ÇAĞRILI KONUŞMALAR / KEYNOTES Invited Speeches ... - TPJD

Sediment Properties and Geological Evolution of the Recent Lake Işıklı
(Denizli, SW Turkey)
Sonay Boyraz 1 , Nizamettin Kazancı 1 , M. Tariq İsmael 1 , Salim Öncel 2 , Özden İleri 3 ,
Özlem Makaroğlu 4
1 Ankara University, Faculty of Engineering, Department of Geological Engineering
2 High Technology of Gebze, Kocaeli
3 General Directorate of Mineral Research And Exploration, Ankara
4 İstanbul University, Faculty of Engineering, Department of Geophysic Engineering, İstanbul
Lakes and lake sediments are the most reliable source of data for climate research. To obtain
information about the Late Quaternary climate in SW Anatolia, Lake Işıklı were investigated and
its findings are presented below. The Lake Işıklı is a shallow lake on the Büyük Menderes River in
the Çivril town boundaries, located western margin of Dinar graben and about 65 km2 surface
area. The six drillings which lengths from 1 to 5 meters have been done inside the lake using
Livingstone samplers. As expected, the water content of the first 2 meter of cores is around
%50, grey-green-black colored and contains abundant plant roots, rush pieces and gastropod
shell. In the lower parts of cores, the water content gradually declining to %30 and colors are
successive with brownish-black and gray tones. The lithological composition of lake sediments are
characterized mostly silt, small quantity fine sand (11 -189 µm) and mean particle size is 55 µm.
Due to the opening of lake to outside, suspended particles reduced. Lithological compositions
are composed of predominantly calcite, quartz, feldispar and very small amount of dolomite
and amorphous mineral. Based on its abundance, the clay content of lake sediments are illite,
smectite and chlorite. These result suggest that the sediments of lake mostly originating by
erosion from surrounding volcanic rocks. The magnetic susceptibility values of Lake Işıklı are not
more interpretable. In general, it increases or decreases to the consistent with organic matter
content. In lake sediments, total organic matter content ranges from %3,2 to %33.3. The total
carbonate amount of lake, 165 cm intervals with the lowest amount of carbonate is %0.2, to the
355 cm depth lake has the highest amount with %14.2 and these values are vertically consistent
with organic matter content. Lake sediments chronology based on AMS-14C measurements
and according to this, the age of longest core (500 cm) is 5455±20 BP. The sedimentation rate
calculated from measurements on cores obtained from different levels, for 0-200 cm interval
is 0.88 – 1.26 mm/year, for 200-500 cm interval is 0.7 mm/year with average of 0.91 mm/
year. In the light of these all analysis, lake sediments of the core could be distinguished three
different level such as 0-140 cm, 140- 345 cm and 345-500 cm. It is interpreted that the first level
corresponds to the stage of being swamp that has prevailed during the last 1260 years, and the
second level corresponds to the stage of being dry that prevailed for 1740 years, while the third
level corresponds to the stage of being lake and swamp that prevailed 2455 years.
Keywords: Lake Işıklı, clay mineralogy, magnetic susceptibility, climate, Holocene
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