oceanography in the kattegat and skagerrak over the past 8000 years in the kattegat between sweden and denmark a large number of cores containing holocene seafloor deposits were investigated stratigraphically sedimentological biostratigraphical and chronostratigraphical variables were especially emphasized palynological and foraminiferal analyses indicate several changes in the oceanographic circulation system in the skagerrak kattegat during the holocene radiocarbon datings and pollen analyses suggest that these changes occurred at 8000 4000 2000 between 1000 and 500 and 300 years b p compilation of stratigraphical data from the region suggests that at about 8000 years b p the english channel opened and the southern jutland current was formed this had a major influence on the skagerrak but only a marginal effect can be traced in the kattegat the major components of the present circulation system in the kattegat skagerrak were established about 4000 years b p and the subsequent changes in the circulation pattern and the inflow outflow system that developed at approximately 2000 500 and 300 years b p are variants of these

late younger dryas to holocene palaeoenvironments of the southern kattegat scandinavia palaeoenvironmental changes since the late younger dryas are reconstructed in the southern kattegat scandinavia and provide a basis for correlating the whole of the north sea skagerrak kattegat

sediment transport resuspension and accumulation rates in the northeastern skagerrak results of watercolumn light transmission measurements in the skagerrak and of 210pb excess and 137cs determinations in boxcore sediments of the eastern skagerrak are combined to study regional sediment transport resuspension and sedimentation patterns and rates in the upper water layer a 20 m thick surface nepheloid layer formed by concentration of particles at the thermocline and pycnocline is best developed in the eastern skagerrak and less well in the southwestern skagerrak off the danish coast bottom nepheloid layers are extensively developed in the southeastern skagerrak and indicate additional sediment input via resuspension in shallow water areas and near bottom sediment transport in suspension following the prevailing current regime locally the transmission in the bnl is reduced by more than 50 compared to clear water transmission values between 85 and 90 210pb and 137cs derived sedimentation rates are highest in the eastern and northeastern skagerrak and least in the central deep basin there is generally a good agreement between 137cs and 210pb data indicating that sediment accumulation on the short 30 year and longer 100 year time scale is of comparable magnitude

dispersal concentration and deposition of suspended matter in the north sea suspended matter comes into the north sea from the atlantic ocean from the channel rivers seafloor erosion coastal erosion the atmosphere and from primary production the contribution of the last source is temporarily large when phytoplankton growth is abundant but is soon decomposed mineralized or consumed so that over the year the net effect is small accumulation and deposition of suspended matter occurs predominantly in only a few areas the waddensea the german bight the skagerrak norwegian channel the remainder of the north sea floor consists of pleistocene and early holocene relict deposits and of reworked sands and gravels the mechanisms resulting in accumulation and deposition are discussed there are strong indications that the amount of suspended matter flowing out from the north sea into the norwegian sea along the norwegian coast is only little more or the same as the amount coming in from the north atlantic although its composition may be different

northern europe climate variations during late holocene evidence from marine skagerrak abstract granulometric and stable oxygen isotope analyses of four sediment cores from two high accumulation areas in the skagerrak ne north sea were carried out in order to reconstruct climate fluctuations and to evaluate climate impact during the upper holocene extremely high sedimentation rates especially in the eastern skagerrak are explained by increased current activity which is responsible for the transport and deposition of high quantities of suspension load during periods of stormy zonal atmospheric circulation patterns these were most frequent during colder periods while warmer phases are characterized by calmer meridional to zonal atmospheric circulation patterns while the subatlantic climate deterioration and the subboreal climate optimum left only indistinct traces in the sediments the roman climate optimum and a colder period between ca 400 and 700 ad are well documented the following medieval warm period is characterized by a clear temperature increase of the waterbody in connection with less frequent advances of atlantic water masses into the skagerak deep and a decrease in bottom current strength a mode of sedimentation prevails similar to that of recent summer conditions suggesting short and mild winters during that period the onset of the little ice age around 1350 ad however shows an intensified bottom current circulation most probably due to amplifying westerly winds and a decrease in water temperatures in connection with more frequent advances of higher saline atlantic waters the little ice age can be divided into 3 phases a stormy zonal onset a calm meridional maximum and a stormy zonal end the stormy phases are characterized by a sedimentation mode similar to that of recent winter conditions while the little ice age maximum shows conditions comparable to exceptional cold modern winters from 1900 ad at the onset of the modern climate optimum the winter type sedimentation decreases and conditions change again to a level comparable to the medieval warm period

a 550 km long moho traverse in the tyrrhenian sea from o b s recorded pn waves six obs deployed on a 550 km line in the tyrrhenian sea furnish reversed and overlapping profiles from 43 shots at 12 km intervals head waves recorded from a 8 km s refractor the moho permitted the computation of the crustal thickness which shows this basin to be underlain by an oceanic type of crust at least in two 100 km wide regions variations of pn arrival times mirror strong topographical changes of the moho differences in dips at the extremities towards corsica and calabria are documented

a palaeoclimatic and palaeoceanographic record of the last 11 000 14c years from the skagerrak kattegat northeastern atlantic margin marine sediments of about 116 m drilled onshore at skagen near the northernmost tip of jutland denmark provides a continuous and detailed palaeoceanographic and palaeoenvironmental record of the last 11 000 14c years in the skagerrak kattegat the whole younger dryas was characterized by an arctic subarctic environment where the north jutland current flows today instead of being succeeded by a minor climate warming at about 10 600 bp as recorded in the southern kattegat and in the areas strongly influenced by the baltic current and currents along the swedish west coast the changes in components of diatom assemblages combined with previously published benthic foraminiferal data from the present core reflect a two step climatic warming and consequently environmental change during the transition from the younger dryas to the preboreal an abrupt warming of the sea surface waters took place at about 10 100 bp which resulted from the inflow of warm atlantic surface water summer sea surface temperature

southwest scandinavia 40 15 kyr bp palaeogeography and environmental change twelve palaeogeographical reconstructions illustrate environmental changes at the southwest rim of the scandinavian ice sheet 40 15 kyr bp synchronised land sea and glacier configurations are based on the lithostratigraphy of tills and intertill sediments dating is provided by optically stimulated luminescence and calibrated accelerator mass spectrometry radiocarbon an interstadial sequence ca 40 30 kyr bp with boreo arctic proglacial fjords and subarctic flora and occasional glaciation in the baltic was succeeded by a last glacial maximum sequence ca 3020 kyr bp with the closure of fjords and subsequent ice streams in glacial lake basins in kattegat and the baltic steadily flowing ice from sweden bordered the norwegian channel ice stream a deglaciation sequence ca 20 15 kyr bp indicates the transgression of arctic waters retreat of the swedish ice and advance of baltic ice streams succeeded by a return to interstadial conditions when ameliorated ice free conditions prevailed in maritime regions glaciers advanced through the baltic and when interstadial regimes dominated the baltic glaciers expanded off the norwegian coast the largest glacier extent was reached in the north sea around 29 kyr bp about 22 kyr bp in denmark and ca 18 kyr bp in the baltic our model provides new data for future numerical and qualitative landform based models copyright c 2003 john wiley sons ltd less

late weichselian glacimarine depositional processes in the southern skagerrak revealed by high resolution seismic facies analysis abstract thirty kilometres of high resolution seismic reflection boomer data were collected in the skagerrak area between norway sweden and denmark to reconstruct the seismic stratigraphy in an area of late weichselian shelf margin progradation by the use of lap out style five depositional units a e were recognised in the boomer profiles no stratigraphic control was available but tentative correlation has been made on the basis of previous studies in the region unit a is interpreted as till in unit b the seismic facies association includes shingled mounded oblique channel fill and parallel bedded reflection configurations which are interpreted to have formed in a channelled proximal pro glacial environment in unit c discrete mounds and semi continuous lensoid bodies with divergent channelled flow style constitute the facies association and are interpreted predominantly as debris flow deposits that accumulated in a distal pro glacial environment in unit d the facies association constitutes mounds and oblique in fill between mounds positive relief and the distribution of facies shows that the deposits were laid down under the influence of a unidirectional current units b d are interpreted as late weichselian in age unit e is interpreted as the holocene marine cover of laminated clay to fine sand this seismic stratigraphic succession reveals a high resolution record of late weichselian deglaciation in this area

late holocene coastal hydrographic and climate changes in the eastern north sea we present a high resolution palaeoenvironmental reconstruction covering the late holocene from the skagerrak and other sites in the north sea area the data which are based on the analyses of marine sediment cores reveal a marked environmental shift that took place between ad 700 and ad 1100 with the most pronounced changes occurring at ad 900 both surface and bottom waters in the skagerrak were subject to major circulation and productivity changes at this time due to an enhanced advection of atlantic waters to the north sea marking the beginning of the mediaeval warm period mwp the observed increase in bottom current strength is especially remarkable as there is hardly any comparable signal in the older part of the record going back to 1000 bc at the transition to the little ice age lia the bottom current strength remains at a high level now probably forced by atmospheric circulation thus despite opposite temperature forcing these two consecutive climate scenarios are apparently able to generate distinctly stronger bottom currents in the skagerrak than observed in the preceding 2000 years and demonstrate the significance of climatic forcing in shaping the marine environment indeed both the mwp and the lia are reported as strong climatic signals in northwest europe being the warmest except the late twentieth century and coldest periods respectively during at least the last 2000 years

seismic stratigraphy records the deglacial history of jakobshavn isbrae west greenland jakobshavn isbrae is one of the largest ice streams in the greenland ice sheet presently draining c 6 5 of the inland ice here we present high resolution chirp and sparker sub bottom profiles from a seismic survey conducted just outside of the jakobshavn isfjord which provides a detailed insight into the glacimarine sedimentary history of the jakobshavn ice stream during the holocene for the first time we observe acoustically stratified and homogeneous sediments that drape an irregular substratum and were deposited between 10 and c 7 6 k cal a bp the stratified lower units are interpreted as the product of ice proximal glacimarine sedimentation deposited rapidly when the grounded ice margin was located close to depositional basins on topographic highs the upper acoustically homogenous units reflect suspension settling of fine grained material and gravitational flows that were extruded from an increasingly unstable ice margin as the ice retreated into the fjord proximity to the ice margin and bedrock topography were the dominant controls on sediment accumulation during deglaciation although the 8 2 ka cooling event probably influenced the position of the ice margin at the fjord mouth the post glacial sedimentary record is characterised by glacimarine and hemipelagic rainout with an increased ice rafted detritus ird fraction that record sedimentation following ice stream retreat into jakobshavn isfjord sometime after c 7 8 k cal a bp

postglacial depositional environments and sedimentation rates in the norwegian channel off southern norway abstract based on seismic profiles multibeam bathymetry and sediment cores an improved understanding of the deglaciation postglacial history of the southern part of the norwegian channel has been obtained the norwegian channel ice stream started to recede from the shelf edge ca 15 5 ka bp 14 c ages are used throughout approximately 500 1000 years later the ice margin was located east of the deep skagerrak trough at that time the norwegian channel off southern norway had become a large fjord like embayment surrounded by the grounded ice sheet along the northern slope and possibly stagnant ice remnants at the southern flank the norwegian channel off southern norway has been the main sediment trap of the north sea and south of egersund more than 200 m of sediments have been deposited since the start of the deglaciation five seismic units are mapped the oldest unit e occurs in some of the deepest troughs and was deposited immediately after the ice became buoyant unit d is acoustically massive and comprises mass movement deposits in eastern skagerrak and south of egersund unit c in the channel southwest of lista egersund is interpreted to comprise mainly bottom current deposits derived from palaeo rivers e g elben during deposition of unit c ca 14 5 13 ka bp there was limited inflow of atlantic water a change in depositional environment at ca 13 ka bp is related to an increased inflow of saline water and more open hydrographic circulation widely distributed acoustically stratified clays of unit b were deposited ca 13 10 ka bp the holocene unit a shows a depositional pattern broadly similar to that of unit b

holocene sedimentation in the skagerrak interpreted from chirp sonar and core data high resolution chirp sonar profiling in the northeastern skagerrak shows acoustically stratified sediments draping a rough surfaced substratum a 32 metre long sediment core retrieved from the survey area encompasses the entire holocene and latest pleistocene the uppermost seismo acoustic units in the chirp profiles represent holocene marine sediments the lowermost unit is interpreted as ice proximal glacial marine sediments rapidly deposited during the last deglaciation the end of ice proximal sedimentation is marked by a strong reflector interpreted to have been formed during latest pleistocene time as a consequence of rapid ice retreat and drastically lowered sedimentation rate the subsequent distal glacial marine sediments were deposited with initially high sedimentation rates caused by an isostatic rebound associated sea level fall based on correlation between the core and the chirp sonar profiles using measured sediment physical properties and ams 14 c dating we propose a revised position for the pleistocene holocene boundary in the seismo acoustic stratigraphy of the investigated area copyright 2005 john wiley sons ltd

quaternary glaciations in southern fennoscandia evidence from southwestern norway and the northern north sea region abstract based on records from the northern north sea and southern norway quaternary fennoscandian glaciations are described and discussed maximum glaciation defined as the presence of shelf edge glaciation an ice stream flowing out of the norwegian channel and most likely an ice divide over the central part of fennoscandia sweden gulf of bothnia occurred for the first time in the late cenozoic at ca 1 1 myr the fedje glaciation this glaciation was followed by a ca 600 kyr period with at least two glaciations with ice extension somewhat larger than the younger dryas event in the region the first maximum glaciation of the bruhnes chron was during isotope stage 12 and was followed by repeated maximum glaciations within each of the light isotopic stages until stage 2 during the weichselian the southwestern part of the fennoscandian ice sheet reached maximum position three times sometime between 22 and 28 37 and 50 and 60 and 80 ka limited glaciations probably occurred during stadials between the early and middle weichselian interstadials between 500 ka and 1 1 myr and most likely also prior to 1 1 myr deep norwegian sea ice rafted detritus ird records reflecting contributions from several different ice sheets fennoscandian barents sea iceland and greenland each with large variations in history of ice extent to their respective margins yet to some degree they reflect the glaciation of the northern north sea region with an increasing ird input around 1 1 myr and a relatively low input of north sea components during some cycles around the b m boundary maximum glaciations occurred during insolation minima in the earlier part of the middle pleistocene however not all such minima are reflected by maximum glaciation in southern parts of fennoscandia the relatively poor chronological control and non continuous character of the data on weichselian interstadials stadials precludes a clear relationship to atmospheric changes recorded in greenland ice cores as well as to precession and or obliquity cycles in insolation

late weichselian marine 14c reservoir ages at the western coast of norway abstract a shallow marine late weichselian deposit on the outer coast of western norway contains both terrestrial plant material and articulated marine shells we have 14 c dated both types of material from eight different stratigraphic levels covering the time interval 12 300 to 11 100 14 c yr b p the difference between 14 c dated terrestrial plant material and marine shell material the marine reservoir age ranges from 200 to 525 yr with a weighted average of 380 32 yr this is almost identical to the present reservoir age of 379 20 yr for southern norway in the mid younger dryas yd interval the reservoir age in the north atlantic 55 n 65 n was 700 800 yr considerably greater than the present reservoir age and the age we have measured for the bolling allerod interval the reason for this increase during the yd is probably a combination of reduced inflow of surface waters to the north atlantic and more extensive sea ice cover evidence from marine cores show that the southeastern norwegian sea experienced rapid fluctuations in the inflow of warm atlantic surface water during the period 12 300 to 11 000 yr b p however the reservoir age apparently did not increase during these colder periods older dryas i and ii the reason is probably that in contrast to the yd these colder periods did not last long enough and or were of too limited extent to alter the reservoir age of the ocean a comparison of the obtained 14 c dates with the varve 14 c chronology from lake suigetsu indicates an age of 12 770 cal yr b p for the al yd boundary

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

the intercept is a poor estimate of a calibrated radiocarbon age intercept based methods of generating a point estimate of a calibrated radiocarbon date are very popular but exhibit undesirable behaviour they are highly sensitive to the mean of the radiocarbon date and to adjustments of the calibration curve other methods give more stable results the weighted average of the probability distribution function is recommended as the best central point estimate but more consideration should be given to using the full probability distribution rather than a point estimate in developing age depth models

structural evolution of the tyrrhenian back arc basin abstract the tyrrhenian basin has developed as a marginal basin through drifting of the calabrian sicilian arc system towards the east southeast the main structural features of the basin result from this movement the tensional structures normal faults of the margins are mainly aligned n10 to n30 e the transform faults are oriented n110 n120 e except for a previous structuralization linked to the western mediterranean rifting and drifting the first extensional movements affected the tyrrhenian area as early as lower miocene time during the post burdigalian nevertheless the main rifting phase which led to oceanic accretion was initiated during the late tortonian the narrow central oceanic area generated mainly around the early pliocene is restricted to the rift s axis the marginal basin type of evolution of the tyrrhenian sea is most probably directly linked to subduction of the ionian lithosphere nevertheless interferences between collision in the surrounding apennines calabria or sicilides and subduction processes have dominated this special back arc basin evolution since late tortonian time the tyrrhenian arc shows a regional n120 e oriented tensional pattern short compressional events occur briefly in middle pliocene and middle pleistocene times correlated with brief paroxysmal phases of extension and subsidence the deformation depends on the presence of a subduction zone parallel to the calabrian arc swell which allows the migration of the unblocked segments of the arc in a n120 e direction

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

rheology of some continental lower crustal rocks abstract to gain insight into the rheology of selected feldspar bearing rocks from the continental lower crust clc three granulites from exposed lower crustal terrains and a microgabbro have been deformed to ca 10 strain at confining pressures of 0 8 1 0 gpa temperatures of 600 900 c and constant strain rates of 10 4 10 7 s 1 the most extensive work was done on the mafic pikwitonei and felsic adirondack granulites the pikwitonei mg hornblende plag an70 2 px has only a limited t range of apparent steady state behavior and strain softens at t 800 c at 10 5 10 6s 1 apparently associated with developing shear zones this strain softening is pressure insensitive from pc 0 8 1 0 gpa at t 850 c 10 6s 1 even though the dominant strain accommodation mechanisms change from semibrittle cataclastic to crystal plastic including dynamic recrystallization with increasing pressure plagioclase appears to bear more of the creep strain than amphibole at most experimental conditions except in those runs where both plagioclase and amphibole recrystallization occurs kapuskasing plag cpx gt granulite deformed at 800 c and at 850 c 10 6 s 1 has deformed in the steady state at stress levels only slightly greater than the pikwitonei the stillwater microgabbro and adirondack granulite are appreciably weaker and the latter exhibits homogeneous semibrittle steady state behavior over the entire range of conditions investigated for the adirondack 2 felds 2 px gt qtz granulite quartz 21 appears to control the creep rate at these low strains and steady state mechanical data fit well a creep power law with a 8 10 3 mpa ns 1 qc 243 kj mol and n 3 1 extrapolation of this flow law and of preliminary power law creep relations for the pikwitonei and microgabbro to a range of physical conditions assumed to encompass those at the continental moho supports geological and geophysical inferences that a mechanical discontinuity occurs at this transition zone with the lower crust generally being the weaker material in addition the stain softening exhibited by the pikwitonei may bear directly on the development of detachment zones at mid to lower crustal depths during prograde metamorphism

postglacial tectonic activity within the skjalfandadjup basin tjornes fracture zone offshore northern iceland based on high resolution seismic stratigraphy abstract multibeam bathymetric and high resolution seismic reflection data chirp have been used to illuminate the structural framework and tectonic evolution of the 300 km2 skjalfandadjup basin one of three large rift basins within the tjornes fracture zone a complex transform zone offshore northern iceland the skjalfandadjup basin together with the nafir seamounts form the nascent nafir skjalfandadjup volcanic system of the oblique grimsey volcanic zone the skjalfandadjup basin is made up of normal faults with maximum displacement of 50 60 m and a dominant strike of n10 20 w correlation of chirp data with tephrochronology from sediment core md99 2275 provided constraints on tectonic movements along individual faults from late glacial time throughout holocene maximum vertical displacement is observed on three listric normal faults marking the eastern boundary of the main basin postglacial tectonic activity commenced as early as 14 15 kyr bp followed by three major rifting episodes prior to 10 kyr bp and three smaller rifting episodes during the last 4 2 kyr the 10 12 kyr period of enhanced tectonic activity was accompanied by eruptions within the tjornes fracture zone isostatic rebound following rapid deglaciation caused rifting with significant vertical displacement on normal faults offshore n iceland

holocene paleoceanography and paleoenvironments of the skagerrak kattegat scandinavia paleoceanographic and paleoenvironmental interpretations based on foraminifera sedimentary data radiocarbon dates and stable isotope measurements were derived from two sections in the skagerrak a 115 m thick holocene marine section drilled onshore at skagen near the northernmost tip of jutland denmark and a 9 m piston core from the skagerrak north of skagen the foraminiferal data show that arctic subarctic environments in the deep skagerrak kattegat area were succeeded by boreal conditions at 9 6 ka this was a result of northward migration of the atlantic polar front and inflow of warm atlantic water into the area through the norwegian channel a gradual warming of the water masses after 9 6 ka is indicated by the data rare foraminifera and high sedimentation rates are found between approximately 8 6 ka and 7 6 ka at both core locations the modern foraminiferal assemblages of the area were fully established at 7 6 ka indicating that the modern circulation pattern in the skagerrak kattegat after the opening of the english channel and the danish straits was not established before this date at 5 5 ka a sudden change to coarser sediments higher energy environments and the appearance of the foraminifer eoeponidella laesoeensis is recorded in the skagen core this indicates a rapid change in the hydrography reflecting altered meteorological and hydrographic conditions in the skagerrak kattegat including a strengthening of the jutland current and increased inflow of north sea water into the kattegat the event is interpreted as a response to cooling at the end of the holocene climatic optimum in late atlantic time and possibly reflects a rapid cooling event of north atlantic surface water masses

thermo mechanical modeling of the tyrrhenian sea lithospheric necking and kinematics of rifting we present the results of quantitative forward modeling of the sardinian rifted margin of the tyrrhenian sea the purpose of this study is to investigate the thermo mechanical structure that affects the thinning of the lithosphere across the margin the role of lithospheric necking during basin formation constrained by basement topography moho depth and gravity anomalies is modeled for different compensation models independent constraints are obtained from the analysis of the predicted thermal structure a deep level of necking 25 km is required to explain the observed crustal geometries and gravity anomaly signature the model predicts spatial and temporal variations in rheology during extension with important implications for kinematics of lithospheric thinning prerift lithospheric conditions strain rate and temperature during extension appear to be the key controls on the style of lithospheric rifting and necking in the tyrrhenian sea a forward model for basin stratigraphy is presented for the polyphase history of the tyrrhenian rifting this model provides quantitative estimates of time space dependent crustal thinning and rates of extension

sand mass accumulation rate as a proxy for wind regimes in the sw barents sea during the past 3 ka aeolian sand mass accumulation rates were determined in a coastal mire complex on the north norwegian island soroya this measure of aeolian activity is used as a proxy for past storm intensity in the sw barents sea region at least until the seventeenth century when human activities began to obscure the natural signal aeolian erosion started to increase in the sixth century and consistently high values are recorded from the eleventh century onwards periods of relatively increased aeolian activity can be seen 1200 800 bc 550 150 bc ad 500 850 ad 1000 1400 and ad 1700 2000 increased aeolian activity here indicates a higher frequency of east tracking storm systems at 70 n potential causes for such conditions are increased advection of atlantic water and intensification and or northward displacement of the main winter storm tracks normally associated with moist westerlies and positive nao conditions other noteworthy climatic events are 1 a short but severe wet spell is recorded in the late tenth

an event stratigraphy for the last glacial holocene transition in eastern middle sweden results from investigations of varved clay and terrestrial sequences this paper presents an event stratigraphy for the last glacial holocene transition in eastern middle sweden the event stratigraphy for eastern middle sweden comprises ten events and covers the tim

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

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

postglacial palaeoceanography in the skagerrak crucial periods of change in the latest glacial to early holocene palaeogeographic and palaeoceanographic evolution in the skagerrak region are portrayed in four time slice maps on a calibrated age scale at 14 0 kyr 11 2 kyr 10 2 kyr and 8 1 kyr the course of palaeoenvironmental events is set in a high resolution chronological framework using images core md99 2286 and a grid of chirp sonar profiles these maps visualize the complex rapid palaeogeographic and palaeoceanographic changes during the glacialinterglacial transition which is characterized by major changes in circulation sediment sources and depositional processes

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

finite extension and low angle normal faulting andersonian theory for infinitesimal strains predicts that normal faults will form at high angles to the surface in extensional terranes in contrast low angle normal faults are sometimes observed on which tens of kilometers of slip has occurred and moderate angle faults with slip of 5 to 15 km are common a simple extension of the theory to account for the stresses required to drive finite deformation shows that low angles are preferred for large extension on individual faults the formation of low angle faults may require inhomogeneities in stress or material properties but once slip begins on a low angle fault it is likely to continue whereas slip on high angle faults is likely to end after modest slip to be replaced by the formation of new high angle faults

seismic stratigraphy and quaternary sedimentation in the skagerrak northeastern north sea abstract ice movement sea level fluctuations and currents are the controlling factors of the late pleistocene and holocene sedimentation processes in the skagerrak the erosional truncation at the top of a mesozoic depositional sequence defines the extent of the norwegian channel and functions as the initial depositional surface for quaternary sedimentation on this surface in shallow waters off the danish coast weichselian glacial sediments are deposited an end morain ridge marks a temporary stillstand of the retreating ice front at the beginning of ice free conditions some 15 000 yrs ago when the sea was about 70 m below the present level the skagerrak was a fjord like forebasin of the northern atlantic and constituted a favorable outlet for rivers draining the subaerial glacial deposits of the southern skagerrak and the present southern north sea fluvial erosion released large amounts of detrital material which was laid down in the form of a progradational delta prodelta complex slumping and mass flow processes led to high sedimentation rates and a rapid infilling of the norwegian channel in front of the delta complex with the rapid transgression of the southern north sea at the beginning of the holocene a dramatic change in the depoenvironment of the skagerrak took place the modern current pattern became established whereby sediment transport and redeposition became the rule along the danish coast sandwaves and megaripples with an apparent northeasterly migration direction were formed as a result of the wind forced jutland current fine suspended particles bypass the coastal zones to settle out in the deep norwegian channel

late glacial and holocene paleoceanography in the skagerrak from high resolution grain size records abstract high resolution grain size analyses of the ams 14c dated 32 m long core md99 2286 from the northeastern skagerrak were performed in order to study late glacial and holocene paleoceanographic and sedimentary changes all ages in this study are given in calibrated thousand years before present ad 1950 abbreviated kyr unless otherwise noted the distinct ending of ird ice rafted debris in core md99 2286 which was retrieved from a location down current from the final calving ice margin in the region indicates that iceberg calving in the skagerrak ended between 10 6 and 10 2 kyr a clay rich sequence in core md99 2286 deposited between 11 3 and 10 3 kyr is attributed to outflow from the baltic basin across south central sweden the sequence is correlated to similar units from cores along the swedish west coast the onset of this clay rich deposition occurs progressively later in cores further south along the coast supporting a previous hypothesis that differential glacio isostatic uplift caused a southward migration of the baltic outflow from the otteid stenselva to the gota alv outlet a distinct coarsening towards younger sediments in core md99 2286 indicates a hydrographic shift at 8 5 kyr which is correlated to a shift previously reported in the skagerrak kattegat and the norwegian channel this shift reflects the establishment of the modern circulation system in the eastern north sea as a consequence of the opening of the english channel and the danish straits and increased atlantic water inflow and the subsequent development of the south jutland current a general trend of coarsening poorer sorting and increasing variability from 8 5 kyr until the present indicates increasing strength and influence of the variable south jutland current a series of changes from ca 6 3 to ca 3 8 kyr in core md99 2286 reflects strengthening of the jutland current towards the present day sedimentation system in the skagerrak kattegat these changes are correlated to previously reported hydrographic shifts at 5 5 14c years bp in the skagerrak and at 4 0 14c years bp in the kattegat it is suggested that these shifts were separate features of a transitional period related to strengthening of the current system the resulting changes are differently manifested in different parts of the skagerrak kattegat due to the complex circulation system the last 800 years are characterised by poorly sorted sediments with a relatively high and variable proportion of coarse material reflecting a circulation system significantly modified by regional climatic conditions especially the general wind directions and storm frequency over the southern north sea

palaeoglaciology of an ice sheet through a glacial cycle the european ice sheet through the weichselian abstract satellite images provide unique means of identifying large scale flow generated lineations produced by former ice sheets they can be interpreted to reconstruct the major elements which make up the integrated large scale structure of ice sheets ice divides ice streams interstream ridges ice shelves calving bays the evolving palaeoglaciological structure of the european ice sheet during its decay from the last glacial maximum lgm is reconstructed by reference to these components and in the context of a new map showing isochrons of retreat during the retreat phase in particular the time dependent dynamic evolution of the ice sheet and the pattern of ice stream development are reconstructed crossing lineations are widespread the older ones are suggested to have formed during molten bed phases of ice sheet growth and preserved by frozen bed conditions during the glacial maximum particularly in areas which lay during deglaciation beneath ice divides and inter ice stream ridges both areas of slow flow and possibly frozen bed conditions four phases of growth a1 to a4 and five phases of decay r1 to r5 are used to describe the major climatically and dynamically determined stages in the evolution of the ice sheet through the last glacial cycle the growth and decay patterns are quite different and associated with major shifts in the ice divide reflecting growth from the fennoscandian mountains and decay away from marine influenced margins these patterns were determined by the locations of nucleation areas spatial patterns of climate and calving at marine margins the prevalence of streaming within the retreating ice sheet suggests that the mean elevation of the ice sheet was lower than predicted from glaciological models which do not include streaming and that this might reconcile glaciological models and earth rheology models which infer paleao ice sheet thickness by inverting sea level data

geothermal structure of the tyrrhenian sea over 200 heat flow measurements have been carried out in the tyrrhenian sea mostly since 1977 as part of the heat flow map for italy and surrounding seas italian program as well as part of the french italian tyrrhenia program all data have been corrected for the influence of the plio quaternary sedimentation measured heat flow values were evaluated according to the sedimentary environment following criteria outlined by sclater et al 1980 in this way areas affected mainly by shallow thermal effects in the zones with maximum density of data have been displayed filtering out these shallow contributions the major regional geothermal trends were obtained the tyrrhenian basin can be divided in two distinct regions with different geothermal characteristics the northern part of the basin appears to be connected with the continental structures involved in the interaction between the corsica and tuscan margins the maximum heat flow area located offshore civitavecchia is related to the tensile structures of the tuscan geothermal province the most important thermal features of the central and southern part are located along the central belt trending nw se the lowest heat flow values are located in the peri tyrrhenian areas and are related to the continental margins of the basin while the maxima are connected with the stretched and thinned area localized in the bathyal plain taking into account the heat flow data as well as other geological and geophysical information an evolutionary model for the tyrrhenian sea is presented suggesting a generalized stretching of an initially continental crust accompanied by intensive rifting phases which may have favoured the onset of oceanic type crust

a model for sedimentation by tidewater glaciers sampling of sediment from the fjord floor in front of tidewater glaciers in glacier bay alaska has provided information about processes in this restricted glacimarine dreimanis 1979 setting sediment sampling in conjunction with oceanographic and glacial dynamics data has also enabled the discrimination of sediment types and their facies associations deposits are strongly controlled by sea water characteristics position and sediment discharge of melt water streams iceberg calving and rate of glacierfront retreat five distinct facies associations have been found to reflect glacier fjord regimes the facies associations and ice fjord conditions responsible for them form the basis for constructing a preliminary model for glacimarine sedimentation by tidewater glaciers the model can be used to predict i rapid retreat of an actively calving ice front ii slow retreat or stabilization of a calving ice front at a channel constriction iii stabilization of a melting very rarely calving ice front when the glacier base is near tidewater elevation and iv large outwash delta progradation into a fjord when the ice front retreats onto land this model can be used to interpret facies associations found in a stratigraphic record

lateglacial and holocene sediment sources and transport patterns in the skagerrak interpreted from high resolution magnetic properties and grain size data lateglacial and holocene changes in circulation sedimentation and provenance in north eastern skagerrak were studied using high resolution mineral magnetic and grain size data from the 32 m long i

glacimarine sedimentary processes and depositional environments in an embayment fed by west greenland ice streams abstract the extent and behaviour of the central west greenland sector of the greenland ice sheet gis during the last glacial maximum lgm and the following deglaciation remains poorly constrained to investigate deglacial marine environments and sedimentary processes in an area fed by several lgm ice streams we now report findings from a 3 5 khz sub bottom profiler survey acquired in and around disko bay in 2009 sediment thicknesses and volumes in three glaciated areas disko bay southern vaigat and egedesminde dyb are fully constrained for the first time acoustic facies types and distributions were also mapped the largest sediment thicknesses 256 m and widest variation in acoustic character was observed in disko bay adjacent to the mouth of jakobshavns isfjord significant sediment thicknesses were also observed in isolated basins in the egedesminde dyb trough and in a trough in southern vaigat strait up to 110 m given low modern sedimentation rates these thick sediment packages are inferred to record the retreat of glaciers from the middle shelf through disko bay and into both the jakobshavns and torssukatak fjord systems in central west greenland our results highlight similarities in deglacial sedimentary processes across the study area when the margins of retreating glaciers supplied large volumes of sediment to the marine environment from sediment laden meltwater plumes and melting icebergs we estimate the sediment flux for the palaeo jakobshavn ice stream while the ice margin was stable at a fjord entrance sill to be 1 6 3 6 10 7 m 3 a 1 assuming a flux at the upper end of our range for the torssukatak fjord system requires the grounded ice margin to be stable for about 450 years during retreat the sediment fluxes we estimate are within the range of previously calculated fluxes for other arctic and antarctic ice streams and suggest that large volumes of meltwater and sediment were available at the base of the outlet glaciers during deglaciation even during periods of quasi stability retreat of the ice margins into the fjord systems is characterised by a rapid transition to ice distal sedimentation by rainout of iceberg rafted detritus ird and hemipelagic material accumulation rates drop to 2 mm a 1 this study demonstrates the variability in glacimarine processes and environments on high latitude continental margins and highlights the importance of local factors such as bedrock morphology as well as glacio dynamic factors on sedimentation

fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model the evolution of ice sheet configuration and flow pattern in fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model i e a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets the model uses mapped flow traces and deglacial melt water landforms as well as relative chronologies derived from cross cutting striae and till lineations as input data flow trace systems were classified into four types i time transgressive wet bed deglacial fans ii time transgressive frozen bed deglacial fans iii surge fans and iv synchronous non deglacial event fans using relative chronologies and aggregation of fans into glaciologically plausible patterns a series of ice sheet configurations at different time slices was erected a chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume geological evidence exists for several discrete ice sheet configurations centred over the scandinavian mountain range during the early weichselian the build up of the main weichselian fennoscandian ice sheet started at approximately 70 ka and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern norway this configuration had a flow pattern which is poorly reproduced by current numerical models of the fennoscandian ice sheet at the last glacial maximum the main ice divide was located overthe gulf of bothnia a major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the scandinavian mountain chain widespread areas of preserved pre late weichselian landscapes indicate that the ice sheet had a frozen bed core area which was only partly diminished in size by inward transgressive wet bed zones during the decay phase

multiple pleistocene ice advances into the skagerrak a detailed seismic stratigraphy from high resolution seismic profiles abstract a detailed pleistocene seismic stratigraphy is proposed for the skagerrak an over 700 m deep elongated depression in the northeastern north sea by comparing our high resolution seismic results with those from glacial environments of canada alaska and antarctica we conclude that at least during the weichselian if not also during the saalian a glacier grounded in the eastern skagerrak and advanced well into its western part as indicated by a thick layer of basal till the surging glacier truncated the basinal flank of a ridge like delta moraine that was presumably deposited under uniform glacial conditions in an ice distal environment the deposition of the hirtshals moraine in shallow waters of hirtshals might originate from a glacier that advanced from sweden into north jutland soon after the ice withdrawal from the skagerrak a layer of well stratified glaciomarine sediments was deposited over the basal till suggesting floating ice conditions in a fjord like environment due to the rising sea level in the late pleistocene fluvioglacial and shallow marine deposits soon dominated over the glaciomarine sediments indicating an end of glacial conditions in this region these post glacial sediments were first deposited in the western skagerrak but as the transgression came to an end in the mid holocene the depocenter shifted to the east today the highest sedimentation rates are found in this eastern part

sedimentation and environmental conditions in the inner skagerrak outer oslofjord abstract sedimentological mineralogical geochemical and some geotechnical properties of holocene clay and silt sediments of the inner skagerrak and outer oslofjord are reported close to the norwegian coast the sea bottom has an irregular relief reflecting the rough features of the crystalline basement here the sediment thickness varies from 0 to 50 m at water depths greater than 150 m the sediment layer becomes thicker and continuous generally the sedimentation rates in the oslofjord and inner skagerrak are high normally 1 2 mm yr areas with higher deposition as well as with non deposition and or erosion occur the inner fjord sediments have high contents of illite and chlorite reflecting that they have been derived from the glacial deposits of scandinavia these clay minerals are also present in the outer fjord and skagerrak sediments which in addition contain smectite and kaolinite that originate from the mesozoic and cenozoic sediments in denmark southern sweden and or from sediments within the north sea basin these clay minerals are transported to the inner skagerrak mainly by the jutland and baltic currents the diagenetic zonation of most bottom sediments consists of an oxic layer on top of an incipient reducing anoxic non sulphidic layer in the oxic top layer of the skagerrak sediments diagnetic calcite grows on foraminiferal tests at depth the calcite dissolves zinc has been used as element reflecting anthropogenic pollution the flux of zinc to the oslofjord skagerrak sediments started to increase about 120 140 years ago today the most polluted waters are locked fjords and coastal waters inside the archipelago as the isostatic rebound still goes on in scandinavia the polluted sediment particles will not deposit in the river but in the fjord and coastal areas except for a few near shore areas and restricted fjord basins the degree of pollution is low

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

mesoscale convective systems over southeastern south america and their relationship with the south american low level jet abstract prior studies have shown that the low level jet is a recurrent characteristic of the environment during the initiation and mature stages of mesoscale convective systems mcss over the great plains of the united states the south american low level jet sallj over southeastern south america sesa has an analogous role advecting heat and moisture from the amazon basin southward into the central plains of southeastern south america generating ideal environmental conditions for convection initiation and growth into mcss this research has two purposes one is to describe the characteristics of a 3 yr mcs sample in south america south of the equator and its related geographical distribution of convection frequency the other is to advance the knowledge of the evolution of favorable environmental conditions for the development of large mcss specifically those that mature under sallj conditions high horizontal and temporal resolution satellite images are used to detect mcss in the area for the

timing and east west correlation of south swedish ice marginal lines during the late weichselian abstract the retreat of the late weichselian ice sheet over the southern part of sweden is marked along the southwest coast by distinct marginal moraine ridges their timing can directly and indirectly be assessed based on a number of radiocarbon dates and pollen stratigraphic investigations on lake sediment sequences adjacent to the ice marginal lines along the southeastern side of the peninsula the ice recession has been reconstructed based on a combination of clay varve chronology pollen and radiocarbon stratigraphy a morphological correlation of ice marginal lines between the west and east coast is problematic since the distinct west coast moraines cannot be followed through the central part of the peninsula towards the east coast this paper is an attempt to reconstruct an age equivalent west east extension of the ice recession lines on the basis of existing data sets for our correlation we use calibrated radiocarbon ages for ice marginal deposits on the west coast and compare these with a partly radiocarbon dated clay varve chronology on the east coast we conclude that the two oldest moraines on the west coast formed at 18 000 16 000 and 15 400 14 500 cal yr bp respectively during the following rapid deglaciation which may have coincided with the beginning of the bolling pollen zone large parts of southernmost sweden became ice free except for higher elevated areas where stagnant ice remained for another 400 500 yr a best guess is that the formation of the next younger ice marginal lines may have occurred at 14 400 14 200 14 200 and 13 400 cal yr bp and during the younger dryas cold event

upper mantle properties of the tuscan tyrrhenian area a framework for its recent tectonic evolution abstract within the alpine mediterranean deformational system several interesting features in the physical properties of the upper mantle have been recognized through the regional analysis of surface wave dispersion a large upper mantle anomaly uma here called the tuscan uma has been identified in the area northeast of corsica which includes part of the northern tyrrhenian sea and part of the north central apennines this anomalous upper mantle area together with the upper mantle characteristics of the tyrrhenian sea located further to the south provides a natural framework for comprehensive interpretation of the large data set of geological and geophysical observations such as land and marine geology volcanism gravity magnetic data seismic data and seismology deep temperatures and surface heat flow

constraints on extension of continental lithosphere the extension of the continental lithosphere is considered in terms of the deformation of a thin viscous sheet with a temperature dependent rheology which is governed primarily by the strength of the upper mantle the lithosphere is subjected either to a constant strain rate or to a strain rate decreasing with time corresponding to the stretching of a region of fixed volume with a constant velocity boundary condition the progress of the extension is influenced by the decrease in strength of the lithosphere owing to its attenuation and by an increase in strength resulting from cooling the relative importance of these two effects depends on two parameters a dimensionless strain rate and the total strain for a given strain rate the extending lithosphere goes through two phases as the strain increases in the first the effect of thinning the lithosphere is predominant and the average strength of the lithosphere remains close to and perhaps slightly below its original strength in the second the effect of cooling of the lithosphere leads to very rapid increase in strength as a function of strain resulting presumably in an effective limit on the degree of stretching that the lithosphere experiences for the case of strain rate decreasing with time when the initial strain rates are of order 10 15s 1 this maximum extension is between 100 and 150 for a strain rate of 10 l4 s 1 the maximum lies around 400 to 500 at higher strain rates than this very large extension may occur before cooling significantly affects the strength of the lithosphere this model accords well with the constraints available from the continental margins of the north atlantic

comparison of instrumental and gdgt based estimates of sea surface and air temperatures from the skagerrak sea surface temperatures ssts and annual mean air temperatures mats are estimated for the last 200 years from glycerol dialkyl glycerol tetraethers gdgts proxies in a marine sediment core from the skagerrak off southern norway the reconstructed values compare well with annual ssts and summer air temperatures obtained from composite regional instrumental records the results provide further confidence in the application of proxies based on gdgts to estimate past temperatures

recent and active tectonics in the calabrian arc southern italy normal faulting which has developed since the middle pleistocene with an overall ese wnw extension is the dominant mode of deformation which has characterized the calabrian arc up to the present quaternary normal faults extend for a total length of about 180 km along the inner side of the arc the different normal fault segments which during the pleistocene controlled the evolution of the main marine sedimentary basins are varying in length from 10 to 20 km and have fault escarpments showing a very young morphology which define the fronts of the major mountain ranges of the arc the morphological features of the fault escarpments suggest slip rates of 0 8 1 1 mm yr for the last 700 k y and values of 0 6 0 9 mm yr for the last 120 k y indicating a uniform rate of faulting since the middle pleistocene crustal seismicity and the mesoseismic areas of historical large events 6 5 m 7 1 which occurred in the calabrian arc are located within a narrow belt along the hanging walls of the quaternary normal fault segments this suggests that the normal faults which dissect the inner side of the calabrian arc may be seismically active

spacing of consecutive normal faulting in the lithosphere a dynamic model for rift axis jumping tyrrhenian sea we propose that the flexure of a broken elastic plate can determine the spacing of consecutive and localized zones of shearing on a lithospheric scale the model provides a dynamic explanation for rift axis migration and as a consequence for a wide rift mode of extension calculated values for rift axis shifting are consistent with the available observations and kinematic modelling results in the tyrrhenian basin the quantitative relation obtained between lithospheric fault spacing and the effective elastic thickness t of the lithosphere can be used in an inverse modelling approach in which paleo t e e values are calculated for a basin where the diachronous and spaced nature of rifting is known

chirp subbottom profiler for quantitative sediment analysis a wide band frequency modulated subbottom profiling system the chirp sonar can remotely determine the acoustic attenuation of ocean sediments and produce artifact free sediment profiles in real time the chirp sonar is controlled by a minicomputer which performs analog to digital and digital to analog conversion correlation processing and attenuation estimation in real time the minicomputer generates an fm pulse that is phase and amplitude compensated to correct for the sonar system response such precise waveform control helps suppress correlation noise and source ringing the chirp sonar which has an effective bandwidth of 5 khz can generate chirp klauder wavelets with a tuning thickness rayleigh s criterion for resolution of approximately 0 1 ms after each return is correlated a computationally fast algorithm estimates the attenuation of subbottom reflections by waveform matching with a theoretically attenuated waveform this algorithm obtains an attenuation estimate by minimizing the m