FOEMATION or THE TRIASSIC BASIN. 373 



The coarser beds are not so well fitted to retain marks of exposure, but 

 the false bedding and the ripple-marking, together with the lack of indica- 

 tions of exposure, convince me that during the earlier portions of the Trias 

 the waters were deeper, and of such depth as to render the strong currents 

 most effective, and that later the broad basin became so shallow that the 

 currents were effective only where concentrated in theii- shoreward portions, 

 while over the broad central and shallower flats, regularlv abandoned by 

 the tide, conflicting currents earned only fine material. 



An inspection of the detailed geological map of the Appalachian chain 

 makes it very plain that the southward trend of the main structure lines 

 across New England must have made a great sigmoid curve to the ^vest in 

 sympathy with the same curves in the more western chains across the Mid- 

 dle States, and that a g-reat post-Carboniferous sinking must have depressed 

 an extended block south of an east-west line running north of Long 

 Island, thus producing the " Rias Coast" ^ of southern New England and 

 admittuig the sea into the deep fjordlike bay of the Connecticut River 

 Trias. The development of the fault system which borders this bay and has. 

 produced it may have been an attendant upon the larger movement, but it 

 is quite clear that the depression of the bottom of the basin was, in part at 

 least, synchronous with the accumulation of the Triassic sands, and in part 

 of later date. 



It is difficult to assign the con-ect value to this cause, the sinking 

 of the bottom of the basin, as another valid cause is recognizable which 

 worked to the same end, namely, the- great Triassic transgression. While 

 the above statements present the true explanation of the formation of the 

 Triassic basin — that it is a nan-ow fault-bounded and sunken block — the 

 presence of a large number of isolated sandstone and conglomerate masses 

 along the Atlantic Coast indicates a general positive motion of the waters 

 over the land along the whole coast — one of those general "transgressions" 

 the importance of which has been so ably enforced by Suess — as the trae 

 explanation of the gradual advance of the waters into the basin. 



I have now collected abundant evidence that the waters in their slow 

 transgi'ession across the bottom and up the sides of the l^asin found a 

 great store of material for their work in the results of the secular disinte- 



' A coast line which truncates mountain chains about at light angles to their trend: Suess, Das 

 Antlitz der Erde. 



