Physicochemical, mineralogical, and geochemical characteristics of lacustrine sediments of the Konya Basin, Turkey, and their significance in relation to climatic change

Abstract

Physicochemical, mineralogical, and geochemical characteristics of 279 highly calcareous lacustrine sediment samples obtained from a 30 m drilling core in the western part of the Great Konya Basin, Turkey were studied. The sediments have a predominance of silt and clay fractions with a median diameter of 3–5 μm. Vertical changes of the amounts of water soluble components, gypsum, carbonates, and non-salt minerals such as quartz, feldspars, and layer silicates in the sediments suggest that there were climatic changes in the Konya Basin. The dominant clay mineral is smectite followed by kaolinite, illite, and palygorskite. The oxygen isotopic ( δ 18O) ratios of six quartz samples from the Konya sediments, a terra rossa soil beside Lake Beyşehir gölü and paleosols at the foot of Mt. Erciyes Daǧ ranged from +18.1 to +20.6‰. The dominant clay minerals and δ 18O ratios suggest that part of quartz and coexisting layer silicates is of long-range transported and/or local aeolian dust origin from arid and semi-arid regions such as North Africa, Israel, and the surroundings. The relatively high deposition rate might be due to aeolian dust input and/or the sediment input introduced by the rivers such as the Çarşamba river from the Toros (Taurus) mountains. The vertical distributions of electro-conductivity, amounts of water soluble and non-salt components, and the gypsum content of the sediments suggest that gypsum-rich layers were formed under shallow, saline waters, possibly associated with warm to hot and dry environments such as the Last Interglacial epoch and the Early Holocene. The sediments characterized by relatively high amounts of non-salt sediments, in which gypsum did not accumulate, could be deeper water phases formed under the cold and/or wet environments such as the Glacial epochs.