| 华南中-晚二叠世之交碳酸盐岩磁学特征及环境意义 |
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| 引用本文： | 李波,薛武强,颜佳新,朱宗敏,王艳,马志鑫.华南中-晚二叠世之交碳酸盐岩磁学特征及环境意义[J].地球科学,2015,40(7):1226-1236. |
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| 作者姓名： | 李波 薛武强 颜佳新 朱宗敏 王艳 马志鑫 |
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| 作者单位： | 1.中国地质调查局广州海洋地质调查局, 广东广州 510075 |
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| 基金项目： | 国家自然科学基金项目，国家重点基础研究发展计划“973”项目，国土资源部海底矿产资源重点实验室开放基金课题 |
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| 摘 要： | 磁学参数作为可靠的古气候和古环境指标, 能为全球环境变化、气候过程研究提供有价值的资料.对广西来宾铁桥剖面瓜德鲁普-乐平统界线地层进行详细岩石磁学研究, 结果表明, 铁桥剖面样品中主要磁性矿物是顺磁性矿物以及少量磁铁矿、赤铁矿.在瓜德鲁普-乐平统界线附近, 岩石磁学特征发生显著变化, 磁化率先增大再减小, 携磁矿物成分呈硬磁性矿物(赤铁矿)→软磁性矿物(磁铁矿)→硬磁性矿物(赤铁矿)的变化趋势, 这些转变仅在界线上下大约4m的岩层内完成, 与中二叠世晚期的海平面变化、古海水温度变化同步.中-晚二叠世之交碳酸盐岩磁学参数的变化显著, 反映磁性矿物在各圈层之间的运移和转换发生了转变, 这一转变起因于当时的气候环境变化.瓜德鲁普世晚期和乐平世早期, 海平面较高, 来宾地区物源少, 铁桥剖面的携磁矿物主要来自粉尘赤铁矿; 中-晚二叠世之交短暂的大规模海退作用使华南古陆面积大幅度增加, 同时陆生植物大规模灭绝, 地表侵蚀加剧, 来宾地区物源增多, 此时, 铁桥剖面的携磁矿物主要来源于河流输入的磁铁矿.
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| 关 键 词： | 华南 铁桥剖面 瓜德鲁普-乐平统 岩石磁学 海退 沉积物 古环境 |
| 收稿时间： | 2014-11-21 |
Magnetic Properties of Middle-Late Permian Carbonates in South China and Their Environmental Significances |
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| Li Bo,Xue Wuqiang,Yan Jiaxin,Zhu Zongmin,WangYan
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Ma Zhixin.Magnetic Properties of Middle-Late Permian Carbonates in South China and Their Environmental Significances[J].Earth Science-Journal of China University of Geosciences,2015,40(7):1226-1236. |
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| Authors: | Li Bo Xue Wuqiang Yan Jiaxin Zhu Zongmin WangYan Ma Zhixin |
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| Abstract: | As a reliable proxy for paleoclimate and paleoenvironment, magnetic parameter could provide valuable data for the research of global environmental changes and climatic processes. A detailed study has been carried out on rock magnetism in order to reveal the change of climate and environment and its reasons across Guadalupian-Lopingian (G-L) boundary at Tieqiao section in Laibin area, Guangxi, China. The results show that the dominant magnetic minerals from Tieqiao section are paramagnetic minerals with a small amount of magnetite and hematite as well. There is a remarkable change in the properties of rock magnetism near the G-L boundary. Magnetic susceptibility increases first and then decreases. Magnetic carriers show the trend of being transformed from hard magnetic minerals (hematite) to soft magnetic mineral (magnetite) and then turning to hard magnetic minerals (hematite). All of these changes occur within 4m-thick strata interval above and below the G-L boundary, and synchronize with the fluctuation of sea-level and ancient seawater temperature during late Middle Permian. The significant changes in magnetic parameters for Middle-Late Permian carbonates suggest that the migration and conversion of magnetic minerals between different spheres in earth system has shifted, which resulted from the climatic and environmental changes. High sea-level during Late Guadalupian and Early Lopingian resulted in the decrease in terrigenous supply in South China. Therefore, the magnetic carriers in Tieqiao section mainly are hematite through aeolian transportation during this period. However, pronounced regression during the Middle-Late Permian transition led to the expansion of exposed land area. Meanwhile, land plants experienced widespread extinction, which led to increased sediment source. The magnetic carriers in contemporaneous sediments of Tieqiao section are mainly fluvial magnetite. |
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| Keywords: | South China Tieqiao section Guadalupian-Lopingian rock magnetism regression sediment paleoenvironment |
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