Sustained wood burial in the Bengal Fan over the last 19 My

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2019-10-21Author
Lee, Hyejung
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Galy, Valier
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Feng, Xiaojuan
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Ponton, Camilo
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Galy, Albert
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France-Lanord, Christian
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Feakins, Sarah J.
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https://hdl.handle.net/1912/25043As published
https://doi.org/10.1073/pnas.1913714116DOI
10.1073/pnas.1913714116Keyword
carbon cycle; wood; lignin; Himalaya; Bengal FanAbstract
The Ganges–Brahmaputra (G-B) River system transports over a billion tons of sediment every year from the Himalayan Mountains to the Bay of Bengal and has built the world’s largest active sedimentary deposit, the Bengal Fan. High sedimentation rates drive exceptional organic matter preservation that represents a long-term sink for atmospheric CO2. While much attention has been paid to organic-rich fine sediments, coarse sediments have generally been overlooked as a locus of organic carbon (OC) burial. However, International Ocean Discovery Program Expedition 354 recently discovered abundant woody debris (millimeter- to centimeter-sized fragments) preserved within the coarse sediment layers of turbidite beds recovered from 6 marine drill sites along a transect across the Bengal Fan (∼8°N, ∼3,700-m water depth) with recovery spanning 19 My. Analysis of bulk wood and lignin finds mostly lowland origins of wood delivered episodically. In the last 5 My, export included C4 plants, implying that coarse woody, lowland export continued after C4 grassland expansion, albeit in reduced amounts. Substantial export of coarse woody debris in the last 1 My included one wood-rich deposit (∼0.05 Ma) that encompassed coniferous wood transported from the headwaters. In coarse layers, we found on average 0.16 weight % OC, which is half the typical biospheric OC content of sediments exported by the modern G-B Rivers. Wood burial estimates are hampered by poor drilling recovery of sands. However, high-magnitude, low-frequency wood export events are shown to be a key mechanism for C burial in turbidites.
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Author Posting. © National Academy of Sciences, 2019. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 116(45), (2019): 22518-22525, doi:10.1073/pnas.1913714116.
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Lee, H., Galy, V., Feng, X., Ponton, C., Galy, A., France-Lanord, C., & Feakins, S. J. (2019). Sustained wood burial in the Bengal Fan over the last 19 My. Proceedings of the National Academy of Sciences of the United States of America, 116 (45), 22518-22525.Related items
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