Interfering sub-parallel rift grabens: insights from combined analogue and numerical models
Abstract
Extensional structures such as rift systems and grabens have been widely studied through analogue and numerical modelling, since these techniques started to be used by the oil industry to understand structural traps. We have performed a study using both analogue and numerical modelling that was inspired by the initial stage of development of the Neoproterozoic Parecis Basin, located in the center-west of Brazil, where two sub-parallel grabens are observed - Pimenta Bueno and Colorado. These structures seem to have been formed as the result of the reactivation of inherited basement structures. The purpose of this work was to use both analogue and numerical models to understand how the distance between these two anisotropies affects the geometric evolution of the two interfering forming grabens. The analogue experiments were performed with a sandbox apparatus that included two basal velocity discontinuities (VDs) attached to the moving walls. We systematically varied the distance between the two VDs for an extension of 3 cm. The 2D numerical experiments were developed with a similar initial configuration as in the analogue models, using upper crustal rheological parameters and two seeds (weak zones) as a means of nucleating extension at different considered intervening distances. Preliminary results show that when the VDs are closer, the resulting interference structures consist of a single wider graben with two depocenters and a middle second-order horst. When the distance between the VDs is increased, two distinct grabens are rather preferably formed, laterally bounding a middle horst that separates both these structures and endures more or less deformation, depending on the considered shorter or greater distance between the grabens, respectively. In the analogue experiments, the grabens showed an asymmetric geometry, which was not observed in the numerical runs, in which the deformation was seemingly more symmetrically distributed. Upgrading of new numerical models is presently ongoing to test a wider range of (geometrical, rheological) parameters.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T33F0416O
- Keywords:
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- 8105 Continental margins: divergent;
- TECTONOPHYSICS;
- 8109 Continental tectonics: extensional;
- TECTONOPHYSICS;
- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS;
- 8159 Rheology: crust and lithosphere;
- TECTONOPHYSICS