Did the Mediterranean sea dry out during the Miocene? A reassessment of the evaporite evidence from DSDP legs 13 and 42A cores

The idea that the Mediterranean Sea dried out completely during the late Miocene (Messinian, 5-6 Ma) is now widely accepted. This idea, first published in 1972 (Hsu 1972a; Hsu 1972b) grew out of the interpretation by Deep Sea Drilling Project (DSDP) scientists that the evaporites recovered from beneath the floor of the Mediterranean by drilling on DSDP Legs 13 (1970) and 42A (1975) were of shallow-water origin. Since that time, there have been a number of advances in understanding of evaporite depositional processes, and with this in mind, we have reexamined the evidence provided by the DSDP evaporite cores. We show that the case for deposition of the Miocene evaporites of the sub-Mediterranean under shallow-water conditions is based on interpretations that are either equivocal or incorrect. Several features of these evaporites used by the DSDP workers as evidence of shallow-water conditions are more compatible with deposition under deep-water (below wave base) conditions, and others can only be considered as of uncertain origin. In addition, coring has sampled only the upper few tens of meters of the evaporites, a factor that seriously limits any interpretation of the origin of the deposit as a whole. In view of these findings, we suggest that the question of the origin of the Miocene evaporites beneath the floor of the Mediterranean Sea be reexamined by the geologic and oceanographic communities.