Jonathan Dean is an Isotope Geochemist at the British Geological Survey. Here he discusses his latest trip to Turkey. See his other post about palaeolimnology in Cappadocia here.
In early April 2014, I lectured on a field trip in Cappadocia, Turkey, where I taught students from Birmingham, Ankara and Isparta Universities about how we can use lake sediments to reconstruct past climate changes.
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| Tortoise hiding from the palaeolimnologists of Nar lake! |
We travelled south from Ankara, the capital, to Nar lake. This is where I carried out my PhD research. Since 1997, members of our team have been monitoring changes in the lake depth and the oxygen isotope composition of its waters and sediments. The aim of all this has been to calibrate the oxygen isotope record locked away in the sediments with the meteorological record, and we have been able to show the oxygen isotope composition of the carbonates found in Nar’s sediments can be used as a robust proxy for hydroclimate (i.e. changes between wet and dry climate). Temperatures in central Turkey have risen by several degrees since the 1990s, which has increased evaporation from the lake, and led to a rise in the oxygen isotope composition of the sediments. This work meant when we retrieved sediment cores spanning thousands of years from the lake, we were able to reconstruct changes in hydroclimate, using oxygen isotopes, with more confidence.
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| Nar lake in central Turkey |
On this field trip, we gave the students hands-on insights into the research techniques we use on the lake. They retrieved sediment cores and took samples and geochemical measurements of waters from different depths in the lake. One of the most exciting things we retrieved this year was a sediment trap we had left in the lake a year before. It is a tube with a funnel attached to the top, which captures sediment as it falls through the water. There is a clear stratification to the captured sediments, with darker organic-rich sediments forming in the autumn and spring and lighter carbonate-rich material forming in the summer.
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| Sediment trap retrieved from Nar lake |
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| Pulling a sediment core from the bottom of the lake back to the boats |
We also enjoyed some nice walks through Pigeon Valley, with its dramatic landscapes carved by wind and rain into the volcanic tuff.
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| Typical Cappadocia, with the unique landscapes resulting from the erosion of the thick layers of volcanic tuff |
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