Imprint of Messinian Salinity Crisis events on the Spanish Atlantic margin

One of the outstanding research questions regarding the Mediterranean's Messinian Salinity Crisis (MSC) is whether mechanisms that generated Messinian events also have an expression outside the basin as a result of changes in ocean circulation, tectonics or isostasy. To assess this, a high resolution astronomically calibrated age model for the entire Messinian of the Guadalquivir Basin, on the Atlantic margin of Spain, has been constructed. Cyclic changes in the elemental composition of the Huelva-1 borehole, visualized through XRF, were tuned to astronomical target curves. In some intervals, the tuning was hampered as a consequence of the borehole's proximity to the basin margin, resulting in disturbances of the cyclic record; nevertheless three distinct correlations with Mediterranean events were observed. Firstly, the onset of cyclicity within the borehole, at 7.16 Ma, is synchronous with the first sign of Mediterranean-Atlantic gateway restriction; this may be related to uplift of the Betic corridor. Secondly, the increase in sedimentation rate starting around 5.55 Ma coincides with the end of the acme of the Messinian Salinity Crisis. Lastly, for the first time a lithological expression has been found outside the Mediterranean which may have been generated by the same mechanism that terminated the Messinian Salinity Crisis. This level corresponds with the onset of a pronounced and extensive glauconite layer, indicating a sudden and significant decrease in sedimentation rate. Two causative mechanisms, or a combination of them, are proposed for the interbasinal correlations during the MSC. The first is based on tectonic events in the Betic region that influence sedimentation within the Guadalquivir Basin while altering the Atlantic-Mediterranean connection. The second explains the increase in sedimentation rate at 5.55 Ma as a consequence of local basin infill and the condensation at 5.33 Ma by sediment winnowing as a result of increased current strength with the opening, or deepening, of the Gibraltar Strait.