Increasing chemical weathering in the Himalayan system since the Last Glacial Maximum

Continental chemical weathering is central in Earth's surface biogeochemical cycles as it redistributes elements across reservoirs such as the crust and the oceans. However the evolution of weathering through time and its response to external forcing such as changes in climate remain poorly con...

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Bibliographic Details
Published in:Earth and planetary science letters 2013-03, Vol.365, p.243-252
Main Authors: Lupker, Maarten, France-Lanord, Christian, Galy, Valier, Lavé, Jérôme, Kudrass, Hermann
Format: Article
Language:English
Subjects:
chemical weathering
Earth Sciences
Himalayan system
Last Glacial Maximum
Sciences of the Universe
source to sink
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Summary:Continental chemical weathering is central in Earth's surface biogeochemical cycles as it redistributes elements across reservoirs such as the crust and the oceans. However the evolution of weathering through time and its response to external forcing such as changes in climate remain poorly constrained. In this work, a composite sediment record from the Bay of Bengal is used to document the evolution of chemical weathering in the Himalayan system (Himalayan range and Indo-Gangetic floodplain), the world largest sediment conveyor to the oceans, since the Last Glacial Maximum (LGM). The degree of weathering of the sediments is documented using mobile to immobile ratios such as K/Si and H2O+/Si as well as detrital calcite abundance. Robust weathering proxies are derived by correcting the chemical composition of sediment for sorting effects that occur during transport and deposition. The Bay of Bengal record is also further compared to the chemical composition of modern river sediments from the Ganga and Brahmaputra basin. Weathering proxies all indicate that the sediments exported by the Ganga and Brahmaputra Rivers became increasingly weathered over the past ∼21kyr, whereas, Sr, Nd and major elements suggest a constant sediment provenance in the system over the last 21kyr. These changes in the degree of weathering of the sediments show that the weathering flux exported by the system to the Indian Ocean during the LGM was significantly lower than at present and demonstrate that chemical weathering in continental scale basins such as the Ganga and Brahmaputra responds to Late Quaternary climate changes. ► Chemical weathering in the Himalayan system is assed using sediment geochemistry. ► Modern river sediments and marine cores allow a weathering reconstruction since LGM. ► Correction for sediment sorting effects yields unbiased weathering proxies. ► Weathering in the Himalayan system increased significantly since the LGM. ► Chemical weathering in continental scale basins reacts to late quaternary climate change.
ISSN:0012-821X
1385-013X
DOI:10.1016/j.epsl.2013.01.038