Abstract

Cores drilled through the carbonate cap of Niue, a mid-oceanic carbonate platform in the South Pacific, contain an unusually well resolved stratigraphic section of the latest Miocene at 35 to 140 m depth below sea level. Intensely leached and chalky intervals associated with pronounced 18O and 13C depletions mark the position of dissolution unconformities representing eight episodes of eustatic falls that outstripped the local rate of subsidence. We demonstrate, on the basis of Sr isotope chronostratigraphy, that these eustatic changes are correlative with the Messinian salinity crisis events in the Mediterranean. Sea-level changes of about 10 m amplitude commenced at 6.14 Ma and culminated in a large sea-level fall that reached at least 30 m at 5.26 Ma, corresponding to the Miocene-Pliocene boundary. Evaluation of the sea-level history reported here and the contemporaneous Mediterranean events supports the model of coupling between tectonic and eustatic factors that caused the onset and demise of the salinity crisis. The available evidence suggests that during Messinian time, glacio-eustatic falls and rises are likely to have modulated the connection between the Atlantic and the Mediterranean and influenced the evaporite deposition, and may have contributed significantly to the final phase of isolation and desiccation of the Mediterranean and its subsequent refilling during the Zan-clean deluge.

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