DESCRIPTIONS OF THE FORMATIONS. 41 



15-18. MESOZOIC. 



16. Triassic. As the railroads from Philadelphia to New York, the greatest 

 lines of travel in this country, run on this formation, it is the most conspicuous 

 and well known in the State of New Jersey, and one in which geologists are now 

 taking great interest. Every observing person must have noticed it, and its aspect 

 and composition are so uniform and well marked, that a description of it here will 

 answer for the whole belt through the States of Pennsylvania, Maryland, Virginia, 

 and North Carolina, from the Hudson River to Deep River, in the latter State, and 

 in the Connecticut Valley. 



The Triassic consists of dark reddish-brown sandstone, soft, crumbly brown 

 shales, and the upper beds are coarse conglomerates. The almost invariable 

 dip is towards the north-west, at angles ranging from 15 to 25. Prof. H. D. 

 Rogers thought this uniform dip was not caused by any uplifting agency, but that 

 the rocks were originally laid down in this manner. His theory is that the 

 formation owes its origin to an extensive ancient river, having its source at the 

 eastern base of the Blue Ridge, in North Carolina. Following the remnants of 

 the Triassic formation thence north-east, it gradually, from small beginnings, 

 becomes larger, and has throughout a descending course. At the James River, it 

 is four, at the Potomac six, at the Susquehanna twelve, and at the Delaware, 

 thirty miles wide the estuary being in the region of the Raritan and the Hudson. 

 In New Jersey, therefore, this river was at its maximum. 



The uniform dip was supposed by Prof. H. D. Rogers to be the result of the 

 oblique or slanting mode in which the sediment has been laid down by a rapid and 

 steady current washing the material from the south-east side or shore of the river. 

 If it were due to an upheaval, this formation, measured in the usual way, would 

 show an unheard-of thickness. In fact, it is very thin, as is shown in the exposures 

 of limestone in the interior of the belt. All the appearances of the formation 

 indicate, and there is much to sustain his opinion, that it never was tilted. 



But more recent study of this interesting formation, has proven two facts : (1) 

 that it was originally extensive, far beyond its present limits ; and, (2) that, in at 

 least its middle beds, the original deposits were horizontal, and have been since 

 upturned. The two great belts of Triassic, which cross from Virginia into North 

 Carolina, and one of them into South Carolina, not only have their rocks dipping 

 in opposite directions, showing a long and broad uplifted country between Raleigh 

 and Danville; but certain groups of coal-beds, which, though now dipping in 

 contrary directions, must of course have been originally horizontal. Traces of 

 coal-beds have been found in the Triassic of Pennsylvania, in York county, and at 

 Phoenixville. The intermediate country in North Carolina was, therefore, pre- 

 sumably once covered with the formation, and probably all Virginia, east of the 

 Blue Ridge, and all south-eastern Pennsylvania. The formation is seen passing 

 under the plastic clays of New Jersey, and may extend far under the bed of the 

 Atlantic, being thus connected with the beds of the Connecticut, and even those of 

 the Bay of Fundy. Lesley. 



