Changes in the Early Holocene lacustrine environment inferred from the subfossil ostracod record in the Varangu section, northern Estonia

Abstract

The Varangu section is located on the southern slope of the Pandivere Upland in northern Estonia. A silty clay bed formed in the study area at 11 ;200–9300 ;cal ;yr ;BP, according to ostracod subfossils (e.g. Tonnacypris estonica, Leucocythere mirabilis, Limnocytherina sanctipatricii) in an oxygen-rich cool and oligotrophic profundal lacustrine environment, with an inflow of surface waters through springs. The record of specific ostracods (e.g. Cyclocypris ovum, Cypridopsis vidua, Metacypris cordata) reflects littoral environments, ongoing eutrophication, temperature increase and a progressive shallowing of the lake in the early Holocene (9300–7400 ;cal ;yr ;BP) when the tufa bed accumulated. A slight cooling and productivity decrease at 9100–8600 ;cal ;yr ;BP preceded further temperature rise and water level lowering, leading to the development of a eutrophic lake and cease of ; ;tufa precipitation (8600–7400 ;cal ;yr ;BP).

Keywords

• ostracods
• palaeoecology
• tufa
• early Holocene
• Varangu
• northern Estonia.