406 MESOZOIC TIME. 



As the several regions are isolated from one another, they naturally differ widely in the 

 succession of beds and in the character of the rocks. They cannot, therefore, be brought 

 into parallelism by reference to mineral characters. * 



In the Connecticut River region, in Massachusetts, according to Hitchcock, these beds 

 consist, beginning below, of — 1. Thick-bedded sandstone through nearly half the thick- 

 ness, in some parts a conglomerate. 2. Micaceous sandstone and shale, with fine- 

 grained sandstone. This shale sometimes contains very thin coal seams and fossil fishes. 

 3. A coarse gray conglomerate, the stones sometimes a foot or more through. Con- 

 glomerate beds, equally coarse, occur near New Haven, Conn., with finer beds both to 

 the west and east. 



The material has come from the crystalline rocks adjoining, — the granite, gneiss, 

 mica schist, etc., and has not, in general, been much assorted by the action of currents 

 or waves. The thickness has not been satisfactorily ascertained, owing to the extent to 

 which the beds are covered by the stratified Drift and alluvium of the valley, conceal- 

 ing all faults: it cannot be less than 3,000 feet, and may be more than double this. 



At Southbury and near Middlefield, Ct., and near Springfield, Mass., there is an im- 

 pure gray or yellowish limestone, fitted for making hydraulic lime. 



In Virginia, the rocks consist, as in New England, of the debris of the older rocks 

 with which they are associated. West of Richmond, where the beds are about 1,800 

 feet thick, there are 20 to 40 feet of bituminous coal, in three or four seams, alternating 

 with shale. The coal is of good quality, and resembles the bituminous coal of the Car- 

 boniferous era. It contains, according to Hubbard, 30 to 35 per cent, of volatile ingre- 

 dients. On the western side of the Virginia areas is generally a coarse conglomerate, 

 which is often a bowlder deposit. The stones are from rocks to the west, and some from 

 points forty miles or more distant. The longest of these conglomerate beds is that which 

 includes the coarse limestone-breccia called Potomac marble, which is well exposed near 

 Point of Rocks, Md. Some of the masses composing it are two feet long. It contains 

 an occasional fragment of Potsdam sandstone (Fontaine). 



The North Carolina beds are divided by Emmons into three groups, beginning below: 

 1. The Lower red sandstone and its underlying conglomerate, estimated at 1,500 to 

 2,000 feet in thickness. 2. The Coal measures, including shales and drab-colored ripple- 

 marked sandstones, in some places 1,200 feet thick. 3. The Upper red or mottled 

 sandstones and marly tes, separated at times from the bed below by a conglomerate. Of 

 the five seams of coal at the Deep River mines, — the first (or upper) 6| feet thick, is 

 the best. Emmons obtained 28 to 31 per cent, of volatile ingredients. Good argilla- 

 ceous iron-ore abounds in the coal region of North Carolina; so that in almost every 

 respect there is a close resemblance to the coal regions of older date. 



(6.) Western Interior Region. — There is still some doubt as to the age of the 

 beds referred to the Triassic period distributed over the eastern slope of the Rocky 

 Mountains south of the parallel of 38°. They seldom contain fossils; and the few found 

 — occasional pieces of fossil wood — are not sufficient to settle the question. The beds 

 are known to underlie unquestionable Jurassic beds, and hence to occupy a position be- 

 tween the Jurassic and Carboniferous. 



(c.) Rocky Mountain Region and Pacific Border. — In the Elk Mountains, of 

 the western part of the Colorado Territory, several of whose peaks are over 14,000 feet 

 high, the lower part, for about a thousand feet, consists of Triassic, or Triassic and Ju- 

 rassic, sandstones and marlytes, nearly horizontally stratified, overlying Carboniferous 

 strata. The high Wahsatch and Uintah Mountains, east of the Great Salt Lake, are 

 also partly Triassic and Jurassic over Carboniferous; in the Wahsatch, the beds consist 

 of sandstones, and are 1,000 to 1,200 feet thick (King). In the West Humboldt range, 

 the Triassic consists of the Koipato group, 4,000 to 5,000 feet thick, and 10,000 feet of 

 "Alpine Trias" (p. 425). containing many characteristic fossils of the genera Halobia, 

 Arcestes, Monotis, etc. (King). The Triassic of the Sierra Nevada is fossiliferous, and 

 has been observed in California, according to Whitney, in El Dorado County, at Spanish 

 Flat, in Plumas County, near Gifford's Ranch, etc. ; also in Owen's Valley, along the 

 western flanks of the Inyo and White Mountains. 



