位于南昌市南部的新建县广泛分布着由沙丘砂-古土壤叠覆堆积组成的沉积序列。在野外调查的基础上,选择位于新建县南部的厚田剖面进行工作,其沉积序列由3层沙丘砂和3层砂质古土壤组成,顶部与底部的光释光(OSL)年代分别为14.9 ka BP和77 ka BP,为末次冰期的产物。结果表明:(1)厚田剖面的末次冰期地层可划分为HTS4 (77~57.1 ka BP)、HTS3c (57.1~49.7 ka BP)、HTS3b(49.7~36.8 ka BP)、HTS3a(36.8~26.5 ka BP)、HTS2 (26.5~14.9 ka BP)5个阶段。(2)以粒级-标准偏差法与主成分因子分析法提取敏感粒度,12.619~20 mum含量与平均粒径和黏粒含量正相关,400~563.667 mum含量与平均粒径和黏粒含量负相关,反映冬季风强度的敏感粒径为400~563.667 mum,反映夏季风强度的敏感粒径为12.619~20 mum。(3)平均粒径、黏粒含量、敏感粒度在剖面上呈现明显的峰谷交替变化,暖阶段基本同步于葫芦洞石笋记录的夏季风强盛期和65°N7月的天文辐射总量的高峰,揭示出HTS3c、HTS3a、HTS2早期为温暖期,砂质古土壤发育;冷阶段对应于葫芦洞石笋记录的夏季风减弱期和65°N7月的天文辐射总量的低值,揭示出HTS4、HTS3b、HTS2晚期为寒冷期,沙丘砂发育。厚田剖面末次冰期的气候变化存在万年尺度的气候波动,是太阳辐射总量和东亚季风共同影响下的结果。
英文摘要:
The sedimentary sequences superimposed by dune sand and paleosol are widely distributed in the southern part of Xinjian County,Nanchang.Based on the field investigation,we found the Houtian section mainly consists of the alternating deposition of 3 layers of dune sands and paleosol,and its top and bottom ages are 14.9 ka BP and 77 ka BP,respectively,which is the product of the last glaciation.According to the contents of grain size and OSL chronology,we got the conclusion as follows:(1) The strata of the Last Glacial Period in the Houtian section can be divided into five stages,as HTS4 (77-57.1 ka BP),HTS3c (57.1-49.7 ka BP),HTS3b(49.7-36.8 ka BP),HTS3a(36.8-26.5 ka BP),HTS2(26.5-14.9 ka BP).(2) The two results extracted by particle size-standard deviation method and principal component factor analysis show that 12.619-20 mum is positively correlated with mean particle size and clay content,and 400-563.667 mum is negatively correlated with mean particle size and clay content,which inspects that the sensitive particle size of winter monsoon is 400-563.667 mum and the sensitive particle size of summer monsoon is 12.619-20 mum.(3)The mean particle size,clay content and sensitive particle size show remarkable variations in alternation of peaks and valleys.The warm periods mainly correspond to strong summer monsoon indicated by stalagmite in Hulu Cave in China,as well as the peak of total amount of astronomical insolation at 65°N in July,which reveals that the sand-paleosol is developed in the warm period of HTS3c,HTS3a and early HTS2.The cold periods mainly correspond to weak summer monsoon indicated by stalagmite in Hulu Cave in China,as well as the valley of total amount of astronomical insolation at 65°N in July,which reveals that the dunes sand is developed in the cold period of HTS4,HTS3b and late HTS2.The climate change in the Houtian section during the Last Glacial Period has a climate fluctuation of ten thousand years,which probably results from the mutual impact of total amount of insolation and East Asian Monsoon.