Analogue Modelling of a Domino-Style System: Influence of Pre-extension Salt During Extension and Compression
摘要
The structural style of deformation, both under extension and compression, is highly influenced by the thickness and distribution of the salt and the overburden. This research investigates, using analogue modelling, how a pre-rift salt layer influences the evolution of basins developed in a basement domino-style system and how inherited extensional structures evolve and constrain the subsequent basin inversion. The experimental apparatus comprises five fault blocks in which a worm-screw motor transmits deformation. A constant velocity of 4.6 mm/h was applied to the blocks that rotate counterclockwise during extension and clockwise during inversion. While extension was characterized by 10 cm of extension, compression was applied up to total basin inversion. The experimental program was constituted of five sets of thick-skinned extensional models in which salt and overburden thicknesses were changed to test the influence of each parameter in the development of salt-bearing rift basins and their associated salt structures. Afterwards, the same extensional models were performed, but after extension, they were inverted to understand the role of extensional inheritances and the evolution of the salt structures. The results showed that the development of salt structures is highly controlled by the thickness distribution of both the salt and the overburden after extension. While models with a thin salt layer develop crestal collapse grabens at the overburden, thick salt results in an effective decoupling between basement and overburden resulting in the development of outcropping salt structures. On the other hand, total basin inversion is influenced not only by inherited faults and salt structures but also by the salt thickness distribution, thus conditioning the style of deformation. Models with a thin and continuous salt layer result in total inversion of extensional structures, while models with well-developed salt structures preserve inherited extensional structures. Finally, the research performed with the analogue models allowed us to characterize better how inherited salt structures (i.e., welds and diapirs) reactivate and rejuvenate during compression.