Analysis of the Dawanqi salt anticline in the Kuqa fold-and-thrust belt and implications for the growth of compressional salt anticlines

Abstract

Well-preserved salt structures in the Kuqa fold-and-thrust belt provide an ideal opportunity to quantitatively study the evolution of compressional salt anticlines. The Dawanqi salt anticline in the northwestern part of the Kuqa fold-and-thrust belt is closely associated with hydrocarbon accumulation. Its structural evolution plays a key role in controlling the timing and distribution of sub-salt faults and reservoirs. Sequential restoration is an effective method for revealing the structural evolution of the Dawanqi salt anticline. In this study, we constructed a 3D model of the structural evolution of the Dawanqi salt anticline and undertook sequential restoration and a quantitative analysis of the morphological changes. The results show that the Dawanqi salt anticline evolved in three stages: slow growth during the Miocene, rapid growth and lateral widening of the salt dome, and significant foreland-ward migration during the early Pliocene, followed by vertical uplift at a fixed location during the late Pliocene. If the regional compressive stress remains unchanged or increases in magnitude over time, the structure may eventually breach the surface and evolve into a salt diapir. We obtained a strong positive correlation between the shortening rate and vertical growth rate of the anticline, while hinge migration is highly sensitive to the thickness of the overlying load. We propose an alternative piercement model for the potential future evolution of the salt anticline, in which sustained vertical growth under compressional stress drives the transition from salt anticline to diapir. This model presents a distinctive halokinetic growth-strata pattern compared with previous models and complements existing thrust and erosional piercement models proposed for compressional settings.