sometimes over 20' thick. 



In Idaho, north of the Wasatch, between the Wyoming and Portneuf ranges (110^°- 

 112° W.), upturned Triassic and Jurassic beds, according to A. C. Peale (1879), enter 

 largely into the structure of the ridges ; and these formations in the Blackfoot Basin, 

 where the Triassic is about 4000' thick and the Jurassic 1500' (more than half limestones), 

 afforded the fossils described by C. A. White in 1879 (page 758). In the Wasatch 

 there are 1000' to 1200' of Trias overlaid by 1600' to 1800' of Jurassic beds (King). In 

 the High Plateaus to the south, north of the Colorado Canon, the "Vermilion Cliffs" of 

 Powell, 1000' to 1500' high, which extend for 100 miles from Hurricane fault to Paria, and 

 the " Shinarump Cliffs" below, are Triassic, while the overlying " White Cliff group," 

 2000' or more thick, consisting of white sandstone and calcareous beds, and the " Flaming 

 Gorge group " in Utah, are referred with some doubt to the Jurassic. The beds are con- 

 tinued southward in plateaus of Arizona and New Mexico. 



The Trias of western Nevada consists, according to King, of a lower Koipato group of 

 siliceous and argillaceous beds, 5000', and above this, great limestone strata and alternating 

 quartzyte of the Star Peak groups, 10,000'. The Trias of this region may have once been 

 connected with that of the Sierra Nevada just west. 



Upon the northern end of the Sierra Nevada, near Taylorville, Diller measured nearly 

 5000' of Upper Trias. It lies apparently unconf ormably upon both sides between the Jurassic 

 and Carboniferous. It consists below of 200' of slates overlaid by 140' of limestone, and 

 above of over 4000' of sandstones and slates. In the two lower members fossils are often 

 abundant, but in the upper slates they are rare and chiefly land plants. The limestone is 

 most persistent, and has been recognized by its fossils near Pit River and elsewhere in the 

 Klamath Mountains, and even as far north as Siskiyou County, near the Oregon line. 

 The presence in that region of large masses of eruptive material, often fossiliferous, shows 



