Interstitial water studies of Late Quaternary Eastern Mediterranean sediments with emphasis on early diagenetic reactions and evaporitic salt influences

Abstract

Interstitial waters of five piston cores from the Eastern Mediterranean were recovered by shipboard squeezing and analyzed for their major elements. Additionally, organic carbon, CaCO3 and HCl extractable Mg were determined in the sediments from these cores. Three cores contain sapropels, which are considered to be the sedimentary expression of anoxic periods during the Quaternary. The pH in the interstitial waters extracted from the sapropels is significantly lower than the pH of the interstitial waters from the surrounding sediment. It is suggested that the low pH in sapropel interstitial waters is induced by bacterial activity. Other dissolved elements are not influenced by these sapropel layers.

Core T83-46, taken in the hypersaline anoxic Tyro Basin, shows a strong downward SO4 decrease, accompanied by a strong NH4 increase. The interstitial water chemistry of the Tyro Basin sediment is attributed to selective leaching of evaporitic salt; first halite dissolution, later followed by gypsum dissolution. The interstitial water chemistry of core T83-45, taken in the adjacent Kretheus Basin, is dominated by diffusive processes, which became important after oxic conditions returned in this formerly anoxic hypersaline basin.