Reconstruction of the Holocene palaeoenvironmental conditions accordingly to the multiproxy sedimentary records from Lake Pilvelis, Latvia Karina Stankevica a , Laimdota Kalnina a, * , Maris Klavins a , Aija Cerina a , Liene Ustupe a , Enn Kaup b a Department of Environmental Science, University of Latvia, Raina Blvd.19, LV 1586 Riga, Latvia b Institute of Geology, Tallinn University of Technology, Ehitajate tee 5,19086 Tallinn, Estonia article info Article history: Available online xxx Keywords: Gyttja Microfossils Macrofossils Pollen Humic substances Elemental composition abstract Reconstruction of the Holocene palaeoenvironment conditions in Southeastern Latvia is based on mul- tiproxy records from Lake Pilvelis: pollen, plant macrofossil and microfossil analysis; loss-on-ignition (LOI) measurements; 14 C dating; humic substances content; humification index; and elemental composition of gyttja organic mass. The data complex obtained in the result of multiproxy studies of sediments in Lake Pilvelis indicates significant changes in the depositional environment during the lake development. Data from Lake Pilvelis show that the start of organic-rich sediments formation before approximately 9750 cal BP, when birchepine forest dominated in the surrounding landscape. Diagrams and data sets show six remarkable comparatively short cooling periods during the Holocene, which are related to changes in temperature and water level and influenced values and variability of remains. The investigation recognized the 8.4 ka BP and 4.6 ka BP cold events, while other cooling events can be recognised conditionally. During the events of 4.0 ka BP, the water level decreased extremely and the climate was probably drier, indicated by the comparison of records from Lake Pilvelis, Mazais Svetinu Bog and Lake Razna. A comparison of pollen data from Lake Pilvelis with Lake Kurjanovas, Mazais Svetinu Bog and Lake Razna shows some similarities, revealing features of cooler climatic conditions approximately at the time characterised by an increase of Betula and herb pollen. © 2015 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction Sediment sequences from small lakes without or with limited inflow/outflow of rivers and springs function as archives for studying long-term fluctuations of environmental conditions, palaeoclimate, the history of vegetation in the lakes, and their catchment areas and human impact on them. Sediment accumu- lation process has been ongoing continually since the formation of these lakes. Therefore, they contain continuous records about the history of these lakes and their surroundings (Meyers, 2003). These insights can be used in forecasting an ecosystem's potential future (Wetzel, 2001). In eutrophic water bodies, which are common in the North Temperate Zone, primary production, such as algae and aquatic macrophytes, dominates because of increasing nutrient inputs instead of mineralization processes in lakes (Cooke et al., 2005). Intensive sedimentation takes place in relatively small lakes in particular, resulting in development of thick organogenic sediment layers of sapropel, gyttja or dy (terminology is dependent more on historical traditions and differences in the sediment composition) (Hansen, 1959). Gyttja or sapropel is a prospective material for diverse applications (Stankevica and Klavins, 2013). In Latvia, the classification is made only for the term ‘sapropel’ to identify organic limnic sediments as valuable resource with a wide range of possible uses in agriculture, balneology and industry, but the term ‘gyttja’ usually is used to define organic rich lake sediments in limnology and for past climate studies. Sapropel type classification (Stankevica and Klavins, 2013) has been used in the current study to identify differences in analysed sediment samples with aim to * Corresponding author. E-mail address: Laimdota.Kalnina@lu.lv (L. Kalnina). Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint http://dx.doi.org/10.1016/j.quaint.2015.02.031 1040-6182/© 2015 Elsevier Ltd and INQUA. All rights reserved. Quaternary International xxx (2015) 1e14 Please cite this article in press as: Stankevica, K., et al., Reconstruction of the Holocene palaeoenvironmental conditions accordingly to the multiproxy sedimentary records from Lake Pilvelis, Latvia, Quaternary International (2015), http://dx.doi.org/10.1016/j.quaint.2015.02.031