青藏高原循化、临夏和贵德盆地新近纪沉积充填速率演化及其对构造隆升的响应

    Cenozoic sedimentation rate of Xunhua, Linxia and Guide basins responding to the uplift of the Tibetan Plateau

    • 摘要: 通过对青藏高原东北部循化盆地、临夏盆地和贵德盆地沉积相和沉积充填速率演化的对比分析,提出研究区新生代4个构造隆升阶段。①渐新世晚期—中新世早期(25~20Ma),3个盆地沉积相和沉积速率的变化表明青藏高原新生代向北东的增生作用在渐新世已抵达西秦岭北缘地区,同时,22Ma拉脊山强烈隆升,区域上整体地势差异不显著。②中新世中期(17~13Ma),随着高原东北缘盆山耦合的相互作用,湖盆进一步扩张,14Ma左右积石山的隆起及西秦岭、拉脊山的持续隆升,使得研究区转变为盆地周缘型。③中新世晚期(11~6Ma),8Ma左右沉积相的转变、沉积速率的增大及不整合面的存在,都说明高原在该段时间内存在强烈的构造隆升活动,裂变径迹热年代学证据反映的构造隆升与沉积响应也是一致的。④上新世(5Ma以来),沉积速率继续增大,区域上地势差异增强,湖盆逐步萎缩消亡。

       

      Abstract: Based on sedimentary facies and sedimentation rate analysis of Neogene sedimentary basins in Xunhua, Linxia and Guide in northeastern Tibetan Plateau, the authors divided the sedimentary evolution responding to tectonic uplift into four processes: ①In the Late Oligocene-Early Miocene period (25-20Ma), the changes of sedimentary facies and sedimentation rate in the three basins showed that the NE-trending accretion arrived in the north margin of West Qingling in Oligocene. At 22Ma, the uplift of Laji Mountain was strong. ② During Middle Miocene (17-13Ma), with the interaction of the basin-mountain coupling of the northeastern plateau, the lake expanded further. The growth of the Jishi Mountain and the continued uplift of the West Qingling and the Laji Mountain at 13Ma turned the study area into basin-margin type. ③ In Late Miocene (11-6Ma), the transition of sedimentary facies, the acceleration of sedimentation rate and the existence of unconformity indicated that the plateau was subjected to strong tectonic uplift activities at this time. Besides, the tectonic uplift reflected by fission track thermochronologic evidence was also consistent with sedimentary response. ④ In Pliocene (5Ma-), the sedimentation rate continued to increase, the differences of terrain were enhanced, and the lakes died out gradually.

       

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