Paleoclimate reconstruction from varved sediments in Köyceğiz Lake, Southwest Anatolia

2022-8-10
Karadaş, Özlem
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Understanding how the Earth's climate has changed in the past is vital to understand the current climate change and forecast the climate in the future. Thus, high resolution paleoclimate archives provide insight into the idea of how climate has changed over time far beyond instrumental records. Among many paleoclimate archives, annually laminated lake sediments “varves” provide the possibility to obtain highly resolved climate proxies as well as excellent chronological time control. The aim of this study is to obtain high resolution paleotemperature records from varved sediments of Köyceğiz Lake in southwest Turkey. Along a 124.95 cm-long gravity core, ITRAX micro-XRF core scanning was performed at a resolution of 0.2 mm. Varve counting in the light of visual inspections together with peaks along Ca/Ti ratio profile results in total of 609 years-long sedimentary record. By using only the ITRAX data at yellowish carbonaceous laminae, which are deposited in summer season, it was found that the ratios of Br, Cl and Zr to clastic elements (CA; Si, S, K, Ti, V, Cr, Mn, Fe, Ni and Rb) have high correlation with the summer (JJAS) temperatures measured at Muğla, Köyceğiz and Dalaman meteorological stations. Accordingly, the AVE[Br-Cl-Zr] / CA profile obtained from Köyceğiz sediments has strong correlation with the Global Average Temperature Change (GATC) reconstruction curve (R2 = 0.67). In order to achieve a quantitative paleotemperature reconstruction, multiple linear regression was applied to estimate regression equation between ITRAX micro-XRF and meteorological data. The obtained paleotemperature reconstruction (REC), which successfully illustrates the recent Global Warming, also achieves a strong correlation with the GATC (R2 = 0.63). By using both AVE[Br-Cl-Zr] / CA and REC, compared to the GATC, two relatively warmer (ca. 1890-1860 CE and 1630-1600 CE) and one relatively colder (ca. 1770-1800 CE) periods were detected in Köyceğiz varve-based paleotemperature record.
Paleoclimate, Paleotemperature Reconstruction, ITRAX micro-XRF Scanning, Principle Component Analysis, Multiple Regression Analysis
https://hdl.handle.net/11511/98623
Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats
Ö. Karadaş, “Paleoclimate reconstruction from varved sediments in Köyceğiz Lake, Southwest Anatolia,” M.S. - Master of Science, Middle East Technical University, 2022.
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