San Jose Formation
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| San Jose Formation | |
|---|---|
| Stratigraphic range: Wasatchian ~ | |
San Jose Formation capping Mesa de Cuba, northern New Mexico | |
| Type | Formation |
| Sub-units | Cuba Mesa, Ditch Canyon, Llaves, Regina & Tapicitos Members |
| Overlies | Nacimiento Formation |
| Thickness | 430 m (1,410 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Shale |
| Location | |
| Coordinates | 36°17′N 107°04′W / 36.29°N 107.06°W |
| Approximate paleocoordinates | 41°12′N 91°42′W / 41.2°N 91.7°W |
| Region | New Mexico |
| Country | United States |
| Extent | San Juan Basin |
| Type section | |
| Named for | San Jose Valley (36°10′48″N 106°55′37″W / 36.180°N 106.927°W) |
| Named by | G.G. Simpson |
| Year defined | 1948 |
The San Jose Formation is an Early Eocene (Wasatchian in the NALMA classification) geologic formation in the San Juan Basin of New Mexico and Colorado.[1]

The San Jose Formation is mostly sandstone but with some mudstone beds.[2][3] The formation was deposited by high-energy streams on a muddy floodplain that was the last preserved sedimentation episode in the San Juan Basin. Stream direction was from the northwest, north, and east towards the south.[4]
The basal Cuba Mesa Member is found throughout the depositional basin and is a coarse-grained sheet sandstone. The Regina Member is floodplain mudstone and disconnected sheet sandstone that intertongues with the sandstone-dominated Ditch Canyon Member in the northwestern part of the basin and the Llaves Member on the east side of the basin. The uppermost member is the siltstone-dominated Tapicitos Member. The Cuba Mesa Member was deposited during subsidence in the basin center, while the later members were deposited during episodes of monoclinal folding along the Nacimiento Fault on the west escarpment of the Nacimiento Mountains.[4]
Paleontology
The mudstone beds of the San Jose Formation are locally rich in fossils.[2] These include the Almagre and Largo faunas of the early Eocene.[5]
Fossil content
Among others, the following fossils have been reported from the formation:[1]
Mammals
- Primates
- Artiodactyls
- Carnivora
- Cimolesta
- Ferae
- Glires
- Hyaenodonta
- Insectivora
- Pantodonta
- Perissodactyla
- Placentalia
- Taeniodonta
- Theriiformes
Reptiles
- Snakes
- Turtles
- Lizards