Sequence Stratigraphic Succession of the Cretaceous Clastic Rock System in Zhangye City: Sedimentological Response to the Cretaceous Uplift of the Qilian Mountains

Key words: 
• uplift of the Qilian Mountains /
• Cretaceous /
• sequence stratigraphy /
• response of sedimentary

Abstract: In the Early Cretaceous, controlled by the uplift of Qilianshan Mountains and the climate, a set of clastic rocks developed in the continental basins before Qilianshan Mountains. The Cretaceous strata develope and outcrop well in Zhangye city of Gansu province, which are made up of particular sedimentary facies successions under the concept framework of the unconventional system tracts, and are very important to the study of Qilianshan Mountains uplift and its impacts on the environment of Asia. The Lower Cretaceous strata of Yinggezui cross-section include the Chijinpu Formation, the Xiagou Formation, and the Zhougou Formation, which can be divided into 10 third-order sequences (S.1-S.10). Generally speaking, the LAST is composed of alluvial fan facies and fluvial facies coarse clastic rocks, while lacustrine facies fine clastic rocks constitute the HAST. The eolian sandstones in the middle-low Chijinpu Formation and the Xiagou Formation, are the products of "foehn effect" caused by Qilianshan Mountains uplift, which are meaningful to the study of the Qilianshan Mountains uplift. In the Early Cretaceous, the climate experienced a series of changes, from semi-arid climate to arid climate to wet climate, which reflects that the Qilianshan Mountains uplift in this period can be charactered by four different stages, i.e. the early episodic uplift stage, the middle fast uplift stage, and the last isostatic uplift stage. In the transition period of Early to Late Cretaceous, the Qilianshan Mountains uplifted fast and intensively, which caused the study area turned into a denuded zone, so the Upper Cretaceous strata have not developed. The Lower Cretaceous sequences of Yinggezui cross-section, not only are the material records of Qilianshan Mountains uplift, but also can provide an important record to the reconstruction of the pattern of the atmospheric circle in the East Asia.