Date

2011

Author

Şekeryapan, Ceran

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Here, we provide results of mid/late Holocene fresh water Ostracoda analyses from coastal modern lake basins in the Thrace region of Istanbul and Sarıkum Lake, on the Black Sea coast near Sinop. While neither diatoms nor Cladocera are abundant in the sediments, Podocopian (fresh water) ostracods preserved well, but with discontinuous occurences during the mid/late Holocene. Un-noded forms of Cyprideis torosa, along with other Podocopian ostracods, dominated the sediments of all three lakes. Studying these three lagoonal basins along the Black Sea and Thracian coasts of Turkey allows reconstruction of long term, regional environmental histories, using the following methods. Loss-on-ignition (LOI) analyses at 1 cm intervals of short and long cores provide stratigraphic cross-correlation and calculations of organic matter, carbonate and mineral weight. At 5 cm intervals, spectrally-inferred chlorophyll-a contents by visible reflectance spectroscopy (Michelutti et al., 2010), provide estimates of algal production. Trace element analysis (Mg/Ca and Sr/Ca) using ICP-AES (coupled plasma atomic emission spectroscopy) is applied to fully calcified adult specimens of un-noded forms of Cyprideis torosa shells (which dominate the uppermost 145 cm of Terkos Lake). 210Pb and 137Cs dating of short cores, and AMS 14C dating of long cores, are used to infer sediment accumulation rates and to place specific ages on inferred environmental changes. Benthic foraminifers, gastropods, bivalves, single valves of fossil Glochidia, and Charophyte seeds are the other biological indicators observed within the sediment archive. Based on these data: 1. Terkos Lake sediments contain records of multiple, sub-millennial scale marine incursion events, over the last 2.8 ka, inferred to be the result of severe storms or tsunami on the Black Sea, including the tsunami in AD 1598 and AD 557-543; 2. short core sediments from Sarıkum Lake reveal sharp decreases in organic matter, carbonate, and increases in algal production and sand amount that suggest a storm or more recent earthquake; such as the Great Erzincan Earthquake (26 December, 1939) or the Bartın earthquake (3 September, 1968) while four more such events appear in the undated sediments of the Sarıkum Lake long core; and 3. a large earthquake in AD 447 that affected the entire Sea of Marmara (Leroy et al., 2002) does not appear in the Büyükçekmece Lake sediment record, but there is evidence for a significant hiatus in these deposits before the development of the dam (AD 1989) and after the youngest AMS date (2400 cal yrs BP). This suggests that Büyükçekmece Lagoon was an environment of net erosion prior to its artificial impoundment, either from gradual processes or from scouring by one or more tsunami.

Subject Keywords

Paleolimnology

URI

http://etd.lib.metu.edu.tr/upload/12613627/index.pdf
https://hdl.handle.net/11511/21206

Collections

Graduate School of Natural and Applied Sciences, Thesis