Basement characteristics of Wan’an Basin in southwestern South China sea based on temporal and spatial evolution

In the evolution of time and space, on the basis of magnetic anomaly reduction-to-the-pole (RTP) and regional field separation data processing techniques, as well as the restriction of geological and drilling data, the basement lithology of Wan’an Basin in the South China Sea has been preliminarily explored in this paper. The result reveals a tripartite basement lithology mainly composed of intermediate-acid granitic intrusive and metamorphic sedimentary rocks, with a small amount of Mesozoic sedimentary rocks. The lithology and structure of basement recorded the tectonic environment of Wan’an Basin in different periods. During the late Jurassic to Cretaceous, based on temporal and spatial evolution, the subduction of the Paleo-Pacific Plate to the East Asian continent resulted in the generation of a large number of intermediate-acid granitoids, which emplaced into the Jurassic and more ancient sedimentary or metamorphic rocks. From the early Paleocene to late Oligocene, the differential uplift caused by lithospheric plate activity resulted in the formation of mountainous paleotopography, leading to the denudation of sedimentary and metamorphic rocks in high structural positions and the preservation of sedimentary rocks at low structural levels. From early Miocene to Quaternary, the Wan’an basin entered a large-scale regional subsidence stage and formed strata more than ten kilometers thick.