Finite date of the Jämtland Interstadial

Enrichment dating procedure (GrN-9394) on a sample from the interstadial site Tåsjö, Ångermanland, Sweden, which is referred to the Jämtland Interstadial, has given the age 54,700±550 B.P. In the northwest European chronology this corresponds to late Odderade.     

The Early and Middle Weichselian in Norway: a review

All Known sites with fossils and ‘non-till sediments’ of possible Early and Middle Weichselian age in Norway are discussed. Along the west coast there are many sites marine shells which have been dated by means of radiocarbon, amino acids and thorium/uranium methods. Some sites are also correlated by means of underlying Eemian sequences. A tentative glaciation curve for western Norway indicates a first glacial advance soon after the end of the Eemian. There are indications of another re-advance around 40,000 B.P., and the Late Weichselian maximum (maxima?) occurred somewhere between 30,000 B.P. and 13,000 B.P. Parts of the coast may have been ice-free for most of the remaining periods. From the central parts of the country are known bones (e.g. mammoth), glaciolacustrine and fluvial sediments, peat, etc. The newly discovered site with peat of Brumunddal can very probably be correlated with the Jämtland Interstadial in Sweden, and the Brørup Interstadial in Denmark. If this is correct, nearly the whole of southern Scandinavia must have been deglaciated during the interstadial.     

A symposium on dating methods covering the period 15–130 ka before the present

A Nordic symposium, with several invited speakers from other countries, was held in Lund, Sweden, in February 1985. The aim was to evaluate dating methods that could be used within the project 'Late Quaternary stratigraphy in Norden'. Some of the conclusions were: A more optimistic view was expressed about uranium-series dating of molluscs. The radiocarbon method offers a potential for some samples of an age up to 40–50 ka. Thermoluminescence dating is now established as an important method for some sediments of Late Quaternary age. Aminoacid analysis is used with success to establish a relative chronology on carbonate fossils.     

粘性泥石流应力应变特征的初步试验研究

采用自己最新研制的泥石流流变仪，测试自然界活泥石流体的样品，发现粘性泥石流体在低速率受剪时具有应力过冲和剪切稀化等特征。这些特征的讨论和认识，为进一步深化泥石流模型理论研究奠定了基础。     

ESTIMATIONS OF THE SHAPE AND VOLUME OF A STONY DEBRIS FLOW FAN

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Marginal formations of the last Kara and Barents ice sheets in northern European Russia

Glacial landforms in northern Russia, from the Timan Ridge in the west to the east of the Urals, have been mapped by aerial photographs and satellite images supported by field observations. An east-west trending belt of fresh hummock-and-lake glaciokarst landscapes has been traced to the north of 67°N. The southern boundary of these landscapes is called the Markhida Line, which is interpreted as a nearly synchronous limit of the last ice sheet that affected this region. The hummocky landscapes are subdivided into three types according to the stage of postglacial modification: Markhida, Harbei and Halmer. The Halmer landscape on the Uralian piedmont in the east is the freshest, whereas the westernmost Markhida landscape is more eroded. The west-east gradient in morphology is considered to be a result of the time-transgressive melting of stagnant glacier ice and of the underlying permafrost. The pattern of ice-pushed ridges and other directional features reflects a dominant ice flow direction from the Kara Sea shelf. Traces of ice movement from the central Barents Sea are only discernible in the Pechora River left bank area west of 50°E. In the Polar Urals the horseshoe-shaped end moraines at altitudes of up to 560 m a.s.l. reflect ice movement up-valley from the Kara Ice Sheet, indicating the absence of a contemporaneous ice dome in the mountains. The Markhida moraines, superimposed onto the Eemian strata, represent the maximum ice sheet extent in the western part of the Pechora Basin during the Weichselian. The Markhida Line truncates the huge arcs of the Laya-Adzva and Rogovaya ice-pushed ridges protruding to the south. The latter moraines therefore reflect an older ice advance, probably also of Weichselian age. Still farther south, fluvially dissected morainic plateaus without lakes are of pre-Eemian age, because they plunge northwards under marine Eemian sediments. Shorelines of the large ice-dammed Lake Komi, identified between 90 and 110 m a.s.l. in the areas south of the Markhida Line, are radiocarbon dated to be older than 45 ka. The shorelines, incised into the Laya-Adzva moraines, morphologically interfinger with the Markhida moraines, indicating that the last ice advance onto the Russian mainland reached the Markhida Line during the Middle or Early Weichselian, before 45 ka ago.     

Stratigraphic architecture and infill history of a deglaciated bedrock valley based on georadar, seismic profiling and drilling

The sediment fill of a silled bedrock valley in Western Norway has been investigated with respect to stratigraphy and infill history using a combination of mapping, georadar, seismic profiling and drilling. A small outlet glacier occupies the head of the valley that displays a stepwise down-valley profile and terminates in a lake at 29 m above sea-level. The valley is surrounded by high, steep bedrock slopes and is characterized by a series of filled basins each limited by sills of bedrock or moraine accumulations. Till, glacial outwash and/or rockslide deposits fill in the lower half of the two larger basins. (Fan) delta deposits fringed by the deposits of alluvial fans and colluvial cones dominate the upper fill of most basins. (Fan) delta deposits interfinger downstream with lake sediments in the larger basins and fluvial deposits comprise the top fill. The overall infill pattern was controlled by deglaciation as well as basin size and shape. An overall decreasing sediment supply following deglaciation is shown in the fill of a larger basin down-valley, whereas a recently increasing sediment supply during glacier growth is reflected primarily in an upstream basin. Only the lowermost basin was exposed to a sea-level drop from 75 m above sea-level to the present lake level associated with incision and river migration. This observation is in contrast to the basins above marine influence where incision has been limited due to fixed downstream sills resulting in insignificant erosion except for some fan-head entrenchment. It follows that the fills of these small valley basins display progradational and aggradational trends of deposition and paraglacial reworking has been limited. Additionally, the study demonstrates that georadar profiling, combined with other methods, is very useful for comprehensive investigation of valley basins.     

Holocene shoreline displacement at Agardhbukta, eastern Spitsbergen, Svalbard

An emergence curve based on nine radiocarbon dated samples of mosses, shells, whale bones and driftwood has been constructed for Agardhbukta. Beach sediments and delta deposits were found up to c. 50 m above sea level, and the oldest date goes back to about 10, 000 yrs BP. However, the possibility of a higher marine limit cannot be excluded. The Agardhbukta curve shows a nearly linear uplift during the entire Holocene. It differs from the western Spitsbergen curves, where a transgression occurs, and is more similar to curves from areas further east in the Svalbard archipelago.     

Late Quaternary foraminiferal stratigraphy from western Svalbard

In the lower part of sections at Skilvika and Linneelva, western Svalbard, marine silts and sands characterized by infinite radiocarbon ages (<40,000 BP) on shells are found. These sediments are covered by at least one basal till of Late Weichselian age. The till is overlain by marine sediments from the last deglaciation (12,800-10,000 BP) which contain shallow-water, subarctic foraminiferal assemblages, similar to modern near-glacial faunas from western Svalbard. The most common foraminifera in all zones in the sub-till sediments are Cassidulina reniforme, Astrononion gallowayi and/or Elphidium excavatum . The richest zones at both localities are found in the sub-till units and contain more than 20 foraminiferal species, including some boreal-arctic species. These faunal assemblages are similar to the living faunas on the west coast of Svalbard. Faunas from the postglacial climatic optimum are not yet described. We suggest that the foraminiferal assemblages in the sub-till sediment reflect Early or Middle Weichselian interstadial environments, although an Eemian interglacial cannot be excluded.