Area in Louisiana and Eastern Texas. 73 



border of the Ouachita region. In Pike County it was 

 originally more than 6,000 feet thick ; its upper part has 

 been removed by erosion. The rocks that are equivalent 

 to the Atoka along the southern border of the Boston 

 Mountains which adjoin the north side of the Arkansas 

 Valley, probably comprise the lower 1,500 feet or more 

 of the Winslow formation in the Winslow quadrangle,^" 

 the lower 600 to 800 feet of the Winslow formation in the 

 Tahlequah quadrangle,^^ and 200 to 400 feet of the Win- 

 slow in the Muskogee quadrangle.^ ^ 



N. F. Drake,^^ in a discussion of the origin of the sedi- 

 ments of the ''Coal Measures" of Oklahoma, which, as 

 defined by him, include not only the Pennsylvanian but 

 also the Mississippian rocks of the Ouachita Mountains, 



says: 



' ' Throughout the Coal Measures the thickness of the sediments 

 gradually decreases northward and westward. The most rapid 

 decrease is toward the north, and the lower beds decrease more 

 rapidly than the higher ones. * * * The relative proportion ^ * * 

 of shales and limestones to sandstones and conglomerates grad- 

 ually increases westward and especially northward. Because of 

 these conditions the sediments are considered to have come from 

 a land area lying to the southeast. ' ' 



A recent study of the Pennsylvanian sandstones and 

 shales in the Bristow quadrangle, in Creek County, Okla., 

 by A. E. Fath-^ has led him to believe that the sediments 

 for them come from a land area to the south-southwest. 



Ice-home hotulders in Caney shale in Oklahoma. 



J. A. Taff^^ has described the occurrence of erratic 

 ice-borne bowlders, up to 60 feet in length, in the Caney 

 shale (Mississippian) in the Ouachita Mountains in 

 southeastern Oklahoma. They have also been described 



" Purdue, A. H., and Miser, H. D., U. S. Geol. Survey Geol. Atlas, Eureka 

 Springs-Harrison folio (No. 202), p. 16, 1916. 



^^Taff, J. A., U. S. Geol. Survey Geol. Atlas, Tahlequah folio (No. 122), 

 p. 5, 1905; Muskogee folio (No. 132), p. 4, 1906. 



^* Drake, N. F., A geological reconnaissance of the coal fields of the In- 

 dian Territory, Am. Philos. Soc. Proc, vol. 36, p. 380, 1898. 



^•^ Oral communication. 



-^ Taff, J. A., Some erratic bowlders in middle Carboniferous shale in In- 

 dian Territory (abstract), Science, new ser., vol. 21, p. 225, 1905. Ice- 

 borne bowlder deposits in mid-Carboniferous marine shales: Geol. Soc. 

 America, Bull., vol. 20, pp. 701-702, 1910. 



