Interglacjalny zbiornik jeziorny w Niewodowie na Wysoczyźnie Kolneńskiej

Abstract

 Kopalny zbiornik jeziorny Niewodowo powstał w jednej z mis wytopiskowych uformowanych w wyniku deglacjacji arealnej. Jezioro istniało tu w fitofazie d interglacjału eemskiego i przekształciło się w zabagnienie w fitofazach od e do g. Wypełnienie pozostałego po jeziorze zagłębienia warstwą glin spływowych wskazuje na silne ochłodzenie połączone z rozwojem procesów soliflukcyjnych (schyłek eemu lub wczesny vistulian), przykrycie zaś tych glin warstwą pyłów eolicznych na klimat suchy, chłodny (późny glacjał). Występowanie osadów eemskich bez przykrycia utworami glacigenicznymi przeczy przyjmowanej przez niektórych autorów koncepcji objęcia Wysoczyzny Kolneńskiej lądolodem we wczesnym vistulianie. INTERGLACIAL LACUSTRINE RESERVOIR AT NIEWODOWO, KOLNO UPLAND The paper presents the results of studies on the section of Eemien Interglacial lacustrine-boggy deposits at Niewadowo, the first hitherto recorded in the Kolno Upland (Fig. 1). The deposits originated in a small reservoir situated at northern side of Narew River gorge near Łomża, in area with relief displaying district traces of areal glaciations. Ablational depression, in which the reservoir is situated, is separated from the gorge by several dead-ice forms (kames and kame fans) and a dry  valley varying in width and with depressions without outflow in its floor (Figs. 2–4). It is also separated by the Drozdowo basin, the shape of which suggests that it represents northerm part of a larger depression, southern part of which was situated at the place of the present-day Narew River gorge. This indicates that the gorge was infilled with dead ice at early stages of its developmel1t.The lacustrine section at Niewodowo begins with (Figs. 5A, B, 7) sands and gyttja and peat (1.05 m thick), ovarlain by various-grained sands with admixture of peat and sand with gravel, and solifluction loams and silts. Palynological analysis showed Eemian age these deposits (Figs. 7, 9).The lake and bog following it existed here in the phytophases d–g in the K. Jessen and V. Milthers (1928) subdivision. Solifluction loams indicate strong cooling at the end of the Eemian Interglacial or the beginning of the Vistulian Glaciation (Vistulian I), and a thin intercalation of muds and peats at the top of the loams (Fig. 5B) – amelioration of climate presumably in one of the Vistulian Glaciation interglacials.Silts covering lacustrine deposits in the Niewodowo section were also found to form fairly large covers in the Kolno Upland and isolated patches in the Łomża Upland (Figs. 6, 10). They were also recorded at Łomżyca, where they rest on accumulational surface covered with gravel-boulder layer and deformed by fissures from thermic contraction, and they are overlain by eolian sands. Such position suggests that these silts were deposited at the beginning of the Late Glacial. The distribution of the silty covers suggests alimentation from the Kurpie Plain and other sanders in the forefield of the Vistulian icesheet.The results of studies on the section of ancient Niewodowo reservoir make possible dating the relief in southern Kolno Upland at the Mid-Polish Glaciation. They give further support to the viewpoint according to which this area does not display traces of icesheets older than that of the Leszno phase of the Vistulian Glaciation, i.e. alternative to that of L.R. Sieriebrianny (1978), J. Stasiakowa (1979) and others. The studies on the relief of the Kolno and Łomża Uplands (A. Musial, 1970, 1978;K. Straszewska, 1975a, b, 1980) do not confirm the point of view of E.P. Zarrina and I.I. Krasnow (1965) that the limit of the Oszmiany–Mińsk stage of the Moscow Glaciation passes across the Narew River gorge and further along the Czerwony Bor dead ice forms.