A 12.8-ka-long palaeoenvironmental record revealed by subfossil ostracod data from lacustrine freshwater tufa in Lake Sinijärv, northern Estonia

Palaeoclimate inferred from δ18O and palaeobotanical indicators in freshwater tufa of Lake Äntu Sinijärv, Estonia

“…This correlates quite well with low water level (Sohar and Kalm 2008), which reflects warmer climate conditions in the region. From 10,500 cal yr BP, there is a decrease in isotope composition till 9,200 cal yr BP (from -10.6‰ to -11.5‰), which most probably 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 indicates the globally known (Yu et al 2010) "9,300 yr" cold event.…”

“…Those data show that precipitation of tufa started at different times in different places in the lake. The beginning of tufa precipitation roughly correlates with the first Äntu low-water period (12,800-10,590 cal yr BP) determined by Sohar and Kalm (2008).…”

“…Deposition of freshwater tufa began ca. 11,800 cal yr BP which is ~2,000 years after the area was deglaciated at 13,800 cal yr BP (Saarse et al 2009) and 1,000 years later than indicated by Sohar and Kalm (2008). According to Männil (1967), freshwater tufa precipitation in the Pandivere area started at ca.…”

“…This 5,700-year long and relatively stable period suggests a local Holocene Thermal Maximum (HTM). Based on ostracod data (Sohar and Kalm 2008), the low-water period also shows correlation between δ 18 O values and climate: the higher values of δ 18 O during 7,500-6,000 cal yr BP and 4,700-3,700 cal yr BP indicate warmer climate with higher temperatures and lower water level (due to more intensive evaporation and lower precipitation rate). This higher temperature trend is also marked by LOI which shows a stable and high carbonate content in the sediment representing this time period, as freshwater tufa precipitates during ice-free periods, with relatively high temperatures and humidity.…”

“…Lake Äntu Sinijärv was chosen for study, because this is the only site in the region where freshwater tufa precipitation is still taking place. The lake has previously been studied by Saarse and Liiva (1995), Punning et al (2000) and Sohar and Kalm (2008). The δ 18 O composition of tufa deposits in the lake reflects also changes in the Atlantic Meridional Overturning Circulation (AMOC) (Bakke et al 2008;Andersson 2010), which in turn gives insight into the deglaciation history of the area.…”