74-1 HISTORICAL GEOLOGY. 



areas were determined not mainly by fluvial action, nor by a great sub- 

 ■inergence, but by the topography of the Continental border as it existed 

 immediately after the Appalachian upturning. 



It is plain that some of the areas were marsh regions along the courses of 

 streams and lakes ; and two or more may have been estuaries, like the 

 Chesapeake or Delaware Bay, receiving the tides during part or all of 

 their history. But it is also proved by the deposits that the broad streams 

 sometimes were great streams, making conglomerates where the water had 

 great velocity, sandstones in gentler currents, shales in the sluggish waters, 

 and beds of vegetable debris, for a coal-bed, where the conditions were those 

 of a great marsh. As in other fluvial regions, conglomerate-beds, sand-beds, 

 and mud-beds may have been forming simultaneously at the same horizon in 

 different portions of an area. Moreover, under fluvial action, different kinds 

 of deposits in flowing waters would be lengthened out in the direction of 

 the flow, making unlike formations, longitudinal with the stream, of parallel 

 position and history, looking, to one traversing the surface, or studying the 

 exposed beds, like consecutive formations. If a region were slowly sub- 

 siding so that the beds could thicken, there would probably be, in a portion 

 having like velocity throughout, four or five rather prominent kinds of de- 

 posits, — one made along the bed of the stream ; two others along the banks ; 

 two others beyond the banks on either side ; and each of these would have 

 their local belts. These and other sources of diversity existed in the Trias- 

 sic areas. 



Where were the sources, and what the directions, of the rivers over the 

 higher lands from New York to North Carolina, which supplied so generally 

 granitic sediments instead of quartzose sands and fine clays, are questions not 

 easily answered. 



The recently made Appalachian Mountains stood along the western side 

 of the Archaean protaxis, and these Triassic formations on the east side. It 

 • would seem to be a necessary consequence that the Appalachians should have 

 sent off streams eastward to the Atlantic and loaded the waters with Appa- 

 lachian sands and other detritus. But it is proved, b}^ the prevailing granitic 

 character of the material of the sandstones, that little if any of these sedi- 

 ments reached the Triassic troughs, either from the Appalachian Mountains of 

 Virginia and Pennsylvania, or from the plateau region of Pennsylvania and 

 the Catskills — the present sources of the mud, sand, and water of the Dela- 

 ware, Chesapeake, and other streams ; that the Archaean protaxis was so high 

 and continuous as to wholly prevent drainage from the west and northwest ; 

 that this range of crystalline rocks and the ridges of more or less crystalline 

 Cambro-Silurian, of the region in the vicinity, supplied the streams with 

 sediments for transportation to the Triassic areas. The drainage from the 

 Appalachian Mountains must have flowed westward or southwestward. 



The river or waters of the time flowing southward just west of the site of 

 New York' City -—where now flows the Hudson — were 25 miles wide, as the 

 bi^eadth ofithe Triassic of the region shows; and they had sources evidently 



