Lautaro Formation

The Lautaro Formation is sedimentary and fossiliferous geological formation that largely crops out near Copiapó (Atacama Region), Chile. It is dated back to the Jurassic period (Toarcian through Aalenian stages). The lithology of the formation comprises limestone and sandstone, formed in marine settings. The Lautaro Formation preserves a marine fossil record, representing molluscs (bivalves, gastropods) and marine reptiles (metriorhynchids, plesiosaurs).^[1][2][3]

Lautaro Formation
Stratigraphic range: Toarcian–Aalenian, ~184–170 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Strata of the Lautaro Formation outcropping at La Puerta locality
Type	Geological formation
Underlies	Quebrada Monardes Formation
Overlies	La Ternera Formation
Thickness	~2,600 m (8,500 ft)
Lithology
Primary	Limestone
Other	Sandstone
Location
Region	Atacama Region
Country	Chile
Extent	Lautaro Basin
Type section
Named for	Lautaro

The strata of the Lautaro Formation and its basin of deposition (the Lautaro Basin) have been subject to intense tectonic movement during the Mesozoic, producing large-scale stratigraphic discontinuity and tectonic inversion.^{[2][4][5][6][7]}

Strata of the Lautaro Formation exposed at the Tranque Lautaro

Fossils of Gryphaea and Lithotrochus at La Puerta

Fossils of Gryphaea at La Puerta

Paleobiota of the Lautaro Formation

Ammonites

Genus	Species	Material	Locality	Unit	Notes	Images
Arieticeras	Indeterminate	Not specified.[8]	Tranque Lautaro		A hildoceratid ammonite.
Oxynoticeras	O. oxynotum	Not specified.[8]	Tranque Lautaro		An oxynoticeratid ammonite.

Bivalves

Genus	Species	Material	Locality	Unit	Notes	Images
Gryphaea	G. darwini	Partial and complete shells.[2]	La Puerta, Tranque Lautaro		A gryphaeid bivalve.
Weyla	W. alata	Partial and complete shells.[8][2]	La Puerta, Tranque Lautaro		A pectinid bivalve.

Brachiopods

Genus	Species	Material	Locality	Unit	Notes	Images
Rhynchonella	R. variabilis	Not specified.[8]	Tranque Lautaro		A rhynchonellid brachiopod.

Crocodyliformes

Genus	Species	Material	Locality	Unit	Notes	Images
Metriorhynchus	Indeterminate	Partial skull.[1]	Quebrada La Iglesia	Upper part	A metriorhynchid.

Gastropods

Genus	Species	Material	Locality	Unit	Notes	Images
Lithotrochus	L. humboldtii	Partial and complete shells.[2]	La Puerta, Tranque Lautaro		A trochid gastropod.

Plesiosaurs

Genus	Species	Material	Locality	Unit	Notes	Images
Plesiosauria indet.	Indeterminate	Three vertebrae.[3]	Quebrada La Iglesia	Upper part	A plesiosaur.

See also

• Pan de Azúcar Formation