Late Quaternary palaeoenvironmental reconstruction from Lakes Ohrid and Prespa (Macedonia/Albania border) using stable isotopes

Abstract

Abstract.Here we present stable isotope data from three sediment records from lakes that lie along the MacedonianAlbanian border (Lake Prespa: 1 core, and Lake Ohrid: 2 cores). The records only overlap for the last 40 kyr, although the longest record contains the MIS 5/6 transition (Lake Ohrid). The sedimentary characteristics of both lakes differ significantly between the glacial and interglacial phases. At the end of MIS 6 Lake Ohrid's water level was low (high δ 18 O calcite ) and, although productivity was increasing (high calcite content), the carbon supply was mainly from inorganic catchment rock sources (high δ 13 C carb ). During the last interglacial, calcite and TOC production and preservation increased, progressively lower δ 18 O calcite suggest increase in humidity and lake levels until around 115 ka. During ca. 80 ka to 11 ka the lake records suggest cold conditions as indicated by negligible calcite precipitation and low organic matter content. In Lake Ohrid, δ 13 C org are complacent; in contrast, Lake Prespa shows consistently higher δ 13 C org suggesting a low oxidation of 13 C-depleted organic matter in agreement with a general deterioration of climate conditions during the glacial. From 15 ka to the onset of the Holocene, calcite and TOC begin to increase, suggesting lake levels were probably low (high δ 18 O calcite ). In the Holocene (11 ka to present) enhanced productivity is manifested by high calcite and organic matter content. All three cores show an early Holocene characterised by low δ 18 O calcite , apart from the very early Holocene phase in Prespa where the lowest Correspondence to: M. J. Leng (mjl@bgs.ac.uk) δ 18 O calcite occurs at ca. 7.5 ka, suggesting a phase of higher lake level only in (the more sensitive) Lake Prespa. From 6 ka, δ 18 O calcite suggest progressive aridification, in agreement with many other records in the Mediterranean, although the uppermost sediments in one core records low δ 18 O calcite which we interpret as a result of human activity. Overall, the isotope data present here confirm that these two big lakes have captured the large scale, low frequency palaeoclimate variation that is seen in Mediterranean lakes, although in detail there is much palaeoclimate information that could be gained, especially small scale, high frequency differences between this region and the Mediterranean.

A Late Glacial to Holocene record of environmental change from Lake Dojran (Macedonia, Greece)

“…6000 and 4300 cal yr BP correlates with a minimum in K and Fe and suggests slightly increased productivity, slightly reduced lake level and lower supply of clastic material. This is likely correlated to warmer temperatures and more arid conditions during the mid-Holocene, such as observed in other paleoclimate records in the Mediterranean region (e.g., Wick et al, 2003;Kotthoff et al, 2008a,b;Roberts et al, 2008;Wagner et al, 2009;Leng et al, 2010;Vogel et al, 2010a;Aufgebauer et al, 2012;Joannin et al, 2012). The shift from more humid to more arid conditions at Lake Dojran was only moderate, as OM, TS, TOC/TS, TOC/TN, δ 13 C org , and δ 18 O carb in core Co1260 are relatively stable between 7900 and 4300 cal yr BP.…”

“…The decreasing δ 18 O carb after 10 200 cal yr BP could be associated with a greater through flow due to further increasing humidity. This corresponds with increasing moisture in southern Italy until 9400 cal yr BP (Joannin et al, 2012), but in particular with increasing δ 18 O carb after 9400 cal yr BP at Lake Prespa, which was explained by increasing summer wetness (Leng et al, 2010). Despite this increasing humidity during the early Holocene, which incidentally coincides partly with the formation of sapropel 1a between ca.…”

“…These low values are probably due the greater contribution of soil derived CO 2 or decomposition of OM relative to the amount of carbon from the carst and the atmosphere (cf. Leng et al, 2010).…”

“…Additional records with highresolution sedimentary information from this region are needed to get a better understanding of Late Glacial to Holocene climatic variability and anthropogenic activity and their spatial variability. As shown by a comparison of records from lakes Prespa and Ohrid (Leng et al, 2010;Wagner et al, 2010), shallower lakes often react more sensitive to environmental change. Hence, we can assume that Lake Dojran with a maximum water depth < 7 m provides a valuable record of climatic change and anthropogenic impact at the Balkan region.…”

Northern Mediterranean climate since the Middle Pleistocene: a 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia)

“…It is therefore vital to investigate the regional response to past climate fluctuations and improve our understanding of global climate dynamics as a prerequisite for establishing future scenarios (Leng et al, 2010a). Stable isotope ratios preserved in sedimentary lacustrine carbonates are a proxy for past climate and hydrological change (Leng and Marshall, 2004), and combinations of lake records can be used to assess the spatial coherence of isotope variations (Roberts et al, 2008).…”