preferred orientation of plagioclase neutron diffraction and u stage data abstract pole figures of anorthosite mylonite an 65 from san juan bautista california were determined with neutron diffraction using a 23 position sensitive detector this novel technique enables us to deconvolute the complex diffraction spectrum of this triclinic mineral into fifteen separate peaks hkl which are measured simultaneously all pole figures display strong preferred orientation with complicated triclinic distributions from which it appears that 001 poles are concentrated normal to the schistosity plane of the specimen the triclinic mineral is well suited to discuss some fundamental issues of texture representation if crystals are measured individually e g on the u stage positive and negative ends of directions can be unequivocally identified and the whole sphere rather than a hemisphere is necessary to represent the distribution of positive axes this is illustrated for a plagioclase rich amphibolite from orno huvud sweden

climatic implications of the quaternary fluvial tufa record in the ne iberian peninsula over the last 500 ka the drainage area of the iberian ranges ne spain houses one of the most extensive quaternary fluvial tufaceous records in europe in this study tufa deposits in the anamaza mesa piedra and ebron river valleys were mapped stratigraphically described and chronologically referenced from u th disequilibrium series amino acid racemization and radiocarbon methods tufa deposits accumulated in cascades barrage cascades and related damming areas developed in stepped fluvial systems the maximum frequency of tufa deposition was identified at 120 ka marine oxygen isotope stage mis 5e 102 ka mis 5c 85 ka mis 5a and 7 ka mis 1 probably under warmer and wetter conditions than today additional phases of tufa deposition appear at 353 ka end of mis 11 258 180 ka mis 7 and 171 154 ka mis 6 although most tufa deposition episodes are clearly correlated with interstadial periods the occurrence of tufa deposits during the penultimate glaciation mis 6 is remarkable indicating that the onset of this stage was climatically favourable in the iberian peninsula biostatic conditions and the dynamics of karstic systems regulating tufa deposition seem to be sensitive to the precipitation regime controlled by shifts in the position of north atlantic atmospheric belts and summer insolation regulated by orbital forcing

the p t d development at the basement cover boundary in the north eastern tauern window eastern alps alpine continental collision at the basement cover boundary of the north eastern tauern window eastern alps the following alpine p t d development has been reconstructed on the basis of macro and micro structures as well as preferred crystallographic orientations mineral parageneses and compositions during increasing p t conditions in the greenschist facies a first period of deformation produced imbrication of the basement gneisses and cover sediments and then monoclinal folds up to the kilometre scale tectonic transport was continuously top to the ene a second period of deformation began at about peak p t conditions of 9 kbar and c 540 560 c in the south and about 7 9 kbar and 490 500 c in the north this continued locally to lower temperature during the second period transport was continuously top to the se crystallographic orientations of white mica and plagioclase give particularly useful information on the kinematic framework in addition data on the ductile behaviour of dolomite and plagioclase can be inferred at c 7 9 kbar dolomite recrystallization starts at 450 480 c and the beginning of plagioclase recrystallization coincides with the oligoclase boundary in general the alpine geodynamic history of the basement cover boundary may be related to continental collision processes between a northerly plate european or brianconnais and a southerly adriatic one the first deformation period possibly reflects subduction of the gneiss sediment boundary toward the wsw to a depth of 31 32 km the second period may be a result of obduction toward the nw followed by late stage uplift most of the basement domes of the eastern tauern window appear as a result of the final stage of the first deformation formed prior to the peak of metamorphism possibly partly influenced by the final collision between the northern and the southern continents

anatomy of a late quaternary carbonate island constraints on timing and magnitude of sea level fluctuations west caicos turks and caicos islands bwi abstract the data set of the island of west caicos consists of a combination of high resolution lidar and digital imagery radiometric data and amino acid racemization aar d l values as well as extraordinary preservation of sedimentary and bio constructed deposits on the island together with a well established regional stratigraphic framework from the neighboring bahamian island chain and detailed field mapping the west caicos data set provides an opportunity to advance our understanding of the link between carbonate stratigraphy and the controlling parameters of sea level sediment supply tectonics and climate the exceptionally well preserved stratigraphic record of the mid late pleistocene from west caicos allows recognition of marine isotope stages mis 9 11 5e and holocene the west coast of the island provides a continuous 8 4 km exposure of the mis 5e record that enhances our understanding of the intra mis 5e bipartite succession in this region and supports a sea level lowering that occurred during the last interglacial lig west caicos accreted as a series of eolian foreshore shoreface barrier reef and fringing reef facies shoreline positions for all but the mis 7 and mis 5a c deposits are now captured in the sub meter geodetic quality topobathy lidar survey the star town unit of mis 9 11 age forms the southern margin of the island as well as the central karst modified spine with uranium thorium u th coral ages of between 368 and 365 thousand years ago ka and a d l glu average of 0 60 early mis 5e strata include the railroad ridge unit in the center of the island which was previously identified as one of the older units the railroad ridge unit is a north south linear dune ridge that has a d l glu average of 0 52 and indicates the onset of sediment sources from the east associated with a flooded central caicos platform approximately synchronously the early mis 5e south reef unit 3 75 4 m sea level elevation nucleated on the western coast of west caicos attached to the middle pleistocene star town unit the south reef corals yield an average coral u th age of 126 5 ka with an average d l glu from skeletal matrix of 0 46 this transitional barrier fringing reef is unconformably overlain by the late mis 5e boat cove unit corals in the basal transgressive phase of this upper mis 5e boat cove unit yield an average 120 6 ka u th and average d l glu of 0 45 shallow marine foreshore and eolian facies of the late mis 5e rest on a wave cut terrace that cuts the early mis 5e south reef unit by as much as 3 m down to a 0 5 m above present sea level elevation the upper mis 5e boat cove unit displays a maximum of 4 5 m elevation above present day sea level measured from the middle of the foreshore this estimate may be a minimum value as the exposures on the west coast are part of a forced regressive foreshore sequence last stages of the upper mis 5e deposition are seen in a series of regressive dune beach ridge deposits referred to as the northeast ridges unit with sea level positions ranging from 4 5 m early in the central part of west caicos to 0 5 m on the far northeast coast eventually building down below present day sea level this sea level history fits well with previously documented records in the bahamas and globally and the extensive erosion supports a short lived between 126 and 120 ka intra mis 5e relative sea level fall holocene deposition on west caicos is restricted to northern and eastern margins of the island as a combination of strandplain and dune ridge mixed skeletal oolitic units using the high resolution digital elevation model dem and linked digital geologic map makes it possible to compare areas of the different pleistocene and holocene units quantitatively and to constrain volumetric assessments and accumulation rates on the island for different units the peak sediment volume production accumulation rate between 6 5 and 8 106 m3 or between 2 2 and 2 7 106 m3 per ka is observed in the upper mis 5e unit this rate is 5 times greater than the 0 5 106 m3 per ka estimated for the holocene ooid dune ridge strandplain complex suggesting that the combination of higher sea level greater wave and wind energy and warmer ocean temperatures may have fostered the higher rate of chemically precipitated sediment supply

chemical and tectonic controls on the formation of sparry magnesite deposits the deposits of the northern greywacke zone austria the sparry magnesite deposits of the northern greywacke zone are situated at the base of thrust sheets model calculations and natural examples suggest that an inverse temperature gradient can only be established at the base of a thrust sheet if thrusting is so rapid as to be geologically unrealistic independently of this thrusting induces a fluid flow from the lower units to the front of the moving thrust sheet stability data of magnesite and dolomite in contact with fluids with different ca ca mg ratios suggest that this tectonically induced fluid flow produce magnesite from preexisting dolomite by metasomatism

sediment flux across the great barrier reef shelf to the queensland trough over the last 300 ky the continental margin off northeast australia comprising the great barrier reef gbr platform and queensland trough is the largest tropical mixed siliciclastic carbonate depositional system in existence we describe a suite of 35 piston cores and two ocean drilling program odp sites from a 130 240 km rectangular area of the queensland trough the slope and basin setting east of the central gbr platform oxygen isotope records physical property magnetic susceptibility and greyscale logs analyses of bulk carbonate content and radiocarbon ages at these locations are used to construct a high resolution stratigraphy this information is used to quantify mass accumulation rates mars for siliciclastic and carbonate sediments accumulating in the queensland trough over the last 31 000 years for the slope highest mars of siliciclastic sediment occur during transgression 1 0 million tonnes per year mt yr 21 and lowest mars of siliciclastic 0 1 mt yr 21 and carbonate 0 2 mt yr 21 sediment occur during sea level lowstand carbonate mars are similar to siliciclastic mars for transgression and highstand 1 1 1 4 mt yr 21 in contrast for the basin mars of siliciclastic 0 0 1 mt yr 21 and carbonate sediment 0 2 0 4 mt yr 21 are continuously low and within a factor of two for lowstand transgression and highstand generic models for carbonate margins predict that maximum and minimum carbonate mars on the slope will occur during highstand and lowstand respectively conversely most models for siliciclastic margins suggest maximum and minimum siliciclastic mars will occur during lowstand and transgression respectively although carbonate mars in the queensland trough are similar to those predicted for carbonate depositional systems siliciclastic mars are the opposite given uniform siliciclastic mars in the basin through time we conclude that terrigenous material is stored on the shelf during sea level lowstand and released to the slope during transgression as wave driven currents transport shelf sediment offshore q 2000 elsevier science b v all rights reserved

pressure temperature deformation history for a part of the mesoproterozoic fold belt in north singhbhum eastern india abstract the supracrustal rocks in the easternmost part of the proterozoic fold belt of north singhbhum eastern india are folded into a series of large upright folds with variable plunges the regional schistosity is axial planar to the folds the folds were produced by a second phase of deformation d2 and were preceded by d1 deformation which gave rise to isoclinal folds mapped outside the study area and the locally preserved bedding parallel schistosity a shearing deformation during d2 was responsible for the sheath like geometry of a major fold the axial planes were curved by d3 warping the first metamorphic episode m1 of low pressure type produced andalusite porphyroblasts prior to or in the early stage of d1 deformation the main metamorphism m2 responsible for the formation of chloritoid kyanite garnet and staurolite porphyroblasts was late to post d2 in occurrence the staurolite isograd separates two zonal assemblages recorded in the high alumina and the low alumina pelitic schists geothermobarometric calculations indicate the peak metamorphic temperature to be 550 c at 5 5 kb fluid composition in the rocks before and during m2 metamorphism was buffered and fluid influx if any was not extensive enough to overcome the buffering capacity of the rocks from m1 to m2 the p t path is found to have a clockwise trajectory that is consistent with a tectonic model involving initial asthenospheric upwelling and rifting followed by compressional deformation leading to loading and heating

a new empirical calibration of the quartz c axis fabric opening angle deformation thermometer abstract the opening angle of quartz c axis fabrics oa is strongly temperature dependent and has proven to be a powerful deformation thermometer for natural metamorphic rocks previous considerations of empirical data have identified a linear correlation between oa and temperature between 250 and 650 c and no correlation above 650 c however possible effects of pressure have not been investigated we expanded the data set of oa versus temperature including data from rocks deformed over 300 1050 c and 2 5 15 kbar disregarding possible effects of pressure the oa temperature relationship can be described by two linear correlations for the intervals 250 650 c and 650 1050 c t c 6 9 o a degrees 48 250 c t 650 c and o a 87 t c 4 6 o a degrees 258 650 c t 1050 c and o a 87 the change on the curve slope of the oa temperature relationship correlates approximately to the low to high quartz transition and to changes in the dynamic recrystallization mechanism from subgrain rotation to grain boundary migration the available data suggest that pressure has a secondary effect accompanying the major temperature dependence of oa which is particularly important for temperatures above 650 c where the correlation between oa and temperature is less pronounced for fixed pressures the oa has logarithmic relationships with temperature over the range 250 1050 c the following thermometer equation is formulated from a multiple regression t c 410 44 ln oa degrees 14 22 p kbar 1272 an uncertainty of 50 c is inherited from the petrological temperature estimates of the natural samples the data suggest the gradual increasing importance of prism c slip relative to slip in quartz with rising temperature under conditions of average geological strain rate and water weakening prism c slip dominates for deformation above 700 c

orogen parallel strike slip faults bordering metamorphic core complexes the salzach enns fault zone in the eastern alps austria abstract the approximately ene trending salzach enns fault eastern alps contributed to late stage exhumation of the tauern metamorphic core complex in response to oblique convergence of european and adriatic plates six stages of kinematic evolution with early ductile and later brittle deformational structures were recognized as follows 1 initial ductile deformation is represented by a combination of sinistral shear dominated noncoaxial strain and coaxial strain 2 early brittle sinistral strike slip is combined with a pure shear deformation and represents roughly n s contraction it is followed by 3 sinistral strike slip and 4 ca n s extension due to normal slip striations 5 subsequent n s compression resulted in counterclockwise rotation of the maximum principal stress from ne to nw and led to final dextral strike slip displacements along the salzach enns fault the exhumation of the tauern window was accommodated by dip slip on the fault plane at shallow levels and coaxial flattening at deeper structural levels brittle sinistral faults at shallow structural levels produced a larger amount of strike slip displacement than ductile shear zones at the deeper structural levels which is explained as a scissors like movement and which resulted in the eastward tilting of the tauern window

eastern alpine tectono metamorphic evolution constraints from two dimensional p t t modeling we use two dimensional 2 d p t t modeling to constrain the thermal and rheological aspects of different scenarios for the late mesozoic and cenozoic tectonic evolution of the eastern alps inferred from excellent data sets from the tauern window tw models invoking subduction of the south penninic sp oceanic lithosphere during thrusting and subsequent erosion of the austro alpine aa upper plate nappe stack are inconsistent with the observed thermal evolution within the aa and penninic units in these models predictions for the aa peak thermal conditions are lower than observed after exhumation and cooling to midcrustal levels and subduction of the continental middle penninic mp block the aa undergoes a phase of renewed heating to almost the previous peak temperatures simultaneously the penninic units experience a phase of heating upon subduction followed by cooling after onset of subduction of the north penninic np basin the model predictions are inconsistent with the observed nearly isothermal uplift path of the sp after subduction and cannot explain observed inverted metamorphic peak conditions in the deeper aa amphibolite facies down to the higher penninic unit greenschist facies a model with the beginning of subduction of the sp occurring after crustal thickening of the aa and subsequent return to normal crustal thicknesses is compatible with the p t t data in this model peak temperature conditions are higher in the aa followed by a phase of strong cooling in the aa upper plate with the onset of underthrusting this model also explains successfully nearly isothermal exhumation of the mp and inverted metamorphic peak conditions in the deeper aa material accreted to the hanging wall from the oceanic crust sp experiences a phase of cooling during ongoing subduction of oceanic lithosphere and begins to heat up to its thermal climax after the subduction of trailing continental lithosphere the subsequent pt path of the penninic units strongly depends on the timing and rates of underthrusting by the foreland observed pt paths in the mp within the tw require continuous subduction of the np and the trailing european foreland under the exhuming mp block documented rapid cooling in the final uplift phase of the penninic units in the tw requires exhumation rates up to approximately 4 mm yr predictions of slightly elevated present day geothermal gradients in the tw area are consistent with available heat flow data as a result of mesozoic rifting followed by late mesozoic crustal thickening of the aa paleorheological reconstructions are characterized by a contrast between relatively strong oceanic lithosphere and adjacent weak continental lithosphere predicted decoupling of weak continental and oceanic lithosphere during subsequent subduction of the penninic units can explain observed late cretaceous crustal extension in the aa units in terms of gravitational spreading ongoing subduction leads to an overall strength increase due to underthrusting of cool oceanic lithosphere whereas subduction of continental lithosphere causes a strength decrease in the upper levels of the lithosphere continuous crustal thickening and relaxation of the depressed isotherms reduce the strength of the lower lithospheric mantle beneath the central orogen further enhanced by rapid late stage uplift predictions for the present day rheological structure of the eastern alps support the existence of a strong upper crustal layer two wedge shaped strong upper mantle layers to the north and the south of the orogen and a weak upper mantle underlying the central orogen

extension in compressional orogenic belts the eastern alps extension in the eastern alps encompasses the following 1 extension accompanying simple shear crustal stacking subhorizontal stretching occurs along flat lying foliations and regionally consistent stretching lineations with associated high strains on a local scale stretching results from extrusion of ductile sediments squeezed between rigid basement blocks basement blocks during thrust sheet imbrication the overall geometric effect is crustal thickening 2 classical extensional tectonics extension first occurs as a consequence of accretion and underthrusting of continental and oceanic material and represents gravitational adjustment of an unstable orogenic wedge extension then occurs as a consequence of terminal continental collision and is accommodated by lateral extrusion of crustal of crustal blocks the overall geometric effect is crustal thinning extension is generally oriented subparallel to the strike of the orogen

response of the ganges dispersal system to climate change a source to sink view since the last interstade the forcing of sediment dispersal systems by climate is widely accepted but there remains disagreement on the general responses to climate change such as how resulting signals propagate downstream and ultimately how they are preserved in the stratigraphic record towards a better understanding of these issues this paper presents a comprehensive overview of ganges dispersal system behavior since the last interstade which reveals major coeval responses to changes in the south asian monsoon at 3000 km from its mountain headwaters to deep sea fan the ganges dispersal system is immense and yet shows tight coupling between source area catchment basin and coastal and marine depocenters furthermore system wide responses and downstream transfer of the signal appear to occur at least as fast as current temporal resolution of 1 2 ky this tight linkage of source to sink components is considered a function of the southwest summer monsoon s overwhelming control on regional hydrology about 80 of the ganges discharge and 95 of its sediment load are delivered to the margin during only 4 months making the system extremely sensitive to this seasonal forcing in addition the regional scale and distribution of the monsoon weather system means that changes in atmospheric circulation affect the entire drainage basin rather than local subcomponents finally despite its present intensity strength of the summer monsoon has varied significantly over the past 150 ky under orbitally driven changes in insolation and global glacial boundary conditions the resulting changes in precipitation both well above and below modern values have forced system wide responses ranging from glacier advance retreat to sediment fluxes to the margin and deep sea fan the overall conclusions are 1 that this immense dispersal system responds to multimillennial scale 104 years climate change in a system wide and largely contemporaneous manner and 2 that major sedimentary signals can be transferred rapidly from source to sink with little apparent attenuation furthermore these acute responses to climate change have produced sedimentary stratigraphic features that diverge from traditional sequence models in their nature and timing

structure mineralogy and pb isotopic composition of the as au ag deposit rotgulden eastern alps austria significance for formation of epigenetic ore deposits within metamorphic domes the abandoned as au ag mining district rotgulden is located within the eastern tauern window of the eastern alps and was reinvestigated in order to evaluate ore deposition during alpine late orogenic tectonic processes four major ore types have been recognized 1 quartz sulfide veins within variscan basement rocks 2 deformed metamorphic massive ores within fold hinge zones saddle reefs of permian to mesozoic cover sequences 3 ores in tension gashes of the cover sequence and 4 irregular replacement ore bodies in marbles of the cover sequence ore deposition was intimately related to late orogenic exhumation by stretching of footwall sequences within the tauern metamorphic core complex during late oligocene and neogene hydrothermal systems developed and metals from apparently distinct sources were deposited under decreasing temperature conditions lead is distinctly radiogenic and resembles the lead in au quartz veins of the mesozoic cover sequence of the hohe tauern

the relationship between water masses and benthic ostracod assemblages in the western coral sea southwest pacific abstract the bathymetric distribution of 67 ostracod genera identified in 42 sediment samples water depth range 370 3776 m from the western coral sea is documented statistical analyses of this dataset support preliminary observations that the vertical distribution of the ostracod fauna is largely controlled by the three water masses present in the studied area four ostracod assemblages are recognised assemblage i consisting mainly of ostracods present in the deep water assemblage ii consisting of ubiquitous ostracods and ostracods mostly confined to the antarctic intermediate water and assemblages iii and iv with ostracods characteristic of the western south pacific central water temperature food supply and dissolved oxygen level are believed to be the most important factors influencing the ostracods bathymetric zonation the present work establishes the potential of ostracods for use in palaeoceanographic reconstruction in the western pacific ocean

metamorphic p t paths from pelitic schists and greenstones from the south west tauern window eastern alps petrological data from intercalated pelitic schists and greenstones are used to construct a pressure temperature path followed by the upper schieferhulle ush series during progressive metamorphism and uplift in the south west tauern window italy pseudomorphs of al epidote fe epidote albite oligoclase chlorite after lawsonite and data on amphibole crystal chemistry indicate early metamorphism in the lawsonite albite chlorite subfacies of the blueschist facies at p 7 8 kbar geothermometry and geobarometry yield conditions of final equilibration of the matrix assemblage of 475 25 c 5 6 kbar calculations with plagioclase and phengite inclusions in garnet indicate early garnet growth at pressures of 7 5 kbar garnet zoning patterns are complex and reversals in zoning can be correlated between samples thermodynamic modelling of these zoning profiles implies garnet growth in response to four distinct phases of tectonic activity fluid inclusion data from coexisting immiscible h2o co2 nacl fluids constrain the uplift path to have passed through temperatures of 380 30 c at 1 3 0 2 kbar there is no evidence for metamorphism of ush at pressures greater than 7 5 kbar in this area of the tauern window this is in contrast to pressures of 10 kbar recorded in the lower schieferhulle only 2 3 km across strike a history of differential uplift and thinning of the intervening section during metamorphism is necessary to reconcile the p t data obtained from these adjacent tectonic units

the precessional phase lag of messinian gypsum deposition in mediterranean marginal basins abstract the uncertainty of the phase relation between the forcing and sedimentary expression is yet unquantified introducing a bias in tuning recurrent facies variations in the sedimentary record to the astronomical forcing the identification of a phase lag between precession and the most recent sapropel in the mediterranean demonstrates that astronomical forcing and its sedimentary expression are not always in phase gypsum deposition in mediterranean marginal basins during the messinian salinity crisis is also forced by precession driven climate changes in contrast to sapropel formation which involves complex interactions of circulation and biogeochemistry gypsum formation in such basins is primarily controlled by salinity using a simple box model to represent the late miocene mediterranean we examine the phase relation between gypsum deposition and precessional forcing for a large range of settings model results show a consistent phase lag between the precessional forcing and salinity in the marginal and deep basins of the mediterranean on the basis of our quantitative modelling results we propose that in the astronomical tuning of the messinian gypsum deposits a phase lag of 3 3 kyr 2 6 kyr should be taken into account for cycles with a duration of 20 kyr accordingly the astronomically tuned ages of the gypsum deposits become on average 3 3 kyr younger in the anomalously short 14 kyr cycle that follows the onset of the messinian salinity crisis the phase lag is smaller and within range of the other uncertainties of astronomical tuning

a pulse of ooid formation in maui nui hawaiian islands during termination i abstract we describe the first recorded occurrence of oolite in the main hawaiian islands well cemented oolite was recovered at several locations at 140 to 150 m depth south of lana i the ooids contain foraminiferal skeletal and peloidal nuclei coated by thin to moderately thick 20 50 of ooid radius tangential cortices and are cemented by fibrous aragonite needles the extent of amino acid racemization aar analysed on 127 ooid grains and 55 pristine foraminifera in the same deposits confirm that the particles formed during a brief interval estimated at 1900 yr duration a single large benthic foraminiferan amphisorus sp intermixed with the ooid grains yielded a calibrated 14 c age of 12 2 0 3 ka in contrast a series of progressive leaches on two splits of ooid grains yielded a sequence of 14 c ages ranging from 27 ka for the nuclei to 14 c leach ages and further research is needed however assuming that the age of the ooids lies between the 14 c ages of the youngest cortex 14 9 ka and the amphisorus 12 2 ka then eustatic sea level history records suggest two intervals of slowing sea level history rise that could accommodate ooid formation these occurred immediately preceding mwp1a 15 ka and mwp1b 12 5 ka in the area of the oolite deposit there is no terrace or hardground morphology that coincides with a 100 m sea stand preceding mwp1a thus we suggest that conditions required for ooid formation converged when a flat carbonate hardground in the broad au au channel was initially flooded with energetic shallow water as sea level rose to and slowed at 60 to 55 m during the onset of the younger dryas yd interval around 12 7 ka ooid formation ensued for a short period 1900 yr and then abruptly ceased most reasonably as a result of a 7 5 m deepening of the sea during mwp1b around 11 5 ka the oolitic sediments were subsequently transported longshore and offshore to southern lana i

integrated late quaternary chronostratigraphy for san salvador island bahamas patterns and trends of morphological change in the land snail cerion abstract reconstructing the phylogeny and biogeography of the caribbean land snail cerion requires a robust stratigraphic and chronological framework to this end we have determined the stratigraphic succession on san salvador a bahamian island with a rich fossil and modern cerion fauna a primary purpose of this paper is to independently verify this succession through whole rock and cerion aminostratigraphies and ams 14c based age models over 150 individual cerion shells were age ranked from 140 ka to modern using stratigraphic position and reverse phase hplc rpc amino acid racemization which was sufficiently sensitive to resolve stratigraphic subunits within the holocene and late pleistocene a secondary purpose of this paper is to assess broad changes in the gross morphology height width of supersets of cerion from age ranked lots spanning this 140 kyr chronostratigraphy through each of the three interglacial sequences i e marine isotope stages 5e 5a and 1 between sample trends in mean gross morphology often greatly exceed within sample variances 1 live collected cerion exhibit a range in gross morphology that nearly encompasses that of the entire fossil sequence a trend of increasing gross shell size characterizes each of the interglacial phases with a major step decrease between marine isotope stages 5a and 1 while between unit variation is often great in cerion from ssi within unit variation appears unimodal through the record

on the structure and origin of major glaciation cycles 1 linear responses to milankovitch forcing time series of ocean properties provide a measure of global ice volume and monitor key features of the wind driven and density driven circulations over the past 400 000 years cycles with periods near 23 000 41 000 and 100 000 years dominate this climatic narrative when the narrative is examined in a geographic array of time series the phase of each climatic oscillation is seen to progress through the system in essentially the same geographic sequence in all three cycles we argue that the 23 000 and 41 000 year cycles of glaciation are continuous linear responses to orbitally driven changes in the arctic radiation budget and we use the phase progression in each climatic cycle to identify the main pathways along which the initial local responses to radiation are propagated by the atmosphere and ocean early in this progression deep waters of the southern ocean appear to act as a carbon trap to stimulate new observations and modeling efforts we offer a process model that gives a synoptic view of climate at the four end member states needed to describe the system s evolution and we propose a dynamic system model that explains the phase progression along causal pathways by specifying inertial constants in a chain of four subsystems solutions to problems involving systems of such complexity are not born full grown like athena from the head of zeus rather they evolve slowly in stages each of which requires a pause to examine data at great lengths in order to guarantee a sure footing and to properly choose the next step victor p starr

a modeling perspective on spatial and temporal variations in messinian evaporite deposits abstract during the messinian salinity crisis msc evaporite dominated sequences formed in marginal and deep basins of the mediterranean sea in the marginal basins the onset of the msc is synchronous and a single depositional framework fits all sequences in contrast msc sequences of the western and eastern deep basins appear to comprise a different number of units and differ greatly in thickness even though there exist numerous scenarios for deposition in the marginal and deep basins the link between the two settings is difficult and scenarios are rarely quantitatively supported we employ a simple box model for the messinian mediterranean to examine the causes of 1 spatial variation in thickness and 2 differences in the time of onset of deposition model results are compared with actual observations on the msc sequences the results show that a large connection between the western and eastern basin is necessary for and some degree of water column stratification is conducive to synchronous onset of the msc in the marginal basins moreover halite deposits in the deep basins are likely to be coeval and have formed in 60 ka after a further restriction of the atlantic mediterranean connection during the msc but without a significant sea level drop a difference in the net salt gain per unit volume caused the different halite deposition rates in the two basins a scenario with only a simple restriction of the atlantic mediterranean connection during the late miocene without significant changes in the mediterranean sea level the fresh water budget or the size of the strait of sicily is able to explain the synchronous onset of the msc the synchronous marginal evaporite formation and the differences in the deep basinal sequences

palaeoenvironmental changes of the early pliocene zanclean in the eastern mediterranean pissouri basin cyprus evidenced from calcareous dinoflagellate cyst assemblages abstract the first 100 ka of the earliest pliocene zanclean sediments of the eastern mediterranean pissouri basin on cyprus have been investigated on calcareous dinoflagellate cyst assemblages these assemblages reflect the return in three phases to the open oceanic conditions following the messinian salinity crisis msc 5 33 ma ago the lowermost phase dominated by leonella granifera cysts indicates substantial land derived nutrient supply and low salinities this confirms earlier observations of enhanced continental water runoff during the earliest pliocene in the eastern mediterranean basin the second phase dominated by caracomia stella and calciodinellum albatrosianum cysts indicates a change to warmer meso to oligotrophic waters the third phase marks the first appearance and still continuing dominance of thoracosphaera heimii in the region in addition the endemic eastern mediterranean species lebessphaera urania peaks within this upper interval it probably survived the salinity crisis in the mediterranean the assemblage reflects the establishment of typical open marine well stratified and oligotrophic surface conditions similar but not yet identical to the situation in the mediterranean sea today this study points out a discrepancy between the fast refilling scenario 1 2 ka in the pissouri basin and a long time 100 ka environmental reorganisation in the surface waters as indicated by the calcareous dinoflagellate cysts the onset of the pliocene is also marked by the first appearance of calciodinellum elongatum and calciodinellum levantinum which must have migrated from the atlantic ocean

kinematics of austro alpine cover nappes changing translation path due to transpression upper and middle austro alpine nappes of the eastern alps the structural uppermost subunits of the alps suffered two major superposed deformations d1 d2 during the eo alpine cretaceous orogeny d1 is characterized by nw to w directed thrusting and nappe internal rock flow d2 by large scale folding and imbrication toward the north and northeast structures strain metamorphic history microfabrics and stretching trajectories indicate that the superposition of d2 over d1 structures can be interpreted as a progressive deformation it is concluded that the emplacement of the nappes follows a curved translation path a model which emphasizes non coaxial deformation structures explains the detachment of the nappes the configuration of the separating thrust planes and the distribution of intense deformation zones the overall kinematic history of the austro alpine nappes fits a model in which strike slip shearing horizontal shortening and vertical lengthening act together continuously over a finite deformation zone transpressional model this model emphasizing a gradually changing strain regime eliminates the space problems encountered in models which consider simple south over north imbrication during the alpine orogeny the study stresses two interpretations 1 1 stretching lineations indicate nappe transport directions 2 2 transpression may be a common feature of orogenic belts

geochemical assessment of the palaeoecology ontogeny morphotypic variability and palaeoceanographic utility of dentoglobigerina venezuelana to better understand the links between the carbon cycle and changes in past climate over tectonic timescales we need new geochemical proxy records of secular change in silicate weathering rates a number of proxies are under development but some of the most promising e g palaeoseawater records of li and nd isotope change can only be employed on such large samples of mono specific foraminifera that application to the deep sea sediment core archive becomes highly problematic dentoglobigerina venezuelana presents a potentially attractive target for circumventing this problem because it is a typically large 355 m diameter abundant and cosmopolitan planktic foraminifer that ranges from the early oligocene to early pliocene yet considerable taxonomic and ecological uncertainties associated with this taxon must first be addressed here we assess the taxonomy palaeoecology and ontogeny of d venezuelana using stable isotope oxygen and carbon and mg ca data measured in tests of late oligocene to early miocene age from ocean drilling program odp site 925 on ceara rise in the western equatorial atlantic to help constrain the depth habitat of d venezuelana relative to other species we report the stable isotope composition of selected planktic foraminifera species within globigerina globigerinoides paragloborotalia and catapsydrax we define three morphotypes of d venezuelana based on the morphology of the final chamber and aperture architecture we determine the trace element and stable isotope composition of each morphotype for different size fractions to test the validity of pooling these morphotypes for the purposes of generating geochemical proxy datasets and to assess any ontogenetic variations in depth habitat our data indicate that d venezuelana maintains a lower thermocline depth habitat at ceara rise between 24 and 21 ma comparing our results to published datasets we conclude that this lower thermocline depth ecology for the oligo miocene is part of an eocene to pliocene evolution of depth habitat from surface to sub thermocline for d venezuelana our size fraction data advocate the absence of photosymbionts in d venezuelana and suggest that juveniles calcify higher in the water column descending into slightly deeper water during the later stages of its life cycle our morphotype data show that 18o and 13c variation between morphotypes is no greater than within morphotype variability this finding will permit future pooling of morphotypes in the generation of the sample hungry palaeoceanographic records

petrologic constraints on imbrication metamorphism and uplift in the sw tauern window eastern alps the pressure temperature time deformation pttd history of two tectonic units in the southwest tauern window austria italy is evaluated from p t paths of metamorphism and uplift geochronologic data and observations on fabric development petrologic data indicate burial of the lower schieferhulle lsh to depths of 35 km and the adjacent upper schieferhulle ush to only 24 28 km the units are now separated by only 2 km of section metamorphism was postkinematic in the lsh and synkinematic in the ush correlation of p t path reversals calculated from zoned garnets in the two units however indicates that juxtaposition of the lsh and ush occurred prior to metamorphism temperature time and depth time diagrams for both units show increasing cooling rates and decreasing uplift rates as the rocks approached the surface both the petrologic data and the depth time profiles for the lsh and ush point to a history of differential uplift in the early stages of decompression textural features indicate that the lsh behaved as an essentially rigid body during uplift whereas the ush experienced extensive ductile shearing the pttd data for the lsh and ush are incorporated into a model for continental collision in the eastern alps initial tectonic uplift of the lsh was accompanied by ductile thinning of the ush and overlying austroalpine units final uplift and erosion affected all of the units en masse

dating deep lake sediments by using amino acid racemization in fossil ostracodes the long term rate of racemization for amino acids preserved in fossil ostracode shells was determined by using independently dated sediment cores from five deep lakes the racemization rates for aspartic and glutamic acids in the common ostracode genus candona were calibrated for the past 100 k y providing the basis for an age equation with a realistic age uncertainty of 20 the new age equation can be applied to other hypolimnic settings because the temperature below the thermocline of deep lakes from middle and high latitude regions can reasonably be assumed to remain close to 4 c the sample size required for analysis is an order of magnitude less than for 14c dating and presents new opportunities to date deposits that are organic matter poor or those with large 14c reservoir effects

development of quaternary travertines in the carbonate mountains of the western costa del sol malaga southern spain the predominantly carbonate nature of the mountains near the coast of malaga and marbella costa del sol southern spain and the presence of springs have favored the formation of travertine buildups during the quaternary the geomorphic characteristics of the slopes and the location of the springs have determined the development of three types of travertine growths 1 spring travertines located preferentially on the south mountainside where the slope is steepest 2 pool dam cascade travertines which form along the north and east edges far from the carbonate relief and with a gentler slope and 3 river valley travertines formed in the courses of the springs of any sector field observations combined with new amino acid racemization aar dating of helicidae gastropods show that most of the travertine formations are polyphasic and that their development was interrupted by stages of erosion and incision five stages of travertine development are evident most of which are related to warm moist episodes corresponding to marine oxygen isotope stages mis 7 5 3 and 1 although local travertine growth also occurred during mis 6 and during the transition from mis 3 to 2

isoleucine epimerization in quaternary benthonic foraminifera from the norwegian continental shelf a pilot study abstract the extent of epimerization of the protein amino acid l isoleucine has been measured in late quaternary benthonic foraminifera found in cores from two areas of the norwegian continental shelf in order to evaluate the potential of this reaction as a geochronological tool measurements were restricted to monospecific assemblages of cibicides lobatulus and elphidium excavatum from 14 c dated and seismostratigraphic units representing a range of ages by comparing with data on the same species from last interglacial and late glacial sites in western norway miller et al 1983 and with the assumption of similar temperature history for the shelf and coastal areas the absolute ages of the samples are discussed of the nine samples analysed one was of holocene seven of late to middle weichselian and one sample of pre weichselian age from this pilot study we conclude that isoleucine epimerization ratios in benthonic foraminifera provide a reliable index of relative age that can be used to correlate sedimentary units that contain in situ faunas and have similar thermal histories absolute ages of the enclosing sediment can be approximated if suitable well studied calibration sites are available

cyclone pumping sediment partitioning and the development of the great barrier reef shelf system a review abstract the modern great barrier reef gbr is part of the world s largest and best known mixed terrigenous carbonate continental margin the gbr shelf contains three shore parallel sedimentary belts an inner shelf zone of terrigenous sedimentation at depths of 0 22 m a middle shelf zone of sediment starvation at depths of 22 40 m and an outer shelf reef tract with its inner edge at ca 40 m depth these zones are controlled by the dynamics of northward fair weather along shelf drift driven by southeasterly trade winds and by the regular passage of tropical cyclones cyclones cause wind driven north directed middle shelf flows in excess of 130 cm s which erode the seabed concentrate the sparse mobile sediment into sand ribbons and advect suspended load onto the outer part of the nearshore terrigenous sediment prism and into inter reef depocentres within the outer shelf reef tract cyclones largely control the input of new sediment into the gbr system via river flooding seabed erosion or reef breakage they also help to control the partitioning and dispersion of the three main shore parallel belts of sediment and hence stratigraphic accumulation acting as a sediment pump especially during interglacial highstands cyclones have exerted great control on the development of the modern gbr province and its sediments by maintaining a broad shelf parallel zone of episodically mobilised sediment and scoured seabed upon which coral reefs have been unable to form cyclones may also have partly controlled the timing of initiation of the first gbr at 0 6 mybp contrary to current models gbr storm beds are most likely to be preserved intact close to the shoreline and become coarser grained away from the shoreline for the central gbr highstand shedding only applies to carbonate sediment at the scale of local reefs system wide oceanographic controls cause high rates of carbonate sedimentation on the slope during both sea level rise and highstand concomitantly terrigenous sediment accumulates fastest on the slope during sea level rise and slowest during sea level lowstand and highstand

auriferous arsenopyrite pyrite and stibnite mineralization from the siflitz guginock area austria indications for hydrothermal activity during tertiary oblique terrane accretion in the eastern alps

the cenomanian turonian boundary event oae2 and palaeoenvironmental change in epicontinental seas new insights from the dinocyst and geochemical records abstract organic walled dinoflagellate cyst dinocyst and geochemical records across the cenomanian turonian boundary ctb are presented for the nw european reference section at eastbourne england dinocyst and nannofossil fertility indexes indicate that an upwelling driven productivity pulse accompanied a eustatic sea level fall that preceded by at least 40 kyr the global rise in 13 c values that marks the onset of oceanic anoxic event 2 oae2 and the deposition of black shales in the deep ocean a marine productivity collapse in the latest cenomanian is evidenced by the falling absolute and relative abundance of peridinioid dinocysts believed to be the product of heterotrophic dinoflagellates this biotic change accompanied transgression and sharply rising sea surface temperatures following an atlantic wide episode of short lived cooling geochemical tracers provide evidence of caribbean colombian plateau volcanism the increase in water depth caused by the latest cenomanian transgression resulted in less eutrophic waters in epicontinental seas where ctb biotic turnover was driven largely by water mass changes rather than oxygen depletion the species richness absolute abundance ratio of dinocysts is proposed as a water mass stability proxy

insolation control on the late cretaceous hydrological cycle and tropical african climate global climate modelling linked to marine climate records data from late cretaceous paleoclimate simulations and their linkage to a geological model derived from long term high resolution proxy data indicate and support strong relationships between african climate and tropical atlantic sedimentation here we present results from an interdisciplinary study by varying only one parameter in the set of orbital boundary conditions of the numeric model we focus on the climatic impact of precessional forcing on the global and regional climate system as a result new insights to the internal dynamics of climate the different compartments and fluxes of the hydrological cycle and finally the sedimentary response within the oceanic realm during greenhouse conditions have been approached the climate models suggest that insolation changes at 25 55 s are the trigger for cyclic variations of the tropical hydrological cycle of northern africa between the various models a maximum difference in insolation at the top of the atmosphere of 14 w m2 is needed to produce the documented changes in the hydrological cycle first of all the simulations do not suggest any substantial latitudinal movement of the itcz over the course of one precessional cycle the models rather indicate cross latitudinal variation of pressure systems and variation in the magnitude and direction of surface winds linking tropical africa to the mid southern latitudes this cross latitudinal atmospheric teleconnection denotes a reduced role of the tropics as driver of cretaceous climate system therefore the linkage of proxy based geological and numeric models rather supports the idea that tropical atlantic black shale formation in the late cretaceous was ultimately triggered by climate change in mid southern latitudes with precipitation and river discharge being the transport mechanisms as a hypothesis that will be tested in the near future we speculate that the mid latitudes represent the ultimate region of climate signal formation during times of extreme global warmth

immediate propagation of deglacial environmental change to deep marine turbidite systems along the chile convergent margin abstract understanding how earth surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment fluxes sedimentary records provide the archives for inferring these processes but their interpretation is compromised by our incomplete understanding of how sediment routing systems respond to millennial scale climate cycles we analyzed seven sediment cores recovered from marine turbidite depositional sites along the chile continental margin the sites span a pronounced arid to humid gradient with variable relief and related sediment connectivity of terrestrial and marine environments these sites allowed us to study event related depositional processes in different climatic and geomorphic settings from the last glacial maximum to the present day the three sites reveal a steep decline of turbidite deposition during deglaciation high rates of sea level rise postdate the decline in turbidite deposition comparison with paleoclimate proxies documents that the spatio temporal sedimentary pattern rather mirrors the deglacial humidity decrease and concomitant warming with no resolvable lag times our results let us infer that declining deglacial humidity decreased fluvial sediment supply this signal propagated rapidly through the highly connected systems into the marine sink in north central chile in contrast in south central chile connectivity between the andean erosional zone and the fluvial transfer zone probably decreased abruptly by sediment trapping in piedmont lakes related to deglaciation resulting in a sudden decrease of sediment supply to the ocean additionally reduced moisture supply may have contributed to the rapid decline of turbidite deposition these different causes result in similar depositional patterns in the marine sinks we conclude that turbiditic strata may constitute reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions however the underlying causes for similar signal manifestations in the sinks may differ ranging from maintained high system connectivity to abrupt connectivity loss

40ar 39ar muscovite ages from the penninic austroalpine plate boundary eastern alps the radstadt mountains eastern alps expose the tectonic boundary between the base of the austroalpine continental plate hanging wall and the penninic oceanic units foot wall parts of the austroalpine basement were penetratively deformed because of ongoing rifting of the continental crust during the permian 290 250 ma austroalpine permo mesozoic cover rocks were deformed during the cretaceous 80 ma and the paleogene 55 50 ma these ages are interpreted as representing two distinct events of nappe stacking the younger ages represent the collision of austroalpine and penninic tectonic units the penninic nappe complex displays a successive decrease of ages from 37 to 25 ma from high to deep tectonic levels a second age group of 22 ma was found both in low temperature release steps and as plateau ages close to the penninic austroalpine boundary it is attributed to a thermal overprint due to ductile extension of the overthickened orogenic wedge

amino acid geochronology of individual foraminifer pulleniatina obliquiloculata tests north queensland margin australia a new approach to correlating and dating quaternary tropical marine sediment cores 1 in this study we demonstrate the utility of amino acid geochronology based on single foraminiferal tests in quaternary sediment cores from the queensland margin australia the large planktonic foraminifer pulleniatina obliquiloculata is ubiquitous in shelf slope and basin sediments of north queensland as well as pantropical oceans fossil tests are resistant to dissolution and retain substantial concentrations of amino acids 2 4 nmol mg 1 of shell over hundreds of thousands of years amino acid d and l isomers of aspartic acid asp and glutamic acid glu were separated using reverse phase chromatography which is sensitive enough to analyze individual foraminifera tests in all 462 pulleniatina tests from 80 horizons in 11 cores exhibit a systematic increase in d l ratios down core d l ratios were determined in 32 samples whose ages are known from ams 14 c analyses in all cases the asp and glu d l ratios are concordant with 14 c age d l ratios of equal age samples are slightly lower for cores taken from deeper water sites reflecting the sensitivity of the rate of racemization to bottom water temperature beyond the range of 14 c dating previously identified marine oxygen isotope stage boundaries provide approximate ages of the sediments up to about 500 000 years for this longer time frame d l ratios also vary systematically with isotope correlated ages the rate of racemization for glu and asp was modeled using power functions these equations can be used to estimate ages of samples from the queensland margin extending back at least 500 000 years this analytical approach provides new opportunities for geochronological control necessary to understand fundamental sedimentary processes affecting a wide range of marine environments index terms 4267 oceanography general paleoceanography 4850 oceanography biological and chemical organic marine chemistry 3022 marine geology and geophysics marine sediments processes and transport keywords queensland margin marine sediment amino acid racemization geochronology foraminifera quaternary stratigraphy citation hearty p j m j o leary d s kaufman m c page and j bright 2004 amino acid geochronology of individual foraminifer pulleniatina obliquiloculata tests north queensland margin australia a new approach to correlating and dating quaternary tropical marine sediment cores paleoceanography 19 pa4022 doi 10 1029 2004pa001059

eustatic and tectonic controls on deposition of hybrid siliciclastic carbonate basinal cycles discussion with examples changes in sea level represent one of the dominant controls on basinal sedimentation adjacent to mixed carbonate siliciclastic sediment source areas sedimentary responses to sea level change of the siliciclastic and carbonate components of these hybrid systems commonly result in deposition of alternating siliciclastic and shelf derived carbonate basinal deposits such deposition is particularly pronounced adjacent to carbonate platforms where alternate immersion exposure of the flat platform top results in carbonate highstand deposition and siliciclastic lowstand deposition in contrast small to moderate amplitude sea level drops in distally steepened ramp settings may expose only the inner part of the gently sloping shelf resulting in lowstand deposition of mixed sil ciclastic allodapic footnote 3 carbonate sediments along active margins tectonic uplift and subsidence of sediment source areas act as additional major controls on deposition of siliciclastic carbonate basinal cycles two of the most important tectonic effects are 1 uplift of siliciclastic sediment source areas resulting in increased erosion and swamping of carbonate shelf sources and 2 exposure or immersion of shelf carbonate sediment source areas due to vertical tectonic movements most published seismic stratigraphic studies of sea level control on deep sea sedimentation focus on lowstand deposition of siliciclastic sediment and commonly neglect the contribution of allodapic carbonate sediment deposited during sea level highstands however the examples discussed in this paper indicate that highstand carbonate deposits may make up a significant proportion of many hybrid carbonate siliciclastic basinal sequences

p t evolution of metasediments from the eclogite zone south central tauern window austria abstract petrologic data on the paragenesis of i kyanite zoisite marbles and ii garnet chloritoid quartz mica schists are presented with the goal of providing constraints on the pressure temperature evolution of the eclogite zone tauern window austria the peak metamorphic assemblages in the two rock types are i kyanite zoisite dolomite quartz zoisite muscovite dolomite calcite quartz and ii garnet chloritoid kyanite muscovite quartz epidote dolomite zn staurolite the estimated peak metamorphic conditions are 19 2 kbar 590 20 c secondary alteration of the kyanite zoisite marbles was accomplished in two stages the early stage resulted in the production of margarite paragonite secondary muscovite and chlorite and the later stage resulted in the formation of sudoite a di trioctahedral mg al layer silicate and kaolinite the early alteration is bracketed at conditions between 3 and 10 kbar 450 550 c and the later alteration between 200 and 350 c p 3 kbar the p t path is characterized by maximum burial to approximately 19 kbar 60 70 km at 590 c followed by nearly isothermal decompression to approximately 10 kbar 30 km and then more gradual decompression with cooling to approximately 3 kbar 10 km alteration was apparently accomplished by the influx of h 2 o rich fluids with the composition of the fluid locally buffered by the mineral assemblage

the relief canyon gold deposit nevada a mineralized solution breccia the relief canyon gold deposit in the humboldt range of western nevada is a low grade high tonnage orebody of tertiary or younger age the host rocks include limestones of the triassic cane spring formation which are overlain by shales of the triassic grass valley formation the rocks were folded and metamorphosed to greenschist grade during jurassic and cretaceous regional tectonic activity mesozoic thrusting may have occurred along the shale limestone contact but evidence has been obscured by later hydrothermal activity the sedimentary rocks were nominally offset along several late tertiary normal faults related to uplift of the range the upper part of the cane spring formation is composed of a poorly sorted breccia composed of limestone clasts with a clay matrix irregular pockets within this zone are filled with clay to pebble sized fragments derived from the grass valley shale the enclosing limestone beds were tilted moderately to the southwest during mesozoic deformation whereas bedding within these pockets is generally horizontal indicating post tilting deposition of the sediments the sediments show graded bedding and other sedimentary features that indicate deposition from flowing water thermally mature carbon derived from the limestone is also concentrated in small pockets in the matrix the breccia unit is likely the product of low temperature solution brecciation ground water dissolved much of the limestone directly beneath the shales progressively creating irregular cavities and the breccia sediments derived from the overlying grass valley shale were fiuvially deposited as a matrix to the developing solution breccia episodic pulses of hydrothermal fluids were introduced along faults and possibly mixed with the ground water in the breccia zone initially jasperoids formed along the faults but later hydrothermal pulses introduced gold silica and fluorine into both the early jasperoids and the unconsolidated cave fill sediments to form the orebody continued solution related brecciation chaotically disrupted the gold deposit gold fluorite pyrite silver calcite and fine grained silica are the principal hydrothermal minerals in the deposit gold was deposited as micron sized flakes of native gold and rarely as electrum during a relatively late stage of silicification of the jasperoids the carbon rich zones and the clay rich matrix of the breccia fluorite was deposited with and later than the gold in the jasperoids and it in part replaced the clay rich breccia matrix antimony arsenic mercury and thallium are directly associated with gold in the orebody the deposit formed at a relatively shallow depth on the basis of fluid inclusion data late stage hydrothermal fluids related to gold and fluorite deposition were extremely dilute and had temperatures near 200 degrees c the fluid inclusions in fluorite show no evidence for boiling but porous crackle breccias in the jasperoids suggest that hydrobrecciation took place

stratigraphy and geochronology of pitfall accumulations in caves and fissures bermuda abstract deep fractures fissures and avens skylights in limestone cave roofs create natural traps for sediments and biota fissures fill quickly with surface sediment and organisms soon after opening debris cones are formed as materials fall wash or drift on air through openings in cave skylights such deposits in admiral s and grand canyon cave bermuda contain distinct beds and are composed of mixtures of sediment and charcoal together with fossils of land snails crabs birds reptiles and bats the pitfall accumulations were periodically sealed over by calcite flowstone a stratigraphic record of surface activity and fauna through both glacial and interglacial periods has been preserved the succession also provides an ideal setting in which to compare several geochronological methods calibrated 14 c ages on charcoal and shells provide dated horizons at 1600 12 800 and about 35 000 14 c yr bp thermal ionization mass spectrometric tims ages on several flowstone layers constrain the entire sequence in the admiral s cave sequence between 126 300 900 yr termination ii and historical times a continuous relative age record generated by amino acid epimerization aae geochronology d alloisoleucine l isoleucine or aile ile on the pulmonate land gastropod poecilozonites verifies the biostratigraphy reveals a minimal degree of mixing between stratigraphic units and establishes an independent temporal link between the subterranean and subaerial deposits of bermuda this convergence between stratigraphy and geochronology yields a precisely dated succession from the oceanic island of bermuda and thus presents a unique opportunity to assess the rates and processes of evolutionary and climate change during that interval

amino acid paleothermometry of quaternary ostracodes from the bonneville basin utah abstract unlike many other proxy climate recorders temperature dependent chemical reactions that take place in fossils are independent of paleoprecipitation changes and therefore allow paleotemperatures to be calculated uniquely in this study i use the extent of amino acid racemization in fossil ostracode shells to reconstruct the temperature history of the bonneville basin utah the enantiomeric composition d l ratios of 64 ostracode samples each comprising an average of 18 subsamples from 25 sites were analyzed by reverse phase hplc the effective diagenetic temperature edt for five intervals of the quaternary including the last full glacial period was calculated for two amino acids aspartic and glutamic acids errors associated with the edt calculations were derived using a monte carlo procedure age control was provided by both new and previously published ams 14 c luminescence tephra and amino acid geochronology the edt for the southern bonneville basin during the middle pleistocene interval from 620 150 ka oxygen isotope stages ois 16 6 was 5 7 1 5 c this compares with an edt of 10 9 1 3 c for the late holocene last 5 8 cal ka and a current mean annual temperature of about 9 4 c at nearby sites 40 n latitude the edt then decreased to 3 3 1 3 c for the interval from ois 6 2 150 12 cal ka during the last full glacial period 24 12 cal ka ois 2 the edt was 1 1 2 5 c or about 10 3 c lower than during the late holocene paleotemperatures this low suggest that reduced evaporation rather than increased precipitation could have accounted for the increased effective moisture and the growth of lake bonneville

preferred lattice orientations of plagioclase from amphibolite and greenschist facies rocks near the insubric line western alps abstract preferred lattice orientations of plagioclase measured by the universal stage from deformed amphibolite and greenschist facies rocks near the insubric line western alps reflect the type and orientation of the strain system either 001 or 010 are oriented parallel or subparallel to the schistosity and form more or less complete girdles around the stretching direction by the preferred orientation patterns dominant 010 001 slip is indicated and additionally slip on 001 parallel to the a direction possibly at somewhat higher temperatures and or at a higher an content of the plagioclase it is suggested that obliquities of the symmetry planes of the orientation patterns against the principle axes of strain are related to the sense of shearing

the enigma of 3400 years bp coastal oolites in tropical northwest western australia why then why there oolites crop out along the northwestern coast of western australia at port smith about 80 km swof broome an oolitic coastal ridge truncated by marine erosion exposes subtidal intertidal and supratidal aeolian facies the deposits are firmly indurated and composed of about 75 tangentially and moderately thickly layered aragonitic ooid grains with over 90 quartz nuclei subtidal sedimentary structures are exposed about a metre above the present high tide mark hinting that sea level may have been somewhat higher when the shoreline was formed however the macrotidal range of up to 7 m and the possibility of cyclonic surges along the coast precludes unequivocal determinations on this point whole rock amino acid racemisation aar geochronology epimerisation of isoleucine d alloisoleucine l isoleucine or a i on each facies of the oolite outcrop averaged 0 106f0 013 n 10 the modern beach contains fewer ooids 30 and nearly half of these are stained brown grey or black perhaps as a result of burial reduction and or mineralization a higher older mean and large standard deviation in whole rock amino acid ratio of 0 145f0 067 n 2 supports our inference that ooids on the modern beach were reworked from fossil deposits reverse phase chronostratigraphy rpc on individual ooid grains holds tremendous promise in this preliminary study rpc results show a narrow variation of d l values cv 6 11 and yield nearly identical d l asp means from light coloured fossil ooids 0 307f0 018 n 17 light 0 323f0 026 n 12 and dark coloured ooids 0 298f0 027 n 10 from the active beach face when compared to a i ratios from 14 c dated mid holocene ooids in the bahamas the mean a i from port smith reflects an age of ca 3500 4500 years that is in agreement with a calibrated ams 14 c age of 3370f50 calendar years bp on the same material thus the ooids were formed transported emplaced strongly cemented and largely eroded from the beach ridge in only 3400 years the environmental conditions that underlie a pulse of ooid deposition during a brief period of the mid holocene almost certainly involve extensive tidal inlets in the area a possible mid holocene oscillation 1 2 m above present and a subsequent fall to present level that terminated the process apparently a unique combination of factors produced ooids here and in only a handful of other sites in australia and the indian ocean d 2005 elsevier b v all rights reserved

low latitude glacial cooling in the southern hemisphere from amino acid racemization in emu eggshells the record of natural climate variability over glacial interglacial timescales provides a framework from which a better mechanistic understanding of the climate system may be derived but this approach is limited by the number and distribution of well dated and reliable palaeoenvironmental archives particularly vexing is the conflicting evidence for low latitude cooling during the last glacial maximum and the apparent synchrony in glacial activity between the hemispheres despite out of phase insolation forcing1 4 here we utilize the temperature dependent amino acid racemization reaction in radiocarbon dated emu eggshell fragments from the continental interior of australia to reconstruct low altitude subtropical temperatures for the past 45 kyr racemization rate changes indicate that millennial scale average air temperatures were at least 9 c lower between 45 and 16 kyr bp than since 16 kyr bp a temperature change of this magnitude coupled with other low latitude palaeotemperature records that indicate substantial cooling3 4 must reflect global processes which we speculate involved glacial age reduction in atmospheric water vapour content

dating late quaternary planktonic foraminifer neogloboquadrina pachyderma from the arctic ocean using amino acid racemization the long term rate of racemization for amino acids preserved in planktonic foraminifera was determined by using independently dated sediment cores from the arctic ocean the racemization rates for aspartic acid asp and glutamic acid glu in the common taxon neogloboquadrina pachyderma were calibrated for the last 150 ka using 14c ages and the emerging quaternary chronostratigraphy of arctic ocean sediments an analysis of errors indicates realistic age uncertainties of about 12 for asp and 17 for glu fifty individual tests are sufficient to analyze multiple subsamples identify outliers and derive robust sample mean values the new age equation can be applied to verify and refine age models for sediment cores elsewhere in the arctic ocean a critical region for understanding the dynamics of global climate change

aspartic acid geochronology of sediments from the ocean margin off of india abstract aspartic acid racemization was studied in the clay and coarse fractions of sediments from southwestern bay of bengal core 1 in order to understand the role of terrestrial organic matter in the amino acid geochronology of indian marginal sediments conventional radiocarbon ages were determined for the coarse carbonate fraction 25 m of sediments the core covering an age back to 40 kyr bp aspartic acid racemization rate constants k asp were calculated for clay and coarse fractions of bulk sediments using a first order kinetic model and three horizons with constant k asp values were identified corresponding to the periods from 0 to 5 5 kyr 5 5 to 19 kyr and 19 kyr best fit models of high significance were derived from the relationship between aspartic acid d l ratio and calibrated radiocarbon ages as an alternative to racemization rate constants to test the applicability of these first order kinetic and logarithmic models derived for core 1 they were used to calculate ages for another sediment core core 2 calculated aspartic acid ages being consistent with radiocarbon ages however the logarithmic model gave better results than the first order kinetic model for older samples suggesting that the logarithmic model is a better choice for the amino acid geochronology of indian margin sediments for both sediment fractions aspartic acid ages based on the logarithmic model gave similar ages consistent with radiocarbon ages and suggesting that there is no significant difference in aspartic acid racemization between both fractions of bulk sediment as a result the clay fraction can also be used for amino acid dating of indian margin sediments

aspartic acid racemization dating of holocene brachiopods and bivalves from the southern brazilian shelf south atlantic abstract the extent of racemization of aspartic acid asp has been used to estimate the ages of 9 shells of the epifaunal calcitic brachiopod bouchardia rosea and 9 shells of the infaunal aragonitic bivalve semele casali both taxa were collected concurrently from the same sites at depths of 10 m and 30 m off the coast of brazil asp d l values show an excellent correlation with radiocarbon age at both sites and for both taxa r2site 9 b rosea 0 97 r2site 1 b rosea 0 997 r2site 9 s casali 0 9998 r2site 1 s casali 0 93 the asp ratios plotted against reservoir corrected ams radiocarbon ages over the time span of multiple millennia can thus be used to develop reliable and precise geochronologies not only for aragonitic mollusks widely used for dating previously but also for calcitic brachiopods at each collection site bouchardia specimens display consistently higher d l values than specimens of semele thermal differences between sites are also notable and in agreement with theoretical expectations as extents of racemization for both taxa are greater at the warmer shallower site than at the cooler deeper one in late holocene marine settings concurrent time series of aragonitic and calcitic shells can be assembled using asp racemization dating and parallel multi centennial to multi millennial records can be developed simultaneously for multiple biomineral systems

on the measurement of plagioclase lattice preferred orientations abstract there are two major difficulties in measuring plagioclase lattice preferred orientations lpos by u stage the first which is caused by dependence of the lpo determination on anorthite content cannot be overcome using the u stage method at present the second difficulty which is caused by the dependence on orientation of thin sections can be overcome by measuring all twinned grains in any two orthogonal sections compared with previous methods published in the literature the present method using two rather than three orthogonal sections is more statistically meaningful and time saving in practice this method was used for measuring lpos of plagioclase an 50 from a typical anorthosite mylonite deformed under the granulite facies conditions in the morin ductile shear zone within the canadian grenville tectonic province

pliocene holocene evolution of depositional conditions in the eastern mediterranean role of anoxia vs productivity at time of sapropel deposition a multiproxy geochemical study of nine sapropel layers from odp hole 964a odp leg 160 in the eastern mediterranean spanning the pliocene holocene time interval provides new insights into the evolution of sapropel deposition paleoenvironmental proxies were used for reconstruction of productivity ba derived from marine barite oxygen conditions trace metal ratios and sedimentary regime clay minerals detrital elements these proxies reveal a significant increase in river runoff relative to decreasing aeolian input during sapropel deposition over the whole time interval ba excess supports the argument that a significant increase in export productivity is the main triggering mechanism for sapropel deposition although preservation also played an important role furthermore major differences exist in depositional conditions including both oxygenation and productivity since the pliocene productivity fluctuated substantially and was higher during the pliocene and pleistocene than during the holocene at the same time decreasing oxygen availability parallels the enhanced productivity dysoxic to anoxic conditions appear to coincide with marine productivity maxima thus suggesting that oxygen depletion may be linked to greater consumption rather than restricted circulation this correspondence supports the hypothesis that productivity fluctuations resulting from climate oscillations were the main cause of enhanced organic matter contents and also a main controlling factor for reduced oxygen availability

amino acid epimerization in planktonic foraminifera suggests slow sedimentation rates for alpha ridge arctic ocean interpretations of the palaeoclimatic and palaeooceanographic histories of the arctic ocean1 2 have been hampered by conflicting chronologies obtained using different dating methods magnetostratigraphic and micropalaeontological data1 4 have suggested a sedimentation rate of 1 mm kyr 1 whereas the rate indicated by amino acid epimerization analyses on foraminifera5 is an order of magnitude higher to establish a firm chronology for cores from the alpha ridge arctic ocean and to help resolve the controversy between the ages assigned by different dating methods we have carried out detailed amino acid epimerization analyses on planktonic foraminifera neogloboquadrina pachyderma sinistral from a long gravity core assuming that the temperature in the arctic ocean did not exceed 3 c during the past 1 myr the alloisoleucine isoleucine alle ile ratios obtained from this core suggest a sedimentation rate of 1 mm kyr 1 supporting previous magnetostratigraphic and micropalaeontological studies

tropical view of quaternary sequence stratigraphy siliciclastic accumulation on slopes east of the great barrier reef since the last glacial maximum generic models of continental margin evolution predict that siliciclastic fluxes to slopes should be maximal and minimal during major sea level lowstands and transgressions respectively here we document the opposite for the northeast australian margin the largest extant mixed siliciclastic carbonate depositional system cores from slopes of this margin consistently contain siliciclastic rich intervals 0 3 1 m thick in the upper few meters radiocarbon dates of planktonic foraminifera show that this interval was deposited between 12 and 7 ka and represents greatly increased siliciclastic fluxes during late transgression this massive terrigenous discharge to slopes occurred along at least 450 km of the margin irrespective of modern variations in bathymetry or climate although we cannot dismiss a significantly different early holocene climate with greatly enhanced sediment discharge available data instead suggest that rivers aggraded on the shelf during lowstand because of an extensive subaerially exposed reef system this phenomenon may occur on other margins rimmed by reefs requiring a major revision of concepts used to interpret mixed siliciclastic carbonate systems

thrust regime and transpression regime tectonics in the tauern window eastern alps below the penninic nappes of the tauern window the deepest level of the alpine thrust system is exposed in the parautochthonous sedimentary sequence of helvetic facies

the western north atlantic record of mis 13 to 10 changes in primary productivity organic carbon accumulation and benthic foraminiferal assemblages in sediments from the blake outer ridge odp site 1058 abstract we used multiple paleoceanographic proxies to examine sediments from the blake outer ridge odp site 1058 2996 m water depth that span the mis 13 10 time interval benthic foraminiferal 13 c organic 13 c and total 15 n values are lower in mis 12 and 10 than in ms 11 and indicate glacial interglacial changes in both thermohaline circulation and ocean wide biogeochemical processes that affect deep and surface waters three time intervals of higher productivity as evidenced by higher organic carbon accumulation rates 1 6 4 5 g m 2 yr 1 occur at the end of mis 13 and during the early and late parts of mis 11 in association with the transition from obliquity minima to obliquity maxima benthic faunas in these intervals show a distinct increase in opportunistic species that feed on phytodetritus epistominella exigua or are adapted to elevated but intermittent organic carbon fluxes bulimina aculeata and bulimina marginata and that imply episodes of recurrent phytoplankton blooms at the surface and consequent export of labile organic matter to the seafloor late interglacial mis 11 3 is a time of low organic carbon fluxes 2 yr 1 and is characterized by higher abundances of epifaunal benthic foraminiferal taxa cibicidoides wuellerstorfi gyroidina spp gyroidinoides spp and nuttallides umbonifera that are typical of modern oligotrophic environments in contrast during glacial mis 12 and 10 higher organic carbon fluxes 0 5 g m 2 yr 1 and benthic assemblages dominated by infaunal taxa uvigerina spp and bulimina alazanensis indicate sustained organic carbon delivery and diminished pore water oxygenation

sea level and surface water change in the western north atlantic across the oligocene miocene transition a palynological perspective from iodp site u1406 newfoundland margin abstract the oligocene miocene transition omt 23 1 ma terminates the late oligocene warming trend and is marked by a transient large amplitude expansion of antarctic ice sheets the associated glacial maximum which is expressed by a 1 positive shift in benthic foraminiferal oxygen isotope values is commonly referred to as the mi 1 isotope event whereas the causes for the glacial maximum at the omt are intrinsically connected to southern hemisphere ice sheet dynamics the behavior of the surface ocean in the northern hemisphere during this time is poorly known to contribute to a better understanding of the paleoceanographic evolution during the omt in the higher latitude north atlantic we have analysed both marine and terrestrial palynomorphs from integrated ocean drilling program iodp site u1406 offshore newfoundland this site has yielded a complete omt section and exhibits a high quality magnetostratigraphy that provides precise age control and allows reliable correlation to other records beyond newfoundland our palynological data which span the interval from 23 3 to 22 5 ma and have a mean temporal resolution of 11 9 kyrs show strong 110 kyr eccentricity paced oscillations during the earliest miocene these oscillations are in phase with similar cyclicity identified in previously published benthic foraminiferal oxygen isotope records more specifically a pronounced sea level variability is documented by the abundances of neritic dinoflagellate cysts dinocysts and terrigenous palynomorphs which both reach maxima during peak glacial intervals as inferred from previously published south atlantic benthic oxygen isotope data a decline in the abundance of warmer water dinocysts suggests a surface water cooling offshore newfoundland from the latest oligocene onwards surface water productivity as derived from the ratio between heterotrophic and autotrophic dinocysts remained generally low throughout the studied interval notably this ratio does not exhibit any correlation with changes in surface water temperature which is estimated from the ratio of warm water over cold water dinocysts together with the consistently low surface water productivity the lack of a correlation between surface water productivity and temperature makes it highly unlikely that the observed paleoceanographic change was caused by a southward migration of the arctic front instead we argue that our data may document an enhanced influence of the proto labrador current on surface waters offshore newfoundland during the earliest miocene that suppressed the influence of the gulf stream in this region of the northwest atlantic we speculate that the enhanced influence of the proto labrador current was triggered by cooling of the northern hemisphere and possibly modulated by high latitude sea ice expansion

testing high resolution magnetic susceptibility and gamma radiation methods in the cenomanian turonian upper cretaceous gssp and near by coeval section abstract low field mass specific magnetic susceptibility and gamma radiation spectra grs field and laboratory data sets for two upper cretaceous marine sedimentary sequences representing the cenomanian turonian c t boundary in the western interior seaway in central colorado have been measured sections including the c t global boundary stratotype section and point gssp and a one kilometer distant co eval sequence the s section it has previously been established that both and grs data sets are controlled by detrital eolian fluxes into the marine environment although the effect of weathering if any on these parameters when exposed in outcrop is not well documented in addition these parameters are controlled by differing detrital eolian components that may be derived from different sources or be differentially concentrated within the marine system of great interest is 1 how well these data sets record climate cycles 2 how the and grs data are affected by weathering and 3 how well the two methods support each other reported here are the results of a number of field and laboratory experiments designed to evaluate instruments and how and grs data sets co vary and to test their usefulness as correlation tools in stratigraphy results show that both and 40k data sets from laboratory measurement on samples collected in the field where rocks are relatively fresh are generally well correlated respond closely to climate and the corresponding detrital eolian flux into the marine environment and can be used for a rough proxy for each other however weathering appears to affect the 40k data by removing 40k thus reducing correlation potential although does not appear to suffer as badly in more weathered sections and good correlations between sections remain field grs measurements produce a broadly smoothed data set that regionally can be very useful for correlation although potential global correlations are not tested here using data reported here and comparing these data to a 100 kyr cyclic eccentricity e1 climate model for the upper cretaceous at 93 9 ma shows that and 40k data measured in the laboratory can be used to build floating point time scales that produce essentially equivalent results as do other studies using absolute dates

plagioclase and quartz preferred orientations in a low grade schist the roles of primary growth and plastic deformation albite in a lower greenschist facies haast schist from new zealand has a maximum of poles to 001 parallel to the elongation direction 010 forms a girdle about grain length plastic deformation with slip dominantly on 010 001 is rejected as the orienting mechanism because 1 the relationship of crystal axes to grain length would require multiple slip systems incompatible with the lack of rotation of albite twin planes 2 euhedral terminations and other textural features indicate primary crystallization 3 albites in quartzose layers are less elongate than those in sheet silicate rich layers the albite fabric is ascribed to growth anisotropy and competition in response to stress driven solution and growth during formation of metamorphic segregation layering this explanation is compatible with the common observation that plagioclase is brittle at low metamorphic grades associated weak quartz c axis fabrics are ascribed to plastic deformation and this deformation enhanced a dimensional preferred orientation already established by primary growth

the accuracy of mid pliocene δ 18 o based ice volume and sea level reconstructions abstract understanding the sensitivity of the polar ice caps to a modest global warming 2 3 c above preindustrial is of paramount importance if we are to accurately predict future sea level change knowledge that will inform both social and economic policy in the coming years however decades of study of the pliocene 2 6 5 3 ma an epoch in recent earth history characterized by atmospheric co2 levels similar to today have so far failed to provide definitive sea level and ice volume estimates for that time here we review the sources of uncertainty in the paired mg ca 18o methodology used to estimate past sea level ice volume and ocean temperature as well as discuss common assumptions that may bias our interpretation of ocean geochemical records including the lr04 benthic 18o stack a global compilation of 57 oxygen isotope records that forms the standard template of climate change history for the last 5 3 million years

alpine metamorphism in the south east tauern window austria 1 p t variations in space and time the pennine rocks exposed in the south east tauern window austria contain mineral assemblages which crystallized in the mid tertiary late alpine regional metamorphism the pressure and temperature conditions at the thermal peak of this event have been estimated for rocks at four different structural levels using a variety of published and thermochemically derived geobarometers and geothermometers the results are a in the garnet chlorite zone 2 5 km structurally above the staurolite biotite isograd t 490 50 c p 7 1 kbar b within 0 5 km of the staurolite biotite isograd t 560 300c p 7 1 kbar c in the staurolite biotite zone c 2 5 km structurally below the staurolite biotite isograd t 610 30 c p 7 6 1 2 kbar d in the staurolite biotite zone 3 4 km structurally below the staurolite biotite isograd t 630 40 c p 6 6 1 2 kbar the pressure estimates imply that the total thickness of overburden above the basement cover interface in the mid tertiary was c 26 4 km this overburden can only be accounted for by the austro alpine units currently exposed in the vicinity of the tauern window if the altkristallin the middle austro alpine nappe was itself buried beneath an upper austro alpine nappe or nappe pile which was 7 4 km thick at that time the occurrence of epidote margarite quartz pseudomorphs after lawsonite in garnet indicates that part of the mesozoic pennine cover sequence in the south east tauern experienced blueschist facies conditions t 450 c p 12 kbar in early alpine times evidence from the central tauern is used to argue that the blueschist facies imprint post dated the main phase of tectonic thickening d1a and was thus a direct consequence of continental collision combined oxygen isotope and fluid inclusion studies on late stage veins thought to have been at lithostatic pressure and in thermal equilibrium with their host rocks during formation suggest that they crystallized from aqueous fluids at 1 1 0 4 kbar and 420 20 c early alpine late alpine and vein formation p t constraints have been used to construct a p t path for the base of the mesozoic cover sequence in the south east tauern window the prograde part of the p t path between early and late alpine metamorphic imprints is unlikely to have been a smooth curve and may well have had a low dp dt overall the decompression presumably due to erosion which occurred immediately before the thermal peak and possibly also earlier in the tertiary was probably partly or completely cancelled by the effects of early to mid tertiary d2a tectonic thickening the thermal peak of metamorphism was followed by a phase of almost isothermal decompression which implies a period of rapid uplift in the middle tertiary the peak metamorphic p t estimates are compared with the solutions of england s 1978 one dimensional conductive thermal model of the eastern alps and are shown to be consistent with the idea that the late alpine metamorphism was caused by tectonic burial of the pennine zone beneath the austro alpine nappes in the absence of extraneous heat sources such as large intrusions at depth

influence of the amazon river development and constriction of the central american seaway on middle late miocene oceanic conditions at the ceara rise abstract sediment samples from odp 154 site 926a ceara rise western equatorial atlantic ocean spanning the neogene from 12 8 to 9 2 ma were investigated on their calcareous dinoflagellate contents to better understand the oceanographic changes in relation to the closure of the central american seaway and the development of the amazon river intervals with increased cyst accumulation rates and dissolution sensitive species occur from 12 4 ma onward they correspond to periods of enhanced north atlantic deep water production indicating the presence of this water mass at the research site during these intervals this suggests that pulses of north atlantic deep waters sporadically flew into the south atlantic related to uplift phases of the panama sill at about 11 2 ma the first appearance of leonella granifera indicates river influence at the sample site this first indication of river influence in the western equatorial atlantic can be linked to the developing amazon river the cyst association changes at about 11 2 ma from almost monospecific to highly diverse and the permanent presence and increased abundance of l granifera suggest that river waters were able to reach the study site by now probably as a result of the southward flowing north brazil current after 10 5 ma the cyst association indicates a decrease in amazon influence at site 926a this change can be correlated to a reducing inflow of pacific waters through the central american seaway leading to a reverse of the north brazil current to its modern northwards flow pattern

short term climate changes in the southern aegean sea over the last 48 000 years abstract high resolution palaeoenvironmental changes corresponding to a mean time interval of 450 years covering the last 48 000 years were examined in a core from the cretan basin in the southern aegean sea the intensity and duration of the climatic and oceanographic events were determined by examining the compositional changes in the planktonic foraminifera and pollen assemblages along with the 18o signal of globigerinoides ruber a reconstruction of sea surface temperatures was attempted using the modern analogue technique mat in total 10 stadials and 6 interstadials occurred over the last 48 000 years these fluctuations in climatic conditions coincide with fluctuations documented in the western and central mediterranean and seem to be associated with dansgaard oeschger events some of these climatic fluctuations are correlated with changes in the vegetation in the surrounding land between 48 and 10 cal kyr bp the most pronounced stadials occurred at 41 cal kyr bp c69 st10 and at 13 cal kyr bp c69 st4 these events are characterized by i high positive 18o values of globigerinoides ruber ii drops in sst and iii increases in aridity these events may be correlated with the heinrich h4 event and the younger dryas event respectively two other stadials at 23 cal kyr bp c69 st6 and at 16 cal kyr bp c69 st5 which are characterized by increases in the abundance of the cold plaktonic foraminifera species and increases in aridity may be correlated with the h2 and h1 events respectively the dominant planktonic foraminiferal species during the stadials witch are correlated with the heinrich events were turborotalita quinqueloba and globorotalia scitula the most pronounced interstadials occurred between 39 5 and 38 5 cal kyr bp c69 ist6 and between 25 and 24 cal kyr bp c69 ist3 and are characterized by depletion in 18o values increases in sst and increases in humidity the former event coincides with the formation of the sapropelitic layer s2 in the holocene the most pronounced stadial occurred between 8 and 6 5 cal kyr bp c69 st2 during the interruption of s1 and is characterized by a reduction in sst and an increase in aridity the most pronounced interstadials of holocene occurred during the formation of s1a and s1b between 9 and 8 cal kyr bp c69 ist1 and between 6 5 and 5 5 cal kyr bp c69 ist2 respectively these events are characterized by depletion in 18o values increased sst and an increase in humidity as is indicated by the expansion of temperate evergreen and mediterranean taxa in the pollen record

mediterranean outflow strengthening during northern hemisphere coolings a salt source for the glacial atlantic abstract high resolution grain size and magnetic susceptibility records from the eastern gulf of cadiz site md99 2339 1170 m water depth reveal contourites formed by the mediterranean outflow mow during the last 47 kyr bp oscillations in the mow s intensity occurred in phase with greenland temperature variations with a stronger outflow during northern hemisphere coolings such as dansgaard oeschger stadials heinrich events and the younger dryas benthic 13c data implies the western mediterranean deep water as one of the main sources feeding the outflow current while differential changes in the properties of the mediterranean source and entrained north atlantic central water largely control the mow s strength detailed studies for heinrich events 1 4 and 5 show that the flow strength peaked only when subtropical surface waters prevailed in the eastern gulf of cadiz while incursions of icebergs and subpolar surface water were not favorable for the mow s intensification as the mow was strong when the atlantic s thermohaline circulation thc was weakened the heat and salt injected by the mow into the intermediate north atlantic waters might have preconditioned the thc to switch from the stadial to the interstadial mode

reconstructing human landscape interactions in the ancient mediterranean harbour of cartagena spain here we sought to reconstruct the pleistocene and holocene evolution of cartagena bay therefore 16 borehole cores were analysed with the following aims 1 to define a chronological framework 2 to obtain data on the palaeoenvironment and 3 to establish the relationship with human activities especially focused on the reconstruction of the carthago nova also known as qart hadasht conquest a total of 147 samples were recovered for amino acid racemisation aar dating 32 for radiocarbon dating 14c and 159 for sedimentological palaeontological and biomarker determination these approaches allowed us to elucidate the evolutionary phases of the palaeolandscape in cartagena the simultaneous use of aar and 14c dating allowed the discrimination of spurious ages and the establishment of a chronological scale during the marine isotope stages mis 7 and 5 the sea level sl in cartagena bay was almost the same as today an alluvial plain developed in the northern area and a delta was formed by

chronology of marine sediments by the racemization reaction of aspartic acid in planktonic foraminifera abstract racemization reaction rate constants of aspartic acid kasp were obtained and compared in bulk foraminifera and in a dissolution resistant foraminiferal species pulleniatina obliquiloculata obtained from marine sediments through ca 20 000 yrbp in the western equatorial pacific the average kasp values were 0 63 10 5 yr 1 for bulk foraminifera and 0 72 10 5 yr 1 for p obliquiloculata this disparity in kasp values could be attributed to the presence of dissolution vulnerable foraminifera in bulk foraminifera it is believed that the leaching of racemized free amino acid having high d l values when the calcareous test was subjected to dissolution through geological time could have led to a lower value of kasp in bulk foraminifera this study thus demonstrates that it is important to analyze a single species of planktonic foraminifera resistant to dissolution in order to avoid spurious changes in kasp values if this condition were satisfied aspartic acid racemization is shown to be extremely useful not only for determining the geological age of marine sediment but also to assess the quality of the sedimentary core stratigraphy

a review of the tagus river tufa deposits central spain age and palaeoenvironmental record here we determined the aminostratigraphy and aminochronology of tufa deposits located in central spain associated w i t h the tagus river and some o f its tributaries the henares dulce cifuentes ruguilla trabaque escabas and guadiela rivers w e used aspartic acid and glutamic acid racemization ratios obtained from the ostracod herpetocypris reptans tufa accumulations were found to be of different origins those in t h e henares cifuentes and ruguilla rivers are of paludal origin w h i l e those in t h e dulce and tagus rivers are o f fluvial origin a generally g o o d correspondence was found b e t w e e n the age o f the deposits and the position of the terraces above the current thalweg however the geomorphological evolution of the henares cifuentes and ruguilla rivers infilling of pre existing valleys has produced deposits of distinct ages at the same elevation above the current river thalweg and sometimes older tufas are located b e l ow younger ones we distinguished eight main tufa deposition episodes these occurred predominantly during even marine isotopic stages mis at 4 0 6 90 mis 11 2 6 4 68 mis 7e 189 4 0 mis 7a 130 27 mis 6 5e 101 2 5 mis 5c 3 2 10 mis 3 1 4 4 mis 1 a n d 6 2 mis l k a these results are in agreement w i t h the dating of similar deposits from nearby areas and other zones of s p a i n a n d europe the tufa stable isotope compositions were similar to other examples in central and southern spain a n d their plot falls in the same field as other lowland european stream tufas o x y g e n stable isotopes were influenced mainly b y temperature a n d rainfall the 51 3c values indicated a major effect o f soil derived carbon rather t h a n carbon from the catchment area but moderated in each tributary b y evaporation flow regime and biological effects photosynthesis

pleistocene stratigraphy in the devils hole area central north sea foraminiferal and amino acid evidence a detailed study of the foraminiferal assemblages from the 229 1 m deep core 81 34 in the central north sea has been combined with a series of measurements of the isoleucine epimerisation of foraminiferal tests a total of 17 foraminiferal zones have been established and both the faunal compositions and the amino acid values suggest that a major part of the sequence represents deposits of early and middle pleistocene age only the uppermost zone is referred to the late pleistocene the sequence mainly comprises a series of marine zones from cold periods but with some barren possibly non marine intervals in between only two of the foraminiferal zones can be referred to interglacial periods the oldest one of these defined here as the devils hole interglacial may belong to the latter part of the cromerian complex while the upper warm interval is correlated with the holsteinian of northwest europe on the basis of its amino acid values a detailed stratigraphical correlation between core 81 34 and the neighbouring core 81 29 is suggested on the basis of their foraminiferal content palaeomagnetic evidence and amino acid measurements from both cores a characteristic feature of both sequences is that most of the quaternary record is missing similar episodic patterns of deposition and erosion have been reported previously from the north sea area

textures and c axis orientations of deformed quartz crystals from porphyric dikes of the alpine root zone western alps deformation textures and c axis preferred orientations of quartz phenocrysts from porphyric dikes of the alpine root zone have been formed under conditions of greenschist to low amphibolite facies it is shown that the deformation textures as shear planes and kink bands boudins grain boundary sutures subgrains coarse and fine recrystallized grains deformation lamellae and fractures are developed in a chronological sequence during first increasing and later decreasing temperatures

alpine metamorphism in the south east tauern window austria 2 rates of heating cooling and uplift existing geochronological data are reviewed and new rb sr k ar and 39ar 40ar ages are presented including a suite of 33 mica ages from a 20 km north south tunnel section these data are discussed in relation to the thermal history from the overthrusting of the autroalpine nappes c 65 myr ago to the present the earliest phase of metamorphism involving lawsonite crystallization is associated with emplacement of these nappes subsequently temperatures in the rocks beneath rose at a mean rate of 3 6 c myr until the climax of metamorphism at high structural levels published data indicate an age 35 myr for the metamorphic climax in contrast a new 39ar 40ar step heating age of 23 8 0 8 myr on amphibole from near the base of peripheral schieferhulle closely approximates the age of metamorphism and provides the first clear indication that the climax of metamorphism occurred later at deeper structure levels following the climax near isothermal uplift and erosion reduced pressure to c 1 kbar before white mica closure at 19 myr this implies uplift at 3 mm yr along the tunnel section white mica k ar ages vary systematically from 24 myr to 16 5 myr with position relative to a late 4 km amplitude dome whereas biotite rb sr ages are uniform at 16 5 myr across the whole profile doming is thus dated at 16 5 myr with transient uplift rates 5 mm yr at other times uplift rates were 1 mm yr

prompt transgression and gradual salinisation of the black sea during the early holocene constrained by amino acid racemization and radiocarbon dating abstract the restricted environment of the black sea is particularly sensitive to climatic and oceanographic fluctuations owing to its connection with the mediterranean sea via the narrow bosphorus strait the exact mechanism and timing of the most recent connection between these water bodies is controversial with debate on the post glacial history of the black sea being dependent on radiocarbon dating for numerical ages here we present new 23 accelerator mass spectrometer ams radiocarbon ages on peat and bivalve molluscs supported by the first amino acid racemization aar dating of bivalve molluscs n 66 in the black sea these data indicate infilling of the black sea during the early holocene from an initial depth 107 m below sea level and 72 m below that of the bosphorus sill these data combined with a review of previous radiocarbon ages has enabled a unique perspective on the post glacial black sea a sea level curve based on conventional and ams radiocarbon ages on peat and ams based ages on dreissena sp shells indicate the water level in the earlier lake phase continued until the early holocene to be lower than the bosphorus sill after the younger dryas ended however the absence of ams dated mollusc ages from the shelves of this basin older than the younger dryas is suggestive of sub aerial exposure of the shelves and comparatively lower water levels when the younger dryas began thus post glacial outflow from the black sea occurred through a lowered or open bosphorus seaway basin wide radiocarbon ages on peat indicate a prompt increase in water level from that of the pre existing and unconnected palaeo lake during the earliest holocene 9600 9200 cal a bp mass colonisation of the black sea by mediterranean taxa did not occur until salinity had risen sufficiently a process which took 1000 a or more from the initial transgressive event this gradual change in salinity contrasts with the prompt transgression which would have taken 400 a to occur

timing and warmth of the last interglacial period new u series evidence from hawaii and bermuda and a new fossil compilation for north america abstract the timing and duration of the last interglacial period have been controversial with some studies suggesting a relatively short duration that is orbitally forced and others suggesting a long duration that is at most only partly related to orbital forcing new high precison thermal ionization mass spectrometric tims u series ages of last interglacial corals from hawaii and bermuda test these competing hypotheses waimanalo formation corals from slowly uplifting oahu hawaii range in age from 134 to 113 ka with most ages between 125 and 115 ka combined with published u series ages from nearby lanai the data suggest a long last interglacial period that may have occurred from 136 to at least 115 ka the results indicate that orbital forcing may not have been the only control on ice sheet growth and decay because sea level would have been high at times of relatively low northern hemisphere summer insolation on tectonically stable bermuda deposits from the 200 ka penultimate interglacial period 120 ka peak last interglacial period and 80 ka late last interglacial period high sea stands have been newly dated fossil corals on bermuda are derived from patch reefs that likely were catch up responses to sea level rise it is expected that u series ages of last interglacial corals on bermuda should overlap with but not be as old as the range of corals on oahu last interglacial corals on bermuda give a range of 125 113 ka which supports this hypothesis a large number of emergent marine deposits on hawaii bermuda and along coastal north america have now been dated to the last interglacial period both oahu and bermuda have marine invertebrate faunas with a number of extralimital southern species of mollusks suggesting warmer than present waters during the last interglacial period warmer waters are also suggested for last interglacial localities around most of north america from florida to canada and greenland and baja california to alaska these observations are consistent with similar warm water faunas of last interglacial age reported from japan the mediterranean basin and western australia it is likely that significant changes in ocean currents took place during the last interglacial period with a movement of relatively warm waters to higher latitudes than is the case today

unconformity bounded stratigraphic units ubsus in an italian alluvial plain area recognizing and dating abstract we studied the coastal zone of the tavoliere di puglia plain puglia region southern italy with the aim to recognize the main unconformities and therefore the unconformity bounded stratigraphic units ubsus salvador 1987 1994 forming its quaternary sedimentary fill recognizing unconformities is particularly problematic in an alluvial plain due to the difficulties in distinguishing the unconformities that bound the ubsus so far the recognition of ubsus in buried successions has been made mostly by using seismic profiles instead in our case the unavailability of the latter has prompted us to address the problem by developing a methodological protocol consisting of the following steps i geological survey in the field ii draft of a preliminary geological setting based on the field survey results iii dating of 102 samples coming from a large number of boreholes and some outcropping sections by means of the amino acid racemization aar method applied to ostracod shells and 14c dating filtering of the ages and the selection of valid ages iv correction of the preliminary geological setting in the light of the numerical ages definition of the final geological setting with ubsus identification of a hypothetical or attributed time range htr or atr for each ubsu the former very wide and subject to a subsequent modification the latter definitive v cross checking between the numerical ages and or other characteristics of the sedimentary bodies and or the sea level curves with their effects on the sedimentary processes in order to restrict also the hypothetical time ranges in the attributed time ranges the successful application of aar geochronology to ostracod shells relies on the fact that the ability of ostracods to colonize almost all environments constitutes a tool for correlation and also allow the inclusion in the same unit of coeval sediments that differ lithologically and paleoenvironmentally the treatment of the numerical ages obtained using the aar method required special attention the first filtering step was made by the laboratory rejection criteria a and b then the second filtering step was made by testing in the field the remaining ages among these in fact we never compared an age with a single preceding and or following age instead we identified homogeneous groups of numerical ages consistent with their reciprocal stratigraphic position this operation led to the rejection of further numerical ages that deviate erratically from a larger homogeneous age population which fits well with its stratigraphic position rejection criterion c after all of the filtering steps the valid ages that remained were used for the subdivision of the sedimentary sequences into ubsus together with the lithological and paleoenvironmental criteria the numerical ages allowed us in the first instance to recognize all of the age gaps between two consecutive samples next we identified the level in the sedimentary thickness that is between these two samples that may represent the most suitable ubsu boundary based on its lithology and or the paleoenvironment the recognized units are i coppa nevigata sands nea htr mis 20 14 atr mis 17 16 ii argille subappennine asp htr mis 15 11 atr mis 15 13 iii coppa nevigata synthem nvi htr mis 13 8 atr mis 12 11 iv sabbie di torre quarto stq htr mis 13 9 1 atr mis 11 v amendola subsynthem mlm1 htr mis 12 10 atr mis 11 vi undifferentiated continental unit uci htr mis 11 6 2 atr mis 9 3 7 1 vii foggia synthem tgf atr mis 6 viii masseria finamondo synthem tpf atr upper pleistocene ix carapelle and cervaro streams synthem rpl subdivided into ixa incoronata subsynthem rpl1 htr mis 6 3 atr mis 5 3 ixb marane la pidocchiosa castello subsynthem rpl3 atr holocene x masseria inacquata synthem naq atr holocene the possibility of recognizing and dating quaternary units in an alluvial plain to the scale of a marine isotope stage constitutes a clear step forward compared with similar studies regarding other alluvial plain areas where quaternary units were dated almost exclusively using their stratigraphic position as a result they were generically associated with a geological sub epoch instead our method allowed a higher detail in the timing of the sedimentary processes for example mis 11 and mis 5 5 deposits have been recognized and characterized for the first time in the study area highlighting their importance as phases of sedimentation

timing of metamorphism in the tauern window eastern alps rb sr ages and fabric formation the peripheral schieferhulle of the tauern window of the eastern alps represents post hercynian penninic cover sequences and preserves a record of metamorphism in the alpine orogeny without the inherited remnants of hercynian events that are retained in basement rocks the temperature time deformation history of rocks at the lower levels of these cover sequences have been investigated by geochronological and petrographic study of units whose p t evolution and structural setting are already well understood the eclogite zone of the central tauern formed from protoliths with penninic cover affinities and suffered early alpine eclogite facies metamorphism before tectonic interposition between basement and cover it then shared a common metamorphic history with these units experiencing blueschist facies and subsequent greenschist facies conditions in the alpine orogeny the greenschist facies phase associated with penetrative deformation in the cover and the influx of aqueous fluids reset sr isotopes in metasediments throughout the eclogite zone and cover schists recording deformation and peak metamorphism at 28 30 ma the peripheral schieferhulle of the south east tauern window yields rb sr white mica ages which can be tied to the structural evolution of the metamorphic pile early prograde fabrics pre date 31 ma and were reworked by the formation of the large north east vergent sonnblick fold structure at 28 ma peak metamorphism post dated this deformation but by contrast to the equivalent levels in the central tauern peak metamorphic conditions did not lead to widespread homogenization of the sr isotopes localized deformation continued into the cooling path until at least 23 ma partially or wholly resetting sr white mica ages in some samples these isotopic ages may be integrated with structural data in regional tectonic models and may constrain changes in the style of crustal deformation and plate interaction however such interpretations must accommodate the demonstrable variation in thermal histories over small distances

turbidite paleoseismology along the active continental margin of chile feasible or not abstract much progress has been made in estimating recurrence intervals of great and giant subduction earthquakes using terrestrial lacustrine and marine paleoseismic archives recent detailed records suggest these earthquakes may have variable recurrence periods and magnitudes forming supercycles understanding seismic supercycles requires long paleoseismic archives that record timing and magnitude of such events turbidite paleoseismic archives may potentially extend past earthquake records to the pleistocene and can thus complement commonly shorter term terrestrial archives however in order to unambiguously establish recurring seismicity as a trigger mechanism for turbidity currents synchronous deposition of turbidites in widely spaced isolated depocenters has to be ascertained furthermore characteristics that predispose a seismically active continental margin to turbidite paleoseismology and the correct sample site selection have to be taken into account here we analyze 8 marine sediment cores along 950 km of the chile margin to test for the feasibility of compiling detailed and continuous paleoseismic records based on turbidites our results suggest that the deposition of areally widespread synchronous turbidites triggered by seismicity is largely controlled by sediment supply and hence the climatic and geomorphic conditions of the adjacent subaerial setting the feasibility of compiling a turbidite paleoseismic record depends on the delicate balance between sufficient sediment supply providing material to fail frequently during seismic shaking and sufficiently low sedimentation rates to allow for coeval accumulation of planktonic foraminifera for high resolution radiocarbon dating we conclude that offshore northern central chile 29 32 5 s holocene turbidite paleoseismology is not feasible because sediment supply from the semi arid mainland is low and almost no holocene turbidity current deposits are found in the cores in contrast in the humid region between 36 and 38 s frequent holocene turbidite deposition may generally correspond to paleoseismic events however high terrigenous sedimentation rates prevent high resolution radiocarbon dating the climatic transition region between 32 5 and 36 s appears to be best suited for turbidite paleoseismology

benthic macrofauna variations and community structure in cenomanian cyclic chalk marl from southerham grey pit se england abstract cenomanian chalk marl couplets from england represent the 20 ka milankovitch precession cycle fossil communities from both chalk and marl are identified to test if the orbital fluctuations and the associated changes in substrate lithology and climate exerted any control on the benthic macrofauna the material comprises washing residues of 24 bulk samples collected from chalk and marl half cycles a total of 5055 invertebrate specimens were retrieved and referred to 68 species forming the basis for the recognition of six guilds in general the fauna is more diverse in marl than in chalk but it is remarkable and somewhat surprising that the guild assemblages of marl and chalk show no difference thus the substrate character of the two lithologies did not exert any influence on the modes of life of the benthic fauna in spite of a difference in clay content of about 20 the fauna was clearly well adapted to both facies and thus to the fine grain size of the substrate rather than to lithology the systematic difference in diversity between chalk and marl samples was possibly caused by long term climatic and oceanographic changes and thus could represent a biological response to milankovitch cyclicity

two middle pleistocene warm stages in the terrace deposits of the apulia region southern italy abstract we studied two middle pleistocene terraced deposits exposed along the trani cliff and at coppa nevigata in the apulia region southern italy in particular our study focused on stromatolitic units that are present at two sites at the trani cliff unit i consists of cemented whitish fine grained massive or bedded limestone the limestone grades upwards into massive porous bioconstructed calcareous bodies composed of in situ charophyta stems and or stromatolites the uppermost part of the unit is composed of whitish calcarenite calcisiltite layers with characeae the interpreted sedimentary environment for this unit is a hypersaline brackish lagoon at coppa nevigata the nvi unit is composed of tawny or yellow ochre sand with rare polygenic centimetric pebbles the sand grades upwards into light yellow and ochre sandy clayey silt or clay some layers are cemented and form marly limestones which contains columnar stromatolites the uppermost part of the unit consists of yellow ochre or tawny marly limestones and marls that are rich in external moulds of abra sp and cerastoderma glaucum the interpreted sedimentary environment for this unit is a brackish lagoon unit i and the nvi unit have been dated to mis 9 and mis 11 respectively by applying the amino acid racemisation aar method to ostracod shells the stromatolites of the nvi unit are ascribable to sh type whereas those of unit i are ascribable to sh and llh types and to colloform type in particular the stromatolites at the trani cliff are similar in shape and sedimentary environment to the modern stromatolites in shark bay australia the water temperature and salinity conditions under which the current stromatolites live indicate that tropical subtropical conditions were present in the mediterranean sea during mis 11 and mis 9 our reconstructions suggest that 1 during mis 11 the sea surface temperatures ssts were consistent with literature data that indicate ssts 3 c higher than the current ones 2 during mis 9 the lagoon in which unit i formed had a mean water temperature of the coldest month at least 10 12 c higher than that in modern southern adriatic and at least 3 4 c higher than that in some modern north african lagoons therefore our study supports the hypothesis that the mediterranean sea experienced tropical subtropical conditions during mis 9 that were similar to those of mis 11