A synthetic pollen record of the eastern Mediterranean sapropels of the last 1 Ma: implications for the time-scale and formation of sapropels

The Quaternary climate of southern Europe (south Italy and Greece) is inves tigated by pollen analysis of the sapropels which were deposited in the dee p eastern Mediterranean Sea during the last I million year (Ma). The time-s cale of core KC01b in the Ionian Sea has been established by tuning its oxy gen isotopic record to the ice volume model of Imbrie and Imbrie (1980). Fo r the last 250,000 year (250 ka), the previous pollen studies and astronomi cal tuning have been confirmed. Sapropels were deposited under a large rang e of Mediterranean climates: fully interglacial, fully glacial, and interme diary, as revealed mainly by the balance between the respective pollen abun dances of oak (Quercus) and sage-brush (Artemisia). The high value of the o ak reveals the warm and wet climate of an Interglacial, and the high value of the sage-brush, the dry and cold climate of a Glacial. Whereas the Medit erranean climate is directly related to the variation of the high-latitude ice sheets, the deposition of sapropels is not so. In contrast with the wid e climatic range, sapropels were deposited only when summer insolation in t he low latitudes reached its highest peaks. However, between 250 ka and 1 M a, that stable pattern is not yet established. Only six sapropels are obser ved, many expected ones do not appear, even as ghosts signalled by peaks of barium abundance, that remain after the post-deposition oxidation of organ ic matter. The pattern of sapropel formation in stable and direct relations hip to highest insolation does not seem to apply. For five of those saprope ls, neither climate extremes are observed; they mainly formed during interm ediary types of Mediterranean climate. In contrast, one sapropel (and one g host) relates to a relatively low peak of insolation, and its climate is of a unique, composite type not seen later. This might suggest an unsuspected , more complex pattern linking the formation of Mediterranean sapropels to the astronomical configuration. (C) 1999 Elsevier Science B.V. All rights r eserved.