O pleniglacjalnej florze z Nowej Huty i osadach czwartorzędu doliny Wisły pod Krakowem

Abstract

On the Pleniglacial flora from Nowa Huta and Quaternary deposits of the Vistula Valley near Cracow A layer of organic gilts, 55 cm in thickness, with streaks of peat," has .been found under an 11-metre cover of loess in a profile of the Pleistocene middle terrace of the Vistula valley at Nowa Huta (district of Cracow). A tooth (tusk) of a mammoth (Mammuthus primigenius) has been met with in this layer. The situation of the locality of the flora under study and the geological profile of the terrace described by J. K. Kozłowski et al. (1970) is Shown in Text-figs. 1 and 2. The pollen diagram (Text-fig. 3) presents a picture of woodless tundra vegetation With a fairly large share of Betula nana, Juniperus and shrubby species of Salix (small pollen grains of the Salix glauca type). It may well be that Populus is also present, groups of its pollen .being encountered in the bottom part of the profile. The AN:NAP ratio suggests that at the time of formation of the deposit the area was covered with herb vegetation to a high degree. This included communities, varying in composition, of sedige-grass meadows of wet tundra with such plants as Selaginella selaginoides, Ranunculus hyperboreus, Polygonum viviparum, Armeria maritima, Pleurospermum austriacum, Polemonium, Solanum dulcamara and many others. In depressions of the area there occurred water and marsh plant’s (Caltha, Phragmites, Sparganium, Hippuris, Myriophyllum spicatum, Potentilla palustris and Potamogeton). A fall in the pollen frequency can (be seen in the upper part of the profile and it perhaps indicates a certain 'loosening of the plant cover, Which was probably conneoted with the deterioration of climatic conditions in the direction of the more continental climate. This is reflected in the plant composition by an increase in the pollen amount of plants of dry habitats (Juniperus, Ephedra fragilis type, E. distachya, Artemisia, Chenopodiaceae, Silene-Arenaria type, Helianthemum nummularium type). RADIOCARBON DATING Three samples for radiocarbon dating were taken at equafl. intervals from the organic silt containing abundant vegetable detritus and thin layers of peat. Dating has been carried out .by Prof. Melbus A. Geyh, Director of the (14)C and (3)H Laboratory, Niedersächsisches Landesamt für Bodenforschunig, in Hannover, to whom we wish to express our heartfelt thanks for his disinterested help with this study. The samples weTe derived from three levels of the 55-centimetre thick deposit: 1. depth 5—15 cm Hv 6386 — 27 745 ± 300 years B. P. 2. depth 25—35 cm Hv 5955 — 18 460 ± 250 years B. P. 3. depth 45—50 cm Hv 7167 — 20 560 ± 735/675 years B. P. The result is astonishing, for the dates obtained for the samples from the lower part of the profile are similar .to each other but at the same time of much younger age than the sample from the top part. The explanation of this phenomenon 'boils down to the answers to at least two questions: 1. whether the upper sample, of the oldest age, happens to come from redeposited material, and 2. whether there are any data which would indicate the possibility of contamination with recent carbon and thus of making (14)C age of the other two samples younger. The answer to the first question is in the negative. The deposit under study is lithologically homogeneous and the pollen spectra connected with the upper (14)C sample do not differ in an essential manner from the palynological picture of vegetation obtained from the levels of middle and lower samples. The answer to the second question probably touches the essence of the problem. The layer of loess and organogenic silts lies on a thick layer of sand-gravel deposits with impervious Miocene clays at the bottom. As has been stated by Kleczkowski (1964), in this main water- -bearing layer there is a marked flow of water, enhanced by its particularly intense exploitation in this region. The water removed is replaced by water from some tributaries of the Vistula, especially from the nearby stream Dłubnia, which flows in a deep cut-in valley. In Kleczkowski’s (I.e.) opinion, the periodically occurring high water level in the streams increases the supplies of ground water. This may contain humus substances, which probably are responsible for the younger age of the samples from the middle and bottom parts of the deposit. In our case this interpretation limits the possibility of acceptance of rainwater infiltration through the loess layer to the layer dated. On the assumption that the lower radiometric age of the middle and bottom samples was caused by the contamination with the humus substances from the water-bearing layer, it remains to consider the question if the upmost sample, the oldest of age, is also rejuvenated to any degree. The answer to this question might be obtained by dating the deposit of the same period but derived from another site of the middle terrace in Cracow, less exposed to the above-mentioned changes in the water-bearing layer. Prof. M. A. Geyh’s opinion on the result of dating for the samples from Nowa Huta is as follows: If sample Hv 6386 does not come from redeposited materials, the probable age of this deposit is 27 750 years B.P. In Geyh and Rohde’s (1972) chronostratigraphic scale this date falls at the beginning of the upper Plen'iiglacial. Assuming that it may be also a little younger, it is possible to refer this deposit to the décline of the Denekamp interstadial, which, according to Geyh and Rohde, lasted from 33 200 to 28 800 years B. P. STRATIGRAPHY The Quaternary deposits that fill up the Vistula valley in Cracow are marked by their fairly great lithological differentiation and morphology, sharply outlined in the terrain. Few patches of moraine clay of Cracovian age, are scattered high at the edge of the valley. They contain boulders of Scandinavian rocks, having a considerable size sometimes. In the profile of the middle terrace, in Which we are specially concerned here, a loess layer, many meters thick, overlies the layers of sand, organogenic deposits, limestone gravels and Carpathian flysch gravels at the bottom. Late glacial and Holocene deposits, with frequent layers of fossil peat, occupy the valley floor within the limits of the maximum floods of the Vistula. Miocene clays occur in the substratum of the Quaternary in the valley, whereas the substratum at its elevated edges is made up of Cretaceous marls and Upper-Jurassic limestones. The above-mentioned layer of organogenic deposits, mostly about 1 m in thickness, separates the layer of loess from that of fluvial sands and gravels. On the base of its thickness we may suppose that in some places it is older than the organic silt from Nowa Huta. It permits us to assume that this layer took rise during the interstadials of the middle Pleniglacial (Hengelo-Denekamp). On the other hand, the layer of limestone and flysch fluvial gravels has been referred to the border period between the Eemian interglacial and the last glaciation. At that time the climate was cool and wet, and so the processes of erosion and accumulation and the transportation power of rivers were much more increased. So far, the layer of gravels ha's been ascribed, in most cases, to the Saalian glaciation. An evaluation of the results of studies carried out ulp to now leads to the conclusion that the Pleistocene deposits of the Vistula valley in Cracow is made up, above all, of formations genetically related to the decline of the Eemian interglacial and the last glaciation. The older stages of the Pleistocene are represented by scanty and not always quite convincing traces. Their slight contribution speaks about the scale and intensity of erosive-accumulative processes in the last glaciation. These processes were favoured by the nearness of the Carpathians, which provided abundant flysch material, readily made movable. Flowing waters of great erosive power were able to strip the valleys of Carpathian rivers of most of their older deposits, which at that time were already markedly reduced. VEGETATION OF POLAND IN THE MIDDLE PLENIGLACIAL So far, we know eleven localities of fossil floras, representing fragments of the interstadials of the middle Pleniglacial in the area of the Polish Carpathians and their foreland. The list of these localities (Table 1) has been extended by adding the flora from Tarzymiechy on Wieprz (Srodoń 1954), which, according to Jahn (1956) and Jersak (1973), probably comes from the last glaciation and not from the interstadial of the Saalian glaciation. In the interstadials of the middle Pleniglacial the territory of southern Poland was occupied by parkland tundra communities (Pinus sylvestris, P. cembra, Larix, Betula t. alba, Alnus, Salix, Hippophae) with strips of galilery forests and scrubs in the valleys of the Vistula and its Carpathian tributaries. The northern range of trees coincided approximately with the southern edge of the Lublin and Kielce—Sandomierz Uplands and further, having traversed the Silesian Upland, ran along the foreland of the Sudetes (Text-fig. 4). In the sheltered Carpathian valleys forests found conditions to become more compact and differentiated (Pinus sylvestris, P. cembra, Larix, Pice a, Betula t. alba, Populus, Alnus cf. incana), the timber line running at 650 m a.s.l. (Nowy Targ—Orawa Basin). Our sources of information concerning the areas situated further to the north are very scanty and controversial as regards age determination. These areas were probably covered by woodless shrubby tundra (Betula nana, Salix, Ephedra). The fossil floras from Kępno and Tarzymiechy suggest this type of vegetation. The relatively small share of plants regarded as steppe plants (Artemisia, Chenopodiaceae, Compositae, Ephedra) along with the abundance of the members of the families Cyperaceae and Gramineae in the composition of the vegetation of the Carpathians and their near foreland is striking. Towards the north-east (Lublin Upland) the share of Artemisia increases markedly (Łążek, Tarzymiechy). The generally high shares of the Cyperaceae, numerous water and peatbog plants and mosses of the genus Sphagnum (Łążek) seem to indicate a humid climate in the period of the middle Pleniglacial. A significant consequence of that was the ice-sheet which covered northern Europe, including a large part of the territory of Poland, in the upper Pleniglacial. This opinion coincides with the results of studies carried out in western Europe, where the middle Pleniglacial, comprising the Hengelo and Denekamp interstadials, is considered to have been more humid than the lower and the upper Pleniglacial (Hammen, Wijmstra, Zagwijn 1971). A NOTE ON THE WOOLLY MAMMOTH There are 15 known localities of bones of Mammuthus primigenius in the Cracow territory (Kubiak 1965, and more recent finds). Only in four cases these bones came from their primary deposition in loess and loess-underlying layers. The other localities provided -bones (chiefly teeth) found redeposited in the layers, generally postglacial, lining the bed of the Vistula. It is noteworthy and not insignificant, as regards the determination of age of the gravels which occur at the bottom of the loess terrace, that no traces of the steppe mammoth (M. trogontherii), recorded manifold from the foreland of the Carpathians and Sudetes (Kubiak I.e.), have hitherto 'been discovered in the Cracow area. This mammoth, regarded as the direct ancestor of the woolly mammoth, belonged to the fauna of the early and middlle Pleistocene of Eurone, up to the end of the Saalian glaciation (Butzer 1972). In southern and south-western Poland there are about 160 known localities of the woolly mammoth (Kubiak I.e.), not including those of other big herbivorous mammals. Their considerable density suggests a compact, exuberant and, at the same time, diverse vegetation of tundra in that period. This has been confirmed by the results of numerous palynological studies. The present knowledge of the history of vegetation during the last glaciation permits the supposition that the woolly mammoth could not be frequent in our territory until the Brorup interstadial, abounding in forests, was over, i.e. in the Pleniglacial. The map of its fossil localities in Poland shows their two distinct groupings, one in the foreland of the Carpathians and Sudetes and the other in the northern part of the country, chiefly in the region of the Lower Vistula (Kowalski 1959, Text-fig. 5). It is not easy to estimate the truthfulness of this picture, for some by-factors come into play here, especially rather great differences in the degree of exploration of particular parts of the country (Kubiak 1965; Karaszewski 1976). Nevertheless, we may venture a tentative interpretation of this, so markedly differentiated, distribution. The aggregation of fossil localities in southern Poland may have resulted from the density of mammoths, which increased under the influence of deteriorating climatic conditions after the Denekamp interstadial and that of the ice sheet, expanding from the north. Here we may therefore assume the dominance of the localities of the upper Pleniglacial. In the North-Polish aggregation the localities representing the lover and middle Pleniglacial and those of the late glacial ought to predominate. These last probably do not belong to the raTest ones, for at that time the mammoth was forced to migrate northwards under the pressure of the forest which spread from the south and in the younger period of the Altered interstadial covered the whole country. Thus, the occurrence of the last woolly mammoths in Poland may be expected in the north. The role of the palaeolithic man, probably responsible for the final fate of the woolly mammoth, i.e. its complete extinction (Butzer 1972; Budyko 1973), has been omitted in these considerations.