The Paleoproductivity Forced by Earth Orbital Forcing in Italy During Early Pliocene

Abstract

We studied the variability of the African monsoon and the Mediterranean sea surface productivity during the early Pliocene based on the analysis of some paleoenvironment proxies such as planktonic foraminifera oxygen isotope and biogenic compositions(carbonate,biogenic opal and organic carbon) in three profiles respectively,Punta Piccola,Cape Spertivento and Punta Rossello in southern Italy.Our results show that during the early Pliocene,the increase of the Northern Hemisphere summer insolation which is also presented as low precession value is usually correlated to organic carbon and opal increases,carbonate decrease and the negative excursions of stable oxygen isotope.The variability of the proxies implies the sea surface productivity controlled by the precession.Enhanced runoff induced by the strengthened African summer monsoon brings abundant terrestrial nutrients and fresh water into the Mediterranean sea,which conduces to productivity blooming and anoxic condition in the Mediterranean sea bottom.Furthermore,opal thrives herein by using deep-nutrient,buildups mats and decline fleetly into sea bottom so that organic carbon is speedily buried and conserved,thus making the sapropels come into being.Diatom layers in Punta Rossello profile confirm the existence of mats,but the content of opal in some layers is not high.