4 Recent Advances in Soil and Paleosol Science
This session highlights recent research in soil and paleosol science. We invite submissions from field, laboratory, and modeling studies that leverage or examine pedogenic processes and archives from deep-time through modern systems.
Sunday, 19 October 2025
8:00 AM - 12:00 PM
HBGCC, 212AB
Paleosol carbonates suggest jet-induced Pliocene rainfall seasonality mediated east Asian C4 expansion
Paper number: 4-8
Program: Technical Sessions
Time: 9:40 AM – 10:00 AM
Authors
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Jiawei DaThe University of Texas at Austin, Austin, TX
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Chijun SunUniversity of California, Davis, Woodland, CA
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Zachary SharpUniversity of New Mexico, Albuquerque, NM
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Junfeng JiNanjing University, Nanjing
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Lily SerachThe University of Texas at Austin, Austin, Texas
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Timothy GallagherKent State, Kent, OH
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Huayu LuNanjing University, Nanjing
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Katharine HuntingtonU Washington, Seattle, WA
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Ran FengThe University of Connecticut, Glastonbury, CT
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Hanzhi ZhangNanjing University, Nanjing
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Hanli WangNanjing University, Nanjing
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Shunchuan JiYunnan Normal University, Kunming
Abstract
C4 grassland expansion during the Neogene transformed terrestrial ecosystems. Occurring first in Africa and then on the Indian subcontinent during the Miocene, C4 vegetation subsequently expanded during the Plio-Pleistocene to higher latitudes. We present paleosol carbonate clumped and triple oxygen isotope evidence suggesting rainfall seasonality controlled extratropical, Plio-Pleistocene C4 distributions in East Asia. Reconstructed soil water d18O values vary sinusoidally with an amplitude of up to 3‰ and a frequency aligning with the 1.2-Myr obliquity amplitude modulation cycle. The highest soil water d18O values occur during the warmest climates, and although D’17O-constrained changes in evaporation intensity account for some of the variability, the observations cannot be explained without higher rainfall d18O values during warmer climates. These results indicate that the Chinese Loess Plateau (CLP) received more spring rain during warmer Pliocene intervals when the subtropical westerly jet was positioned further poleward, and more summer rain during cooler climates when the jet was further south. This variability was driven by obliquity and global climate-controlled meridional shifts in the position of the summer rain band, dynamically similar to the annual Meiyu front migration but operating on longer timescales. A similar spatiotemporal pattern in organic carbon d13C records indicates that the most C4-rich ecosystems followed the summer rain band as it oscillated north-south across East Asia. The C4-rich ecosystems eventually migrated across the southern margin of the CLP during early Pleistocene cooling, probably due to the same westerly jet – summer rain band mechanism. Our model refines the East Asian paleomonsoon concept and explains the enigmatic equatorward migration of extratropical C4 ecosystems during cooling, which is inconsistent with a direct atmospheric CO2 control.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-414780
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