in West Texas and Southeast JVew Mexico. 337 



The upper Carboniferous strata in the area considered are 

 separated from underlying and overlying rocks by major ero- 

 sional unconformities. The lower beds are Pennsylvanian and 

 the upper beds are Permian, but the separation of the two series 

 is not well marked. 



The total thickness is enormous, the stratigraphy is extremely 

 varied, and two local unconformities occur in the upper Car- 

 boniferous section. In the east central New Mexico section, 

 excepting a relatively thin deposit of limestone at the base of 

 the section, almost the entire upper Carboniferous record is 

 of red bed deposition. In southeast New Mexico a great 

 body of sandstone and limestone occurs between and merges 

 into red beds. In west Texas, north of the Texas and Pacific 

 Pail way, red beds are practically confined to the top of the 

 upper Carboniferous section, and in the Chinati Mountain 

 region no red beds have been reported. 



The sections which have been described can be approxi- 

 mately correlated and together they comprise the local com- 

 plete upper Carboniferous column. It appears : (a) that the 

 Hueco formation embraces both the Magdalena and Manzano 

 groups of the Rio Grande Valley section in New Mexico ; (b) that 

 the Guadalupian series lies between the Hueco formation and 

 the red beds of Pecos Valley ; (c) that the red beds of Pecos 

 Yalley constitute a variable group, the base of which is not a 

 definite horizon, the occurrence of the red color extending 

 irregularly across the strike of the rocks ; (d) and that the 

 upper part of the red beds of Pecos Valley is equivalent to the 

 upper part of the Permian red beds of northwest Texas and 

 Oklahoma. 



The varied stratigraphy is an expression of changing geo- 

 graphic conditions which accompanied the emergence of the 

 continent at the close of Paleozoic time. Apparently an open 

 sea gave way, with some alterations, to shallower water and 

 to local enclosed basins.. The Guadalupian fauna probably 

 migrated from the south, and its spread northward and eastward 

 seems to have been checked by changing environment. It is to 

 be noted that while from Kansas to Oklahoma shales and lime- 

 stones merge into red beds from north to south, in west Texas 

 and New Mexico a similar transition occurs from south to 

 north, indicating an east-west zone in the upper Carboniferous 

 area of deposition in which red beds accumulated. 



