Geologic History. Extension in this the main Rio Grande rift started about 36 million years back.

Geologic History. Extension in this the main Rio Grande rift started about 36 million years back.

Expansion in this area of the Rio Grande rift started 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). Continue reading “Geologic History. Extension in this the main Rio Grande rift started about 36 million years back.”