###### Abstract  
In order to clarify the provenance of the 1 st member of the Zhongjiangou formation in Wudun sag, Dunhuang basin, the structural attributes, weathering and sedimentary characteristics of the provenance area were analyzed by means of element geochemistry, so as to determine the differences of sediment sources in different well areas. The results show that the higher the Al\({}_{2}\)O\({}_{3}\) and K\({}_{2}\)O contents, the higher the enrichment of large ion lithophile elements and high field strength elements, while the iron and magnesium elements are relatively deficient, and there are characteristics of medium degree differentiation of light and heavy rare earth elements in Well XC1 and Well D2. The lower the Al\({}_{2}\)O\({}_{3}\) content and the higher the SiO\({}_{2}\) content, a loss of large ion lithophile elements and high field strength elements are observed, while the ferrophilic magnesium elements show serious loss, as shown in the characteristics of the high degree of differentiation of light and heavy rare earth elements in Well D1. In the UCC-normalized element spidergrams, the trend of Well XC1 and Well D2 is similar, which is different from that of well D1, indicating that the sediments of Well XC1 and Well D2 come from the same provenance area, while the sediment of Well D1 comes from a different provenance area. The provenance area of Well XC1 and Well D2 shows strong tectonic activity and strong weathering, while the provenance area of well D1 exhibits relatively weak tectonic activity and weathering. Combined with previous research results, Wudun sag is mainly characterized by a faulted lacustrine basin controlled by the southern boundary fault in the Jurassic layer. Therefore, the sediments of Well XC1 and Well D2 mainly come from the southern Sanweishan uplift provenance area, with strong tectonic activity; the sediments of Well D1 mainly come from the northern Beishan provenance area, with relatively weak tectonic activity. Wudun sag; element geochemistry; provenance; tectonic background; weathering degree 2022150620220215062022021506202  
However, the degree of exploration of Wudun sag is low. At present, there are only three exploration wells with data and seventeen 2D poor\(-\)quality seismic lines, and there are few Jurassic outcrops around Wudun sag. In view of the provenance conditions of the J\({}_{2}\)z\({}_{1}\) Formation, our predecessors used drilling and logging data, combined with the development degree of coarse clastic sediments and heavy mineral analysis, and considered that the northern Beishan provenance area and the Southern Sanweishan uplift provenance area have material source contributions to the sediments. This area mainly develops distal braided river delta deposits, dominated by relatively fine\(-\)grained sediments in the northern provenance system, and proximal fan delta deposits, dominated by relatively coarse\(-\)grained sediments, in the southern provenance system [3,4]. These studies generally suggest that the Zhongjiangou Formation in Wudun sag is developed in a sedimentary environment, with multiple provenance supplies, and the provenance may come from Beishan and Sanweishan. However, these results are limited by drilling and seismic data and cannot accurately reflect the provenance attribution of different well areas. It is necessary to use other methods to further determine the provenance attribution in different well areas, so as to implement the possible provenance conditions. Clastic sedimentary rocks are an important part of the earth's material cycle. Their chemical composition characteristics contain information closely related to the evolution of the sedimentary environment. These chemical compositions are mainly controlled by the material composition, weathering and climatic conditions, sedimentary transportation process, diagenesis and other factors of the provenance area [5].