青藏高原东北部新近纪古流向与物源分布对隆升的响应

摘要

Based on paleocurrent and provenance analysis of Neogene sedimentary basins in the Northeastern Qinghai-Tibetan Plateau,sedimentary evolution responsing to tectonic uplift can be divided into four processes:① During Early Miocene (23 ～ 19.5 Ma):paleocurrent and provenance analysis of the Ayakkum,Qaidam,Delingha and Jiuquan Basin show that the East Kunlun and Altyn area had uplifted into land.The evidence from the Xunhua,Guide and Linxia Basin indicate that the Western Qinling and Lajishan area was also main uplift area.At the same time,thermochronological data of the Altyn area contrasts well with sedimentary record.Overall,the terrain was not outstanding.② During early Middle Miocene (17.5～15 Ma),the sedimentary basins expanded,the Xorkol Basin appeared,and data from these basins reflect the mountain ridge,including the Eastern Kunlun,Altyn,Qilian,Western Qinling and Lijishan,uplifted significantly.Regional differential uplift caused expansion of these basins.③ In Late Miocene (10 ～ 7 Ma),the granularity and sedimentary rate of these basins increased abruptly,indicated a rapid uplift of the surrounding mountains,consistent with thermochronological evidence of the Altyn,Qilian and Western Qinling.However,paleocurrent and provenance data of the Guide,Xunhua and Linxia Basin show a sensible multi-source,and paleocurrent in the Xigou area turned to NWW,inferring uplift of the Jishishan Mountain.④ During Pliocene (since 5.3 Ma onwards),paleocurrent directions in the research area remained unchanged,but granularity and sedimentary rate continued to increase,The uplift of Altyn and Qilian Mountain accelerated rapidly.Paleocurrent of the northern Guide Basin was SSW,indicating the Lajishan Mountain was regional source area.Overall,the terrain differences strengthened in this area,and the sedimentary basins shrank and withered away gradually.%通过对青藏高原东北部11个新近纪沉积盆地的沉积相演化、古流向和物源演变的详细对比研究,揭示了研究区新近纪4次沉积演变与构造隆升的响应.①中新世早期(23～19.5Ma):阿牙克库木湖、柴达木、德令哈和酒泉盆地的古流向和物源分析表明东昆仑和阿尔金已经抬升成剥蚀区.循化、贵德和临夏等盆地物源和古流向指示西秦岭和拉脊山也已成为隆起区.区域上整体地势差异不显著.②中新世早中期(17.5～15Ma):区域湖盆面积扩大,阿牙克库木湖、索尔库里、柴达木和酒泉盆地的资料反映东昆仑、阿尔金和祁连山已经全面隆升,贵德循化、临夏盆地的古流向反映为盆地周缘型,指示西秦岭和拉脊山明显抬升,区域差异隆升造成盆地凹陷扩张进入湖泛期.③中新世中晚期(10～7Ma):阿牙克库木湖、索尔库里、柴达木和酒泉盆地沉积物的粒径和沉积速率增大,与热年代学证据一致,揭示出阿尔金山和祁连山进一步快速隆升.贵德、循化和临夏盆地古流向和物源反映为显著的多源性,除西秦岭和拉脊山外,位于循化和临夏两盆地间的积石山也开始隆起.④上新世(5.3Ma以来):索尔库里、柴达木和酒泉盆地古流向没有明显变化,沉积速率和粒径继续增大,阿尔金和祁连山加速隆升为高海拔地貌.贵德盆地主物源区是拉脊山.区域上,地势差异加强,湖盆被肢解后逐步萎缩消亡.