New age constraints for the Salamanca Formation and lower Rio Chico Group in the western San Jorge Basin, Patagonia, Argentina: Implications for Cretaceous-Paleogene extinction recovery and land mammal age correlations
Year: 2014
Type: article
Abstract: The Salamanca Formation of the San Jorge Basin (Patagonia, Argentina) preserves critical records of Southern Hemisphere Paleo cene biotas, but its age remains poorly resolved, with estimates ranging from Late Cretaceous to middle Paleocene.We report a multi-disciplinary geochronologic study of the Salamanca Formation and overlying Río Chico Group in the western part of the basin .New constraints include (1) an 40 Ar/ 39 Ar age determination of 67.31 ± 0.55 Ma from a basalt fl ow underlying the Salamanca Formation, (2) micropaleontological results indicating an early Danian age for the base of the Salamanca Formation, (3) laser ablation HR-MC-ICP-MS (high resolutionmulti collector-inductively coupled plasmamass spectrometry) U-Pb ages and a high-resolution TIMS (thermal ionization mass spectrometry) age of 61.984 ± 0.041(0.074)[0.100] Ma for zircons from volcanic ash beds in the Peñas Coloradas Formation (Río Chico Group), and (4) paleomagnetic results indicating that the Salamanca Formation in this area is entirely of normal polarity, with reversals occurring in the Río Chico Group.Placing these new age constraints in the context of a sequence stratigraphic model for the basin, we correlate the Salamanca Formation in the study area to Chrons C29n and C28n, with the Banco Negro Inferior (BNI), a mature widespread fossiliferous paleosol unit at the top of the Salamanca Formation, corresponding to the top of Chron C28n.The diverse paleo botanical assemblages from this area are here assigned to C28n (64.67-63.49Ma), ~2-3 million years older than previously thought, adding to growing evidence for rapid Southern Hemisphere fl oral recovery after the Cretaceous-Paleogene extinction.Important Peligran and "Carodnia" zone vertebrate fossil assemblages from coastal BNI and Peñas Coloradas exposures are likely older than previously thought and correlate to the early Torrejonian and early Tiffanian North American Land Mammal Ages, respectively.
DOI: 10.1130/b30915.1
Institutions: University of New Hampshire, Pennsylvania State University, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Comahue, Utrecht University, Smithsonian Institution, National Museum of Natural History, University of Arizona, University of Wisconsin–Madison, Museum of Paleontology Egidio Feruglio, Universidad Nacional de La Plata, Boise State University, Universidad de Buenos Aires
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
Awards: G4691379826, Facility Support: Multi-User Facility Support for U-Th-Pb Geochronology at the Arizona LaserChron Center, Facility Support: Multi-User Facility for U-Th-Pb Geochronology Utilizing a Laser-Ablation Multicollector ICPMS, Collaborative Research: Ancient Biodiversity Hotspot in Southern South America: Evolution of Speciose Floras in Patagonia from latest Cretaceous to middle Eocene
OpenAlex ID: W2139693275