关键词: 塔里木盆地, 塔河地区, 寒武纪, 碳酸盐岩, 沉积演化, 地层沉积正演模拟

Abstract: Comprehensively using cores, logging and seismic data, the types, internal structure, and sedimentary facies distribution of the Cambrian depositional system in Tahe area are investigated by qualitative analysis and stratigraphic forward modelling. The formation and evolution process of the Cambrian carbonate platforms in this study area is also reconstructed. Based on quantitatively characterizing the distribution laws of sedimentary facies in each period, in combination with modelling parameter analysis, this paper explores the formation and evolution mechanism of the platforms in Tahe area. The results show that Tahe area experienced five evolution stages during the Cambrian. A continental shelf developed in the Early Cambrian Yuertusi Formation period; a carbonate ramp developed in the Early Cambrian Xiaoerbulake Formation period (dominated by the development of low-energy sediments in middle-outer ramp in the early stage, and that of high-energy mound-shoal complexes in middle ramp in the late stage); a weakly rimmed carbonate platform developed in the Early Cambrian Wusonggeer Formation period, with aggrading and prograding microbial reef-shoal complexes developed in one stage at the platform margin; large-scale prograding strongly-rimmed carbonate platform developed in the Middle to Late Cambrian, with prograding microbial reef-shoal complexes developed in three stages at the platform margin. On the whole, the depositional system is characterized by multiple types, multiple stages and complex stacking patterns, which is the result of the coupling of physical accommodation space (controlled by global sea-level change and differential subsidence), carbonate sediments (types, quantity, accumulation capacity and location of sediments), and hydrodynamic transport. Moreover, migration tendency of the Cambrian carbonate platforms is also driven by the subsidence resulted from east-west differentiation and initial topography of east and west areas. The combined action of sediment types, hydrodynamic transport and high frequency sea-level oscillation leads to the formation of carbonate ramp and staged differentiation in Xiaoerbulake Formation period. The interactions between physical accommodation and ecological accommodation are crucial controlling factors of the transition from carbonate ramp to weakly-rimmed carbonate platform during the Early Cambrian, as well as the growth of large-scale prograding rimmed platform in the Middle to Late Cambrian.

Key words: Tarim Basin, Tahe area, Cambrian, carbonates, depositional evolution, stratigraphic forward modelling