Early Pliocene transgressive coastal lags (Bajo Segura Basin, Spain) : a marker of the flooding after the Messinian salinity crisis

Abstract

The Messinian salinity crisis is recorded on the northern margin of the Bajo Segura Basin by lacustrine and fluvial deposits coeval to the evaporites that precipitated in the basin’s central areas. These syn-evaporitic Messinian deposits are bounded at the top by an erosional surface caused by a fall in base level (end-Messinian unconformity) on which an early Pliocene sequence is located. The latter begins with a coastal lag, consisting of oncoliths and carbonate clasts intensely bored and encrusted by lithobionts, that records the installation of beach environments at the beginning of the Pliocene transgression. A succession of pelagic marls rich in planktonic and benthic foraminifers lies on this basal lag and indicates the complete marine flooding of the basin and the definitive conclusion of the salinity crisis.