The 95 km-long Lapstone Structural Complex is a segmented structural association consisting of north-trending faults and monoclines in the western Sydney Basin between the Cumberland Basin to the east and lower Blue Mountains to the west. It has developed in a compressional regime. At depth, the Lapstone Structural Complex is most likely a deeply penetrating, west-dipping thrust fault that is seismogenic in the brittle middle crust. This structure has propagated upwards into the overlying Sydney Basin in the top ∼3 km of the crust and formed a suite of distinct fault and fault–monocline structures, including: (a) in the north, inferred imbricate faults at depth in the lower Sydney Basin dying out upwards into a well-displayed, major east-facing monocline (central limb has an overall consistent <20°E dip); (b) in the middle part of the complex, an east-facing monocline with dips increasing from west to east formed as a fault-propagation fold; and (c) as found in the south, a sin