## 6 Conclusions  
The S-wave data are unaffected by biogenic gas, and proved to be valuable for constructing the first isochronous framework in the Quaternary biogenic gas-bearing Taidong area in the Sanhu Depression of the Qaidam Basin. By calibrating the S-wave acoustic wireline log, the framework of standard zones interpreted from the seismic data was successfully tied to geological ages.  
Seismic sedimentological techniques--such as phase rotation, frequency decomposition, RGB fusing, and striatal slicing--are proved effective in mapping facies at different depths from K2 upward across the Taidong area. By integrating regional climate data, water salinity information, lithologies of outcrop and borehole samples, and modern analogs, seismic sedimentology slices were comprehensively interpretated to be sedimentary facies based on their geomorphological and frequency characteristics.  
The sub-circular polygons recognized on the striatal slices generated by seismic sedimentology were interpreted as evaporite facies, i.e., brackish lake, brine saline lake, and dry saline pans for the first time in Taidong area. The evaporite facies in Taidong area occur from K2 (1.51 Ma BP) and increase in frequency thereafter. The evaporite intensity generally increased in response to regional rises in aridity and water salinity. Spatial variation of different evaporite environments is identified, with fresh water lakes in the west, brack  
Figure 14: Stratal distribution with a gentle declination (**a**) and evaporites in the strata (**b**) at Upper Pleistocene Yanshan outcrop east of Taidong area, Sanhu Depression, Qaidam Basin. The red square in subfigure (**a**) show the location of subfigure (**b**). The pink and green arrow in subfigure (**b**) point out the location of anhydrite and halite.  
ish lakes in the middle, and brine saline lakes and/or dry saline pans covered by silt in the east.  
The lateral distribution and vertical evolution of evaporite facies in the Taidong area provide critical insights into the hydrological changes related to regional climates during the Quaternary period. The outcomes of this study not only assist in identifying optimal sealing rocks for biogenic gas accumulation but also provide valuable locations for the exploration and extraction of evaporite resources in the region.  
Conceptualization, G.L. and Z.X.; methodology, G.L., Z.X., H.Z. and X.Z.; validation, Z.X. and Y.S.; formal analysis, J.L. and C.L.; investigation, G.L., Z.X., J.L., C.L., J.T. and L.J.; resources, G.L., Z.X., J.L., C.L. and J.T.; writing--original draft preparation, Z.X. and G.L.; writing--review and editing, G.L., H.Z., Y.S. and X.Z.; funding acquisition, Z.X. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Science and Technology Major Project of China, grant number 2024 ZD1003307; PetroChina Science and Technology Projects, grant numbers 2022-N/G-47808, 2023-N/G-67014, and 101023h0001b93001; International Cooperation Projects between PetroChina Research Institute of Petroleum Exploration & Development and The University of Texas at Austin, grant numbers 15 HT10500000010 and 19 HTY5000008.  
Not applicable.  
**Data Availability Statement:** Embargo on data due to commercial restrictions.  
Authors [PERSON], [PERSON] and [PERSON] were employed by PetroChina Qinghai Oilfield Company. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.