GEOTECTONICS OF ESTANCIA PLAINS 445 



on the west face of the Sandia Mountains there are shown about 

 4,000 feet of schists, highly metamorphosed elastics, and old intruded 

 granites. These are without much doubt Azoic in age. 



Following the fundamental complex are blue limestones of great 

 thickness. They are Mid-Carbonic in age. Above the limestones 

 is normally a remarkable succession of red-beds consisting of shales 

 and shaly sandstones which are doubtless, in great part at least, also 

 of Mid-Carbonic age. 



Then comes a prodigious mass of yellow sandstones and shales 

 belonging to the Mid- and Late Cretacic Ages. Finally, are the sur- 

 face loams, sands and gravels of variable thickness, of Tertiary and 

 Quaternary ages. 



Besides the five general classes of rock-masses referred to there is 

 a variety of igneous types. 



Geologic formations represented. — The general lithologic character, 

 thickness, and stratigraphic relationships of the various geologic 

 formations which are represented within the limits of the Estancia 

 Plains area need not be described in detail at this time. Two terranal 

 features should, however, be noted: The presence, in this region, of 

 a great succession of "red-beds" fully 1,000 feet in thickness which 

 is not the correlative homologe of the Kansas red-beds; and the 

 remarkable sandstone forming the base of the Cretacic section of the 

 region and to which the term Dakota sandstone has been long applied. 



The red-beds of the Sandia side of the Estancia Plains have been 

 termed the Bernalillo shales' and they represent the uppermost and 

 third member of the Maderan series.^ The fact that these " red-beds" 

 are neither of- Permian nor of Jura-Trias Age was first made known 

 in 1900 by Herrick^ who discovered in them a large and characteristic 

 fauna, that clearly connected the section with the so-called Permo- 

 Carboniferous section of central Kansas. The Kansas red-beds or 

 Cimarronian series, and the Triassic red-beds have been shown to be 

 entirely absent in central New Mexico. ^ The title Manzano for- 

 mation which has been used for the beds in question is inapplicable. 



1 Ores and Minerals, Vol. XII, p. 48; also Report of the Governor of New Mexico 

 to Secretary of the Interior, for IQOJ, p. 339, 1903. 



2 This Journal, Vol. XIV, p. 152, 1906. 



3 This Journal, Vol. VIII, p. 116, 1900. 



4 American Journal of Science (4), Vol. XX, p. 423, 1905. 



