Wyniki wyszukiwania - BazTech

1

Substratum morphology and significance during the Weichselian Odra ice lobe advance in northeast Germany and northwest Poland

Hermanowski P.

Geologos

|

2015

|

Vol. 21, No. 4

241--248

EN

In the Polish Lowlands, three main ice lobes, referred to as Odra, Vistula and Mazury, formed during the Last Scandinavian Glaciation. These lobes protruded at least several kilometres beyond the main ice margin and it is believed that they represent terminal parts of the ice streams. Applied geostatistical analysis based on numerous geological data has allowed an approximate reconstruction of the Odra ice lobe substratum in the area of northwest Poland and northeast Germany. A spatial representation of the Odra lobe substratum clearly illustrates the adverse slope of the glacier bed, but also indicates areas morphologically prone to ice streaming. It is suggested that the ice took advantage of local topography that enabled advance out of the Baltic basin; consequently, the ice followed a topographic low which, in combination with favourable hydraulic conditions of its substratum, likely initiated ice streaming.

2

Basal till and subglacial conditions at the base of the Upper Odra Lobe (southern Poland) during the Odranian Glaciation

Salamon T.

Geological Quarterly

|

2014

|

Vol. 58, No. 4

779–-794

EN

The objective of this contribution is detail characteristics of the basal till and the conditions in the base of Upper Odra Lobe. The lobe was formed in a foremountain area. Its central part was a Niemodlin Plain and the W part of the Racibórz Basin, surrounded by areas that have a much more varied relief.Particular attention is paid to the conditions at the ice sheet base, generatingthe dynamics ofglaciermovement. The study is based on analysis of the basal till. Three sites with basal till lying on different types of substratum (more typical for the study area) are presented. The basal till of the Upper Odra Lobe is characterized by spatial variations. Different intensities of its deformation indicate that large lateral differences in conditions occurred in the lobe substratum. The lithology controlled the rate of basal water pressure, and thus the strength of both the subglacial sediments and the ice-bed coupling. Various strain rates in the till profiles indicate that the conditions at the ice-sheet base also changed with time. The ice sheet was highly mobile, even on the coarse-grained substratum. The low permeability of the Quaternary substratum, and the relatively small thickness of the Quaternary sands and gravels resulted in a high water pressure at the ice-sheet base. The movement of the Upper Odra Lobe was concentrated in the basal zone of the ice sheet. The main mechanism of basal motion was sliding and deformation of the subglacial sediments. Deformation probably occurred in restricted areas and did not have a pervasive character.

3

Mikrostrukturalne i mikroteksturalne cechy glin lodowcowych jako wskaźnik warunków subglacjalnych na przykładzie stanowiska Lusowo (Pojezierze Poznańskie)

Morawska M., Morawski M., Woronko B.

Landform Analysis

|

2010

|

Vol. 13

61-76

PL

Wielokierunkowym badaniom sedymentologicznym poddano gliny lodowcowe budujące wysoczyznę morenową rozciągającą się na południe od moren czołowych fazy poznańskiej zlodowacenia wisły. Teren badań zlokalizowano około 10 km na NW od Poznania. W jego obrębie zaznacza się obecność wielkoskalowych lineacji glacjalnych, będących efektem funkcjonowania w czasie zlodowacenia wisły szybkiego paleostrumienia lodowego. Przeprowadzono analizy: litofacjalną osadów, uziarnienia, charakteru powierzchni ziarn kwarcu frakcji piaszczystej według Cailleux (1942) i w SEM oraz analizę mikrostrukturalną na podstawie płytek cienkich. Uzyskane wyniki pozwoliły wnioskować o prawdopodobnym źródle osadów. Ponadto uwidoczniła się duża jednorodność osadów pod względem uziarnienia, jak również charakteru obtoczenia i zmatowienia powierzchni ziarn kwarcu frakcji 0,8-1,0 mm oraz znikomy wpływ transportu w środowisku glacjalnym na charakter mikrorzeźby powierzchni ziarn kwarcu. Natomiast wyniki analizy mikrostrukturalnej płytek cienkich pokazały zróżnicowanie glin lodowcowych w profilu pionowym, odpowiadające zmiennym warunkom towarzyszącym akumulacji osadów. Zapis mikrostrukturalny uwidocznił obecność ciągłej, ale o zmiennej miąższości warstwy deformacyjnej. Czynnikiem modelującym zmiany była zawartość i ciśnienie wody porowej.

EN

Multiproxy sedimentological analyses were carried out on glacial till building morainic plateau which extends south from the terminal moraines of the Pomorska phase, Vistulian Glaciation. The study area was located about 10 km to the north-west from Poznań. Mega-scale glacial lineations occur among the plateau. They are the effect of a fast flowing paleo- ice stream existing during the Vistulian Glaciation. Following analysis were performed: lithofacial analysis of sediments, the granulometric composition of deposit, the frosting and rounding analyses of sand quartz grains (1.0–0.8 mm) according to Cailleux (1942) and in SEM and analysis of thin sections. The results suggest probable source of the deposits and show homogeneity in terms of granulometry and rounding and frosting of quartz grains in fraction of 0.8-1.0 mm. Glacial transport appears to have limited influence on the microstructure of quartz grains surface. Analysis of thin sections show the vertical differentiation of glacial till according to variable conditions accompanying its deposition. Microstructures recorded continuous deformation layer which varied in thickness. The volume and pressure of pore water were the factors responsible for the changes.