Problemy stratygrafii neoplejstocenu Litwy

Petras Vajtiekunas

Abstract


STRATIGRAPHICAL PROBLEMS OF NEOPLEISTOCENE IN LITHUANIA

Summary

The moraine deposits of the last (Neman, North-Polish) glaciation in the area of Lithuania are characterized by their common occurrence. However their thickness and structure are various (Fig. 1). As a rule, the moraine cover of the last Glacial Epoch is separated from the similar Mesopleistocene cover with a bed of fluvioglacial and limnological deposits as well as with a series of lacustrine-marshy deposits of Eemian Interglacial. The amount of the sections of this age characterized palynologically exceeds 30. For the most part, the interglacial deposits are developed in continental facies due to the overgrowing of interglacial lakes, dead channels and marshes. The sections characteristic of the Eemian Interglacial are most frequently found in the vicinity of the village Miarkinie, in the southern area of Lithuania. This region is a stratotype as concerns determination of the interglacial horizon in the regional stratigraphical scheme of Lithuania. The name of the Miarkinie Interglacial was taken from the name of this village (O.P. Kondratiene, 1965, P. Vajtekunas, 1967).
A subdivision of the deposits belonging to the last Glacial Epoch in Lithuania is highly difficult. The Lithuanian authors lean towards the subdivision of this epoch into stages. The results of the examinations of drill sections in the vicinity of Miarkinie allow us to state that after the withdrawal of the inland ice of the Moscow (Warta) Glaciation, a large lake was formed in the vicinity of Jionionis, Maksimonis, Niatiesos and Paszylingi in South Lithuania. During the whole interglacial time, and at the beginning of the Neman Glaciation, a continuous sedimentation took place in the lake. Palynological examinations of the section at Jionionis have demonstrated that two warming periods of interstadial type are expressed in the upper part of its deposits. These took place after the Eemian  Interglacial (Figs. 2 and 3). The first warming period was called the first Jionionis Interstadial (O. P. Kondratiene, 1965), and the second one – the second Jionionis Interstadial. The first interstadial is known in its, whole sequence, whereas only the lower part of the deposits has been preserved within the second interstadial. The deposits of these interstadials are neither overlain, nor underlain with moraines. This is an evidence of the fact that at the beginning of the last glaciation the area of Lithuania was under periglacial conditions.
According to H. Gross (1964), the further history of the last glaciation is approximate to the course of the Middle-Würm Interpleniglacial, but so far has not precisely been examined. The stratigraphical situation of the “Dange Interstadial” (according to W. P. Gudelis, 1961) has not yet been explained, whereas the stratigraphy of the strata from the later part of the last glaciation seems to be much more substantiated. According to the data taken from the area of Lithuania, this part begins with the deposits of the Grudas (Leszno, Brandenburg) Stage. Stratigraphic, palynologic and geomorphologic data, as well as C14 method allow us to subdivide this period of glaciation into three stages, i.e.: Grudas, Zoglas and Aukshtey Stages as the probable equivalents of the Brandenburg, Frankfort and Pomerania Stages in West Europe, and into two interstadials: Antavil and Ula interstadials. Moreover, both Bolling and Allerod Interphases are well known in Lithuania. The stratigraphic subdivision of the Neopleistocene of Lithuania is presented in Tab. 1.

 


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