Osady interglacjalne w Boczowie koło Rzepina (Polska zachodnia)

Abstract

Osady interglacjału mazowieckiego w Boczowie występują pod dwoma poziomami glin zwałowych zlodowaceń: północnopolskiego i środkowopolskiego. Z osadów z głęb. 81,5-89;7 m wykonano analizę pyłkową oraz oznaczono owoce, nasiona i megaspory, z czego uzyskano obraz sukcesji roślinnej odpowiadający interglacjałowi. Do interglacjału mazowieckiego zaliczono te osady na podstawie fauny i sytuacji geologicznej oraz korelacji ze stanowiskami interglacjału holsztyńskiego z NRD.

INTERGLACIAL DEPOSITS FROM BOCZÓW NEAR RZEPIN (WESTERN POLAND)

In the profile of the Quaternary from the vicinities of Boczów (Fig. 1) the deposits of the North and Middle Polish Glaciations are best developed. The thickness of the Quaternary changes from 40 to over 100 m depending on morphology of both the terrain surface and the top surface of the Tertiary. The latter is characterized by large denivellations as Tertiary deposits are glacitectonically piled up to about 140 m a.s.l. on one hand and incised by valleys to 120 m below s.l. on the other hand.

At Boczów the deposits of the Masovian Interglacial were penetrated by drilling at depths ranging from 66.5 to 94.0 m below terrain surface (from 21.0 m a.s.l. to 6.5 m below s.l.) so they are 27.5 m thick.

The Interglacial series comprises silts, silty sands and gyttja, that is deposits of stagnant and very slowly flowing waters. The list of molluscans identified (Tab. 1) mainly comprises species inhabiting stagnant waters.

The profile of Interglacial deposits may be divided into 2 parts: lower, highly variable in lithology and yielding fauna of molluscans, and upper, more monotonous in lithology and usually without faunal remains. They are separated by a cocquina layer about 7 cm thick and mainly consisting of shells of gastropod Paludina diluviana K u n t h (depth interval from 87.53 to 87.60 m). The subdivision into lower and upper parts is further supported by results of palynological studies as the boundary between the phytophases II and III was delineated at the depth of 87.6 m.

The pollen analysis covered Interglacial deposits derived from depth interval 81.5-89.7 m (Fig. 2). The results of the analysis as well as identifications of fruits, seeds and megaspores (Tab: 2) made it possible to reconstruct vegetational succession corresponding to Interglacial period.

During the first part of this Interglacial (period I) the climate was cold, boreal. Vegetation predominating in these times was forming pine-birch forests. The share of herbaceous plants ,(NAP) was initially fairly high, equal 25010 (Tab. 3). Grasses (Gramineae) and sedges (Cyperaceae) were most common here. There were also :present Chenopodiaceae, Caryophyllaceae, Compositae, Ranunculaceae, Artemisia and other plants. Herbaceous plants were presumably forming wide meadows among pine-birch forests at the beginning of the first period of development of vegetation from Boczów. Pines and birches were accompanied by spruce (Picea) and, sometimes alder (Alnus) whilst stenothermal deciduous trees (Quercus, Ulmus, Tilia) appeared in negligible amounts.

The second period was characterized by retreat of birch and a drop in share of pine. Spruce (Picea) and alder (Alnus) were predominating at these times as their share increased up to 34.5% and 32% at the most, respectively. The share of other trees was almost negligible and that of herbaceous plants was also low. This period displayed a marked warming up of climate in relation to the former.

A further amelioration of climate took place in the third period which corresponds to the climatic optimum. The resulting climate was of the temperate type. Forests from this period were characterized by predominance of fir (Abies), the share of which was equal 52.5% at the most. The share of alder (Alnus) was equal about 20%. From these times there are also recorded the highest shares of trees such as oak (Quercus - 10.5%), lime-tree (Tilia - 5.0%), hazel (Corylus - 8.0%) and hornbeam (Carpinus - 10.0%). The shares of these stenothermal deciduous trees are not very high as for the climatic optimum but, nevertheless, it may be stated that the whole floral assemblage from this period and shares of its particular components make it possible to allocate the pollen spectrum from Bocz6w in interglacial period.

The climate deteriorated during the fourth period, following the climatic optimum. Fir (Abies) as well as hazel (Corylus) and hornbeam (Carpinus) gradually disappeared and the share of oak (Quercus) and alder (Alnus) decreased at the advantage of pine (Pinus) and birch (Betula). The share of herbaceous plants (NAP) also increased, up to 26.5%. The climate predominating at the end of the fourth period was rather cool, boreal.

The results of palynological, paleozoological and lithological analyses evidence that this is interglacial deposit. Its age is indicated by the presence of gastropod Paludina diluviana K u n t h. Some conclusions concerning its stratigraphic position may be also grawn from geological setting and correlations with profiles of the Holstein Interglacial in eastern parts of the German Democratic Republic (M. Hannemann, 1964; A. G. Cepek, 1968).