Macro‑and micro‑scale study and chronology of Late Weichselian aeolian sediments in Estonia, north‑eastern European Sand Belt

摘要

Patchy aeolian landforms, representing the NE part of the European Sand Belt, occur in NE Estonia, between the Gulf of Finland and Lake Peipsi. The dunes are restricted to the former glacial lakebed, thus lying directly in contact with glaciolacustrine sediments, and have so far prompted different opinions regarding their genesis and age. This study aims to answer these open questions regarding the age and origin of these landforms and to provide information on the associated past sedimentary processes. To achieve this, we combine macro-scale (sedimentary structures and ground-penetrating radar survey) and micro-scale (grain-size, shape and character of quartz grain surfaces and mineral composition) studies with optically stimulated luminescence dating. The glaciolacustrine fines in the study area are wavy stratified, with the occurrence of mica horizons and prevalence of quartz sand grains with aeolian characteristics. Therefore, these sediments argue for near-standing/low-energy water conditions in the glacial lake, where allochthonous material was delivered by wind. A fall in the lake level and the occurrence of dry land on the northern coast of the regressive Late Weichselian Lake Peipsi favoured aeolian activity from ca. 13.5 to 10.5 ka in the region. The aeolian accumulation was brief-as apparent from the results of the micro-scale study-and lacks evidence of sediment recycling. Only easily-removable mica was deflated at the end of the aeolian depositional phase. Aeolian activity terminated ca. 10.5 ka due to a rising groundwater level that is apparent from the onset of paludification in the region.