Los Colorados Formation

For other uses, see Colorado Formation.
Los Colorados Formation
Stratigraphic range: Norian
~
Los Colorados massif, La Rioja Province, Argentina
Type Geological formation
Unit of Agua de la Peña Group
Underlies Cerro Rajado Formation
Overlies Ischigualasto Formation
Thickness 600 m (2,000 ft)
Lithology
Primary Sandstone, siltstone, mudstone
Other Conglomerate, gypsum
Location
Coordinates 29.8°S 67.9°W / -29.8; -67.9
Approximate paleocoordinates 38.9°S 31.4°W / -38.9; -31.4
Region San Juan Province
La Rioja Province
Country Argentina
Extent Ischigualasto-Villa Unión Basin
Type section
Named for Los Colorados Massif
Los Colorados Formation is located in Argentina
Los Colorados Formation
Los Colorados Formation (Argentina)

The Los Colorados Formation is a sedimentary rock formation of the Ischigualasto-Villa Unión Basin, found in the provinces of San Juan and La Rioja in Argentina. The formation dates back to the Norian age of the Late Triassic.

The up to 600 metres (2,000 ft) thick formation comprises sandstones, siltstones, mudstones and conglomerates with gypsum layers deposited in a fluvial to lacustrine environment. The formation is the uppermost stratigraphic unit of the Agua de la Peña Group, overlying the Lagerstätte of the Ischigualasto Formation. Los Colorados Formation is partly covered by the Cretaceous Cerro Rajado Formation, separated by an unconformity.

The formation is known for its fossils of early dinosaurs, including the coelophysoid Zupaysaurus and the "prosauropods" Coloradisaurus, Lessemsaurus, and Riojasaurus. Magnetostratigraphic analysis suggests that the Los Colorados Formation was deposited between 227 and 213 million years ago.

Description

Extent of the formation in the Ischigualasto-Villa Unión Basin

Los Colorados Formation is a unit with an approximate thickness of 600 metres (2,000 ft) of the Agua de la Peña Group in the Ischigualasto-Villa Unión Basin, where it is exposed in the Ischigualasto Provincial Park, a World Heritage Site in Argentina. The formation gradually overlies the Ischigualasto Formation and is unconformably overlain by the Cretaceous Cerro Rajado Formation. The formation comprises red-colored, fine- to medium-grain–size sandstones together with siltstones and ancillary floodplain mudstones with early calcisol development. The formation was deposited in a fluvial to lacustrine environment.

Fossil content

Anapsids

Anapsids of Los Colorados Formation
Genus Species Location Material Notes Images

Palaeochersis

P. talampayensis

Synapsids

Synapsids of Los Colorados Formation
Genus Species Location Material Notes Images
Chaliminia C. musteloides
Jachaleria J. colorata
Tessellatia T. bonapartei

Archosauromorphs

Archosauromorphs of Los Colorados Formation
Taxa Location Notes Images

Genus:

  1. F. tenax
 La Rioja Province

Genus:

  1. N. engaeus
 Quebrada de los Jachaleros, El Salto (San Juan)

Genus:

  1. R. tenuisceps

Crocodylomorpha

Crocodylomorphs of Los Colorados Formation
Taxa Location Notes Images

Genus:

  1. C. abelini
 La Rioja Province

Genus:

  1. H. leali
 Quebrada de los Jachaleros, El Salto (San Juan)

Genus:

  1. P. jachaleri
 Quebrada de los Jachaleros, El Salto (San Juan)

Dinosaurs

Indeterminate theropod remains present in the Provincia de la Rioja.

Dinosaurs of Los Colorados Formation
Taxa Location Notes Images

Genus:

  1. C. brevis
 La Rioja Province "Skull, adult"

Genus:

  1. L. sauropoides
 La Rioja Province "Partial cervical, dorsal, and sacral vertebrae, adult."

Infraorder:

  1. Indeterminate remains
 La Rioja & San Juan Provinces Includes Strenusaurus procerus. "Dorsals, caudals, partial fore- and hindlimb."

Genus:

  1. P. podocitus
 Ischigualasto-Villa Unión Basin Known from previously undescribed partial hindlimbs

Genus:

  1. R. incertus
 La Rioja Province

Genus:

  1. Z. rougieri
 La Rioja Province

Ichnofossils

See also