陇中盆地及周边地区主夷平面演化与高原隆升

Evolution of the main planation surfaces in the Longzhong Basin and its surrounding areas and its significance for the uplift of the Tibetan Plateau

陇中盆地及周边地区是青藏高原向北东方向扩展的最前缘部位,其地貌演化过程的研究对于深入理解高原的隆升与扩展过程具有重要意义。鉴于夷平面在探讨高原隆升年代、幅度和过程方面的可靠性,首先总结陇中盆地及周边地区夷平面相关研究的前期成果,并结合最新年代数据,确定了不同区域主夷平面的发育和解体年代;再利用古河道拟合等方法定量评估了相关夷平面的隆升量;最后探讨了主夷平面的性质及其隆升过程。研究发现,陇中盆地及周边的地区的高海拔低起伏地貌面是被抬高的先存夷平面;不同区域主夷平面的发育与解体时间整体同步,它们自晚渐新世开始发育,并于晚中新世8~6 Ma左右解体;模拟结果表明,美武高原主夷平面自晚中新世以来相对陇中盆地隆升了约1400~1600 m,并且早更新世以来的隆升速率明显大于晚中新世-早更新世时期。

The Longzhong Basin is the front of the Tibetan Plateau expanding to the northeastern.The study of its landscape evolution plays a significance role for understanding the process and mechanism of the Tibetan Pla⁃teau uplift.In this paper,we date several different main planation surfaces in the Longzhong Basin and its sur⁃rounding area through in-depth summary of lots of previous researches and our new data.Moreover,we quanti⁃tatively evaluate the uplift of the main planation surfaces using reconstruction of relict landscape channel pro⁃files.Our results suggest that these low-relief,high-elevation surfaces in the Longzhong Basin and its surround⁃ing area are identified as elevated,preexisting low-relief planation surfaces,not in situ formation of low-relief landscape patches.The main planation surfaces have been developed synchronously.They began to develop since the Late Oligocene,and disintegrated at 8~6 Ma.The simulation results show that the Meiwu planation surface has been uplifted about 1400~1600 m relative to the Longzhong Basin since the Late Miocene.And the uplifting rate since Early Pleistocene is significantly higher than that during the interval of Late Miocene-Early Pleistocene.