ANNUAL-RESOLUTION PALYNOLOGICAL ANALYSES OF TWO EARTHQUAKE EVENTS IN THE DEAD SEA: 31 BC AND AD 363 AND THEIR IMPACT ON AGRICULTURE

As part of a multidisciplinary international project founded by the British Academy, annual resolution palynological analyses and geochemistry have been made on a yearly laminated lake sequence with the aims of highlighting the impact of earthquakes on the environment (such as modification of the vegetation by the earthquake consequences or following a change in land use). A joint German-Israel project has allowed taking cores in the centre of the Dead Sea. A pollen diagram covering the last 3000 years shows a sharp decline of agriculture without return to the previous state around AD500 (Heim et al., 1997). The Ze'elim outcrop, at the western margin of the Dead Sea, has been radiocarbon-dated and seismites have been linked to historical earthquakes by previous work (Ken Tor et al., 2001). Pollen analyses, in individual laminites above the 31 BC and the AD 363 earthquake seismites, indicate a short-term (a few years), but intense, impact. The lack of clear variation in the palynological concentration (and hence influx) as well as the absence of clear soil in-wash in the geochemistry indicate that the changes of taxa percentages are not due to a different taphonomy but directly reflect a change in pollen rain. Hence the pollen diagram can unequivocally be interpreted in terms of change in vegetation cover. The two earthquakes caused changes in the local agriculture when cereal fields and olive grooves were abandoned.