北天山四棵树河流域渐新世-中新世古高程重建

The Tianshan has experienced rapid uplift since the late Cenozoic, and it has had a significant impact on the tectonic deformation process and climate change of the Tianshan in the late Cenozoic. Due to the lack of quantitative data constraints, it is difficult to accurately describe the uplift amplitude and process of this geological event. In recent years, the method based on stable isotopes to reconstruct the paleo-altitude has developed rapidly, which provides a possibility to solve this problem. In this study, pedogenic carbonate minerals which were not altered by later diagenesis were selected in the Sikeshu River drainage basin, North Tianshan. Reconstructing the temperature of autogenic carbonate precipitation by Clumped Isotope (T△47), and restore oxygen isotope value of surface water. Using atmospheric thermodynamics formula and the empirical formula of the oxygen isotope value of surface water and the elevation in the North Tianshan, we can reconstruct the paleo-altitude of Sikeshu drainage basin during Oligocene – Miocene, and accurate description of the uplift range and process of the Oligocene-Miocene in the North Tianshan. The implementation of the project will provide support for explaining the causes of climate change in the late Cenozoic in Tianshan area and understanding the coupled evolution of tectonic uplift and weathering denudation.

天山造山带晚新生代以来发生了快速隆升，该地质事件对天山晚新生代的构造变形过程和气候变化都产生了明显的影响。由于一直缺乏定量数据的约束，致使无法精细刻画这一重要地质事件的隆升幅度和隆升过程。近年来，基于稳定同位素重建古高度的方法快速发展，为解决这一难题提供了可能。由此，本申请拟选择北天山四棵树河流域内未被后期成岩作用改造的古土壤碳酸盐，利用团簇同位素测温的方法重建自生碳酸盐形成时的温度，恢复地层沉积时的地表水氧同位素值；结合北天山现今的地表水氧同位素值-高程的经验关系式和热动力学模型，估算四棵树河流域在渐新世-中新世的平均古高程，精确刻画北天山渐新世-中新世的隆升幅度和隆升过程。项目的实施将为解释天山地区晚新生代的气候变化原因，理解构造抬升和风化剥蚀耦合演化提供支撑。

以北天山四棵树河流域内中生代以来的地层为研究对象，利用稳定同位素古高程计的方法，结合碎屑锆石和低温热年代学技术，探讨了北天山四棵树河流域新生代地层的物质来源，反演了北天山晚侏罗世以来的盆-山格局演变过程。同时，结合前人在天山地区的低温热年代学数据，总结了天山中生代以来的隆升-剥露历史。认为东天山四期隆升过程分别为：晚侏罗世至早白垩世（152Ma~106Ma）、古新世初期（65Ma）、始新世中期（45Ma）和渐新世末（25Ma）；西天山四个阶段的隆升过程可划分为：三叠纪末-早侏罗世（220Ma~180Ma）、侏罗纪中期（170~140Ma）、白垩纪中期（110Ma~80Ma）和晚新生代（24Ma以来）。这表明天山山脉自中生代以来具有明显的差异性隆升的特征。