| 泸定昔格达组时代认定与古环境* |
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| 引用本文： | 王书兵,赵志中,乔彦松,蒋复初.泸定昔格达组时代认定与古环境*[J].第四纪研究,2006,26(2):257-264. |
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| 作者姓名： | 王书兵 赵志中 乔彦松 蒋复初 |
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| 作者单位： | 中国地质科学院地质力学研究所,北京,100081 |
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| 基金项目： | 中国地质调查局地质调查项目;国家高技术研究发展计划(863计划) |
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| 摘 要： | 文章对泸定海子坪昔格达组重新进行了详细的古地磁测试,结果显示昔格达组发育时代为4.2~2.6MaB.P.,地质时代属上新世中、晚期,与前人的研究结果一致。泸定海子坪剖面是目前所知的记录昔格达古湖沉积起始年代最早的剖面。泸定海子坪剖面记录了5个大的从粗→细的沉积旋回,15个沉积阶段。沉积物中值粒径的值直接指示了各旋回的沉积阶段,值小,水动力较强,为动荡的沉积环境;值大,水动力较弱,为稳定的沉积环境。另外,沉积记录显示在约2.8MaB.P.青藏高原的强烈隆升就已开始,昔格达古湖为过水湖;至2.6MaB.P.,昔格达古湖完全消失,与黄土高原风尘沉积环境由红粘土堆积转变为黄土堆积的显著的改变相一致。海子坪剖面TOC高值段,沉积物的值也较大,沉积物为粘土、粉砂质粘土沉积;TOC低值段,沉积物的值也较小,沉积物为中、粗砂沉积,表明昔格达古湖沉积物有机质含量主要受岩性控制。
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| 关 键 词： | 昔格达组 磁性地层学 沉积旋回 中值粒径值 TOC 海子坪 泸定 |
| 文章编号： | 1001-7410（2006）02-257-08 |
| 收稿时间： | 2005-09-29 |
| 修稿时间： | 2005年9月29日 |
AGE AND PALEOENVIRONMENT OF XIGEDA FORMATION IN LUDING,SICHUAN |
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| Wang Shubing,Zhao Zhizhong,Qiao Yansong,Jiang Fuchu.AGE AND PALEOENVIRONMENT OF XIGEDA FORMATION IN LUDING,SICHUAN[J].Quaternary Sciences,2006,26(2):257-264. |
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| Authors: | Wang Shubing Zhao Zhizhong Qiao Yansong Jiang Fuchu |
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| Institution: | Institute of Geomechanics, Chinese Academy of Geological Sciences, Beifing 100081 |
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| Abstract: | A detailed re-study of the paleomagnetic polarity stratigraphy of Xigeda Formation with an approximate thickness of 400m in Haiziping, Luding, Sichuan suggests that the upper and lower parts separated at a depth of 360m from the surface belong to the Gauss normal polarity chron and the Gilbert reverse polarity chron respectively. According to the Candes polarity time scale, the age of the Xigeda Formation ranges from 4.2MaB.P. to 2.6MaB.P., assigned to the Middle and the Late Pliocene, which is consistent with our previous result. This series is known to be the earliest in the Xigeda lacustrine deposition. Based on the value of the median size, the sedimentation in Haiziping displays five cycles from coarse to fine including fifteen sedimentary stages. Furthermore, the low value indicating strong hydropower infers a queasy sedimentary environment; while the high value infers a stale sedimentary environment. The sediments records indicates that the strongest rising of the Tibetan Plateau begins at about 2.8MaB.P., and ends at 2.6MaB.P., consisting with the result from the obvious change of the eolian sedimentary environment in the Loess Plateau. The high TOC value corresponds to the high value and the low TOC value the low value, showing that the content of the organic matter in lacustrine sediments of the Xigeda Formation is mainly controlled by the lithology. |
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| Keywords: | TOC |
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