岷江上游新磨村湖相沉积物粒度端元反演及其记录的构造和气候事件
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本文为国家自然科学基金项目(编号 41807298,41572346)和中国博士后基金(编号 2019M650788)及中国地质调查局项目(编号 DD20160271,DD20190059)资助的成果。


End member inversion of Xinmocun lacustrine sediments in the upper reachesof the Minjiang River and its recorded tectonic and climate events
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    摘要:

    应用沉积物粒度端元分析模型对岷江上游新磨村湖相沉积高分辨率粒度数据序列进行了反演,分离出2个端元。根据端元的频率分布曲线和沉积学分析,并结合岷江上游的地质构造背景,分析了各端元与研究区物源和古地震活动的对应关系。EM1为震间期的湖泊沉积,代表风力近源搬运的极细颗粒组分;EM2为极端灾变(地震等)期间的湖泊沉积,代表风力为主和部分水力近距离搬运的细颗粒组分。对新磨村剖面分离出的EM2百分含量与中值粒径、20~63 μm、63~200 μm粒径组分、磁化率值及地球化学比值(SiO2/Al2O3、TiO2/Al2O3、CaO/Al2O3、Sr/Al2O3、Rb/Sr,Na2O/Al2O3)进行对比分析,各指标的突变明显受粒度变化控制,指示可能的地震事件,进而识别出26次地震事件。为确定地震事件所代表的地震震级,基于震级与累积砂层厚度关系进行估算,共获得16次5~6级,5次6~7级,5次>7级地震。因此,采用粒度端元模拟不仅可以分离出不同的粒径组分和各组分百分含量,有效识别出不同动力组分和沉积动力环境,还可以较好地厘定出沉积记录的构造事件(地震等)等,更好地理解构造活动在地质、地貌演化中的作用。

    Abstract:

    Two end members of the Xinmocun lacustrine sediment grain size in the upper reaches of the Minjiang River were inverted using the end member (EM) model of sediment grainsize. The provenance of sediments and activity of paleoearthquake of each EM were discussed based on the frequency of the EMs, sedimentology analysis, geological and tectonic background. EM1 deposited in lacustrine environments during a seismic period and represents very fine particles brought by wind nearby; EM2 deposited in lacustrine environments in an extremely disastrous condition (e. g. earthquakes, landslides etc.) and represents the dust and few fluvial deposits from nearby sources. Comparative analysis of EM2 percentage, mean grain size, magnetic susceptibility and geochemical ratios (e. g. SiO2/Al2O3, TiO2/Al2O3, CaO/Al2O3, Sr/Al2O3, Rb/Sr, Na2O/Al2O3) indicates that all the indexes vary greatly with grain sizes and possibly point to seismic events. A total of twenty- six possible earthquake events have been identified. Based on the relation of the cumulative thickness of sand sediments with magnitudes of earthquakes, earthquake magnitudes representing seismic events were obtained in this study: sixteen earthquakes of magnitude 5. 0~6. 0, five 6. 0~7. 0 and five more than 7. 0. Compared to the traditional method of sediment grain size analysis, the EM model can not only determine the EMs and percentage of each component, identify the sediment provenance and dynamic regional sedimentary environment, but also recognize the tectonic events (earthquake, etc.) of sedimentary record. Therefore, this method can better explain the role of tectonic activity in geological and geomorphological evolution.

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钟宁,蒋汉朝,李海兵,徐红艳,梁莲姬,时伟.2020.岷江上游新磨村湖相沉积物粒度端元反演及其记录的构造和气候事件[J].地质学报,94(3):968-981.
ZHONG Ning, JIANG Hanchao, LI Haibing, XU Hongyan, LIANG Lianji, SHI Wei.2020. End member inversion of Xinmocun lacustrine sediments in the upper reachesof the Minjiang River and its recorded tectonic and climate events[J]. Acta Geologica Sinica,94(3):968-981.

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  • 收稿日期:2019-06-04
  • 最后修改日期:2019-08-20
  • 录用日期:2019-08-24
  • 在线发布日期: 2019-08-27
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