Abstract
Structural inheritance describes the influence of pre-existing structures on younger structures. During continental rifting, inheritance can affect rift-related structures at various scales. For example, lithospheric-scale weaknesses can localize or segment rifts, while pre-existing crustal fabrics and faults can experience reactivation or interact with the far-field stress or strain, affecting the orientations, distributions, and growth of faults in cover sequences from basin to outcrop scales. An example of the multi-scale expressions and mechanisms of structural inheritance is evident in the Gippsland Basin. This basin formed during Jurassic-Cretaceous rifting between Australia and Antarctica and is now located at the eastern end of Australia's southern margin. Faults in the eastern, offshore part of the Gippsland Basin strike mainly E-W, consistent with the inferred N-S regional paleoextension. In contrast, faults in the western, onshore part strike ENE-WSW. Here, folded and faulted basement rocks have a NNE-SSW structural grain which may have locally re-oriented the far-field strain, resulting in rift-related faults oblique to both the inferred paleoextension direction and basement structures. Following rifting, the Gippsland Basin experienced regional uplift and inversion. Pervasive NNW-SSE trending joints, conjugate N-S to NNE-SSW and NW-SE strike-slip faults, and reactivated NNE-SSW striking basement faults in outcrop all indicate NNW-SSE maximum horizontal shortening during this phase. Regional-scale expressions of this shortening include basin uplift and reverse reactivation of ENE-WSW striking rift-related faults. The different types and kinematics of shortening-related structures observed at outcrop and regional scales highlight that structural inheritance is scale-dependent. Advancing our understanding of structural inheritance requires examining its mechanisms and scale dependency across tectonic settings. Insights from such studies can help recognize the influence of pre-existing structures where direct reactivation is not evident, identify the geometric and genetic relationships between deep and shallow structures, and understand fault behavior near pre-existing structures. This knowledge is important for inferring fluid transport pathways in the crust and assessing seismic hazard.
Invited presentation