modeling of the mesoscale structure of coupled upwelling downwelling events and the related input of nutrients to the upper mixed layer in the gulf of finland baltic sea 1 a high resolution numerical study is undertaken to simulate an upwelling event along the northern coast of the gulf of finland 21 29 july 1999 which was documented well by in situ and remote measurements the simulated sequence of sst maps shows a reasonably good resemblance to that of satellite infrared imagery including both mesoscale coherent structures filaments or squirts and the whole process of post upwelling relaxation of the temperature field upwelling along the northern coast of the gulf is accompanied by downwelling along the southern coast so that two longshore baroclinic jets and related fronts are developed simultaneously when the strong westerly winds producing the upwelling downwelling weaken the longshore jets become unstable and produce transverse jets cold warm water squirts using pseudo random simulated fields of temperature and velocity of currents the apparent lateral diffusivity due to squirts is directly estimated at 500 m2 s 1 the model is also applied to estimate nutrient transport simulated phosphate concentration in the surface layer at the cold side of upwelling front is found to be about 0 3 mmol m 3 which is consistent with observations the total content of phosphorus and nitrogen in the upper 10 m layer of the gulf introduced by the upwelling event is estimated to be 387 and 36 tons respectively it follows that the upwelling event transports nutrients into the upper layer with clear excess of phosphorus n p 36 387 0 093 compared to the redfield ratio of 7 2 therefore phosphorus input caused by upwelling during summer most likely promotes nitrogen fixing cyanobacteria blooms

u pb zircon geochronology of silicic tuffs and chronostratigraphy of the earliest old red sandstone in the munster basin sw ireland

regionally consistent western north america paleomagnetic directions from 15 to 35 ka assessing chronology and uncertainty with paleosecular variation psv stratigraphy abstract new paleomagnetic secular variation psv data from fish lake utah usa along with previously published regional records allow us to build an independently dated western north america psv stack wnam17 from about 35 to 15 ka that quantifies dating and paleomagnetic uncertainties in february 2014 we recovered a composite 11 m long sediment record from fish lake utah that retrieved glacially influenced and post glacial sediments computed tomography ct scans and magnetic susceptibility were used to build a precise depth scale while radiocarbon dating of terrestrial macrofossils and tephrostratigraphy provide tight age control glacially influenced sediments have well defined characteristic remanent magnetizations with all maximum angular deviation values

secular variation as recorded in lake sediments a discussion of north american and european results type curves depicting secular variations in declination and inclination through holocene time have been constructed by stacking data from individual cores of lake sediment from east central north america and the u k there is a strong positive correlation in declination with zero phase shift froiti 0 to 4500 14 c years b p but from 4500 to 8500 14 c years b p the correlation is strongly negative which we interpret in terms of fluctuations in intensity of standing geomagnetic sources a source located under the atlantic ocean appears to have been dominant before ca 4500 14c years b p and then another similar source located either to the east or to the west of both observation areas gained dominance however the inclination type curves show optimum positive correlation for a phase shift of ca 400 years suggesting that the geomagnetic sources that caused them were drifting westward at ca 0 2 degrees a year there is no way of adjusting the timescales so as to obviate this apparent paradox secular variations of the total geomagnetic vector have been investigated by noting the sense clockwise anticlockwise of looping of the v g p paths though this cannot be interpreted uniquely in terms of westward or eastward drifting sources in the core as demonstrated by specific radial dipole models

congruent paleomagnetic and archeomagnetic records from the western united states a d 750 to 1450 two independently dated high resolution paleomagnetic records one lacustrine and one archeological record the passage across western north america of the same nondipole feature of the geomagnetic field during the time interval from a d 750 to 1450 although these sequences indicate that correlation between paleomagnetic and archeomagnetic records is feasible under certain conditions differences between the records underscore the difficulty of dating accurately an archeological site by correlation of a single archeomagnetic direction with a secular variation curve

holocene secular variation in western north america paleomagnetic record from fish lake harney county oregon an 8 9 m composite section of lake sediment from fish lake steens mountain southeastern oregon has provided a high resolution record of holocene geomagnetic secular variation in western north america the section is composed of overlapping core segments with stratigraphic control based on six tephra layers and other thin distinct bands and with age control from 37 radiocarbon dates the 455 paleomagnetic samples possess a strong and stable magnetic remanence which is carried by pseudo single domain magnetite paleomagnetic records for individual core segments show low scatter and high serial correlation and where the segments overlap there is excellent agreement between records the azimuthal orientation of the composite section was recovered from the known direction of the geomagnetic field at the time of the climactic eruption of mount mazama tephra which is present in fish lake both internal and external evidence including the correspondence with an archaeomagnetic record from the southwestern united states support the conclusion that the fish lake record represents the history of geomagnetic field behavior during at least the last 10 000 years b p analysis of that record reveals that the average geomagnetic direction can not be distinguished from that of a geocentric axial dipole field and that the overall circularity of the field was clockwise but the detailed behavior was quite complex angular standard deviations of both field directions and virtual geomagnetic poles differ significantly from the values predicted from theoretical models of secular variation but are consistent with those of other holocene records when the record from fish lake is compared to the proposed type curve for east central north america there is excellent agreement for the past 6000 years provided the curves are offset by about 400 years this offset corresponds to a rate of westward drift of about 0 062 yr beyond about 6000 radiocarbon years ago good agreement between the two curves occurs when there is no offset suggesting that the field was standing rather than drifting during this time

palaeozoic sedimentary sequence as a reflection of deep structure in southwest ireland abstract in county cork southwest ireland the upper devonian tournaisian succession is spectacularly thick maximum approximately 8 km a thick visean carbonate succession exists in the ground around cork city and northward from there but that apart there is only a meagre representation of carboniferous rocks younger than tournaisian namurian and westphalian are better developed in areas to the north and to the south of the locus of maximum thickness of upper devonian tuffisitic intrusions occur close to the trace of a large fracture in the bantry bay area they have been suspected to include material derived from the mantle the whole association is interpreted as a palaeozoic example of an inversion structure the inversion is attributed to heating arising from a lithospheric delamination occasioned by the collision which closed the iapetus ocean early in devonian time the possibly mantle derived intrusions are set within the dome produced during the course of the inversion variscan folding took place during the development of the dome and certain irregularities in the pattern of outcrop of variscan folds can be regarded as interference effects imposed on the folds by late continuation of the doming brief comments are appended on the means of dating the progress of the process of delamination on the outworn notion of a variscan front and on the open question of the state of palaeozoic rocks whether metamorphic or non metamorphic in the celtic sea region a strong causal relationship is demonstrated between the sequence of tectonic events and the regional facies associations the patterns of megafacies from upper devonian to westphalian are described and discussed in this context

late quaternary paleomagnetic field secular variation from two minnesota lakes detailed paleomagnetic records from the wet sediments of two minnesota lakes are the basis for estimating the local secular variation of the earth s magnetic field during late quaternary time results from lake st croix cover the interval 0 9500 years b p and results from kylen lake cover the interval 4000 14 000 years b p paleomagnetic data were recovered from two replicate cores in each lake by sampling the sediments at 3 to 10 cm intervals analysis of the potential errors in the results indicates that all cores were correctly oriented in the vertical plane but that some azimuthal offsets of individual core segments did occur various methods for correcting the occasional azimuthal offsets are described the final paleomagnetic data sets from each lake show a high degree of internal consistency these results also show close correspondence 1 between the two lakes 2 with the known historic magnetic field variation and 3 with paleomagnetic results from dated archeological material and lava flows from the western united states rock magnetic analysis of the lake sediments indicates that the natural remanent magnetization is the result of a physical remanence acquisition process detrital remanent magnetization active at or near the sediment water interface there is no evidence for a systematic inclination error in the results statistical analysis of vector time series determined from the paleomagnetic data indicates that both the field vector and virtual geomagnetic pole vgp distributions are non fisherian and essentially axial dipolar when averaged over 10 000 years spectral analysis of the scalar inclination and declination suggests that the field behavior is separable into a dominant low frequency dipolelike waveform period of 9500 years and a higher frequency band irregular waveform fundamental period of 2400 years with multiples at 1200 800 and 600 years that may represent the nondipole field this irregular waveform is interpreted as resulting from zonal drift of the nondipole field past minnesota on the basis of waveform morphology and vgp circularity zonal drift of the nondipole field plus a low frequency dipole variation can account for almost all of the observed paleomagnetic field variation

an eifelian u pb zircon date for the enagh tuff bed from the old red sandstone of the munster basin in nw iveragh sw ireland the first geochronological data from the minister basin sw ireland contradict the accepted biostratigraphical maximum age late givetian early frasnian of the oldest alluvium in the basin depocentre magmatic zircons from the enagh tuff bed a sub plinian air fall tuff within fluviatile old red sandstone of nw iveragh give a pb pb isotope age of 384 9 0 7 ma this confirms middle devonian probably eifelian sedimentation and allows possible early devonian basin initiation associated second cycle gravels suggest a pre 385 ma minimum age for the caherbla group of the dingle basin correlation with alluvium containing tetrapod trackways indicates a pre 385 ma age for the trace maker

sub greenschist facies metamorphism from the variscides of sw ireland an early syn extensional peak thermal event illite crystallinity studies on metaclastics from the variscides of sw ireland range in value from 0 18 to 0 25 2 indicating a metamorphic grade in the upper anchizone lower epizone c 275 325 c chlorite geothermometry yields a similar metamorphic temperature range 280 315 c combining these data with known overburden estimates for the area c 5km implies late palaeozoic geothermal gradients in excess of 60 ckm 1 fluid inclusion studies on quartz veins in these metaclastics reveal two vein types characterized by fluid densities of 0 7 0 93 g cm 3 group 1 and 0 9 1 0gcm 3 group 2 respectively this variation in fluid density is thought to be dominantly controlled by temperature with group 1 veins linked to late palaeozoic extension and high geothermal gradients and group 2 veins associated with subsequent variscan deformation and lower temperature conditions

crustal evolutionary model for the variscides of ireland and wales from swat seismic data the swat seismic reflection profiles recently acquired across the celtic sea demonstrate that the crust which underlies the munster and pembroke variscan foldbelts contains extensive south dipping reflections interpreted as hercynian foreland directed ramp thrusts largely involving the pre devonian basement these large scale crustal ramps developed without any intervening flat lying decollement levels and are thought to have originated in a deep infra crustal decoupling zone not imaged on the swat profiles because it lies within the present day layered lower crust at approximately 25 km depth the pre existing extensional basinal pattern is assumed to have highly influenced the geometry of these deeply rooted thrusts and in particular that of the frontal ramp which emerges along a discontinuous n100 trending thrust zone located above the faulted extensional margin of the munster pembroke and mendips devonian basins shortening of the irish and welsh external zones is hence assigned to dominantly crustal stacking achieved along steep ramps dying out upwards and giving way to mainly undisrupted folds in the thick overlying devonian infill in addition a shallow thin skinned fold thrust system developed above an intra namurian master decollement still preserved in the footwall of the frontal ramp where it either stays blind ireland or emerges pembroke above a dominantly wrench faulted caledonian basement compiling swat seismic data and structural geology leads to a crustal evolutionary model for the irish and south welsh external variscides from a devonian basin template to a final deformation pattern

geomagnetic secular variation from recent lake sediments ancient fireplaces and historical measurements in southeastern australia abstract compilations of historical observations archaeomagnetic data from ancient fireplaces and palaemagetic results from short cores of sediment from lakes in southeastern australia particularly lake keilambete provide a detailed record of the geomagnetic secular variation during the last 3000 years the independent sets of data are in good agreement if the radiocarbon time scale for the lacustrine record is about 450 years too old the error is attributed to systematic incorporation of ancient carbon into the lake floor sediments mainly through erosion of sediment on the crater walls at times of low water level a significant lag between deposition and the acquisition of stable magnetic remanence is ruled out inclination has been abnormally steep during the last 500 years but remained fairly close to the axial dipole field value prior to that during the last 1000 years the predominant sense of looping of the magnetic vector corresponds to westward drift of the nondipole field secular variations on a time scale of 100 years can be resolved by the lacustrine record

historic and paleomagnetic secular variation and the earth s core dynamo process this paper attempts to summarize briefly the recent and ongoing efforts of the geomagnetism and paleomagnetism community to understand both the earth s magnetic field secular variation and its implications for the core dynamo process secular variation is defined in this paper as the general spatio temporal variation of the field secular change will refer to the first time derivative of the spatial field strict geomagnetic definition of secular variation we will emphasize here the long term 10 year or longer behavior of the historic secular variation hsv for this is the variation that is comparable with the paleomagnetic secular variation psv two important related topics the 1969 1970 geomagnetic jerk in secular acceleration and the spatial geomagnetic field components due to crustal or mantle sources are treated more fully in other reviews

the role of nearshore slope on cross shore surface transport during a coastal upwelling event in gulf of finland baltic sea abstract the wind induced coastal upwelling process often contains a mid phase that involves coherent long living cross shore surface jets of cooler water these jets extend to 40 45 km from the coast and tend to start from particular coastal locations we develop a simple method for evaluating the depth in the water column from where the upwelled water originates we also test the hypothesis that the development of cross shore surface jets may be triggered by some permanent characteristics such as the bathymetry or the slope of the nearshore seabed the analysis is performed for a strong and well documented upwelling in the gulf of finland the baltic sea using high resolution bathymetry data satellite derived sea surface temperature surface currents measured by in situ drifters and properties of water masses in two sampling locations the results indicate that the cross shore jets originate exclusively from the shore sections with much steeper slopes 0 0075 than in the rest of the study area the cooler water most likely origins from intermediate water masses at depths between 15 and 30 m the resulting identification of the source depth of the upwelled water and its spatial location assists in understanding the flux of nutrients during upwelling events and their link to the onset of cyanobacteria blooms

contemporaneous faulting and the eruption and preservation of the lough guitane volcanic complex co kerry interbedded with the clastic fluvial sediments of the munster basin the lough guitane volcanic complex represents a rare volcanic episode in the upper devonian of sw ireland from three distinctly separate volcanic centres an exclusively rhyolitic suite of thick lava flows and tuffs were erupted the largest of the centres possessed a system of contemporaneous faults producing a subcircular depressed area itself enclosed within a graben 1 5 km across these faults lead to rapid thickness variations in many volcanic units and a pooled lava flow reaches a thickness of 300 m the site of a major elongate vent lies along one such fault and rapid erosion of its poorly lithified walls generated coarse sandstone boulder agglomerates and is related to the absence throughout the complex of normal air fall tuffs unmixed with terrigenous sand the containment of the bulk of the volcanics by contemporaneous faults and subsequent rapid burial by terrigenous sediments has led to preservation of the volcanic succession virtually intact

vitrinite reflectance data from the kinsale harbour old head of kinsale area southern ireland and its bearing on the interpretation of the munster basin vitrinite reflectance of the upper devonian carboniferous succession in the kinsale harbour old head of kinsale area ranges from 4 06 5 21 m and 6 21 7 82 max which is indicative of meta anthracite coal rank no correlation is apparent between vitrinite reflectance and stratigraphic position through c 2 km of section suggesting that near maximum temperatures were maintained until after variscan folding low reflectance values of 0 62 and 0 30 0 35 m at the local base of the jurassic succession in the north celtic sea basin well 48 30 1 and onshore at cloyne respectively indicate a major discontinuity in the maturation profile in the region comparison with high reflectance gradients from upper palaeozoic successions in the halen and turnhout boreholes in belgium and the munsterland no 1 borehole in west germany suggests that a thick 5 7 km cover of pre permo tnassic rocks must once have been present in the munster basin to account for the high maturation levels observed whether the cover was emplaced by silesian sedimentation or by late palaeozoic thrusting is unclear

structural evolution of the irish variscides the effects of the variscan orogeny on the upper palaeozoic succession are recognizable throughout central and southern ireland the deformation can be zoned using structural styles and trends which illustrate a northward decrease in deformation intensity coupled with increasing control by pre variscan structures in the basement the most intense deformation occurs to the south of the dingle dungarvan line where shortening approaches 50 as a result of layer parallel shortening followed by buckling and finally thrusting the deformation is considered to have developed above a shallow dipping sole thrust which has been located offshore by the swat seismic reflection profiles cross faults which are common throughout the orogen resulted from n s shear couples this is consistent with their origin as accommodation structures due to differential shortening along strike the original shape of the munster basin has exerted a control on the distribution and overall facing of the major structures the sole thrust extends to the north of the dingle dungarvan line and the structural zonation of the orogen is due to variations in the stratigraphic level of this thrust the leinster massif is considered to be essentially autochthonous slip on the sole thrust decays towards the massif which acted as a rigid passive block and was partially responsible for the arcuate trend of the orogen

the paleomagnetism and u th dating of mexican stalagmite das2 a 72 cm high stalagmite from mexico das2 has been analyzed for its paleomagnetism and has provided a record of secular variation beginning about 1200 years ago to present the stalagmite did not grow uniformly and a low content of magnetic material has rendered the record less precise in some parts a topographic test involving the magnetic measurement of coeval specimens from the sides of the stalagmite has shown that the record is detectably free from depositional errors age data were provided by the u th method and concordancy checked by14c and226ra methods shallow inclinations at the base of the record are followed by a partial anticlockwise loop in the declination inclination plot there is good agreement between the das2 data and the southwest u s a archeomagnetic record and with a lacustrine record from oregon from 750 to 1400 ad comparison of the record with the present field at the site latitude shows that westward drift of the field has persisted for at least 1200 years at a drift rate of about 0 30 yr 1 a close match in declinations with the present field at the site latitude suggests that the stalagmite may have recorded the passing of the northern edge of the gulf of guinea negative anomaly about 1000 years ago though the corresponding inclination feature is not present in the record an archeomagnetic synthesis by merrill and mcelhinny of worldwide data to estimate positions of the main dipole shows that it was tilted away from mexico from 500 to 1250 ad and this may account for the shallow inclinations seen at the start of the record

simulated halocline variability in the baltic sea and its impact on hypoxia during 1961 2007 1 salinity and halocline depth variations in the baltic sea during 1961 2007 are studied using a three dimensional ocean circulation model significant interannual and interdecadal variations in the halocline depth are found together with distinct periods characterized either by shallow 1970 1975 or deep halocline 1990 1995 the model simulation indicates that the mean top layer salinity in the baltic sea is mainly controlled by the accumulated river runoff while the mean below halocline salinity in the baltic proper which comprises bornholm and gotland basins is more dependent on the low pass filtered zonal wind stress with cutoff period of 4 years henceforth called the mean zonal wind stress the halocline depth and stratification strength in the baltic sea are significantly affected by the mean zonal wind stress while the impact of runoff is smaller the ventilation of the halocline from bottom layers is stronger during the shallow and from surface layers during the deep halocline period due to changes in ventilation variations in halocline depth systematically affect bottom oxygen concentrations on seasonal and decadal but not on interannual time scales for instance a deeper halocline reduces hypoxic oxygen concentration in bottom water below 2 ml l and anoxic anoxic conditions in bottom water areas and increases the bottom oxygen concentrations in the gulf of finland but decreases them in the deeper parts of the baltic proper model results suggest that due to undersampling during 1961 2007 mean hypoxic and anoxic areas calculated from observed profiles are underestimated by 41 and 43 respectively

the vein hosted copper deposits of the allihies mining area sw ireland a new structural and chronological evaluation this paper presents new data for historical vein hosted copper sulfide deposits in the late paleozoic munster and south munster basins of sw ireland detailed mapping 3d modelling fluid inclusion microthermometry and geochronology from the allihies area of the beara peninsula have led to a new interpretation of the timing and development of ore mineralization macro and microstructural studies reveal that the ore bearing mainly east west striking quartz veins are directly related to early extensional basinal normal faults molybdenite re os dating of the main stage cu lode yields ages from 367 3 5 5 to 366 4 1 9 ma this early vein system experienced subsequent late carboniferous variscan deformation including cleavage development sinistral sw ne strike slip faulting cataclastic deformation and recrystallization the new timing of cu mineralization in sw ireland has major implications for its relationship to the base metal deposits of the irish midlands supplementary material a video file showing a 3d model of the major lodes and the underground workings at mountain mine and excel spreadsheets showing fluid inclusion measurements and sample locations of the allihies copper mining district are available at https doi org 10 6084 m9 figshare c 4875015

high latitude holocene paleosecular variation and magneto stratigraphic correlation between two lakes on spitsbergen 78 n abstract paleomagnetic signals in cores from two nearby lakes linnevatn and skardtjonn on spitsbergen 78 n record high latitude geomagnetic field variations for the last 10000 years although the paleomagnetic signal in the lake linnevatn core has probably been modified by subsampling effects application of a latitude invariant transformation procedure yields logs with directional amplitudes similar to the transformed holocene paleosecular variation master curve from the uk stratigraphic correlations based on pattern recognition suggest maximum ages of the lacustrine sediments in agreement with 14c age determinations age depth curves based on more than six magnetic datum horizons from each core reveal an abrupt increase in sedimentation rate in linnevatn from about 0 4 mm year 1 to about 0 8 mm year 1 around 2500 b p vertical inclinations in both cores between about 3500 and 6000 b p are interpreted to reflect a stationary magnetic pole in the region of the sampling sites this adds further arguments for the proposed sudden dipole shift recognized around 3500 b p in paleomagnetic records from high latitude 63 n lacustrine sediments in alaska

a comparison of holocene paleomagnetic secular variation records from north america the comparison of nine holocene 0 12 000 years b p records of paleomagnetic field secular variation psv obtained from across north america indicates that distinctive field features in inclination and declination often can be traced for more than 4000 km without significant change in pattern independent age determinations corroborate these correlations while also suggesting that westward or eastward drift is not significant on the other hand northward drift may be a significant process at least between 1500 and 5500 years b p several methods of analyzing the overall psv character point to circularity vector looping as a preferred means of defining coherent space time vector variations which are termed waveforms a few distinctive waveforms each discernible for about 1400 years dominate psv across north america during the holocene 4 5 loops and 2 loops being associated with clockwise and counterclockwise circularity respectively the clockwise loops appear to be periodic occurring every 2400 years and most likely result from the recurrence of a distinctive regional dynamo source in the outer core the pattern of circularity noted in north america during the last 3000 years correlates in time with similar circularity changes seen globally this may indicate that there is some degree of coupling between different regional dynamo sources within the outer core the fact that some north american waveforms are almost identical to waveforms observed elsewhere around the world at different times may indicate that similar distinctive regional dynamo sources recur randomly throughout the outer core

diagnostic and prognostic numerical circulation studies of the south atlantic bight some of the results from a series of diagnostic and prognostic numerical simulations of the circulation in the south atlantic bight sab are described the numerical model developed for the study is a three dimensional primitive equation time dependent coordinate model with an imbedded turbulent closure submodel which should yield realistic ekman surface and bottom layers an implicit numerical scheme in the vertical direction and a mode splitting technique in time are adopted for computational efficiency a significant portion of the paper is concerned with realistic specification of initial conditions for temperature and salinity surface forcing and lateral open boundary conditions the latter are determined by a simple diagnostic geostrophic and ekman dynamics model which provides dynamically consistent temperature salinity and velocity boundary conditions it appears from an exaination of the numerical simulations that the full model yields results that share many features in common with our general understanding of the circulation of the south atlantic bight the region includes shallow shelf waters as well as deeper water dominated by the gulf stream data for synoptic skill assessment however are not available

a comparison of geomagnetic secular variation as recorded by historical archaeomagnetic and palaeomagnetic measurements palaeomagnetic methods can extend the documentary record of changes in the earth s magnetic field far into the past tolerable agreement is found between various methods demonstrating the geophysical value of palaeomagnetic experiments combining results from the different approaches of investigating secular change can lead to a better perspective and to superior models of geomagnetic field behaviour lake sediments have recently been found to hold remarkably detailed signatures of past field changes a mathematical approach to formulating an empirical description of global geomagnetic field behaviour is proposed and applied to palaeomagnetic data spanning the last 10 ka

the strain pattern in the western hellenic arc deduced from a microearthquake survey summary than loo0 earthquakes recorded during 7 weeks in 1986 in the peloponnese and surrounding areas show shallow seismicity spread over a wide area bounded by the hellenic trench the highest level in the energy release is for clusters located along the hellenic trench where changes in the morphology are seen a few clusters are also observed as at the intersection between the gulf of corinth and the gulf of patras near the lake trikhonis or between kythira and crete in the peloponnese the shallow earthquakes do not define single faults but are diffusely distributed a higher concentration and a deepening of the foci within the whole crust towards the west seem to reflect a higher strain rate there fault plane solutions exhibit a scattered pattern for earthquakes shallower than 11 km but for earthquakes deeper than 11 km they show some consistency in the orientation of p t and b axes gently dipping nodal planes are seen all over the peloponnese with the conjugate vertical plane striking in various directions and with no consistency in the sense of motion these earthquakes are located between 8 and 18 km deep and could reflect a decoupling between the lower and the upper crust reverse faulting is seen in the gulf of kefallinia and the western peloponnese the p axes trend ne sw to e w normal faulting is seen in the gulf of corinth and in central peloponnese with the t axes trending n s and in the southern peloponnese where the t axes trend nw se the deformation over the western hellenic arc revealed by fault plane solutions of earthquakes with depth between 11 and 40 km appears to be the superposition of two phenomena first throughout the aegean crustal extension with orientation roughly parallel to the trench dominates with crustal shortening and subduction along the aegean arc superimposed on this is a more local effect of the collision between the aegea and apulia which seems to induce horizontal compression roughly perpendicular to the aegean arc west of the peloponnese and epirus the compression due to this decays eastward at a distance comparable with the width of the collision zone the deepening of the brittleductile transition is likely to be due to an increase of the strain field towards the ionian islands

the acquisition of post depositional detrital remanent magnetization in a variety of natural sediments summary post depositional detrital remanent magnetization pdrm is the primary means whereby many sediments acquire their palaeomagnetic signal we have studied the acquisition of this magnetization in a variety of natural sediments our technique involves determining the magnetic direction recorded by a sediment as a function of the water content present in the sediment when the sediment experiences a change in the direction of the applied magnetic field most of the sediments used in this study were collected wet from natural environments and were preserved in their original state until they were used in the experiments grain sizes were measured by the settling tube method which led to the determination of the clay silt and sand fractions in each sediment isothermal remanent magnetization acquisition studies indicated that the predominant magnetic carriers were magnetite in the pdrm acquisition studies two distinct modes of behaviour were found for sediments with a sand content less than 60 per cent the original direction of magnetization was preserved regardless of the water content such behaviour is not consistent with a theoretical model which assumes that at high water contents the magnetic carriers remain mobile within fluid filled voids and hence are able to realign along a new magnetic field direction for sediments with a sand content in excess of 60 remagnetization along a new magnetic field direction occurred as expected provided the sediments were sufficiently wet studies of natural sediments and corresponding samples of dried and reconstituted sediments have demonstrated that the magnetic characterization of a sediment can be reliably determined even for older desiccated sediments

formation and decay of a longshore baroclinic jet associated with transient coastal upwelling and downwelling a numerical study with applications to the baltic sea 1 a numerical study is undertaken on the formation and decay of a longshore baroclinic jet lbj caused by a transient wind stress favorable for upwelling and downwelling the two pycnocline type of stratification typical for the baltic sea summertime results in a nonmonotonic growth of the lbj velocity with wind stress and time and a two branch structure of the jet with domination of a branch related to the seasonal thermocline permanent halocline in the case of fully developed downwelling upwelling the lbj associated with the fully developed upwelling downwelling is found to display baroclinic instability and its decay is accompanied by selective formation of mostly cyclonic anticyclonic eddies if upwelling or downwelling is not fully developed the lbj formed in a flat bottom basin does not display baroclinic instability unless the effect is included the effect causes a detachment of the lbj jet from the shoreline in the eastern half basin and thereby stimulates baroclinic instability as a result mesoscale eddies are generated only in the eastern half basin and only if the basin diameter d is large enough to satisfy the inequality d where ri is the baroclinic rossby radius f is the coriolis parameter and df dy effect of topography on baroclinic instability makes it possible to develop eddies even if the lbj related to partially developed upwelling or downwelling is considered at 0

alluvial sedimentation patterns in the munster basin ireland post caledonian southern ireland witnessed the development of a ne sw orientated half graben known as the munster basin more than 7 km of non marine sediments accumulated in the basin during the late middle and late devonian marine conditions became established in the southern part of the basin at the end of the devonian in this paper a model for the evolving style of sedimentation in the basin and its periphery is constructed with the aim of identifying the major factors which controlled sedimentation patterns and the architecture of the basin fill the depositional history of the basin is considered in terms of four successive episodes during episode i gravelly alluvial fans flanked upland areas around the northeastern and northern basin perimeter these graded southwestwards to a floodplain dominated by sheet floods in the western part of the basin the first of three major fluvial influxes into the basin commenced during episode ii the first influx developed into a large sandy braided complex the sediment was derived from a distant source area located to the north and west of the basin and was transported diagonally across the basin towards the southeast episode iii witnessed a second influx which drained into the basin from the northeast and north river channels were of low sinuosity and graded distally to an ephemeral playa lake episode iv was marked by a third fluvial influx from the west and northwest this was confined to the southern half of the basin and drainage was directed towards the east the fluvial distributaries were flanked by permanently flooded overbank areas this influx coincided with the first marine transgression which advanced westwards the end of episode iv coincided with the beginning of the carboniferous and was marked by a major marine transgression sediment input to the basin was influenced by stable areas occupied by granitic plutons on either side of the basin and a southward downthrowing fault along its northern margin the drainage direction was principally controlled by e w trending within basin faults and an e w trending stable area located to the south the basin was fundamentally of the axial transport type the main drainage having been directed towards the east though there was also a strong lateral influx from the north northwest and northeast stable areas around the basin periphery resulted in either no sediment preservation or sequences of multistorey channel deposits while thick sequences dominated by fine grained floodplain or overbank deposits characterized areas of higher subsidence rate within the basin movement on the northern basin margin fault was probably the major cause of the first fluvial influx while regional subsidence of the basin and its northern periphery resulted in the second influx the third influx was a response to local subsidence in the southern part of the munster basin this also contributed to the simultaneous westward marine transgression in this area towards the end of the devonian source area denudation and retreat in association with a sea level rise were ultimately responsible for terminating the alluvial regime in the munster basin

wind produced water exchange between the deep basins of the baltic sea abstract the renewal of oxygen rich water in the deep basins of the baltic sea depends mainly on the proper wind conditions strong westerly winds over the western baltic yield an inclination in sea level from the skagerrak to the baltic proper and strong inflow of saline and oxygen rich water into the western baltic this water then penetrates into the bornholm basin numerical model runs show that northerly and easterly winds are necessary in order to transport these waters from the bornholm basin into the gotland basin a comparison between model results and observations in the bornholm basin and in stolpe channel supports these results

archaeomagnetic investigations of geomagnetic secular variations bulgarian archaeomagnetic directions and intensities show a satisfactory agreement with those for ukraine and paris bauer plots of declination against inclination show both clockwise and anticlockwise looping through the last eight millennia the necessity for accurate dating of samples studied is stressed

a 3500 year paleomagnetic record of late holocene secular variation from blue lake idaho three meters of sediment from blue lake idaho have provided a 3500 year paleomagnetic record with low scatter and good serial correlation comparison of the blue lake record with the record from fish lake oregon reveals differences of up to 963 years for secular variation extrema based on the separate radiocarbon chronologies for blue lake and fish lake to achieve a common time scale the blue lake record was redated using the fish lake ages for five major inclination extrema with this adjusted time scale the excellent correspondence between the declination records confirms the extremal correlations and demonstrates that paleomagnetic correlations may provide more accuracy for relative stratigraphy than radiocarbon dating the morphological agreement between the smoothed records documents secular variation features with wavelengths of 1000 2000 years and amplitudes of 10 20 in inclination and 20 30 in declination examination of the unsmoothed records indicates that features with wavelengths of less than a few hundred years and amplitudes of less than 5 are probably noise

time series analysis of the 10 000 yr geomagnetic secular variation record from se australia summary a 10 000 yr continuous secular variation record from intensively dated lake sediments in se australia has been subjected to periodogram and maximum entropy method analysis tests on synthetic data reveal some of the limitations of the latter method particularly when applied to complex number series anticlockwise precession of the magnetic vector at a period of 5000 1000 yr is tentatively ascribed to dipole precession and clockwise precession at a period of about 2800 yr is probably due to westward drift of features of the non dipole field the effect of calibrating the radiocarbon time scale is important and results in periodicity shifts of up to 25 per cent even for well dated lacustrine sequences power spectra are poorly constrained it is thus possible that the geomagnetic secular variation on a time scale of thousands of years is more uniform than often supposed mismatches between declination and inclination spectra can arise as a natural consequence of certain types of source mechanism and should not be simply attributed to figments of the analysis employed

a model for the development of the irish variscides a clear correlation exists in the southern irish variscides between extensional structures which controlled late palaeozoic sedimentation in the munster basin and contractional thrusts and folds of end carboniferous age this correlation is interpreted to indicate that the extensional structural framework of the basin including a basal low angle detachment and an array of superjacent normal faults was reused during transpressive inversion of the basin to produce the fold thrust belt the extensional framework which in turn was to some extent derived by reactivation of caledonian structures therefore exerted a fundamental control on the geometry and style of contractional deformation it is not evident that the detachment had a discrete link to the fold belt in south wales or the main variscan orogen in europe