Irregular relief of the surface of the salt deposits of the Red Sea

What is it about?

Giant bodies of rock salt have been found offshore many parts of the Atlantic coasts and Gulf of Mexico. They are difficult to investigate because they are deep, old and now highly deformed by movements of the rock salt. The Red Sea, in contrast, has salt deposits reaching kilometres in thickness and are covered by only a thin veneer of sediments. This article looks into the present topography of the surface of those deposits and finds that it's relief is irregular, with no characteristic wavelength or spacing of diapirs (places where the rock salt has risen). High-resolution seismic data also show alternations between areas where the top of the salt was eroded and areas where it was not, suggesting that it had some relief at the end of the Miocene when the salt stopped depositing.

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Photo by Sifan Liu on Unsplash

Photo by Sifan Liu on Unsplash

Why is it important?

The results confirm a growing body of evidence that Rayleigh-Taylor models for salt diapirism, in which the salt and overburden are treated as simple fluids, are inappropriate for these "salt giants". Instead, diapirism occurs with a range of length-scales. Diapirism occurred in part because of denser anhydrite deposited between diapirs, causing an internal density inversion. The irregular spacings of diapirs may relate to the varied spacings of faults (both active and inactive) beneath the salt. The Red Sea likely almost completely dried out at the end of the Miocene because we find a prominent unconformity throughout much of the Red Sea in high-resolution seismic data. However, some areas lacking an unconformity are underlain by layered evaporites, which we interpret as areas that were depressed. Hence, in detail the basin likely contained small lakes of highly saline water.

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