iron in plagioclase as a monitor of the differentiation of the skaergaard intrusion several recent publications suggest that the appearance of fe ti oxides terminates iron enrichment and starts pronounced silica enrichment the bowen trend during the differentiation of tholeiitic basalt however this does not appear to hold for the skaergaard intrusion new data from a 950 m long drill core 90 22 through its upper zone reveal that 1 iron in plagioclase increases from 0 25 to 0 45 wt feot with fractionation of evolved oxide ferrodiorites an46 32 and 2 the evolving liquid which is modelled by incremental bulk rock summation increased its iron content from 20 1 to 26 5 wt feot and its silica content from 47 4 to 49 6 wt sio2 with fractional crystallisation the fenner trend positive correlation between modelled iron content of the magmas and measured iron content of plagioclase confirms that iron enrichment is petrologically feasible even with fe ti oxides in the fractionating assemblage as suggested by previous authors fractional crystallisation closed to oxygen exchange is the likely reason why some layered intrusions diverge from the bowen mechanism of differentiation it is emphasised that both trends seem to exist in nature

from greenhouse to icehouse organic walled dinoflagellate cysts as paleoenvironmental indicators in the paleogene abstract dinoflagellates are an important component of the extant eukaryotic plankton their organic walled hypnozygotic cysts dinocysts provide a rich albeit incomplete history of the group in ancient sediments building on pioneering studies of the late 1970s and 1980s recent drilling in the southern ocean has provided a wealth of new dinocyst data spanning the entire paleogene such multidisciplinary studies have been instrumental in refining existing and furnishing new concepts of paleogene paleoenvironmental and paleoclimatic reconstructions by means of dinocysts because dinocysts notably exhibit high abundances in neritic settings dinocyst based environmental and paleoclimatic information is important and complementary to the data derived from typically more offshore groups as planktonic foraminifera coccolithophorids diatoms and radiolaria by presenting case studies from around the globe this contribution provides a concise review of our present understanding of the paleoenvironmental significance of dinocysts in the paleogene 65 25 ma representing earth s greenhouse icehouse transition this episode holds the key to the understanding of extreme transient climatic change we discuss the potential of dinocysts for the reconstruction of paleogene sea surface productivity temperature salinity stratification and paleo oxygenation along with their application in sequence stratigraphy oceanic circulation and general watermass reconstructions

late palaeocene early eocene dinoflagellate cysts from the turgay strait kazakhstan correlations across ancient seaways abstract the results of a quantitative palynological analysis emphasizing organic walled dinoflagellate cysts dinocysts of palaeocene eocene deposits exposed in the sokolovsky quarry turgay trough northern kazakhstan are presented here located in the ancient turgay strait a former seaway presumed to have connected the tethyan and boreal oceans and seas in the early palaeogene the sokolovsky quarry outcrop occupies a key position for the analysis of connections between these realms in general the dinocyst succession of sokolovsky closely resembles coeval arctic ocean north sea basin counterparts only in one interval endemic and or possibly tethyan species co occur the successive dinocyst assemblages allow recognition of the late palaeocene early eocene p5a p5b p6a p6b and e2 zones established in the north sea basin the succession is interpreted to represent parts of several third order sea level cycles correlative with those recognised in the north sea basin detailed comparison with similar studies from southeastern england allows the recognition of parts of third order cycles thanetian 1 tht 1 2 4 5 and ypresian ypr 3 in addition two important stratigraphic gaps within the palaeocene eocene succession are recognised possibly reflecting times of sea level lowering these gaps are inferred from 1 the absence of a complete p5b p6a transition 2 the absence of zone e1 and 3 bio sequence stratigraphy combined results indicate that the turgay strait flooded from the north between 57 8 and 57 1 ma cycles tht 1 and 2 in part with a minor missing section during the second phase of turgay flooding 56 4 55 3 ma evidence may be taken to indicate increased influence from the tethyan ocean and or warmer conditions deposits reflecting the late palaeocene thermal maximum associated with this interval are present at sokolovsky quarry this interval is marked by abundant apectodinium spp including a augustum and organic rich layers a third flooding is correlative to the london clay transgression from 54 5 ma from our study no decisive evidence has become available that confirms that a connection between the arctic and tethyan oceans via the turgay strait in the early palaeogene existed nevertheless during intervals of major sea level fall the turgay strait depression may be regarded to have been an important feature for migrating terrestrial biota four new wetzeliellioid taxa apectodinium sp a apectodinium sp b wilsonidium sp a and wilsonidium sp b are described from the palaeocene part of the section

the late crystallization stages of low ti low fe tholeiitic magmas insights from evolved antarctic and tasmanian rocks abstract examples of the latest stages of crystallization in evolved tholeiitic rocks can be found in the low ti low p ferrar magmatic province in antarctica e g thern promontory and archambault ridge and tasmania e g the red hill intrusion and mount wellington sill evolved rocks of this magmatic province include a rocks of basaltic andesite composition containing plagioclase augite pigeonite and interstitial fe ti oxides b rocks of andesitic composition with plagioclase as a liquidus phase a single fe rich subcalcic clinopyroxene and fe ti oxides and c rocks of dacitic composition displaying granophyric texture containing sodic plagioclase alkali feldspar ferrohedenbergite fayalite fe ti oxides quartz and accessory phases the latest crystallization stages are thus characterized by the striking chemical convergence of subcalcic fe augite and fe pigeonite followed by more evolved rocks that preserve quartz alkali feldspar cotectic granophyric relationships lack subcalcic clinopyroxene and contain coexisting olivine and calcium rich clinopyroxene these features are consistent with crystallization at or below the quartz fayalite magnetite oxygen buffer at temperatures close to 800 c the trace element geochemistry of coexisting pyroxenes feldspar and fe ti oxides are entirely consistent with magmatic evolution caused by fractional crystallization of the observed phases similarities and differences with other silicic volcanic rocks elsewhere are also described there is no evidence for liquid immiscibility

late eocene to early oligocene dinoflagellate cysts from the priabonian type area northeast italy biostratigraphy and paleoenvironmental interpretation abstract marginal marine late eocene through early oligocene dinoflagellate cyst successions have been studied from the type area of the priabonian stage northeast italy the results allow the recognition of dinoflagellate zones previously defined in bio and magnetostratigraphically well calibrated pelagic sequences from central italy thus providing a first order correlation of the priabonian stage to the standard chronostratigraphic scale with unprecedented precision within this detailed biostratigraphic framework successive shifts in the composition of the dinoflagellate cyst assemblages are interpreted in terms of sea level and sea surface temperature sst fluctuations the evaluation of ecologically and sedimentary controlled changes in the composition of dinoflagellate cyst assemblages in combination with sequence stratigraphic analysis allows the reconstruction of third and fourth order sea level fluctuations the third order sea level fluctuations appear to correspond to exxon cycles ta4 1 4 5 the stratigraphically and palaeoenvironmentally important late eocene dinoflagellate cyst species glaphyrocysta priabonensis sp nov is formally described

precursors of the paleocene eocene thermal maximum petm in the subathu group nw sub himalaya india abstract the paleocene eocene thermal maximum petm is one of the most pronounced and widely documented global warming events in the geological history that occurred at the beginning of the eocene 56 ma causing substantial changes in biota and geochemistry it is marked worldwide by a negative isotopic excursion of 13c the biotic changes associated with the petm in marine realm include bloom of the dinoflagellate apectodinium turnover of larger foraminiferids diversification of planktic foraminiferids and carbonate dissolution of calcareous test shells etc while the geochemical changes include decrease in carbonates and increase in abundance of silicates and phyllosilicates etc conspicuously there has been no attempt to identify the petm in the himalaya even though some himalayan sections are known to have paleocene eocene transition beds to fill this lacuna we investigated the basal part of the late paleocene middle eocene subathu group exposed at the village kurla near subathu in himachal pradesh nw sub himalaya for biotic mineralogical and geochemical signatures of this abrupt warming event the significant results of this study include carbon isotope excursion cie of 3 4 occurrence of index dinoflagellate genus apectodinium and carbonate dissolution of the larger benthic foraminiferids the mineralogical changes noted across the paleocene eocene transition include increase in quartz and phyllosilicates and decrease in carbonates the geochemical changes include i increase in sio2 al2o3 k2o and fe2o3 ii decrease in caco3 iii decreasing trend of si al fe al and mg al ratios iv increasing trend of k al ti al and zr al ratios v changes in trace element abundance vi maximum chemical index of alteration cia of 85 89 and vii increase in abundance of rare earth elements the aforementioned dataset is clearly very close to the petm and even reflects its probable onset and peak phases however it is insufficient to definitively identify the petm in the studied section nevertheless since this study is the first from a himalayan section and brings out considerable new information all results and interpretations are presented and discussed here

liquid immiscibility and the evolution of basaltic magma this experimental study examines relationships between alternative evolution paths of basaltic liquids the so called bowen and fenner trends and silicate liquid immiscibility synthetic analogues of natural immiscible systems exhibited in volcanic glasses and melt inclusions were used as starting mixtures conventional quench experiments in 1atm gas mixing furnaces proved unable to reproduce unmixing of ferrobasaltic melts yielding instead either turbid opalescent glasses or crystallization of tridymite and pyroxenes in contrast experiments involving in situ high temperature centrifugation at 1000g g 1 4 9 8 m s did yield macroscopic unmixing and phase separation centrifugation for 3 4 h was insufficient to complete phase segregation and resulted in sub micron immiscible emulsions in quenched glasses for a model liquid composition of the middle zone of the skaergaard intrusion at super liquidus temperatures of 1110 11208c centrifugation produced a thin silicic layer 64 5 wt sio2 and 7 4 wt feo at the top of the main fe rich glass 46 wt sio2 and 21 wt feo the divergent compositions at the top and bottom were shown in a series of static runs to crystallize very similar crystal assemblages of plagioclase pyroxene olivine and fe ti oxides we infer from these results that unmixing of complex aluminosilicate liquids may be seriously kinetically hampered presumably by a nucleation barrier and thus conventional static experiments may not correctly reproduce it in the light of our centrifuge experiments immiscibility in the skaergaard intrusion could have started already at the transition from the lower to the middle zone thus magma unmixing might be an important factor in the development of the fe enrichment trend documented in the cumulates of the skaergaard layered series

eocene stratigraphy of the north sea basin abstract the eocene of the north sea basin has been divided into five stratigraphic sequences named the dornoch balder frigg alba and grid the palaeocene eocene boundary lies at the base of the dornoch sequence whereas the grid extends into the lower oligocene the sequences display consistent and predictable patterns on electric log data and are bounded by high gamma log peaks which mark thin condensed claystone sections the sequences have been calibrated using a detailed dinocyst zonation that recognizes a succession of 30 biovents it can be shown that individual sequence boundaries consistently fall within the same dinocyst subzone giving a high degree of confidence that these boundaries represent time lines the sequences can be mapped over the whole of the north sea basin retaining their internal character from quadrant 3 in the north to quadrants 21 and 22 in the south a distance of 400 km the high gamma peaks marking the sequence boundaries are interpreted as surfaces of maximum condensation that record the effect of greatly reduced sediment input into the basin these surfaces are believed to have a variety of origins including eustatic sea level rise changes in sediment supply to the basin and changes in rates of tectonic subsidence or uplift

climatic and environmental changes across the early eocene climatic optimum at mid waipara river canterbury basin new zealand abstract the cretaceous paleogene marine sedimentary succession exposed in the banks of the middle reaches of the waipara river referred to as mid waipara north canterbury new zealand has been the subject of several high profile studies of paleogene paleoclimate over the past decade it is one of relatively few sections globally where a multi proxy approach is possible due to the good preservation of microfossils and organic biomarkers the eocene section is also well dated by magnetostratigraphy and biostratigraphy based on planktic foraminifera calcareous nannofossils and dinoflagellate cysts dinocysts here we build on this previous work and undertake a comprehensive analysis of paleontological and geochemical indicators of climatic and environmental changes through the early middle eocene part of the section with particular focus on the early eocene climatic optimum eeco 53 26 49 14 ma we correlate a 33 5 m thick interval with the eeco based on biostratigraphy magnetostratigraphy tex86 paleothermometry and bulk carbonate 13c our new sea surface temperature sst record based on tex86 agrees with a previous lower resolution record based on tex86 and planktic foraminiferal 18o and mg ca ratios the eeco interval in this section extends from the upper part of the new zealand waipawan stage to the mangaorapan heretaungan stage boundary at 49 27 ma the eeco onset is not exposed but the termination is well constrained by a fall in sst and shift to more positive 13c values six negative carbon isotope excursions cies are recognised within the eeco and are tentatively correlated with cies j k m o q t and c22nh4 in the global 13c compilation the cies are associated with warmer ssts indicating that they represent hyperthermals the bayspar tex86 calibration indicates sst increased by as much as 12 c from the early eocene 55 ma to the eeco where sst peaked at 35 c sst gradually declined from mid eeco 51 ma into the middle eocene the marked warming in the early eeco is associated with the highest abundance of warm water taxa in calcareous nannofossil and dinocyst assemblages the highest proportion of planktic foraminifera and a coeval long term shift to abundant angiosperm vegetation primarily driven by a rise in casuarinaceae there is good agreement between tex86 and marine microfossil based proxies for temperature providing confidence that both approaches are useful guides to past water temperature warm water marine taxa are most abundant in the eeco but are not dominant comparison of the abundance of nannofossil warm water taxa between mid waipara and a low latitude site on shatsky rise suggests the latitudinal temperature gradient between mid and low latitudes in the eeco was greater than the tex86 proxy implies there is no clear evidence for enhanced sedimentation rates associated with the eeco in contrast to evidence from the nearby mead stream section superabundant homotryblium a euryhaline dinocyst in the early and middle eeco suggests elevated salinity and or stratified surface waters and there is no clear evidence of increased surface productivity associated with the eeco declining sst in the late eeco 50 ma corresponds with an increase in cool water taxa and terrigenous material this article highlights the importance of combining well calibrated paleontological and geochemical records to better constrain and understand past warm climate states

towards quantitative environmental reconstructions from ancient non analogue microfossil assemblages ecological preferences of paleocene eocene dinoflagellates abstract we explore a novel approach towards quantification of paleo ecological signals from non analogue microfossil assemblages by quantifying relations between assemblages and high quality geochemical and sedimentological data from sedimentary archives we test this approach using one group of microfossils the organic cysts of dinoflagellates dinocysts which are widely used in shelf and open marine settings for biostratigraphy and reconstructions of past environments and environmental change similar to other microfossil groups dinocysts can be used to reconstruct environments with relatively high confidence for recent time periods as species affinities can be derived from observational and instrumental data in the absence of such data the ecology of extinct species is much less certain and as a result reconstructions in deep time are often limited to qualitative interpretations to explore if quantitative empirical relations between extinct dinocysts and high quality geochemical data can be established we study a major event of climate change the paleocene eocene thermal maximum petm 56 ma ago the petm is a particularly suitable period for this exercise as there is a multitude of large environmental perturbations associated with the transient global warming such as deoxygenation sea level rise and an accelerated hydrological cycle the synthesized published dataset exhibits better spatial and temporal coverage compared to any other period in deep time we extract empirical relations for the abundance of previously proposed paleoecological groups as a function of independent environmental proxies for example sea surface temperature and terrestrial organic matter input the results unequivocally illustrate that many dinocysts show relations to several of the reconstructed environmental variables notably we show that one genus apectodinium and an ecogroup epicystal goniodomidae required sea surface temperatures in excess of 20 c and 25 c respectively while one species florentinia reichartii was only abundant between 30 and 35 c other groups apparently favored either a limited spiniferites or high senegalinium terrestrial input to the study site relating to salinity nutrient levels or suspended sediment load i e murkiness crucially our work shows that the validation and quantification of ecological signals by independent environmental proxy data provides the opportunity to extract more quantitative information from a wide range of non analogue microfossil assemblages while this approach is not limited to any specific group of microfossils or macrofossils we stress that proper calibration datasets high quality sedimentological and geochemical proxy records are needed and should ideally have decent geographical coverage and include one or more environmental perturbations using this approach such empirical relations can be established for a wide range of microfossil groups that have highly complementary geological records which increases the value of existing data and ensures future application of microfossil based paleoecology

iron rich fragments in the yamansu iron deposit xinjiang nw china constraints on metallogenesis abstract volcanic rock hosted iron deposits are among the important iron ores in china however the nature of primary magma and petrogenesis associated with these iron ores remains controversial here we report iron rich fragments irf from the yamansu iron deposit in eastern tianshan mountains nw china which occurs in association with volcanic breccia submarine volcanic breccia and ignimbrite the irf is composed of five types including oligoclase iron oxide type oio oligoclase albite iron oxide type oaio albite iron oxide type aio albite k feldspar iron oxide type akio and k feldspar iron oxide type kio these fragments display typical volcanic fabric features such as porphyritic texture hyalopilitic texture of the groundmass and vesicles filled by minerals to form amygdales the feldspar phenocrysts of irf are dominantly albite the groundmass of irf consists of magnetite and feldspar the magnetite is distributed in between the feldspar laths and together display hyalopilitic texture which could be observed only in volcanic rocks the vesicles are filled with magnetite feldspar chlorite and calcite from the margin to the interior the irf has high si al fe ca ti na and k contents and low mg content the average total fe is 26 wt the magnetite is mostly titanium vanadium magnetite with the tio2 content ranging up to 4 86 wt and v2o3 content up to 3 20 wt the irf probably came from iron rich melts and represent the products of the fenner magma evolution the basaltic magma evolved into the fe na rich residual melts by crystallization under low oxygen fugacity condition in a closed magma chamber after intruding into the shallow crust the fe na rich residual melts were emplaced in hypabyssal environments or erupted generating the orebodies or providing the material source for the generation of the high grade iron ores which were subsequently enriched by the late stage hydrothermal fluids

petrology and geochemistry of the loch ba ring dyke mull n w scotland an example of the extreme differentiation of tholeiitic magmas the loch ba ring dyke in the tertiary igneous central complex of mull n w scotland is composed predominantly of a banded rhyolitic welded tuff the rhyolite contains numerous inclusions of dark aphanitic rock the textural relationships between the different rocks indicate rapid violent and intimate mixing during emplacement of the dyke the dark glassy component varies continuously from basaltic andesite to andesite dacite and rhyolite these glasses are enriched in feo and depleted in mgo at a given sio2 content in comparison to other tholeiitic highly differentiated volcanic rocks the rhyolite contains an average of 4 phenocrysts and is associated with the mineral assemblage plagioclase an32 to an21 sanidine or50 60 hedenbergite fayalite magnetite ilmenite apatite zircon mineral aggregates involving either plagioclase hedenbergite ilmenite or plagioclase fayalite magnetite are common but aggregates containing fayalite and hedenbergite together are scarce the dark glassy components are either phenocryst free or contain less than 0 2 phenocrysts the main phenocrysts associated with the dark glasses are plagioclase an65 an30 high calcium clinopyroxene ranging continuously from augite to pure hedenbergite pigeonite magnetite ilmenite and rare apatite zoning in minerals is generally weak or absent the plagioclase feldspar high calcium clinopyroxenes and pigeonites have similar compositional ranges to the minerals observed in the middle and upper zones of the skaergaard intrusion the mineral compositions are systematically related to sio2 content and mg number of the glasses the data demonstrate that mineral compositions and assemblages similar to the skaergaard form from silica rich andesitic to rhyolitic liquids the various mafic glasses are interpreted to have been derived from a zoned magma chamber underlying an upper layer of rhyolitic magma differentiation is attributed to fractional crystallization of the observed mineral assemblages causing sio2 enrichment and feo depletion however glasses with less than 57 sio2 have unusual compositions with very low mgo and p2o5 as well as variable al2o3 and tio2 their peculiarities could be explained by andesitic magmas assimilating cumulate mineral aggregates precipitated from more differentiated dacite and rhyolite magmas the bulk compositions of these cumulates have high feo low sio2 and negligible mgo and p2o5 it is suggested that the high density of the mineral aggregates containing fayalite hedenbergite magnetite and ilmenite caused them to settle through the zoned chamber to be assimilated by high temperature less differentiated magmas

eustatic variations during the paleocene eocene greenhouse world we reconstruct eustatic variations during the latest paleocene and earliest eocene 58 52 ma dinoflagellate cysts grain size fractions and organic biomarkers in marine sections at four sites from three continents indicate an increased distance to the coast during the paleocene eocene thermal maximum petm the same trend is recognized in published records from other sites around the world together the data indicate a eustatic rise during the petm beginning 20 to 200 ka before the globally recorded negative carbon isotope excursion cie at 55 5 ma although correlations are tentative we recognize other global transgressions during chrons c25n and c24n the latter may be associated with eocene thermal maximum 2 53 5 ma or the x event 52 ma these results suggest a link between global sea level and hyperthermal intervals potentially because of the melting of small alpine ice sheets on antarctica thermal expansion of seawater or both however the early onset of sea level rise relative to the cie of the petm suggests contributions from other mechanisms perhaps decreasing ocean basin volume on sea level rise copyright 2008 by the american geophysical union

dinoflagellate cyst assemblages biostratigraphy and paleoenvironment of a paleocene early eocene sedimentary succession in the northern niger delta basin comparison with low mid and high latitude regions abstract this study represents a contribution to the late paleocene early eocene biostratigraphy in a low latitude stratigraphic setting where published studies are few in comparison with mid and high latitude regions we generated data for 62 dinoflagellate cysts from a comprehensive analysis of 33 samples covering a 713 m interval in the alo 1 well in the northern niger delta anambra basin nigeria dinoflagellate cyst recovery in the samples varies from very good to poor and the specimens are commonly well preserved we calibrate the dinoflagellate cyst data with recent biozonation schemes for odp hole 959d cote d ivoire ghana transform margin in the eastern equatorial atlantic which allowed for a valid comparison with published studies in well dated rock sections in northwestern europe the mediterranean region new zealand and tasmania our observations show that there is better correlation between tropical and mid latitude dinoflagellate cyst assemblages compared to those in high latitude regions we use the last occurrence and or last abundance events of dinoflagellate cysts to identify four biostratigraphic zones zone e to zone h in the alo 1 well lithostratigraphic and biostratigraphic analyses suggest a late selandian age for the contact between the imo and nsukka formations abundant thermophilic taxa that include the cordosphaeridium group and apectodinuim dominate the assemblage recovered in the depositional succession the late selandian to early thanetian sediments are dominated by the cordosphaeridium group and are succeeded by abundant to superabundant marker species of apectodinium in the late thanetian to ypresian the superabundance of apectodinium is significant because it is indicative of the global intense climatic warming that characterized the late thanetian to early ypresian the alo 1 well dinoflagellate cyst data also suggest deposition under proximal inner neritic conditions that preserved an assemblage dominated by species of cordosphaeridium damassadinium ifecysta and polysphaeridium

sea level and salinity fluctuations during the paleocene eocene thermal maximum in arctic spitsbergen palaeoenvironmental manifestations of the palaeocene eocene thermal maximum petm 56 ma are relatively well documented in low to mid latitude settings and at high southern latitudes but no documented high northern latitude sites record the entire hyperthermal event we present high resolution multi proxy records from a petm succession on spitsbergen in the high arctic palaeolatitude 75 n by comparing our results with those from integrated ocean drilling program site 302 4a we document regional palaeoenvironmental variations in the expression of the petm with evidence for major differences in basin margin vegetation and water column oxygen depletion sedimentological palynological and geochemical data demonstrate a pre petm sea level rise in spitsbergen before the delta13ctoc excursion which culminated in maximum flooding during the peak of the event the appearance of the dinoflagellate cyst apectodinium before the onset of the carbon isotope excursion cie corroborates environmental change in the arctic had begun prior to the cie sedimentological and palynological evidence indicate that elevated terrestrial runoff resulted in water column stratification providing further evidence for an intensification of the hydrological cycle during the petm

salinity of the eocene arctic ocean from oxygen isotope analysis of fish bone carbonate stable isotope analysis was performed on the structural carbonate of fish bone apatite from early and early middle eocene samples 55 to 45 ma recently recovered from the lomonosov ridge by integrated ocean drilling program expedition 302 the arctic coring expedition the 18o values of the eocene samples ranged from 6 84 to 2 96 vienna peedee belemnite with a mean value of 4 89 compared to 2 77 for a miocene sample in the overlying section an average salinity of 21 to 25 was calculated for the eocene arctic compared to 35 for the miocene with lower salinities during the paleocene eocene thermal maximum the azolla event at 48 7 ma and a third previously unidentified event at 47 6 ma at the azolla event where the organic carbon content of the sediment reaches a maximum a positive 13c excursion was observed indicating unusually high productivity in the surface waters

palaeocene biostratigraphy and sequence stratigraphy of the uk central north sea abstract the palaeocene of the central north sea can be divided into four stratigraphic sequences named the ekofisk maureen lista and forties these sequences display consistent and predictable patterns on electric log data and are bounded by high gamma log peaks which represent thin condensed mudstones five additional subsequences are recognized within the lista sequence biostratigraphic analysis has enabled the palaeocene to be divided into six dinocyst zones and 11 subzones based on last occurrence or last abundance events that are considered to have chronostratigraphic significance across the north sea basin the dinocyst zonation has been integrated with bioevents based on other microfossil groups and correlated with onshore nw european sections permitting calibration with the standard worldwide nannoplankton and planktonic foraminiferal zones these bioevents display a consistent relationship with the stratigraphic sequences allowing the construction of a confident stratigraphic framework for the palaeocene

a discussion of hunter and sparks contrib mineral petrol 95 451 461 silica poor iron rich liquids like those estimated for skaergaard by wager and brown are preserved in labrador as chilled pillows iron rich rocks in the kiglapait intrusion have likewise been produced by liquids poor in silica there is no reason to expect such liquids in volcanoes so their absence as lavas means nothing about their possible plutonic occurrence successful tests of the siliceous liquid hypothesis would include showing that the proposed rhyolitic liquids can produce the observed olivines in the range fo 10 40 they would require showing that the observed low f o 2 oxide mineral assemblages can occur at the high silica contents proposed and that the silicate mineral assemblages and compositions can represent high silica liquids i doubt very much that these critical tests can be met

the apectodinium acme and terrestrial discharge during the paleocene eocene thermal maximum new palynological geochemical and calcareous nannoplankton observations at tawanui new zealand manifestations of profound perturbations in biogeochemical systems during the paleocene eocene thermal maximum petm include a prominent global negative 13c and a pronounced increase in the relative abundance of dinoflagellate cysts dinocysts assigned to the genus apectodinium while motile representatives of apectodinium were most likely thermophilic and heterotrophic the underlying causes of this dinoflagellate response are not well understood here we provide new insight by examining the palynology chemistry and calcareous nannoplankton across the petm in a continental slope section at tawanui new zealand across the petm marked changes in the relative abundance of apectodinium vary antithetically with significant changes in the 13c of carbonate and organic matter in general the high relative abundance of apectodinium relates to enhanced concentrations of dinocysts signifying a bloom of apectodinium in surface waters during the petm changes in apectodinium and 13c records correspond to variations in many other parameters including a smaller negative shift in bulk carbonate 13c than expected increased terrestrial palynomorphs elevated toc and c n ratios lower carbonate contents higher sio2 and al2o3 contents and lower si al ratios all of these variations can be explained by an increase in delivery of terrigenous material to the continental margin a peak in the relative abundance of glaphyrocysta dinocysts at the onset of the petm may indicate greater down slope transport of neritic material changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the petm the combined results show that apectodinium dominated assemblages global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at tawanui a sudden and massive carbon injection to the ocean atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the petm we further suggest that these inputs caused the apectodinium acme by elevating primary productivity in marginal seas

an experimental study of the influence of oxygen fugacity on fe ti oxide stability phase relations and mineral melt equilibria in ferro basaltic systems

paleogene early neogene paleoenvironmental reconstruction based on palynological analysis of odp hole 959a west africa abstract five paleoenvironmental intervals interval 1 interval 5 are established in the late paleogene early neogene of the ocean drilling program odp site 959 hole 959a cote d ivoire ghana transform margin in the eastern equatorial atlantic the intervals are based on dinoflagellate cyst and palynofacies analyses of 30 samples covering a 273 3 m interval we observed an abundance of the filisphaera group filisphaera filifera and bitectatodinium tepikiense which is interpreted as an arctic migration to equatorial regions during a narrow interval in the early oligocene early rupelian in addition we document one hiatus within interval 3 in the early miocene aquitanian the dominance of typically restricted marine species of the polysphaeridium group homotryblium plectilum and polysphaeridium zoharyi at several horizons in the open oceanic sediments of odp hole 959a appear to be very distinctive events upon integrating dinoflagellate cyst data with prior lithologic and microfossil data we interpret these dominance events as being due to offshore transportation by turbidity currents intervals 1 and 2 hiatus event interval 3 or hyperstratification conditions intervals 3 and 4 in addition the dominance of cribroperidinium spp c giuseppei and c tenuitabulatum in the upper part of the section within paleoenvironmental interval 5 is suggestive of cold water masses during a strong upwelling period in the latest early miocene burdigalian the general abundance of amorphous organic matter alongside the dinoflagellate cyst assemblage supports an outer neritic oceanic depositional environment for the studied site the consistent occurrence of degraded phytoclasts in the sediments also suggests fluvial outflows to this offshore site

immiscible silicate liquid partition coefficients implications for crystal melt element partitioning and basalt petrogenesis this study investigates partitioning of ele ments between immiscible aluminosilicate and boro silicate liquids using three synthetic mixtures doped with 32 trace elements in order to get a good spatial separation of immiscible liquids we employed a high temperature centrifuge experiments were performed at 1 050 1 150 c 1 atm in sealed fe and pt containers quenched products were analysed by electron micro probe and la icp ms nernst partition coefficients d s between the fe rich and si rich aluminosilicate immiscible liquids are the highest for zn 3 3 and fe 2 6 and the lowest for rb and k 0 4 0 5 the plots of d values against ionic potential z r in all the composi tions show a convex upward trend which is typical also for element partitioning between immiscible silicate and salt melts the results bear upon the speciation and structural position of elements in multicomponent silicate liquids the ferrobasalt rhyolite liquid immis cibility is observed in evolved basaltic magmas and may play an important role in large gabbroic intrusions such as skaergaard and during the generation of unusual lavas such as ferropicrites

evolution of the skaergaard magma evidence from crystallized melt inclusions polymineralic aggregates composed of clinopyroxene fe ti oxide minerals apatite and accessory k feldspar biotite and amphibole are enclosed in cumulus plagioclase grains in the middle zone of the skaergaard intrusion the chemistry of the minerals in the aggregates and the textural relations between the aggregates and the host plagioclase grains indicate that they represent inclusions of the contemporaneous melt of the skaergaard intrusion through mass balance calculations a quantitative estimate of the melt composition for this level in the intrusion can be obtained and this estimate confirms that the silica content in the middle zone melt was similar to or possibly even lower than the silica content in the initial skaergaard melt and relatively enriched in iron

on the sensitivity of ocean circulation to arctic freshwater input during the paleocene eocene thermal maximum abstract the paleocene eocene thermal maximum petm 55 ma ago corresponds to a time characterized by extreme global warming caused by a massive carbon input into the ocean and atmosphere climate proxies from sedimentary records suggest that fresh water flow from an ice free arctic into the remainder of the global ocean increased due to tectonic changes enhanced runoff and thermal expansion in this study we use the community climate system model version 3 ccsm 3 including a carbon cycle model to examine the sensitivity of the ocean circulation to freshwater outflow from the arctic ocean during the petm and whether these changes may have contributed to an additional warming during the petm two experiments the first with freshwater exchange between the arctic and pacific oceans and the second between the arctic and atlantic oceans are compared with a reference experiment with exchange between the arctic and indian oceans and with independent stratigraphic and geochemical records from the ocean drilling program odp as freshwater is transported from the arctic into the north pacific ocean stratification is enhanced in the north pacific due to a significant reduction in surface salinity as a consequence intermediate to deep water sources shift from both hemispheres in the pacific ocean to a dominant source in the south pacific ocean and an additional source in the northern tethys ocean this simulated shift of deep water sources during the petm is in agreement with recent nd isotope measurements the circulation patterns in the pacific are similar to those inferred from stable isotope reconstructions but contradicting a strong north atlantic deep water source during the petm freshwater input into the pacific ocean results in a warming of intermediate water masses of 2 c in the north pacific when freshwater flow is routed from the arctic into the atlantic ocean surface density changes are too small to change vertical stratification substantially contrary to a previous study in summary based upon circulation patterns and temperature increases due to freshwater flux through the bering strait arctic freshwater input into the north pacific may have contributed to methane hydrate destabilization an event suggested to have accelerated warming during the petm

water erosion susceptibility mapping by applying stochastic gradient treeboost to the imera meridionale river basin sicily italy abstract soil erosion by water constitutes a serious problem affecting various countries in the last few years a number of studies have adopted statistical approaches for erosion susceptibility zonation in this study the stochastic gradient treeboost sgt was tested as a multivariate statistical tool for exploring analyzing and predicting the spatial occurrence of rill interrill erosion and gully erosion this technique implements the stochastic gradient boosting algorithm with a tree based method the study area is a 9 5 km 2 river catchment located in central northern sicily italy where water erosion processes are prevalent and affect the agricultural productivity of local communities in order to model soil erosion by water the spatial distribution of landforms due to rill interrill and gully erosion was mapped and 12 environmental variables were selected as predictors four calibration and four validation subsets were obtained by randomly extracting sets of negative cases both for rill interrill erosion and gully erosion models the results of validation based on receiving operating characteristic roc curves showed excellent to outstanding accuracies of the models and thus a high prediction skill moreover sgt allowed us to explore the relationships between erosion landforms and predictors a different suite of predictor variables was found to be important for the two models elevation aspect landform classification and land use are the main controlling factors for rill interrill erosion whilst the stream power index plan curvature and the topographic wetness index were the most important independent variables for gullies finally an roc plot analysis made it possible to define a threshold value to classify cells according to the presence absence of the two erosion processes hence by heuristically combining the resulting rill interrill erosion and gully erosion susceptibility maps an integrated water erosion susceptibility map was created the adopted method offers the advantages of an objective and repeatable procedure whose result is useful for local administrators to identify the areas that are most susceptible to water erosion and best allocate resources for soil conservation strategies

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

petrogenesis of uivfaq iron disko island greenland massive blocks of native iron and iron carbide weighing up to 22 tons have been found at uivfaq disko island western greenland the iron blocks are associated with tertiary basalts that erupted during rifting between greenland and baffin island early in the opening of the davis strait the iron is an asemblage of iron and iron carbide cohenite and various silicate sulphide and oxide inclusions containing highly reduced and iron rich phases including fayalite wustite troilite ulvospinel ilmenite ferriferous pigeonite and feo rich glass the chemistry and petrography of the inclusions are used to derive a paragenetic history for the uivfaq iron assemblage petrographic study of a massive uivfaq iron block shows that the block formed through accumulation of partly molten spherules of iron and cohenite 0 5 to 1 0 mm in diameter basaltic liquid was trapped by the accumulating metal spherules and reacted with the metal to form various highly reduced and iron enriched immiscible liquids these liquids solidified as inclusions in the iron mass various models are considered for the origin of the iron cohenite spherules at present a carbon reduction mechanism is preferred the association of graphite rich plagioclase spinel xenoliths thought to be derived from sediments with the iron masses suggests a genetic relation between the two we suggest that graphite was assimilated by mantle derived basaltic magma the carbon reduced iron oxide components of the basalt at a depth of 3 km or less and formed small immiscible droplets of high carbon iron carbon liquid these droplets were erupted with the magma the droplets settled and accumulated near or at the base of a flow or sill to form massive iron blocks

a high resolution north sea eocene dinocyst zonation abundant dinoflagellate cysts dinocysts from eocene strata of the north sea exhibit a consistent succession of events based on the analysis of 120 wells from quadrant 3 in the north to quadrants 21 and 22 in the south these events have a constant relationship with stratigraphic sequences and subsequences throughout the area eight eocene dinocyst zones and 23 subzones and the uppermost palaeocene apectodinium augustum biozone are defined by last occurrence or abundance events the north sea dinocyst succession is similar to that in denmark northwest germany belgium the netherlands and southern england permitting correlation with calcareous nannoplankton zones for sections in these areas and hence allowing correlation of north sea stratigraphy with northwest european and worldwide events

geochemical evidence for volcanic activity prior to and enhanced terrestrial weathering during the paleocene eocene thermal maximum abstract the re os and major element geochemistry of an expanded gray shale sequence from the central basin in spitsbergen svalbard archipelago norway over the paleocene eocene thermal maximum petm is presented the data suggest that a significant volcanic episode as indicated primarily by a large drop in 187 os 188 os occurred just prior to or coincident with the onset of the petm the distinct geochemistry of the inferred ash component is consistent with the geochemistry of contemporaneous ashes previously sampled in denmark and persists in the sedimentary record for 8 ka based on the substantial size of the 187 os 188 os decrease 187 os 188 os 0 23 the volcanic event must have involved widespread ash deposition in the local catchment the terrestrially deposited ash weathered rapidly shifting the 187 os 188 os of the basin water column to 187 os 188 os to more radiogenic values and depositing clastic materials with higher chemical index of alteration and lower na ti persistently anoxic sedimentary pore fluids interpreted to reflect bottom water anoxia initiated close to the onset of the petm anoxic mainly euxinic conditions persisted for 50 ka ending abruptly 55 77 ma anoxia appears related to enhanced high latitude hydrological cycling and consequent basinal stratification during the petm

trace element partitioning between immiscible lunar melts an example from naturally occurring lunar melt inclusions evidence for liquid immiscibility on the moon has been documented in melt inclusions in minerals that crystallized from mare basalts within mesostasis in mare basalts and in at least one sample of a lunar plutonic rock this study focuses on trace element partitioning between immiscible melt pairs occurring as inclusions in plagioclase these inclusions are blade like in shape and range in length from 2 to 150 m they consist of two coexisting glasses separated by a sharp meniscus the colorless low index glass felsite is spherical and immersed in a dark brown high index glass high fe basalt the fe rich basaltic component of the inclusion is quartz hypersthene normative with low mg mg fe and variable sio2 content between 34 and 45 wt the felsic component has a sio2 content between 72 and 82 wt and variable k2o 4 4 to 8 5 wt in most cases the partitioning behavior of the trace elements agrees with behavior either predicted or measured in experimental and natural systems the high charge density elements preferentially partition into the basaltic component high p2o5 and a wider solvus increase the d basalt felsite for these elements in contrast to many experimental studies and in agreement with studies of natural silicate liquid immiscibility the d basalt felsite for ba indicates a preference for the felsic component this difference in ba behavior between experimental and natural samples has been attributed to differences in melt polymerization and compensation for charge unbalance within the polymerized melt structure the apparent differences in d basalt felsite for sr and divalent eu between the apollo 11 high ti basalts and apollo 12 low ti basalts may be a result of either subtle differences in bulk composition or the extent of plagioclase plating on inclusion walls based on our partitioning data from melt inclusions and the chemical characteristics of lunar felsites the latter cannot be a product of simple fractional crystallization silicate liquid immiscibility can account for fractionation of ba la k u and ba u in the lunar felsites and the limited variation in zr la however it cannot account for the ree pattern of the lunar felsites or the fractionation of u la these characteristics must be attributed to whitlockite crystallization prior to the onset of liquid immiscibility

experiments on silicate melt immiscibility in the system fe2sio4 kalsi3o8 sio2 cao mgo tio2 p2o5 and implications for natural magmas the effect of cao and mgo with or without tio2 and p2o5 on the two melt field in the simplified system fe2sio4 kalsi3o8 sio2 has been experimentally determined at 1 050 1 240 c 400 mpa despite the suppressing effect of mgo cao and pressure on silicate melt immiscibility our experiments show that this process is still viable at mid crustal pressures when small amounts 0 6 2 0 wt of p2o5 and tio2 are present our data stress that the major element partition coefficients between the two melts are highly correlated with the degree of polymerisation nbo t of the sio2 rich melt whatever temperature pressure or exact composition experimental immiscible melt compositions in natural systems at 0 1 mpa from the literature lunar and tholeiitic basalts plot on similar but distinct curves compared to the simplified system these relations between melt polymerisation and partition coefficients which hold for a large range of compositions and fo2 are extended to various volcanic and plutonic rocks this analysis strengthens the proposal that silicate melt immiscibility can be important in volcanic rocks of various compositions from tholeiitic basalts to lamprophyres however the majority of proposed immiscible compositions in plutonic rocks are at least not coexisting melts but may have suffered accumulation of early crystallized minerals

the differentiation of the skaergaard intrusion mcbirney and naslund have missed the two central points that we reiterate for clarity first the composition of the cotectic cumulate extract for the lzc best estimated from the average composition of adcumulate rocks had a substantially lower silica content than any conceivable basaltic liquid so silica enrichment is unavoidable this is true of all the dyke compositions reported by brooks and nielsen even the anomalous rock e with sio2 46 second it is the normal behaviour of tholeiite basaltic magma to produce increasingly iron rich cumulate extracts with little change in silica until feti oxide precipitation occurs when silica enrichment and compositional divergence begins such divergence between equivalent cumulate plutonic and fractionated volcanic rocks hads been widely documented skaergaard magmas do have some uncommon features however similar assemblages exist in volcanic rocks as in the andesitic to rhyolitic glasses of the loch ba ring dyke mull sparks 1988 it is also a basic principle that elements enriched in cumulate rocks often become depleted in the corresponding liquids iron enrichment in the skaergaard cumulates is complementary to iron depletion in liquids

apatite hosted melt inclusions from the panzhihua gabbroic layered intrusion associated with a giant fe ti oxide deposit in sw china insights for magma unmixing within a crystal mush the 2 km thick panzhihua gabbroic layered intrusion in sw china is unusual because it hosts a giant fe ti oxide deposit in its lower zone the deposit consists of laterally extensive net textured and massive fe ti oxide ore layers the thickest of which is 60 m to examine the magmatic processes that resulted in the fe enrichment of parental high ti basaltic magma and the formation of thick fe ti oxide ore layers we carried out a detailed study of melt inclusions in apatite from a 500 m thick profile of apatite bearing leucogabbro in the middle zone of the intrusion the apatite hosted melt inclusions are light to dark brown in color and appear as polygonal rounded oval and negative crystal shapes which range from 5 to 50 m in width and from 5 to 100 m in length they have highly variable compositions and show a large and continuous range of sio2 and feot with contrasting end members one end member being fe rich and si poor 40 2 wt feot and 17 7 wt sio2 and the other being si rich and fe poor 74 0 wt sio2 and 1 20 wt feot this range in composition may be attributed to entrapment of the melt inclusions over a range of temperature and may reflect the presence of m scale and immiscible fe rich and si rich components in different proportions simulating results for the motion of si rich droplets within a crystal mush indicate that si rich droplets would be separated from fe rich melt and migrate upward due to density differences in the interstitial liquid when the magma unmixed migration of the si rich immiscible liquid component from the interstitial liquid caused the remaining fe rich melt in the lower part to react with plagioclase primocrysts an59 60 as evidenced by fine grained lamellar intergrowth of an rich plagioclase an79 84 clinopyroxene in the oxide gabbro of the lower zone therefore magma unmixing within a crystal mush combined with gravitationally driven loss of the si rich component resulted in the formation of fe rich melagabbro and major fe ti oxide ores in the lower part and si rich leucogabbro in the upper part of the intrusion

early to middle eocene history of the arctic ocean from nd sr isotopes in fossil fish debris lomonosov ridge strontium and neodymium radiogenic isotope ratios in early to middle eocene fossil fish debris ichthyoliths from lomonosov ridge integrated ocean drilling program expedition 302 help constrain water mass compositions in the eocene arctic ocean between 55 and 45 ma the inferred paleodepositional setting was a shallow offshore marine to marginal marine environment with limited connections to surrounding ocean basins the new data demonstrate that sources of nd and sr in fish debris were distinct from each other consistent with a salinity stratified water column above lomonosov ridge in the eocene the 87sr 86sr values of ichthyoliths 0 7079 0 7087 are more radiogenic than eocene seawater requiring brackish to fresh water conditions in the environment where fish metabolized sr the 87sr 86sr variations probably record changes in the overall balance of river sr flux to the eocene arctic ocean between 55 and 45 ma and are used here to reconstruct surface water salinity values the nd values of ichthyoliths vary between 5 7 and 7 8 compatible with periodic or intermittent supply of nd to eocene arctic intermediate water aiw from adjacent seas although the norwegian greenland sea and north atlantic ocean were the most likely sources of eocene aiw nd input from the tethys sea via the turgay strait in early eocene time and the north pacific ocean via a proto bering strait also contributed

the differentiation of the skaergaard intrusion we find no support for the claim that the skaergaard magma followed the trend of common tholeiitic volcanic magmas such as those of iceland and the scottish tertiary the end product of differentiation was not a large mass of rhyolite but an iron rich silica poor liquid not unlike that deduced by wager in 1960 the proposal that a large mass of rhyolitic liquid occupied the upper levels of the intrusion finds no support in the field the thick series of ferrogabbos which became richer in iron and poorer in silica until they reached a field of immiscibility cannot be reconciled with crystallization of a large mass of felsic magma mass balance calculations that indicate otherwise are invalid because they fail to take into account large volumes of rocks that differ in composition from those assumed in the calculations while ignoring the existence of major units of the intrusion hunter and sparks propose that lavas in scotland and iceland are more relevant to the liquid compositions than rocks that are intimately associated with the intrusion their argument that the skaergaard intrusion followed a trend of silica enrichment that is universal to tholeiitic magmas is based on an incomplete knowledge of the rocks and faulty calculations of mass balance relations we agree that much remains to be learned about the skaergaard intrusion and the basic mechanisms of magmatic differentiation in this case however we are ready to hang our case on well established field relations and a mass of laboratory data for what must be the most intensely studied body of rock on earth

cenozoic paleo environmental evolution of the pamir tien shan convergence zone abstract the retreat of the tethys sea and the uplift of the tibetan plateau play the critical roles in driving asian climatic changes during the cenozoic in the pamir tien shan convergence zone over 3000 m of cenozoic successions consisting of marine deposits in the lower continental clay and fine sand in the middle and molasse in the upper part record the evolution of the tethys sea the asian aridification and the deformation of the pamir in this work the existing biostratigraphic subdivisions and new electronic spinning resonance dating results were used to assign ages to formations within the ulugqat section sedimentary facies analysis and multi proxy indices were used to reconstruct the paleo environmental evolution the results show 1 the pamir tien shan convergence zone has undergone progressive environmental changes from shallow marine before 34 ma to arid land at 23 ma and finally to inter mountain basin by 5 3 ma 2 the overall increase in mean size of grains decrease in redness in magnetic susceptibility and in proportion of the ultrafine component of the sediments studied revealed a long term strengthening in potential energy to transporting medium cooling and enhanced continental aridity respectively 3 the easternmost edge of the tethys sea prevailed in the western tarim basin from late cretaceous to early cenozoic and finally retreated from this region around the eocene oligocene transition which in turn strengthened the asian aridification 4 accumulation of molasse with an upper age of 1 ma suggests that the deformation front of the pamir migrated to this area at or before that time

the differentiation trend of the skaergaard intrusion and the timing of magnetite crystallization iron enrichment revisited abstract initial studies of the skaergaard intrusion l r wager j petrol 1 1960 364 398 and much of the subsequent work r j williams am j sci 271 1971 132 146 s a morse et al am j sci 280a 1980 159 170 a r mcbirney h r naslund contrib mineral petrol 104 1990 235 247 c tegner contrib mineral petrol 128 1997 45 51 a r mcbirney contrib mineral petrol 132 1998 103 105 concluded that the skaergaard magma followed an iron enrichment trend with little or no silica enrichment until the final stages of crystallization several recent reports r h hunter r s j sparks contrib mineral petrol 95 1987 451 461 r h hunter r s j sparks contrib mineral petrol 104 1990 248 254 however have suggested that the skaergaard magma began to follow a silica enrichment trend in lower zone c lzc of the layered series where magnetite first became an abundant mineral magnetite in lzc however generally occurs in aggregates of magnetite ulvospinel and ilmenite hematite that have undergone extensive subsolidus reequilibration and exsolution e a vincent neues jahrb mineral abh 94 1960 993 1016 e a vincent geochim cosmochim acta 6 1954 1 26 a f buddington d h lindsley j petrol 5 1964 310c357 h r naslund j petrol 25 1984 185 212 a r mcbirney j petrol 30 1989 363 397 y d jang petrological geochemical and mineralogical variations in the skaergaard intrusion east greenland ph d dissertation state university of new york binghamton ny 1999 219 pp as a result it is not clear if magnetite in these samples was an equilibrium liquidus mineral fractionated from the main magma reservoir or if magnetite crystallized as a later interstitial mineral and did not directly affect the differentiation trend of the main skaergaard magma the timing of the initial crystallization of abundant magnetite and ilmenite is a key factor in understanding the trend of skaergaard differentiation because v is a strongly included element in oxides and is not strongly included in silicate minerals the v content of an evolving magma is generally controlled by the fractionation of oxide minerals in particular magnetite the initial crystallization of magnetite should therefore be accompanied by a sudden decrease in the v content of the evolving magma and in all of the coexisting mafic phases in equilibrium with that magma as well the v content in skaergaard pyroxene does not decrease significantly until the upper part of the middle zone mz suggesting that the onset of extensive magnetite fractionation is much later than has previously been thought and that the magnetite in lzc and the lower part of the mz might not have been a liquidus phase at that level the observed v trend in skaergaard pyroxene can be modeled almost perfectly using published partition coefficients for the coexisting minerals in the skaergaard intrusion assuming that no magnetite fractionation occurred until the upper part of the mz independently calculated trends for f o 2 in the skaergaard magma r j williams am j sci 271 1971 132 146 s a morse et al am j sci 280a 1980 159 170 a r mcbirney h r naslund contrib mineral petrol 104 1990 235 247 change in the upper part of the mz to more reducing conditions the onset of magnetite fractionation would remove fe 2 o 3 from the magma and could initiate such a change the timing of magnetite fractionation will have a strong effect on whether magma evolves towards iron enrichment or silica enrichment

environmental change across the paleocene eocene transition from eastern new zealand a marine palynological approach abstract recent improvements in the resolution and calibration of dinoflagellate cyst dinocyst bioevents across the paleocene eocene p e transition in new zealand allow better understanding of the relation between dinocyst variations and environmental change in southern mid high latitudes during this greenhouse climate combining information from land spore pollen assemblages with coeval dinocyst records allows evaluation of plant changes in a marine based timeframe palynological associations at tawanui and moeraki hampden eastern new zealand fluctuate across the p e transition and local palynological phases are recognized the onset of major fluctuations in dinocyst assemblages coincide with the intense warmth and excess carbon of the initial eocene thermal maximum ietm changes in sea surface temperature sst appear to have been the main environmental factor that affected dinoflagellates short lived intervals of higher ssts suggested by a high relative abundance of the apectodinium complex are seen during the ietm and lower eocene abundant cysts of probable heterotrophic dinoflagellates suggest surface waters remained relatively eutrophic for up to 0 5 myr after the onset of the ietm perhaps in response to enhanced terrigenous input related to changes in the character and pattern of continental weathering in contrast to dinocysts spore pollen assemblages suggest plant communities remained rather stable across the p e transition vegetation was dominated by a mesothermal conifer dominated multistratal rainforest and low latitude nypa mangroves were established by the uppermost paleocene plants in this region show no clear response to the ietm and the predominant vegetation change may have occurred at least 1 5 myr later characterized by an increase in mesothermal megathermal angiosperm plants

low pressure phase relationships in the system na2o cao feo mgo al2o3 sio2 at 1100 c with implications for the differentiation of basaltic magmas

dinoflagellate cyst stratigraphy of the palaeogene strata from the hellefisk 1 ikermiut 1 kangâmiut 1 nukik 1 nukik 2 and qulleq 1 wells offshore west greenland abstract a new palaeogene dinoflagellate cyst stratigraphy from offshore west greenland has been described based on the strata from the hellefisk 1 ikermiut 1 kang miut 1 nukik 1 nukik 2 and qulleq 1 wells twenty one palynological intervals are defined from the late eocene to the late early paleocene this stratigraphy has been correlated with a new microfossil zonation and previous established north sea zonations the stratigraphy and well correlation are based on last appearance datum events and abundances of stratigraphically important species from 355 samples 148 of which are sidewall core samples a major middle eocene hiatus spanning the early lutetian and a major early paleocene hiatus spanning the late santonian late cretaceous to the early danian have been recognised from the offshore deposits

combined igneous and hydrothermal source for the kiruna type bafq magnetite apatite deposit in central iran trace element and oxygen isotope studies of magnetite abstract the main deposits of the bafq district choghart se chahun and chadormalou deposits are magnetite apatite ore bodies with early cambrian age hosted by early cambrian volcano sedimentary rocks showing lava flow structure with miarolitic cavities and occasional brecciation the texture and geochemistry trace elements and o isotope of the studied magnetite crystals show three types of magnetite with different proportions in different parts of the district and the deposits these are primary ignious magnetite and high temperature hydrothermal magnetite in the massive parts of the deposits and foam like magnetite in the veins or in the fractures of the massive part the lack of zonation high ti fe ratios and 18o values 2 than the massive magnetites the magmatic origin for the main part of the ores in the bafq is more plausible contamination of the primary magmas of the bafq magmatic rocks with crustal phosphorus and evaporate units was the major agent for triggering iron rich melt immiscibility from the original magma concentration of volatiles in the iron rich melt involving in crystallization of the primary magnetite and nucleation of the aqueous fluid bubbles on magnetite surfaces led to ascending the buoyant fluid bubble magnetite aggregates this caused continuation of the magmatic magnetite microlites growth from the iron rich magmatic hydrothermal fluid and formed high temperature hydrothermal magnetite formation of hypersaline fluid due to crystallization of iron rich melt at shallow depth led to crystallization of titanite and th u ree bearing minerals and sodic calcic alteration related to magnetite mineralization microscopic evidence replacement of magnetite by hematite and filling of fractures of thorite by magnetite show that degassing continued at shallow depth which led to re crystallization of the primary magnetites and formation of the foam like magnetites

sequence biostratigraphy and paleoenvironmental reconstruction in the early eocene figols group of the tremp graus basin south central pyrenees spain the dinoflagellate cyst palynofacies and foraminiferal records from the early eocene figols group of the spanish pyrenees exhibit major changes associated with relative sea level fluctuations and variations in efficiency of the fluvial systems the mixed siliciclastic carbonate marine succession exposed in the merli esdolomada area was deposited on the shelf in a tectonically active basin under oxic conditions in shallow to moderately deep marine waters close to the lower boundary of the photic zone influenced by river discharge from adjacent emerged lands sedimentary cycles are mainly recorded by fine grained deposits the paleoenvironmental interpretation of palynological and calcareous microfaunal records allows the definition of depositional sequences and enables to trace basinward surfaces identified in more proximal settings by means of sedimentological facies analysis at the same time the solid regional stratigraphic framework already available for the figols group allows new insights on the paleoecology of extinct taxa the merli esdolomada section me spans two 3rd order sequences the upper sequence reflects more marginal marine conditions than the lower one thus pointing to an overall shallowing trend with time in the lower sequence the maximum flooding interval is characterised by a rich and diverse microfauna highest relative abundances of marine phytoplankton and typically neritic dinoflagellate cyst dinocyst assemblages dominated by spiniferites and cordosphaeridium the final phase of the highstand systems tract in proximity of the main sequence boundary is characterised by a decrease in abundance and diversity of dinocysts with the dominance of the lagoonal genus polysphaeridium and by decreased microfaunal diversity discorbids miliolids larger foraminifers palynological records permit the reconstruction of activation and deactivation phases of the fluvial systems variations in runoff from the hinterland nutrient delivery to the sea and productivity in surface waters of the tremp graus basin the overall abundance of spiniferites and the scarcity of peridinioid cysts lingulodinium pediastrum and botryococcus algae are interpreted to indicate oligotrophic conditions during the deposition of the investigated succession recurrent intervals where the temporary disappearance of spiniferites corresponds to highest relative abundances of operculodinium and herbaceous debris are the main evidence for river plumes and denote periods of enhanced fluvial discharge reflecting a milankovitch type cyclicity the rotalia group which shows abundance peaks of cuvillierina spp in the shallower intervals is often associated with these episodes thus suggesting for this taxon more tolerance to turbidity than larger foraminifera within the maximum flooding zone a thalassiphora patula acme corresponding to the local disappearance of homotryblium is deemed to record the distal expression of a fluvial activation which triggered water salinity stratification despite broad morphological similarities homotryblium exhibits more cosmopolitan preferences than polysphaeridium which is instead confirmed as a lagoonal euryhaline taxon the increase of spinizonocolpites pollen toward the top of the figols group records the northwestward migration of nypa mangrove palms from southern europe during the mid early eocene