444 THE TRIASSIC PERIOD 



Distribution of the Trias 



American. — In the early part of the Triassic period both North 

 and South America extended farther eastward than they do now. 

 It is a remarkable fact that no marine deposits of this period 

 are known to exist on the Atlantic slope of either continent, 

 but numerous isolated bodies of brackish and fresh-water deposits 

 occur in lines approximately parallel to the present eastern coasts 

 of North and Central America. At some time during the period, 

 perhaps in its latter half, there were formed in the northern con- 

 tinent a series of long, narrow troughs, running closely parallel to 

 the trend of the Appalachian Mountains, though separated from that 

 range by the ridges of crystalline, metamorphic rocks which had 

 formed the western border of the Appalachian land in Palaeozoic 

 times. In these troughs water was accumulated, forming some- 

 times tidal estuaries, sometimes fresh-water lakes, streams, and 

 bogs. A great mass of rocks was laid down upon the slowly 

 subsiding bottoms of the troughs. The thickness of these rocks 

 has not yet been definitely measured, but is very great, — so great 

 that some authorities maintain that their formation must have 

 begun in the Permian, at least in Pennsylvania. 



At the present time the Triassic rocks of the Atlantic border 

 are found in separate patches from Nova Scotia to South Carolina, 

 the largest continuous area extending from the Hudson River 

 across New Jersey, southeastern Pennsylvania and Maryland, into 

 Virginia. Other areas occur in Nova Scotia, Prince Edward 

 Island, Massachusetts, Connecticut, and several scattered ones 

 in Virginia and North Carolina. The rocks are prevailingly red 

 sandstones, but coarse conglomerates and breccias are common 

 at the base of the series ; ferruginous shales are frequently inter- 

 bedded with the sandstones, and some thin beds of impure lime- 

 stones are locally developed. In Virginia and North Carolina the 

 conditions of Carboniferous times were once more established, and 

 in the peat bogs and swamps of those regions workable coal of 

 good quality was accumulated. This coal can be distinguished 

 from that of the preceding periods by the character of the plants 



