Late Quaternary palaeoenvironmental reconstruction from Lakes Ohrid and Prespa (Macedonia/Albania border) using stable isotopes
journal contributionposted on 24.10.2012, 09:23 by M. J. Leng, C. N. Jex, I. Baneschi, G. Zanchetta, B. Wagner, H. Vogel
Abstract. Here we present stable isotope data from three sediment records from lakes that lie along the Macedonian-Albanian 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[superscript: 18]O[subscript: calcite]) and, although productivity was increasing (high calcite content), the carbon supply was mainly from inorganic catchment rock sources (high δ[superscript: 13]C[subscript: carb]). During the last interglacial, calcite and TOC production and preservation increased, progressively lower δ[superscript: 18]O[subscript: 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[superscript: 13]C[subscript: org] are complacent; in contrast, Lake Prespa shows consistently higher δ[superscript: 13]C[subscript: org] suggesting a low oxidation of [superscript: 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[superscript: 18]O[subscript: 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[superscript: 18]O[subscript: calcite], apart from the very early Holocene phase in Prespa where the lowest δ[superscript: 18]O[subscript: 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[superscript: 18]O[subscript: calcite]suggest progressive aridification, in agreement with many other records in the Mediterranean, although the uppermost sediments in one core records low δ[superscript: 18]O[subscript: 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.