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New age constraints for early Paleogene strata of central Patagonia, Argentina; implications for the timing of South American land mammal ages

J. Marcelo Krause, William C. Clyde, Mauricio Ibanez-Mejia, Mark D. Schmitz, Timothy Barnum, Eduardo S. Bellosi and Peter Wilf
New age constraints for early Paleogene strata of central Patagonia, Argentina; implications for the timing of South American land mammal ages
Geological Society of America Bulletin (March 2017) 129 (7-8): 886-903

Abstract

The Rio Chico Group in the San Jorge Basin of central Patagonia (Argentina) preserves some of South America's most significant Paleogene records of biotic and climatic change. Three of its constituent formations, the Penas Coloradas, Las Flores, and Koluel-Kaike, host vertebrate faunas referred to the "Carodnia faunal zone," the Itaboraian South American Land Mammal Age (SALMA), and the Riochican SALMA. However, the precise absolute ages of these units, and thus their associated faunas and paleoclimate records, are poorly resolved. Herein, we report new paleomagnetic and geochronologic results from these formations in south-central Chubut Province, Argentina. U-Pb dating of four volcanic ashes, using both laser ablation-multicollector-inductively coupled plasma-mass spectrometry and high-resolution chemical abrasion-isotope dilution-thermal ionization mass spectrometry, indicates ages of igneous crystallization of 51.403 + or - 0.037 (0.045) [0.071] Ma for a level within the middle Las Flores Formation and 46.714 + or - 0.012 (0.026) [0.057] Ma, 44.579 + or - 0.013 (0.026) [0.054] Ma, and 42.856 + or - 0.017 (0.027) [0.054] Ma for levels in the lower, middle, and upper Koluel-Kaike Formation, respectively. Combining these with previous isotopic ages in our new magnetostratigraphic framework, we correlate the Penas Coloradas Formation to chrons C27n-26r (ca. 62.5 to ca. 61.6 Ma; late Danian) and the section from the middle Las Flores to the uppermost Koluel-Kaike to chrons C23n to C19r (ca. 51.4-42.2 Ma; mid Ypresian-late Lutetian). We combine these data with other recently published chronostratigraphic results from Paleogene units in Patagonia to better constrain the ages of noteworthy Paleogene plant and mammal fossil sites in Patagonia and to develop a revised temporal calibration of the Las Flores, Vacan, and "Sapoan" faunas.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 129
Serial Issue: 7-8
Title: New age constraints for early Paleogene strata of central Patagonia, Argentina; implications for the timing of South American land mammal ages
Affiliation: Consejo Nacional de Investigaciones Cientificas y Tecnicas, Museo Paleontologico Egidio Feruglio, Trelew, Argentina
Pages: 886-903
Published: 20170316
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 103
Accession Number: 2017-026020
Categories: StratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017078
Illustration Description: illus. incl. 1 table, sketch map
S46°00'00" - S44°00'00", W70°00'00" - W68°00'00"
Secondary Affiliation: University of New Hampshire, USA, United StatesMassachusetts Institute of Technology, USA, United StatesBoise State University, USA, United StatesMuseo Argentino de Ciencias Naturales, ARG, ArgentinaPennsylvania State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201716
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