Weichselian till stratigraphy in borings from northern Falster, Denmark

A detailed lithological and petrographical investigation of 102 borings across the island of Falster, Denmark, shows that four till-beds can be distinguished. The borings are on both sides of the recessional ice border line of the G-stage of the Young Baltic Ice. The stratigraphy indicates that the morphological petrographical parameters show regional significance in differentiating the two uppermost tills. The upper one is referred to the Weichselian Young Baltic advance on the basis of stone counts and till fabrics. The lower one is referred to the Weichselian Northeast advance on the basis of stone counts and the orientation of a chalk floe. In one boring additional till-beds were recognized, one of which referred to the Weichselian Old Baltic advance, because of the clast petrography and content of reworked Eemian foraminifera. The lowermost till is interpreted as being of Saalean age on the basis of the counts of the tine gravel fraction (3–5 mm). The landscape is dominated by the morphology produced by the Northeast Ice advance, whereas the later Young Baltic advance had only a drumlinizing effect.     

Weichselian glacial stage in Murchisonfjorden, Nordaustlandet, Svalbard

Compared to the other islands in the Svalbard archipelago, Nordaustlandet offers only limited stratigraphical or sedimentological information on its Quaternary deposits. This article aims to fill the gap by presenting new results from glacial geological, sedimentological and chronological studies in the southern Murchisonfjorden area. Field data include reconnaissance mapping and detailed logging of vertical sections along cliff-face outcrops a few metres high adjacent to the present-day shoreline. Combined with OSL and AMS age determinations, these data provide evidence of three successive Weichselian sequences, each represented by the deposition of till followed by the accumulation of shallow marine deposits. Contrary to earlier conclusions, this study demonstrates that the area was occupied by a Late Weichselian glacier (LWG), although the LWG till is thin and discontinuous. Interstadial sublittoral sand related to the Mid-Weichselian interstadial was dated to 38–40 kyr, and an Early Weichselian interstadial to 76–80 kyr. The preservation of older sediments, multiple striae generations and abundant observations of weathered local bedrock material indicate weak glacial erosion within the study area. We suggest that the Late Weichselian glacier was relatively inactive and remained mainly cold-based until the deglaciation. The Isvika sections can be considered a new key site that offers further potential to improve our understanding of the Weichselian stage within the northwestern sector of the Barents–Kara Ice Sheet.     

Middle Weichselian marine sediments from eastern Kattegat, Scandinavia

Foraminifera, pollen, lithology and radiocarbon dates from a core in the southern Kattegat provide a rare opportunity to obtain data relating to environmental conditions during the Middle Weichselian in the offshore Kattegat. This core is also correlated with an adjacent second core. Redeposited Eemian foraminifera and pollen occur in the Middle Weichselian sediments. This is interpreted as a result of reworking by an active Middle Weichselian ice present in, or advancing from, a northeasterly to easterly direction. During a second phase the Middle Weichselian sediments were compacted, probably a result of overriding by an ice from the northeast during the Middle Weichselian and/or the Late Weichselian Maximum. The Middle Weichselian sequence is overlain by a Holocene sequence which, in turn, is overlain by an admixture of Middle Weichselian and Holocene sediments. This mixing may be a result of tectonic activity some time between 7300 and 1000 BP. The core ends in Holocene fine sediments representing the last c. 1000 years.     

Late Weichselian glacial maximum on Andøya, North Norway

Morphological, seismic and lithostratigraphic investigations of a moraine deposit at Bleik (the Bleik moraine), northern Andøya, show short-distance transported till overlying long-distance transported predominantly glaciofluvial ice-marginal deposits. Consolidated glaciomarine sediments from a core at present sea-level, c . 400 m distally to the moraine complex, contain 31 species of foraminifera, among which Cassidulina reniforme, Islandiella helenae and Trifarina fluens dominate, and fragments of the molluscs Mya truncata and Astarte sp. and the echinoid Strongylocentrotus sp. Amino acid analyses of the foraminifera Cibicides lobatulus and the mollusc Mya truncata indicate ages between 22,000 and 16,000 BP. Radiocarbon dating of fragments of Mya truncata from the upper part of the core gave an age of 17,940 ± 245 BP, while a dating of unidentified shell fragments from the lower part gave an infinite age (>40,000 BP). The sediment was probably disturbed by icebergs beyond the end moraine zone, and the radiocarbon and amino acid dating of Mya truncata therefore represent a maximum age for this process. This new evidence indicates two phases with a higher relative sea-level than at present at Bleik, c . 18,000 and >40,000 BP. The Bleik moraine probably represents the early Late Weichselian glacial maximum ( c . 22,000 BP), while the underlying deglaciation deposit and associated beach-ridge (Bruvollen) is of pre-Late Weichselian age. Moraine ridges 3–4 km to the south of Bleik probably indicate advances of local glaciers between 22,000 and 18,000 BP.     

Palaeoecology of a Late Weichselian vertebrate fauna from Nmre Lyngby, Denmark

Investigations at a Late Weichselian freshwater basin in northwestern Jutland, Denmark, yielded a fairly rich assemblage of vertebrate remains, mostly bones and teeth of small mammals. The remains are primarily allochthonous and the bones have been subjected to different taphonomic pathways and agents. AMS ¹⁴C-dates on terrestrial organic remains provided ages of Middle to Late Allerød time. Identifications revealed the first fossil record in Scandinavia of Rana arvalis, Sorex minutus, Ochotona cf. pusilla, Microtus gregalis, Microtus oeconomus , and Sicista cf. betulinu. Spermophilus cf. major and Desmana moschata , previously found only once and twice respectively, were retrieved, and Sorex araneus and Arvicola terrestris were recovered for the first time beyond the Atlantic chronozone. Ecologically, the Nørre Lyngby small mammal fauna can be characterized by its very high and almost equal proportions of boreal forest and steppe elements followed by a relatively high proportion of tundra elements. The fossil species share a modern area of sympatry north of the Caspian Sea from the river Volga in the west to the southern and western slopes of the Urals. If, however, the large Allerød mammals are added, the fauna is without modern analogues. The Nørre Lyngby fauna can be seen as a last expansion of the North European glacial fauna. Provided that an absolute chronology and a differentiated sea-level curve for the area can be established, the Nsrre Lyngby fauna could become important for studies in mammalian dispersal and migration rates.     

Kineto-stratigraphic glacial drift units on Hindsholm, Denmark

Geological sections from gravel pits and coastal cliffs at Hindsholm, Funen, Denmark are described. By combining information from these sections at least three kineto-stratigraphic drift units can he demonstrated. The oldest unit is represented by glacial drift and structures which are the result of an ice sheet moving from NE. The intermediate unit consists of glacial drift and structures formed by a movement from SW. The youngest unit is associated with a glacial movement from SSE. This last movement drumlinized preexisting kames and dislocated earlier glacial drifts. Younger kames and real drumlins were also formed at this stage. A stationary ice margin along the line Skoven - Fyns Hoved - Røsnas is proposed.     

Ground-penetrating radar detection of small-scale channels,joints and faults in the unconsolidated sediments of the Atlantic Coastal Plain

The geological characterization of the shallow subsurface in the unconsolidated sediments of the Atlantic Coastal Plain, and other unconsolidated sediment regimes, may involve jointing, faulting, and channeling not readily detectable by conventional drilling and mapping. A knowledge of these features is required in environmental, geotechnical, and geomorphological studies. Ground-penetrating radar (GPR) may be used to routinely map these structures. Three principal shallow subsurface features are readily detectable using GPR: paleochannels, joints or fractures, and faults. The detection of paleochannels is dependent on the scale of the GPR survey and the attitude of the channel within the survey area. Channel morphological features such as scour surfaces, point bars, and thalwegs are observable. Joints and fractures are more difficult to detect depending upon size, patterns, orientation, and fill material. Vertical joints may not be visible to radar unless they are wider than the sampling interval or are filled with radar-opaque materials such as limonite. Angled joints or fractures may be distinguished by an apparent continuous reflector on the radar profile. Faulting on radar profiles may be observed by the offset of reflectors, the image of the fault plane, or the coherent interpretation of a fault system.     

Granulometric analysis of glacial sediments,Schirmacher Oasis,East Antarctica

Granulometric analysis of nineteen sediment samples has been carried out for their statistical and textural parameters. The samples are collected from the northern and southern margins of Schirmacher Oasis extending below the polar ice sheet and grading to coastal area respectively and main rocky land of Schirmacher including lakes. The analysis shows that most of the sediments are of medium grain size and fall in poor to very poor sorted category. An attempt has been made to interpret the depositional set-up by plotting the scatter patterns between various textural parameters, including C-M plot and arithmetic log-probability curves. The influence of physical parameters viz. low to high velocity winds, ice and meltwater on sediment characteristics has been discussed.     

Rapid tunnel-valley formation beneath the receding Late Weichselian ice sheet in Vendsyssel, Denmark

Interpretation of Transient ElectroMagnetic (TEM) data and wire-line logs has led to the delineation of an intricate pattern of buried tunnel valleys, along with new evidence of glaciotectonically dislocated layers in recessional moraines in the central part of Vendsyssel, Denmark. The TEM data have been compared with recent results of stratigraphical investigations based on lithological and biostratigraphical analyses of borehole samples and dating with Optically Stimulated Luminescence (OSL) and radiocarbon. This has provided an overview of the spatial distribution of the late Quaternary lithostratigraphical formations, and the age of the tunnel valleys has been estimated. The tunnel valleys are typically 5–10 km long, 1 km wide and are locally eroded to depths of more than 180 m b.s.l. The valleys are interpreted to have been formed by subglacial meltwater erosion beneath the outermost part of the ice sheet during temporary standstills and minor re-advances during the overall Late Weichselian recession of the Scandinavian Ice Sheet. The formation of the tunnel valleys occurred after the retreat of the Main ice advance c . 20 kyr BP and before the Lateglacial marine inundation c . 18 kyr BP. Based on the occurrence of the tunnel valleys and the topography, four ice-marginal positions related to the recession of the northeastern Main advance and seven ice-marginal positions related to the recession from the following eastern re-advance across Vendsyssel are delineated. All the tunnel valleys were formed within a time interval of a few thousand years, giving only a few hundred years or less for the formation of the tunnel valleys at each ice-marginal position.     

Signature of the Baltic Ice Stream on Funen Island, Denmark during the Weichselian glaciation

Ice streams are major dynamic elements of modern ice sheets, and are believed to have significantly influenced the behaviour of past ice sheets. Funen Island exhibits a number of geomorphological and geological features indicative of a Late Weichselian ice stream, a land-based, terminal branch of the major Baltic Ice Stream that drained the Scandinavian Ice Sheet along the Baltic Sea depression. The ice stream in the study area operated during the Young Baltic Advance. Its track on Funen is characterized by a prominent drumlin field with long, attenuated drumlins consisting of till. The field has an arcuate shape indicating ice-flow deflection around the island's interior. Beneath the drumlin-forming till is a major erosional surface with a boulder pavement, the stones of which have heavily faceted and striated upper surfaces. Ploughing marks are found around the boulders. Exact correspondence of striations, till fabric and drumlin orientation indicates a remarkably consistent flow direction during ice streaming. We infer that fast ice flow was facilitated by basal water pressure elevated to the vicinity of the flotation point. The ice movement was by basal sliding and bed deformation under water pressure at the flotation level or slightly below it, respectively. Subglacial channels and eskers post-dating the drumlins mark a drainage phase that terminated the ice-stream activity close to the deglaciation. Identification of other ice streams in the Peribaltic area is essential for better understanding the dynamics of the land-based part of the Scandinavian Ice Sheet during the last glaciation.     

Lacustrine sedimentation and tectonics: an example from the Weichselian at Lønstrup Klint, Denmark

Sedimentological analysis of the Weichselian deposits exposed in the coastal cliff section at Lønstrup Klint, northern Jutland, Denmark, demonstrates the presence of four sedimentary units comprising fine-grained lacustrine and fluvial deposits of the latest Middle Wcichselian. The Lønstrup Klint section also shows an interplay between glaciotectonics and sedimentation. The two lower sedimentary units are separated by an erosional unconformity of pretectonic origin, whereas the upper two units are syntectonic. The glaciotectonic processes reflect the Late Weichselian expansion of the Scandinavian ice cap into northern Jutland. The sedimentary structures indicate high rates of deposition. The area underwent dramatic palaeogeographic changes from deep lake to proglacial fluvial plain in a time-span of a few thousand years.     

Coleoptera from the Late Weichselian deposits at Nørre Lyngby, Denmark and their bearing on palaeoecology, biogeography and palaeoclimate

The freshwater sediments exposed on the cliffs at Nørre Lyngby northern Jutland has long been a classical locality for the study of Danish Quaternary geology, palaeontology and archaeology. These deposits date from the latter part of the Allerød period (i.e. G I-1). Samples for insect analysis have been taken from both the northern and southern exposures of these deposits. Ninety-five- taxa of Coleoptera (beetles) were obtained, of which 69 could be named to species. Of the latter, 23 are not found living in Denmark today. Most of these are still living in northern Fennoscandia but one species is now confined to Mongolia. These assemblages have enabled a detailed picture of the local environment to be reconstructed, showing that the basin-like profile of the deposits represents a section through a channel with slowly moving water. It has been possible to quantify the thermal climate of the time using the Mutual Climatic Range method indicating that mean July temperatures were about 10°C and mean January temperatures were about – 12°C. These figures are considered in the context of Lateglacial climatic reconstructions obtained from coleopteran assemblages elsewhere in northwestern Europe.     

Late Quaternary mollusks from glacial Lake Algonquin,Nipissing, and transitional sediments from southwestern Ontario,Canada

Mollusks were studied from six sites in Lake Algonquin deposits (12,000-10,000 yr B.P.), five transitional (Lake Stanley low stage; 10,000 – 6000 yr B.P.), and six Nipissing stage sites (6000-4000 yr B.P.) east of Lake Huron in southwestern Ontario. The sites represent a variety of near-shore, lagoonal, estuarine, and fluvial environments. Eighteen species were limited to occurrences in Algonquin stage deposits; 8 were found only in the transitional age sites; and 14 species were restricted to Nipissing stage localities. With the possible exception of Goniobasis livescens, which occurred at five of the six Nipissing stage sites, the remaining stratigraphically limited species were usually restricted to one or two localities and probably cannot be used as zone fossils. Some cold-tolerant species (e.g., Anodonta grandis simpsoniana) were very early migrants into the study area, while others arrived later, apparently from eastern, southern, and western sources. Mollusks proved useful in paleoenvironmental reconstructions and to a lesser extent in biostratigraphic zonation.     

Depositional environments and sea-level changes deduced from Middle Weichselian tidally influenced sediments, Arkhangelsk region, northwestern Russia

Deposits from a Middle Weichselian transgression, the Mezen Transgression, are found in coastal sections in the Mezen and Chyorskaya Bays, northwestern Russia. The marine event is bracketed between two ice advances from the Barents and Kara Sea shelves and dated by Optically Stimulated Luminescence (OSL) to around 60 kyr BP. The deposits represent a shallowing upward succession from offshore marine to intertidal coastal environments. Relative sea-level maximum was at least 40 m above the present owing to significant isostatic subsidence. The sedimentary record is dominated by shallow-marine, subtidal deposits bounded below by an erosion surface representing a downward shift in facies and above by subaerial exposure. The succession reflects deposition during forced regression due to isostatic uplift. A rapidly aggrading succession of subtidal deposits at one site suggests a relative sea-level rise or stillstand superimposed on the isostatically controlled sea-level fall. The rhythmic tidal deposits allow identification of semi-monthly to yearly cycles, providing an estimate of the sedimentation rate of 39 cm/year. This implies a high sediment yield and a rapid relative sea-level rise. We correlate this signal with the rapid eustatic sea-level rise at the end of OIS 4 known from deep-sea records.     

Luminescence and radiocarbon ages from laminated Lateglacial aeolian sediments in western Jutland, Denmark

The chronology of two adjacent Danish Lateglacial sedimentary sequences with well-developed layering of alternating aeolian sand and organic matter has been investigated using both Optically Stimulated Luminescence (OSL) and Accelerator Mass Spectrometry (¹⁴C). Both sites are known to cover at least the period Bølling to Younger Dryas, with the so-called older and younger coversand types present at both localities. Typical overall uncertainties with the OSL data are about two to five times those of the ¹⁴C ages, but both data sets contain clear outliers. When these are excluded, OSL ages appear to be systematically slightly younger than the ¹⁴C ages, by about 10%; possible reasons for this are discussed. The investigation stresses the importance of making several age estimates from any single locality. The older coversand type makes up the pre-Bølling and most, or possibly all, of the Bølling (which also has the highest net accumulation rate). Deposits of the younger coversand type are dominant in layers younger than the Bølling.     

An Early or Middle Weichselian sequence of proglacial, shallow marine sediments on western Svalbard

A 20 m thick shallow marine sequence, capped by a Late Weichselian lodgement till, is exposed for 200111 along the river in Linnedalen on the west coast of Svalbard. Five formations are recognized: Formation A, the oldest, consists of a shallow marine, proglacial fan, of channelized sandy turbidites, possibly fed from an ice-contact deposit. Formation B, a sequence of proglacial channels and ice-rafted debris, was formed during a small oscillation of the glacier. Formation C, a prograding, storm-dominated shoreline sequence, was formed during a sea level fall, assumed to be a result of glacio-isostatic uplift.
Formation D, a lodgement till formed during the last glacier advance in Linnedalen and formation E, a coarsening upwards sequence, were formed during the post-glacial sea level fall. The subtill sequence (fm. A, B and C) is dated to between 40,000BP (radiocarbon dates) and 120,000BP (thermoluminescence and amino acid D/L ratios). The glacier front was 10 km downvalley during deposition of formations A and B, relative to the present glacier terminus, and more than 12km during the late Weichselian maximum.     

A Middle Weichselian interstadial lake deposit on Sejerø, Denmark: macrofossil studies and dating

Studies of lake sediments on Sejerø in southern Kattegat indicate a treeless arctic environment with the dwarf shrub Salix polaris, herbs and wetland mosses. The mean July temperature was around 8 to 10°C. An AMS radiocarbon age determination of a Salix twig yielded an age of around 36 000 ¹⁴C yr BP, which is in accordance with previous conventional dating of bulk sediment samples. Copyright © 2006 John Wiley & Sons, Ltd.     

A Late Weichselian find of polar bear (Ursus maritimus Phipps) from Denmark and reflections on the paleoenvironment

The mandible of a polar bear (Ursus maritimus Phipps) found in about 1920 at Kjul Å, North Jutland, and described by Nordmann & Degerbol in 1930. has been ^l4C dated to 11.100 ± 160 B.P. It is so far the only find of polar bear in Denmark. Comparison with recent ¹⁴C datings of Swedish and Norwegian polar bears shows that the Danish specimen was a member of a southern Scandinavian Late Weichselian population. The contemporaneous Zirphaeu sea deposits can be regarded as the boreal-arctic shallow water equivalent of the arctic Upper Saxicava sand deposits from northern Jutland. The polar bear mandible, however, was deposited on land, as was the metacarpal bone of a brown bear ( Ursus arctos ) from the nearby Nr. Lyngby locality of Allerød age. The overall picture of the Late Weichselian mammal fauna in Denmark shows a mixed composition of different ecotypes. Their sympatric occurrence points at a unique environment not comparable to any now existing, and probably related to the very low latitude of the Weichselian ice sheet.     

Evidence of ameliorated Middle Weichselian climate and sub‐arctic environment in the western Baltic region: coring lake sediments at Klintholm,Møn,Denmark

Coring through glaciotectonically stacked Quaternary sediments situated below sea level on the island of Møn, Denmark, recovered a succession of interstadial sediments of Middle Weichselian age. Plant and animal remains including insects found in laminated sand and mud indicate deposition in a lake surrounded by dwarf shrubs, herbs, mosses and rare trees. The insect fauna indicates a mean July temperature of 8–12 °C, suggesting an arctic to sub‐arctic environment, while winter temperatures around ?8 to ?22 °C suggest periglacial conditions with permafrost. Luminescence dating of sediment samples gave ages from 48–29 ka, and radiocarbon dating indicates deposition of plant fragments between 45 and 36 ka BP. The fossil assemblage from Møn shows close resemblance to those from other sites with similar ages found in the vicinity of the western Baltic Basin.     

Lithostratigraphy of the Late Saalian to Middle Weichselian Skærumhede Group in Vendsyssel, northern Denmark

The Quaternary sedimentary succession in Vendsyssel, northern Denmark, contains a unique, high‐resolution record of the last interglacial and glacial periods. There is still much debate, however, about the timing and ice extent in this southwestern part of the Scandinavian Ice Sheet, particularly during the Middle Weichselian. In this study, a detailed lithostratigraphical subdivision is established for the Late Saalian to Middle Weichselian Skærumhede Group on the basis of numerous, up to 250 m deep, boreholes in Vendsyssel. The sediments mainly consist of marine clays, glaciolacustrine sediments and tills, and the total thickness of the Skærumhede Group is up to 140 m. Marine intervals have been used as stratigraphical marker units to separate the formations indicative of ice‐sheet activity in Vendsyssel, and the timing of the events has been constrained by a large number of optically stimulated luminescence (OSL) and radiocarbon ages. The Skærumhede Group is subdivided into seven formations and two members, reflecting shifts between marine and terrestrial sedimentation caused by fluctuations of the Scandinavian Ice Sheet and changes in sea level. The lowermost Skærumhede Till Formation was deposited directly on top of the bedrock during the Warthe advance c. 160–140 kyr BP. Above, there are fine‐grained marine sediments, subdivided into the Lower, Middle and Upper Skærumhede Clay Formations. The marine formations are separated by the Brønderslev Formation related to the Sundsøre ice advance from the north c. 65–60 kyr BP, and the Åsted Formation, deposited during the Ristinge advance from an east–southeastern direction c. 55–50 kyr BP. The uppermost formation in the group is the Lønstrup Klint Formation, which is an upwards‐coarsening sequence of mainly glaciolacustrine sediments deposited prior to the Kattegat advance c. 30–29 kyr BP. The new evidence from Vendsyssel has shown that the Skærumhede Group covers a large area, and that it can be used as a regional stratigraphical marker horizon. Furthermore, it contributes to a better understanding of the timing and extent of glacial events during the Late Saalian to Middle Weichselian in southwest Scandinavia.