La Irene Formation

La Irene Formation is a Maastrichtian geologic formation in southern Patagonia, Argentina. The formation is 230 m thick and underlies the Chorrillo Formation and rests on top of the Cerro Fortaleza Formation.

Description
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 m 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.

Fossil content
The formation has provided many fossil pollen of:
 * Podocarpaceae
 * Monocotyledoneae
 * Liliidae
 * Cycadopsida
 * Pteridopsida
 * Polypodiopsida
 * Schizaeaceae
 * Gleicheniaceae
 * Selaginellaceae
 * Lycopodiaceae
 * Magnoliopsida
 * Dinophyceae