78 TRIASSIC SYSTEM. 



CHAPTER XXXV. 



TRIASSIC SYSTEM. 



§ 170. The Mesozoic era is divided into three grand ages — Triassic, Jurassic, 

 and Cretaceous. The name Triassic was applied to the rocks in Germany, in allu- 

 sion to a threefold 'division which they present in that country ; but no such 

 division exists in America. Indeed, notwithstanding the vast thickness of the 

 rocks, they have thus far baffled all attempts to divide them into Groups, and, on 

 account of the similarity of the rocks with the Jurassic, and the barrenness of fos- 

 sils in the eastern exposures, these Systems have uot been satisfactorily defined ami 

 separated. On the eastern part of the continent they fill synclinal troughs, and 

 have been very much disturbed by intrusive rocks and volcanic action. They gen- 

 erally rest on Laurentian or Taconic strata, and, of course, the bed is always un- 

 conformable. But on the western part of the continent they are frequently 

 undisturbed, and spread over great areas of country, resting on unconformable 

 rocks. The Triassic in the Connecticut Valley extends from Northfield, in the 

 northern part of Massachusetts, across the latter State and Connecticut to New 

 Haven, on Long Island Sound, a distance of 105 miles. It fills a synclinal trough, 

 and has its greatest width at the mouth of the Farmington River, which is about 

 20 miles. The rocks consist of red sandstones, conglomerates, shales, and occa- 

 sionally impure limestone. The maximum thickness is about 20,000 feet, but the 

 upper 8,500 feet is referred to the Jurassic, leaving 11,500 feet for the Triassic. 

 A great many reptilian tracks, some fish and a few land-plants and fucoids, have 

 been described from these rocks. Much excellent building-stone has been quarried 

 from the sandstone. About 15 miles west of the exposure, on Long Island Bound, 

 there is another exhibit, about 6 or 7 miles long and 2 miles wide. 



S 171. A long trough and great exposure begins at Stony Point, on the Hud- 

 son, and extends across New Jersey, Pennsylvania, and Maryland to Culpeper 

 County, Virginia. It has a length of about 350 miles, and, though frequently 

 narrowing to a breadth of 4 or 5 miles, expands in New Jersey to a width of about 

 36 miles. The general character of the rocks is like those in the Connecticut Val- 

 ley, and the total thickness on the Delaware River is 27,000 feet, part of which is 

 probably Jurassic. Another rauge crosses the Potomac near Washington City, and 

 extends 25 or 30 miles beyond Richmond, and another exists 25 miles west of 

 this one. There is a valuable coal-field in this System in Virginia, which is about 

 26 miles long and 4 to 12 wide. The James River flows through the middle of it, 

 about 15 miles from the northern extremity, while the Appomattox traverses it 

 near its southern border, and on its eastern side it is distant from Richmond about 

 13 miles. A great many fossil plants have been described from this locality. 

 There are two basins in North Carolina. One begins at Lakeville, and extends 

 about 30 miles south-west to Germantown, being from 4 to 6 miles wide; and the 

 other commences in Granville County, six miles south of Oxford, and extends 

 south-west about 120 miles, reaching 6 miles intb South Carolina. Its width 

 is generally about 6 miles, but at the widest part 18 miles. The thickness in some 

 places exceeds 25,000 feet; the area is about 1,000 square miles, nearly one-third 



