CARBONIFEROUS FORMATIONS IN NEW MEXICO 151 



of the American continent. Their definition, range, distribution, 

 and comparison with those of other provinces promise interesting 

 and instructive resuhs. In the New Mexican province a most 

 inviting and unique field awaits students of Carboniferous life. 



Enough is now known of the fossils to enable their general affin- 

 ties to be made out with reasonable certainty. Much that is new 

 is to be found among them. The careful determination of the 

 range and distribution of the various faunas and faunules is neces- 

 sary before exact comparisons can be made with those of other 

 provinces, and correlation made according to biotic methods alone. 



The serial subdivisions of the New Mexican Carboniferous 

 succession is based partly upon biologic data, but largely upon 

 direct stratigraphic grounds. Correlation with the Kansas section 

 has been mainly by organic content, and secondarily by general 

 formational relationships. The correspondence of the two per- 

 fectly independent records is close to a degree that is quite remarkable. 



As already intimated, six distinct and easily recognizable sub- 

 divisions of the great succession of strata have been defined. Taxo- 

 nomically they hold the rank of series. Special mention of the 

 numerous minor formations which go to make up these series need 

 not be made at this time. However, the several series may be 

 briefly characterized. 



The basal series to which the title Socorran has been given com- 

 prises all of the Early Carboniferous sediments in the Southwestern 

 province. It corresponds to the original Mississippian series of 

 the Continental Interior province, though it manifestly does not 

 include so much. According to present faunal and stratigraphi- 

 cal evidence, its equivalent in the Upper Mississippi valley is the 

 Chouteau and Burlington limestones. A prolific Lower Burling- 

 ton fauna, including most of the most typical crinoids, is found 

 at Lake Valley. Nothing higher than the strata containing the 

 Lower Burlington fauna has yet been found in this region. Whether 

 this later part is present and concealed, or actually absent altogether, 

 cannot be at present stated. A profound erosion plane bevels off 

 all known Early Carboniferous strata; hence it is quite probable 

 that considerable more of the basal portion of the general section 

 will sooner or later be brought to light in this region. 



