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La Irene Formation is a Maastrichtian geologic formation in southern Patagonia, Argentina. The formation is 230 metres (750 ft) thick and underlies the Chorrillo Formation and rests on top of the Cerro Fortaleza Formation.[1]
| La Irene Formation | |
|---|---|
| Stratigraphic range: Maastrichtian ~ | |
| Type | Geological formation |
| Underlies | Chorrillo Formation |
| Overlies | Cerro Fortaleza Formation |
| Thickness | 230 m (750 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Shale |
| Location | |
| Location | Patagonia |
| Coordinates | 50.4°S 72.2°W |
| Approximate paleocoordinates | 52.3°S 62.0°W |
| Region | Santa Cruz Province |
| Country | Argentina |
| Extent | Austral Basin |
  La Irene Formation (Argentina) | |
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 230 metres (750 ft) 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]
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