Keyes — Significance of Certain Unconformities. 299 



have been removed through erosion prior to the Manzanan 

 period. In the south all of the series bear unconformable 

 relationships to one another. 



The thick Manzanan and Maderan limestones are wide- 

 spread. They are found exposed in all of New Mexico west 



1 



Tp/^ssjc 



MyArJz/^AfJ 



Fig. 1. Eelationships of Late Carboniferous Formations 

 south of the Rocky Mountains. 



of the Pecos river and the Rocky Mountain front. They form 

 the foundation of the entire High Plateau dome to the Grand 

 Canyon. In all this vast region no trace has yet been discov- 

 ered of any formation occupying the interval between the 

 upper surface of the great limestone plate and the Red Beds. 

 In southeastern New Mexico in the Guadalupe range there 

 are over 2,500 feet of sandstones and limestones in this inter- 

 val. This is the Guaclalupan series and carries an extensive 

 fauna, first made known by Shumard in 1858, but unknown 

 elsewhere on the American continent. 



The Red Beds are widespread. Very marked unconformi- 

 ties occur both at the base and at the top. Whether they are 

 Permian or Triassic in age has long been a theme of discussion. 

 A great unconformity lately determined in the very middle of 

 the Red Beds succession appears to clearly separate the inferior 

 Carboniferous part from the superior Triassic portion.* 



Special interest centers in the probable existence of Jurassic 

 deposits in the Morrisonian and Zunian formations. The gen- 

 eral stratigraphic relationships are represented below (fig. 2). 



Fig. I 



Mexico. 



Relationships of Mesozoic and Paleozoic Rocks of Northern New 



As for the other unconformities they may be passed over 

 for the present. 



In the course of the work of delimitating the formations 

 composing the geological section of New Mexico, as set forth 

 * This Journal, vol. xx, pp. 423-429, 1905. 



