stratigraphic overview of palaeogene tuffs in the faroe shetland basin ne atlantic margin tuffs form key stratigraphic markers that assist with determining the timing of volcanic margin development a number of laterally extensive tuffs are preserved along the north atlantic margin in the offshore faroe shetland basin fsb a product of early palaeogene volcanism associated with the break up and seafloor spreading between greenland and nw europe these tuffs which are dominantly basaltic in composition are widely preserved in the contiguous north sea basin however less attention has been paid to them in the fsb this study integrates multiple regional datasets including 3d seismic data and released commercial well logs to detail the character and distribution of early palaeogene tuffs in the fsb the earliest tuffs are more locally identified by their presence in core whereas later tuffs are more regionally recognizable highlighting more widespread volcanism with time the distribution of tuffs also reveals the timing of formation of the previously enigmatic volcanic centres importantly owing to constraints of vertical resolution in well data we argue that the number of tuffs in the north atlantic margin is probably underestimated and biased towards basaltic tuffs which are easier to identify on well logs

sedimentary trace element constraints on the role of north atlantic igneous province volcanism in late paleocene early eocene environmental change abstract a growing body of geologic evidence suggests that emplacement of the north atlantic igneous province naip played a major role in global warming during the early paleogene as well as in the transient paleocene eocene thermal maximum petm event a 5 million year record of major and trace element abundances spanning 56 to 51 ma at deep sea drilling project sites 401 and 549 confirms that the majority of naip volcanism occurred as subaerial flows thus the trace element records provide constraints on the nature and scope of the environmental impact of the naip during the late paleocene early eocene interval subaerial volcanism would have injected mantle co2 directly into the atmosphere resulting in a more immediate increase in atmospheric greenhouse gas abundances than co2 input through submarine volcanism the lack of significant hydrothermalism contradicts recently proposed mechanisms for thermally destabilizing methane hydrate reservoirs during the petm any connection between naip volcanism and petm warming had to occur through the atmosphere

the development of polygonal fault systems by syneresis of colloidal sediments abstract polygonal fault systems occur in numerous sedimentary basins worldwide are generally located on passive margins in onlap fill units and tend to comprise the finest grained sediments in this geological setting these fault systems have been most thoroughly described in the central north sea basin and the detailed structure shows a significant correlation with lithological variations both vertically and laterally extension measured in stacked decoupled tiers of polygonal faults correlates positively with both clay fraction and smectite content lateral facies variations are also observed and indicate that time equivalent sequences upslope from the smectite rich polygonally faulted sediments are coarse grained clay poor and undeformed this leads us to believe that the structure and geometry of the fault system are controlled by the colloidal nature of the sediments and that the volumetric contraction measured on seismic sections can be accounted for by syneresis of colloidal smectitic gels during early compaction syneresis results from the spontaneous contraction of a sedimentary gel without evaporation of the constituent pore fluid this process occurs due to the domination of interparticle attractive forces in marine clays dependent on environment and is governed by the change of gel permeability and viscosity with progressive compaction the process of syneresis can account for a number of structural features observed within the fault systems such as tiers of faults the location of maximum fault throw and growth components at upper fault tips as such this paper represents the first attempt to correlate microscale properties of clay rich sediments to their macroscale seismic character

magmatic tectonic evolution of a volcanic rifted margin abstract many north atlantic continental margins are underlain by huge volcanic edifices near the continent ocean boundary a deep crustal hole drilled on the voring plateau odp leg 104 has provided important constraints on the initial breakup history and the subsequent margin evolution by penetrating more than 900 m of igneous rocks and interbedded sediments below a post early eocene cover the rocks constitute two distinct different volcanic series the upper series comprising a seaward dipping reflector wedge consists of transitional mid oceanic tholeiitic lava flows and thin volcaniclastic sediments dacitic flows some dikes and thicker interbedded sediments constitute the lower series the margin evolved by paleocene crustal extension accompanied by uplift and pervasive intrusion of the rift zone just prior to breakup magma from shallow crustal melts produced the lower series the upper series was constructed during an intense rapidly waning subaerial volcanic surge following breakup near the paleocene eocene transition it covers both the new oceanic crust and large areas of the continental crust the dipping wedge was formed by subsidence due to loading and thermal contraction possibly amplified by tectonism when the surge abated the injection center rapidly subsided and normal oceanic crust was formed there is a direct temporal and compositional relationship between the onshore north atlantic volcanic province and the margin volcanism compared to the transverse part of the province including the iceland hotspot which has been active over 60 m y the volcanic margins reflect a 2500 km long transient segment related to continental breakup lasting only about 3 m y the volcanic surge and uplift at breakup are related to a modest regional increased temperature at the base of the lithosphere this mode of margin formation has had important paleoenvironmental implications

stratigraphic correlation of late palaeocene sand deposits in the sogne basin area of the danish and norwegian central north sea a stratigraphic analysis of late palaeocene sands of the sogne basin and the western part of the norwegian danish basin shows that the sand bodies are of differenct ages the geographic distribution of the sand deposits shows that they are related to underlying mesozoic structures suggesting a controlling effect of tertiary tectonics on the deposition of sand during the late palaeocene however the structural setting of various sand bodies varies from reactivation of older faults and reactivation of salt structures the local character of the structures active during the late palaeocene introduces minor depressions with no lateral connection the sand bodies which are interpreted as having been deposited in these depressions are thus in general separate bodies with no lateral connection the fennoscandian shield and eroded mesozoic sediments along the fennoscandian border zone are suggested as source area for the late palaeocene sand deposits

crystallization sequence and magma chamber processes in the ferrobasaltic sept iles layered intrusion canada the sept iles layered intrusion quebec canada 564 ma is a large plutonic body with a diameter of 80 km and a thickness of 6 km made up from its base to top of a layered series with troctolite and gabbro and an upper border series with anorthosite capped by cupolas of a type granite chilled margin compositions suggest a ferrobasaltic parental magma close to that of the skaergaard intrusion but much richer in iron and titanium samples from drill cores and surface sampling of the 4 7 km thick layered series reveal a succession of massive troctolites and layered gabbros that contain 24 fe ti oxide layers cm to m thick and many anorthositic autolithic blocks the sequence of crystallization in the layered series is plagioclase an72 34 and olivine fo75 21 followed by magnetite and ilmenite then ca rich pyroxene and finally apatite an olivine gap is observed between fo66 and fo59 the saturation of fe ti oxides before ca rich pyroxene is interpreted to be the result of the high feot and tio2 contents and the low cao content of the parental magma contamination by old continental crust has occurred during crystallization of the layered series as indicated by sr isotopic compositions 87sr 86sr564 0 70360 0 70497 the differentiation trend of the intrusion is interrupted by two large and many small reversals to more primitive compositions of cumulus phases cr content of magnetite and lower sr isotope ratios these reversals and the intermittent disappearance of some phases are interpreted as resulting from magma chamber replenishments by undifferentiated primitive basaltic magma and mixing with the resident magma the author 2010 published by oxford university press all rights reserved for permissions please e mail journals permissions oxfordjournals org

magnetostratigraphic correlation of palaeogene sediments in the hampshire and london basins southern uk magnetostratigraphic studies of the late palaeocene and early to middle eocene formations in the hampshire and london basins indicate that the geomagnetic field maintained a predominantly reverse polarity throughout the period of deposition of these sediments eight discrete normal polarity magnetozones have been identified within this dominantly reverse polarity interval three of these lie within the bracklesham group three within the london clay formation one in the oldhaven 9formation9 and one within the lowermost part of the thanet formation assuming that the magnetozone boundaries represent absolute time planes except where they correspond with stratigraphic hiatuses they may be used to provide a time framework for chrono stratigraphic correlation between sections and for investigating the dynamics of early palaeogene sedimentation patterns in this region the results indicate that the majority of the marine transgressive and regressive events which form the basis of king9s 1981 subdivisions of the london clay occurred very rapidly and may be regarded as being effectively 9instantaneous9 in marked contrast the boundaries between the sedimentary cycles of the bracklesham group represented by the wittering earnley selsey and huntingbridge divisions are significantly diachronous in relation to the absolute time planes provided by the magnetozone boundaries it is clear that the bracklesham group transgressive events occurred systematically earlier in the east than in the west as might be expected for westward directed transgressions certain biostratigraphic zonal boundaries within the bracklesham group appear also to have been influenced by the changing environmental conditions which accompanied these transgressive regressive cycles

environmental impact of volcanic margin formation late rift stage uplift and subsequent massive transient volcanism during breakup of rifted volcanic continental margins constrain paleoenvironments by modifying basin geometry and the composition of the atmosphere hydrosphere and thus biosphere on regional and global scales the early tertiary north atlantic breakup history shows that lava emplacement was accompanied by regional ashfalls and that extrusive complexes influenced paleogene oceanic and continental margin circulation and sedimentation temporal correspondence with the terminal paleocene deep sea extinction event and the earliest eocene greenhouse suggests a global impact possibly by enhanced atmospheric co 2 levels leading to polar warming and thereby changing patterns of deep water formation in this context transient subaerial volcanism at continental margins should be considered with the much discussed continental flood basalt provinces and oceanic plateaus

giant irregular pockmark craters in the palaeogene of the outer moray firth basin uk north sea a cluster of irregular pockmark craters of palaeogene age in block 15 18 in the outer moray firth uk north sea have been mapped on 3d seismic data with well control the craters range from 0 5 to 4 km in diameter between 50 and 200 m in depth and have been buried by tertiary subsidence and sedimentation to present day depths of between 1000 and 1400 m sub sea they are circular to elliptical in plan view and are located in a delta front and upper pro deltaic slope position on the dornoch delta the structures are confined to the top of the lower eocene balder formation and regional mapping across the moray firth basin shows they are restricted to an area of ca 15 15 km2 well data show that the craters are sand filled and have excavated an argillaceous and tuffaceous unit the crater filling sands are sealed by overlying mudstone units planar wing like features emanate from the margins of the craters well control indicates that these seismically identified wings consist of sandstone suggesting that the craters have been modified by an episode of sand remobilisation and injection the proposed mechanism for the formation of these structures is large scale fluid eruption probably shallow gas at the early eocene seafloor these craters are significantly larger in size than those typically observed on contemporary sea floors we argue that the gas is more likely to have been sourced from deeper jurassic or carboniferous sediments within the witch ground graben than from shallow biogenic origins these structures rank in scale alongside the largest known pockmarks and demonstrate that natural fluid and hydrocarbon seeps have a long ancestry in this basin

nannoplankton zonation and the palaeocene eocene boundary beds of nw europe an indirect correlation by means of volcanic ash layers correlation of early palaeogene ash layers in dsdp hole 550 leg 80 goban spur with those of the north sea basin indicates that the base of nannoplankton zone np10 approximates the base of the sele formation of the north sea area the bases of the danish ash series the german ash bearing untereozan 1 and the paris basin sparnacian and the top of the woolwich reading bottom bed of the london basin if as is now common practice the palaeocene eocene boundary is placed at the np9 np10 boundary then the units listed above would constitute the basal units of the eocene in their respective countries the cessation of large scale pyroclastic activity took place at about the middle of the zone np10 interval

3d seismic reflection mapping of the silverpit multi ringed crater north sea the first comprehensive mapping of the silverpit multi ringed crater is presented based on five adjoining 3d seismic surveys that together provide 78 216 km2 areal coverage of the structure with spatial and depth sampling of 10 m the top cretaceous surface shows an excavated crater 3 km in diameter surrounded by 10 15 concentric ring structures out to a radius of 9 4 km seismic sequence stratigraphy and drilled wells indicate the lower age bound is a disconformity spanning 74 54 ma the upper bound is eocene termination of concentric ring fault growth ca 45 ma the inner rings are extensional faults defining rotated fault blocks that would be considered part of the crater in an impact structure interpretation giving a final impact crater diameter of 8 km the outer rings show a surprising variation in style from graben in the west to compressional structures in the east this may be explained by postcratering gravity spreading on easterly dipping intra cretaceous detachments within the crater the top cretaceous seismic reflector is disrupted and blocky but defines a central uplift with a slight crestal depression below this uplift the prominent base cretaceous seismic reflector shows jurassic strata rising into a cone 300 m high and 1 km wide characterized by radial faults this central uplift within the crater may structurally balance the inner ring fault blocks via a slumping model but we also identify low seismic velocity in the uplifted jurassic so fracturing may have contributed to growth of the central peak at a radius of 2 5 km base cretaceous shows a dish shaped depression that we interpret as marking either the extent of slumping toward the crater at this structural level or the limit of shockwave induced porosity collapse seismic reflectors above the top cretaceous excavated crater show differential compaction during the eocene accommodated by drape structure plus two conical faults that define narrow ring graben and represent the final phase of crater related tectonics

the structure and subsidence of rockall trough from two ship seismic experiments coincident multichannel seismic reflection and refraction profiles acquired northwest of britain during a two ship seismic experiment in the southern rockall trough provide evidence for a thin 6 km syn rift crust below rockall trough the variation of seismic velocity with depth is consistent with either oceanic crust similar to that found in other parts of the north atlantic or with thinned continental crust heavily intruded by syn rift igneous rocks the syn rift crust beneath rockall trough is now buried by nearly 5 km of sediments that are intruded by tertiary volcanics varying in extent from isolated sills to a large sill complex extending 100 km laterally the basement imaged on seismic profiles exhibits a band of subhorizontal reflectors that extend laterally over distances of up to 40 km which they interpret as sediments intercalated with submarine lava flow generated during the opening of the trough estimates of stretching from crustal thinning and from subsidence indicate that rockall trough has undergone extensive rifting beta 6 upwelling asthenosphere beneath the thinned lithosphere generated at least 1 3 km thickness of melt as it decompressed the molten rock rose upward from the mantle until it was in part extruded as lava flows and in partmore intruded into the crust less

latest on the absolute age of the paleocene eocene thermal maximum petm new insights from exact stratigraphic position of key ash layers 19 and 17 abstract we constructed a precise early eocene orbital cyclostratigraphy for dsdp site 550 leg 80 goban spur north atlantic utilizing precession related cycles as represented in a high resolution x ray fluorescence based barium core log based on counting of those cycles we constrain the exact timing of two volcanic ash layers in site 550 which correlate to ashes 19 and 17 of the fur formation in denmark the ashes relative to the onset of the paleocene eocene thermal maximum petm are offset by 862 kyr and 672 kyr respectively when combined with published absolute ages for ash 17 the absolute age for the onset of the petm is consistent with astronomically calibrated ages using the current absolute age of 28 02 ma for the fish canyon tuff fct standard for calibrating the absolute age of ash 17 is consistent with tuning option 2 in the astronomically calibrated paleocene time scale of westerhold et al 2008 westerhold t rohl u raffi i fornaciari e monechi s reale v bowles j and evans h f 2008 astronomical calibration of the paleocene time palaeogeography palaeoclimatology palaeoecology v 257 p 377 403 using the recently recalibrated absolute age of 28 201 ma for the fct standard is consistent with tuning option 3 in the astronomically calibrated paleocene time scale the new results do not support the existence of any additional 405 kyr cycle in the early paleocene astronomically tuned time scale

stratigraphy of the paleocene continental sedimentary succession of the northern pyrenean basin corbieres southern france using δ13corg isotopes continental dominated successions are often poorly constrained stratigraphically due to a lack of robust biostratigraphic markers this study provides the first dataset of 13corg together with magnetostratigraphic and biostratigraphic data from a thick continental dominated succession at lairiere northern pyrenees france this section encompasses the latest cretaceous up to the paleocene eocene thermal maximum interval and is characterized by fluvial deposits occasionally intercalated with continental carbonates lacustrine deltaic deposits and shallow marine sediments this work identifies 13corg events and assigns them to global 13c geochemical events defined in pyrenean and tethyan marine successions in which the stage boundaries are well calibrated as the isotopic measurements are performed on dispersed organic matter in sedimentary rocks with a low organic content we propose that analyses of the signal should take into consideration the depositional environment because variations in the organic matter content might affect the signal we establish a high resolution chronostratigraphy in terrestrial paleocene deposits in the ne pyrenean zone recognize a late selandian interval and define the paleocene eocene thermal maximum event supplementary material palaeomagnetic results geochemistry details and palynological analysis are available at https doi org 10 6084 m9 figshare c 4871214

early eocene volcanic ashes on greifswalder oie and their depositional environment with an overview of coeval ash bearing deposits in northern germany and denmark unconsolidated bentonites and carbonate cemented volcanic ashes occur in northern germany within the clay sequence of the lamstedt and schlieven formations documented by several wells ash bearing carbonate concretions so called cementstones are also known from glacially transported rafts and erratic boulders on the baltic sea island greifswalder oie representing the easternmost exposures of early eocene sediments in the north sea basin the ashes can be correlated with water lain ashes of the danish fur and olst formations mo clay generated during the opening of the north atlantic ocean about 55 ma ago two types of cementstones can be distinguished on the basis of the mineralogical composition sedimentary features and fossil content greifswalder oie type i contains a black up to 12 cm thick ash deposit that follows above two distinct thin grey ash layers the major ash unit has a rather homogeneous lower part only a very weak normal grading and faint lamination are discernible in the upper part however intercalations with light mudstone in part intensively bioturbated together with parallel and cross lamination suggest reworking of the ash in a shallow marine environment major and trace element compositions are used to correlate type i ashes with those of the danish positive series which represent rather uniform ferrobasalts of the danish stage 4 probably related to the emergence of proto iceland in contrast type ii ash comprises a single normally graded about 5 cm thick layer of water lain air fall tuff which is embedded in fine grained sandstone to muddy siltstone type ii ash is characterised by very high tio2 but low mgo contents exceptional ree patterns with a pronounced positive eu anomaly suggest intense leaching of the glass that hampers exact correlation with pyroclastic deposits within the north atlantic igneous province

did paleogene north atlantic rift related eruptions drive early eocene climate cooling abstract the delivery of volcanogenic sulphur into the upper atmosphere by explosive eruptions is known to cause significant temporary climate cooling therefore phreatomagmatic and phreatoplinian eruptions occurring during the final rifting stages of active flood basalt provinces provide a potent mechanism for triggering climate change during the early eocene the northeast atlantic margin was subjected to repeated ashfall for 0 5 m y this was the result of extensive phreatomagmatic activity along 3000 km of the opening northeast atlantic rift these widespread predominantly basaltic ashes are now preserved in marine sediments of the balder formation and its equivalents and occur over an area extending from the faroe islands to denmark and southern england these ash bearing sediments also contain pollen and spore floras derived from low diversity forests that grew in cooler drier climates than were experienced either before or after these highly explosive eruptions in addition coeval plant macrofossil evidence from the bighorn basin wyoming usa also shows a comparable pattern of vegetation change the coincidence of the ashes and cooler climate pollen and spore floras in northwest europe identifies volcanism as the primary cause of climate cooling estimates show that whilst relatively few phreatomagmatic eruptive centres along the 3000 km opening rift system could readily generate 0 5 1 c cooling on an annual basis only persistent or repeated volcanic phases would have been able to achieve the long term cooling effect observed in the floral record we propose that the cumulative effect of repeated balder formation eruptions initiated a biodiversity crisis in the northeast atlantic margin forests only the decline of this persistent volcanic activity and the subsequent climatic warming at the start of the eocene thermal maximum allowed the growth of subtropical forests to develop across the region

gigantic volcanic eruptions and climatic change in the early eocene 23 layers of altered volcanic ash bentonites originating from the north atlantic igneous province have been recorded in early eocene deposits of the austrian alps about 1 900 km away from the source area the austrian bentonites are distal equivalents of the main ash phase in denmark and the north sea basin we have calculated the total eruption volume of this series as 21 000 km3 which occurred in 600 000 years the most powerful single eruption of this series took place 54 0 million years ago ma and ejected ca 1 200 km3 of ash material which makes it one of the largest basaltic pyroclastic eruptions in geological history the clustering of eruptions must have significantly affected the incoming solar radiation in the early eocene by the continuous production of stratospheric dust and aerosol clouds this hypothesis is corroborated by oxygen isotope values which indicate a global decrease of sea surface temperatures between 1 and 2 c during this major phase of explosive volcanism

along strike variations in rifted margin crustal architecture and lithosphere thinning between northern voring and lofoten margin segments off mid norway abstract an extensive geophysical and geological database is used to integrate observations and structural and stratigraphic modelling along the northern voring and lofoten margins off mid norway subsidence and fault analysis demonstrates depth dependent lithosphere stretching along both margin segments and the modelling concurs with an emergent or relatively shallow water emplacement environment for the breakup lavas along the northern voring margin however off lofoten subsidence modelling predicts 1500 m of bathymetric relief during breakup in contradiction to the view of subaerial volcanic emplacement environment off mid norway a distinct early eocene bathymetric gradient from voring to lofoten margin is suggested exhibiting depths in the order of 500 1000 m on the latter margin and thus an environment for submarine lava emplacement the water depth may even have reached 1250 m following breakup due to an initial rapid margin subsidence of the lofoten margin along a deep rooted low angle detachment fault the differences between northern voring and lofoten margin segments in pre and post breakup evolution are attributed to the bivrost lineament a transfer zone separating the two margin segments which appears as a major across margin boundary in terms of margin physiography and paleogeography differential sediment accommodation space crustal and lithosphere scale structure and breakup magmatism furthermore gravity inversion results appear to independently predict a significantly greater volcanic addition on the voring than on the lofoten margin

tarawera 1886 new zealand a basaltic plinian fissure eruption abstract new zealand s biggest and most destructive volcanic eruption of historical times was that of tarawera in 1886 the resulting scoria fall has a dispersal very similar in extent to that of the vesuvius a d 79 pumice fall and is one of the few known examples of a basaltic deposit of plinian type a new estimate of the volume 2 km 3 is significantly greater than previous estimates the basalt came mainly from a 7 km length of fissure and emission and exit velocity were fairly uniform along at least 4 km of it this is one of the few documented examples of a plinian eruption from a fissure vent primary welding of the scoria fall resulted where the accumulation rate exceeded about 250 mm min 1 a model of the eruption dynamics is proposed which leads to an estimate of 28 km for the height of the eruption cloud and implies a magma volatile fraction of 1 5 3 violent phreatic explosions occurred in the southwestern extension of the fissure across the rotomahana geothermal field and it is thought that some of the water responsible for the power of the plinian eruption came from this source though its amount was not sufficient to turn the eruption into a phreatoplinian one

northwestern european paleogene magnetostratigraphy biostratigraphy and paleogeography calcareous nannofossil evidence global calcareous nannofossil biostratigraphy is used to correlate the paleogene chronostratigraphic units of northwestern europe and standard nannofossil biozones such biostratigraphic correlations show that the lithostratigraphic sequence is discontinuous and allows interpretation of the paleogeography of northwestern europe during the paleogene and evaluation of the influence of global sea level eustatic changes on northwestern european stratigraphy a well documented unconformity occurs near the lower middle eocene boundary in the paris basin this unconformity which also can be traced in the london hampshire basin and in belgium correlates with a coastal offlap event presumed sea level of vail et al on the basis of magnetostratigraphic biostratigraphic correlations the duration of the hiatus associated with this unconformity can be estimated to be 0 6 to 1 5 m y in the hampshire basin and 2 to 4 m y in the paris basin

testing global synchronism in peri pacific arc volcanism abstract episodicity of arc volcanism along the pacific rim is quantitatively analysed based on the record preserved by ash layers in deep sea sediments drilled by the deep sea drilling project and the ocean drilling program two major pulses of arc volcanism have been found one during middle miocene times 18 13 ma the other during pliocene quaternary times 5 0 ma these pulses are shown to relate to the tectonic stress regime of the arc lithosphere rather than to subduction rate these episodes of arc volcanism activity coincide with major tectonic events documented on circum pacific subduction zones as a consequence a global control of plate kinematics could influence both volcanic and tectonic evolution of pacific convergent margins

diagenetic clinoptilolite and opal ct from the middle eocene wittering formation isle of wight u k abstract thinly interbedded estuarine sandstones and mudstones in the middle eocene wittering formation bracklesham group isle of wight contain authigenic clinoptilolite opal ct and possibly authigenic smectite over a thickness of 8 5 m the clinoptilolite and opal ct cements have resulted in these beds being the only ones tightly cemented in the wittering formation the rest being soft sands and muds the unit contains abundant siliceous sponge spicules many of which are preserved as voids and were the likely source of the opal ct the presence of an organic rich rooted paleosol histosol immediately overlying the unit is believed to have contributed significantly to the early diagenetic history of the estuarine sediments in particular the formation of zeolite although the ph and dissolved silica of unmodified seawater are too low for zeolite formation high concentrations of dissolved silica are believed to have resulted from dissolution of siliceous sponge spicules opal a and formation of silica organic acid complexes organic acid dissolution of feldspars absent from the zeolite bearing interval is the most probable source of alumina and cations for zeolite formation ree data show that volcanic ash was never present and cannot therefore have been the source of the zeolite this investigation therefore demonstrates a novel route by which the pore fluid chemistry required for zeolite formation can be achieved

hydrography and through flow in the north eastern north atlantic ocean the nansen project abstract the circulation and hydrography of the north eastern north atlantic has been studied with an emphasis on the upper layers and the deep water types which take part in the thermohaline overturning of the oceanic conveyor belt over 900 hydrographic stations were used for this study mainly from the 1987 1991 period the hydrographic properties of subpolar mode water in the upper layer which is transported towards the norwegian sea showed large regional variation the deep water mass was dominated by the cold inflow of deep water from the norwegian sea and by a cyclonic recirculation of lower deep water with a high antarctic bottom water content at intermediate levels the dominating water type was labrador sea water with only minor influence of mediterranean sea water in the permanent pycnocline traces of antarctic intermediate water were found geostrophic transports have been estimated and these agreed in order of magnitude with the local heat budget with current measurements with data from surface drifters and with the observed water mass modification a total of 23 sv of surface water entered the region of which 20 sv originated from the north atlantic current while 3 sv entered via an eastern boundary current of this total 13 sv of surface water left the area across the reykjanes ridge and 7 sv entered the norwegian sea while 3 sv was entrained by the cold overflow across the iceland scotland ridge approximately 1 4 sv of norwegian sea deep water was involved in the overflow into the iceland basin which with about 1 1 sv of entrained water and 1 1 sv recirculating lower deep water formed a deep northern boundary current in the iceland basin at intermediate depths where labrador sea water formed the dominant water type about 2 sv of entrained surface water contributed to a saline water mass which was transported westwards along the south icelandic slope