Una edad eocena tardía propuesta para la Formación Loreto (península de Brunswick, extremo sur de Chile), basada en peces cartilaginosos fósiles, paleobotánica y evidencia radiógena

Translated title of the contribution: A Late Eocene age proposal for the Loreto Formation (Brunswick Peninsula, southernmost Chile), based on fossil cartilaginous fishes, paleobotany and radiometric evidence

Rodrigo A. Otero, Teresa Torres, Jacobus P. le Roux, Francisco Hervé, C. Mark Fanning, Roberto E. Yury-Yáñez, David Rubilar-Rogers

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)

Abstract

We present new data on the paleoichthyology, paleobotany and radiometric results of the Loreto Formation in the Brunswick Peninsula of southernmost Chile, that allow us to propose a Late Eocene age. The rich diversity of fossil cartilaginous fishes (Chondrichthyes, Elasmobranchii) recognized in upper levels of this unit includes the taxa Carcharias aff. 'hopei' (Agassiz), Odontaspis sp., Carcharoides catticus (Philippi), Striatolamia macrota (Agassiz), Anomotodon sp., Macrorhizodus praecursor (Leriche), Galeorhinus sp., Abdounia sp., Hexanchus sp., Squatina sp., Hexanchidae indet., Myliobatis sp., Myliobatoidea indet., and Ischyodus dolloi Leriche. This assemblage has clear ecological affinities with Eocene Tethyan fauna previously described in the Northern Hemisphere, and also has common elements with Eocene cartilaginous fishes from Antarctica. Additionally, a paleobotanic study of this unit identified leaf imprints of Asplenium sp., Pteris sp., Podocarpus sp., and abundant angiosperms including Nothofagus lanceolata Dusén, N. simplicidens Dusén, N. variabilis Dusén, N. cf. alessandri Espinosa, N. subferruginea (Dusén), Hydrangea sp. and Phyllites spp. Wood remains of Nothofagoxylon scalariforme Gothan and Araucariaceae cf. Araucarioxylon Kraus were also identified. Additionally, pollen grains indicate gymnosperms and angiosperms: Podocarpidites otagoensis Couper, Retitricolpites sp., Tricolpites sp., Liliacidites sp., Polyporina sp., Nothofagidites cincta Cookson, and Nothofagidites cranwellae Couper, having affinities with Eocene florae, and being consistent with the age of the fossil fishes. Finally, a SHRIMP U-Th-Pb analysis of two samples collected from the studied beds provided thirty-eight and sixty zircon grains, indicating a clear main peak at 36.48±0.47 Ma (MSWD=1.5) and 36,73±0.50 Ma (MSWD=0.65). The integrated results indicate that the upper part of the Loreto Formation has a minimum Priabonian age, supporting previous reassignations of this part of the formation into the Late Eocene, and differing from the Oligocene age proposed in its original definition.

Translated title of the contributionA Late Eocene age proposal for the Loreto Formation (Brunswick Peninsula, southernmost Chile), based on fossil cartilaginous fishes, paleobotany and radiometric evidence
Original languageSpanish
Pages (from-to)180-200
Number of pages21
JournalAndean Geology
Volume39
Issue number1
DOIs
Publication statusPublished - Jan 2012

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology
  • Stratigraphy
  • Palaeontology

Fingerprint

Dive into the research topics of 'A Late Eocene age proposal for the Loreto Formation (Brunswick Peninsula, southernmost Chile), based on fossil cartilaginous fishes, paleobotany and radiometric evidence'. Together they form a unique fingerprint.

Cite this