284 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



I'age 



Oscilliitioiis iu the Mississippi Valley 4JtJ 



Yellville oscillations 420 



Post-Ordovician oscillations in North America 421 



General character 421 



Early Silurian oscillations 422 



Niagaran oscillations 424 



Devonian, Waverlyan, and Tennessean tilting 425 



General discussion 425 



Devonian and Waverlyan tilting of the Ozark uplift 425 



Tennessean differential movements 427 



Tilting accomplished during interformational intervals 428 



Dome tilting illustrated in the peninsula of Florida 4.'i0 



Causes of differential oscillations of continental seas and interior 



land areas 4H0 



Note respecting normal faulting 482 



Horizontal movements due to compressive forces 4.'54 



Discussion 4H4 



Inland migration of Appalachian belts of folding 4.'i5 



Relative importance of periods of folding 4.'>(» 



Importance of movements at close of Ordovician 48(5 



Suggestion concerning causes of inland migration of belt of active 



folding 480 



Overthrust troughs in eastern New York and western New Eng- 

 land .442 



Relation of lateral creep of continental platforms to suboceanic 



spreading 44(5 



Inland transmission of suboceanic thrusts 447 



Structural criteria 44S 



General discussion 4-IS 



Progressive overlap of marine deposits 440 



Rate of progress 440 



General prevalence of overlap structure 452 



Interfingering overlaps 458 



Peculiarities of initial deposits at base of overlapping formations 454 



Littoral conditions recorded by initial deposits 45fi 



Stratigraphic hiatuses 457 



Frequent absence of clastic material at base of overlapping forma- 

 tions not extraordinary 457 



Time values of stratigraphic hiatuses 450 



Illustrative examples 450 



Physical evidence of sea withdrawal 461 



Physical criteria of stratigraphic unconformity 462 



Gradational and lithological criteria 467 



General discussion 467 



Pre-Paleozoic periods of diastrophic activity indicated by gradational 



criteria 468 



Late Ordovician-early Silurian period of activity 468 



Neopaleozoic diastrophic periods 470 



Relative importance of Devonian deformative movements 474 



The late Tennessean-early Pennsylvanian period of diastrophic ac- 

 tivity 475 



