OSCILI^ATORY CHARACTER OF CONTINENTAL SEAS 363 



Atlantic. Low lands bordering these seas and the deposits which accu- 

 mulated in the deeper basins consisted in great part of fine calcareous 

 ooze. Under these conditions non-deposition and marine scour have been 

 favored on shallows along shores and in straits, and in any such places 

 a corresponding hiatus must occur in the stratigraphic sequence. '' This 

 suggestion attacks and seeks to supplant the more commonly accepted 

 belief that a stratigraphic hiatus generally implies a corresponding time 

 of emergence, and it discredits all the stratigraphic and faunal evidence 

 on which minor oscillation of continental seas is based. The proposition 

 is readily tested and I believe easily refuted. 



The general improbability of marine scour being an important cause 

 of even the minor discontinuities of sedimentation commonly ascribed 

 (see Part II of this paper) to oscillations of the sea-bottom and to con- 

 sequent migrations of the strandline is suggested at once when we con- 

 sider (1) the almost universal shallowness of the continental seas, and 

 (2) their usually limited extent. In such seas currents of the necessary 

 efficiency could be developed only in narrow passages, or straits, connect- 

 ing broad basins, and then chiefly when a great volume of water is re- 

 quired to replace that lost in the basins by evaporation. Disregarding 

 the limited extent of the basins and admitting, for the sake of the argu- 

 ment, the probable tendency of strong oceanic currents to enter them, 

 there yet remains the certainty that their strength must soon be dimin- 

 ished by bottom friction to merely gentle circulation in the island-studded 

 interior seas. Tidal currents doubtless were effective in narrow, or 

 merely shallow, passages connecting inland basins with the oceanic seas, 

 but these likewise must soon have lost their efficiency. 



Cases indicating local prevention of sedimentation and bottom scour 

 by marine currents. — In a rather wide experience in the Paleozoic rocks 

 of America I have met with no instance of simple interruption, or even 

 diminution, of sedimentation in the interior continental basins that may 

 be unquestionably ascribed to marine currents. Though numerous cases 

 suggesting local channeling and dissection of tidal flats have been 

 observed, only two instances of erosion that may with any show of 

 reason be referred to marine scour were noted. One of these occurs 

 within the Lowville limestone near Watertown, New York, the other 

 on War Eagle Creek, in northwestern Arkansas, where the Boone sea, 

 or some other agent, removed nearly 100 feet of older Waverlyan lime- 

 stone before sedimentation was resumed. 



Possibly current action may be responsible also for the absence of 

 certain thin beds in the normal succession where submergence of the 

 area is proved by the preservation of deposits of the age in question 



