Unraveling extreme events from deep water cores of the south Caspian Sea
Résumé
South Caspian Sea sub-basin, as the deepest part of the Caspian Sea (CS) remained as land-locked basin even during extreme sea level fall that most part of the CS desiccated. Therefore, bottom sediments of the south CS continuously recorded many past intra-basinal and extra-basinal events. In the current research we have used four short cores (<2 m) from deep waters of the south CS (300–800 m) to unravel past extreme events based on the sedimentological and geochemical analysis. Presence of coarse grained sediment laminae in the deep basin represents frequent slope failure that transported materials from lower shelf. XRF core scanning along with Magnetic Susceptibility measurements showed multiple changes along the cores. Elements incorporating in biological activities (Ca, Sr) have sharp contrast with lithogenic elements (Zr, Ti) mainly during rapid environmental changes. The deepest core has significant changes in the basal part that covers certainly Younger Dryas or even older sediments. Material influx into the deep basin of the south CS demonstrate both basinal extreme events as turbidite and mass wasting as well as catchment basin events e.g. river avulsion that caused changes in sediment properties.