Antarctic glacio-eustatic contributions to late Miocene Mediterranean desiccation and reflooding.

Christian Ohneiser,Robert M Deconto,Paolo Stocchi,Fabio Florindo,David Pollard,Andrew P Roberts

doi:10.1038/ncomms9765

Abstract

The Messinian Salinity Crisis (MSC) was a marked late Neogene oceanographic event during which the Mediterranean Sea evaporated. Its causes remain unresolved, with tectonic restrictions to the Atlantic Ocean or glacio-eustatic restriction of flow during sea-level lowstands, or a mixture of the two mechanisms, being proposed. Here we present the first direct geological evidence of Antarctic ice-sheet (AIS) expansion at the MSC onset and use a δ18O record to model relative sea-level changes. Antarctic sedimentary successions indicate AIS expansion at 6 Ma coincident with major MSC desiccation; relative sea-level modelling indicates a prolonged ∼50 m lowstand at the Strait of Gibraltar, which resulted from AIS expansion and local evaporation of sea water in concert with evaporite precipitation that caused lithospheric deformation. Our results reconcile MSC events and demonstrate that desiccation and refilling were timed by the interplay between glacio-eustatic sea-level variations, glacial isostatic adjustment and mantle deformation in response to changing water and evaporite loads.

Highlights

The Messinian Salinity Crisis (MSC) was a marked late Neogene oceanographic event during which the Mediterranean Sea evaporated
The modern configuration of the Mediterranean region resulted from relative motions of the African, Arabian and Eurasian plates[11], and early arguments focused on tectonic restriction between the Mediterranean Sea and the Atlantic Ocean[1]
We reviewed 60 Southern Ocean and Antarctic margin sedimentary successions to reconstruct Antarctic ice-sheet (AIS) evolution during the MSC

Summary

Introduction

The Messinian Salinity Crisis (MSC) was a marked late Neogene oceanographic event during which the Mediterranean Sea evaporated. Antarctic sedimentary successions indicate AIS expansion at 6 Ma coincident with major MSC desiccation; relative sea-level modelling indicates a prolonged B50 m lowstand at the Strait of Gibraltar, which resulted from AIS expansion and local evaporation of sea water in concert with evaporite precipitation that caused lithospheric deformation. Our results reconcile MSC events and demonstrate that desiccation and refilling were timed by the interplay between glacio-eustatic sea-level variations, glacial isostatic adjustment and mantle deformation in response to changing water and evaporite loads. We combine geological evidence from the Southern Ocean and Antarctic margin with GIA simulations to show how Antarctic ice-sheet (AIS) evolution, combined with the isostatic response of Gibraltar Strait to water evaporation and salt precipitation, initiated and terminated the MSC

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Results

Conclusion