palaeomagnetism and magnetostiatigraphy of triassic strata in the sangre de cristo mountains and tucumcari basin new mexico usa summary we report palaeomagnetic data and a composite magnetic polarity sequence for middle and upper triassic rocks assigned to the anton chico member of the moenkopi formation and chinle group respectively exposed along the eastern flank of the sangre de cristo mountains and in the tucumcari basin of eastern and northeastern new mexico thermal demagnetization isolates a well defined dual polarity characteristic magnetization carried in most cases by haematite and interpreted as an early acquired chemical remanent magnetization crm characteristic magnetizations from 74 palaeomagnetic sites one site one bed are used to define a magnetic polarity sequence which we correlate with previously published triassic data obtained from both marine and non marine rocks preliminary correlation suggests that the resolution of magnetostratigraphic data derived from continental strata is not necessarily of lesser quality than that from marine rocks on the basis of the magnetostratigraphic data a profound unconformity is believed to separate lower middle norian and upper norian rhaetian strata of the chinle group palaeomagnetic poles derived from selected sites in steeply dipping 85 strata for the middle triassic anisian 240 ma 50 n 121 e n 8 late carman early norian 225 ma 53 n 104 e n 16 and late norian rhaetian 208 ma 59 n 77 e n 8 are in relatively good agreement with previously published data for the moenkopi formation and chinle group and related strata in southwest north america none the less comparison with palaeomagnetic poles obtained from gently dipping or flat lying triassic strata from this study anisian 46 n 112 e n 13 late carnian 54 n 87 e n 12 and previously published triassic poles in southwest north america suggest that a modest apparent rotation not greater than about 5 affects declinations from steeply dipping rocks the distribution of palaeomagnetic poles indicates 25 angular distance of apparent polar wander between about 240 and 208 ma

carnian norian biomagnetostratigraphy at silicka brezova slovakia correlation to other tethyan sections and to the newark basin correlations of upper triassic magnetic stratigraphies from tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy and discontinuous sedimentation particularly in the hallstatt limestones of turkey and austria the magnetic stratigraphy and conodont biostratigraphy from the upper carnian to upper norian limestones exposed at silickabrezova slovakia can be correlated to other tethyan sections and to the continental succession in the newark basin the resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations and result in a revised correlation to north american terrestrial vertebrate and palynological zones the correlations imply that the norian rhaetian boundary lies within newark polarity zone e17r at v207 ma the carnian norian boundary lies close to the base of newark polarity zone e7r at v226 ma this implies durations for the norian and rhaetian stages of 19 myr and 7 myr respectively 2002 elsevier science b v all rights reserved

integrated upper carnian to lower norian biochronology and implications for the upper triassic magnetic polarity time scale abstract we summarize the ammonoid conodont and halobiid biochronology of the upper carnian to lower norian based on a discussion of data in the alps sicily balkans turkey himalayas and timor with this integrated biostratigraphic scale the pizzo mondello section sicily can be recalibrated and the carnian norian boundary more precisely located there as a result the magnetostratigraphy of this section is now in good agreement with previous results from turkey although the latter series are more condensed cross correlation of available magnetostratigraphic data from marine tethyan sections allow us to construct a composite upper carnian to upper norian geomagnetic polarity time scale gpts this gpts leads us to question previously proposed magnetobiostratigraphic and chronostratigraphic correlations within the upper triassic newark non marine sedimentary sequence

seawater ph pco2 and co2 3 variations in the caribbean sea over the last 130 kyr a boron isotope and b ca study of planktic foraminifera abstract here a new analytical methodology is described for measuring the isotopic composition of boron in foraminifera using multicollector inductively coupled plasma mass spectrometry mc icpms this new approach is fast 10 samples analysed in duplicate per analytical session and accurate to better than 0 25 at 95 confidence with acceptable sample size requirements 1 3 mg of carbonate a core top calibration of several common planktic and two benthic species from geographically widespread localities shows a very close agreement between the isotopic composition measured by mc icpms and the isotopic composition of b oh 4 in seawater as predicted using the recently measured isotopic equilibrium factor of 1 0272 at the depth of habitat a down core and core top investigation of boron concentration b ca ratio shows that the partition coefficient is influenced by co2 3 complicating the application of this proxy nevertheless it is demonstrated that these two proxies can be used to fully constrain the carbonate system of surface water in the caribbean sea odp site 999a over the last 130 kyr this reconstruction shows that during much of the holocene and the last interglacial period surface water at site 999a was in equilibrium with the atmosphere with respect to co2 during the intervening colder periods although the surface water pco2 was lower than the holocene it was a minor to significant source of co2 to the atmosphere possibly due to either an expansion of the eastern equatorial atlantic upwelling zone or a more local expansion of coastal upwelling in the southern caribbean such reorganisation of the oceanic carbonate system in favour of a larger source of co2 to the atmosphere from the equatorial ocean may require mechanisms responsible for lowering atmospheric co2 during glacial periods to be more efficient than previously supposed

a study of cleaning procedures used for foraminiferal mg ca paleothermometry the various cleaning steps required for preparation of foraminiferal samples for mg ca and sr ca analysis are evaluated for their relative importance and effects on measured elemental ratios it is shown that the removal of silicate contamination is the most important step for the measurement of mg ca ratios in an example bulk sample mg ca decreases from 10 5 to 2 5 mmol mol 1 during clay removal oxidation of organic material causes a lowering of sample mg ca in the order of 10 or approximately 1 c when converted to temperature use of dilute acid leaching to remove adsorbed contaminants causes partial dissolution of the sample carbonate and a corresponding decrease in mg ca reductive treatment also causes dissolution of the sample and a decrease in the mg ca ratio of up to 10 15 sample preparation for sr ca analysis does not require the same degree of rigor as is necessary for mg ca work the within run reproducibility of the method described here for g ruber in a core top sample from the arabian sea was 1 8 mean sample ratio was 4 72 mmol mol 1 when converted to temperature this becomes 28 0 2 c the equivalent result for sr ca was 0 5 mean ratio 1 44 mmol mol 1

tracing the strength of the southwest monsoon using boron isotopes in the eastern arabian sea here we present the first boron isotope based pco2sw pco2 of seawater reconstruction from the eastern arabian sea using the planktic foraminifera species globigerinoides ruber our results from sediment core aas9 21 show that pco2sw varied between 160 and 300 atm during the last 23 kyr the pco2 the sea air pco2 difference is relatively small during the last glacial maximum and becomes more negative toward the holocene with the exception of a significant excess during the last deglaciation centered on the bolling allerod throughout the record pco2 is predominantly negative probably as a result of enhanced biological productivity and higher nutrient and carbon utilization during the southwest monsoon a reduction in pco2 during the last glacial maximum is therefore consistent with a reduction in the strength of this monsoon system

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

phenomenology and modeling of explosion generated shear energy for the source physics experiments abstract we present a mechanism for shear wave generation from buried explosions as part of the source physics experiment spe series the spe series includes sensitized heavy ammonium nitrate fuel oil sources of various sizes detonated in a borehole in the jointed climax stock granite the cylinder shaped shots were grouted in the borehole to couple the energy to the rock a high fidelity site model with explicit inclusion of the cylindrical explosive the grout filled borehole and site joint sets was included in a numerical simulation that mimics the near field velocity environment measured by an array of in ground accelerometers this approach was accommodated through a coupled euler lagrange code that allows simultaneous solving of a euler domain to model the high deformation source region and a lagrange domain that includes the complex geology with full contact specific laboratory measured geomechanical properties for the rock and the joint sets were included in the model the simulations compare favorably to the data and provide a possible physical mechanism for unexpected shear motion through the release of stored shear strain on the joints this research will advance our understanding of explosion generated shear wave energy from low yield nuclear tests

aspects of pre tertiary paleomagnetism of spitsbergen and their tectonic implications abstract paleomagnetic investigations were carried out on cretaceous dolente dykes and sills permian limestones permo carboniferous limestones and lower devonian sandstones from different parts of spitsbergen detailed rock magnetic studies showed that the main magnetic minerals in dolentes limestones and sandstones are titanomagnetite magnetite and hematite respectively the rocks were demagnetized thermally and in alternating fields vector analysis of the demagnetization path separates the different components of nrm and establishes a characteristic remanence the paleomagnetic poles for cretaceous dolentes permo carboniferous limestones and lower devonian sandstones from spitsbergen are respectively 65 n 222 e 34 n 140 e and 12 n 135 e when compared with the european and north american apparent polar wander paths all spitsbergen poles he at a distance from both apwps suggesting that spitsbergen has been rotated and even translated in relation to europe during the opening of the labrador sea and greenland norwegian sea

organic matter apatite pyrite relationships in the botneheia formation middle triassic of eastern svalbard relevance to the formation of petroleum source rocks in the nw barents sea shelf abstract the middle triassic botneheia formation of eastern svalbard edgeoya and barentsoya comprises an organic carbon rich fine grained clastic succession 100 m thick that makes the best petroleum source rock horizon in the nw barents sea shelf the succession records a transgressive regressive interplay between the prodelta depositional system sourced in the southern barents sea shelf black shale facies of the lower and middle parts of the muen member and the open shelf phosphogenic system related to upwelling and nutrient supply from the panthalassic ocean phosphogenic black shale facies of the upper part of the muen member and the blanknuten member the relationships between organic matter authigenic apatite and pyrite in these facies allow to characterize the relative roles of redox conditions and oceanic productivity in the organic carbon preservation the accumulation of terrestrial and autochthonous marine organic matter in the black shale facies occurred under dominating oxic conditions and increasing upward productivity related to early transgressive phase and retrogradation of the prodelta system the phosphogenic black shale facies deposited in an oxygen minimum zone omz of the open shelf environment during the late transgressive to regressive phases under conditions of high biological productivity suppressed sedimentation rates and changing bottom redox the phosphatic black shales occurring in the lower and upper parts of the phosphogenic succession reveal depositional conditions indicative of the shallower part of omz including high input of autochthonous organic matter into sediment oxic to dysoxic episodically suboxic and or anoxic conditions intense phosphogenesis and recurrent reworking of the seabed the massive phosphatic mudstone occurring in the middle of the phosphogenic succession reflects the development of euxinia in the deeper part of omz during high stand of the sea high input of autochthonous organic matter in this environment was coupled with mineral starvation and intermittent phosphogenesis in mature sections in eastern svalbard the petroleum potential of the botneheia formation rises from moderate to good in the black shale facies and from good to very good in the phosphogenic black shale facies attaining maximum in the massive phosphatic mudstone

oceanic ph control on the boron isotopic composition of foraminifera evidence from culture experiments culture experiments were carried out with the species orbulina universa at four different ph values 7 70 0 05 8 15 0 05 8 60 0 05 and 9 00 0 10 in order to establish the ph dependence of boron isotope fractionation between seawater and foraminifera a clear relationship between the boron isotopic composition of the foraminifera and the ph of the seawater culture solutions was found showing heavier boron isotopic composition at higher ph this finding supports the viability of boron isotopes as a paleo ph tool it is important to note that orbulina universa cultured in natural seawater as well as those obtained from coretop samples have a significantly lighter boron isotopic ratio than globigerinoides sacculifer from coretop samples suggesting that at least for this species a vital effect is active

planktonic foraminifera of the northern indian ocean distribution and preservation in surface sediments in the northern indian ocean planktonic foraminiferal tests accumulate in a wide variety of surface water environments and depositional settings this variability enables us to isolate the effects that surface water ecology and differential dissolution have on the distribution of planktonic foraminifera from 251 geographically widespread surface sediment samples foraminiferal abundance varies from 0 to 104 whole foraminifera in the greater than 150 m fraction per gram dry sediment values 10 characterize the three deep basins of the equatorial indian ocean and the western bay of bengal foraminiferal tests are most abundant on carbonate covered ninety east and carlsberg ridges absolute abundance patterns are mainly controlled by non ecological processes variations in dissolution resistant species rsp with water depth reveal that the foraminiferal lysocline fl varies regionally the fl is deepest 3 800 m in the equatorial region rises abruptly to 3 300 m in the arabian sea and varies from 2 600 m to near 2 000 m moving northward in the bay of bengal deep samples with anomalously low rsp 30 suggest redeposition systematic geographic and depth related variation is observed for the 17 most abundant foraminiferal species dissolution resistant species g menardii g tumida g dutertrei p obliquiloculata generally exhibit a rapid and continuous increase in relative abundance at and below the fl susceptible species g ruber g bulloides g glutinata for example exhibit a rapid and continuous decrease in relative abundance at and below the fl moderately susceptible species g conglobatus g aequilateralis g conglomerata for example rapidly increase in abundance at the fl and systematically decrease with depth below the fl principal components analysis pca of faunal data from minimally dissolved 30 rsp samples reveals important ecologically related species intercorrelations the major biogeographic gradient is the negative covarying relationship between ag bulloides g glutinata species pair and a grouping ofg sacculifer g conglobatus g aequilateralis andg ruber pca of all samples demonstrates how differential dissolution alters this and other species relationships species groupings that incorporateg ruber g menardii andg dutertrei are particularly affected by dissolution comparison of average faunal data from minimally dissolved samples in the northern indian ocean with similar samples from other tropical regions suggests varying environmental factors produce distinct faunas within the tropical ocean for example g bulloides g falconensis andg hexagona are significantly more abundant in northern indian ocean surface sediments while such species asg ruber g sacculifer g dutertrei andp obliquiloculata dominate in other tropical regions

biota and palaeoenvironment of a high middle latitude late triassic peat forming ecosystem from hopen svalbard archipelago a siliceous permineralized peat block recovered from hopen in the svalbard archipelago hosts a low diversity late triassic flora dominated by autochthonous roots and stems of bennettitaleans and lycophytes and parautochthonous leaves sporangia spores and pollen from a small range of pteridophytes and gymnosperms some parenchymatous bennettitalean root cells show interactions with chytrid fungi and bacteria the remains of other fungi and fungi like organisms are dispersed within the peat s detrital matrix cavities excavated through some roots and compacted detritus contain abundant coprolites probably derived from sapro xylophagous oribatid mites although no body fossils have yet been identified sparse larger coprolites containing leaf fragments attest to the presence of invertebrate folivores in the ancient ecosystem the low diversity flora relatively few trophic levels and simple nutritional web together with sedimentological aspects of the host formation and the peat structure collectively favour accumulation of the organic mass as a fibric root dominated peat within a temperate high middle latitude well aerated mire

paleomagnetism of permian through early triassic sequences in central spitsbergen implications for paleogeography upper carboniferous through lower triassic sediments from spitsbergen have yielded paleomagnetic results with those for the late gzhelian early permian being the more reliable the corresponding pole 38 n 171 e is fully concordant with the early permian segment of the apparent polar wander path for baltica it does not support hypotheses about post carboniferous mobilism of spitsbergen with respect to stable europe neither mesozoic nor later rifting processes changed the position of spitsbergen considerably in relation to the stable europe

drilling induced remanence in carbonate rocks occurrence stability and grain size dependence summary a strong grouping of the directions of natural remanent magnetization in a collection of ordovician limestones and dolomites prior to correction for the in situ orientation of the samples led us to suspect the presence of a substantial spurious magnetization acquired during sample collection and preparation a close correspondence between the directions of the remanence vectors and the direction of the ambient magnetic field during sawing and drilling of the samples suggested that the remanence was dominated by a component acquired during cutting of the samples ten specimens of the camp nelson limestone and shakopee dolomite were demagnetized to 100 mt given an anhysteretic remanence along their axes and then sawed again a substantial magnetization parallel to the ambient field during cutting was acquired by all of the specimens and the resultant directions deviated by 7 70 from the direction of the anhysteretic magnetization stepwise alternating field and thermal cleaning to 60 mt and 400 c respectively failed to remove preferentially the cutting induced magnetic contamination since the fraction of magnetite grains cut during drilling and sawing must be a linear function of grain size modified lowrie fuller tests were carried out and the results are interpreted to indicate the presence of a multidomain magnetite fraction in the shakopee dolomite camp nelson limestone and oregon dolomite ratios of initial to anhysteretic susceptibility dxarm correlate well with the angular deviation of magnetic directions produced by sawing this indicates that acquisition of drilling induced remanence is a function of magnetite grain size compatible with the notion that the drillinginduced component resides in large magnetite grains which have been cut

origin of the magnetization of permo carboniferous sediments of spitsbergen svalbard archipelago rock magnetic investigations of permo carboniferous carbonate sediments from two areas on spitsbergen are described conducted to identify the carriers of the nrm in these rocks since microscopic and magnetic separation techniques could not profitably be applied the nature of magnetic minerals was investigated by thermal demagnetization of the nrm and decay of saturation isothermal remanence irs during heating to 600 c as well as by the distribution of the median destructive fields of the nrm and observation of magnetic susceptibility after subsequent heatings the results show that the nrm of these limestones resides mainly in magnetite but creation of magnetic pyrrhotite and of fresh magnetite is observed during heating to 600 c presence of sulphides indicates that magnetite is an oxidation product of pyrite or of non magnetic pyrrhotite examination of rock magnetic properties of limestones leads to the conclusion that most of the magnetite in the rocks of the bellsund area is of detrital origin whereas the rocks at festningen contain magnetite derived from pyrite probably during an early stage of the diagenetic process

reconstructing sea surface temperature and salinity using δ 18 o and alkenone records the oxygen isotope 18o composition of foraminiferal tests from deep sea sediments is widely used as a palaeoclimate proxy but it includes contributions from sea surface temperature global ice volume and local salinity which are difficult to separate recently a new technique for deriving palaeotemperatures has been developed which is based on the abundance ratios of unsaturated alkenones in phytoplankton algae1 2 here we use a combination of oxygen isotope and alkenone records in a deep sea core from the juncture of the arabian sea and the bay of bengal to extract the salinity signal from the former record variations in salinity are related to the balance between evaporation and precipitation3 and are thus a sensitive indicator of climate change our 170 kyr salinity record enables us to reconstruct changes in the indian monsoon over this period considerably extending earlier studies which reached back to 18 kyr ago 4 8 like these previous studies we find that large variations in the monsoon occurred during the transition from the last glacial period to the present interglacial but our results also provide a view of the monsoon throughout the last glacial and demonstrate the potential of this approach for reconstructing palaeosalinity

core top calibration of b ca in pacific ocean neogloboquadrina incompta and globigerina bulloides as a surface water carbonate system proxy abstract practical methods for reconstructing past ocean carbonate chemistry are needed to study past periods of ocean acidification and improve understanding of the marine carbonate system s role in the global climate cycles planktic foraminiferal b ca may fill this role but requires better understanding and improved proxy calibrations we used pacific ocean core top sediments to generate new calibrations of the b ca proxy for past carbonate system parameters in two upwelling subpolar species of asymbiotic planktic foraminifera globigerina bulloides and neogloboquadrina incompta both species show significant positive correlation of b ca with calcite saturation calcite and carbonate ion concentration co 3 2 across a broad range of environmental conditions this suggests a calcification rate control on b ca incorporation as calcite regulates calcification rate in agreement with recent inorganic calcite studies this is also consistent with a surface entrapment model of trace element incorporation into caco3 in neither species is b ca significantly correlated with ph suggesting that ph does not directly regulate boron incorporation and that calculation of ph directly from foraminiferal b ca is not suitable correlations between b ca and b oh 4 b oh 4 hco3 and b oh 4 dic are weaker than with calcite boron partition coefficients k d b ca solid b oh 4 hco 3 seawater show little or no correlation with co32 or temperature and vary widely providing no support for application of kd to calculate carbonate system parameters from b ca we also discuss potential effects of depth related dissolution temperature and salinity on b ca these empirical calibrations linking foraminiferal calcite b ca with calcite provide a strong tool for reconstructing the past ocean carbonate system and improve our understanding of the proxy s geochemical basis

the universal ratio of boron to chlorinity for the north pacific and north atlantic oceans abstract we report seawater boron concentration mg kg 1 and chlorinity values measured in seawater samples n 139 collected at various depths in the north pacific and north atlantic oceans and the east japan sea located in the western temperate north pacific our results indicate that variations in seawater boron concentration are strongly coupled to variations in chlorinity and salinity yielding a mean boron to chlorinity ratio of 0 2414 0 0009 mg kg 1 1 boron to salinity ratio 0 1336 0 0005 mg kg 1 1 this ratio was surprisingly universal throughout the water column in the three marine basins and across widely different ocean surface regimes but differs from the generally accepted ratio of 0 232 0 005 mg kg 1 1 determined by uppstrom 1974 which was based on only 20 measurements at four sites in the tropical pacific ocean in converting total alkalinity to carbonate alkalinity and vice versa for thermodynamic calculations the difference between these two ratios leads to a difference of 5 mol kg 1 in estimates for ocean surface waters where the contribution of borate to total alkalinity is typically greatest we suggest the use of the new boron to chlorinity ratio for predicting seawater boron concentrations using chlorinity or salinity data

evaluating the utility of b ca ratios in planktic foraminifera as a proxy for the carbonate system a case study of globigerinoides ruber b ca ratios in foraminifera have attracted considerable scientific attention as a proxy for past ocean carbonate system however the carbonate system controls on b ca ratios are not straightforward with inline image inline image in situ inline image at saturation correlating best with b ca ratios in benthic foraminifera rather than ph inline image or inline image as a simple model of boron speciation in seawater and incorporation into caco3 would predict furthermore culture experiments have shown that in planktic foraminifera properties such as salinity and b sw can have profound effects on b ca ratios beyond those predicted by simple partition coefficients here we investigate the controls on b ca ratios in g ruber via a combination of culture experiments and core top measurements and add to a growing body of evidence that suggests b ca ratios in symbiont bearing foraminiferal carbonate are not a straightforward proxy for past seawater carbonate system conditions we find that while b ca ratios in culture experiments covary with ph in open ocean sediments this relationship is not seen in fact our b ca data correlate best with inline image a previously undocumented association and in most regions salinity these findings might suggest a precipitation rate or crystallographic control on boron incorporation into foraminiferal calcite regardless our results underscore the need for caution when attempting to interpret b ca records in terms of the ocean carbonate system at the very least in the case of mixed layer planktic foraminifera

seasonal sea surface temperature contrast between the holocene and last glacial period in the western arabian sea ocean drilling project site 723a modulated by monsoon upwelling 1 annual summer and winter sea surface temperatures ssts in the western arabian sea were reconstructed through the last 22 kyr using artificial neural networks anns based on quantitative analyses of planktic foraminifera down core sst estimates reveal that annual summer and winter ssts were 2 1 2 and 2 6 c cooler respectively during the last glacial period than in the holocene a 2 5 c sst increase during termination 1a hereinafter referred as glacial to holocene transition in the western arabian sea the study reveals a strong seasonal sst contrast between winter and summer from 18 to 14 calendar kyr owing to the combined effect of weak upwelling and strong cold northeasterly winds minor or no seasonal sst changes were noticed within the holocene period which is attributed to the intense upwelling during the summer monsoon this causes a lowering of sst to values similar to those of the winter season in analogy with the present day a 3 c rise in winter ssts during the glacial to holocene transition coincides with a strengthening of the monsoon suggesting a link between winter sst and monsoon initiation from the beginning of the holocene strikingly annual summer and winter ssts show a cooling trend from 8 ka to the present day implying tropical cooling in the late holocene

linear and planar structure in ordered multivariate data as applied to progressive demagnetization of palaeomagnetic remanence summary consider a sequence of say 10 to 20 vector observations in threedimensional space it is suspected that a few subsets of consecutive observations are made up of collinear points the purpose of this paper is to construct a statistically based algorithm to find such linear segments and to assess their accuracy a similar assessment is made for coplanar sets of points this algorithm is applied here to palaeomagnetic data and is claimed to be superior to previous methods of palaeomagnetic analysis in terms of completeness and balance of analysis treatment of measurement errors and other sources of scatter criteria for identification of linear and planar sets of points and statistical rigour stability spectra with statistically based confidence limits are obtained as a by product 1 palaeomagnetic analysis background to the geometrical problem the natural remanent magnetization nrm in rocks is known in general to have originated in one or more relatively short time intervals during their formation and subsequent history i e during rock forming or metamorphic events during which nrm is frozen in stabilized by falling temperature grain growth etc the nrm acquired during each such event is a single vector magnetization parallel to the then prevailing geomagnetic field and is called a component of nrm rocks which have suffered more than one event of this kind are therefore liable to carry multi component nrm in the laboratory these components can be identified by demagnetizing the rock step by step usually by thermal alternating field or chemical demagnetization which involves the analysis of the distribution of blocking rzmperature coercivity and chemical leaching respectively resistance to these treatments is called stability of remanence and the range of treatment over which a particular component is removed is called the stability range of the component the various discrete

glacial to holocene redistribution of carbonate ion in the deep sea we have reconstructed the glacial age distribution of carbonate ion concentration in the deep waters of the equatorial ocean on the basis of differences in weight between glacial and holocene foraminifera shells picked from a series of cores spanning a range of water depth on the western atlantic s ceara rise and the western pacific s ontong java plateau the results suggest that unlike today s ocean sizable vertical gradients in the carbonate ion concentration existed in the glacial age deep ocean in the equatorial pacific the concentration increased with depth and in the atlantic it decreased with depth in addition the contrast between the carbonate ion concentration in deep waters produced in the northern atlantic and deep water in the pacific appears to have been larger than in today s ocean

a 300 kyr record of upwelling off oman during the late quaternary evidence of the asian southwest monsoon in the northwest arabian sea upwelling occurs each summer driven by the strong sw monsoon winds upwelling results in high biological productivity and a distinctive assemblage of plankton species in the surface waters off oman that are preserved in the sediments along the oman continental margin creating a geologic record of monsoon driven upwelling sediments recovered from the oman continental margin during ocean drilling program leg 117 provide an opportunity to examine how upwelling has varied during the late quaternary spanning a longer interval than piston cores recovered prior to the odp cruise variations in foraminifer shell accumulation and in the relative abundance of globigerina bulloides indicate dominant cycles of variation at 1 100 kyr the dominant frequency of glacial interglacial variations and at 1 23 kyr the frequency of precessionally driven cycles in seasonal insolation the strongest monsoon winds indicated by increased upwelling occurred during interglacial times when perihelion was aligned with the summer solstice an orbital change that increased the insolation received during summer in the northern hemisphere during glacial times upwelling was reduced and although the precessional cycles were still present their amplitude was smaller at both frequencies the upwelling cycles are in phase with minimum ice volume evidence that glacial interglacial climate changes also include changes to the climate system that influence the low latitude monsoon we attribute the decrease in the monsoon winds observed during glacial times to changes in bare land albedo over asia and or to changes in the areal extent and seasonal cycle in asian snow cover that decrease the summer land sea temperature contrast other mechanisms may also be involved these new upwelling time series differ substantially from previous results however the previous work relied on cores located farther offshore where upwelling is less intense and other physical mechanisms become important our results support the observations derived from atmospheric general circulation models of the atmosphere that indicate that both glacial boundary conditions and the strength of summer insolation are important variables contributing to cycles in the monsoon winds during the late quaternary

the apparent polar wander path of the european plate in upper triassic lower jurassic times and the liassic intraplate fracturing of pangaea new palaeomagnetic constraints from nw france and sw germany summary in order to constrain the european plate motions during triassic lower jurassic times new palaeomagnetic data were acquired from various triassic liassic sediments of northeastern france and southwestern germany a carnian palaeopole 49 n 131 e k 193 a95 7 n 4 was obtained for keuper marls with consistent directions of normal and reversed polarities rhaetian sandstones also with both polarities and carnian dolomites with a magnetization of probable secondary origin provide a mean pole 51 n 112 e k 109 a95 6 n 6 more westerly than that given above the lower hettangian sampled in limestones of the xeuilley quarry near nancy shows a n r n polarity sequence with well defined anti parallel directions the mean hettangian pole is 55 n 100 e k 123 a95 11 n 3 induan sandstones from the northern vosges show two distinct overprints one consistent with the ladinian carnian magnetizations already observed in the same region the second consistent with the recalculated mean lower jurassic pole of europe five other sites with different rock types also exhibit late overprints with lower jurassic directions the mean pole calculated from these overprints is 74 n 124 e k 125 a95 6 n 6 the revised apparent polar wander path apwp presented here shows that for the mid permian to the earliest jurassic the palaeopoles of europe stayed around 50 latitude while the longitudes drifted from 185 e to 100 e the previously established upper triassic lower jurassic loop of the apwp is shifted westwards by about 25 the revised apwp involves the following plate motions after the late alleghanian tectonic phase which marked the end of the variscan orogeny central western europe rotated counterclockwise during about 70 myr up to the earliest jurassic the south north drift in latitude by 35 nearly 4000 km remained regular from 320 to 205 ma with a constant rate of 3 4cm yr 1 around 205 ma this motion ceased probably because of a collision somewhere in the north of eurasia then in the lower liassic the plate underwent a rapid counterclockwise rotation with a eulerian pole located in northeastern asia synchronous with fracturing in the atlantic and the neotethys areas it is proposed that the intraplate fracturing of pangaea was initiated by the rapid change of the megacontinent motion at the end of the trias

inclination flattening and the geocentric axial dipole hypothesis abstract william gilbert first articulated what has come to be known as the geocentric axial dipole hypothesis the gad hypothesis is the principle on which paleogeographic reconstructions rely to constrain paleolatitude for decades there have been calls for permanent non dipole contributions to the time averaged field recently these have demanded large contributions of the axial octupole which if valid would call into question the general utility of the gad hypothesis in the process of geological recording of the geomagnetic field earth filters distort the directions many processes for example sedimentary inclination flattening and random tilting can lead to a net shallowing of the observed direction therefore inclinations that are shallower than expected from gad can be explained by recording biases northward transport or non dipole geomagnetic fields using paleomagnetic data from the last 5 million years from well constrained lava flow data allows the construction of a statistical geomagnetic field model such a model can predict not only the average expected direction for a given latitude but also the shape of the distribution of directions produced by secular variation the elongation of predicted directions varies as a function of latitude from significantly elongate in the up down direction at the equator to circularly symmetric at the poles sedimentary inclination flattening also works in a predictable manner producing elongations that are stretched side to side and the degree of flattening depending on the inclination of the applied field and a flattening factor f the twin tools of the predicted elongation inclination relationship characteristic of the geomagnetic field for the past 5 million years and the distortion of the directions predicted from sedimentary inclination flattening allows us to find the flattening factor that yields corrected directions with an elongation and average inclination consistent with the statistical field model the method can be tested using sediments deposited in a known field application of the elongation inclination correction method to two magnetostratigraphic data sets from red beds in asia and pakistan brings the inclinations into agreement with those predicted from modern gps measurements and from global paleomagnetic data there appears to be no compelling reason at this time to abandon the geocentric dipole hypothesis which has provided such an excellent working model for so long

depositional history of the upper triassic kapp toscana group on svalbard norway inferred from palynofacies analysis and organic geochemistry abstract upper triassic sediments in the svalbard archipelago were deposited in several transgressive regressive cycles understanding their deposition and distribution is of vital importance because of their potential as hydrocarbon reservoir rocks in this study we integrate palynofacies with organic geochemistry in order to reconstruct the depositional environment of the upper botneheia fm up to the lower the knorringfjellet fm from two sections located in central spitsbergen for which distinctive palynofacies zones have been distinguished these are mainly terrestrially dominated but occasionally contain amorphous organic matter and marine palynomorphs rock eval pyrolysis reveals overall mature kerogen type iii iv samples our results indicate that at least partially restricted marine conditions prevailed during deposition of the botneheia fm the botneheia fm is overlain by a regressive cycle from the lower part of the tschermakfjellet fm up to the top of the de geerdalen fm with terrestrially dominated palynofacies assemblages the knorringfjellet fm contains increased marine palynofacies and marine dinoflagellate cysts which is in accordance with a transgression at the base of this unit this study integrates for the first time in the spitsbergen area quantitative palynofacies and sedimentary organic matter characterization and shows the generally accepted paleo environmental development for the svalbard archipelago

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

palynological correlation of carnian humid pulses throughout western tethys abstract the carnian pluvial event is an upper triassic swing toward increased rainfall best documented in the tethys tropical belt and mainly recognized on its effects on sedimentary systems as the demise of carbonate platforms and the enhanced siliciclastic supply in some portions of western tethys and particularly in the raibler schichten of the northern calcareous alps and in the dolomites the carnian pluvial event is recorded by four discrete siliciclastic pulses in the raibler schichten three siliciclastic intervals are documented and take the name of first second and third shale in order to correlate these pulses at the basinal scale the study of the palynological assemblages in a section of the raibler schichten near rubland austria and of the classical succession of the lunz nappe have been carried out more than eighty palynomorph species are recorded most of them correspond to typical carnian morphospecies of the carnian pluvial event in europe on the base of their stratigraphic distribution three different palynomorph assemblages are described aulisporites astigmosus assemblage lagenella martinii assemblage and granuloperculatipollis rudis assemblage a fourth older assemblage is also informally defined a palynostratigraphic correlation between the nca the germanic basin and the dolomites has been obtained the four siliciclastic pulses recognized in the raibler schichten and lunz are also found in the dolomites and yield the same palynological associations the base of the schilfsandstein that record the carnian pluvial event in the germanic basin is correlated to the second or third siliciclastic pulse first or second shale of the raibler schichten siliciclastic pulses are thus correlated throughout western tethys and can thus be interpreted as short lived humid climate wiggles within the carnian pluvial event a quantitative analysis of the carnian successions of the nca highlights a shift toward hygrophytic elements in the uppermost julian and an abrupt return to xerophytic associations in the lower tuvalian the palynological hygrophytic associations that characterize the aulisporites astigmosus and lagenella martinii assemblages are present in many other parts of europe and middle east suggesting that the carnian pluvial event determined a humid climate perturbation in a wide area of the northern hemisphere spanning from tropical to high latitudes

climate variations in the boreal triassic inferred from palynological records from the barents sea this paper presents palynological evidence from the late early triassic late smithian to the late triassic rhaetian of the barents sea area a continuous palynological succession from an exploration well 7228 7 1a in the nordkapp basin sw barents sea and palynological data from a series of shallow cores drilled at the svalis dome central barents sea representing selected triassic intervals these fully marine sediments are independently dated by marine faunas both records show significant shifts in the distribution of the main floral elements changing ratios of spore pollen taxa grouped as hygrophytes versus xerophytes and spores versus pollen reveal major changes of the floras within the studied interval one distinct turnover coincides with the smithian spathian boundary where lycopsid and pteridophyte spores dominated assemblages change to pollen pteridosperms and conifers dominated assemblages lower middle triassic assemblages are again dominated by lycopsid spores while the assemblages from the upper part of the middle triassic and the lower part of the late triassic are characterised by dominance of coniferous pollen and show the decline of pteridosperms in the latest triassic fern spores are abundant and diverse in contrast to the middle triassic the pollen assemblages are characterized by cycadophytes and araucariacites these distribution patterns are interpreted to reflect climatic changes the presented results from norwegian boreal areas confirm the significant differences between quantitative distribution of specific taxa as well as diversity of major groups in plant assemblages from low and mid latitudes the present survey opens new perspectives for more detailed comparisons and climatic interpretations of floras from the triassic period a time during which mesozoic vegetation established the major changes in the dominance of specific floral elements especially the diversification and spreading of the conifers can probably be related to climatic changes

biomagnetostratigraphy of the vikinghogda formation svalbard arctic norway and the geomagnetic polarity timescale for the lower triassic a bio magnetostratigraphy for the lower triassic is constructed using the ammonoid biostratigraphy from arctic boreal successions combined thermal and alternating field demagnetisation determines the triassic magnetic field polarity in 86 of specimens with 36 showing linear trajectory line fits and the remainder great circle trends towards the characteristic magnetisation mean pole directions for the deltadalen 50 159 dp dm 3 9 5 1 lusitaniadalen 56 163 dp dm 4 4 5 4 and vendomdalen 57 143 dp dm 4 4 5 4 members fall close to the european lower triassic apparent polar wander path mean directions for two of these member means pass the reversal test the remanence is predominantly carried by magnetite the polarity stratigraphy when integrated with the ammonoid and meager conodont data is similar to that determined from successions in the sverdrup basin canada the permian triassic boundary post dates a pronounced palynofloral turnover and pre dates a short duration reverse magnetozone lt1n 1r in the correlated shangsi section in s china lt1n 1r occurs after the fad of h parvus but in the arctic is within the otoceras boreale zone the late griesbachian to early smithian is mostly reverse polarity with three normal polarity intervals overlain by mid and late smithian normal polarity the spathian contains four reverse polarity intervals the oldest one within the early spathian with the remainder in the late spathian transition into the anisian is within the uppermost reverse magnetozone a feature documented in other sections of this age the polarity pattern is correlated to other marine sections indicating the robustness of the bio magnetostratigraphic composite and its utility in calibrating lower triassic time

palaeomagnetic argument for a stationary spitsbergen relative to the british isles western europe since late devonian and its bearing on north atlantic reconstruction abstract palaeomagnetic results from the devonian of central spitsbergen mimer valley formation billefjorden suggest an average palaeofield direction for the late devonian early carboniferous with declination 227 5 inclination 30 6 corresponding to a relative pole position at lat 24 s long 325 e this magnetization which is post tectonic is regarded as acquired chemically linked with the upper devonian svalbardian phase of deformation this result together with some recent data from central spitsbergen defines a devonian polar wander segment that accords extremely well with corresponding british data we interpret this in terms of no major displacement of central spitsbergen as compared with western europe since devonian time svalbard and the barents sea region have probably formed a fairly stable platform since the early devonian on the balance of available geological and palaeomagnetic evidence from spitsbergen the british isles and newfoundland the north atlantic region does not appear to have been subjected to strike slip motions in the order of thousands of kilometers in or since the late devonian

integrated stratigraphy and palaeoclimate history of the carnian pluvial event in the boreal realm new data from the upper triassic kapp toscana group in central spitsbergen norway the late triassic climate is characterized by arid conditions interrupted by a humid phase known as the carnian pluvial event cpe this wet phase is well documented in the tethyan realm but evidence from the boreal realm is scarce here we present evidence from quantitative palynology for the cpe from the kapp toscana group on central spitsbergen integrated with organic carbon isotope data linked to the geomagnetic polarity time scale our data reveal an early to mid julian 1 age for the tschermakfjellet formation the transition to the julian 2 is located in the de geerdalen formation and the isfjorden member is confirmed as mostly tuvalian 3 in age the aulisporites astigmosus pollen assemblage zone that marks the base of the cpe in the tethys realm at the base of the julian 2 is assigned to the julian 1 in the boreal region palaeoclimate proxy data inferred from principal component analysis indicate wetter conditions from the julian 2 onwards which is in agreement with the establishment of local swamp vegetation on top of a delta plain the palaeotemperature curve indicates a period of cooler climate during the early julian 1 followed by warming during the late julian 1 supplementary materials a list of all identified morphotaxa of pollen spores and aquatic palynomorphs is available at http www geolsoc org uk sup18879

calibration of the boron isotope proxy in the planktonic foraminifera globigerinoides ruber for use in palaeo co2 reconstruction abstract the boron isotope ph proxy applied to mixed layer planktic foraminifera has great potential for estimating past co2 levels which in turn is crucial to advance our understanding of how this greenhouse gas influences earth s climate previous culture experiments have shown that although the boron isotopic compositions of various planktic foraminifera are ph dependent they do not agree with the aqueous geochemical basis of the proxy here we outline the results of culture experiments on globigerinoides ruber white across a range of ph 7 5 8 2 and analysed via multicollector inductively coupled plasma mass spectrometry mc icpms and compare these data to core top and sediment trap samples to derive a robust new species specific boron isotope ph calibration consistent with earlier culture studies we show a reduced ph dependency of the boron isotopic composition of symbiont bearing planktonic foraminifera compared to borate ion in seawater we also present evidence for a size fraction effect in the 11b of g ruber finally we reconstruct atmospheric co2 concentrations over the last deglacial using our new calibration at two equatorial sites odp site 999a and site geob1523 1 these data provide further grounding for the application of the boron isotope ph proxy in reconstructions of past atmospheric co2 levels

a core top assessment of proxies for the ocean carbonate system in surface dwelling foraminifers we have assessed the reliability of several foraminifer hosted proxies of the ocean carbonate system 11b b ca and u ca using holocene samples from the atlantic and pacific oceans we examined chemical variability over a range of test sizes for two surface dwelling foraminifers globigerinoides sacculifer and globigerinoides ruber measurements of 11b in g ruber show no significant relationship with test size in either atlantic or pacific sites and appear to provide a robust proxy of surface seawater ph likewise there is no significant variability in the 11b of our atlantic core top g sacculifer but we find that 11b increases with increasing test size for g sacculifer in the pacific these systematic differences in 11b are inferred to be a consequence of isotopically light gametogenic calcite in g sacculifer and its preferential preservation during postdepositional dissolution the trace element ratio proxies of ocean carbonate equilibria u ca and b ca show systematic increases in both g ruber and g sacculifer with increasing test size possibly as a result of changing growth rates this behavior complicates their use in paleoceanographic reconstructions in keeping with several previous studies we find that mg ca ratios increase with increasing size fraction in our well preserved atlantic g sacculifer but not in g ruber in contrast to previous interpretations we suggest that these observations reflect a proportionally larger influence of compositionally distinct gametogenic calcite in small individuals compared to larger ones as with 11b this influences g sacculifer but not g ruber which has negligible gametogenic calcite

a 20 million year record of planktic foraminiferal b ca ratios systematics and uncertainties in pco2 reconstructions we use new and published data representing a 20 million long record to discuss the systematics of interpreting planktic foraminiferal b ca ratios b ca based reconstructions of seawater carbonate chemistry and atmospheric pco 2 assume that the incorporation of boron into foraminiferal tests can be empirically described by an apparent partition coefficient k d b ca caco 3 b oh 4 hco 3 seawater hemming and hanson 1992 it has also been proposed that there is a species specific relationship between k d and temperature yu et al 2007 as we discuss although these relationships may be robust there remain significant uncertainties over the controls on boron incorporation into foraminifera it is difficult to be certain that the empirically defined correlation between temperature and k d is not simply a result of covariance of temperature and other hydrographic variables in the ocean including carbonate system parameters there is also some evidence that k d may be affected by solution hco 3 co 2 3 ratios i e ph or by co 2 3 in addition the theoretical basis for the definition of kd and for a temperature control on k d is of debate we also discuss the sensitivity of pco 2 reconstructions to different k d temperature calibrations and seawater b ca if a k d temperature calibration is estimated using ice core pco 2 values between 0 and 200 ka b ca ratios can be used to reasonably approximate atmospheric pco 2 between 200 and 800 ka however the absolute values of pco 2 calculated are sensitive to the choice of k d temperature relationship for older time periods the absolute values of pco 2 are also dependent on the evolution of seawater b concentrations however we find that over the last 20 ma reconstructed changes in declining pco 2 across the mid pleistocene transition pliocene glacial intensification and the middle miocene climate transition are supported by the b ca record even if a constant coretop k d is used or different k d temperature calibrations and models of seawater b evolution are applied to the data the inferred influence of temperature on k d from coretop data therefore cannot itself explain the structure of a published pco 2 reconstruction tripati et al 2009 we conclude the raw b ca data supports a coupling between pco 2 and climate over the past 20 ma finally we explore possible implications of b ca based pco 2 estimates for the interpretation of other marine pco 2 proxies

a middle triassic paleomagnetic pole for the eurasian plate from heming france the paleomagnetic study of middle triassic limestones 91 cores 160 samples from a 40 m thick section in heming france yields a paleomagnetic pole for stable europe at lat 53 5 n lon 140 8 e dp 2 3 dm 3 9 this pole fills an important gap of the apparent polar wander path apwp of the eurasian plate the comparison of this pole with available data shows a standstill of the eurasian plate from the late paleozoic to the middle triassic followed by a rapid drift until the lower jurassic the beginning of the rapid drift is contemporaneous with the initiation of main rifting processes in the tethyan oceans

magnetostratigraphy and biostratigraphy of the carnian norian boundary interval from the pizzo mondello section sicani mountains sicily the 146 5 m thick upper triassic limestone section at pizzo mondello in the sicani mountains of western sicily is characterized by high quality of exposure accessibility and stratigraphic continuity magnetostratigraphic results delineate 12 normal and reverse polarity magnetozones labelled successively from the base upwards as pm1n pm1r pm6n pm6r the carnian norian boundary based on conodont biostratigraphy falls somewhere in the pm3n to pm5n interval which corresponds to the e14n to e16n magnetozone interval in the newark reference sequence of polarity reversals comparison of magnetobiostratigraphic data from the newark basin pizzo mondello and other late triassic marine sections available from the literature suggests the existence of a reduction in sedimentation rate in the tethyan marine domain at around the carnian norian boundary although the newark and the expanded pizzo mondello sections correlate well with each other correlation with the condensed kavur tepe and scheiblkogel sections is unsatisfactory a re interpretation of the kavur tepe results suggests that the section is younger than its previous correlation with the newark section and that it was deposited in the northern instead of the southern hemisphere most of the condensed tethyan marine sections are seen to be highly discontinuous as evidenced by concantenated conodont total range zones q 2001 elsevier science b v all rights reserved

b ca in planktonic foraminifera as a proxy for surface seawater ph boron isotope systematics indicate that boron incorporation into foraminiferal caco3 is determined by the partition coefficient k d frac left rm b rm ca right rm caco3 left rm b left rm oh right 4 rm hco 3 right rm seawater and b oh 4 hco3 seawater providing in principle a method to estimate seawater ph and pco2 we have measured b ca ratios in globigerina bulloides and globorotalia inflata for a series of core tops from the north atlantic and the southern ocean and in globigerinoides ruber white from ocean drilling program odp site 668b on the sierra leone rise in the eastern equatorial atlantic b ca ratios in these species of planktonic foraminifera seem unaffected by dissolution on the seafloor k d shows a strong species specific dependence on calcification temperature which can be corrected for using the mg ca temperature proxy a preliminary study of g inflata from southern ocean sediment core chat 16k suggests that temperature corrected b ca was 30 higher during the last glacial correspondingly ph was 0 15 units higher and aqueous pco2 was 95 atm lower at this site at the last glacial maximum the covariation between reconstructed pco2 and the atmospheric pco2 from the vostok ice core demonstrates the feasibility of using b ca in planktonic foraminifera for reconstructing past variations in ph and pco2

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

multi proxy reconstruction of surface water pco2 in the northern arabian sea since 29ka we report here the results of a multi proxy study to reconstruct surface water pco2 concentrations in the northern arabian sea our results show that delta 11b and mg ca measurements of the planktonic foraminifer globigerinoides sacculifer yield consistent pco2 values with those reconstructed from the delta 13c of alkenones when used in conjunction with foraminifera delta 13c and cd ca values they reveal that this area of the oceans has been a constant source of co2 to the atmosphere during the interval 5 29 ka and that the intensity of this source was greatest between 11 and 17 ka when atmospheric co2 levels were rising rapidly we interpret our data as reflecting variation in the strength of the asian summer monsoon asm thus indicating that the strength of the asm varied in phase with summer insolation over the tibetan plateau between 5 and 29 ka in contrast to a previous study clemens and prell 2003 we observe no significant lag between the rise in insolation and the response of the asm rather our data support a recent study by rohling et al 2009 that northern hemisphere climatic forcing factors play a greater role in controlling the intensity of the asm during times of intense monsoon activity and that the southern hemisphere forcing is more important during times of weak monsoons

boron calcium ratios in globigerinoides ruber from the arabian sea implications for controls on boron incorporation abstract culture and downcore studies have been used to argue that b ca ratios in planktic foraminifera are correlated with seawater ph and may record seawater borate bicarbonate ratios although other factors may also control b ca specimens of globigerinoides ruber from the ocean drilling program odp site 723a western arabian sea and core aas9 21 eastern arabian sea from the last 22 kyr were analysed for b ca 18 o and mg ca b ca was compared to reconstructed salinity and sea surface temperature sst records to gain insight into the processes controlling the incorporation of boron in both cores b ca and mg ca are positively correlated which suggests that temperature governs the incorporation of boron in g ruber to some extent higher b ca ratios at the site affected by upwelling odp 723a than in the non upwelling region core aas9 21 and a positive correlation between b ca and shell size in g ruber are observed we observe no significant correlation between b ca in g ruber and salinity ph or dissolved inorganic carbon dic in either the western or eastern arabian sea which throws considerable doubt on the utility of b ca ratios as a ph or pco 2 proxy

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

magneto biostratigraphy of the middle to upper triassic transition central spitsbergen arctic norway palaeomagnetic and biostratigraphic data were obtained for the latest ladinian and most of the carnian botneheia formation to basal kapp toscana group from two sections in central spitsbergen svalbard archipelago thermal and alternating field af demagnetization reveals a magnetization of both normal and reversed polarities the mean directions pass reversal and fold tests and are similar to other european late triassic palaeopoles one of the sections displays 15 of vertical axis clockwise tectonic rotation on a decollement in the underlying botneheia formation the magnetostratigraphy is dominated by normal polarity in the uppermost botneheia formation and into the tschermakfjellet and basal de geerdalen formations a substantial hiatus characterizes the ladinian carnian boundary in central spitsbergen so reverse magnetozones identified in tethyan sections near this boundary are absent magnetostratigraphic correlation along with palynostratigraphic constraints indicates that most of the de geerdalen formation is lower carnian the magnetostratigraphy and palynology indicates that the isfjorden member upper unit of the de geerdalen formation is probably mid carnian in age change in the lithological architecture in the isfjorden member compared with the underlying parts of the de geerdalen fm suggests a hiatus near the base of the member which may represent a mid carnian unconformity not previously recognized on spitsbergen

a paleomagnetic pole position of late jurassic early cretaceous dolerites from hinlopenstretet svalbard and its tectonic implications abstract paleomagnetic examination of late jurassic early cretaceous dolerites hinlopenstretet reveal a mean paleofield direction d 181 i 71 95 4 2 k 117 9 17 sites 96 samples which is argued to represent a deuteric magnetization formed at the time of cooling the resultant paleopole 66 n 200 e dp 7 dm 8 accords with paleomagnetic poles of similar age for north america after taking into account post jurassic continental separation the result from the present study is interpreted to represent a late jurassic early cretaceous paleopole for eurasia the similarity of the paleopoles from cratonic north america and eurasia in its pre drift configuration at about 145 ma makes it reasonable to conclude that relative displacement due to extension between eurasia and north america prior to the onset of sea floor spreading must have taken place after 145 ma and before the start of sea floor creation in the cretaceous

a high resolution record of late quaternary upwelling along the oman margin arabian sea based on planktonic foraminifera planktonic foraminiferal abundances fluxes test sizes and coiling properties are influenced in various ways by the southwest monsoon winds and associated upwelling in the western arabian sea to determine the short term changes in the southwest monsoon we have carried out a high resolution time series analysis of three upwelling indices total flux of planktonic foraminiferal tests and flux and relative abundance of the planktonic foraminiferal species globigerina bulloides from ocean drilling program odp site 723a oman margin western arabian sea spanning the last 19 kyr in addition we have determined the relationships between upwelling intensity and the relative abundance fluxes and shell concentrations of various planktonic foraminiferal species upwelling indices suggest that from 19 to 16 ka 22 to 18 2 cal kyr b p the sw monsoon was relatively strong compared to the period 15 8 to 12 5 ka 17 8 to 13 8 cal kyr b p the intensification of the sw monsoon took place at 12 ka 13 1 cal kyr b p and reached a peak between 10 and 5 ka 10 6 and 4 8 cal kyr b p the high resolution data further demonstrate that the sw monsoon has started weakening from 5 ka 4 8 cal kyr b p and the weakest phase was in place at 3 5 ka 3 cal kyr b p which coincides with evidence of an arid climate in western tibet fluxes and shell concentrations of many of the planktonic foraminiferal species increased between 12 and 5 ka in response to the intensification of the sw monsoon winds after the last glacial period globigerina bulloides shows a fivefold to tenfold increase in flux during this period of intense upwelling the other species whose fluxes are influenced by this upwelling change are in order from strongest to weakest response globigerinita glutinata globigerinoides ruber neogloboquadrina dutertrei globigerinella aequilateralis globigerina falconensis and globigerinoides sacculifer the relative abundances of g bulloides and g ruber increased during intense upwelling whereas the relative abundances of g glutinata n dutertrei g falconensis and g sacculifer did not increase during this period which might be due to differences in the productivity of various species in relation to upwelling change therefore the fluxes and shell concentrations provide better and more reliable information about the changes in the monsoon system in the arabian sea than relative abundance data

palaeomagnetic rock magnetic and mineralogical investigations of the lower triassic vardebukta formation from the southern part of the west spitsbergen fold and thrust beltk dudzisz and otherspalaeomagnetism of triassic rocks spitsbergen

tethyan magnetostratigraphy from pizzo mondello sicily and correlation to the late triassic newark astrochronological polarity time scale we present the magnetostratigraphy and stable isotope stratigraphy from an expanded 430 m thick upper triassic marine limestone section at pizzo mondello sicily and review published biostratigraphic information that can be used to defi ne the location of the conodont carnian norian and norianrhaetian boundaries in this section pizzo mondello offers good potential for magnetostratigraphic correlation of marine biostratigraphic and chemostratigraphic data with the continental newark astrochronological polarity time scale apts for development of an integrated late triassic time scale the relatively stable average values of 18 o centered on 0 are a strong indication that the cherty limestone at pizzo mondello suffered very little diagenetic overprinting the conodont carnian norian boundary is located 12 5 m above a positive shift of 13 c a statistical approach was applied to evaluate various pizzo mondello to newark magnetostratigraphic correlations two correlation options have the highest correlation coeffi cients in option 1 the base of pizzo mondello correlates with the middle part of the newark apts whereas in option 2 the base of pizzo mondello starts toward the early part of the newark apts we prefer option 2 in which the carnian norian boundary based on conodonts as well as its closely associated positive 13 c shift correspond to newark magnetozone e7 at ca 228 227 ma adopting newark astrochronology implying a long norian with a duration of 20 m y and a rhaetian of 6 m y duration these ages are in fact not inconsistent with the few high quality radiometric dates that are available for late triassic time scale calibration based on its good exposure accessibility stratigraphic thickness and continuity and multiple chronostratigraphic correlation possibilities we propose pizzo mondello as global stratigraphic section and point for the base of the norian

magnetostratigraphy of the mayerling section austria and erenkolu mezarlik turkey section improvement of the carnian late triassic magnetic polarity time scale abstract we present a magnetostratigraphic study of two carnian late triassic pelagic limestone sections from the northern calcareous alps mayerling section and southwestern turkey erenkolu mezarlik section biostratigraphic control is based on conodont zonation for the mayerling section and both on conodonts and ammonoids for the erenkolu mezarlik section in both sections the characteristic magnetization is essentially carried by a mineral of the magnetite family eight magnetic intervals are obtained from the mayerling section and fourteen from erenkolu mezarlik when these results are compared to the carnian magnetostratigraphic sequence obtained from the bolucektasi tepe section satisfactory correlations are observed and a composite carnian magnetic polarity time scale containing 24 intervals can be proposed by combining all these results the lower part of the upper carnian is however missing tuvalian 1 zone and lower part of the tuvalian 2 zone no clear correlation is observed between our composite sequence and the other published magnetostratigraphic data of carnian age the satisfactory correlation observed between the mayerling and the bolucektasi tepe sections indicates that both sections were deposited in the northern hemisphere thus providing constraints on the origin of the antalya nappes

possible roles of ph temperature and partial dissolution in determining boron concentration and isotopic composition in planktonic foraminifera 1 we present the first continuous records from 0 to 5 ma in 0 333 m y integrated time steps of paired boron calcium b ca ratios and boron isotopes 11b in the planktonic foraminifera globogerinoides sacculifer without sacc from a site in the western equatorial pacific ocean ocean drilling program site 806 these measurements the first made in conjunction with calcification temperature magnesium calcium ratios and average shell mass measurements indicate that ph is not the sole environmental variable controlling b in planktonic foraminiferal calcite our data are consistent with calcification temperature exerting a primary control on b concentration and isotopic composition in planktonic foraminifera if so calcification temperature must be taken into account if ph for past oceans and atmospheric pco2 are to be estimated from b isotope measurements in foraminiferal calcite doing so will substantially increase the uncertainty of ph estimates although this work was designed as a temporal study its results define new aspects of calibrating the 11b paleo ph tracer

reconstructions of the continents around the north atlantic at about the 60th parallel abstract late carboniferous early tertiary apparent polar wander apw paths 300 40 ma for north america and europe have been tested in various reconstructions these paths demonstrate that the 500 fathom bullard et al fit is excellent from late carboniferous to late triassic times but the continental configuration in northern pangea changed systematically between the late triassic ca 214 ma and the mid jurassic ca 170 ma due to pre drift extension best fit north atlantic reconstructions minimize differences in the late carboniferous early jurassic and late cretaceous tertiary segments of the apw paths but an enigmatic difference exists in the paths for most of the jurassic whereas for the early cretaceous the data from europe are nearly non existent greenland s position is problematic in a bullard et al fit because of a late triassic early jurassic regime of compression 300 km that would be inherently required for the norwegian shelf and the barents sea but which is geologically not defensible we suggest a radically new fit for greenland in between europe and north america in the early mesozoic this fit keeps greenland locked to europe for the late paleozoic early mesozoic and maintains a reconstruction that better complies with the offshore geological history of the norwegian shelf and the barents sea pre drift a24 extension amounted to approximately 450 km on the mid norwegian shelf but with peak extension in the late cretaceous

monsoon upwelling effects on test size of some planktonic foraminiferal species from the oman margin arabian sea variation in upwelling may be monitored using various micropaleontological indices such as the relative abundance or accumulation rate of the planktonic foraminiferal species globigerina bulloides or mass accumulation rate of planktonic foraminifera we have analyzed the relationships between the upwelling history and mean test size variations in the planktonic foraminiferal species globigerinoides ruber globigerinita glutinata g bulloides and neogloboquadrina dutertrei through the last 19 000 years in ocean drilling program hole 723 a from the oman margin arabian sea the study reveals that these species were larger on average between 11 and 5 ka which coincides with a period of strong upwelling on the other hand these species showed smaller mean test sizes during the last glacial period and late holocene when upwelling was weaker mass accumulation rates of these species are linearly proportional to their mean test sizes indicating that both mean size and productivity of individual species are related to the upwelling intensity therefore we propose that the size variations in g ruber g glutinata g bulloides and n dutertrei can be used as an additional micropaleontological index of upwelling intensity in the arabian sea

upper anisian to lower carnian magnetostratigraphy from the northern calcareous alps austria we present a magnetostratigraphic study of three pelagic limestone sections gamsstein mendlingbach and mayerling from the eastern part of the northern calcareous alps together these sections which contain a rich conodont fauna yield a sedimentary record encompassing the uppermost anisian the ladinian and the lower carnian thermal demagnetization and isothermal remanent magnetization experiments indicate that the magnetization is essentially carried by a mineral of the magnetite family the high unblocking temperature components isolated from the three sections provide clear magnetic polarity zonations correlations between these results based on the biostratigraphic data and tephrochronology allow the construction of a composite magnetic polarity sequence from the illyrian substage upper anisian to the julian 2 zone lower carnian this sequence contains 17 well defined polarity reversals and eight more poorly defined intervals correlations can be suggested between the new data and other magnetostratigraphic results previously obtained from marine sections we estimate that the magnetic reversal frequency was 2 5 to 3 6 reversals per million years during the ladinian

global warming leads to early triassic nutrient stress across northern pangea the largest extinction in earth history in the latest permian was followed throughout most of the early triassic by a prolonged period of ecologic recovery what factors delayed biotic recovery are still under debate and partly revolve around impacts of global warming on primary marine productivity we examined n isotope records from the festningen section on spitsbergen to examine changes in nutrient availability through the early to middle triassic along the northern margin of pangea our results show progressive decline in n availability throughout the griesbachian leading to severe nutrient limitations through the remainder of the early triassic until returning to a highly productive continental margin in middle triassic time these results are consistent with other studies from northern and western pangea and thus show regional nutrient limitations occurred in what should have been the main zone of marine primary productivity such nutrient limitation likely stressed primary production and consequently contributed to prolonged marine recovery we suggest this was driven by high ocean temperatures depressing the marine nutricline

yield and emplacement depth effects on acoustic signals from buried explosions in hard rockyield and emplacement depth effects on acoustic signals from buried explosions in hard rock

evaporation precipitation changes in the eastern arabian sea for the last 68 ka implications on monsoon variability 1 variations in sea surface temperature sst 18o of sea water 18ow and salinity were reconstructed for the past 68 ka using a sediment core aas9 21 from the eastern arabian sea eas in order to understand the changes in evaporation and precipitation associated with the monsoon system the mg ca derived sst record varies by 4 c it shows that marine isotope stage mis 4 was warmer than mis 3 that the last glacial maximum was 4 c cooler than the present and that there was a 2 c increase within the holocene mis 4 records higher 18ow and salinity values than mis 2 suggesting variable flow of low salinity bay of bengal flow into the eas during glacial periods the transition from mis 4 to mis 3 was marked with a conspicuous shift from higher to lower 18ow values which reflects a decrease in the evaporation precipitation budget in the eas perhaps due to the strengthening of southwest monsoon monsoon reconstructions based on 18ow reveal that monsoon driven precipitation was higher during mis 3 and mis 1 and was lower during mis 2 and mis 4 this is consistent with earlier monsoon reconstructions based on upwelling indices from the western arabian sea however the amplitude of monsoon fluctuations derived through upwelling indices and 18ow varies significantly which may indicate spatial variability of monsoon rainfall

shear waves produced by explosive sources shear waves s waves created by an explosion at or near an interface have been observed in experimental field studies and in mathematical model studies but the observations have been separated so widely in time place and publication that their relation has not been apparent recent papers on the s wave are referenced here and study of their implications for field work is recommended from earlier papers illustrations of s waves designated source shear waves at three gulf coast sites were selected for examples the source shear wave was found to be strong directional and the likely cause of downgoing compressional waves by wave conversion the mathematical s wave and the source shear waves are sv waves at observation points along any line through the source position if the line has an inclination of 45 degrees along a vertical line through the source the wave is not detected because of difficulties in assembling observations at points both deep and of large offset it is highly desirable to

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

determination of multiple element calcium ratios in foraminiferal calcite by quadrupole icp ms a method has been developed for rapid and precise simultaneous determination of nine element ca ratios in foraminiferal tests directly from intensity ratios using external matrix matched standards on a quadrupole inductively coupled plasma mass spectrometer icp ms all quantification isotopes are determined in pulse mode to avoid cross calibration small argide 40ar26mg interferences on 66zn are corrected by using two additional mg and zn standards a stable signal conducive for high precision measurements is obtained by cone conditioning variable calcium concentration has negligible effect on li al mn and sr but ca concentrations for standards and samples need to be constrained at a similar level for precise measurements of zn cd and u aliquots of samples are first analyzed for ca concentrations on an inductively coupled plasma atomic emission spectrometer icp aes and the remaining solutions are diluted to ca concentration of 100 ppm for ratio measurements to assure data quality the long term reproducibility of the method yielded precisions of li ca 2 4 b ca 4 2 mg ca 1 4 al ca 14 mn ca 0 9 zn ca 2 8 1 2 7 8 mol mol and 5 1 0 5 1 2 mol mol sr ca 0 9 cd ca 2 4 0 07 0 24 mol mol and 4 8 0 01 0 07 mol mol and u ca 2 5 for foraminiferal samples as small as 60 g

coupling of co2 and ice sheet stability over major climate transitions of the last 20 million years the co2 content of the atmosphere has varied cyclically between 180 and 280 ppmv over the last 800 000 years closely coupled with temperature and sea level for earlier periods in earth s history pco2 is much less certain and the relationship between pco2 and climate remains poorly constrained we use boron calcium ratios in foraminifera to estimate pco2 during major climate transitions of the last 20 million years myr during the middle miocene when temperatures were 3 to 6 c

environmental controls on b ca in calcite tests of the tropical planktic foraminifer species globigerinoides ruber and globigerinoides sacculifer abstract the ratio of boron to calcium b ca in the calcite tests of planktic foraminifers may serve as a proxy for past seawater chemistry but controls on b incorporation are not yet certain here we present the results of laboratory culture experiments with live specimens of globigerinoides ruber pink and globigerinoides sacculifer which provide new insight into b incorporation controls we find that in g sacculifer b ca increases with increasing ph lower hco3 higher co32 and b oh 4 but decreases with increasing total dissolved inorganic carbon dic higher hco3 and co32 constant b oh 4 this suggests competition between aqueous boron and carbon species for inclusion into the calcite lattice similar to previous experiments with the subtropical temperate orbulina universa b ca increases with salinity but not with temperature we evaluate possible carbonate system control parameters and compare our tropical culture calibrations with new and published core top data

two sources of nonisotropic radiation from underground explosions in granite significant tangential ground motion observed during underground explosions makes it difficult to distinguish them from natural earthquakes such motion can be generated by the source geometry and emplacement conditions by the heterogeneous nature of the rock mass mechanical properties may vary in space due to the presence of cracks joints faults and various geologic layers and also by the nonuniform in situ stress state the last mechanism is increasingly important with depth when the difference in main principal stresses becomes significant this paper is focused on the role of material strength of the rock mass in generation of non radial motion during explosions in pre stressed media numerical modeling of underground chemical explosions in granite at various depths have been conducted to compare two possible mechanisms of shear wave generation the first caused by rock mass anisotropy is important at shallow depth the second is related to elastic plastic relaxation around the cavity created by the explosion tangential motions for these two mechanisms have different signatures

the direction correction tilt test an all purpose tilt fold test for paleomagnetic studies abstract the tilt or fold test in paleomagnetism is used to infer whether paleomagnetic remanence was acquired before or after tectonic tilting while several tilt test formulations have been proposed none fully satisfies the requirements of statistical validity applicability to all bedding geometries and ease of use this paper introduces the direction correction dc test which examines the relationship between the paleomagnetic site mean directions and their corresponding bedding tilt corrections the dc test is similar to mcfadden s correlation test because both test whether or not the site directions contain information about the bedding tilts however the dc test gives greater weight to sites with greater counter bedding the dc test is similar to watson s numerical tilt tests because they determine the degree of untilting which gives optimal concentration of site directions however the dc test uses analytical rather than numerical methods graphical output aids the researcher in recognizing problem sites using both real and simulated data the dc test is demonstrated to be more discriminating than other tilt test formulations for all bedding geometries the simulations show that the power of the tilt test is inversely proportional to the 95 confidence interval 95 of the overall mean as a rule of thumb paleomagnetists should attempt to sample sufficient sites to obtain an 95 less than 1 6 of the bedding attitude difference