During the Pomeranian phase of the Weichselian glaciation (~17–16 ka), the Toruń-Eberswalde ice-marginal valley (NW Poland and easternmost Germany) drained water from the Pomeranian ice sheet, while intensive aeolian processes took place across Europe in the foreland of the Scandinavian ice sheet (‘European Sand Belt’). The micromorphology of the quartz grains in the Toruń-Eberswalde ice-marginal valley shows no traces of these aeolian processes, or only vague signs of aeolian abrasion. This is unique among the aeolian sediments in other Pleistocene ice-marginal valleys in this part of Europe. The study of the surfaces of the quartz grains shows that the supply of grains by streams from the south was minimal, which must be ascribed to the climate deterioration during the Last Glacial Maximum, which resulted in a decrease of the discharge of these extraglacial rivers to the ice-marginal valley.
The heavy-mineral composition of the Weichselian fluvial successions deposited by an ephemeral meandering river and by a sand-bed braided river in the Toruń Basin (central Poland) was analysed. On the basis of a lithofacies analysis, in combination with the composition of the heavy-mineral assemblages, the fluvial processes and river-channel morphology were reconstructed. This allows determining the provenance of the fluvial deposits and the rivers’ discharge regimes. A model is proposed which can explain the changes in the amount of individual minerals in the fluvial sediments of different ages under the conditions of the oscillating Scandinavian ice sheet. The model assumes that, during the ice-sheet advances, the proglacial streams supplied large amounts of heavy minerals that were less resistant to mechanical abrasion. During the main phase of the ice-sheet retreat, the distance between the ice sheet and the Toruń Basin increased, and the amount of non-resistant minerals diminished as a result of sediment reworking in proglacial rivers. Due to the unique location of the Toruń Basin at the front of the Scandinavian ice sheet during the Weichselian glaciation, the heavy-mineral assemblages in the fluvial deposits form a valuable tool for the recognition of the ice-sheet extent.
This article attempts to determine the course of geological strata in part of the G³ogów-Baruth Ice-Marginal Valley, using the multilayer neural networks of a sigmoidal type, trained by the back propagation method that is based on the known theory of gradient optimization methods. Determination of the trend of individual layers was made based on the coordinates (x, y) and the following data: depth of the top, depth of the base and thickness of the strata, obtained from field studies.
In the year 1966 a well field supplying the city of Zielona Góra with water was opened in the ice-marginal valley of the Odra River, near the village of Zawada. After three years of water pumping from 22 wells tapping the shallow valley aquifer, a significant deterioration of water quality, especially involving the increase of concentrations of iron, sulphates, manganese and water hardness, as a result of the process of sulphide oxidation accumulated within the recent Holocene deposits, was observed. Despite drastic changes in quality (the increase of iron concentration to approximately 30 mg/l and sulphate concentration to above 300 mg/l), the well field was still operated as its water was used for purifying (coagulation) of the polluted surface water supplying the city of Zielona Góra. Based on the analysis of over 30-year-long period of water pumping, it was stated that the effect of the sulphide oxidation process on the quality of water was noticeable for the period of 19 years. The period of persisting very high concentrations of iron of above 15 mg/l amounted to approximately 6 years. It was also stated that the process of reducing the concentrations following the period of their maximum increase proceeded in two stages – the stage of rapid reduction of concentrations which lasted for about 4 years and the stage of slow changes which took about 10 years. The first one was related to the exhaustion of sulphides within the formations marked by good permeability, and the period of semi-decomposition of sulphides, which lasted for about 3 years, was determined based on the changes in iron concentrations. On the other hand, the reduction of concentrations at the stage of slow changes may be linked to the oxidation of sulphides occurring in the formations marked by weak permeability (silts, clays, peats).
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