QUASI-ANNUAL-RESOLUTION PALYNOLOGICAL ANALYSES OF EARTHQUAKE EVENTS IN LAKE SAPANCA (NORTH ANATOLIAN FAULT) TURKEY) OVER THE LAST DECADES, AND IMPLICATIONS FOR THE LAST 2000 YEARS

As part of a multidisciplinary European Union project (RELIEF), quasi-annual resolution palynological analyses have been made on a sedimentary sequence from Lake Sapanca (Turkey). This lake is located on the North Anatolian Fault, east of Istanbul. The aim was to establish tools to detect earthquake signatures in palynology (via for example taphonomy) and in other proxies. The analyses of the top 40 cm of the cores, dated by radionuclides (210Pb and 137Cs), have provided a strong signal of sediment dilution by soil (low pollen concentrations, reworked palynomorphs and preferential preservation) following four events in the last 50 years. Three of them can be correlated to earthquakes: AD 1999, 1967 and 1957. A fourth one could perhaps be linked to human activities around the lake (building of roads and of a railway). One the long cores (6 m), dated by AMS radiocarbon, has been studied at a lower resolution. Similar signals are also found over the last 2000 years, the base of the diagram shows the end of the Beysehir Occupation Phase. The sedimentary infill seems to be almost dominated by external inputs rather than by in situ lake sediment. Only a detailed sedimentary analysis could allow building a robust chronology for such a lake by deleting from the sequence the reworked sediment zones.