pronounced zonal heterogeneity in eocene southern high latitude sea surface temperatures paleoclimate studies suggest that increased global warmth during the eocene epoch was greatly amplified at high latitudes a state that climate models cannot fully reproduce however proxy estimates of eocene near antarctic sea surface temperatures ssts have produced widely divergent results at similar latitudes with ssts above 20 c in the southwest pacific contrasting with ssts between 5 and 15 c in the south atlantic validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites here we present multiproxy data from seymour island near the antarctic peninsula that provides well constrained evidence for annual ssts of 10 17 c 1 sd during the middle and late eocene comparison of the same paleotemperature proxy at seymour island and at the east tasman plateau indicate the presence of a large and consistent middle to late eocene sst gradient of 7 c between these two sites located at similar paleolatitudes intermediate complexity climate model simulations suggest that enhanced oceanic heat transport in the south pacific driven by deep water formation in the ross sea was largely responsible for the observed sst gradient these results indicate that very warm ssts in excess of 18 c did not extend uniformly across the eocene southern high latitudes and suggest that thermohaline circulation may partially control the distribution of high latitude ocean temperatures in greenhouse climates the pronounced zonal sst heterogeneity evident in the eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands

a search for seismic radiation from late slip for the december 26 2004 sumatra andaman mw 9 15 earthquake 1 the great 2004 sumatra andaman mw 9 15 earthquake ruptured a 1300 km long segment of the sumatra andaman islands subduction zone in about nine minutes the possibility of continued fault slip after the primary rupture has been raised by tsunami excitation models and by discrepancies between seismic slip models and geodetic observations we examine the global seismic wavefield to identify any late seismic radiation that occurred during the first hour after the main rupture using stacking of deconvolutions and cross correlations of complete ground motion observations and point source responses green s functions we find no evidence for delayed seismic radiation larger than mw 7 5 any major slip within an hour after the main sliding with mechanism similar to the main shock involved deformation so slow that it radiated no detectable seismic waves in the body wave or surface wave passband for periods less than 500 s

temperature limits for preservation of primary calcite clumped isotope paleotemperatures abstract solid state reordering of c o bonds in the calcite lattice can alter the clumped isotope composition of paleotemperature archives such as fossil brachiopod shells without inducing significant changes in shell microstructure and trace element concentrations metrics commonly used to gauge preservation quality to correctly interpret the paleoenvironmental significance of clumped isotope derived paleotemperatures it is necessary to understand the temperature time domain in which solid state c o bond reordering is important we address this question using a combination of laboratory and natural geological experiments on paleozoic brachiopod shells the laboratory experiments involve heating fossil brachiopod calcite at different temperatures and times to directly observe rates of 13 c 18 o bond reordering the resulting arrhenius parameters are indistinguishable from values previously determined for an optical calcite with similar trace element compositions we develop an alternative kinetic model for reordering that accounts for non first order reaction progress observed during the initial several hundred minutes of laboratory heating experiments and show that the simplified first order approximation model passey and henkes 2012 predicts reaction progress equally well for temperatures and timescales relevant to sedimentary basins we evaluate our laboratory based rate predictions by studying brachiopod calcite from several sedimentary basins with independently constrained burial temperature histories specifically we use the laboratory derived arrhenius parameters to predict the evolution of brachiopod calcite clumped isotope compositions during successive one million year time steps reflecting the burial and exhumation temperature paths of each basin while this exercise is limited by the relatively large uncertainties in the temperature histories of these basins we find general correspondence within error between predicted and observed clumped isotope values we present simplified temperature time diagrams for calcite showing domains where primary clumped isotope compositions will be preserved partially reordered and fully reordered in conclusion calcite samples dwelling at 100 c or lower for 10 6 10 8 year timescales should not be affected by solid state c o bond reordering

high archean climatic temperature inferred from oxygen isotope geochemistry of cherts in the 3 5 ga swaziland supergroup south africa new and compiled oxygen isotope data combined with the results of geological and sedimentological studies demonstrate that enclaves of synsedimentary to very early diagenetic cherts are widely preserved in the 3 5 3 2 ga swaziland supergroup barberton greenstone belt south africa the low 1 8 o values of these cherts indicate extremely high ocean temperatures of 55 85 c previously the large depletion in 1 8 o shown by all barberton cherts relative to their phanerozoic counterparts has been attributed to low 1 8 o in archean oceans chert formation during late diagenesis wholesale loss of 1 8 o during alteration and or regional silicification of sediments around hot springs these alternative explanations are not compatible with the new results cherts in the onverwacht group display an isotopic stratigraphy that is inversely repeated in conglomerates in the overlying fig tree and moodies groups demonstrating that the chert 8 0 o values were fixed prior to archean uplift and erosion which started at 3 26 ga the maximum 1 8 o value in barberton cherts 22 is lower than the minimum values 23 in phanerozoic bedded cherts precluding late diagenesis as the explanation of the overall low 1 8 o values regional metamorphic hydrothermal or long term resetting of original 1 8 o values is also precluded by preservation of 1 8 o values across different metamorphic grades and by systematic 1 8 o differences among interbedded chert types stratigraphic units and conglomerate clasts the 7 1 8 o variation of these archean cherts is similar to that of phanerozoic deep sea cherts formed when opal converted to microquartz during burial but the actual archean values are 10 lower marine opal was apparently converted to microquartz during burial to depths of 1 km cherts with 1 8 o 15 reflect conversion during deepest burial or in local areas of enhanced geothermal gradient and or hydrothermal activity cherts with higher 1 8 o values formed during early diagenesis and indicate an extremely hot archean ocean and surface environment

facies stratigraphy and evolution of a middle ediacaran carbonate ramp khufai formation sultanate of oman the khufai formation is the oldest carbonate platform of the cryogenian to lowermost cambrian huqf supergroup a stratigraphic characterization of this unit includes detailed facies descriptions a sequence stratigraphic interpretation and evaluation of lateral heterogeneity and overall ramp evolution the khufai formation comprises one and one half depositional sequences with a maximum flooding interval near the base of the formation and a sequence boundary within the upper peritidal facies most of the deposition occurred during highstand progradation of a carbonate ramp facies tracts include outer ramp and midramp mudstones and wackestones ramp crest grainstone shoal deposits and extensive inner ramp microbially dominated peritidal deposits outcrops in the oman mountains are deep water deposits including turbiditic grainstone and wackestone interbedded with siliciclastic rich siltstone and crinkly laminite facies patterns and parasequence composition are variable both laterally across the outcrop area and vertically through time because of a combination of ramp morphology siliciclastic supply and possible syndepositional faulting the lithostratigraphic boundary between the khufai formation and the overlying shuram formation is gradational and represents significant flooding of the carbonate platform the stratigraphic characterization presented here along with the identification of key facies and diagenetic features will help further future exploration and production of hydrocarbons from the khufai formation

massive recrystallization of low mg calcite at high temperatures in hydrocarbon source rocks implications for organic acids as factors in diagenesis we document massive recrystallization of low mg calcite lime mudstone source rocks at moderately high temperatures in the smackover formation of mississippi this process was driven by organic acids produced during kerogen maturation and holds the implications for studies of primary migration of hydrocarbons secondary porosity generation in reservoirs and global environmental change this interpretation is based on contrasting the following petrographic and bulk rock geochemical characteristics of organic poor vs organic rich lime mudstones

evaluating formation fluid models and calibrations using clumped isotope paleothermometry on bahamian dolomites abstract the use of stable oxygen isotopes to understand the mechanisms of dolomite formation has been hampered by the inability to precipitate well ordered dolomite under normal earth surface conditions several studies have attempted to address this problem either by precipitating high temperature ordered dolomites and extrapolating the data to low temperatures or by using more disordered very high mg calcites as a proxy for low temperature dolomites the result is eight equations that disagree significantly from each other by as much as 3 6 in the 18o value of the precipitating fluid at 25 c and produce differences which can greatly affect the interpretation of the formation mechanisms for low temperature dolomites however by combining the recently developed clumped isotope paleothermometer an independent isotopic measurement 47 that directly relates to the temperature of formation to late miocene to pleistocene aged dolomites from the bahamas with a well constrained thermal and fluid history we have attempted to narrow down the viable equations used to interpret the 18o values of dolomites the clumped isotope temperatures measured on the bahamian dolomites 16 37 c agrees with the range of temperatures expected in the bahamas pairing these temperatures with geological and mineralogical arguments we favor the equation suggested by matthews and katz 1977 as it is the only one that produces realistic 18o fluid values across the range of clumped isotope temperatures both the clumped isotope temperatures and 18o values of the precipitating fluid show a strong positive covariance that we have interpreted as reflecting the mixing of surface brines that have undergone varying amounts of evaporation and normal seawater the different mechanisms driving these fluids included formation by normal marine seawater driven by the compensatory flow of the mixing zone bank wide kohout convection and evaporative brine reflux

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

evolution of a terminal neoproterozoic carbonate ramp system buah formation sultanate of oman effects of basement paleotopography the buah formation is a carbonate unit of late neoproterozoic age exposed in the jabal akhdar of northern oman and the huqf region of central oman the buah formation is interpreted as a distally steepened storm dominated ramp containing inner ramp tidally influenced oolitic shoal and back shoal lagoon fades and storm dominated mid ramp facies a slope break separates mid ramp facies from outer ramp facies characterized by accumulation of redeposited carbonates on gently inclined slopes 1 2 degrees combined facies stacking patterns and outcrop correlation via 1 3 c profiles suggest that buah carbonates formed as a highstand systems tract characterized by a general upward shallowing of facies and strong lateral progradation on a regional scale buah facies distributions across oman were controlled by the presence of basement highs defining areas of reduced subsidence which promoted lateral progradation of the buah carbonate ramp for tens of kilometers while the faster subsiding areas became sites of deep water deposition

seismology energy radiation from the sumatra earthquake we determined the duration of high frequency energy radiation from indonesia s great sumatra andaman earthquake 26 december 2004 to be about 500 seconds this duration can be translated into a rupture length of about 1 200 km which is more than twice as long as that inferred from body wave analyses performed soon after the event our analysis was able rapidly to define the extent of rupture thereby aiding the assessment of seismic hazard in the immediate future

slip distribution of the 1952 tokachi oki earthquake m 8 1 along the kuril trench deduced from tsunami waveform inversion 1 we inverted 13 tsunami waveforms recorded in japan to estimate the slip distribution of the 1952 tokachi oki earthquake m 8 1 which occurred southeast off hokkaido along the southern kuril subduction zone the previously estimated source area determined from tsunami travel times hatori 1973 did not coincide with the observed aftershock distribution our results show that a large amount of slip occurred in the aftershock area east of hatori s tsunami source area suggesting that a portion of the interplate thrust near the trench was ruptured by the main shock we also found more than 5 m of slip along the deeper part of the seismogenic interface just below the central part of hatori s tsunami source area this region which also has the largest stress drop during the main shock had few aftershocks large tsunami heights on the eastern hokkaido coast are better explained by the heterogeneous slip model than previous uniform slip fault models the total seismic moment is estimated to be 1 87 1021 n m giving a moment magnitude of mw 8 1 the revised tsunami source area is estimated to be 25 2 103 km2 3 times larger than the previous tsunami source area out of four large earthquakes with m 7 that subsequently occurred in and around the rupture area of the 1952 event three were at the edges of regions with relatively small amount of slip we also found that a subducted seamount near the edge of the rupture area possibly impeded slip along the plate interface

depositional facies and platform architecture of microbialite dominated carbonate reservoirs ediacaran cambrian ara group sultanate of oman intrasalt carbonates of the ediacaran cambrian ara group constitute a significant reservoir element of the intrasalt stringer play in oman in which dolomitic carbonates are encased in salt at depths of 3 to 7 km 1 9 to 4 3 mi these reservoir carbonates have significant microbial influences although ara group reservoirs are mostly latest precambrian the models developed here may be applicable to younger microbially dominated carbonate reservoirs in basins of higher salinity when higher organisms are excluded in lacustrine settings where calcified invertebrates are not a significant source of carbonate or after periods of mass extinction before faunal recovery a broad range of carbonate facies provides the context in which to understand the origin of the microbialite dominated reservoirs developed across both ramp and rimmed shelf profiles major facies associations include carbonate evaporite transition zone deep ramp and slope subtidal microbialites clastic textured carbonates and restricted peritidal carbonates microbialites are subdivisible into a number of facies that all have significance in terms of understanding environmental history as well as reservoir properties and that help in predicting the location of reservoir fairways microbially influenced facies include shallow subtidal thrombolites with massive clotted textures and very high initial porosities 50 shallow subtidal pustular laminites with cm scale variability of lamina morphology deeper subtidal crinkly laminites that show mm scale variability of lamina morphology and intertidal tufted laminates that show mm to cm scale tufted textures other reservoir facies are more conventional grainy carbonates including ripple cross stratified grainstone packstone hummocky cross stratified grainstone packstone flat pebble conglomerate ooid and intraclast grainstone packstone and cloudina grainstone packstone these facies are almost invariably dolomitized and all have moderate to excellent reservoir quality these facies comprise carbonate platforms broken up during salt tectonics that range up to 160 m 525 ft in thickness and extended laterally prior to halokinesis for tens to over 50 km 31 mi the distribution of reservoir facies follows sequence stratigraphic predictions with microbialites occurring in every accommodation profile late highstand and early transgressive systems tracts favor greater lateral extent of thrombolite build ups whereas later transgressive to early highstand system tracts favor greater lateral discontinuity and compartmentalization of buildup reservoir facies pustular laminites occur in close association with thrombolite buildups but form laterally extensive sheets in late transgressive to late highstand periods crinkly laminites form during late transgressive to early highstand systems tracts and may represent maximum flooding intervals when the flux of carbonate sediment was greatly reduced allowing pelagically derived organics to accumulate

high temperature environments of human evolution in east africa based on bond ordering in paleosol carbonates many important hominid bearing fossil localities in east africa are in regions that are extremely hot and dry although humans are well adapted to such conditions it has been inferred that east african environments were cooler or more wooded during the pliocene and pleistocene when this region was a central stage of human evolution here we show that the turkana basin kenya today one of the hottest places on earth has been continually hot during the past 4 million years the distribution of 13c 18o bonds in paleosol carbonates indicates that soil temperatures during periods of carbonate formation were typically above 30 c and often in excess of 35 c similar soil temperatures are observed today in the turkana basin and reflect high air temperatures combined with solar heating of the soil surface these results are specific to periods of soil carbonate formation and we suggest that such periods composed a large fraction of integrated time in the turkana basin if correct this interpretation has implications for human thermophysiology and implies a long standing human association with marginal environments

polyphase thermal evolution in the infra cambrian ara group south oman salt basin as deduced by maturity of solid reservoir bitumen petrographic and organic geochemical analyses on solid reservoir bitumen from the late precambrian to early cambrian ara group indicate polyphase thermal evolution in the south oman salt basin sosb the ara group constitutes a complex petroleum system in the deep subsurface 3 5 km of interior oman salt diapirs encase isolated partly highly overpressured carbonate bodies intra salt stringers which represent a predominantly self charging hydrocarbon system a large number of stringer cores show that reservoir quality is decreased by the presence of solid reservoir bitumen by using different microscopy techniques this solid reservoir bitumen has been identified within pores pore throats and microfractures of the carbonates solid bitumen reflectance measurements brr were converted to vitrinite reflectance vrr using a new improved calibration vitrinite reflectance geothermometry shows that maximum paleo temperatures have a highly heterogeneous distribution paleo temperatures of 380 c were obtained from coke like solid reservoir bitumen which most likely formed from thermal cracking of oil in our model this process is related to hydrothermal fluids deriving from deeper pre salt strata of the sosb which entered the intra salt carbonate stringers during times of basement tectonic activity via hydrofractures this caused the formation of high maturities pyrobitumens in close vicinity to the fractures and precipitation of migrabitumens with increasing distance to the ht source which is supported by the geochemical composition of the solid reservoir bitumens the influx of these fluids into the carbonate stringers is considered to represent a major contribution to their strong overpressures 2007 elsevier ltd all rights reserved

compilation and time series analysis of a marine carbonate δ18o δ13c 87sr 86sr and δ34s database through earth history abstract the sr s o and c isotope database of marine carbonates contains over 55 000 published isotope values of low mg calcite from diagenetically little altered phanerozoic fossil shells as well as samples of whole rocks and calcite cements of ordovician to archean age carbon and oxygen isotope data for the shell material are divided into habitat subsets high mid low latitude and deep sea and whole rock data are separated by mineralogy into calcite dolomite subsets trend correlation wavelet and spectral analyses on gaussian filtered isotope records were applied to detect and quantify similarities and patterns in temporal records with the following results 1 oxygen isotope trends from the high latitude and deep sea habitats are almost indistinguishable through the last 115 ma consistent with the existence of the oceanic conveyor belt throughout this interval 2 all oxygen isotope habitat records show a strong coherent 30 45 ma 38 ma cyclicity throughout the cretaceous and the cenozoic 3 up to 70 of the multi million year variability in the 18o record of the last 115 ma can be simulated by the following equation 18 o 0 64 sin 2 t 120 ma 0 9 x sin 2 t 38 3 ma 1 1 with x ranging from 0 4 0 6 for the low high latitude and deep sea habitats to 0 8 for the mid latitude realm 1 a 120 20 ma cycle occurs in the paleozoic and neoproterozoic 18o record consistent with paleoclimate variability as interpreted from sedimentological and faunal records 2 the offset of 13c values between deep water and high latitude vs surficial habitats at lower latitudes is consistent with the operation of a biological pump in the oceans since at least the cretaceous 3 sr and s isotope records exhibit a 60 70 ma cyclicity throughout the phanerozoic

seismology speed and size of the sumatra earthquake we now have a clearer picture of the seismic features of last year s gigantic event our seismological results reveal that indonesia s devastating sumatra andaman earthquake on 26 december 2004 was 2 5 times larger than initial reports suggested second only to the 1960 chilean earthquake in recorded magnitude they indicate that it slowly released its energy by slip along a 1 200 km fault generating a long rupture that contributed to the subsequent tsunami now that the entire rupture zone has slipped the strain accumulated from the subduction of the indian plate beneath the burma microplate has been released and there is no immediate danger of a similar tsunami being generated on this part of the plate boundary although large earthquakes on segments to the south still present a threat

geochemical evidence for an early cambrian origin of the q oils and some condensates from north oman abstract the q family of oils from oman was previously recognized as highly unusual and distinct from the more prevalent huqf oil family by having an extraordinarily high c27 c29 sterane ratio and 13c values near 30 a re evaluation of the hydrocarbon constituents of the q oils using gc ms ms analyses resulted in identification of other useful geochemical discriminators that include gammacerane hopane ratios between 0 5 and 0 9 c24t c23t 0 7 combined with c22t c21t cheilanthane ratios although we were unable to identify a source facies within the sediments of the south oman salt basin that convincingly correlated with the hydrocarbons of the q oils the geochemistry of q oils provided valuable clues about their origin sterane and terpane patterns indicated that the q source rock is most likely a marine shale deposited under intermittently anoxic and hypersaline conditions the absence of a carbon isotopic ordering anomaly for normal alkanes and isoprenoids points to a cambrian age for the q oils moreover trends in the patterns of norsteranes in south oman carbonate stringer oils suggest the q oil source originates from one of the upper units of the ara carbonate and evaporite sequence more specifically our results point to a siliciclastic source rock lying stratigraphically above the a6 carbonates from the dhahaban formation the high relative abundances of 24 isopropylcholestanes in q oils likely originate from demosponges and we hypothesize that the 17 methylpentatriacontane which is so abundant in q oils is a biomarker for early arthropods that inhabited the salt basins of oman at the very beginning of the cambrian period

latitudinal temperature gradients and high latitude temperatures during the latest cretaceous congruence of geologic data and climate models a major challenge in paleoclimatology is disagreement between data and models for periods of warm climate data generally indicate equable conditions and reduced latitudinal temperature gradients while models generally produce colder conditions and steeper latitudinal gradients except when using very high co2 here we show congruence between temperature indicators and climate model output for the cool greenhouse interval of the latest cretaceous maastrichtian using a global database of terrestrial and marine indicators and fully coupled simulations with the community climate system model version 3 in these simulations we explore potential roles of greenhouse gases and properties of pre anthropogenic liquid clouds in creating warm conditions our model simulations successfully reproduce warm polar temperatures and the latitudinal temperature gradient without overheating the tropics best fits for mean annual temperature are simulations that use 6 preindustrial levels of atmospheric co2 or 2 preindustrial levels of atmospheric co2 and liquid cloud properties that may reflect pre anthropogenic levels of cloud condensation nuclei the siberian interior is problematic but this may relate to reconstructed elevation and the presence of lakes data and models together indicate tropical sea surface temperatures 5 c above modern an equator to pole temperature difference of 25 30 c and a mid latitudinal temperature gradient of 0 4 c per 1 latitude similar to the eocene modified liquid cloud properties allow successful simulation of maastrichtian climate at the relatively low levels of atmospheric co2 indicated by proxies and carbon cycle modeling this supports the suggestion that altered properties of liquid clouds may be an important mechanism of warming during past greenhouse intervals

clumped isotope fractionation during phosphoric acid digestion of carbonates at 70 c the application of clumped isotopes 47 in carbonate minerals as a sensitive temperature proxy in paleo environments depends on a well constrained clumped isotope fractionation for the necessary step of phosphoric acid digestion of the carbonate mineral to produce co2 published estimates for clumped isotope fractionations vary and the effect of different carbonate mineralogies is still under debate differences in the sample preparation design and sample digestion temperatures are potential sources for varying acid fractionations and could be a source for discrepant 47 temperature calibrations observed in different laboratories to evaluate the clumped isotope acid fractionation at 70 c and simultaneously account for a potential cation effect we analyzed a set of eight carbonate minerals calcite aragonite dolomite and magnesite that were driven to a stochastic isotope distribution by heating them to temperatures of 1000 c our study reveals significant cation and mineral specific differences for the 47 acid fractionation of carbonate minerals digested at 70 c or 100 c the 47 acid fractionation at 70 c for calcite is 0 197 0 002 for aragonite 0 172 0 003 whereas dolomite has a significantly larger acid fractionation of 0 226 0 002 for magnesite digested at 100 c we observed a 47 acid fractionation of 0 218 0 020 projected to an acid digestion at 25 c our acid fractionation for calcite of 0 260 is statistically indistinguishable from existing studies we further show that the 47 of the calcite standards eth 1 and eth 2 of 0 265 and 0 267 respectively are in the range of the determined acid fractionation projected to 25 c suggesting that they have an identical and near stochastic isotope distribution the observed differences in the 47 acid fractionation between calcite and aragonite 47 0 025 and between calcite and dolomite 47 0 029 does not correlate with the phosphoric acid fractionation of oxygen isotopes but rather depends on the radius of the cation as well as on the mineral structure our results reveal that the acid fractionation of dolomite at 70 c is significantly distinct from the one of calcite but at 90 c the two are within error of each other due to the different acid fractionation temperature dependence of calcite and dolomite thus it is necessary to use a mineral specific 47 acid fractionation factor for dolomite to avoid differences in the final 47 signal from dolomites digested at 90 c and dolomites digested at lower temperatures similar effects may apply also to other carbonates such as magnesite and siderite however their mineral specific 47 acid fractionation at digestion temperatures around 90 c might be also similar to the one of calcite so that potential differences could be within the range of the analytical error

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

carbon oxygen and strontium isotopes in paleozoic carbonate components an evaluation of original seawater chemistry proxies abstract brachiopods trilobites cements and whole rock matrix material were evaluated for their reliability as proxies of original seawater carbon oxygen and strontium isotope chemistry in this process coeval material was evaluated from individual horizons of formations spanning the permian to cambrian unaltered shells of low mg calcite articulated brachiopods retain original seawater oxygen carbon and strontium isotope compositions as old as late ordovician assessments of older specimens are hampered by a lack of suitable material coeval brachiopod whole rock sets a definitive assessment of cement marine chemistry is difficult due to the paucity of material but despite this caveat cements hold some promise for retaining original carbon and possibly strontium isotope seawater values in contrast the potential of whole rock material as a proxy of original seawater chemistry is quite complex in some but not all instances the carbon isotopic composition of whole rock after detailed scrutiny and evaluation appears to represent an original seawater chemistry signal in a few instances their oxygen isotope compositions reflect original seawater values unlike the stable isotope compositions the strontium isotopes of all studied whole rock material permian to upper cambrian appear not to reflect original seawater chemistry values thus the potential for retaining original seawater isotope chemistry and serving as specific proxies in order of decreasing reliability are 1 unaltered low mg calcite brachiopods c o and sr isotopes 2 pristine marine cements c and sr isotopes and 3 whole rock material c isotopes carbon oxygen and strontium isotope compositions of ordovician trilobites mirror those of coeval unaltered brachiopods cambrian trilobites hold significant promise as an important proxy of original seawater isotope chemistry but further studies are needed to ascertain their full potential the survey of isotopes in some ordovician and cambrian intermediate low mg calcite trilobites demonstrates their potential as an important proxy of original seawater chemistry

microbial communities and their primary to early diagenetic mineral phases the record from neoproterozoic microbialites of qarn alam oman

the clumped isotope geothermometer in soil and paleosol carbonate we studied both modern soils and buried paleosols in order to understand the relationship of temperature t c 47 estimated from clumped isotope compositions 47 of soil carbonates to actual surface and burial temperatures carbonates from modern soils with differing rainfall seasonality were sampled from arizona nevada tibet pakistan and india t c 47 obtained from these soils shows that soil carbonate forms in the warmest months of the year in the late morning to afternoon and probably in response to intense soil dewatering t c 47 obtained from modern soil carbonate ranges from 10 8 to 39 5 c on average t c 47 exceeds mean annual temperature by 10 15 c due to summertime bias in soil carbonate formation and to summertime ground heating by incident solar radiation secondary controls on t c 47 are soil depth and shading site mean annual air temperature maat across a broad range 0 30 c of site temperatures is highly correlated with t c 47 from soils following the equation maat c 1 20 t c 47 0 21 72 r 2 0 92 where t c 47 0 is the effective air temperature at the site estimated from t c 47 the effective air temperature represents the air temperature required to account for the t c 47 at each site after consideration of variations in t c 47 with soil depth and ground heating the highly correlated relationship in this equation should now permit mean annual temperature in the past to be reconstructed from t c 47 in paleosol carbonate assuming one is studying paleosols that formed in environments generally similar in seasonality and ground cover to our calibration sites t c 47 0 decreases systematically with elevation gain in the himalaya following the equation elevation m 229 t c 47 0 9300 r 2 0 95 assuming that temperature varied similarly with elevation in the past this equation can be used to reconstruct paleoelevation from clumped isotope analysis of ancient soil carbonates we also measured t c 47 from long sequences of deeply buried 5 km paleosol carbonate in the himalayan foreland in order to evaluate potential diagenetic resetting of clumped isotope composition we found that paleosol carbonate faithfully records plausible soil t c 47 down to 2 5 4 km burial depth or 90 125 c deeper than this and above this temperature t c 47 in paleosol carbonate is reset to temperatures 40 c we observe 40 c as the upper limit for t c 47 in modern soils from soil depths 25 cm and therefore that t c 47 40 c obtained from ancient soil carbonate indicates substantially warmer climate regimes compared to the present or non primary temperatures produced by resetting during diagenesis if representative this limits the use of t c 47 to reconstruct ancient surface temperature to modestly buried 3 4 km paleosol carbonates despite diagenetic resetting of 47 values 18 o and 13 c values of the same deeply buried paleosol carbonate appear unaltered we conclude that solid state reordering or recrystallization of clumping of carbon and oxygen isotopes can occur in the absence of open system exchange of paleosol carbonate with significant quantities of water or other phases

determining the δ47 acid fractionation in dolomites abstract this paper reports the fractionation of 47 during the digestion of dolomite in phosphoric acid between 25 c and 90 c using five different samples including three of pliocene age from the bahamas one from the jurassic in the middle east and one obtained from the national institute of standards nist 88b the composition of the dolomites analyzed varied from ca0 56mg0 44co3 to ca0 50mg0 50co3 fractionation values were also compared between the common acid bath and sealed vessel techniques at various temperatures no statistically significant differences were observed either between these two methods or as a function of the dolomite s stoichiometry these data produce a difference in fractionation of 0 153 0 011 for dolomite samples digested at 90 c compared to those reacted at 25 c a value higher and statistically different to previously published values utilization of this value in a study of dolomites from a core drilled on the island of san salvador in the bahamas yielded temperatures and 18ofluid values which agree with previous interpretations on the formation of these dolomites application of this value to other published studies produces lower estimates of temperature and 18ofluid values for the dolomitization process that are more consistent with the geologic models suggested for these studies

numerical modeling of the great 2004 indian ocean tsunami focus on the mascarene islands on 26 december 2004 the m w 9 2 sumatra earthquake triggered the greatest tsunami ever observed in recent times the unprecedented quality and variety of observations on modern instruments provide opportunities to refine modeling techniques as well as our perception of tsunami hazard in oceanic regions where historical events are not as frequent as in the pacific ocean we present a numerical modeling of the 2004 tsunami on the mascarene islands with refined computations on la reunion island where postevent survey observations and one tide gauge record are available we use two different source models models a and b to account for the observations and we also test an additional source model model c to study the effect of a tsunami originating in the 1833 epicentral area southern sumatra a wave trapped on the edge of la reunion may explain the greatest water heights reached in the western coastline of the island the observed tide gauge data are reasonably well fit models a and b the run up data can also be explained with our models late disturbances observed in la pointe des galets may be explained by a late tsunami reflection from madagascar or by harbor resonances finally we also show that model c 1833 like strikes la reunion more heavily than models a and b

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

climate model and proxy data constraints on ocean warming across the paleocene eocene thermal maximum article constraining the greenhouse gas forcing climatic warming and estimates of climate sensitivity across ancient large transient warming events is a major challenge to the palaeoclimate research community here we provide a new compilation and synthesis of the available marine proxy temperature data across the largest of these hyperthermals the paleocene eocene thermal maximum petm this includes the application of consistent temperature calibrations to all data including the most recent set of calibrations for archaeal lipid derived palaeothermometry this compilation provides the basis for an informed discussion of the likely range of petm warming the biases present in the existing record and an initial assessment of the geographical pattern of petm ocean warming to aid interpretation of the geographic variability of the proxy derived estimates of petm warming we present a comparison of this data with the patterns of warming produced by high pco2 sim ulations of eocene climates using the hadley centre atmosphere ocean general circulation model aogcm hadcm3l on the basis of this comparison and taking into account the patterns of intermediate water warming we estimate that the global mean surface temperature anomaly for the petm is within the range of 4 to 5 c

carbonate deposition and hydrocarbon reservoir development at the precambrian cambrian boundary the ara group in south oman abstract the ediacaran early cambrian ara group in the south oman salt basin consists of six evaporite carbonate cycles a0 a1 to a6 that record tectono eustatic sea level changes the a4 cycle developed at the precambrian cambrian boundary 542 ma it forms a single depositional sequence with evaporites deposited in a lowstand systems tract lst overlying carbonates represent an open marine shallowing upward ramp succession that developed in transgressive tst and highstand systems tracts hst the low energy carbonate ramp occupied a relatively protected site between a large shelf and an exposed paleogeographical high the tst facies include sulfates evaporite carbonate laminites and organic rich carbonate laminites that record initial flooding deepening of the basin and establishment of an outer ramp depositional environment carbonate sediment flux was low and the environment was partly subject to cyclically elevated salinity subsequent hst facies comprise mostly fine grained clastic carbonates and stromatolites that formed in middle and inner ramp settings these facies show evidence of shoaling and establishment of a carbonate factory that probably operated over most of the middle and inner ramp sediment was redistributed in suspension by muddy turbidity currents muddy debris flows storm and shallow water currents during the late hst carbonate facies were affected by elevated salinity and recorded the gradual transition to the overlying lst evaporite unit a combination of strong tectonic subsidence and transient flooding caused significant shallow water evaporite deposition to occur not only down dip but also on top of the former carbonate platform where several hundreds of meters of evaporites accumulated the transgressive carbonate laminites are the main reservoir facies and thus represent a relatively unusual reservoir unit the presence of organic material and the relative scarcity of carbonate mud influenced diagenesis and reservoir properties distribution of organic material and carbonate mud can be linked to specific environmental conditions low physical and biogenic disturbance of sediment and stratified water mass and the sequence stratigraphic position low flux of fine grained carbonate during tst in contrast diagenetic evaporite formation has largely degraded reservoir quality in porous shallow water facies near the top of the a4c

calibrating the coevolution of ediacaran life and environment the rise of animals occurred during an interval of earth history that witnessed dynamic marine redox conditions potentially rapid plate motions and uniquely large perturbations to global biogeochemical cycles the largest of these perturbations the shuram carbon isotope excursion has been invoked as a driving mechanism for ediacaran environmental change possibly linked with evolutionary innovation or extinction however there are a number of controversies surrounding the shuram including its timing duration and role in the concomitant biological and biogeochemical upheavals here we present radioisotopic dates bracketing the shuram on two separate paleocontinents our results are consistent with a global and synchronous event between 574 0 4 7 and 567 3 3 0 ma these dates support the interpretation that the shuram is a primary and synchronous event postdating the gaskiers glaciation in addition our re os ages suggest that the appearance of ediacaran macrofossils in northwestern canada is identical within uncertainty to similar macrofossils from the conception group of newfoundland highlighting the coeval appearance of macroscopic metazoans across two paleocontinents our temporal framework for the terminal proterozoic is a critical step for testing hypotheses related to extreme carbon isotope excursions and their role in the evolution of complex life

on the use of satellite altimetry to infer the earthquake rupture characteristics application to the 2004 sumatra event summary standard data and methods such as the inversion of seismic and gps data have been used extensively to infer the details of the 2004 december 26 earthquake the unprecedented large size of this event gave the opportunity to modern altimeters to provide the first clear records of a tsunami in deep ocean therefore allowing us to study the rupture history from an independent perspective we invert the jason 1 and topex poseidon altimetry records considering the new constraints available on the geometry of the fault plane and taking them into account in a 3 d rupture model the data are corrected for the non negligible effect of satellite motion during measurements our results show that the rupture propagated over the 1500 km of subduction zone initially identified by the aftershock distribution with a magnitude of mw 9 1 our solution compares well with the latitudinal distribution of slip inferred from other data sets with a maximum of energy release north of sumatra and two other slip patches near the nicobar and andaman islands based on waveform comparison we assert that the shallow portion of the megathrust offshore banda aceh had slip amplitudes of more than 20 m also we find that significant amounts of slip about 10 m concentrated below the andaman islands and did not propagate on the shallow portion of the interface although synthetic tests tend to show less resolution in the northern part of the rupture this solution is compatible with the near field data gps coral heads and imagery and would allow one to explain the apparent paradox between the large local displacements and the moderate tsunami observed locally finally we demonstrate the rapidly dominating effect of propagation and slip distribution over the rupture velocity and how it precludes the direct estimate of this latter parameter

burial and thermal history of proterozoic source rocks in oman abstract a geological and thermal history of the proterozoic sedimentary basin in oman was reconstructed to determine the time of hydrocarbon generation from the proterozoic huqf group source rocks data from 97 exploration wells and supplementary seismic reflection profiles were used to establish the burial graphs for the source rocks at all 97 locations the overburden removed during formation of regional unconformities was estimated from regional geological data compaction trends and fission track analyses the thermal history was reconstructed on the basis of present day temperature data in the wells heat flow models and the palaeo surface temperature history the calculated present day surface heat flow map shows very low values 35 40 mw m 2 over the basin axis while on the edges the values are in the range 55 65 mw m 2 the results of the maturity calculations show that in northwest oman oil generation occurred mainly during the mesozoic and that probably a large proportion of the traps in which reserves have been discovered was formed just before the last oil generation phase however in the central and southeastern part of the country hydrocarbon generation stopped about 400 ma ago this is due to the maximum burial temperature being reached at around that time considering the fact that almost all traps in which reserves have been located are significantly younger than the time of oil generation one has to invoke processes of remigration to explain the oil occurrences the geological data from oman show that the eastern margin of the country presently facing the arabian sea has been a high for most of its phanerozoic history the data on quantities of eroded and deposited sediments lend support for the theory that the margin was formed by a transform fault

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

use of hydroacoustic and seismic arrays to observe rupture propagation and source extent of the mw 9 0 sumatra earthquake 1 the rupture of the sumatra earthquake mw 9 0 is complex and quite difficult to estimate using classical source inversion methods due to the exceptional rupture duration to fix the problem of geographical extent and rupture duration we use array processing of hydroacoustic and regional seismic data the cmar seismic array and the diego garcia hydroacoustic station h08s installed by the international monitoring system are respectively 15 2 and 25 7 far from the hypocenter the estimation of azimuth and velocity variations of homogeneous wave fronts across the arrays gives us the opportunity to understand how the rupture propagates the smooth and regular variations of azimuth fit a rupture extension of 1235 km and a duration of 515 s this study proves that the combination of array analysis using the different technologies installed for the ctbt is an interesting way of research for a rapid estimation of tsunamigenic earthquakes

temperatures and oxygen isotopic composition of phanerozoic oceans abstract the temperature of ancient oceans is an important constraint for understanding the climate history of our planet the classical oxygen isotope paleothermometry on fossil shells while very proficient when applied to the younger cenozoic portion of the geologic record is believed to yield only unreliable results for the phanerozoic deep time either because the empirically well documented secular trend to more negative 18 o values with increasing age was generated by post depositional recrystallization processes or if primary implies ecologically unpalatable hot early oceans here we present a compilation of 18 o measurements for 58 532 low mg calcite marine shells that cover almost the entire phanerozoic eon argue that the secular decline of about 6 is primary propose that it reflects the changing oxygen isotopic composition of sea water and define a new baseline trend for 18 o of paleo sea water the latter providing a new template for calculation of ambient habitat temperatures of fossil specimens the resulting pattern for fossil taxa foraminifera brachiopods belemnites and bivalves mimics their modern counterparts in temperature ranges and modes this conceptual framework enables application of actualistic concepts to ambient habitat temperatures of fossils and provides us with a long overdue tool for interpretation of deep time geologic history

heat transport deep waters and thermal gradients coupled simulation of an eocene greenhouse climate for the first time a coupled general circulation model with interactive and dynamical atmospheric oceanic and sea ice components is used to simulate an eocene 50 ma greenhouse climate we introduce efficient ocean spin up methods for coupled paleoclimate modeling sea surface temperatures ssts and salinities evolve unconstrained producing the first proxy data independent estimates for these eocene climate parameters tropical and extratropical model predicted ssts are warmer than modern values by 3 and 5 c respectively salinity driven deep water formation occurs in the north atlantic and tethys the zonal average overturning circulation is weaker than modern eocene ocean heat transport is 0 6 pw less than modern in the northern hemisphere and 0 4 pw greater in the southern hemisphere the model predicted near modern vertical and meridional eocene temperature gradients imply that the dominant theory for maintaining low gradients increased ocean heat transport is incorrect or incomplete and other mechanisms should be explored

clumped isotope geochemistry the study of naturally occurring multiply substituted isotopologues clumped isotope geochemistry is concerned with the state of ordering of rare isotopes in natural materials that is it examines the extent to which rare isotopes d 13 c 15 n 18 o etc bond with or near each other rather than with the sea of light isotopes in which they swim abundances of isotopic clumps in natural materials are influenced by a wide variety of factors in most cases their concentrations approach within ca 1 relative the amount expected for a random distribution of isotopes deviations from this stochastic distribution result from enhanced thermodynamic stability of heavy isotope clumps slower kinetics of reactions requiring the breakage of bonds between heavy isotopes the mass dependence of diffusive and thermo gravitational fractionations mixing between components that differ from one another in bulk isotopic composition biochemical and photochemical fractionations that may reflect combinations of these simpler physical mechanisms and in some cases other processes we do not yet understand although clumped isotope geochemistry is a young field several seemingly promising applications have already emerged most importantly it appears that proportions of 13 c 18 o bonds in carbonate minerals are sensitive to their growth temperatures independent of bulk isotopic composition thus clumped isotope analysis of ancient carbonates can be used as a quantitative paleothermometer that requires no assumptions about the 18 o of waters from which carbonates grew this approach has been used to reconstruct marine temperatures across the phanerozoic reaching back to the silurian terrestrial ground temperatures across the cenozoic thermal histories of aqueously altered meteorites among other applications clumped isotope geochemistry is also placing new constraints on the atmospheric budget and stratospheric photochemistry of co 2 and should be capable of placing analogous new constraints on the budgets of other atmospheric gases finally this field could be extended to encompass sulfates volatile hydrocarbons organic moieties and other materials

temperature evolution and the oxygen isotope composition of phanerozoic oceans from carbonate clumped isotope thermometry abstract surface temperature is among the most important parameters describing planetary climate and habitability and yet there remains considerable debate about the temperature evolution of the earth s oceans during the phanerozoic eon 541 million years ago to present the time during which complex metazoan life radiated on earth here we critically assess the emerging record of phanerozoic ocean temperatures based on carbonate clumped isotope thermometry of fossil brachiopod and mollusk shells and we present new data that fill important gaps in the late paleozoic record we evaluate and reject the hypothesis that solid state reordering of 13c 18o bonds has destroyed the primary clumped isotope temperature signal of most fossils during sedimentary burial at elevated temperatures the resulting phanerozoic record which shows a general coupling between tropical seawater temperatures and atmospheric carbon dioxide co2 levels since the paleozoic indicates that tropical temperatures during the icehouse climate of the carboniferous period were broadly similar to present 25 30 c and suggests that benthic metazoans were able to thrive at temperatures of 35 40 c during intervals of the early and possibly the latest paleozoic when co2 levels were likely 5 10 higher than present day values equally important there is no resolvable trend in seawater oxygen isotope ratios 18 o over the past 500 million years indicating that the average temperature of oxygen exchange between seawater and the oceanic crust has been high 270 c since at least the early paleozoic which points to mid ocean ridges as the dominant locus of water rock interaction over the past half billion years

origin of petroleum in the neoproterozoic cambrian south oman salt basin abstract the south oman salt basin sosb is host to the world s oldest known commercial deposits most of the south oman oils have been proven to be associated with the source rocks of the neoproterozoic to cambrian huqf supergroup but the assignment of oils to specific huqf intervals or facies has been hampered by the geochemical similarity of the organic matter across the entire huqf sequence possibly as a consequence of limited change in the local palaeoenvironment and biota over the time of its deposition this study was conducted to establish improved correlations between organic rich rock units and reservoir fluids in the sosb through detailed molecular and isotopic analysis of the huqf supergroup with special emphasis directed towards understanding the ara carbonate stringer play unusual biomarkers tentatively identified as a norsteranes show distinctive patterns among carbonate stringer oils and rocks different from those observed in nafun sediments and ara rocks from the athel basin these putative a norsteranes form the basis for new oil source correlations in the sosb and provide for the first time geochemical evidence of a self charging mechanism for the carbonate stringer play the paucity of markers specific to the nafun group shuram buah and masirah bay formations confounds attempts to quantify their respective contributions to huqf oil accumulations nafun inputs can only be determined on the basis of subtle differences between nafun and ara biomarker ratios the most useful geochemical characteristics delineating nafun group organic matter from ara group intra salt source rocks included low relative abundance of mid chain monomethyl alkanes x compounds low relative abundance of gammacerane 28 30 dinorhopane 25 28 30 trinorhopane and 2 methylhopanes low c 22 t c 21 t and high c 23 t c 24 t cheilanthanes ratio values based on these parameters molecular evidence for major contributions of liquid hydrocarbons from nafun group sediments shuram buah and masirah bay formations is lacking our results suggest that the majority of sosb hydrocarbon accumulations originate from within the ara group either from the carbonate stringers or from the package of sediments that comprises the thuleilat athel silicilyte and u shale formations subtle aspects of the composition of some carbonate stringer and post salt huqf oils could suggest some degree of sourcing from the nafun rocks but stronger evidence is needed to confirm this

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

a 600 million year carbonate clumped isotope record from the sultanate of oman carbonate clumped isotope thermometry is a promising technique that has the potential to help decode the significance of the variability of both physical and geochemical compositions of ancient carbonate rocks this study utilizes a 600 million year record of marine carbonate rocks from the subsurface and surface of the sultanate of oman to explore how burial and exhumation affected the carbonate clumped isotope thermometer samples span 6 km of burial depth and include calcite and dolomite mineralogies and a range of carbonate rock textures we find evidence for two broad patterns in the physical and geochemical behavior of carbonate rocks during burial the first group of carbonates yield water 18 o vsmow compositions slightly enriched or equal to an expected ice free seawater composition of 1 2 and display good to fair textural preservation suggesting that cementation and lithification occurred within tens of meters of the sediment water interface temperatures from the second group sit on the present day geotherm yield highly enriched water 18 o vsmow compositions and display fair to poor textural preservation we find no evidence for solid state reordering in paired analyses of calcites and dolomites our results contribute to a growing body of work that indicates that the seawater 18 o vsmow composition has not changed significantly over 600 myr and was not 6 in the ediacaran

temperature dependence of oxygen and clumped isotope fractionation in carbonates a study of travertines and tufas in the 6 95 c temperature range conventional carbonate water oxygen isotope thermometry and the more recently developed clumped isotope thermometer have been widely used for the reconstruction of paleotemperatures from a variety of carbonate materials in spite of a large number of studies however there are still large uncertainties in both 18o and 47 based temperature calibrations for this reason there is a need to better understand the controls on isotope fractionation especially on natural carbonates in this study we analyzed oxygen carbon and clumped isotopes of a unique set of modern calcitic and aragonitic travertines tufa and cave deposits from natural springs and wells together these samples cover a temperature range from 6 to 95 c travertine samples were collected close to the vents of the springs and from pools and tufa samples were collected from karstic creeks and a cave the majority of our vent and pool travertines and tufa samples show a carbonate water oxygen isotope fractionation comparable to the one of tremaine et al 2011 with some samples showing higher fractionations no significant difference between the calcite water and aragonite water oxygen isotope fractionation could be observed the 47 data from the travertines show a strong relationship with temperature and define the regression 47 0 044 0 005 106 t2 0 205 0 047 the ph of the parent solution mineralogy and precipitation rate do not appear to significantly affect the 47 signature of carbonates compared to the temperature effect and the analytical error the tufa samples and three biogenic calcites show an excellent fit with the travertine calibration indicating that this regression can be used for other carbonates as well this work extends the calibration range of the clumped isotope thermometer to travertine and tufa deposits in the temperature range from 6 c to 95 c

the enigma of neoproterozoic giant ooids fingerprints of extreme climate geologists have documented at least fourteen occurrences of giant ooids a geologically rare type of carbonate allochem in neoproterozoic successions at low paleo latitudes recent experiments a

source depth dependence of micro tsunamis recorded with ocean bottom pressure gauges the january 28 2000 mw 6 8 earthquake off nemuro peninsula japan abstract micro tsunami waves with a maximum amplitude of 4 6 mm were detected with the ocean bottom pressure gauges on a cabled deep seafloor observatory south of hokkaido japan following the january 28 2000 earthquake m w 6 8 in the southern kuril subduction zone we model the observed micro tsunami and estimate the focal depth and other source parameters such as fault length and amount of slip using grid searching with the least squares method the source depth and stress drop for the january 2000 earthquake are estimated to be 50 km and 7 mpa respectively with possible ranges of 45 55 km and 4 13 mpa focal depth of typical inter plate earthquakes in this region ranges from 10 to 20 km and stress drop of inter plate earthquakes generally is around 3 mpa the source depth and stress drop estimates suggest that the earthquake was an intra slab event in the subducting pacific plate rather than an inter plate event in addition for a prescribed fault width of 30 km the fault length is estimated to be 15 km with possible ranges of 10 20 km which is the same as the previously determined aftershock distribution the corresponding estimate for seismic moment is 2 7 10 19 nm with possible ranges of 2 3 10 19 3 2 10 19 nm standard tide gauges along the nearby coast did not record any tsunami signal high precision ocean bottom pressure measurements offshore thus make it possible to determine fault parameters of moderate sized earthquakes in subduction zones using open ocean tsunami waveforms

late precambrian cambrian sediments of huqf group sultanate of oman the huqf group is the oldest known sedimentary sequence overlying crystalline basement in the sultanate of oman it crops out on a broad regional high the huqf axis which forms a dominating structural element on the southeastern edge of the arabian peninsula subsurface and outcrop evidence within and outside of oman suggests that the sediments of the huqf group lie within the age span of late precambrian to early middle cambrian the huqf group is subdivided into five formations corresponding to an alternation of clastics abu mahara and shuram formations and carbonates khufai and buah formations deposited in essentially shallow marine to supratidal or fluviatile conditions and terminated by an evaporitic sequence ara formation evaporites are absent on the huqf axis but they are thickly developed to the west over a large part of southern and central oman where they acted as the major structure former of most of oman s oil fields and even locally pierced up to the surface in the subsurface the huqf group has been reached by the drill mainly in southern oman where its lithostratigraphy resembles that defined in the type area in central oman the oldest sediments exposed in the core of the oman mountains may be correlative with the huqf group regional correlations suggest that the predominantly carbonate evaporitic facies of the huqf group was widely distributed in late precambrian early cambrian time the huqf basin is tentatively considered part of a belt of evaporitic basins and intervening carbonate platforms which stretched across the pangea landmass from the indian subcontinent salt range of pakistan through south yemen oman and saudi arabia into the gulf states and iran hormuz series and carbonate platform north of the zagros

chemostratigraphic and sedimentological framework of the largest negative carbon isotopic excursion in earth history the neoproterozoic shuram formation nafun group oman abstract oman records in its neoproterozoic nafun group huqf supergroup an essentially complete carbonate rich ediacaran succession the nafun group overlies the presumed marinoan rift related fiq member ca 635 ma and ends just below the precambrian cambrian boundary 542 ma tectonic subsidence caused by thermal contraction following fiq aged rifting allowed the preservation of about 1 km of postrift stratigraphy with no major stratigraphic breaks the nafun group above the marinoan cap carbonate hadash formation represents two siliciclastic to carbonate grand cycles both initiated by significant transgressions these cycles comprise the masirah bay khufai formations and the shuram buah formations the khufai shuram boundary is associated with the start of a major carbon isotope perturbation the uppermost ramp carbonates of the khufai formation record a smooth decrease in 13c from about 4 to values around 0 followed by two descending steps across which values plunge to a nadir of 12 in the overlying red siltstones and shales interbedded with thin limestones of the shuram formation this fall in isotopic values is temporally rapid and coincident in both shallow and deep water sections in the time span of a single parasequence the 13c nadir is then followed by 50 million years of monotonic recovery the shuram shift represents the largest 13c inorganic carbon negative excursion in earth history although the snowball earth theory links periods of depleted carbon isotopic ratios with periods of global glaciation the non glaciated context of the shuram formation suggests that the causal relationship between global glaciation and negative carbon isotopic excursions is non unique although the precise mechanism driving this major perturbation of the carbon cycle remains enigmatic the long term remineralization of an isotopically depleted organic carbon reservoir in ocean water is a promising candidate

a paired apatite and calcite clumped isotope thermometry approach to estimating cambro ordovician seawater temperatures and isotopic composition the secular increase in 18 o values of both calcitic and phosphatic marine fossils through early phanerozoic time suggests either that 1 early paleozoic surface temperatures were high in excess of 40 c tropical mat 2 the 18 o value of seawater has increased by 7 8 vsmow through paleozoic time or 3 diagenesis has altered secular trends in early paleozoic samples carbonate clumped isotope analysis in combination with petrographic and elemental analysis can deconvolve fluid composition from temperature effects and therefore determine which of these hypotheses best explain the secular 18 o increase clumped isotope measurements of a suite of calcitic and phosphatic marine fossils from late cambrian to middle late ordovician aged strata the first paired fossil study of its kind document tropical sea surface temperatures near modern temperatures 26 38 c and seawater oxygen isotope ratios similar to today s ratios

stratigraphy and environmental conditions of the terminal neoproterozoic cambrian period in oman evidence from sulphur isotopes terminal neoproterozoic and cambrian evaporite rocks worldwide record a marked sulphur isotope excursion to very heavy 34 s isotopes that reflect a period of significant burial of reduced sulphur new 34 s data from anhydrite and pyrite of the ara group in oman extend this record to arabia depositional history of the ara group spans c 8 ma across the terminal neoproterozoic cambrian boundary therefore these rocks provide a detailed record of sulphur isotopic evolution in this important time interval ara group sulphur isotope values include a mean 34 s anhydrite of 39 4 2 6 1 range 32 4 46 4 n 61 and a mean 34 s pyrite of 1 4 7 3 1 range 10 8 to 11 4 n 12 the isotope signatures were not altered significantly during diagenesis and are representative of the isotopic composition of parent waters in the basin marine bromine concentrations in halite and marine fossils in associated carbonate rocks indicate that these waters had a marine origin bacterial sulphate reduction was the dominant process leading to the segregation between isotopically heavy sulphur incorporated in evaporite rocks and isotopically light sulphur buried in pyrite and organic matter strong sulphate reduction operated in a hypersaline and partly anoxic basin these environmental conditions were also conducive to the preservation of organic material and make the ara group a prolific hydrocarbon province significant variation of the observed values is attributed to the inherent variability of bacterial sulphate reduction including partially closed system behaviour disproportionation processes limited diagenesis and possibly secular variation of sulphur isotopes within the basin ara group 34 s anhydrite values overlap with data from other terminal neoproterozoic to cambrian basins but the mean 34 s anhydrite is highest in oman this observation cannot be attributed solely to the specific anoxic conditions and strong bacterial sulphate reduction in oman because such conditions were widespread in most evaporite basins of the terminal neoproterozoic cambrian periods instead slight age differences between these basins can introduce a bias in the sulphur isotope curve excellent preservation of ara group deposits and in particular the precise age constraints make the ara group representative for the seawater sulphur isotopic composition at the terminal neoproterozoic cambrian boundary as a result of the inherent variability of bacterial sulphate reduction 34 s values at the lower end of the spectrum should be most representative for the global signal based on results of this study the global signal is estimated to be approximately 35 40

cenozoic deep sea temperatures and global ice volumes from mg ca in benthic foraminiferal calcite a deep sea temperature record for the past 50 million years has been produced from the magnesium calcium ratio mg ca in benthic foraminiferal calcite the record is strikingly similar in form to the corresponding benthic oxygen isotope 18o record and defines an overall cooling of about 12 c in the deep oceans with four main cooling periods used in conjunction with the benthic 18o record the magnesium temperature record indicates that the first major accumulation of antarctic ice occurred rapidly in the earliest oligocene 34 million years ago and was not accompanied by a decrease in deep sea temperatures

slow slip below port blair andaman during the great sumatra andaman earthquake of 26 december 2004 1 although several studies suggest that a slow slip followed the seismic slip on the northern half of the 1300 km long plate interface that ruptured during the great sumatra andaman earthquake the onset and duration of the slow slip remain unresolved in this paper we analyze a tide gauge record at port blair situated about 1000 km north of the epicenter our preferred model which fits the observed data well consists of a mixed mode of slip half of the total slip occurring seismically in less than 5 min after the rupture arrival and the rest developing in the next 30 min a scenario of slow slip on the northern half of the rupture area that is consistent with seismic data and gps data consists of slip on the time scale of 1 hour over the rest

rock buffered recrystallization of marion plateau dolomites at low temperature evidenced by clumped isotope thermometry and x ray diffraction analysis abstract much debate exists on the extent to which early dolomites recrystallize and preserve the signature of their primary diagenetic setting here we combine clumped isotopes thermometry with x ray diffraction and thin section petrography to study dolomite recrystallization under shallow burial