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Aridity-driven decoupling of δ¹³C between pedogenic carbonate and soil organic matter

Da, Jiawei and Zhang, Yi Ge and Li, Gen and Ji, Junfeng (2020) Aridity-driven decoupling of δ¹³C between pedogenic carbonate and soil organic matter. Geology, 48 (10). pp. 981-985. ISSN 0091-7613. doi:10.1130/g47241.1.

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Pedogenic carbonate is an invaluable archive for reconstructing continental paleoclimate and paleoecology. The δ¹³C of pedogenic carbonate (δ¹³C_c) has been widely used to document the rise and expansion of C₄ plants over the Cenozoic. This application requires a fundamental presumption that in soil pores, soil-respired CO₂ dominates over atmospheric CO₂ during the formation of pedogenic carbonates. However, the decoupling between δ¹³C_c and δ¹³C of soil organic matter (δ¹³C_(SOM)) have been observed, particularly in arid regions, suggesting that this presumption is not always valid. To evaluate the influence of atmospheric CO₂ on soil δ¹³C_c, here we performed systematic δ¹³C analyses of paleosols across the Chinese Loess Plateau, with the sample ages spanning three intervals: the Holocene, the Late Pleistocene, and the mid-Pliocene warm period. Our paired δ¹³C_c and δ¹³C_(SOM) data reveal broadly divergent trending patterns. Using a two-component CO₂-mixing model, we show substantial incorporations of atmospheric CO₂ (up to 60%) into soil pore space during carbonate precipitation. This result readily explains the enrichment of δ¹³C_c and its divergence from δ¹³C_(SOM). As a consequence, δ¹³C of pedogenic carbonates formed under semiarid and/or arid conditions are largely driven by regional aridity through its control on soil CO₂ composition, and thus cannot be used to evaluate the relative abundance of C₃ versus C₄ plants. Nonetheless, these carbonates can be applied for atmospheric CO₂ reconstructions, even for periods with low CO₂ levels.

Item Type:Article
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URLURL TypeDescription
Da, Jiawei0000-0002-4483-4651
Zhang, Yi Ge0000-0001-7331-1246
Li, Gen0000-0002-6300-3570
Additional Information:© 2020 Geological Society of America. Manuscript received 22 November 2019; Revised manuscript received 11 May 2020; Manuscript accepted 14 May 2020. This work was supported by the National Science Foundation of China (grants 41773118 and 41991321 to J.Ji). We thank Enlou Zhang from the Nanjing Institute of Geography and Limnology, Chinese Academy of Science, for his laboratory assistance. Greg Retallack and two anonymous reviewers are acknowledged for their constructive and thoughtful reviews, which helped improve this paper.
Funding AgencyGrant Number
National Natural Science Foundation of China41773118
National Natural Science Foundation of China41991321
Issue or Number:10
Record Number:CaltechAUTHORS:20200616-071746451
Persistent URL:
Official Citation:Jiawei Da, Yi Ge Zhang, Gen Li, Junfeng Ji; Aridity-driven decoupling of δ13C between pedogenic carbonate and soil organic matter. Geology ; 48 (10): 981–985. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103936
Deposited By: Tony Diaz
Deposited On:22 Jun 2020 17:37
Last Modified:16 Nov 2021 18:26

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