Evolution of a small Eemian lake in a unique location on a kame hill: Ha  cki site, NE Poland Miroslawa Kupryjanowicz, Danuta Drzymulska * University of Bialystok, Institute of Biology, Department of Botany, K. Ciolkowskiego 1J, 15-245 Bialystok, Poland article info Article history: Available online 13 June 2015 Keywords: Eemian interglacial Early Weichselian Kame hill Lake development Pollen analysis Plant macrofossils abstract An Eemian lake in a unique location at the top of a kame hill was found in NE Poland. Results of pollen and microscopic plant remains analyses show that despite the unusual location, its development and terrestrialization were typical for small meso-/eutrophic lakes of the temperate zone. At the end of the interglacial period an overgrown basin was flooded with water and again transformed into a lake. It existed until the beginning of the Brørup interstadial, and then it was covered with diluvia and/or aeolian sediment and finally disappeared. © 2015 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction During geological mapping for the Detailed Geological Map of Poland, 1:50 000 scale, a fossil hollow filled with peat-lacustrine sediments located at the top of a kame hill was discovered (the vicinity of Ha cki village, Bielsk Plain, NE Poland) (Brud and Kupryjanowicz, 2002). The palaeobasin is only several dozen me- ters in diameter and is not reflected in the contemporary relief. On the basis of pollen analysis, the deposits have been dated to the post-optimal part of the Eemian interglacial, as well as the begin- ning of the Early Vistulian. The occurrence of Eemian peat-lacustrine sediments on kame hills is very rare. In Poland, apart from the Ha cki site, only one location has been described: Proniewicze, also located on Bielsk Plain (Krupi  nski, 1995; Mycielska-Dowgiallo et al., 1995). Contem- porary lakes and mires situated at the top of hills are a great rarity. Two were noted in northeastern Poland, Tatarska G ora, near Goldap, and G ora Zamkowa, near Orzysz. There is no knowledge about analogous objects in other parts of Poland or abroad. The aim of this study, based on palynological and macrofossil analyses, was to reconstruct the developmental stages of the Eemian lake in a unique location at the top of a kame hill. 2. Study area The studied site is located on the Bielsk Plain (Fig. 1), which is part of the North Podlasie Lowland (Kondracki, 1998). The Bielsk Plain is a vast morainic plateau with ice-dammed lake deposits. The age of this plain is considered to be Saalian, i.e. Wartanian in Polish stratigraphy (Nowicki, 1971; Ber, 2005). The most common landforms occurring in the central part of Bielsk Plain are kames (Fig. 2). They rise from a few to about a dozen metres above extensive melt-out depression. Of particular interest are small closed depressions filled with Eemian organic deposits, situated on top of flat kame surfaces (Proniewicze PR.1/93 profile; Krupi  nski, 1995). West of the depression, a vast kame terrace occurs. Its flat surface is pitted by small and shallow melt-out depressions, which during the Eemian interglacial existed as lakes or peat-bogs. In one of these depressions, organic sediments of this interglacial were recognised (Proniewicze P-3 profile; Kupryjanowicz, 2008). Within the extensive depression, in the vicinity of Ha cki village, a small isolated melt hollow is situated (Fig. 2). Kame hills and kame ridges are present. The main kame ridge is linguoid. On its top, shallow boreholes (Ha cki S-3 profile; Figs. 2 and 3) showed the presence of a palaeodepression filled with Eemian biogenic deposits (Brud and Kupryjanowicz, 2002), which are the subject of this study. 3. Material and methods Pollen analysis was carried out by a standard method according to Berglund and Ralska-Jasiewiczowa (1986). Analysis of plant * Corresponding author. E-mail addresses: m.kupryjanowicz@uwb.edu.pl (M. Kupryjanowicz), drzym@ uwb.edu.pl (D. Drzymulska). Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint http://dx.doi.org/10.1016/j.quaint.2015.05.043 1040-6182/© 2015 Elsevier Ltd and INQUA. All rights reserved. Quaternary International 386 (2015) 203e207