The Soncco Formation is a

Late Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...

Early Oligocene The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chatti ...

geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

in southern

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

. The base of the formation at the contact with the K'ayra Formation is dated using

fission track Ion tracks are damage-trails created by swift heavy ions penetrating through solids, which may be sufficiently-contiguous for chemical etching in a variety of crystalline, glassy, and/or polymeric solids. They are associated with cylindrical da ...

analysis at 43 Ma and the top, the contact with the Punacancha Formation, at 30 Ma.Carlotto, 2016, p.522 In other places the Tinajani Formation overlies the Soncco Formation.La Torre et al., 2004, p.116 The formation has a thickness of .Cusco.gob, 2015, p.120

Misattributed ornithopod tracks

The formation was first dated to the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

, and fossil

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous wo ...

tracks had been reported.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607. Over 9,000 fossil tracks are said to be found within this formation. As the formation has been dated to the

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

, the tracks could not be attributed to dinosaurs.

References

Bibliography

* * * * {{ISBN, 0-520-24209-2 Geologic formations of Peru Paleogene Peru Eocene Series of South America Oligocene Series of South America Tinguirirican Divisaderan Mustersan Rupelian Stage Priabonian Stage Conglomerate formations Coal formations Limestone formations Sandstone formations Lacustrine deposits Fossiliferous stratigraphic units of South America Paleontology in Peru Geography of Cusco Region Geography of Puno Region