418 B. R. Semmes — Tertiary Intrusives of 



Alamogordo consists of a series of siliceous limestones, 

 shaly limestones, and sandstone in the lower part, and 

 massive gray and dark limestone (Madera) toward the 

 top, the series aggregating some 1,500 feet in thickness. 2 

 This massive limestone is not exposed in the Pecos Valley, 

 but it is possible that it has some representatives in this 

 area now bnried beneath the Permian sediments. 



Abo Sandstone. — The Abo sandstone, the basal member 

 of the Manzano group, is also exposed near Alamogordo. 

 The formation consists of a series of red sandstone and 

 sandy shales with occasional thin layers of gypsum. The 

 Abo is unexposed in the Pecos Valley. 



Yeso Formation. — This formation as developed in the 

 Sacramento Mountains near Alamogordo consists of 

 1,000-1,200 feet of red shales, thin-bedded gray cherty 

 limestone and occasional layers of massive gypsum. On 

 the eastern flank of the mountain near Lincoln the series 

 is again exposed in part and there consists of red shales 

 and shaly sandstones some 200 feet thick overlying a 

 series of alternating red and greenish shales and sand- 

 stones and thin-bedded fossiliferous limestones. That 

 portion of the Yeso which is exposed in this locality aggre- 

 gates about 1,000 feet in thickness and is sharply folded, 

 lying unconformably below the San Andreas limestone. 

 Farther away from the Capitan Mountains the Yeso 

 appears to show less intense folding, and where last 

 exposed near Picacho it is only slightly unconformable 

 with the overlying San Andreas. There is little doubt 

 that it will be found approximately conformable with the 

 Permian series if encountered by the drill in the Pecos 

 Valley. 



San Andreas Limestone. — The Sacramento range, 

 which is actually a dissected limestone plateau, is formed 

 by continuous limestone formations from its western edge 

 to where this limestone dips below the red-beds of the 

 Pecos Valley. This limestone where exposed near Ala- 

 mogordo has been correlated with the San Andreas, 

 by Darton, 3 which if correct undoubtedly indicates that 

 the limestone developed from Roswell westward to the 

 Sierra Blanca and the Sacramentos is equivalent to the 



2 N. H. Darton : A Comparison of the Paleozoic sections in Southern. 

 New Mexico. U. S. Geol. Survey, Prof. Paper 108, pp 31-55, 1917. 



3 Op. cit. p. 50. 



