central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

authigenic greigite in mud from the continental shelf of the yellow sea off the southwest korean peninsula abstract this is the first reported occurrence of greigite in korea which was found in semi consolidated near surface mud on the continental shelf of the southeastern yellow sea the seafloor 70 m of water in the sampling site is composed of alternating massive sand and homogeneous mud which are presumably part of the holocene transgressive deposits greigite grains 0 1 2 mm in size are disseminated or form a single lamina in the mud the mineral is strongly magnetic and black with metallic luster some grains have a reddish brown tarnish caused by oxidation in reflected light greigite occurs as yellowish white to pale creamy tint and isotropic globular aggregates the mineral greigite has a chemical composition of fe 54 4 s 42 4 as 0 14 si 2 3 wt and the empirical formula on the basis of s 4 is fe2 95s4 cell dimensions cubic are measured as a 9 8635 ra v 959 6 a 3 and d 4 094 g cm3 it probably formed in a reducing micro environment around decaying organic matter

late weichselian and early holocene shore displacement in the central baltic sea abstract the glacial unloading and resulting isostatic land uplift have together with hydro isostasy eustatic rise of sea level and geoidal changes ruled the shore displacement of fennoscandia within the baltic basin periods of damming and shifts of outlet further complicated the shore displacement during the period studied ca 12 2 8 4 ka bp information on the baltic history was derived from shoreline observations and studies on sediment cores from lakes formerly directly affected by the baltic these cores were analyzed with respect to pollen diatoms and lithology to determine sequences of baltic sediments and dated by a combination of radiocarbon dates and biostratigraphy the studied areas of southeastern sweden mainly central gotland and the oskarshamn area eastern smaland display a similar course of shore displacement the late weichselian period shows a regression of a slightly decreasing rate between ca 12 2 and 10 3 ka bp then followed a fast drop 25 m of the baltic s water level the final drainage of the baltic ice lake during the next ca 700 years the yoldia stage a regression of ca 17 m occurred this period is mainly characterized by freshwater diatoms in the baltic but at ca 10 ka bp there is evidence of a shortlasting 100 150 year period with brackish water the ancylus transgression of ca 11 m began ca 9 6 ka bp and culminated ca 9 3 ka bp it was followed by a fast regression of 8 10 m thereafter the rate of regression decreased shoreline gradients showed that the fastest shoreline tilting occurred around 10 ka bp thus ca 2 ka after deglaciation

stratigraphic evidence for a high marine shore line during the late weichselian deglaciation on the kullen peninsula southern sweden mineral magnetic properties and the carbon content of a sediment sequence in lake kullatorpssjon on the kullen peninsula in northwest scania southern sweden were investigated diatom and ostracod analyses were undertaken for palaeoecological reconstruction and a chronology was constructed from accelerator mass spectrometry ams radiocarbon dating of terrestrial plant remains and mosses five stratigraphical units were identified units 1 5 from oldest to youngest the two lowermost units consist of clay the lowest clay unit 1 is strikingly black 2 m thick and has magnetic properties dominated by high concentrations of authigenic greigite fe3s4 in contrast the overlying clay unit 2 is grey 1 18 m thick and has magnetic properties dominated by low concentrations of detrital magnetite fe3o4 a major palaeoecological change is reflected in the diatom flora and ostracod fauna at the transition from unit 1 to unit 2 the sediment stratigraphy geochemical mineral magnetic and palaeoecological analyses also point to a significant change in depositional environment at this transition which is proposed to represent the isolation of lake kullatorpssjon from the kattegat sea earlier investigations have determined the marine limit to ca 65 m a s l on the kullen peninsula the separate independent lines of evidence presented here however suggest that the late weichselian marine limit developed at 85 90 m a s l at the deglaciation ca 17 200 cal yr bp ca 14 500 yr bp this limit is ca 25 m higher than assumed previously lake kullatorpssjon formed ca 1000 cal yr later when the basin became isolated from the kattegat sea copyright c 1999 john wiley sons ltd less

a model for the exchange of water and salt between the baltic and the skagerrak abstract a model for the exchange of salt and water between the baltic and the sea the skagerrak is presented because of strong inter basin interactions in the baltic entrance area the model must include the kattegat and the belt sea these are modeled by horizontally homogeneous two layer sub models the most prominent dynamical properties of the sub models are wind driven entrainment flows and rotational baroclinic hydraulic controls the model is driven by a meteorologically forced barotropic transport qh calculated from the freshwater supply to the baltic qf and the sea level fluctuations in the kattegat and turbulent entrainment flows coupled to the wind speed w and in the belt sea also to the barotropic transport the most important bathymetric features of the basins are included the model equations are integrated numerically for a test period of 1 years the stratification in the kattegat as well as in the belt sea is quite well predicted it is found that approximately one half of

the mineral magnetic properties of an annually laminated holocene lake sediment sequence in northern sweden detailed mineral magnetic measurements were conducted on a 9000 year varved lake sediment sequence in northern sweden lake sarsjon the results demonstrate that the paramagnetic susceptibility reflects the concentration of detrital minerogenic material in the lake sediments which is controlled to a large extent by the intensity of the spring snow melt in contrast the concentration of ferrimagnetic magnetite reflected by initial magnetic susceptibility and magnetic hysteresis parameters is positively correlated to the concentration of organic carbon which is most likely of an autochthonous origin this magnetite has magnetic properties that are characteristic of stable single domain magnetite grains produced by magnetotactic bacteria the paramagnetic susceptibility record clearly points to a climatic excursion in the early holocene between 6100 174 bc and 5700 167 bc which can be correlated to an d18o excursion a cold event in the greenland ice cores and lake sediments in southern germany an

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

high resolution record of the upper olduvai transition from po valley italy sediments support for dipolar transition geometry abstract a detailed record of the upper olduvai polarity transition composed of 100 transitional directions has been obtained from the crostolo section in northern italy a careful examination of the rock magnetic properties of the sediments using standard paleomagnetic techniques thermomagnetic scanning electron microscopy microprobe x ray diffraction and mossbauer analysis shows that greigite is the main magnetic carrier of the remanence the correlation of a shift in the magnetic record to a small scale sedimentary feature observed in the section indicates that the magnetization was acquired at deposition or very shortly after the virtual geomagnetic pole vgp path is largely confined along a great circle over north and south america 90 west of the site and consists of three stages first the vgp moves to southern mid latitudes then after a period of standstill it comes back to almost true north and finally the south pole is reached in a third step although different from a record from the southern indian ocean this path is virtually identical to those obtained for the same transition from north pacific deep sea cores and partly coincides with a north atlantic record which suggests that a dipolar component may be present in the transitional field during the upper olduvai reversal a review of the recently obtained records of various transitions shows that in more than two thirds of the cases the vgp paths are similarly confined along a meridian over the americas or antipodal to them irrespective of the sampling site and of the sense of the transition although not deterministic this tendency suggests that a similar dipolar component might be present in the transitional fields of other reversals of different ages

linear theory of the sea breeze in a thermal wind this article investigates the linear dynamics of the sea breeze in an along shore thermal wind shear the present analysis shows that the sea breeze circulation is tilted towards the slanted isentropes associated with the thermal wind at a critical value of the thermal wind shear the tilt of the sea breeze circulation becomes equal to the slope of the background isentropes the present analysis also shows a spatial shift between the heating pattern and the sea breeze circulation the present linear theory is then applied to interpret measurements made in the vicinity of new york city where there is a warm season synoptic southwesterly jet it is compared with observations and past numerical simulations agreement is found with respect to the enhanced along coast wind that follows the tilted isentropes the order of magnitude of the isentrope tilt and the clockwise rotating wind hodograph showing the jet maximum peaking at 1800 solar time there is a disagreement between theory and observations on the phase lag between the jet maximum and the cross shore pressure gradient maximum however this disagreement can reasonably be attributed to either the angle made by the synoptic jet to the coastline and or the presence of friction the inland spatial shift of the breeze indicated by the theory might also be indirectly confirmed by the coastal inlan dw ind observations of al arger diurnal amplitude for a stronger synoptic jet copyright c 2011 royal meteorological society

bacterial magnetite and the magnetic properties of sediments in a swedish lake a comparison of the magnetic properties of lake sediments and catchment materials from pajep njakajaure north sweden demonstrates that high concentrations of single domain sd magnetite in the upper 70 cm of gyttja in the deepest part of the basin are not of detrital origin tem and light microscope examination revealed the existence of bacterial cells and magnetosomes in the upper sediments which are responsible for the presence of the sd magnetite most of the fossil magnetosomes appear to have been dissolved through reductive processes at lower depths although some are preserved in the lower sediments and carry a post depositional remanent magnetization pdrm the results highlight the complex effects of post depositional processes on mineral magnetic assemblages and natural remanent magnetization aquisition and demonstrate how mineral magnetic measurements may be used to identify magnetic grain size changes brought about by sediment diagenesis

should fluorescence alteration replace vitrinite reflectance as a major tool for thermal maturity determination in oil exploration abstract the fluorescence alteration multiple macerals famm technique is closely related to vitrinite reflectance until recently fluorescence alteration study of dispersed organic matter dom in sedimentary rocks has been regarded as technically difficult with the introduction of optical microprobes equipped with small continuous wave gas lasers having a very stable output of blue radiation readily focused to 1 2 m on the sample this work has now become routine famm has important advantages over vitrinite reflectance stemming from the possibility of resolving the data into two parameters one related to the level of maturation and the other related to the hydrogen richness of a maceral this enables the resolution of what are often difficult problems for the single parameter vitrinite reflectance technique namely the identification of indigenous vitrinite in dom the recognition of caved and reworked organic matter and the suppression of vitrinite reflectance for these reasons famm is a powerful tool for investigating vitrinite reflectance anomalies especially those associated with unconformities it is also well suited to investigate the tacit assumption in the vitrinite reflectance technique that all telocollinite matures along a single compositional pathway the famm technique is not without problems the range is restricted to equivalent mean random vitrinite reflectance rm o 0 4 1 2 the results are more sensitive to ambient temperature oxidation than vitrinite reflectance and the technique demands a high level of technical expertise the famm technique is calibrated on coals and it is therefore more likely to give high quality results on types ii and iii kerogens rather than type i kerogens which have not yet been intensively investigated although famm is unlikely to replace vitrinite reflectance considerable confidence may be had in a maturation assessment when consistent results are obtained from these two closely related but independent techniques

magnetic discrimination of pyrrhotite and greigite bearing sediment samples by using bulk samples rock magnetic measurements were performed to discriminate between pyrrhotite and greigite bearing shallow marine sediments that are now uplifted above sea level in southwestern taiwan thermal demagnetization of a composite isothermal remanent magnetization irm was found to be effective in differentiating between the two types of sediments to check the thermal instability and estimate the true unblocking temperature tb spectra of sediments containing these minerals saturation irms sirms were imparted at each temperature step during demagnetization while pyrrhotite bearing samples showed unambiguous tb temperature spectra greigite bearing samples underwent considerable alteration which is responsible for most of the decrease in magnetization during thermal demagnetization such thermal instability of greigite is a practical and important clue for its identification zero field warming of irm from 5 to 300 k sensitively indicates the presence of pyrrhotite and trace magnetite in bulk samples without any magnetic separation

gyroremanent magnetization and the magnetic properties of greigite bearing clays in southern sweden summary the acquisition of a gyroremanent magnetization grm by single domain sd greigite particles during alternating field af demagnetization is demonstrated previous palaeomagnetic studies failed to identify the presence of authigenic greigite in the glacio marine clays studied these clays formed the subject of an earlier debate about the validity of a late weichselian geomagnetic excursion the gothenburg flip in southern sweden the greigite carries a stable chemical remanent magnetization crm which coexists with a detrital remanent magnetization drm carried by magnetite af demagnetization could not isolate the primary remanence in the sediments where magnetite and greigite coexist due to the overlapping coercivity spectra of the two minerals and the inability to determine the time lag between sediment deposition and crm formation thermal demagnetization removed the crm at temperatures below 400 dc but this method was hindered by the unconsolidated nature of the sediments and the formation of secondary magnetic minerals at higher temperatures the results suggest that the low coercivity drm carried by magnetite was mistaken for a viscous component in the earlier studies hence the former debate about the record of the gothenburg flip may have been based on erroneous palaeomagnetic interpretations or non reproducible results af demagnetization procedures applied to samples suspected of bearing sd magnetic particles such as greigite should be carefully selected to recognize and account for grm acquisition

bacterial magnetite in swedish varved lake sediments a potential bio marker of environmental change abstract detailed mineral magnetic measurements were carried out on three varved lake sediment sequences in sweden which extend to ca 7000 bc the comparison of the magnetic properties of the organic rich varved lake sediments with their respective catchment materials indicates that the magnetic properties of the sediments are dominated by relatively high concentrations of single domain magnetite magnetosomes produced by magnetotactic bacteria the dimictic nature of the lakes which help form and preserve the varves due to the weakly oxic or suboxic environment also appear to be suitable for a high degree of magnetosome preservation the concentration of the magnetosomes in two of the sequences as determined by mass specific magnetic measurements exhibits a positive linear relationship with the total organic carbon content and suggests that magnetic remanence measurements reflect lake productivity via processes of organic matter accumulation and decomposition further research should focus on the potential to use the fossil magnetosomes as proxy climate environmental change indicators and as recorders of geomagnetic field variations and behaviour

a regional 8200 cal yr bp cooling event in northwest europe induced by final stages of the laurentide ice sheet deglaciation the most notable change in 18o in greenland ice cores during the holocene occurs at 8200 cal yr bp here we present a new high resolution marine record from the northern north sea along with tree ring data from germany which contain evidence of a pronounced temperature drop 2 c contemporaneous with that of the greenland ice core records the synchronous timing of the cooling event in the greenland ice cores marine record and tree ring data from northwest europe reflects a regional influence on the north atlantic ocean atmospheric system suggesting a prominent role of the north atlantic thermohaline circulation the operation of the north atlantic ocean circulation is sensitive to variation in the freshwater budget implying that any change in freshwater flux is capable of altering the north atlantic circulation system we hypothesise minor but long term freshwater fluxes in the final stages of the deglaciation of the laurentide ice sheet as a forcing mechanism 1998 john wiley sons ltd

late pleistocene and early holocene paleogeography of the darss sill area southwestern baltic abstract today about 73 of the water exchange between the baltic and the north sea takes place through the darss sill area in hydrographic terms the darss sill is a major morphological unit separating the deeper areas of the mecklenburg bay and the arkona basin from each other it is characterized by an average water depth of 16 m the main bathymetric features are the gedser reef with a water depth of less than 10 m and the kadet channel which has a maximum water depth of 32 m according to previous authors there are two different ice marginal lines between falster denmark and the darss peninsula germany the recent kadet channel is regarded as a large glacial valley cutting the ice marginal lines joint danish and german investigations in the darss sill area 1989 1991 indicate the existence of only one marginal line in this region which is represented by a till cropping out in the area between falster and the german coast the formation of the marginal line ca 13 500 bp caused a damming of a pre existing subglacial drainage system in the gedser reef area southeast of the recent kadet channel glaciofluvial drainage occurred towards the ne through a deep channel into the baltic ice lake immediately after the retreat of the ice during the baltic ice lake transgression the channel was filled by sandy sediments from sources east of the investigated area this accumulation process resulted in the blocking of the channel at the time of the baltic ice lake highstand maximum at this time occasional overflow in the kadet channel area must have started the main erosion and deepening of the kadet channel must however be ascribed to the ancylus lake overflow

hydrographic thresholds in the western baltic sea late quaternary geology and the dana river concept abstract since the final weichselian deglaciation the water exchange between kattegat and the baltic sea and hence the palaeogeographical development of the western baltic has been controlled by a number of sills major thresholds are found at the southern entrance of the great belt and in the darss sill area the easternmost of these structures is formed by late weichselian sands at a level of 24 m below present sea level bsl at the falster rugen sand plain a second threshold consisting of till was found within the kadet channel at a level of 23 24 m bsl thus we exclude water exchange between mecklenburg bay and the arkona basin at levels below 24 m since the end of the pleistocene a high resolution sediment echosounder survey at the triple junction area of langeland channel vejsnaes channel and winds grave channel showed outcropping glacial deposits narrow channels incised at a level below 25 m bsl are filled partly with fine grained organic rich late and postglacial sediments assuming no substantial crustal movements in this area in the holocene no ancylus lake drainage at a level deeper than 25 m bsl is likely to have occurred here

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

rapid early holocene environmental changes in northern sweden based on studies of two varved lake sediment sequences mineral magnetic organic carbon and pollen studies of two varved holocene lake sediment sequences in the boreal forest of northern sweden indicate that significant environmental changes took place between c 6000 and 5700 bc this interval is characterized by an increase in mineral matter accumulation which is a proxy for winter snow accumulation and a statistically significant decrease in total pollen influx predominantly pinus betula and alnus which may reflect lower spring and summer temperatures and increased frost frequency notable increases in the influx of deciduous tree species including quercus and corylus suggest a rapid change to warmer conditions between 5700 and 5600 bc given dating errors associated with the varve chronologies and the greenland ice core timescales the cold interval can be considered to reflect a regional possibly global climatic cooling which is often referred to as the 8 2 kyr bp cooling event however the younger age of the cold event in northern sweden does not support the hypothesis of forcing by the sudden drainage of laurentide glacial lakes into the north atlantic unless a minimal 300 year delay in ocean atmospheric coupling is accepted the data contribute to a complex picture of early holocene environmental change in response to deglaciation of the northern hemisphere

early holocene history of the baltic sea as reflected in coastal sediments in blekinge southeastern sweden integrated palaeoecological studies of two fiord sediment sequences in the province of blekinge se sweden covering the time span 11 000 5000 cal bp reveal the timing and the environment for the ancylus lake littorina sea transition 9800 8500 cal bp the first ingression of saline water into the baltic sea through the danish straits occurred earlier than formerly assumed new evidence particularly mineral magnetic and palaeobotanical analyses demonstrate that on the general trend of the eustatically caused littorina transgression several minor fluctuations of the water level can be identified between 8500 and 5000 cal years bp a distinct regression phase around 8 100 cal bp is correlated with the greenland ice core cold event dated to 8200 ice core years bp this is described as a regional climatic catastrophe for the baltic sea region the coastal stratigraphy is compared with the offshore stratigraphy earlier studied a tentative shore displacement curve for early and middle holocene is presented

holocene history of the baltic sea as recorded in a sediment core from the gotland deep a 4 m long sediment core from the gotland deep baltic sea was investigated by means of biostratigraphical and chemical parameters and c 14 datings this multidisciplinary approach allows us to ev

diagenetic formation of ferrimagnetic iron sulphide minerals in rapidly deposited marine sediments south island new zealand abstract detailed magnetostratigraphic studies of late neogene siliciclastic sediments of the awatere group south island new zealand 41 45 s 174 05 e have revealed a wide range of palaeomagnetic behaviour examination of rock magnetic properties was undertaken using conventional palaeomagnetic techniques and thermomagnetic x ray diffraction and electron microprobe analyses these analyses indicate that the ferrimagnetic iron sulphide minerals greigite and pyrrhotite are responsible for a stable and intense magnetic remanence in fine grained sediments whereas titanomagnetite is the only remanence bearing mineral identified in coarser grained sediments which are less strongly and less stably magnetised than the fine grained sediments detrital titanomagnetite grains are likely to have undergone dissolution during early diagenesis as a result of iron sulphide formation which occurs commonly in rapidly deposited anoxic sediments that support active sulphate reduction and h 2 s formation preservation of greigite and pyrrhotite is inferred to result from the arrest of the pyritisation process probably due to the low permeability of the fine grained sediments and consumption of available h 2 s before full reaction to pyrite occurred relative palaeomagnetic instability and weak remanence intensities in coarser grained sediments is likely to be due to low titanomagnetite concentrations resulting from titanomagnetite dissolution

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

shoreline displacements in southern central sweden and the evolution of the baltic sea since the last maximum glaciation during late and post glacial times the baltic basin has been periodically isolated from the atlantic and freshwater and saline conditions have alternated this is a consequence of the interactions between the spatially variable glacial rebound of the region and the simultaneous eustatic sea level rise in the adjacent atlantic observations of the timing of these isolations and of the location of the barriers therefore provide constraints on the rebound models high resolution numerical models of rebound of southern sweden the danish straits and the baltic have been developed and tested against observations of lake level change as well as against the observed elevations of the last baltic ice lake shoreline which formed before about 10 3 ka bp predictions of sea and lake levels are used to test two alternative hypotheses about the ice thickness over scandinavia and to estimate parameters that describe the earth s response optimum values for the latter are lithospheric thickness of 60 20 km upper mantle viscosity of 3 3 10 20 pa s and lower mantle viscosity of 10 22 pa s the rapid lake level fall at the end of the baltic ice lake stage is estimated to be 30 5 m the optimum ice model for scandinavia is one in which the ice thickness over southeastern and southern scandinavia was relatively thin compared with the ice thickness over sweden and norway the ice thickness in the southeast and south changes slowly with distance inwards of the ice margin whereas over sweden and norway the ice thickness profiles are considerably steeper the earth and ice models have been combined with high resolution digital terrain data to develop a comprehensive model for the evolution of the baltic basin since the time the area last became ice free the reconstructions predict the occurrence of barriers at certain times which impede free flow between the atlantic and baltic and confirm that the baltic lake levels are controlled by rebound at four localities degerfors in the narke region of southern central sweden the vanern outlet through the gota alv oresund and the darss langelands store baelts in denmark

magnetic properties of sedimentary greigite fe3s4 new data are presented here that document the previously poorly known magnetic characteristics of sedimentary greigite fe3s4 several diagnostic magnetic properties can be used in conjunction to rapidly screen sediments to detect the presence of greigite such discriminants are necessary because greigite displays a similar or higher range of coercivities compared to most ferrimagnetic minerals and the commonly used method of alternating field demagnetization cannot be used to distinguish between palaeomagnetic remanence components due to greigite and other ferrimagnetic minerals sedimentary greigite has high ratios of the saturation isothermal remanent magnetization to magnetic susceptibility mrs which are accompanied by hysteresis ratios of mrsms 0 5 and bcr bc 1 5 ms is the saturation magnetization bc is the coercive force and bcr is the coercivity of remanence greigite has no low temperature phase transition whereas the ferrimagnetic iron sulphide pyrrhotite undergoes a major phase transition at about 34 k and unoxidized magnetite displays the verwey transition at 118 k low temperature measurements may therefore prove valuable in distinguishing between magnetite pyrrhotite and greigite although the absence of a low temperature transition cannot be taken as definitive evidence for the presence of greigite greigite also displays characteristic high temperature behaviour with a major drop in magnetization between 270 and 350 c determination of the mrs ratio is an excellent means of rapidly screening sediments to identify stratigraphic intervals that may contain greigite subsequent low and high temperature analyses can then provide unambiguous identification of greigite and enable the evaluation of the presence of other magnetic minerals