geochemistry and stratigraphic correlations application to the investigation of geothermal and mineral resources of tuscany italy contribution to the knowledge of the ore deposits of tuscany ii abstract major element geochemistry 364 analyses is used to obtain quantitative information on the initial mineralogical composition and the depositional environment of paleozoic more or less metamorphic rocks from tuscany and elba furthermore this method can be used to improve stratigraphic correlations by comparing the chemical compositions of the metamorphic rocks and their possible non metamorphic counterparts of known stratigraphic position the stratigraphic units were divided into two sets the first includes the units of known stratigraphic or tectonic position taken as reference groups permian red porphyries carboniferous rocks buti group l s porphyritic schists porphyroids lower phyllites and metabasites from the apuan alps and elba the second set comprises the units of uncertain position metapelites and metapsammites from outcrops mines and boreholes from the boccheggiano niccioleta area calamita schists and metabasites associated with these two units micaschists gneisses and associated amphibolites the main results are 1 1 the porphyroids and porphyritic schists differ strongly from the permian red porphyries thus confirming that they belong to two different volcanic episodes 2 2 all the reference units consist of shales sandstones s s or graywackes differing by their degree of maturity increasing from the lower phyllites to the buti group and to the carboniferous formations 3 3 the carboniferous rocks the buti group and the lower phyllites have distinct chemical compositions 4 4 the boccheggiano formation l s and the calamita schists are similar and include rocks chemically equivalent to the lower phyllites the buti group and the carboniferous formations 5 5 the micaschists and gneisses derive from shales and graywackes respectively and chemically recall the lower phyllites 6 6 the metabasites from the apuan alps and from niccioleta are within plate basalts whereas the amphibolites interlayered within the micaschists and gneisses seem ocean floor basalts

impact of eastern arctic shelf waters on the nansen basin intermediate layers the eurasian shelves supply water to the nansen basin intermediate layers in two ways as buoyancy driven plumes of dense winter water and as permanent inflow of the barents sea branch of atlantic water while the plumes are local and seasonal phenomena the barents sea flow is part of the large scale circulation both interact with atlantic water which enters the arctic ocean through fram strait and moves as a subsurface boundary current eastward along the continental slope during the polarstern cruise ark ix 4 in summer 1993 the fram strait branch was observed as a narrow core within tens of kilometers of the barents sea shelf edge here several patches of cold low salinity water spread across the slope down to about 500 m depth their origin is assumed to be the northern barents sea they mix with the warm saline fram strait branch water fsbw so that the core properties of the latter become modified downstream in the eastern nansen basin the fram strait branch is displaced toward the inner basin by inflow of the barents sea branch of atlantic water bsbw this inflow appears as a broad 200 km wedge extending from 200 to 1300 m depth bsbw is colder and less saline than water of the fram strait branch and it is less dense and less stratified than the ambient water both branches appear to undergo vigorous mixing while spreading eastward so that any eastward continuation of the boundary flow transports about 50 bsbw and 50 fsbw above 600 m and about 80 bsbw and 20 fsbw below that level toward the canadian basin according to available observations the barents and kara seas are the only source areas for shelf waters ventilating the nansen basin below the halocline and these waters constitute a freshwater input rather than a salt input winter shelf water from the laptev sea cannot contribute to layers deeper than the upper halocline

foraminiferal biofacies on the mid latitude lincoln shelf south australia oceanographic and sedimentological implications foraminiferal assemblages on the southern mid latitude lincoln shelf comprise mixtures more strongly in shallow waters of holocene and relict pleistocene specimens over 200 benthic and 15 planktonic species were recorded and a higher diversity was found in the central and deeper parts of the shelf and slope cluster analysis identified five assemblages or biofacies nearshore assemblage a 50 m and inner mid shelf assemblage b 50 90 m are dominated by relict and recent shallow water species the outer mid shelf assemblage c 90 120 m contains more cibicidids and is transitional between the shallow and deep water assemblages outer shelf assemblage d 120 170 m is characterized by cibicidids and anomalinids and by a higher planktonic and benthic diversity and it can be subdivided into three sub assemblages d1 d3 unlike others assemblage d was not recognized from the most western transect samples the outer shelf to slope assemblage e 170 400 m is typically deep water having forms like hoeglundina elegans pullenia bulloides and melonis affinis the western great australian bight sector has the larger epifaunal benthic sorites marginopora group while the infauna is higher in the eastern neptune sector of the shelf we attribute these contrasts to the influence of the warm leeuwin current and to the mixing between gulf shelf and oceanic waters respectively a former lagoonal environment is largely responsible for the accumulation of relict tests during lower sea level periods of the late pleistocene when climate was more arid the lack of recent sediments preserved on the inner shelf is considered to be due to strong wave abrasion causing sediment starvation richer forarniniferal assemblages from the outer shelf to upper slope parallel an increasingly calcareous sediment faunal evidence indicates a warmer nearly oligotrophic condition on lincoln shelf compared to the mesotrophy on the adjacent lacepede shelf this difference may be due to the separation of these two shelves by kangaroo island acting as a local oceanographic environmental and biogeographic barrier

organic matter rain rates oxygen availability and vital effects from benthic foraminiferal δ13c in the historic skagerrak north sea abstract the sediment cores 225514 and 225510 were recovered from 420 and 285 m water depth respectively they were investigated for their benthic foraminiferal 13c during the last 500 years both cores were recovered from the southern flank of the skagerrak the 13c values of uvigerina mediterranea and other shallow infaunal species in both cores indicate that organic matter rain rates to the seafloor varied around a mean value until approximately ad 1950 after which they increased this increase might result from changes in the north atlantic current system and a co occurring persistently high north atlantic oscillation index state in the 1980s to 1990s rather than from anthropogenic eutrophication using 13c mean values of multiple species we reconstruct 13c gradients of dissolved inorganic carbon dic within pore waters for the time periods ad 1500 to 1950 and ad 1950 to 2000 the calculated 13cdic ranges interpreted as indicating total organic matter remineralization due to respiration are generally bigger in core 225514 than in core 225510 since mean 13c values of u mediterranea suggest that organic matter rain rates were similar at both locations differences in total organic matter remineralization are attributed to differing oxygen availability however oxygen concentrations in the overlying bottom water masses are not likely to have differed significantly thus we suggest that organic matter remineralization was controlled by oxygen availability within the sediments reflecting strong differences in sedimentation rates at the two investigated core sites based on the assumptions that tests of benthic foraminiferal species inhabiting the same microhabitat depth should show equal 13c values unless they are affected by vital effects and that globobulimina turgida records pore water 13cdic we estimate microhabitat corrected vital effects for several species with respect to g turgida 0 7 for cassidulina laevigata 1 3 for hyalinea balthica and 0 7 for melonis barleeanus melonis zaandami seems to closely record pore water 13cdic

stable oxygen and carbon isotopes in modern benthic foraminifera from the laptev sea shelf implications for reconstructing proglacial and profluvial environments in the arctic measurements of 18o and 13c isotopes in three benthic foraminiferal species from surface sediments of the eastern laptev sea are compared to water 18o values and 13c values of dissolved inorganic carbon dic samples investigated originate from two environmentally contrasting core locations which are influenced by riverine freshwater runoff to a varying degree at the river distal site located within relatively stable marine conditions on the outer shelf elphidiella groenlandica haynesina orbiculare and elphidium excavatum forma clavata show a positive specific offset of 1 4 1 5 and 1 respectively in their 18o values relative to the expected value for inorganic calcite precipitated under equilibrium conditions at the site close to the lena river confluence with enhanced seasonal hydrographic contrasts calculated 18o offsets in e groenlandica and in h orbiculare remain about the same whereas e e clavata displays a distinctly negative offset of 1 8 the 18o variation in e e clavata is interpreted as a vital effect a finding which limits the potential of this species for reconstructing freshwater influenced shelf paleoenvironments on the basis of oxygen isotopes this interpretation gains support when comparing foraminiferal 13c with the 13cdic of the water while some of the difference in the carbonate 13c seems to be controlled by a riverine related admixture of dic clearly defined 13c ranges in each of the three foraminifera at the river proximal site shows that also the carbon isotopic signature in e e clavata is particularly affected by environmental factors

linking the modern distribution of biogenic proxies in high arctic greenland shelf sediments to sea ice primary production and arctic atlantic inflow the eastern north coast of greenland is considered to be highly sensitive to the ongoing arctic warming but there is a general lack of data on modern conditions and in particular on the modern distribution of climate and environmental proxies to provide a baseline and context for studies on past variability here we present a detailed investigation of 11 biogenic proxies preserved in surface sediments from the remote high arctic wandel sea shelf the entrance to the independence hagen and danmark fjords the composition of organic matter organic carbon c n ratios 13c 15n biogenic silica and ip25 and microfossil assemblages revealed an overall low primary production dominated by benthic diatoms especially at the shallow sites while the benthic and planktic foraminiferal assemblages underline the intrusion of chilled atlantic waters into the deeper parts of the study area the distribution of organic walled dinoflagellate cysts is controlled by the local bathymetry and sea ice conditions the distribution of the dinoflagellate cyst polarella glacialis matches that of seasonal sea ice and the specific biomarker ip25 highlighting the potential of this species for paleo sea ice studies the information inferred from our multi proxy study has important implications for the interpretation of the biogenic proxy signal preserved in sediments from circum arctic fjords and shelf regions and can serve as a baseline for future studies this is the first study of its kind in this area

living stained benthic foraminifera within surficial sediments of the skagerrak abstract an analysis of living stained benthic foraminifera within four box cores raised from water depths of 74 to 621 m in the skagerrak shows that faunal patterns at different water depths are strikingly different within this relatively shallow organicrich marginal sea environment although some genera show vertical stratification within the sediments a number of taxa are found over wide intervals or have different patterns between cores the vertical distributional data are compared with deep sea data from the eastern margin of north america benthic foraminifera from a deep core at 530 m in the skagerrak have similar faunal patterns within the surficial sediments as found in the deep sea but shallow cores at 74 and 212 m have more complex patterns this difference between shallow and deep cores within the skagerrak and the north atlantic is attributed to higher biological activity in the shallow environments which creates a greater amount of heterogeneity within the shallow water sediments than is found in deeper environments the faunal data suggest that the use of benthic foraminifera for paleoenvironmental reconstructions in shallow organicrich regions will be complicated in future studies the ecology of individual species is difficult to assess because of the complex faunal patterns observed within the surficial sediments geochemical studies for estimating bottom water oxygen or organic carbon flux will also be difficult since these studies assume that taxa occupy particular microhabitats within the surficial sediments

correlation between seismic reflectivity and rheology in extended lithosphere southern tuscany inner northern apennines italy abstract in southern tuscany inner zone of the northern apennines the lithosphere has been affected by extensional deformation since the middle miocene and is characterized by high heat flow 120 mw m 2 both local shallow and regional deep seismic reflection profiles clearly show the occurrence of a sharp reflector k horizon within the upper crust which is probably located at the top of a shear zone acting as the decollement horizon for the latest pliocene quaternary normal faults its depth varies between 3 and 6 km in geothermal areas and 9 and 12 km elsewhere borehole control in the geothermal areas shows that it occurs at a temperature of approximately 450 c the hypothesis that the k horizon represents the top of the brittle ductile transition agrees with two lines of evidence a it approximately follows the same isotherm over the whole region and b its depth coincides with rheological predictions of the brittle ductile transition for the range of high pore fluid pressures and strain rates estimated for southern tuscany it appears therefore that at least under specific conditions very high pore fluid pressures strain concentration the brittle ductile transition may have a seismic signature

pathways and modification of the upper and intermediate waters of the arctic ocean 1 the purpose of this study is to investigate the pathways and the ventilation of source water masses of the upper and intermediate waters of the arctic ocean for the arctic and subarctic domain a coupled ice ocean general circulation model is set up to be integrated for several decades it is driven by a climatological seasonal cycle of monthly mean atmospheric data from 1980 to 1989 and by restored sea surface salinities passive tracers are used to visualize and interpret the modeled flow and to compare it with observations the model is able to reproduce known features of the arctic ocean circulation like the inflow of two branches of atlantic origin via the fram strait and the barents sea and their subsequent passage at middepths in several cyclonic circulation cells the fate of these atlantic source water masses river water and bering strait inflow water in the model are studied the branch crossing the barents sea is subject to an intense heat loss and ice formation as a result water of this branch leaves the shelf toward the central part of the arctic ocean not only at the surface but also in denser varieties which finally feed the central arctic at halocline and middepths the lightest part turns northward and finally westward joining the transpolar drift the densest part 200 1000 m depth moves eastward along the continental slope a similar path is taken by the atlantic water branch from the fram strait the inflowing branch over the barents sea turns out to be the dominant source for the lower atlantic water layer in the arctic ocean in this investigation atlantic tracers starting in fram strait need 6 years to reach the northern laptev sea slope travel times to return to fram strait are 15 20 years along the lomonossov ridge and about 30 years along the continental slope of the canadian basin tracers that mark the pacific water or the mackenzie river water flow eastward and leave the arctic mainly via the canadian archipelago the siberian river water tracers at the surface penetrate far into the canadian basin before they join the transpolar drift the travel times of the river water from the river mouths are 2 3 years to the shelf edge and 12 14 years to fram strait

the effects of multiple stressors on the distribution of coastal benthic foraminifera a case study from the skagerrak baltic sea region abstract coastal ecosystems are subjected to both large natural variability and increasing anthropogenic impact on environmental parameters such as changes in salinity temperature and ph this study documents the distribution of living benthic foraminifera under the influence of multiple environmental stressors in the skagerrak baltic sea region sediment core tops were studied at five sites along a transect from the skagerrak to the baltic sea with strong environmental gradients especially in terms of salinity ph calcium carbonate saturation and dissolved oxygen concentration in the bottom water and pore water we found that living foraminiferal densities and species richness were higher at the skagerrak station where the general living conditions were relatively beneficial for foraminifera with higher salinity and calc in the water column and higher ph and oxygen concentration in the bottom and pore water the most common species reported at each station reflect the differences in the environmental conditions between the stations the dominant species were cassidulina laevigata and hyalinea balthica in the skagerrak stainforthia fusiformis nonionella aff stella and nonionoides turgida in the kattegat and n aff stella and nonionellina labradorica in the oresund the most adverse conditions such as low salinity low calc low dissolved oxygen concentrations and low ph were noted at the baltic sea stations where the calcareous tests of the dominant living taxa ammonia spp and elphidium spp were partially to completely dissolved probably due to a combination of different stressors affecting the required energy for biomineralization even though foraminifera are able to live in extremely varying environmental conditions the present results suggest that the benthic coastal ecosystems in the studied region which are apparently affected by an increase in the range of environmental variability will probably be even more influenced by a future increase in anthropogenic impacts including coastal ocean acidification and deoxygenation

on the dynamics of atlantic water circulation in the arctic ocean 1 we use a subset of models from the coordinated experiment of the arctic ocean model intercomparison project aomip to analyze differences in intensity and sense of rotation of atlantic water circulation we focus on the interpretation of the potential vorticity pv balance results differ drastically for the eurasian and the amerasian basins of the arctic ocean we find indications that in the eurasian basin the lateral net flux of pv is a significant factor for the determination of the sense of rotation of atlantic water circulation on timescales beyond pentades the main source of high pv causing cyclonic circulation in the eurasian basin is the barents sea where the seasonal cycle of surface buoyancy fluxes forms stratified water that leaves the shelf and feeds the atlantic water layer awl in the arctic basins however in the amerasian basin vertical pv fluxes are the more important factor these are closely related to wind field changes we find an intense response of the awl flow to wind forcing approximated by the sea level pressure difference between the bering sea and the central canadian basin which describes about half the variance of awl flow of the amerasian basin an experiment driven with a repeated atmospheric climatology exhibits an extreme case where a permanent high pressure system over the beaufort sea dominates the circulation in the amerasian basin demonstrating the potential of the beaufort gyre to adjust in such a way as to suppress a cyclonic awl flow in the amerasian basin in more realistic cases the beaufort gyre still modulates the amerasian basin awl circulation significantly

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

microhabitats of salt marsh foraminifera st catherines island georgia usa abstract salt marsh foraminifera of st catherines island georgia occupy a range of epibenthic to deep infaunal to 30 cm micro habitats freshly collected specimens of arenoparrella mexicana from 27 to 30 cm below the marsh surface extruded pseudopodial nets and actively collected foreign material about the aperture salt marsh foraminifera may be primarily epibenthic 0 1 cm epibenthic to intermediate infaunal 0 10 cm or deep infaunal 0 30 cm most of the twelve commonly occurring species in st catherines island marshes are epibenthic to intermediate infaunal species distributional patterns differ with regard to maximum depth of infaunal occurrences infaunal microhabitat utilization in different marsh zones and environments and the presence or absence of subsurface population maxima selective preservation impacts both calcareous and agglutinated foraminifera intense bioturbation primarily by halophytes and decapod crustaceans may contribute to the deep infaunal occurrences of foraminifera in these environments

geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy abstract serri g innocenti f and manetti p 1993 geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy in m j r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 117 147 the neogene quaternary magmatism of the northern apenninic arc took place in four phases separated in space and time which become progressively younger from west to east phase i 14 ma phase ii 7 3 6 0 ma phase iii 5 1 2 2 ma phase iv 1 3 0 1 ma this magmatism is the result of the activation of three physically separate sources 1 the adriatic continental crust extracted from the mantle in the late proterozoic 2 a strongly refractory recently k enriched harzburgitic mantle located in the mechanical boundary layer mbl of the lithosphere and 3 a recently metasomatized cpx rich mantle compositionally variable from iherzolite to wehrlite clinopyroxenite interpreted as an ephemerally k enriched asthenosphere the adriatic continental crust is the dominant source of the acid plutonic and volcanic rocks of the tuscan region the acid magmatism is mostly found inside an ellipsoidal area about 150 300 km centred on giglio island here defined as the tuscan crustal dome within this area mantle derived magmas unaffected by important crustal contamination processes and mixing with crustal anatectic melts have so far not been found pure crustal magmas are rare but are represented for example by some of the san vincenzo and roccastrada rhyolites virtually all the tuscan acid centres show evidence of mixing with potassic mantle derived magmas major and trace elements as well as 87 sr 86 sr and 143 nd 144 nd data on primitive rocks mg 65 reveal two groups of mantle derived magmas these define two distinct mantle enrichment trends both essentially due to the additions of k rich components which metasomatized separate compositionally diverse upper mantle sectors in both cases the most remarkable mineralogical effect of these enrichment processes is the production of variable amount of phlogopite through reaction between fluids and or melts with the mantle the rocks of group i ol hy and q normative lamproites ultrapotassic high mg latites ultrapotassic shoshonites and shoshonites saturated trend are considered to be derived by partial melting at low pressure 87 sr 86 sr 0 717 ce sr 0 3 and k 2 o na 2 o 6 7 and low ratios of 143 nd 144 nd 0 5121 0 5120 and ba la 87 sr 86 sr 0 712 and k 2 o na 2 o 8 9 values and low 143 nd 144 nd ba la 0 10 ratios these constraints do not allow to exclude a complete identity between the k rich components which metasomatized the mantle sources of the saturated and undersaturated trend magmas the geochemical and isotopic features of the components that metasomatized the mantle sources of the northern apenninic arc magmatism can be explained by a geodynamic process which causes a large amount of crustal materials to be incorporated within the upper mantle we propose that the delamination and subduction of the adriatic continental lithosphere related to the still ongoing northern apennine continental collision provide a viable mechanism to explain the genesis and eastward discontinuous migration of the magmatism in central italy the subduction of delaminated lithospheric mantle with lower crustal slivers would have exposed uppermost mantle adriatic mbl and crustal units previously imbricated in the apennine chain to the heating advected by the upwelling of a recently and ephemerally k enriched asthenospheric mantle wedge and by the underplating of magmas derived from it we consider that the diapiric uprising of a hot crustally contaminated asthenosphere occurs in the wake left above the sinking of the adriatic delaminated subducting continental lithosphere the delamination subduction process of the adriatic lithosphere has probably started in the early middle miocene but earlier than 15 14 ma ago as indicated by the age and petrologic characteristics of the first magmatic episode sisco lamproite of the northern apennine orogenesis

microhabitat preferences and stable carbon isotopes of endobenthic foraminifera clue to quantitative reconstruction of oceanic new production seventeen surface sediment samples from the north atlantic ocean off ne greenland between 76 and 81 n and nine samples from the south atlantic ocean close to bouvet island between 48 and 55 s were taken with the aid of a multiple corer and investigated for their live rose bengal stained benthic foraminiferal content within the upper 15 cm of sediment preferentially endobenthic melonis barleeanum m zaandami and bulimina aculeata as well as preferentially epibenthic lobatula lobatula were counted from 1 cm thick sediment slices each and analyzed for stable carbon and oxygen isotopic compositions of their calcareous tests live and dead specimens were counted and measured separately the carbon isotopic composition of the foraminifera was compared to that of the dissolved inorganic carbon dic of simultaneously sampled bottom water during a period of one month one station off ne greenland was replicately sampled once every week and samples were processed as above live specimens of lobatula lobatula are confined to the uppermost two centimeters of sediment live specimens of melonis spp are found down to eight centimeters within the sediment but with a distinct sub surface maximum between two and five centimeters the down core distribution of live bulimina aculeata shows a distinct surface maximum in the top centimeter and constant but low numbers down to 11 cm subbottom depth the average stable carbon isotopic composition d13c per mil vpdb of live l lobatula off ne greenland is by 0 4 0 1 per mil higher than the d13cdic of the ambient bottom water at the time of sampling there is evidence that this species calcify before the ice free season when bottom water d13cdic is supposed to be higher this would reconfirm the one to one relationship between d13c of ambient water dic and cibicids widely used by paleoceanographers live m barleeanum show a negative offset from bottom water dic of 1 7 0 6 per mil in the uppermost sediment and of 2 2 0 5 per mil in three to four centimeters subbottom depth all d13c values of live melonis spp decrease within the upper four centimeters regardless of the time of sampling and site investigated the offset of live b aculeata from bottom water d13cdic values of eight stations rather constantly amounts 0 6 0 1 per mil no matter what subbottom depth the specimens are from at one station however where is strong indication of elevated organic carbon flux the negative offset averaged over all sub bottom depths increases to 1 5 0 2 per mil buliminids actively move within the sediment and by this either record an average isotope signal of the pore water or the signal of one specific calcification depth the recorded signal however depends on the organic carbon flux and reflects general but site specific pore water d13cdic values if compared with epibenthic d13c values from the same site not influenced by pore water and related phytodetritus layer effects bulimina d13c values bear some potential as a paleoproductivity proxy specimens of melonis spp seem to prefer a more static way of life and calcify at different but individually fix depths within the sediment although live specimens thus record a stratified pore water d13c signal there is no means yet to correct for bioturbational and early diagenetic effects in fossil faunas

relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in monterey bay california 1 as part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release we compared ambient pore water chemistry with the distribution and stable isotopic composition of living rose bengal stained foraminifera in mbari rov ventana tube cores taken from modern seepage areas about 1000 m water depth in monterey bay california benthic foraminiferal isotopic differences between sites clearly indicate that methane influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry carbon isotope signatures of living benthic foraminifera did not conform to the very negative 30 to 48 methane influenced carbon isotope values of the pore waters they live in instead the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published 13c values of foraminifera living in nonseep habitats it is not clear what relative influences biological ecological and physical factors have on the carbon isotopic signatures observed in seep foraminifera substantial carbon isotope differences can exist between individuals of the same seep species for instance 13c values of living globobulimina pacifica varied by as much as 2 9 between seeps within 8 km of each other whereas 13c values of living uvigerina peregrina varied by as much as 1 95 within the same seep provided there is no diagenetic alteration of the test carbonate isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage

crustal models of the geothermal areas of southern tuscany italy abstract geological and geophysical data gathered in the geothermal areas of southern tuscany located in the inner part of the northern apennines indicate the presence of granite intrusions the most relevant data are 1 regional asthenospheric ascent to a depth of 40 50 km 2 granitic dykes as old as 3 8 2 9 ma and a widespread contact aureole found in several deep geothermal wells 3 very high heat flow values interpreted as the result of convective circulation of hot fluids above shallow magmatic bodies 4 the presence of low density bodies inferred from low gravity values often correlated with positive heat flow anomalies 5 the occurrence of a highly reflective horizon named k in a depth range of 3 12 km in the geothermal areas as shown by seismic reflection data 6 a 30 40 km wide low velocity body below the k horizon whose existence is supported by local earthquake tomography and teleseismic studies 7 the presence of a conductive body which correlates well with the anomalous tomographic and teleseismic body as revealed by magnetotelluric surveys the goal of the paper is to test different alternative crustal models by using these data the models are 1 granite intrusion 2 geopressurized fluids below impervious layers 3 contact metamorphic aureole 4 mylonite layers at the upper lower crust transition and 5 some combination of the four the occurrence of shallow intrusive bodies still partially molten and associated with saline brines is considered the most tenable model

upper crustal structure of the larderello geothermal field as a feature of post collisional extensional tectonics southern tuscany italy abstract reflection seismic profiles crossing the larderello geothermal field permit the distinction of three different seismic facies units in the upper continental crust the upper 3 4 km of the crust is characterized by low reflectivity its base corresponding to a reflector referred to as the k horizon and recognized in many other areas of southern tuscany beneath this reflector a seismic facies of 0 8 1 0 twt thickness is characterized by strong convergent and divergent reflections forming a lozange shaped geometry the lowermost seismic facies is characterized by almost horizontal reflections based on the distribution of the hypocentral microearthquakes temperature data recorded in deep boreholes and the geometry of normal faults the k horizon is explained here as a kinematically active rheological boundary which separates a brittle upper part from a ductile lower part according to this hypothesis the k horizon and the lozange reflections could originate from a mylonite band located at the contact between two geological bodies characterized by different rheological behavior it is inferred that this horizon acts as a decoupling plane in the upper continental crust it developed as a consequence of the extensional tectonics and the high heat flow which characterize southern tuscany

impact of north atlantic current changes on the nordic seas and the arctic ocean 1 the impact of north atlantic current nac volume heat and salt transport variability onto the nordic seas and the arctic ocean is investigated using numerical hindcast and sensitivity experiments the ocean sea ice model reproduces observed propagation pathways and speeds of sst anomalies signals reaching the entrance to the nordic seas between iceland and scotland originate partly in the lower latitude north atlantic response experiments with different prescribed conditions at 50 n show that changes in the barotropic flow across 50 n have no impact on the seas north of the greenland scotland ridge because of the strong deformation of the f h field a temperature anomaly inserted in the upper 500 m at 50 n on the other hand has a widespread effect on the temperature distribution and the circulation in the high latitude north atlantic nac induced variability in the nordic seas and locally induced variability have similar magnitude the local atmospheric influence and the complexity of north atlantic nordic seas advection pathways make it unlikely that detection of signal propagation in the nac could lead to a prediction of oceanic conditions in the nordic seas and the arctic ocean with several years lead time

benthic foraminiferal distribution and abundance changes in skagerrak surface sediments 1937 hoglund and 1992 1993 data compared both living stained and dead unstained foraminiferal assemblages from surface sediments 0 2 cm in the northwestern part of the skagerrak have been studied in order to 1 define and characterize the distribution of various modern benthic environments and 2 by comparing these findings with surface samples collected 40 60 years ago to document possible faunal changes that might have occurred the investigated area is physiographically divided into the norwegian slope the skagerrak basin and the danish slope the latter is under the influence of the jutland current while the basin and the investigated parts of the norwegian slope are bathed in atlantic water all areas have bottom waters with a high oxygen concentration three living stained and three dead unstained assemblages occupy the three physiographic areas only one assemblage on the norwegian slope is common to both the living and dead assemblages but the boundaries between them lie at comparable depths the higher standing crops are found on the fertile danish slope while the lower ones are in the deep basin where the diversity is at a maximum in the dead assemblages the relative abundance of agglutinated tests increases with depth comparison with data collected 40 to 60 years ago shows increases in absolute numbers of tests especially in the deep basin there are changes in assemblage compositions in all areas the dominant species found in 1937 are different from those of 1992 1993 there is a major change in the basin where one agglutinated species has changed its depth distribution downslope and two present day abundant species are new arrivals these faunal events are probably linked to environmental changes

effects of carbon dioxide sequestration on california margin deep sea foraminiferal assemblages abstract deep sea sequestration of co2 is being considered as a possible mitigation tool to decrease atmospheric co2 concentrations and its associated negative effects this study investigated potential effects of liquid carbon dioxide co2 injection on deep sea foraminiferal assemblages foraminifera are ideal for this ecological impact investigation because of differing test composition calcareous and non calcareous and thickness and diverse epifaunal and infaunal depth preferences the experiment was conducted on august september 2003 at 3600 m off the coast of monterey bay california aboard the r v western flyer using the rov tiburon the ph of the site was monitored throughout the experiment sediment push cores were collected both from the experimental and control sites and stained to distinguish live stained from dead unstained individuals effects of co2 injection on assemblages have been tracked both vertically to 10 cm depth below sea floor and horizontally up to 10 m from co2 injection sites as well as between live and dead individuals within corrals containing the injected co2 and their underlying sediments severe ph changes near 4 0 units were recorded this compares with a record of small average reductions in ocean ph 0 05 units combined with large episodic excursions 1 7 units over the experimental area due to the injection of co2 exposure to this gradient of low ph caused increased mortality and dissolution of calcareous forms within corrals as far as 5 m from the injection site and to at least 10 cm depth in the sediments this experiment revealed several major effects of co2 injection on foraminiferal assemblages in surficial sediments 1 total number of foraminifera in a sample decreases 2 foraminiferal species richness decreases in both stained and unstained specimens and 3 relative percentage of stained live forms in the remaining tests increases down core trends to 10 cm below sea floor have revealed 1 percent agglutinated forms decline and calcareous forms increase with depth 2 agglutinated species richness decreases with depth and 3 experimental core assemblages become increasingly similar with depth to those in control cores not subjected to co2 injection these results imply almost complete initial mortality and dissolution in the upper 10 cm throughout the corrals following liquid co2 injection since calcareous foraminifera represent more than 50 of the total assemblages this clearly indicates that emplacement of co2 will result in negative effects to diversity and survivorship of the deep sea benthic meiofauna

tracing seafloor methane emissions with benthic foraminifera results from the ana submarine landslide eivissa channel western mediterranean sea article the hypothesis that benthic foraminifera are useful proxies of local methane emissions from the seafloor has been verified on sediment core ks16 from the headwall of the ana submarine landslide in the eivissa channel western mediterranean sea the core ms312 from a nearby location with no known methane emis sions is utilised as control the core was analysed for biostratigraphy benthic foraminiferal assemblages hyalinea balthica and uvigerina peregrina carbon and oxygen stable isotope composition and sedimentary structures the upper part of the core records post landslide deglacial and holocene normal marine hemipe lagic sediments with highly abundant benthic foraminifera species that are typical of outer neritic to upper bathyal environment in this interval the 13 c composition of benthic foraminifera indicates normal marine environment analogous to those found in the control core below the sedimentary hiatus caused by the em placement of the slide the foraminiferal assemblages are characterised by lower density and higher shannon index markedly negative 13 c shifts in benthic foraminifera are attributed to the release of methane through the seabed the mean values of the 13 c anomaly in u peregrina are 0 951 0 208 in the pre landslide sediments and 0 269 0 152 in post slide reworked sediments deposited immediately above the hiatus the 13

holocene sedimentation in the skagerrak a review abstract stratigraphic sedimentological geochemical and micropaleontological aspects of holocene sedimentation processes in the skagerrak are reviewed published data show the skagerrak to be the main depositional basin of the north sea with additional inputs from the north atlantic the baltic and the scandinavian mainland as this area is a highly dynamic and complex environment it is difficult to define overall controlling factors and processes from a consideration of available and lacking approaches and data suggestions are made for future research

structure and late cenozoic evolution of the upper lithosphere in southwest tuscany italy abstract geological and geophysical data on southwest tuscany are reviewed in order to define the structure and evolution of the upper lithosphere from the miocene to the quaternary petrologic studies reveal the existence below all of tuscany of hercynian and older polyphased metamorphic rocks and of hercynian granite whose top is an important seismic reflecting horizon the basement is characterized by ne sw trending structures in contrast with the main nw se alpine structures of the uppermost levels the heat flow map shows two broad areas with values higher than 80 mw m2 reaching maximum values of 10 5 and 15 h f u in the geothermal areas which are also characterized by negative bouguer anomalies a landsat study revealed a ne sw band of subcircular structures passing through larderello and coinciding with a regional fault system and a steep rise in the moho petrologic geochemical and radiometric data on the tuscan igneous rocks show that partial melting took place in the tuscan crust at different levels and to varying degrees from the miocene to quaternary producing a continuous alpine granitic layer the known tuscan intrusive bodies and two batholiths below the larderello and mt amiata geothermal fields represent culminations of the alpine granite the rise of the tuscan magmas was closely correlated to a post tortonian tensional tectonics and followed its n e migration tensional tectonics started after the last compressional phase 10 11 ma b p as a consequence of the anticlockwise rotation of italy the opening of the tyrrhenian sea and the swelling of the mantle below southwest tuscany

possible seismic signature of the α β quartz transition in the lithosphere of southern tuscany italy abstract this paper intends to throw some doubt on the consolidated practice of interpreting seismic data without considering mineral phase transitions reference is made to southern tuscany where seismic surveys revealed the presence within the crystalline basement of a prominent high amplitude reflector exhibiting local bright spot features known as the k horizon according to some researchers the k horizon is a layer of fractured rocks hosting high pressure fluids but its ultimate origin is unclear on the basis of the extrapolation of measured temperatures in the larderello and amiata geothermal fields and gas geotemperatures from the san pompeo 2 deep well we propose that the k horizon might be largely governed by the transition of quartz and by the very high volumetric thermal expansion of quartz a main constituent of local crystalline rocks with respect to other minerals the effects of these processes are probably suppressed almost everywhere by the abundance of minerals other than quartz and by the occurrence of partial melting but might be evident in relatively quartz rich rocks and in regions of very high geothermal gradient such as southern tuscany as a consequence of these processes a layer of fractured rocks roughly following the quartz transition temperature would develop and locally host high pressure fluids thus justifying in part the high reflectivity of the k horizon this hypothesis concords with previous interpretations although the ruling factors in this case would be the transition and the peculiar physical characteristics of quartz compared to other minerals in our interpretation the k horizon is expected to fade away in rocks where quartz is scarce or absent where microfractures are not produced by the phase transition the local disappearance of the k horizon could therefore depend on lithology whereas its reflectivity would depend on the quantity and type of fluids trapped in the porous layer micro fractured by the volumetric expansion of quartz

arctic warming evolution and spreading of the 1990s warm event in the nordic seas and the arctic ocean 1 observations in the arctic ocean revealed changes in oceanic temperature salinity and ice cover of the 1990s as compared with earlier data with a numerical model we favorably reproduce the development and subsequent propagation of temperature anomalies in water of atlantic origin in the 1980s and 1990s these propagated into the arctic ocean via the barents sea and the fram strait two warm anomalies entered the arctic ocean through these passages while the first smaller anomaly only warmed up the western eurasian basin the second large anomaly spread far into the eastern eurasian basin and across the lomonossov ridge into the western arctic basins intensified boundary currents during the high nao state in the first half of the 1990s significantly influenced the amplitude and speed of propagation of the temperature anomalies inside the arctic ocean in contrast to the notion of a continuous warming process during the 1990s our model results suggest the warming of the atlantic layer in the arctic ocean occurred in the form of events the event with the largest anomalous heat input during the modeled period entered the arctic between 1989 and 1994 it is possible to trace back the additional heat input into the arctic to an increased volume inflow via the faroer scotland passage and reduced heat loss to the atmosphere in the early 1990s after a weaker warm inflow in the second half of the 1990s the most recent observations and the model results point to a recurring warm anomaly in the inflow from 1999 onward

the shift of the α β transition temperature of quartz associated with the thermal expansion of granite at high pressure abstract measurements are presented of volume changes in granite during room temperature compression to 100 200 and 300 mpa confining pressure followed by temperature increase to 900 c comparison with thermal expansion and compressibility data for the constituent minerals allows changes in porosity to be estimated under confining pressure porosity is found to decrease with heating to 200 c through expansion of the minerals into cracks which are thought to be related to the geological cooling history of the rock between 200 c and 840 c porosity increases as a result of differential thermal expansion of the constituent minerals but crack opening is increasingly suppressed at higher confining pressures extrapolation of the results indicates that differential thermal expansion can no longer cause crack opening in dry granite at confining pressures in excess of 450 mpa the quartz transition temperature in granite is marked by a kink in the thermal expansion curve of the rock and it is found to increase by 60 c 70 c per 100 mpa confining pressure as opposed to the published value of 26 c per 100 mpa for single crystals of quartz equations are presented which allow calculation of the effects of confining pressure and temperature on the stresses and displacements in and around a spherical inclusion embedded in a matrix of different elasticity and thermal expansion the theory together with a simple self consistent model for granite accounts semiquantitatively for the observations of thermal expansion and the effect of confining pressure thereon and for the observed transition temperatures for quartz in granite

waters of the makarov and canada basins abstract hydrographic measurements from the 1994 arctic ocean section show how the makarov and canada basins of the arctic ocean are related and demonstrate their oceanographic connections to the eurasian basin the inflow into the makarov basin consists largely of well ventilated water within a broad band of densities from a boundary flow over the siberian end of the lomonosov ridge the boundary flow contains a significant component of dense shelf water likely originating in the barents kara and laptev seas earlier ice camp data show that the canada basin is relatively more isolated from this ventilation source in the canada basin shelf sources influenced by bering sea water appear to add cold waters with high silicate concentrations to the halocline and deeper in 1994 the halocline silicate maximum over the central makarov basin was absent evidence of the recent displacement of the upper s 33 1 halocline water from the chukchi east siberian sea region by water from the eurasian basin much of the makarov basin water in and below the halocline is in fact from the eurasian basin with admixture of waters from the canada basin suggested by their higher silicate concentrations mid depth eddies may transport anomalous properties into the central arctic and create property gradients or fronts in mid depth and deep waters the complex topography of the mendeleyev ridge chukchi plateau region also may assist spreading of water from the boundary into the interior atlantic layer characteristics in 1994 differed from previous general depictions in particular the core temperatures at the chukchi mendeleyev boundary were at least 0 2 c warmer on average than indicated in earlier work the recent warming at intermediate depth has resulted from inflow of atlantic waters that have been cooled relatively little during their transit of the norwegian sea

seismic depth imaging of a geothermal system in southern tuscany this work represents a case study concerning the application of reflection seismic imaging methods in the context of geothermal exploration our goal is to obtain accurate structural images of a geothermal active area in southern tuscany these images will be required in subsequent studies as the input for geological model building and numerical simulation of the heat transport and fluid flow the target region exhibits great geologic complexity including strong velocity contrasts lateral nearsurface inhomogeneities fracture zones and significant topography those features are typical for a volcanic hard rock environment and pose significant challenges to conventional seismic imaging methodology therefore we apply a sophisticated and robust depth imaging workflow to previously acquired surface seismic data within our workflow we focus on estimating the seismic velocities of the predominant rock units and subsequently carry out kirchhoff pre stack depth migration and fresnel volume migration to obtain high resolution images of the subsurface our results demonstrate that the applied methodology provides a valueable tool for imaging in a complex environment such as a volcano geothermal area in detail the resulting reflector images show the main horizons that delineate the tuscan sedimentary rocks in the target region the images from standard kirchhoff migration can be significantly enhanced by utilizing fresnel volume migration which eliminates migration artefacts and provides a better result moreover we obtain the migration velocities and depths for an important regional reflector known as the k horizon which is of major interest for geothermal characterization

circulation features in the central arctic ocean revealed by nuclear fuel reprocessing tracers from scientific ice expeditions 1995 and 1996 measurements of the tracer radionuclides 129 i and 137 cs were conducted on seawater samples collected during the scientific ice expedition cruises to the arctic ocean of the u s navy nuclear submarines uss cavalla and uss pogy in 1995 and 1996 respectively these radionuclides are derived mainly from discharges from the sellafield england united kingdom and la hague france nuclear fuel reprocessing plants and are subsequently transported with atlantic water into the arctic ocean through fram strait and the barents sea iodine 129 results from halocline waters water depths of 59 and 134 m collected virtually synoptically throughout the central arctic ocean during the uss cavalla cruise clearly show the front between atlantic origin water having high 129 i levels 100 10 7 atoms l 1 and pacific origin water labeled mainly by fallout 30 10 7 atoms l 1 measured in central regions of the canada basin indicate that the interior is more efficiently ventilated than previously thought possibly by separation from boundary currents flowing over the continental margin north of the chukchi plateau the 129 i and 137 cs data were interpreted using a transit time model that provided estimates of 6 7 years 0 5 years for the passage of halocline and atlantic water from the norwegian coastal current 60 n to the continental slope of the makarov basin and a lower limit of 8 years for transport to interior regions of the makarov and amundsen basins

the impact of paleocene eocene boundary events on middle neritic benthic foraminiferal assemblages from egypt abstract a 25 m upper paleocene to lower eocene marly sequence exposed at gebel duwi quseir red sea coast of egypt provides a good opportunity for studying paleocene eocene p e boundary stratigraphy and events various bio eco and isotope stratigraphic correlations accurately delineate the position of the p e boundary i e the level of stable isotopic excursions and deep sea benthic extinctions in the middle part of this section within zones p5 and np9 in this paper the impact of p e boundary environmental perturbations on benthic foraminiferal communities of the shallow tethyan shelf is examined benthic foraminiferal assemblages from gebel duwi characterized by large frondicularia phosphatica and f nakkadyi in addition to a number of other neritic taxa but without any typical outer neritic bathyal taxa suggest middle neritic 75 100 m deposition throughout the studied interval and only minor relative sea level variations perhaps some 10 20 m across the boundary sea level appears to have been stable yet a distinct faunal turnover marks the p e boundary of this shallow site which in contrast to deep sea records is less abrupt being preceded by a gradual diversity decrease starting some four meters below the boundary moreover most exits are either local or just temporary and thus not true extinctions many lazarus taxa reappear at some point above the boundary while all but one of the disappearing taxa are known from other lower eocene neritic deposits in egypt in general benthic foraminiferal assemblages display low diversities and high dominance values notably anomalinoides aegyptiacus up to 74 suggesting high levels of environmental stress at the sea floor in combination with occasionally very high p b ratio s up to 98 p and generally laminated sediments the character of the benthic assemblage points to a strong influence of recurrent dysoxia and or anoxia we suggest that these resulted from surface eutrophication by intermittent coastal upwelling and reduced ventilation of the bottom environment although these conditions prevailed during most of the time interval studied they were most severe during the latest paleocene and early eocene when eutrophication intensified and the organic carbon flux to the sea floor increased enhanced atmospheric contrasts between the tethys seaway and the african continent resulting in intensified longshore tradewinds may have controlled these changes at the p e boundary the bottom environment became minimally ventilated perhaps due to reduced oxygen advection from deeper waters three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual decrease of environmental stress and a return to more normal conditions although the organic carbon flux to the sea floor remained high

holocene climatic development in skagerrak eastern north atlantic foraminiferal and stable isotopic evidence a high resolution multiproxy study of core md99 2286 reveals a highly variable hydrographic environment in the skagerrak from 9300 cal yr bp to the present the study includes foraminiferal faunas stable isotopes and sedimentary parameters as well as temperature and salinity reconstructions of a c 29 m long radiocarbon dated core record the multivariate technique fuzzy c means was applied to the foraminiferal counts and it was extremely valuable in defining subtle heterogeneities in the foraminiferal faunal data corresponding to hydrographic changes the major early mid holocene littorina transgression led to flooding of large former land areas in the north sea the opening of the english channel and danish straits and initiation of the modern circulation system this is reflected by fluctuating c n values and an explosive bloom of hyalinea balthica a slight indication of ameliorated conditions between 8000 and 5750 cal yr bp is related to the holocene thermal maximum a subsequent increase in

extensional shear zones as imaged by reflection seismic lines the larderello geothermal field central italy the larderello geothermal field is located in the inner northern apennines in an area which has been subject to extension since the early miocene the latest extensional episode pliocene present has resulted in the formation of nw trending nedipping listric normal faults whose geometry is controlled down to f3 km by borehole data in this paper we integrate a new interpretation of seismic reflection lines with existing seismic field and borehole data to analyse the relations among listric normal faults the top of the brittle ductile transition and the migration of geothermal fluids in accordance with previous interpretations we consider the strong reflector k horizon marking the top of the reflective mid lower crust and located at a depth of 3 5 km in the geothermal area to represent the top of the brittle ductile transition its reflectivity most probably derives from the presence of overpressured fluids we identify three main nw trending nedipping extensional brittle shear zones showing listric geometry and soling out in the vicinity of the k horizon the latter appears to be dislocated in correspondence of the soling out of the shear zones these shear zones because of the associated intense fracturing represent the most natural channels of upward migration of geothermal fluids from the magmatic sources located below the k horizon we suggest that these two conclusions that listric normal faults root at or near the brittle ductile transition and that they act as preferential upward migration paths for magmatic fluids may be of general validity for geothermal fields located in extensional settings d 2002 elsevier science b v all rights reserved

recent sediments and foraminiferal distribution in the skagerrak northeastern north sea abstract a number of bottom sediment samples from the skagerrak have been studied the surface sediment samples reflect the presence of three main sediment types with a fourth which occurs more scattered a selection of 50 samples was used for the study of the foraminifers of the 125 m fraction benthic foraminifers dominate the assemblages using factor analysis and the computer program cabfac the benthic foraminiferal data were reduced to five factors eight species have proven to be significant the factors benthic foraminiferal assemblages are dominated by bolivina cf b robusta elphidium excavatum cassidulina laevigata bulimina marginata melanis barleeanum globobulimina turgida and hyalines balthica respectively the first factors are clearly related to known hydrographic and bottom conditions

the calculated seismic properties of quartz mylonites with typical fabrics relationship to kinematics and temperature summary quartz mylonites produced by intense ductile deformation in shear zones are often invoked as seismic reflectors in the lower continental crust the seismic properties vp vsl v av and polarization planes of v and v have been calculated for five quartz mylonites that display typical lattice preferred orientations lpos all specimens display considerable seismic anisotropy with v anisotropy coefficients of between 8 and 12 per cent there are good correlations between the lpo of the a axes and the minimum v direction and the c axes and the maximum v direction the other seismic properties are not reliable indicators of lpo as the a axis is the major flow direction in quartz a correlation between the ductile flow direction and the v minimum can be made with increasing temperature and pressure alpha quartz transforms to beta quartz in the beta field quartzites are seismically transverse isotropic furthermore there is a considerable increase in v from 6 km s l in the alpha field to nearly 7 km s in the beta field the transition is instantaneous and hence will result in a sharp seismic discontinuity with a reflection coefficient of 0 08 between pure aggregates of alpha and beta phases however under typical conditions of the continental crust the seismological importance of this phase transition will be limited by the presence of secondary minerals and partial melting

high resolution holocene record in the southeastern bay of biscay global versus regional climate signals abstract core ks10b north east atlantic 43 50 n 2 03 w water depth 550 m was recovered at a location of high sediment deposition and hence includes a high resolution palaeoclimatic record for the southeastern bay of biscay over the last 9000 cal yr bp the effect of global and regional climatic forcing factors e g orbital forcing north atlantic oscillation nao and their subsequent control on water temperature sea level hydrology and continental influence were investigated by studying planktic and benthic foraminiferal faunas 150 m sedimentology and stable isotopes results indicate probable episodic long term incursions of the warm and salty iberian poleward current ipc into the bay of biscay during the holocene by the intermittent presence of subtropical globigerinoides ruber in the otherwise temperate fauna these incursions seem to be triggered by negative nao like conditions our data show five main climatic periods which are in general agreement with the literature data on the climatic variability in the north atlantic and the iberian peninsula the early holocene 9000 7400 cal yr bp is characterized by low sea level significant downslope transport eutrophic benthic settings and high surface water productivity these environmental characteristics are probably due to the general wet and warm climate under a prevailing negative nao increasing precipitation and river runoff and favouring the incursion of the ipc into the bay of biscay the climatic optimum appears between 7400 and 6000 cal yr bp under a generally positive nao index in the following 6000 3500 cal yr bp surface water cooling is matching a steep decline of the northern hemisphere summer insolation meanwhile benthic settings are changing progressively towards present day trophic conditions the time interval from 3500 to 1800 cal yr bp encompasses the iberian roman humid period characterized by warm and humid conditions and increasing primary production under a prevailing negative nao index the last 1800 years were characterized by stable cool conditions reflecting a change towards a positive nao state

effect of phase transitions on seismic properties of metapelites a new high temperature laboratory calibration we report new measurements of the seismic properties of an upper amphibolite facies metapelite from the serie dei laghi basement southern alps northern italy presenting evidence for the transition using elastic wave velocity methods and under in situ conditions measurements were made using an internally heated gas apparatus under hydrostatic conditions to 500 mpa and temperatures to 1075 k p wave and s wave velocities were measured parallel and normal to both lineation and foliation at room temperature an average v p at 400 mpa of 6 4 km s and v p anisotropy of 15 were found and an average v s1 of 3 6 km s 8 2 anisotropy and v s2 of 3 5 km s 4 1 anisotropy were also measured to observe the effects of the quartz transition under hydrostatic conditions elastic wave velocity was monitored continuously as the sample was heated to 1075 k at 400 mpa v p was seen to decrease monotonically with increasing temperature to 950 k as temperature continued to increase v p rapidly increased until 1075 k the effect was found to be reversible and is interpreted in terms of the transition in quartz in broad agreement with previous studies a simple interpretation of the data taking into account a field case from southern tuscany as well as natural and elevated geothermal gradient suggests that thermal and hydraulically driven fracture is a likely cause of bright spots seen in these areas with knowledge of the depth of such features the transition additionally allows the temperature at depth to be estimated

relationship of surface sediments and benthic foraminiferal distribution patterns in the norwegian channel northern north sea abstract our study of the distribution of benthic foraminifers in surface sediment samples from the norwegian channel has shown that eight species and five different assemblages are important the assemblages are dominated by uvigerina peregrina bolivina skagerrakensis cassidulina laevigata elphidium excavatum and bulimina marginata respectively hyalinea balthica melonis barleeanum and trifarina angulosa are also abundant the first four assemblages and their dominant species can be related to certain water masses with known characteristics two species are related to certain types of substrate m barleeanum seems to prefer a fine grained substrate while t angulosa occurs most abundantly where the content of silt and clay is low b skagerrakensis and h balthica occur most abundantly in sediments with a high content of organic carbon while t angulosa shows inverse correlation to the organic carbon content

a time series study of the carbon isotopic composition of deep sea benthic foraminifera 1 variation of the 13c of living rose bengal stained deep sea benthic foraminifera is documented from two deep water sites 2430 and 3010 m from a northwest atlantic ocean study area 275 km south of nantucket island the carbon isotopic data of hoeglundina elegans and uvigerina peregrina from five sets of multicorer and soutar box core samples taken over a 10 month interval march may july and october 1996 and january 1997 are compared with an 11 5 month time series of organic carbon flux to assess the effect of organic carbon flux on the carbon isotopic composition of dominant taxa carbon isotopic data of hoeglundina elegans at 3010 m show 0 3 lower mean values following an organic carbon flux maximum resulting from a spring phytoplankton bloom this 13c change following the spring bloom is suggested to be due to the presence of a phytodetritus layer on the seafloor and the subsequent depletion of 13c in the pore waters within the phytodetritus and overlying the sediment surface carbon isotopic data of h elegans from the 2430 m site show an opposite pattern to that found at 3010 m with a 13c enrichment following the spring bloom this different pattern may be due to spatial variation in phytodetritus deposition and resuspension or to a limited number of specimens recovered from the march 1996 cruise the 13c of uvigerina peregrina at 2430 m shows variation over the 10 month interval but an analysis of variance shows that the variability is more consistent with core and subcore variability than with seasonal changes the isotopic analyses are grouped into 100 m size classes on the basis of length measurements of individual specimens to evaluate 13c ontogenetic changes of each species the data show no consistent patterns between size classes in the 13c of either h elegans or u peregrina these results suggest that variation in organic carbon flux does not preferentially affect particular size classes nor do 13c ontogenetic changes exist within the 250 to 750 m size range for these species at this locality on the basis of the lack of ontogenetic changes a range of sizes of specimens from a sample can be used to reconstruct 13c in paleoceanographic studies the prediction standard deviation which is composed of cruise core subcore and residual replicate variability provides an estimate of the magnitude of variability in fossil 13c data it is 0 27 for h elegans at 3010 m and 0 4 for u peregrina at the 2430 m site since these standard deviations are based on living specimens they should be regarded as minimum estimates of variability for fossil data based on single specimen analyses most paleoceanographic reconstructions are based on the analysis of multiple specimens and as a result the standard error would be expected to be reduced for any particular sample the reduced standard error resulting from the analysis of multiple specimens would result in the seasonal and spatial variability observed in this study having little impact on carbon isotopic records

distribution of live benthic foraminifera in the ria de vigo nw spain abstract the spatial and vertical distributions of live benthic foraminifera from the muddy central axis of the ria de vigo were examined under downwelling and upwelling conditions the spatial distribution of the main benthic foraminiferal species is controlled by salinity variations san simon assemblage food availability outer ria assemblage and oxygen concentrations and or reducing microenvironmental conditions in the sediment inner ria assemblage the microhabitat distribution of benthic foraminifera is mainly dependant on the oxygenation redox conditions in the sediment and the vertical segregation of food in the inner areas of the ria low oxygen and or reducing microenvironmental conditions prevent the vertical segregation of microhabitats in outer areas oxygen penetration is deep but microhabitat partitioning only occurs in the presence of additional food resources mainly fresh organic carbon from phytoplankton blooms which triggers the colonisation of the surface layer by new species and the migration upwards and reproduction of opportunistic species

foraminiferal record of marine transgression during deposition of the middle miocene badenian evaporites in central paratethys borkow section polish carpathian foredeep benthic and planktonic foraminifera from a marly clay intercalation sandwiched between mid badenian middle miocene gypsum deposited in an environment of an evaporitic shoal 1 m deep at borkow southern poland indicate a major marine flooding event in the previously isolated carpathian foredeep basin central paratethys after this very short term environmental change benthic foraminifers started to colonize a new niche which was previously defaunated and the pattern of benthic foraminiferal colonization is similar to that related to the reflooding which terminated the badenian evaporite deposition the benthic foraminifer assemblages are composed of pioneer opportunistic r selected species dominated by elphidiids the connection of the carpathian foredeep basin with the marine reservoir was short lived the marly clay intercalations in evaporite sequences originating in bared basins can thus register major environmental changes

hydrographic observations in denmark strait in fall 1997 and their implications for the entrainment into the overflow plume denmark strait is the most important exit for water masses formed in the arctic mediterranean sea and supplies a substantial fraction of the north atlantic deep water observations obtained from rv aranda in august september 1997 indicate that the water crossing the 620m deep sill is mainly drawn from the intermediate waters of the east greenland current the overflow plume was stratified and capped by a less saline layer as it descended beyond 2000m the presence of a low salinity lid implies that entrainment of ambient water is small and that the downstream evolution of the plume characteristics is due to mixing within the plume between the initial overflow waters low salinity but dense water from the east greenland current flowing over the shelf may cross the shelf break south of the sill and add a less dense fraction to the overflow

stable oxygen and carbon isotope systematics of exquisitely preserved turonian foraminifera from tanzania understanding isotopic signatures in fossils the interpretation of 18o and 13c analyses of extinct foraminifera is hampered by insufficient knowledge on the contribution of environmental versus biological factors on the measured values we present single species stable isotope data for 18 benthic and 11 planktic foraminiferal species and one calcareous dinoflagellate cyst species from a turonian equatorial record measured on samples collected in se tanzania all microfossils analyzed were excellently preserved and results are compared to isotopic measurements from bulk sediment of the same material remarkably low intra specific variability standard deviations 0 2 across the studied interval and consistently large benthic planktic offsets in 18o 2 8 and 13c 1 5 indicate absence of major long term environmental fluctuations and presence of a well stratified water column stratigraphic isotopic trends show small shifts that are parallel in all studied benthic species with the exception of the 13c record of lenticulina species but within sample inter specific offsets reflect a combination of habitat differences and species specific isotopic disequilibrium fractionation among planktic taxa closely related taxa tend to have similar isotopic values biserial taxa have the lowest 18o values 4 7 but also have relatively low 13c values 1 6 indicating that for the assumption of a surface water habitat additional metabolic effects need to be involved which supports the concept of their opportunistic lifestyle among trochospiral planktics the keeled taxa with compressed chambers have slightly higher 18o 4 2 and lower 13c 2 3 values than taxa with globular chambers 4 4 and 2 4 respectively suggesting differences in habitat or in peak seasonal abundance benthic taxa are subdivided into three isotopically distinct groups with differences reflecting mineralogy life strategy and habitat group i aragonitic taxa epistomina colomia africana group ii calcitic trochospiral taxa with isotopic values seemingly close to equilibrium berthelina berthelini oridorsalis umbonatus lingulogavelinella globosa lingulogavelinella convexa and group iii calcitic taxa with low 18o values and large scatter in 13c values lenticulina four other benthic species show values between groups ii and iii the wealth and consistency of data especially for benthic taxa permit refined conclusions the five studied species of epistomina have a similar isotopic signature and are inferred to form their aragonitic shells with close to equilibrium values small isotopic offsets are seen among species that differ in orientation of the septal foramen but no offsets are seen that seem to co vary with test shape or ornamentation the conical species c africana has 18o values 0 2 lower and 13c values 0 7 lower than species of epistomina the latter offset probably reflects an infaunal habitat for c africana epistomina and group ii species are recommended for paleoenviromental studies mono specific lenticulina 18o values may be used if increased by correction factors of 0 4 to 0 9 but this taxon s low and variable 13c values are interpreted to reflect incorporation of respiratory co2 possibly combined with fast growth rates related to opportunism rather than equilibrium with benthic dissolved inorganic carbon the observed stability of inter specific isotopic offsets suggests disequilibrium isotopic effects are relatively consistent for many taxa in this section and correction factors are proposed that may help to generate more robust upper cretaceous foraminiferal isotopic records however 18o 13c covariance in some benthic inter specific comparisons suggests offsets might vary with changes in temperature food supply or other factors so the appropriateness of the correction factors should be confirmed before being applied at different sites similarities between the observed single species isotopic patterns from this and other studies are used to present a summarizing scheme of influences on the stable isotopic composition in foraminiferal tests by applying the new insights from our study to data from other cretaceous studies we demonstrate that the selection of species for isotopic analysis and understanding these signals are critical to the outcome of paleoceanographic interpretations