Mid-Holocene changes in the geochemical and biotic conditions of an aquatic ecosystem, in Eastern Mediterranean

Mediterranean Temporary Ponds (MTPs) are unique and sensitive aquatic ecosystems that due to their hydrological characteristics constitute an ideal setting for the study of past environmental dynamics. A 176 cm core was retrieved from the littoral zone of Omalos MTP in Lefka Ori massif, to provide a general view of the processes that drove its Lateglacial and Holocene evolution. The sedimentary sequence is partitioned in two major units: (i) Unit II (similar to 17-4.7 ka BP), characterized by the catchment-derived transport, allogenic deposition of fine, Al2O3 -rich, sediments and endogenic deposition of clays, under overall anoxic and dry climatic conditions, and (ii) Unit I (similar to 4.7 ka to present), characterized by increasing wetness, establishment of watershed, aquatic and herbaceous vegetation and by SiO2 dominated sedimentation under overall oxic conditions. The enrichment of SiO2 in the littoral sediments since the mid-Holocene, can be of elastic, aeolian and biogenic origin, but the undertaken analyses did not permit such distinction. The overall dryness of Unit II was interrupted between similar to 14.7 and 13 ka BP by wet conditions, evidenced by the establishment of littoral vegetation. The transition to the mid-Holocene system reorganization, was expressed by peak values of Al2O3 , Fe2O3 , K2O, MgO and Cr2O3 and by the deposition of calcite under warm and dry conditions. The mid-Holocene (similar to 4.7 ka BP) period of Omalos MTP ecosystem disturbance, likely corresponds to the "4.2 ka mega drought event" widespread in the eastern Mediterranean region. The potential of MTP's sedimentary sequences in reconstructing past environmental conditions is emphasized.