Timing and hydrological conditions of Sapropel events in the Eastern Mediterranean, as evident from speleothems, Soreq cave, Israel

Abstract

This paper explores the connection between the timing of sapropel events in the Eastern Mediterranean Sea and the time of low δ 18O events in speleothems of the Soreq cave (Israel). A new well-dated δ 18O and δ 13C profile of the Soreq cave speleothems for the last 140 kyr reveals five prominent low δ 18O events dated at: 124 to 119 kyr, with the main peak at 122 kyr (event #V); 108 to 100 kyr with peaks at 107 and 102 kyr (event #IV); 85 to 79 kyr with peak at 80 kyr (event #III); 55 to 52 kyr with a peak at 54 kyr (event #II) and 8.5 to 7 kyr with peaks at 8.5 and 7 kyr (event #I). These events are characteristic of period of enhanced rainfall in the Eastern Mediterranean area, particularly so for events #V and #I, where the marked decrease in δ 18O and the correspondingly marked increase in δ 13C indicate very wet conditions. The chronology of the low δ 18O events #V, IV, III and #I match the ages estimated for the formation of sapropels S5, S4, S3 and S1 which are also associated with high hydrological activity. Thus, it is suggested that the low δ 18O events in the Soreq cave speleothems constrain the maximum duration of the sapropel formation. Pollen data from the sapropel layers and the isotopic pattern of the speleothems indicate that sapropels S5 and S1 were deposited during very wet periods when there were major decrease in the sea surface salinity, coupled with frost-free winters and drought-free summers. Sapropels S4 and S3 were formed during periods of increased precipitation, but ones in which the general climate was Mediterranean semi-arid.