Toward an Astrochronology-Based Age-Model for a Messinian Pre-Evaporitic Succession: The Example of Torrente Vaccarizzo Section in Sicily (Italy)

Abstract

Tectonic, paleoenvironmental, and paleoclimatic unstable conditions preceding the onset of the Messinian Salinity Crisis (MSC) highly affected marine life. Changes in calcareous plankton association are overall registered in the Mediterranean. They consist of a general transition from abundant and well-diversified planktonic associations to strictly oligotypic assemblages that precede their total disappearance at the onset of evaporitic precipitation. In this work, an accurate quantitative analysis of calcareous plankton, both foraminifers and nannofossils, has been carried out in the Torrente Vaccarizzo Section of Sicily (southern Italy). The aim is to independently define a chronostratigraphic pattern of bioevents preceding the MSC in the absence of magnetostratigraphic or radiometric constraints. The fluctuating abundance of the genus Orbulina fits well with the 100 ky Eccentricity maxima, and it is successfully applied to build an astronomically calibrated age-model for the section. On this basis, all the biohorizons have been recalibrated and discussed with regard to the previous literature. Abundant influxes of selected species demonstrated to be of local significance since they are highly affected by paleoenvironmental and paleoclimatic conditions. A chronological sequence of foraminifer and nannofossil events marks the onset of the MSC with a derived age of 5.957 My, which agrees well with previous findings from other Mediterranean sections. This methodology and the new biostratigraphic events may be useful for future studies on pre-evaporitic successions of the Mediterranean.

Keywords

• pre-evaporitic deposits
• Messinian Salinity Crisis
• calcareous plankton
• cyclicity