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

Abstract

Abstract. Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δ 18 O) and carbon (δ 13 C) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOP-SCO) project. The investigated sediment succession covers the past ca. 637 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the total inorganic carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial-interglacial cycle. Sediments corresponding to warmer periods contain abundant endogenic calcite; however, an overall low TIC content in glacial sediments is punctuated by discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ 18 O c and δ 13 C c ) reveal variations both between and within interglacials that suggest the lake has been subject to palaeoenvironmental change on orbital and millennial timescales. We also measured isotope ratios from authigenic siderite (δ 18 O s and δ 13 C s ) and, with the oxygen isotope composition of calcite and siderite, reconstruct δ 18 O of lake water (δ 18 O lw ) over the last 637 ka. Interglacials have higher δ 18 O lw values when compared to glacial periods most likely due to changes in evaporation, summer temperature, the proportion of winter precipitation (snowfall), and inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability from marine isotope stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial. Climate conditions became progressively wetter during MIS 11 and MIS 9. Interglacial periods after MIS 9 are characterised by increasingly evaporated and drier conditions through MIS 7, MIS 5, and the Holocene. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within Lake Ohrid.

The environmental and evolutionary history of Lake Ohrid (FYROM/Albania): interim results from the SCOPSCO deep drilling project

“…Lake-level reconstructions (modified from Lindhorst et al, 2010; for details see Sect. 4.3.2 of this study), pollen , sedimentological, and geochemical data over the last 637 kyr Lacey et al, 2016) indicate a long-term shift from cooler and wetter to drier and warmer glacial and interglacial periods around 300 ka. Pollen curves have been corrected with respect to those reported in Sadori et al (2016).…”

“…During MIS 12, Fe peaks in X-ray fluorescence data are positively correlated with TIC and indicate the formation of early-diagenetic siderite in response to a shift in bottom water redox conditions towards a more oxic environment (Fig. 5;Lacey et al, 2016). The Fe peaks during the coldest period of this glacial match particularly well with the number of IRD grains and with maxima in the quartzite-calcite or dolomite-calcite ratio in the U1313 record from the North Atlantic (Fig.…”

“…The oxygen isotope composition of lake water (δ 18 O lakewater ), calculated from δ 18 O of endogenic calcite, shows only moderate variability between interglacial periods with a relatively stable climate from MIS 15 to MIS 13, progressively wetter conditions during MIS 11 and MIS 9, and increasingly evaporated, drier conditions in more recent interglacials ( Fig. 4; Lacey et al, 2016). In particular, higher δ 18 O lakewater through MIS 5 and the Holocene indicates higher evaporation due to dry and warm conditions prevailing under a Mediterranean-type climate.…”

Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)

“…IR spectra were measured on a Bruker Vertex 70 Fourier transform infrared (FTIR) spectrometer at the Institute of Geological Sciences at the University of Bern. Details on measurement set up and data evaluation procedures are outlined in Lacey et al (2016).…”

“…objectives, we jointly investigated mineral magnetic properties and organic proxies, X-ray fluorescence (XRF) data and Fourier transform infrared spectroscopy (FTIRS; Lacey et al, 2016).…”