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La Irene Formation

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La Irene Formation
Stratigraphic range: Maastrichtian
~70–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
TypeGeological formation
UnderliesChorrillo Formation
OverliesCerro Fortaleza Formation
Thickness230 m (750 ft)
Lithology
PrimarySandstone
OtherShale
Location
LocationPatagonia
Coordinates50°24′S 72°12′W / 50.4°S 72.2°W / -50.4; -72.2
Approximate paleocoordinates52°18′S 62°00′W / 52.3°S 62.0°W / -52.3; -62.0
RegionSanta Cruz Province
CountryArgentina
ExtentAustral Basin
La Irene Formation is located in ArgentinaLa Irene FormationLa Irene Formation (Argentina)

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.

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 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.

Fossil content

The formation has provided many fossil pollen of:

References

  1. Marenssi et al., 2003, p.406
  2. La Irene Formation at Fossilworks.org
  3. Povilauskas et al., 2008

Bibliography

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