Abstract
What process triggered the Mediterranean Sea restriction remains debated since the discovery of the Messinian Salinity Crisis (MSC). Recent hypotheses infer that the MSC initiated after the closure of the Atlantic-Mediterranean Betic and Rifean corridors, being modulated through restriction at the Gibraltar Strait. These hypotheses however, do not integrate contemporaneous speciation patterns of the faunal exchange between Iberia and Africa and several geological features like the evaporite distribution. Exchange of terrestrial biota occurred before, during and after the MSC, and speciation models support an exchange path across the East Alborán basin (EAB) located a few hundreds of km east of the Gibraltar Strait. Yet, a structure explaining jointly geological and biological observations has remained undiscovered. We present new seismic data showing the velocity structure of a well-differentiated 14–17-km thick volcanic arc in the EAB. Isostatic considerations support that the arc-crust buoyancy created an archipelago leading to a filter bridge across the EAB. Sub-aerial erosional unconformities and onlap relationships support that the arc was active between ~10–6 Ma. Progressive arc build-up leading to an archipelago and its later subsidence can explain the extended exchange of terrestrial biota between Iberia and Africa (~7–3 Ma), and agrees with patterns of biota speciation and terrestrial fossil distribution before the MSC (10–6.2 Ma). In this scenario, the West Alboran Basin (WAB) could then be the long-postulated open-marine refuge for the Mediterranean taxa that repopulated the Mediterranean after the MSC, connected to the deep restricted Mediterranean basin through a sill at the Alboran volcanic arc archipelago.
Highlights
Models for the onset of the MSC1–3 infer that uplift closed the Betic and Rifian marine gateways[4,5] at ~7.6 Ma6 and ~6.7–6.2 Ma3 respectively (Fig. 1), which triggered evaporite deposition in the Mediterranean starting at 5.97 Ma7
During part of the Tortonian (10–7.2 Ma) when great part of southern Iberia was below sea level[17], taxa speciation patterns indicate that SE Iberia was an important center of diversification before the MSC13 requiring local emerged biological hotspots (Fig. 1)
The large terrestrial vertebrate fossil record supports that faunal exchange between Africa and Iberia occurred before the MSC17–19
Summary
Models for the onset of the MSC1–3 infer that uplift (perhaps related to lithospheric delamination) closed the Betic and Rifian marine gateways[4,5] at ~7.6 Ma6 and ~6.7–6.2 Ma3 respectively (Fig. 1), which triggered evaporite deposition in the Mediterranean starting at 5.97 Ma7. The first Late Miocene large vertebrate exchange between Africa and Iberia is dated at ~6.2 Ma, or slightly before for Hippopotamous/Hexaprotodon crusafonti[19], being recorded in the eastern basins of the Betics and Rif[17,18,19] (Fig. 1). In this scenario, the Gibraltar Strait is interpreted as an effective physical barrier to genetic exchange during the Messinian time[12], with controversial evidence of terrestrial biota exchange occurring only during the MSC12–16. The top of the Messinian unit is deeply incised near the Gibraltar Strait in the WAB, recent work suggests that the canyons at the Gibraltar Strait may be older than Zanclean, developed during the MSC and under submarine conditions[9]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
