Organic-walled sub-fossil invertebrate remains (non-pollen palynomorphs) from the Mid-Late Holocene (~5 kyrs) sediments of Lake Hazar (Eastern Anatolia, Turkey); implications for lake level changes

Abstract

Non-Pollen Palynomorphs (NPP) recorded in palynological slides of the sediments of Lake Hazar, Eastern Anatolia were investigated in this study. Radiocarbon datings revealed that the studied interval covers a time span of the last similar to 5 kyrs corresponding to Mid- to Late Holocene. Non-biting midges (Chironomidae, Diptera) constituted 39.3 % of the total amount of remnants. Midges recorded were representatives of Tanypodinae, Chirominae and Orthocladiinae subfamilies. Specimens grouped under worm-like particles (HZR-12, 18 and 21) were found as the second abundant group with 30.6 %. An unknown morphotype (HZR-11, bone-like structures) and testate amoebae each constituted 9.8 % and HZR-14, 15, 19 and 20 (?Rotifera) 2.7 %. Based on absolute and relative abundance of these groups, the studied interval was delineated into three zones; ZI, ZII and ZIII. It was suggested that, after Mid-Holocene climatic optimum, the shallowest lake level existed between similar to 4.8-4.3 kyrs B.P. in Zone I due to the onset of cold and arid climatic conditions in the area. Low lake levels may have been repeated in Zone II (similar to 3.5-2.9 kyrs B.P.) and Zone III (similar to 1.4-0 kyrs B.P.) but were not as effective as in Zone I. Changes in the hydrological regime of the lake during the Zones II and III might have been due to climatic variations and/or changes in tectonic regime and that can be resolved with further studies.