南昌市厚田剖面末次冰期风沙沉积的粒度分维特征及其揭示的古环境意义  

Grain-Size Fractal Dimension of Aeolian Sand during the Last Glacial Period:The Houtian Section of Nanchang and Its Paleoenvironmental Significance

作　　者：詹江振 李志文[1,2] 王志刚 孙丽 黎武标[1] 杜兰 Zhan Jiangzhen;Li Zhiwen;Wang Zhigang;Sun Li;Li Wubiao;Du Lan(School of Earth Science,East China University of Technology,Nanchang 330013,China;School of Environmental and Chemical Engineering,Foshan University,Foshan 528225,China)

机构地区：[1]东华理工大学地球科学学院,南昌330013 [2]佛山科学技术学院环境与化学工程学院,广东佛山528225

出　　处：《热带地理》2020年第6期1075-1084,共10页Tropical Geography

基　　金：国家自然科学基金项目(41201006,41571007);江西省数字国土重点实验室开放基金(DLLJ201913)。

摘　　要：赣江下游阶地上断续发育着系列沙丘砂-砂质古土壤序列,有助于探讨亚热带地区粒度分维特征对古环境的指示意义。在多次综合考察的基础上,选择南昌市新建区的厚田剖面开展工作,在OSL年代和粒度测试基础上,采用分形理论中的幂指函数关系法分析了粒度分维特征,并将其与黏粒体积分数、平均粒径、冬夏季风敏感粒径、南京葫芦洞石笋氧同位素进行对比。结果表明:1)厚田剖面的沙丘砂-砂质古土壤序列主要形成于末次冰期(14.9—77.0 ka),其中沙丘砂的分维值为2.04~2.62(平均值2.34),砂质古土壤为2.24~2.70(平均值2.51)。2)分维值与夏季风强度敏感粒径呈正相关性,与冬季风强度敏感粒径呈负相关性,且与粒度分选性密切相关,标准偏差越小则分维值越小,反之则越大。3)分维值在垂向上呈现峰谷交替旋回,峰值分别对应MIS2早期、MIS3c和MIS3a阶段,该时期夏季风强盛,气候暖湿,砂质古土壤发育;谷值分别对应MIS2晚期、MIS3b和MIS4阶段,该时期冬季风强盛,气候干冷,沙丘砂发育。说明厚田沙地在末次冰期发生了3次气候冷暖旋回,其中还明显记录了H5、H6的极端寒冷事件。由此可见,鄱阳湖地区的风沙沉积序列基本同步于区域乃至全球性气候变化事件。Fractal theory can be used to reveal the fractal features of many geographic phenomena,and the composition of sediment grain size has been successfully applied to the study of the evolution of geographic environments.The fractal dimension has widely been used as a new grain size index,which is consistent with the environmental changes reflected in the traditional analysis of grain size and composition;however,whether the fractal dimension can also reveal environmental changes in the Poyang Lake area in the mid-subtropics has not yet been determined.This study analyzes the fractal dimension characteristics of Houtian sandy land based on the results of grain size and the power of the exponential function relation method in fractal theory.A series of dune sand-sandy paleosol sequences were developed intermittently on the terraces of the lower reaches of the Ganjiang River.Based on multiple comprehensive investigations,the Houtian section,with rich sequences and a relatively continuous deposition,was selected in Houtian sandy land,Xinjian County,and Nanchang City.With the research carried out,Optically Stimulated Luminescence(OSL)age and grain size tests were completed.A comparison of the fractal dimensions with clay,average grain size,winter and summer monsoon intensity-sensitive grain size,and the Nanjing Hulu Cave stalagmite oxygen isotope gave the following results:1)Combined with the results of OSL dating and deep-sea oxygen isotope and stratigraphic characteristics,an age-depth framework was constructed based on the segmented sedimentation rate interpolation.The sand dune-sandy paleosol sequence of the Houtian section was mainly formed during the last glacial period(14.9-77.0 ka).The entire section has a good fractal structure,with the dune sand's fractal dimension at 2.04-2.62(average 2.34)and the sandy paleosol at 2.24-2.70(average 2.51).2)The fractal dimension is positively correlated with the summer monsoon intensitysensitive grain size,negatively correlated with the winter monsoon intensity-sensitive grain

关 键 词：厚田沙地 沙丘砂-砂质古土壤序列 末次冰期 粒度分维特征 季风演变 

分 类 号：P532[天文地球—古生物学与地层学] P512.2[天文地球—地质学]