esr dating of fault movement using various defect centres in quartz the case in the western south fossa magna japan the dates of movements of the itoigawa shizuoka tectonic line i s t l and minobu fault in the western south fossa magna have been obtained by esr dating measurements were made on various lattice defects of the ohc ge al and e centres in quartz grains of fault clay and quartz veins intruded at the time of movement all the dates obtained from these centres in quartz grains from two localities of the i s t l and iwo localities of the minobu fault fall in the range of 0 30 0 55 ma this suggests that all the centres were annihilated completely and that the obtained age can be admitted as the actual data of the latest fault movement meanwhile esr dates of quartz vein and fault clay in other localities locations 3 6 7 are divided into 0 30 0 55 ma and 1 5 2 0 ma which suggest incomplete resetting the dates of 0 30 0 55 and 1 5 2 0 ma might correspond to the clino unconformities observed in plio pleistocene sequence of this region

an inverse modeling study in fram strait part i dynamics and circulation abstract in order to reconstruct the circulation in the northern greenland sea between 77 n and 81 n and the exchanges with the arctic ocean through fram strait a variational inverse model is applied to the density field observed in summer 1984 during the mizex 84 experiment an estimate of the three dimensional large scale pressure field is obtained in which the solution is decomposed into a limited number of vertical modes and the mode amplitudes are described by piece wise polynomials on a finite element grid the solution should be consistent with a frictional depth integrated vorticity balance and with the density data the global model parameters are tuned to ensure agreement between the retrieved geostrophic velocity and independent currentmeter data in a companion paper schlichtholz and houssais 1999b the same method but without dynamical constraint is applied to the same hydrographic dataset to perform a detailed water mass analysis and to estimate individual water mass transports a comprehensive picture of the summer geostrophic circulation in fram strait is obtained in which northward recirculations in the east greenland current egc and various recirculations from the west spitsbergen current wsc to the egc are identified it is suggested that the branch of the wsc following the upper western slope of the yermak plateau turns westward beyond 81 n and recirculates southward along the lower slope then merging with a westward recirculating branch south of 79 n at 79 n a southward net transport of 6 5 sv is found in the egc which combined with a northward net transport of only 1 5 sv in the wsc results in a fairly large outflow of 5 sv from the arctic ocean to the greenland sea the inverse solutions show that in summer the local induction of vorticity by the wind stress curl or by meridional advection of planetary vorticity should be small so that in the egc and in the wsc the vorticity balance is mainly achieved between the bottom pressure torque and dissipation of vorticity through bottom friction a substantial barotropic flow associated with along slope potential energy gradients is indeed identified on both sides of the strait

spatial variability of major frontal systems in the north atlantic norwegian sea area 1980 81 abstract locations of strong frontal systems in the upper 350 m of the north atlantic norwegian sea area are identified using data from nearly 2300 axbts deployed over a period spanning both winter and summer seasons approximate bounds on frontal widths and frontal meandering are given and the variations in frontal locations with depth are also described seasonal variations in the horizontal and vertical structure of the fronts are examined sea surface expression of fronts is shown to decrease in summer months and a general dependence of frontal locations on bathymetry is seen

variability in the greenland sea as revealed by a repeated high spatial resolution conductivity temperature depth survey this paper deals with the mesoscale variability of water masses in the greenland sea and its implications for bottom water formation the results are based on two conductivity temperature depth surveys performed in successive years the same section in the central greenland basin was sampled in 1989 and 1990 an additional transect across fram strait was carried out in 1990 the transects extended from shelf to shelf with a station spacing of 18 km throughout the data set reveals a surprisingly strong horizontal variability of space scales between 20 and 60 km in the entire greenland sea not only in the frontal zones the area investigated is subdivided into four hydrographical regimes for which mesoscale variability is discussed in detail a noteworthy result is the major change of the deep sea thermal structure within 1 year the classical pattern with upward doming cold waters in the central basin was found in 1989 but was replaced by a capped structure with a warm intermediate layer in 1990 the implications of the observed changes are discussed with respect to deep water formation a mechanism based on differential compressibility is proposed which is able to introduce negative heat input selectively into the bottom layer it is shown that the fine structure of temperature profiles observed in summer can be used as a tracer for the occurrence of deep convection during the preceding winter convective depths are concluded of about 2200 m for 1989 and of only about 250 m for 1990

esr studies for absolute dating of fault movements the principle of absolute dating of fault movements is based on the initialization or resetting of some clock system by faulting in the case of esr dating heating is more effective in resetting esr signals than fracturing according to a computer simulation of resetting by shear heating during faulting the esr signals can never be completely reset at depths of less than 100 200 m below the surface of the earth therefore esr samples must be collected from depth by coring or tunnelling or from outcrop with consideration of the rate of exhumation of the fault outcrop in general unpaired electrons trapped at lattice defects in crystals can diffuse much more easily than atoms hence samples for other dating methods which are based on the diffusion of atoms should be collected at even greater depth on the other hand if no esr signal is observed from unfractured quartz in the wall rocks one may directly determine the age of the fault movement using esr signals in the fractured quartz whose precursors were formed by faulting the age obtained t should then satisfy the following relationship t b t t e where t b and t e are the ages of the beginning and end of the fault movements and it may show the time of a fault movement

esr isochron dating of the nojima fault gouge southwest japan using icp ms an approach to fluid flow events in the fault zone

a deglacial middle holocene record of biogenic sedimentation and paleoproductivity changes from the northern norwegian continental shelf 1 the relative proportions of marine organic carbon and biogenic carbonate in a high resolution record from a glacial trough on the northern norwegian continental shelf were used to decipher changes in biogenic sedimentation and paleoproductivity from the last deglaciation to the middle holocene decadal scale to century scale oscillations in biogenic sedimentation and surface ocean productivity recorded in the andfjorden sediments are synchronous with abrupt climate changes in open oceanic and atmospheric regimes of the high northern latitudes following several fluctuations during the bolling allerod interstadial the most dramatic drop in marine organic carbon and biogenic carbonate proportions occurred during the younger dryas however many short term and low amplitude events during the preboreal and the holocene have also affected biogenic sedimentation in the outer andfjorden apparently these abrupt changes in biogenic sedimentation were caused by the suppression of a potential upwelling center in the outer andfjorden by variable atlantic water inflow over the past 14 000 years the adjustment of decadal high productivity coastal systems to freshwater forced multiple cooling events during the late glacial to middle holocene highlights the impact of global climate changes on the climate sensitive local ecosystems off coastal norway

mixing in the west spitsbergen current abstract twenty eight profiles of temperature and salinity down to 1 km depth have been measured in the area north from the coast of svalbard to latitude 84 40 n between 0 and 32 e longitude they show atlantic waters of the west spitsbergen current entering the arctic ocean in a bifilimentary mode one filament following the coastline and the other 300 km farther north apparently following the continental shelf break the profiles show these filaments mixing into the ambient water in a series of intrusive layers which are remarkably uniform over distances of hundreds of kilometers a triple peak structure at the atlantic water maximum is the dominant oceanographic characteristic of the area with salt fingering occurring on the upper surface of the cold intrusions and indications of double diffusive exchanges through the lower surface a system or eddies or meanders is postulated as the mechanism for the production of multiple fronts allowing the intrusive layers to extend to distances much greater t

late quaternary lithofacies provenance and depositional environments 12 30 cal ka north and south of the denmark strait this paper describes the lithofacies and chronology of cores from north and south of the denmark strait for a period when ice sheets flanked both sides of the strait a wide range of sediments have been recovered indicating a complex of depositional processes jm96 1229ggc1 1047 m water depth is from the base of the nw iceland slope at the southern edge of the blosseville basin whereas jm96 1226ggc4 retrieved sediments south of the sill in 1519 m of water additional information is based on jm96 1220ggc2 and 1221ggc2 which were recovered from the upper w iceland slope at 500 m water depth below the latra moraine of possible last glacial maximum age and upslope of jm96 1226 ams 14c dates indicate that jm96 1226 and 1229 span the last 10 to 27 32 ka bp whereas jm96 1220 and 1221 recovered sediments dated between ca 8 and 18 ka bp closely spaced radiocarbon dates on jm96 1229 indicate an erosional hiatus of 7 ky between 12 and 19 cal ka lithofacies descriptions are based on visual descriptions and x radiographs jm96 1229 consists of fine grained sediments sometimes graded with scattered ice rafted debris whereas jm96 1226 consists largely of beds of matrix supported diamicton provenance indicators mass magnetic susceptibility and geochemistry for jm96 1229 support the delivery of sediments from nw iceland but there is a substantial difference in these properties between sediments from the w iceland upper slope and the sediments in jm96 1226 south of the denmark strait this indicates that the diamictons on the floor of the strait did not derive entirely from the iceland ice sheet and adjacent upper slope the general absence of sediments 12 cal ka on the slopes and floor of the denmark strait indicates that denmark strait overflow waters inhibited sediment accumulation during the holocene between ca 12 and 30 cal ka however a combination of more proximal sediment sources ice sheets and reduced thermohaline activity resulted in the accumulation of sediments on the slopes and basin floors

sortable silt cycles in svalbard slope sediments 74 0 ka the grain size of sortable silt ss 10 63 m was studied in sediment core jm04 025pc from a sediment drift on the lower part of the western svalbard slope the study aims to reconstruct the bottom current activity and intermediate water circulation in the greenland sea the ss record covers the last 74 ka and shows consistent millennial scale oscillations in grain size the youngest part of the record 25 ka is well correlated with the few available previously published reconstructions of grain size from the north atlantic ocean and the nordic seas fining of ss occurs during four well known regional cold climatic intervals the 8 2 ka cold spell the younger dryas and north atlantic heinrich events h1 and h2 as well as during a local meltwater event at 14 4 14 7 ka possibly coinciding with the older dryas also before 25 ka grain size oscillated in pace with the northern hemisphere climate with finer grain sizes during cold periods and coarser grain sizes during warm periods the fining of ss indicates reduced bottom current strength and reduced water exchange between the greenland sea and the arctic ocean during regional climate cooling events and probably also reduced deep ocean convection in the greenland sea gyre

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

holocene climate variability of the norwegian atlantic current during high and low solar insolation forcing 1 a high resolution sediment core from the voring plateau has been studied to document the centennial to millennial variability of the surface water conditions during the holocene climate optimum hco and the late holocene period lhp in order to evaluate the effects of solar insolation on surface ocean climatology quantitative august summer sea surface temperatures sssts with a time resolution of 2 40 years are reconstructed by using three different diatom transfer function methods spectral and scale space methods are applied to the records to explore the variability present in the time series at different time scales the ssst development in core md95 2011 shows a delayed response to northern hemisphere maximum summer insolation at 11 000 years b p the record shows the maximum ssst of the hco to be from 7 3 to 8 9 kyr b p which implies that the site was located in the regional warm water pool removed from the oceanic fronts and arctic waters superimposed on the general cooling trend are higher frequency variabilities at time scales of 80 120 210 320 320 640 and 640 1280 years the climate variations at the time scale of 320 640 years are documented both for periods of high and low solar orbital insolation we found evidence that the submillennial scale mode of variability 640 900 years in ssst evident during the lhp is directly associated with varying solar forcing at the shorter scale of 260 450 years the ssst during the lhp displays a lagged response to solar forcing with a phase locked behavior indicating the existence of a feedback mechanism in the climate system triggered by variations in the solar constant as well as the role of the thermal inertia of the ocean the abruptness of the cooling events in the lhp especially pronounced during the onsets of the holocene cold period i approximately 2300 years b p and the little ice age approximately 550 years b p can be explained by a shutdown of deep convection in the nordic seas in response to negative solar insolation anomalies these cooling events are on the order of 1 5 c

the east greenland polar front in autumn closely spaced salinity and temperature measurements in the region of the east greenland polar front from 75 n to 79 n in october november 1981 are presented the return atlantic current rac having a core of relatively warm and saline atlantic intermediate water aiw t 0 5 to 3 0 c s 34 9 to 35 0 was found everywhere along a steep front separating it from the colder fresher polar water a narrow frontal jet was found to have velocities greater than 0 80 m s where the station density was great enough to resolve its concentrated character notable fine structure was present especially in the warm aiw just east of the front a cold saline water forming a knee in the temperature salinity correlation was present in the upper margins of the rac the knee is formed primarily by warm aiw or atlantic water flowing under the upper layers of water flowing from the arctic ocean calculations are presented to show that an initially isothermal underflow could be modified to a thick thermocline by double diffusion calculations of the rate of cooling of fine structure elements by double diffusion indicate that the fine structure would have a limited lifetime about 12 days if its waters were not continually replenished

the contribution of the greenland and barents seas to the deep water of the arctic ocean the deep waters of the arctic ocean are traditionally held to be fed by an influx of norwegian sea deep water nsdw via the northward flowing west spitsbergen current discrete sample and ctd observations obtained from the greenland spitsbergen passage in august 1981 during the transient tracers in the ocean tto north atlantic expedition showed a 100 m thick layer of modified greenland sea deep water gsdw colder and fresher than nsdw at 2500 m spreading northward along the bottom of a deep unimpeded channel underneath the nsdw since the available data indicate that arctic ocean deep water aodw has a higher salinity than nsdw mixing of nsdw and gsdw can not produce aodw therefore other sources such as the peripheral arctic shelf seas must contribute dense saline water to the arctic ocean concentrations of 137cs and 90sr observed in aodw are greater than those observed in gsdw and nsdw the concentrations of these radionuclides on the barents sea shelf are sufficiently high and in the correct relative proportions to support this proposition

late glacial and holocene palaeoceanography of the north icelandic shelf high resolution gravity cores and box cores from the north icelandic shelf have been studied for palaeoceanographic history based on lithological and biostratigraphical foramin iferal data results from two outer shelf cores covering the last 13 6 k 14 c yr bp are presented in this paper the sediments accumulated in north south trending basins on each side of the kolbeinsey ridge at water depths of ca 400 m sedimentation rates up to 1 5 m kyr 1 are observed during the late glacial and holocene the vedde and saksunarvatn tephras are present in the cores as well as the hekla 1104 a new tephra kol gs 2 has been identified and dated to 13 4 k 14 c yr bp and another tephra geochemically identical to the borrobol tephra has been found at the same level at present the oceanographic polar front is located on the north icelandic shelf which experiences sharp oceanographic surface boundaries between the cold east icelandic current and the warmer irminger current past changes in sedimentological and biological processes in the study area are assumed to be related to fluctuations of the polar front the area was deglaciated before ca 14 kyr bp but there is evidence of ice rafting up to the end of the gs 1 greenland stadial 1 younger dryas period increasing again towards the end of the holocene foraminiferal studies show a relatively strong gs 2 pre 13 kyr bp palaeo irminger current followed by severe cooling and then by unstable conditions during the remainder of the gi 1 greenland interstadial 1 bolling allerod and gs 1 younger dryas another cooling event occurred during the preboreal before the holocene current system was established at about 9 kyr bp after a climatic optimum between 9 and 6 kyr bp the climate began to deteriorate and fluctuate copyright 2000 john wiley sons ltd

north atlantic sea surface temperatures and their relation to the north atlantic oscillation during the last 230 years august sea surface temperatures assts based on fossil diatom assemblages are generated with 2 year average resolution from a 230 year long sediment core rapid 21 12b from the reykjanes ridge in the subpolar north atlantic the results indicate a warming trend of 0 5 c of the surface waters at the reykjanes ridge for the last 230 years superimposed on this warming trend there is a multidecadal to decadal asst variability of up to 1 c the interval from the 1770s to the 1830s represents the coldest period whereas 1860 1880 represents the warmest period during the last 230 years the last 25 years is characterized by a warming trend showing strong decadal asst variability with several warm years but also the coldest years since the 1820s the time of these cold years in the mid 1970s 1980s and 1990s correspond with the documented great salinity anomalies gsa in the north atlantic suggesting increased fluxes of cold low salinity waters from the arctic during the last decades the asst record and the august north atlantic oscillation anao index show similar multidecadal scale variability indicating a close coupling between the oceanic and atmospheric patterns the asst record shows a negative correlation with the anao indicating cold asst during the positive anao trend and vice versa results suggest that the wind driven variation in volume fluxes of the north atlantic surface waters could be the major mechanism behind the observed relationship

the distribution of aluminium in the greenland sea and its relationship to ventilation processes during two cruises to the greenland sea in 1988 and 1989 a total of 690 on board aluminium al determinations were performed on samples collected from profiles located along four transects in the greenland sea as part of the greenland sea project al concentrations range from extremely low values 0 4 nm in the polar waters of the east greenland current draining the arctic ocean to 17 9 nm in the newly formed norwegian sea deep water nsdw at the periphery of the greenland gyre the al content in the component water masses serves to constrain the make up of these water masses from the various mixing products of the region the enrichment of al in the nsdw both at its site of formation within the greenland sea up to 17 9 nm and in the lofoten basin of the norwegian sea up to 40 3 nm leads to the conclusion that there must be an additional external source of al to these water masses the apparent inability of water column or sedimentary diagenetic processes to provide this enrichment and the observation of enriched al values associated with a high salinity shelf brine leads us to the conclusion that these brines may be responsible for the observed enrichments the high concentration of al in the greenland sea deep water compared with the water masses that produce it suggests that al may be acting as an inverse tracer of the processes that ventilate this basin by convective overturn i e the al concentration which increases with time as a result of continuous brine or other external inputs is reduced during convective events it is also argued that this flushing of elevated al water during convective events may have a similar counterpart in the iceland sea and that this mechanism could go some way toward solving the al deficit that exists between the enriched north atlantic deep water and its depleted precursor water masses observed in the intermediate waters of the greenland and iceland seas

lateglacial and early holocene climatic oscillations on the western svalbard margin european arctic abstract a multi proxy sediment core record on the continental margin off western svalbard european arctic reflects large climatic and oceanographic oscillations at the lateglacial early holocene transition based on studies of planktonic foraminifera their stable oxygen and carbon isotopic composition and ice rafted debris we have reconstructed the last 14 cal ka bp the period 14 13 5 cal ka bp was characterized by highly unstable climatic conditions short lived episodes of warming alternated with meltwater pulses and enhanced iceberg rafting this period correlates to a regional warming of the northern north atlantic an overall decrease in meltwater took place during the deglaciation 14 10 8 cal ka bp the late younger dryas and subsequent transition into the early holocene is characterized by a reduced flux of planktonic foraminifera and increased iceberg rafting a major warming took place from 10 8 to 9 7 cal ka bp the influence of meltwater ceased and the flux of warm atlantic water increased from 9 7 to 8 8 cal ka bp the western svalbard margin surface waters were significantly warmer than today this warm period the thermal maximum was followed by an abrupt cooling at 8 8 cal ka bp caused by an increased influence of arctic water from the arctic ocean the results document that the european arctic was very sensitive to climatic and oceanographic changes at the end of the last glacial and during the holocene

high resolution alkenone sea surface temperature variability on the north icelandic shelf implications for nordic seas palaeoclimatic development during the holocene the palaeoceanography of the northern icelandic shelf for the holocene period was reconstructed from alkenone indices measured in core jr51 gc35 this contains a continuous record of holocene sedimentation spanning 0 10 2 cal kyr bp with a resolution of 20 yr cm we have identified a general holocene cooling trend that has superimposed millennial scale oscillations of 28c their timing is in close agreement with the timing of glacier advances in northern iceland for the later half of the holocene the alkenone sea surface temperature sst record from jr51 gc35 correlates with proxy data for the strength of nadw formation recorded in cores south of iceland this is interpreted as evidence of a close connection existing between north icelandic sea surface temperatures and the north atlantic meridonal overturning circulation the timing of the millennial scale sst variability in our core off north iceland is found to be out of phase or anti phased with the sst variability of a record in the eastern nordic seas md952011 this suggests that the evolution of holocene climate in the nordic seas was more complex than previously proposed and it is likely to be caused by differential responses of the irminger and norwegian currents and modulated by changes in atmospheric circulation analogous to the north atlantic oscillation

variability of frontal structure in the southern norwegian sea abstract a hydrographic survey ctd was conducted in the vicinity of the iceland faeroe island oceanic front iff north of the faeroe islands during october 1980 it consisted of ctd transects on three horizontal scales ranging from kilometers to hundreds of kilometers intense interleaving of different water masses is found in the iff in the presence of horizontal current shear significant alongfront variability on scales of about 50 km is present consistent with earlier findings estimates of cross front heat flux of 5 16 104 w m 2 and salt flux of 1 58 g m 2 s 1 are greater than those found for the antarctic polar front but are of the same order as eddy heat flux across the iff found by willebrand and meincke evidence suggests that intrusive interleaving in the iff on 50 m vertical scales is driven by double diffusive convection

temperature reconstructions for sw and n iceland waters over the last 10 cal ka based on δ18o records from planktic and benthic foraminifera abstract we have obtained 18 o carb data from planktic n pachyderma s and benthic foraminifera c lobatulu s m barleeanu s from eight cores between 40 and 500 m water depth along the sw core b997 347 and n iceland margins cores b997 321 324 327 328 329 330 and 332 that span the last 10 cal ka sampling resolution varies between centuries to millennial scales over this time range changes in 18 o carb in foraminifera are the product of changes in the global ice volume and the temperature and salinity of the water at the level in which the foraminifera live in order to evaluate the relative roles of these variables we investigate 1 the salinity s and 18 o water values for present day waters off iceland and 2 the present day relationships between 18 o carb or calcite values of foraminifera and water column temperature and salinity data we estimate the average error in the temperature estimate to be 0 3 c based on a monto carlo simulation of the various error terms we argue that around iceland the variations in 18 o carb of both benthic and planktic species over the last 10 cal ka are principally controlled by temperature variations while salinity changes prove less important spatial and temporal changes are examined for both bottom water and 50 m water temperature reconstructions based on six and four cores respectively reconstructed temperatures for sites around sw n iceland indicate that surface and seafloor water temperatures were warmest in the early holocene 10 6 cal ka beginning at 6 cal ka surface and seafloor temperatures began to cool in n iceland and to become less stratified in sw iceland over the last 5000 yrs sea surface temperature variations have been 1 c for 50 of the observations with a maximum range of 2 5 c a profound decrease in temperature of 1 5 c is recorded in our fjord site b997 328 during the little ice age an abrupt earlier cold event is well expressed in at least three n iceland cores around 5 cal ka

the gin sea a synthesis of its physical oceanography and literature review 1972 1985 abstract a synthesis and review of the physical oceanography of the gin sea greenland iceland and norwegian seas is presented an accompanying bibliography is included from 1972 through 1985 some 1986 works are also noted emphasis is placed on describing the gin sea as a major semi enclosed basin that plays a role unique among the world s oceans by providing a strong two way advective exchange between the ice covered polar sea and the north atlantic ocean and at the same time acting as the primary site for northern hemisphere bottom water formation the water masses for the gin sea are defined in a manner as consistent as possible with the literature the large scale oceanographic and meteorological factors influencing the water mass formation and circulation are described a sample calculation of the various horizontal and vertical thermohaline driven exchanges is given

unstable younger dryas climate in the northeast north atlantic the younger dryas stadial greenland stadial 1 has long been recognized in proxy records throughout the north atlantic region as a stable cool period that started and ended abruptly however modeling experiments in which the younger dryas cooling was forced by meltwater predict much more unstable climatic conditions compared to the proxy records here we present evidence of a climatically unstable younger dryas based on a decadal resolution marine proxy record from the norwegian continental shelf this record shows that the north atlantic was characterized in the early younger dryas by arctic water and an increasing accumulation of fresh surface water that peaked at 12 500 calendar yr b p for 300 yr during the late younger dryas the sea surface temperatures fluctuated between glacial values 2 c and interglacial values 10 c on a subdecadal to multidecadal time scale this period of extreme instability preceded the more stable and warm holocene starting ca 11 500 calendar yr b p these results are consistent with modeling experiments that link the younger dryas climate changes to fluctuations of the north atlantic thermohaline circulation

geochemical profiles in the central arctic ocean their relation to freezing and shallow circulation temperature salinity nutrient tritium and oxygen isotope data collected during the lomonosov ridge experiment along a drift track between the makarov and fram basins over the lomonosov ridge are presented the relationship of these quantities to the processes that maintain the halocline in particular to the production of more saline waters by addition of brines formed during the freezing of seawater is described the results support the idea that the wide continental shelves of the arctic ocean play an important role in maintaining the halocline productivity and to the chemical and physical effects of freezing sea water a comparison of this ocean with its low productivity at least during winter with other oceanic regions should help to elucidate some of the effects of biological activity on marine chemistry for example trace metal cycling and speciation aagaard et al 1981 discussed the way in which the cold waters of the halocline which lie immediately below the surface mixed layer and extend to the top of the warm atlantic layer could be produced on the wide continental margins surrounding the arctic ocean the processes in volve freezing with release of highly saline brines having a temperature close to the freezing point of surface sea water this water flows over the shelves and into the central basin sinking then to the appropriate density surface the distribu tions of various chemical parameters will be affected in predictable ways by these processes as a part of the lomonosov ridge experiment lorex which ran from late march until the end of may 1979 a program was undertaken aimed at describing more accurate ly the hydrography of the central arctic ocean and studying the geochemistry of selected trace elements in this unusual environment to this end water samples were collected from a drifting ice station lorex satellite camp 1 for the measurement of salinity silicate phosphate 5 80 trace metals moore 1981 1983 carbon 14 tritium helium 3 caesium 137 caesium 134 strontium 90 plutonium ameri cium h d livingston et al manuscript in preparation 1983 alkalinity and ph ice cores were collected to investi gate the possibility of deducing the extent of temporal changes in the tritium content of the surface waters

resetting experiment of e centres by natural faulting the case of the nojima earthquake fault in japan abstract the resetting state of e centres in quartz in fault clay gouge has been examined using the nojima earthquake fault that moved during the southern hyogo prefecture earthquake in 1995 as a result the e centres have never been reset by this faulting event furthermore there is no regular tendency among the d e values obtained from the grain samples and the plateau region of the esr ages does not exist in the case of the nojima fault therefore it is not possible to judge the complete resetting of esr signals by natural faulting on the other hand the increase of radiation sensitivity of the e centres may be ascribed to the formation of the precursors by rays emitted from the radioactive elements adhered around the grain samples since the adherence of the radioactive elements may begin with fracturing the quartz grains by faulting the esr ages obtained from the unsaturated e centres with high radiation sensitivity may give the age of beginning of the fault movements the esr ages obtained from these unsaturated e centres of the nojima fault 0 88 0 3 ma 1 51 0 51 ma or 1 07 0 36 ma 1 75 0 59 ma are consistent with the geological age estimate of the beginning of the fault movements

oceanographic conditions in the marginal ice zone north of svalbard in early fall 1979 with an emphasis on mesoscale processes during september october 1979 the norwegian remote sensing experiment was carried out in the marginal ice zone north of svalbard convergence of the ice cover is correlated with along ice edge winds with the ice to the right while divergence occurs during office winds or calm conditions a wind driven ice edge jet is observed wind driven upwelling of the pycnocline of up to 7 m was present along the ice edge during a 10 to 15 m s easterly wind event the upwelling is due to ekman divergence at the ice edge caused by higher wind stress over ice than over open water the ice edge meanders with a scale of 20 40 km and sheds eddies with a scale of 5 to 15 km into the open water this scale is of the same order as the rossby radius of deformation eddies with the same scale are also seen in the conductivity temperature and depth observations conditions during the experiment were such that barotropic instabilities could have generated these eddies

esr dating of north anatolian turkey and nojima japan faults abstract electron spin resonance esr ages were obtained on al e and oh centres in quartz extracted from fault gouge from the north anatolian fault naf in turkey and the nojima fault nf in japan the data were used to test two contradictory criteria which have been used for the recognition of complete signal resetting during the fault movement the grain size plateau and the isochron models the grain size plateau method predicts decreasing ages with decreasing gain sizes because the fine grains are more intensely stressed during the faulting process for those grains that were completely reset a plateau of constant age is obtained and esr ages derived from centres with different stress sensitivity converge the isochron method is based on the fact that newly formed fracture surfaces are exposed to external alpha and beta radiation thus smaller grains ought to accumulate larger dose values the plot of grain size versus external dose rate yields an isochron which gives the age of the fracturing process it was found that most samples yielded smaller doses with decreasing grain sizes thus confirming the underlying principles of the grain size plateau method however only one sample yielded an extended plateau over a wider particle size range and converging ages for the different centres the e centre of the sample from the nf yielded the only result that indicated that the isochron method might work the results derived from the e centre of the other samples may have been interferred with by the so called counterfeit e signal which may render those results unreliable the esr ages obtained on the naf burdigalian to pliocene agree with those derived from geological estimates sample b which gave the extended plateaux and an age estimate of 2 54 0 58 ma indicates the time when faulting began the youngest age of 0 59 0 1 ma may indicate the last major faulting episode of the naf the minimum age of 1 56 0 22 ma obtained on the sample from the nf coincides with the commencement of the uplift of awaji island at about 1 2 ma ago which was caused by movements of the nf as well as a range of other fault systems in the area

esr dating of fault gouge the effect of grain size abstract esr signals of quartz grains in fault gouge have been partially or completely reset by movements on the fault which allows the dating of the last fault movement in order to better understand the zeroing process we have studied the variation in esr signal ad and age in various grain sizes since it can be expected that larger grains will be less affected by stress than smaller grains we propose that a plateau of constant lower age for the smallest grains indicates total resetting this is confirmed in gouge from a fault in california only such samples should be used for dating

microscopic features of quartz and clay particles from fault gouges and infilled fractures in granite discriminating between active and inactive faulting abstract to assist in identifying faults that have a significant potential for displacement at or near the ground surface we carried out in depth investigations on fault gouges and a fracture infilled with clay clay vein in the kojaku granite on the tsuruga peninsula central japan we sampled several fault gouges at different stages of evolutions and clay rich infilling of a fracture with no evidence of offset based on our field observations gouge in an active fault is characterized by 1 stacked layers of different colors made up of comminuted fragments and clays and 2 injection of the fragments and clays from the gouge into the surrounding rocks indicating an accumulation of seismic induced shearing our thin section observations and x ray diffraction analyses show that all our samples are similar in the degree of fragmentation and mineral composition and because of this our study became focused mainly on microscopic features using laser diffraction particle size analysis scanning electron microscopy sem and transmission electron microscopy tem we identified the mineralogical and textural characteristics of the samples in order to improve our ability to discriminate between active and inactive faulting particle size distribution analysis showed that the gouge in the active fault contains the greatest abundance of finer particles due to multiple slip events which contrasts with the clay rich infilling of a fracture sem examination of the quartz particles showed that the gouge in the active fault contains more particles that have retained sharp and smooth crystal surfaces formed by fracturing than do either the gouges in minor faults that show no evidence of recent shear or the clay rich infilling of a fracture in contrast tem observations of very fine clay minerals approximately

palaeoceanographic reconstruction of surface ocean changes in the southern norwegian sea for the last 130 000 years based on diatoms and with comparison to foraminiferal records abstract fossil marine diatom assemblages in a sediment core from the central northern faroe slope in the norwegian sea were used to reconstruct palaeoceanographic changes in the surface water mixed layer from the last 130 000 years marine isotope stage mis 6 5 transition to mis 1 including the eemian and holocene interglacials and to compare the results with previously published results on planktic foraminifera representing the subsurface conditions of the thermocline diatom floras from mis 5 of the nordic seas have rarely been studied in detail before and never the entire period from pre eemian to present the composition of diatom species together with maxima in absolute abundance of diatoms indicate two periods of warmer sea surface temperatures correlating with the eemian and holocene interglacials respectively the eemian differs from the holocene in that the iceland faroe front never developed suggesting the cold east icelandic current originating from the east greenland current running north of iceland was reduced or more mixed with atlantic water than during the holocene and that the surface temperature and salinity gradients were weaker the northern faroe slope was in the early weichselian of mis 5d 5a mainly influenced by weaker inflow of atlantic water and stronger influence of the east icelandic current and by seasonal sea ice cover during the later part of the weichselian mis 4 mis 2 cold conditions prevailed with extensive sea ice cover except during the warmer interstadials the diatom floras were more sensitive to climate changes than the planktic foraminifera and indicate longer periods with warm surface conditions and increased influence of the warm atlantic surface water from the faroe current in mis 5 suggesting a shallower and much steeper thermocline during the transitional periods compared to today the diatoms are good indicators for atlantic water inflow and possible convection in the nordic seas not merely reflecting orbital variations in insolation as previously suggested

thermohaline circulation in the arctic mediterranean seas the renewal of the deep north atlantic by the various overflows of the greenland scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north the arctic ocean and the greenland iceland and norwegian seas collectively called the arctic mediterranean the traditional site of deep ventilation for these basins is the greenland sea but a growing body of evidence also points to the arctic ocean as a major source of deep water this deep water is relatively warm and saline and it appears to be a mixture of dense brine enriched shelf water with intermediate strata in the arctic ocean the deep water exits the arctic ocean along the greenland slope to mix with the greenland sea deep water conversely very cold low salinity deep water from the greenland sea enters the arctic ocean west of spitsbergen within the arctic ocean the lomonosov ridge excludes the greenland sea deep water from the canadian basin leaving the latter warm saline and rich in silica in general the entire deep water sphere of the arctic mediterranean is constrained by the greenland scotland ridges to circulate internally therefore it is certain of the intermediate waters formed in the greenland and iceland seas which ventilate the north atlantic these waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface induced signals into the deep north atlantic

topographic generation of an eddy at the edge of the east greenland current wadhams and squire 1983 describe an ice water eddy at the edge of the east greenland current located at about 79 and 1 e the eddy has been sighted earlier vinje 1977 and appears to occur in that general location with some regularity wadhams and squire explain the eddy in terms of baroclinic instability the criteria of griffiths and linden 1982 and phillips 1954 suggest that the east greenland current is baroclinically unstable and phillips theory indicates that the most unstable wavelength of a sinusoidal velocity perturbation is 50 km in agreement with the approximate size of the observed eddy

the ice cover in the greenland and norwegian seas the seasonal sea ice cover of the northern north atlantic is reviewed comprising the ice of the east greenland current the ice cover around svalbard and the ice of the barents sea as far east as franz josef land the review considers various types of ice cover 1 the fast ice along the coasts and in fjords including sikussak or very old fast ice of exceptional thickness 2 the transition zone between the fast ice and the main pack including the positions and causes of recurring winter polynyas and the nature of the shear zone in ne greenland 3 the constitution dynamics and seasonal extent of the drifting pack ice including interannual variations 4 the processes of air ice ocean interaction which occur in the marginal ice zone where the pack ice is influenced by an open ocean boundary

oxygen isotope composition of fjord and river water in the sognefjorden drainage area western norway implications for paleoclimate studies abstract during two cruises and one field expedition from 1996 to 1998 32 water samples from 10 stations in sognefjorden and tributary fjords and six samples from rivers draining into the fjord were obtained for oxygen isotope measurements in addition ctd profiles were obtained from all of the fjord locations the river samples show a large gradient in the oxygen isotopic composition from the outer fjord region to the rivers at the fjord head the difference is more than 6 with highest values recorded at the fjord mouth decreasing inward along the fjord the low oxygen isotope values are found in areas with a high altitude from the watershed the gradient in the river water is explained by distance to the moisture source topographic effects and temperature of precipitation the isotopic composition of the fjord waters suggest a mixing line for sognefjorden of 0 31 for a salinity change of 1 which is slightly higher than the north sea mixing line israelson buchardt 1991 and lower than the north atlantic mixing line craig gordon 1965 the river samples are not used in the calculation of the mixing because of the large differences in the isotopic composition of river water along the fjord and large seasonal differences of precipitation

contour current driven continental slope situated sandwaves with effects from secondary current processes on the barents sea margin offshore norway abstract seabed data acquired from the southern barents sea continental margin offshore norway reveal detailed morphology of large sandwave fields multibeam echosounder bathymetry and backscatter shallow seismic sediment samples and seabed video data collected by the mareano program have been used to describe and interpret the morphology distribution and transport of the sandwaves the bedforms lie on a slope dominated by relict glacial forms and muddy sandy gravelly sediments sandwave migration across small gravity mass failures of the glacial mud constrains the field initiation as early post glacial or later the contour parallel nature of the fields and crestlines normal to the bathymetry contours and the geostrophic norwegian atlantic current nwac demonstrate that the nnw flowing oceanographic circulation is the primary driving current the fields coincide with the depth range at which a transition between warm saline and underlying cooler less saline waters fluctuate across the seabed statistically rigorous measurements of height width and various parameters of slope and symmetry confirm a tendency to downstream nnw sandwave migration but with significant exceptions anomalous bedform symmetry domains within the fields are tuned to meso scale topography along relict glacial debris flow chutes indicating current focusing upstream and upper slope derived winnowed sand transport eroded from the glacial sediments is the supposed source sandwave flank slope values are comparable to the regional slope such that the gravitational vector would have a cumulative downslope migration affect unless balanced by upslope drivers perpendicular cross cutting of stoss face 3 d ripples by linear 2 d ripples in the sandwave troughs and lee faces is evidence for non synchronous episodic current variations though deep ekman transport and internal wave action are unproven here these could explain chute related tuning of bedform symmetry through funneling in the debris flow chutes and favor sand recycling thus contributing to long term maintenance of the sandwave field

an ice water vortex at the edge of the east greenland current during the y mer 80 cruise in august 1980 we observed an ice feature of 60 km diameter having the shape of a breaking wave it lay at the edge of the east greenland drift ice in fram strait with its center at 79 15 n 00 38 e and the wave was breaking upstream relative to the east greenland current two conductivity temperature and depth sections across the feature in n s and e w directions revealed warm up to 4 3 c water some 60 km inside the polar front in lenses centered at 40 m depth but with an effect to beyond 600 m the temperature anomalies were accompanied by salinity anomalies so that there was little net effect on the density profile the form of the sections together with the ice distribution observed by vertical photography from a helicopter and surface motion observed by tracking four radar transponders all suggest that the feature is a vortex produced by an instability in the polar front it has similar characteristics to vortices investigated experimentally and theoretically by griffiths and linden 1981a b 1982 and observationally by wadhams et al 1979

study of two alteration systems as natural analogues for radionuclide release and migration abstract u deposit hosted in hydrothermally altered tuffs in mexico together with weathering profiles from cameroon were studied as natural analogues of radionuclide release and migration using petrological and spectroscopic methods infrared and electron paramagnetic resonance we have distinguished successive secondary mineral parageneses and the behaviour of radionuclides in the u deposit the mineral parageneses show that uranium migration is mainly controlled by the redox potential and silica activity of the altering solutions the high silica content of the solutions is caused by the intense alteration of volcanic rocks two types of secondary clay mineral parageneses are evidenced a kaolinization intense where uranium is accumulated in the welded tuffs and a smectitization mainly developed in the underlying weakly welded tuffs several types of kaolinite have been defined according to their genesis fillings in fissures and feldspar pseudomorphs their location relative to a breccia pipe where uranium has accumulated core and rim of the pipe surrounding rhyolitic tuffs and particle morphology structural order and substitutional fecontent it is shown that the variations of the concentration of paramagnetic defect centres always more than ten times as important than those measured in weathering kaolinites are only correlated to the location of the kaolinites the highest values correspond to the breccia pipe kaolinites e g kaolinites located in the uranium accumulation zones moreover one or two main defects centres are detected depending on the intimate association of kaolinites with uranium bearing minerals besides in weathering kaolinites from u depleted laterites defect centre concentrations are correlated to the total fe203 content in bulk samples this means that the defect centre acts as a memory of the travel of uranium when this element was sorbed onto iron gels in the first stage of weathering it is concluded that paramagnetic defect centres in kaolinites might allow an efficient fingerprint of successive irradiations in the natural analogues under study and could be an useful tool to control radionuclides migration through kaolinite containing clayey materials such as those used for waste repository a better understanding of radiation efficiency as well as accurate dose ratekaolinite containing clayey materials such as those used for waste reposit estimation are needed for a quantitative tracing of the migration ofa better understanding of radiation efficiency as well as accurate dose ratekaolin radionuclide elements with this aim a simulation has been undertaken withestimation are needed for a quantitative tracing of the migration of various radiations sources we have determined for each irradiation the parameters of the paramagnetic centres created in order to understand the way they are forming the knowledge of the parameters governing the formation and the stability of the radiation centres in kaolinites allow to use this mineral as a natural dosimeter

sea surface temperature variability of the iceland faeroe front several advanced very high resolution radiometer avhrr images with spatial resolution of 1 1 3 3 km together with several concurrent aircraft deployed expendable bathythermograph axbt surveys and conductivity temperature depth ctd stations from spring 1989 are used to describe the iceland faeroe sea surface temperature sst front in the avhrr images sst fronts are located by maximizing sst single large gradient segments of the sst front do exist with some exceeding 100 km in length indicating a multiple frontal structure these single frontal lines are also segments where 2sst is small and they can be followed uniquely by a single isotherm eastward from iceland for a distance of 300 km with a 35 km sampled axbt survey two small subsurface cold eddies were located south of the surface front in an area 170 km 270 km east of iceland from a may 1987 avhrr image on 1 1 km resolution a population of seven such cold eddies are found between iceland and the faroes they appear to be generated along the surface expression of the iceland faroes front and populate the northern slope of the iceland faroes ridge historical data from towed high resolution instruments suggest that the cold eddies are 30 50 km in size and uplift the main thermocline by 150 m

assessment of fault activity by esr dating of fault gouge an example of the 500 m core samples drilled into the nojima earthquake fault in japan abstract fault gouge in the 500 m core samples drilled into the nojima fault which caused the 1995 kobe earthquake was used for electron spin resonance esr dating the fault gouge was located at a depth of 388 4 m however all the esr signals in the fault gouge had been incompletely reset by the 1995 faulting as a result of esr dating using quartet esr signals in montmorillonite the youngest esr age about 0 15 0 29 ma is obtained from the 0 3 mm sheet part of the fault gouge just on the fault plane this age corresponds to middle late pleistocene for protection against earthquake disaster active faults which have moved since late pleistocene have high seismic risk so it is important to evaluate the esr age of the fault gouge even though it does not always mean the age of the latest fault movement meanwhile the oldest age is about 0 39 0 73 ma obtained from the 33 50 mm part this age may mean not only the production age but also the age of the first fault movement along the fault plane

supercooling and energy exchange near the arctic ocean surface conductivity temperature and depth ctd measurements made north of svalbard centered around 83 n 10 e show regions in which the surface waters are supercooled to a depth of about 8 m at other locations warm atlantic waters advected into the area by the west spitzbergen current are melting the sea ice the resulting large horizontal salinity gradients cause intrusive layering with layers at depth sometimes being below their surface freezing point supercooling is explained in terms of the pressure dependence of freezing temperature and the existence of ice keels well below the surface it is noted that the potential heat sink for surface freezing provided by supercooling can be of the same order as that available from heat loss to the atmosphere at the same time an equivalent amount of ice is being melted off the keels thus constituting an ice pump

history of the greenland ice sheet paleoclimatic insights abstract paleoclimatic records show that the greenland ice sheet consistently has lost mass in response to warming and grown in response to cooling such changes have occurred even at times of slow or zero sea level change so changing sea level cannot have been the cause of at least some of the ice sheet changes in contrast there are no documented major ice sheet changes that occurred independent of temperature changes moreover snowfall has increased when the climate warmed but the ice sheet lost mass nonetheless increased accumulation in the ice sheet s center has not been sufficient to counteract increased melting and flow near the edges most documented forcings and ice sheet responses spanned periods of several thousand years but limited data also show rapid response to rapid forcings in particular regions near the ice margin have responded within decades however major changes of central regions of the ice sheet are thought to require centuries to millennia the paleoclimatic record does not yet strongly constrain how rapidly a major shrinkage or nearly complete loss of the ice sheet could occur the evidence suggests nearly total ice sheet loss may result from warming of more than a few degrees above mean 20th century values but this threshold is poorly defined perhaps as little as 2 c or more than 7 c paleoclimatic records are sufficiently sketchy that the ice sheet may have grown temporarily in response to warming or changes may have been induced by factors other than temperature without having been recorded

late quaternary glacial and deglacial history of eastern vestfirdir iceland using cosmogenic isotope 36cl exposure ages and marine cores the late glacial and deglacial history of vestfirdir nw iceland is interpreted from terrestrial field based evidence and compared with marine cores and seismic studies understanding the timing of deglaciation is complicated by a lack of dateable organic material on land uncertainties associated with interpretation of diamictons and ambiguities in radiocarbon dating new 36cl exposure ages of boulders and bedrock surfaces suggest that at least part of the coastal uplands were ice free by approximately 20 ka deglaciation of the valleys followed boulders from the crest of an end moraine in the sela river valley have a mean 36cl age of 14 6 ka 0 8 ka n 4 and the outermost moraine in the valley adjacent to kaldalonjokull has a mean 36cl age of 11 7 ka 0 9 ka n 2 tephrochronology provides a link between the terrestrial and marine sequences around vestfirdir the vedde ash ca 12 k cal yr bp is present in some offshore cores but it is absent from terrestrial sites suggesting that its distribution provides a constraint on ice extent during the younger dryas the saksunarvatn ash 10 2 0 6 k cal yr bp confirmed by geochemical analyses and radiocarbon dating is present in at least three terrestrial locations on eastern vestfirdir and in many cores from the fjords and shelf which constrains early holocene ice extent copyright 2006 john wiley sons ltd

northern hemisphere glaciation and the evolution of plio pleistocene climate noise 1 deterministic orbital controls on climate variability are commonly inferred to dominate across timescales of 104 106 years although some studies have suggested that stochastic processes may be of equal or greater importance here we explicitly quantify changes in deterministic orbital processes forcing and or pacing versus stochastic climate processes during the plio pleistocene via time frequency analysis of two prominent foraminifera oxygen isotopic stacks our results indicate that development of the northern hemisphere ice sheet is paralleled by an overall amplification of both deterministic and stochastic climate energy but their relative dominance is variable the progression from a more stochastic early pliocene to a strongly deterministic late pleistocene is primarily accommodated during two transitory phases of northern hemisphere ice sheet growth this long term trend is punctuated by stochastic events which we interpret as evidence for abrupt reorganization of the climate system at the initiation and termination of the mid pleistocene transition and at the onset of northern hemisphere glaciation in addition to highlighting a complex interplay between deterministic and stochastic climate change during the plio pleistocene our results support an early onset for northern hemisphere glaciation between 3 5 and 3 7 ma and reveal some new characteristics of the orbital signal response such as the puzzling emergence of 100 ka and 400 ka cyclic climate variability during theoretical eccentricity nodes

eemian and early weichselian 140 60 ka paleoceanography and paleoclimate in the nordic seas with comparisons to holocene conditions paleoceanographic and paleoclimatic time series were extracted from norwegian iceland and greenland sea the nordic seas sediment sequences covering the time intervals 60 140 ka and 0 15 ka on the basis of stable isotope stratigraphy planktonic foraminiferal faunas and sedimentological methods the proxy temperature records from the norwegian iceland sea display a number of high frequency and high amplitude variations within the last interglacial the eemian indicating marked changes in heat flux at high northern latitudes eemian holocene comparisons document that the climate of the norwegian iceland sea in the last interglacial was less stable than that of the present interglacial and that the distribution of surface water masses in the eemian differed from that of the holocene within the greenland sea uniform cold conditions prevailed throughout both interglacials cooling of the nordic seas as well as the initial growth of the surrounding ice sheets began within the eemian interval before the main increase in global ice volume heat flux to the nordic seas was significantly higher during the interglacials than at any time during the early weichselian 60 113 ka and no marked stadial interstadial changes in sea surface temperature and deep water ventilation are documented in the early weichselian records contrary to the pattern found in north atlantic sediment records however fluctuations in planktonic foraminiferal content planktonic 13c and ice rafting on suborbital timescales mostly comparable in number and age to the stadial interstadial fluctuations in the greenland ice cores are demonstrated in our records the ice rafted detritus records provide a more detailed account of ice sheet variability than previously known for the early weichselian period and demonstrate that glaciers advanced to sea level somewhere around the nordic seas several times during this interval

the subpolar mode water of the north atlantic ocean abstract the warm waters of the subtropical and subpolar basins of the north atlantic have tight regional temperature salinity relationships and are conventionally called the regional central waters a volumetric census of the temperature salinity characteristics of the north atlantic by wright and worthington 1970 shows that waters characterized by certain segments of the t s relationships have large volumes compared to those of other segments volumetric mode waters such mode waters appear as layers with increased vertical separation between isopycnals pycnostads the present study reports on the existence of pycnostads in the central and eastern north atlantic these subpolar mode waters are formed by deep winter convection in the subpolar north atlantic and participate in the upper water circulation of the northern north atlantic the seasonal outcropping of the pycnostads occurs within and adjacent to the north atlantic current the irminger current the east and west greenland currents and

dating past earthquakes and related sediments by thermoluminescence methods a review abstract applications of luminescence dating of geological materials have undergone extensive development and refinement since 1986 when mccalpin first attempted to date faults using thermoluminescence tl today luminescence methods offer high potential for dating paleoearthquakes and coseismic and post seismic deformation features over timescales ranging from 102 to 106 a while luminescence approaches generally do not possess the precision obtained by for example 40ar 39ar and 14c methods they offer a useful alternative approach with advantages in terms of age range and scope of material although the application of luminescence dating has in some cases been successfully described a comprehensive study outlining and defining protocols for routine luminescence methods to paleoseismology and neotectonic studies has not been forthcoming this review surveys previous attempts to apply tl techniques to paleoseismology and determination of the age of sediments associated with seismic events however while the use of tl has been a great success the wide application of tl has been hampered by the problem of daylight signal resetting

direct esr dating of fault gouge using clay minerals and the assessment of fault activity abstract the esr dating method has been applied to the fault gouge of the nojima fault the outcrop of which arose due to the southern hyogo prefecture earthquake on january 17th 1995 and to the fault gouge of the median tectonic line mtl which is a major active fault in japan without considering the resetting of esr signals the esr ages obtained for clay minerals in the fault gouges are considered to indicate the age of the beginning of the fault movements at the outcrop assuming no radon loss and the general values of water content and ray efficiency the esr ages of the fault gouges of the nojima fault and mtl are estimated as 0 55 1 16 and 6 76 9 28 ma respectively the esr age of the nojima fault is consistent with the age of the beginning of the rokko movements in the kinki districts estimated geologically on the other hand the esr age obtained from the mtl is younger than the k ar age about 11 ma which is presumably overestimated due to the existence of the source minerals in the k ar dating sample since it is geologically known that the mtl at the outcrop had moved until the late pleistocene holocene the fault movement of the mtl at this outcrop probably began at 6 76 9 28 ma b p after the intrusion of the felsitic dyke 12 16 ma which is the source rock of the fault gouge into the fault boundary the esr dating of clay minerals in the fault gouge may be effective for assessing fault activity if no quaternary deposit exists at the outcrop the younger the esr age of the fault gouge is the higher the fault activity is if not indurated and the freshest clay gouge can be collected at the outcrop the esr age of the most recent movement may be obtained from the clay gouge

electron spin resonance esr dating of pre quaternary faults in the sichuan basin sw china abstract the electron spin resonance esr dating method is thought to be limited to the quaternary period in this study we attempt to expand the esr dating range to the pre quaternary using three fault zone samples collected from faults in the sichuan basin and its surroundings we adopt a ray radiation dose of up to 2 104 gy which is much greater than that typically employed and find that the esr intensity of the e1 center a type of signal for esr dating in quartz continuously increases with the ray dose and is slightly influenced by the radiation dose rate this indicates the potential of esr to date pre quaternary faults by simulating environmental radiation under geological burial conditions we use esr to date the latest extension event in the western hubei and hunan thrust belt to 9 17 0 76 ma and the thrusting of the longmenshan fault zone toward the sichuan basin to approximately 6 14 0 73 ma conversely the saturated esr intensity of fault zone samples from the daba fault zone suggests a lack of strong tectonic activity in the southern daba fault zone in the last 10 ma our results are consistent with fission track ages and the regional tectonic evolution history therefore esr is a practical method for dating pre quaternary faults in structural and petroleum geology applications

high resolution stratigraphy of the faeroe shetland channel and its relation to north atlantic paleoceanography the last 87 kyr abstract two piston cores from the faeroe shetland channel have been investigated for stratigraphic and paleoceanographic correlation with atlantic ocean and norwegian sea records the high resolution cores have been analyzed for the downcore distribution of planktic and benthic foraminifera and oxygen isotopes ams 14 c dates and the position of ash layers i and ii form the basis for the correlation core na81 10 covers the period from isotope stage 3 to recent stage 1 while core na81 04 covers isotope stages 5a to 1 the holocene is well represented in core na81 10 by 2 m of sediment whereas it is only 50 cm in core na81 04 which is situated directly under the main core of the norwegian sea deep water outflow the transition of isotope stage 2 to stage 1 is affected by dissolution and thus is less clearly represented ams 14 c dates show that termination ia begins at 16 ka and ends at about the 13 ka level the last glacial maximum lgm defined at 19 16 ka is characterized by an ird peak faunal planktic foraminifera maxima dated at 17 3 and 18 25 ka and a high percentage of globigerina quinqueloba apparently open water conditions and circulation within the norwegian sea prevailed at least from 22 5 to 14 8 ka during the greatest part of stage 2 including the lgm and well onto termination ia a preservation maximum is observed throughout stage 2 isotope stage 3 with a nearly complete record of isotope substages is well represented in both cores oxygen isotope depletion peaks correlate with fauna minima and in time to north atlantic heinrich events h5 h1 faunal data indicate that deep water is generated within the norwegian greenland sea repeatedly since 26 ka with stops prior to 26 ka 22 5 20 8 20 5 ka and between 14 9 and 13 ka h3 h2 and h1 all isotope depletion peaks since ca 50 ka are anticorrelated with fauna and are mainly controlled by surface salinity changes isotope stages and substages are directly correlated to fauna peaks and temperature between 87 and ca 50 ka the faeroe shetland channel record shows that repeated presences of atlantic surface water and deep convection alternating with convection shutdowns have occurred within the norwegian sea greenland sea from the beginning of stages 5a to 1

a salt flux model for salinity change through ice production in the greenland sea and its relationship to winter convection 1 a salt flux model which incorporates ice formation advection and melt as well as time dependent brine drainage from frazil pancake ice has been developed for the central greenland sea in winter information from ice drifting buoys suggests that this region can be thought of as similar to a latent heat polynya with the wind blowing newly formed sea ice constantly in a southerly or southeasterly direction such that it melts in a different area from that of its formation the result is a salt refinement process generating a net positive salt flux over the ice formation region which may play an important role in stimulating deep open ocean convection by combining buoy data ecmwf meteorological data and passive microwave ice concentration data the model is used to estimate the sea ice derived salt flux over the 1996 1997 winter salt fluxes of over 40 kg m 2 were obtained in the center of the region which corresponds closely an area where a maximum depth of convection is seen in winter cruises the model gives realistic results when compared with in situ ice and oceanographic data gathered in the region and suggests that ice formation and drift play an important role in the preconditioning of surface waters for deep water formation events

paleoceanographic development in the sw barents sea during the late weichselian early holocene transition abstract the late weichselian early holocene variability of the north atlantic current has been studied with focus on the zonal component of this meridional transport during the transition from glacial to interglacial conditions the investigated sediment core is from 409 m water depth in the sw barents sea eight accelerator mass spectrometry ams 14c dates show that the core covers the last 20 000 cal yr b p with a centennial scale resolution during late weichselian early holocene planktic foraminiferal assemblages were analyzed using the 100 m size fraction and foraminiferal planktic and benthic 13c and 18o isotopes were measured furthermore a range of physical and chemical analyses has been carried out on the bulk sediment samples four time periods have been identified which represent the varying oceanographic conditions in ingoydjupet a glacial trough located off the north coast of norway in the sw barents sea 1 the late glacial before ca 15 000 cal yr b p influenced by the nearby ice sheets with high amounts of sea ice or iceberg transported detritus 2 the late oldest dryas stadial and the bolling allerod interstadial ca 15 000 12 700 cal yr b p with cold surface water conditions influenced by the collapse of the nearby ice sheets high amounts of sea ice or iceberg transported detritus and melt water and weak subsurface inflow of atlantic water 3 the younger dryas cold stadial 12 700 11 650 cal yr b p with low primary productivity and extensive sea ice cover and 4 the preboreal and early holocene 11 650 6800 cal yr b p cal yr b p with strong influx of atlantic water into the area near absence of ice rafted debris and generally ameliorated conditions in both surface and bottom water masses as seen from a high flux of foraminifera and increased marine primary production

tracing kaolinites through their defect centers kaolinite paragenesis in a laterite cameroon stable structural point defects a centers have been studied in kaolinite using electron paramagnetic resonance epr the variation in the concentration of defect centers s a has been systematically investigated along seven lateritic weathering profiles from cameroon petrological and geochemical data have been obtained on the same samples a centers result from an external irradiation of kaolinite there is no relation between defect center concentration and textural changes the fe content of the kaolinite lattice and the crystalline order of this mineral on the contrary there does exist a relationship between the integrated intensity of the epr signal on one hand and the fe and the u th content of the bulk samples on the other a possible radiation source has to be sought in the radioactive elements disseminated through the weathered materials and mainly accumulated in ferruginous materials however the present day u th content is too low to explain the measured concentration of defect centers by taking into account the efficient chemisorption of radioactive elements on poorly crystallized iron oxides the a center defects are attributed to an inherited irradiation of the kaolinites during the first stages of rock weathering and their subsequent crystallization the major implication of the proposed model is that iron oxide gels precipitate at the weathering front and adsorb the radionuclides released by primary minerals the evolution of iron oxides toward a more crystalline structure leads to a release of the radioactive elements and the a centers are thus the memory of their transit at the same time the concentration of defect centers gives an efficient fingerprint of the successive generations of kaolinites during weathering processes

distribution patterns of dinoflagellate cysts and other organic walled microfossils in recent norwegian greenland sea sediments dinoflagellate cysts and other organic walled microfossils have been studied in recent surface sediments from the entire norwegian greenland sea more than 30 taxa have been recognized of which only few show a distinct distribution pattern and allow description of four assemblages the occurrence of most taxa is related to the relatively warmer waters of the norwegian sea algidaspaeridium minutum s 1 brigantedinium simplex and impagidinium pallidum are the only species showing a preference for colder water masses two species i pallidum and nematosphaeropsis labyrinthus are mainly restricted to the oceanic environment whereas the other species have also been reported from neritic environments in previous studies due to the limited knowledge of the ecological and sedimentological factors influencing the occurrence of dinoflagellate cysts in oceanic environments their distribution in recent sediments can be only related to surface water masses in a broad sense although the distribution of assemblages correlates with specific surface water masses comparison with assemblages recovered from sediment traps deployed basinwide in the norwegian greenland sea dale and dale 1992 revealed some major discrepancies in species composition and percentage abundances the differences cannot be explained with certainty at the moment although there is some evidence that transport of dinoflagellate cysts and other fossilizable microplankton in water masses by currents in sea ice and sediments may modify the assemblages found in recent oceanic surface sediments from the norwegian greenland sea

utilizing physical sediment variability in glacier fed lakes for continuous glacier reconstructions during the holocene northern folgefonna western norway the maritime plateau glacier of northern folgefonna in western norway has a short subdecadal response time to climatic shifts and is therefore well suited for reconstructing high resolution glac

decadal to millennial scale periodicities in north iceland shelf sediments over the last 12 000 cal yr long term north atlantic oceanographic variability and solar forcing giant piston core md99 2269 recovered 25 m of sediment in hunafloaall a deep trough on the north iceland margin fronting the iceland sea and the site of a shelf sediment drift the rate of sediment accumulation is 2 m kyr 5 yr cm the core terminated in the vedde tephra v12 cal ka the sediment was sampled at between 5 and 50 yr sample including rock magnetic grain size and sediment properties data reduction was carried out using principal component analysis two pc axes for the 5 yr sample magnetic data are strongly correlated with measures of coercivity arm20 mt arm and magnetic concentrations karm in turn arm20 mt arm is highly correlated negatively with grain size and the mean size of the sortable silt fraction analyses of the two pc axes with mtm spectral methods indicate a series of significant s 99 periodicities at millennial to multidecadal scales including those at v200 125 and 88 yr which are associated with solar variability we also document a strong correlation between the sediment magnetic properties and the d 18 o on benthic foraminifera on the north iceland inner shelf we hypothesize that the links between variations in grain size magnetic concentrations and solar forcing are controlled by atmospheric and oceanographic changes linked to changes in the relative advection of atlantic and polar waters along the north iceland margin today these changes are associated with variations in the deep convection in the greenland and iceland seas the precise linkages are however presently elusive although a combination of coarser sediments and low d 18 o values define a holocene thermal maximum between v8 and 6 cal ka 2003 elsevier science b v all rights reserved