La Irene Formation

La Irene Formation is a Maastrichtian geologic formation in southern Patagonia, Argentina. The formation is 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 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: