CONCLUDING REMARKS. 737 



CONCLUDING REMARKS ON THE DYNAMIC FEATURES OF 

 THE CRETACEOUS ROCKS WORKED IN EL PASO COUNTY. 



It is observed that in all the uplifts and disturbances noted as being con- 

 nected with the Eagle, Quitman, and Sierra Blanca mountains Cretaceous 

 rocks are affected. It is observed also that there are four principal trends 

 or lines of fracture of the strata in these uplifts, with many subtrends or 

 local disturbances. One of the principal uplifts extends from Eagle Moun- 

 tain in the line of Devil's Ridge to the Sierra Blanca Mountains, bearing about 

 north 55° west, magnetic. This line, if extended, will approach the Hueco 

 Mountains, which are suspected of being in the same trend. Another is 

 that of South Quitman Mountain, extending from the Rio Grande north- 

 ward, including the porphyritic portion of the mountain north of Quitman 

 Pass, bearing about north 30° west, magnetic. These two uplifts are the 

 same in character. The remarkable feature of them is that the rocks almost 

 invariably dip to the southwest ward, even in spite of eruptive mountains of 

 porphyry *and basaltic rock two thousand feet high. It is pretty evident 

 that there are fault lines or immense isoclinal folds, and that in their forma- 

 tion there was a major stress from the southwest. If they were isoclinal 

 folds the axes are now hidden by the basin debris that occupies the valleys. 



A third trend is that of North Quitman Mountain. There is evidence 

 going to show that this is the oldest uplift. Rocks on the west side of North 

 Quitman Mountain strike north 20° west, magnetic. If the extensive folds 

 of South Quitman, Eagle, and Sierra Blanca mountains had extended over 

 the area now occupied by Quitman Mountain the dip would undoubtedly 

 have been different. Around the bases of North Quitman Mountain the 

 rocks wherever exposed dip regularly away from the mountain, and do not 

 show indications that they were broken by the uplift of South Quitman 

 Mountain. The most southerly exposed trends of Devil's Ridge break up on 

 approaching Quitman Mountain, while those on the north side of the ridge 

 pass on through Sierra Blanca Peak. 



The fourth principal uplift is that of Malone Mountain. This uplift con- 

 forms in part to both the uplift of North Quitman and of the Eagle- Sierra 

 Blanca uplift. The strike of the rocks in the southeast end of Malone Moun- 

 tain agree nearly with that of North Quitman Mountain, while that of the 

 northwest end of Malone Mountain conforms to that of the Eagle-Sierra 

 Blanca uplift. 



The sharp isoclinal folds, with south westward dipping axis planes and in- 

 verted strata toward the northeastward on the northeast side of the mountain, 

 plainly indicate that the Malone Mountain is the result of thrusts from the 

 southwest into the obtuse angle of the North Quitman and Eagle-Sierra 

 Blanca trends. 



