Paleogeography and paleoenvironment of Nong Han Kumphawapi, Changwat Udon Thani

The Southwest monsoon and the Norteast monsoon mainly controls climate and its circulation related with change in wind and precipitation pattern over Thailand. Changes in this convectively active region can result in severe drought or flood over large regions. Lake sediment is one of geological archives which have potential to reconstruct past monsoon intensity. Then, this research aims to study the relationship between Asian monsoon, geographical feature, paleogeographical and paleoenvironment of Nong Han Kumphawapi. The investigate of physical and chemical properties of lake sediment, and the measurement of AMS ¹⁴C radiocarbon dating were made at Nong Han Kumphawapi, Udon Thani Province. Sediment cores were collected by a Russian corer (chamber Ø: 10 cm and 7.5 cm, chamber length: 1 m) and with 0.5 m overlap. The coring point’s co-ordinates were identified by GPS to improve the accuracy of sediment cores’ position. The most complete sequence (CP3A) was selected for high-resolution multi-proxy sub-sampling in the laboratory. Magnetic Susceptibility (MS), X-ray fluorescence (XRF), Loss-on-ignition method (LOI) and AMS ¹⁴C dating were use in the sediment cores analysis. In addition, we combine the data from aerial photos interpretation and GIS based map in order to investigate geographical feature and paleogeographical. The results show that the oldest sediment sample is around 7,763 cal years B.P. and the youngest sample dates to around 436 cal years B.P. In conclusion,the sediment and the combined proxy data indicate that Nong Han Kumphawapi underwent several phases with higher/lower lake levels, which potentially could be related to changes in monsoon intensity.泰国地区的气候及其与风场和降水格局变化相关的环流，主要受西南季风与东北季风控制。该对流活跃区域的变化可引发大范围严重干旱或洪涝灾害。湖泊沉积物是具备重建过去季风强度潜力的地质档案之一。本研究旨在探究亚洲季风与农汉-库姆哈瓦皮湖（Nong Han Kumphawapi）的地理特征、古地理及古环境之间的关联。研究人员在乌隆他尼省的农汉-库姆哈瓦皮湖开展了湖泊沉积物理化性质分析，并进行了加速器质谱碳-14（AMS ¹⁴C）放射性碳定年测试。沉积物岩芯采用俄罗斯式取样器（腔体直径：10 cm与7.5 cm，腔体长度：1 m）采集，采样间距存在0.5 m的重叠。利用全球定位系统（GPS）确定取样点位的坐标，以提升沉积物岩芯的定位精度。选取完整性最佳的序列（CP3A），在实验室中开展高分辨率多代用指标分样工作。沉积物岩芯分析采用了磁化率（Magnetic Susceptibility, MS）、X射线荧光光谱（X-ray fluorescence, XRF）、烧失量法（Loss-on-ignition, LOI）以及AMS ¹⁴C定年技术。此外，本研究结合航空照片解译数据与基于地理信息系统（GIS）的地图资料，以探究该区域的地理特征与古地理状况。研究结果显示，最古老的沉积物样品年代约为7763个校准年前（cal years B.P.），最年轻的样品年代约为436个校准年前。综上，沉积物与多代用指标的综合数据表明，农汉-库姆哈瓦皮湖经历了多次高/低湖水位阶段，该现象可能与季风强度的变化存在关联。