Abstract

The detailed kinematics of natural salt walls remain elusive because such structures are typically poorly exposed at outcrop, only partly exposed in mine workings, and diapiric salt is typically poorly reflective in seismic data. We use three-dimensional seismic and borehole data from offshore Brazil to investigate how structural styles vary along strike within a spectacularly well-imaged salt wall. Deformed layering in the salt allows us to map complex, seismic-scale structures in the wall; within the wall’s relatively simple external shape is a range of previously undocumented structural styles produced by: (1) initial upwelling and formation of a wall-parallel anticline due to regional extension and differential overburden load, (2) breaching of the anticline, Rayleigh-Taylor overturn, and emplacement of an intrasalt allochthonous sheet driven by a density inversion, and (3) internal thrusting of the mature diapir caused by regional compression. This study is arguably the first detailed documentation of the internal structure and kinematics of a natural salt wall, highlighting the presence of abruptly varying intrasalt structural styles. The structures identified and the inferred kinematics suggest that, given specific mechanical stratigraphy, density-driven overturn within salt diapirs can play a key role in their growth.

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