CAJ | 학술논문

对黄土高原的灵台和泾川黄土-红粘土序列进行了磁性地层学和沉积学研究.古地磁研究表明,泾川剖面的底界年龄为8.0 Ma,这比灵台剖面的底界年龄老1.0 Ma.通过空间上红粘土剖面的地层对比,发现灵台红粘土序列相对较为完整和连续.该剖面可以作为中国北方晚第三纪红粘土的标准剖面.野外观察和粒度分析均表明灵台和泾川红粘土沉积为风成沉积.通过对南北向黄土大断面粒度参数的系统分析,初步建立了"粉尘沉积的粒度参数一沉积区距源区最小距离"的半定量模型.根据这些模型推测,红粘土的主要源区可能在现代的巴丹吉林沙漠及其以西地区.灵台剖面的游离铁/全铁值变化表明,晚中新世以来东亚夏季风经历了非线性的演化历史.约4.1～4.8 Ma间为黄土高原地区7.0 Ma以来东亚夏季风最为强盛的时期.该气候事件的出现可能同全球温度背景较高及全球冰量较小有着动力学上的联系.
대황토고원적령태화경천황토-홍점토서렬진행료자성지층학화침적학연구.고지자연구표명,경천부면적저계년령위8.0 Ma,저비령태부면적저계년령로1.0 Ma.통과공간상홍점토부면적지층대비,발현령태홍점토서렬상대교위완정화련속.해부면가이작위중국북방만제삼기홍점토적표준부면.야외관찰화립도분석균표명령태화경천홍점토침적위풍성침적.통과대남북향황토대단면립도삼수적계통분석,초보건립료"분진침적적립도삼수일침적구거원구최소거리"적반정량모형.근거저사모형추측,홍점토적주요원구가능재현대적파단길림사막급기이서지구.령태부면적유리철/전철치변화표명,만중신세이래동아하계풍경력료비선성적연화역사.약4.1～4.8 Ma간위황토고원지구7.0 Ma이래동아하계풍최위강성적시기.해기후사건적출현가능동전구온도배경교고급전구빙량교소유착동역학상적련계.
In this study, two thick loess-red clay sequences located at Lingtai and Jingchuan, theChinese Loess Plateau, are studied with emphases on magnetostratigraphy and sedimentology. Paleo-magnetic measurements show that the Jingchuan red clay has a basal age of 8.0 Ma, which is one mil-lion years older than the previously studied Lingtai section. Field observations and grain size analysesboth suggest an eolian origin of the red clay sediments at Lingtai and Jingchuan, thus extending avail-able records of the eolian deposits in the Loess Plateau from 2.6 Ma back to 7.0 ～ 8.0 Ma. Correla-tion of five red clay sections in the Loess Plateau suggests that the Lingtai red clay sequence has a rel-atively continuous nature of sedimentation and can be regarded as the type-section of the Tertiary redclay deposits in northern China. On the basis of spatial changes in the grain size of one northwest-southeast loess transect, several semiquantitative models of grain size parameters versus the minimumdistance from the source region to depositional areas were developed. According to these models, theestimated southeastern margin of the desert in northern China during the Tertiary red clay developmentis similar to that of the present Badain Jaran desert. To reconstruct the long-term East-Asia monsoonhistory from the celebrating eolian red clay-loess deposits, the ratios of CBD-extractable Fe2O3to totalFe2O3 concentrations in the Lintai red clay-loess sequence, the proxy indicator for the summer mon-soon changes, were measured. The Lingtai Fe2 O3 ratio record indicates that the East-Asia summermonsoon has experienced a non-linear evolution over the past seven million years. The strongest EastAsia summer monsoon may occur between 4.1 and 4.8 Ma, which may be causally related to the rela-tively small ice volume and high global temperature during the early Pliocene.