The role of velocity and thermal structure in the construction of asymmetric rifted margins

Abstract

The development of asymmetric conjugate rifted margins has been explained by processes such as rift migration and sequential faulting (Brune et al., 2014; Ranero & Pérez-Gussinyé, 2010), and by the effects of lithospheric strength and strain-softening (Svartman Dias et al., 2015; Huismans & Beaumont, 2003) during rifting. Briefly, rift migration consists of sequential faulting of the upper crust that moves oceanward and is associated with lower crustal flow. Nonetheless, there are other thermal and dynamic parameters that might either facilitate or hinder the construction of an asymmetric margin, also depending on the coupling degree between the continental and mantle lithosphere. Since there are a considerable number of asymmetric margins around the world, mostly associated to petroleum fields, and more recently emerging as green hydrogen reservoirs, there is a need to understand which and how much the parameters influence the construction of asymmetric margins during the rifting phase. For that reason, this work aims to contribute to the understanding of this subject through thermo-mechanical numerical models. Velocity and thermal structure were the principal factors considered in the context of a decoupled lithosphere. Our models show that rift velocity is the principal parameter that controls width and margin asymmetry, being followed by thermal structure. High rift velocities (~5 cm/year) developed wide and asymmetric margins, while a thick upper crust is shown to be crucial to develop the distal domain in the late stages of rifting. When both parameters are combined, the generated margins can reach about 360 km long. In some scenarios, the margin width is up to 550 km, with a distal domain which exceeds 130 km long.Funded by Petrobras Project 2022/00157-6. Brune, S. et al. Rift migration explains continental margin asymmetry and crustal hyper-extension. Nature communications, v. 5, n. 1, p. 4014, 2014.Huismans, R. S. & Beaumont, C. Symmetric and asymmetric lithospheric extension: Relative effects of frictional-plastic and viscous strain softening. Journal of Geophysical Research: Solid Earth, v. 108, n. B10, 2003.Ranero, C. R. & Pérez-Gussinyé, M. Sequential faulting explains the asymmetry and extension discrepancy of conjugate margins. Nature, v. 468, n. 7321, p. 294-299, 2010.Svartman Dias, A. E. et al. Conjugate rifted margins width and asymmetry: The interplay between lithospheric strength and thermomechanical processes. Journal of Geophysical Research: Solid Earth, v. 120, n. 12, p. 8672-8700, 2015.