Late Miocene paleoenvironmental changes in North Africa and the Mediterranean recorded by geochemical proxies (Monte Gibliscemi section, Sicily)

The astronomically tuned marls of the Monte Gibliscemi section, Sicily, constitute an archive to trace the late Miocene palaeoenvironmental conditions (~ 9.7-7.0 Ma) in North Africa. Here we have utilised carbonate content and Al-normalised geochemical proxies to trace changes in terrigenous source area and bottom-water ventilation. The terrigenous input into the section is dominated by North African river systems draining into the Eastern Mediterranean. The proxy parameters indicate that the palaeoenvironmental conditions in North Africa were humid from 9.5 Ma onward with high fluvial input to the Mediterranean. Increases in the Si/Al and Mg/Al ratios occurred from 8.4 to 8.2 Ma and from 8.05 to 7.75 Ma, with maximum values similar to those of Messinian diatomites. These peaks indicate conditions of enhanced biosiliceous productivity and the presence of authigenic clay formation. Sluggish water circulation in the Mediterranean during those times is inferred from the Mn/Al and V/Al behaviour. Late Miocene changes of the Betic (southern Spain) and Rifian (Morocco) Mediterranean-Atlantic gateways are interpreted as the driving force for the changes in water circulation and the transgression associated with the opening of the Rifian corridor is interpreted to occur at 7.8 Ma.