The clays both the plateau like hills and ramparts were accumulated in the relatively small and deep englacial basins. Modeling of ice thickness Вейнбергс и др



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A. S. Savvaitov
About ways of reconstruction of thickness of ice cover for earlier

Stages of last deglaciation in eastern latvia
Сonsidering the reconstruction of the thickness of the ice covers N. I. Kriger (Кригер, 1972) has expressed an opinion on its insignificant thickness (from several tens to a few hundred meters) within peripherial zones of the Fennoscandian Ice Sheet within the Russian Plain (Belarus, Smolensk Region, etc.). He also concluded that the maximal ice cover thickness during maximal glaciation stage could exceed 2000 m. Approaches for the ice thickness determinations discussed below differ from those used by N. I. Kriger.

The eastern part of Latvia is a key area. It is possible to reconstruct the ice cover thickness at earlier stages (insular deglaciation stage, of the Last Deglaciation) for this time span of the glacial history using typical glacial formations (Аболтиньш и др., 1972 a). Such formations on the one hand are plateau like hills (zvonci) in the insular uplands and ramparts in the lowlands with their tops composed of clays (Вейнбергс и др., 2001) and on the other hand the formations of the contact zones of the Lubāns Ice Lobe studied in details (Dauškans, 2011).

The clays both the plateau like hills and ramparts were accumulated in the relatively small and deep englacial basins. Modeling of ice thickness (Вейнбергс и др., 2001) was executed at the following assumptions: (1) an altitude of the top surface of the clay reflects a hypsometric level of the englacial basin bottom; (2) a height of an ice shore over the bottom of this basin supposedly could be around 20–25 m. Besides, it is supposed that the calculated altitude of an ice surface (according to the parameter of the englacial basin bottom (1) and of the height of ice shore (2)) for each glacial stage had a distribution on a whole space of the ice cover for the corresponding glacial stage. Using these assumptions and combining them with the internal structure of the Pleistocene cover (for uplands) and also a bedrock surface only individually within the Eastern Latvian Lowland, sketches of the spatial distribution of ice thickness were compiled for the pre-Kaldebruņa (Gaiziņkalns interval), Kaldebruņa and Vaiņode-Gulbene Stages (the terms are from Savvaitovs, Veinbergs 1996; Stelle, Savvaitov 2004; Savvaitov, Stelle 2005; and Аболтинь и др. 1972 b). Zelčs et al. (2011) consider these stages as the recessional deglaciation phases (Dagda, Kaldebruņa, Gulbene).

Based on the modern topography the altitude of the glacier surface for the Gaiziņkalns stage of the pre-Kaldabruņa Stage (Gaiziņkalns plateau-like hill) could be suggested approximately 340 m, the Kaldabruņa Stage (Šķaune rampart) – 220 m and for the Vaiņode-Gulbene Stage (Šķeles and other ramparts within the Eastern Latvia Lowland) – 130 m (a. s. l.). The calculated ice thicknesses for each glacial stage are respectively could to be 180–280, 100–140 and 30–50 m. The ice cover during the pre-Kaldabruņa Stage was spread over the whole area of Eastern Latvia. It existed only within the Eastern Latvian Lowland during the Kaldabruņa and Vaiņode-Gulbene stages. The Widzeme Upland and other eastern ones represented the isolated «nunataks» during the Kaldabruņa and Vaiņode-Gulbene stages.

Dauškans (2011) clearly showed that the kame terraces on the southeastern slope of the Widzeme Upland reflect the contact zone of the Lubāns Ice Lobe. Hypsometric levels of the terraces by author mind approximately depended from the surfaces of this lobe. The highest erosion terraces (195–185 m) could be connected with the earlier activity of the Lubāns Ice Lobe during the Kaldabruņa Stage and were formed in the time of higher altitudes of the glacier surface. Their hypsometry was close to the surface of ice masses (Вейнбергс и др., 2011). Levels of the accumulative terraces (145–120 m) could be corresponding to the glacier surfaces during the Vaiņode-Gulbene Stage. Such conformity certainly is debatable but it shows the further perspectives of the ice thickness reconstruction.

The ice cover thickness was about 1500 m during the time of its maximal spreading of the Fennoscandian Ice Sheet of the Weichselian according to the model of Ehlers within the area of the Eastern Latvia (Satkūnas, 1997).


Аболтиньш О. П., Вейнбергс И. Г., Даниланс И. Я., Стелле В. Я., Страуме Я. А., Эберхардс Г. Я. Основные черты ледникового морфогенеза и особенности дегляциации последнего ледникового покрова на территории Латвии: Путеводитель полевого симпозиума IV Всесоюзн. межвед. совещ. по изучению краевых образований материкового оледенения. Рига, Латвийский гос. ун-т им. П. Стучки. 1972 a. C. 3–16.

Aболтинь О. П., Вейнбергс И. Г., Стелле В. Я., Эберхард Г. Я. Основные комплексы маргинальных образований и отступание ледника на территории Латвийской ССР: Сб. «Краевые образования материковых оледенений». Издательство «Наука». Москва. 1972 b. С. 30–37.

Вейнбергс И., Савваитов А., Стелле В., Цериня А. Мощность льда ранних стадий отступания последнего ледникового покрова и стратиграфическая идентификация ранних межстадиалов в Латвии // Бюллетень комиссии РАН по изучению четвертичного периода. 2001. № 64. C. 70–77.

Кригер Н. И. О мощности плейстоценовых ледниковых покровов // Ледниковый морфогенез. Рига: Зинатне, 1972. С. 5–18.

Dauškans M., 2011. Kēmu terašu morfoloģija un uzbūve īpatnības Vidzemes augstienē. Krāj: Zelčs. V. (galv. red.), Latvijas Universitātes Raksti 767. Sējums. Zemes un vides zinātnes. Latvijas Universitāte. Rīga. Lp. 17–34. (In Latvian).

Satkūnas J. Outline of Quaternary stratigraphy of Lithuania // The Late Pleistocene in Eastern Europe: stratigraphy, palaeoenvironment and climate. Abstract volume and excursion guide of the INQUA-SEQS Symposium. Vilnius. 1997. P. 65–68.

Savvaitov A., Stelle V. The development of the ice-sheet during Weichselian Glaciation in Latvia // The sixth Baltic Stratigraphical Conference. St. Peterburg. 2005. P. 116–119.

Savvaitovs A., Veinbergs I. Pēdējā ledāja dinamikas īpatnības Latvijas teritorijā dažādos tā attīstības etapos // Latvijas devona un kvartāra nogulumu pētījumu materiāli, Latvijas Universitāte Ģeoloģijas institūts. Rīga. 1996. Lp. 47–57. (in Latvian).



Stelle V., Savvaitov A. Evolution of Weichselian Glaciation curve in Latvia // International Field Symposium on Quaternary Geology and Modern Terrestrial Processes Western Latvia, September 12–17, 2004. Rīga. P. 49–50.

Zelčs V., Markots A., Nartišs M., Saks T. Pleistocene Glaciations in Latvia, Ch. 18. In: J. Ehlers, P. L. Gibbard, P. D. Hughes (Eds.): Developments in Quaternary Science, Vol. 15. Quaternary Glaciations – Extent and Chronology. Europe. Elsevier B. V. 2011. P. 221–229.
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