626 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



tain, and he found fossils by which the age was "determined as lower Cretaceous 

 of the horizon of the Shasta group of the California geologists." He says further: 



Along tlie eastern shore of the lake these rocks, as already mentioned, appear to overlie 

 those, of the Porphyrite series. * * * The series is no doubt conformable throughout, the 

 upper beds * * * showing, however, a greater development of conglomerates. The rocks 

 may be described as being compact bluish-gray quartzites or hard sandstones and conglomerates 

 of all grades in regard to size of particles, associated with blackish or dark-colored slaty and 

 shaly beds, which recur frequently at different horizons. Great fragments of highly f ossilif erous 

 quartzite strew the lower slopes in some places, but fossils were only observed in situ about 

 2,000 feet above the lake, where they are found not only in the quartzite but in black shaly 

 beds. * * * It is highly probable that softer shaly beds may bear a larger proportion to the 

 quartzites than now appears, as there are extensive hollows following the strike in which no 

 exposures occur. Many of the beds are somewhat calcareous, and some of the shales are dark 

 colored from carbonaceous matter. Together with the marine fossils, in some layers surfaces 

 are found covered with obscure plant impressions, like fragments of stems or bladelike leaves. 

 No indications of coal were, however, observed. The thickness of the entire series, as shown on 

 the east side of Tatlayoco Lake, probably does not fall short of 7,000 feet. 



In 1877 Dawson ^" reexamined the Jackass Mountain rocks in the type locality 

 and found " Syncydonema meekiana Wh., Ancyloceras percostatus Gabb, Crioceras 

 lotus Gabb, Pleuromya n. sp. allied to P. papyracea Gabb, an Area * * * ^nd 

 a badly preserved cast of a CucuUsea." These fossils confirm the correlation with 

 the rocks on Tatlayoco Lake." 



The small basin of the Jackass Mountain occurrence, above described, is crossed 

 by the fiftieth parallel. That of Tatlayoco Lake is the south end of a large area 

 which widens toward the north and extends nearly to latitude 58°. A section along 

 Skeeha River and across the mountains to Babine Lake, near the fifty-fifth parallel, 

 is described by Dawson.^^^ Referring to the rocks cut by the Skeena and its tribu- 

 taries, he notes that they are chiefly feldspathic rocks of purplish, grayish, greenish, 

 or bluish tints. They "are sometimes brecciated, and the breccias occasionally 

 pass into water-formed conglomerates, with well-rounded fragments, the finer 

 materials graduating into ordinary quartzites, sandstones, and argillites by inter- 

 mediate varieties. Fossils were found in some abundance in a bluish feldspathic 

 rock. * * * They include belemnites, a Trigonia, with other mollusks and a 

 branching coral." 



Near Kitseguecla the rocks change somewhat in character. The sandstones are not highly 

 indurated, as before, but rather soft, and associated with carbonaceous shales, which occur at 

 different stages in the formation and are sometimes 10 or more feet in thickness. At a little 

 distance these quite resemble coal seams, and on closer examination are in fact found to include 

 films and small lumps of a material, which, though very impure and ashy, may be called true 

 coal. Ironstone in nodules and sheets occurs in abundance in some parts of the formation, 

 and obscure plant impressions were observed in the sandstones. The rocks have been irregularly 

 deposited in many instances, the carbonaceous shales in particular showing a tendency to 

 lenticular forms. * * * 



It will have been observed that while the porphyrite and other feldspathic and often 

 brecciated rocks prevail toward the western margin of the region, comparatively soft sandstone, 

 argillites, and carbonaceous argillites characterize the eastern, the intervening region showing 

 rocks more or less intermediate in hthologic character and degree of induration. * * * 



"■ This list indicates correlation with the Horsetown of California. — T. W. Stanton. 



