Przyczynek do znajomości flory kopalnej w Cimoszkowicach

M. Gawłowska


Contribution to the knowledge of the fossil flora of Cimoszkowicze

I. Geological structure of the territory. Materials for investigation were collected in the ravine of Cimoszkowicze well knowrn in literature thanks to its interglaeial formations. It is one of the numerous ravines cutting across the territory covered with loess in the central part of the Waywodeship of Nowogródek. The geological investigations of this territory, carried 011. during recent years, have confirmed the succession of the strata in the ravine of Cimoszkowicze. At the bottom we see the red-brown moraine superposed by a layer of gyttja and turf covered with fluvioglacial formations. Upward, appears a deposit of loess, and above it a humus sediment passing into turf. This layer is covered again with loess. The fact that in the ravine of Cimoszkowicze turfs lie above the red-brown moraine has a great importance for the definition of the age of the formation of the interglacial depo sits. As the red-brown moraine belongs to the central-Polish glacial period (Varsovien I), therefore the turfs in Cimoszkowicze must have been formed only after the retreat of the glacier covering the Polish territory at the period of this glaciation. II. Fossil flora from Cimoszkowicze. Tending to obtain an exact knowledge of the interglacial flora in Cimoszkowicze, I have examined as well the lower turf — relatively the so-called grob detritus lying on the red moraine (figl) — as also the upper layer of humus and turf 70 cm thick and situated between two loess deposits (fig. 2). In the lower turf, samples for research could not have been collected from the whole layer, therefore its upper strata alone were investigated. I have effected macroscopic investigations according to the method of L. v o n Post , counting 200 pollen grains in each sample, boiled first in NaOH. A. Lower flora. In the lower deposit of turf were found macroscopic remains of plants (p. 5). The results of the pollen analysis permit us to get a still better knowledge of the interglacial flora from Cimoszkowicze. The microscopic remains of plants thus discovered are presented on tab. I. A scrupulous examination of the corresponding pollen diagram permits to discover three floristic, climatic periods which must have succeeded each other at the time of the development of the investigated layers of lower turf. PHASIS I. Among pollen grains of trees the quantitative predominancy belongs to those of the pine (Pinus — in average 62,1%)), and of the mixed oak forest (Quercetum mixtum = Quercus sp. + TJlmus sp. + Tilia cordata + Tilia platyphyllos), where the oak (Quercus — in average 27,1%) is dominant, with but a very scanty addition of elm (TJlmus sp. — in average 3,7%). In this phasis the oak reaches its maximum. PHASIS II. A high percentage of pollen grains of hazel (Corylus — in average 92,4%), which attains here its maximum (199,5%), characterizes this phasis. The hazel must have been abundant in the undergrowth of woods. The number of Quercetum mixtum pollen grains is somewhat smaller. Among the components of Quercetum mixtum the part of the oak is greatly reduced (in average 10,2%), while, on the contrary, increases the number of the pollen grains of the elm (in average 5,2%) which reaches here its maximum (13,5%). In this phasis appears also the lime-tree. The number of its pollen grains increases constantly obtaining towards the close of this phasis the preponderance7 over the oak and the elm. There appear here both kinds of the lime: Tilia cordata and T. platyphyllos, and their number is more or less equal. Among the pollen grains of other trees, the pine presents the highest percentage (in average 53%). Steadily appear also the birch (Betula — in average 10,1%) and the alder (Alnus 9,9%). PHASIS III. It is characterized by a yet higher percentage than previously of Quercetum mixtum pollen grains (maximum 48%) in which however reigns almost exclusively the lime (Tilia cordata and T. platyphyllos, the last is rather more abundant). In this phasis the part of the pine in the composition of forests is greatly reduced (20,3%), while the alder reaches high percentages (in average 39%). Hazel pollen grains attain (in average 26,1%). On the ground of the above described composition of forest vegetation in all three phases, one may infer of the climate reigning at that time. It was probably distinguished by a rather warm temperature for the forests of that age belonged principally to the Quercetum mixtum type. The period of time characterized by the culmination of the hazel, later by a great preponderancy of the lime over the pollen grains of other trees, must be considered as the climatic optimum of this interglacial. Phasis I with an abundance of oak pollen grains might have had certain traits characteristic of continental climate. The results of my investigations are quite concordant to those of St. Kulczyński, who examined in 1928 the fossil flora in Cimoszkowicze (1°). Comparison with other interglacial floras. If we compare the above description of the fossil flora, in Cimoszkowicze with other interglacial floras known in Poland we must observe above all its remarkable resemblance to the pollen analysis of interglacial turfs in Samostrzelniki near Grodno (11). The flora of Cimoszkowicze corresponds to two lower periods discerned in Samostrzelniki, namely phasis I and II to the period of preponderancy of the pine and the hazel, and phasis III to the period of preponderancy of the lime. This resemblance is so much the more characteristic that the turfs in Samostrzelniki have been recognized as belonging to the interglacial Masovien I which preceeds the central-Polish glaciation. Among the diluvial floras of the interglacial period Masovien II, which came after the central-Polish glaciation; we find in Żoliborz near Warsaw (12) a phasis of vegetation resembling that of Cimoszkowicze. In other interglacial Polish floras belonging to Masovien II, there lack phases correspondent to the fossil flora of Cimoszkowicze; on the contrary j ą great resemblance links that flora to Russian fossil floras of the same period. We can find out common traits by comparing the pollen diagram from Cimoszkowicze with diagrams from the locality Lojew in the district Gomel, and Potylicha near Moscow (15). B. Flora of the upper turf. In the upper turf which lies between two deposits of loess appear macroscopic remains of plants in a rather small quantity (p. 12). Comparatively more numerous are here the seeds of larch (Larix) which, on the ground of the effected measurements (fig. 3), I consider as belonging to the species Larix polonica (16). The results of the pollen analysis are presented on table II. On the ground of the correspondent pollen diagram II, we can divide into three unequal phases the period of time in which \yas found the upper turf. PHASIS I embraces only the lowest layer of the upper turf and is characterized by a very scanty forest vegetation and high percentages of pine (Pinus — 44%) and birch (Betula 42%). Besides the above mentioned species, there appears here only the alder (Alnus — 13,5%), and are found traces of spruce (Pice a). Such a composition of forests indicates a cold, but relatively moist climate. PHASIS II is characterized by a great number of pollen grains of the pine (in average 72,3%). The alder has a remarkable share in the first part of this phasis, and in its second part the birch. In a small quantity appear the pollen grains of the components of Quercetum mixtum (maximum 5,5%), the pollen grains of the hazel and the spruce. The climate of this phasis must have been warmer than that of the preceding one, but also cool enough. In the second part of the phasis the temperature grew probably lower again, which is suggested by the gradual disappearance of the components of the mixed oak forest in the upper levels and the ever higher percentages of the birch. PHASIS III. The curve of the pollen grains of the pine sinks violently in this phasis, while the number of pollen grains of the birch increases immensely attainig 95%. The willow appears in a rather greater quantity reaching 5%. Pollen grains of other trees lack almost completely. Such floristic conditions give evidence to a still greater deterioration of the climate which must have been characterized by relatively very low temperatures. The flora of the upper turf has also been precedently described by St. Kulczynski (10). The results I have obtained are in perfect concordance to those of his researches. It is rather difficult to establish at what time took place the formation of the upper part of the fossil flora in Cimoszkowicze. The initial and final cold phases and the amelioration of the climate at the time of the middle phasis would indicate that the flora of the upper turf is a quite separate interglacial flora. This supposition seems so much the more probable that the upper turf is situated between layers of loess, namely between two formations of glacial proveniency. It is not yet exactly known at what time those layers were deposited. It may be that the loess covering the upper turf corresponds to the glaciation which has not yet reached Poland, but has revealed itself only in the northern European countries. On the contrary, the lower loess is probably a formation which was deposited at the time of the Baltic glaciation, the last that covered the territory of Poland.

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