CAJ | 학술논문

青藏高原东北部西宁-互助地区堆积的厚层黄土是认识高原第四纪环境演化和气候变化的重要信息载体.对西宁泮子山厚层黄土钻孔(181.7m)进行了间隔5cm的采样,在实验室测量了全部样品的粒度,以粒度和北半球高纬太阳辐射数据为材料,选择古地磁年龄作为独立年代控制点,采用改进的自动轨道调谐方法,建立了西宁黄土早更新世以来天文轨道调谐的时间标尺.调谐后的粒度时间序列与ETP曲线在轨道周期上高度相关,在一定程度上证明了轨道调谐方法建立西宁厚层黄土堆积年代标尺的可行性.泮子山厚层黄土的沉积速率在1.0Ma前后发生了明显变化,1.0Ma以来沉积速率的相对高值可能反映了粉尘源区的干旱化程度增强,也指示了亚洲中部和青藏高原干旱环境的急剧发展.西宁厚层黄土年代标尺的建立,对深入认识晚新生代亚洲干旱气候发展过程和青藏高原的环境演化具有积极意义.
청장고원동북부서저-호조지구퇴적적후층황토시인식고원제사기배경연화화기후변화적중요신식재체.대서저반자산후층황토찬공(181.7m)진행료간격5cm적채양,재실험실측량료전부양품적립도,이립도화북반구고위태양복사수거위재료,선택고지자년령작위독립년대공제점,채용개진적자동궤도조해방법,건립료서저황토조경신세이래천문궤도조해적시간표척.조해후적립도시간서렬여ETP곡선재궤도주기상고도상관,재일정정도상증명료궤도조해방법건립서저후층황토퇴적년대표척적가행성.반자산후층황토적침적속솔재1.0Ma전후발생료명현변화,1.0Ma이래침적속솔적상대고치가능반영료분진원구적간한화정도증강,야지시료아주중부화청장고원간한배경적급극발전.서저후층황토년대표척적건립,대심입인식만신생대아주간한기후발전과정화청장고원적배경연화구유적겁의의.
The thick loess-palaeosol deposit in North Eastern Qinghai-Tibetan Plateau (NQTP) is sensitive to reflect paleoclimatic changes,thus providing a good opportunity to investigate regional palaeoclimatic and palaeoenvironmental variations and the relationship with the global climatic changes.During August-November of 2004,we undertook a drill project at the site with the thickest loess deposit in the NETP,this drilling penetrates the loess and reaches fluvial gravels and pebbles underlaid the loess.The Panzishan core(181.7m) was sampled every 5cm,all samples were measured for grain size distribution which is regarded as an excellent proxy index of East Asian monsoon variations during Pleistocene.In this paper,paleomagnetic ages are chosen as independent control points instead of establishing an initial age framework by comparing the grain size variations with the previous typical grain size time series.And,the ETP curve is selected as target and the APC automatically orbital tuning method is used.A preliminary orbit-tuned time scale for Xining thick loess has been developed based on comparison between the mean grain size variations and the insolation of 65°N since the Early Pleistocene.After tuning,the new time scale is tested by cross spectral analysis.The results show that either the grain size record or the ETP curve has changed at a lager amplitude and higher frequency in orbital periods.In addition,the grain size record and ETP curve are highly correlated in the orbital periods.To a certain extent,this proves that our method to establish time scale for the Xining thick loess deposit in the past 2.0Ma is feasible.The sedimentation rate of Panzishan loess deposit shifts sharply at 1.0Ma,the average sedimentation rate is twice after 1.0Ma than that of the before one.The relative high sedimentation rate during the past 1.0Ma reveal aridity of dust resource was strong,probably imply a rapid development of the arid environment in Central Asia.We believe that this orbit-tuned time scale for Xining thick loess will bring further awareness for understanding paleoclimatic changes in Qinghai-Tibetan Plateau.