Late Burdigalian to early Messinian environmental and climatic evolution of the central paleo Adriatic domain from the shallow water sedimentary record (Bolognano Fm, Eastern Majella, Central Apennines)

During the Miocene, Earth's climate evolved from a prolonged phase of global warmth into a colder mode. In the same time interval, the Mediterranean area was affected by important geodynamic and oceanographic changes evolving from a wide open basin to small enclosed basins. This work aims identifying the controlling factors of the paleoadriatic basin evolution, in one of the enclosed basins of the Mediterranean analyzing the ramp succession in the eastern Majella (Central Apennines). The stratigraphic architecture of the investigated succession shows an initial regressive phase, testified by the deposition of middle to outer ramp deposits followed by a long lasting transgressive phase between late Burdigalian to Tortonian during which hemipelagic to outer ramp sediments were deposited. At the end of the Tortonian a drop in sea level caused an erosional unconformity, reworking and deposition of inner ramp sediments. The succession evolves upward to alternating bioclastic and fine laminated organic rich deposits showing a deepening upward trend interrupted by a major sea level drop linked to the Messinian Salinity Crisis. The lower Messinian portion of the succession shows high TOC values, Al and redox-sensitive trace elements correlated with laminated sediments interpreted as deposited under anoxic conditions. The lithological alternation (bioclastic and laminated deposits) of the early Messinian interval, was likely produced in an astronomically-controlled humid and arid climate fluctuation. The increase of the terrigenous fraction coincides with an increase of Al concentrations that is associated with terrestrial organic matter. The increasing terrigenous input in the sediments is related to approaching Adriatic foredeeps during the early Messinian, promoting the progressive decay of environmental conditions in the basin.