Geochemistry of Marmara Lake sediments - Implications for Holocene environmental changes in Western Turkey

Abstract

Beginning from the Early Holocene marked environmental changes have been revealed by a multi-proxy study of two radiocarbon-dated sediment cores from Lake Marmara. Both cores are composed of fine clastic sediments deposited over the last 1845 years. The core taken from the western depocentre supplementary consists of a 20 cm thick interval which represents a time period of 10.28 to 8.28ka yrBP. A desiccation event caused 6435 year hiatus in the sedimentary record. The lake was established again at 1.85ka yrBP. After a transitional humid phase at the beginning of the Late Holocene, overall arid conditions were continuously effective.Especially the difference between the geochemical composition of Early and Late Holocene sediments indicates distinctive environmental conditions. Respective humid phases took place in between 10.28 and 8.28ka yrBP (Early Holocene) and 1.85 to 1.72ka yrBP (Late Holocene). The Early Holocene phase is characterized by higher fluvial activity controlled by the humid climate and active tectonics. Right after the Middle Holocene droughts, a short-termed tendency to relatively fresh and oxic conditions prevailed. However, the small surface area of the lake and its shallow conditions caused fast variations of hydrology, oxidation level, salinity and organic productivity during the last 1850 years. We suggest that a combination of the instability of the Eastern Mediterranean climate and local conditions is the main control on the changing paleo-environment during the study period.