Integrating Restorations, Microstructural Analyses, and Forward Finite Element Modeling to Understand Deformation in Contractional Salt Systems

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Description

Salt diapirism exerts a high-order influence on the dynamic and structural evolution of many low-grade deformational provinces such as foreland fold-thrust belts and passive margin basins. Most diapirs are interpreted to result from reactive behavior, wherein cover sequence extension leads to diapirism, or passive behavior, wherein the diapir remains exposed at the surface as sediment is deposited on the flanks. However, the interpretation that most salt diapirs are either reactive or passive implies that salt is mostly responding to structural evolution, rather than driving it, which may be incompatible with a number of observations, including: (1) most large diapirs are located in the more transitional and contractional parts of salt systems where cover sequence extension is presumably more limited, (2) a pronounced geometric transition from stock to canopy in many diapirs and the existence of large allochthonous salt sheets emplaced over long lateral distances (kms) likely indicate salt pressure-driven catastrophic emplacement, and (3) observed deformation of thick wall rock sequences and megaflaps that are difficult to explain in a reactive or passive mechanical framework. Active diapiric mechanisms are generally not invoked because it is believed that salt is too weak to deform thick overburden and wall rock sequences. Although many outcrop studies of diapir-wall rock zones yield limited observation of discrete deformation, we propose that much of the strain in these systems is accommodated by pervasive plastic yielding rather than brittle failure. Here, we propose to integrate kinematic restoration and forward finite element modeling with microstructural analyses of two well-established contractional salt basins to test the hypotheses that: (H1) salt diapirism, and particularly active and passive diapirim, can drive substantial and pervasive overburden and wall rock deformation through thick (>2 km) cover sequences, and (H2) deformation in these systems is primarily accommodated by pervasive plastic strain that can be microstructurally characterized. If correct, these ideas may yield a step change in how we understand and characterize strain accommodation in contractional sedimentary systems.
StatusActive
Effective start/end date8/1/198/31/23

Funding

  • American Chemical Society: $110,000.00

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