Soncco Formation

The Soncco Formation is a Late Eocene to Early Oligocene geologic formation in southern Peru. The base of the formation at the contact with the K'ayra Formation is dated using fission track analysis at 43 Ma and the top, the contact with the Punacancha Formation, at 30 Ma.^[1] In other places the Tinajani Formation overlies the Soncco Formation.^[2] The formation has a thickness of 1,600 metres (5,200 ft).^[3]

Soncco Formation
Stratigraphic range: Late Eocene-Early Oligocene 43–30 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	San Jerónimo Group
Sub-units	C, D & E Members
Underlies	Punacancha Fm., Tinajani Fm.
Overlies	K'ayra Formation
Thickness	1,600 m (5,200 ft)
Lithology
Primary	Conglomerate, sandstone
Other	Coal, lacustrine limestone
Location
Coordinates	13°20′12″S 71°44′28″W
Region	Puno & Cusco Regions
Country	Peru
Type section
Named for	Soncco
Paleogeography of Northern South America, 35 Ma by Ron Blakey

Type locality of the Soncco Formation in Peru

Misattributed ornithopod tracks

The formation was first dated to the Cretaceous, and fossil ornithopod tracks had been reported.^[4] Over 9,000 fossil tracks are said to be found within this formation.^{[citation needed]} As the formation has been dated to the Paleogene, the tracks could not be attributed to dinosaurs.^[1]