Abstract

The Messinian Stage in the Mediterranean region is known mainly because of a major evaporitic event whose causes and global implications are still under discussion. Correlations between basinal evaporite-bearing series and marginal carbonate platforms allow for improvement of the classical depositional models, especially concerning the eustatic control of theenvironmental changes in the Mediterranean. These changes were controlled by the interplay of aperiodic and periodic factors: (1) tectonics, related to the relative motions of the African and Eurasian plates and resultant linear increase in basin restriction; (2) sea- level fluctuations that alternately aggravated the restriction or allowed marine replenishment, and (3) climatic fluctuations that controlled the level of the Mediterranean during stages of isolation. The Messinian sedimentary succession reflects a typical sequence of progressive isolation: marine marls → laminites → transitional deposits → evaporites → lacustrine deposits. The structure of the carbonate platforms shows that during early Messinian time, the sea-level regime changed from a highstand (TB3.2 cycle) that was responsible for widespread extension of the carbonate platforms to the classical "Messinian regression" that induced final isolation of the Mediterranean water body and onset of the so-called "salinity crises." The first stage of the crisis was characterized by a Mediterranean lowstand that resulted in erosion of former platforms and deposition of the lower evaporites. During the next stage, sea level rose (TB3.3 cycle) high enough to temporarily replenish the basin (cyclic upper evaporites, with development of stromatolite-rich deposits). Finally, the uppermost Messinian freshwater to brackish lacustrine deposits reflect both the cessation of sea-water input (maximum tectonic isolation, low sea level) and freshwater input related to increasing runoff.

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