Tres Cruces Formation

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Tres Cruces Formation
Stratigraphic range: Sinemurian-Pliensbachian,
~199–184  Ma
Type Geological formation
Underlies Algarrobal Formation
Overlies Tonalite basement
Thickness~390 m (1,280 ft)
Lithology
Primary Sandstone, conglomerate, limestone
Other Mudstone
Location
Region Coquimbo Region
Country Chile
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]

Contents

Paleobiota of the Tres Cruces Formation

Ammonites

GenusSpeciesMaterialLocalityUnitNotesImages
Acanthopleuroceras IndeterminateNot specified. [1] Quebrada DoloresA polymorphitid ammonite.
Amaltheus IndeterminateNot specified. [1] Quebrada DoloresA amaltheid ammonite.
Arieticeras ?IndeterminateNot specified. [1] Quebrada Tres CrucesA hildoceratid ammonite.
Radstockiceras ?IndeterminateNot specified. [1] Quebrada DoloresA oxynoticeratid ammonite.

Bivalves

GenusSpeciesMaterialLocalityUnitNotesImages
Cardinia IndeterminateNot specified. [1] Quebrada Tres CrucesA cardiniid bivalve.
Exogyra IndeterminateNot specified. [1] Quebrada Tres CrucesA gryphaeid bivalve.
Gryphaea IndeterminateNot specified. [1] Quebrada DoloresA gryphaeid bivalve.
Ostrea IndeterminateNot specified. [1] Quebrada Tres CrucesA ostreid bivalve.
Panopea IndeterminateNot specified. [1] Quebrada Tres CrucesA hiatellid bivalve.
Pholadomya IndeterminateNot specified. [1] Quebrada Tres CrucesA pholadomyid bivalve.
Weyla W. alataNot specified. [1] [2] Quebrada Tres Cruces, Quebrada Dolores, Quebrada MatahuaicoA pectinid bivalve.

Brachiopods

GenusSpeciesMaterialLocalityUnitNotesImages
Spiriferina S. rostrataNot specified. [1] Quebrada Tres Cruces, Quebrada DoloresA spiriferinid brachiopod.
Terebratula IndeterminateNot specified. [1] Quebrada DoloresA terebratulid brachiopod.
Zeilleria IndeterminateNot specified. [1] Quebrada Tres CrucesA zeilleriid brachiopod.

Gastropods

GenusSpeciesMaterialLocalityUnitNotesImages
Lithotrochus L. humboldtiiNot specified. [1] [2] Quebrada Tres Cruces, Quebrada DoloresA trochid gastropod.
Nerinea IndeterminateNot specified. [1] Quebrada Tres CrucesA nerineid gastropod.
Pleurotomaria IndeterminateNot specified. [1] Quebrada Tres CrucesA pleurotomariid gastropod.

Ichthyosaurs

GenusSpeciesMaterialLocalityUnitNotesImages
Ichthyosauria indet.IndeterminateTwelve vertebrae centra. [2] Quebrada Tres CrucesAn ichthyosaur.

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Dediós, P. A. (1967). "Cuadrángulo Vicuña, Provincia de Coquimbo, Escala 1:50000". Carta Geológica de Chile (16): 1−74.
  2. 1 2 3 4 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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