across 



Mississippi, Louisiana, and Texas. 369 



These facts are all in keeping with the theory put forward. 

 It is to be expected that the sediments would be thicker near 

 the supplying land area, such as existed along the Appalachian 

 highlands, and where the drainage became sluggish near the 

 waters into which it is discharged, that is, in Texas, west 

 Arkansas, and Indian Territory. And unless it be admitted 

 that there was a land area across eastern Texas, Louisiana, and 

 Mississippi, we are at a loss to explain the source of supply for 

 the 5600 feet of upper Carboniferous sediments* in central 

 Texas. In the Arkansas valley, where these sediments have 

 been shown to have a thickness of 23,780 feet,f and in Indian 

 Territory, where the Coal Measures are 25,000 feet thick, or 

 with the Permian 26,500 feet (N. F. Drake), the supply of the 

 coarser materials could hardly have come from elsewhere than 

 the Ozark mountains in Missouri. 



The central Texas coal area and the Indian Territory- 

 Arkansas basin seem to represent the ends or mouths of syn- 

 clinal valleys in which conditions favored the deposition of 

 enormous beds of sandstones and shales. In the neck of Upper 

 Coal Measures rocks near San Saba, Texas, where they almost 

 abut against the pre-Silurian area, these beds strike about ~N. 

 35° E. This suggests a southeast origin for these sediments. 

 In Arkansas and Indian Territory the upper beds strike across 

 the trough of the valley in this fashion, while the lower ones 

 are more nearly parallel with its sides. In the same way it is 

 to be supposed that the earlier Coal Measures beds of the 

 Texas trough swing round and strike east-west. 



Marine Coal Measitres fossils. — South of the Ouachita 

 uplift the Coal Measures beds have yielded comparatively few 

 fossils, and most of these are coal plants. A few crinoid 

 stems and bryozoa, however, have been found near Antoine in 

 Pike county (8 South, 23 West, sec. 24), enough to show that 

 the conditions on the south side of the fold were very or quite 

 like those on the north side. These conditions were : a low- 

 lying region occasionally invaded by the sea. This idea is also 

 borne out by the nature of the Carboniferous beds of central 

 Texas, where limestones are interbedded with the usual sand- 

 stones and shales.^: 



The Arkansas valley syncline sank occasionally during Coal 

 Measures times so as to admit the sea across the region : this is 

 shown by the marine fossils found in the rocks there.§ This 



*R. S. Tarr (Amer. G-eol., 1892, ix, 169) gives 8000 feet as the thickness of 

 these rocks. Later work by N. F. Drake shows that earlier estimates are a little 

 too high, probably because the dip is not so steep along the western edge of the 

 Carboniferous. Fourth Ann. Rep G-eol. Sur. Texas, 355-446. 



f This Journal, 1896, vol. clii, p. 235. 



X N. F. Drake, Rep. on the Colorado Coal Field of Texas, Fourth Ann. Rep. 

 Geol. Surv. Tex., 355-446. 



§ J. P. Smith, Proc. Am. Phil. Soc, vol. xxxv, No. 152. 



