| La Irene Formation | |
| Type: | Geological formation |
| Period: | Maastrichtian |
| Age: | Maastrichtian ~ |
| Prilithology: | Sandstone |
| Otherlithology: | Shale |
| Location: | Patagonia |
| Region: | Santa Cruz Province |
| Country: | Argentina |
| Coordinates: | -50.4°N -72.2°W |
| Paleocoordinates: | -52.3°N -62°W |
| Underlies: | Chorrillo Formation |
| Overlies: | Cerro Fortaleza Formation |
| Thickness: | 230m (760feet) |
| Extent: | Austral Basin |
La Irene Formation is a Maastrichtian geologic formation in southern Patagonia, Argentina. The formation is 230m (760feet) thick and underlies the Chorrillo Formation and rests on top of the Cerro Fortaleza Formation.[1]
The formation comprises lithified, sandy sandstones and lithified, argillaceous, sandy shales deposited in a fluvial deltaic environment.
At the base of Cerro Calafate a column of about 230m (760feet) in thickness was measured along the road. The 110 m below represent a succession of sandy banks clear yellowish brown color to white and dark pelitic packages fining upwards cycles are stacked to form a sequence with a clear trend growing grain and stratum. Sandy banks (coarse to fine sand) show increasing thickness from 2 m at the base to more than 9 m, whereas intercalated mudstones show an opposite trend with thickness ranging from 15 m at the base to 1 m. At the top of lower shaly packets (the thickest) are preserved carbonaceous shale intervals, thinly laminated. 120 m above correspond to a succession of amalgamated conglomeratic sandy banks where preservation is extremely rare shaly intervals.[2]
The formation has provided many fossil pollen of:[3]