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Abstract:
Extensional tectonics in continental settings usually results in lithospheric stretching of narrow (e.g. Upper Rhine Graben), as well as wide regions (e.g. Basin and Range). Some rift systems bear evidence of a transition between the two styles: the West Antarctica Rift System (WARS) have likely progressed from diffuse to focused rifting (Cretaceous - Middle Neogene). The system currently covers a length of 1000 km, at the boundary between East and West Antarctica and is composed of four main basins (Victoria Land Basin, Central Trough, Northern Basin and Eastern Basin). The deformation pattern and available geological reconstructions suggest that, at least for some part of the rifting, the extension occurred concurrently in multiple sections.Inheritance of prior structural, thermal, and rheological heterogeneities is likely a controlling factor in this evolution [1]. Consequently, with the goal of identifying the most likely initial conditions, we designed a series of 2-D numerical models, analysing the effect of variations in the temperature field, rheology, accumulated strain, distribution of extensional pulses on the basins’ geometry. To this aim, we used the open source Underworld2 [2] and BGR-02 and ACRUP2 profiles [3], as 2-D analogue of the WARS structures in the Southern Ross Sea.The results show that the models most consistent with the observations are those that include inherited weakness zones at the cratonic boundary. Early onset of focused extension often occurs, with high sensitivity to the pattern of inherited weakening.[1] Perron et al. (2021). DOI:10.1051/bsgf/2020038[2] Mansour et al. (2020). DOI:10.21105/joss.01797[3] Trey et al. (1999). DOI:10.1016/S0040-1951(98)00155-3
