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The usefulness of ground-penetrating radar images for the research of a large sand-bed braided river: case study from the Vistula River (central Poland)

Lejzerowicz A., Kowalczyk S., Wysocka A.

Geologos

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2014

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Vol. 20, No. 1

35--47

EN

Ground-penetrating radar (GPR) surveys and sedimentological outcrop analyses were combined in order to determine the reflection patterns and internal architecture of terrace deposits of the Vistula River at Kępa Zawadowska in the southern part of Warsaw (central Poland). The sedimentary analyses concerned the granulometric composition and lithofacies analysis. The 34 GPR profiles, which were obtained in two outcrops, using a Malå RAMAC/GPR system with 500-MHz and 250-MHz shielded antennas, were up to 100 m long. The most characteristic ground-penetrating radar profiles are presented; they show a high-resolution data set of radar facies. The GPR data suggest the presence of three geophysically different units, namely with high-angle inclined reflections (radar facies 1), with discontinuous undulating or trough-shaped reflections (radar facies 2), and with low-angle reflections (radar facies 3). The internal structure of the fluvial deposits was obtained by integration of the GPR and sedimentological data, which combination provides a more accurate visualisation of sedimentary units than do reconstructions that are based only on standard lithologic point data.

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Transformacja form korytowych na przykładzie aluwiów piaskodennych rzek roztokowych środkowego vistulianu w Kotlinie Toruńskiej

Weckwerth P.

Landform Analysis

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2013

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Vol. 25

169--177

PL

Wyniki badań sedymentologicznych prowadzonych w północnej części Kotliny Toruńskiej pozwoliły na rozpoznanie zmian architektury środowiska sedymentacji korytowej piaskodennych rzek roztokowych. Rzeki te funkcjonowały w czasie środkowego vistulianu, a ich osady należą do górnego ogniwa formacji z Zielonczyna. Ewolucja sedymentacji fluwialnej następowała w dwóch fazach, którym odpowiadają odmienne formy korytowe. W pierwszej fazie dno koryta roztokowego zdominowane było przez pojedyncze odsypy poprzeczne, zaś w drugiej doszło do rozwoju złożonych odsypów śródkorytowych w wyniku łączenia się odsypów pojedynczych. Główną przyczyną transformacji morfologii koryta rzeki była zmiana reżimu rzek z niwalnego na proglacjalny w czasie awansu czoła lądolodu w stadiale głównym zlodowacenia wisły oraz rozwój systemu pradolinnego. Transformacja morfologii koryt skutkowała także wzrostem tempa agradacji ich osadów.

EN

The results of sedimentological research documented changes of architectural elements of fluvial sedimentary environment of sand-bed braided rivers in the Toruń Basin. These rivers existed at the middle Weichselian and their deposits belong to the upper member of Zielonczyn Formation. The evolution of fluvial sedimentation took place in the two phases, which correspond to different channel macroforms. The braided river bed was dominated by a unit bars during the first phase, while in the second phase were evolved compound mid-channel bars as a result of the amalgamation of unit bars. The main causes of the transformation of river channel morphology in the area of the Toruń Basin during the Weichselian glaciation included changes in river regime from nival to proglacial and development of ice-marginal valley. Transformation of channel morphology resulted in an increase in the aggradation rate.

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Palaeoslopes of Weichselian sand-bed braided rivers in the Toruń Basin (Poland): results of a palaeohydraulic analysis

Weckwerth Piotr

Geologos

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2011

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Vol. 17, No. 4

227--238

EN

Palaeoslopes of Weichselian sand-bed braided rivers have been reconstructed for two stages of fluvial development in the Toruń Basin. (1) The palaeoslope of the ‘fossil’ fluvial succession (buried under Weichselian tills) was calculated on the basis of the median grain size and the Shields parameter. The hydraulic gradient thus found is comparable with the hydraulic gradient of the present-day river. (2) The second developmental stage of the Toruń Basin (as a apart of the Noteć-Warta ice-marginal valley) took place after deglaciation. The slopes of river terraces are a few times lower than those calculated on the basis of the Shields parameter. The palaeoslope of the then river was estimated on the basis of a constant interdependency between the braidplain width, the channel geometry and the grain size. The river gradient that was thus calculated is similar to the measured terrace slope. Palaeoslope estimates in valleys similar to those in the Toruń Basin should consider the width of the braidplain.