Moscovian (Carboniferous) microfossils (Bryozoa, Conodonta, and Fusulinida) from Novaya Zemlya, Arctic U.S.S.R.     

HANS A. NAKREM  INGER NILSSON  BJØRN T. SIMONSEN 《Polar research》1991,9(1):45-64

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Central Scandinavian winter precipitation variability during the past five centuries reconstructed from Pinus sylvestris tree rings     

HANS W. LINDERHOLM  DELIANG CHEN 《Boreas: An International Journal of Quaternary Research》2005,34(1):43-52

Using Scots pine ( Pinus sylvestris L.) tree-ring data, winter (September-April) precipitation variability in west central Scandinavia was reconstructed for the past five centuries. The main growth-limiting factor for pine growing in the studied area is summer temperature, but there is an additional influence of precipitation. Using principal components analysis on three tree-ring-width chronologies, a time series was yielded that contained information on winter precipitation (P_w). Using tree rings, only a small part (20%) of the interannual P_w variability could be explained. However, better agreement between the modelled and measured P_w data on semi-decadal time scales (45% variance explained) suggests that tree-ring data from the west-central part of Scandinavia contain useful information on those time scales. The driest winters, disregarding the absolute beginning of the record, were found at the beginning of the 18th century; the last half of the 20th century seems to be the wettest, at least for the past 400 years. Since our precipitation reconstruction agrees fairly well with previously published precipitation proxies, it is suggested that tree rings may add useful information to future multi-proxy reconstructions.  相似文献   

Lateglacial landform associations at Jæren (SW Norway) and their glaci-dynamic implications     

STÅLE RAUNHOLM  HANS PETTER SEJRUP  EILIV LARSEN 《Boreas: An International Journal of Quaternary Research》2003,32(3):462-475

The Jæren lowland is located on the southwestern coast of Norway between a mountainous region in the east and the offshore Norwegian Channel in the west. During the Last Glacial Maximum, Jæren was in an intermediate position between an ice stream following the Norwegian Channel northwards, and westward flowing inland ice. The dynamic behaviour of the inland ice and the interaction with the ice stream are examined by means of geomorphological analysis of digital terrain models and sedimentological investigations. SW-trending drumlins were formed at Jæren below tributary ice from the inland, feeding into the Norwegian Channel Ice Stream. The presence of Rogen moraine in the central part of Jæren indicates a frozen substratum prior to their formation, and this suggests a transition to cold-based ice between the tributaries. The deglaciation of the Norwegian Channel at about 15 ka BP resulted in an unstable ice front for the inland ice sheet. The formation of Rogen moraine may be explained by a dynamic advance resulting in extensional flow and fracturing of the frozen substratum between the tributaries. The dynamic advance was followed by an early deglaciation of the coastal areas as evidenced by shallow marine sediments. Deformation of the shallow marine sand indicates a glacial readvance through the valleys formerly acting as tributaries to the ice stream.  相似文献   

DIFFERENT SOURCES CONTRIBUTING TO A BEACH SAND, SOUTHEASTERN BORNHOLM (DENMARK)     

HANS FÜCHTBAUER and  JOHN M. ELROD 《Sedimentology》1971,17(1-2):69-79

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NUMERICAL INTERPRETATION OF RESISTIVITY SOUNDINGS OVER HORIZONTAL BEDS*     

HANS A. MEINARDUS 《Geophysical Prospecting》1970,18(3):415-433

The digital computer technique described for interpreting resistivity soundings over a horizontally stratified earth requires two steps. First, the kernel function is evaluated numerically from the inverse Hankel transform of the observed apparent resistivity curve. Special attention is given to the inversion of resistivity data recorded over a section with a resistant basement. The second step consists in the least-squares estimation of layer resistivities and thicknesses from the kernel function. For the case of S or T-equivalent beds only one layer-parameter can be obtained, either the longitudinal conductance, or the transverse resistance respectively. Two examples given in the paper show that a wide tolerance is permitted for Choosing the starting values of the layering parameters in the successive approximation procedure. Another important feature for practical applications is good convergence of the iterations. The method is probably best suited for interpreting profiles of electrical soundings with the purpose of mapping approximately horizontal interfaces at depth.  相似文献   

Maximum extent of the Eurasian ice sheets in the Barents and Kara Sea region during the Weichselian   总被引：1，自引：0，他引：1  

JOHN INGE SVENDSEN  VALERY I. ASTAKHOV  DMITRI YU. BOLSHIYANOV  IGOR DEMIDOV  JULIAN A. DOWDESWELL  VALERY GATAULLIN  CHRISTIAN HJORT  HANS W. HUBBERTEN  EILIV LARSEN  JAN MANGERUD  MARTIN MELLES  PER MÖLLER  MATTI SAARNISTO  MARTIN J. SIEGERT 《Boreas: An International Journal of Quaternary Research》1999,28(1):234-242

Based on field investigations in northern Russia and interpretation of offshore seismic data, we have made a preliminary reconstruction of the maximum ice-sheet extent in the Barents and Kara Sea region during the Early/Middle Weichselian and the Late Weichselian. Our investigations indicate that the Barents and Kara ice sheets attained their maximum Weichselian positions in northern Russia prior to 50 000 yr BP, whereas the northeastern flank of the Scandinavian Ice Sheet advanced to a maximum position shortly after 17 000 calendar years ago. During the Late Weichselian (25 000-10 000 yr BP), much of the Russian Arctic remained ice-free. According to our reconstruction, the extent of the ice sheets in the Barents and Kara Sea region during the Late Weichselian glacial maximum was less than half that of the maximum model which, up to now, has been widely used as a boundary condition for testing and refining General Circulation Models (GCMs). Preliminary numerical-modelling experiments predict Late Weichselian ice sheets which are larger than the ice extent implied for the Kara Sea region from dated geological evidence, suggesting very low precipitation.  相似文献   

Permian bryozoans from southern Spitsbergen and Bjørnøya. A review of bryozoans described by J. Malecki (1968, 1977)     

HANS A. NAKREM 《Polar research》1988,6(1):113-121

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Weichselian stratigraphy and palaeoenvironments at Bellsund, western Svalbard   总被引：1，自引：0，他引：1  

JON Y. LANDVIK  MAGNE BOLSTAD  ANNE KATRINE LYCKE  JAN MANGERUD  HANS PETTER SEJRUP 《Boreas: An International Journal of Quaternary Research》1992,21(4):335-358

A coastal cliff facing the ocean at the west coast of Spitsbergen has been studied, and seven formations of Weichselian and Holocene age have been identified. A reconstruction of the palaeoenvironment and glacial history shows that most of the sediments cover isotope stage 5. From the base of the section, the formation 1 and 2 tills show a regional glaciation that reached the continental shelf shortly after the Eemian. Formation 3 consists of glacimarine to marine sediments dated to 105,000–90,000 BP. Amino acid diagenesis indicates that they were deposited during a c . 10,000-year period of continuous isostatic depression, which indicates contemporaneous glacial loading in the Barents Sea. Foraminifera and molluscs show influx of Atlantic water masses along the west coast of Svalbard at the same time. Local glaciers advanced during the latter part of this period, probably due to the penetration of moist air masses, and deposited formation 4. A widespread weathering horizon shows that the glacial retreat was succeeded by subaerial conditions during the Middle Weichselian. Formation 5 is a till deposited during the Late Weichselian glacial maximum in this area. The glaciation was dominated by ice streams from a dome over southern Spitsbergen, and the last deglaciation of the outer coast is dated to 13,000 BP. A correlation of the events with other areas on Svalbard is discussed, and at least two periods of glaciation in the Barents Sea during the Weichselian are suggested.  相似文献   

DAMOCLES: a DAshing MOnolith Cutter for fine sectioning of peats and sediments into LargE Slices     

HANS JOOSTEN  PIM DE KLERK 《Boreas: An International Journal of Quaternary Research》2007,36(1):76-81

Simple cutting devices such as used in the printing industry allow precise and fine sectioning of frozen peats and sediments, thus enabling research with high temporal resolution. Large slices are useful in the collection of multiple synchronous subsamples for multidisciplinary research. This article describes the apparatus (called DAMOCLES) and its operation, and presents some examples from practice. These include combined microfossil, macrofossil and chemical analyses of the same sample with a sample resolution of 0.5 cm (temporal resolution c. 1 year): rapid changes occur that would have remained unnoticed with a coarser sampling distance. The final example presents a sample resolution of only 0.5 mm. These examples illustrate the possible uses of the DAMOCLES apparatus in palaeoecological research.  相似文献   

A stable isotope record from freshwater lake shells of the eastern Tibetan Plateau, China, during the past two centuries     

JINGLU WU  GERHARD HANS SCHLESER  REAS LÜCKE  SHIJIE LI 《Boreas: An International Journal of Quaternary Research》2007,36(1):38-46

Lake Xingcuo is a small, closed, hardwater lake situated in the eastern Tibetan Plateau. Stable isotope data (δ¹⁸O and δ¹³C) from the freshwater snail Gyraulus sibirica (Dunker) in a 34-cm-long, radioactive isotope-dated sediment core represent the past 200 years of Lake Xingcuo environmental history. Carbon and oxygen isotope ratios in the shells of the snail yield information on the isotopic composition of the water in which the shell was formed, which in turn relates to climatic conditions prevailing during the snail's life-span. Living and fossil shells from Lake Xingcuo were collected. δ¹⁸O values in the living shells from Lake Xingcuo are in equilibrium with ambient waters, while δ¹³C values may trace snail dietary carbon. On comparing δ¹⁸O and δ¹³C in the shell of Gyraulus sibirica with monitored data for the period 1954-1995, we found that the δ¹⁸O composition in the shell is an efficient proxy revealing air temperature during the warmer months from April to September. There is a positive correlation between the δ¹⁸O in the shells of Gyraulus sibirica and the running average temperature of the warmer months. Climatic variability in the eastern Tibetan Plateau for the past two centuries has been inferred from the δ¹⁸O record from the freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years' palaeoclimatic record for this region can be separated into three periods representing oscillations between warm and cool conditions consistent with the Guliya ice record in the Tibetan Plateau.  相似文献