## 3 Seismic Observations and Interpretation  
One seismic reflection profile that clearly imaged the igneous sills and structure of the surrounding rocks was selected as a case study. Seismic interpretation of the host rock and the igneous sills in the central part of the Tarim Basin generally follows earlier published works [18;22;30]. Diagnostic seismic facies of sills in the sedimentary basin include high amplitude, abrupt termination, and distinctive geometry [17;22]. The seismic interpretation was also confirmed by drilling holes such as the Adong 1 well. Since the seismic profile in the vertical direction is on a time scale, time-depth conversion is needed to obtain a realistic cross-section of the sill and the peripheral faults. The velocity of the strata in the time-depth conversion is expressed as 0.5\(t\) + 1.98 km/s, where \(t\) is the two-way travel time in seconds (s), according to the Adong 1 well. According to seismic reflection characterization and geological evolution, the host rock surrounding the sills is divided into eight structural units (Figure 3), including Triassic strata (T), Upper Permian strata (P\({}_{3}\)), Middle Permian strata (P\({}_{2}\)), Lower Permian strata (P\({}_{1}\)), Upper Devonian to Carboniferous strata (D\({}_{3}\)-C), Silurian to Middle Devonian strata (S-D\({}_{1-2}\)), Upper Ordovician strata (O\({}_{3}\)), and Upper Cambrian to Middle Devonian strata  
Figure 2: Location and structural units of the Tarim Basin after [18]. Bathymetric data of the inlet and the Tarim Basin are derived from GEBCO. (E-O1-2). The seismic profile shows that the host layers are generally flat and dip slightly northwestward at \(<\)1\({}^{\circ}\) (Figure 3a). Sill 1 (sill 13 in [18]) is a typical saucer-shaped sill consisting of a flat inner sill, inclined sheets, and flat outer sills. Seismic discontinuities and breaks can be clearly observed within the Silurian to Carboniferous strata close to sill 1 terminations (Figure 3a). As the strata across these discontinuities shift, these breaks can be interpreted as the cutoff points for a fault (Figure 3b). The faults link closely to the termination of the sill and have a near-vertical dip angle. The strata bound by the fault over sill 1 were uplifted. Based on the spatial relationship between the uplift and the sill, it can be concluded that the uplift was induced by the emplacement of the underlying sill 1. Fault displacement diminished within the Upper Devonian and Carboniferous strata and was consumed by fault-propagation folding of the overlying strata. The seismic interpretation also shows that the structural relief of the uplift over the mafic sill gradually vanished within the Middle Permian strata. The stratigraphic layers thinning toward the uplift area are outlined and defined as growth strata (Figure 3b) as these layers are deposited synchronously with the uplifting of preexisting strata, i.e., the growth of peripheral faults. The stratigraphic units above this section are defined as post-growth strata, whereas the layers below this section are the pre-growth strata. It can also be concluded that the actual emplacement depth of the mafic sills is the current depth minus the thickness of the Middle Permian and overlying strata, which is 2-3 km. Figure 3: (**a**) Semi-interpreted and (**b**) interpreted seismic profiles showing sill intrusions and peripheral faults in the central part of the Tarium Basin (for location, see Figure 2) after [18; 22]. T, P3, P2, P1, D3-C, S-D1-2, O3, E-O1-2 are the strata symbols of structural units. T—Triassic strata; P3—Upper Permian strata; P2—Middle Permian strata; P1—Lower Permian strata; D3-C—Upper Devonian to Carboniferous strata; S-D1-2—Silurian to Middle Devonian strata; O3—Upper Ordovician strata; E-O1-2—Upper Cambrian to Middle Devonian strata. The seismic profile in the yellow box is used for time–depth conversion. The growth strata depicted here represent the strata deposited during the uplift.