holocene reef growth in torres strait the platform and fringing reefs of torres strait are morphologically similar to reefs of the northern great barrier reef to the south except that several are elongated in the direction of the strong tidal currents between the coral sea and the gulf of carpentaria surface and subsurface investigations and radiocarbon dating on yam warraber and hammond islands reveal that the initiation and mode of holocene reef growth reflect antecedent topography and sea level history on the granitic yam island fringing reefs have established in some places over a pleistocene limestone at about 6 m depth around 7000 years bp emergent holocene microatolls of porites sp indicate that the reefs have prograded seawards while sea level has fallen gradually from at least 0 8 m above present about 5800 years bp on the warraber island reef platform drilling near the centre indicated a pleistocene limestone foundation at a depth of about 6 m over which reefs established around 6700 years bp reef growth lagged behind that on yam island microatolls on the mature reef flat indicate that the reef reached sea level around 5300 years bp when the sea was around 0 8 1 0 m above present on the reef flat on the western side of hammond island bedrock was encountered at 7 8 m depth overlain by terrigenous mud a progradational reef sequence of only 1 2 m thickness has built seaward over these muds as sea level has fallen over the past 5800 years reef flat progradation on these reefs is interpreted to have occurred by a series of stepwise buildouts marked by lines of microatolls parallel to the reef crest marking individual coalescing coral heads detrital infill has occurred between these this pattern of reef progradation is consistent with the radiocarbon dating results from these reefs and with seismic investigations on the torres reefs

carbonate factories a conundrum in sedimentary geology abstract describing characterizing and interpreting the nearly infinite variety of carbonate rocks are conundrums intricate and difficult problems having only conjectural answers that have occupied geologists for more than two centuries depositional features including components rock textures lithofacies platform types and architecture all vary in space and time as do the results of diagenetic processes on those primary features approaches to the study of carbonate rocks have become progressively more analytical one focus has evolved from efforts to build reference models for specific phanerozoic windows to scrutinize the effect of climate and long term oscillations of the ocean atmosphere system in influencing the mineralogy of carbonate components this paper adds to the ongoing lively debates by attempting to understand changes in the predominant types of carbonate producing organisms during the mesozoic cenozoic while striving to minimize the uniformitarian bias our approach integrates estimates of changes in ca2 concentration in seawater and atmospheric co2 with biological evolution and ecological requirements of characteristic carbonate producing marine communities the underlying rationale for our approach is the fact that co2 is basic to both carbonates and organic matter and that photosynthesis is a fundamental biological process responsible for both primary production of organic matter and providing chemical environments that promote calcification gross photosynthesis and hypercalcification are dependent largely upon sunlight while net primary production and e g subsequent burial of organic matter typically requires sources of new nutrients n p and trace elements our approach plausibly explains the changing character of carbonate production as an evolving response to changing environmental conditions driven by the geotectonic cycle while identifying uncertainties that deserve further research with metazoan consumer diversity reduced by the end permian extinctions excess photosynthesis by phytoplankton and microbial assemblages in surface waters induced by moderately high co2 and temperature during the early mesozoic supported proliferation of non tissular metazoans e g sponges and heterotrophic bacteria at the sea floor metabolic activity by those microbes especially sulfate reduction resulted in abundant biologically induced geochemical carbonate precipitation on and within the sea floor for example with the opening of tethyan seaways during the triassic massive sponge microbe boundstones the benthic automicrite factory formed steep massive and thick progradational slopes and locally mud mounds as tectonic processes created shallow epicontinental seas photosynthesis drove lime mud precipitation in the illuminated zone of the water column the resulting neritic lime mud component of the shallow water carbonate factory became predominant during the jurassic paralleling the increase in atmospheric pco2 while the decreasing importance of the benthic automicrite factory parallels the diversification of calcifying metazoans phytoplankton and zooplankton with atmospheric pco2 declining through the cretaceous the potential habitats for neritic lime mud precipitation declined at the same time peak oceanic ca2 concentrations promoted biotically controlled calcification by the skeletal factory with changes produced by extinctions and turnovers at the cretaceous tertiary boundary adaptations to decreasing ca2 and pco2 coupled with increasing global temperature gradients i e high latitude and deep water cooling and strategies that efficiently linked photosynthesis and calcification promoted successive changes of the dominant skeletal factory through the cenozoic larger benthic foraminifers protist protist symbiosis during the paleogene red algae during the miocene and modern coral reefs metazoan protist symbiosis since late miocene

first principles modeling of sulfate incorporation and 34s 32s isotopic fractionation in different calcium carbonates abstract incorporation mechanism of sulfate groups in major calcium carbonates calcite aragonite and vaterite is investigated using first principles quantum mechanical calculations for each mineral the stable structure of the substituted site is determined in calcite and aragonite a tilting of the sulfate group with respect to the orientation of planar carbonate groups is observed the theoretical vibrational properties of the sulfate bearing carbonates are determined together with those of anhydrite caso4 and isolated so2 molecule comparison with experimental data supports the substitution of sulfate for carbonate groups in carbonate minerals the energetic of sulfate incorporation is increasingly unfavorable in the order vaterite calcite and aragonite regarding isotopic fractionation properties our calculations suggest that the equilibrium 34s 32s isotopic fractionation factor between vaterite and calcite is small 0 5 at 0 c a slightly larger fractionation factor 1 at 0 c is expected between aragonite and calcite whereas a negative fractionation 1 5 at 0 c is expected between anhydrite and calcite finally it is suggested that the isotopic fractionation between calcite and aqueous sulfate is smaller than 4

simulating reef response to sea level rise at lizard island a geospatial approach abstract sea level rise will result in changes in water depth over coral reefs which will influence reef platform growth as a result of carbonate production and accretion this study simulates the pattern of reef response on the reefs around lizard island in the northern great barrier reef two sea level rise scenarios are considered to capture the range of likely projections 0 5 m and 1 2 m above 1990 levels by 2100 reef topography has been established through extensive bathymetric profiling together with available data including lidar single beam bathymetry multibeam swath bathymetry lads and digitised chart data the reef benthic cover around lizard island has been classified using a high resolution worldview 2 satellite image which is calibrated and validated against a ground referencing dataset of 364 underwater video records of the reef benthic character accretion rates are parameterised using published hydrochemical measurements taken in situ and rules are applied using boolean logic to incorporate geomorphological transitions associated with different depth ranges such as recolonisation of the reef flat when it becomes inundated as sea level rises simulations indicate a variable platform response to the different sea level rise scenarios for the 0 5 m rise the shallower reef flats are gradually colonised by corals enabling this active geomorphological zone to keep up with the lower rate of rise while the other sand dominated areas get progressively deeper in the 1 2 m scenario a similar pattern is evident for the first 30 years of rise beyond which the whole reef platform begins to slowly drown to provide insight on reef response to sea level rise in other areas simulation results of four different reef settings are discussed and compared at the southeast reef flat barrier reef coconut beach fringing reef watson s bay leeward bay with coral patches and mangrove beach sheltered lagoonal embayment the reef sites appear to accrete upwards at a rate commensurate with the rate of rise thereby maintaining their original profile and position relative to the sea surface and the leeward and lagoonal sites with a low accretion rate maintain a similar profile but slowly gain depth relative to sea level the result of this variable response is that elevated features of the reef platform such as reef patches and crests tend to become more pronounced

a reappraisal of the 1835 eruption of cosiguina and its atmospheric impact in the great january 1835 eruption of cosiguina volcano nicaragua andesitic magma and lithic material were erupted over a period of at least three days proximal facies consist of clastogenic lava scoria fall and lithic ash fall produced by phreatomagmatic to vulcanian or plinian activity together with surge deposits and lithic block falls pyroclastic flow deposits covered some flanks of the volcano and entered the sea in the gulf of fonseca little record exists of the distal ash fall thus the total bulk volume erupted can only be roughly constrained to 2 9 5 6 km3 furthermore the amount of juvenile material is thought to be small a recent study of volatiles in 1835 scoria suggests sulfur release from the magma was negligible this reappraisal indicates that the cosiguina eruption probably had little global climatic impact despite its violent nature the magnitude of the eruption was modest the eruption occurred too late to initiate the northern hemisphere cooling trend form 1828 1836 dry fogs and other atmospheric optical phenomena usually observed after eruptions that contribute significantly to the stratospheric aerosol burden were not recorded after 1835

volatile emission during the eruption of baitoushan volcano china north korea ca 969 ad magma volume dre 24 5 km3 the main phase ca 95 vol is represented by comenditic tephra deposited dominantly as widespread fallout blankets and proximal ignimbrites the eruption column is estimated to have reached ca 25 km and thus entered the stratosphere a late phase 5 vol is represented by trachyte emplaced chiefly as moderately welded ignimbrites the comendites contain 3 and the trachytes 10 20 vol phenocrysts mainly anorthoclase hedenbergite and fayalite primary glassy melt inclusions with no signs of leakage were found only in phenocrysts in the comenditic tephra whereas those in phenocrysts in the trachytes are devitrified the comendite magma is interpreted to have been generated by fractional crystallization from a trachyte magma represented by melt inclusions in the phenocrysts in the comendite tephra the mass of volatiles emitted to the atmosphere during the eruption was estimated using the petrologic method the average h2o concentration of the comenditic matrix glass is 1 5 wt probably largely secondary and of the corresponding melt inclusions 5 2 wt melt inclusions in feldspar and quartz present the highest halogen concentrations with a calculated average for chlorine of 4762 ppm and for fluorine of 4294 ppm the comenditic matrix glasses are represented by a fluorine rich 3992 ppm f and fluorine poor group 2431 ppm f averaging 3853 ppm for chlorine only 20 of all sulfur analyses of the comenditic matrix glasses and melt inclusions are above the detection limit of 250 ppm s the difference between pre and post eruptive concentration of h2o is at least 3 7 0 6 wt h2o taking into consideration re hydration of the matrix glass and possible leakage of melt inclusions the difference between pre and post eruptive concentrations of the halogens amounts to 909 90 ppm cl and 1863 280 ppm and 302 40 ppm f the difference for s was estimated based on the average of the maximum s concentrations in the melt inclusions 455 ppm s and the detection limit resulting in 205 40 ppm s the calculated mass of volatiles injected into the atmosphere based on the erupted magma volume and volatile data is 1796 453 megatons for h2o 45 10 megatons for chlorine 42 11 megatons for fluorine and 2 0 6 megatons for sulfur the 969 20 ad eruption of baitoushan volcano one of the largest eruptions of the past 2000 years is thought to have had a substantial but possibly short lived effect on climate

ice core paleovolcanic records from the st elias mountains yukon canada 1 we previously reported a record of regionally significant volcanic eruptions in the north pacific using an ice core from eclipse icefield st elias mountains yukon canada the acquisition of two new ice cores from eclipse icefield along with the previously available eclipse icefield and mount logan northwest col ice cores allows us to extend our record of north pacific volcanism to 550 years before present using a suite of four ice cores spanning an elevation range of 3 5 km comparison of volcanic sulfate flux records demonstrates that the results are highly reproducible especially for the largest eruptions such as katmai a d 1912 correlation of volcanic sulfate signals with historically documented eruptions indicates that at least one third of the eruptions recorded in st elias ice cores are from alaskan and kamchatkan volcanoes although there are several moderately large volcanic explosivity index vei 4 eruptions recorded in only one core from eclipse icefield the use of multiple cores provides signals in at least one core from all known vei 4 eruptions in alaska and kamchatka since a d 1829 tephrochronological evidence from the eclipse ice cores documents eruptions in alaska westdahl redoubt trident and katmai kamchatka avachinsky kliuchevoskoi and ksudach and iceland hekla several unidentified tephra bearing horizons with available geochemical evidence suggesting alaskan and kamchatkan sources were also found we present a reconstruction of annual volcanic sulfate loading for the north pacific troposphere based on our ice core data and we provide a detailed assessment of the atmospheric and climatic effects of the katmai eruption

the statistics of natural shapes in modern coral reef landscapes abstract spatial heterogeneity is a fundamental characteristic of modern and ancient depositional settings and the scaling of many carbonate environments has been shown to follow power function distributions the difficulty in obtaining information on the horizontal persistence of sedimentary lithotopes at the basin scale has however hampered evaluation of this fact over larger geographic areas in recent years large scale maps of reef facies derived from remotely sensed data have become widely available allowing for an analysis of reef scale map products from 26 sites spread through four reef provinces covering 7000 km2 of shallow water habitat in the u s territorial pacific for each site facies maps were decomposed to polygons describing the perimeter of patches of differing sedimentologic benthic character a suite of geospatial metrics quantifying unit shape fractal dimension and frequency area relations was applied to investigate the intra and intersite variability the spatial architect

estimating regional coral reef calcium carbonate production from remotely sensed seafloor maps carbonate production on coral reefs is responsible for the provision of beach sands for the maintenance of seawater chemical balances and for the growth of reef structure and associated habitat complexity key carbonate producers including hard coral crustose coralline algae foraminiferal sand and halimeda were mapped from satellite imagery spatial resolution 2 5 m mean overall accuracy 81 and an upscaling model was applied to estimate carbonate production a sensitivity analysis was conducted to evaluate the influence of employing different calcification rates for live coral on the upscaling model contemporary coral reef carbonate production for the 21 reef platforms of the capricorn bunker group southern great barrier reef is estimated to be between 489 000 and 659 000 t per year based on seawater chemistry community composition calcification rates and reef structural complexity rugosity the upscaling model was relatively insensitive to different parameterisations of live coral calcification employed probably due to live coral being a relatively minor contributor by area approximately 18 of total reef area throughout the study region this suggests regional scale seafloor characteristics such as percentage of area dominated by substrates prone to dissolution e g coral rubble have a strong bearing on calcium carbonate production and need to be given greater consideration the upscaling framework presented provides a new method for quantifying regional carbonate production that could be applied globally and provides a valuable baseline against which future changes to carbonate production in this region can be assessed

frost rings in trees as records of major volcanic eruptions new data about climatically effective volcanic eruptions during the past several thousand years may be contained in frost damage zones in the annual rings of trees there is good agreement in the timing of frost events and recent eruptions and the damage can be plausibly linked to climatic effects of stratospheric aerosol veils on hemispheric and global scales the cataclysmic proto historic eruption of santorini thera in the aegean is tentatively dated to 1628 26 bc from frost ring evidence

inter hemispheric transport of volcanic ash from a 1259 a d volcanic eruption to the greenland and antarctic ice sheets a strong volcanic sulfuric acid signal corresponding to an age of 1259 a d has been reported in ice cores from greenland antarctica and arctic canada tiny 5 m volcanic glass shards were reported previously in samples from this layer in an ice core from the south pole here we report the discovery of volcanic glass shards from a contemporaneous layer in an ice core from summit greenland the major element composition of the glass shards in the greenland sample are identical to those from the south pole confirming the assumption that has been made previously that the sulfuric acid signal in the ice cores is an inter hemispheric time stratigraphic marker the composition of these glass shards is similar to those produced by a 550 700 yrs b p eruption of el chichon volcano in mexico suggesting that it may be the source of the widely dispersed material

a northern hemisphere volcanic chemistry record 1869 1984 and climatic implications using a south greenland ice core the effect of volcanic emission of acidic aerosols on climate is well documented the presence of acid droplets in the stratosphere can reduce transmissivity and hence decrease surface temperatures since the amount and chemical composition of erupted material has important effects on regional climate knowledge of past volcanic events is of extreme importance detailed glaciochemical records provide the only milieu wherein the geochemistry of paleovolcanic events can be fully documented we present a detailed sulfate and chloride record from an ice core drilled at site 20 d 40 km sw of dye 3 in southern greenland the record spans the time period 1869 1984 with chemical analyses of approximately eight samples per year time series decomposition and locally weighted scatter plot smoothing techniques were used to extract long term trends from the data so that individual volcanic eruptions could be documented a number of events identified here have been unnoticed previously and a high percentage of the major chemical signatures documenting these events is associated with large decreases in temperature in the latitudinal zone 60 90 on many authors have pointed out that the amount of volcanic acids such as hci and h2s04 injected into the atmosphere has a very important influence on global climate yet this volcanic input has been difficult to quantify prior to 1960 our data help to alleviate this problem these individual events can be compared to available frost tree ring data from north america further establishing a volcanism climatic linkage

automated object based classification of topography from srtm data we introduce an object based method to automatically classify topography from srtm data the new method relies on the concept of decomposing land surface complexity into more homogeneous domains an elevation layer is automatically segmented and classified at three scale levels that represent domains of complexity by using self adaptive data driven techniques for each domain scales in the data are detected with the help of local variance and segmentation is performed at these appropriate scales objects resulting from segmentation are partitioned into sub domains based on thresholds given by the mean values of elevation and standard deviation of elevation respectively results resemble reasonably patterns of existing global and regional classifications displaying a level of detail close to manually drawn maps statistical evaluation indicates that most of classes satisfy the regionalization requirements of maximizing internal homogeneity while minimizing external homogeneity most objects have boundaries matching natural discontinuities at regional level the method is simple and fully automated the input data consist of only one layer which does not need any pre processing both segmentation and classification rely on only two parameters elevation and standard deviation of elevation the methodology is implemented as a customized process for the ecognition software available as online download the results are embedded in a web application with functionalities of visualization and download

fore reef carbonate production development of a regional census based method and first estimates abstract fore reef carbonate production is important but is poorly known as a result of methodological limitations this paper reports on the development of a regional census based method to calculate the average carbonate production of tropical subtropical coral dominated fore reefs the estimates are based on coral cover and extension rates by growth form of fore reefs with framework and biodetrital facies ecological data from many parts of the indopacific and procedures to evaluate ramose coral data are most needed to further develop the method the first estimates suggest that the common production in very shallow fore reefs with dense ramose coral framework is around 10 kg caco 3 m 2 yr 1 or more an analogous estimation suggests that shallow biodetrital fore reefs produce around 1 5 kg m 2 yr 1 the production rates decrease exponentially with depth fore reef production is an important component of the global carbonate budget but remains difficult to assess

expanding the utility of uranium series dating of speleothems for archaeological and palaeontological applications uranium series u series dating of speleothems is frequently used for palaeoclimate studies but its archaeological and palaeontological applications are limited to stratigraphically significant speleothem formations such as flowstones to provide maximum and minimum temporal points this study targeted soda straw stalactites for u series dating in contrast to other speleothem formations soda straw stalactites are fragile have typically short life spans usually only years but rarely up to a few hundred years and are frequently incorporated into cave deposits results of thermal ionisation mass spectrometry tims u series dating of soda straw stalactites from palaeontological excavations at blanche cave south australia show that small dense clean straws tend to yield ages closest to the time of stratigraphic deposition a correlation between soda straw u series ages and radiocarbon ages of charcoal from the site is shown multiple soda straw age determinations for a single stratigraphic unit are required in order to verify age concordance in conjunction with other dating methods u series dating of soda straw stalactites may help to significantly constrain the age of stratigraphic units and associated archaeological and palaeontological deposits in order to provide more robust chronologies here we advocate the collection of soda straw stalactites at future excavations of limestone cave sites

calcite and aragonite precipitation under controlled instantaneous supersaturation elucidating the role of caco3 saturation state and mg ca ratio on calcium carbonate polymorphism abstract for many decades researchers have attempted to clarify the factors controlling the precipitation of calcium carbonate polymorphs and the incorporation of mg into calcite precipitating in natural systems in this study a novel experimental approach delineates the role of instantaneous supersaturation and solution mg ca ratio in calcium carbonate mineralogy and composition the results of this study show that in solutions with different mg ca ratios the transition between the aragonite and the calcite aragonite precipitation fields is controlled by a combination of the saturation state of the solution with respect to caco3 and the mg ca ratio in solution the data show that for increasing solution mg ca ratios progressively higher supersaturation level is required for calcite precipitation the predominance of aragonite at high solution mg ca and low supersaturations is attributed to a relative decrease in calcite growth rates as a result of increasing incorporation of mg2 in the calcite lattice at higher solution mg ca ratios as suggested by abundant experimental work increasing solution mg ca decreases the growth rate of calcite while aragonite growth rates stay unaffected our experiments do demonstrate that despite decreased growth rate the percentage of mgco3 in calcite increases with increasing solution mg ca ratio as calcite growth rates decrease aragonite growth rates stay constant and it becomes the dominant mineral phase in solutions with high mg ca ratio and low supersaturations these findings are relevant to present day mineralogical distributions in carbonate systems and might be the key to elucidate the environmental conditions responsible for mineralogic changes through geologic time the observed dependence of calcium carbonate mineralogy on solution composition and supersaturation suggests that carbonate mineralogy is controlled by kinetics of growth

a 220 year continuous record of volcanic h2so4 in the antarctic ice sheet continuous h2so4 profiles observed in snow from several antarctic locations reveal four major volcanic events of the past two centuries agung krakatoa tambora and another large scale event not recorded historically acid deposition and interhemispheric distribution mechanisms are quantified and then used to obtain an order of magnitude estimate for the h2so4 emissions from these eruptions

the combined influence of hydrodynamic forcing and calcification on the spatial distribution of alkalinity in a coral reef system 1 we investigated the influence of hydrodynamic forcing waves tides alongshore currents and winds and net calcification by coral reef organisms on the spatial distribution of total alkalinity ta in a fringing reef system through a combination of field measurements and numerical modeling a field experiment was conducted over 10 days in coral bay ningaloo reef western australia during which we measured wave heights currents and tides as well as the spatial distribution of ta across the fore reef reef crest and lagoon we used observed changes in ta on the adjacent reef flat along with synoptic measurements of cross reef transport to estimate in situ rates of net calcification gcv using a control volume approach based on the gcv estimated we simulated light driven diurnal variations in benthic net calcification within a three dimensional ocean circulation model roms regional ocean modeling system by coupling roms with a spectral wave model simulating waves nearshore we were able to simulate currents within coral bay reef lagoon system that were in good agreement with the field observations and demonstrate that circulation with the system was wave dominated both the field measurements and numerical model output confirmed that both residence time r and ta varied primarily with offshore wave heights and location within the bay however variations in ta were also affected by the nonlinear interaction between rates of net calcification that varied as a function of diurnally changing light and water residence time that varied as a function of offshore wave heights

trace elements in speleothems as recorders of environmental change speleothems are now established as important palaeoenvironmental archives and contain a number of suitable proxies although trace elements have been much less widely used than oxygen and carbon isotopes the complexity of the cave environment helps to explain this since the fluids from which speleothems form vary greatly in composition in space even within a cave chamber seasonally and over longer periods understanding the forcing factors for this variability is the key to decoding the significance of the trace element records a variety of techniques are available for trace element work and it is important to understand the strengths and limitations of each and also to seek an understanding e g by micro imaging techniques of whether the elements are associated with inclusions in the caco3 or are isolated within the crystal lattice for some elements there is a more or less predictable relationship between element ratios to ca in the water and in the calcite individual trace elements may be derived from atmospheric deposition superficial deposits or bedrock and can be recycled in soil processes before being transferred to the cave some components show an instantaneous response to water infiltration whereas others are only leached by slow flowing seepage waters changing in the proportion of water from fracture fed and seepage flow aquifer compartments is an important factor in influencing trace element supply high flows lead to higher fluxes of soil derived colloidally transported elements conversely under relatively dry conditions degassing of co2 results in prior calcite precipitation upflow of the site of speleothem deposition and leads to higher ratios of sr ca and mg ca some trace element variations in speleothems over time are induced during crystal growth whereby faster growth leads to a greater departure from equilibrium element partitioning despite the demonstrated temperature dependence of mg partitioning into calcite attempts at deriving palaeotemperature records from speleothems have been so far confounded by variations in solution mg ca and or crystallographic effects a number of case studies have effectively used trace elements such as speleothem mg as records of palaeo aridity using supporting arguments from modern monitoring or covariations with other parameters such as stable isotopes sr and u isotopes can also be indicators of palaeohydrology although sr isotope variations can also reflect varying aeolian input considerable progress has been made in decoding the meaning of annual trace element variations using criteria for understanding dripwater hydrology and ph this should lead in the future to more specific interpretations of how seasonality evolves through time

tidally incised valleys on tropical carbonate shelves an example from the northern great barrier reef australia the formation of incised valleys on continental shelves is generally attributed to fluvial erosion under low sea level conditions however there are exceptions a multibeam sonar survey at the northern end of australia s great barrier reef adjacent to the southern edge of the gulf of papua mapped a shelf valley system up to 220 m deep that extends for more than 90 km across the continental shelf this is the deepest shelf valley yet found in the great barrier reef and is well below the maximum depth of fluvial incision that could have occurred under a 120 m eustatic sea level low stand as what occurred on this margin during the last ice age these valleys appear to have formed by a combination of reef growth and tidal current scour probably in relation to a sea level at around 30 50 m below its present position tidally incised depressions in the valley floor exhibit closed bathymetric contours at both ends valley floor sediments are mainly calcareous muddy gravelly sand on the middle shelf giving way to well sorted gravely sand containing a large relict fraction on the outer shelf the valley extends between broad platform reefs and framework coral growth which accumulated through the late quaternary coincides with tidal current scour to produce steep sided locally vertical valley walls the deepest segments of the valley were probably the sites of lakes during the last ice age when torres strait formed an emergent land bridge between australia and papua new guinea numerical modeling predicts that the strongest tidal currents occur over the deepest outer shelf segment of the valley when sea level is about 40 50 m below its present position these results are consistent with a pleistocene age and relict origin of the valley based on these observations we propose a new conceptual model for the formation of tidally incised shelf valleys tidal erosion on meso to macro tidal rimmed carbonate shelves is enhanced during sea level rise and fall when a tidal hydraulic pressure gradient is established between the shelf lagoon and the adjacent ocean basin tidal flows attain a maximum and channel incision is greatest when a large hydraulic pressure gradient coincides with small channel cross sections our tidal incision model may explain the observation of other workers that sediment is exported from the great barrier reef shelf to the adjacent ocean basins during intermediate rather than last glacial maximum low stand sea level positions the model may apply to other rimmed shelves both modern and ancient

greenland ice core signal characteristics an expanded view of climate change the last millenium of earth history is of particular interest because it documents the environmental complexities of both natural variability and anthropogenic activity we have analyzed the major ions contained in the greenland ice sheet project 2 gisp 2 ice core from the present to 674 a d to yield an environmental reconstruction for this period that includes a description of nitrogen and sulfur cycling volcanic emissions sea salt and terrestrial influences we have adapted and extended mathematical procedures for extracting sporadic e g volcanic events secular trends and periodicities found in the data sets finally by not assuming that periodic components signals were stationary and by utilizing evolutionary spectral analysis we were able to reveal periodic processes in the climate system which change in frequency turn on and turn off with other climate transitions such as that between the little ice age and the medieval warm period

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

the structure of monohydrocalcite and the phase composition of the beachrock deposits of lake butler and lake fellmongery south australia samples of beachrock from lakes butler and fellmongery near robe south australia were examined by neutron and x ray powder diffraction considerable variation in phase composition was observed although all samples possessed monohydrocalcite calcite aragonite and magnesiancalcite the rietveld refinement of the structure of monohydrocalcite showed significant changes in the orientation of water molecules and a major change in the orientation of a carbonate group with respect to the currently accepted structure the current refinement shows that the hydrogen bonding structure consists of three distinct networks with each of the three carbonate groups being bonded to a single water molecule via one linear and one bifurcated hydrogen bond

characteristics and possible source of a 1479 a d volcanic ash layer in a greenland ice core abstract a microparticle concentration peak in a gisp2 ice core contains volcanic glass shards of rhyolitic composition that correspond in age to the 1479 1480 a d mt st helens wn eruption these glass shards are compositionally similar to the wn tephra and constitute 83 of the total particle population the shards are very coarse grained up to 40 m diameter suggesting rapid transport from their source to greenland a major sulfate peak in the ice occurs approximately 4 months after deposition of the glass shards this difference in depositional timing suggests primarily tropospheric transport of the ash and stratospheric transport of the sulfate aerosol large scale climatic perturbations following this eruption were evidently negligible glaciochemical seasonal indicators suggest a late fall to early winter 1479 a d eruption

latest aspects of earthquake prediction in greece based on seismic electric signals ii abstract since 1983 continuous monitoring of the electrotelluric field has been carried out using an array of measuring stations located at various sites in greece the basic physical properties of the transient changes seismic electric signals ses in the electrotelluric field that are forerunners of earthquakes were first described six years ago since then a large body of data has been collected resulting in new insight into various aspects of the method the present paper reviews the latest developments in ses based earthquake prediction and describes the current procedures used to predict the epicenter and magnitude of an impending earthquake a detailed list of the predictions officially issued in greece during the past 3 years january 1 1987 november 30 1989 is also given public warnings were issued well before the most destructive seismic activity

morphological characterisation of reef types in torres strait and an assessment of their carbonate production coral reefs represent major accumulations of calcium carbonate caco3 the particularly labyrinthine network of reefs in torres strait north of the great barrier reef gbr has been examined in order to estimate their gross caco3 productivity the approach involved a two step procedure first characterising and classifying the morphology of reefs based on a classification scheme widely employed on the gbr and then estimating gross caco3 productivity rates across the region using a regional census based approach this was undertaken by independently verifying published rates of coral reef community gross production for use in torres strait based on site specific ecological and morphological data a total of 606 reef platforms were mapped and classified using classification trees despite the complexity of the maze of reefs in torres strait there are broad morphological similarities with reefs in the gbr the spatial distribution and dimensions of reef types across both regions are underpinned by similar geological processes sea level history in the holocene and exposure to the same wind wave energetic regime resulting in comparable geomorphic zonation however the presence of strong tidal currents flowing through torres strait and the relatively shallow and narrow dimensions of the shelf exert a control on local morphology and spatial distribution of the reef platforms a total amount of 8 7million tonnes of caco3 per year at an average rate of 3 7kg caco3m 2yr 1 g were estimated for the studied area extrapolated production rates based on detailed and regional census based approaches for geomorphic zones across torres strait were comparable to those reported elsewhere particularly values for the gbr based on alkalinity reduction methods however differences in mapping methodologies and the impact of reduced calcification due to global trends in coral reef ecological decline and changing oceanic physical conditions warrant further research the novel method proposed in this study to characterise the geomorphology of reef types based on classification trees provides an objective and repeatable data driven approach that combined with regional census based approaches has the potential to be adapted and transferred to different coral reef regions depicting a more accurate picture of interactions between reef ecology and geomorphology

environmental changes at the younger dryas preboreal transition and during the early holocene some distinctive aspects in central europe data on environmental change at the younger dryas preboreal transition and during the early holocene are reviewed with particular reference to evidence from poland and neighbouring areas of central europe various factors modified the rate of environmental change during the general warming and reforestation the preservation in central europe of coniferous forest at the beginning of the holocene and the relatively late development of deciduous forest were connected with the continuation of a continental climate until 9000 8500 bp this is the main cause for a distinct division of the early holocene into three phases 1 10 300 9500 bp rapid warming 2 preboreal boreal continuous transformation 10 000 8500 bp 3 change to oceanic climate 8700 7700 bp during the eoholocene period the various environmental systems such as biological aeolian fluvial and lacustrine exhibited diachronous evolution with different rates of change the distinctive changes in central europe are contrasted with other re

kinetic control of morphology composition and mineralogy of abiotic sedimentary carbonates abstract conventional thinking has long held that the abiotic precipitation of calcium carbonate occurs with a causal relationship between fluid my ca ratios and crystal morphology crystal composition and carbonate mineralogy resulting in the formation of meteoric equant low magnesium calcite and marine acicular high magnesium calcite and aragonite problematically calcites with varying amounts of incorporated magnesium occur either as equant or acicular crystals and aragonite may coexist with calcite in either environment commonly however a systematic relation exists between crystal morphology composition mineralogy and rates of reactant supply to growing crystal surfaces for example equant rather than acicular crystals of calcite form in modern deep and or cold marine meteoric phreatic and deep burial settings where the degree of carbonate saturation and or rates of fluid flow are low in areas of higher saturation and or fluid flow such as in warm shallow marine and meteoric vadose environments acicular calcite may predominate this relation is also seen in systems in which aragonite and calcite form in intimate association aragonite precipitation is favored when rates of reactant supply are high calcite forms when rates are low such relations suggest that crystal morphology composition and mineralogy are controlled by the kinetics of surface nucleation and the amount of reactants principally carbonate ions at growth sites precipitating phases are the ones which can best accommodate such excess reactants ambient mg ca ratios only indirectly control the nature of inorganically precipitated carbonate phases

preliminary paleoclimate reconstruction based on a 12 500 year old speleothem from vancouver island canada stable isotopes and u th disequilibrium dating abstract a combination of 13 c and 18 o analyses with u th disequilibrium dating on a stalagmite and groundwater from the deep and extensive arch cave network on northeastern vancouver island has produced a preliminary 12 200 y paleoclimatic profile speleothem depositional rates vary from 6 to 41 mm ka and are consistent with the hendy test for speleothem deposition under high humidity equilibrium conditions relative to present day conditions warmer periods are indicated at the end of the younger dryas during the holocene maximum a possible medieval warming event with the warmest period represented by a narrow peak at 8000 y bp relatively cooler periods are recorded at 3500 8200 9300 and 11 500 y bp with indications of minor cooling during the little ice age and indications of relatively dry conditions during the earlier part of the younger dryas followed by warmer wetter conditions the profile shows excellent agreement with other paleoclimatic indicators locally most notably some partial speleothem records from vancouver island and oregon and some high resolution global records such as the greenland ice cores and speleothems from the hulu cave china

spatial and temporal variations in wave characteristics across a reef platform warraber island torres strait australia a field experiment was conducted at warraber island torres strait australia to investigate spatial and temporal variations in wave characteristics and energy across a mesotidal coral reef platform measurements of water depth were obtained using five pressure sensors deployed across a 2 7 km section of reef flat from july 3 5 2001 the reef surface was uneven and consisted of an outer reef flat a central reef flat depression an inner reef ramp a palaeo reef surface and the shoreline water levels decreased landward across the platform with tide ranges at the shoreline being almost 50 lower than at the outer reef flat rising and falling tides were characterised by a bimodal energy distribution with both short period 0 3 s and wind 3 8 s waves present higher water levels were dominated by wind waves the highest waves occurred at high tides associated with nocturnal tidal cycles with hs decreasing from 0 5 to 0 2 m from the outer reef flat to the shoreline wave energy at swell 8 20 s and infragravity 20 s frequencies was negligible across the reef platform although there was evidence of wave groups at higher water levels reef geometry and changes in water level determine the magnitude of wave energy on the reef platform up to 85 95 of incident wave energy is attenuated by the central reef flat depression at high and low tide respectively and strong linear relationships exist between hs and h at all locations both wave height and wave type are strongly depth dependent critical reef rim depths required to produce hs of a given size vary spatially across the reef rim due to variations in reef topography a distinct depth related threshold exists at which short period and wind wave dominance reverses over a 14 day spring neap tidal cycle the time of occurrence of wave action diminishes across the reef platform to the shoreline larger waves hs 0 2 m occur for only 9 of time at the outer reef flat and for less than 0 5 over the remaining reef platform this implies that on mesotidal reef platforms sediment entrainment and transport are severely constrained under normal wave energy conditions and significant change is likely restricted to extreme events

diversity in the geomorphology of shallow water carbonate depositional systems in the saudi arabian red sea article i nfo coral reefs and their associated accumulations of carbonate sediment adopt particularly complex planform geometries atop the coastal shelf of the saudi arabian red sea by assembling 95 000 km 2 of remote sensing data into a gis this study aims to relate the morphology of these shallow water depositional environments to processes that sculpt the coastal zone a typology that sorts carbonate systems into end members on the basis of their morphology and relationship to the coastline is developed the resulting gis was interrogated for spatial patterns in the distribution and abundance of the end members while several depositional morphologies are present throughout the length of the saudi arabian red sea the occurrence of others is restricted to narrow re gionsof latitude suchdifferencesindistributioncanbeexplainedinprocess termsbytherifttectonicsof thered sea basin spatial variability in the presence of sub seafloor evaporites and the input of siliciclastic detritus onto the coastal shelf via wadis this paper provides a foundation for understanding the morphological diversity of shallow water carbonate systems in both the modern ocean and rock records

environmental controls on the petrology of a late holocene speleothem from botswana with annual layers of aragonite and calcite abstract a carbonate stalagmite from drotsky s cave in northwestern botswana consists of alternating layers of calcite and aragonite layer counts and radiocarbon ages indicate that the calcite aragonite pairs are annual layers representing about 1500 years of deposition the annual layering probably resulted from highly seasonal rainfall comparison of the uppermost layers of the speleothem with meteorological records shows that precipitation of caco3 in drotsky s cave was controlled by climate thickness of calcite layers correlates with rainfall suggesting that calcite precipitation was largely dependent on the quantity of water supplied to the speleothem by contrast thickness of aragonite layers correlates with temperature although variation in temperature cannot explain greater aragonite abundance on the sides of the speleothem compared to its center mg ca ratios in calcite layers increase upward to the bases of overlying aragonite layers and analyses of cave waters suggest that fluid mg ca ratios reach levels sufficient to cause aragonite precipitation increasing evaporation which caused greater ionic strength and supersaturation resultant increasing mg ca ratios in the fluid and perhaps increasing temperature probably combined to cause aragonite precipitation detailed petrographic analysis suggests that each annual cycle of caco3 precipitation began with relatively intense fluid flow sometimes sufficient to dissolve some of the underlying aragonite before precipitation of calcite calcite precipitation under a thick fluid layer allowed euhedral crystals to form at first but thinning of the fluid to a film allowed only flatly terminated calcite crystals by season s end as fluid flow diminished increasing evaporation increasing mg ca ratios in the fluid and perhaps increasing temperature combined to cause aragonite precipitation to begin particularly on the sides of the speleothem in some years fluid flow diminished to the point that dust accumulated on aragonite surfaces before the onset of the next year s precipitation p

fennoscandian summers from ad 500 temperature changes on short and long timescales quantitative estimates of 1480 years of summer temperatures in northern fennoscandia have previously been derived from continuous treering records from northern sweden here we show the results of spectral analyses of these data only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub periods relatively timestable peaks are apparent at periods of 2 1 2 5 3 1 3 6 4 8 32 33 and for a range between 55 100 years these results offer no strong evidence for solar related forcing of summer temperatures in these regions our previously published reconstruction was limited in its ability to represent long timescale temperature change because of the method used to standardize the original tree ring data here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales considerable variance is now reconstructed on timescales of several centuries in comparison with modern normals 1951 70 generally extended periods when cool conditions prevailed prior to the start of the instrumental record include 500 700 790 870 1110 1150 1190 1360 1570 1750 a d with the most significant cold troughs centred on about 660 800 1140 1580 1620 and 1640 predominantly warm conditions occurred in 720 790 870 1110 and 1360 1570 with peaks of warmth around 750 930 990 1060 1090 1160 1410 1430 1760 and 1820

timing and climatic impact of greenland interstadials recorded in stalagmites from northern turkey a 50 kyr long exceptionally well dated and highly resolved stalagmite oxygen 18o and carbon 13c isotope record from sofular cave in northwestern turkey helps to further improve the dating of greenland interstadials gi 1 and 3 12 timing of most gi in the sofular record is consistent within 10 to 300 years with the iconic hulu cave record larger divergences 500 years between sofular and hulu are only observed for gi 4 and 7 the sofular record differs from the most recent ngrip chronology by up to several centuries whereas age offsets do not increase systematically with depth the sofular record also reveals a rapid and sensitive climate and ecosystem response in the eastern mediterranean to gi whereas a phase lag of 100 years between climate and full ecosystem response is evident finally results of spectral analyses of the sofular isotope records do not support a 1 470 year pacing of gi

probability of earthquake occurrence in greece with special reference to the van predictions the van earthquake predictions were made on the basis of seismic electric signals ses but the debate seems to be directed toward the statistical significance of the predictions from seismic data only accordingly applying a logistic regression model to seismicity we present our estimation of the probability of earthquake occurrence in greece the main purpose of our study is to examine whether or not we can find a specific seismicity pattern that can be used to considerably increase probability estimates our estimation of the probability of occurrence of an earthquake of ms 5 0 is less than 0 25 in all the cases that we have examined if we lower the threshold magnitude from 5 0 to 4 3 we can find cases in which the probability becomes as high as 0 75 comparable to the success rate of the van method estimated by hamada 1993 in these cases however such a high probability is due mostly to aftershocks and if aftershocks are removed from the data set the probability falls below 0 5

record of volcanism since 7000 b c from the gisp2 greenland ice core and implications for the volcano climate system sulfate concentrations from continuous biyearly sampling of the gisp2 greenland ice core provide a record of potential climate forcing volcanism since 7000 b c although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions only about 30 percent of the events from 1 to 7000 b c were matched to such events several historic eruptions may have been greater sulfur producers than previously thought there are three times as many events from 5000 to 7000 b c as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions this increased volcanism in the early holocene may have contributed to climatic cooling

a budget of carbonate framework and sediment production kailua bay oahu hawaii abstract sediments of the bay and coastal plain of kailua oahu hawaii are 90 biogenic carbonate produced by destruction of primary reef framework coral and encrusting coralline algae and by direct sedimentation through the biological activity of calcifying organisms the green alga halimeda the branching coralline alga porolithion gardineri molluscs and benthic foraminifera field measurements of benthic community structure gross carbonate production bioerosion and direct sedimentation in 17 physiographic zones in kailua bay are used to calculate modern calcareous sediment production rates in the 12 km2 fringing reef system total gross carbonate productivity by corals and encrusting coralline algae based on mapped percent cover and known growth rates occurs at an average rate of 1 22 0 36 kg m 2 y 1 over hard substrates of the reef platform corresponding to 0 8 0 2 mm y 1 using a bulk density of 1 48 g cm 3 the average of coral and coralline algae coralline algae contributes 42 of the total gross productivity bioerosion of coral and coralline algae facies at and near the reef surface estimated from slabbed reef samples occurs at average rates of 0 10 1 15 kg m 2 y 1 and releases 1 911 436 m3 of unconsolidated carbonate sediment annually mechanical erosion coral breakage likely contributes an additional 315 m3 y 1 carbonate sediment is also produced directly by the green alga halimeda branching coralline algae molluscs and benthic foraminifera at a combined rate of 1 822 200 m3 y 1 using densities specific to sediment origin the total rate of production of unconsolidated carbonate sediment in kailua bay is the sum of these sources amounting to 4 048 635 m3 y 1 normalizing gross sediment production in kg y 1 by reef habitat area in m2 generates average rates of productivity in kg m 2 y 1 that are directly comparable to each other and to the literature such rates can also be employed and tested in other reef settings in kailua bay the total production of calcareous sediment corresponds to an average normalized rate of 0 53 0 19 kg m 2 y 1 with 0 33 0 13 kg m 2 y 1 contributed through erosion of the coralgal framework and 0 20 0 06 kg m 2 y 1 contributed by direct sediment production on the reef surface applying these modern sediment production rates over the 5 000 years that kailua bay has been completely inundated by postglacial sea level rise an estimated 20 2 3 2 106 m3 of unconsolidated carbonate sediment has been produced in the system the volume of sediment stored in the various reef channels and holes in kailua bay is 3 7 0 3 106 m3 or 19 of that produced since 5 000 y bp the volume of sand in the modern beach is 1 0 0 1 106 m3 or 5 of holocene sediment production the volume of carbonate sediment stored in the coastal plain is estimated using core log data and associated radiocarbon ages to be 10 0 1 8 106 m3 or 51 of holocene sediment production the remaining 25 likely represents sediment loss due to the natural processes of dissolution attrition and transport offshore these export terms are not well understood and emphasize the need for sediment dynamics to be incorporated into reef and sediment budgets although sediment production in this reef system is prodigious the rate of new sediment supplied to the beachface is less than 2 of what moves on and off the beach seasonally

from platform top to adjacent deep sea new source to sink insights into carbonate sediment production and transfer in the sw indian ocean glorieuses archipelago abstract over the past ten years a huge amount of source to sink studies have aimed to unravel the tectonic climatic and other processes that shape the landscape from mountains to the deep ocean interestingly these studies have been mainly dedicated to siliciclastic or mixed systems for which the connection between drainage basins continental shelves slope and basin environments are often well constrained here we present a study focusing on a source to sink study dedicated to a pure carbonate system located in the sw indian ocean glorieuses archipelago extensive field sampling and geophysical acquisition across the carbonate platform have allowed us to estimate the composition the lateral variability and volumes of neritic sands deposited on the platform top additional seismic and bathymetric surveys across the platform interior illustrate the presence of plurimetric sandy bodies deposited along the leeward platform edge corresponding to the export of carbonate sediments from the platform top toward the platform edge under the influence of dominant currents and wind driven processes high resolution seismic bathymetric data and sediment cores acquired along the leeward slope and basin adjacent to the carbonate platform highlight the presence of channel levee complexes and turbiditic lobes which have accumulated on the seafloor on top of a 250 m thick sedimentary basin at 2000 3400 m water depth our study points out that carbonate sands and aragonitic mud produced on the platform top during the holocene have been shed to the adjacent basin we also demonstrate that this routing system was active at least throughout the last three glacial interglacial cycles this study has important consequences for our understanding of carbonate sedimentation processes occurring in the vicinity of isolated carbonate platforms 1 it highlights the role of oceanographic conditions in the distribution of sediment on a platform top and its export along the platform edge and the adjacent basin 2 it contributes to quantify the productivity of a carbonate platform as well as its sediment storage capacity 3 a first estimate of a carbonate source to sink system is proposed demonstrating that 0 57 km3 of sediments have been produced during the holocene 0 3 km3 being presently stored on the platform and the remaining having been exported to the deep basin

electromagnetic precursors to earthquakes in the ulf band a review of observations and mechanisms despite over 2 decades of international and national monitoring of electrical signals with the hope of detecting precursors to earthquakes the scientific community is no closer to understanding why precursors are observed only in some cases laboratory measurements have demonstrated conclusively that self potentials develop owing to fluid flow and that both resistivity and magnetization change when rocks are stressed however field experiments have had much less success many purported observations of low frequency electrical precursors are much larger than expectations based on laboratory results in some cases no precursors occurred prior to earthquakes or precursory signals were reported with no corresponding coseismic signals nonetheless the field experiments are in approximate agreement with laboratory measurements maximum resistivity changes of a few percent have been observed prior to some earthquakes in china but the mechanism causing those changes is still unknown anomalous electric and magnetic fields associated with fluid flow prior to earthquakes may have been observed finally piezomagnetic signals associated with stress release in earthquakes have been documented in measurements of magnetic fields

trace element variation in speleothem aragonite potential for palaeoenvironmental reconstruction trace element variation in annually laminated stalagmites has the potential to record long term high resolution palaeoclimatic data provided both 1 the relationship between trace element content in the carbonate and the climate and 2 the mechanism of stalagmite growth are understood here we report a secondary ion mass spectrometry sims study of an aragonitic speleothem t7 from cold air cave southern africa which achieves small m spatial resolution and ppm precision t7 has a series of fine visible laminae believed to be annual to subannual this article establishes 1 the usefulness of sims in analyzing speleothem aragonite at the spatial resolution and precision relevant to climatic studies 2 the distribution of trace elements in aragonite on micron scales and their relationship to models for speleothem growth and 3 the potential of aragonite speleothems to encode climatic data at subannual resolution complex reproducible oscillations in sr ca and ba ca are observed parallel to the growth direction of the speleothem however in addition to this variability we observe trace element oscillations perpendicular to the growth direction and infer that aragonite crystallites in the speleothem are laterally as well as vertically zoned stepscans parallel to the growth direction demonstrate complex zoning patterns from which simple climatic data are difficult to extract due to small scale lateral heterogeneity in the aragonite however time series analysis of the whole data set reveals regular cycles in sr ca and ba ca at a scale that matches the magnitude of the visible laminae on this basis it appears that within the complex geochemical variability there resides a regular environmental control possibly variation in water throughput hence rainfall

speleothems as sensitive recorders of volcanic eruptions the bronze age minoan eruption recorded in a stalagmite from turkey mounting evidence exists that variations in sulphur content in stalagmites are closely linked to changes in volcanic or anthropogenic atmospheric sulphur the strong dependency of sulphur on soil ph and ecosystem storage however can result in a delay of several years to decades in the registration of volcanic eruptions and anthropogenic emissions by stalagmites here we present synchrotron radiation based trace element analysis performed on a precisely dated section of a stalagmite from sofular cave in northern turkey as this section covers the time interval of the intensively studied minoan volcanic eruption between 1600 and 1650 bc we can test whether this vigorous eruption can be traced in a stalagmite of all measured trace elements only bromine shows a clear short lived peak at 1621 251621 25 bc whereas sulphur and molybdenum show peaks later at 1617 251617 25 and 1589 251589 25 respectively we suggest that all trace element peaks are related to the minoan eruption whereas the observed phasing of bromine molybdenum and sulphur is related to differences in their retention rates in the soil above sofular cave for the first time we can show that bromine appears to be an ideal volcanic tracer in stalagmites as it is a prominent volatile component in volcanic eruptions can be easily leached in soils and rapidly transferred from the atmosphere through the soil and bedrock into the cave and stalagmite respectively highly resolved oxygen and carbon isotope profiles indicate that the minoan eruption had no detectable climatic and environmental impact in northern turkey

the sulphur isotopic composition of trace sulphates in carboniferous brachiopods implications for coeval seawater correlation with other geochemical cycles and isotope stratigraphy the carboniferous 34s record based on the analysis of structurally substituted sulphate sss in brachiopod shells is characterized by a significant decline from values around 21 1 in the tournaisian to 12 1 in the gzelian superimposed on this broad evolution is a higher order structure with a relative minimum in the late visean followed by a maximum in the bashkirian on the 107 year time scale 34s is positively correlated with 13ccarb in contrast to the long term negative linkage between sulphur and carbon observed for the entire phanerozoic this indicates that mechanisms other than the redox balance control the carbon and sulphur cycles on this time scale the 87sr 86sr and 34s records display parallel trends during the tournaisian to moscovian this positive correlation suggests that tectonics may be of importance for the evolution of 34s on time scales of 107 years a possible scenario to explain the co evolution of the isotope systems and their linkage to tectonism and palaeoclimate invokes an increased nutrient supply to the oceans during periods of enhanced uplift and continental weathering this nutrient flux may have resulted in increased burial of organic matter and enhanced bacterial sulphate reduction

development of a bathymetric grid for the gulf of papua and adjacent areas a note describing its development 1 a new bathymetric grid for the gulf of papua and northern australia was produced for the area 140 150 e 6 14 s with a 3 6 110 m cell size new multibeam sonar surveys have added much needed detail to a region of the seabed where previously little was known in shallow australian waters bathymetry derived from landsat satellite imagery was used to supplement traditionally acquired bathymetric data for onshore areas shuttle radar topography mission data were used for topographic control the final grid revealed numerous features not observed in previous compilations of bathymetric data for the region bathymetric surveys on the continental shelf revealed an incised shelf with highly variable valley morphology prograding clinoforms are infilling valleys on the continental shelf and mark the seaward extension of the fly river delta a linear relict shelf edge barrier marks the shelf break in the northern ashmore trough region elsewhere the shelf break is scalloped and incised by canyons large mass transport deposits are widespread on the continental slope and indicate regions where mass wasting is common

coral reefs may start dissolving when atmospheric co2 doubles 1 calcification rates in stony corals are expected to decline significantly in the near future due to ocean acidification in this study we provide a global estimate of the decline in calcification of coral reefs as a result of increase in sea surface temperature and partial pressure of co2 this estimate unlike previously reported estimates is based on an empirical rate law developed from field observations for gross community calcification as a function of aragonite degree of saturation arag sea surface temperature and live coral cover calcification rates were calculated for more than 9 000 reef locations using model values of arag and sea surface temperature at different levels of atmospheric co2 the maps we produced show that by the time atmospheric partial pressure of co2 will reach 560 ppm all coral reefs will cease to grow and start to dissolve

molybdenum and sulfur incorporation as oxyanion substitutional impurities in calcium carbonate minerals a computational investigation abstract marked increases in sulfur and molybdenum concentration in stalagmites have been proposed as possible evidence of volcanic activity in the past thus speleothems have great potential to deliver long and continuous records of volcanic activity however little is known about the chemical nature of these impurities in the calcium carbonate caco3 phases forming stalagmites which hinders the rationalization of the incorporation mechanisms while sulfur is known to incorporate as a sulfate anion in caco3 polymorphs the nature and stability of molybdenum incorporation in these minerals has not been investigated before here we present a computer simulation study based on density functional theory comparing the thermodynamics of incorporation of sulfur and molybdenum as tetrahedral oxyanions xo4 2 x s mo in anion sites of caco3 polymorphs calcite aragonite vaterite monohydrocalcite and ikaite among the different polymorphs vaterite incorporates xo4 2 ions most favourably which reflects the relatively low density of this carbonate phase we show that molybdate anions are very unstable more so than sulfate anions in the bulk of all three anhydrous carbonate phases with respect to the formation of naturally occurring competing phases most of the mo impurities found in typical calcite aragonite stalagmites is therefore likely to concentrate at surface interface regions such as grain boundaries using the calcite 10 4 surface as a model we show that the energies of substitution are indeed much lower at the surface than at the bulk our results suggest that factors affecting the crystallinity of caco3 in stalagmites and therefore the specific surface area will have a significant effect on the concentration of incorporated molybdenum which should be a key consideration when interpreting data from mo based speleothem archives

use of paleo records in determining variability within the volcanism climate system abstract volcanic eruptions that inject large quantities of sulfur rich gases into the stratosphere have the capability of cooling global climate by 0 2 0 3 c for several years after the eruption equatorial eruptions will impact global climate whereas mid latitude eruptions can cool climate in the hemisphere of origin magnitude of cooling varies by latitude and it is possible for warming to occur in certain regions primarily during the winter although instrumental records have been used to quantify the volcanic impact on climate they are limited in their temporal and spatial coverage and the style and magnitude of eruptions occurring over the two centuries of instrumental records is limited a thorough evaluation of the range of variability in the volcanism climate system requires a multidisciplinary approach that includes the analysis of ice core records geological data atmospheric measurements and visual phenomena tree ring records and other proxy data evaluation of these longer time series indicates that multiple volcanic eruptions have the potential to force climate over decadal to multi decadal time frames especially when these eruptions enhance or extend pre existing cool conditions on the other hand a lack of climatically significant eruptions may result in warmer average temperatures over decadal time frames because the volcanic cooling component within the climate system is absent mega eruptions like the toba eruption of 71 000 73 000 yr ago may impact climate on centennial time frames through positive feedback mechanisms evidence exists which indicates that environmental changes associated with rapid climatic fluctuations such as crustal loading unloading with glaciation deglaciation and variability in glacial meltwater loading on ocean basins may cause an increase in volcanic activity

evaluation of current statistical approaches for predictive geomorphological mapping abstract predictive models are increasingly used in geomorphology but systematic evaluations of novel statistical techniques are still limited the aim of this study was to compare the accuracy of generalized linear models glm generalized additive models gam classification tree analysis cta neural networks ann and multiple adaptive regression splines mars in predictive geomorphological modelling five different distribution models both for non sorted and sorted patterned ground were constructed on the basis of four terrain parameters and four soil variables to evaluate the models the original data set of 9997 squares of 1 ha in size was randomly divided into model training 70 n 6998 and model evaluation sets 30 n 2999 in general active sorted patterned ground is clearly defined in upper fell areas with high slope angle and till soils active non sorted patterned ground is more common in valleys with higher soil moisture and fine scale concave topography the predictive performance of each model was evaluated using the area under the receiver operating characteristic curve auc and the kappa value the relatively high discrimination capacity of all models auc 0 85 0 88 and kappa 0 49 0 56 implies that the model s predictions provide an acceptable index of sorted and non sorted patterned ground occurrence the best performance for model calibration data for both data sets was achieved by the cta however when the predictive mapping ability was explored through the evaluation data set the model accuracies of cta decreased clearly compared to the other modelling techniques for model evaluation data mars performed marginally best our results show that the digital elevation model and soil data can be used to predict relatively robustly the activity of patterned ground in fine scale in a subarctic landscape this indicates that predictive geomorphological modelling has the advantage of providing relevant and useful information on earth surface processes over extensive areas such data being unavailable through more conventional survey methods

a half century of coastline change in diego garcia the largest atoll island in the chagos abstract being low and flat atoll islands are often used as case studies against which to gauge the likely impacts of future sea level rise on coastline stability furnished with lengthy temporal datasets pacific atolls form the majority of studies with scant information published for sites in the indian ocean to address this imbalance this study considers diego garcia an atoll island situated in the remote equatorial indian ocean which has undergone pronounced natural and anthropogenic change in the last fifty years to explore the former time separated remote sensing images spanning the years 1963 2013 are assembled to provide insight into the natural dynamics of the shoreline of this island and ocean climate data are compiled to investigate possible controls disregarding the precinct of the atoll on which a military complex has been constructed overall land area of diego garcia decreased by a net value of only 0 92 between 1963 and 2013 while net island area is relatively unchanged 12 of the shoreline that is not in the military precinct displayed discernible accretion and 15 has receded with the lagoon facing coastline having undergone the most pronounced changes and at rates higher than recorded for the island s exterior broad trends in the morphological adjustment of the island exist the north eastern limb of the atoll has generally receded while the south eastern limb has extended the south of the island has also extended the south western region has eroded and the north western part has generally also eroded with the exception of notable shoreline extension at simpson point the most common mechanism by which the lagoon ward coastline has aggraded is through the in filling of cuspate embayments with sediment which is later stabilized by the expansion of terrestrial vegetation this evolution is most active in the complex network of embayments in the south of the atoll lagoon the ocean facing coastline by contrast typically aggrades and erodes through the linear shift of the vegetated coast along the strike of the beach line while the areal extent of diego garcia has been almost static for the last half century the annualized rate of flux of the coastline is considerable at 0 30 m yr 1 a rate comparable to other atoll islands the literature consistently reports two factors as relevant to increasing the rate of shoreline migration human modification of it and sea level rise both are foreseeably set to increase for diego garcia the former due to its strategic importance not least its use as a military base and the latter due to global environmental change the findings of this work serve to remind that the coastline of diego garcia as for all atoll islands is naturally dynamic and will likely become more so in the future

irish tree rings santorini and volcanic dust veils there has recently been renewed interest in the dating of the violent eruption of the aegean island of santorini in the second millennium bc both by its possible effects on tree ring growth in the united states1 suggesting a date of 1628 1626 bc and by acidity peaks in ice cores from south greenland2 suggesting 1645 bc we now show that oak trees growing on bogs in northern ireland produce significant concentrations of extremely narrow rings within a few periods less than 20 years long and that these periods correspond to the dates suggested by other methods for major volcanic eruptions in particular one of them corresponding to a short period beginning in 1628 bc was probably caused by santorini this date is qualitatively better than those derived from carbon 14 or ice cores because it is based on an absolute tree ring chronology

mapping reef features from multibeam sonar data using multiscale morphometric analysis classification of seafloor habitats from geomorphological proxies is increasingly being applied to understand the distribution of benthic biota particularly as more and larger datasets collected with high resolution multibeam echo sounders are becoming available with increased capacity to collect and use sonar data there is a need for automated approaches to identify seafloor structures and habitats for a survey area of approximately 2 5 2 5 km a generic feature extraction algorithm similar to terrestrial topographic analysis has been developed and applied to a spatially complex submerged mid shelf reef in the great barrier reef lagoon multibeam data collected with a reson seabat 8101 was gridded at 1 m resolution and an automated feature extraction method was applied that analyses the seafloor geomorphology to predict reef features from geomorphological proxies quadric surface fitting was used to determine various surface parameters based on multiple spatial scales subsequently 6 morphometric feature types plane channel ridge pass pit and peak were derived for all mapping scales weighted multiscale fuzziness was then applied to extract the dominant morphometric feature classes finally seafloor morphology patterns in combination with seafloor rugosity measurements were analysed in order to predict reef features these reef features cover significant patches of bioturbation beyond the submerged platform reef as well as the dominant reef features such as outer reef crest and inner reef flat layback corrected and manually classified towed video transects support the classification algorithms used to extract the reef features

wave transformation in the nearshore zone a review this paper reviews works related to nearshore wave propagation with an emphasis on several aspects related to coastal morphodynamic modelling including randomness and directionality of waves energy transfer and dissipation in the surf zone shallow water non linearities and long period motions the first part briefly reviews four main issues in laboratory experiments and field campaigns the second part is devoted to spectral and probabilistic approaches then recent developments of advanced numerical models based on boussinesq equations are reviewed the last part is devoted to low frequency waves and vortical motions

holocene sediments of wistari reef towards a global quantification of coral reef related neritic sedimentation in the holocene wistari reef within the southern great barrier reef is a shallow coral reef platform featuring a very clearly defined leeward accretionary wedge of carbonate sediments the total global area of shallowly submerged coral reef has been quantified as 255 000 km 2 the question then becomes what additional area of sediment of significant thickness is associated with the measured shallow reef areas t at wistari reef the leeward sedimentary wedge has an area and a thickness that are roughly equal to the holocene sediments that have accumulated on the platform several important observations can be made from these data firstly the area of significant neritic carbonate sedimentation 1 m ka associated with coral reefs is near 500000 km 2 secondly the production rate of neritic carbonates at wistari reef is almost 50 less than the accumulation rate needed to obtain the volume of holocene reef sediments observed this implies that both production and accumulation neritic carbonate must have been more than a factor of two higher in the early to mid holocene c 2001 elsevier science b v all rights reserved

statistical evaluation of the ses predictions issued in greece alarm and success rates earthquake prediction based on continuous measurements of the electric field of the earth has been systematically carried out by varotsos and co workers in greece predictions were issued by telegrams to greek authorities statistical evaluation of these predictions was made by comparing telegram prediction information with earthquake parameters determined by the us geological survey the space time domain selected for this evaluation was 20 24 e 36 41 n from january 1987 to june 1989 successfully predicted earthquakes are defined here as those that occurred within 22 days of the prediction within 100 km of the predicted epicenter and with a magnitude difference predicted minus true rot greater than 0 7 twelve predictions were issued for earthquakes with expected ms 5 3 following our criteria ten were successful two were not the magnitudes of the predicted earthquakes varied from 4 1 to 5 5 for earthquakes with mb usgs 5 0 the ratio of the predicted to the total number of earthquakes is 6 12 50 and the success rate of the prediction is also 612 50 with a probability gain of a factor of 4 with a confidence level of 99 8 the possibility of this success rate being explained by a random model of earthquake occurrence taking into account a regional factor which includes high seismicity in the prediction area can be rejected for earthquakes with mb usgs 4 5 a statistical significance could not be obtained because of the large number of small earthquakes

a new bipolar ice core record of volcanism from wais divide and neem and implications for climate forcing of the last 2000 years volcanism is a natural climate forcing causing short term variations in temperatures histories of volcanic eruptions are needed to quantify their role in climate variability and assess human impacts we present two new seasonally resolved annually dated non sea salt sulfur records from polar ice cores wais divide wdc06a from west antarctica spanning 408 b c e to 2003 c e and neem neem 2011 s1 from greenland spanning 78 to 1997 c e both analyzed using high resolution continuous flow analysis coupled to two mass spectrometers the high dating accuracy allowed placing the large bi hemispheric deposition event ascribed to the eruption of kuwae in vanuatu previously thought to be 1452 1453 c e and used as a tie point in ice core dating into the year 1458 1459 c e this new age is consistent with an independent ice core timescale from law dome and explains an apparent delayed response in tree rings to this volcanic event a second volcanic event is detected in 1453 c e in both ice cores we show for the first time ice core signals in greenland and antarctica from the strong eruption of taupo in new zealand in 232 c e in total 133 volcanic events were extracted from wdc06a and 138 from neem 2011 s1 with 50 ice core signals predominantly from tropical source volcanoes identified simultaneously in both records we assess the effect of large bipolar events on temperature sensitive tree ring proxies these two new volcanic records synchronized with available ice core records to account for spatial variability in sulfate deposition provide a basis for improving existing time series of volcanic forcing

the effect of volcanic aerosols on global climate abstract the surface temperature decrease after major volcanic eruptions has been demonstrated by a number of groups to be the order of a few tenths of a degree at first the stratospheric aerosol is usually restricted to a narrow range of latitudes and the volcanically induced temperature decrease is found to be nonuniform over the surface of the earth in fact because of the differential cooling of land and ocean there should always be volcanically induced temperature gradients these temperature gradients will induce a redistribution of air mass and anomalous sea level pressure gradients anomalous winds and anomalous climate on a global scale in this paper a hypothesis is presented which assumes that volcanic aerosols by reducing the solar radiation induces surface temperature gradients and sea level pressure gradients between the land and the oceans since cooling of the land occurs before the oceans there will be at first an increase of sea level pressure over land relative to the oceans conservation of total air mass on a global scale requires the sea level pressure over the ocean to be reduced because the majority of the land area is in the northern hemisphere the volcanically induced cooling will transfer air mass from the oceanic anticyclones in both the northern and southern hemisphere to the continents and especially to southern eurasia the anomalous sea level pressure pattern slp which would be obtained higher slp over southern eurasia and lower slp over the southern oceans is very close to the pattern first named by sir gilbert walker called the negative phase of the southern oscillation the positive phase of the southern oscillation can occur when no volcanic aerosols are present and the stratosphere is clear then the additional radiation and heating of the land increases the transfer of air mass from the northern hemisphere land mass to the world s oceans the positive phase of the global southern oscillation in this paper it will be shown that this hypothesis has the potential to explain the observed association between low latitude volcanic aerosols and the el nino southern oscillation it also has the potential to explain why el chichon s eruption induced a very strong el nino compared to the weaker el nino events induced by the eruptions of agung and krakatau it also explains why almost all monsoon countries experience below normal precipitation just prior to the maximum of the el nino warming the hypothesis also has the potential to explain why low and high latitude aerosols will affect the global climate system differently this hypothesis represents a return to the ideas of sir gilbert walker who first defined the southern oscillation as a global scale anomaly rather than an index between just two stations

coral reefs and sea level change abstract coral reefs provide significant evidence for former sea level positions because of their geological preservation and suitability for dating interpretation of this evidence presumes an understanding of reef geomorphology modern reef organism distributions and environmental factors influencing them fossil reef terraces formed during the last interglacial marine oxygen isotope mis substage 5e 128 116 ka are prevalent on many tropical shorelines and there has been ongoing debate as to the height reached by sea level during that highstand observations from numerous last interglacial sites suggest that sea level was at least 3 m above present sea level implying less extensive icesheets than at present an elevation of 6 m has commonly been adopted when correcting tectonically active sites for uplift recent compilations suggest elevations up to 8 9 m but incorporate few observations from reefs where the last interglacial is found below sea level oscillation of sea level during mis 5e has been interpreted from several sites with recent studies inferring rapid rise of several metres at the end of the interglacial these interpretations are at the limits to the precision with which corals can currently be dated and their palaeo water depths inferred it is not surprising that constraining last interglacial sea level changes within uncertainties of less than 1 2 m remains controversial considering sea level variations recognised between reef sites in the holocene and observed geographical variation in isostatic or flexural adjustments fossil coral reefs on uplifting margins also provide clear evidence for mis substages 5c and 5a and those on huon peninsula indicate fluctuations related to heinrich events mis 3 interpretations show considerable variability between sites with still greater uncertainties about sea level timing and elevation during previous interglacials future study of extensive sequences of fossil reefs preserved on rapidly subsiding margins could address these uncertainties submerged reefs have already yielded important information about sea level rise during the last deglaciation coring around barbados and tahiti as well as on the huon peninsula has produced a broadly consistent picture of ice melt reflecting eustatic change since the last glacial maximum these studies have shown the sensitivity of reefs to rapid sea level rise associated with meltwater pulses with some reefs drowning while others back stepped integrated ocean drilling program iodp expeditions to tahiti and recently the great barrier reef extended these records but details of timing nature and impact of deglacial meltwater pulses remain elusive studies of holocene reefs have indicated different growth strategies some kept up with sea level while others caught up when sea level decelerated holocene sea level appears to have experienced a gradual rise up to present across the caribbean providing accommodation space for reefs to accrete vertically whereas in the indo pacific sea level has been near its present level since 7 ka with many reef flats emergent following a slight fall of sea level caused by ocean siphoning microatolls on reef flats provide perhaps the clearest evidence of past sea level position but in their absence novel biological or other sea level indicators are required to better constrain palaeo water depths there is an urgent need for further research from additional key reef locations not only to decipher processes driving past sea level change and its geographical variability but also to better understand how coral reefs will respond in the context of future sea level rise

reassessment of crete greenland ice core acidity volcanism link to climate change previous comparisons of the crete greenland ice core acidity record with climate variations of the last 1 400 years suggested that changes in volcanism may have significantly influenced climate on this time scale however the ice core acidity record consists of volcanically induced spikes superimposed on a background acidity of nonvolcanic origin that varied significantly in amplitude herein the authors produce a record of crete volcanism based solely on an objective definition of individual volcanic events in the ice core record there are 92 acidity peaks in the 1 420 year record since at least 26 of the post 1 600 eruptions are of local icelandic origin they estimate a mean recurrence interval of 20 8 years for hemispheric scale eruptions rich in sulphate on decadal time scales volcanism has varied by a factor of three four over the last 1 400 years however the climate volcanism correlation is considerably less impressive r minus 0 23 than previously concluded r minus 0 52 the good correspondence between volcanism and climate previously reported are due to background acidity levels that show a significant little ice age increase the background increase may reflect changes in ocean productivity 24 refs 5 figs 1 tab

estimation of the probability of earthquake occurrence on the basis of logistic models high probability of an earthquake of m 6 5 near the arc junction off northeast japan the probability of the occurrence of an earthquake of m 6 5 is estimated by applying logistic models to seismicity in the hokkaido tohoku region northeast japan it is found that the probability of an earthquake occurrence near the arc junction off northeast japan is high when a specific seismicity pattern appears that is seismic activity increases 7 10 years or decreases 3 6 years before an event of m 6 5 because seismic activity is currently extremely low near the arc junction it is possible that an earthquake of m 6 5 may occur there within a few years specifically the probability estimated on the basis of logistic models is higher than 0 9 for the year of 1988