We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Magnetoclimatological Record of Late Pleistocene Loess in the Southern Hunshandake Sandy Land, Inner Mongolia: A Threshold Response to the East Asian Summer Monsoon Variations.
- Authors
Sheng, Mei; Jiang, Kai; Wang, Xisheng; Jiang, Zhaoxia; Tang, Ling; Zhou, Zaizheng
- Abstract
We report the first complete loess–paleosol record spanning the last 130 kyr from the southern extremity of the Hunshandake Sandy Land (HSL) in central‐eastern Mongolia. Our combined mineral magnetic and geochemical results demonstrate that during the last interglacial, the front of the East Asian summer monsoon (EASM) extended to central‐eastern Inner Mongolia, consistent with modern observations of climate change. However, during the last glacial, typical magnetic parameters (e.g., magnetic susceptibility and anhysteretic remanent magnetization and their ratios), which have been successfully adopted to denote the EASM variations on the Chinese Loess Plateau (CLP), show only muted temporal variations and cannot be readily correlated with equivalent records from the main body of the CLP. Remarkably, the Zr/Rb ratio, a robust geochemical indictor of the winter monsoon, is positively correlated with saturation isothermal remanent magnetization and saturation magnetization during the last glacial, demonstrating the strong control of wind vigor on high‐field magnetization signals dominated by lithogenic ferrimagnetic minerals. In contrast to the variable response of magnetic parameters to regional paleoclimatic fluctuations, the Rb/Sr and Ba/Sr ratios (two summer monsoon indicators) faithfully track weak chemical weathering processes and fine‐scale monsoon oscillations, especially during the last glacial. Additionally, we found that higher proportions of pedogenic high‐coercivity magnetic minerals were formed during the last interglacial, which may reflect relatively low rainfall but higher evapotranspiration in the southern extremity of the HSL compared with the CLP. We therefore attribute this complex magnetic record to a threshold response to the EASM variations in eastern Inner Mongolia. Plain Language Summary: Located at the present‐day northern limit of the East Asian summer monsoon (EASM), the arid and semi‐arid central‐eastern Inner Mongolia is highly sensitive to the advance and retreat of the EASM. To date, paleoclimatic history over the last interglacial–glacial cycle in this region is poorly documented due to the spatial scarcity of reliable sedimentary archives. Here, we present mineral magnetic, diffuse reflectance, and geochemical results for a well‐preserved loess–paleosol record from the southern extremity of the Hunshandake Sandy Land since the last interglacial, aimed at furthering our understanding of paleoclimatic history and possible forcing mechanisms in this region. Our results clearly demonstrate that during the last interglacial the EASM could penetrate to the studied site, and weaker precipitation but higher evapotranspiration compared with that on the Chinese Loess Plateau led to a lower degree of ferrimagnetic enhancement but higher proportions of pedogenic hematite. During the last glacial, we propose that the combination of mineral magnetic and geochemical analyses is critical to discriminating the weakest soil forming processes from strong lithogenic signals controlled by wind vigor/advance of sandy land margin. We attribute this "atypical" mineral magnetic record to a threshold response to the EASM variations in eastern Inner Mongolia. Key Points: We report the first loess–paleosol record since the last ∼130 kyr in the southern Hunshandake Sandy Land, central‐eastern Inner MongoliaGeochemical ratios yield less ambiguous paleoclimate interpretations in the northern limit of the East Asian summer monsoon (EASM) compared with magnetic parametersWe attribute this atypical mineral magnetic record in monsoonal margin to a threshold response to the EASM variations
- Subjects
INNER Mongolia (China); MONGOLIA; MONSOONS; REMANENCE; LOESS; CHEMICAL weathering; PLEISTOCENE Epoch; MAGNETIC susceptibility
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2023, Vol 24, Issue 7, p1
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2023GC010905