Plioceński profil z Ruszowa w świetle analizy botanicznej

Abstract

PLIOCENE SECTION AT RUSZÓW IN THE LIGHT OF BOTANICAL ANALYSISSummaryAs a res lilt of the geological researches carried on from 1960 to 1964 in the area of West Sudetes and their foreland, the age of the Young Tertiary series (sands, quartz-feldspar gravels, kaolin clays) has been determined to be Upper Pliocene.Material for palaeobotanical examinations was taken in a brick field at Ruszów. The purpose of the examinations was to prove the age of white gravels and kaolin clays, and, if possibly, to define the age of a given series within the Upper Pliocene in more detail.The examinations were made by means of macroscopic and palynologic methods. With the aid of the results of botanical analysis conclusions are drawn as to the conditions and course of the sedimentation here considered. According to a spore-and-pollen diagram, the successive stages of plant development were reconstructed.Data on climatic conditions were obtained owing to the distinguished geographical plant elements; age of the deposits in study was determined, using the data from a comparison with some Upper Pliocene diagrams of certain European countries, to be middle Upper Pliocene (Reuverian B).Geological investigations demonstrate that at the Pliocene time an armlet of the ancient Nysa Łużycka River flowed across the area considered. Initially, it was a rapid water-course depositing coarse-grained sands and gravels (lower part of the section); then, it reduced its speed and fine-grained sands and clays were sedimented (upper part of the section here examined). Numerous plant macrofossils found at the top of the sequence are, for the most part, represented by aquatic, marshy and boggy plants that probably grew on watery grounds, morasses and quagmires, situated in the neighborhood of the river. Polen grains of trees and shrubs were brought here from slightly remote forests and brushwoods.Some geographic-vegetal elements are reported to occur in the plant material examined. This allows to subdivide the plants into two groups as follows: 1 – genera, so far living in the area of Middle Europe, 2 – genera, known to occur beyond the Middle European regions, exotic in our country at present, among them those characteristic of the Pliocene, with a predominant asseblage of the so-called “Reuver elements”, and relict genera of Miocene age, occurring sporadically.Age determination of the deposits from Rusz6w was made with the aid of W. H. Zagwijn's works (1959, 1960). Three stages have been distinguished by him in Pliocne: lower stage (Susterian), middle stage (Brunssumian), and upper stage (Reuverian). On the basis of the results obtained from palynological examinations, both middle and upper stages are subdivided by him into A, B and C periods. The diagram of the plants from Ruszów shows a striking resemblance to those of the interval Reuverian B, distinguished in some Upper Pliocene sections (e.g. the diagrams from Meinweg and Brachterwald). The following are features characteristic of the period Reuverian B:1 – low values of Pinus, a permanent predominance of Alnus that at several horizons exceeds 70%, a relatively high percentage of the Taxodium type and feeble traces of the Sequoia type;2 – occurrence of an almost whole set of the “Reuver elements” although in small quantities, and occurrence of relict Miocene forms in traces only;3 – deposits showing that they were laid down at the time of slackened flow of the river, and during the formation of local stagnation basins (upper part of the section).As compared with the flora from Rippersroda (Maj, Majewski, Unger), the flora from Ruszów is somewhat older and richer in Pliocene plant elements. Most probably, it corresponds to the upper member of Mizerna II (W. Szafer, 1954).