Ice, water, humans Quaternary landscape evolution in the Peribaltic Region 35th Annual conference of the German Quaternary Association DEUQUA e.v. 12th Annual Conference of the INQUA PeriBaltic WG 13th-17th September 2010, Greifswald Wojciech Wysota, Paweł Molewski, Włodzimierz Juśkiewicz, Anna Groblewska, Włodzimierz Narloch & Karol Tylmann Reconstruction of the Vistula ice stream lobe during LGM: preliminary results of the research project Institute of Geography Nicolaus Copernicus University, Toruń, Poland
The ongoing research project: Reconstruction of the Vistula ice stream lobe during the Main Stage of the Last glaciation on the basis of sedimentological and geomorphological signature in geospatial record It is financially supported by the Polish Ministry of Science and Higher Education on the basis of the project no. N N306 316835 The project webpage: http://www.lgm.umk.pl/
The first ideas of an ice-streaming within the southern part of the last Scandinavian Ice Sheet have been based on indicator erratic fans (eg. Jentsch, 1909; Milthers, 1909, 1934; Hasemann, 1931, 1935). Presumable ice streams, including the Baltic Ice Stream and secondary ice streams, were already mentioned by Kummerow (1950/51) and Kliewe (1961). The Baltic Ice Stream according to Kummerow (1950/51). The limit of the Vistula ice lobe on the geologicalmorphological map by P. Woldstedt (1935). Palaeo-Ice Streams in the southern Baltic Sea basin according to Kliewe (1961).
The Vistula ice stream was suggested as one of the secondary former ice streams within the southern Baltic depression (Punnkari, 1993). However, its activity has not been documented on the basis of geomorphological and sedimentological criteria. The existing works are only of conceptual character (eg. Marks, 2002, 2005; Morawski, 2009). Reconstruction of of the Vistula ice stream by Morawski (2009). Major ice streams according to Marks (2005)
The Vistula ice lobe area (~ 30 tys. km 2 ) is located in central Poland within the maximum extension of the Late Weichselian glaciation. It includes the eastern Great Poland (Wielkopolska) and Kujawy Lowland, part of the Lower Vistula valley and surrounding moraine plateaus.
Aims of the project (1) to identify and analyse geospatially the geomorphological and sedimentological record of the Vistula ice lobe, (2) to reproduce the subglacial processes against in bed conditions, (3) to determine the ice-flow pattern as well as delimit the parts of diverse ice dynamics, (4) to investigate the dynamics of the Vistula ice lobe in relation to the existing models and analogies to other palaeo- and modern ice streams.
The methods Three groups of methods were used in the study: GIS/geostatistic, field research and laboratory investigations. The geospatial analysis of geological and geomorphological data from published and archival sources as well as the results of the field and laboratory research remains the main study method. Strategy of reconstruction The chart shows stages and course of action in geospatial analysis.
Topographic maps Orthophotomaps Basic topographic maps at the scale 1:25 000 applied to location of sites/boreholes known from archival material and publications. Orthophotomaps at the scale 1:26 000 applied to detail identification of land cover and analysis of topolineaments.
Satellite images Multi-spectral images (satellite Landsat 7) Multi-spectral images (satellite Quickbird) Satellite images were applied to the analysis of topolineaments and verification of lineaments distinguished on the other images and DEM.
DEM Degital Elevation Model, DTED Level 1 (1:250 000) low-resolution (90-120 m) Degital Elevation Model, DTED Level 2 (1:50 000) resolution up to 25 m
The basic DEM at the scale 1 : 10 000 used to the analysis of glacial landforms in detail; high-resolution (up to 15 m). Note of a broad trough-shaped depression in central part of the area. This is a low till plain relief representing the bed of the former Vistula ice stream lobe.
GMP Geological Map of Poland at the scale 1:200 000 applied to the general recognition of geological structure in the area. Detailed Geological Map of Poland at the scale 1:50 000 (published sheets and available archival material) applied to study geological structure and glacial landforms in detail.
Collected bore-holes applied to the analysis of geological structure of the study area. Pleistocene Substratum An example of 380 bore-holes set from the one DGMP sheet prepared for statistical analysis of potential number of Weichselian till sheets.
Collected geomorphological maps at the scale 1:100 000 (appendices to DGMP shets), which were applied to the study morphology, morphometry and origin of glacial landscape in the area.
The map of glacial landforms Legend accumulative end moraines thrust end moraines ice-contact marginal landforms hummocky moraines tunnel valleys marginal valleys and channels eskers crevasse-filling landforms kames erosional glacial depressions the maximum limit of the Late Weichselian glaciation lakes rivers, creeks the DGMP sheet An example of ArcGIS cataloguing of glacial landforms prepared for the geospatial analysis in the study area.
Elongated landforms Red arrows shows elongated landforms which can interpret as a signature of fast ice flow.
Research localities Site type exposure exposure and drilling bore-hole the maximum limit of the Late Weichselian glaciation borders of regions 98 research sites Research at sites sites investigated by authors of the project sites known from the literature sites known from the literature and studied by authors the maximum limit of the Late Weichselian glaciation borders of regions 61 sites studied by authors of the project (included 18 sites previously studied and known from publications), 37 sites sites known from the literature and archival sources
Research localities Weichselian tills two tills one till lack till research site the maximum limit of the Late Weichselian glaciation borders of regions The one Wiechselian till occurs at more than 60% all research sites OSL/TL dating sites with OSL/TL dates lack of OSL/TL dating the maximum limit of the Late Weichselian glaciation borders of regions Absolute dating of inter-till sediments (mainly OSL/TL method). 37 form 98 studied sites have OSL/TL dates coming from different sources.
Aggregation of stratigraphic data Wysota et al., 2009 (modified)
Till fabric Palaeocurrents An example of sedimentological studies The site Nieszawa Late Weichselian tills Striae Late Saalian till Faceted boulders with striae at the base of Weichselian tills. (Molewski, 2007)
An example of sedimentological studies The site Nieszawa The upper Late Weichseian till The lower Late Weichseian till Sand wedges developed within the lower Weichselian till. The wedges have been deformed subglacially during ice sheet re-advance.
Sampling An example of sedimentological studies The site Obórki Late Weichselian till Fluvio-periglacial sediments Late Saalian till reworked by periglacial processes OSL ages 17.3 ka 27.1 ka 19.4 ka Glaciotectonically deformed sands and gravels 222 ka 272 ka Ventifacts lag Late Saalian till Ventifacts lag Late Saalian till Narloch et al., 2010 (in preparation)
An example of sedimentological studies The site Obórki Textural and petrographical data in the till succession. Microstructures distinguished in thin sections analysis: grain stacks (strings of at least four bridged grains), crushed grains, turbate structures (circular arrangement of grains), and grain lineations (microshears marked by alignments of elongated grains) Narloch et al., 2010 (in preparation)
The scenario of ice advances The extents of two ice advances in the Vistula ice lobe area during the Late Weichselian. Main ice flow directions in the Poznań re-advance have been based on till fabric, striae, ploughing marks, sub-till deformations. Wysota et al., 2009 (modified)
The scenario of ice advances Time-distance diagram (N-S) North South Wysota et al., 2009 (modified)
Conclusins The Vistula lobe area experienced two ice advances of varied extent during the Late Weichselian: the older one during the Leszno=Brandenburg Phase (~20.5 ka) and the younger one in the Poznań=Frankfurt Phase (~18.5 ka). Significant ice sheet retreat was followed by an ice re-advance during the Poznań Phase, overriding the extent of the Leszno Phase. Collected sedimentological and geomorphological data suggest fast ice flow, which was related with previously suggested the ice stream. It is supposed this palaeo-ice stream was mainly active during the Poznań Phase re-advance. The Vistula lobe, which at that time developed at the ice sheet margin, was a terrestrial termination of the ice stream.
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