REGIONAL MOVEMENTS 501 



tion with the ascertained land movements, but that the emergences were 

 nearly always associated with folding or uplift. This was especially true 

 ■of the revolutions closing the eras. It is also clear that the time divisions, 

 as here delimited, were more often due to world causes — the ensemble of 

 all movements — and that the major records were not established by the 

 inadequate movements of the lands. 



During the Paleozoic, more than at any time afterwards, tangential 

 thrusts of the oceans caused synclinoria to form on the inner sides of the 

 lands away from the ocean, and these were deepest immediately on the 

 inner sides of the moved block. Such synclinoria were repeatedly flooded 

 by the sea, were always narrow elongate waterways, and in the Ordovicic 

 were complicated by subsiding seas, all having the same general trend as 

 the main trough. Such invasions were apt to be even smaller than the 

 minor transgressions, particularly along the Atlantic region. The thrusts 

 from the Pacific seem to have been of a grander order, producing extensive 

 and wide but shallow synclines. 



These thrusts, it is thought, were also more or less directly connected 

 with the buckling of the medial region of the continent, and in the conti- 

 nental seas produced the parmas of Suess (II: 34), the geanticlines 

 of Dana (1895, 387), or the barriers of Ulrich and Schuchert (1902). 

 As the thrusts were not only of the Atlantic and Pacific oceans, but of the 

 Gulf of Mexico mediterranean as well, two sets of these barriers were de- 

 veloped nearly at right angles to each other, of which those having a north 

 and south trend were by far the most effective. Where these intersected, 

 nodes were produced that often appeared as islands or peninsulas in the 

 •continental seas, while the intermediate areas of the axis may have been 

 submerged. 



Owing to the variable loading and the irregular subsiding of the conti- 

 nental seas, their different basins were also variously warped, causing the 

 strand-lines to alternate irregularly between positive and negative condi- 

 tions. In other words, the strand-lines of continental seas were decidedly 

 and locally oscillatory. 



Thus far nothing has been said of vertical movements of the lands. 

 There can be no doubt that, in addition to the more frequent tangential 

 movements, decided vertical uplifts have also taken place, when great 

 regions were lifted in mass. Such was the elevation of the peneplain of 

 the Appalachian region, which was raised to a maximum of about 2,000 

 feet following the close of the Cretacic and during the Cenozoic, or the 

 entire Eocky Mountain country, where far greater altitudes were attained 

 in the late Cenozoic. Similar elevations may have taken place in the 

 Paleozoic, but the area of the American continental seas records no 



