Chorrillo Formation
| Chorrillo Formation | |
|---|---|
| Stratigraphic range: | |
Satellite image of the Chorrillo Formation site (in the middle on the right). In the bottom left is the Perito Moreno Glacier. | |
| Type | Geological formation |
| Underlies | Calafate Formation |
| Overlies | La Irene Formation |
| Thickness | >50 m (160 ft) |
| Lithology | |
| Primary | Claystone |
| Location | |
| Location | Patagonia |
| Coordinates | 49°54′S 72°30′W / 49.9°S 72.5°W |
| Approximate paleocoordinates | 51°48′S 62°12′W / 51.8°S 62.2°W |
| Region | Santa Cruz Province |
| Country | Argentina |
| Extent | Southeast of Viedma Lake North of Argentino Lake Austral Basin |
| Type section | |
| Named by | Arbe & Hechem |
| Year defined | 1984 |
Chorrillo Formation (Argentina) | |
The Chorrillo Formation, also named as Chorillo Formation, is a Maastrichtian (Late Cretaceous Epoch, 72.1–66 million years ago) geologic formation in southern Patagonia, Argentina. The formation is more than 50 metres (160 ft) thick and underlies the Calafate Formation and rests on top of the La Irene Formation. It constitutes a significant uppermost Cretaceous continental sedimentary sequence within the Magallanes Basin, located in Santa Cruz Province, Argentina, approximately 30 km southwest of El Calafate. Initial investigations in the 1990s laid the groundwork, with detailed paleontological studies emerging since 2019, revealing a rich biotic assemblage. The formation correlates with the lower Dorotea Formation in Chile, sharing dinosaurian ecotypes, while both are clearly different from other northern Patagonian Maastrichtian units (e.g., Allen Formation, Los Alamitos Formation), which are dominated by saltasaurine sauropods and abelisaurids, suggesting potential temporal or environmental distinctions.