Paleolimnology in Cappadocia, Turkey – Jonathan Dean

Jonathan Dean standing on the sacred rock
For the past 4 years, as a PhD student at the University of Nottingham and now as a postdoc at the British Geological Survey, I have been undertaking field work in the Cappadocia region of central Turkey. This is a very important area to study, as it is close to some key Neolithic sites where humans started to develop agriculture ~10,000 years ago. It is also close to the Hittite site of Hattusa, which I visited in 2010 to see the sacred rock on which the first peace treaty in human history was signed between the Hittites and the Egyptians.
Location of Nar Gölü
Because of the importance of the region in human societal development, there is a requirement for more knowledge of how regional climate has changed through the late glacial and Holocene. So, in a project with British, Turkish and French researchers, we have taken sediment cores from a lake, Nar Gölü. It is a maar lake, which means it was formed by water infilling of a crater produced by an explosion resulting from groundwater-magma interaction.
The lake in July 2010
Our coring platform
Carbonate precipitates in the lake waters in the summer and diatom and other algal growth occurs in the autumn and spring, and because the lake is relatively deep (21 m) for its area (~0.7 km2), turbidity is limited and there are anoxic bottom waters, which means  varves are formed – every year there is a light carbonate-rich  layer and a dark organic-rich layer. Around 90% of the 21.5 m sequence has these varves, so we were able to use varve counting, combined with U-Th dating, to estimate our sequence covered the period from the present day back to ~15,000 years ago.

Carbonate forming of the lake surface
The varved sediment
I have been using oxygen isotopes on the carbonates, which in this lake we have shown to be a strong proxy for regional water balance (basically precipitation:evaporation). We have also been experimenting with combining these data with oxygen isotopes from diatoms (siliceous algae), to try to reconstruct palaeoseasonality (see my article in Quaternary Science Reviews). One of the ways I’ve been able to work out what the oxygen isotope record is a proxy for is by going to the lake every year, and through different seasons, to collect water samples and sediments – by working out how oxygen isotopes change in the present as lake levels change, we can better understand what was driving them in the past. The most interesting trip was in February 2012, when Turkey experienced its worst winter in many years and we ended up having to dig our van out of a snowdrift. Luckily, a 4* spa hotel has been built near the hotel, so camping is not necessary!
Having fun in the snow
Not having fun in the snow
Aside from the wonders of Nar Gölü, the geology of Cappadocia is fascinating. There are many hoodoos, known locally as fairy chimneys, formed from erosion of the tuff, and the best way to see the landscape is by hot air ballooning!

Hot air ballooning over the badlands of Cappadocia

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