• DOI:10.1130/B30915.1
• Corpus ID: 129962470

New Age Constraints for the Salamanca Formation and Lower Río Chico Group in the Western San Jorge Basin, Patagonia, Argentina: Implications for Cretaceous-Paleogene Extinction Recovery and Land Mammal Age Correlations

@article{Clyde2014NewAC,
  title={New Age Constraints for the Salamanca Formation and Lower R{\'i}o Chico Group in the Western San Jorge Basin, Patagonia, Argentina: Implications for Cretaceous-Paleogene Extinction Recovery and Land Mammal Age Correlations},
  author={William C. Clyde and Peter Wilf and Ari Iglesias and Rudy Slingerland and Timothy J Barnum and Peter K. Bijl and Timothy J. Bralower and Henk Brinkhuis and Emily E. Comer and Brian T. Huber and Mauricio Ib{\'a}{\~n}ez-Mejia and Brian R. Jicha and J. Marcelo Krause and Jonathan Douglas Schueth and Brad S. Singer and Mar{\'i}a Sol Raigemborn and Mark D. Schmitz and Appy Sluijs and Maria C. Zamaloa},
  journal={Geological Society of America Bulletin},
  year={2014},
  volume={126},
  pages={289-306}
}

• W. Clyde, P. Wilf, +16 authors Maria C. Zamaloa
• Published 1 March 2014
• Environmental Science, Geography
• Geological Society of America Bulletin

The Salamanca Formation of the San Jorge Basin (Patagonia, Argentina) preserves critical records of Southern Hemisphere Paleocene 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 Rio Chico Group in the western part of the basin. New constraints include (1) an 40Ar/39Ar age determination of 67.31 ± 0.55 Ma from a basalt flow 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 resolution-multi collector-inductively coupled plasma-mass 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 Penas Coloradas Formation (Rio Chico Group), and (4) paleomagnetic results indicating that the Salamanca Formation in this area is entirely of normal polarity, with reversals occurring in the Rio 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 paleobotanical assemblages from this area are here assigned to C28n (64.67–63.49 Ma), ∼2–3 million years older than previously thought, adding to growing evidence for rapid Southern Hemisphere floral recovery after the Cretaceous-Paleogene extinction. Important Peligran and “Carodnia” zone vertebrate fossil assemblages from coastal BNI and Penas Coloradas exposures are likely older than previously thought and correlate to the early Torrejonian and early Tiffanian North American Land Mammal Ages, respectively.