Riachuelo Formation
| Riachuelo Formation | |
|---|---|
| Stratigraphic range: Late Aptian-Early Cenomanian ~ | |
Reconstruction of the fauna from the Riachuelo Formation | |
| Type | Geological formation |
| Sub-units | Angico Member
Taquari Member Maruim Member |
| Underlies | Cotinguiba Formation |
| Overlies | Muribeca Formation |
| Thickness | 500 m (1,600 ft) |
| Lithology | |
| Primary | Packstone, Grainstone |
| Other | Mudstone, siltstone, siliciclastic |
| Location | |
| Region | Sergipe-Alagoas Basin of Northeastern Brazil |
| Country | Brazil |
| Extent | 20 kilometres (12 mi) |
| Type section | |
| Named for | Riachuelo, Sergipe |
| Named by | Moraes Rego (1929) |
The Riachuelo Formation is a geologic formation of the Early to Late Cretaceous (Late Aptian to Cenomanian) age in northeastern Brazil's Sergipe-Alagoas Basin. It is the first Formation of the Basin to contain sediments deposited under fully marine conditions. The formation is subdivided into three members: Angico, Taquari and Maruim.
The formation has provided fossils of ammonites, gastropods, bivalves, brachiopods, serpulids, equinoderms, ostracoids, radiolarians, lobsters and Crabs. Several fish species reported from the Santana Formation also occur in this formation, namely: Cladocyclus gardneri, Neoproscinetes penalvai, Notelops brama, Rhacolepis buccalis, Tharrhias araripis and Vinctifer comptoni. Santanichthys diasii is also reported from the Taquari Member of the Riachuelo Formation. Teeth and vertebrae of elasmobranchii have also been found in the formation.