| Ancha Formation | |
|---|---|
| Stratigraphic range: Pleistocene, | |
 Ancha Formation at type section | |
| Type | Formation |
| Unit of | Santa Fe Group |
| Overlies | Tesuque Formation |
| Thickness | 28 m (92 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Siltstone, conglomerate |
| Location | |
| Coordinates | 35°44′54″N 106°06′40″W / 35.74834°N 106.11108°W |
| Region | New Mexico |
| Country |  United States |
| Type section | |
| Named for | Canada Ancha |
| Named by | Baltz et al. |
| Year defined | 1952 |
  Ancha Formation (the United States)  Ancha Formation (New Mexico) | |
The Ancha Formation is a geologic formation found near Santa Fe, New Mexico. It is estimated to be between 1 and 3 million years in age, corresponding to the late Pliocene and Pleistocene.[1]
Study of the formation has provided clues on the development of rivers systems in the region. In particular, evidence from the formation suggests that the Pecos River may originally have flowed west to join the Santa Fe River, rather than east to join the Rio Grande as it now does.
The formation is one of the youngest of the Santa Fe Group formations deposited in the Rio Grande rift. It is an important local aquifer.[1]
- ^ a b Koning et al. 2002.