modification and preservation of environmental signals in speleothems speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system however the climatological meaning of many speleothem records cannot be interpreted unequivocally this is particularly so for more subtle shifts and shorter time periods but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward

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

climate and vegetation history of the midcontinent from 75 to 25 ka a speleothem record from crevice cave missouri usa four missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago ka the thorium 230 dated records reveal that between 75 and 55 ka the midcontinental climate oscillated on millennial time scales between cold and warm and vegetation alternated among forest savanna and prairie temperatures were highest and prairie vegetation peaked between 59 and 55 ka climate cooled and forest replaced grassland at 55 ka when global ice sheets began to build during the early part of marine oxygen isotope stage 3

high latitude forcing of the south american summer monsoon during the last glacial the climate of the last glacial period 10 000 to 110 000 years ago was characterized by rapid millennial scale climate fluctuations termed dansgaard oeschger d o and heinrich events we present results from a speleothem derived proxy of the south american summer monsoon sasm from 16 000 to 50 000 years ago that demonstrate the occurrence of d o cycles and heinrich events this tropical southern hemisphere monsoon reconstruction illustrates an antiphase relationship to northern hemisphere monsoon intensity at the millennial scale our results also show an influence of antarctic millennial scale climate fluctuations on the sasm this high resolution precisely dated tropical precipitation record can be used to establish the timing of climate events in the high latitudes of the northern and southern hemispheres

earthquake supercycles inferred from sea level changes recorded in the corals of west sumatra records of relative sea level change extracted from corals of the mentawai islands sumatra imply that this 700 kilometer long section of the sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years the moment magnitude 8 4 earthquake of september 2007 represents the first in a series of large partial failures of the mentawai section that will probably be completed within the next several decades

uranium series dating of fossil coral reefs extending the sea level record beyond the last glacial cycle abstract absolutely dated records of past sea level change are extremely important for understanding the advance and retreat of the large ice sheets when combined with other complementary climate archives and climate models such records offer the potential to gain an improved understanding of earth s natural climate cycles providing a firmer basis for assessing the role of anthropogenic effects such as greenhouse gas emissions in modifying climate the u series dating of fossil coral reefs has been widely utilized to provide absolutely dated records of past sea level change and numerous observations now exist for the past 130 000 years spanning the last glacial cycle despite this controversies still exist regarding the exact timing and character of sea level events within this time interval and extending the sea level history further back in time on the basis of robust and independent age constraints for older fossil reefs remains very elusive this is primarily due to a progressive loss in the resolution of the u series chronometer as one goes further back in time coupled to a lack of well preserved dateable coral in older fossil reefs to overcome these limitations the primary challenges are three fold first new analytical protocols are required to improve the resolution of the u series chronometer enhanced analytical precision must be coupled to accuracy through continued refinement of the u series decay constant determinations and via the implementation of rigorous inter laboratory calibration exercises second efforts should continue to be focussed on gaining an improved understanding of the mechanisms controlling open system exchange of the u series isotopes in fossil reef systems this will allow the number of reliable u series observations to be extended third alternative dateable archives of past sea level change must continue to be emphasized to further complement the coral reef database these limitations are discussed in the context of current developments that further advance the application of u series chronology to older fossil reef systems formed prior to the last glacial cycle

seismic recurrence intervals and timing of aseismic subduction inferred from emerged corals and reefs of the central vanuatu new hebrides frontal arc the recognition and dating of corals that have been killed by tectonic uplift allow us to date paleoseismic uplifts in the vanuatu island arc we recognize corals that record paleouplifts by their similarity to those known to have died during contemporary sudden uplifts and date them 1 by counting annual coral growth bands only if part of the coral is alive at the time of collection or 2 by newly developed techniques for obtaining 230 th ages by mass spectrometry the mass spectrometric method produces isotopic ages with precisions of 3 to 9 years 2 in the 0 1000 years b p time range the 230 th ages in this time range appear to be accurate samples whose ages are known by counting coral growth bands give 230 th ages that are indistinguishable from their growth band ages by dividing the average increment of uplift for the latest holocene uplifts by the mean holocene uplift rate we can estimate average seismic uplift recurrence intervals for the past 6000 years the results for each of four central vanuatu arc segments are 1 north santo emerged 1 2 m in 1866 a d and 0 6 m 107 years later in 1973 a d the average coseismic uplift of 0 9 m and mean holocene uplift rate of 4 3 mm yr 1 suggest a longer recurrence interval of 212 years 2 south santo emerged 0 29 m in 1946 and 0 26 m 19 years later in 1965 including the related 1971 event here the mean holocene uplift rate is 5 5 mm yr 1 the uplift data suggest a longer average recurrence interval of about 51 years 3 north malekula emerged 1 23 m near 1729 a d and 1 05 m 236 years later in 1965 the mean holocene uplift rate of 2 7 mm yr 1 and mean coseismic uplift of 1 14 m for dated events suggest a longer recurrence interval of 422 years 4 part of southernmost malekula has uplifted continuously or episodically by about 0 35 m from about 1957 until at least mid 1983 a d the maximum uplift of 2 7 mm yr 1 occurs near a nest of small earthquakes both the earthquakes and rapid uplift suggest that interplate slip beneath south malekula may be continuous rather than episodic episodes of 0 35 m uplift would have to recur every 130 years to maintain the 2 7 mm yr 1 uplift rate in contrast we find no evidence of interseismic vertical movements for the other three blocks the most reasonable interpretation of these results is that the seismic recurrence intervals and processes for accommodation of slip are quite different on adjacent arc segments we have used the most widely accepted moment magnitude relationship to evaluate the accumulated seismic slip caused by large earthquakes occurring since 1920 in all four arc segments this analysis suggests that the seismically radiated moments account for less than one third to one tenth of the slip associated with plate convergence the similarity between the paleoseismic record of uplifts and the contemporary record of coseismic uplifts suggests that this analysis can be generalized to times before 1920 for the northern three segments of central vanuatu aseismic slip probably occurs in the same years as large earthquakes because the contemporary coral record records uplifts only in years having large historic earthquakes this suggests that aseismic slip is not continuous and does not occur at rates which vary slowly over the course of the earthquake cycle the south santo segment may have the highest proportion of seismic slip because the mean recurrence interval of 51 years is shortest and the mean holocene uplift rate of at least 5 5 mm yr 1 is the fastest

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

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

assessing coral sr ca sst calibration techniques using the species diploria strigosa the coral species diploria strigosa is a promising archive for paleoclimate reconstruction in the tropical atlantic but limited work has been accomplished thus far to quantify the relationship between strontium to calcium ratios and sea surface temperatures in this species in this study we collected three modern d strigosa coral colonies from anegada british virgin islands to refine the use of this species as a paleoclimate archive three regression techniques including ordinary least squares reduced major axis and weighted least squares were used to assess how assumptions implicit in these regression methods influence the calibration our analysis demonstrated that regression slopes were strongly impacted by the assumptions about data uncertainty we recommend using the unbiased weighted least squares regression technique for calibrating the sr ca paleothermometer especially when precise local sea surface temperature data are unavailable combining our sr ca data with previously published data from this species results in a multi site multi colony temperature sensitivity of 0 046 0 001 mmol mol c for mean centered monthly data 0 059 0 001 mmol mol c for monthly anomalies and 0 063 0 004 for annual anomalies we suggest these relationships are the best available characterization of the temperature dependence of sr ca in d strigosa and can be utilized in future paleoclimate reconstructions

crustal deformation at the sumatran subduction zone revealed by coral rings analyses of coral rings grown in the interval 1970 1997 reveal a geographically distinct pattern of interseismic uplift off sumatra s western coast at distances less than 110 km from the sumatran trench coral reefs are submerging as fast as 5 mm y at 130 and 180 km distance from the trench they are emerging at similar rates we suggest that a locked or partially locked patch located above 30 km depth on the upper surface of the subducting oceanic plate generates this pattern

speleothems from the earliest quaternary snapshots of paleoclimate and landscape evolution at the northern rim of the alps abstract ancient cave systems in the northern calcareous alps today located well above the timberline at altitudes of 2400 2500 m host u rich speleothems that preserved growth layers on the microscopic scale of presumably annual origin two flowstone samples were dated to 2 019 0 037 0 069 ma and 1 730 0 032 0 068 ma respectively using u pb isochron techniques these ages are corroborated by the late pliocene to early pleistocene pollen spectrum extracted from one of the samples we use a multiproxy approach and exploit laminated speleothem sequences to tie high resolution stable isotope data to a floating lamina counted chronology o isotope values of growth intervals when calcite deposition was close to isotopic equilibrium are low compared to modern and holocene speleothems from other alpine caves and are inconsistent with the current altitudinal setting of the caves a vegetated but geomorphologically stable alpine catchment i e 2000 m asl no peri glacial processes combined with a deep seated cave the thickness of the vadose zone might have exceeded 1000 m is required in order to reconcile the isotopic data with the pollen record and the petrographic evidence furthermore the data can be used to constrain the rate for quaternary rock uplift to 0 8 mm annum for this frontal part of the european alps collectively the data suggest that these speleothems formed both during interglacials mis 59 or 61 and interglacial glacial transitions mis 75 74 or 77 76 but the seasonal precipitation pattern was arguably markedly different from today s provided that the highly regular microscopic laminae are indeed annual lamina counts suggest a minimum length of ca 6 ka for interglacials during the earliest pleistocene

oxygen and carbon isotopic systematics of aragonite speleothems and water in furong cave chongqing china abstract to understand oxygen and carbon stable isotopic characteristics of aragonite stalagmites and evaluate their applicability to paleoclimate the isotopic compositions of active and fossil aragonite speleothems and water samples from an in situ multi year october 2005 july 2010 monitoring program in furong cave located in chongqing of china have been examined the observations during october 2005 june 2007 show that the meteoric water is well mixed in the overlying 300 500 m bedrock aquifer reflected by relatively constant 18o 0 11 0 14 1 of drip waters in the cave which represents the annual status of rainfall water active cave aragonite speleothems are at oxygen isotopic equilibrium with drip water and their 18o values capture the surface water oxygen isotopic signal aragonite to calcite transformation since the last glaciation is not noticeable in furong stalagmites our multi year field experiment approves that aragonite stalagmite 18o records in this cave are suitable for paleoclimate reconstruction with high u 0 5 7 2 ppm and low th 20 1270 ppt the furong aragonite stalagmites provide very precise chronology as good as 20s yrs 2 of the climatic variations since the last deglaciation the synchroneity of chinese stalagmite 18o records at the transition into the bolling allerod t ba and the younger dryas from furong hulu and dongge caves supports the fidelity of the reconstructed east asian monsoon evolution however the furong record shows that the cold older dryas od occurred at 14 0 thousand years ago agreeing with greenland ice core 18o records but 200 yrs younger than that in the hulu record the od age discrepancy between chinese caves can be attributable to different regionally climatic environmental conditions or chronological uncertainty of stalagmite proxy records which is limited by changes in growth rate and subsampling intervals in absolute dating seasonal dissolved inorganic carbon 13c variations of 2 3 in the drip water and 5 7 in the pool and spring waters are likely attributed to variable degrees of co2 degassing in winter and summer the variable 13c values of active deposits from 11 to 0 could be caused by kinetically mediated co2 degassing processes the complicated nature of pre deposition kinetic isotopic fractionation processes for carbon isotopes in speleothems at furong cave require further study before they can be interpreted in a paleoclimatic or paleoenvironmental context

measurements of natural uranium concentration and isotopic composition with permil level precision by inductively coupled plasma quadrupole mass spectrometry a new analytical technique using inductively coupled plasma quadrupole mass spectrometry icp qms has been developed that produces permil level precision in the measurement of uranium concentration u and isotopic composition 234u in natural materials a 233u 236u double spike method was used to correct for mass fractionation during analysis to correct for ratio drifting samples were bracketed by uranium standard measurements a sensitivity of 6 7 108 cps ppm was generated with a sample solution uptake rate of 30 l min with a measurement time of 15 20 min standards of 30 ng uranium produced a within run precision better than 3 2 r s d for 234u and better than 2 for u replicate measurements made on standards show that a between run reproducibility of 3 5 for 234u and 2 for u can be achieved icp qms data of 234u and u in seawater coral and speleothem materials are consistent with the data measured by other icp ms and tims techniques advantages of the icp qms method include low cost easy maintenance simple instrumental operation and few sample preparation steps sample size requirements are small such as 10 14 mg of coral material the results demonstrate that this technique can be applied to natural samples with various matrices

climate forced sea level lowstands in the indian ocean during the last two millennia sea level reconstructions over the past two millennia provide a pre industrial context to assess whether the magnitude and rate of modern sea level change is unprecedented sea level records from the indian ocean over the past 2 000 years are sparse while records from the atlantic and pacific oceans show variations less than 0 25 m and no significant negative excursions here we present evidence of two low sea level phases in the maldives indian ocean based on fossil coral microatolls microatoll growth is constrained by low water levels and consequently they are robust recorders of past sea level u th dating of the maldivian corals identified lowstands at ad 234 605 and ad 1481 1807 when sea level fell to maximum depths of 0 88 m and 0 89 m respectively these lowstands are synchronous with reductions in radiative forcing and sea surface temperature associated with the late antiquity little ice age and the little ice age our results provide high fidelity observations of lower sea levels during these cool periods and show rates of change of up to 4 24 mm yr 1 our data also confirm the acceleration of relative sea level rise over the past two centuries and suggest that the current magnitude and rate of sea level rise is not unprecedented two intervals of distinctly lower indian ocean sea level during the last two millennia occurred during times of relatively low incoming solar radiation according to an analysis of u th dated coral microatolls in the maldives

high precision and high resolution carbonate 230th dating by mc icp ms with sem protocols abstract to facilitate the measurement of u th isotopic compositions suitable for high precision and high resolution 230th dating of coral and speleothem carbonates secondary electron multiplier sem protocol techniques for multicollector inductively coupled plasma mass spectrometry mc icp ms have been developed the instrumental sensitivities are 1 2 with a precision of 1 2 2 for abundance determination of 50 200 fg 234u 1 4 ng 238u or 230th this method features chemistry refinements improvements to procedural and instrumental blanks spectral inference reductions and careful consideration of non linear sem behavior measurement consistency of this mc icp ms combined with previous mass spectrometric results on u th standards and a variety of carbonates demonstrates the validity of the sem protocol method for fossil corals a routine u th isotopic determination at permil level precision requires only 10 50 mg of carbonate as little as 200 mg of young coral with an age of less than 20 yr can be dated with a precision of 0 3 0 8 yr about 20 200 mg speleothem samples with sub ppm to ppm u are required to earn a 5 precision on ages from 5 to 100 kyr requirement of small sample size 10 100s mg carbonate can permit high temporal resolution to date speleothems with slow growth rates i e 1 10 mm kyr this high precision 230th chronology is critical to accurately establish age models date events and splice geochemical proxy time series records from multiple samples in the fields of paleoclimatology and paleoceanography the u th isotopic determination techniques described here can also be applied to different environmental samples such as waters rocks and sediments

a stalagmite δ18o record from jinfo cave southern china reveals early mid holocene variations in the east asian summer monsoon abstract the stability of the east asian summer monsoon easm during the early holocene and the timing of the holocene optimum have been intensely debated both stalagmite and lake records from northern china imply that there was a millennium scale monsoon weakening event during the early holocene but whether this phenomenon is common across the asian monsoon region remains unclear due to a paucity of records from southern china we present results from u th dating and 433 stable carbon and oxygen isotope datapoints in order to investigate variations in the easm during the early mid holocene in southern china the results show that stalagmite 18o values are relatively low in the period of 10 1 9 6 ka bp indicating enhanced monsoon activity in the early holocene the stalagmite 18o values for the period of 9 1 8 1 ka bp are characterized by a w type oscillation indicating that there was a period of monsoon recession in contrast the period of 8 0 6 0 ka bp is characterized by relatively low implying a strong monsoon the results of our study indicate there was a millennial scale weakening of the monsoon during the early holocene in southern china this suggests that the early holocene monsoon weakening events are widespread throughout the monsoon region of eastern china

u th systematics and 230th ages of carbonate chimneys at the lost city hydrothermal field the lost city hydrothermal field lchf is a serpentinite hosted vent field located 15 km west of the spreading axis of the mid atlantic ridge in this study uranium thorium u th geochronological techniques have been used to examine the u th systematics of hydrothermal fluids and the 230th ages of hydrothermally precipitated carbonate chimneys at the lchf fluid sample analyses indicate that endmember fluids likely contain only 0 0073 ng g u or less compared to 3 28 0 03 ng g of u in ambient seawater for fluid samples containing only 2 21 ambient seawater 1 1 11 mmol kg mg th concentration is 0 11 0 13 pg g and surrounding seawater concentrations average 0 133 0 016 pg g the 230th 232th atomic ratios of the vent fluids range from 1 10 10 6 to 11 5 10 6 are less than those of seawater and indicate that the vent fluids may contribute a minor amount of non radiogenic 230th to the lchf carbonate chimney deposits chimney 238u concentrations range from 1 to 10 g g and the average chimney corrected initial 234u is 147 2 0 8 which is not significantly different from the ambient seawater value of 146 5 0 6 carbonate 232th concentrations range broadly from 0 0038 0 0003 to 125 16 ng g and 230th 232th atomic ratios vary from near seawater values of 43 8 10 6 up to 530 25 10 3 chimney ages corrected for initial 230th range from 17 6 yrs to 120 13 kyrs the youngest chimneys are at the intersection of two active steeply dipping normal faults that cut the atlantis massif the oldest chimneys are located in the southwest portion of the field vent deposits on a steep fault bounded wall on the east side of the field are all 4 kyrs old indicating that mass wasting in this region is relatively recent comparison of results to prior age dating investigations of submarine hydrothermal systems shows that the lchf is the most long lived hydrothermal system known to date it is likely that seismic activity and active faulting within the atlantis massif and the atlantis fracture zone coupled with volumetric expansion of the underlying serpentinized host rocks play major roles in sustaining hydrothermal activity at this site the longevity of venting at the lchf may have implications for ecological succession of microorganisms within serpentinite hosted vent environments

uranium series dating of marine and lacustrine carbonates of the possible uranium series dating schemes the most important and most widely applied to marine carbonates is 230th dating with 231pa dating playing an increasingly important role for this reason this review will focus on these two methods 230th dating also referred to as u th dating or 238u 234u 230th dating involves calculating ages from radioactive decay and ingrowth relationships among 238u 234u and 230th 232th is also typically measured as a long lived essentially stable index isotope over the time scales relevant to 230th dating at present 230th dating can in principle be used to date materials as young as 3 years and in excess of 600 000 years edwards et al 1987a 1993 edwards 1988 see stirling et al 2001 for an example of dating corals in excess of 600 000 years old 231pa dating also referred to as u pa dating involves calculating ages from the ingrowth of 231pa from its grandparent 235u at present 231pa dating can be used to date materials as young as 10 years and as old 250 000 years edwards et al 1997 230th dating covers all of the 231pa time range and more with somewhat higher precision and is therefore the method of choice if a single method is applied however the combination of 231pa and 230th dating is of great importance in assessing possible diagenetic mobilization of the pertinent nuclides and thereby the accuracy of the ages allegre 1964 ku 1968 even if the primary age exceeds the 250 000 year limit of 231pa dating the combined methods can be used to assess the degree to which the samples have remained closed over the past 250 000 years e g edwards et al 1997 thus

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

the importance of independent chronology in integrating records of past climate change for the 60 8 ka intimate time interval this paper provides a brief overview of the most common dating techniques applied in palaeoclimate and palaeoenvironmental studies including four radiometric and isotopic dating methods radiocarbon 230th disequilibrium luminescence cosmogenic nuclides and two incremental methods based on layer counting ice layer varves for each method concise background information about the fundamental principles and methodological approaches is provided we concentrate on the time interval of focus for the intimate integrating ice core marine and terrestrial records community 60 8 ka this dating guide addresses palaeoclimatologists who aim at interpretation of their often regional and local proxy time series in a wider spatial context and therefore have to rely on correlation with proxy records obtained from different archives from various regions for this reason we especially emphasise scientific approaches for harmonising chronologies for sophisticated and robust proxy data integration in this respect up to date age modelling techniques are presented as well as tools for linking records by age equivalence including tephrochronology cosmogenic 10be and palaeomagnetic variations finally to avoid inadequate documentation of chronologies and assure reliable correlation of proxy time series this paper provides recommendations for minimum standards of uncertainty and age datum reporting

short and long term ground deformation due to cyclic steam stimulation in alberta canada measured with interferometric radar short and long term ground deformation at the cyclic steam stimulation css enhanced oil recovery sites in the cold lake region of alberta canada was measured with radarsat 2 differential interferometric synthetic aperture radar dinsar during 2011 2016 the interferometric processing of 84 high resolution spotlight images revealed extensive short term ground uplift and subsidence greater than 15 cm over the 24 day satellite revisit cycle time series analysis based on the multidimensional small baseline subset msbas methodology demonstrated that while the predominant deformation signal is cyclical in nature a long term subsidence and uplift with maximum deformation rates greater than 5 cm year is also present these measurements suggest that css injection and production operations result in the long term semipermanent deformation in the area of reservoir operations and that the response to injection and extraction can differ from the previous cycles

role of a ductile decollement in the development of pull apart basins experimental results and natural examples abstract traditional models describe pull apart basins as graben or half graben basins with normal or normal oblique slip master faults analogous to death valley california yet many pull aparts are characterized by asymmetric basins with strike slip master faults indicating that not all pull apart basins conform to the simple death valley models we present analogue modelling results that show developmental sequences and structural styles of pull aparts are dramatically different when overburden rides over a ductile horizon and that thickness of the ductile horizon exerts control on basin development in our models synthetic and antithetic strike slip faults control basin geometries while localized normal faulting and local oblique slip on strike slip faults accommodate basin subsidence faults evolve from initial strike slip to normal oblique and normal dip slip to form a system of either isolated sub basins in the case of thick ductile layers or coalescing sub basins in the case of thin ductile layers these results demonstrate distinct differences between non ductile and ductile decollement pull apart structures basin boundaries dominated by normal faults suggest a decollement within or at the base of a non ductile layer similar to death valley california basin bounding faults dominated by strike slip and oblique slip faults indicate basin formation over a ductile layer similar to the gulf of elat aqaba or gulf of paria venezuela and trinidad

high precision u series measurements of more than 500 000 year old fossil corals robust independent age constraints on the absolute timing of climate events based on the u series dating of fossil coral are sparse before the last glacial cycle using multiple collector inductively coupled plasma mass spectrometry with multiple faraday protocols we are able to date 600 ka samples with an uncertainty of better than 15 ka 2 representing a three fold improvement in precision compared with previous techniques using these methods we report u series measurements for a suite of 500 thousand year old ka corals from henderson island an emergent atoll in the south central pacific ocean the fossil corals show extraordinarily little diagenetic alteration for their age and the best preserved sample yields a u series age of 600 15 ka 2 which overlaps with the timing of the warm marine isotope stage mis 15 interglacial the open system model of villemant and feuillet villemant b and feuillet n 2003 dating open systems by the 238u 234u 230th method application to quaternary reef terraces earth and planetary science letters 210 1 2 105 118 and the linear regression or open system isochron is clearly limited for such old samples however the open system model developed by thompson et al thompson w g spiegelman m w goldstein s l and speed r c 2003 an open system model for u series age determinations of fossil corals earth and planetary science letters 210 1 2 365 381 appears to reliably correct for open system effects in roughly half of the corals giving a mis 15 origin for these thus the data provide evidence that the systematic addition of 230th and 234u through recoil is a dominant open system process occurring in the henderson island fossil reef system several coral samples yield significantly older thompson et al open system ages between 650 and 750 ka the uncertainty on these ages typically 30 kyrs is too great for precise assignment but most data overlap with the mis 17 interglacial the reliability of these ages is currently unclear it is shown that separate aliquots of the same coral can yield different thompson model ages therefore there appear to be additional diagenetic mechanisms that create further anomalous excursions in the u series systematics limiting the reliability of the thompson et al open system model

new views of tropical paleoclimates from corals abstract corals offer a rich archive of past climate variability in tropical ocean regions where instrumental data are limited and where our knowledge of multi decadal climate sensitivity is incomplete in the eastern equatorial pacific coral isotopic records track variations in enso related changes in sea surface temperature further west corals record variability in sea surface temperature and rainfall that accompanies zonal displacement of the indonesian low during enso events these multi century records reveal previously unrecognised enso variability on time scales of decades to centuries outside the enso sensitive equatorial pacific long term trends towards recent warmer wetter conditions suggest the tropics respond to global forcings new coral paleothermometers indicate that surface ocean temperatures in the tropical southwestern pacific were depressed by 4 6 c during the younger dryas climatic event and rose episodically during the next 4000 yr high temporal resolution measurements of sr ca and 18 o in corals provide information about the surface ocean hydrologic balance and can resolve the seasonal balance between precipitation and evaporation radiocarbon measurements in corals coupled with ocean circulation models may be used to reconstruct near surface ocean circulation past mixing rates and the distribution of fossil fuel co2 in the upper ocean most recently seasonal to interannual variations in the radiocarbon of corals from the equatorial pacific have been linked to the redistribution of surface waters associated with the enso

δ18o δ13c elemental content and depositional features of a stalagmite from yelang cave reflecting climate and vegetation changes since late pleistocene in central guizhou china abstract a 13 5 cm long stalagmite from yelang cave in central guizhou provides another example of ams 14 c dating on stalagmites which are not suitable for 230 th u dating due to very low u content and low 230 th 232 th ratio this record duplicates the published stalagmite record of 20120824 13 from the same cave zhao et al 2015 not only on 18 o and 13 c records but also on major growth hiatuses facilitating speleothem 18 o and 13 c as climate and vegetation proxies respectively based on the two stalagmite records climate and vegetation conditions can be deciphered as follow relatively cool and dry climates with c4 dominated plants during 33 4 36 ka very cold and dry climates with poor vegetation coverage during the last glacial maximum cold and dry climates with poor vegetation during younger dryas warming and very wet climates with the best vegetation mainly c3 plants coverage during 9 11 5 ka bp corresponding to a maximum insolation drying climate and decreased vegetation intensity from 9 ka to 8 ka relatively good vegetation coverage during 5 6 ka the summer monsoon strength decreased from 5 ka to 1 5 ka bp but increased during the medieval warm period to produce wet climates and abundant vegetation and strongly decadal variations in moisture budget and strong deforestation due to human impact during the past 600 years high fe mn and al contents from detritus caused dark bands near the hiatuses strong positive correlation of mg and sr with high mg sr values 23 in this study reflects source control on the mg and sr variations so that mg sr is not a function of cave temperature in such a case for pure calcite without detrital influence mg sr may register changes in cave temperature with higher mg sr indicating warmer temperature this study calls for the attention to find out climatic conditions in central guizhou during the bolling allerod warming and the middle holocene 6 8 ka intervals because of lacking deposition during these intervals in yelang cave using stalagmite 18 o alone to decipher climatic conditions on decadal to millennial scales needs to consider multiple factors such as amount source and temperature effects on the 18 o

an evaluation of quantitative reconstruction of past precipitation records using coral skeletal sr ca and δ18o data abstract coupled records of 18o and sr ca in porites coral have been used to derive hydrological conditions by removing the sr ca inferred temperature component from the 18o signal nanwan a semi enclosed bay in southern taiwan provides an opportunity to demonstrate the feasibility of quantitatively reconstructing past precipitation history recurrence of seawater 18o offsets between wet and dry seasons in the early 1990s is well correlated with the precipitation record even though the hydrological signal only accounts for 20 of the total annual coral 18o variation of ca 1 offsets can be found in the residual 18o of modern corals after removing the thermal effect which contributes to the other 80 the observed timing and amplitude of the seasonal seawater 18o offsets in nanwan and their correlation with precipitation are reproduced by hydrological models in the mid holocene the seasonal anomaly of residual 18o was twice that of the modern value based on the 9 yr sr ca 18o data recorded in a 6 73 ka porites coral hydrological models suggest an annual rainfall of 1800 3000 mm yr at the window during mid holocene 20 higher than that of the average of 30 yr modern instrumental records of 1500 2500 mm consistent with the qualitative pollen record from lake sediments the seasonal decrease of residual 18o in 5 of 9 yr was earlier than the increase of the coral sr ca inferred temperature which implies that these rainy seasons probably occurred from the early mid spring to mid summer earlier than that from late spring to late summer today the driving force may be related to the changes of solar insolation and the east asian monsoon it is cautioned that the variability of hydrographic conditions imposes restrictions on a precise calculation of the amount of paleo precipitation the dynamic nature of local tectonics monsoons and water circulation should be further addressed to precisely quantify precipitation over the past 10 000 yr from coral geochemical records

genesis and diagenesis of travertine futamata hot spring japan abstract genetic and diagenetic processes of travertine were examined at futamata hot spring where both active and inactive subfossil and fossil travertines are present geochemical and geomicrobiological analyses of active travertines reveal that abiotic process of caco3 precipitation is predominant photosynthetic inhibition of caco3 precipitation occurs at the upstream while the cyanobacterial population is low in the downstream resulting in photosynthesis induced caco3 precipitation only in the midstream nonetheless microorganisms have an effect upon depositional fabrics and filamentous cyanobacteria possessing non acidic sheaths contribute to the particle trapping binding and the generation of pore space both active and inactive travertines are mainly composed of calcite however active travertine in the up midstream also contains some aragonite due to high rates of co2 degassing active and subfossil travertines are characterized by domal topography and relatively high flow rates are assumed due to the dominance of slope facies on the other hand fossil travertines are characterized by fissure ridge topography and relatively low flow rates are assumed due to the dominance of crest and marsh facies the elemental composition of travertines primarily reflects their constituent minerals and the active travertines consisting of both aragonite and calcite show higher sr ba na and k contents whereas travertines consisting solely of calcite show higher mg and mn contents due to elevated mn content bright cathode luminescence is exhibited by the primary calcite of active travertines most fossil travertines have experienced prominent diagenetic alteration in the vadose zone and are commonly cemented and recrystallized in addition to meteoric water percolating hot spring water was also involved in the diagenetic process combined with the results of u th dating our results suggest that the formation of fissure ridge travertines at futamata hot spring began approximately 20 thousand years ago ka via fault activity which terminated at around 7 ka and the domal travertines were formed by hot spring water discharging from several vents

calcite veining and feeding conduits in a hydrothermal system insights from a natural section across the pleistocene golemezli travertine depositional system western anatolia turkey abstract linking the architecture of structural conduits with the hydrothermal fluids migrating from the reservoir up to the surface is a key factor in geothermal research a contribution to this achievement derives from the study of spring related travertine deposits but although travertine depositional systems occur widely their feeding conduits are only rarely exposed the integrated study carried out in the geothermal golemezli area nearby the well known pamukkale area denizli basin western anatolia turkey focused on onyx like calcite veins banded travertine and bedded travertine well exposed in a natural cross section allowing the reconstruction of the shallower part of a geothermal system the onyx like veins represent the thickest vein network 150 m so far known new field mapping and structural kinematic analyses allowed to document a partially dismantled travertine complex bedded travertine formed by proximal fissure ridges and distal terraced pools depositional systems the banded calcite veins wnw trending and up to 12 m thick developed within a 200 m thick damaged rock volume produced by parallel fault zones th u dating indicates a long lasting middle late pleistocene fluids circulation in a palaeo geothermal system that due to its location and chemical characteristics can be considered the analogue of the nearby still active pamukkale system the isotopic characteristics of the calcite veins together with data from fluid inclusions analyses allow the reconstruction of some properties i e temperature salinity and isotopic composition and processes i e temperature variation and intensity of degassing that characterized the parent fluids and the relation between degassing intensity and specific microfabric of calcite crystals elongated microsparite micrite bands controlled by changes fluctuations of the physico chemical fluid characteristics

rapid and accurate u th dating of ancient carbonates using inductively coupled plasma quadrupole mass spectrometry here the potential for rapid and accurate u th dating technique of marine aragonite skeletons deep sea corals lophelia pertusa and secondary calcite deposits speleothems and stalagmites has been explored using inductively coupled plasma quadrupole mass spectrometry icp qms the analytical procedure includes a largely simplified chemical separation technique for uranium u and thorium th using uteva resin the developed technique permits simultaneous quantification of uranium 238u and thorium 232th concentrations and their respective isotopic composition required for u series disequilibrium dating up to 50 u th dates per day can be achieved through icp qms with 234u and 230th reproducibility 2 of 3 4 and 1 respectively the high sensitivity 3 0 105 cps ppb together with low background 0 5 cps on each mass between 228 and 236 amu allowed u th dating of ancient deep water corals 15 260 kyr and stalagmites 30 85 kyr at precision levels of less than 2 consequently the combination of simplified chemistry using uteva with state of the art icp qms isotopic measurements that do not require a u th separation step now provides an extremely rapid and low cost u series dating technology the level of precision is most convenient for numerous geochronological applications such as the determination of climatic influences on ecosystem development and carbonate precipitation as a first example application we present icp qms u th dates of north atlantic deep water coral fragments retrieved in the southeastern porcupine seabight md01 2463g mound therese indicating a purely interglacial growth of deep water corals on so called carbonate mounds over several climate cycles

holocene itcz and indian monsoon dynamics recorded in stalagmites from oman and yemen socotra abstract high resolution oxygen isotope 18o profiles of holocene stalagmites from four caves in northern and southern oman and yemen socotra provide detailed information on fluctuations in precipitation along a latitudinal transect from 12 n to 23 n 18o values reflect the amount of precipitation which is primarily controlled by the mean latitudinal position of the itcz and dynamics of the indian summer monsoon ism during the early holocene rapidly decreasing 18o values indicate a rapid northward displacement in the mean latitudinal position of the summer itcz and the associated ism rainfall belt with decadal to centennial scale changes in monsoon precipitation correlating well with high latitude temperature variations recorded in greenland ice cores during the middle to late holocene the summer itcz continuously migrated southward and monsoon precipitation decreased gradually in response to decreasing solar insolation a trend which is also recorded in other monsoon records from the indian and east asian monsoon domains importantly there is no evidence for an abrupt middle holocene weakening in monsoon precipitation although abrupt monsoon events are apparent in all monsoon records they are short lived and clearly superimposed on the long term trend of decreasing monsoon precipitation for the late holocene there is an anti correlation between ism precipitation in oman and inter monsoon spring autumn precipitation on socotra revealing a possible long term change in the duration of the summer monsoon season since at least 4 5 ka bp together with the progressive shortening of the ism season gradual southward retreat of the mean summer itcz and weakening of the ism the total amount of precipitation decreased in those areas located at the northern fringe of the indian and asian monsoon domains but increased in areas closer to the equator

east asian monsoon evolution and reconciliation of climate records from japan and greenland during the last deglaciation abstract east asian monsoon eam evolution during the last deglaciation has been shown repeatedly to be aligned with paleoclimatic changes in the north atlantic based on climate reconstructions comparing asian speleothem records with greenland ice cores in contrast to this finding paleoclimatic reconstructions based on lake suigetsu sediment cores suggest that past eam variability in japan was not always coherent with climatic variability recorded in greenland ice cores we resolve this discrepancy using an absolute dated stalagmite 18 o record that covers the period between 15 5 and 10 7 thousand years before present ka before ad 1950 this stalagmite record is from nearby maboroshi cave japan and shows climate changes that are synchronous with those of chinese caves and greenland ice cores our results support an effective teleconnection between low and high latitudinal climate systems during the transitions into the bolling allerod ba warming at 14 6 ka and the younger dryas cooling at 12 8 ka in the north atlantic however our results also indicate monsoonal intensification during the ba coincident with decreasing temperatures in greenland from 14 6 to 12 8 ka we explain this decoupling as a result of the interhemispheric bipolar seesaw climate system discrepancies between lake suigetsu radiocarbon age data sets and other radiocarbon calibration archives can also be removed when our maboroshi record is used to adjust the lake suigetsu age model as well as resolving temporal ambiguities in the lake suigetsu paleoclimate record

upper plate splay fault earthquakes along the arakan subduction belt recorded by uplifted coral microatolls on northern ramree island western myanmar burma abstract upper plate structures that splay out from the megathrusts are common features along major convergent plate boundaries however their earthquake and tsunami hazard potentials have not yet received significant attention in this study we identified at least one earthquake event that may have been produced by an upper plate splay fault offshore western myanmar based on u th ages of uplifted coral microatolls this event is likely an earthquake that was documented historically in c e 1848 with an estimated magnitude between 6 8 and 7 2 based on regional structural characteristics such magnitude is consistent with the observed co seismic uplift amount of 0 5 m although these events are smaller in magnitude than events produced by megathrusts they may produce higher earthquake and tsunami hazards for local coastal communities due to their proximity our results also indicate that earthquake events with co seismic uplift along the coast may not necessarily produce a flight of marine terraces therefore using only records of uplifted marine terraces as megathrust earthquake proxies may overlook the importance of upper plate splay fault ruptures and underestimate the overall earthquake frequency for future seismic and tsunami hazards along major subduction zones of the world

stable isotope compositions of speleothems from the last interglacial spatial patterns of climate fluctuations in europe abstract studies on the last interglacial lig can provide information on how our environment behaved in a period of slightly higher global temperatures at about 125 4 ka even if it is not the best analogue for the holocene the available lig climate proxy records are usually better preserved and can be studied at a higher resolution than those of the preceding interglacials allowing detailed comparisons this paper presents complex stable hydrogen carbon and oxygen isotope records obtained for carbonate 13 c and 18 o carb and fluid inclusion hosted water d and 18 o w of a stalagmite from the baradla cave system in central europe that covers most of the lig as proven by u th dates comparing its c and o isotope data with records reported for other speleothem cave hosted carbonate deposits from europe revealed the complex behavior of these climate proxies with a concerted relative increase in 18 o of carbonates from 128 to 120 ka and synchronized shifts in the opposite direction after 119 ka the hydrogen isotope analyses of inclusion hosted water extracted from the bar ii stalagmite also correspond to the regional climate proxy records with meaningful deviations from global temperature trends beside following the general paleotemperature pattern from the climate optimum high d values up to 64 around 120 ka to the subsequent cooling starting at about 119 ka low d values down to 90 at about 109 ka a period between 126 5 and 123 ka with low d values down to 81 is detected in the bar ii stalagmite although the isotope shifts are muted in the c o isotope data of carbonate due to competitive fractionation processes the 13 c data show a positive relationship with the d pattern indicating humidity and possibly temperature variations the periods with low d values fit well to temperature and humidity changes inferred from proxy records from western europe to the eastern mediterranean spatial distributions of these variables show that at about 125 2 ka the mediterranean region was characterized by warm humid conditions and enhanced seasonality with elevated winter precipitation the combined interpretation of stable isotope data revealed that the alpine and mediterranean regions behaved differently during greenland stadial 26 gs26 119 to 116 2 ka while the alpine records fluctuated in close agreement with the central greenland ice core 18 o data the bar ii stalagmite show a positive 18 o carb anomaly the baradla data indicate enhanced aridity and seasonality for a part of gs26 with the relative dominance of summer precipitation and mediterranean moisture contribution following the gs26 event the effect of long term global cooling becomes dominant in the baradla isotope records and leads to glacial inception at about 109 ka

climatic constraints on growth rate and geochemistry sr ca and u ca of the coral siderastrea stellata in the southwest equatorial atlantic rocas atoll brazil although relatively rare compared to similar latitudes in the pacific or indian oceans massive coral colonies are present in the tropical equatorial southwestern atlantic ocean however detailed geochemical compositions of these corals are still largely unknown in this work we present growth rates sr ca and u ca ratios of the coral colony siderastrea stellata sampled at rocas atoll off the brazilian coast these variables are primarily affected by sea surface temperature sst at seasonal scale and by wind stress at interannual scale these results represent a broad new finding a lower significance at the interannual time scale between sr ca and u ca with respect to sst is attributed to the low sst amplitude closed to equator an investigation on the dependence of coral growth rates with respect to the cloud shading effect promoted by the intertropical convergence zone itcz does not show significant influence additionally rain seems to act on local geochemistry of sr ca ratios and growth rate at the decadal scale

rupture and variable coupling behavior of the mentawai segment of the sunda megathrust during the supercycle culmination of 1797 to 1833 we refer to periods of subduction strain accumulation beneath the mentawai islands sumatra as supercycles because each culminates in a series of partial ruptures of the megathrust in its final decades the finale of the previous supercycle comprised two giant earthquakes in 1797 and 1833 and whatever happened in between this behavior between two great ruptures has implications for how the megathrust will behave between its more recent partial failure during the m w 8 4 earthquake of 2007 and subsequent large ruptures we synthesize previously published coral microatoll records and a large new coral data set to constrain not only these two giant ruptures but also the intervening interseismic megathrust behavior we present detailed maps of coseismic uplift during the two earthquakes and of interseismic deformation during the periods 1755 1833 and 1950 2000 as well as models of the corresponding slip and coupling on the underlying megathrust the large magnitudes we derive m w 8 6 8 8 for 1797 and m w 8 8 8 9 for 1833 confirm that the 2007 earthquakes released only a fraction of the moment released during the previous rupture sequence whereas megathrust behavior leading up to the 1797 and 2007 earthquakes was similar and comparatively simple behavior between 1797 and 1833 was markedly different and more complex several patches of the megathrust became weakly coupled following the 1797 earthquake we conclude that while major earthquakes generally do not involve rupture of the entire mentawai segment they may significantly change the state of coupling on the megathrust for decades to follow influencing the progression of subsequent ruptures

the tracing of riverine u in arctic seawater with very precise 234u 238u measurements abstract the riverine flux of u that enters the deep oceans is not well constrained since the net losses during estuarine mixing are difficult to quantify riverine dissolved u normally has a higher 234 u 238 u activity ratio 234 u 238 u ar than the uniform value that characterizes open ocean seawater and could be used as a tracer of riverine inputs if one could resolve subtle variations in seawater composition using new mass spectrometry techniques we achieve a long term reproducibility 0 3 on 234 u 238 u ar which permits the tracing of riverine u in seawater samples from the arctic a partially restricted basin that is ideal for such a study we find that surface waters from the arctic basins carry elevated 234 u 238 u ar when compared with deep ocean seawater samples from the canada basin have a significant freshwater component and provide evidence that the mackenzie river loses 65 of its u in the mackenzie shelf estuary zone before entering the deeper basin this is in contrast to samples from the makarov basin which provide evidence that all of the freshwater input is derived from the major yenisey river alone despite the proximity of the lena and ob rivers the differing behaviour of u between the mackenzie and yenisey rivers is most likely a consequence of the strong binding of u to dissolved organic matter doc or secondary phases in these rivers the yenisey river appears to transport the majority of the doc through the shelf and into the makarov basin in contrast the mackenzie river appears to lose a significant amount of doc 50 in the estuary shelf zone which may lead to loss of associated u these findings offer a more detailed picture of the fresh riverine water flow patterns in the arctic ocean when compared to other geochemical proxies the non conservative behaviour of u in the mackenzie river through the shelf estuaries has important implications for u input into oceans and the total marine budget

the nature of annual lamination in carbonate flowstones from non karstic fractures vinschgau northern italy abstract the vinschgau is an inneralpine valley in the southern alps whose steep flanks are composed of strongly sheared gneisses and schists affected by deep seated gravitational slope deformations fractures generated by these movements host a groundwater system characterised by high amounts of dissolved solids which reflect long residence times and water rock interactions driven by sulphide oxidation this in combination with high air and soil temperatures on the south facing slope sonnenberg of the valley favoured the deposition of calcite and aragonite flowstone in shallow parts of this fractured non karstic aquifer about 5 of these speleothems exhibit well developed regular lamination whose annual origin was confirmed by radiometric dating a stable isotope petrographic and trace element study combined with u th dating was undertaken to disentangle the processes controlling lamina formation a succession of darker and lighter laminae forms distinct macroscopic couplets 0 2 2 mm wide in three of the samples while one sample comprises alternating white and translucent laminae microscopically the darker and white laminae show a higher abundance of opaque particles whose organic origin is confirmed by their strong epifluorescence the crystal fabric is dominated by the fascicular optic type the calcite shows regular 18 o oscillations with an amplitude of up to 1 2 with the exception of one sample 13 c lacks such a regular pattern and only shows smaller variations which do not correlate with 18 o in a consistent way all samples exhibit regular low amplitude mg sr ba and u cycles in three samples mg shows oscillations similar to the 18 o cycles in their frequency but opposite in phasing 18 o and mg oscillations are primarily attributed to surface temperature variations that are transmitted to the shallow subsurface by thermal conduction low amplitude trace element cycles mg sr ba and u are most probably driven by intra annual variations in the degree of prior aragonite precipitation in the seepage path which relates to seasonal changes in evaporation

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

huge erratic boulders in tonga deposited by a prehistoric tsunami along some coastlines there are erratic boulders apparently emplaced by tsunamis or cyclonic storms evaluating their origin and time of emplacement places constraints on the frequency severity and location of coastal hazards seven such large coral limestone boulders are present near fahefa village on tongatapu island southwest pacific apparently emplaced by a prehistoric tsunami these boulders are 10 20 m above sea level and above any possible source and all are 100 400 m from the present shoreline coral 230th ages indicate that the limestone formed during the last interglacial sea level highstand ca 120 130 ka the largest boulder is 20 times more massive than any reported boulders emplaced by historically documented storms and may be the largest known tsunami or storm erratic worldwide situated above its source we performed computer simulations to assess whether tsunamis produced by earthquakes undersea landslides or volcanoes could emplace the boulders the simulations indicate that either volcanic flank collapse along the tofua arc 30 40 km to the southwest or undersea landslides on the submarine slopes of tongatapu could be responsible either could explain why these boulders are not widespread on tongatapu and instead occur in a localized group along the western coast this study demonstrates that small 1 km3 submarine slope failures sometimes generate locally large tsunamis the fahefa boulders are in a well studied and well populated area yet were unknown to the scientific community until recently this suggests that systematic searches elsewhere for erratic boulders and other tsunami deposits might provide new information for assessing the size and extent of prehistoric tsunamis

intra annual variation in the stable oxygen and carbon and trace element composition of sclerosponges 1 this paper presents data to support the presence of 1 intra annual signals in the chemical composition 18o and sr ca of the skeletons of sclerosponges from the bahamas and 2 variable rates of skeletal accretion these conclusions are based on data obtained by using a microsampling method for the stable oxygen and carbon isotopes in which material was extracted at a resolution of one sample every 34 m and a laser microprobe which obtained trace element data every 20 m sr mg and pb an age model was established using a combination of changes in the concentration of pb the change in the 13c of the skeleton of the sclerosponges and u th isotopic measurements these methods yield a mean growth rate of 220 m yr but suggest that the growth rate in this particular sclerosponge was not constant the calculated growth rate is within error identical to that determined by u th methods the variable growth rate was confirmed through spectral analysis of the 18o and sr ca data that showed peaks corresponding to the annual cycle in these parameters as well as peaks corresponding to growth rates of approximately 128 212 270 and 400 m yr the presence of these additional frequencies suggests a growth rate between approximately 100 and 300 m yr these conclusions were supported by modeling of oxygen isotopic data measured on a scleractinian coral as well as model isotope data generated on synthetic time series these findings have important implications for the use of sclerosponges as proxies of paleoclimate because they emphasize the need for a precise yearly chronology in order that proxy data can be compared with climatic variables

variation of initial 230th 232th and limits of high precision u th dating of shallow water corals one hundred eighty u th data including 23 isochrons on 24 pristine modern and holocene corals and 33 seawater samples were analyzed using sector field mass spectrometry to understand the variability of initial 230th 232th 230th 232th0 this dataset allows us to further assess the accuracy and precision of coral 230th dating method by applying quality control including careful sampling and subsampling protocols and the use of contamination free storage and workbench spaces the resulting low procedural blanks give an equivalent uncertainty in age of only 0 2 0 3 yr for 1 2 g of coral sample using site specific 230th 232th0 values or isochron techniques our study demonstrates that corals with an age less than 100 yrs can be 230th dated with precisions of 1 yr six living subtidal coral samples were collected from two continental shelf sites nanwan off southern taiwan in the western pacific and son tra off central vietnam in the south china sea one coral core was drilled from an open ocean site santo island vanuatu in the western tropical pacific and modern and fossil intertidal coral slabs 17 in total were cut from six sites around the islands of simeulue lago north pagai and south pagai of sumatra in the eastern indian ocean the results indicate that the main source of thorium is the dissolved phase of seawater with variation of 230th 232th0 depending on local hydrology with intense input of terrestrial material low 230th 232th0 atomic ratios of 4 9 10 6 and 3 2 10 6 with a 10 variation are observed in nanwan and son tra respectively at the santo site we find a value of 5 6 10 6 at 4 horizons and one high value of 24 10 6 in a sample from ad 1974 6 0 5 likely due to the upwelling of cold water during a la nina event between ad 1973 and 1976 the natural dynamics of 230th 232th0 recorded in the intertidal corals at sites in the sumatran islands are complicated so that this value varies significantly from 3 0 to 9 4 10 6 three of the 141 modern coral 230th ages differ from their true ages by 23 to 4 indicating the presence of detrital material with anomalous 230th 232th values duplicate measurement of coeval subsamples is therefore recommended to verify the age accuracy this improved high precision coral 230th dating method raises the prospects of refining the age models for band counted and tracer tuned chronologies and of advancing coral paleoclimate research

dating earthquakes with high precision thorium 230 ages of very young corals mass spectrometric techniques have recently yielded significant increases in precision and sensitivity over previous methods for measuring 230 th abundance in corals to assess the accuracy of 230 th ages three corals from vanuatu whose ages were known from counting annual growth bands were analyzed for each sample the date of growth determined by 230 th analysis a d 1969 3 1932 5 and1806 5 2 uncertainties based on analytical error was indistinguishable from the date determined by counting bands a d 1971 1973 1935 1937 and 1804 1810 indicating that the 230 th dates are accurate 230 th dates were also determined for two adjacent emerged heads from santo is vanuatu which were thought to have died when they were raised above sea level during coseismic uplift the dates a d 1864 4 1866 4 were the same indicating that the heads died at the same time and consistent with the idea that they were killed by coseismic emergence around a d 1865 the difference between this date and the date of the only major historically documented earthquake that caused uplift a d 1973 m s 7 5 suggests a seismic recurrence interval of108 4y for santo analogous emerged corals from malekula is vanuatu yielded 230 th dates that were similar to each other a d 1729 3 1718 5 and are inferred to have died during coseismic emergence around a d 1729 in conjunction with the date of the only large historically documented earthquake that caused uplift a d 1965 m s 7 5 the recurrence interval for malekula is236 3y if similar emerged corals can be found this appraoch may be extended back in time and to other localities because it appears that such features can now be dated both accurately and precisely

increasing australian indonesian monsoon rainfall linked to early holocene sea level rise the australian indonesian summer monsoon affects rainfall variability across the indo pacific region reconstructions of monsoon strength from stalagmites show that precipitation increased from 11 000 to 7 000 years ago as rising global sea level caused the flooding of the indonesian continental shelf the australian indonesian summer monsoon affects rainfall variability and hence terrestrial productivity in the densely populated tropical indo pacific region it has been proposed that the main control of summer monsoon precipitation on millennial timescales is local insolation1 2 3 but unravelling the mechanisms that have influenced monsoon variability and teleconnections has proven difficult owing to the lack of high resolution records of past monsoon behaviour here we present a precisely dated reconstruction of monsoon rainfall over the past 12 000 years based on oxygen isotope measurements from two stalagmites collected in southeast indonesia we show that the summer monsoon precipitation increased during the younger dryas cooling event when atlantic meridional overturning circulation was relatively weak4 monsoon precipitation intensified even more rapidly from 11 000 to 7 000 years ago when the indonesian continental shelf was flooded by global sea level rise5 6 7 we suggest that the intensification during the younger dryas cooling was caused by enhanced winter monsoon outflow from asia and a related southward migration of the intertropical convergence zone8 however the early holocene intensification of monsoon precipitation was driven by sea level rise which increased the supply of moisture to the indonesian archipelago

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

timing duration and transitions of the last interglacial asian monsoon thorium 230 ages and oxygen isotope ratios of stalagmites from dongge cave china characterize the asian monsoon and low latitude precipitation over the past 160 000 years numerous abrupt changes in 18o 16o values result from changes in tropical and subtropical precipitation driven by insolation and millennial scale circulation shifts the last interglacial monsoon lasted 9 7 1 1 thousand years beginning with an abrupt less than 200 years drop in 18o 16o values 129 3 0 9 thousand years ago and ending with an abrupt less than 300 years rise in 18o 16o values 119 6 0 6 thousand years ago the start coincides with insolation rise and measures of full interglacial conditions indicating that insolation triggered the final rise to full interglacial conditions