| Tres Cruces Formation | |
|---|---|
| Stratigraphic range:Sinemurian-Pliensbachian, ~199–184 Ma | |
| Type | Geological formation |
| Underlies | Algarrobal Formation |
| Overlies | Tonalitebasement |
| Thickness | ~390 m (1,280 ft) |
| Lithology | |
| Primary | Sandstone,conglomerate,limestone |
| Other | Mudstone |
| Location | |
| Region | Coquimbo Region |
| Country | Chile |
| Type section | |
| Named for | Quebrada Tres Cruces |
| Named by | Dediós, 1967 |
TheTres Cruces Formation issedimentary andfossiliferousgeological formation that crops out acrossPaihuano in theCoquimbo Region ofChile. It is dated back to theEarly Jurassic period (Sinemurian throughPliensbachian stages). Thelithology of the formation comprisesclastic rocks, such assandstone,conglomerate, and fossil-richlimestone, formed in marine settings. As such, the Tres Cruces Formation preserves a marine fossil record represented bybrachiopods,molluscs (ammonites,bivalves,gastropods), andmarine reptiles (ichthyosaurs).[1][2] The formation is named after Quebrada Tres Cruces, whhich is an important fossiliferous locality.[1]
| Genus | Species | Material | Locality | Unit | Notes | Images |
|---|---|---|---|---|---|---|
| Acanthopleuroceras | Indeterminate | Not specified.[1] | Quebrada Dolores | Apolymorphitid ammonite. | ||
| Amaltheus | Indeterminate | Not specified.[1] | Quebrada Dolores | Aamaltheid ammonite. | ||
| Arieticeras? | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Ahildoceratid ammonite. | ||
| Radstockiceras? | Indeterminate | Not specified.[1] | Quebrada Dolores | Aoxynoticeratid ammonite. |
| Genus | Species | Material | Locality | Unit | Notes | Images |
|---|---|---|---|---|---|---|
| Cardinia | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Acardiniid bivalve. | ||
| Exogyra | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Agryphaeid bivalve. | ||
| Gryphaea | Indeterminate | Not specified.[1] | Quebrada Dolores | Agryphaeid bivalve. | ||
| Ostrea | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Aostreid bivalve. | ||
| Panopea | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Ahiatellid bivalve. | ||
| Pholadomya | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Apholadomyid bivalve. | ||
| Weyla | W. alata | Not specified.[1][2] | Quebrada Tres Cruces, Quebrada Dolores, Quebrada Matahuaico | Apectinid bivalve. |
| Genus | Species | Material | Locality | Unit | Notes | Images |
|---|---|---|---|---|---|---|
| Spiriferina | S. rostrata | Not specified.[1] | Quebrada Tres Cruces, Quebrada Dolores | Aspiriferinid brachiopod. | ||
| Terebratula | Indeterminate | Not specified.[1] | Quebrada Dolores | Aterebratulid brachiopod. | ||
| Zeilleria | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Azeilleriid brachiopod. |
| Genus | Species | Material | Locality | Unit | Notes | Images |
|---|---|---|---|---|---|---|
| Lithotrochus | L. humboldtii | Not specified.[1][2] | Quebrada Tres Cruces, Quebrada Dolores | Atrochid gastropod. | ||
| Nerinea | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Anerineid gastropod. | ||
| Pleurotomaria | Indeterminate | Not specified.[1] | Quebrada Tres Cruces | Apleurotomariid gastropod. |
| Genus | Species | Material | Locality | Unit | Notes | Images |
|---|---|---|---|---|---|---|
| Ichthyosauria indet. | Indeterminate | Twelve vertebrae centra.[2] | Quebrada Tres Cruces | Anichthyosaur. |
