Bajo de Véliz Formation
| Bajo de Véliz Formation | |
|---|---|
| Stratigraphic range: Kasimovian-Asselian ~ | |
| Type | Geologic formation |
| Unit of | Paganzo Group |
| Sub-units | Cautana, Pallero & Lomas members |
| Overlies | San Luis Formation |
| Thickness | 168 m (551 ft) |
| Lithology | |
| Primary | Siltstone |
| Other | Sandstone |
| Location | |
| Coordinates | 32°18′41″S 65°24′48″W / 32.31139°S 65.41333°W |
| Approximate paleocoordinates | 49°06′S 59°30′W / 49.1°S 59.5°W |
| Region | San Luis Province |
| Country | Argentina |
| Extent | Paganzo Basin |
| Type section | |
| Named for | Bajo de Véliz Provincial Park |
| Named by | Flores |
| Year defined | 1969 |
The Bajo de Véliz Formation is stratigraphic formation of the Paleozoic located in the Paganzo Basin, Argentina. This formation lies in the northwestern sector of San Luis, about 25 km west of Santa Rosa de Conlara. Containing a slice of the Carboniferous-Permian transition, it is one of the key upper Paleozoic successions characterizing that era in westernmost Gondwana, which South America was a part of in the Paleozoic.
It consists of Cautana (Upper Carboniferous), Pallero (end-Pennsylvanian to Cisuralian), and Lomas (Permian) units. Based on the paleoflora found in the middle upper Pallero unit, it was suggested to be of earliest Cisuralian age of the early Permian, though there is still ambiguity as insects associated with that layer have been assigned to the late Pennsylvanian of the Carboniferous.
It is one of the key windows into the fossil life of the Gzhelian to Asselian, and is known as the formation where the thought-to-be giant spider Megarachne, actually a eurypterid, was discovered.