atoll reef island formation and response to sea level change west island cocos keeling islands abstract reef islands around the margin of coral atolls generally comprise unconsolidated holocene sands and gravels overlying a reef flat or cemented conglomerate platform such islands have accreted within the last 3000 4000 years since sea level has reached a level close to present and the reef flat and conglomerate platform have formed island morphology consists of an oceanward ridge a less distinct lagoonward ridge and low lying central depression several alternative models of how such reef islands might have developed are examined in relation to chronology and sediment provenance particularly in the context of the cocos keeling islands where this issue has been debated since darwin visited the atoll which of these models appears most appropriate for an elongate reef island on the atoll margin is assessed using conventional radiocarbon dating of coral shingle and accelerator mass spectrometry ams radiocarbon dating of individual sand grains from pits across west island the dating results suggest that both coral clasts and individual grains of various components are generally reliable and replicable indicators of the chronology of island accumulation implying rapid transport of skeletal material after death of the contributing organisms across the reef flat zone and relatively little reworking the central part of west island appears to have formed first with oceanward accretion up until about 2000 years bp gradual oceanward accretion with lesser lagoonward extension has continued beyond 2000 years bp at the northern and southern ends of the island and a sequence of lagoonward recurving spits has formed adjacent to the inter island passage at the southern end of the island radiocarbon dating of fossil microatolls indicates a gradual fall of sea level over this period which appears to have had little effect on the pattern of island accretion

on applications of micro photogrammetry and geometric morphometrics to studies of tooth mark morphology the modern olduvai carnivore site tanzania abstract recent application of photogrammetric and geometric morphometric approaches to the study of cut marks on bones has yielded positive results in discriminating different types of tools and even some raw materials here we apply this analytical technique to the study of carnivore tooth scores the goal is twofold on the one hand we intend to differentiate carnivore types and on the other one we show the application of this approach to a sample of tooth scores from long bones documented at the modern assemblage of the olduvai carnivore site ocs previous taphonomic work at ocs suggested that this bone assemblage constituted a good evidence of a carcass accumulation behavior by lions followed by hyena ravaging the application of these 3d techniques to the selected sample of tooth marks shows that lions as well as spotted hyenas did indeed impart marks on the ocs assemblage this reinforces the dual nature of the assemblage and the implication of lions in its formation

composition of characteristic soils on the raised atoll bellona solomon islands abstract knowledge is scarce about the composition of soils on bellona and other pacific atolls such knowledge is important as it is closely related to sustainable land use of these special soils formed on carbonatic phosphatic materials therefore the micromorphological chemical and mineralogical composition of samples from genetic horizons in three dominant bellonese soils malanga kenge ungi and kenge toaha and underlying rock tanahu were investigated tanahu mainly consists of dolomite but this mineral is absent in the three soils which are dominated by phosphate containing minerals the malanga soil is strongly dominated by ca and p with minor amounts of al f and fe present in fluorapatite hydroxyapatite and crandallite in contrast al fe and p dominate in the kenge ungi and kenge toaha soils in accordance with a mineralogy consisting of crandallite together with aluminum oxides gibbsite boehmite and iron oxides mainly goethite with minor contents of hematite the observed carbonate for phosphate substitution in the apatites and crandallite is important as it indicates an increased phosphate availability in the soils all three soil samples contain 1 si and very little k and mg total contents of essential microelements are considered adequate but the rather high contents of sr and u especially in the kenge ungi soil may be problematic although the composition of the soils suggests substantial fertility and resilience the lack of k containing weatherable minerals silicate minerals is in line with a very low k and low mg content and explains why fertilization may be needed to sustain future cultivation of these special soils due to a possible low bioavailability of fe mn and maybe other micronutrients at the circumneutral ph of these carbonatic phosphatic soils as well as the rather high contents of sr and u it may be recommended to test element availability using appropriate chemical soil tests supplemented by plant experiments to ensure safe and sustainable optimal soil use however according to the local farmers the malanga kenge toaha and kenge ungi soils are considered well suited for production of the preferred crops

indian monsoon variability in the last 2000 years as inferred from benthic foraminifera abstract the effect of ambient conditions on living rose bengal stained benthic foraminifera has been studied from the shelf and slope of the central western bay of bengal to assess the applicability of temporal changes in benthic foraminiferal morpho groups angular asymmetrical and rounded symmetrical to reconstruct past monsoon changes we report that the riverine influx and associated processes control the relative abundance of angular asymmetrical aabf and rounded symmetrical rsbf benthic foraminiferal morpho groups in the central western bay of bengal subsequently temporal variations in relative abundance of aabf in a gravity core collected from outfall region of the pennar river are used to reconstruct decadal scale past monsoon variability during the last 1887 years an increased monsoon discharge is observed during the medieval warm period mwp and lower during the little ice age lia the periodic changes with a frequency of 123 and 238 years are also identified indicating a close relationship between monsoon and solar activity

last glacial interglacial productivity and associated changes in the eastern arabian sea abstract we reconstruct paleo productivity and bottom water oxygenation changes during the past 32 ka from the southeastern arabian sea using absolute abundance of planktic foraminifera relative abundance of globigerina bulloides angular asymmetrical benthic foraminifera aabf measurements of total organic carbon c org caco 3 and globigerinoides ruber 18 o and 13 c the faunal and geochemical proxies suggest that productivity in the southeastern arabian sea was high during mis 3 a distinct decrease in productivity is inferred during the last glacial maximum 19 23 ka lgm bottom water was well oxygenated during mis3 only to become oxygen depleted during the lgm productivity decreased abruptly during heinrich stadial 1 hs 1 but the response to heinrich stadial 2 hs 2 was different low productivity during the early deglaciation is also synchronous with an increase in ice volume corrected 18 o 18 o sw ivc a salinity proxy between 18 9 18 3 18 9 ka bp and 15 9 15 0 16 3 ka bp and a concomitant decrease in 13 c between 18 2 17 5 18 7 ka bp and 16 4 15 3 16 7 ka bp these patterns suggest that the global 13 c minimum event during the last deglaciation was associated with the weak monsoon interval during hs 1 and a drop in productivity in tropical regions a progressive increase in productivity is observed throughout the holocene with a distinct jump at 5 4 3 8 6 3 ka bp we infer that although productivity was higher in the eastern arabian sea during most of the last glacial interval the overall resultant carbon sequestration was confined only to a restricted zone and not large enough to substantially alter atmospheric co 2

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

mapping climatological seasonal variations of surface currents in the tropical atlantic using ship drifts the seasonal variability of current velocities in the tropical atlantic was studied by grouping ship drift velocity observations into 2 5 boxes and calculating monthly mean velocity values these values were used to calculate and map the annual mean velocity the seasonal variation about the mean the annual and semiannual harmonics and the first two empirical orthogonal functions eofs the seasonal variation is primarily zonal in the equatorial band and in the north equatorial countercurrent necc and primarily alongshore near the coast of south america maxima of seasonal variation of 23 cm s are centered in the necc near 6 n 42 5 w and in the gulf of guinea near 2 n 7 5 w most 80 of the variance in the necc and along the western boundary of the area studied has an annual period most of the variance along the equator in the mid atlantic has a semiannual period over the whole region 49 of the seasonal variance is explained by the annual harmonic and 69 is explained by a combination of the annual and semiannual harmonics the second eof contains 29 of the variance of the data set and shows a simultaneous speeding slowing of the major equatorial currents the south equatorial current sec the north brazil current the necc and the guinea current along their principal axes of variation with a concurrent slowing speeding of the guyana current and the brazil current the pattern of variation resembles a large equatorial gyre centered along 4 n that flows clockwise from may to september and counterclockwise most of the rest of the year the first eof accounts for 35 of the variance and shows a simultaneous speeding slowing of eastward velocity from 5 s to 10 n except in the western sec the western end of the north brazil current and the guinea current the out of phase fluctuations apparent in the western sec near the equator are explained by the slowing and reversal of the south equatorial current near 2 n 40 w between april and june this slowing of the sec is associated with the start up of the necc which accelerates eastward in may june and july and flows eastward across the atlantic from july through december the sec divides seasonally near the eastern tip of brazil where residual alongshore velocities are northward for half the year peaking during may and june and southward for the other half of the year a second division can be seen north of the amazon where the north brazil current continues up the coast into the guyana current during the first half of the year but partially retroflects into the necc during the last half of the year a fast eastward flow in the necc coincides with below average velocities in the guyana current and above average velocities in the western sections of the north brazil current and the sec north of the equator

lithium in foraminiferal shells implications for high temperature hydrothermal circulation fluxes and oceanic crustal generation rates the lithium content of planktonic foraminiferal calcite has been determined to evaluate temporal variability of seawater li concentrations over the past 116 m y mean foraminiferal calcite lithium calcium in each time interval is no more than 16 greater nor 25 less than the mean li ca of all samples li ca minima are observed for samples from 50 60 m y and 80 90 m y with li ca about 25 lower than in adjacent time intervals at no time during the past 40 m y does mean li ca appear to be higher than that at present subject to the limitations imposed by sample coverage and diagenesis a similar conclusion holds for the past 116 m y coupled with an oceanic mass balance model for li these data suggest that 1 oceanic li concentrations and therefore high temperature hydrothermal circulation fluxes during the past 40 m y and perhaps the past 100 m y have not been more than perhaps 30 40 greater than at present for intervals any longer than a million years at most and 2 these fluxes werenot a factor of two higher 100 m y ago by inference variations in oceanic crustal generation rates over these time periods are similarly limited decreases in hydrothermal circulation fluxes and crustal generation rates or fluctuations up to 20 in these rates of a few million years duration arenot necessarily ruled out by the li ca data the lack of variability in li ca over time is not unequivocal evidence that hydrothermal fluxes have not varied because the rates of removal processes may be linked to changes in input fluxes

approaching raw material functionality in the upper magdalenian of coimbre cave asturias spain through geometric morphometrics abstract coimbre cave penamellera alta asturias is an upper palaeolithic site in northern spain spanning an occupation sequence from the gravettian to the magdalenian periods the upper layers layer i and ii corresponding to the upper magdalenian register the highest intensity of human activity in this paper we analyse raw material functionality at the site through the study of cut marks found on bone remains at coimbre we have documented mainly quartzite followed by flint other raw materials are found in very low frequencies there are several types of local quartzite that appear mainly as flaking debitage and stone tools such as burins and scrappers on the other hand flint is mainly knapped to elaborate blades and bladelets as well as specialised implements such as different types of side scrappers retouched flakes on flint are relatively more abundant than those made on quartzite in this paper we employ the use of photogrammetry geometric morphometrics and statistics to analyse the cut marks from the upper magdalenian assemblage of coimbre cave our aim is to determine the lithic raw material preferentially used for carcass processing at the site

application of geometric morphometrics to the analysis of cut mark morphology on different bones of differently sized animals does size really matter abstract recent techniques applied to taphonomy have made advances in our understanding of bone surface modifications for many years differences in bone density according to element and variations in animal size have been considered conditioning factors for many taphonomic processes while several studies highlight how animal size and density affect fracture patterns and bone preservation rates variations in cut mark morphology are yet to be confronted against these variables here we assess the effect of these variables and their potential effect on cut mark morphology by comparing a considerable amount of cut marks on different anatomical elements of both suids and bovids experimentally produced cut mark samples were then digitally reconstructed using a david laser scanner that allowed the statistical analysis of each cut mark s shape and form geometric morphometric analysis using 2d and 3d landmark models were unable to find substantial differences in cut mark morphologies caused by either element type of carcass size

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

tectonic stresses seaward of an aseismic ridge trench collision zone a remote sensing approach on the loyalty islands sw pacific abstract the loyalty islands are a series of limestone karstified islands on the australian plate that are presently approaching the vanuatu subduction zone sw pacific they are deformed due to the combined effects of the bulging of the subducting lithosphere and the beginning collision between the loyalty ridge and the vanuatu subduction zone therefore they constitute a series of markers for early phases of ridge arc collision lineaments deduced from remote sensing images aerial photos spot3 spot4 and envisat data termed here as fractures are analyzed by comparison with planar structures measured during field studies and termed as geological data fracture data indicate a stable main n110 direction with a large variance of nearly 15 in rms and two minor directions 45 apart which may constitute shear directions associated to the major one a scale dependent analysis shows that fractures longer than 2000 m are close to the n110 direction and that their orientation shifts progressively to reach the n125 direction for l

seasonal stable isotopic variations in living planktonic foraminifera from bermuda plankton tows abstract seasonal variations in surface water temperature and the 18o 16o ratios of calcite tests of living planktonic foraminifera collected in the upper 10 mare are coincident in the sargasso sea off bermuda the 18o of seasonally restricted globorotalia truncatulinoides and globigerinoides ruber pink and white may be used to determine the seasonal temperature contrast of the oceans in the past a preliminary model based on yearly absolute abundance and isotopic composition of these two species is able to approximate the composite 18o of fossil specimens of these species carbon and oxygen isotopic compositions of most species are size dependent with the largest differences occuring in 13c as a function of size the calcite tests of all living species were depleted in 13c relative to the 13c of total dissolved co2 at 0 and 50 m with no seasonal pattern in 13c being discernible in any species in almost all cases fossil specimens from box core sediments are significantly enriched in 13c and slightly enriched in 18o relative to their counterparts in the living fauna because the sediment populations are generally composed of larger sized specimens compares to the plankton of larger size specimens compared to the plankton

oxygen minimum expansion in the sulu sea western equatorial pacific during the last glacial low stand of sea level the sulu sea in the western equatorial pacific is presently a shallowly silled dysaerobic deep marine basin deep waters in the sulu sea are ventilated through a single sill at 420 m depth which connects it to the china sea benthic and planktonic foraminiferal oxygen and carbon isotope records benthic and planktonic foraminiferal census data and total organic carbon measurements have been used to evaluate changes in water mass conditions in the sulu sea between the last glacial maximum 18 000 yrs b p and the present day an increase in the abundance of the planktonic foraminiferaneogloboquadrina dutertrei and relatively light planktonic foraminiferal 18o values suggest that during the last glacial maximum surface water salinities were reduced in the sulu sea enhanced isolation of the basin due to glacio eustatic lowering of sea level and reduced surface salinities resulted in stagnation of deep water and an expansion of the mid water oxygen minimum layer increased organic carbon preservation at mid water depths occurs at this time benthic carbon isotope data and an increase in the abundance of benthic foraminiferal species considered to prefer low oxygen environments support the conclusion of an oxygen minimum expansion at mid water depths during the last glacial maximum at water depths greater than 4000 m bottom waters appear to have maintained some degree of oxygenation during the last glacial maximum stronger pacific ocean trade winds at this time may have caused the influx of denser celebes sea surface water into the southern part of the sulu sea the slow sinking of this water would have then ventilated bottom waters in this part of the basin at the transition from glacial to interglacial conditions rising sea level caused denser water to flow over the deepest sill into the sulu sea vertical circulation increased resulting in a greater downward flux of oxygen and a dissipation of the oxygen minimum continued post glacial sea level rise caused periodic ventilation of deep water until the present dysaerobic conditions were established

comparison of atlantic and pacific paleochemical records for the last 215 000 years changes in deep ocean circulation and chemical inventories abstract detailed cd ca and 13 c data have been obtained for benthic foraminifera from western north atlantic and equatorial pacific sediment cores in the modern ocean both tracers are closely linked to nutrient distributions the sedimentary records for both tracers indicate that bottom waters overlying the atlantic site have been nutrient depleted relative to those at the pacific site over the last 215 000 years from this evidence it is reasonable to infer that there has been a continuous net flux of nutrient depleted water from the western north atlantic into the pacific this exchange has undergone significant fluctuations with the export of nutrient depleted atlantic water diminishing by about a factor of two relative to the inflow from southern ocean sources over the last 215 000 years carbon isotope fluctuations in both regions are dominated by variable storage of isotopically light carbon on continents with a lesser contribution from these deep ocean circulation changes the cadmium signal in the north atlantic is dominated by changes in deep ocean circulation patterns cadmium shows less variability in the pacific which may reflect changes in the global average cadmium content or minor changes in deep pacific circulation patterns using these records to estimate global averages it appears that glacial ocean water had 22 more cd and 0 46 less 13 c than the modern ocean these numbers are estimates which may be revised as more data become available although they are not likely to be as much as 20 in error for cd or 0 2 for 13 c relative north atlantic deep water nadw formation rates are modulated with a significant 41 kyr periodicity linked to obliquity induced variations in high latitude insolation nadw lags 8 2 kyr behind insolation however

micro photogrammetric characterization of cut marks on bones in the last few years the study of cut marks on bone surfaces has become fundamental for the interpretation of archaeological sites and prehistoric butchery practices due to the difficulties in the correct identification of cut marks many criteria for their description and classifications were suggested this article presents an innovative methodology which supplements the microscopic study of cut marks despite the benefits of using scanning electron microscopy sem for the two dimensional identification of these marks it has a number of drawbacks such as the high costs and consequently the limited sample studied in this article a low cost technique for the analysis of cut mark micromorphology from a tri dimensional perspective is introduced it provides a high resolution approach to cut mark characterisation such as morphology depth width and angle estimation as well as section determination measured directly on the marks on bones macro photogrammetry records quantitative and qualitative information which can be statistically processed with standard multivariate and geometric morphometric tools

proloculus size variation in recent benthic foraminifera implications for paleoclimatic studies abstract ratios of dimorphic microspheric megalosperic forms of foraminifera are affected by temperature and hence are useful in paleoclimatic studies in some cases however it is not possible to distinguish between the dimorphic forms and therefore mean proloculus size is useful a higher ratio means more microspheric forms and thus a lower mean size of the proloculus to test this possibility the mean proloculus size of cavarotalia annectens parker jones was measured in 14 surface sediment samples from the near shore region along the west coast of india bombay to kannyakumari covering a stretch of 10 latitude in this region temperature varies from 27 5 to 29 25 c and salinity from 33 7 to 36 0 the results show that mean proloculus size varies from 0 045 to 0 103 mm and is inversely proportional to temperature r 0 78 and salinity r 0 71 variations it is proposed therefore that this parameter mean proloculus size of foraminifera can be used as an additional tool in paleoclimatic studies

13c record of benthic foraminifera in the last interglacial ocean implications for the carbon cycle and the global deep water circulation the 13c 12c ratios of upper holocene benthic foraminiferal tests genera cibicides and uvigerina of deep sea cores from the various world ocean basins have been compared with those of the modern total carbon dioxide tco2 measured during the geosecs program the 13c difference between benthic foraminifera and tco2 is 0 07 0 04 for cibicides and 0 83 0 07 for uvigerina at the 95 confidence level 13c analyses of the benthic foraminifera that lived during the last interglaciation isotopic substage 5e about 120 000 yr ago show that the bulk of the tco2 in the world ocean had a 13c value 0 15 0 12 lower than the modern one at the 95 confidence level reflecting a depletion compared to the present value of the global organic carbon reservoir regional differences in 13c between the various oceanic basins are explained by a pattern of deep water circulation different from the modern one the antarctic bottom water production was higher than today during the last interglaciation but the eastward transport in the circumpolar deep water was lower

comparison between radiocarbon ages obtained on coexisting planktonic foraminifera as a test of the reliability of paleocean ventilation rates reconstructed from radiocarbon age differences between planktonic and benthic foraminifera measurements have been made on coexisting species of planktonic foraminifera while ideally no differences should exist we do find them in this paper we discuss the possible causes for these differences and attempt to evaluate their impact on the interpretation of benthic planktonic age differences

paired carbon isotope and cadmium data from benthic foraminifera implications for changes in oceanic phosphorus oceanic circulation and atmospheric carbon dioxide abstract the carbon isotope and cadmium content of foraminiferal shells from oceanic sediments provides information on past chemical distributions in the ocean starting from reasonable assumptions it can be shown that paired data on both tracers provides more information than does either separately the slope of paired isochronous 13c and cd ca data from fossil benthic foraminifera depends on oceanic p cd and gd 13c p ratios the zero cd ca intercept of this line depends on mean oceanic 13c p and the 13c p ratio given data sufficient to define oceanic mean 13c and cd contents it is possible to place quantitative constraints on the product of the c p redfield ratio and mean oceanic phosphorus and to estimate a circulation parameter which is independent of changes in ocean chemical inventories with the limited available data no significant changes in oceanic p cd can be detected between the holocene and most recent glacial maximum if this data is taken to be representative of the whole ocean then the p and cd contents of the ocean were about 17 higher during the last glacial maximum than at present ocean box models indicate that this change in oceanic p and a 2 c deep ocean cooling during glacials would cause a 47 ppmv reduction in atmospheric pco2 during glacial intervals

development of a pliocene mixed carbonate siliciclastic reef limon costa rica the miocene to pleistocene limon group of costa rica is a mixed carbonate siliciclastic succession that formed in association with the emergence of the central american isthmus our study focuses on a lower late pliocene reef unit the newly excavated contact cut which is located at the contact between the siliciclastic sediments of the rio banano formation and the mixed reefal and coral bearing deposits and siliciclastic sediments of the quebrada chocolate formation the siliciclastic sediments were deposited in a thick deltaic setting sourced by erosion of the cordillera de talamanca deposits of the limon group preserve a sequence of progressively shallowing near shore sediments that were exposed by uplift during the early to middle pleistocene the contact cut outcrop shows the first reef sequence in the stratigraphic sequence and thus illustrates the reestablishment of caribbean coral reef predominance in the neogene it shows extensive reef growth during a rise in sea level and a slight progradation during the succeeding sea level highstand three stages of reef evolution are recognized based on faunal diversity the contact cut reef complex is comparable to the time equivalent reef of the las islas roadcut situated west of limon which shows a rapid burial of the corals by siliciclastics both reefs document a distinct facies diversification during the final stages of the closing of the central american seaway the reefs developed in an environment stressed by siliciclastic input which ultimately caused a decrease in coral diversity and abundance followed by a temporary demise of the reefs the biotic composition of the patch reefs that occurred during the sea level rise las islas and contact cut did not differ from the reefs that developed during the final highstand in sea level the reefs of the overlying moin formation limon group differences in the position on the shelf relative to the source of the siliciclastics might have been the cause for the different response to the rise in sea level of the transgressive reefs with a very fast give up scenario for las islas reef and a catch up followed by a give up phase for contact cut reef

carbon isotope composition of tropical surface water during the past 22 000 years carbon isotope values of many species of planktonic foraminifera are size dependant values of 13c of individual size fractions are therefore an integration of low 13c values of calcite precipitated in the juvenile growth stage and high values precipitated in later stages in general the selection of a particular size fraction for downcore studies has been subjective analysis of different size fractions of planktonic foraminifera however yields different time series in downcore studies by measuring the 13c of many size fractions the 13c precipitated throughout the growth of the foraminifera can be calculated time series of the 13c of calcite precipitated in the late growth stages of planktonic foraminifera from two nearby cores from the caribbean sea result in a better correlation than time series of constant size fractions these 13c records indicate similar 13c values during the last glaciation and the late holocene and a broad deglacial minimum approximately synchronous with a minimum in the 13c records of benthic foraminifera from intermediate depth atlantic cores the deglacial minimum may be a reflection of the isotopic composition of the underlying intermediate water which may be affected by circulation changes or changes in preformed 13c values and or of the flux of water upwelled into the surface layer the small 0 2 to 0 0 glacial interglacial 13c difference in tropical surface water is also believed to be affected by the chemistry of the underlying source water

hurricane deposits on carbonate platforms a case study of hurricane irma deposits on little ambergris cay turks and caicos islands the study of modern hurricane deposits is useful in both identifying ancient hurricane deposits in the rock record and predicting patterns of deposition and erosion produced by future storm events hurricane deposits on carbonate platforms have been studied less frequently than have been those along continental coasts here we present observations of the characteristics of deposition and scour caused by hurricane irma on little ambergris cay a small uninhabited island located near the southeastern edge of the caicos platform in the turks and caicos islands hurricane irma passed directly over little ambergris cay on 7 september 2017 as a category 5 hurricane we described and sampled multiple types of hurricane deposits and determined that the washover fans were the best sedimentological records for hurricane conditions as they were subject to very little reworking over time we compared different model predictions of storm tide and wave height with eyewitness reports and distributions of scour examining the washover fans allowed for the construction of a conceptual model for hurricane deposits formed in a high energy storm event on a carbonate platform characteristics of the washover fans were their small size the lack of sedimentary structures and very well sorted sediment the size and distribution of carbonate boulders eroded and transported by the storm are consistent with depth averaged flow velocities in the range of 1 5 5 3 m s the strength of the storm and the low lying topography distinct features of a carbonate platform setting contributed to high levels of sediment bypass and high flow velocities resulting in small unstructured deposits

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

the response of benthic foraminifera to productivity cycles in the eastern equatorial pacific faunal and geochemical constraints on glacial bottom water oxygen levels the stage 2 glacial maximum in eastern equatorial pacific ocean sediments is characterized by a pronounced increase in the organic carbon content which has been attributed either to increased upwelling and higher production along the equatorial divergence during the last glacial period or to enhanced preservation as a consequence of a lower concentration of dissolved o2 in glacial bottom water several lines of evidence are presented based on data from two gravity cores collected from the central panama basin which support the former interpretation first both the abundance and the size of benthic foraminifera of the genus uvigerina increase in stage 2 coincident with the increase in organic carbon concentration most probably because of the greater availability of organic detritus during the glacial period the increase in foraminiferal size and associated greater requirement of oxygen for respiration argues against the probability that oxygen was substantially depleted in the upper centimeter where uvigerina spp are thought to live second the number of meiofaunal faecal pellets increases markedly during the stage 2 maximum indicating a more populous and active infauna which again argues against oxygen depletion third there is no significant decrease in the iodine organic carbon i corg ratio in the stage 2 sediments because iodine is depleted relative to carbon in anoxic basins but enriched in association with organic matter in oxic environments the absence of a depletion in the i corg ratio in stage 2 is evidence that bottom water remained oxygen replete during the last glacial fourth molybdenum is not enriched in sediments deposited in stage 2 the presence of anoxic or dysaerobic bottom water or shallow pore waters during that time would have been recorded by the addition of mo to the sediments via coprecipitation with authigenic iron sulphides the combined faunal and geochemical data are consistent with the notion that panama basin deep waters remained oxygen replete during the last glacial maximum it is concluded that the late stage 2 carbon enrichment in the eastern equatorial pacific more probably reflects higher productivity rather than enhanced preservation

the δ13c of equatorial atlantic surface waters implications for ice age pco2 levels carbon isotopic records of nutrient depleted surface water place constraints on the past fertility of the oceans and on past atmospheric pco2 levels the best records of nutrient depleted 13c are obtained from planktonic foraminifera living in the thick mixed layers of the western equatorial and tropical atlantic ocean we have produced a composite stacked globigerinoides sacculifer 13c record from the equatorial atlantic which exhibits significant spectral power at the 100 000 and 41 000 year milankovitch periods but no power at the 23 000 year period similar to the record presented by shackleton and pisias 1985 surface deep ocean 13c produced with the g sacculifer record leads the 18o ice volume record however the glacial interglacial amplitudes of 13c differ between our record and shackleton and pisias 1985 record although large changes in 13c occur in the equatorial atlantic during early stages of the last three glacial cycles surface deep 13c at glacial maxima 18o stage 2 late stage 6 and late stage 8 was only about 0 2 greater than during the subsequent interglacial our results imply that nutrient driven pco2 changes account for about one third of the pco2 decrease observed in ice cores and consequently 13c should not be used as a proxy pco2 index enough variance in the ice core pco2 records remains to be explained that conclusions about pco2 and ice volume phase relationships should also be reexamined as much as 40 ppm pco2 change still has not been accounted for by models of past physics and chemistry of the ocean

compressive marks from gravel substrate on vertebrate remains a preliminary experimental study abstract lakeshore sites such as cerro de la garita miocene of teruel spain and seneze pliocene of haute loire france yielded fossils with distinct puncture marks these marks were described as punctures surrounded by plastically deformed bone and were proposed to have been caused by compression or trampling on bones against coarse sediment grain when deposited in damp environments a series of experiments was performed to test this hypothesis cow red deer and fallow deer metapodials were compressed by applying a mechanical load on them against a gravel substrate under dry damp environments results confirm that these characteristic puncture marks are associated with compression efforts on bones in wet environments

can benthic foraminiferal morpho groups be used as indicators of paleomonsoonal precipitation a technique is proposed for the quick and easy assessment of paleomonsoonal precipitation through the study of morphological groups of foraminifera in a shallow water 20 m water depth sediment core collected off karwar near kali river mouth central west coast of india the percentage distribution of two morpho groups i e rounded symmetrical and angular asymmetrical morpho groups showed considerable fluctuations which correlate well with the 7 years average rainfall over a period of 116 years of the catchment area of kali river the dominance of rounded symmetrical forms indicates a period of higher rainfall whereas angular asymmetrical forms tend to increase in abundance during dry periods poor monsoons the inferences drawn shown high potential in generating proxy data for paleomonsoonal precipitation required to develop predictive climatic models

taphonomic identification of cut marks made with lithic handaxes an experimental study abstract recent experimental studies have developed new diagnostic criteria to differentiate between trampling and cut marks within cut marks these diagnostic criteria have been useful to differentiate between marks made with simple and retouched flakes the present study expands the application of these criteria using a multivariate analysis to discriminate marks created with handaxes from those made with stone tool flakes a discriminant analysis resulted in a selection of specific variables which can successfully differentiate cut marks made with handaxes from those created with retouched flakes in more than 80 of occasions the utility of this analogical taphonomic signature created by handaxes is discussed in the light of their potential value as butchering tools

dimorphic forms of recent foraminifera an additional tool in paleoclimatic studies limited culture studies of foraminiferal species show that the ratios of dimorphic forms are not constant and are affected by extremes of temperature this feature might be utilized for paleoclimatic studies to test this possibility ratios of microspheric megalospheric forms were obtained for bolivina skagerrakensis qvale and nigam at different levels in a core 15530 4 from the skagerrak eastern north sea the values show considerable fluctuations and can be correlated with two other paleotemperature scales the total number of benthic foraminifera and the oxygen isotope ratio it is concluded that the microspheric megalospheric ratios of foraminifera can be used as index of paleoclimate and that the higher ratios indicate relatively warm climates however this inference needs to be confirmed by additional culture studies under controlled temperature conditions and faunal studies of cores where paleotemperatures are already established with the help of oxygen isotopes

major change in atlantic deep and bottom waters 700 000 yr ago benthonic foraminiferal evidence from the south atlantic abstract in the modern south atlantic the transition between deep water and bottom water is marked by a clear change in the associated benthonic foraminiferal fauna uvigerina and globocassidulina characterize oxygen poor circumpolar deep water which has long been isolated from the surface planulina and miliolids are found associated with the more newly formed oxygen rich north atlantic deep water antarctic bottom water is characterized by epistominella umbonifera analysis of the benthonic foraminiferal faunas in two sediment cores recovered from the vema and hunter channels in the western south atlantic shows that the level of the transition between deep and bottom waters shallowed sharply about 700 000 yr ago this rise indicates a sharp sustained increase in the volume of bottom water flowing through the south atlantic after this time prior to about 700 000 yr ago the amount of antarctic bottom water entering the western south atlantic was greatly reduced and circumpolar deep water apparently accounted for the bulk of northward flow production of southward flowing north atlantic deep water seems not to have been affected the timing of this change in circulation regime suggests a possible causal link to similar changes in records of terrestrial and sea surface climate

very high energy sedimentation supratidal hurricane deposits and mid holocene highstand on carbonate platforms andros bahamas an alternative view abstract twenty eight 14 c dates were obtained from 90 cores drilled through the tidal flats of western andros island a large area 2000 km 2 mostly covered by mangroves and stromatolitic deposits these dates are correlated with location of the samples sedimentological description position of the samples at the time of deposition and their present day sedimentological position measurements were made on bulk algal sediments and location of the relative paleo sea level is inferred from paleobathymetric reconstructions on the basis of 14 c dates i conclude that the whole area was flooded about 5000 years bp and then was covered by the subtidal greyish mud facies rich in peneroplids in the area of deep creek north of the study area pelican creek and wide opening southeast of the study area the level of this paleo great bahama bank sea continued to rise until 3500 years bp and then slowly fell asymptotically toward the present day level thick hurricane marks aragonitic lime mud with didemnids spicules several cm thick previously defined as hurricane trails can be observed throughout the cores from 2000 years bp onwards from 2000 years bp onwards it seems that the modern physiography was already established including tidal estuaries channels and stromatolite bearing swamps paleogeographic maps and sections have been drawn and accumulation rates calculated in the various sedimentological zones of the tidal flats of western andros these vary between 0 5 to 0 04 mm yr the modern topography of the tidal flats was established by 2000 years bp similarly the modern geological features controlled by a tropical climate strictly dependent on hurricanes were already established by 2000 years bp and seem to have been initiated between 2500 and 2000 years bp

changes in the oceanic 13c 12c ratio during the last 140 000 years high latitude surface water records detailed records of the carbon and oxygen isotopic ratios of neogloboquadrina pachyderma are compared between nine high latitude sediment cores from the northern and southern hemispheres covering the last 140 000 yrs the strong analogies between the 13c records permit to define a 13c stratigraphic scale with three clear cut transitions simultaneous with the oxygen isotopic transitions 65 125 kyrs 54 65 kyrs and 21 13 kyrs the 13c records of n pachyderma in the high latitude cores which follow the changes in 13c of the surface water tco2 near areas of deep water formation present trends similar to the benthic foraminifera 13c records in cores v19 30 and m12 392 although amplitudes of the isotopic shifts are different this implies that a large part of the observed variations represents global changes in the carbon distribution between biosphere and ocean the 13c12c ratios of n pachyderma in the north atlantic cores display larger regional variations at 18 kyrs b p than at present to explain these differences we have plotted the 18 kyrs b p 13c values of n pachyderma from 17 cores distributed n of 40 n comparison with published surface water temperature distribution at 18 kyrs b p indicates that a strong divergent cyclonic cell centered approximatively 55 n and 15 w was active during most of the last ice age maximum this hydrology analogous to the present weddell sea explains the published evidences of bottom water formation if located on the northern flank of the gyre and the strong polar front on the southern flank probable location of intermediate water formation

sedimentation et fracturation de haute energie en milieu recifal tsunamis ouragans et cyclones et leurs effets sur la sedimentologie et la geomorphologie d un atoll motu et hoa a rangiroa tuamotu pacifique se abstract a longitudinal festoon fracture of the reef flat widened by slow biological and mechanical erosion transverse along the grooves divides the nw coral rim of rangiroa tuamotu se pacific into colossal blocks 15 10 5 m 1500 t the elaboration of these blocks can be attributed to the dislocation of the top of the reef flat by catastrophic events tsunamis or hurricanes typhoons in the sw and s pacific the shifting of these blocks mega boulders would necessitate a considerable amount of energy and at present we cannot decide which one of these phenomena was responsible various examples observed in the pacific are cited to illustrate abrupt changes in the sea level these could be attributed either to meteorological events hurricanes cyclones or typhoons or to seismic events of very high energy ground sea or tsunamis the reader is reminded of the different characteristics that these phenomena produce this study is mainly concerned with tsunamis especially the frequency of their occurrence energy and effects on the coasts of small oceanic islands hurricanes cyclones and typhoons roughly originate from the n ne and e whereas tsunamis originate from all directions except from se s and sw angle these very high energy events hurricanes and tsunamis seem then to be responsible for 1 the decreasing grain size of the coral rim sediments from the ocean to the lagoon through the range of colossal blocks smaller boulders scree gravels coarse and fine sands 2 the sedimentary accretion of the motu itself at each very high energy so called catastrophic event they are also responsible for the preservation of the two characteristic geomorphic forms of an atoll motu and hoa 3 finally the alternation motu hoa motu etc on the coral rim this alternation seems to result from the interaction between oceanic disturbances hurricanes or tsunamis and the water volume which must flow over the coral rim the transported material the reef flat and the angle of incidence between the swell and the coast during these catastrophic events

a new method for the quantitative analysis of cutmark micromorphology abstract cutmarks found on the fossilised bones of butchered animals provide direct evidence for the procurement of meat through technological means as such they hold some of the oldest available information on cognitive ability and behaviour in human evolution here we present a new method that allows a three dimensional reconstruction of cutmark morphology and the quantification of profile parameters we have tested this new technique on cutmarks that were experimentally inflicted on a pig rib using a steel knife and an un retouched flint flake at different angles the method allows for the cross sectional shape the sharpness and depths of the resulting cutmarks to be quantified the data show that knife mark sections are characterised by a v shape or shape depending on the inclination of the knife cutmarks produced with the flint flake were less clearly defined and generally less sharp than those produced by the knife we discuss the method s potential to provide new information on butchery technique and cognitive abilities developed by the human lineage from the earliest tool using hominins through to modern homo sapiens

deep circulation of the north atlantic over the last 200 000 years geochemical evidence variations in the cadmium calcium ratio of north atlantic deep water are recorded in the fossil shells of benthic foraminifera the oceanic distribution of cadmium is similar to that of the nutrients hence the cadmium calcium ratio in shells records temporal variations in nutrient distributions data from a north atlantic sediment core show that over the past 200 000 years there has been a continuous supply of nutrient depleted waters into the deep north atlantic the intensity of this source relative to nutrient enriched southern waters diminished by about a factor of 2 during severe glaciations this evidence combined with carbon isotope data indicates that the continental carbon inventory may have been less variable than previously suggested

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

variability in the deep and intermediate water circulation of the atlantic ocean during the past 25 000 years northern hemisphere modulation of the southern ocean the relative flux of north atlantic deep water nadw out of the atlantic can be monitored in the southern ocean where high 13c nadw mixes rapidly with low 13c recirculated pacific water before forming antarctic bottom water aabw by using 13c measured in benthic foraminifera as a water mass tracer it is shown that the southern ocean was dominated by pacific water with little nadw contribution during the last glaciation these tracer results document the direct physical connection between insolation controlled northern hemisphere oscillations and changes in the chemical and physical properties of southern ocean water the 13c records from the deep tropical atlantic document the transition from an atlantic dominated by southern ocean water during the last glaciation to an atlantic dominated by nadw during the holocene with more southern ocean water in the deep atlantic during the last glaciation the boundary between nadw and southern ocean water was north of its modern position allowing more southern ocean water to enter the eastern atlantic through the romanche fracture zone carbon isotope records from the caribbean and mediterranean seas suggest that the influence of mediterranean overflow water mow extended to the caribbean during the last glaciation and therefore was a volumetrically much more important water mass in the intermediate depth atlantic than it is today

timing cause and consequences of mid holocene climate transition in the arabian sea abstract we reconstruct centennial scale quantitative changes in surface seawater temperature sst evaporation precipitation from mg ca and 18o of surface dwelling planktic foraminifera productivity from relative abundance of globigerina bulloides carbon burial from caco3 and organic carbon corg and dissolved oxygen at sediment water interface covering the entire holocene from a core collected from the eastern arabian sea from the multi proxy record we define the timing consequences and possible causes of the mid holocene climate transition mhct a distinct shift in evaporation precipitation e p is observed at 6 4 ka accompanied by a net cooling of sst the shift in sst and e p is synchronous with a change in surface productivity a concurrent decrease is also noted in both the planktic foraminiferal abundance and coarse sediment fraction a shift in carbon burial as inferred from both the caco3 and corg coincides with a change in surface productivity a simultaneous decrease in dissolved oxygen at the sediment water interface suggests that changes affected both the surface and subsurface water a similar concomitant change is also observed in other cores from the arabian sea as well as terrestrial records suggesting a widespread regional mhct the mhct coincides with decreasing low latitude summer insolation perturbations in total solar intensity and an increase in atmospheric co2

changes in the distribution of δ13c of deep water σco2 between the last glaciation and the holocene carbon isotopic measurements on the benthic foraminiferal genus cibicidoides document that mean deep ocean 13c values were 0 46 lower during the last glacial maximum than during the late holocene the geographic distribution of 13c was altered by changes in the production rate of nutrient depleted deep water in the north atlantic during the late holocene north atlantic deep water with high 13c values and low nutrient values can be found throughout the atlantic ocean and its effects can be traced into the southern ocean where it mixes with recirculated pacific deep water during the glaciation decreased production of north atlantic deep water allowed southern ocean deep water to penetrate farther into the north atlantic and across low latitude fracture zones into the eastern atlantic mean southern ocean 13c values during the glaciation are lower than both north atlantic and pacific 13c values suggesting that production of nutrient depleted water occurred in both oceans during the glaciation enriched 13c values in shallow cores within the atlantic ocean indicate the existence of a nutrient depleted water mass above 2000 m in this ocean

multiple thermal maxima during the holocene the astronomical theory of climatic change provides an alternative to the traditional chronology for holocene climatic change which calls for one thermal maximum about 6000 years ago the theory predicts a series of maxima during the holocene one for each season because the relation of the perihelion to the spring equinox changes with a 22 000 year period late summer insolation would have been greatest 5000 years ago whereas early summer insolation would have been greatest 13 000 years ago climatic reconstructions based on the response of ecosystems to late summer climate indicate a later holocene thermal maximum than paleoclimatic data sensitive to early summer climate in southern idaho three different vegetation types indicate thermal maxima at different times during the holocene depending on the climatic variable controlling each type

cut marks and raw material exploitation in the lower pleistocene site of bell s korongo bk olduvai gorge tanzania a geometric morphometric analysis the lower pleistocene site of bell s korongo bk in olduvai gorge tanzania has been a key site for the study of the origin of human behaviour the lower archaeological levels of bk are characterized by anthropogenic activity related to the exploitation of megafauna elephant hippopotamus sivatherium and smaller game zebra wildebeest and antelopes these remains display a high frequency of cut marks the exceptional state of preservation of the bk fossil assemblage has allowed a wide range of different analyses that among other things detected the use of quartzite in butchering activities through the study of cut marks following up previous analyses this paper presents the study of a series of cut marks from the bk faunal assemblage using a 3d geometric morphometric methodological approach in order to determine the mineralogical properties of the quartzite used at the site bk cut marks are compared with experimentally produced cut marks using 9 mineralogically different quartzite types from olduvai gorge this comparative analysis provides valuable hints about the exact nature of the raw materials used in butchering activities the results presented here identify a preferential use of quartzite with a finer granular composition suggesting that hominin populations were already selecting the best raw materials for their use in specific activities 1 3 mya

the role of high energy events hurricanes and or tsunamis in the sedimentation diagenesis and karst initiation of tropical shallow water carbonate platforms and atolls abstract karst morphology appears early even during carbonate sediment deposition examples from modern to 125 ka old sub inter and supratidal sediments are given from the bahamas atlantic ocean and from tuamotuan atolls southeastern pacific ocean with mineralogical and hydrological analyses karstification is favoured by the aragonitic composition of bioclasts coming from the shallow marine bio factory lithification by aragonite cements appears as a rim around carbonate deposits and dissolution and non cementation start at the same time on modern supratidal deposits andros micrite or atoll coral rudite and provoke the formation of a central depression on small or large carbonate platforms in fact this early solution of the centre of platforms is closely related to the location of each of the studied examples on hurricane tracks high energy events such as hurricanes and tsunamis affect sediment transport but hurricanes also affect diagenesis as a result of the enormous volume of freshwater carried and discharged along their paths this couple lithification solution is localised at sea level and accompanies sea level fluctuations along the eustatic curve because of the precise location of hurricane action all around the earth early karstification by aragonite solution cementation and supratidal carbonate sediment accumulations high energy trails act together on all the platforms and atolls located inside the tropics 23 27 between roughly 5 10 and 25 on both hemispheres however early karstification acts alone on shallow carbonate platforms including atolls along the equatorial belt between 5 10 n and 5 10 s these early steps of karstification are linked to the ocean atmosphere interface due to the bathymetrical position of shallow carbonate platforms including atolls they lead to complex karstified emerged platforms called high carbonate islands where carbonate diagenesis together with the development of bauxite and or a phosphate rich cover and phreatic lens will occur

benthic isotope evidence for changes of the mediterranean outflow during the late quaternary a suit of sediment cores close to and south of the strait of gibraltar 12 36 n 500 2800 m water depth were analyzed for stable isotopes in epibenthic foraminifers cibicidoides wuellerstorfi and planulina ariminensis during peak glacial times the data exhibit higher 13c values of up to 1 6 at intermediate depths near the strait of gibraltar 36 n the values decrease to the south as evidenced by our data but also to the north as revealed by data of intermediate depth cores north of 38 n in duplessy et al 1987 thus the distribution pattern of 13c provides crucial evidence for an increased influence of nutrient depleted mediterranean outflow water mow on the glacial northeast atlantic hydrography during oxygen isotope terminations i and ii the meridional carbon isotope gradient indicates a significantly decreased but still active mow as deduced from the 18o fluctuations the temperatures of the mow in the atlantic were lower during glacial times by as much as 5 c during glacial times and during termination i the maximum 13c values of the mow correlate with minimum values of the north atlantic deep water nadw and vice versa this inverse response to climatic change of the carbon isotope signals of both water masses indicates that the supply of saline mow to the north atlantic may be less important for the formation of nadw than previously assumed

rapid sea level changes at the close of the last interglacial substage 5e recorded in bahamian island geology rapid and abrupt relative sea level changes within the last interglacial substage 5e are recorded in the island geology of the tectonically stable bahamas from 132 to 118 ka reef growth reached a maximum elevation near 2 m as indicated by fossil reef elevation across the platform whereas bioeroded notches are incised in coastal cliffs as high as 6 m the end of the interval is characterized by voluminous eolianites exhibiting palm tree and frond impressions it is inferred that sea level for most of the interval remained near 2 m restraining reef growth and that the notch at 6 m represents a rapid and brief excursion just before the close of the substage the subsequent fall must have been rapid in order to leave the notch profile intact and mobilize windward lagoon ooids into dunes before cementation could anchor them in order to explain the rapid rise to 6 m glacial surging is invoked the subsequent fall also rapid may be a consequence of the surge flooding high latitudes and providing enough moisture to initiate reglaciation and drawdown

coastal evolution on volcanic oceanic islands a complex interplay between volcanism erosion sedimentation sea level change and biogenic production abstract the growth and decay of oceanic hotspot volcanoes are intrinsically related to a competition between volcanic construction and erosive destruction and coastlines are at the forefront of such confrontation in this paper we review the several mechanisms that interact and contribute to the development of coastlines on oceanic island volcanoes and how these processes evolve throughout the islands lifetime volcanic constructional processes dominate during the emergent island and subaerial shield building stages during the emergent island stage surtseyan activity prevails and hydroclastic and pyroclastic structures form these structures are generally ephemeral because they can be rapidly obliterated by marine erosion with the onset of the subaerial shield building stage coastal evolution is essentially characterized by rapid but intermittent lateral growth through the formation of lava deltas largely expanding the coastlines until they typically reach their maximum extension with the post shield quiescence in volcanic activity destructive processes gradually take over and coastlines retreat adopting a more prominent profile mass wasting and marine and fluvial erosion reshape the landscape and if conditions are favorable biogenic processes assume a prominent role post erosional volcanic activity may temporarily reverse the balance by renewing coastline expansion but islands inexorably enter in a long battle for survival above sea level reef growth and or uplift may also prolong the island s lifetime above the waves the ultimate fate of most islands however is to be drowned through subsidence and or truncation by marine erosion

occurrence of rhodolites in the tropical pacific a consequence of mid miocene paleo oceanographic change abstract rhodolites occurring over wide areas of the tropical pacific solomons loyalties vanuatu and australes are dated in many places by diagnostic larger foraminifera as of middle miocene age they are preceded in early miocene and succeeded in late miocene by hermatypic coral deposits the processes linking this facies change with time to paleo oceanographic events documented in deep sea sediments are identified as sea level rise drowning the reefs a slight drop of winter surface water temperature and an increase of the fertility of surface waters inhibiting compensatory growth of hermatypic corals until sea level fall restored the earlier original conditions of deposition