CRETACEOUS BED OF MESILLA VALLEY. 169 



that series, and would class it with the posterior deposits — the psamerythic, the lower new red 

 sandstone of English geologists, the roth-todt — liegende of Thuringia, the Gres rouge of the 

 peneen bed of France, and from its composition " roches a psephitis," by Cordier. 



The minerals associated with this rock on tnis latitude — gypsum and rock salt — which efflor- 

 esce on the degraded surface of the horizontal beds, refer it also to this place. 



Further north in the Territory, Mr. Marcou has met with similar rocks, and classed them 

 along with the red clay rocks east of the Rio Grande, including the whole under the term Trias. 

 I am inclined, however, to the opinion that this bed is older than the trias, and lithologically 

 on parallel 32°, it certainly bears no resemblance to the sandstones of Texas, with the excep- 

 tion of the bed of greenish ferruginous sand found between Dona Ana and the Horse mountains, 

 already alluded to, lying unconformable to the elevated sandstones ; there were no strata of creta- 

 ceous rocks exposed. This bed was observed by chance, while keeping up a dry creek bed to reach 

 the hills at a favorable point. The creek had worn its way some 25 feet deep below the general 

 level, exposing below the alluvial covering, which was a brownish sand 5 to 6 feet in thickness, 

 a layer of greenish sand ferruginous and crumbling under the finger. The bed was horizontal ; 

 a depth of 16 to 20 feet was exposed, but its bottom was not reached ; a layer of silicified stems 

 lay horizontally in the sand about six feet below the upper surface, and a second layer eight 

 feet below the first. Many of these had been washed out and carried down the creek bed. The 

 wood was of various sizes, from an inch in diameter to six inches, and from six inches to two 

 feet long. Most of the specimens had the external configuration of an equisetum. As this 

 horizontal stratum lay on the upper terrace, or the mesa east of the Doiia Ana, it can scarcely 

 be supposed to dip under the river, which lies one hundred feet below. The present bottom of 

 the Eio Grande being well defined on each side by an abrupt ascent from it to the mesa, the 

 river may be supposed, therefore, to have worn its way through and removed this bed, leaving 

 only these slight traces now observed on the upland. 



The silicified stems gathered here were lost in the subsequent transportation. 



22 U 



