Area in Louisiana and Eastern Texas. 87 



none of them does he show a westward extension of the 

 Appalachians across the lower Mississippi Valley. 



Charles Schuchert^*^ holds that there was a land connec- 

 tion between Texas and the Appalachians during the 

 ^ ^ Upper Acadic'' (Middle Cambrian) and ''Upper Silur- 

 ic," but he^^ and E. 0. Ulrich*^*^ hold that the Appalachian 

 land area was separated by epicontinental seas from the 

 land area in Louisiana and eastern Texas at all other 

 times during the Paleozoic era. Schuchert^^ also holds 

 that no part of the present Gulf Coastal Plain was 

 submerged during the Triassic and Jurassic periods, 

 except southern Texas, which he thinks was submerged 

 during late Upper Jurassic time. 



Llanoria as a positive element and its location dy 

 paleogeographers. 



All paleogeographers agree that Llanoria was one of 

 the positive elements of North America during the Paleo- 

 zoic era, and was thus undergoing erosion during most of 

 the era, but although they agree as to its general location 

 they differ as to its boundaries. This disagreement, 

 however, is not surprising, as the outlines of Llanoria 

 changed from time to time, and as our knowledge of these 

 changes is very scant. 



Willis states as follows :^^ ''It is bounded by the Gulf of 

 Mexico on the southeast ; on the north it probably extends 

 to the folded zone of Paleozoics in Indian Territory 

 [Oklahoma] ; and on the west it appears to be separated 

 by the zone of folding in central New Mexico from the 

 similar [positive] elements in Colorado and Arizona.'' 

 On a recent map he^^ shows that the land area under 

 discussion was connected with Ozarkia to the north and 



®® Schuchert, Charles, Paleogeography of North America, Geol. Soc. 

 America, Bull., vol. 20, maps, 1910. 



" Ulrich, E. O., and Charles Schuchert in Chas. Sehuchert, Paleogeography 

 of North America, Geol. Soc. America, Bull. vol. 20, maps, 1910. 



Ulrich, E. O., Eevision of the Paleozoic systems, Geol. Soc. America, Bull., 

 vol. 22, fig. 7, 1911. 



Ulrich, E. O., The Ordovician-Silurian boundary. Int. Geol. Cong. XII, 

 Canada, 1913, C. R., pp. 660-667, 1914. 



^® Schuchert, Charles, op. cit. 



®® Willis, Bailey, A theory of continental structure applied to North 

 America, Geol. Soc. America, Bull., vol. 18, pp. 394-395, 1909. 



^^ Willis, Bailey, Discoidal structure of the lithosphere, Geol. Soc. America, 

 Bull., vol. 31, Plate 11, 1920. 



