variability of the north atlantic thermohaline circulation during the last interglacial period studies of natural climate variability are essential for evaluating its future evolution greenland ice cores suggest that the modern warm period the holocene has been relatively stable for the past 9 000 years much less is known about other warm interglacial periods which comprise less than 10 of the climate record during the past 2 5 million years here we present high resolution ocean sediment records of surface and deep water variables from the bermuda rise spanning the last interglacial period about 118 000 127 000 years ago in general deep water chemical changes are coincident with transitions in surface climate at this site the records do not show any substantial fluctuations relative to the much higher variability observed during the preceding and subsequent cool climates the relatively stable interglacial period begins and ends with abrupt changes in deep water flow we estimate using 230 th measurements to constrain the chronology that transitions occur in less than 400 years

history of stage 5 sea level in bermuda review with new evidence of a brief rise to present sea level during substage 5a abstract oxygen isotope substage 5e is represented by the devonshire formation in bermuda the occurrence of these coastal marine deposits to about 5 m indicates pleistocene sea level data in bermuda do not need tectonic corrections a few published u series coral dates suggest that a conglomerate spencer s point formation may have formed during substage 5c geologic mapping however indicates that the eolianite beneath the conglomerate is pre rather than post devonshire formation in age as was previously thought and the aminostratigraphy of marine sheels also confirms the correlation of the spencer s point and devonshire formations substages 5c and 5a are represented by the southampton formation large eolianites comprise the bulk of this formation they are onlapped by a few small younger marine 1 m and eolian deposits aminostratigraphy confirms that these late southampton age deposits are significantly younger than the devonshire formation and u series dates indicate a substage 5a age the setting of some of these deposits along a protected shoreline precludes discounting their position as anomalous due to large storms this evidence that sea level in bermuda was at about present datum late in substage 5a agrees with interpretations of neotyrrhenian deposits of mediterranean shorelines but not with inferences from the deep sea oxygen isotope record or with data from uplifted coral reefs

modern and glacial tropical snowlines controlled by sea surface temperature and atmospheric mixing during the last glacial maximum tropical glacier snowlines were lower than expected based on estimates of tropical sea surface temperatures sea surface temperature reconstructions suggest the indo pacific warm pool was cooler than previously thought these temperatures and convective mixing processes can explain snowline altitude in this region

structure and breakup history of the rifted margin of west antarctica in relation to cretaceous separation from zealandia and bellingshausen plate motion 1 geophysical data acquired using r v polarstern constrain the structure and age of the rifted oceanic margin of west antarctica west of the antipodes fracture zone the 145 km wide continent ocean transition zone cotz of the marie byrd land sector resembles a typical magma poor margin new gravity and seismic reflection data indicates initial continental crust of thickness 24 km that was stretched 90 km farther east the bellingshausen sector is broad and complex with abundant evidence for volcanism the cotz is 670 km wide and the nature of crust within the cotz is uncertain margin extension is estimated to be 106 304 km in this sector seafloor magnetic anomalies adjacent to marie byrd land near the pahemo fracture zone indicate full spreading rate during c33 c31 80 68 myr of 60 mm yr 1 increasing to 74 mm yr 1 at c27 62 myr and then dropping to 22 mm yr 1 by c22 50 myr spreading rates were lower to the west extrapolation towards the continental margin indicates initial oceanic crust formation at around c34y 84 myr subsequent motion of the bellingshausen plate relative to antarctica 84 62 myr took place east of the antipodes fracture zone at rates 40 mm yr 1 typically 5 20 mm yr 1 the high extension rate of 30 60 mm yr 1 during initial margin formation is consistent with steep and symmetrical margin morphology but subsequent motion of the bellingshausen plate was slow and complex and modified rift morphology through migrating deformation and volcanic centers to create a broad and complex cotz

iceberg scours along the southern u s atlantic margin rapid climate fluctuations associated with ice sheet oscillations have resulted in pulses of iceberg discharge that are recorded by iceberg scour marks along continental shelves and ice rafted debris deposits across the north atlantic iceberg transport is largely controlled by ocean surface currents therefore iceberg trajectories can serve as a proxy for paleo circulation studies records of iceberg transport from ice rafted debris i e heinrich layers in the north atlantic suggest that most icebergs released during quaternary glaciations were entrained in a cyclonic subpolar gyre restricted to polar and mid latitudes however new data suggest that there may have been an additional southerly component of transport along the western atlantic margin here we present evidence of extensive iceberg scouring across the upper slope offshore of south carolina 1000 km south of the proximal ice margin during quaternary glacial maximums the location and orientation of the keel marks suggest that icebergs were entrained in a southwestward flowing coastal current at present warm waters of the rapid northeastward flowing gulf stream bathe the upper slope off the southeastern united states an offshore shift in the gulf stream axis during sea level lowstand may have allowed glacially fed coastal currents to penetrate farther south this may be the first evidence of iceberg rafting to subtropical latitudes in the north atlantic

bipolar seesaw control on last interglacial sea level our current understanding of ocean atmosphere cryosphere interactions at ice age terminations relies largely on assessments of the most recent last glacial interglacial transition1 2 3 termination i t i but the extent to which t i is representative of previous terminations remains unclear testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control however such age control has been lacking for even the penultimate glacial termination t ii which culminated in a sea level highstand during the last interglacial period that was several metres above present4 here we show that heinrich stadial 11 hs11 a prominent north atlantic cold episode5 6 occurred between 135 1 and 130 2 thousand years ago and was linked with rapid sea level rise during t ii our conclusions are based on new and existing6 7 8 9 data for t ii and the last interglacial that we collate onto a single radiometrically constrained chronology the hs11 cold episode5 6 punctuated t ii and coincided directly with a major deglacial meltwater pulse which predominantly entered the north atlantic ocean and accounted for about 70 per cent of the glacial interglacial sea level rise8 9 we conclude that possibly in response to stronger insolation and co2 forcing earlier in t ii the relationship between climate and ice volume changes differed fundamentally from that of t i in t i the major sea level rise clearly post dates3 10 11 heinrich stadial 1 we also find that hs11 coincided with sustained antarctic warming probably through a bipolar seesaw temperature response12 and propose that this heat gain at high southern latitudes promoted antarctic ice sheet melting that fuelled the last interglacial sea level peak

cambrian stratigraphy of kashmir and its boundary problems abstract the biostratigraphy of the cambrian of kashmir based on trilobite assemblage zones and trace fossils has been attempted faunal gaps occur in lower part of lower cambrian upper lower cambrian lower middle cambrian and upper part of upper cambrian in the lower cambrian cruziana rusophycus and redlichia zones in the middle cambrian solenopleura tonkinella tonkinella anomocare anomocare bailiella and bolaspidella zones and in the upper cambrian chuangia and dikelocephalites zones are recognized the position of intrasystem boundaries is also discussed while the various taxa have lithological preferences and are not necessarily found in a continuous sequence an attempt has been made to interpret the ranges of different genera the affinities of the fauna with that of other cambrian basins of the world are discussed it is concluded that the bulk of the fauna is of a cosmopolitan nature

gridded isopach maps from the south pacific and their use in interpreting the sedimentation history of the west antarctic continental margin large scale maps of sediment thicknesses are essential prerequisites for the next generation of high resolution paleobathymetric reconstructions in addition maps of sediment thicknesses on continental margins are useful for studies of terrigenous sediment supply and sediment distribution on the ocean floor based on a compilation of more than 10000 km of single and multichannel seismic reflection data and correlations with ocean drilling sites we model isopach grids of the southern pacific margin of west antarctica following recent seismic stratigraphic models we differentiate between pre glacial and glacially transported sediments the subsequent modelling of sediment thickness grids allows us to compare the pre glacial and glacial sedimentary development in the study area based on available drillhole dates we estimate the onset of accumulation of glacially transported sediments to have occurred at about 10 ma based on approximate sediment deposition rates the thickest glacial sediment accumulations occur in front of major glacial drainage outlets i e marguerite trough on the western antarctic peninsula margin belgica trough in the bellingshausen sea and the trough off pine island bay in the amundsen sea sedimentation rates between 140 and 170 m m y are calculated for these sites

changes in meridional temperature and salinity gradients in the north atlantic ocean 30 72 n during the last interglacial period eight deep sea sediment cores from the north atlantic ocean ranging from 31 to 72 n are studied to reconstruct the meridional gradients in surface hydrographic conditions during the interval of minimum ice volume within the last interglacial period using benthic foraminiferal 18o measurements and estimates of sea surface temperature sst and sea surface salinity sss we show that summer ssts and ssss decreased gradually during the interval of minimum ice volume at high latitude sites 52 72 n whereas they were stable or increased during the same time period at low latitude sites 31 41 n this increase in meridional gradients of ssts and ssss may have been due to changes in the latitudinal distribution of summer and annual average insolation and associated oceanic and atmospheric feedbacks these trends documented for the eemian ice volume minimum period are similar to corresponding changes observed during the holocene and may have had a similar origin

siderite clumped isotope thermometry a new paleoclimate proxy for humid continental environments abstract clumped isotope measurements can be used to exploit the paleoclimatic potential of pedogenic siderite feco3 however the applicability of this method is held back by the lack of clumped isotope calibrations of mineralogies other than calcite and aragonite here we present an inorganic calibration of siderites grown in the laboratory between 21 and 51 c linear regression of 47 values and temperature 106 t2 k yields the following relationship r2 0 997 47 rf 0 0356 0 0018 10 6 t 2 0 172 0 019 we demonstrate that this calibration is indistinguishable from calcite at current levels of analytical precision our observations suggest that there is likely no large systematic bias in the clumped isotope acid fractionation factors between the two different carbonate minerals we also present clumped isotope measurements of a natural siderite collected from holocene sediments of the mississippi river delta we find that siderites record warm season marsh water temperatures instead of mean annual temperatures as it has long been presumed this finding has important implications for the accuracy of siderite stable isotope and clumped isotope based climate reconstructions

marine climate and hydrography of the coralline crag early pliocene uk isotopic evidence from 16 benthic invertebrate taxa abstract the taxonomic composition of the biota of the coralline crag formation early pliocene eastern england provides conflicting evidence of seawater temperature during deposition some taxa indicating cool temperate conditions by analogy with modern representatives or relatives others warm temperate to subtropical tropical conditions previous isotopic 18 o evidence of seasonal seafloor temperatures from serial ontogenetic sampling of bivalve mollusk shells indicated cool temperate winter 18 o the shell 18 o data either strongly indicate or are at least consistent with cool temperate seafloor conditions the subtropical tropical conditions suggested by the presence of the bryozoan metrarabdotos did not exist microgrowth increment and 13 c evidence indicate summer water column stratification during deposition of the ramsholt member unlike in the adjacent southern north sea at present well mixed due to shallow depth and strong tidal currents summer maximum surface temperature was probably about 5 c above seafloor temperature and thus often slightly higher than now 17 19 c rather than 16 17 c but only sometimes in the warm temperate range winter minimum surface temperature was below 10 c and possibly the same as at present 6 7 c an expanded surface temperature range compared to now may reflect withdrawal of oceanic heat supply in conjunction with higher global temperature

seismic and bathymetric evidence for four different episodes of iceberg scouring on the new jersey outer shelf possible correlation to heinrich events abstract re analysis of dense chirp seismic surveys on the outer new jersey shelf reveals two sets of shallowly buried incisions the incisions are linear to slightly sinuous oriented ne sw and exhibit cross cutting relationships we interpret both sets as paleo iceberg scours one set cuts into the r horizon a regional unconformity that formed 45 40 ka and which was subsequently buried by the finer grained outer shelf sediment wedge osw the second set is part of an erose boundary between a layered lower unit of the osw and an upper more transparent unit the erose boundary scours are deeper and have steeper slopes than the r horizon scours the latter often exhibit bermed edges whereas the former do not these differences in cross sectional morphology are likely determined by the material properties of the sediments being scoured sand at the r horizon and clay at the erose boundary the orientation of both sets of scours is consistent with previously recognized iceberg scours in stratigraphically younger seafloor on the outer new jersey shelf in 110 150 m water depths located 40 km to the northeast we argue that heinrich events recurring periods of massive iceberg flux into the north atlantic represent the most likely times for transporting icebergs to these latitudes based on stratigraphic relationships a recently published ambient sea level curve and radiocarbon age constraints we attribute the r horizon scours to heinrich event h4 37 cal ka the erose boundary scours to h3 30 cal ka and the seafloor scours to h2 23 cal ka and or h1 17 cal ka facies changes immediately following the r horizon and erose boundary scours may be related to heinrich event forced climate changes perhaps the onset of interstadial conditions and associated melt water pulses floods these pulses floods repeatedly carried fine grained rock flour produced by widespread glacial erosion to the new jersey shelf

temporal and spatial structure of multi millennial temperature changes at high latitudes during the last interglacial the last interglacial lig 129e116 thousand of years bp ka represents a test bed for climate model feedbacks in warmer than present high latitude regions however mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial a spatio temporal picture of lig temperature changes is difficult to obtain here we have selected 47 polar ice core and sub polar marine sediment records and developed a strategy to align them onto the recent aicc2012 ice core chronology we provide the first compilation of high latitude temperature changes across the lig associated with a coherent temporal framework built between ice core and marine sediment records our new data synthesis highlights non synchronous maximum temperature changes between the two hemispheres with the southern ocean and antarctica records showing an early warming compared to north atlantic records we also observe warmer than present day conditions that occur for a longer time period in southern high latitudes than in northern high latitudes finally the amplitude of temperature changes at high northern latitudes is larger compared to high southern latitude temperature changes recorded at the onset and the demise of the lig we have also compiled four data based time slices with temperature anomalies compared to present day conditions at 115 ka 120 ka 125 ka and 130 ka and quantitatively estimated temperature uncertainties that include relative dating errors this provides an improved benchmark for performing more robust model data comparison the surface temperature simulated by two general circulation models ccsm3 and hadcm3 for 130 ka and 125 ka is compared to the corresponding time slice data synthesis this comparison shows that the models predict warmer than present conditions earlier than documented in the north atlantic while neither model is able to produce the reconstructed early southern ocean and antarctic warming our results highlight the importance of producing a sequence of time slices rather than one single time slice averaging the lig climate conditions

ice sheet collapse following a prolonged period of stable sea level during the last interglacial sea level during the last interglacial period reached a peak of between 5 and 9 m above the present day level a detailed reconstruction of sea level and isostatic rebound from western australia indicates a prolonged period of sea level stability at 3 4 m above present followed by an abrupt sea level rise of 5 6 m

onset of hudson strait heinrich events in the eastern north atlantic at the end of the middle pleistocene transition 640 ka 1 heinrich events are well documented for the last glaciation but little is known about their occurrence in older glacial periods of the pleistocene here we report scanning xrf and bulk carbonate 18o results from integrated ocean drilling program site u1308 reoccupation of deep sea drilling project site 609 that are used to develop proxy records of ice rafted detritus ird for the last 1 4 ma ca sr is used as an indicator of ird layers that are rich in detrital carbonate i e heinrich layers whereas si sr reflects layers that are poor in biogenic carbonate and relatively rich in detrital silicate minerals a pronounced change occurred in the composition and frequency of ird at 640 ka during marine isotope stage mis 16 coinciding with the end of the middle pleistocene transition at this time hudson strait heinrich layers suddenly appeared in the sedimentary record of site u1308 and the dominant period of the si sr proxy shifted from 41 ka prior to 640 ka to 100 ka afterward the onset of heinrich layers during mis 16 represents either the initiation of surging of the laurentide ice sheet lis off hudson strait or the first time icebergs produced by this process survived the transport to site u1308 we speculate that ice volume i e thickness and duration surpassed a critical threshold during mis 16 and activated the dynamical processes responsible for lis instability in the region of hudson strait we also observe a strong coupling between ird proxies and benthic 13c variation at site u1308 throughout the pleistocene supporting a link between iceberg discharge and weakening of thermohaline circulation in the north atlantic

revised pacific antarctic plate motions and geophysics of the menard fracture zone a reconnaissance survey of multibeam bathymetry and magnetic anomaly data of the menard fracture zone allows for significant refinement of plate motion history of the south pacific over the last 44 million years the right stepping menard fracture zone developed at the northern end of the pacific antarctic ridge within a propagating rift system that generated the hudson microplate and formed the conjugate henry and hudson troughs as a response to a major plate reorganization 45 million years ago two splays originally about 30 to 35 km apart narrowed gradually to a corridor of 5 to 10 km width while lineation azimuths experienced an 8 counterclockwise reorientation owing to changes in spreading direction between chrons c13o and c6c 33 to 24 million years ago we use the improved pacific antarctic plate motions to analyze the development of the southwest end of the pacific antarctic ridge owing to a 45 counterclockwise reorientation between chrons c27 and c20 61 to 44 million years ago this section of the ridge became a long transform fault connected to the macquarie triple junction following a clockwise change starting around chron c13o 33 million years ago the transform fault opened a counterclockwise change starting around chron c10y 28 millions years ago again led to a long transform fault between chrons c6c and c5y 24 to 10 million years ago a second period of clockwise reorientation starting around chron c5y 10 million years ago put the transform fault into extension forming an array of 15 en echelon transform faults and short linking spreading centers

eemian interglacial reconstructed from a greenland folded ice core efforts to extract a greenland ice core with a complete record of the eemian interglacial 130 000 to 115 000 years ago have until now been unsuccessful the response of the greenland ice sheet to the warmer than present climate of the eemian has thus remained unclear here we present the new north greenland eemian ice drilling neem ice core and show only a modest ice sheet response to the strong warming in the early eemian we reconstructed the eemian record from folded ice using globally homogeneous parameters known from dated greenland and antarctic ice core records on the basis of water stable isotopes neem surface temperatures after the onset of the eemian 126 000 years ago peaked at 8 4 degrees celsius above the mean of the past millennium followed by a gradual cooling that was probably driven by the decreasing summer insolation between 128 000 and 122 000 years ago the thickness of the northwest greenland ice sheet decreased by 400 250 metres reaching surface elevations 122 000 years ago of 130 300 metres lower than the present extensive surface melt occurred at the neem site during the eemian a phenomenon witnessed when melt layers formed again at neem during the exceptional heat of july 2012 with additional warming surface melt might become more common in the future

sea level controls on carbonate beaches and coastal dunes eolianite lessons from pleistocene bermuda 2015 geological society of america coastal dune accumulations at locations around the world have formed during sea level highstands rising sea levels falling sea levels and fluctuating sea levels initially episodes of maximum pleistocene dune activity in bermuda which is the type location for eolianite were correlated with glacio eustatic regressions this model had been abandoned by the 1970s in favor of a rising sea level model for bermuda s north shore and autogenic sediment supply model for the south shore we report the results of a detailed investigation of the intercalated mid late pleistocene beach and coastal dune deposits on the islands of bermuda and we test the existing models for these deposits we contend that the north shore model is invalidated by past misidentification of eoliandeposits as transgressive beach deposits on the south shore facies analysis of the marine isotope stage 7 mis 7 belmont formation reveals that coastal deposition was divided into two phases s1 which includes foreshore and shoreface progradation is predominantly marine and coincided with rising relative sea level s2 which commenced with protosol development on top of the marine section prior to burial by advancing dunes is nonmarine we conclude that the two successions s1 and s2 resulted from forcing by glacio hydro isostatic relative sea level change spanning a highstand rising and then falling rather than from transgressive or autogenic processes the finding that in bermuda the construction of protective coastal dunes depends on a falling relative sea level has potential implications for many vulnerable shorelines that face rising relative sea levels associated with climate change

variability in the surface temperature and melt extent of the greenland ice sheet from modis 1 satellite derived moderate resolution imaging spectroradiometer modis ice surface temperature ist of the greenland ice sheet shows a positive trend and two major melt events from 2000 to present ist increased by 0 55 0 44 c decade with the greatest increase 0 95 0 44 c decade found in northwestern greenland where coastal temperatures and mass loss are also increasing and outlet glaciers are accelerating ist shows the highest rates of increase during summer 1 35 0 47 c decade and winter 1 30 1 53 c decade followed by spring 0 60 0 98 c decade in contrast a decrease in ist was found in the autumn 1 49 1 20 c decade the ist trends in this work are not statistically significant with the exception of the trend in northwestern greenland major surface melt covering 80 or more of the ice sheet occurred during the 2002 and 2012 melt seasons where clear sky measurements show a maximum melt of 87 and 95 of the ice sheet surface respectively in 2002 most of the extraordinary melt was ephemeral whereas in 2012 the ice sheet not only experienced more total melt but melt was more persistent and the 2012 summer was the warmest in the modis record 6 38 3 98 c our data show that major melt events may not be particularly rare during the present period of ice sheet warming

deglacial diatom productivity and surface ocean properties over the bermuda rise northeast sargasso sea 1 diatom assemblages document surface hydrographic changes over the bermuda rise between 19 2 and 14 5 ka subtropical diatom species and chaetoceros resting spores dominate the flora as in north atlantic productive regions today from 16 9 to 14 6 ka brackish and fresh water diatoms are common and their contribution is generally coupled with total diatom abundance this same interval also contains rare grains of ice rafted debris coupling between those proxies suggests that successive discharge of icebergs might have stimulated productivity during heinrich event 1 h1 iceberg migration to the subtropics likely created an isolated environment involving turbulent mixing upwelled water and nutrient rich meltwater supporting diatom productivity in an otherwise oligotrophic setting in addition the occurrence of mode water eddies likely brought silica rich waters of southern ocean origin to the euphotic zone the persistence of lower salinity surface water beyond the last ice rafting suggests continued injection of fresh water by cold core rings and advection around the subtropical gyre these results indicate that opal productivity may have biased estimates of meridional overturning based on 231pa 230th ratios in bermuda rise sediments during h1

sea level rise due to polar ice sheet mass loss during past warm periods background although thermal expansion of seawater and melting of mountain glaciers have dominated global mean sea level gmsl rise over the last century mass loss from the greenland and antarctic ice sheets is expected to exceed other contributions to gmsl rise under future warming to better constrain polarice sheetresponse to warmer temperatures we draw on evidence from in terglacial periods in the geologic record that ex perienced warmer polar temperatures and higher gmsls than present coastal records of sea level from these previous warm periods dem onstrate geographic variability because of the influence of several geophysical processes that operate across a range of magnitudes and time scales inferring gmsl and ice volume changes from these reconstructions is nontrivial and generally requires the use of geophysical models advances interdisciplinary studies of geo logic archives have ushered in a new era of deciphering magnitudes rates and sources of sea level rise advances in our understanding of polar ice sheet response to warmer climates have been made through an increase in the number and geographic distribution of sea level reconstructions better ice sheet constraints and the recognition that several geophysical processes cause spatially complex patterns in sea level in particular accounting for glacial isostatic processes helps to decipher spatial variability in coastal sea level records and has reconciled a number of site specific sea level reconstructions for warm periods that have oc curred within the past several hundred thou sand years this enables us to infer that during recent interglacial periods small increases in

time scales of magma transport and mixing at kīlauea volcano hawai i modeling of volcanic processes is limited by a lack of knowledge of the time scales of storage mixing and final ascent of magmas into the shallowest portions of volcanic plumbing systems immediately prior to eruption it is impossible to measure these time scales directly however micro analytical techniques provide indirect estimates based on the extent of diffusion of species through melts and crystals we use diffusion in olivine phenocrysts from the a d 1959 k lauea iki hawai i usa eruption to constrain the timing of mixing events in the crustal plumbing system on time scales of months to years before eruption the time scales derived from zonation of fe mg in olivines combined with contemporaneous geophysical data suggest that mixing occurred on three time scales 1 as much as 2 yr prior to eruption in the deep storage system 2 in a shallow reservoir between incoming hot melts and resident melt for several weeks to months prior to eruption and 3 in the conduit and summit reservoir between the resident magma and cooled surface lava draining back into the vent on time scales of hours to several days during pauses between episodes synchronous inflation of the shallow reservoir with deep earthquake swarms and mixing suggests an intermittently open transcrustal magmatic system

carbonate clumped isotope bond reordering and geospeedometry carbonate clumped isotope thermometry is based on the preference of 13c and 18o to form bonds with each other at elevated temperatures such bond ordering is susceptible to resetting by diffusion of c and o through the solid mineral lattice this type of bond reordering has the potential to obscure primary paleoclimate information but could also provide a basis for reconstructing shallow crustal temperatures and cooling rates we determined arrhenius parameters for solid state reordering of c o bonds in two different calcites through a series of laboratory heating experiments we find that the calcites have different susceptibilities to solid state reordering reaction progress follows a first order rate law in both calcites but only after an initial period of non first order reaction that we suggest relates to annealing of nonequilibrium defects when the calcites are first heated to experimental temperature we show that the apparent equilibrium temperature equations or closure temperature equations for carbonate clumped isotope reordering are analogous dodson s equations for first order loss of daughter isotopes for each calcite the sensitivity of apparent equilibrium temperature to cooling rate is sufficiently high for inference of cooling rates within a factor of 5 or better for cooling rates ranging from tens of degrees per day to a few degrees per million years however because the calcites have different susceptibilities to reordering each calcite defines its own cooling rate apparent equilibrium temperature relationship the cooling rates of carrara marble inferred from carbonate clumped isotope geospeedometry are 10 6 10 3 degrees per annum and are in broad agreement with rates inferred from thermochronometric methods cooling rates for 13c depleted calcites from the late neoproterozoic doushantou cap carbonates in south china are on the order of 102 104 degrees per annum consistent with rapid cooling following formation of these calcites by a short lived hydrothermal event bristow et al 2011 nature v 474 p 68 71 most of the uncertainty in these estimates relates to uncertainty in arrhenius parameters for different calcites thus while the carbonate clumped isotope geospeedometer shows promise for recording cooling rates in settings and lithologies where other geospeedometers may not be applicable the uncertainty in cooling rate will be large without independent knowledge of the reordering kinetics of each study material thus the full potential of the method will only be realized if reordering kinetics can be accurately determined for each study material or predicted on the basis of mineral composition texture or other observable parameters

life of the bellingshausen plate the onset of independent bellingshausen plate movement in the south pacific is estimated at just after chron c33o this event closely follows a change in the offset sense on the transform arm of the late cretaceous pacific phoenix antarctic triple junction and accompanies the creation and or lengthening by different mechanisms of long offsets on the pacific antarctic ridge at the udintsev tharp heezen and v transforms as the triple junction stepped away from the ridge at around chron c27 the bellingshausen plate ceased to move independently and the pacific antarctic ridge inherited the set of long offset transforms shortly afterwards the gravity fabric on the flanks of much of the ridge displays evidence for a spreading rate decrease possibly related to transpression on the long offset transforms we speculate on a link between these events and regional tectonic changes around chron c27

a revised calibration of the clumped isotope thermometer abstract a growing number of materials and environmental settings are studied using the carbonate clumped isotope 47 thermometer the method has been applied in both biogenic and non biogenic carbonate systems in marine and terrestrial settings over a wide range of geological timescales the current 47 temperature calibration gives good temperature estimates for most biogenic materials however systematic biases are commonly observed at low temperatures in this study we report additional calibration data that covers a wider temperature range at more evenly distributed temperatures and are measured at higher analytical precision than the original calibration combining these data with the original calibration yields a 47 t relationship that is similar to the original calibration though slightly less steep 47 0 0526 0 0025 10 6 t 2 0 0520 0 0284 this revised calibration is in better agreement with biogenic carbonates including those grown at low temperatures the difference between the original and revised calibrations is significant for carbonates forming below 16 c or above 49 c 47 values of 0 68 and 0 56 additionally we include a comprehensive analysis of the sources of error associated with 47 measurements and estimated temperatures and recommend measurement strategies for obtaining the desired precision as an illustration we apply the revised calibration and uncertainty analysis to 3 previously published studies at low temperatures the revised calibration results in significant differences from the original calibration and hence affects the interpretation of the environmental signal recorded in light of our 47 errors analysis in cases where the temperature signals are small we find that replicate analyses are critical to identify a temperature signal

a palaeomagnetic reconnaissance of kashmir northwestern himalaya india abstract thermal demagnetization studies of 800 palaeozoic and lower mesozoic samples mainly carbonates from 14 localities in kashmir showed four magnetic components a a recent field component of normal polarity and large intensity b a middle to late tertiary secondary component of large intensity and of reversed and normal polarity which indicates clockwise rotation of central and eastern kashmir over approximately 45 with respect to peninsular indo pakistan c primary magnetic components of triassic late permian early carboniferous siluro ordovician and middle to early ordovician age the triassic and late permian components show a 20 30 cumulative counterclockwise offset with respect to the indo pakistan apparent polar wander path apwp this indicates a post middle to late triassic counterclockwise rotational movement of kashmir over 65 75 with respect to peninsular indo pakistan d a component of low inclination and predominantly east west declination which is observed only in rocks of pre panjal traps age a secondary origin associated with extrusion of the panjal traps flows is surmised but could not be established beyond doubt alternatively this component may be related to the regional foliation the triassic and late permian primary component directions are predominantly of normal polarity this suggests a pre punjabian late permian upper age limit for the permo carboniferous kiaman reversed polarity interval which is earlier than the early to late tatarian limit observed in the u s s r

geophysics of the pitman fracture zone and pacific antarctic plate motions during the cenozoic multibeam bathymetry and magnetometer data from the pitman fracture zone fz permit construction of a plate motion history for the south pacific over the past 65 million years reconstructions show that motion between the antarctic and bellingshausen plates was smaller than previously hypothesized and ended earlier at chron c27 61 million years ago the fixed hot spot hypothesis and published paleomagnetic data require additional motion elsewhere during the early tertiary either between east antarctica and west antarctica or between the north and south pacific a plate reorganization at chron c27 initiated the pitman fz and may have been responsible for the other right stepping fracture zones along the ridge an abrupt 8 clockwise rotation in the abyssal hill fabric along the pitman flowline near the young end of chron c3a 5 9 million years ago dates the major change in pacific antarctic relative motion in the late neogene

timing and nature of the penultimate deglaciation in a high alpine stalagmite from switzerland abstract the timing and nature of the penultimate deglaciation also known as termination ii t ii is subject of controversial discussions due to the scarcity of precisely dated palaeoclimate records here we present a new precisely dated and highly resolved multi proxy stalagmite record covering t ii from the high alpine schafsloch cave in switzerland an area where climate is governed by the north atlantic the inception of stalagmite growth at 137 4 1 4 kyr before present bp indicates the presence of drip water and cave air temperatures of above 0 c and is related to a climate induced change in the thermal state from cold to warm based of the glacier above the cave the cessation of stalagmite growth between 133 1 0 7 and 131 9 0 6 kyr bp is most likely related to distinct drop in temperature associated with heinrich stadial 11 the resumption of stalagmite growth at 131 9 0 6 kyr bp is accompanied by an abrupt increase in temperature and precipitation as indicated by distinct shifts in the oxygen and carbon isotopic composition as well as in trace element concentrations the mid point of t ii is around 131 8 0 6 kyr bp in the schafsloch cave record is significantly earlier compared to the age of 129 1 0 1 kyr bp in the sanbao cave record from china the different ages between both records can be best explained by the competing effects of insolation and glacial boundary forcing on seasonality and snow cover extent in eurasia

sea level oscillations during the last interglacial highstand recorded by bahamas corals whether sea level was stable during the last interglacial remains a subject of debate an analysis of the u th ages of coral reefs in the bahamas corrected for open system behaviour confirms the presence of at least one oscillation within the sea level highstand

evaluation of meteoric calcite cements as a proxy material for mass 47 clumped isotope thermometry abstract meteoric diagenetic cements are ubiquitous throughout geologic history affecting most carbonate exposures worldwide they can often be difficult to interpret as it is usually difficult to separate the influences of water 18o and temperature on isotopic signals contained within the carbonate rock body despite this difficulty in interpretation meteoric phreatic cements can potentially be a useful proxy material as they form slowly in equilibrium at mean annual temperature and are not affected by any biogenic effects that can bias other proxy materials we applied the mass 47 clumped isotope paleothermometer to pleistocene and holocene carbonates from bermuda and barbados in order to investigate the effects of meteoric diagenesis on 47 signals and to determine their suitability as a paleotemperature proxy phreatic calcite cements are found to record the same temperatures as unaltered carbonate sediments while any sample exhibiting vadose characteristics is biased towards unreasonably hot apparent formation temperatures burial heating and re equilibration are not geologically viable explanations for the anomalously hot temperatures recorded in vadose cements as neither bermuda or barbados has any burial history instead it is likely that precipitation in the vadose zone occurs on timescales quicker than isotopic equilibrium can be achieved driven by a combination of co2 degassing and evaporation which have been previously shown to cause problems in speleothems and pedogenic carbonates we conclude by suggesting that meteoric phreatic calcites may be an ideal phase for paleotemperature reconstruction as they accurately record mean annual temperatures and form under equilibrium conditions while also being resistant to further mineral driven diagenesis vadose cements and any sample likely affected by processes similar to vadose diagenesis should be avoided for climate reconstructions using the mass 47 clumped isotope thermometer

shallow burial alteration of dolomite and limestone clumped isotope geochemistry carbonate clumped isotope paleothermometry is a promising method for paleoclimate reconstructions and understanding diagenetic processes although clumped isotope compositions measured as 47 values can be altered by recrystallization and thermal resetting several studies have investigated the effects of deep burial and exhumation on 47 values we present 47 values of samples from an 4500 m long drill core from andros island bahamas which represent the spectrum from shallow to deep burial conditions these limestones and dolomites originally formed under near surface temperature conditions which are reflected by 27 c 47 temperatures in samples buried to 1 3 km depth below this depth calculated 47 temperatures increase by 10 c indicating a shift from preserved near surface temperatures to diagenetically modified values importantly this shift is not accompanied by a change in 18o and 13c values or cathodoluminescence and non uniform micrometer scale crystallization is observed in both 47 altered and unaltered rocks similar 47 temperatures recorded by each carbonate phase suggest that mineral specific differences are minor fine grained dolomites and calcites are viable materials for recording surface temperature conditions and both are susceptible to alteration of their primary clumped isotope abundances during burial diagenesis our results demonstrate that original 47 values of fine grained carbonates can be altered under mild diagenetic conditions

temperature and salinity of the late cretaceous western interior seaway the western interior seaway wis was a shallow and expansive body of water that covered the central united states during the late cretaceous attempts to reconstruct temperatures in the seaway using the oxygen isotopic composition of biogenic carbonates have suffered from uncertainty in the oxygen isotopic composition of seawater 18 o w in the semi restricted basin we present new reconstructed temperature and 18 o w data from marine and estuarine environments in the wis and freshwater environments in wis source rivers derived from clumped isotope analyses of bivalve and gastropod shells we find temperatures of 5 21 c 18 o w values below contemporaneous gulf of mexico marine sites and a strong correlation between 18 o w and environmental setting we propose that decreasing 18 o w values reflect decreasing salinity driven by an increasing contribution of continental runoff using a two end member salinity 18 o w mixing model we estimate salinities of 29 35 psu practical salinity units for the deep marine 20 32 psu for the shallow marine and 11 26 psu for the estuarine environments of the wis new climate model simulations agree with reconstructed temperatures and salinities and suggest the presence of salinity driven stratification within the seaway

anomalous mis 7 sea level recorded on bermuda three new u series ages from coral fragments found in the belmont formation of bermuda fall in a range of 198 ka to 196 ka these late mis 7 ages are consistent with those of 201 ka and 199 ka measured in a previous study the disputed interpretation of the belmont formation as a unit that is allostratigraphically distinct from subsequent mis 5e deposits of the rocky bay formation is vindicated by a minimum age of 196 3 ka for the total of 6 coral fragments it has yielded emergent marine deposits of the belmont formation include sedimentary lithofacies that are considered to be reliable relative sea level indicators prominent among these is a facies representing the beach step a feature that develops sub tidally directly at the base of the swash zone from this facies and others preserved along 6 km of belmont formation coastal exposure it is concluded that mis 7 relative mean sea level reached 4 5 m and likely peaked at or above 6 0 m relative to present sea level at bermuda lower mis 7 sea level positions that are evidenced and that have been quoted in the past are considered transitory positions not maxima the mis 7 sea level elevations on bermuda reconstructed in this study are above the majority of those reported from elsewhere in the world this challenges the long standing notion of bermuda as a vertically stable tide gauge but is consistent with glacio hydroisostatic models which predict land mass subsidence at intermediate field sites such as bermuda at the end of long interglacials however because of evidence of instability at bermuda in the form of seismic activity and faulting which require further investigation judgement is reserved on the global implications of this palaeo sea level anomaly

characterizing seawater oxygen isotopic variability in a regional ocean modeling framework implications for coral proxy records reconstructions of the el nino southern oscillation enso are often created using the oxygen isotopic ratio in tropical coral skeletons 18o however coral 18o can be difficult to interpret quantitatively as it reflects changes in both temperature and the 18o value of seawater small scale 10 100 km processes affecting local temperature and seawater 18o are also poorly quantified and contribute an unknown amount to intercoral 18o offsets a new version of the regional ocean modeling system capable of directly simulating seawater 18o isoroms is therefore presented to address these issues the model is used to simulate 18o variations over the 1979 2009 period throughout the pacific at coarse o 50 km resolution in addition to 10 km downscaling experiments covering the central equatorial pacific line islands a preferred site for paleo enso reconstruction from corals a major impact of downscaling at the line islands is the ability to resolve fronts associated with tropical instability waves tiws which generate large excursions in both temperature and seawater 18o at palmyra atoll 5 9 n 162 1 w tiw related sea surface temperature gradients are smaller at neighboring christmas island 1 9 n 157 5 w but the interaction of mesoscale features with the steep island topography nonetheless generates cross island temperature differences of up to 1 c these nonlinear processes alter the slope of the salinity seawater 18o relationship at palmyra and christmas as well as affect the relation between coral 18o and indices of enso variability consideration of the full physical oceanographic context of reef environments is therefore crucial for improving 18o based enso reconstructions

wally was right predictive ability of the north atlantic conveyor belt hypothesis for abrupt climate change linked abrupt changes of north atlantic deep water formation north atlantic sea ice extent and widespread climate occurred repeatedly during the last ice age cycle and beyond in response to changing freshwater fluxes and perhaps other causes this paradigm developed and championed especially by w s broecker has repeatedly proven to be successfully predictive as well as explanatory with high confidence much work remains to fully understand what happened and to assess possible implications for the future but the foundations for this work are remarkably solid

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

the salinity contrast between the atlantic and pacific oceans during glacial time in today s ocean the salinity of low latitude surface waters in the pacific is on the average 1 per mil lower than in the atlantic oxygen isotope records for planktonic foraminifera suggest that an even larger salinity deficit may have existed for pacific surface water during glacial time if so the transport of water vapor from the atlantic to the pacific must have been as strong as or even stronger to balance the tendency toward salt buildup the atlantic would have had to export during glacial time waters saltier than it received from the other oceans

subtropical iceberg scours and meltwater routing in the deglacial western north atlantic during the last deglaciation northern hemisphere ice sheets discharged ice and meltwater seafloor scours and numerical modelling suggest that freshwater and icebergs from the laurentide ice sheet reached the subtropical north atlantic

proterozoic sedimentation and pan african geodynamic development in the himalaya abstract the purana or proterozoic lower cambrian continental margin sedimentary succession of the lesser himalaya comprises three lithological divisions a lower argillo arenaceous group a middle carbonate succession and an upper argillo calcareous assemblage the poorly sorted basal sediments consisting of wacke slate alternations of the lower group were emplaced by currents including turbidity currents which in the early stage flowed northwards from the aravalli and satpura mountains of peninsular india lenticular deposits of diamictite within the flysch succession represent submarine slides penecontemporaneous basaltic lavas and associated tuffs interbedded with shallow water arenites making up the bulk of the upper part of the lower group were related to rifting of the basins the overlying dolomites and dolomitic limestones were laid down on a very shallow stable shelf and are characterised by columnar branching stromatolites and lenticular units of crystalline magnesite and associated talc lenticular diamictites towards the top of the upper group of slates and limestone are harbingers of tectonic movements culminating towards the end of the early cambrian in an upheaval which abruptly terminated sedimentation throughout the lesser himalaya and peninsular india and caused a pronounced interruption of sedimentation in the tethyan domain in the northern himalaya the cambro ordovician 500 25 ma granites intruding the lesser himalayan thrust sheets of lower proterozoic metamorphic rocks and the upwarped northern front of the himalaya signify an important tectonic event that terminated the purana proterozoic lower cambrian sedimentation in the indian subcontinent this seems to be related to the tectonic movements that occurred towards the close of the late proterozoic or early cambrian

exploring the potential of clumped isotope thermometry on coccolith rich sediments as a sea surface temperature proxy understanding past changes in sea surface temperatures ssts is crucial however existing proxies for reconstructing past ssts are hindered by unknown ancient seawater composition foraminiferal mg ca and 18o or reflect subsurface temperatures tex86 or have a limited applicable temperature range uk 37 we examine clumped isotope 47 thermometry to fossil coccolith rich material as an sst proxy as clumped isotopes are independent of original seawater composition and applicable to a wide temperature range and coccolithophores are widespread and dissolution resistant the 47 derived temperatures from 63 m fraction removes most non mixed layer components however the 47 derived temperatures display an unexpected slight decreasing trend with decreasing size fraction this unexpected trend could partly arise because larger coccoliths 5 12 m are removed during the size fraction separation process the c1 and 63 m c2 47 derived temperatures are comparable to concurrent uk 37 ssts the 20 10 and 2 5 m c2 47 derived temperatures are consistently cooler than expected the 47 uk 37 temperature offset is probably caused by abiotic diagenetic calcite present in the c2 2 5 m fraction 53 by area which potentially precipitated at bottom water temperatures of 6 c our results indicate that clumped isotopes on coccolith rich sediment fractions have potential as an sst proxy particularly in tropical regions providing that careful investigation of the appropriate size fraction for the region and timescale is undertaken this article is protected by copyright all rights reserved

aminostratigraphy and ages of pleistocene limestones of bermuda the pleistocene stratigraphy of bermuda offers important information for sea level history corals are rare in bermuda pleistocene carbonates and so many deposits are not appropriate for u series dating we have extended the geochronological base in bermuda by determining the extent of isoleucine epimerization a i ratios in 1 marine shells glycymeris and others from deposits of sea level high stands 2 land snails poecilozonites from protosols associated with the eolianites that comprise the bulk of bermuda and 3 whole rock samples of bioclastic calcarenites the three distinct types of samples provide independent aminostratigraphies aminozones c e f g h j and k that are mutually consistent and in agreement with the mapped lithostratigraphy correlation of the amino acid ratios with ages based on previously published u series coral dates verifies the utility of the apparent parabolic kinetics model for estimation of amino acid racemization ages extrapolation of ages based on the model to deposits beyond the range of u series dating reveals that a significant middle pleistocene section is present in bermuda

calibration and application of the clumped isotope thermometer to foraminifera for high resolution climate reconstructions the reconstruction of past ocean temperatures is fundamental to the study of past climate changes therefore considerable effort has been invested in developing proxies for seawater temperatures one of the most recent and promising new proxy is carbonate clumped isotope thermometry in particular because it is based on thermodynamic equilibrium and not on biogeochemical proxies here we present a new calibration of the clumped isotope thermometer to foraminifera based on seven species of planktic and benthic foraminifera spanning a growth temperature range of 2 28 c we used a newly developed technique for the measurements of small samples to improve the applicability of this method to paleoceanography our data have a comparable precision 0 005 0 013 and confirm previous calibration studies based on biogenic and inorganic calcite we discuss possible sources of uncertainty such as over underestimation of the calcification temperatures species specific vital effects ph variations between the seawater and the vacuole water of the species and possible kinetic effects on the clumped isotope calibration to validate our calibration study and test the applicability of our measuring technique to paleoclimate and paleoceanographic studies we measured the isotope composition of globigerinoides ruber white at high resolution in a sediment core covering the last 700 years in the gulf of taranto mediterranean sea the results show that it is necessary to average a relatively large number of analyses to achieve a consistent temperature signal for the detection of small sea surface temperature changes although with the current analytical system clumped isotope thermometry is only applicable to the analysis of relatively large sst changes in marine sediments further technical improvements may make this a very powerful technique for paleoceanographic studies

u series and amino acid racemization geochronology of bermuda implications for eustatic sea level fluctuation over the past 250 000 years abstract bermuda is a stable mid oceanic carbonate platform for which a particularly complete record of late pleistocene eustatic sea level fluctuation has been reconstructed from a detailed study of geological field relationships combined with an extensive programme of u series and amino acid racemization geochronology only twice in the past 250 000 yr has sea level in bermuda been above its present level once at approximately 200 k y when it stood at about 2 m and most recently at 125 4 k y when it stood at 5 1 m these times of interglacial high sea level are characterized by the development of patch reefs and marine calcarenites at elevations above present sea level episodes of lower sea stand onto the bermuda platform at elevations higher than 20 m are observed within the two interglacial periods and are characterized by the deposition of eolianites by contrast glacial periods are times of residual soil formation and deposition of speleothems in caves at elevations below present sea level excellent correlation is observed between the bermuda glacio eustatic sea level record and other marine and terrestrial paleoclimate records

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

paleoclimate reconstruction using carbonate clumped isotope thermometry carbonate clumped isotope thermometry is a relatively new paleotemperature proxy based on measurements of the degree of ordering of 13 c and 18 o into bonds with each other making the 13 c 18 o 16 o 2 2 ion group in lattices of carbonate minerals this technique has several unusual properties that complement existing methods of paleoclimate reconstruction most importantly it is based on a homogeneous isotope exchange equilibrium and thus constrains temperature independent of the isotopic composition of waters from which carbonates grew this method also appears to be generally insensitive to vital effects that compromise many other paleothermometers based on the chemical properties of biominerals or organic matter at least for those organisms that have been subjected to systematic study to date corals and foraminifera however discrepancies among some calibrations particularly at low temperatures may point toward the existence of vital effects in mollusks and other organisms this review discusses the principles and calibrations of the technique its uses in combination with conventional stable isotope measurements to constrain the 18 o of past waters preservation of paleotemperatures in ancient materials as well as current problems in our understanding of calibrations and interlaboratory data comparisons

the himalayan passive margin from precambrian to cretaceous times abstract the himalaya passive margin should be separated into the indian himalaya and the pakistan himalaya divided by the nanga parbat haramosh basement uplift in the northwestern syntaxes the indian passive margin shows a complex history involving splitting of microcontinents off the northern gondwana margin from early paleozoic times until the jurassic in contrast the pakistan himalaya formed part of the stable indian shelf until separation from africa started in the jurassic each margin has a distinct stratigraphic history until the mid mesozoic after which they show similar histories until the tertiary the himalaya mountains in india consist of three distinct tectonic units juxtaposed during the neogene by southward thrusting of the northern indian precambrian to mesozoic passive margin the lesser himalaya on the south forms a late precambrian passive margin usually directly overlain by late cretaceous to tertiary clastics its stratigraphy is closest to that of the indian shield in contrast the high himalaya has a thin ordovician to carboniferous shelf sequence deposited after early ordovician deformation and granite intrusion above this thick permian and mesozoic shelf sequences mark the separation of continental blocks off the northern indian margin and the opening of the neotethys ocean the north himalaya formed the slope and basin of this ocean and consists of reactivated paleozoic gneiss domes overlain by thick mesozoic sediments which pass in the northeastern himalaya into an enormously thick sedimentary sequence resting on oceanic crust paleomagnetic and structural evidence indicates at least 500 km of southward thrusting along the main central thrust between the lesser and high himalaya this thrusting together with a further 250 km of erosion at the front of the nappes has removed the entire inner shelf of the himalaya passive margin and can explain the startling contrast between the high and lesser himalaya stratigraphic sequences but there are still discrepancies particularly in the eastern himalaya where precambrian basement is juxtaposed with the north himalaya mesozoic slope these discrepancies can be partly resolved by strike slip movements roughly parallel to the himalaya which have removed parts of the northern indian passive margin such faults of the requisite orientation displacement and age occur in southeast asia where their cumulative displacements can add up to several thousand kilometres similar faults of undoubted pre tertiary age occur in the pakistan himalaya here the passive margin shows a much simpler history of jurassic to miocene subsidence

dnsc08 mean sea surface and mean dynamic topography models 1 the danish national space center data set dnsc08 mean sea surface mss is a new enhanced mapping of the mean sea surface height of the worlds oceans derived from a combination of 12 years of satellite altimetry from a total of eight different satellites covering the period 1993 2004 it is the first global mss without a polar gap including all of the arctic ocean by including laser altimetry from the icesat mission the mean dynamic topography mdt is the quantity that bridges the geoid and the mean sea surface constraining large scale ocean circulation here we present a new high resolution 1 min global mdt called dnsc08 mdt derived from the slightly smoothed difference between the dnsc08 mss and the egm2008 geoid the derivation and quality control of the new dnsc08 mss and dnsc08 mdt is presented in this paper along with suggestions for time period standardization of the mss and mdt models this way a consistent modeling of the interannual sea level variability is carried out before different mss and mdt models are compared altimetric derived physical mss can be converted into an inverse barometer corrected mss by correcting the altimeter range for the inverse barometer effect of the atmosphere on the sea surface height it is demonstrated that it is important to choose the right version of the mss when comparing with hydrodynamic models and gps measured tide gauges

meltwater pulse recorded in last interglacial mollusk shells from bermuda the warm climate of bermuda today is modulated by the nearby presence of the gulf stream current however iceberg scours in the florida strait and the presence of ice rafted debris in bermuda rise sediments indicate that during the last deglaciation icebergs discharged from the laurentide ice sheet traveled as far south as subtropical latitudes we present evidence that an event of similar magnitude affected the subtropics during the last interglacial potentially due to melting of the greenland ice sheet using the clumped isotope paleothermometer we found temperatures 10 c colder and seawater 18o values 2 lower than modern in last interglacial cittarium pica shells from grape bay bermuda in contrast last interglacial shells from rocky bay bermuda record temperatures only slightly colder and seawater 18o values similar to modern likely representing more typical last interglacial conditions in bermuda outside of a meltwater event the significantly colder ocean temperatures observed in grape bay samples illustrate the extreme sensitivity of bermudian climate to broad scale ocean circulation changes they indicate routine meltwater transport in the north atlantic to near equatorial latitudes which would likely have resulted in disruption of the atlantic meridional overturning circulation these data demonstrate that future melting of the greenland ice sheet a potential source of the last interglacial meltwater event could have dramatic climate effects outside of the high latitudes

antarctic ice growth before and after the eocene oligocene transition new estimates from clumped isotope paleothermometry across the eocene oligocene transition the oxygen isotopic composition 18o of benthic and planktonic foraminifera increased by over 1 this shift is thought to represent a combination of global cooling and the growth of a large ice sheet on the antarctic continent to determine the contribution of each of these factors to the total change in 18o we measured the clumped isotopic composition of planktonic foraminifera tests from ocean drilling program site 689 in the southern ocean near surface temperatures were 12 c in the intervals 0 1 5 myr before and 1 2 myr after the major oi 1 transition in agreement with estimates made using other proxies at nearby sites temperatures cooled by 0 4 1 1 c between these intervals indicating that the long term change in 18o seen in planktonic foraminifera at this site is predominantly due to changes in ice volume a larger instantaneous cooling may have occurred during oi 1 but is not captured in this study due to sampling resolution the corresponding change in the isotopic composition of seawater 18osw is 0 75 0 23 which is within the range of previous estimates and represents global ice growth equivalent to roughly 110 120 of the volume of the modern antarctic ice sheet or 80 90 m of eustatic sea level change

anatomy of a transgressive lag panther tongue sandstone star point formation central utah the panther tongue of the star point formation in central utah contains a variety of transgressive lag deposits that when mapped regionally show a sensitive dependence upon pre existing topography of the palaeoshoreline the panther tongue consists of a coarsening upward sandstone wedge that prograded into the western interior seaway during late cretaceous santonian time high resolution sequence stratigraphic analysis revealed that this member was deposited during the long distance 50 km regression and transgression of a delta into shallow marine environments containing basal highstand forced regression lowstand and transgressive systems tracts based on grain size clast composition lateral extent and stratigraphic position the coarse sandstones on top of the panther tongue were classified into four types 1 simple 2 dispersed 3 oxidized and 4 local lags the simple lag is composed of dark grey coarse sandstone with oyster fragments and shark teeth this lag is typically extensively bioturbated and massive laminated and cross bedded units are also common this type of coarse sandstone is interpreted as a typical transgressive lag the dispersed lag differs in that it contains abundant mud and commonly occurs as multiple beds in thick intervals of muddy sandstone mixing of bay estuarine and shallow marine mud with simple lag sand may be responsible for deposition of this type of coarse sandstone the oxidized lag is distinctive in its reddish colour with extensive bioturbation and is commonly overlain by a simple lag the local lag is composed of thin bedded dark grey coarse sandstone occurring locally between the mouth bar and distributary channel the variation in types grain size and bed thickness of the coarse grained lags was mainly controlled by antecedent topography as suggested by immediately underlying lithofacies relatively thick 30 cm simple lags are present on top of mouth bar sandstones whereas dispersed lags are common on top of the distributary channel sandstone and in bay estuarine and shallow marine mudstones erosion of topographic highs mouth bar resulted in relatively thick accumulation of simple lags in topographic low areas such as distributary channel estuary bay and shallow marine environments fine grained muddy sands that were eroded from the nearby topographic highs were redeposited intermittent storm waves transported coarse sands both landward and seaward forming a dispersed lag the net effect was reworking of local topographic relief during overall transgression forming an apparently planar transgressive surface of erosion

surface and deep ocean variability in the northern sargasso sea during marine isotope stage 3 new geochemical proxy data from bermuda rise piston cores reveal ocean and climate conditions in the northern sargasso sea during marine isotope stage 3 using 18o on the planktonic foraminifer globigerinoides ruber we can correlate explicitly with every stadial interstadial change in greenland ice between 32 and 58 ka these data suggest repetitive changes of 4 c in the annual average sea surface temperature sst with maximum cooling comparable to or greater than sst during glacial maximum conditions the extent of sst depression is about the same for typical stadial events and for heinrich events 4 and 5 which we have identified on the bermuda rise by traces of ice rafting benthic foraminiferal 13c decreases during every stadial event consistent with reduced production of the deepest component of north atlantic deep water and shoaling of its interface with antarctic bottom water this interpretation is supported by benthic cd ca data from the climate cycle associated with interstadial 8

greenland was nearly ice free for extended periods during the pleistocene measurements of cosmic ray produced 10be and 26al in a bedrock core from beneath the summit of the greenland ice sheet show that greenland was nearly ice free for extended periods under pleistocene climate forcing the greenland ice sheet is a main contributor to modern sea level rise but its stability during past warm periods is uncertain thus compromising our ability to robustly predict future rates and magnitudes of ice loss joerg schaefer and colleagues present cosmogenic isotope evidence from bedrock samples from beneath an ice core near the summit of the ice sheet to show that the greenland ice sheet was largely ice free at some point during the pleistocene the data cannot constrain the time or duration of ice free conditions and seem incompatible with our current understanding of ice sheet behaviour nevertheless alternative explanations for the cosmogenic data are lacking suggesting that our understanding of the response of the greenland ice sheet to past warmth remains incomplete the greenland ice sheet gis contains the equivalent of 7 4 metres of global sea level rise1 its stability in our warming climate is therefore a pressing concern however the sparse proxy evidence of the palaeo stability of the gis means that its history is controversial compare refs 2 and 3 to ref 4 here we show that greenland was deglaciated for extended periods during the pleistocene epoch from 2 6 million years ago to 11 700 years ago based on new measurements of cosmic ray produced beryllium and aluminium isotopes 10be and 26al in a bedrock core from beneath an ice core near the gis summit models indicate that when this bedrock site is ice free any remaining ice is concentrated in the eastern greenland highlands and the gis is reduced to less than ten per cent of its current volume our results narrow the spectrum of possible gis histories the longest period of stability of the present ice sheet that is consistent with the measurements is 1 1 million years assuming that this was preceded by more than 280 000 years of ice free conditions other scenarios in which greenland was ice free during any or all pleistocene interglacials may be more realistic our observations are incompatible with most existing model simulations that present a continuously existing pleistocene gis future simulations of the gis should take into account that greenland was nearly ice free for extended periods under pleistocene climate forcing

geochronology biostratigraphy and changing shell morphology in the land snail subgenus poecilozonites during the quaternary of bermuda shells from over 280 collections representing all known forms of subgenus poecilozonites zonitidae from bermuda have been ranked in stratigraphic order and relative age aminostratigraphy the samples were first grouped by their source lithostratigraphic unit with additional refinements being made based on the epimerization ratio d alloisoleucine l isoleucine or a i from nearly 400 representative individual shells of each of the forms a plot of a i frequency defines several modes or aminozones the aminozones correlate strongly with defined lithostratigraphy with some minor variation resulting from less optimally preserved shells the succession of land snails is ranked over chronological range from the middle and early pleistocene with greatest resolution since 500 ka this 500 ka age range and density of sampling is among the most extensive for any organism on an oceanic island morphological analysis of poecilozonites demonstrates oscillation and repetition of morphotypes over multiple sea level cycles shells from the small island s that formed during interglacial times are generally small and show little variation in form during glacial periods when bermuda reached maximal size shells are much larger extreme variation in shell size and shape occurs at interglacial glacial transitions in as little as 2 4 ka because the subgenus has been endemic to bermuda for at least ca 1000 ka such dramatic and rapid shifts in shell morphology cannot be the result of recolonization from outside sources an intact and undisturbed 130 ka long biostratigraphic record of poecilozonites is contained in a single vertical 2 m thick talus accumulation in admirals cave that has been dated at high resolution by three independent techniques the bio and chronostratigraphy show that snails were very large at the close of glacial stage marine isotope stage mis 6 small during interglacial mis 5 re evolved identical large size during the last glaciation mis 4 2 and changed abruptly to the small paedomorphic modern form at the onset of the holocene mis 2 1 about 10 12 ka ago when assessed with care shells of poecilozonites may be used as guide fossils for rapid field identification of lithostratigraphic units in surface deposits and as chronological indicators in cave and fissure fills when used in combination with vertebrate remains

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

the precambrian cambrian boundary problem and its prospects northwest himalaya india the precambrian cambrian boundary problem is studied in an areno argillaceous sequence in the kashmir and spiti valley northwest himalaya india in kashmir a rich and diversified microbiota cryptarchs and algae of the late precambrian and low lower cambrian trace fossils are recorded in the spiti valley the yield of microbiota is poor and the trace fossils are late lower cambrian modified journal abstract

the uncertainties of finite rotations in plate tectonics incomplete knowledge of the pattern of magnetic lineations and fossil transform faults represented by sea floor spreading data on two plates generated by the same spreading center leads to uncertainties in a reconstruction of the past relative configuration of the plates a reconstruction may be represented by the finite rotation that describes one configuration relative to another in this paper a method of reconstruction is provided that reflects the uncertainties in the data the method minimizes a weighted least squares measure of fit as a function of the rotation parameters for a given rotation the measure of fit represents the sum of squares of the weighted distances of fixed and rotated data points representing corresponding former plate margin segments from a common plate margin the common margin is estimated from the locations of both fixed and rotated data points the estimated margin consists of a set of great circle arcs it is shown how the method of reconstruction may be utilized to obtain an uncertainty region for the pole and angle of rotation that characterize the finite rotation these techniques are then used to study the uncertainties of reconstructions in the south pacific for the times of anomalies 13 and 18 the best fit reconstructions and the uncertainty region for the anomaly 18 pole are in good agreement with previous work however the uncertainties in the anomaly 13 pole were substantially underestimated by previous investigators

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

the climate of the late cretaceous new insights from the application of the carbonate clumped isotope thermometer to western interior seaway macrofossil abstract we apply the carbonate clumped isotope thermometer 47 to macrofossils from the baculites compressus 73 5 ma and the hoploscaphites nebrascensis 67 ma ammonite zones of the western interior seaway wis of north america and nearby coeval terrestrial and open marine environments the carbonate clumped isotope thermometer is based on a single phase isotope exchange equilibrium that promotes the clumping of two heavy isotopes together within a single carbonate molecule as temperature decreases due to the thermometer s isotopic independence from water coupled measurements of 47 and the bulk oxygen isotopic composition of a carbonate 18 o c enable the reconstruction of both paleotemperature and the isotopic composition of the water in which the organisms grew before applying the technique to the aragonite shells of fossil marine organisms mostly ammonites but also some gastropods bivalves and one belemnite we measure the clumped isotopic composition of modern nautilus and cuttlefish two of the nearest living relatives to the cretaceous ammonites modern cephalopods exhibit disequilibrium isotope effects with respect to 47 but not 18 o c therefore a simple correctional scheme is applied to the late cretaceous macrofossil data before reconstructing paleotemperatures diagenesis is also assessed by visual preservation and previously measured sr concentrations cochran et al 2003 temperatures reconstructed for the late cretaceous western interior seaway range from 16 4 3 5 c for an offshore interior seaway environment from the h nebrascensis zone to 24 2 0 4 c for the b compressus ammonite zone the seaway itself has an isotopic composition of approximately 1 relative to vsmow the expectation for an ice free global ocean average while a nearby freshwater environment has an isotopic composition approaching 20 we compare the attributes of the reconstructed climate to predictions based on late cretaceous climate models and previous reconstructions of the seaway and also assess the sensitivity of our results to the modern cephalopods correction by comparisons to suitable modern analogs finally our clumped isotope data are consistent with cooling between the late campanian and maastrichtian as also seen in benthic foraminfera 18 o

sr nd pb isotope evidence for ice sheet presence on southern greenland during the last interglacial to ascertain the response of the southern greenland ice sheet gis to a boreal summer climate warmer than at present we explored whether southern greenland was deglaciated during the last interglacial lig using the sr nd pb isotope ratios of silt sized sediment discharged from southern greenland our isotope data indicate that no single southern greenland geologic terrane was completely deglaciated during the lig similar to the holocene differences in sediment sources during the lig relative to the early holocene denote however greater southern gis retreat during the lig these results allow the evaluation of a suite of gis models and are consistent with a gis contribution of 1 6 to 2 2 meters to the 4 meter lig sea level highstand requiring a significant sea level contribution from the antarctic ice sheet

quantitative tectonic reconstructions of zealandia based on crustal thickness estimates zealandia is a key piece in the plate reconstruction of gondwana the positions of its submarine plateaus are major constraints on the best fit and breakup involving new zealand australia antarctica and associated microplates as the submarine plateaus surrounding new zealand consist of extended and highly extended continental crust classic plate tectonic reconstructions assuming rigid plates and narrow plate boundaries fail to reconstruct these areas correctly however if the early breakup history shall be reconstructed it is crucial to consider crustal stretching in a plate tectonic reconstruction we present a reconstruction of the basins around new zealand great south basin bounty trough and new caledonia basin based on crustal balancing an approach that takes into account the rifting and thinning processes affecting continental crust in a first step we computed a crustal thickness map of zealandia using seismic seismological and gravity data the crustal thickness map shows the submarine plateaus to have a uniform crustal thickness of 20 24 km and the basins to have a thickness of 12 16 km we assumed that a reconstruction of zealandia should close the basins and lead to a most uniform crustal thickness we used the standard deviation of the reconstructed crustal thickness as a measure of uniformity the reconstruction of the campbell plateau area shows that the amount of extension in the bounty trough and the great south basin is far smaller than previously thought our results indicate that the extension of the bounty trough and great south basin occurred simultaneously