Expansion in this right the main Rio Grande rift began about 36 million years back. Rock debris that eroded through the developing rift-flank highlands, in addition to wind-blown and playa pond deposits, accumulated within the subsiding Mesilla Basin. These basin fill deposits, referred to as Santa Fe Group, are 1500 to 2000 legs dense beneath Kilbourne Hole (Hawley, 1984; Hawley and Lozinsky, 1993). The uppermost sand, silt, and clay regarding the Pliocene to very early Pleistocene Camp Rice development, the youngest device regarding the Santa Fe Group in this the main basin, are exposed into the base of Kilbourne Hole. The Camp Rice development ended up being deposited by way of a south-flowing river that is braided emptied in to a playa pond when you look at the vicinity of El Paso.
The Los Angeles Mesa surface, a flat work surface that developed in addition to the Camp Rice development, represents the utmost basin fill for the Mesilla Basin by the end of Santa Fe Group deposition about 700,000 years back (Mack et al., 1994). This area is all about 300 ft over the Rio Grande that is modern floodplain. The top created during a time period of landscape security. Basalt moves from the Portillo volcanic field are intercalated with all the upper Camp Rice development and lie regarding the Los Angeles Mesa area.
The Rio Grande began to decrease through the older Santa Fe Group deposits after 700,000 years back in reaction to both changes that are climatic integration of this river system with all the gulf. This downcutting had not been a constant procedure; there have been a few episodes of downcutting, back-filling, and renewed incision. Continue reading “Geologic History. Expansion in this area of the Rio Grande rift started about 36 million years back.”