Evidence of Mediterranean water in the Atlantic margin during the Messinian

At present, the Mediterranean is connected to the Atlantic Ocean through the narrow Strait of Gibraltar (only 13 km wide). The latter, in the late Miocene, most probably did not exist, and the Mediterranean – Atlantic water exchange took place through the Betic (Southern Spain) and Rifian (Northern Morocco) corridors. Studying the evolution of such gateways is fundamental when investigating the extraordinary event known as the Messinian Salinity Crisis (5.96 – 5.33 Ma), when the connection between the Mediterranean Sea and Atlantic Ocean significantly diminished or even ceased. In this work we present a new high resolution geochemical (XRF and stable isotope) record of the Tortonian – Messinian interval of the Montemayor-1 and Huelva-1 cores located in the Betic corridor, current Guadalquivir Basin. Our new data enabled in the first place the high-resolution tuning of the 7.4 – 5.8 Ma time interval, and consequently to precisely date environmental changes and relate them to Mediterranean and global events.

Our results indicate that, at 7.17 Ma and in concomitance with a shallowing of the basin, the bottom water residence time, temperature and salinity increased. These changes have been associated with a reduction of the Mediterranean Outflow Water reaching the Guadalquivir Basin as a consequence of the restriction of the last strand of the Betic corridor connecting the Mediterranean and the Atlantic. This hypothesis is in line with the analogous changes observed in several Mediterranean Sea locations, where from 7.17 Ma a reduced Mediterranean – Atlantic connection is visible. Nonetheless, even if such reduction of the connection was feasible, the same changes in isotope record and analogous cyclicity observed both in the Guadalquivir and Alboran Basin record imply that the Mediterranean signal was still reaching the Betic gateway to some degree. In addition, the significant offset present between our and North Atlantic oxygen stable isotope records entails how the signal in the Guadalquivir basin could not have been purely Atlantic. Consequently, we conclude that a significant Mediterranean signal was still present in the Betic corridor during the Messinian.