740' HISTORICAL GEOLOGY. 



Lower and Middle Triassic liave rarely been 2>osith'ely identified ; only those 

 of the later part have been found on the Atlantic border; and none of 

 either of the periods are yet known to exist on the Gulf border beneath its 

 Cretaceous and Tertiary formations. 



ROCKS— EQUIVALENCE, DISTRIBUTION, AND KINDS. 



1. Triassic of the Atlantic Border, or the Newark Group. 



1. Equivalence. — The Triassic beds of the Atlantic border, according to 

 the most recent authorities, correspond with the iipper part of the Trias, or 

 the Keuper and Khaetic of Europe. The evidence is based on the characters 

 of the fossil Plants and Vertebrates, marine Invertebrates being absent. 



In 1819, A. Brongniart, on the basis of specimens of fossil fishes of the Connecticut 

 valley (received from E. Hitchcock), which he referred to Falceonisctis (Palceothris- 

 stnn) Freieslebeni of De Blainville {Am. Jour. Sc, iii., 1821, and vi., 1823, with figures 

 on a plate), made the age of the beds Middle Permian. In 1835, E. Hitchcock added to 

 the evidence from the fossil fishes additional facts from the bones of a Saurian discovered 

 at East Windsor, Conn., in 1820, and pronounced the age that of the New Eed Sandstone, 

 — a term that then covered both the Permian and Trias. In 1842, William B . Rogers, after a 

 study of the coal-plants from Virginia beds, referred the fossils to the bottom of the Oolyte, 

 and in 1854 to the base of the Jurassic. In 1855, E. Hitchcock, Jr., concluded, from the 

 presence, in the beds in Massachusetts, of a Fern of the genus Clathro2)teris, that the age 

 of the Connecticut River New Red Sandstone was that of the Upper Trias and Lower 

 Lias. In 1856, William C. Redfield advocated the equivalency of the beds with the Lias 

 and Oolyte on the basis of the fossil fishes ; and at the same time he proposed the name 

 Newark Group (from Newark, N.J.) for all the Triassic deposits of the Atlantic border. 

 More recently the evidence from the fossil plants has been discussed, and the reference of 

 the beds to the Upper Triassic sustained by Newberry, Fontaine, and Ward in this country, 

 and by Stur and others abroad. The Vertebrate fossils lead to the same conclusion. 



2. Distribution. — The Triassic beds of the Atlantic border occur in long, 

 narrow independent areas, which are east of and closely parallel to the Appa- 

 lachian protaxis, as shown on the map, page 412. They lie in troughs or 

 basins over this border region of upturned Archaean, Cambrian, and some 

 later Paleozoic rocks. Over the region southeast of New England these 

 later rocks comprise only the Lower Silurian. But in Xova Scotia, the beds 

 rest on the upturned Carboniferous, Subcarboniferous, and Devonian ; and 

 in New England, probably on Devonian or Upper Silurian. The areas are 

 nearly parallel in direction to the mountain ranges to the west of them. 



The most important of these areas are : the Acadian, of Nova Scotia, 120 

 miles long ; that of the Connecticut valley, extending north and south along 

 the Connecticut valley through Massachusetts and Connecticut, 110 miles 

 long and mostly about 20 wide ; the Palisade belt, extending from the Pali- 

 sades on the west side of the Hudson through New Jersey, Maryland, and 

 Pennsylvania to Orange County, Va., parallel wdth the Appalachians, 350 miles 

 long and mostly 10 to 30 miles wide ; the Richmond belt, west of Eichmond, 



