seasonal variability in the production of lower cretaceous calcareous nannoplankton the lower cretaceous munk marl bed in the central north sea area consists of alternating laminae of calcareous nannofossils and clayey material the lamination was most likely caused by seasonal variation in the production rate of calcareous nannofossils calcareous nannofossil deposition reflects short blooms many blooms were totally dominated by a single species and at least nine species occasionally monopolized the flora the production rate and mode of deposition is comparable to that of the modern black sea the munk marl bed contains a diverse marine calcareous nannofossil flora comprising 48 species the species composition exhibits changes that show similarities to the seasonal fluctuations in the modern atlantic ocean

a paleoslope model of late albian to early turonian foraminifera of the western atlantic margin and north atlantic basin abstract a paleoslope model of albian to turonian benthic foraminifera reveals seven successive biofacies which are associated with increasing paleodepth the paleoslope model indicates that the biofacies occupied inner neritic to abyssal environments of deposition 10 m to 3500 m water depth biofacies 1 and 2 characterize paleodepths of less than 60 m the biofacies contain abundant species of epistomina and gavelinella and exhibit a rapid stratigraphic alternation in response to local sea level change which considerably aids in the identification of depositional sequences species of globorotalites eggerellina and neobulimina characterize biofacies 3 which principally occurs between 60 m and 130 m paleodepth biofacies 3 is the only biofacies to occur in both the new jersey coastal plain and the baltimore canyon trough biofacies 4 is composed of species of gavelinella gyroidinoides and valvulineria and is abundant in outer neritic to middle bathyal paleodepths of 130 m to 600 m it is largely replaced by biofacies 5 during times of maximum flooding during sea level rise a diverse assemblage of species of lingulogavelinella and lenticulina characterize biofacies 5 paleodepths of 600 m to greater than 3500 m contain abundant species of osangularia pleurostomella praebulimina pseudopatellinella and quadrimorphina which define biofacies 6 and 7 in addition four biofacies of much more limited distribution are recognized biofacies 1 characterizes shallow water open marine paleoenvironments of the north atlantic and is composed of spirillinids and species of epistomina turonian dysaerobic environments are indicated by biofacies dsa and dsb which are composed mostly of agglutinated species dysaerobic environments expanded rapidly from middle bathyal to outer neritic depths in the early turonian on the western atlantic margin biofacies daa represents disturbed benthic environments and is dominated by species of psammosphaera and reophax biostratigraphy and species composition of the studied biofacies are similar to previously described european and south atlantic assemblages major speciation events occur among the genera gavelinella lingulogavelinella and valvulineria well defined neritic and bathyal biofacies formed during a rapid late albian species diversification concomitant with the first major cretaceous flooding of continental margins

isotopic evidence for early to mid cretaceous ocean temperature variability abstract stable isotopic measurements have been made on planktonic and benthic foraminifera of early to mid cretaceous early albian cenomanian age from dsdp site 463 located in the pacific ocean the degree of alteration of the foraminifera has been assessed through the application of scanning electron microscopy the oxygen isotope data support the view that during the cenomanian globigerine foraminifera such as the genus hedbergella inhabited near surface waters whilst the flattened keeled morphotypes lived deeper within the water column the carbon isotope data reveal a more complex pattern as the 13 c values from planktonic species essentially show a large overlap which is interpreted in terms of a weak 13 c gradient existing in the upper part of the ocean in contrast the oxygen isotope data from planktonic foraminifera from the late albian display no discernible depth stratification pattern and the 13 c data also show a large overlap of values indicative of a complete disruption of the upper part of the thermocline a relatively low surface to bottom water temperature gradient within the early middle albian part of the succession may reflect a well mixed ocean inferred cool ocean temperatures and or high salinities for the early albian may reflect increased oceanic poleward heat transport an increase in temperature and or decrease in salinity in the cenomanian suggests a reduction of the poleward heat flux promoting the build up of limited polar ice during this period of tropical warmth

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

the variety of lithologies in the yamato 86032 lunar meteorite implications for formation processes of the lunar crust abstract we performed a petrologic mineralogical geochemical and isotopic study of several lithologies in the y 86032 feldspathic breccia this study leads us to conclude that y 86032 likely originated on the lunar farside y 86032 is composed of several types of feldspathic clasts granulitic breccias and minor basaltic clasts set in a clastic matrix we identify an an97 anorthosite that has an contents similar to those of nearside fans mg molar mg mg fe 100 values vary significantly from 45 to 80 covering the ranges of both nearside fans and the mg gap between fans and the mg suite a light gray feldspathic lg breccia making up 20 of the investigated slab 5 2 3 6 cm2 mainly consists of fragments of anorthosites an93 anorthosite more sodic than nearside fans lg also contains an augite plagioclase clast which either could be genetically related to the an93 anorthosite or to slowly cooled basaltic magma intruded into the precursor rock the na rich nature of both an93 anorthosite and this clast indicates that the lg breccia was derived from a relatively na rich but incompatible element poor source the mg variation indicates that the an97 anorthosite is a genomict breccia of several types of primary anorthosites granulitic breccias in y 86032 have relatively high mg in mafic minerals the highest mg values in mafic minerals for the an97 anorthosite and granulitic breccias are similar to those of mg rich lithologies recently described in dhofar 489 basaltic clasts in the dark gray matrix are aluminous and the zoning trends of pyroxene are similar to those of vlt or lt basalts the crystallization of these basaltic clasts pre date the lithification age of the clastic matrix at 3 8 ga the low k contents of plagioclase in both the anorthositic and basaltic clasts and generally low incompatible element abundances in all the lithologies in y 86032 indicate that kreep was not involved during the formation of the precursor lithologies this observation further suggests that urkreep did not exist in the source regions of these igneous lithologies all these facts support the idea that y 86032 was derived from a region far distant from the pkt and that the lithic clasts and fragments are indigenous to that region an an97 anorthositic clast studied here has distinct sm nd isotopic systematics from those previously found for another an97 anorthositic clast and an93 anorthosite and suggests either that an97 anorthosites come from isotopically diverse sources or that the sm nd isotopic systematics of this clast were reset 4 3 ga ago these lines of geochemical isotopic and petrologic evidence suggest that the lunar crust is geochemically more heterogeneous than previously thought

forcing mechanisms for mid cretaceous black shale formation evidence from the upper aptian and lower albian of the vocontian basin se france calcareous nannoplankton palynomorph benthic foraminifera and oxygen isotope records from the supraregionally distributed niveau paquier early albian age oceanic anoxic event 1b and regionally distributed niveau kilian late aptian age black shales in the vocontian basin se france exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid cretaceous low latitudes to quantify surface water productivity and temperature changes nutrient and temperature indices based on calcareous nannofossils were developed the nutrient index strongly varies in the precessional band whereas variations of the temperature index reflect eccentricity since polar ice caps were not present during the mid cretaceous these variations probably result from feedback mechanisms within a monsoonal climate system of the mid cretaceous low latitudes involving warm humid and cool dry cycles a model is proposed that explains the formation of mid cretaceous black shales through monsoonally driven changes in temperature and evaporation precipitation patterns the lower albian niveau paquier which has a supraregional distribution formed under extremely warm and humid conditions when monsoonal intensity was strongest bottom water ventilation in the vocontian basin was diminished probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes surface water productivity in the vocontian basin was controlled by the strength of monsoonal winds the upper aptian niveau kilian which has a regional distribution only formed under a less warm and humid climate than the niveau paquier low latitude deep water formation was reduced to a lesser extent and or on regional scale only the threshold for the formation of a supraregional black shale was not reached the intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale at least in the vocontian basin the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity

environmental significance of foraminiferal morphogroups in jurassic north sea deltas abstract the distribution of morphological groups of foraminifera has been analysed in toarcian and bajocian deposits of the northern north sea and the yorkshire coast the deposits are referred to prodeltaic lower delta front and interdistributary bay environments and contain mainly or entirely agglutinating assemblages of low to intermediate diversity a total of 33 agglutinating species are recognized in the studied material and these are arranged into eleven morphotypes composing seven subgroups and four morphogroups the categories are distinguished on the basis of main morphological features of the taxa combined with their life positions and micro habitats as inferred from modern analogues the prodelta deposits were formed in a normal saline and slightly stagnant depositional setting with foraminiferal faunas composed mainly of surficial and infaunal morphogroups the lower delta front and interdistributary bay sediments were deposited in shallow hyposaline waters strongly dominated by an epifaunal morphogroup with a partly phytal association a model of agglutinated morphotype distribution reveals increasing morphotype diversity and by inference ecological niche span from interdistributary bay through lower delta front to prodeltaic environments

latest jurassic early cretaceous events and the late cimmerian unconformity in north sea area each of several regional or local unconformities may have been identified locally as the late cimmerian unconformity a supposed major break at the base of the valhall formation or roedby formation over most of the north sea the base of the valhall formation is isochronous and conformable with underlying sediments it is detected on seismic reflection profiles because it represents a widespread facies change marking the late ryazanian transgression most of the unconformities are of eustatic origin and the effects of eustatic sea level changes were never completely masked by local tectonics thus in the modeling of individual oil fields the possibility of sedimentary breaks occurring can be predicted in part by reference to regional or eustatic events modified journal abstract

response of middle jurassic benthic foraminiferal morphogroups to dysoxic anoxic conditions in the pieniny klippen basin polish carpathians abstract the distribution of foraminiferal morphological groups has been analyzed in upper aalenian lower bajocian black siltstones and mudstones of the pieniny klippen belt polish carpathians the deposits are assigned to middle neritic outer and upper bathyal zones represented by three succession and contain agglutinated and calcaeous foraminifera assemblages separate classifications of agglutinated and calcareous morphogroups are established and used for a palaeocological study the groups are distinguished on the basis of morphological features modes of life and feeding habits as inferred from modern analogues infaunal preferences of some foraminifera have been supported by comparison with other infaunal indicators such as trace fossil tiering and abundance of infaunal ostracods a new quantitative method to estimate dissolution of calcareous tests has been tested on the most common genus lenticulina it reveals a special survival strategy of this genus in suboxic muddy and flocculent substrate the distribution of morphogroups in comparison with other palaeoecological taphonomical and sedimentological indicators allows interpretations of organic input rate of sedimentation level of oxygenation position of the redox boundary and p h the studied deposits represent regional anoxic dysoxic event which occured within a semienclosed silled basin

coupled primary production benthic foraminiferal assemblage and sulfur diagenesis in organic rich sediments of the benguela upwelling system abstract episodically deposited dark organic rich pleistocene and late pliocene sediments from the lower continental slope off southwest africa reveal complex interactions between changes in primary production benthic foraminiferal assemblage and anaerobic microbial processes the organic rich layers contain diatom assemblages characteristic of intense seasonal coastal upwelling whereas stratigraphically adjacent sediments reflect pelagic primary production coastal upwelling dominated depositional intervals coincide with periods of enhanced carbon flux to the seafloor enhanced organic carbon export during dark layer deposition was accompanied by decreases in the diversity of benthic foraminifera to few opportunistic species adapted to high phytodetritus accumulation rates and low o 2 conditions in all sediments the sulfur isotopic composition of pyrite indicates redox cycling of sulfide close to the sediment water interface the sulfur isotopic evidence and the permanent presence of abundant low o 2 adapted benthic foraminifera throughout the organic rich layers suggest an oxygenated benthic environment efficient oxidation of sulfide and removal of sulfide by sulfidization of organic matter inhibited buildup of toxic hydrogen sulfide from bacterial sulfate reduction at the sediment water interface these data imply that in continental slope sediments underneath productive surface waters benthic dysoxic conditions are maintained by the lateral advection of dissolved oxygen to support a small but well adapted benthic community

theoretical seismic wave radiation from a fluid filled borehole this paper concerns far field radiation of compressional p and shear s waves into the surrounding medium from a fluid filled borehole in an infinite medium and tube waves propagating along a borehole using a low frequency approximation two kinds of sources are considered 1 a volume displacement point source acting on the axis of a borehole and 2 a uniform radial stress source acting on the wall of a borehole when the tube wave velocity is close to the shear wave velocity the effect of the borehole fluid on the p wave radiation pattern and on the s wave radiation pattern is substantial

borehole seismic source radiation pattern in transversely isotropic media we extend previous discussions on crosswell tomography in anisotropic formations by deriving the radiation patterns of three typical downhole seismic sources impulsive air gun or dynamite wall clamped vertical vibrators and cylindrical bender inside a fluid filled borehole embedded in a transversely isotropic ti formation the method of steepest descents in conjuncture with the low frequency and far field assumptions is applied to the exact displacement integrals of these sources to obtain their radiation patterns asymptotically in spite of complications caused by quasi p and quasi sv wave coupling and wavefront triplication in homogeneous ti media the final results can still be expressed in slowness components determined by a ray direction which is desired when source radiation effects are to be accounted for by ray based tomography techniques tests with the radiation patterns show that while the effect of anisotropy on p waves is moderate its effect on the s wave pattern is significant eve

atlantic paleobathymetry paleoproductivity and paleocirculation in the late albian the benthic foraminiferal record spatial distribution patterns of benthic foraminifers in upper albian sediments from 25 dsdp odp sites and 31 onshore sections of the north and south atlantic ocean are used to generate paleobathymetric reconstructions and to identify areas of high primary production such as coastal and equatorial upwelling zones new paleobathymetric estimates are provided for dsdp odp sites and onshore locations that are not situated on oceanic crust paleobathymetric reconstructions indicate shallow water exchange between the north and south atlantic but show the existence of a deep water connection between the western and eastern tethys 2500 m through the gibraltar gateway strikingly there is no evidence for a strong latitudinal gradient in deep water benthic foraminiferal distribution during the late albian south atlantic assemblages show close affinity to north atlantic and tethyan assemblages exhibiting only a minor degree of provincialism biogeographic patterns reveal a distinct asymmetry in late albian paleoproductivity for the north atlantic as for the present day the eastern margins of the atlantic were generally more productive than the western margins and a belt of enhanced carbon aux export to the seafloor can be traced around the north african coast which probably corresponded to a zone of vigorous coastal upwelling by contrast assemblage composition in the south atlantic generally reflects mesotrophic to oligotrophic conditions benthic foraminiferal distribution patterns thus provide robust proxy data to test predictions from paleocirculation and paleobathymetric models for the mid cretaceous atlantic ocean and adjacent margins c 2001 elsevier science b v all rights reserved

testing the cretaceous greenhouse hypothesis using glassy foraminiferal calcite from the core of the turonian tropics on demerara rise glassy turonian foraminifera preserved in clay rich sediments from the western tropical atlantic yield the warmest equivalent 18o sea surface temperatures ssts yet reported for the entire cretaceous cenozoic we estimate turonian ssts that were at least as warm as conservative mean 30 c to significantly warmer warm mean 33 c than those in the region today however if independent evidence for high middle cretaceous pco2 is reliable and resulted in greater isotopic fractionation between seawater and calcite because of lower sea surface ph our conservative and warm sst estimates would be even higher 32 and 36 c respectively our new tropical ssts help reconcile geologic data with the predictions of general circulation models that incorporate high cretaceous pco2 and lend support to the hypothesis of a cretaceous greenhouse our data also strengthen the case for a turonian age for the cretaceous thermal maximum and highlight a 20 40 m y mismatch between peak cretaceous cenozoic global warmth and peak inferred tectonic co2 production we infer that this mismatch is either an artifact of a hidden turonian pulse in global ocean crust cycling or real evidence of the influence of some other factor on atmospheric co2 and or ssts a hidden pulse in crust cycling would explain the timing of peak cretaceous cenozoic sea level also turonian but other factors are needed to explain high frequency 10 100 k y instability in middle cretaceous ssts reported elsewhere

formation of the late aptian niveau fallot black shales in the vocontian basin se france evidence from foraminifera palynomorphs and stable isotopes abstract we present paleoceanographic models for the formation of the marlstone facies and the most prominent black shale intervals of the late aptian niveau fallot black shale succession from the vocontian basin se france in the lower part of the succession the composition of benthic foraminiferal assemblages of the niveau fallot 2 and 2 black shales suggests an enhanced burial of organic matter due to more eutrophic conditions and resulting low oxygen conditions at the seafloor in the upper part of the succession including niveau fallot 3 and 4 a third order sea level fall indicated by a decrease in the stable carbon isotope values may have resulted in a reduced water mass exchange between the vocontian basin and the western tethyan ocean this may have led to dysoxic conditions at the seafloor of the vocontian basin and may have favored the formation of organic rich sediments as shown by benthic foraminiferal assemblages decreased evaporation however is proposed as the most important mechanism causing a restriction of deep water formation within the basin which finally led to the formation of the niveau fallot 3 and 4 black shales based on our investigations the formation of the niveau fallot black shales was caused by different factors the most prominent ones include sea level fluctuations increasing productivity and changes in precipitation and evaporation rates furthermore niveau fallot 3 can probably be correlated with the thalmann black shale event in california and a dark horizon at the mazagan plateau dsdp site 545

radiation from seismic sources in cased and cemented boreholes far field stationary phase approximations are often used to study the radiation of p and s waves from seismic sources located in boreholes usually with an assumption of low frequency and in application to uncased boreholes these two assumptions allow explicit analytical results for the radiation patterns to be derived as boundary condition equations can be solved analytically in fairly simple forms applying the same methodology to cased and cemented boreholes however is much more difficult because of the increased number of simultaneous boundary condition equations i circumvent this difficulty by solving the boundary condition equations numerically using propagator matrices as is generally done in the calculation of synthetic full waveform acoustic logs in this way the assumption of low frequency is also avoided and a generalized stationary phase solution for sources in general concentrically layered borehole models is easily obtained computation of the radiation patterns for cased and uncased boreholes in various formations shows that the amplitude reduction because of the introduction of casing is a function of both source type and of formation velocities axial stress sources are less affected by the casing than either radial stress or volume injection sources and as formation velocity decreases the effect of the casing becomes more significant as the impedance contrast between steel and the formation becomes larger the new generalized stationary phase solution also shows that as frequency approaches 1000 hz the results obtained by low frequency approximations for stress sources can be inaccurate and that the energy radiated from the source becomes more highly directed in the horizontal directions the radiation pattern begins to change relatively rapidly as a function of frequency so that the resulting observations from broad band sources will show changes in waveforms that mimic the effects of attenuation these changes occur because the length of the source becomes important as wavelength decreases demonstrating the need to consider the influence of frequency as well as casing and cement on source radiation

cogenetic rock fragments from a lunar soil evidence of a ferroan noritic anorthosite pluton on the moon abstract the impact that produced north ray crater apollo 16 landing site exhumed rocks that include relatively mafic members of the lunar ferroan anorthositic suite bulk and mineral compositions indicate that a majority of 2 4 mm lithic fragments from sample 67513 including impact breccias and monomict igneous rocks are related to a common noritic anorthosite precursor compositions and geochemical trends of these lithic fragments and of related samples collected along the rim of north ray crater suggest that these rocks derived from a single igneous body this body developed as an orthocumulate from a mixture of cumulus plagioclase and mafic intercumulus melt after the plagioclase had separated from any cogenetic mafic minerals and had become concentrated into a crystal mush 70 wt plagioclase 30 wt intercumulus melt we present a model for the crystallization of the igneous system wherein system is defined as cumulus plagioclase and intercumulus melt the initial accumulation of plagioclase is analogous to the formation of thick anorthosites of the terrestrial stillwater complex however a second stage of formation is indicated involving migration of the cumulus plagioclase intercumulus melt system to a higher crustal level analogous to the emplacement of terrestrial massif anorthosites compositional variations of the lithic fragments from sample 67513 are consistent with dominantly equilibrium crystallization of intercumulus melt the highly calcic nature of orthocumulus pyroxene and plagioclase suggests some reaction between the intercumulus melt and cumulus plagioclase perhaps facilitated by some recrystallization of cumulus plagioclase bulk compositions and mineral assemblages of individual rock fragments also require that most of the mafic minerals formed in close contact with cumulus plagioclase not as separate layers the distribution of compositions and by inference modes has a narrow peak at anorthosite and a broader larger peak at noritic anorthosite characteristics of the samples and their geochemical trends imply an origin in a system that was large relative to the unknown size of the impact that produced the brecccas of ferroan noritic anorthosite composition that were excavated later by the formation of north ray crater and they appear to be consistent with an origin of the suite within a perched plagioclase cumulate if the moon s crust formed by accumulation of plagioclase in a magma ocean ferroan noritic anorthosite formed as an orthocumulate is an alternative to extensive adcumulus formation of ferroan anorthosite 90 vol plagioclase this provides a relatively mafic ferroan anorthositic component 15 vol mafics which is required by mass balance models of compositions of polymict lunar crustal materials the inferred bulk composition of the system of cumulus plagioclase and intercumulus melt is similar to that of ferroan regolith breccia macalpine hills 88104 5 a lunar highland meteorite and may represent a common and widespread component of the moon s early highland crust

the adhi kot breccia and implications for the origin of chondrules and silica rich clasts in enstatite chondrites abstract the adhi kot eh4 enstatite chondrite breccia consists of silica rich clasts 12 mn 5 vol chondrule rich clasts 55 mn 10 vol and matrix 35 mn 10 vol the silica rich clasts are a new kind of enstatite chondritic material which contains more cristobalite 18 28 wt than enstatite 12 14 wt as well as abundant niningerite and troilite the bulk atomic mg si ratios of the clasts 0 22 0 40 are much lower than the average for enstatite chondrites 0 79 kamacite and martensite with 8 11 wt ni and a martensitic structure occur in all three breccia components the clasts have kamacite rich rims and kamacite rich aggregates occur in the matrix a unidirectional change in the ambient ps2 po2 ratio in the region of the solar nebula where adhi kot agglomerated can explain many of the breccia s petrologic features if this region initially had a very high ps2 po2 ratio in a gas of non cosmic composition sulfurization of enstatite and metallic fe e g mgsio3 2fe c 3h2s mgs sio2 2fes h2o ch4 may have occurred producing abundant niningerite free silica and troilite at the expense of enstatite and metallic fe the ni content of the residual metal would have increased perhaps to 8 10 wt the silica rich clasts agglomerated under these conditions a significant fraction of the originally produced niningerite was lost perhaps by aerodynamic size sorting processes lowering the clasts bulk mg si ratios the ps2 po2 ratio then decreased perhaps because of infusion of additional h2o and sulfurization of metallic fe and enstatite ceased the chondrule rich clasts agglomerated under these conditions acquiring little free silica and niningerite an episode of chondrule formation occurred at this time by melting millimeter sized agglomerates of this relatively silica poor enstatite chondrite material and concomitant fractionation of an immiscible liquid of metallic fe ni and sulfide the chondrule rich clasts agglomerated many such chondrules subsequently the matrix agglomerated acquiring the few remaining chondrules kamacite rich aggregates formed after the cessation of metal sulfurization and agglomerated with the matrix the kamacite rich clast rims were acquired at this time the components of adhi kot accreted to the eh chondrite parent body where the breccia was assembled buried beneath additional accreting material and metamorphosed at temperatures of 700 c impact excavation of the breccia and deposition onto the surface caused the formation of martensite from taenite inside the clasts and the matrix at the surface impact melting produced an albite glass spherule which was incorporated into the matrix however the absence of solar wind implanted rare gases in bulk adhi kot indicates that the breccia spent little time in a regolith

the blithfield meteorite and the origin of sulfide rich metal poor clasts and inclusions in brecciated enstatite chondrites abstract blithfield el6 is one of five known enstatite chondrite breccias it consists of troilite rich clasts 35 5vol embedded in an extremely metallic fe ni rich matrix 65 5 vol that contains metal nodules up to 17 mm in size clasts and matrix agglomerated independently in the solar nebula under conditions of high and low ps 2 po 2 ratios respectively the matrix accreted to an el chondrite planetesimal and was metamorphosed to 1000 c above the fe ni s eutectic chondrule textures were obliterated the s rich eutectic melt was lost from the matrix the matrix material was buried to a depth of at least 3 km accreting troilite rich material was incorporated into the matrix as clasts the breccia cooled through 500 c at 1000 10 000 c myr after cooling below 500 c blithfield was quenched possibly by impact excavation from depth and deposition onto the surface clasts or inclusions that are enriched in sulfide and depleted in metallic fe ni are common in brecciated enstatite chondrites variations in the ps 2 po 2 ratio in the nebular regions where these materials formed may explain many of their petrologic properties the silica rich clasts in adhi kot eh4 formed at very high ps 2 po 2 ratios 10 27 niningerite free silica and troilite were produced from the sulfurization of enstatite and metallic fe the troilite rich clasts in blithfield and atlanta el6 as well as the troilite rich regions of the hvittis el6 matrix formed at somewhat lower ps 2 po 2 ratios where sulfurization of metalic fe produced troilite the ni content of the residual metal increased forming some metal of martensitic composition the dark inclusions in abee eh 4 which contain up to 9 wt oldhamite formed at high ps 2 po 2 ratios in the presence of an additional ca rich component

the importance of a small wall deformation in the three dimensional acoustic logging results summary a variety of seismic techniques use fluid filled boreholes to host detectors and seismic sources the complexity of the wavefield generated depends on the position of the receivers and the source frequency excited type of formation and type of source in the present paper the boundary element method is used to study the wavefield elicited by monopole or dipole sources within a fluid filled cylindrical cavity drilled through an unbounded elastic formation this model is used to assess the effects of the existence of a small localized wall deformation on the response such a deformation may occur through the mechanical action of the drill string rock failure adjacent to a drilled borehole plastic deformation and washing out of the borehole in soft or poorly consolidated rocks in addition the effect of a source receiver tool placed in an off centre and or tilted position inside the fluid filled borehole on the propagation of both axisymmetric and non axisymmetric wave modes are studied

the barremian aptian turnover of biota in northwestern europe evidence from belemnites abstract neocomian valanginian barremian and gault aptian albian are lithostratigraphic terms used in the last century to divide the sub chalk cretaceous of northern europe the division is based on significant palaeoceanographic and palaeogeographic changes in the early aptian these changes are linked to a major turnover of marine floras and faunas which occurred simultaneously in the boreal realm the tethys and the indo pacific ocean various floral and faunal elements became extinct in the aptian both in the tethys and in the boreal realm while on the other hand new genera and species evolved marked changes in the diversification rate were observed for organisms with a different mode of life plankton nekton benthos apart from calcareous nannofossils foraminifera and ammonites this turnover also occurs in belemnites and the suborder belemnitina was completely replaced by the suborder belemnopseina the northwestern european barremian is characterised by the very successful belemnite family oxyteuthididae belemnitina which was completely replaced by the genus neohibolites belemnopseina in early aptian times this aptian turnover which is expressed by a homogenisation of marine floras and faunas is best explained by significant palaeoceanographic changes occurring in the early aptian the sea floor spreading rate which increased at the barremian aptian boundary significantly peaked in the late early aptian a mantle plume in the pacific possibly caused an additional production of oceanic crust both processes caused a major sea level rise this in turn resulted in a major change of the palaeoceanographic setting and restricted marginal seas like the northwestern european basins in barremian times became drowned the more open oceanic setting of the aptian enabled cosmopolitan floras and faunas to spread worldwide the aptian saw the radiation of planktonic foraminifera which played only a minor role in pre aptian times these palaeoceanographic changes from restricted marginal seas to a more homogeneous pelagic setting are considered to be the main cause for the significant changes in the composition of belemnite faunas

evolved mare basalt magmatism high mg fe feldspathic crust chondritic impactors and the petrogenesis of antarctic lunar breccia meteorites meteorite hills 01210 and pecora escarpment 02007 antarctic lunar meteorites meteorite hills 01210 and pecora escarpment 02007 are breccias that come from different regolith lithologies on the moon met 01210 is composed predominantly of fractionated low ti basaltic material and is classified as an immature predominantly basaltic glassy matrix regolith breccia pca 02007 is a predominantly feldspathic regolith breccia consisting of metamorphosed feldspathic noritic troctolitic and noritic anorthosite clasts agglutinate and impact glasses as well as a number of basaltic clasts with mare and possible non mare affinities the basalt clasts in met 01210 have undergone fenner trend enrichments in iron and may also have witnessed late stage crystallization of zircon or a zirconium rich mineral some of the features of met 01210 are similar to other basaltic lunar breccia meteorites e g northwest africa 773 elephant moraine 87521 96008 yamato 793274 981031 but it is not paired with them the presence of metamorphic anorthositic clasts as well as agglutinates indicates a small regolith component similarities with previously discovered evolved e g lapaz icefield 02205 northwest africa 032 and ferroan e g asuka 881757 yamato 793169 basaltic lunar meteorites suggest a similar mare source region for met 01210 despite lack of evidence for pairing pca 02007 shares many features with other feldspathic regolith breccias e g yamato 791197 queen alexandra range 94281 including a high mg fe whole rock composition glass spherules agglutinate fragments and a diverse clast inventory spanning the range of ferroan anorthosite and high magnesium suite rocks some of the basalt fragments in this sample are fractionated and have an igneous origin however the majority of the basalt fragments are impact melt clasts pca 02007 supports previous studies of feldspathic lunar meteorites that have suggested an aluminous crust for the moon with compositions more similar to magnesium granulite breccias than ferroan anorthosites a chondrule like fragment found in pca 02007 and unlike any previously described lunar material is described and tentatively identified as the remnants of a chondritic lunar impactor this clast is porphyritic with equant olivines that have forsterite rich cores fo 98 extreme normal zonation to more fayalitic rims fo 44 and a mineral assemblage with rare earth element abundances distinct from described lunar material and more similar to chondrules found in ordinary or carbonaceous chondrites its discovery and description is significant for understanding the composition of lunar impactors previously the main evidence for chondritic lunar impactors was from chondritic relative abundances and near chondritic ratios of highly siderophile elements in lunar impact melt breccias however the presence of this clast along with two other chondritic clasts from apollo soils 12037 and 15602 provides clues to the identity of ancient meteorite impactors on the moon

influence of oceanic anoxic events on the evolution of mid cretaceous radiolaria in the north atlantic and western tethys abstract mid cretaceous aptian turonian extinction radiation events of radiolaria from the north atlantic and western tethys are summarized in relation to oceanic anoxic events oae from investigations of radiolarian faunas black shales and stable carbon isotopes extinction and radiation events of radiolaria can be observed from the late early aptian the earliest albian the latest albian and the cenomanian turonian boundary these events correlate well with organic carbon rich sediments that contain type ii kerogen and show positive 13c excursions they correspond to the oceanic anoxic events oae in the early aptian oae 1a selli level early albian oae 1b late albian oae 1d and latest cenomanian oae 2 bonarelli level detailed investigations of the two most significant events the selli and the bonarelli level in the umbria marche basin of central italy show that extinctions coincide with the first occurrence of marine black shales type ii kerogen and the most prominent rise of 13corg values stepwise extinctions and continuous radiations precede and follow the events similar patterns are evident for the oae 1b and 1d black shales dominated by terrestrial organic matter type iii kerogen e g oae 1c are not characterized by isotopic excursions or by radiolarian extinction radiation events contemporaneous drowning events documented from carbonate platforms around the investigated basins provide a link to a model where flooding of lowlands and leaching of nutrients during a relative rise of sea level lead to an increased productivity and an expansion of the oxygen minimum zone omz because of the loss of deep habitats deeper dwelling forms become extinct shallower dwelling radiolarians survive a narrowing of the omz during highstands and relative sea level falls together with a coupled decrease of the nutrient supply leads to the development of new niches and therefore to radiation

insolation cycles as a major control of equatorial indian ocean primary production analysis of a continuous sedimentary record taken in the maldives indicates that strong primary production fluctuations 70 to 390 grams of carbon per square meter per year have occurred in the equatorial indian ocean during the past 910 000 years the record of primary production is coherent and in phase with the february equatorial insolation whereas it shows diverse phase behavior with 18o depending on the orbital frequency eccentricity obliquity or precession examined these observations imply a direct control of productivity in the equatorial oceanic system by insolation in the equatorial indian ocean productivity is driven by the wind intensity of westerlies which is related to the southern oscillation therefore it is suggested that a precession forcing on the southern oscillation is responsible for the observed paleoproductivity dynamics

migration and evolution patterns of floras and faunas in marine early cretaceous sediments of nw europe the distribution and migration patterns of marine nannofloras and faunas in the early cretaceous berriasian aptian of nw europe are described boreal nannofloras and faunas dominate in the latest berriasian the early valanginian the mid late valanginian the late early hauterivian and the mid late hauterivian sea level highstands linked to warming enabled tethyan nannofloras and faunas to spread into nw europe during three intervals 1 in the earliest late valanginian 2 in the latest valanginian and earliest hauterivian and 3 in short influxes in the late hauterivian culminating in the latest hauterivian during the barremian regression the palaeoceanography of nw europe changed totally from a marginal sea to a restricted basin this oceanographic setting allowed the evolution of endemic nannofloras and faunas a major sea level rise caused by increased sea floor spreading changed the palaeoceanographic situation significantly in the aptian due to widespread oceanic conditions nannofloras and faunas became homogenised and cosmopolitan nevertheless the peak of the transgression was again linked to a widespread influx of tethyan nannofloras and faunas in the mid late aptian nutfieldiensis zone the dispersal and evolution patterns of the nannofloras and faunas in the early cretaceous were mainly controlled by the suitability of sea ways regressions transgressions and temperature planktonic benthic and nectonic organisms reacted in similar ways their distribution pattern differs however significantly due to different modes of life

sulfidation of mg rich olivine and the stability of niningerite in enstatite chondrites abstract when heated with excess fe ni monosulfide and graphite in a sealed silica glass tube at 1200 c mg rich olivine fo90 is sulfidized to niningerite mg fe s and clinoenstatite by the reaction mg 2 sio 4 1 2 s 2 c mgsio 3 mgs co minor amounts of fe ni suicides and silicon sulfides are also produced the distribution coefficient for ni fe exchange between mg fe s and fe ni s is about 24 and is significantly greater than that for coexisting niningerite and troilite in eh enstatite chondrites experimental studies in the ni free system at both subsolidus and liquid iron sulfide temperatures are in good overall agreement with the calculated phase relations for niningerite the quenched experimental assemblage clinoenstatite troilite niningerite alloy suicide graphite is equivalent to the reduced mineral assemblage of eh enstatite chondrites the present phase relations suggest that niningerite in eh chondrites could have been produced by sulfidation of mg rich silicates during either accretion or metamorphism at low fugacities of co however niningerite is not stable under the anticipated conditions of recrystallization of el enstatite chondrites the assemblage olivine graphite pyrrhotite is unstable under magmatic conditions at low and moderate crustal pressures

an ancient sm nd age for a ferroan noritic anorthosite clast from lunar breccia 67016 strontium and neodymium systematics have been examined in a clast of ferroan noritic anorthosite from apollo 16 breccia 67016 two splits 328 and 326 of the same clast give different sm nd results split 328 gives a well defined internal isochron age of 4 562 0 068 ga and an initial 143nd 144nd ratio of 0 50673 10 corresponding to nd 0 1 0 2 2 optimized error relative to the murchinson carbonaceous chondrite the pyroxene separate from split 326 lies on the same isochron in contrast the plagioclase and whole rock from split 326 fall below this line indicating a small scale disturbance of the sm nd system this may reflect either an isotopic exchange between the plagioclase and a low sm nd mineral or a loss of radiogenic 143nd from the plagioclase possibly during the period of major impacts at 3 9 ga the preservation of an extremely old age for the noritic ferroan anorthosite 67016 328 suggests a rapid cooling of this rock at an early stage in the evolution of the lunar magma ocean this old age is also consistent with giant impact models for the formation of the moon but implies a relatively early event pre 4 50 ga and therefore rapid accretion and differentiation of the terrestrial planets

recent benthic foraminiferal associations and ecology of the scotia sea and argentine basin abstract we investigated 88 surface sediment samples taken with a multiple corer from the southwestern south atlantic ocean for their live rose bengal stained and dead benthic foraminiferal content using q mode principal component analysis six live and six dead associations are differentiated live and dead association distributions correspond fairly well differences are mainly caused by downslope transport and selective test destruction in addition four potential fossil associations are calculated from the dead data set after removal of non fossilizable species these potential fossil associations are expected to be useful for paleoceanographic reconstructions environments are described in detail for the live and potential fossil associations and for selected species along the upper argentine continental slope strong bottom currents control the occurrence of live dead and potential fossil angulogerina angulosa associations here particles of a high organic carbon flux rate remain suspended below this high energy environment live dead and potential fossil uvigerina peregrina dominated associations correlate with enhanced sediment organic carbon content and still high organic carbon flux rates the live a angulosa and u peregrina associations correlate with high standing crops furthermore live and dead epistominella exigua nuttallides umbonifer associations were separated dominance of a nuttallides umbonifer potential fossil association relates to coverage by antarctic bottom water aabw and lower circumpolar deep water lcdw above the calcite compensation depth ccd three associations of mainly agglutinated foraminifera occur in sediments bathed mainly by aabw or cdw a reophax difflugiformis association was found in mud rich and diatomaceous sediments below the ccd a psammosphaera fusca association occurs in coarse sediments poor in organic carbon while a cribrostomoides subglobosus ammobaculites agglutinans association covers a more variable environmental range with mud contents exceeding 30 one single eggerella bradyi martinottiella communis association poor in both species and individuals remains from the agglutinated associations below the ccd if only preservable species are considered for calculation

onset of the mid cretaceous greenhouse in the barremian aptian igneous events and the biological sedimentary and geochemical responses basalts and biostratigraphy dated at 125 120 ma from the ontong java and manihiki plateaus in the western pacific evidence the largest volcanic event in earth history in at least the past 160 m y the intervening nova canton trough rifted at about 121 118 ma and a number of guyots and seamounts formed concurrently or slightly later geological events that probably were responses to these volcanic tectonic events occurred in the following chronostratigraphic order biotic fluctuations began at about 122 5 ma at about 122 0 ma 87sr 86sr began to decline slowly metal concentrations of co mn pb yb and cu in sediments peaked at about 121 5 121 2 ma changes in planktonic communities and sedimentation culminated in a nannoconid crisis just prior to 120 5 ma and in the selli black shale oae la at about 120 5 119 5 ma a sharp drop in 13c occurred at the beginning of the selli event and rebounded into a longer positive excursion that reached a peak after the selli event at about 119 5 118 5 ma at 120 5 ma 87sr 86sr declined rapidly and reached a minimum at about 116 113 ma we speculate that the intensity of these latter responses suggests a corresponding peak in volcanic tectonic activity at about 121 119 ma

petrology and geochemistry of alkali gabbronorites from lunar breccia 67975 clasts of an unusual type of lunar highlands igneous rock alkali gabbronorite have been found in apollo 16 breccia 67975 the alkali gabbronorites form two distinct subgroups magnesian and ferroan modes and bulk compositions are highly varied the magnesian alkali gabbronorites are composed of bytownitic plagioclase or2 5an82 89 hypersthene wo3 5en49 62 augite wo39 42en36 44 a silica mineral and trace ba rich k feldspar the ferroan alkali gabbronorites are composed of ternary plagioclase or11 22an65 74 pigeonite wo6 9en35 47 augite wo38 40en29 35 ba rich k feldspar and a silica mineral trace minerals in both subgroups are apatite ree rich whitlockite and zircon the magnesian and ferroan alkali gabbronorites appear to have formed by progressive differentiation of the same or closely related parent magmas the compositional data indicate that these magmas were ree rich the ternary plagioclase is probably a high temperature metastable phase formed during crystallization in composition and mineralogy the 67975 alkali gabbronorites show many similarities to apollo 12 and 14 alkali norites alkali gabbronorites and alkali anorthosites and all these rocks together constitute a distinctive alkali suite in addition the alkali gabbronorites show some similarities to kreep basalts mg norites and some felsites these data suggest genetic links between some or all of these types of pristine rocks two types of relationships are possible the first is that alkali suite rocks crystallized in plutons of kreep basalt magma and kreep basalts are their extrusive equivalents the second is that the alkali suite rocks and some felsites all crystallized in plutons of mg norite parent magmas and kreep basalt magmas formed by remelting of these plutons additional studies are needed to resolve which of these hypotheses is correct

additional complexity in the lunar crust petrology of sodic anorthosites and sulfur rich ferroan noritic anorthosites lunar breccia 67016 contains two suites of unusual highlands rocks sulfur rich noritic anorthosites and sodic anorthosites mineral compositions of the sulfur rich noritic anorthosites closely match those of ferroan anorthosites unusually large amounts of sulfides and sulfidation reactions involving olivine in these clasts probably reflect endogenous volatile transfer the sodic anorthosites are mafic poor with mineral compositions intermediate between those of pristine ferroan and alkali anorthosites rare examples of pristine rocks with similar mineral compositions are known and may represent a distinct class of lunar crustal rocks

benthic foraminifera off west africa 1 n to 32 s do live assemblages from the topmost sediment reliably record environmental variability abstract recent benthic foraminifera 125 m were investigated from multicorer samples on a latitudinal transect of 20 stations between 1 n and 32 s along the upper slope off west africa samples were selected from a narrow water depth interval between 1200 and 1500 m so that changes in water masses are minimized but changes in surface productivity are important and the only significant environmental variable live rose bengal stained benthic foraminifera were counted from the surface sediment down to a maximum of 12 cm dead foraminifera were investigated in the top 5 cm of the sediment only five live and five dead benthic foraminiferal assemblages were identified using q mode principal component analysis matching distinct primary productivity provinces characterized by different systems of seasonal and permanent upwelling differences in seasonality quantity and quality of food supply are the main controlling parameters on species composition and distribution of the benthic foraminiferal faunas to test the sensitivity of foraminiferal studies based on the uppermost centimeter of sediment only a comparative q mode principal component analysis was conducted on live and dead foraminiferal data from the top 1 cm of sediment it has been demonstrated that on the upper slope off west africa most of the environmental signals as recorded by species composition and distribution of the total live and dead assemblages i e including live and dead foraminifera from the surface sediment down to 12 cm and 5 cm respectively can be extracted from the assemblages in the top centimeter of sediment only on the contrary subsurface abundance maxima of live foraminifera and dissolution of empty tests strongly bias quantitative approaches based on the calculation of standing stocks and foraminiferal numbers in the topmost centimeter

geochemistry of lunar crustal rocks from breccia 67016 and the composition of the moon global differentiation of the moon has produced a plagioclase rich crust overlying an ultramafic mantle we have conducted a major and trace element study of anorthositic clasts from an apollo 16 breccia to investigate the geochemical features of these highlands lithologies and their role in lunar crustal evolution samples analyzed for this study have aluminous alkali poor compositions and varied feo and mgo contents al2o3 25 35 na2o 0 3 1 k2o 1 ferroan noritic and 1 magnesian troctolitic respectively these mafic enriched varieties have considerably higher lithophile element concentrations at levels similar to that of the bulk lunar crust the ferroan noritic clasts may represent a fundamental type of igneous rock in the lunar crust which has not been widely recognized liyb ratios of highlands and mare rocks demonstrate the complementary nature of the lunar crust and mantle which is best explained by a global differentiation event such as crystallization of a magma ocean the most primitive mantle derived lunar material for which data are available the apollo 15 green glass has liyb virtually identical to those of the mafic enriched anorthosites providing an estimate of the magma ocean composition the moon and the earth have liyb ratios that are similar to each other but the absolute abundances of both li and yb appear to be higher in the moon the liyb ratios of the earth and moon are distinct from those of ci and ordinary chondrites and the eucrite parent body but are similar to those of cv co and el chondrites precluding a unique match between the composition of the earth and moon

radiation patterns of a shear wave vibrator in near surface shale two shallow surface to borehole field tests were conducted to investigate the radiation patterns of a shear wave vibrator in near surface shale in the in line direction for which baseplate motion is transverse to the source geophone raypath the vibrator produces a broadband high amplitude signal of the sh type and virtually no signal of the sv or p types the amplitude of the sh radiation is approximately constant as a function of polar angle but it falls off as the cosine of the azimuthal angle measured with respect to the in line direction in the broadside direction the vibrator produces a strong uncontaminated signal of the sv type the radiation pattern of the sv signature is lobate in the polar plane and peaks at an incident angle of 30 to 35 degrees in the horizontal plane the sv radiation varies as the sine of the azimuthal angle measured with respect to the in line direction the field tests were conducted on a permian shale in oklahoma and an eocene shale in east texas comparison between sh and sv wave surfaces indicates that both shales behave approximately like transversely isotropic solids with a vertical axis of symmetry theoretical wave surfaces are fit to the observed data by using elastic moduli determined from the field measurements and by making the assumption that the near surface shale at each field site is a single homogeneous inherently transversely isotropic material the analyses indicate that horizontal sh group velocity is about 30 percent greater than horizontal sv group velocity in the permian shale and about 25 percent greater in the eocene shale

florisphaera profunda a possible nannoplankton indicator of late quaternary changes in sea water turbidity at the northwestern margin of the pacific three piston cores from the ryukyu trench slope northwestern margin of the pacific ocean contain nearly continuous paleoceanographic records of the last 320 165 and 105 kyr ages of the cores are constrained by planktic 18o stratigraphy and roughly substantiated by the presence of two calcareous nannofossil events spectral analysis of the changes in relative abundance offlorisphaera profunda a nannoplankton species presently living in the lower euphotic zone reveals a maximum power at 0 01 cycles kyr corresponding to the 100 kyr cycle of orbital eccentricity much lower power is observed at the 23 kyr precessional band this differs from the equatorial atlantic ocean variations which show dominant power in the 23 kyr precessional band in the changes off profunda abundances molfino and mcintyre 1990a besides our cores were taken outside the equatorial divergence zone we also show a rather close relationship betweenf profunda abundance and sea water transparency secchi depth in the present northwest pacific based on data from 204 sites of surface sediment samples because sea water transparency is primarily affected by bio productivity change in open ocean stratigraphic changes off profunda abundances in our cores seem to have been caused by productivity change as well pointed out by molfino and mcintyre 1990a b a mechanism proposed by them for its change however is not applied to our cases due to differences in spectral analysis results and in geographic situation alternatively we suggest that geographic change of the northwestern margin of the pacific during the late quaternary causedf profunda abundance change through the sea water turbidity change which has been affected not only by bio productivity but also by land origin particles supply

planktic foraminifera from the mid cretaceous barremian early albian of the north sea basin palaeoecological and palaeoceanographic implications abstract a marine cretaceous succession barremian albian of a cored borehole bgs 81 40 located in the central north sea basin has been examined with respect to its planktic and benthic foraminiferal content as well as for calcareous nannofossils the distribution patterns of foraminifera and calcareous nannofossils allow for a two fold division of the investigated interval 1 the barremian earliest aptian interval which reflects a marine temporary restricted setting this is indicated by sporadic occurrences of planktic foraminifera with very rare planispiral forms suggesting short term connections of the boreal and tethyan realms the benthic foraminiferal assemblages indicate aerobic sometimes dysaerobic bottom water conditions high abundances of nannoconids in the barremian suggest enhanced stratification and or warm oligotrophic surface water 2 the late aptian early albian interval which was characterised by an open oceanic environment with cool and aerobic surface water conditions planktic foraminifera are more abundant and diverse than in the lower interval trochospiral hedbergellids dominate the foraminiferal assemblages the episodic occurrences of planispiral clavate and trochospiral flattened planktic morphotypes indicate the existence of a seaway between the boreal and the tethyan realms aerobic to dysaerobic bottom water conditions are suggested by the composition of the benthic foraminiferal assemblages high abundances of cool water taxa within the calcareous nannofossil assemblages indicate a cooling trend across the latest aptian and earliest albian

reconstruction of short term palaeoceanographic changes during the formation of the late albian niveau breistroffer black shales oceanic anoxic event 1d se france the niveau breistroffer black shale succession in the vocontian basin se france is the regional equivalent of the widely distributed late albian oceanic anoxic event 1d the studied black shale rich interval at the col de palluel section is 6 28 m thick and comprises four black shale units with up to 2 5 wt total organic carbon toc intercalated with marlstones calcareous nannofossil palynomorph planktic foraminifera and stable isotopic data from the niveau breistroffer succession suggest that short term climate changes influenced its deposition with relatively warm and humid climate during black shale formation in comparison with relatively cool and dry climatic conditions during marlstone deposition an increase in the terrigenous marine ratio of palynomorphs indicates enhanced humidity and higher runoff during black shale formation a nutrient index based on calcareous nannofossils and the abundance pattern of small 63 125 m hedbergellid foraminifera show short term changes in the productivity of the surface water surface water productivity was reduced during black shale formation and increased during marlstone deposition a calcareous nannofossil temperature index and bulk rock oxygen isotope data indicate relative temperature changes with warmer surface waters for black shale samples at these times warm humid climate and reduced surface water productivity were accompanied by greater abundances of subsurface dwelling calcareous nannofossils nannoconids and planktic foraminifera rotaliporids these taxa presumably indicate more stratified surface water conditions we suggest that the formation of the niveau breistroffer black shales occurred during orbitally induced increase in monsoonal activity that led to increasing humidity during periods of black shale formation this in turn caused a decrease in low latitude deep water formation and probably an increase in surface water stratification the combination of these two mechanisms caused depleted o 2 concentrations in the bottom water that increased the preservation potential of organic matter

correlating environmental changes during early albian oceanic anoxic event 1b using benthic foraminiferal paleoecology abstract the nature and consequences of mid cretaceous oceanic anoxic events oaes are the subject of ongoing debate and recent studies have shown that different scenarios are needed to explain each of these events nevertheless similarities between the different oaes can be observed here we have reconstructed paleoenvironmental changes during the early albian oae 1b using benthic foraminiferal distributions and lithologies in three sections from different basins and paleowater depths eutrophic conditions as indicated by the presence of infaunal as well as opportunistic genera such as gyroidinoides pseudobolivina pleurostomella and bolivinitids prevailed before and during the oae and led to dysoxic to anoxic conditions dysoxia was most intense in the bathyal sections but also occurred in the outer shelf where more heterogeneous patterns of foraminiferal distributions are believed to reflect fluctuations of the upper boundary of an oxygen minimum zone a change from eutrophic to mesotrophic conditions caused the termination of oae 1b and opportunistic benthic foraminifera e g pseudobolivina pleurostomella were the first to subsequently repopulate the bathyal sea floor repopulation occurred rapidly in the shallow settings and gradually in the deeper sites where a normal diverse pre event fauna was established a few tens of thousands of years after oae 1b

chronology geochemistry and petrology of a ferroan noritic anorthosite clast from descartes breccia 67215 clues to the age origin structure and impact history of the lunar crust the petrology major and trace element geochemistry and nd ar sr isotopic compositions of a ferroan noritic anorthosite clast from lunar breccia 67215 have been studied in order to improve our understanding of the composition age structure and impact history of the lunar crust the clast designated 67215c has an unusually well preserved igneous texture mineral compositions are consistent with classification of 67215c as a member of the ferroan anorthositic suite of lunar highlands rocks but the texture and mineralogy show that it cooled more rapidly and at shallower depths than did more typical ferroan anorthosites fans incompatible trace element concentrations are enriched in 67215c relative to typical fans but diagnostic signatures such as ti sm sc sm plagiophile element ratios and the lack of zr hf and nb ta fractionation show that this cannot be due to the addition of kreep alternatively 67215c may contain a greater fraction of trapped liquid than is commonly present in lunar fans 147sm 143nd isotopic compositions of mineral separates from 67215c define an isochron age of 4 40 0 11 gyr with a near chondritic initial 143nd of 0 85 0 53 the 40ar 39ar composition of plagioclase from this clast records a post crystallization thermal event at 3 93 0 08 gyr with the greatest contribution to the uncertainty in this age deriving from a poorly constrained correction for lunar atmosphere 40ar rb sr isotopic compositions are disturbed probably by the same event recorded by the ar isotopic compositions trace element compositions of fans are consistent with crystallization from a moderately evolved magma ocean and do not support a highly depleted source composition such as that implied by the positive initial 143nd of the ferroan noritic anorthosite 62236 alternatively the nd isotopic systematics of lunar fans may have been subject to variable degrees of modification by impact metamorphism with the plagioclase fraction being more strongly affected than the mafic phases 147sm 143nd isotopic compositions of mafic fractions from the 4 ferroan noritic anorthosites for which isotopic data exist 60025 62236 67016c 67215c define an age of 4 46 0 04 gyr which may provide a robust estimate for the crystallization age of lunar ferroan anorthosites

mineral compositions in pristine lunar highland rocks and the diversity of highland magmatism high precision electron microprobe analyses of olivine and pyroxene in pristine lunar highland rocks confirm the dichotomy between ferroan anorthosites and the mg suite ferroan anorthosites plot as coherent trends consistent with formation in a complex global magma system lack of coherent compositional trends in the mg suite rocks indicates derivation from numerous magmas

a potpourri of pristine moon rocks including a vhk mare basalt and a unique augite rich apollo 17 anorthosite analysis of previously unstudied apollo lithic fragments continues to yield surprising results among this year s samples is a small anorthosite fragment 76504 18 the first pristine anorthosit e found from apollo 17 this unique lithology strongly resembles the main type of apollo anorthosites ferroan anorthosites but 76504 18 has a far higher ratio about 9 of high ca pyroxene to low ca pyroxene higher na in its plagioclase higher contents of incompatible elements such as ree and a higher eu al ratio assuming that 76504 18 is a cumulate with less than 45 trapped liquid its parent melt probably had a negative eu anomaly in all these respects 76504 18 seems more likely than other ferroan anorthosites to be closely related to typical mare basalts apparently this anorthosite was among the latest to form by plagioclase flotation above a primordial magmasphere typical mare basalt source regions probably accumulated at about the same time or even earlier another previously unstudied fragment 14181c is a vhk very high potassium basalt that is similar in most respects to typical aluminous apollo 14 mare basalt but has a k la ratio of 1050 this lithology probably formed after a normal apollo 14 mare basaltic melt partially assimilated granite new data for siderophile elements in apollo 12 mare basalts indicate that only the lowest of earlier data are trustworthy as being free of laboratory contamination

reconstructing nutricline dynamics of mid cretaceous oceans evidence from calcareous nannofossils from the niveau paquier black shale se france abstract a high resolution calcareous nannofossil record is presented from the lower albian niveau paquier black shale from the vocontian basin se france the niveau paquier black shale represents the regional equivalent of the supraregionally distributed oceanic anoxic event 1b oae 1b to reconstruct surface water fertility a nutrient index based on zeugrhabdotus erectus discorhabdus rotatorius high fertility indicators and watznaueria barnesae low fertility indicator was established using principal component analysis in addition the distribution of nannoconus spp and absolute abundances of coccoliths coccoliths per gram were used for reconstructing nutricline dynamics of the surface waters high surface water fertility coincides with low percentages of nannoconids and vice versa moreover high percentages of nannoconids correlate with low absolute abundances of all other coccoliths based on the observed nannoplankton distribution pattern and a suggested similarity in ecological requirements between nannoconids and the modern taxon florisphaera profunda a model is proposed that couples nannoconid abundances with dynamics of the nutricline time series analyses of the nutrient index show fluctuations within the precessional band the precession controlled fluctuations of the surface water fertility may represent a monsoonal signal with the nutrient supply in the surface waters depending on the strength of monsoonal activity during periods of enhanced monsoonal activity which were characterized by humid conditions and stronger winds mixing of the upper water column was enhanced during that time the abundance of nannoconids decreased as a consequence of enhanced wind stress that improved vertical mixing and led to an entrainment of nutrients into the surface waters this resulted in an increase of primary production during periods of reduced monsoonal activity marked by drier conditions and reduced wind stress the surface waters were depleted in nutrients as a result of a deep nutricline and a reduced nutrient supply to the upper photic zone in a stratified water column percentages of nannoconids increased according to the mechanisms outlined above fluctuations of the nutrient index and nannoconid percentages have been used as a proxy for reconstructing the physical structure of mid cretaceous oceans steered by precession forced monsoonal activity the results of the study show that the formation of the lower albian oae 1b from the vocontian basin occurred under strongly fluctuating surface waters fertility

nannofossils and superplumes the early aptian nannoconid crisis a group of calcareous nannoplankton named nannoconids experienced a crisis in the early aptian and recovered only later in the late aptian after a period of virtual absence although no extinctions occurred the widespread nature of the nannoconid crisis suggests a global causal factor this crisis is recorded within the chiastozygus litterarius nannofossil and globigerinelloides blowi planktonic foraminiferal zones postdates magnetic chronozone m0 by approximately 300 kyr and precedes the oceanic anoxic subevent 1a and associated 13c anomaly by some 40 100 kyr selective dissolution and anoxia cannot explain the crisis because nannoconids are dissolution resistant forms and their crisis clearly precedes the deposition of anoxic sediments at least 1 m y prior to the nannoconid crisis the onset of a nannoplankton speciation event may be the response of nannofloras to a major rise in relative sea level the nannoconid crisis seems to be synchronous with the early aptian volcanic eruptions in the pacific ocean hence calcareous nannoplankton were severely affected by the superplume volcanic episode the coccolithophorid bloom nannoconid crisis was possibly induced by the excessive co2 levels in the atmosphere and or caused by changes in nutrient content of oceanic surface waters fertility was enhanced by rapid turnover of nutrients due to the abnormal volcanic activity and accelerated transfer of nutrients from the continents into the oceans under warm and humid conditions of the mid cretaceous greenhouse climate the nannoconid crisis may represent a competition between phytoplankton groups for nutrients or more likely competition between different calcareous nannoplankton the biologic affinity and mode of life of nannoconus are unknown because there is no modern analog of this genus however comparison of lower cretaceous nannofossil assemblages with modern nannoplankton cummunities suggests that nannoconids like extant florisphaera profunda possibly inhabited the lower photic zone concentrations of nutrients in the upper euphotic zone may have triggered blooms of coccolithophorids and nannoconid depletion this model implies that the nannoconid crisis is the result of an abrupt major change in the structure of surface waters caused directly or indirectly by the superplume the adjustments of the biosphere to the new paleoceanographic and climatic conditions required some 40 100 kyr before changing into abnormally high primary productivity and deposition of organic carbon rich sediments with dinoflagellates outcompeting nannoplankton

palaeobiogeography of early cretaceous berriasian barremian calcareous nannoplankton in order to assess early cretaceous nannoplankton biogeography we studied a series of sites which provide a north south transect across the atlantic ocean supplemented by sections from the north sea basin barents sea falkland plateau weddell sea antarctica argo abyssal plain nw of australia and neuquen basin argentina quantitative assemblage data were gathered from each site for seven time slices within the berriasian to barremian interval each horizon being determined by a nannofossil datum trends in species relative abundance and measures of diversity evenness and richness provide revealing biogeographic information a broad low to mid palaeolatitude zone 50 degrees n 50 degrees s is flanked in both northern and southern hemispheres by distinct high palaeolatitude zones major changes in assemblage abundance and composition occur across a sharp biogeographic front at around 50 degrees n and s palaeolatitude high palaeolatitude assemblages are lower in species richness and diversity and characterised by the presence of abundant typically bipolar taxa e g crucibiscutum salebrosum a less distinct biogeographic boundary at similar to 40 degrees n is distinguished by the presence absence of rarer but biogeographically significant taxa many of which have previously been assigned to boreal or tethyan provinces continental shelf sites are characterised by lower diversity assemblages with common to dominant diagnostic taxa which vary with palaeolatitude nannoconus and micrantholithus at low palaeolatitudes and biscutum constans and zeugrhabdotus spp at higher palaeolatitudes the latter two taxa are considered to be indicative of elevated surface water fertility and the former two may have been similarly adapted the genus watznoueria is ubiquitously dominant giving the populations an unevenness which appears to be a common feature throughout coccolithophore history c 2000 published by elsevier science b v all rights reserved

early cretaceous calcareous nannofossils from high latitudes implications for palaeobiogeography and palaeoclimate abstract in order to better understand the palaeoceanography and palaeoclimate of the early cretaceous nannofossil data have been obtained from high latitudinal sites from offshore mid norway and from the barents sea no consistent nannofossil data are yet available for early cretaceous high latitudes which should more clearly reflect possible palaeoclimatic changes as recorded in fluctuations of diversity and abundance existing data from france italy romania poland and nw europe germany north sea england have been complemented by material from higher latitudes in order to record the arctic boreal nannofossil assemblages 400 samples from the norwegian shelf and the barents sea have been analysed sixty samples covering the berriasian barremian interval yielded calcareous nannofossils these are derived from cores between 63 and 73 n of present day latitudes the nannofossil assemblages recorded are generally of a low diversity and characterized by abundant watznaueria barnesae and crucibiscutum salebrosum whereas biscutum constans is less common c salebrosum rare or absent at low latitudes is extremely common in the norwegian samples it shows a bipolar distribution especially during valanginian hauterivian times in the early valanginian a distinctive latitudinal gradient in the abundance of c salebrosum impoverished in low latitudes and abundant in high latitudes possibly reflects latitudinal differences in temperature restricted palaeoceanographic settings caused by a sea level lowstand may have amplified these thermal gradients palaeoclimatically this implies the existence of climatic belts throughout parts of the early cretaceous early valanginian hauterivian resulting from considerable temperature gradients from north to south the palaeobiogeographic patterns discussed resulted in the formation of distinctive latitudinally bound nannofossil zones which to a certain extent are similar to those of modern oceans the palaeobiogeographic patterns described support the idea of an ice house phase for the early valanginian and disagree with the suggestion of a globally warm equable climate during that time