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New constraints on the closure of the Betic Seaway and the western Mediterranean palaeoclimate during the Messinian Salinity Crisis from the Campo Coy Basin (SE Spain)

Abstract:

The Campo Coy Basin (SE Spain) exposes >1 km of sedimentary succession with a variety of rocks including a thick evaporitic succession previously associated with the Messinian time. These evaporites were supposedly deposited in a restricted Mediterranean-Atlantic seaway connecting the Lorca and Guadix-Baza basins, although no chronological or geochemical data existed. Here we use palaeomagnetism together with vertebrate and foraminifera biostratigraphy to constrain the age of the Campo Coy succession between <9 Ma and 4.7 Ma. We use geochemistry (δ34S, δ18O and 87Sr/86Sr values) of the gypsum deposits to evaluate their marine or continental origin. In addition, we describe the underlying and overlying lithostratigraphic units to reconstruct the palaeogeographic evolution of this region. Our results show that the sediments were deposited in a continental environment, indicating that the Betic Seaway was already closed in this region during the late Tortonian and that the neighbouring marine basins of Guadix-Baza and Lorca were disconnected during that time. The δ34S, δ18O and 87Sr/86Sr values of the gypsum indicate recycling from the Triassic sulphates. Sedimentary facies of the evaporites point to an environment dominated by a saline lake with continental sabkha episodes developed during the driest periods. Well-defined and laterally continuous evaporitic cyclicity suggests an orbital forcing and high sedimentation rates preceding the Messinian Salinity Crisis (MSC). Alluvial deposits are contemporaneous with the MSC indicating a dry continental environment in this region during the Mediterranean restriction. Overlaying lacustrine carbonates are rich in small vertebrate fauna including African species that migrated to Europe during the MSC. These carbonates have low δ18O and δ13C values characteristic for freshwater input in an open lake just after the Zanclean flood, suggesting that a wet climate followed the MSC.