Ice-marginal Valley Research Articles

In front of the retreating ice-sheet: Fauna complex of central-western Poland in MIS 3–2 (Krosinko site)

A new locality in Central Europe (Krosinko, Poland) yields a rich fossil material of great taxonomical variety. Its location in the Warsaw–Berlin ice-marginal valley, where it forms a 1-m horizon at a the depth of 6–8 m, is suited to a taphonomic analysis aimed at reconstructing the paleoevents and depositional history of the late Pleistocene (MIS 3–2).Our analysis revealed that the material accumulated as the result of high-energy fluvial transport. This transport disturbed the original bone associations, as indicated by the lack of articulation, low refitting, and bone surface modification. During water movement, the bones were polished, abraded, pitted, and fragmented. Prior to that, however, taphonomic signatures were left behind by predators, humans, and plant roots. This is the first time that unquestionable burning marks have been found on woolly rhino remains from Poland.The secondary context of the faunal assemblage was confirmed by neodymium isotope studies of the faunal fragments and sediment. Given the results of sedimentological analysis from previous studies, these sediments can be associated with a high-energy braided river. The remains were moved along with paleobotanical material and flints in a westerly direction; this is suggested by the direction of water flows in the valley and the river waters supplying it.The deposition occurred within a single geologic event around 26 ka BP, as indicated by the youngest radiocarbon date of the remains, or ca. 19 ka BP, considering the geochronological constraints for the local LGM ice margin position in central and eastern Poland ∼22–18 ka, and the specified accumulation time of the sediments in which they were found. Secondary mineralization of manganese and iron on the bones was the final taphonomical process that impacted the remains.The combined taphonomic, palaeozoological, isotopic and geological results show for the first time for a Polish paleontological site how data integration improves interpretation and highlights the advantages of a multiproxy approach.

Sand sources and migration of the dune fields in the central European Sand Belt – A pattern analysis approach

Long-standing studies of the fixed late-glacial dune fields of the European Sand Belt (ESB) indicate that its development was driven by the degradation of permafrost and the widespread incision of rivers. Ice-marginal valleys, smaller valleys and limnic sediments are considered to be the main sand sources for dune fields within the ESB. However, the provenance of particular dune fields has not been independently assessed. Hence, discussion on the dynamics of the ESB dune fields has been limited to general statements about the distance and duration of aeolian transport. This problem was addressed through the geomorphological (pattern) analysis of 40 dune fields located within the central ESB. Using the calculated construction times and assumed migration rates, we identified the distances covered by the dune fields and their potential sand sources. The study confirmed that fluvial and fluvioglacial sediments were the main sand sources for the ESB dune fields. Most dune fields were found to have migrated over distances of 5–15 km during their development, confirming the short and local aeolian transport. At the same time, long-distance migration of dunes in areas located far from the Fennoscandinavian Ice Sheet was not ruled out. Results indicate dune migration rates as low as 0.5–3.5 m/yr. comparable to contemporary dune fields in cold regions. The methods used have the potential for use in studies in dune fields of other climatic zones, although the results need further verification based on geochemical studies.

Eastern periphery of the Magdalenian world. Wierzawice 31 hunting campsite (SE Poland)

Wierzawice 31 site is one of the easternmost Magdalenian sites, situated in the south-eastern corner of the Kolbuszowa Plateau surrounded, to the east, by the broad San River valley and, on the south, by the sub-Carpathian ice-marginal valley. This archaeological site lies in an area with surface deposits developed as periglacial stratified silty-sandy sediments about 10 m thick, adjoined in the NW by an isolated patch of loess of the island type. The lithic artefacts occur in a small area of about 40 sqm, with the main concentration of artefacts centred around the focus. Almost 70% of the tools are hunting weapon elements. Both technology and tool typology are typical for Magdalenian assemblages. Absolute dating (14C and TL) indicates a very young, Allerød age for the site. The raw materials used indicate connections with the northern part of the Sandomierz Upland. Imports of “Volhynian flint” suggest possible contacts with areas beyond the limits of the Magdalenian range.

The evolution of meandering and anabranching rivers in postglacial and loess landscapes of Europe

This study aims to explain the influence of sediments and landforms of postglacial and loess landscapes of Europe on processes forming meandering and anabranching rivers. Based on a literature review, sedimentary architecture, types and grain-size of deposits, and channel planform changes since the Late Pleniglacial were collected for extensive set of European rivers. These data were used to create a conceptual model explaining the evolution of meandering and anabranching rivers in both types of landscape. The present study shows that the inheritance of glacial and fluvioglacial landforms and sediments, and loess formation, influence types of processes forming anabranching and meandering rivers. Point bar accretion formed meandering rivers in postglacial zone whereas oblique accretion dominated in loess areas. Anabranching rivers of postglacial zone evolved through the formation of crevasse channels and meandering anabranches. Anabranching rivers of loess zone formed sustained bifurcations. Postglacial and loess rivers reacted differently to increased deposition and humidity in the Late-Holocene. Meanders of postglacial zone formed channel bars owing to increase in stream power and sediment load. In cases of flow energy decrease, and sustained upstream sediment delivery, they turned into anastomosing rivers. Anabranching rivers in ice-marginal valleys maintained its courses until hydro technical works in the 19th century. Low-energy meandering rivers of loess areas became wetlands owing to deposition of silts. High-energy meandering and anabranching rivers maintained the planforms throughout the Holocene. These findings need to be refined by detailed studies on the evolution of rivers in subarctic zone, and large rivers of Europe.

The Elbe Palaeovalley: Evolution from an ice-marginal valley to a sedimentary trap (SE North Sea)

The southeastern North Sea was a sub-aerially exposed periglacial environment during the late Weichselian. At that time, the approximately 210 km long and 40 km wide SE–NW trending Elbe Palaeovalley (EPV) was the main conduit for meltwater from the southern margin of the Scandinavian ice sheet and rivers draining the North European plain. Only few studies investigated the environmental organization of the Northwest European shelves during deglacial sea level rise resulting in vague reconstructions of the drainage systems. Here, a detailed analysis of sediment echo-sounder data and core samples are presented to study the EPV morphology and stratigraphic infill. The valley base is about 65 m below the present sea-level. This SE-NW palaeo-drainage with its braided system developed during the MIS 2 sea level fall and lowstand in a periglacial environment. During deglacial sea-level rise, the EPV evolved into an estuary with tributaries, intertidal and subtidal flats. After the early Holocene (∼10 cal ka BP), ongoing sea-level rise drowned the EPV system which became the major sedimentary trap in the southern North Sea. Successive sea level rise and associated changes in the hydrodynamic regime led to three stages of shelf organization that were recorded in the valley infill successions: (1) shallow basin with restricted connections to Atlantic water; (2) the southwestern connection with the Dover Strait; (3) the open marine environment at 5.8 cal ka BP after the drowning of Dogger Bank.

MIS 3–1 fauna from Krosinko: Implications for the past biogeography, chronology and palaeoenvironments of Poland

A faunal assemblage was recently recovered from the Krosinko site in Poland, marking a new site in the Warsaw–Berlin ice-marginal valley. Analysis and radiocarbon dating of the remains revealed the presence of two subassemblages: one Late Pleistocene (at least MIS 3–2) and one Holocene (MIS 1), with the former being taxonomically highly diverse. By referring to previous Polish studies, the Pleistocene mammal bone assemblage allowed us to reconstruct the biogeography of its individual components: woolly mammoths, woolly rhinoceri, horses, giant deer, red deer, fallow deer, reindeer, steppe bison, aurochses, bears, and cave lions. The biogeography was later combined with radiocarbon chronology using 21 dates from Krosinko. The wide range of radiocarbon dates (48.4–26.4 ka BP) probably reflects different chronological distributions of species resulting from the changing climate and environment as well as the diverse original sources of the bones. The remains, which constituted a single, compact geological horizon, was possibly deposited in a single geological event around 26 ka BP, as inferred from the most recently produced radiocarbon date. Radiocarbon datings of woolly rhinoceros remains have shown the species to have been present around 38 ka BP, a time that it had previously been considered to have been non-existent in Europe (with no evidence having been discovered for the period 40–34 ka BP). This result alters the stratigraphic gap range for the woolly rhinoceros in Europe to 40–38 ka BP. The clear dominance of woolly mammoth and woolly rhinoceros specimens reflects the structure of the Mammuthus–Coelodonta faunal complex. The main representatives of this complex preferred the dry and cold conditions that characterized the palaeoenvironmental conditions in Krosinko in MIS 2 and thus in Central Europe, as shown by the integration of the results of the fauna and those of the sediments in which they were deposited. These palaeoenvironmental features are related to the mammoth steppe, which was a long-lived biome in Eurasia and whose diversity influenced the faunal distribution. Thus, the species-by-species review of taxa performed in this paper, against the background of previous results from Poland, illuminates the individual responses of taxa to changing environmental conditions in response to climatic ones. These changes led to the disappearance of the mammoth steppe and near or total extinction of the fauna species inhabiting it.

Integrated environmental records in Late Pleistocene Poland: The paleofluvial regime and paleoclimate inferred from Krosinko site

Multiproxy analyses performed at the Krosinko site in the Warsaw–Berlin ice marginal valley have provided data that characterize the depositional conditions, the paleofluvial regime, and the paleoclimate and help reconstruct the paleo-environment at a time of significant sediment (alluvium) accumulation (starting in central Poland ca. 45 ka BP). The sedimentological study, including sand-grain morphology and micromorphology analyses, reveals the presence at Krosinko of a meandering river and of a braided river during the Eemian (MIS 5e) and Upper Pleniweichselian (MIS 2), respectively. The fluvial regime changed over time, from low-energy, through high-energy, to low-energy, as documented by the differently formed sedimentary units A–D (vertical sedimentary succession from base to top: sandy silt, sand, gravelly sand, and sand). Sedimentary unit A and the lower part of unit B were accumulated in the Eemian interglacial (MIS 5e) by the low-energy meandering river. The high-energy fluvial environment during the Weichselian is associated with long, intense sediment transport, organic remains, and flints, as confirmed by taphonomic studies on conifer cones (Picea cf. abies) and wood remains (Juniperus). The river operated under distinct environmental conditions. First, during the accumulation of the upper part of unit B and unit C, there was a strong influence of freezing and aeolian weathering, which weakened significantly over time (unit D). This in turn indicates a change in climate from periglacial (upper part of unit B and unit C), when we also document the presence of permafrost in the subsurface or relatively deep seasonal frost, to temperate (unit D). With warming in the Holocene (MIS 1), an oxbow lake developed in Krosinko, the presence of which is recorded by peat.

Detrital zircon geochronology and provenance of Pleistocene loess and contributing glacial sources, midcontinental USA

Midcontinental North America contains extensive loess deposits that have been studied with geochemical, mineralogical, and stratigraphic techniques to explore glacial history and sediment provenance. Much of this analysis has focused on loess deposits that accumulated during the last glacial maximum (LGM), in part because of the ubiquity of unweathered Peoria Silt deposits. We test the utility of detrital zircon (DZ) U–Pb dating, which offers a weathering-resistant approach to the determination of loess provenance and can uniquely be applied to both LGM and older (commonly more altered) pre-LGM loess units. We determined DZ U–Pb age distributions (n = 1385 U–Pb ages) for the lobes that contributed sediment to Mississippi and Illinois River valley loess: Des Moines Lobe, Superior Lobe, Green Bay Lobe, Lake Michigan Lobe and Huron-Erie Lobe. We also measured DZ U–Pb age distributions (n = 4466 U–Pb ages) sampled from loess sites located along the bluffs of the Illinois River Valley and Mississippi River Valley. Samples were collected from Peoria Silt (Wisconsin Episode; Marine Isotope Stage (MIS 2)), Roxana Silt (Wisconsin Episode; MIS 3), Loveland Silt (Illinois Episode; MIS 6), and Crowley's Ridge Silt (pre-Illinois Episode).LGM glacial tills provide distinct DZ age signatures that can be used to identify glacial source contributions to loess deposits. Loess DZ age signatures in the Peoria Silt of the Illinois River Valley and the Roxana Silt of the northern lower Mississippi River Valley change temporally in a manner consistent with blockage and avulsion of the ancient Mississippi River, representing a proof-of-concept for the DZ loess provenance method in the midcontinent. The loess DZ record also provides insight into the pre-LGM drainage network and glacial lobe extents. DZ signatures for the MIS 3 Roxana Silt, along the Mississippi Valley, implies minimal sediment input from the Des Moines Lobe, suggesting this lobe was short-lived, existed further northward, or provided only limited sediment to meltwater valleys during this time. The dominant Huron-Erie Lobe signature throughout pre-LGM loess units shows that ice flow from the eastern Labrador Dome was a persistent feature during earlier glaciations. Finally, some western-derived DZ ages in pre-MIS 2 loess of the middle and lower Mississippi River Valley suggests that drainage networks that followed the modern Missouri River system were present prior to the LGM and integrated with the Mississippi River system.

Mire Development and Disappearance due to River Capture as Hydrogeological and Geomorphological Consequences of LGM Ice-Marginal Valley Evolution at the Vistula-Neman Watershed

The advances and retreats of ice sheets during Pleistocene significantly changed high- and mid-latitude landscapes and hydrological systems, albeit differently, in North America and Europe. On the southern margin of the Last Glacial Maximum (LGM) in the Baltic Sea basin, a specific type of valley has developed between glacial margins and upland or mountain slopes. We studied new geological data (boreholes, electrical resistivity imaging (ERI) from this geomorphic setting in Northeast Poland to understand: (1) how the landscape and river network evolved to eventually produce peat mires during the Holocene, and (2) the nature of groundwater recharge to fens in the upper Biebrza Valley. We present the results on a geological cross-section with hydrogeological interpretation. We also discuss regional geomorphology. In addition, we present the LGM extent derived from a spatial distribution of Vistulian (Weichselian) terminal moraines. These end moraines are also interpreted as Saalian kames. Thus, we additionally present another method of LGM extent delineation from a physicogeographical division. We link the steep slopes of the studied valley walls (kame terrace fronts) with thermokarst erosion in the periglacial zone. We then document the hydrogeological window (DISCONTINUITY in the till layer over the confined aquifer), which enables the outflow of groundwater into the peat bog. Although minerotrophic fen mire development in the study area is likely to be sustained in the near future through sufficient groundwater supply, the projected capture of the Biebrza River by the Neman River will not allow for sustaining peatland development.

Types of underfit stream valleys on the territory of Belarus

According to the materials of geological and geomorphological mapping and the results of the analysis of remote sen sing data (ERS), the authors identify several types of valleys of underfit rivers in Belarus. They differ from each other according to their relief, features of sediment accumulation and stages of postglacial evolution of river valleys. Their sections are located in the section of the meltwater valleys and within outwash plains. Authors distinguish: Dnieperian type (one active and one dead channel of the valley), Drutian type (narrow fluvial and wide non-fluvial zones within one valley, the valley bends may resemble the channel bends of the palaeo-river that formed the valley), West Berezinian type with erosion and non-erosion variant (all stages of river development are presented – from braided channels through large mean ders to small meanders), the Palaeo-Islochian type (dead river channels, including meandering on the outwash plains).

The evolution and disappearance of “false delta” multi-channel systems in postglacial areas (Central Europe)

Abstract River deltas are complex aggradational systems preserving the history of their evolution in the depositional record. While coastal deltas are extensively studied, little is known about “false delta”, multi-channel systems situated at a certain distance from the sea. The term “false delta” is used here in reference to a system of bifurcating alluvial channels influenced by sea level changes, and variations in discharge and sediment delivery. These interactions resulted in the formation of a multitude of channel planforms, and a “delta-like” fluvial landscape. We present the first study that aims to determine the influence of downstream controls (sea level changes) and upstream controls (discharge and sediment delivery) on the evolution of a “false delta” multi-channel system in the postglacial areas of central Europe. Our study is based on geophysical, geological and remote sensing methods, alongside radiocarbon dating (AMS–accelerator mass spectrometry). We use the example of a “delta-like” system of palaeochannels that connected the Obra and Odra Rivers (central Europe, Poland). The “false delta” formed within an ice-marginal valley by the activity of large-scale meandering channels in the Late Glacial period. Between 13,300 and 11,200 cal. BP, a transition to an anabranching and sinuous planform was caused by the coupled effects of a lowering Baltic Sea level, an increase in flood frequency and in sediment delivery. During this period, bifurcation began conveying 30% of the flow through a former subglacial tunnel to the Warta River. The Holocene evolution of this multi-channel system was driven by the interplay of successive sea level rise and sediment delivery from the middle Obra valley, and former subglacial tunnels. The upstream controls dominated during the last 4400 cal. BP, and were enhanced by mill constructions and deforestation in the last millennium. The false delta “disappeared” in the 18th century owing to a 63% decrease in flows. Based on these findings, we propose a model describing the evolution of “false delta” river systems in postglacial areas of Europe. Three stages of evolution are identified: i) formation by high flows, ii) sustaining the flow through particular branches in conditions of dominating deposition, and iii) discontinuation of the false deltas by hydro technical works. The model can be extrapolated to other areas in postglacial Europe and North America after refinement by further field studies.

RECONSTRUCTION OF GROUNDWATER FLOW IN THE WATER-BEARING SYSTEM OF THE WARSAW-BERLIN ICE-MARGINAL VALLEY IN THE KOŚCIAN–WOLSZTYN AREA BASED ON LOCAL AND REGIONAL MODELS

Hydrogeological research of river and ice-marginal valleys, which are conducted for groundwater resources assessment, involve modelling of local (map scale below 1 : 25 000) or regional (map scale below 1 : 50 000) systems. Usually, these systems are discrete water-bearing subsystems related to surface waters and ascent recharge from deep aquifers (Przybyłek, Dąbrowski, 2013), which require detailed reconstruction of recharge and drainage systems (Dąbrowski et al., 2011). This paper presents and compares the results of modelling research of the Warsaw-Berlin Ice-Marginal Valley in the Kościan–Wolsztyn area conducted on two circulation system models to estimate disposable resources. These are the local, two- aquifer model of the study area, developed using Hydrylib software in 2003, and the regional, four-aquifer model of the Obra catchment for the study area, created using Groundwater Vistas software in 2017.

Record of glacial outburst floods in marginal zones and forelands of Scandinavian glaciations in Poland

In international literature, much attention has been paid to sedimentological and geomorphological evidence of extreme floods in the forelands of both contemporary and Pleistocene glaciers and ice sheets. Reports on this subject come from areas and periods of different glaciations. In Poland such events have been documented in more than ten works. This situation prompts us to establish whether or not the occurrence of such extreme events was more frequent and widespread in the area of Poland than it has been believed to date. The article reviews the existing research concerning within the extent of Pleistocene glaciations in Poland, which include the occurrence of high energy glacial outburst floods in the interpretation of sediments or landforms. Its objective is to determine the current state of knowledge and to indicate the direction of further research. The review also includes a study of palaeogeographic conditions of the previously documented jökulhlaup in Siedlątków, on the border of the Łask Heights. The analysis of works and the conducted comparisons lead to the conclusion that the state of knowledge about great glacial floods in the Polish Lowland is not satisfactory. It indicates the need to undertake intense studies on the record of such events and their reconstruction as their morphogenetic role e.g. in the formation of ice-marginal valleys and other elements of glacigenic landscape is underrated.

The morphological units between the end moraines of the Pomeranian phase and the Eberswalde ice-marginal valley (Urstromtal), Germany – a critical examination by means of a high-resolution DEM

Abstract. Die Geländeformen im Gebiet zwischen der Pommerschen Endmoräne und der Stadt Eberswalde, die im Thorn-Eberswalder Urstromtal (IMV) liegt, sind lange Zeit als eine typische proglaziale Abfolge im Sinne der Glazialen Serie von Penck & Brückner (1901–1909) gedeutet worden. Die deutlichste morphologische Erscheinung ist die Pommersche Endmoräne, die um 20 ka gebildet wurde. Die Schmelzwasserablagerungen gehören jedoch nicht nur zur Pommerschen Eisrandlage sondern wurden auch durch die Abflüsse der jüngeren Parsteiner und Angermünder Staffeln während des Abschmelzens des Skandinavischen Inlandeises gebildet. Es wurde davon ausgegangen, dass der Hauptabfluss durch einen Taldurchbruch, der heute eine Lücke in dem Endmoränenrücken bildet, erfolgte. Die Analyse der Geländeformen hinsichtlich ihrer Höhenlagen und ihrer Oberflächenformen mittels eines LiDAR-gestützten Höhenmodells (DGM) erlaubt nun eine neue Interpretation. Die neue, relative Chronologie der Schmelzwasserabflüsse in dem Gebiet zeigt ein deutlich komplexeres Bild: Der Britzer Forst, die am höchsten gelegene glazifluviale Geländeform, wurde bisher als ein Sander einer Rückzugsstaffel angesehen; nun wird das Gebiet als eine prä-Pommersche Schmelzwasserablagerung gedeutet. Diese Interpretation basiert auf der Höhe und der geglätteten Oberfläche. Der Ragöse Sander, der Stadtforst, die Mönchsheide und auch der Amtsweg Sander wurden entweder als Sander des Pommerschen Stadiums, die teilweise von Toteis unterlagert waren, oder als Sander von Rückzugsstaffeln beschrieben. Aber in dem DGM wird deutlich, dass die Oberfläche des Ragöse Sanders keine fluvialen Muster aufweist, sondern aus sedimentären Loben besteht, die von der Endmoräne ausgehen. Ein ähnlicher Aufbau kennzeichnet auch den Amtsweg Sander. Beide werden daher auf viele kleine Schmelzwasser-Ausflüsse an der Endmoräne zurückgeführt. Der Klosterbrücke Sander ist durch mehrere aufeinander folgende Prozesse gebildet worden, aber seine Anlage wird auf Schmelzwässer der Pommmerschen Eisrandlage zurückgeführt. Im Gegensatz dazu zeigen der Stadtforst und die Mönchsheide eine deutlich ost-west ausgerichtete fluviale Oberflächenstruktur und sind daher keine Sanderablagerungen vor der Pommerschen Eisrandlage. Die Stadtseerinne und die Neuehütter Rinne können quer durch das Urstromtal verfolgt werden, ihre Entstehung wird daher auf einen prä-Pommerschen Eisvorstoss zurückgeführt mit anschliessender Konservierung durch Toteis während des Pommerschen Stadiums und der folgenden Rückzugsstaffeln. Aufgrund der Reliefanalyse auf der Basis des DGM wird nunmehr davon ausgegangen, dass die Schmelzwasserabflüsse geringer waren als bisher angenommen. Ausserdem haben die Geländeformen offensichtlich eine längere und komplexere Entstehungsgeschichte. Die Reliefinterpretation auf der Basis des DGM stützt auch die Annahme, dass die Veränderung der Landschaft durch periglaziale Prozesse eine bedeutende Rolle gespielt habt.

Asynchronous development of two Late Glacial lake basins near the Drwęca ice-marginal valley (N Poland)

Lacustrine organic sediments were sampled at Gronowo (Chelmno Plateau) and Piotrkowo (Dobrzyn Plateau) located within a widespread system of subglacial channels separated by the large Drweca ice-marginal valley. They have been examined for their pollen, plant macro-remains and geochemistry, as well as radiocarbon-dated. The analyses have allowed reconstructing the evolution of the area and presenting an asynchronous appearance of two lakes. Before lake sedimentation, glaciolimnic sediments from the end of Plenivistulian, at the site of Piotrkowo, was dated. Lacustrine sedimentation started during the AllerÝd at Gronowo, and during the Preboreal at Piotrkowo. The different age of the two lakes is ascribed mainly to differences in the Late Glacial drainage conditions which directly affected the melting away of dead-ice blocks buried in the channels.

Osadnictwo późnomeozolityczne na stanowisku 29 w Kopanicy, gm. Siedlec

Kopanica, site 29, is situated on the eastern edge of a former glacial trough, which now channels the Obra River north, and the latitudinal Warsaw-Berlin ice marginal valley. 2003 archaeological excavations at the site revealed evidence of intensive Late Mesolithic settlement. Trenches located on the sandy and gravel fluvial terrace of the Obra and in the zone of biogenic sediments yielded a substantial flint assemblage and remains of a dwelling structure sunken into the ground. The structure was radiocarbon dated owing to a fragment of a burnt animal bone from the fill deposit. The radiocarbon date coincides with the results of technological and typological analyses of the flint inventory. The Mesolithic settlement at the site can accordingly be attributed to a stay of a group representing the Chojnice–Pienkow (post-Maglemose) culture in the second half of the Atlantic period.

Położenie małych miast na tle środowiska przyrodniczego dna pradoliny warszawsko-berlińskiej

Pradolina warszawsko-berlińska jest ważnym elementem w krajobrazie Polski Środkowej. Forma ta ma złożoną budowę geologiczną i mozaikowy układ siedlisk. Dno pradoliny jest szerokie (1,2–5 km) i zbudowane z dwóch powierzchni: fragmentów terasy piaszczystej i równiny zalewowej (namuły). W dwóch odcinkach pradoliny duże powierzchnie zajmują torfowiska. Takie warunki miały wpływ na rozwój osadnictwa. Artykuł przedstawia środowiskowe uwarunkowania lokalizacji małych miast w dnie pradoliny. Przeanalizowano położenie topograficzne dziesięciu miast. Analiza różnych elementów środowiska przyrodniczego wskazuje, że głównym czynnikiem decydującym o lokalizacji miast były walory geomorfologiczne i hydrologiczne. Większość miast została ulokowana na wysokim stoku pradoliny, a tylko jedno miasto zostało zbudowane na obydwu brzegach rzeki. Środowisko przyrodnicze dna pradoliny jest barierą w rozwoju przestrzennym miast. W dnie pradoliny zachowało się cenne środowisko przyrodnicze, dlatego przedstawiono położenie miast na tle obszarów chronionych (park krajobrazowy, obszar Natura 2000). Małe miasta i środowisko przyrodnicze dna pradoliny tworzą harmonijny krajobraz.

Reconstruction of sediment provenance and transport processes from the surface textures of quartz grains from Late Pleistocene sandurs and an ice-marginal valley in NW Poland

Abstract 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 role of sediment supply in esker formation and ice tunnel evolution

Meltwater is an important part of the glacier system as it can directly influence ice sheet dynamics. Although it is important that ice sheet models incorporate accurate information about subglacial meltwater processes, the relative inaccessibility of contemporary ice sheet beds makes direct investigation challenging. Former ice sheet beds contain a wealth of meltwater landforms such as eskers that, if accurately interpreted, can provide detailed insight into the hydrology of former ice sheets. Eskers are the casts of ice-walled channels and are a common landform within the footprint of the last Laurentide and Cordilleran Ice Sheets. In south-western Alberta, esker distribution suggests that both water and sediment supply may have been important controls; the longest esker ridge segments are located within meltwater valleys partially filled by glaciofluvial sediments, whereas the shortest esker ridge segments are located in areas dominated by clast-poor till. Through detailed esker ridge planform and crest-type mapping, and near surface geophysics we reveal morpho-sedimentary relationships that suggest esker sedimentation was dynamic, but that esker distribution and architecture were primarily governed by sediment supply. Through comparison of these data with data from eskers elsewhere, we suggest three formative scenarios: 1) where sediment supply and flow powers were high, coarse sediment loads result in rapid deposition, and rates of thermo-mechanical ice tunnel growth is exceeded by the rate of ice tunnel closure due to sediment infilling. High sedimentation rates reduce ice tunnel cross-sectional area, cause an increase in meltwater flow velocity and force ice tunnel growth. Thus, ice tunnel growth is fastest where sedimentation rate is highest; this positive feedback results in a non-uniform ice tunnel geometry, and favours macroform development and non-uniform ridge geometry. 2) Where sediment supply is limited, but flow power high, the rate of sedimentation is less than the rate of thermo-mechanical ice tunnel growth. Here the ice tunnel enlarges faster than it fills with sediment and its evolution is independent of sedimentation, resulting in more uniform ice tunnel geometry. In these cases esker architecture is dominated by extensive vertical accretion of tabular units and ridge geometry is more uniform. 3) Where sediment is truly supply-limited the sedimentation rate is negligible regardless of water supply and, like scenario 2, ice tunnel growth is independent of sediment deposition, forming a relatively uniform ice tunnel (or eroding the bed). Because meltwater flows transport few gravel clasts the ice tunnel is not completely filled with gravel and, instead, saturated and pressurized diamicton or bedrock (if deformable) from beneath the surrounding ice is “squeezed” into the relatively low pressure ice tunnel during waning flow (or after ice tunnel shutdown), resulting in deformation of limited gravels deposited within the ice tunnel and a landform cored with diamicton or deformed bedrock, and with a relatively uniform ridge geometry. Our data demonstrate that an esker map is a minimum map of ice-walled channel location and that continued detailed investigation of morpho-sedimentary relationships is essential to gaining a complete picture of esker forming processes. Validating the morpho-sedimentary relationships identified in south-western Alberta (and other areas) with a larger data set may allow improved remote predictive esker mapping over larger areas and inferences to be made about spatial and temporal variations in esker depositional environments and ice tunnel evolution.

Factors controlling sedimentation in the Toruń-Eberswalde ice-marginal valley during the Pomeranian phase of the Weichselian glaciation: an overview

Abstract During the Pleistocene the Scandinavian ice sheet drained huge quantities of sediment-laden meltwaters. These meltwaters supplied ice-marginal valleys that formed parallel to the front of the ice sheet. Not without significance was the supply of ice-marginal valleys from extraglacial rivers in the south. Moreover, periglacial conditions during and after sedimentation in ice-marginal valleys, the morphology of valley bedrocks, and erosion of older sediments played important roles in the depositional scenarios, and in the mineralogical composition of the sediments. The mechanisms that controlled the supply and deposition in ice-marginal valleys were analysed on the basis of a Pleistocene ice-marginal valley that was supplied by northern and southern source areas in the immediate vicinity. Investigations were conducted in one of the largest ice-marginal valleys of the Polish-German lowlands, i.e., the Toruń-Eberswalde ice-marginal valley, in sandurs (Drawa and Gwda) supplied sediments and waters from the north into this valley, and on extraglacial river terraces (pre-Noteć and pre-Warta rivers), formed simultaneously with the sandurs and ice-marginal valley (Pomeranian phase of Weichselian glaciation) supplied sediments and waters from the south into this valley. A much debated question is how similar, or different, depositional processes and sediments were that contributed to the formation of the Toruń-Eberswalde ice-marginal valley, and whether or not it is possible to differentiate mostly rapidly aggraded sandur sediments from ice-marginal valley sediments. Another question addresses the contribution of extraglacial feeding of the Toruń-Eberswalde ice-marginal valley. These matters were addressed by a wide range of analyses: sediment texture and structure, architectural elements of sediments, frequency of sedimentary successions, heavy-mineral analysis (both transparent and opaque heavy minerals), analysis of rounding and frosting of quartz grains, and palaeohydrological calculations. Additionally, a statistical analysis was used. The specific depositional conditions of distribution of sediments in ice-marginal valley allow to distinguish new environment of ice-marginal valley braided river. The spectrum of depositional conditions in the Toruń-Eberswalde ice-marginal valley and their specific palaeohydraulic parameters allow to distinguish three coexisting zones in the ice-marginal valley braided-river system: (1) deep gravel-bed braided channel zone with extensive scours, (2) deep sand-bed braided channel zone with transverse bars, and (3) marginal sand-bed and gravel-bed braided channel zone with diamicton and breccia deposition, which were characterised in detail. Some of the results have been published previously, which is why they are discussed in the present paper within the context of new data