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Late Oligocene Precipitation Seasonality in East Asia Based on δ13C Profiles in Fossil Wood
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  • Jamie R. Vornlocher,
  • William E. Lukens,
  • Brian A Schubert,
  • Cheng Quan
Jamie R. Vornlocher
University of Louisiana at Lafayette
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William E. Lukens
James Madison University

Corresponding Author:[email protected]

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Brian A Schubert
University of Louisiana at Lafayette
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Cheng Quan
Chang'an University
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The wet summers and dry winters of monsoon systems in East Asia are a first-order control on food and water security for a significant portion of the global population today. The onset, characteristics, and drivers of paleo-monsoonal conditions in East Asia, however, are debated. Records from the Eocene suggest pronounced rainfall seasonality consistent with monsoon rainfall across China, likely driven by migrations of the Inter-Tropical Convergence Zone. Model simulations indicate that modern-like monsoon circulation of China was established by the early Miocene at the latest, but uncertainty remains due to a paucity of proxy records from the Oligocene. Here we provide the first annually resolved, quantitative estimates of precipitation from East Asia during the Oligocene, based upon intra-annual variation in carbon isotopes across growth rings of exquisitely preserved fossil wood from southern China. We find a clear pattern of consistent, summer-dominated precipitation with ~4 times more precipitation in summer than winter. These data demonstrate that by the late Oligocene, precipitation patterns in East Asia had similar strength and seasonality to modern conditions, which suggests the presence of an East Asian Monsoon-style system prior to the Neogene.