Tres Cruces Formation

Tres Cruces Formation
Stratigraphic range: Sinemurian-Pliensbachian,
~
TypeGeological formation
UnderliesAlgarrobal Formation
OverliesTonalite basement
Thickness~390 m (1,280 ft)
Lithology
PrimarySandstone, conglomerate, limestone
OtherMudstone
Location
RegionCoquimbo Region
CountryChile
Type section
Named forQuebrada Tres Cruces
Named byDediós, 1967

The Tres Cruces Formation is sedimentary and fossiliferous geological formation that crops out across Paihuano in the Coquimbo Region of Chile. It is dated back to the Early Jurassic period (Sinemurian through Pliensbachian stages). The lithology of the formation comprises clastic rocks, such as sandstone, conglomerate, and fossil-rich limestone, formed in marine settings. As such, the Tres Cruces Formation preserves a marine fossil record represented by brachiopods, molluscs (ammonites, bivalves, gastropods), and marine reptiles (ichthyosaurs).[1][2] The formation is named after Quebrada Tres Cruces, whhich is an important fossiliferous locality.[1]

Paleobiota of the Tres Cruces Formation

Ammonites

Genus Species Material Locality Unit Notes Images
Acanthopleuroceras Indeterminate Not specified.[1] Quebrada Dolores A polymorphitid ammonite.
Amaltheus Indeterminate Not specified.[1] Quebrada Dolores A amaltheid ammonite.
Arieticeras? Indeterminate Not specified.[1] Quebrada Tres Cruces A hildoceratid ammonite.
Radstockiceras? Indeterminate Not specified.[1] Quebrada Dolores A oxynoticeratid ammonite.

Bivalves

Genus Species Material Locality Unit Notes Images
Cardinia Indeterminate Not specified.[1] Quebrada Tres Cruces A cardiniid bivalve.
Exogyra Indeterminate Not specified.[1] Quebrada Tres Cruces A gryphaeid bivalve.
Gryphaea Indeterminate Not specified.[1] Quebrada Dolores A gryphaeid bivalve.
Ostrea Indeterminate Not specified.[1] Quebrada Tres Cruces A ostreid bivalve.
Panopea Indeterminate Not specified.[1] Quebrada Tres Cruces A hiatellid bivalve.
Pholadomya Indeterminate Not specified.[1] Quebrada Tres Cruces A pholadomyid bivalve.
Weyla W. alata Not specified.[1][2] Quebrada Tres Cruces, Quebrada Dolores, Quebrada Matahuaico A pectinid bivalve.

Brachiopods

Genus Species Material Locality Unit Notes Images
Spiriferina S. rostrata Not specified.[1] Quebrada Tres Cruces, Quebrada Dolores A spiriferinid brachiopod.
Terebratula Indeterminate Not specified.[1] Quebrada Dolores A terebratulid brachiopod.
Zeilleria Indeterminate Not specified.[1] Quebrada Tres Cruces A zeilleriid brachiopod.

Gastropods

Genus Species Material Locality Unit Notes Images
Lithotrochus L. humboldtii Not specified.[1][2] Quebrada Tres Cruces, Quebrada Dolores A trochid gastropod.
Nerinea Indeterminate Not specified.[1] Quebrada Tres Cruces A nerineid gastropod.
Pleurotomaria Indeterminate Not specified.[1] Quebrada Tres Cruces A pleurotomariid gastropod.

Ichthyosaurs

Genus Species Material Locality Unit Notes Images
Ichthyosauria indet. Indeterminate Twelve vertebrae centra.[2] Quebrada Tres Cruces An ichthyosaur.

See also

References

  1. ^ a b c d e f g h i j k l m n o p q r s Dediós, P. A. (1967). "Cuadrángulo Vicuña, Provincia de Coquimbo, Escala 1:50000". Carta Geológica de Chile (16): 1−74.
  2. ^ a b c d Suárez, M. E.; Otero, R. A. (2010). "Dos nuevas localidades con presencia de ictiosaurios (Reptilia; Ichthyosauria) en el Jurásico Inferior del norte de Chile". II Simposio Paleontología en Chile: 53.
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