TY - JOUR
T1 - Provenance Control on Chemical Weathering Index of Fluvio-Lacustrine Sediments
T2 - Evidence From the Qaidam Basin, NE Tibetan Plateau
AU - Ren, Xueping
AU - Nie, Junsheng
AU - Saylor, Joel E.
AU - Li, Hua
AU - Bush, Meredith A.
AU - Horton, Brian K.
N1 - Funding Information:
Data supporting figures are available in Data Sets S1?S3 in the supporting information. Comments by two reviewers improved the paper significantly. This work was financially supported by the Second Tibetan Plateau Scientific Expedition (grant 2019QZKK0704), the National Natural Science Foundation of China (grants 41672157, 41761144063, and 41422204), the Fundamental Research Funds for the Central Universities (grant lzujbky-2018-ot05), Program of Introducing Talents of Discipline to Universities (BP2018001) from China's Ministry of Education, and the open fund from State Key Laboratory of Loess and Quaternary Geology (SKLLQG1819), Institute of Earth Environment, CAS. Thanks to Shunchuan Ji, Wenbin Peng, Kuang He, and Yunfa Miao for their field assistance. We thank Yibo Yang for the helpful discussions and advice.
Publisher Copyright:
©2019. American Geophysical Union. All Rights Reserved.
PY - 2019
Y1 - 2019
N2 - Carbon dioxide drawdown resulting from enhanced chemical weathering during orogenesis has been invoked to explain late Cenozoic global cooling. Establishing chemical weathering records from the India–Asia collision zone is important to test this hypothesis because uplift of the Tibetan Plateau is thought to be responsible for Cenozoic cooling. However, proxies for the intensity of chemical weathering can be affected by additional factors, such as sediment grain size and provenance. Here we report major element compositions and calculated chemical weathering intensity records of three size fractions (0–5, 5–20, 20–63 μm) from the Dahonggou section of the Qaidam Basin in the northeastern Tibetan Plateau, and compare those records with published provenance data from the same section. Results show that the indices of the fine (0–5 μm) fraction vary in coordination with provenance shifts, but variations of the 5–20 and 20–63 μm fractions are less affected by provenance variations. Comparison with Upper Continental Crust reveals that some labile elements are not leached but instead are enriched in the fine fraction, indicating that it does not faithfully record chemical weathering intensity. In addition, weathering can result in clay mineral transformation instead of elemental variations, complicating the relationship between element-based parameters and weathering intensity. This work suggests that changes in sediment provenance must be accounted for when inferring variations in chemical weathering intensity on the basis of element-based weathering intensity indices of the clay fraction.
AB - Carbon dioxide drawdown resulting from enhanced chemical weathering during orogenesis has been invoked to explain late Cenozoic global cooling. Establishing chemical weathering records from the India–Asia collision zone is important to test this hypothesis because uplift of the Tibetan Plateau is thought to be responsible for Cenozoic cooling. However, proxies for the intensity of chemical weathering can be affected by additional factors, such as sediment grain size and provenance. Here we report major element compositions and calculated chemical weathering intensity records of three size fractions (0–5, 5–20, 20–63 μm) from the Dahonggou section of the Qaidam Basin in the northeastern Tibetan Plateau, and compare those records with published provenance data from the same section. Results show that the indices of the fine (0–5 μm) fraction vary in coordination with provenance shifts, but variations of the 5–20 and 20–63 μm fractions are less affected by provenance variations. Comparison with Upper Continental Crust reveals that some labile elements are not leached but instead are enriched in the fine fraction, indicating that it does not faithfully record chemical weathering intensity. In addition, weathering can result in clay mineral transformation instead of elemental variations, complicating the relationship between element-based parameters and weathering intensity. This work suggests that changes in sediment provenance must be accounted for when inferring variations in chemical weathering intensity on the basis of element-based weathering intensity indices of the clay fraction.
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U2 - 10.1029/2019GC008330
DO - 10.1029/2019GC008330
M3 - Article
AN - SCOPUS:85068722011
SN - 1525-2027
VL - 20
SP - 3216
EP - 3224
JO - Geochemistry, Geophysics, Geosystems
JF - Geochemistry, Geophysics, Geosystems
IS - 7
ER -