Eastern Mediterranean sapropel S1 interruption: an expression of the onsetof climatic deterioration around 7 ka BP

We discuss the palaeoclimatic interpretation of unprecedented high-resoluti on micropalaeontological studies of shortterm (2 to 4 centuries) interrupti ons within early Holocene organic-rich layer (sapropel) S1 from the eastern Mediterranean. Results for cores from the Adriatic and Aegean seas that co ntain 'double' S1 sapropels indicate that these interruptions, which are ce ntred roughly around 7000 years C-14(nc) BP, are genuine and related to cli matic deterioration. This interpretation is endorsed by a coeval dry event recorded in terrestrial records and indications of climatic deterioration a ffecting human migration patterns and early societies in Egypt. The presenc e of sapropel interruptions in the two major source areas of deep water for the entire eastern Mediterranean likely implies that similar intervals may be found throughout the basin, provided that sedimentation rates and sampl ing resolutions allow the detection of events with a duration of only sever al centuries. Moreover, our results show that the 'sapropel mode' of circul ation comprises a delicate balance between reduced ventilation and enhanced productivity, which is easily disturbed through surface water cooling trig gering a short time of improved deep water ventilation. (C) 1999 Elsevier S cience B.V. All rights reserved.