298 Keyes — Significance of Certain Unconformities. 

 Great Unconformities in the JVew Mexican Succession. 



Age. 



Series. 



Thickness. 



Eocks. 





Quaternary 



(Not differentiated) 



200 

 200 



Gravels 



o 



M 



o 





Llano Estacadan 



Shales 



O 



z 



Tertiary 



Arriba n 



Wasatchan 



500 

 1700 



Sandstones 

 Sandstones 



O 





Nacimientan 



800 



Shales 







Laramian 



3600 



Sandstones 







Montanan 



1500 



Shales 



o 



Cretaceous 



Coloradan 

 Dakotan 



1000 

 500 



Shales 

 Sandstones 



c 





Comanchan 



100 



Sandstones 





Jurassic 



Morrisonian 



200 



Shales 







Triassic 



Zunian 



Shinarurapan 



1200 

 1500 



Shales 

 Shales 













Cimarronian 



1000 



Shales 







Guadalupan 



2500 



Limestones 





Carboniferous 



Maderan 

 Manzanan 



1000 

 1000 



Limestones 

 Limestones 



o 





Ladronesian 



100 



Shales 



o 





Socorran 



300 



Limestones 



fd 







Hi 



Pu 



Devonian 



(Not differentiated) 



400 



Limestones 





Silurian 



(Not differentiated) 



100 



Limestones 





Ordovician 



El Pasan 



1200 



Limestones 





Cambrian 



Tontoan 



300 



Sandstones 





Chuarian 



[■ 3000 



Shales 



Proteeozoic 



Grand Canyon 



Sandstones 





Vishnuan 



> 



Quartzites 



Avchezoic 



(Not differentiated) 



5000 



Schists 



sion intervals. These may correspond to the three principal 

 unconformities found farther west in Arizona. In northern 

 New Mexico the three planes are believed to be superimposed. 

 The Paleozoic formations older than the Manzanan lime- 

 stone (Mid-Carboniferous) are found only in the southwestern 

 part of ISTew Mexico, around the southern margin of the broad 

 dome known as the Colorado High Plateau. To the north all 



