ABSTRACT Recent geological surveys and drilling of scientific exploration well QK‐1 in the Qiangtang Basin have confirmed that the Middle Jurassic Xiali Formation comprised a thick evaporite sedimentary sequence with regional continuous distribution crucial for sealing hydrocarbon resources. However, the formation of these evaporites is still debated, with some attributing their development solely to climate while others emphasise the control of basin tectonics. Here, field outcrop investigations combined with sedimentological, geochemical and clay mineral content analyses of the evaporite‐bearing sediments from well QK‐1 were conducted. Geochemical paleoclimate indicators, including clay mineral content, Sr/Cu, Sr/Ba and other proxy data derived from fine‐grained interlayers in evaporite sedimentary sequences, suggest a climatic shift from semi‐humid to prevalent arid conditions, associated with a progressive increase in paleosalinity during deposition of the Xiali Formation. Provenance analysis of the Xiali Formation is interpreted based on bivariate diagrams (K 2 O/Na 2 O‐SiO 2 , TiO 2 ‐Al 2 O 3 , TiO 2 ‐Zr), along with elevated REE signatures and (La/Yb) n , which reveal that the detrital material was primarily derived from felsic and intermediate igneous rocks within active continental margin and continental island‐arc tectonic settings. Increased tectonic subduction during the Middle Jurassic led to the development of a semi‐enclosed, tidal flat‐lagoon depositional environment in the northern Qiangtang Depression. This indicates that the coupled interplay between enhanced arid paleoclimate and a semi‐enclosed basin configuration jointly controlled the formation of the thick evaporite succession in the Xiali Formation. These findings provide new geological evidence for elucidating evaporite depositional mechanisms and their crucial role in sealing and preservation of hydrocarbon resources in the Qiangtang Basin.
Pan et al. (Mon,) studied this question.