AGE RELATIONS OF THE CRETACEOUS FORMATIONS 



593 



sented by limestone concretions from which no fossils have yet been 

 collected. 



Table shotving the Age Relations of the Cretaceous Formations of central and 

 western 'New Mexico and southwestern Colorado 



Systems 



Groups 



Formations 



Zones and meml)ers 



Tertiary 





G. 

 Cer 



an( 

 fo 



S 



ilisteo of 

 rillos field 

 1 Tertiary 

 rmations 



of 



an Juan 



Basin 



^aramie " 



"Pictured CliflPs sandstone" member 



Punta de la Mesa sandstone member* 

 Cephalopod zone 



Concretion (Septaria) Zone 



Tres Hermanos sandstone member 



Gastropod zone 



Cretaceous 



Montana 



"] 





Lewis 

 shale 



Mesaverde 





0) 



1—1 



03 

 03 



o 

 « 



c 



OS 



. 



Colorado 





~" "•" ^^ ^^ ^~ 





Dakota 

 sandstone 



DAKOTA SANDSTONE 



A quartzose sandstone locally conglomeratic occurs at the base of the 

 Cretaceous series in northern New Mexico. No fossils have been found 



* The Punta de la Mesa sandstone at its type locality in tlie Rio Puerco field is here 

 placed at the base of the Mesaverde, inasmuch as it is the lowest sandstone of the coal- 

 bearing formation. However, it seems to be the age equivalent of a part of the Mancos 

 shale as developed farther north. 



