GEOTECTONICS OF ESTANCIA PLAINS 451 



place the line of movement is marked by a long, high ridge formed 

 of Cretacic sandstones standing on edge. 



The southern, or Mesa Jumanes, cross-section passes eastward 

 from the crest of the Manzano Mountains, over the northern extremity 

 of the plateau plain known as the Mesa Jumanes, to beyond the Cerro 

 del Pino near Torrance (section G-H, Group, Fig. 10) . The western 

 part of the section is synclinal in character with Cretacic beds as the 

 surface rock. The Mesa Jumanes is a tableland with even surface 

 which is elevated 300 feet above the level of the surrounding plains. 

 Its sides are very steep. It appears to have an anticlinal structure, 

 with Carbonic limestones forming the central part. The margins are 

 composed of Cretacic sandstones. The explanation of this remark- 

 able plateau plain appears to be found in the physiography of the 

 region farther to the northeastward. It is believed that the Estancia 

 Plains once formed a part of the Las Vegas plateau which extends 

 northward to the Colorado line, and that the elevated Mesa Jumanes 

 is a remnant of the Ocate plateau so conspicuous to the north of the 

 city of Las Vegas. 



