LOWER CRETACEOUS SERIES. 715 



of last year was confined. While the co-ordinate branches of structural, 

 dynamical, and economical geology have not been neglected in the field 

 studies, they will only be referred to in general terms at this time. It may 

 be remarked, however, that the dynamic features especially are of surpassing 

 interest and importance, and their correct determination will be of much value 

 in working out adjacent areas. These rocks seem to owe their present expo- 

 sure, for the most part, to certain disturbances having axes running in direc- 

 tions varying from northwest-southeast to nearly north and south, accom- 

 panied by very considerable folding and faulting, which in the Malone Moun- 

 tains especially has developed some beautiful dynamical effects. 



The development of the Cretaceous rocks as studied in El Paso County is 

 very much greater than those of the same formation found in the Colorado 

 River section, and by far the greater part of them belong to the Lower Cre- 

 taceous Series, although the Upper is also present. 



The same general classification given in the First Annual Report will be 

 adhered to in this Report* 



LOWER CRETACEOUS SERIES. 



Development and General Character. — As stated above, the Cretaceous 

 rocks of El Paso County are much beyond those of the same formation yet 

 studied in any other part of the State in the magnitude of their development, 

 as will be seen by evidence given beyond, and yet neither the base nor the 

 highest beds have been found, and there are, moreover, indications that point 

 to greater depths of rock in the region lying towards the southeast. 



Much of the rock is very similar to that of the same beds occurring be- 

 tween the Colorado and Red rivers, while others are widely different. The 

 range in lithologic character is wide, including almost every phase from a 

 deep sea foraminiferal massive limestone to a coarse conglomeritic bowlder 

 breccia, and from the same pure limestone through various grades of siliceous 

 limestone to a coarse, shell brecciate, gritty rock. Then there are grades of 

 sandstone from a fine-grained pure glassy quartzite up through coarse false 

 laminated sandstone and grit to a very coarse siliceous conglomerate. 



Clay is, however, especially scarce in the Sierra Blanca region, but to the 

 south and southeast it largely takes the place of the more arenaceous beds here. 



TRINITY DIVISION. 



BASAL SAND BED ITS RELATION TO THE COLORADO-RED RIVER BED. 



This, the lowest bed seen, is not very different from the Trinity sand oc- 

 curring along the base of the Lower Cretaceous, between the Colorado and 

 Red rivers, and in the Abilene country, except in the degree of metamorph- 



