| 湘中地区南华系沉积序列、物源特征及区域对比 |
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| 引用本文： | 宋芳,牛志军,何垚砚,杨文强.湘中地区南华系沉积序列、物源特征及区域对比[J].地球科学,2019,44(9):3074-3087. |
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| 作者姓名： | 宋芳 牛志军 何垚砚 杨文强 |
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| 作者单位： | 1.中国地质调查局武汉地质调查中心, 湖北武汉 430205 |
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| 基金项目： | 中国地质调查局地质矿产调查评价专项121201102000150012-19中国地质调查局地质矿产调查评价专项12120114039301中国地质调查局地质矿产调查评价专项DD20179385 |
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| 摘 要： | 新元古代晚期湘中地区为扬子地台向盆地过渡的区域，是进行南华系地层对比的重要研究区.通过对宁乡菜花田及桃源马金洞剖面的测制并结合区域地质资料，厘定研究区南华系地层沉积序列为长安组、富禄组（局部地区顶部为古城组）、大塘坡组、南沱组（洪江组），宁乡菜花田剖面为长安组出现的北界.在宁乡菜花田剖面长安组底部取得的碎屑锆石最年轻一组锆石谐和年龄为752.5±4.2 Ma（n=3，MSWD=2.4），可限定长安组沉积下限不早于760 Ma，碎屑锆石年龄谱显示长安组物源来自扬子地台.对比沉积特征并结合已发表的研究成果，认为长安组为明确的冰期地层，沉积下限可对应Sturtian冰期，区域上古城组冰期沉积可作为富禄组顶部，与下伏长安组一起构成一个冰期→间冰期→冰期的沉积体系，共同组成Sturtian冰期在区域上的沉积记录.由于冰期的阶段性和区域性，沉积显示在各地有所不同；大塘坡组是温暖气候下的间冰期沉积，南沱组/洪江组代表了一次分布范围很广的冰期，对应Marinoan冰期.虽然由于缺少同位素年龄的卡定，大塘坡组之下的地层精细对比还有待新的研究材料支撑，但Sturtian冰期在华南的多次沉积响应对认识当时古气候及早期生命演变历史仍有重要意义.
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| 关 键 词： | 湘中地区 南华系 沉积序列 物源 碎屑锆石 地层学 |
| 收稿时间： | 2018-11-23 |
Sedimentary Sequence,Provenance and Stratigraphic Correlation of Nanhuan System in Middle Hunan Province |
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| Abstract: | During the Late Neoproterozoic, the Middle Hunan Province was located in the Yangtze platform marginal basin, making the deposits of this area as key for stratigraphic correlations. By the sedimentary measurement of Caihuatian section in Ningxiang and Majindong sections in Taoyuan, the sequence of Nanhuan System in the Middle Hunan is defined as Changan, Fulu (Gucheng included in some areas), Datangpo and Nantuo/Hongjiang formations. And to the north of Caihuatian section, no Changan Formation has been recognized. One detrital zircon sample from the lower part of Changan Formation of Caihuatian section shows the Yangtze provenance and 752.5±4.2 Ma (n=3, MSWD=2.4) deposition age. On the basis of sedimentary characteristics and research results in the area, the Changan Glaciation might be the correspondence of the bottom part of Sturtian Glaciation (760 Ma) and Changan and Fulu (Gucheng included) formations could correspond to the whole Sturtian Glaciation with different glacial deposition phases for diverse and periodical glacier in the area. Datangpo Formation was deposited in warm climate and Nantuo/Hongjiang Formation corresponded to Marinoan. Further research should be done to identify the correlation to strata below Datangpo Formation. |
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