476 E. 0. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



cayed silicious limestone soil. Another peculiarity of the Chester sand- 

 stones in southeastern Missouri, southern Illinois and western Kentucky, 

 tending to show the same source, is the rarity or total absence of mica 

 flakes. It proves at the same time that these sandstones were neither 

 derived from distant areas of crystalline rocks, nor from older misaceous 

 sandstones that were subjected to erosion at this time. This mineral, 

 however, is a common constitutent of the Chester sandstones in northern 

 Arkansas and in the Appalachian Valley, while it is rarely absent in any 

 of the Pennsylvania sandstones of southeastern America. 



Though considerable beds of limestone occur in the Chester, particu- 

 larly in the lower half, the greater part of the total thickness of the 

 deposits of this epoch in southeastern America consists of shale and 

 sandstone. Ozarkia was emerged throughout the Chester, but not as a 

 fixed land, oscillatory movements and occasional accentuation of its up- 

 warps being clearly suggested by adjacent deposits. Thus upward move- 

 ment is indicated at the close of the Tribune limestone by thin local 

 chert conglomerates at the base of the shaly and sandy Birdsville forma- 

 tion in southeastern Missouri. The repeated alternation of sandstone, 

 shale and limestone deposition in northern Arkansas, beginning with the 

 Batesville sandstone and ending with the Pitkin limestone, the local 

 distribution of some of the beds, and the petrologic character of the 

 elastics indicate yet other differential movements in Ozarkia and proba- 

 bly in Llano as well. A later post-Birdsville Chester movement is 

 recorded in the Appalachian valley by the conglomeratic Princeton sand- 

 stone. This preceded the last of the deposition of rather finely divided 

 elastics (Bluestone formation of southeastern West Virginia and the 

 Parkwood formation in Alabama) with which the known sedimentary 

 record of the Tennessean closed in southeastern America. An hiatus of 

 great but undetermined time value succeeded. 



Great shrinkage movements, resulting in extraordinary elevation of 

 marginal lands, especially of southern Appal achia and Llano, probably 

 began in this interval. This is indicated by the enormous thickness of 

 lower Pottsville shales and sandstones found in northeastern Alabama 

 and in the Ouachita geosyncline in Arkansas and eastern Oklahoma. In 

 the Ouachita region these attained a maximum thickness of something 

 like 15,000 feet before the northward and westward overlap of the Caney 

 shale, which is in part represented by the upper black shale of the Morrow 

 group in northern Arkansas, set in. In the meantime considerable 

 progress had been made toward baseleving of interior areas of uplift, like 

 Ozarkia, so that this shale transgression rapidly covered a wide area in 

 the Mississippi Valley. The importance of this period of diastrophism 



