Glacial varves at Pärnu, south-western Estonia: a local varve chronology and proglacial sedimentary environment

A new varve chronology comprising 584 consecutive varve years, varve thickness changes and proglacial sedimentary environment are analysed across the Pandivere-Neva (>13 300yrBP) belt of ice-recessional formations in coastal Estonia, eastern Baltic. Varved clays in the area have been deposited in the Baltic Ice Lake. All investigated sequences display a normal varve series with decreasing varve thickness upwards. According to the varve correlation, two groups of varve graphs could be distinguished: those representing sequences from the distal side and from the proximal side of the Pandivere-Neva ice marginal formations. Accumulation of varved clays started ca. 100yr earlier in the distal part. A massive clay unit with corresponding 20 silty varves in some sequences precedes the beginning of varve formation at the proximal part of the basin and could therefore correspond to a ca. 20yr long ice-stagnation period during the Pandivere-Neva Stade. Ice proximal conditions on both sides of the recessional formations (within 30km distance) ceased simultaneously within a period of 10-15yr, which is reflected in reduced total varve thickness accompanied with the beginning of winter layer dominance within a single varve. Because of post-sedimentary erosion, the length of the presented chronology underestimates the duration of proglacial conditions. Good visual correlation between the mean varve thickness graphs from the Pärnu area and from Lake Peipsi, eastern Estonia, indicate the possible regional causes of varve thickness changes and simultaneous varve formation in two basins.