Paleoclimate, provenance, and tectonic setting of the First Member of the Paleogene Shahejie Formation in the southern slope of Huanghekou Sag

The major and trace elements in clastic sedimentary rocks record abundant geochemical information, and can be used to reconstruct paleoclimate, provenance, and tectonic setting. Geochemical analysis of inorganic element in clastic sedimentary rocks of the first member of the Paleogene Shahejie Formation (E₁s¹) in the southern slope of Huanghekou Sag was conducted, and the paleoclimate, provenance and tectonic setting of the Es¹ were discussed. Th/Sc-Zr/Sc diagram and index of compositional variability (ICV) indicate that the source of the Es¹ in the study area was the first deposition unit after weathering of the parent rocks, and the compositional maturity was relatively high. The corrected chemical index of alteration (CIA_corr) and plagioclase index of alteration (PIA) indicate that the source of the Es¹ underwent moderate weathering, and the sedimentary period was warm and humid paleoclimatic conditions. Major, trace, and rare earth elements show that the provenance of Es¹ is characterized by upper crust derived felsic igneous rocks, featuring obvious negative Eu anomaly, and the materials of provenance was mainly derived from Precambrian granitoids and some intermediate-basic mixture sources. The tectonic background of the provenance area was active continental margin and continental island arc. The complex tectonic background was related to the subduction of the Western Pacific plate to the East Asian continent.