In search of the source a sudden and short-lived salinity peak linked to an early Byzantine seismic event recorded in Lake Manyas sediment (N-W Turkey)
by
Salim M. Oncel
Gebze Institute of Technology, 41400 Gebze, Kocaeli, Turkey
Coauthors: S. Leroy (Department of Geography and Earth Sciences, Brunel University, Uxbridge, Middlesex UB8 3PH, (West London), UK), Ö. Ileri (Department of Geological Engineering, Ankara University, Faculty of Sciences, 06100 Besevler, Ankara, Turkey), N. Kazanci (Department of Geological Engineering, Ankara University, Faculty of Sciences, 06100 Besevler, Ankara, Turkey), Ö Emre (Geology Department of General Directorate of Mineral Research and Exploration, 06520 Ankara, Turkey)

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, 14 m asl) 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.

An early Byzantine seismic event at 4 m sediment depth is manifest, amongst other parameters, as a brief and sudden saline inundation. Palaeoecological (pollen, seeds, ostracods, organic-walled algae and cyanobacteria) and geochemical (major oxides and trace elements) evidences are presented.

For the source of salinity increase, 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 (between the sea and the lake). If only the lake-bounding fault moved (Manyas Fault), 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.

Date received: August 16, 2002