Geodynamic modelling of salt-bearing rifted margins: from minibasin- to margin-scale salt tectonics across different margin types

Abstract

The largest and majority of salt basins form along rifted continental margins during the latest stages of rifting and prior to continental breakup. We use 2D thermo-mechanical finite-element modelling of lithospheric extension to investigate the interplay between rifted margin architecture, late syn-rift salt deposition, and post-rift salt tectonics across different types of continental margins. We evaluate the: 1) interplay between syn-rift extension, salt deposition and post-rift salt tectonics, 2) influence of salt basin architecture on salt flow, 3) distribution of salt-related structural domains, and 4) contrasting salt tectonic styles for different margin types. Narrow margins form partially-isolated salt sub-basins with prominent base-salt relief, limited translation but significant diapirism and minibasin development. Wide margins form wide salt basins with subtle base-salt relief, pronounced seaward salt expulsion and overburden translation, which result in updip extension with development of post-rift normal faults and rollovers, mid-margin translation and downdip diapir shortening. All margins develop a distal salt nappe that varies in width and complexity. The contrasting styles of diapirism and minibasin geometries as well as basin-scale salt deformation between different margin types are controlled by margin width, base-salt relief, salt thickness and the relative rate of progradation. The results are comparable to several examples of salt-bearing rifted margins worldwide, from minibasin- to margin-scale, and improve our understanding of their dynamics and structural variability.