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Título

IMPACT OF RHEOLOGY ON STRUCTURAL RIFT ARCHITECTURE - INSIGHTS FROM ANALOG MODELING

Texto do resumo

The structural framework of rift basins plays a crucial role in developing conduits, barriers, and traps, directly impacting fluid migration and the economic potential of sedimentary basins. In this context, the present study investigated the influence of rheology on the evolution of the structural framework of such basins under extensional tectonics. Physical experiments simulated extensional tectonics with the formation of orthogonal rifts. The experiments were conducted using various materials with different rheological properties: quartz sand (QS), glass microspheres (GM), corundum sand (CS), multilayer with silicone and quartz sand (M1), and multilayer with silicone, sand quartz, glass microsphere and corundum sand (M2). The experimental observations revealed the formation of a characteristic orthogonal rift framework represented by synthetic and antithetic normal faults alongside internal faults, mainly oriented at a high angle with the extension direction. In the initial deformation increment (d = 0.5 cm), there was a greater number of faults and fractures in the experiment M2 (177), followed by CS (89), M1 (69), GM (44), and QS (12). CS was the only experiment with internal faults at the initial increment (d = 0.5 cm). As small segments of faults coalesced, fewer and longer faults formed in subsequent increments (d = 1.5 and 2.5 cm), resulting in a decline in fractures and fault numbers. Subsurface analysis of cross-sections revealed a faulted eastern margin and synthetic faults on the western margin in all experiments, with the north represented perpendicular to the extension direction. Antithetic internal faults were identified in experiments QS, CS, M1, and M2. Listric faults were significant in experiments with a ductile basal layer (M1 and M2). The rift border faults exhibited different dip angles in each model. The CS model showed a higher angle (~73°) and GM a smaller angle (~60°), while M2 showed the greatest range of dip angles (between 49° and 74°). Cross-sections revealed the formation of isolated tilted blocks bounded by faults, with bedding dip angles reaching up to 28°. The rheology of each experiment influenced the depth of the basin depocenter. The M1 model had the shallowest depocenter, the CS model had the deepest, and the M2, GM, and QS models exhibited intermediate depocenter depths. Basin width was smaller in the CS experiment, followed by M2, QS, and GM, and larger in M1. The basin area was smaller in the brittle-ductile experiments (M1 and M2) and larger in the brittle experiments, especially in CS and GM. In general, the basement was shallower in M1 and deeper in CS. The rheological behavior significantly influenced structure development, with corundum sand developing more structures than quartz sand and glass microspheres due to its more brittle nature. The rheological contrast between layers in multilayer experiments accentuated structure development during extension, and the rheology of the ductile basal layer influenced the formation and geometry of new faults during extension. In conclusion, rheology plays a significant role in the evolution of the structural architecture of sedimentary basins, influencing the formation, geometry, and distribution of structures during extension. Understanding these nuanced dynamics is imperative for refining exploration targets and enhancing resource exploration efficiency.

Palavras Chave

rift basin; rheology; physical modeling