Offshore evidence of polyphase erosion in the Valencia Basin (Northwestern Mediterranean): Scenario for the Messinian Salinity Crisis

The Messinian Salinity Crisis at the end of the Miocene strongly affected the physiography of the Mediterranean margins, and in particular that of the Valencia Basin and its margins. The Valencia Basin, which is an aborted Tertiary rift related to the opening of the oceanic Provençal Basin, shows evidence of two major Messinian erosion surfaces — a Basal Erosion Surface (BES) and a Top Erosion Surface (TES) — bracketing the Messinian evaporite succession; the basin's margins show only a single erosion surface, here termed the Margins Erosion Surface (MES). In examining the geometrical relationships of these erosion surfaces with the deep basin facies deposited in the abyssal Provençal Basin during the Messinian Salinity Crisis, we have been able to establish a chronology for the Messinian in the Valencia Basin. Briefly, the Basal Erosion Surface extends the Margins Erosion Surface into the Central Valencia Basin and records an early and important sea-level fall at the beginning of the Messinian Salinity Crisis. The Miocene basin series were incised by canyons, while the exposed margins underwent substantial subaerial erosion. The basin's detrital products linked to this basal erosion grade laterally into the massive Messinian Salt layer of the Provençal Basin. The overlying Upper Evaporites unit appears to be widely transgressive beyond the edge of the Messinian Salt and onlaps the Basal Erosion Surface in the Valencia Basin. This disposition suggests a progressive sea-level rise during the deposition of the Upper Evaporites, possibly due to the rapid accumulation of thousands of metres of shallow-water evaporite facies in the Provençal Basin. The Top Erosion Surface at the top of the Upper Evaporites shows a network of incisions, and we suggest that this final erosion was linked to the Lago-Mare event recorded elsewhere in the Mediterranean at the end of the Messinian Salinity Crisis.