the baltic ice lake in south finland and its outlets abstract in finland the earliest stages of the ancient baltic have traditionally been divided into the pre baltic ice lake s the baltic ice lake and the yoldia phase the pre baltic ice lake stage has also been called the late glacial yoldia sea and karelian ice lake there are certain indications of a low water level during the allerod in southern finland before the earlier phase of the baltic ice lake two drainages of the baltic into the atlantic ocean seem to have occurred the first through the oresund strait in denmark from about 12 7 to 10 2 ka bp bolling allerod younger dryas and the second last one at the end of the baltic ice lake period through the area of billingen central sweden at about 10 2 ka bp younger dryas the possible connection of the baltic with the white sea arctic ocean has also been under discussion for a long time recently finnish geologists have been studying this problem in north and south russian karelia but no evidence of a connection between the white sea and the baltic has been found the last drainage of the baltic ice lake is not clearly proved by the finnish varve chronology morphologically the drainage can be seen as a lowering by about 25 26 m of the highest baltic coast line in the zone between the 2nd and 3rd salpausselka in western finland the subsequent rapid yoldia regression took place before the beginning of the ancylus transgression some sediment series demonstrate a brief marine influence from the ocean along the finnish coast during the yoldia phase

parameterization of stream channel geometry in the distributed modeling of catchment dynamics a simple and efficient procedure for incorporating the effects of stream channel geometry in the distributed modeling of catchment dynamics is developed at a station and downstream fluvial relationships are combined and the obtained laws of variability in space and time for water surface width and wetted perimeter are incorporated into a diffusion wave routing model based on the muskingum cunge method with variable parameters the parameterization obtained is applied to the approximately 840 km 2 sieve catchment central italian apennines to test the possibility of estimating channel geometry parameters from cross section surveys and to assess the impact of dynamic variations in the channel geometry on catchment dynamics the use of the estimated channel geometry in surface runoff routing produces a significant improvement in the flood hydrograph description at the catchment outlet with respect to less detailed network parameterizations in addition the results obtained from a downstream analysis of the velocity field indicate that the stream characteristics related to the locally varying cross section shape may have a strong control on flow velocities and thus they should be monitored and synthesized for a comprehensive description of the distributed catchment dynamics

postglacial uplift neotectonics and seismicity in fennoscandia abstract fennoscandia has experienced major uplift in postglacial time which is assumed to reflect a glacial isostatic process connected to the melting of the last ice sheets extensive modelling of the isostatic movements show that the applied deglaciation and uplift model fit the observations well there are however areas with significant deviations between uplift measurements and regional model predictions the misfit between observations and the isostatic uplift modelling is interpreted here to reflect a tectonic component of the uplift the objective of the present investigation is to isolate this tectonic uplift component interestingly enough the areas found partly correspond to areas with pronounced seismic activity and the assumption that the postglacial rebound is responsible for much of the observed onshore seismicity is substantiated we conclude that there seems to be present day deformation along the shoreline of mid norway southern norway shoreline and mountain areas and along the swedish east coast with the centre northeast of the gulf of bothnia that cannot be explained by glacial isostasy not all of the deformations in these areas are necessarily co seismic the study suggests that such vertical deformations are small in magnitude and overprint the glacial rebound the deformations may be a consequence of the plio pleistocene erosional pattern which is of glacial origin

biostratigraphy of the last glacial period in europe the european early weichselian early wurmian is characterized by two long and relatively warm interstadials brorup and odderade which can be traced and correlated with certainty across large parts of europe the amersfoort interstadial described earlier from the netherlands has been included in the brorup and represents the older part of it both great interstadials were forested in north west central and southern europe in the north conifer forests prevailed giving way towards the south to deciduous forests the climatic gradient was distinctly steeper mainly due to southward displacement of the gulf stream the two great interstadials are synchronous with the isotopic stages 5a and 5c in the deep sea cores subsequent to eemian brorup and odderade and from within the context of a continuous series two additional and clearly delimited interstadials have been recorded in a new standard profile from oerel nw germany these are now described as the oerel and glinde interstadials they were not forested and belong to the early pleni weichselian the lower one oerel can probably be correlated with the 3rd weichselian wurmian interstadial in southern central europe ognon ii durnten samerberg 3 while the upper one glinde has so far no known counterpart for the younger pleni glacial it is assumed that there was a long phase during which it was not too cold the formation of humic layers during this phase took place at different times partly due to local edaphic factors so that the relevant 14c dates show a wide scatter the hengelo and denekamp interstadials represent only slight ameliorations which facilitated the formation of shrub tundra and can be recorded in certain regions only

on the prediction of channel heads in a complex alpine terrain using gridded elevation data 1 threshold conditions for channel initiation are evaluated by using gridded elevation data derived from a lidar survey a reliable algorithm for the determination of surface flow paths and field observations of channel heads for a study area located in the eastern italian alps these threshold conditions are determined by considering the channel heads observed across a portion of the study area and computing the related values of 1 drainage area a 2 area slope function as2 with s being the local slope and 3 strahler order of surface flow paths extracted from gridded elevation data attention is focused on the dependence of the obtained threshold values on the size of grid cells involved and on the ability of the identified threshold conditions to provide reliable predictions of channel heads across the entire study area the results indicate that the threshold values of a as2 and are all significantly dependent on grid cell size and the uncertainty in the determination of threshold values of is significantly smaller than that affecting the determination of threshold values of a and as2 the comparison between predicted and observed channel heads indicates that the considered methods display variable reliability and sensitivity over different drainage basins and grid cell sizes with a general tendency to predict more channel heads than can be observed in the field acceptable predictions are normally obtained where channel heads are formed essentially by surface runoff more comprehensive methods seem however to be needed to predict channel heads affected by groundwater seeping upward

physicochemical and biological influences on sedimentary fabric formation in a salinity and oxygen restricted semi enclosed sea gotland deep baltic sea two ca 8000 year long sediment cores from the gotland deep the central sub basin of the baltic sea were studied by means of digital images x radiographs and scanning electron microscopy energy dispersive x ray mineralogical analysis to gain understanding of the physicochemical and biological influences on sedimentary fabric formation in modern and ancient seas with a high flux of organic carbon and associated oxygen stress and depauperate ichnofauna four lithofacies were recognized i sharply laminated mud ii biodeformed mud iii burrow mottled mud and iv sedimentation event bed the sharply laminated and burrow mottled facies dominate the cores as alternating long intervals whereas the biodeformed and sedimentation event facies occur as thin interbeds within the sharply laminated intervals the sharply laminated mud comprises alternating diatom rich and lithic laminae with occasional mn carbonate laminae lamination discontinuity horizons within the laminites where the regular lamination is overlain sharply by gently inclined lamination challenge the traditional view of mud accumulation by settling from suspension but indicate localized accumulation by particle trapping microbial mats and potentially by the rapid lateral accretion of mud from bedload transport the biodeformed interbeds record brief few years to few decades oxic dysoxic conditions that punctuated the anoxic background conditions and permitted sediment surface grazing and feeding by a very immature benthic community restricted to the surface mixed tier the likely biodeformers were meiofauna and nectobenthic pioneers passively imported with currents the sedimentation event interbeds are distal mud turbidites deposited from turbidity currents probably triggered by severe storms on the adjacent coastal areas the turbidite preservation was favoured by the anoxic background conditions the long burrow mottled intervals are characterized by intensely bioturbated fabrics with discrete planolites rare arenicolites polykladichnus and very rare lockeia trace fossils as well as bivalve biodeformational structures which represent shallowly penetrating endobenthic feeding and grazing strategies and permanent dwellings these burrowed intervals represent longer periods several years to few centuries of oxic dysoxic conditions that permitted maturation in the benthos by means of larval settling of opportunistic worm like macrofauna and bivalves resulting in the development of a transition tier these observations imply more dynamic and oxic depositional conditions in gotland deep than previously thought comparison to previous zoobenthic studies in the area allowed discussion of the benthic dynamics and the identification of probable biodeforming and trace producing species implications for current biofacies and trace fossil models are discussed

downstream hydraulic geometry relationships gathering reference reach scale width values from lidar abstract this paper examines the ability of lidar topography to provide reach scale width values for the analysis of downstream hydraulic geometry relationships along some streams in the dolomites northern italy multiple reach scale dimensions can provide representative geometries and statistics characterising the longitudinal variability in the channel improving the understanding of geomorphic processes across networks starting from the minimum curvature derived from a lidar dtm the proposed algorithm uses a statistical approach for the identification of the scale of analysis and for the automatic characterisation of reach scale bankfull widths the downstream adjustment in channel morphology is then related to flow parameters drainage area and stream power with the correct planning of a lidar survey uncertainties in the procedure are principally due to the resolution of the dtm the outputs are in general comparable in quality to field survey measurements and the procedure allows the quick comparison among different watersheds the proposed automatic approach could improve knowledge about river systems with highly variable widths and about systems in areas covered by vegetation or inaccessible to field surveys with proven effectiveness this research could offer an interesting starting point for the analysis of differences between watersheds and to improve knowledge about downstream channel adjustment in relation for example to scale and landscape forcing e g sediment transport tectonics lithology climate geomorphology and anthropic pressure

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

authigenic sulfide and carbonate mineral formation in holocene sediments of the baltic sea formation of authigenic sulfides and carbonates in holocene 14c dated sediments is interpreted based on analyses of cations fes s fes2 s corg and sulfur isotopes mineral distribution was studied in thin sections and mineral morphology with sem eds the sediments were deposited in the gotland deep baltic sea during freshwater and brackish stages calcium rich rhodochrosite mnco3 occurs in concentrations up to 17 dw in brackish water sediments and are mainly confined to 0 02 0 5 mm thick laminae the frequency with which these laminae occur suggests that they formed with a periodicity of one to a few years and their purity suggests that formation took place in a few weeks we propose that these carbonate laminae resulted from oxic water inflow to the euxinic basin mn ii dissolved in the water column was rapidly oxidized and large amounts of mn oxides reached the sediment reduction of these mn oxides in a high alkalinity environment facilitated rhodochrosite precipitation at the sediment surface pyrite in the brackish water sediments formed at or above the sediment water interface in an iron limited environment due to alternating oxic and euxinic conditions fes was oxidized resulting in a high fes2 sfes s ratio median 170 formation of iron sulfides in the freshwater sediments occurred below the sediment water interface in a sulfate limited environment as a result of the rapid exhaustion of reactive iron in the brackish water sediments excess h2s diffused downwards to pyritize the uppermost part of the underlying freshwater sediments

iron isotope heterogeneity in pyrite fillings of holocene worm burrows we present 54fe and 56fe data on pyrite from burrow like and irregularly shaped pyrite concretions from holocene postglacial lacustrine clays in the northern baltic sea collected using a secondary ion mass spectrometry sims microanalysis technique the burrow like concretions were formed in reducing mucus coated worm burrows in oxic surface sediments framboidal pyrite in the cores of the burrow like concretions shows extensively fractionated 56fe values down to 3 1 the framboids are cemented by poorly crystalline fes2 with 56fe values between 2 1 and 1 4 the irregularly shaped concretions with microcrystalline textures were formed in organic poor sediment pore spaces and display a wide spread of 56fe values up to 4 1 the measured 56fe values reflect the preferential capture of 54fe to pyrite in the diagenetic sequence and the 56fe enrichment of remaining pore water the diagenetic sequence of the pyrite materials is supported by previous petrographical study and 34s 32s microanalysis of the same samples our results demonstrate substantial early diagenetic 56fe and 34s heterogeneity within individual pyrite grains underlining the necessity of high spatial resolution measurements in studying biological and abiological isotopic signatures

high resolution seismic stratigraphy of late quaternary deposits in manitounouk sound northern quebec effects of rapid postglacial emergence manitounouk sound contains a succession of postglacial deposits consisting of three acoustic units separated by disconformities from base to top these are 1 a stratified draped unit interpreted as of glaciolacustrine and glaciomarine origin 2 an onlapping basin fill unit of thick transparent beds interpreted as gravity flow deposits and 3 a divergent fill unit of stratified and transparent modern marine deposits the gravity flow deposits of unit 2 pass laterally into slide scars that truncate unit 1 pollen and dinoflagellate analysis of cores correlated with the acoustic sections indicate that unit 1 is of early holocene age and confirms a glaciomarine environment unit 3 contains modern assemblages of pollen and dinoflagellates the slide scar and gravity flow deposits of unit 2 correspond to the period of transition from glaciomarine to modern conditions and are interpreted to result from a period of relatively intense earthquake activity due to stress release along faults during or shortly

dynamics of the laurentide ice sheet in hudson bay canada abstract interpretation of sidescan sonar and high resolution sub bottom seismic data from hudson bay has led to the development of a model for final disintegration of the laurentide ice sheet the well preserved geomorphic features observed from the bay floor are similar to subaerially exposed glaciogenic features observed around the perimeter of hudson bay and can be related to the following three paleoenvironments subglacial erosion deposition ice margin deposition and reworking and post glacial reworking and burial subglacial features observed include fluted terrains with superimposed rogen moraines relief attributed to ice surging eskers subglacial channels and dead ice topography de geer moraines and recessional moraine complexes indicate the mechanism and orientation of ice breakup retreat the orientations of these features are locally consistent with regional trends indicating the overall direction of ice sheet flow and retreat during the last phase of the laurentide ice sheet subglacial channel complexes incised into the till and bedrock and high energy bedforms deposited on the till surface occur in present day water depths down to 160 m due to isostatic depression these could have been as much as 315 m deeper at the time of formation they indicate a wet based glacier with high energy subglacial drainage during the late phases of ice retreat the sidescan sonar data also reveal numerous zones of distinctive morphology attributed to ice breakup and post glacial processes cross cutting relationships allow the determination of the relative ages of these zones from oldest to youngest these zones are interpreted to represent scouring of the bedrock and overburden by the remnants of the ice sheet seafloor scouring by tabular icebergs which moved in a tidally induced arcuate pattern or under the influence of massive glacial lake outflows development of dead ice topography under residual ice masses and random iceberg scouring by smaller icebergs restricted to present day water depths of less than 180 m recently published reconstructions of the collapse of the laurentide ice sheet based on dated quaternary sections on land suggest that the bay was rapidly deglaciated in approximately 400 years the well preserved and distinctive glaciogenic and stratigraphic indicators observed from the bay floor suggest that they were formed by a succession of mechanisms which were too short lived to obliterate the underlying evidence of deglaciation this supports the interpretation of extremely rapid deglaciation of hudson bay and points out that subsequent marine processes have not been sufficient to obliterate the glacial features

annually laminated sediments date the drainage of the ancylus lake and early holocene shoreline displacement in central finland abstract three independent varve annually laminated chronologies verified by paleomagnetic dating were used in the present biostratigraphical study to investigate the history of the baltic basin in central finland diatom analyses of the studied sediment sequences show the transition from the ancylus lake taxa to small lake diatoms at the isolation boundary these three varved profiles provide the following data and information on early holocene events in central finland i a shoreline displacement curve between the deglaciation at ca 9000 bc and ca 7000 bc ii relative emergence of the land area between 116 and 96 m above the present day sea level which proceeded at a rate of ca 2 6 cm year 1 iii the calendar year age for the lake ancylus at ca 8250 8200 bc and iv the calendar year age for the betula pinus pollen zone boundary ca 8100 bc and alnus arrival ca 7100 bc

ice dammed lakes and rerouting of the drainage of northern eurasia during the last glaciation during the quaternary period ice sheets centred over the barents and kara seas expanded several times onto mainland russia and blocked northflowing rivers such as the yenissei ob pechora and mezen large ice dammed lakes with reversed outlets e g toward the caspian sea formed south of these ice sheets some lakes are reconstructed from shorelines and lacustrine sediments others mainly from ice sheet configuration ice dammed lakes considerably larger than any lake on earth today are reconstructed for the periods 90 80 and 60 50 ka the ages are based on numerous optically stimulated luminescence osl dates during the global last glacial maximum lgm about 20 ka the barents kara ice sheet was too small to block these eastern rivers although in contrast to the 90 80 and 60 50 ka maxima the scandinavian ice sheet grew large enough to divert rivers and meltwater across the drainage divide from the baltic basin to the river volga and that way to the caspian sea climate modelling shows that the lakes caused lower summer temperatures on the continent and on the lower parts of the ice sheet the final drainage of the best mapped lake is modelled and it is concluded that it probably emptied within few months we predict that this catastrophic outburst had considerable impact on sea ice formation in the arctic ocean and on the climate of a much larger area c 2003 elsevier ltd all rights reserved less

palaeosecular variation of the earth s magnetic field during the last 10000 years based on the annually laminated sediment of lake nautajarvi central finland a palaeomagnetic study of the lake nautajarvi sediment sequence in central finland demonstrates that varved lake sediments can provideregionally applicable secular variations curves for holocene stratigraphic correlation and age control based on x ray radiography and digital image analysis techniques we constructed an inherent and continuous varve chronology for the lake nautajarvi varve sequence which covers nearly 10000 years with an estimated counting error of less than 1 and a mean sedimentation rate of 0 66 mm yr 1 we reconstructed a record of the palaeomagnetic secular variation psv of the earth s magnetic field in this nearly 7 m long section of clastic organic varves mineral magnetic measurements indicated that pseudosingle domain magnetite is the major carrier of the remanence psv shows many of the familiar features of declination and inclination that have previously been recorded in northern europe in addition the lake nautajarvi record contains a continuous record of relative palaeoi

late pleistocene and holocene depositional history of sediments in flathead lake montana evidence from high resolution seismic reflection interpretation abstract this paper presents an interpretation of 3 5 khz reflection seismic data together with information from lower frequency seismic data and sediment cores from flathead lake in northwestern montana flathead lake is located at the margin of the cordilleran ice sheet during the last glacial maximum and is the repository for about 160 m of syn and post glacial sediment six seismic stratigraphic units a f are identified in flathead lake above the acoustic basement reflector the deepest unit is interpreted to be late pleistocene glacial till unit a overlain by well layered glaciolacustrine sediments unit b overlying seismic reflectors unit c include slump deposits turbidites fed by meltwater surges associated with retreat of the flathead glacial lobe and homogeneous silty mud preliminary age models suggest that the transition from glacial rhythmites unit b to more homogenous lake sediments unit c occurred approximately between 14 500 and 13 180 cal y b p parallel high amplitude reflectors of the oldest holocene unit unit d drape pleistocene stratigraphy sediment core analyses suggest that these fine sediments were deposited below wave base by suspension settle out in a lake similar to today s the mt mazama tephra 7630 80 cal y b p is interpreted as the top reflector of unit d onlap geometries between units d and e imply a significant drop in lake level before deposition of unit e sedimentation of unit e was confined to several sub basins that were separated by bedrock highs lake level rose gradually during deposition of unit e to form the well developed basal onlap geometry parallel high amplitude reflectors of the youngest holocene sediments unit f drape all of the older stratigraphy and bedrock highs across the lake basin suggesting a late holocene lake highstand

pyritic and baritic burrows and microbial filaments in postglacial lacustrine clays in the northern baltic sea abstract holocene postglacial lacustrine clays in the northern baltic sea were studied for ichnofossils petrography and microscale elemental and 34 s 32 s composition to understand the impact of benthos produced organic matrices on the early diagenesis of sediments x radiographs of these clays display intense burrow mottling with discrete palaeophycus mycellia9 and rare arenicolites small burrow like and irregularly shaped concretions were separated from these clays the burrow like concretions are composed of framboidal pyrite and poorly crystalline fes 2 cement they formed within worm produced burrows by the decomposition of mucous coatings on the burrow walls by sulphate reduction 34 s cdt composition of the framboids indicates saline inflows from the north sea as the sulphate source the irregular concretions are microcrystalline pyritic masses that formed in pore spaces with less reactive organic compounds their 34 s cdt values reflect precipitation from the ambient porewater sulphate by sulphate reduction the burrow like and irregular concretions are microcrystalline barite in the lower parts of the clays mycellia9 are mineral replaced filaments produced by large sulphur oxidizing bacteria or mycelial fungi they concentrate in monosulphide bands in the lower substrate levels but are associated with organic patches upward this study demonstrates that substantial amounts of pyrite formed within organic matrices close to the sediment water interface this differs from previous studies that proposed a deeper burial origin and allochthonous sulphur source supplementary material sulphur isotope data are available at http www geolsoc org uk sup18426

ichnological trends along an open water transect across a large marginal marine epicontinental basin the modern baltic sea article i nfo late holocene sediments in the baltic sea provide an opportunity to study lateral changes in the assemblages of identifiable biogenic sedimentary structures ichnofossils in a large high latitude semi enclosed sea with instrumentally determined gradients in biodiversity and environmental factors such as salinity and ox ygen availability integrated sedimentological and ichnological analysis is carried out on 6 long cores collect ed along an open sea declining salinity transect across the basin muddy sediments in euhaline kattegat and polyhaline mecklenburg bight sites are characterized by the archetypal cruziana ichnofacies portrayed by subsurface deposit feeding structures scolicia and planolites surface deposit feeding structures sko lithos and structures that reflect both these feeding strategies palaeophycus arenicolites polykladichnus and unnamed biodeformational structures produced by bivalves the ichnofossils are tiered to 3 levels the cruziana ichnofacies is impoverished in the higher mesohaline arkona basin and even more so with de clining salinity farther inland the deepest oxygen restricted study sites gotland deep and the western gulf of finland below a permanent halocline are characterized by very small and shallow deposit feeding struc tures planolites and rare flat arenicolites polykladichnus and poorly developed tiering the nearly freshwa ter eastern gulf of finland is characterized by the cenozoic archetypal mermia ichnofacies dominated by narrow and shallow subsurface and surface deposit feeding structures planolites and flat arenicolites polykladichnus large planolites 3 7 mm in diameter at this site are untypical of mermia ichnofacies assem blages these results confirm the earlier observations that marine forms dominate brackish water ichnoas semblages with the ichnofossil size and diversity decreasing with declining salinity the results also confirm the predicted decreases in the ichnofossil size and vertical extent at low oxygen levels poorly devel oped tiering is a particularly useful indicator of oxygen stress in the salinity restricted system

sea bottom anoxia in the archipelago sea northern baltic sea implications for phosphorus remineralization at the sediment surface abstract the effects of the hydrophysical environment on oxygen conditions and p remineralization at sediment surface were studied in the archipelago sea northern baltic sea at 94 sites the water column was profiled for conductivity temperature and oxygen and the topmost sediment was collected for p and c fractions and oxy hydroxide fe analysis the near bottom water and sediment parameters as well as visual observations on the vertical colour distribution in the sediment cores were used to statistically classify the sediment surfaces into oxic anoxic and suboxic fluctuating oxygen conditions bottoms the anoxic bottoms occurred in the basins with water depths less than 47 m and the suboxic bottoms were most common in the basins with depths between 20 60 m while the oxic bottoms dominated in the depths over 60 m it was concluded that the preferential development of oxygen deficiency in the shallow basins results from the combined effects of complex topography and seasonal temperature stratification on both vertical and lateral bottom water exchange in the anoxic bottoms c p ratios suggest enhanced release of p compared to the oxic and suboxic bottoms in the suboxic bottoms high inorganic p concentrations and the strong coupling between p and fe suggest active transformation of organic p to the inorganic p phases probably due to the fluctuating oxygen conditions differences in the spatial distribution of the p c and fe were insignificant except for detrital p which decreased seawards

coring induced sediment fabrics at iodp expedition 347 sites m0061 and m0062 identified by anisotropy of magnetic susceptibility ams criteria for accepting palaeomagnetic data anisotropy of magnetic susceptibility data obtained from discrete subsamples recovered from two integrated ocean drilling program sites expedition 347 sites m0061 and m0062 in the baltic sea by a

phosphorus forms and reactive iron in lateglacial postglacial and brackish water sediments of the archipelago sea northern baltic sea abstract glacial transport is an important agent of p and reactive fe delivery to the ocean margins however whereas p may travel through salinity gradients reactive fe is substantially trapped in estuaries studies of glaciolacustrine to brackish water depositional successions elucidate processes associated with the glacial p and reactive fe flux into the oceans the sedimentary p species reactive fe oxide associated fe and al and mn c n and s geochemistry for sediment cores from three sites in the archipelago sea northern baltic sea were determined in order to understand the distribution and coupling of these geochemical components in the glaciolacustrine to post glacial lacustrine to brackish water depositional succession the up to 6 m long cores record deposition after 11 350 cal bp previous studies suggest that the studied depositional succession records development common for the deglaciation phase of large low relief epicontinental basins all the studied geochemical components are strongly coupled in the basal glaciolacustrine rhythmites which reflect their rapid deposition by glacial meltwaters low corg preac ratios suggest that a part of the rhythmite material is reworked from pre glacial deposits delivery rates are drastically lower in the successive post glacial lacustrine setting due to the decrease of sedimentation rate by an order of magnitude decoupling of reactive fe and associated components in the post glacial lacustrine clays reflect increasing contribution of sediment from the emerging shoreline and rivers but also post depositional overprinting by sulphidization the onset of brackish water conditions soon after 7600 cal bp led to 1 decoupling of reactive fe from the detrital flux due to the establishment of salinity gradients at the river mouths and 2 increased nutrient availability and production in water as the intensified accumulation and burial of reactive p species organic c and n indicate the higher organic deposition led to deteriorated seafloor oxygen conditions alternating thinly laminated to strongly bioturbated lithofacies characterise the brackish water muds and record temporal changes in the seafloor oxygenation the temporal changes in the seafloor oxygen conditions appear to be broadly linked to the holocene climate variability brackish water muds at the northern end of paimionlahti bay record anoxia during the medieval warm period 1250 450 cal bp oxic conditions during the little ice age 450 300 cal bp and anoxia until the present day on a finer scale the redox histories in adjacent sub basins differ considerably due to patchy topography sluggish bottom water exchange and high organic deposition in the area terrestrial organic influx can temporally overprint marine organic deposition in areas close to river mouths

acoustic architecture of glaciolacustrine sediments deformed during zonal stagnation of the laurentide ice sheet mazinaw lake ontario canada abstract in north america the last laurentide ice sheet retreated from much of the canadian shield by zonal stagnation masses of dead ice severed from the main ice sheet by emerging bedrock highs downwasted in situ within valleys and lake basins and were commonly buried by sediment consequently the flat sediment floors of many valleys and lakes are now pitted by steep sided enclosed depressions kettle basins that record the melt of stagnant ice blocks and collapse of sediment at mazinaw lake in eastern ontario canada high resolution seismic reflection magnetic and bathymetric surveys integrated with onland outcrop and hammer seismic investigations were conducted to identify the types of structural disturbance associated with the formation of kettle basins in glaciolacustrine sediments basins formed as a result of ice blocks being trapped within a regionally extensive proglacial lake glacial lake iroquois 12 500 to 11 400 years bp that flooded eastern ontario during deglaciation kettles occur within a thick 30 m succession of parallel high frequency acoustic facies consisting of rhythmically laminated varved iroquois silty clays iroquois strata underlying and surrounding kettle basins show large scale normal faults fractures rotational failures and incoherent chaotically bedded sediment formed by slumping and collapse mazinaw lake lies along part of the ottawa graben and while neotectonic earthquake activity cannot be entirely dismissed deformation is most likely to have occurred as a result of the rapid melt of buried ice blocks seismic data do not fully penetrate the entire basin sediment fill but the structure and topography of bedrock can be inferred from magnetometer data the location and shape of buried ice masses was closely controlled by the graben like form of the underlying bedrock surface

on the spatial variation of resistance to flow in upland channel networks 1 detailed field measurements of channel properties and flow characteristics collected in the ashley and cropp catchments new zealand are used to investigate the spatial variation of resistance to flow across upland channel networks the application of the darcy weisbach equation and semilogarithmic flow resistance relationships reveals that mean flow velocities calculated from local measurements of bed material particle size hydraulic depth and channel bed slope may be inaccurate the manning gauckler strickler equation with resistance coefficient independent of bed material particle size is found to be relatively more reliable but not sufficiently general to reproduce the spatial variation of resistance to flow across a complex channel network a new methodology is developed by combining a hydraulic equation of the manning gauckler strickler type a flow discharge upstream drainage area relationship and geomorphological fluvial relationships for mean flow velocity gauckler strickler resistance coefficient hydraulic depth and friction slope this methodology is found to improve the reproduction of the spatial variation of mean flow velocity across the ashley catchment and appears of general applicability for the parameterization of resistance to flow in distributed catchment models

varve microfabric record of seasonal sedimentation and bottom flow modulated mud deposition in the coastal northern baltic sea abstract eutrophication induced hypoxia has resulted in preservation of laminated sedimentary fabric in coastal areas of the northern baltic sea these laminites offer a potential technique for dating recently deposited organic rich muds but their formation mechanisms have been inadequately understood in this study microfabric of the modern laminated sediments in the coastal gulf of finland and archipelago sea was investigated through x radiography and scanning electron microscopy of samples embedded in epoxy resin the sedimentary fabric comprises rhythmic biogenic and lithogenic lamina successions reflecting seasonal changes in the composition of accumulating material the diatom rich biogenic lamina succession is formed during the vernal phytoplankton bloom through rapid sedimentation of aggregates composed of intact diatom frustules and minor proportions of clay rich lithic material that are enclosed in a sticky matrix of amorphous phytodetritus analogous to the formation of the marine snow accumulation of the lithogenic lamina succession results from decline in primary production towards late summer enhanced recycling of organic carbon due to grazing by zooplankton and intensified resuspension of lithic rich terrigenous material concomitantly with increased cyclonic activity towards late autumn and winter the inclusion of silt grains and isolated diatoms and faecal pellets in the lithogenic laminae attests to lateral transport and deposition from near bottom flows contradicting the generally accepted view that laminated sediments accumulate by suspension settling under quiescent conditions only accumulation rates inferred from 137 cs dating are consistent with the biogenic lithogenic lamina succession couplet thickness supporting the interpretation that the couplets reflect an annual cycle of deposition the results indicate that these modern laminated sediments provide a high resolution archive for assessing recent human induced environmental changes as well as a robust tool for evaluating the lateral expansion of seafloor oxygen deficiency due to anthropogenic eutrophication in the area during the past decades

geochemistry of surface sediments in the archipelago sea sw finland a multiparameter and multivariate study this study investigates the geochemistry of soft organic rich brackish water surface sediments in the archipelago sea sw finland the area is one of the world s largest archipelagos and although it is scarcely populated frequent ship and boat traffic along with fish farming occurs from 76 sites 47 chemical elements were determined after aqua regia digestion other parameters determined were grain size water organic and nitrogen contents at sampling the sediments were visually classified into groups representing oxic anoxic and fluctuating intermediate oxic seafloor conditions the results show that the element concentrations are quite similar to other studies in the region but with clear signs of lower anthropogenic loading point source pollution was identified in one sample taken nearby a fish farm and a cable ferry this site was strongly enriched in cu zn and sn derived from chemicals used in either or both activities at the site overall the sediments can be divided into two groups that separate chemically and geographically one group contains more fine grained sediments that occur near shore while the other group contains more anoxic organic and sulfur rich sediments occurring more offshore the second group is interpreted to reflect material reworked from previous deposits as a result of shoaling of the area due to glacio isostatic land uplift the visual classes were included in both partial least squares regression plsr and pls discriminant analysis these analyses showed that the oxic and anoxic seafloor sediments can be predicted from the chemical variables and grain size distribution

impact of river bed morphology on discharge and water levels simulated by a 1d saint venant hydraulic model at regional scale summary river cross sections data are required to represent channel geometry in hydrodynamic models in the absence of accurate data at regional scale simplified or parameterized cross sections are often used which might affect the performance of the hydrodynamic model in this study we assess the sensitivity of a 1d saint venant hydraulic model to different types of river morphological data the question is addressed using a 1d unsteady hydraulic model hec ras with lateral inflows provided by the hydro geo logical model eau dyssee to explore a wide spectrum of river geometry scenarios regarding river bed slopes and cross sectional shapes the target scale is the one of the seine river france as a gateway for larger and more complex regional hydro geo logical applications our case study covers a well described 89 km reach in a sub tributary of the seine river river morphology is described by high resolution cross sections and manning s roughness coefficient n is used for calibration against observed discharges and river stages in a mid reach control point with satisfactory performances over the 8 year simulation period the resulting model still simulates realistic discharge hydrographs when forced with degraded channel geometry data using either fewer cross sections or approximated ones in such cases however the hydraulic model does not always satisfactorily predict the associated water levels when compared to observations in certain geometry scenarios the rmse between simulated water levels using degraded geometry and observations may go up to 0 3 m the study confirms that the accuracy of predicted water levels and maximum water depths simulated by a saint venant model relies on an accurate representation of channel geometry and bed level slopes along the river reach from the various scenarios it appears that the longitudinal description of the bed level profiles has a larger impact on the simulation of water levels than the cross sectional shapes this offers interesting implications for flood forecast mapping applications and regional scale models that often use simplified river geometry and digital elevation models dems built by remote sensing technologies to simulate the water levels

late quaternary slumps and debris flows on the scotian slope the scotian slope just west of verrill canyon was surveyed using the sea marc i deep towed sidescan sonar system high resolution seismic reflection profiles and 25 piston cores the generally smooth continental slope has a gradient of 2 5 it is crossed by 2 small valleys that are 1 km wide and 100 m deep much of the sea bed shows evidence of surficial sliding that removed 10 20 m of sediment and the slide scars give the sea bed a steplike morphology from the 600 m isobath to 1 800 m there extend 2 zones of disturbed sediment these disturbed zones have the rough surface and transparent acoustic character previously regarded as characteristic of debris flows but sidescan sonar images and cores suggest that they are principally rotational slide deposits with true debris flows at their distal limits streamlined erosional depressions near the downslope edge of the debris flows cut both the flow and sediment farther down slope these may have been produced by a turbidity current associated with the debris flows sorted coarse sand in piston cores provides further evidence of current activity this widespread sediment failure on relatively low slopes was probably the result of a large earthquake that can be dated from cores as occurring between 5000 and 12000 yr b p

role of channel and floodplain cross section geometry in the basin response 1 we investigate the role of cross section geometry in flow routing by developing an analytical framework based on the instantaneous response function irf and relationships of river basin geomorphology the cross section geometry is included explicitly within the framework by assuming a power law cross section that is in turn used to derive expressions for the at a site hydraulic geometry the analysis performed using the illinois river basin indicates that the cross section geometry takes on different roles depending on whether flows are in the channel or floodplain the cross section geometry where width dominates over depth width dominant i e the at a site width depth ratio increases with increasing depth tends to produce a larger network celerity and dispersion for the channel and the trend reverses for the high floodplain flows we found that the cross section geometry can influence the relative contribution of hydrodynamic and kinematic dispersion for the channel the depth dominant cross section produces a lower hydrodynamic dispersion than the width dominant cross section and vice versa for the floodplain we found that the nonlinear dependence of the irf on effective rainfall expressed in the irf time to peak and peak flow may vary depending on the cross section geometry with the nonlinearity decreasing for the width dominant cross sections additionally the effect of cross section geometry on the basin response can alter the relative contribution of the stream network and hillslopes to the basin dispersion the derived framework has potential as an a priori tool for incorporating channel and floodplain geometry into distributed rainfall runoff models

iron behavior in a northern estuary large pools of non sulfidized fe ii associated with organic matter the estuaries of the northern baltic sea gulf of bothnia receive an abundance of diagenetically reactivecatchment derived fe which is to a large degree complexed with organic matter or present a

field determination of the spatial variation of resistance to flow along a steep alpine stream accurate field data have been collected along the febbraro river central italian alps during quasi steady low flow conditions to investigate the spatial variations of hydraulic and geomorphologic quantities potentially affecting resistance to flow detailed uncertainty analysis and weighted least squares fitting of simple power function relationships to field derived data are carried out to identify possible interdependencies between observed variables mean flow velocity is found to depend on water surface slope bed material particle size and upstream drainage area whereas its dependence on hydraulic depth appears less susceptible to quantification upstream drainage area is found to explain the variations of hydraulic depth water surface slope gauckler strickler conductance coefficient and although less significantly flow discharge specifically a highly significant positive dependence of the gauckler strickler conductance coefficient on the upstream drainage area is found to exist although anomalies in the variations of hydraulic depth and flow discharge are observed along the stream the combined use of uncertainty analysis hydraulic equations and geomorphological relationships allows a possible characterization of resistance to flow along a steep alpine stream and perhaps more importantly provides useful guidelines for future investigative efforts copyright 2006 john wiley sons ltd

semi determinate hydraulic geometry of river channels south island new zealand data to describe the morphologic hydrologic and sedimentologic characteristics of 72 south island new zealand rivers were collected and analysed nearly 70 per cent of variation in channel morphology is accounted for by differences in cross sectional area slope and cross section shape only 53 per cent of the morphologic variability could be statistically explained by the hydrologic and sediment variables used the level of explanation varied for different morphologic variables nearly 90 per cent of the variability in cross sectional area could be explained but aspect ratio maximum depth divided by hydraulic radius was completely independent apart from the inadequacy of the measured variables as indices of the true underlying controlling factors and the imperfect measurement and sampling procedures the low level of explanation is probably due to the influence of factors such as floodplain vegetation high quasi random variability in bark sediment character boundary effects imposed by bedrock bluffs and the precise sequence of flood events none of which are easily quantified in addition observations indicate that there is a large random variation in channel form which cannot be related to any factor an attempt to relate channel morphology to flow variability using simple indices of the latter was unsuccessful

intense earthquakes and seismotectonics as a function of glacial isostasy abstract old shields and plate interiors have often been assumed to exhibit a high crustal stability during the last decade or two we have learnt more and more about the fragility not to say untenability of this concept however high magnitude earthquakes and large scale fault movements have been recorded where they were not supposed to be able to occur within formerly glaciated areas like northern europe scotland and northern north america a rapidly increasing number of field observations indicates that the glacial isostatic readjustment process was linked to intense seismotectonic activity we will here investigate the fennoscandian situation and propose a novel causation model for the high deglaciation seismicity in comparison with the present day situation

the ancylus and litorina transgressions of the baltic in southwest finland abstract the extent and age of the ancylus and litorina transgressions in the salpausselka younger dryas end moraine zone of southwest finland were studied by means of morphology and radiocarbon dated biostratigraphical studies of isolation basins the rapid regression in the baltic between ca 10 2 and 9 7 ka bp yoldia regression was followed by the ancylus transgression which involved a 2 8 m rise in water level in the research area the rise has been identified in 10 basins and has been dated to the betula pollen zone from 9 7 9 5 to 9 2 9 ka bp the rise in water level has not been identified inland of the 3rd salpausselka moraine and it is concluded that the area north of this moraine lay beyond the limits of the transgression the amplitude of the transgression decreases from 8 m in the se to 2 m in the nw whilst the shoreline associated with it ancylus i rises from 62 m to 82 m with a gradient of about 0 4 0 5 m km the following ancylus regression was initially rapid but became slower at ca 8 5 8 ka bp when the rate of land uplift became nearly as high as the rise in water level in the study area the subsequent litorina transgression involving a rise in water level of 1 4 m was dated to the beginning of the atlantic 7 to 6 4 ka bp the transgression has an amplitude of 1 2 m in bastukarr basin which lies between the 1st and 2nd salpausselka end moraine zones the shoreline associated with the transgression li varies from 35 m in the se to 45 m in the nw with a gradient of about 0 15 0 2

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

seismic deformation of varved sediments in southern fennoscandia at 7400 cal bp abstract soft sediment deformation structures are preserved in clastic biogenic varves of the lake nurmijarvi sequence from central southern finland deformation structures include centimeter scale folding and faulting structures and larger convolute bedding which are separated from the overlying undisturbed varved section by a turbidite dated at 7400 cal bp the soft sediment deformation provides evidence for postglacial seismic activity ca 3500 years after the deglaciation of the study area by screening the sizes of potential source faults for the event the maximum earthquake moment magnitudes associated with the deformation structures were constrained to mw 5 1 6 9 with realistic 40 rupture scenarios or up to mw 5 1 7 7 if more conservative scenarios are considered the results of the study thus indicate a relatively high magnitude postglacial seismic event in southern finland which adds to the evidence that the postglacial seismic activity was not just restricted to northern fennoscandia but was a more widespread phenomenon the age of the lake nurmijarvi seismic event further demonstrates that high magnitude seismic activity was not restricted to a relatively short period after deglaciation but the period of high magnitude postglacial seismic activity was much longer than previously thought by assessing the orientations of faults that are presently active and using available focal mechanism data our results suggest that strike slip faulting may be a more important mechanism for the generation of both present day and postglacial earthquakes in southern finland than reverse faulting which should further be accounted for in the assessment of long term seismic hazards

the origin of soft sediment deformation structures in permo carboniferous glacial and proglacial beds south africa abstract soft sediment deformational structures in subsurface glacial and proglacial beds of the permo carboniferous dwyka formation include faults folds boudins sigmoidally shaped laminae and sandstone siltstone injections within specific zones ranging in thickness from 1 to 12 m the zones consist of rhythmite shale with ice rafted debris siltstone and minor sandstone and diamictite but often the original character of the sediments is completely destroyed by the deformation the deformation structures predominantly formed during extensional strain of the sediments and form part of complex shear zones diapiric structures load coasts and convolute lamination the deformation zones are lithologically controlled and intimately associated with debris flow deposits indicating that gravitational forces giving rise to slumping were the predominant cause of the deformation excess pore water pressures and subsequent liquefaction of the fine grained sediments on oversteepened depositional slopes apparently generated the sheetlike slumps but the possibility of grounded ice initiating slumps in the lowermost deformation zone cannot be excluded a new type of coarse grained matrix supported deposit designed melange diamictite which formed during slumping under a soft sediment slab is described for the first time

trace fossils as indicators of environmental change in holocene sediments of the archipelago sea northern baltic sea abstract biogenic structures in holocene sediments from the archipelago sea northern baltic sea were characterized through the analysis of x ray images of four cores collected from water depths between 32 and 66 m in the area initial colonization of endobenthic invertebrates occurred at 7800 80 calendar years bp the trace assemblage at this level is low diversity small diameter shallowly tiered and palaeophycus dominated rare arenicolites are also observed early colonization coincides with increasing marine influence in the post glacial lacustrine setting just before the dramatic onset of brackish water conditions established after 7600 bp the post incursion brackish water assemblage possesses a higher diversity of traces planolites arenicolites lockeia teichichnus which is taken to reflect the enhanced salinity and trophic state of the basin the shift from palaeophycus mottling to a planolites dominated fabric represents changed behavioural patterns in the endobenthic community due to changed substrate properties the ethology of the succeeding trace assemblage also represents a switch from domicile based activities such as predation scavenging and interface dominated deposit feeding to shallow tier deposit feeding finally traces are excluded from thinly laminated intervals demonstrating that seafloor oxygen deficiency commonly reached levels that were detrimental to colonization of the sediment substrate

deglaciation seismotectonics a principal influence on intraplate seismogenesis at high latitudes abstract in many high latitude stable continental regions deglaciation dominates the current crustal strain field interference between polarised tectonic and radial deglaciation strain fields affects the deviatoric stress state and fault stability margins and in consequence both the levels and properties of seismicity throughout glacial loading and unloading the most notable present day affects of this strain interference are predicted to include alternating quadrants of enhanced seismicity and aseismicity around rebound domes and former peripheral forebulges such strain interference can explain much of the geography and timing of holocene earthquake occurrence across northern europe and eastern north america

liquefaction and varve deformation as evidence of paleoseismic events and tsunamis the autumn 10 430 bp case in sweden coastal seismic events generate instantaneous changes in relative sea level i e land level vs sea level tsunamis may cause disastrous damage to coasts and coastal habitation liquefaction and deformations of annually varved sediments provide information on paleoseismic events the evidence for a major earthquake and associated tsunami waves in sweden are explored thanks to the varve chronology liquefaction structures and varve deformations caused by this event can be dated at the autumn 10 430 varve years bp the magnitude is estimated at 8 or more on the richter scale the tsunami washed the previously blocked outlet of the baltic free of icebergs and pack ice so that marine water could suddenly invade the entire baltic forming the yoldia sea

acoustic evidence of a baltic ice lake drainage debrite in the northern baltic sea abstract the sudden drainage of the baltic ice lake bil at the end of the younger dryas chron was one of the major events within the pleistocene holocene boundary in scandinavia thus far the effects it might have had on sedimentary environments have been inadequately recorded outside of central and southern sweden in the present study high quality acoustic sounding data was used to examine and describe possible traces of the event from the north eastern baltic proper and gulf of finland sediments five acoustic facies were identified two of them bearing frequent indications of sediment deformation slumping sliding and homogenization the lower deformation zone is in the glacial clay deposited in the ice proximal environment the middle zone in the ice distal glacial clay and the upper zone in late glacial clay we suggest that the middle deformation unit may have basin wide significance because it represents a debrite system originating from sediment instability due to the sudden water level drop associated with the bil drainage at the transition of the younger dryas preboreal chrons

submarine holocene sedimentary disturbances in the olkiluoto area of the gulf of bothnia baltic sea a case of postglacial palaeoseismicity abstract high resolution echo soundings were used to study the fault activity in the olkiluoto area of the gulf of bothnia southwestern finland echo sounding profiles in holocene submarine sediments show normal faults structures related to gas or groundwater seepage submarine slides and slumps and debris flow type structures the faults and other disturbance structures occur along two bedrock lineaments all faults occur at the same stratigraphical level whose age is estimated at 10 700 calendar years bp 9500 radiocarbon years bp it is suggested that their movement has been triggered by palaeoseismic event s when the late weichselian ice sheet was retreating from the site and bedrock stresses were released through lineaments and fracture zones these are the first observations of postglacial fault movements in quaternary sediments from southern finland but the timing of these movements is contemporaneous with the incidence of postglacial bedrock faulting 9000 10 000 radiocarbon years bp in northern fennoscandia the origin of the gas groundwater seepages remains unclear their reflections in the echo sounding profiles imply that part of the gas is derived from the organic bearing litorina and recent gyttja clays however at least some part of the gas is derived from the bedrock deep gas

the use of varved clay chronology for dating paleoseismic events the erstavik record in the stockholm area south sweden abstract geological structures suggest that the fennoscandian shield was subjected to a higher seismicity at the end of the last glaciation than today this article demonstrates the use of varved clay chronology for dating paleoseismic events it is argued that the deposited annually layered glacial varves were sensitive to past ground movements in the stockholm area the erstavik varved clay chronology suggests four paleoseismic events a first i dating from varve year 10 473 to 10 468 bp a second ii 10 451 to 10 445 bp a third iii 10 429 to 10 425 bp and a fourth iv 10 409 to 10 404 bp in de geer s old 1940 chronology the first i dating corresponds with 1117 to 1112 the second ii with 1095 to 1089 the third iii with 1073 to 1069 and the fourth iv with 1053 to 1048 the most pronounced event was the one at around varve year 10 429 bp varve 1073 in de geer s old chronology the recurrence time of about 20 years suggests a totally different seismic regime at the time of deglaciation than what exists today it coincided with the period of maximum isostatic uplift the complexity of the varved clay response to seismic events is also discussed

automatically derived catchment boundaries and channel networks and their hydrological applications abstract a method of generating drainage networks and catchment boundaries from gridded ground elevation data a digital terrain model is presented the method includes an algorithm for coping with localised low points in the data the paper suggests two objective ways of comparing the conventionally mapped with the automatically generated drainage network emphasis is placed on the way that this approach is capable of benefiting a variety of hydrological applications in particular the automatic estimation of flow statistics from catchment characteristics

middle holocene to present sedimentary environment in the easternmost gulf of finland baltic sea and the birth of the neva river abstract the easternmost gulf of finland is the recipient of the neva river the largest river draining to the baltic sea the depositional history and endozoobenthic activity in the area have not been studied before based long sediment cores although such studies are desirable to provide a paleoenvironmental context for the recent environmental changes and the ecosystem projections for the future baltic sea two replicate long sediment cores from the easternmost gulf of finland record brackish water mud accumulation beginning at 5900 60 calendar years before present cal bp the brackish water muds are characterized by thin beds with erosional bases fining upward grain sizes and increasing upward organic contents a storm induced flow origin is inferred for the thin mud beds contrasting with previous interpretations that these muds accumulate by quiescent suspension settling the bed primary microstructures are overprinted by biodeformation and burrow mottling by incipient small planolites and arenicolites polykladichnus ichnofossils of the continental skolithos ichnofacies left behind by endobenthic oligochaetes and chironomid larvae the depositional succession is cut by a strong erosional hyperpycnal flow event at 3320 40 cal bp caused by the birth of the neva river which is now documented offshore for the first time mineral magnetic properties show pseudosingle domain magnetite as the main magnetic mineral present increased magnetic grain sizes and reduced loi values indicate a strong lithic influx immediately after the neva river birth the dominance of riverborne material in the accumulating sediments ever since highlights the strong influence of reworking in the shallow sea area increased diameters and the deeper penetration of biogenic sedimentary structures demonstrate improved seafloor oxygenation after the river birth during the medieval warm period ca 1000 700 cal bp and the last century increased sedimentary lithic contents and magnetic grain sizes indicate an elevated riverine influx due to increased precipitation and or the increased reworking of sediments by storms the results provide a paleoenvironmental context for the study area and deepen the understanding of storm induced sediment dispersal and the formation of sedimentary fabric in shallow wave dominated sea areas

active channel geometry and discharge relations of u s piedmont and midwestern streams the variable exponent model revisited morphometric discharge and sediment data were gathered for 51 streamflow gaging locations in the piedmont and nontidal coastal plain of virginia and north carolina the piedmont data are compared to those obtained in the midwestern united states to calibrate a variable exponent channel geometry model least squares regression of the midwestern data demonstrates that estimated discharge width exponents for high silt and clay gravel or cobble bed channels deviate significantly from those estimated for alluvial beds with 30 or greater sand content however no significant trend is apparent for the estimated exponents among other sand silt clay channel categories analyses of the piedmont data indicate no significant departure of the discharge width relations if sediment categories are used to group stream types this may be due in part to the relative homogeneity of the sediments that compose the bed and banks of the piedmont stream channels sampled for this study least squares regression of the midwestern and piedmont data indicate that estimated width discharge exponents for groups of streams with width depth ratios less than 45 range from 0 35 to 0 46 but are statistically indistinguishable for groups of streams having width depth ratios greater than 45 the width discharge exponents decrease toward values less than 0 15 this trend suggests systematic variation in the exponents and a diminished influence of channel shape on width discharge functions for streams with width depth ratios greater than 45 these findings do not support the results of a previous investigation that used envelope curves to estimate width discharge exponents for midwestern streams and they suggest that the assumptions regarding the variable exponent channel geometry model should be reevaluated

palynostratigraphy of the last interglacial glacial cycle in germany abstract the last interglacial glacial cycle comprises the eemian and the weichselian in the area of the scandinavian glaciation respectively the riss wurm and the wurm in southern germany drastic changes of the vegetation have occurred several times during this period in europe the best known in germany is the development of the forests of the last interglacial stage and of the two succeeding early glacial interstadial phases the brorup and the odderade above the odderade sediments of two more middle weichselian interstadials the oerel and the glinde with a shrub tundra vegetation have been found at one site in northern germany in southern germany the palynological record ends somewhat earlier i e with the equivalent of the oerel interstadial which here in the south had a forest vegetation numerous single occurrences of interstadial sediments of different age and vegetation have been studied but unfortunately their stratigraphic position is most frequently unclear therefore a general survey can only rely on few but long sequences their comparison shows that vegetational gradients of different steepness existed at different times which mirror the changing climatic gradients of this period the main points of the vegetational zonation as far as it is known from germany for the cycle are summarized

testing the fidelity of sediment chronology comparison of varve and paleomagnetic results from holocene lake sediments from central finland abstract a careful construction of independent varve and paleomagnetic chronologies from three varved lake sediment records from central finland resulted in detailed and continuous age depth profiles cumulative varve calculation errors were estimated to be 3 for lake alimmainen savijarvi 10 295 340 varve years and 1 for lakes nautajarvi 9898 97 varve years and korttajarvi 9590 103 varve years paleomagnetic secular variation psv curves demonstrate good consistency between these sites and within a margin of varve chronology error they show similar declination and inclination features commonly described in the uk and sweden the timing of psv patterns from finnish varved sites agree well with uk curves between the present and 2000 bc and in pre 6000 bc deposits and with swedish data between the present and 5000 bc combined inclination records from three independently dated finnish varved sites possess an opportunity for accurate paleomagnetic comparisons within the margin of varve chronology errors and throughout the last 10 000 years

surface subsurface flow modeling with path based runoff routing boundary condition based coupling and assimilation of multisource observation data received 21 october 2008 revised 2 september 2009 accepted 16 september 2009 published 13 february 2010 1 a distributed physically based model incorporating novel approaches for the representation of surface subsurface processes and interactions is presented a path based description of surface flow across the drainage basin is used with several options for identifying flow directions for separating channel cells from hillslope cells and for representing stream channel hydraulic geometry lakes and other topographic depressions are identified and specially treated as part of the preprocessing procedures applied to the digital elevation data for the catchment threshold based boundary condition switching is used to partition potential atmospheric fluxes into actual fluxes across the land surface and changes in surface storage thus resolving the exchange fluxes or coupling between the surface and subsurface modules nested time stepping allows smaller steps to be taken for typically faster and explicitly solved surface runoff routing while a mesh coarsening option allows larger grid elements to be used for typically slower and more compute intensive subsurface flow sequential data assimilation schemes allow the model predictions to be updated with spatiotemporal observation data of surface and subsurface variables these approaches are discussed in detail and the physical and numerical behavior of the model is illustrated over catchment scales ranging from 0 0027 to 356 km 2 addressing different hydrological processes and highlighting the importance of describing coupled surfacesubsurface flow

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

northwest european palaeoclimate as indicated by growth frequency variations of secondary calcite deposits a compilationn for the northwest of europe of over 500 uranium series speleothen and travertine dates is presented using a cumulative distributed error frequency approach these secondary carbonate deposits require both significant groundwater supply and a biogenic soil carbon dioxide source for their growth during glacial periods soil co2 production is inhibited and the water supply is ice locked therefore growth is slowed significantly if not stopped thus deposits can be used on a chronological basis to give a signal of glacial and non glacial periods however sensitivity to the groundwater supply modifies this signal with growth also limited in times of high aridity the palaeoclimatic signal is thus complex the compilation presented is used both as a chronology for comparison with the orbitally tuned marine oxygen isotope record and as a palaeoclimatic indicator attention is focused on two periods of the last glacial interglacial cycle where the record provides a significantly different palaeoclimatic record to other terrestrial and oceanic records these are the isotope stages 5 4 transition for which a relatively low cumulative growth frequency indicates an earlier increase in aridity than observed elsewhere and isotope stage 3 the pleniglacial where both statistically significant high 49 62 ka and low 22 35 44 46 ka levels of growth are observed and can be used to constrain the timing of many of the interstadial events within this period

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

examination of the seepage face boundary condition in subsurface and coupled surface subsurface hydrological models a seepage face is a nonlinear dynamic boundary that strongly affects pressure head distributions water table fluctuations and flow patterns its handling in hydrological models especially under complex conditions such as heterogeneity and coupled surface subsurface flow has not been extensively studied in this paper we compare the treatment of the seepage face as a static dirichlet versus dynamic boundary condition we assess its resolution under conditions of layered heterogeneity we examine its interaction with a catchment outlet boundary and we investigate the effects of surface subsurface exchanges on seepage faces forming at the land surface the analyses are carried out with an integrated catchment hydrological model numerical simulations are performed for a synthetic rectangular sloping aquifer and for an experimental hillslope from the landscape evolution observatory the results show that the static boundary condition is not always an adequate stand in for a dynamic seepage face boundary condition especially under conditions of high rainfall steep slope or heterogeneity that hillslopes with layered heterogeneity give rise to multiple seepage faces that can be highly dynamic that seepage face and outlet boundaries can coexist in an integrated hydrological model and both play an important role and that seepage faces at the land surface are not always controlled by subsurface flow the paper also presents a generalized algorithm for resolving seepage face outflow that handles heterogeneity in a simple way is applicable to unstructured grids and is shown experimentally to be equivalent to the treatment of atmospheric boundary conditions in subsurface flow models

is deep water formation in the baltic sea a key to understanding seabed dynamics and ventilation changes over the past 7 000 years abstract numerous hydro acoustic studies of the seabed of the baltic sea have revealed the unusual occurrence of sediment contourite drifts and re suspension at greater water depths in addition radiocarbon dating of bulk sediments indicates significant age reversals we present new geophysical sediment proxy data including extensive radiocarbon dating and hydrographic measurements which are combined with results of numerous marine geological studies performed during the last decades these data indicate that a deep water formation process significantly affected the seabed dynamics during regional climatically cold phases during the last c 7 000 years we propose that during the colder periods e g the little ice age newly formed bottom waters likely caused widespread re suspension of organic carbon rich laminated sediments that were deposited during the preceding warm periods in shallower areas and this material was transported to and re deposited in the deeper parts of the baltic sea sub basins in our scenario a topographic feature known as the baltic sea klint acted as a hydrographic barrier for deep water formed in the northern baltic thus during the cold periods increased lateral matter influx from the northern baltic led to the accumulation of much thicker macroscopically homogenous clayey sediments in sub basins north of the klint moreover deep water formation produced bottom currents that led to the formation of sediment contourite drifts at water depths of 200 m in the bothnian sea the aland deep and northern central baltic sea sub basins bottom water ventilation in the baltic sea is generally assumed to be determined solely by the inflow of oxygen rich saline water from the north sea but we challenge this assumption and postulate that deep water formation is a key process that ventilates the bottom waters of the baltic sea during climatically cold periods with substantial implications for its sedimentary archive

role of hypsometry and planform in basin hydrologic response the effects of variations of drainage basin morphometry and relief characteristics on flood peak magnitude and time to peak are investigated using simulated stream networks the networks are produced by three models headward growth systematic capture and minimum power relaxation translational and kinematic wave flood routing were used to generate synthetic hydrographs peak discharge and time to peak are predictable to a high degree by five different sets of morphometric relief parameters in order of decreasing order of importance in predictive ability the parameters characterize basin size relative relief basin concavity and basin shape both simulated and natural stream networks exhibit strong dependence of planimetric morphometry upon basin concavity the effect of this dependency is to increase the effect of basin concavity upon flood hydrographs

svecofennian magmatic and metamorphic evolution in southwestern finland as revealed by u pb zircon sims geochronology abstract zircons from six samples collected from igneous and metamorphic rocks were dated using the nordsim ion microprobe in order to investigate the tectonic evolution of the palaeoproterozoic svecofennian orogen in southwestern finland these rocks represent pre collisional collisional and post collisional stages of the orogeny the ion microprobe results reveal two age groups of granodioritic tonalitic rocks the intrusions have different tectonic settings the orijarvi granodiorite represents pre collisional 1 91 1 88 ga island arc related magmatism and yielded an age of 1898 9 ma whereas the collision related masku tonalite was dated at 1854 18 ma the latter age accords with more accurate previous conventional zircon age data and constrains the emplacement age of collisional granitoids to 1 87 ga this is interpreted to reflect the collision between the southern svecofennian arc complex with the central svecofennian arc complex and the formation of a suture zone between them during d2 deformation granulite facies metamorphism in the turku area was dated at 1824 5 ma using zircons from leucosome in the lemu metapelite this age constrains d3 folding related to post collisional crustal shortening in this area crustal melting continued until 1 81 ga as indicated by the youngest leucosome zircons and metamorphic rims of enderbite zircons new metamorphic zircon growth took place in older granitoids at granulite facies but not at amphibolite facies detrital zircons with ages between 2 91 and 1 97 ga were found in the mesosome of the lemu metapelite and 2 64 1 93 ga inherited cores were found in the 1 87 ga masku tonalite

holocene history of the baltic sea as a background for assessing records of human impact in the sediments of the gotland basin sediment cores from the gotland basin were studied for their siliceous microfossil assemblages and organic carbon content to compare recent environmental changes in the baltic sea with its natural

late glacial and post glacial deposition in a large low relief epicontinental basin the northern baltic sea this paper presents a model of late glacial and post glacial deposition for the late neogene sedimentary succession of the archipelago sea in the northern baltic sea four genetically related facies associations are described i an ice proximal acoustically stratified draped unit of glaciolacustrine rhythmites ii an onlapping basin fill unit of rotated rhythmite clasts in an acoustically transparent to chaotic matrix interpreted as debris flow deposits iii an ice distal acoustically stratified to transparent draped unit of post glacial lacustrine weakly laminated to homogeneous deposits and iv an acoustically stratified to transparent unit of brackish water organic rich sediment drifts the debris flow deposits of the unit 2 pass laterally into slide scars that truncate the unit 1 they are interpreted to result from a time interval of intense seismic activity due to bedrock stress release shortly after deglaciation of the area ice berg scouring and gravitational failure of oversteepened depositional slopes may also have contributed to the debris flow deposition comparisons to other late neogene glaciated basins such as the hudson bay or glacial lakes formed along the laurentide ice sheet suggest that the archipelago sea succession may record development typical for the deglaciation phase of large low relief epicontinental basins the carboniferous permian glacigenic dwyka formation in south africa may provide an ancient analogue for the studied succession chronological control for the studied sediments is provided by the independent palaeomagnetic and ams 14c dating methods in order to facilitate dating of the organic poor early post glacial deposits of the northern baltic sea the 10 000 year long lake nautajarvi palaeomagnetic reference chronology ojala saarinen 2002 is extended by 1200 years

an acoustic view into holocene palaeoseismicity offshore southwestern finland baltic sea abstract the baltic sea basin consists of palaeoproterozoic crystalline bedrock which is to the greatest extent covered by younger proterozoic and phanerozoic sedimentary bedrock the basin contains several ancient deep seated tectonic lineaments and fracture zones that divide the seabed into blocks high resolution low frequency echo sounding was used to study the holocene submarine sedimentary structures and palaeoseismic activity in the northern baltic sea with the aim of tidying previous more site specific results at olkiluoto into a larger regional context echo sounding profiles of holocene submarine sediments show slides and slumps normal faults debris flows and turbidite type structures the profiles show also pockmarks and other structures related to gas or groundwater seepages some of the observed structures are suggested to be associated with palaeoseismic activity 10 700 cal yr bp 9500 radiocarbon years bp in the northern baltic sea post glacial fault activation and possible gas and or fluid discharges under high hydraulic heads have relevance in the safety assessment of a planned spent nuclear fuel repository in the region evidence of post glacial faulting in the study area is found only along old bedrock fracture zones indicating reactivation of the old fracture zones since no younger or repeated traces of possible seismic events were found it corroborates the suggestion that the major seismic activity occurred within a short time during and after the last deglaciation