| 鄱阳湖滨沙岭地区网纹层的顶界年代 |
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| 引用本文： | 韩志勇,李徐生,陈英勇,弋双文,鹿化煜,杨达源.鄱阳湖滨沙岭地区网纹层的顶界年代[J].地理科学,2012(1):110-115. |
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| 作者姓名： | 韩志勇 李徐生 陈英勇 弋双文 鹿化煜 杨达源 |
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| 作者单位： | 南京大学地理与海洋科学学院 |
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| 基金项目： | 国家自然科学基金项目(40771023、40930103、40971004)资助 |
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| 摘 要： | 鄱阳湖滨沙岭地区的沙山由交替出现的砂层与粉砂层构成。对3个剖面的调查发现,该地区发育的网纹大体可分为3种类型,Ⅰ类网纹密集且粗大,为典型的网纹,位于剖面底部,Ⅱ类网纹较稀疏、细,位于Ⅰ类网纹之上,Ⅲ类网纹界线模糊,位于剖面上部。Ⅰ类、Ⅱ类网纹属于成熟的网纹,而Ⅲ类属于不成熟的网纹。对剖面中砂层的光释光测年表明,测量等效剂量时没有出现信号饱和的问题,年剂量也没有受风化作用的影响,因而OSL年龄可以视为砂层的沉积年龄。基于砂层的沉积年龄,我们判断成熟网纹层的沉积时代早于80 ka,不成熟网纹层的沉积时代略晚于71 ka,而早于29 ka。
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| 关 键 词： | 网纹 沙山 光释光 鄱阳湖 |
Top Boundary Age of the Vermiculated Beds in the Shaling Area of the Poyang Lake |
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| HAN Zhi-yong,LI Xu-sheng,CHEN Ying-yong,YI Shuang-wen,LU Hua-yu,YANG Da-yuan.Top Boundary Age of the Vermiculated Beds in the Shaling Area of the Poyang Lake[J].Scientia Geographica Sinica,2012(1):110-115. |
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| Authors: | HAN Zhi-yong LI Xu-sheng CHEN Ying-yong YI Shuang-wen LU Hua-yu YANG Da-yuan |
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| Institution: | (School of Geographic and Oceanographic Sciences,Nanjing University,Nanjing,Jiangsu 210093,China) |
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| Abstract: | Sand hills distributed along shores of the Poyang Lake are composed of alternate eolian sand layers and silt layers.The Shaling sand hill,about 2 km in width and 5 km in length,is located in Liaohua Town of Xingzi County.On its north and west margins,three sections(SS1,SS2 and SS3) were investigated.Vermiculated mottles in this hill can be divided into three types.Vermiculated mottles of type Ⅰ are thick and dense and only occur in the lower part(layer 1) of section SS1.Vermiculated mottles of type Ⅱ are relatively thin and sparsely scattered and occur in the beds(layer 2) above type Ⅰ.Vermiculated mottles of type Ⅲ are indistinctly shaped and occur in the upper part(layer 5) of the section SS1and the upper part(layer 2) of the section SS2.A sand bed(layer 4) separates the vermiculated mottles of type Ⅲ from that of type I and type Ⅱ in section SS1.Vermiculated mottles of type Ⅲ cover a sand bed(layer 1) in section SS2.The section SS3 only comprises one sand bed(layer 1) and develops no vermiculated mottle.Vermiculated mottles of types I and type II are mature vermiculated mottles,whereas type Ⅲ are immature.OSL samples were collected from each sand bed.125-250 μm quartz grains were separated from sand samples following the sequences of the standard pretreatment.The equivalent dose was measured using the Single Aliquot Regeneration protocol in the Laboratory of Surface Process of Nanjing University.The annual dose was determined by contents of U,Th and K measured using the neutron activation method in China Institute of Atomic Energy.In OSL dating of sand samples,no evidence indicates that the samples show OSL saturation signals and the annual dose of the samples was affected by weathering.So,the OSL ages can be interpreted as the deposition ages.The sand layers of Section SS1 and SS2 were deposited about 80 ka and 71 ka ago respectively and the sand layer of Section SS3 has been accumulated since 29 ka.From these OSL ages,it can be thought that the age of the layers with mature vermiculated mottles is older than 80 ka and the age of the layers with immature vermiculated mottles ranges from 71 ka to 29 ka.The top boundary age of vermiculated beds can be inferred to be 80-29 ka if the layers with immature vermiculated mottles are taken as the vermiculated beds.The top boundary age of vermiculated beds is older than 80 ka if the layers with mature vermiculated mottles are taken as the vermiculated beds.Both inferred top boundary ages are much younger than 400 ka,which was previously reported as the formation age of the vermiculated beds.However,this conclusion is drawn on three OSL ages in Shaling area and should be validated by other studies in the future. |
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| Keywords: | vermiculated mottle sand hill OSL Poyang Lake |
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