| 青藏高原东北缘西宁黄土的磁学记录及其环境意义 |
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| 引用本文：盛美,李宗耀,仝亚博,蒋凯,易施钰,胡珂,王喜生.2025.青藏高原东北缘西宁黄土的磁学记录及其环境意义[J].地球学报,46(6):1082-1094. |
| DOI：10.3975/cagsb.2025.070611 |
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| 基金项目:国家自然科学基金项目(编号: 42104080; 42474101; 42530304; 42130720)；中国地质科学院地质力学研究所基本科研业务费项目(编号: DZLXJK202404) |
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| 中文摘要:青藏高原隆升深刻调控亚洲季风演化。然而如何有效区分东亚季风演化过程中源于太阳辐射、全球冰量以及青藏高原隆升的贡献仍存争议。本研究基于青藏高原东北缘260 m连续沉积的西宁黄土钻孔岩心, 通过高分辨率粒度与多参数磁气候学研究, 取得以下主要认识: (1)岩石磁学结果表明, 古土壤层磁性增强主要受成土成因的细粒亚铁磁性矿物控制, 而黄土层磁化率和等温剩磁呈逐渐增强的趋势主要源于碎屑粗粒磁铁矿输入通量增加。(2)综合磁参数和粒度结果揭示1.3~0.2 Ma期间青藏高原东北缘东亚冬季风强度与干旱化趋势较黄土高原典型记录显著增强, 从而证实了在全球变冷背景下青藏高原的隆升在增强东亚季风环流和亚洲内陆干旱化中发挥了重要作用。(3)青藏高原东北部物理侵蚀与化学风化速率间的负相关揭示了区域强烈的气候-硅酸盐-风化正反馈机制; 该结果为青藏高原东北缘及邻区地形地貌的存在增强了轨道尺度气候变化信号, 并加剧了亚洲内陆干旱化的不可逆过程提供了有力佐证。 |
| 中文关键词:青藏高原隆升 西宁黄土 环境磁学 东亚季风 亚洲内陆干旱化 |
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| Magnetic Properties of the Xining Loess on the Northeastern Tibetan Plateau and Their Environmental Implications |
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| Abstract:The uplift of the Tibetan Plateau has exerted profound impacts on the evolution of the Asian monsoon. However, due to the scarcity of continuous Quaternary sedimentary records across the plateau and its margins, disentangling the respective signals of solar radiation, global ice volume variations, and Tibetan Plateau uplift in driving East Asian monsoon evolution remains highly contentious. The 260-m-thick Xining loess–paleosol sequence on the northeastern Tibetan Plateau (NETP) provides an exceptional archive to resolve the contribution of NETP to East Asian monsoon dynamics. This study investigates a high-quality drill core from the Dadunling section in Xining, employing high-resolution granulometric and multi-proxy magnetic climatic analyses, yielding the following key findings: (1) Detailed rock magnetic analyses reveal that pedogenically derived fine-grained ferrimagnetic minerals dominate magnetic enhancement in paleosol layers, while the gradual increase in saturation isothermal remanent magnetization in overlying loess units reflects enhanced inputs of detrital coarse-grained ferrimagnetic minerals. (2) Integrated bulk grain-size and magnetic parameter records demonstrate that the intensification of East Asian winter monsoon and long-term aridification trends documented in the Xining loess during 1.3–0.2 Ma were markedly more pronounced than those of typical loess on the Chinese Loess Plateau. This verifies the critical role of Tibetan Plateau uplift in amplifying East Asian monsoon circulation and promoting Asian interior aridification against the backdrop of global cooling. (3) The negative relationship between physical erosion and chemical weathering in the NETP does not conflict with the widely accepted uplift-weathering hypothesis but instead highlights a strong positive feedback mechanism involving climate, silicate weathering, and tectonic activity in this dynamic region. These results offer strong evidence that the NETP, along with its surrounding topography, has significantly impacted the irreversible increase in aridity within Asia interior. |
| keywords:Tibetan Plateau uplift Xining loess environmental magnetism East Asian monsoon Asian interior aridification |
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