364 



CHARLES R. KEYES 



Arkansas. South of the Ozark crest, if the inferences already 

 drawn are to be relied upon, deposition was continuous, not only 

 through the Lower Carboniferous period, but also during the 



Fig. 1. — Ideal Conditions of Sedimentation. 



interval when the region farther north was a land surface being 

 rapidly eroded. As shown elsewhere, 1 the present Ozark dome 

 had, of course, not begun to bow up. It was not a large island 

 during the Carboniferous, as has been generally regarded. The 



ARKANSA5 



Fig. 2. — Cross Section of Mississippi Basin — Minnesota to Arkansas. 



products of land degradation were, without doubt, dumped into 

 the adjoining seas, just as the sediments of the present continent 

 are being carried into the ocean to form the thick fringe of 

 coarse shore deposits. 



In general, the deposition of coarse sediments along the 

 coast must have been represented by degradation on land. This 

 phenomenon may be shown by the subjoined sketch (Fig. 1), in 

 which a is the original shore line ; b, the land surface ; c, the 

 sediments removed and transported from the eroded parts of the 

 strata d, d, which had been subjected to deformation since their 

 formation. Identically the same conditions obtained in the case 



1 Missouri Geol. Surv., Vol. VIII, p. 352, 1895. 



