Is there a link between an early Byzantine seismic event (recorded in Lake Manyas sediment, N-W Turkey) and the end of the Beysehir Occupation Phase?
by
Suzanne Leroy
Department of Geography and Earth Sciences, Brunel University, Uxbridge, Middlesex UB8 3PH, (West London), UK
Coauthors: Kazanci N. (Gebze Institute of Technology, 41400 Gebze, Kocaeli, Turkey), Ileri Ö. (Department of Geological Engineering, Ankara University, Faculty of Sciences, 06100 Besevler, Ankara, Turkey), Oncel S. (Gebze Institute of Technology, 41400 Gebze, Kocaeli, Turkey), Emre O. (Geology Department of General Directorate of Mineral Research and Exploration, 06520 Ankara, Turkey), Løvlie R. (Institute of Solid Earth Physics, Allegt. 41, N-5007 Bergen, Norway)

A belt of lakes that straddles the western strand of the North Anatolian Fault offers possibilities for establishing Holocene earthquake histories and their environmental impact.

Lake Manyas (10 km from the southern shore of the Sea of Marmara) is a shallow, open and eutrophic freshwater lake. A coring campaign in 1998, using a hand-pushed Livingstone piston corer operated from a raft, retrieved a total of eleven cores from three stations along a 7 km-long transect from the north shore to the lake centre.

Palaeoecological analysis revealed sedimentological, biological (pollen, seeds, ostracods, organic-walled algae and cyanobacteria) and geochemical evidence for at least two Holocene seismic events (Leroy et al. 2002). The most recent event (at 4 m depth) dates to the Early Byzantine period and is manifest, amongst other parameters, as a saline inundation.

A large and a small scenario may be proposed. If the event is caused by a large offshore earthquake on the Sea of Marmara, the increased salinity may be due to a tsunami surge up the Kocasu Gorges (directly upstream of river mouth). If only the lake-bounding fault moved, the salinity may have increased by hydrothermal fluid expulsion (several hot springs south of the lake) or by temporary river inflow shortage by divergence to a previous channel.

Typical pollen indicators of the Beysehir Occupation Phase are found mostly up to the 4 m event. It is questioned whether there is a link between the abrupt decline of arboriculture (also found elsewhere in Turkey and in the Middle-East) and the earthquake recorded in lake Manyas (with a local or regional cause).

Date received: August 6, 2002

Copyright © 2002 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caji-50.