Geochemical and paleomagnetic evidence for the occurrence of "missing" sapropels in eastern Mediterranean sediments

Abstract

The cyclic occurrence of sapropels appears to be associated with maxima in the 65°N summer insolation target curve. Studies of the most recent sapropel have revealed extensive oxidation of organic matter or even the complete removal of this unit. Geochemical and magnetic signals allow for the detection of such a "missing" sapropel. In older sediments, these signals are altered by ongoing diagenetic processes. An important parameter to reveal missing sapropels is Ba. Elevated concentrations of Ba are always found in visible sapropels, and even after oxidation of part of the sapropel, the initial Ba profile remains visible. We use this tool to trace down missing sapropels in KC01B, a 37-m Kullenberg core from the Calabrian Ridge, eastern Mediterranean. At least 8 of 11 sampled intervals around insolation maxima contain evidence of a completely oxidized sapropel: Ba, trace metal distributions, and magnetic parameters are similar to those observed around visible sapropels.