3期以来青藏高原东北缘古环境变迁：来自黄河第二阶地的地磁证据

IF 5.4 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena Pub Date : 2025-05-24 DOI:10.1016/j.catena.2025.109161

Jiawen Zhao , Longsheng Wang , Yuzhu Zhang , Yinglu Chen , Shouyun Hu , Liwei Meng , Guiye Zhang , Yanju Ge , Chao Zhan , Qing Wang

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Higher values of χ, SIRM, χ<sub>ARM</sub>/χ, and χ<sub>ARM</sub>/SIRM indicate predominance of fine-grained magnetic minerals due to strong weathering in the watershed, suggesting a warm and humid climate with increased precipitation and meltwater. The paleo-shallow lake deposits (A) formed between 51.01 ± 2.19 and 39.54 ± 1.72 ka. Lower values of χ, χ<sub>ARM</sub>, SIRM, χ<sub>ARM</sub>/χ, and χ<sub>ARM/</sub>SIRM indicating dry and cold conditions that led to coarse-grained sediments with minimal weathering. The paleo-shallow lake deposits (B), formed between 36.73 ± 2.04 ka and 31.44 ± 1.97 ka, show increased hard magnetic minerals, reflecting enhanced Yellow River input of coarse sediments. Under the dual influence of a warm and humid climate and the neotectonics of the East Kunlun Fault, headward erosion of Yellow River has intensified, triggering a decline in paleo-lake water level. 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引用次数: 0

摘要

青藏高原若尔盖盆地黄河二阶地NYQ-A剖面环境磁学分析为区域古环境演化提供了新的思路。结果表明，这些沉积物中的磁性矿物主要由伪单畴（PSD）磁铁矿和单畴（SD）灰长岩组成。古深湖沉积(A)形成于51.82±2.34 ka之前，古深湖沉积(B)形成于39.18±2.03 ~ 36.77±1.66 ka之间。χ、SIRM、χ arm /χ、χ arm /SIRM值均较高，表明该流域受强风化作用影响，以细粒磁性矿物为主，气候温暖湿润，降水增多，融水增多。古浅湖沉积(A)形成于51.01±2.19 ~ 39.54±1.72 ka。χ、χ arm、SIRM、χ arm /χ、χ arm /SIRM值越小，表明干燥和寒冷条件下沉积颗粒粗，风化作用最小。古浅湖沉积(B)形成于36.73±2.04 ka ~ 31.44±1.97 ka，硬磁性矿物增多，反映黄河粗质沉积物输入增强。在温暖湿润的气候和东昆仑断裂新构造的双重影响下，黄河上游侵蚀加剧，导致古湖泊水位下降。2个滩上洪水沉积物（OFD）中磁性矿物含量较高，表明其为暖气候风化，χ arm /χ和χ arm /SIRM值较低，表明其为强水动力条件。东亚夏季风的增强和冰川融化引发了OFD1，发生在30.43±3.76 ka和27.47±3.57 ka之间，对应于MIS 3a期。OFD2发生在15.30±1.04 ka和12.93±1.63 ka之间，与b ølling- allerd事件一致。在这两个时期，水主要来源于盆地周围山地冰川的加速融化和（或）大尺度降水，导致了河岸洪水的发生。这些研究成果促进了环境磁学在河流阶地沉积层序研究中的应用。

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Paleoenvironmental changes in the northeastern margin of the Tibetan Plateau since MIS 3: Magnetic evidence from the second terrace of the Yellow River

Environmental magnetic analysis of profile NYQ-A from the second terrace of the Yellow River in Zoige Basin, Tibetan Plateau, provides insights into regional paleoenvironmental evolution. The results indicate that the magnetic minerals in these sediments are primarily composed of Pseudo-Single-Domain (PSD) magnetite and Single-Domain (SD) greigite. The paleo-deep lake deposits (A) represent sedimentation occurring before 51.82 ± 2.34 ka, while paleo-deep lake deposits (B) formed between 39.18 ± 2.03 and 36.77 ± 1.66 ka. Higher values of χ, SIRM, χ_ARM/χ, and χ_ARM/SIRM indicate predominance of fine-grained magnetic minerals due to strong weathering in the watershed, suggesting a warm and humid climate with increased precipitation and meltwater. The paleo-shallow lake deposits (A) formed between 51.01 ± 2.19 and 39.54 ± 1.72 ka. Lower values of χ, χ_ARM, SIRM, χ_ARM/χ, and χ_ARM/SIRM indicating dry and cold conditions that led to coarse-grained sediments with minimal weathering. The paleo-shallow lake deposits (B), formed between 36.73 ± 2.04 ka and 31.44 ± 1.97 ka, show increased hard magnetic minerals, reflecting enhanced Yellow River input of coarse sediments. Under the dual influence of a warm and humid climate and the neotectonics of the East Kunlun Fault, headward erosion of Yellow River has intensified, triggering a decline in paleo-lake water level. High magnetic minerals contents of two overbank flood deposits (OFD) suggest warm-climate weathering, while low χ_ARM/χ and χ_ARM/SIRM values indicate strong hydrodynamic conditions. The intensification of the East Asian Summer Monsoon and glacial melting initiated OFD1, which occurred between 30.43 ± 3.76 ka and 27.47 ± 3.57 ka, corresponding to MIS 3a period. OFD2 occurred between 15.30 ± 1.04 ka and 12.93 ± 1.63 ka, coinciding with the Bølling-Allerød event. At these two periods, the water was mainly derived from the accelerated melting of mountain glaciers surrounding the basin and/or the large-scale precipitation, which led to the overbank ﬂoods. The research findings enhance the application of environmental magnetism in the study of river terrace sedimentary sequences.

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来源期刊

Catena 环境科学-地球科学综合

CiteScore

10.50

自引率

9.70%

发文量

816

审稿时长

54 days

期刊介绍： Catena publishes papers describing original field and laboratory investigations and reviews on geoecology and landscape evolution with emphasis on interdisciplinary aspects of soil science, hydrology and geomorphology. It aims to disseminate new knowledge and foster better understanding of the physical environment, of evolutionary sequences that have resulted in past and current landscapes, and of the natural processes that are likely to determine the fate of our terrestrial environment. Papers within any one of the above topics are welcome provided they are of sufficiently wide interest and relevance.