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Zastosowanie mikrotomografii komputerowej do badania orientacji klastów w glinach lodowcowych

Hermanowski Piotr, Duda Piotr

Przegląd Geologiczny

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2019

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Vol. 67, nr 8

653--661

EN

Limitations of macroscopic measurements and observations of glacial tills, no matter how informative they are, have contributed to the development of micromorphological analysis first in thin sections, since the 80’s using X-ray computed tomography, and recently X-ray computed microtomography (μ-CT). The цCT has found wide applications in science including earth sciences where is used for imagining various geological samples in the 3D view. The sampling procedure and preparation of samples do not generate much effort, and eventually, allow analysis of samples with a preserved undisturbed structure. Herein, we present a short review and methodology of μCT as well as its application to the study of glacial tills. For example, we analyzed a subglacial till sample from the lee side of a drumlin located in the Stargard drumlin field area, NW Poland. The results show a distinctive bimodal pattern of clast fabrics which is interpreted as a result of subglacial till squeezing. Smaller clasts are obliquely oriented to the major direction of the ice flow whereas the larger clasts orientation is approximately in accordance with the major shear stress direction. Overall, our data emphasize the potential of the μ-CT in glacial till studies.

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Unravelling the complex nature of the Upper Weichselian till section at Gdynia Babie Doły, northern Poland

Woźniak P. P., Czubla P.

Geologos

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2016

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Vol. 22, No. 1

15--32

EN

The complexity of glacial sequences may increase when these formed underneath ice sheets despite subsequent changes in their extent that are accompanied by alterations in the direction of the ice flow. Our aim was to determine whether or not changes in ice sheet dynamics during the Late Weichselian are also recorded in sediments formed north of the area of its fluctuating margin (i.e., where the ice sheet prevailed independent of such fluctuations). It is shown that in these areas such a record could have occurred, as documented by results of till studies at Babie Doły. The examination was carried out using several analyses: lithofacies properties of sediments, petrographic till composition (fine gravel fraction, indicator erratics), till matrix CaCO3 content, till fabric, as well as orientation of striae on the top surfaces of large clasts. In parallel, datings of sub- and supra-till sediments using the TL method were carried out. The basal till at Babie Doły represents almost the entire Upper Weichselian, but it can be divided into subunits whose features indicate different ice flow directions and debris supply. The lower subunit developed as a result of the palaeo-ice stream along the main axis of the Baltic Sea (from the north), expanding to areas adjacent to the depression of the Gulf of Gdańsk. The upper subunit developed when the influence of the palaeo-ice stream in the study area decreased, the main role having been taken over by the ice flowing from the northwest. The till analysed also shows considerable lateral variation, indicative of the mosaic nature of subglacial sedimentation. We consider the diversity of permeability of deposits over which the ice sheet extended to be the prime factor that determined such a situation.

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Mikromorfologia glin lodowcowych jako narzędzie w rekonstrukcji procesów subglacjalnych

Narloch W., Piotrowski J. A.

Przegląd Geologiczny

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2013

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Vol. 61, nr 5

294--303

EN

Micromorphology has become an important tool in investigations of glacial tills. Structure and texture of tills studied in thin sections can be used to decipher the origin of tills, in particular their depositional and deformational history, but also to shed light on the nature of subglacial erosion, transport and deposition processes in general. In combination with laboratory experiments on till shearing under controlled conditions, micromorphology yields useful, quantitative data on till rheology that helps understanding the processes of ice movement over soft, deformable beds.This paper is a review of micromorphology applications to the study of subglacial tills as reported in the leading modern literature and presentation of a case study from Obórki site in north-central Poland that illustrates the potential of this method in the context of the last Scandinavian Ice Sheet.

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Przetrwałe moreny czołowe na NW skłonie Garbu Lubawskiego : struktura i mechanizmy formowania

Tylmann K., Wysota W., Piotrowski J. A.

Landform Analysis

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2013

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Vol. 25

143--157

PL

W artykule przedstawiono wyniki badań litofacjalnych i strukturalnych osadów budujących przetrwałe moreny czołowe na NW skłonie Garbu Lubawskiego. Uzyskane rezultaty wskazują na złożoną genezę badanych wzgórz oraz na wyraźne cechy świadczące o ich przetrwałości. Zaproponowano modele genetyczne dla analizowanych form, prezentujące główne etapy ich formowania oraz mechanizmy sprzyjające ich zachowaniu w strefie subglacjalnej. Analiza budowy badanych form sugeruje ich „palimpsestowy” charakter oraz możliwy wpływ wieloletniej zmarzliny na procesy przetrwania wzgórz pod ostatnim lądolodem skandynawskim.

EN

This article presents the results of lithofacies and structural studies of deposits in the palimpsest terminal moraines on the NW slope of Lubawa Upland. The results document a complex origin of these hills and some distinct features suggesting their palimpsest nature. We propose genetic models highlighting the main stages of their formation as well as the mechanisms of their preservation in the subglacial system. The inner structure of the hills suggests a crucial role of permafrost in preservation protecting the hills from erosion under the last Scandinavian Ice Sheet.

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Geneza i transformacja rzeźby morenowej w północno-zachodniej części Garbu Lubawskiego (Polska północna)

Tylmann K., Wysota W.

Przegląd Geologiczny

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2011

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Vol. 59, nr 11

739-750

EN

The paper presents the investigation results concerning the origin and transformation of the morainic landscape in the northwest part of Lubawa Upland. Detailed sedimentological studies of the sediments within the morainic hill in Rożental and the reconstruction of their depositional and deformational processes are presented. We proposed a model of landscape formation and transformation in examined area. The reconstruction of the palaeogeographical conditions which have been prevailed during the late Pleistocene is also proposed. Collected data show that morainic landscape in the northwestern part of Lubawa Upland reveal landforms of an older origin. It is suggested that relief of examined area consist some features of "palimpsest landscape". The older glacial landforms, formed before the last ice advance, can exist here.