Abstract
ABSTRACTIndividual palaeoenvironmental records represent a combination of regional‐scale (e.g. climatic) and site‐specific local factors. Here we compare multiple climate proxies from two nearby maar lake records, assuming that common signals are due to regional‐scale forcing. A new core sequence from Nar Lake in Turkey is dated by varves and U–Th to the last 13.8 ka. Markedly dry periods during the Lateglacial stadial, at 4.3–3.7 and at 3.2–2.6 ka BP, are associated with peaks in Mg/dolomite, positive δ18O, elevated diatom‐inferred electrical conductivity, an absence of laminated sediments and low Quercus/chenopod ratios. Wet phases occurred during the early–mid Holocene and 1.5–0.6 ka BP, characterized by negative δ18O, calcite precipitation, high Ca/Sr ratios, a high percentage of planktonic diatoms, laminated sediments and high Quercus/chenopod ratios. Comparison with the record from nearby Eski Acıgöl shows good overall correspondence for many proxies, especially for δ18O. Differences are related to basin infilling and lake ontogeny at Eski Acıgöl, which consequently fails to register climatic changes during the last 2 ka, and to increased flux of lithogenic elements into Nar Lake during the last 2.6 ka, not primarily climatic in origin. In attempting to separate a regional signal from site‐specific ‘noise’, two lakes may therefore be better than one.
Highlights
Most records of past climatic and environmental change derive from a specific archive at a defined location, such as a lake, a cave or a peat bog
The multi-proxy approach has rightly been applauded as a key way to achieve a ‘rounded’ reconstruction of past environmental conditions (Lotter, 2003). Combining this with a multi-site approach can offer additional insights, as we have tried to illustrate in this comparative study of two maar lake records
This has meant that basin infilling has led to a long-term trend towards lake shallowing at Eski Acıgol unrelated to climate
Summary
Most records of past climatic and environmental change derive from a specific archive at a defined location, such as a lake, a cave or a peat bog. If proxies were a perfect match for environmental variables, if chronological control were perfect and if environmental variability across space were minimal (as in the open ocean), proxy records from otherwise similar sites in the same region should show a near linear correspondence. It remains an open question how far any individual sequence represents a signal of regional-scale environmental change, and how much of it comprises site-specific factors which palaeoclimatologists, for example, might view as local-scale ‘noise’. How can we know this, and how far does the signalto-noise ratio vary between different proxies? A priori, the separation of local from regional factors is more significant and more challenging in some archives than others, for example lacustrine compared to marine sediments
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