S-wave seismic data are unaffected by natural gas trapped in strata, making them a
valuable tool to study evaporite facies comparing to P-wave data. S-wave seismic data
were utilized to construct an isochronous framework and analyze evaporite facies by
seismic sedimentology methods in the Quaternary biogenic gas-bearing Taidong area,
Sanhu Depression, Qaidam Basin, NW China, with calibration from wireline logs, geochemical
evidences, and modern analogs. Techniques of phase rotation, frequency decomposition,
R (Red), G (Green), B (Blue) fusion, and stratal slices were integrated to reconstruct
seismic geomorphological features. Linear and sub-circular morphologies, resembling
those observed in modern saline pans such as Lake Chad, were identified. Observations
from Upper Pleistocene outcrops of anhydrite and halite at Yanshan (east of the Taidong
area), along with lithological and paleo-environmental records from boreholes SG-5,
SG-1, and SG-1b (northwest of the Taidong area), support the seismic findings. The
slices generated from the S-wave seismic data indicate a progressive increase in the
occurrence of evaporite features from the K2 standard zone upwards. The vertical occurrence
of evaporite facies in the Taidong area increases, which coincides with the contemporary
regional and global arid paleo-environmental changes. The interpretation of Quaternary
stratal slices reveals a transition from a freshwater lake to brackish, saline, and
finally, a dry saline pan, overlaid by silt. This analysis provides valuable insights
into locating evaporites as cap rocks for biogenic gas accumulation and also into
mining the evaporite mineral resources in shallow layers of the Taidong area.
