238 C. L. HERRICK 



ites, in common with the immediately overlying strata, have suffered 

 great erosion in the early part of the so-called Permian. This period 

 of elevation, disturbance, and oscillation does not, however, seem 

 to mark any great lost interval, so far as the record shows, while the 

 interval represented by the granite contact is undoubtedly a consid- 

 erable and variable one. The disturbance which lifted the granites 

 above the reach of the sea may not have been very extreme, and it is 

 not likely that the present extreme of metamorphism was reached till 

 long after, though it was certainly before the time in which the 

 breccias and sandy beds of the Permian were formed, for these strata 

 contain granite fragments in abundance. 



At any rate, when the sea began to return by subsidence of the 

 granite, this encroachment was gradual, and from the south toward 

 the north and northwest. This is proved by the fact that the expos- 

 ures in the southeastern counties reveal vast deposits between the 

 granite and the Carboniferous in which we have identified strata as 

 old as the Burlington, superposed upon others yet older, but not 

 identified as yet. In the southwestern part of New Mexico there are 

 still earlier strata, some of which have been referred to the Devonian 

 {Hamilton). The writer hopes to enter upon this subject more in 

 detail in another place; at present it will be sufficient to indicate that 

 as far north as in Socorro county the stratified rocks overlying the 

 granite have revealed no remains indicating an age earlier than the 

 Carboniferous, and the writer knows of no positive datum repre- 

 senting anything older than the Coal Measures. It is true that there 

 are reports of Subcarboniferous crinoids from the Graphic-Kelly 

 beds lying upon the crystallines near Magdalena, but inasmuch as 

 this 100 feet or more of crystalline limestone, which is so interestingly 

 developed in the lead district, is not found in the locality under dis- 

 cussion east of the Rio Grande, nor yet farther north in the Rio 

 Grande valley, it may be said roughly that the boundary between 

 the lower formations and the Coal Measures passes through Socorro 

 county. 



Corresponding to the change just described is a still more pro- 

 nounced geographical change in the character of the Permian and 

 ''red bed" deposits, which have an entirely different facies and suc- 

 cession in the northwestern counties from the typical Texas sequence 

 exhibited in the southeast. 



