--> Abstract: Evolution of the Mediterranean Water Body During the Messinian Salinity Crisis: The Record from Marginal Basins on Sicily, by Robert W. H. Butler; #90039 (2005)

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Evolution of the Mediterranean Water Body During the Messinian Salinity Crisis: The Record from Marginal Basins on Sicily

Robert W. H. Butler
University of Leeds, Leeds, United Kingdom

The Messinian Salinity Crisis in the Mediterreanean resulted from plate reorganizations in western Tethys, with resulting regional climate change within a framework of eustatic sealevel variation. On Sicily, evaporite accumulation was modulated through a bathymetrically linked array of variably confined minibasins developed across an active thrust belt. They contain two distinct groups of evaporites (one regressive, one transgressive), separated by a major sequence boundary with associated palaeovalleys and emergent surfaces. Combined sequence stratigraphic, facies, astro-magnetostratigraphy and Sr isotopic studies reveal the rates of base level change and the nature of the Mediterranean water body through time. Relative sea level fall, manifest by the “first cycle” evaporates (including halite a K-salts) took at least 700ka, with base-level fall of c. 300m and concomitantly diachronous evaporite accumulation through the minibasin array. Aridity is indicated by the absence of clastic input to the basins. Each minibasin was linked to world ocean, as indicated by precession-cyclic base-level variations, faunal assesmblages and Sr isotopic composition. Regional low-stand (and Mediterranean-wide isolation from world ocean) happened between 6.0 and 5.5 Ma, followed by increased run-off. Transgression was much more rapid (200-300 ka), returning base-level to above that which recorded world ocean conditions during the regression. Yet the transgressive water body was not fully linked to world ocean (distinct Sr signature). The start of the Pliocene (5.3 Ma) is manifest by only a minor rise in base-level on Sicily (although it represents a dramatic change in the biology and chemistry of the water body), indicating that the Mediterranean was largely filled prior to a renewed connection to world ocean.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005