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

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• 作者：Scott A. Hynek^a ; ^{scott.hynek@utah.com} ; Benjamin H. Passey^a ; ¹ ; José ; Luis Prado^b ; Francis H. Brown^a ; Thure E. Cerling^a ; Jay Quade^c
• 关键词：C4 plants ; tooth enamel ; carbon isotopes ; laser ablation ; rodent ; notoungulate
• 刊名：Earth and Planetary Science Letters
• 出版年：2012
• 期刊代码：18_0012821x
• 类别：ph
• 出版时间：1 March, 2012
• 卷：321-322
• 期：Complete
• 页码：177-188
• 文件大小：1994 K

摘要

The late Miocene expansion of plants using the C₄ photosynthetic pathway in South America has been documented by tooth enamel carbon isotope ratios (未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 未¹³C_en record from a single 2500 m-thick stratigraphic section in subtropical South America. Strata at Puerta de Corral Quemado (PCQ), northwestern Argentina, span 9 to 3.5 Ma in age, and existing paleosol carbonate data (未¹³C_pc) document C₄ expansion across the Miocene-Pliocene boundary. Comparison of 未¹³C_en data with 未¹³C_pc data at high stratigraphic resolution refines understanding of this ecological event in South America. Small mammal 未¹³C_en data in particular are complementary to that of large mammal and paleosol 未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 C₃ and C₄ plants. Explicit consideration of the distinctive carbon isotope enrichment factor between enamel and diet for rodents (蔚*en-diet = 11鈥? as opposed to 14鈥?for large mammals) allows for unequivocal inference of C₄ vegetation ~ 1 Ma prior to that inferred from large mammal 未¹³C_en data, and ~ 2 Ma prior to 未¹³C_pc data. This multiproxy record demonstrates that C₄ plants were a stable component of the ecosystem hundreds of thousands of years prior to their major ecological expansion, and that the expansion of C₄ plants was pulsed at PCQ. Two periods of ecological change are demonstrated by 未¹³C and 未¹⁸O data at ~ 7 Ma and 5.3 Ma (coincident with the Miocene-Pliocene boundary). Development of small mammal 未¹³C_en records on other continents may provide similar insight into the early stages of the global C₄ event.