青藏高原中北部沱沱河盆地晚始新世—早中新世古高度变化及其构造指示意义——基于碳酸盐碳同位素记录

青藏高原古高度研究可以为理解高原的构造隆升过程和机制等提供重要的信息，但是由于受到研究材料和条件的限制，相较于高原南部而言高原中北部的古高度研究相对滞后。鉴于此，笔者等在羌塘地体东北部可可西里盆地的一个次级盆地—沱沱河盆地中选取了一个剖面（命名为沱沱河剖面），基于适于盆地的古高度计经验公式重建了沱沱河盆地晚始新世到早中新世的古高度演化历史。结果表明，沱沱河盆地的构造挤压隆升可以分为3个阶段：第一阶段为~37. 0~30. 5 Ma，海拔高度从2397 m变化到2940 m，为构造隆升活动的活跃阶段；第二阶段为30. 5~26. 0 Ma，海拔高度从2940 m变化到3100 m，为构造隆升活动的相对减弱阶段；第三阶段为26. 0~19. 7 Ma，海拔高度从3100 m变化到约3150 m，为构造隆升活动的相对静止阶段。综合沱沱河剖面的古高度和构造变形结果，同时结合紧邻盆地周边的古高度、地壳缩短等地质证据，文章认为沱沱河盆地在新生代中晚期经历了明显的两阶段隆升过程，分别是晚始新世到早中新世和中中新世（~16. 0 Ma）到现在，其隆升的机制分别可以用上地壳缩短变形和“地幔对流去根”或者“下地壳流”或者“岩浆底侵”等理论加以解释。

Late Eocene—Early Miocene paleoelevation changes and its tectonic implications in the Tuotuo River Basin, central—northern Qinghai—Xizang(Tibetan) Plateau——based on carbonate carbon isotope records

The paleoelevation change can provide important information for understanding the tectonic uplift processes and mechanisms of the Qinghai—Xizang(Tibetan) Plateau. Meanwhile, the study of paleoelevation in the central—northern parts of the Qinghai—Xizang(Tibetan) Plateau lags behind compared with the southern part of the plateau due to the limitations of research materials and conditions. Based on this, we selected a profile (named the Tuotuo River section) in the Tuotuo River Basin, a sub- basin of the Hoh Xil Basin, in the northeast of the Qiangtang Terrane, to reconstruct the paleoelevation change of this section.Methods: Analyzing carbonate carbon isotopes and then applying empirical formulas of paleoelevation, which is suitable to the Tuotuo River Basin, to reconstruct the late Eocene to Early Miocene paleoelevation of the Tuotuo River Section.Results:The tectonic uplift of the Tuotuo River Basin can be divided into three stages. The first stage is ~37.0~30.5 Ma, and the altitude changes from 2397 m to 2940 m, which is the active stage of tectonic uplift; the second stage is 30.5~26.0 Ma, and the altitude changes from 2940 m to 3100 m, which is relative weaker of the tectonic uplift; the third stage is 26.0~19.7 Ma, and the altitude changes from 3100 m to about 3150 m, which is a relatively static stage of tectonic uplift activity.Conclusions: The Tuotuo River Basin experienced an obvious two- stage uplift process during the Cenozoic, from the late Eocene to the early Miocene and the middle Miocene (~16.0 Ma) to the present. The upper crust shortening and deformation and “mantle convective removal” or “lower crustal flow” or “magmatic inflation” could be applied to explain the two phases uplift, respectively.