Figure 1. (a) Location of the Songliao Basin (SLB) in northeastern China. (b) Tectonic units in the SLB - I, II, III, IV, V, VI - represent  the SLB six first-order tectonic units: central depression zone, west slope zone, southeast uplift zone, north plunge zone, northeast uplift zone, and southwest uplift zone. (c) Simplified stratigraphy of the Upper Jurassic to Cretaceous in the SLB. The lake-level curve is from Gao et al. (1994).