Small mammal carbon isotope ecology across the Miocene-Pliocene boundary, northwestern Argentina

Scott A. Hynek, Benjamin H. Passey, José Luis Prado, Francis H. Brown, Thure E. Cerling, Jay Quade

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

The late Miocene expansion of plants using the C 4 photosynthetic pathway in South America has been documented by tooth enamel carbon isotope ratios (δ 13C en). However, a more detailed understanding of this ecological event is hampered by poor chronological control on the widespread fossil localities from which isotopic data are derived. This study develops a δ 13C en record from a single 2500m-thick stratigraphic section in subtropical South America. Strata at Puerta de Corral Quemado (PCQ), northwestern Argentina, span 9 to 3.5Ma in age, and existing paleosol carbonate data (δ 13C pc) document C 4 expansion across the Miocene-Pliocene boundary. Comparison of δ 13C en data with δ 13C pc data at high stratigraphic resolution refines understanding of this ecological event in South America. Small mammal δ 13C en data in particular are complementary to that of large mammal and paleosol δ 13C data. Small mammal teeth integrate isotopic data over much shorter temporal and spatial scales than large mammal teeth, providing a sensitive measure of local vegetation and placing constraints on the landscape distribution of C 3 and C 4 plants. Explicit consideration of the distinctive carbon isotope enrichment factor between enamel and diet for rodents (ε*en-diet=11‰, as opposed to 14‰ for large mammals) allows for unequivocal inference of C 4 vegetation ~1Ma prior to that inferred from large mammal δ 13C en data, and ~2Ma prior to δ 13C pc data. This multiproxy record demonstrates that C 4 plants were a stable component of the ecosystem hundreds of thousands of years prior to their major ecological expansion, and that the expansion of C 4 plants was pulsed at PCQ. Two periods of ecological change are demonstrated by δ 13C and δ 18O data at ~7Ma and 5.3Ma (coincident with the Miocene-Pliocene boundary). Development of small mammal δ 13C en records on other continents may provide similar insight into the early stages of the global C 4 event.

Original languageEnglish (US)
Pages (from-to)177-188
Number of pages12
JournalEarth and Planetary Science Letters
Volume321-322
DOIs
StatePublished - Mar 1 2012

Keywords

  • C4 plants
  • Carbon isotopes
  • Laser ablation
  • Notoungulate
  • Rodent
  • Tooth enamel

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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