Inheritance without reactivation: Insights from crustal-scale analogue experiments

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Anindita Samsu , Alexander Crudden, Nicolas E. Molnar, Roberto F. Weinberg


During rifting, pre-existing basement weaknesses can affect new faults in cover rocks by a mechanism that does not appear to involve reactivation. This subtle form of inheritance can significantly impact fault network architecture above laterally variable basement domains with geomechanical anisotropies. Here we use multi-layer, brittle-ductile, crustal-scale analogue experiments to study the influence of lower crustal anisotropies on fault patterns in the overlying upper crust during a single phase of orthogonal rifting. The experiments were designed to test whether lower crustal anisotropies, oriented 45° to the extension direction, can lead to the formation of rift faults that are oblique to both the imposed extension direction and lower crustal anisotropies. This work builds on previous field-based studies of the onshore Gippsland Basin (southeast Australia). Here, basin-scale (>1 km long) NE-SW to ENE-WSW trending faults, which formed during Early Cretaceous N-S or NNE-SSW rifting, are prevalent above two levels of anisotropic basement with NNE-SSW to NE-SW structural trends. Our experiments show that a pervasive, vertically layered, mm-wide lower crustal anisotropy creates “extension-oblique” rift faults in the overlying basin within the upper crust. We interpret this to arise when local strike-slip kinematics along the interfaces of mechanically contrasting materials in the lower crust combine with the regional imposed orthogonal extension, creating a transtensional regime. Our findings highlight that the geometry of lower crustal zones of different strengths interacts with rift kinematics, impacting the orientation, kinematics and spacing of new faults.



Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure


Structural inheritance, Australia, rifting, extensional tectonics, faults, analogue modelling, Gippsland Basin, rift basins


Published: 2019-10-24 17:15

Last Updated: 2021-01-08 14:30

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CC BY Attribution 4.0 International

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