stacking paleointensity and oxygen isotope data for the last 1 5 myr piso 1500 coupled relative geomagnetic paleointensity rpi and oxygen isotope records are used to construct rpi and oxygen isotope stacks for the last 1 5 myr the coupled correlations are accomplished using the match algorithm lisiecki l e and lisiecki p a 2002 application of dynamic programming to the correlation of paleoclimate records paleoceanography 17 1049 doi 10 1029 2001pa000733 to simultaneously correlate isotope and rpi records the simultaneous match reduces the degree of freedom associated with correlations using rpi or oxygen isotope records alone the overall compatibility of rpi and oxygen isotopes indicates a dominant global but independent component in both signals the local wavelet power spectrum lwps for the rpi stack indicates little significant orbital power although the accompanying oxygen isotope stack has all the lwps characteristics expected of a high resolution oxygen isotope record containing orbital frequencies the piso 1500 stack represents a new stratigraphic template that can be used to correlate among marine sediment records and link them to polar ice cores via variations in cosmogenic nuclide production scaling the stack to values for virtual axial dipole moment vadm indicate maxima at 15 1022 am2 and minima that imply a threshold of 2 5 1022 am2 below which values are associated with either polarity reversals or magnetic excursions

aeolian transport of coarse sand over beach ridges in ne australia a reply to a discussion of beach ridges and prograded beach deposits as palaeoenvironment records abstract nott 2013 argued that tamura s 2012 review of beach ridges as palaeoenvironment records comprises an incorrect interpretation of the processes of building coarse sand beach ridges in ne australia nott 2013 stressed no possibility of aeolian transport of coarse sand onto beach ridges during both cyclone and non cyclone conditions the facts presented by nott 2013 however fail to completely rule out the possibility that aeolian transport could be at least contributing to the building of the beach ridges this reply aims to clarify the original intentions of tamura 2012 which nott 2013 appears to have misunderstood and further examines the possibility of aeolian transport of coarse sand onto the beach ridges from incipient ridges if this does occur then it is appropriate to question how this might affect the theory and algorithm employed by nott et al 2009 and forsyth et al 2010 to assess the intensity and frequency of prehistoric cyclone landfall

10be evidence for delayed acquisition of remanent magnetization in marine sediments implication for a new age for the matuyama brunhes boundary abstract fluxes of the meteoric cosmogenic radionuclide 10 be vary with changes in the incoming cosmic rays modulated by geomagnetic field intensity variations the variability in the 10 be flux can be used to synchronize ice cores as well as marine sediments by comparison with the relative paleointensity variations of the geomagnetic field however lock in of the paleomagnetic signal at some depth below the sediment water interface in marine sediments through acquisition of a post depositional remanent magnetization pdrm adds uncertainty to synchronization despite the long history of such studies the magnitude of the pdrm lock in depth remains controversial in this article we present clear evidence for a downward offset of the paleointensity minimum relative to the 10 be flux anomaly at the matuyama brunhes m b geomagnetic polarity boundary which we interpret to result from a 15 cm pdrm lock in depth this lock in depth indicates that up to several tens of thousands years of age offset probably occurs when a paleomagnetic record is used for dating marine sediments and the age of the m b boundary should be revised to ca 10 kyr younger which is consistent with a younger ice core derived age of 770 6 ka 2 this cosmogenic age tuning strategy will contribute to refining paleomagnetic based age models for marine sediments and identifying of lead lag relationships for global abrupt environmental changes

enso and solar driven sub milankovitch cyclicity in the palaeogene greenhouse world high resolution pollen records from eocene lake messel germany the annually laminated oil shale from the eocene maar lake at messel germany provides unique palaeoenvironmental and palaeoclimatological information for the palaeogene greenhouse phase two palynological analyses of 6 3 and 70 kyr long records with a temporal resolution of 70 and 700 years respectively confirm vegetation and climate variability in the sub milankovitch range this variability clearly corresponds to cyclic climate fluctuations indicating the influence of solar activity and a millennial scale variability of the el nino southern oscillation also seen during the quaternary icehouse system this provides strong evidence of cyclic fluctuations in the sub milankovitch frequency band that represent a pervasive and persistent system not only of the quaternary icehouse but also throughout the entire neogene and the palaeogene greenhouse this is proof for the long term stability of the driving forces of natural climate change on earth fluctuations in the frequency of palynomorphs indicate cyclic short term quantitative changes in the composition of the vegetation these changes were related to precipitation and corresponding fluctuations of the lake level as well as to changes in pollen production transport and deposition supplementary material a complete list of variables and palynomorphs used for pollen diagrams and statistical analyses as well as additional time series analyses are available at https doi org 10 6084 m9 figshare c 3458778

early pliocene vegetation changes forced by eccentricity precession example from southwestern romania repetitive changes in early pliocene marine and continental sediments were forced by astronomical cycles eccentricity precession and related to low amplitude climatic fluctuations as demonstrated at capo rossello and monte san nicola sicily this work aims to establish if such climatic fluctuations have also controlled changes in the vegetation during the warm early pliocene high resolution pollen analysis of the lupoaia section sw romania provides evidence of a clear response owing to its location within a delta system which constitutes a reliable area for pollen deposition near the carpathians i e capable of registering all the vegetation ecosystems from edaphic coastal associations up to the highest altitudinal belts and owing to its southeastern european longitude probably where warm humid air masses arrived regularly making the region a highly favourable refuge for thermophilous plants eccentricity appears to have controlled fluctuations in temperature development of thermophilous elements during eccentricity minima and descent of altitudinal trees during eccentricity maxima while precession appears to have forced changes in humidity expansion of cypress swamps related to precession maxima and spread of herbaceous marshes requiring more humidity related to precession minima with respect to increased precipitation and run off

beach ridge plain evidence of a variable late holocene tropical cyclone climate north queensland australia abstract to date most studies of long term tropical cyclone records from beach ridge plains coral shell and sand have suggested that there has been little variation in the intensity of these events over the late holocene this study of a sand beach ridge plain in northeast queensland australia using sedimentary analysis and luminescence chronology suggests there has been considerable variation in both the intensity and frequency of tropical cyclones here since the mid holocene most of the previous beach ridge studies have been of relatively uniform elevation coral shingle shell and sand beach ridges within the plain here at rockingham bay the sediments are composed of coarse grained sand and there is considerable variation in ridge height and the number of ridges emplaced over different time intervals it may be that pure sand ridges provide a more sensitive record of variations in long term tropical cyclone climatology which in turn may contribute to a considerably improved understanding of the behaviour of this natural hazard

new palynology based astronomical and revised 40ar 39ar ages for the eocene maar lake of messel germany the annually laminated oil shale from the eocene maar lake at messel federal state of hessen germany provides unique paleoenvironmental data for a time interval of 640 ka during the paleogene greenhouse phase as a consequence of orbitally controlled changes in the vegetation in the vicinity of the lake the lacustrine laminites can now be astronomically tuned dating is based on the short eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical la2010a la2010d solutions in combination with a revised 40ar 39ar age of a basalt fragment from a lapilli tuff section below the first lacustrine sediments depending on different newly suggested ages for the fish canyon sanidine used as monitor for neutron irradiation the age for the eruption at messel is between 48 27 0 22 and 48 11 0 22 ma this allows for the first time the exact correlation of a paleogene lacustrine sequence to the marine record in central europe the messel oil shale becomes now slightly older than previously assumed and includes the ypresian lutetian boundary that moves the base of the european land mammal age geiseltalian mp 11 into the lower eocene this opens a window for establishing an independent chronostratigraphic framework for paleogene terrestrial records and their correlation to the marine realm furthermore the study reveals that higher amounts of pollen from wet and thermophilous plants indicate less seasonal and more balanced precipitation and slightly higher temperatures during a well expressed eccentricity minimum

beach ridges and prograded beach deposits as palaeoenvironment records abstract beach ridges are landforms commonly developed on prograded coasts with beach shorelines a sequence of beach ridges coupled with their subsurface deposits can be regarded as a time series of coastal evolution methodological advances in field surveying and chronology applicable to beach ridges have led to detailed palaeoenvironmental reconstructions to be derived from such sequences this paper reconsiders the basic aspects of beach ridges and deposits which need to be properly understood for their comprehensive interpretation in a palaeo environmental context it also reviews case studies in which beach ridge sequences have been used to unveil past sea level history catastrophic events and climate changes proposed formative processes of beach ridges include 1 progradation of sandy beach and berm formations in relation to fairweather waves coupled with aeolian foredune accumulation 2 building of gravel ridges by storm waves 3 welding of longshore bars beach ridge formation through sea level oscillation is thought to be questionable and caution is suggested for this process when undertaking palaeoenvironmental reconstruction beach deposit stratification is known to dip either landwards or seawards but landward dips are uncommon seaward dipping stratification is formed in relation to beachface progradation and is usually dissected in places by erosion surfaces resulting from episodic beach retreat the boundary between the foreshore and the underlying shoreface is well defined only in the case that longshore bars lead to complex bedding structure relative to that of the foreshore reliable chronology of beach ridges can be determined by radiocarbon and optically stimulated luminescence osl dating radiocarbon dating of articulated shells which are considered not to be extensively reworked provides robust results but osl dating is more useful as it enables direct dating of sediment grains it is noted that there are restrictions in chronological resolution and continuity inherent to beach ridge and beach deposits the plan view geomorphic expression of beach ridges typically consists of ridge sets with multi decadal intervals whereas their internal sedimentary structures define shorter time scales records of beach sedimentation and erosion are likely to be reworked by episodic high magnitude beach retreat and the resultant record of the net progradation is likely to be sporadic and discontinuous the height of sandy beach ridges is often variable due to differing degrees of aeolian sand accumulation and they are thus not used as sea level indicators unless purely wave built gravel ridge height is a relatively reliable indicator of sea level but can vary in response to storminess fluctuations subsurface sediment facies boundaries are preferred as sea level indicators and those proposed include boundaries of aeolian beach foreshore shoreface and upper lower shorefaces catastrophic events are expressed in both erosional and depositional records erosion surfaces or scarp imprints revealed in a cross section of beach deposits indicate storm or tsunami events however erosional events are likely to rework previous records of sedimentation and even other erosional events and thus the apparent history decoded from the resultant deposits tends to be biased several attempts for estimating the frequency and intensity of prehistoric cyclones rely on assumed relationships between the level of coarse sand beach ridges and cyclone inundation the formative process of coarse sand ridges remains uncertain and needs to be clarified as it constitutes the fundamental basis of these attempts the growth rates of beach ridge systems are expected to reflect fluctuations in river sediment discharge to the coast and in aeolian sand flux due to onshore winds both of which are affected by climate change assessment of the growth rate is potentially improved by ground penetrating radar survey of subsurface structure and by detailed chronology orientation of beach ridges reflects long term trends in wave direction inferred relationships between beach ridges and cyclic fluctuations of sea level and climate rely on weak assumptions and are not substantiated by rigid chronological evidence and thus remain highly questionable correlation between the inherently decadal signal of beach ridge intervals and possible climate cycles such as sunspot activity is probably coincidental as it lacks causal explanations

warm and wet conditions in the arctic region during eocene thermal maximum 2 several episodes of abrupt and transient warming each lasting between 50 000 and 200 000 years punctuated the long term warming during the late palaeocene and early eocene 58 to 51 myr ago epochs1 2 these hyperthermal events such as the eocene thermal maximum 2 emt2 that took place about 53 5 myr ago2 are associated with rapid increases in atmospheric co2 content however the impacts of most events are documented only locally86 here we show on the basis of estimates from the tex 86 proxy that sea surface temperatures rose by 3 5 c in the arctic ocean during the emt2 dinoflagellate fossils demonstrate a concomitant freshening and eutrophication of surface waters which resulted in euxinia in the photic zone the presence of palm pollen implies5 that coldest month mean temperatures over the arctic land masses were no less than 8 c in contradiction of model simulations that suggest hyperthermal winter temperatures were below freezing6 in light of our reconstructed temperature and hydrologic trends we conclude that the temperature and hydrographic responses to abruptly increased atmospheric co2 concentrations were similar for the etm2 and the better described palaeocene eocene thermal maximum7 8 55 5 myr ago 2009 macmillan publishers limited all rights reserved

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

reconciling astrochronological and 40ar 39ar ages for the matuyama brunhes boundary and late matuyama chron when five matuyama brunhes m b boundary records from the north atlantic are placed on isotope age models produced by correlation of the 18o record directly or indirectly to an ice volume model the m b boundary lies consistently at the young end of marine isotope stage 19 with a mean age for the midpoint of the reversal of 773 1 ka standard deviation 0 4 kyr 7 kyr younger than the presently accepted astrochronological age for this polarity reversal 780 781 ka two recently proposed revisions of the age of the 40ar 39ar fish canyon sanidine fcs standard to 28 201 0 046 ma and 28 305 0 036 ma would adjust 40ar 39ar ages applicable to the m b boundary and other reversals and excursions back to 1 2 ma to ages older than the new astrochronological ages by 8 24 kyr the variables used to construct the ice volume models cannot account for the discrepancy the fcs standard age that best fits the astrochronological ages is 27 93 ma which is within the uncertainty associated with the commonly used value of 28 02 0 16 ma but younger than the recently proposed fcs ages the edc2 and edc3 age models in the dome c antarctic ice core yield ages of 771 7 ka and 766 4 ka respectively for the 10be flux peak that denotes the paleointensity minimum at the reversal boundary implying that the edc2 rather than edc3 age model is consistent with the observations from marine sediments at least close to the m b boundary

high frequency of super cyclones along the great barrier reef over the past 5 000 years understanding long term variability in the occurrence of tropical cyclones that are of extreme intensity is important for determining their role in ecological disturbances1 2 3 4 5 for predicting present and future community vulnerability and economic loss6 and for assessing whether changes in the variability of such cyclones are induced by climate change7 our ability to accurately make these assessments has been limited by the short less than 100 years instrumented record of cyclone intensity here we determine the intensity of prehistoric tropical cyclones over the past 5 000 years from ridges of detrital coral and shell deposited above highest tide and terraces that have been eroded into coarse grained alluvial fan deposits these features occur along 1 500 km of the great barrier reef and also the gulf of carpentaria australia we infer that the deposits were formed by storms with recurrence intervals of two to three centuries8 9 10 11 and we show that the cyclones responsible must have been of extreme intensity central pressures less than 920 hpa our estimate of the frequency of such super cyclones is an order of magnitude higher than that previously estimated which was once every several millennia12 13 14 and is sufficiently high to suggest that the character of rainforests and coral reef communities were probably shaped by these events

a refined astronomically calibrated 40ar 39ar age for fish canyon sanidine abstract intercalibration between the astronomical and radio isotopic dating methods provides a means to improving accuracy and reducing uncertainty of an integrated multi chronometer geologic timescale here we report a high precision 40 ar 39 ar age for the fish canyon sanidine fcs neutron fluence monitor by multi collector noble gas mass spectrometry through cross calibration with a1 tephra sanidines a1ts of the direct astronomically tuned faneromeni section crete the astronomically intercalibrated 40 ar 39 ar age of fcs of 28 172 0 028 ma 2 external errors is within the uncertainty of but more precise 0 10 than the previous 40 ar 39 ar age determined by intercalibration with astronomically tuned tephras from the melilla basin morocco using this proposed age for fcs combined with measurements using the a1ts as the neutron fluence monitor a weighted mean bishop tuff 40 ar 39 ar sanidine age of 0 7674 0 0022 ma 2 external errors is indistinguishable from the id tims u pb zircon age 0 7671 0 0019 ma the consistency between the astronomically calibrated 40 ar 39 ar sanidine age and u pb zircon age for this quaternary unit suggests that agreement between these two radio isotopic dating techniques is now achievable at better than 0 3 2 in the youngest part of geologic time

significant southern ocean warming event in the late middle eocene a prominent middle eocene warming event is identified in southern ocean deep sea cores indicating that long term cooling through the middle and late eocene was not monotonic at sites on maud rise and the kerguelen plateau a distinct negative shift in 1 8 o values 1 0 is observed ca 41 5 ma this excursion is interpreted as primarily a temperature signal with a transient warming of 4 c over 600 k y affecting both surface and middle bathyal deep waters in the indian atlantic region of the southern ocean this isotopic event is designated as the middle eocene climatic optimum and is interpreted to represent a significant climatic reversal in the midst of middle to late eocene deep sea cooling the lack of a significant negative carbon isotope excursion as observed during the paleocene eocene thermal maximum and the gradual rate of high latitude warming suggest that this event was not triggered by methane hydrate dissociation rather a transient rise in pco 2 levels is suspected possibly as a result of metamorphic decarbonation in the himalayan orogen or increased ridge arc volcanism during the late middle eocene

mean mixed depth of sediments the wherefore and the why the activities and consequently the bioturbational effects of deposit feeding organisms are largely restricted to a narrow surficial zone of marine sediments with a worldwide environmentally invariant mean of 9 8 cm with a standard deviation of 4 5 cm currently available theories of infaunal behavior cannot predict quantitatively this observation a new simple model that accounts for the feedback between resource food abundance its reactivity and the intensity of bioturbation leads to a quantitative estimate of 9 7 cm this model constitutes a fundamental advance in our understanding bioturbation

paleomagnetic directions and 40ar 39ar ages from the tatara san pedro volcanic complex chilean andes lava record of a matuyama brunhes precursor the same volcanic sequence overlain by flows with normal polarity the 40 ar 39 ar incremental heating experiments on lavas within the two sections provide nine independent age determinations and yield a weighted mean of 791 7 3 0 ka 2s for the paleomagnetic transition the sections are linked by geological mapping the precise radioisotopic dating and geochemical correlations alternating field and thermal demagnetization studies rock magnetic analyses and petrographic observations indicate that the magnetization is primary and carried by titanomagnetite the polarity change is characterized by a jump from reverse poles to a quasi stationary cluster of virtual geomagnetic poles over australia followed by a jump to normal polarity latitudes magnetization of these lavas is thus consistent with either a brief period when the field was dominated by a subequatorial dipole or a more complex nondipolar field that may reflect the influence of a long lived regional lower mantle control over a weakened dynamo the quebrada turbia lavas are circa 16 kyr older than those dated by exactly the same methods which record a later more complex portion of the reversal at haleakala volcano maui moreover the 792 ka radioisotopic age of these chilean lavas is older than most astronomical estimates for the matuyama brunhes reversal suggesting that this section may in fact record a precursor to the actual field reversal that is expressed by low paleointensities in more than a dozen well studied marine sediment cores index terms 1535 geomagnetism and paleomagnetism reversals process timescale magnetostratigraphy 1030 geochemistry geochemical cycles 0330 9360 information related to geographic region south america 9604 information related to geologic time cenozoic keywords paleomagnetism reversal

quantifying rates of coastal progradation from sediment volume using gpr and osl the holocene fill of guichen bay south east south australia guichen bay on the south east coast of south australia faces west towards the prevailing westerly winds of the southern ocean the bay is backed by a 4 km wide holocene beach ridge plain with more than 100 beach ridges the morphology of the guichen bay strandplain complex shows changes in the width length height and orientation of beach ridges a combination of geomorphological interpretation shallow geophysics and existing geochronology is used to interpret the holocene fill of guichen bay six sets of beach ridges are identified from the interpretation of orthorectified aerial photographs the ridge sets are distinguished on the basis of beach ridge orientation and continuity a 2 25 km ground penetrating radar gpr profile across the beach ridges reveals the sedimentary structures and stratigraphic units the beach ridges visible in the surface topography are a succession of stabilized foredunes that overlie progradational foreshore and upper shoreface sediments the beach progrades show multiple truncation surfaces interpreted as storm events the gpr profile shows that there are many more erosion surfaces in the subsurface than beach ridges on the surface the width and dip of preserved beach progrades imaged by gpr shows that the shoreface has steepened from around 2 9 to around 7 5 the changes in beach slope are attributed to increasing wave energy associated with beach progradation into deeper water as guichen bay was infilled at the same time the thickness of the preserved beach progrades increases slightly as the beach prograded into deeper water using the surface area of the ridge sets measured from the orthophotography and the average thickness of upper shoreface foreshore and coastal dune sands interpreted from the gpr profile the volume of holocene sediments within three of the six sets of beach ridge accretion has been calculated combining optically stimulated luminescence osl ages and volume calculations rates of sediment accumulation for ridge sets 3 4 and 5 have been estimated linear rates of beach ridge progradation appear to decrease in the mid holocene however the rates of sediment accumulation calculated from beach volumes have remained remarkably consistent through the mid to late holocene this suggests that sediment supply to the beach has been constant and that the decrease in the rate of progradation is due to increasing accommodation space as the beach progrades into deeper water changes in beach ridge morphology and orientation reflect environmental factors such as changes in wave climate and wind regime

geomagnetic excursions and paleointensities in the matuyama chron at ocean drilling program sites 983 and 984 iceland basin 1 we report natural remanent magnetization nrm directions and geomagnetic paleointensity proxies for part of the matuyama chron 0 9 2 2 ma interval from two sites located on sediment drifts in the iceland basin at ocean drilling program sites 983 and 984 mean sedimentation rates in the late matuyama chron are 15 9 and 11 5 cm kyr 1 respectively for the older part of the record 1 2 ma oxygen isotope data are too sparse to provide the sole basis for age model construction the resemblance of the volume susceptibility record and a reference 18o record led us to match the two records to derive the age models this match based on site 983 984 susceptibility is consistent with available site 983 984 benthic 18o data paleointensity proxies were derived from the slope of the nrm versus anhysteretic remanent magnetization plot for alternating field demagnetization in the 30 60 mt peak field range paleointensity lows correspond to polarity reversals at the limits of the jaramillo olduvai cobb mountain and reunion subchrons and to seven excursions in nrm component directions magnetic excursions defined here by virtual geomagnetic polar latitudes crossing the virtual geomagnetic equator are observed at 932 1048 1115 1190 1215 cobb mountain subchron 1255 1472 1480 1567 1575 gilsa subchron and 1977 ka the results indicate that geomagnetic directional excursions associated with paleointensity minima are a characteristic of the matuyama chron and probably of polarity chrons in general

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

the northern upper rhine graben basin geometry and early syn rift tectono sedimentary evolution a large scale transfer zone subdivides the northern parts of the upper rhine graben into a northern and a southern sub basin these sub basins display the geometry of asymmetric half grabens with opposing tilt directions the transfer zone connects the western master fault of the northern half graben with the eastern master fault of the southern half graben in the northern upper rhine graben early syn rift sedimentation late priabonian to late rupelian was controlled by the tectonically induced subsidence of these half grabens autogenetic as well as by regional third order sea level variations allogenetic within the graben lateral changes in subsidence rates in dip and strike direction of fault blocks controlled the development of accommodation space and thus sediment thickness and facies furthermore a low displacement segment along the western border fault acted as a sediment entry point tectonics controlled the distribution of early syn rift deposits and the palaeogeography of the northern upper rhine graben

deep sea temperature and ice volume changes across the pliocene pleistocene climate transitions earth has undergone profound changes since the late pliocene which led to the development 2 7 million years ago ma and intensification 0 9 ma of large scale northern hemisphere ice sheets recorded as transitions in the benthic foraminiferal oxygen isotope 18ob record here we present an orbitally resolved record of deep ocean temperature derived from benthic foraminiferal magnesium calcium ratios from the north atlantic which shows that temperature variations are a substantial portion of the global 18ob signal the record shows two distinct cooling events associated with the late pliocene lpt 2 5 to 3 ma and mid pleistocene mpt 1 2 to 0 85 ma climate transitions whereas the lpt increase in ice volume is attributed directly to global cooling the shift to 100 000 year cycles at the mpt is more likely to be a response to an additional change in ice sheet dynamics

does mean annual insolation have the potential to change the climate long term climatic changes such as glacial interglacial cycles are usually explained in term of changes in solar energy received at the top of the atmosphere in particular daily insolation in the high northern hemisphere latitudes during summer is widely used in interpreting palaeoclimate records this insolation forcing is strongly marked by changes in precession however some climate variations are much more imprinted by changes in obliquity this was the case for sea surface temperature in the north atlantic during the eemian period as well as for the vostok ice core deuterium excess history over the last 250 ka therefore we investigate the insolation forcing in order to identify characteristics that could explain the observed climate response this is mainly the case for annual mean insolation variations simple hypotheses for how this forcing could act on climate are also suggested these being mainly related to changes in the moisture transport induced by the annual insolation gradient between low and high latitudes along these lines a simple conceptual model of annual mean temperature variations illustrates the role of annual mean insolation on climate c 2004 elsevier b v all rights reserved

astronomical calibration of the paleocene time the first complete cyclic sedimentary successions for the early paleogene from drilling multiple holes have been retrieved during two odp expeditions leg 198 shatsky rise nw pacific ocean and leg 208 walvis ridge se atlantic ocean these new records allow us to construct a comprehensive astronomically calibrated stratigraphic framework with an unprecedented accuracy for both the atlantic and the pacific oceans covering the entire paleocene epoch based on the identification of the stable long eccentricity cycle 405 kyr high resolution x ray fluorescence xrf core scanner and non destructive core logging data from sites 1209 through 1211 leg 198 and sites 1262 1267 leg 208 are the basis for such a robust chronostratigraphy former investigated marine odp sites 1001 and 1051 and land based e g zumaia sections have been integrated as well the high fidelity chronology is the prerequisite for deciphering mechanisms in relation to prominent transient climatic events as well as completely new insights into greenhouse climate variability in the early paleogene we demonstrate that the paleocene epoch covers 24 long eccentricity cycles we also show that no definite absolute age datums for the k pg boundary or the paleocene eocene thermal maximum petm can be provided by now because of still existing uncertainties in orbital solutions and radiometric dating however we provide two options for tuning of the paleocene which are only offset by 405 kyr our orbitally calibrated integrated leg 208 magnetostratigraphy is used to revise the geomagnetic polarity time scale gpts for chron c29 to c25 we established a high resolution calcareous nannofossil biostratigraphy for the south atlantic which allows a much more detailed relative scaling of stages with biozones the re evaluation of the south atlantic spreading rate model features higher frequent oscillations in spreading rates for magnetochron c28r c27n and c26n

resolution effect on image based conventional and tight sandstone pore space reconstructions origins and strategies abstract a suitable choice of spatial resolution is essential to the three dimensional 3d image based reconstruction of rock pore space a too low spatial resolution may result in the omission of sub resolution porosity while too high spatial resolution may lead to a field of view smaller than the representative volume in this work the 3d pore spaces of conventional and tight sandstone specimens are reconstructed by x ray computed tomography with spatial resolutions of 2 m 5 m 10 m and 20 m and equal image voxel quantities 600 600 600 to study the influence of spatial resolution on the reconstruction quality petrophysical properties such as porosities permeabilities and pore throat structure parameters are calculated from the 3d images and measured by helium porosity klinkenberg corrected permeability and mercury intrusion capillary pressure porosimetry for comparison high resolution images are sampled from different positions in the specimens to evaluate the core scale heterogeneities rock textures and pore throat structures of the specimens are analyzed through casting thin sections and micp to find out the origin of the resolution effect the results show that 3d images with any single spatial resolution have limited detectivities to recover the full pore and throat distribution of sandstone specimens which is the root cause of the resolution effect the contributions of different pore genetic types with various pore sizes to petrophysical properties vary with simulation targets and methods for conventional sandstone specimens with only one dominate pore genetic type the appropriate spatial resolution can be chosen by calibrating the simulated petrophysical properties to actual measurements for tight sandstone specimens with several pore genetic types the contents and contributions to the petrophysical properties should be investigated before pore space reconstructions

orbital forcing in pliocene pleistocene mediterranean lacustrine deposits dominant expression of eccentricity versus precession abstract milankovitch forcing of climate is expressed in the sedimentary record as lithological cycles that can have one or more of four typical periods related to precession 21 kyr obliquity 41 kyr and eccentricity 100 and 400 kyr in several mediterranean continental successions striking differences in the expression of particularly precession and eccentricity appear we present the results of an additional lower pliocene lacustrine succession from lupoaia southern romania and compare the cyclic expression in this lignite siliciclastic basin in detail with the time equivalent lignite carbonate basin of ptolemais northern greece the middle pleistocene lignite siliciclastic basin of megalopolis southern greece and the miocene carbonate clay basin of orera north eastern spain it appears that carbonate basins dominantly express precession while siliciclastic basins dominantly express eccentricity in their lithological cycles this can be explained by a more linear response to insolation forcing in carbonate basins than in siliciclastic basins alternatively it can be explained by the low amplitude of 100 kyr eccentricity at the times the carbonate sections were deposited this reduced 100 kyr amplitude was caused by minima in the 2 35 myr eccentricity cycle that co occurred with the deposition in both carbonate basins finally the expression of 100 kyr eccentricity appears to be independent of glacial cyclicity

astronomical tuning of the cenomanian scaglia bianca formation at furlo italy abstract the astronomical tuning of the upper cenomanian rhythmic succession of marine limestones and black shales that prelude to the bonarelli level oceanic anoxic event 2 in the classic furlo section of central italy was achieved using cyclostratigraphic analyses on environmentally controlled rock magnetic properties and the caco 3 content of the limestones the astronomical tuning was based on the stable 405 kyr long eccentricity cycle observed in the rock magnetic record and correlated to the orbital solution of laskar et al 2004 and the phase relationship was established by the eccentricity modulated precession signal observed in the caco 3 record according to our tuning pre bonarelli black shales formed during eccentricity minima and reduced seasonality when reduced deep water circulation sea bottom ventilation in a paleogeographically constricted alpine tethys central atlantic ocean promoted organic matter preservation and possibly a reduced carbonate dissolution resulting in a higher sedimentation rate in compliance the onset of the oae2 at furlo corresponds to the eccentricity minimum nominally placed at 93 92 ma with the full development of oae2 persisting much longer than any black shale precursor across at least one long eccentricity maximum

anatomy of sand beach ridges evidence from severe tropical cyclone yasi and its predecessors northeast queensland australia 1 four well identified tropical cyclones over the past century have been responsible for depositing distinct units of predominantly quartzose sand and gravel to form the most seaward beach ridge at several locations along the wet tropical coast of northeast queensland australia these units deposited by tropical cyclones display a key sedimentary signature characterized by a sharp basal erosional contact a coarser grain size than the underlying facies and a coarse skewed trend toward the base coarse skewed distributions with minimal change in mean grain size also characterize the upper levels of the high energy deposited units at locations within the zone of maximum onshore winds during the tropical cyclone these same coarse skew distributions are not apparent in sediments deposited at locations where predominantly offshore winds occurred during the cyclone which in the case of northeast australia is north of the eye crossing location these sedimentary signatures along with the geochemical indicators and the degraded nature of the microfossil assemblages have proven to be useful proxies to identify storm deposited units within the study site and can also provide useful proxies in older beach ridges where advanced pedogenesis has obscured visual stratigraphic markers as a consequence more detailed long term histories of storms and tropical cyclones can now be developed

is burial velocity a master parameter for bioturbation abstract the intensity of biological mixing in a marine sediment is widely believed to be related to the flux of labile organic matter at the same time this flux has been shown to be strongly correlated to the burial velocity one would then expect a significant correlation between biological mixing coefficient d b and burial velocity a nonlinear regression of existing data with a power law eqns 2 and 3 of the text produces a statistically significant correlation the statistical significance of the regression in no way implies causation and in fact it accounts for only about 22 of the total variance in the dataset thus reducing its physical significance a number of additional processes contribute to the large observed variance including timing of mixing events temporal and spatial heterogeneity differences in temporal scales sampling artifacts and specific particle associations with due care the d b relationship may prove useful in defining the likely range of d b values in a particular environment a similar analysis of the tracer identified surface mixed depth shows that it is essentially independent of burial velocity with a worldwide mean of 9 8 4 5 cm depth of mixing is probably more closely related to the energetic costs of deep burrowing

ar ar ages from transitionally magnetized lavas on la palma canary islands and the geomagnetic instability timescale 1 a detailed study of 43 lava flows comprising two stratigraphic sequences exposed along the north and south walls of barranco de los tilos on the island of la palma canary islands reveals a complex temporally segmented record of geodynamo behavior that contains no less than three distinct geomagnetic events the matuyama brunhes m b reversal is recorded in five transitionally magnetized lava flows from the north tn section the isochrons obtained from three of the lower four m b lavas are defined by 14 incremental heating experiments that together with a previous age determination yielded a weighted mean of 798 4 6 2 ka all uncertainties 2s in addition a 780 3 10 3 ka isochron was determined for the overlying transitionally magnetized flow indicating that it was erupted during a distinctly younger portion of the transition near the base of the south ts section one finds a sequence of weakly magnetized flows associated with virtual geomagnetic pole vgp positions in the southwest indian ocean between latitudes 56 s and 65 s suggesting instability of the geomagnetic field beyond that of typical secular variation 40 ar 39 ar isochrons from three of these flows defined by 11 separate incremental heating experiments gave a weighted mean of 822 2 8 7 ka this anomalous field behavior recorded 24 11 kyr prior to the m b reversal may coincide with an event featured in several marine sediment records directly above two normal polarity flows 40 ar 39 ar isochrons of 751 9 18 1 ka and 675 0 15 7 ka are nine transitionally magnetized lavas having magnetization directions associated with low to midlatitude vgps spanning 23 60 n these flows are then capped by a single flow possessing normal polarity based on 12 incremental heating experiments 40 ar 39 ar isochrons of five of these nine lavas along with the uppermost flow gave a weighted mean age of 580 2 7 8 ka for this period of transitional to normal field behavior from these same transitional lavas quidelleur et al 1999 reported three unspiked k ar ages with a weighted mean of 602 24 ka and proposed a new event called the la palma excursion however the 40 ar 39 ar age presented here is three times more precise than the k ar age and is indistinguishable at the 95 confidence level from the 40 ar 39 ar age of a lava from the snake river plain idaho that originally defined the big lost event transitional field behavior of similar age observed in astronomically dated marine cores further establishes that the big lost event recorded at la palma was indeed global in extent rigorous temporal and geomagnetic constraints for several additional periods of geomagnetic field instability during the last several million years will comprise a geomagnetic instability timescale that can be factored confidently into models of the dynamo process index terms 1560 geomagnetism and paleomagnetism time variations secular and long term 1520 geomagnetism and paleomagnetism magnetostratigraphy 1035 geochemistry geochronology 1513 geomagnetism and paleomagnetism geomagnetic excursions keywords argonargon dating lavas excursion paleomagnetism reversal

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

new biostratigraphic magnetostratigraphic and isotopic insights into the middle eocene climatic optimum in low latitudes the middle eocene climatic optimum meco was a warming event that interrupted the long term eocene cooling trend while this event is well documented at high southern and mid latitudes it is poorly known from low latitudes and its timing and duration are not well constrained because of problems of hiati microfossil preservation and weak magnetic polarity in key sedimentary sections here we report the results of a study designed to improve the bio magneto and chemostratigraphy of the meco interval using high resolution records from two low latitude sections in the atlantic ocean ocean drilling program odp sites 1051 and 1260 we present the first detailed benthic foraminiferal stable isotope records of the meco from the low latitudes as well as the biostratigraphic counts of orbulinoides beckmanni and new magnetostratigraphic results our data demonstrate a 750 kyr long duration for the meco characterized by increasing 13c and decreasing 18o with minimum 18o values lasting 40 kyr at 40 1 ma coincident with a short lived negative 13c excursion thereafter 18o and 13c values recover rapidly the shift to minimum 18o values at 40 1 ma is coincident with a marked increase in the abundance of the planktonic foraminifera o beckmanni consistent with its inferred warm water preference o beckmanni is an important eocene biostratigraphic marker defining planktonic foraminiferal zone e12 with its lowest and highest occurrences lo and hos our new records reveal that the lo of o beckmanni is distinctly diachronous appearing 500 kyr earlier in the equatorial atlantic than in the subtropics 40 5 versus 41 0 ma we also show that at both sites the ho of o beckmanni at 39 5 ma is younger than the published calibrations increasing the duration of zone e12 by at least 400 kyr in accordance with the tropical origins of o beckmanni this range expansion to higher latitudes may have occurred in response to sea surface warming during the meco and subsequently disappeared with cooling of surface waters

new chronology for the late paleocene thermal maximum and its environmental implications the late paleocene thermal maximum lptm is associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle we have developed a new orbital chronology for ocean drilling program odp site 690 weddell sea southern ocean by using spectral analysis of high resolution geochemical records the lptm interval spans 11 precessional cycles yielding a duration of 210 to 220 k y the 13 c anomaly associated with the lptm has a magnitude of about 2 5 to 3 we show that about 2 of the excursion occurs within two steps that each were less than 1000 yr in duration the remainder developed through a series of steps over 52 k y the timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial further we are able to correlate the records between odp sites 690 and 1051 western north atlantic on the scale of 21 k y cycles which demonstrates that the details of the 13 c excursion are recognizable between distant sites comparison of cycle records at sites 690 and 1051 suggests that sediment representing the interval 30 k y just prior to and at the onset of the lptm are missing in the latter location this unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k y of the start of the lptm

palaeocene eocene paratropical floral change in north america responses to climate change and plant immigration the initial eocene thermal maximum ietm at c 55 ma represents a period of rapid global warming that lasted less than 200 ka the response of vegetation to such an event and particularly warm adapted highly diverse vegetation types is poorly understood using pollen floral clay mineral and stable carbon isotope analyses of sediments from the upper tuscahoma formation on the eastern us gulf coast eastern mississippi and western alabama we document paratropical floral changes across the palaeocene eocene boundary from the wahalak 2 and lower harrell cores data indicate strong changes in the abundance of kaolinite that correlate with changes in relative abundance of native pollen taxa there is no evidence for a transient extra tropical flora on the us gulf coast that may characterize the ietm immigration and extinction are not associated with this event instead early eocene plant immigration occurs in pulses and therefore is not associated directly with climate change during the ietm the two cores share the same regional species pool but compositional differences are stronger between cores than they are either through changes in environment increased soil erosion or chemical weathering or through the introduction of non native plants our data suggest that vegetation change across the palaeocene eocene boundary is not a single event but rather a sequence of cascading events

the last two geomagnetic polarity reversals recorded in high deposition rate sediment drifts high resolution records of geomagnetic polarity transitions are rare owing to the difficulty of preserving in the geological record details of a process with a duration of only a few thousand years lavas can record the instantaneous field on cooling but lava records are themselves discontinuous and therefore polarity transition fields are seldom captured sedimentary records are more continuous but typical deep sea sedimentation rates of a few cm kyr 1are too low to record transition fields adequately here we report transition records from north atlantic drift deposits with high sedimentation rates 12 cm kyr 1 at the ocean drilling program sites 983 and 984 virtual geomagnetic polar vgp paths are similar within and between sites for the last two geomagnetic reversals attesting to a memory effect spanning back to back reversals the complex vgp paths feature two vgp clusters one located in northeastern asia and the other in the south atlantic ocean off south america and provide a link between the longitudinally constrained transitional vgps often recorded in sediments1 2 which represent highly smoothed renditions of transition fields and the scattered transitional vgps3 and vgp clusters4 observed in lava records

the representative sample size in shale oil rocks and nano scale characterization of transport properties abstract the experimental determination of petrophysical properties for shale rocks is dependent on measurement techniques and often produces inconsistent results alternatively high resolution three dimensional imaging techniques coupled with image analysis and direct numerical simulations have been employed to estimate these parameters in shale samples nevertheless the application of these results at the core and reservoir scales are uncertain due to the limited size of imaged samples here focused ion beam milling and scanning electron microscope tomography is employed to study transport properties for the three upper layers of the bakken formation the representative size of each shale sample is characterized pore types their connectivities and pore size distributions are studied using high resolution micrographs and their implications to mass transport at the macro scale are discussed porosity and permeability of the samples are also calculated from three dimensional images and the results are compared to experimentally measured values at the core scale it is shown that the representative size of shale samples is dependent on the scale of analysis and could range from tens to hundreds of microns we found that the upper bakken layer is rich in clay and organic materials the dominant pore type is pores associated with organic matter and no connected porosity was observed in the preserved core samples in contrast the middle bakken layers upper and lower layers have about 1 connected porosity mainly as intraplatelet pores within clay aggregates and interparticle pores resulting in permeabilities between 4 and 30 d moreover comparison of pore types and modeled flow pathways suggests the presence of water wet connected pores in the middle bakken rocks whereas mainly oil wet pores are present in the upper bakken shale

fractal dimension lacunarity and succolarity analyses on ct images of reservoir rocks for permeability prediction abstract an explicit relationship between seepage properties and microscopic structure of porous media is being sought for the development of oil and gas resources an effective method to accurately characterize and quantify the microscopic structure of porous media is a key issue fractal geometry can take advantage of several physically based parameters to analyze microstructures of reservoir rocks in this study three fractal structural parameters fractal dimension lacunarity and succolarity were employed to characterize scale invariant complexity heterogeneity and anisotropy of rock microstructures respectively twelve three dimensional digital cores of sandstone reservoir rocks were used to evaluate permeability in terms of fractal dimension lacunarity and succolarity the parameters were utilized to quantitatively characterize differences in core micro structure and predict their effects on permeability due to the confounding influence of porosity the fractal dimension was not an accurate predictor of the variation in permeability on its own instead the results reveal that lacunarity and succolarity were better able to predict differences in structure and permeability succolarity in particular showed an exponential relationship with permeability yielding a coefficient of determination of 0 940 using a combination of fractal structural parameters in the place of pore size distribution can provide a better explanation of the relationship between fluid flow and the heterogeneous structure and anisotropic physical properties of reservoir rocks

orbitally forced azolla blooms and middle eocene arctic hydrology clues from palynology the high abundances and cyclic distribution of remains of the freshwater fern azolla in early middle eocene sediments from the arctic ocean have previously been related to episodic surface water freshening which was speculated to be orbitally modulated our integrated palynological and cyclostratigraphical analysis of the recovered azolla interval in integrated ocean drilling program iodp core 302 m0004a 11x resulted in the recognition of two clear periodicities a dominant 1 2 m cyclicity which we relate to changes in obliquity 40 k y and a weaker 0 7 m cyclicity which we link to precession 21 k y cycles in the abundances of azolla cysts of freshwater tolerant dinoflagellates and swamp vegetation pollen show covariability in the obliquity domain this strong correlation suggests periods of enhanced rainfall and runoff during azolla blooms presumably linked to increased local summer temperatures during obliquity maxima larix and bisaccate conifer pollen covary at the precession frequency with peak occurrences corresponding to precession minima possibly as a result of enhanced continental runoff from a more remote source area and a stronger seasonal contrast following the sudden demise of azolla ca 48 1 ma runoff cycles continued to influence the central arctic at decreased intensity this and a concomitant decline in swamp vegetation pollen suggest edaphically drier conditions on land and decreased runoff into the arctic ocean causing salinity changes which might have been fatal for azolla moreover a sea level rise inferred from overall decreasing total terrestrial palynomorph concentrations possibly facilitated oceanic connections 2011 geological society of america

unit stratotypes for global stages the neogene perspective abstract recent developments in integrated high resolution stratigraphy and astronomical tuning of continuous deep marine successions invalidate arguments against the designation of unit stratotypes for global stages the basic building blocks of the standard global chronostratigraphic scale gcs for the late neogene global stratotype section and point gssp sections may also serve as unit stratotypes covering the interval from the base of a stage up to the level that time stratigraphically correlates with the base of the next younger stage in a continuous and well tuned deep marine succession the added value of such sections as unit stratotype lies in the integrated high resolution stratigraphy and astronomical tuning which combined provides an excellent age control with an unprecedented resolution precision and accuracy within the entire stage as such they form the backbone of the new integrated late neogene time scale and provide the basis for reconstructing earth s history in this way a stage is also defined by its content and not only by its boundaries our unit stratotype concept strengthens the importance of time rock units by allowing the introduction of astronomically defined chronozones as formal chronostratigraphic units thereby arguing against the elimination of the dual classification of chronostratigraphy and geochronology extending this concept to older time intervals requires that well tuned continuous deep marine sections are employed thus necessitating the employment of multiple hole i odp sites for defining remaining stages and stage boundaries in at least the cenozoic and cretaceous and possibly the entire mesozoic evidently the construction of the geological time scale including the gcs should be based on the most appropriate sections available while where possible taking the historical concept of global stages into account

pore throat sizes in sandstones tight sandstones and shales pore throat sizes in siliciclastic rocks form a continuum from the submillimeter to the nanometer scale that continuum is documented in this article using previously published data on the pore and pore throat sizes of conventional reservoir rocks tight gas sandstones and shales for measures of central tendency mean mode median pore throatsizes diameters are generally greater than2 mm in conventionalreservoir rocks range from about 2 to 0 03 mm in tight gas sandstones and rangefrom0 1to0 005 mminshales hydrocarbonmolecules asphaltenes ring structures paraffins and methane form another continuum ranging from 100 a 0 01 mm for asphaltenes to 3 8 a 0 00038 mm for methane the pore throat size continuum provides a useful perspective for considering 1 the emplacement of petroleum in consolidated siliciclastics and 2 fluid flow through fine grained source rocks now being exploited as reservoirs

mid latitude continental temperatures through the early eocene in western europe branched glycerol dialkyl glycerol tetraethers brgdgts are increasingly used to reconstruct mean annual air temperature maat during the early paleogene however the application of this proxy in coal deposits is limited and brgdgts have only been detected in immature coals i e lignites using samples recovered from schoningen germany 48 n palaeolatitude we provide the first detailed study into the occurrence and distribution of brgdgts through a sequence of early eocene lignites and associated interbeds brgdgts are abundant and present in every sample in comparison to modern studies changes in vegetation type do not appear to significantly impact brgdgt distributions however there are subtle differences between lignites representing peat forming environments and siliciclastic nearshore marine interbed depositional environments using the most recent brgdgt temperature calibration matmr developed for soils we generate the first continental temperature record from central western continental europe through the early eocene lignite derived maat estimates range from 23 to 26 c while those derived from the nearshore marine interbeds exceed 20 c these estimates are consistent with other mid latitude environments and model simulations indicating enhanced mid latitude early eocene warmth in the basal part of the section studied warming is recorded in both the lignites 2 c and nearshore marine interbeds 2 3 c this culminates in a long term temperature maximum likely including the early eocene climatic optimum eeco although this long term warming trend is relatively well established in the marine realm it has rarely been shown in terrestrial settings using a suite of model simulations we show that the magnitude of warming at schoningen is broadly consistent with a doubling of co2 in agreement with late paleocene and early eocene pco2 estimates

holocene evolution of the chan may coastal embayment central vietnam changing coastal dynamics associated with decreasing rates of progradation possibly forced by mid to late holocene sea level changes abstract southeast asian coastal environments are undergoing massive transformations with unprecedented population and infrastructure development these transformations are occurring on a backdrop of intense natural and anthropogenic environmental change which are increasing the risk to the burgeoning coastal population little is known about how central vietnamese coastal environments have changed naturally since the mid holocene sea level highstand and how recent anthropogenic change and sea level variation have affected the coastal system the chan may embayment in central vietnam allows us to examine how recent changes in both anthropogenic development and sea level change have affected the coastline the embayment preserves a series of prograding beach ridges and is subject to intense human pressures with the construction of a large economic and industrial park and expansion of tourist facilities using ground penetrating radar and quartz optical dating we identify a switch from 6000 years of prograding beach ridges to transgressive dunes within the past century resulting in a decreasing rate of beach ridge progradation possibly in the last 100 years the recent modes of sediment deposition through washovers and a transgressive dune indicates that coastal progradation has slowed and might have stopped

age and duration of the matuyama brunhes geomagnetic polarity reversal from 40ar39ar incremental heating analyses of lavas abstract constraints on the timing of geomagnetic polarity reversals have come mainly from k ar or more recently 40 ar 39 ar age determinations of lavas or their k rich phenocrysts that erupted prior or subsequent to particular geomagnetic events we have obtained 40 ar 39 ar isochron ages using incremental heating techniques on groundmass separates phenocryst poor whole rock samples or plagioclase from eight basaltic to andesitic lavas that erupted during the matuyama brunhes m b polarity transition at four geographically dispersed sites these eight lavas range from 784 6 7 1 ka to 770 8 5 2 ka 1 errors the weighted mean 778 7 1 9 ka gives a high precision age that is remarkably consistent with revised astronomical age estimates for the m b polarity transition 6 12 13 despite uncertainties in absolute calibration of 40 ar 39 ar ages relative to mineral standards used as neutron fluence monitors our age determinations are consistent with five other 40 ar 39 ar studies focused on the m b transition these results confirm that the earlier k ar based geomagnetic polarity time scale underestimated the age of the m b reversal by about 6 none of the eight isochron ages are distinguishable from one another at the 95 confidence level however we are tantalizingly close to testing for the duration of this reversal one lava at the base of a sequence of transitionally magnetized flows in chile and the uppermost lava in a similar sequence on maui are only just indistinguishable in age at the 95 confidence level and preserve different magnetic orientations we suggest that the 12 kyr difference in age represents an upper limit for the duration of the reversal and is similar to the period of low magnetic field intensity associated with records of the m b reversal from deep sea sediment cores together with the short duration 2 kyr of the directional reversal observed in several different marine sediment sections our data suggest that reversal of the field s direction could have occurred at slightly different times depending on the position of the recording site

a 600 k y record of el nino southern oscillation enso evidence for persisting teleconnections during the middle eocene greenhouse climate of central europe the el nino southern oscillation enso is a globally important factor in today s climate dynamics annually laminated oil shales from the maar lake of messel germany provide high resolution sedimentological and paleoenvironmental data of a time interval of 600 k y during the eocene greenhouse phase individual laminae consist of a light spring and summer algal layer tetraedron minimum layer and a dark winter layer composed of terrigenous background sediment four sections were selected from the core of the messel 2001 well in order to count varves and to measure total varve thickness and the thickness of light and dark laminae spectral analyses were done in order to detect possible cyclic fl uctuations in varve thickness fluctuations are signifi cant in the quasi biennial 2 1 2 5 yr and low frequency band 2 8 3 5 yr 4 9 5 6 yr thus showing that algal growth as well as the background sedimentation were controlled by enso effects at least over a time interval of 600 k y this confirms the existence of a previously postulated robust eocene enso significant peaks within a quasi decadal 10 11 yr interdecadal 17 26 yr and multidecadal band 52 yr 82 yr show either the enduring influence of more or less cyclic instabilities or the influence of solar cycles

graben width controlling syn rift sedimentation the palaeogene southern upper rhine graben as an example eocene to early oligocene syn rift deposits of the southern upper rhine graben urg accumulated in restricted environments sedimentation was controlled by local clastic supply from the graben flanks as well as by strong intra basinal variations in accommodation space due to differential tectonic subsidence that in turn led to pronounced lateral variations in depositional environment three large scale cycles of intensified evaporite sedimentation were interrupted by temporary changes towards brackish or freshwater conditions they form three major base level cycles that can be traced throughout the basin each of them representing a stratigraphic sub unit a relatively constant amount of horizontal extension l in the range of 4 5 km has been estimated for the urg from numerous cross sections the width of the rift lf however varies between 35 and more than 60 km resulting in a variable crustal stretching factor between the bounding masterfaults apart from block tilting tectonic subsidence was therefore largely controlled by changes in the initial rift width l0 the along strike variations of the graben width are responsible for the development of a deep trough like evaporite basin potash basin in the narrowest part of the southern urg adjacent to shallow areas in the wider parts of the rift such as the colmar swell in the north and the rhine bresse transfer zone that delimits the urg to the south under a constant amount of extension the along strike variation in rift width is the principal factor controlling depo centre development in extensional basins

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

millennial scale variability of deep water temperature and δ18odw indicating deep water source variations in the northeast atlantic 0 34 cal ka bp 1 paired measurements of mg ca and 18occ calcite 18o in benthic foraminifera from a deep sea core recovered on the iberian margin md99 2334k 37 48 n 10 10 w 3 146 m have been performed in parallel with planktonic 18occ analyses and counts of ice rafted debris ird the synchrony of temperature changes recorded in the greenland ice cores and in north atlantic planktonic 18occ allows the proxy records from md99 2334k to be placed confidently on the gisp2 time scale this correlation is further corroborated by ams 14c dates benthic mg ca measurements in md99 2334k permit the reconstruction of past deep water temperature tdw changes since 34 cal ka bp calendar kiloyears before present using these tdw estimates and parallel benthic 18occ measurements a record of deep water 18o 18odw has been calculated results indicate greatly reduced tdw in the deep northeast atlantic during the last glaciation until 15 cal ka bp when tdw warmed abruptly to near modern values in parallel with the onset of the bolling allerod interstadial subsequently tdw reverted to cold glacial values between 13 4 and 11 4 cal ka bp in parallel with the younger dryas cold reversal and the h0 ice rafting event similar millennial scale tdw changes also occurred during the last glaciation indeed throughout the last 34 cal ka millennial 18odw and tdw changes have remained well coupled and are linked with ird pulses coincident with heinrich events 3 2 1 and the younger dryas when transitions to lower tdw and 18odw conditions occurred in general millennial tdw and 18odw variations recorded in md99 2334k describe an alternation between colder low 18odw and warmer high 18odw conditions which suggests the changing local dominance of northern sourced north atlantic deep water nadw versus southern sourced antarctic bottom water aabw the observed similarity of the tdw and gisp2 18oice records would therefore suggest a common component of variability resulting from the coupling of nadw formation and greenland climate a link between greenland stadials and the incursion of cold low 18odw aabw in the deep northeast atlantic is thus implied which contributes to the relationship between greenland climate and the millennial benthic 18occ signal since 34 cal ka bp

upper rhine graben role of preexisting structures during rift evolution 1 the evolution of the cenozoic upper rhine graben was controlled by a repeatedly changing stress field and the reactivation of a complex set of crustal discontinuities that had come into evidence during permo carboniferous times a comparison of the spatial and temporal thickness distribution of synrift deposits with preexisting fault patterns permits to infer a sequence of distinct basin subsidence phases that can be related to changes in the ambient stress field reactivation of a system of late palaeozoic fault systems outlining troughs and highs controlled the nucleation of initially separated middle and late eocene basins the depocenters of which coincided with a preexisting wsw ene trend during oligocene crustal extension the individual basins coalesced resulting in the development of the ssw nne striking upper rhine graben during the late oligocene chattian change in stress field the upper rhine graben was probably reactivated as a dextral strike slip system with the central graben segment forming a releasing bend during the early miocene aquitanian a major reorientation of the regional stress field is held responsible for the main subsidence phase of the northern parts of the upper rhine graben this is reflected by a counterclockwise rotation and northeastward shift of the depocenter axis and later by the middle miocene uplift and erosion of the southern parts of the upper rhine graben during the plio quaternary the upper rhine graben was reactivated as a sinistral strike slip system with the central graben segment forming a restraining bend

brunhes matuyama magnetic reversal dated at 790 000 yr b p by marine astronomical correlations abstract the presence of the brunhes matuyama magnetic reversal in deep sea core sediments makes possible an alternative to the usual k ar radioistope method of dating the reversal as found in rocks the alternative method uses correlations of northern hemisphere summer insolation with oxygen isotope ratios from tropical cores the latitude dependent insolation variations are calculated from planetary mechanics and thus provide a highly accurate astronomical time scale the insolation variations strongly influence glacial ice volume fluctuations that dominate the oxygenisotope ratio changes recorded in core sediments the summer half year insolation variations are identified with corresponding isotope ratio changes in cores from the present through glacial stage 20 misleading effects of discontinuities or major nonuniformities of sediment deposition are avoided by an analysis of the uniformity of v28 238 and v28 239 the principal cores studied and by comparisons with other cores the top section stages 1 to 10 of v28 238 is uniformly deposited and for this section an isotope ratio time scale is chosen that agrees with the thorium uranium date for the high sea stand of the last interglacial extreme over this interval major glacial extremes strong isotope ratio minima coincide consistently with major insolation minima at times of low orbital eccentricity in addition interstadials are directly associated with precessional insolation peaks and the envelope of isotope ratio peaks resembles the envelope of precessionally dominated insolation peaks the assumption that the glacial extremes depended similarly on insolation minima during stages 10 to 20 permits minor age shifts of strong isotope ratio minima in the two cores relative to ages based on uniform overal deposition to match the ages of low eccentricity insolation minima the age shifts reflect residual nonuniformities of deposition the validity of this matching procedure is supported by a resulting consistent identification of principal isotope ratio peaks with high and low latitude coincident insolation maxima the brunhes matuyama reversal is found intinterglacial stage 19 and is dated on the astronomical time scale at 790 000 5000 yr b p

geomagnetic field intensity during the last 60 000 years based on 10be and 36cl from the summit ice cores and 14c abstract based on 10 be 36 cl and 14 c records we reconstruct past changes in the geomagnetic field intensity under the assumption that radionuclide records are mainly influenced by changes in their production rates subsequent comparison of these records with independent geomagnetic field reconstructions allows us to assess the reliability of our approach and to identify periods where our method or the geomagnetic field reconstructions might be problematic the geomagnetic field derived from the 10 be flux to summit in central greenland agrees well with independent geomagnetic field intensity reconstructions however compared to independent palaeomagnetic data the radionuclide record suggests increased geomagnetic field intensities especially for the period from 20 000 to 30 000 years bp 36 cl from the grip ice core agrees well with the 10 be record for the last ice age and hence also the reconstructed geomagnetic field based on the tree ring radiocarbon record it is possible to reconstruct geomagnetic field intensity changes during the holocene a comparison of radiocarbon based and independent geomagnetic field reconstructions indicates that changes in the carbon cycle significantly influenced the atmospheric radiocarbon concentration before 10 000 years bp

grain size and the origin of wave constructed beach ridges a discussion of beach ridges and prograded beach deposits as palaeoenvironment records tamura 2012 has provided a comprehensive review except for the role of tectonics of the origin of beach ridges globally as highlighted in the review beach ridges can develop by a variety of processes depending upon the location and the prevailing climatic and oceanographic conditions one of the types of beach ridges the medium to coarse grained sand beach ridges along the northeast australian coast has been suggested by nott et al 2009 to be deposited by waves and surge during tropical cyclones and as such register a millennial scale record of these events tamura 2012 suggests that they could have been deposited by wind presumably because they are composed of sand and not gravel however the evidence as discussed here shows that tamura 2012 is incorrect

paratropical floral extinction in the late palaeocene early eocene the palaeocene eocene thermal maximum petm at c 55 8 ma marks a transient c 100 ka duration interval of rapid greenhouse warming that had profound effects on marine and terrestrial biota plant communities responded rapidly with major compositional turnover the long term effects on tropical vegetation communities that stem from the brief period of global warming are unclear we present pollen data from the paratropical us gulf coast eastern mississippi western alabama and georgia which had background palaeogene mean annual temperatures of 26 27 c sporomorph data pollen and spores demonstrate that taxonomic diversity increases over c 1 ma in the late palaeocene but this trend is replaced with the first occurrences of taxa that mark the early eocene by a pronounced extinction into the early eocene c 20 of the palynoflora taxonomic diversity also decreases by up to 38 in the early eocene the timing of the extinction is not clearly resolved but may be restricted to the earliest part of the early eocene two richness estimators chao 2 and jackknife 2 both demonstrate that late palaeocene samples contain significantly more taxa than those in the early eocene extinction on the us gulf coast proves that ancient tropical ecosystems were highly susceptible to changes in diversity mediated directly or indirectly by environmental change even during equable greenhouse climates in the early palaeogene

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

dependence of the duration of geomagnetic polarity reversals on site latitude an important constraint on the processes governing the geodynamo the flow in the outer core responsible for generating earth s magnetic field is the duration of geomagnetic polarity reversals that is how long it takes for earth s magnetic field to reverse1 it is generally accepted that earth s magnetic field strength drops to low levels during polarity reversals and the field direction progresses through a 180 change while the field is weak1 the time it takes for this process to happen however remains uncertain with estimates ranging from a few thousand up to 28 000 years here i present an analysis of the available sediment records of the four most recent polarity reversals these records yield an average estimate of about 7 000 years for the time it takes for the directional change to occur the variation about this mean duration is not random but instead varies with site latitude with shorter durations observed at low latitude sites and longer durations observed at mid to high latitude sites such variation of duration with site latitude is predicted by simple geometrical reversal models in which non dipole fields are allowed to persist while the axial dipole decays through zero and then builds in the opposite direction and provides a constraint on numerical dynamo models

short term fluctuations in vegetation and phytoplankton during the middle eocene greenhouse climate a 640 kyr record from the messel oil shale germany the palaeogene was the most recent greenhouse period on earth especially for the late palaeocene and early eocene several superimposed short term hyperthermal events have been described including extremes such as the palaeocene eocene thermal maximum major faunal and floral turnovers in the marine and terrestrial realms were recorded in association with these events high resolution palynological analysis of the early middle eocene maar lake sediments at messel near darmstadt germany provides an insight into the dynamics of a climax vegetation during the middle eocene greenhouse climate in a time span without significant climatic excursions numerical techniques like detrended correspondence analysis and wavelet analysis have been applied to recognize cyclic fluctuations and long term trends in the vegetation through a time interval of approximately 640 kyr based on the numerical zoning of the pollen diagram three phases in the development of the vegetation may be distinguished throughout these phases the climax vegetation did not change substantially in qualitative composition but a trend towards noticeably less humid conditions probably in combination with a drop of the water level in the lake may be recognized a shift in algal population from the freshwater dinoflagellate cyst messelodinium thielepfeifferae to a dominance of botryococcus in the uppermost part of the core is interpreted as a response to changes in acidity and nutrient availability within the lake time series analyses of pollen assemblages show that variations in the milankovitch range of eccentricity obliquity and precession can be distinguished in addition fluctuations in the sub milankovitch range are indicated this demonstrates that floral changes during steady depositional conditions in the middle eocene of messel were controlled by orbital forcing

representation of multiscale heterogeneity via multiscale pore networks 1 developing a better understanding of single multiphase flow through reservoir rocks largely relies on characterizing and modeling the pore system for simple homogeneous rock materials a complete description of the real pore structure can be obtained from the pore network extracted from a rock image at a single resolution and then an accurate prediction of fluid flow properties can be achieved by using network model however for complex rocks e g carbonates heterogeneous sandstones deformed rocks a comprehensive description of the real pore structure may involve several decades of length scales e g from submicron to centimeters which cannot be captured by a single resolution image due to the restriction of image size and resolution hence the reconstruction of a single 3 d multiple scale model of a porous medium is an important step in quantitatively characterizing such heterogeneous rocks and predicting their multiphase flow properties in this paper we present a novel methodology for the numerical construction of the multiscale pore structure of a complex rock from a number of ct images models of a carbonate sample at several length scales the success of this reconstruction relies heavily on image segmentation pore network extraction and stochastic network generation which are provided by our existing software system referred to as pore analysis tools pat specifically the statistical description of pore networks of 3 d rock images at multiple resolutions makes it possible for us to a construct an arbitrary sized network which is equivalent in a specified domain and b integrate multiple networks of different sizes into a single network incorporating all scales using multiscale networks of carbonate rocks generated in this manner two phase network modeling results are presented to show how the resulting flow properties are dependent on inclusion of information from multiple scales these outcomes reinforce the importance of capturing both geometry and topology in the hierarchical pore structure for such complex pore systems the example presented reveals that isolated large scale e g macro pores are mainly connected by small scale e g micro pores which in turn determines the combined effective petrophysical properties capillary pressure absolute and relative permeability it is also demonstrated that multi three scale networks reveal the effects of the interacting multiscale pore systems e g micropores macropores and vugs on bulk flow properties in terms of two phase flow properties

mapping permeability in low resolution micro ct images a multiscale statistical approach we investigate the possibility of predicting permeability in low resolution x ray microcomputed tomography ct lower resolution whole core images give greater sample coverage and are therefore more representative of heterogeneous systems however the lower resolution causes connecting pore throats to be represented by intermediate gray scale values and limits information on pore system geometry rendering such images inadequate for direct permeability simulation we present an imaging and computation workflow aimed at predicting absolute permeability for sample volumes that are too large to allow direct computation the workflow involves computing permeability from high resolution ct images along with a series of rock characteristics notably open pore fraction pore size and formation factor from spatially registered low resolution images multiple linear regression models correlating permeability to rock characteristics provide a means of predicting and mapping permeability variations in larger scale low resolution images results show excellent agreement between permeability predictions made from 16 and 64 m voxel images of 25 mm diameter 80 mm tall core samples of heterogeneous sandstone for which 5 m voxel resolution is required to compute permeability directly the statistical model used at the lowest resolution of 64 m voxel similar to typical whole core image resolutions includes open pore fraction and formation factor as predictor characteristics although binarized images at this resolution do not completely capture the pore system we infer that these characteristics implicitly contain information about the critical fluid flow pathways three dimensional permeability mapping in larger scale lower resolution images by means of statistical predictions provides input data for subsequent permeability upscaling and the computation of effective permeability at the core scale

response to the comment by w h schwarz et al on joint determination of 40k decay constants and 40ar 40k for the fish canyon sanidine standard and improved accuracy for 40ar 39ar geochronology by p r renne et al 2010

sand beach ridges record 6000 year history of extreme tropical cyclone activity in northeastern australia sand beach ridges are considered to be derived either from aeolian processes and or waves but their deposition by individual or multiple storms has not been investigated in any detail we use numerical meteorological and oceanographic models to determine the origin of a sequence of 29 shore parallel sand beach ridges in northeastern australia the results suggest that the ridges were constructed by waves and that the final form or height of the ridges is a function of high energy tropical cyclone generated waves plus storm tides hence these landforms archive a nearly 6000 year long history of intense tropical cyclones the record implies that these extreme tempests occur considerably more frequently than that suggested by the short historical record for this region the genesis of this sand beach ridge plain has implications for the interpretation of similar sequences elsewhere along the northeast coast of australia and in comparable environments globally if other similar sand beach ridge plains have also been deposited by like processes it stands to reason that these long term records of high intensity tropical cyclones can be used to ascertain a regional scale risk assessment from this hazard

astronomical tuning of the la vedova high cliff section ancona italy implications of the middle miocene climate transition for mediterranean sapropel formation article i nfo continuous marine successions covering the middle miocene climate transition mmct 15 13 7 ma are scarce and the lack of a high resolution magnetobiostratigraphic framework hampers the construction of astronomically tuned age models for this time interval the la vedova high cliff section exposed along the coast of the conero riviera near ancona italy is one of the few mediterranean sections covering the critical time interval of the mmct starting from an initial magnetobiostratigraphic age model a robust astronomical tuning was constructed for the interval between 14 2 and 13 5 ma using geochemical element data and time series analysis a shift in 18 o of bulk sediment towards heavier values occurs between 13 92 and 13 78 ma and could be related to the mi3b oxygen isotope event which reflects the rapid expansion of the east antarctic ice sheet in the middle miocene the onset of the cm6 carbon excursion is reflected in the bulk record by a rapid increase in 13 c at 13 86 ma our results confirm the proposition that these events coincide with a 405 kyr minimum in eccentricity and a node in obliquity related to the 1 2 myr cycle from 13 8 ma onwards distinct quadruplet cycles containing sapropelitic sediments were deposited this may suggest a causal connection between the main middle miocene cooling step and the onset of sapropel formation in the

paleomagnetic record at odp site 980 feni drift rockall for the past 1 2 myrs 1 a detailed record of variations in the direction and intensity of the geomagnetic field over the past 1 2 myrs has been obtained from an 120 m thick sedimentary section cored at odp site 980 on the feni drift north atlantic the record has high resolution due to high mean sedimentation rates 11 3 cm kyr for the brunhes chron and 5 5 cm kyr for the matuyama chron paleomagnetic measurements every 1 cm along u channel samples and high quality isotopic age control the iceland basin event is manifest by virtual geomagnetic poles crossing the equator at 190 ka the base of the recovered section lies immediately below the cobb mountain subchronozone that occurs within marine isotope stage 35 normalized remanence data can be correlated to paleointensity records from odp sites 983 and 984 700 km to the nw from site 980 and with lower resolution paleointensity data from the pacific ocean differences between the site 980 paleointensity record and the pacific records are attributed to variable sedimentation rates variable quality age control and inadequacies in the normalization procedure used to derive the paleointensity proxies

palynology and organic carbon isotope ratios across a terrestrial palaeocene eocene boundary section in the williston basin north dakota usa abstract the palaeocene eocene thermal maximum petm at 55 ma marks the palaeocene eocene p e boundary and represents a discrete period of abrupt transient global warming there are few vegetation records from within the petm and such an absence of data prevents modelling of the vegetation response to climate warming outcrops exposing the sentinel butte member upper fort union formation and the golden valley formation bear den and lower camels butte members within the williston basin of western north dakota usa are known to span the p e boundary pollen and spore floras at the farmers butte locality stark county north dakota 46 92 n 102 11 w record changes in abundance of some reed fern and understorey plants across the sentinel butte bear den contact but no other composition changes occur until the arrival of eocene immigrants platycarya spp walnut pecan family and intratriporopollenites instructus linden sterculia cotton tree families at the top of the bear den member c 11 m above the change in co occurrence and relative abundance patterns of range through taxa the exact stratigraphic level at which these eocene marker taxa first occur is unclear owing to the heavily weathered nature of bear den strata below the alamo bluff lignite this pattern of stratigraphic change may be correlative to the well documented floral gap of petm records in wyoming though bulk 13 c org ratios decrease by 2 4 across the alamo bluff lignite degradation of organic carbon within the upper bear den member partially masks full expression of the carbon isotope excursion associated with the petm hence strata around the alamo bluff lignite may represent a new terrestrial record of the petm in agreement with terrestrial petm records from other u s western interior localities palynological data indicate no floral extinction and little composition change across the palaeocene eocene boundary

time scale controversy accurate orbital calibration of the early paleogene 1 timing is crucial to understanding the causes and consequences of events in earth history the calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating uncertainties in the computations of earth s orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 ma attempts to construct a robust astronomically tuned time scale for the early paleogene by integrating radioisotopic and astronomical dating are only partially consistent here using the new la2010 and la2011 orbital solutions we present the first accurate astronomically calibrated time scale for the early paleogene 47 65 ma uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the fish canyon standard comparison with geological data confirms the stability of the new la2011 solution back to 54 ma subsequent anchoring of floating chronologies to the la2011 solution using the very long eccentricity nodes provides an absolute age of 55 530 0 05 ma for the onset of the paleocene eocene thermal maximum petm 54 850 0 05 ma for the early eocene ash 17 and 65 250 0 06 ma for the k pg boundary the new astrochronology presented here indicates that the intercalibration and synchronization of u pb and 40ar 39ar radioisotopic geochronology is much more challenging than previously thought

controls on sedimentation and vegetation in an eocene pull apart basin prinz von hessen germany evidence from palynology tectonically controlled lakes may experience a complex history of deposition and subsidence which can influence their ecology and environment to correlate controls on sedimentation with changes in vegetation within a small pull apart basin at grube prinz von hessen hessen germany during paleogene greenhouse conditions 47 core samples were analysed palynologically the lower eocene succession includes 34 m of clastic sediments overlain by 54 m of massive mudstone finely laminated bituminous claystone and lignite a fluvial lacustrine and a profundal deep lake facies association are distinguished statistical analysis of the diverse and well preserved palynoflora reveals five distinct associations throughout the sedimentary record there is a strong correlation between major changes in vegetation and lithology which were controlled mainly by changes in humidity together with tectonic activity which led to lake basin subsidence and a rise in lake level based on the association of pollen and spores which are typical for the lower eocene it can be shown that the basin is older than previously assumed supplementary material a complete list of variables and palynomorphs used for pollen diagrams and statistical analyses as well as their abundance percentages is available at https doi org 10 6084 m9 figshare c 4108016

coarse sand beach ridges at cowley beach north eastern australia their formative processes and potential as records of tropical cyclone history storm surges generated by tropical cyclones have been considered a primary process for building coarse sand beach ridges along the north eastern queensland coast australia this interpretation has led to the development of palaeotempestology based on the beach ridges to better identify the sedimentary processes responsible for these ridges a high resolution chronostratigraphic analysis of a series of ridges was carried out at cowley beach queensland a meso tidal beach system with a 3 m tide range optically stimulated luminescence ages indicate that 10 ridges accreted seaward over the last 2500 to 2700 years the ridge crests sit 3 5 to 5 1 m above australian height datum ca mean sea level a ground penetrating radar profile shows two distinct radar facies both of which are dissected by truncation surfaces hummocky structures in the upper facies indicate that the nucleus of the beach ridge forms as a berm at 2 5 m australian height datum equivalent to the fair weather swash limit during high tide the lower facies comprises a sequence of seaward dipping reflections beach progradation thus occurs via fair weather wave accretion of sand with erosion by storm waves resulting in a sporadic sedimentary record the ridge deposits above the fair weather swash limit are primarily composed of coarse and medium sands with pumice gravels and are largely emplaced during surge events inundation of the ridges is more likely to occur in relation to a cyclone passing during high tide the ridges may also include an aeolian component as cyclonic winds can transport beach sand inland especially during low tide and some layers above 2 5 m australian height datum are finer than aeolian ripples found on the backshore coarse sand ridges at cowley beach are thus products of fair weather swash and cyclone inundation modulated by tides knowledge of this composite depositional process can better inform the development of robust palaeoenvironmental reconstructions from the ridges this article is protected by copyright all rights reserved

reply to the discussion by john nott on coarse sand beach ridges at cowley beach north eastern australia their formative processes and potential as records of tropical cyclone history by tamura et al 2018 sedimentology 65 721 744

tempo and scale of late paleocene and early eocene carbon isotope cycles implications for the origin of hyperthermals abstract the upper paleocene and lower eocene are marked by several prominent 1 carbon isotope 13c excursions cie that coincide with transient global warmings or thermal maxima including the paleocene eocene thermal maximum petm the cie which are recorded mainly in marine sedimentary sequences have also been identified in continental sequences occurred episodically and yet appear to be paced or triggered by orbital forcing to constrain the timing and scale of the cie relative to long term baseline variability we have constructed a 4 52 million year myr long high resolution 3 kyr bulk sediment carbon isotope record spanning the lower eocene to upper paleocene c25r c24n from a pelagic sediment section recovered at odp site 1262 in the southeast atlantic this section which was orbitally tuned utilizing high resolution core log physical property and geochemical records is the most stratigraphically complete upper paleocene to lower eocene sequence recovered to date time series analysis of the carbon isotope record along with a high resolution fe intensity record obtained by xrf core scanner reveal cyclicity with variance concentrated primarily in the precession 21 kyr and eccentricity bands 100 and 400 kyr throughout the upper paleocene lower eocene in general minima in 13c correspond with peaks in fe i e carbonate dissolution both of which appear to be in phase with maxima in eccentricity this covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity this relationship includes all late paleocene and early eocene cie confirming pacing by orbital forcing the lone exception is the petm which appears to be out of phase with the 400 kyr cycle though possibly in phase with the 100 kyr cycle reinforcing the notion that a mechanism other than orbital forcing and or an additional source of carbon is required to account for the occurrence and unusual scale of this event