maceral composition and origin of organic matter input in neoproterozoic lower cambrian organic rich shales of salt range formation upper indus basin pakistan abstract the appropriate thermal maturity oil window or lower of the neoproterozoic rocks is a prerequisite for preserving robust and primary biological assemblages the neoproterozoic lower cambrian organic rich shales present in the upper part of salt range formation pakistan with abundant organic matter om total organic carbon toc up to 46 at relatively low thermal maturity protobitumen reflectance bro 0 2 0 4 represents by far the lowest thermal maturity neoproterozoic lower cambrian rocks analyzed to date the detailed petrographic description of neoproterozoic lower cambrian organic matter in the current study was lacking from previous source rock studies of coeval strata from oman eastern siberia australia and elsewhere eight organic rich shales of the salt range formation from three different outcrops have been analyzed for maceral composition and source rock characterization using organic petrography scanning electron microscopy and standard source rock assessment techniques the organic petrography reveals the organic rich shales are predominantly composed of alginites lamalginite and telalginite bituminite protobitumen and mineral bituminous groundmass overall the maceral assemblages suggest the deposition of these shales took place under a salinity stratified water column in a shallow restricted basin where both oxygenic and anoxygenic modes of primary production were operative the top oxygenated part of the water column was populated with the phototropic mat forming cyanobacterium whereas the lower low dissolved oxygen zone was dominated by algal mats and sulphate reduction bacteria the rare and scattered thucholites present within the salt range formation shales were derived from the radiation induced polymerization of adjacent om by the radioactive grains the heat from the radioactive grains however found to have a negligible effect on the overall thermal maturity of these shales

real time earthquake forecasting in italy abstract we have applied an earthquake clustering epidemic model to real time data at the italian earthquake data center operated by the istituto nazionale di geofisica e vulcanologia ingv for short term forecasting of moderate and large earthquakes in italy in this epidemic type model every earthquake is regarded at the same time as being triggered by previous events and triggering following earthquakes the model uses earthquake data only with no explicit use of tectonic geologic or geodetic information the forecasts are displayed as time dependent maps showing both the expected rate density of m l 4 0 earthquakes and the probability of ground shaking exceeding modified mercalli intensity vi pga 0 01 g in an area of 100 100 km 2 around the zone of maximum expected rate density in the following 24 h for testing purposes the overall probability of occurrence of an m l 4 5 earthquake in the same area of 100 100 km 2 is also estimated the whole procedure is tested in real time for internal use only at the ingv earthquake data center forecast verification procedures have been carried out in forward retrospective way on the 2006 2007 ingv data set making use of statistical tools as the relative operating characteristics roc diagrams these procedures show that the clustering epidemic model performs up to several hundred times better than a simple random forecasting hypothesis the seismic hazard modeling approach so developed after a suitable period of testing and refinement is expected to provide a useful contribution to real time earthquake hazard assessment even with a possible practical application for decision making and public information

probabilistic forecasting of earthquakes we present long term and short term forecasts for magnitude 5 8 and larger earthquakes we discuss a method for optimizing both procedures and testing their forecasting effectiveness using the likelihood function our forecasts are expressed as the rate density that is the probability per unit area and time anywhere on the earth our forecasts are for scientific testing only they are not to be construed as earthquake predictions or warnings and they carry no official endorsement for our long term forecast we assume that the rate density is proportional to a smoothed version of past seismicity using the harvard cmt catalogue this is in some ways antithetical to the seismic gap model which assumes that recent earthquakes deter future ones the estimated rate density depends linearly on the magnitude of past earthquakes and approximately on a negative power of the epicentral distance out to a few hundred kilometres we assume no explicit time dependence although the estimated rate density will vary slightly from day to day as earthquakes enter the catalogue the forecast applies to the ensemble of earthquakes during the test period it is not meant to predict any single earthquake and no single earthquake or lack of one is adequate to evaluate such a hypothesis we assume that 1 per cent of all earthquakes are surprises assumed uniformly likely to occur in those areas with no earthquakes since 1977 we have made specific forecasts for the calendar year 1999 for the northwest pacific and southwest pacific regions and we plan to expand the forecast to the whole earth we test the forecast against the earthquake catalogue using a likelihood test and present the results our short term forecast updated daily makes explicit use of statistical models describing earthquake clustering like the long term forecast the short term version is expressed as a rate density in location magnitude and time however the short term forecasts will change significantly from day to day in response to recent earthquakes the forecast applies to main shocks aftershocks aftershocks of aftershocks and main shocks preceded by foreshocks however there is no need to label each event and the method is completely automatic according to the model nearly 10 per cent of moderately sized earthquakes will be followed by larger ones within a few weeks

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

perspectives on proterozoic surface ocean redox from iodine contents in ancient and recent carbonate abstract the proterozoic eon hosted the emergence and initial recorded diversification of eukaryotes oxygen levels in the shallow marine settings critical to these events were lower than today s although how much lower is debated here we use concentrations of iodate the oxidized iodine species in shallow marine limestones and dolostones to generate the first comprehensive record of proterozoic near surface marine redox conditions the iodine proxy is sensitive to both local oxygen availability and the relative proximity to anoxic waters to assess the validity of our approach neogene quaternary carbonates are used to demonstrate that diagenesis most often decreases and is unlikely to increase carbonate iodine contents despite the potential for diagenetic loss maximum proterozoic carbonate iodine levels are elevated relative to those of the archean particularly during the lomagundi and shuram carbon isotope excursions of the paleo and neoproterozoic respectively for the shuram anomaly comparisons to neogene quaternary carbonates suggest that diagenesis is not responsible for the observed iodine trends the baseline low iodine levels in proterozoic carbonates relative to the phanerozoic are linked to a shallow oxic anoxic interface oxygen concentrations in surface waters would have at least intermittently been above the threshold required to support eukaryotes however the diagnostically low iodine data from mid proterozoic shallow water carbonates relative to those of the bracketing time intervals are consistent with a dynamic chemocline and anoxic waters that would have episodically mixed upward and laterally into the shallow oceans this redox instability may have challenged early eukaryotic diversification and expansion creating an evolutionary landscape unfavorable for the emergence of animals

trace metal concentrations in sediments from two closed basin lakes antarctica abstract sediment samples from two lakes in antarctica have been analyzed for 25 hcl leachable fe mn cu pb zn the data were normalized to 100 silt clay the pb concentrations in the sediment of don juan pond were extremely low indicating pb remobilization from these sediments by cacl 2 rich brines a possible surficial enrichment of pb was observed in shea sisters lake samples from northern victoria land

mineralogical constraints on the paleoenvironments of the ediacaran doushantuo formation assemblages of clay minerals are routinely used as proxies for paleoclimatic change and paleoenvironmental conditions in phanerozoic rocks however this tool is rarely applied in older sedimentary units in this paper the clay mineralogy of the doushantuo formation in south china is documented providing constraints on depositional conditions of the ediacaran yangtze platform that host the earliest animal fossils in the geological record in multiple sections from the yangtze gorges area trioctahedral smectite saponite and its diagenetic products mixed layer chlorite smectite corrensite and chlorite are the dominant clays through the lower 80 m of the formation and constitute up to 30 wt of the bulk rock saponite is interpreted as an in situ early diagenetic phase that formed in alkaline conditions ph 9 the absence of saponite in stratigraphically equivalent basin sections 200 400 km to the south indicates that alkaline conditions were localized in a nonmarine basin near the yangtze gorges region this interpretation is consistent with crustal abundances of redox sensitive trace elements in saponitic mudstones deposited under anoxic conditions as well as a 10 difference in the carbon isotope record between yangtze gorges and basin sections our findings suggest that nonmarine environments may have been hospitable for the fauna preserved in the yangtze gorges which includes the oldest examples of animal embryo fossils and acanthomorphic acritarchs

nitrogen isotope chemostratigraphy of the ediacaran and early cambrian platform sequence at three gorges south china abstract the appearance of multicellular animals and subsequent radiation during the ediacaran cambrian transition may have significantly changed the oceanic ecosystem nitrogen cycling is essential for primary productivity and thus its connection to animal evolution is important for understanding the co evolution of the earth s environment and life here we first report on coupled organic carbon and nitrogen isotope chemostratigraphy from the entire ediacaran to early cambrian period by using drill core samples from the yangtze platform south china the results show that 15ntn values were high 6 until middle ediacaran gradually dropping down to 1 at the earliest cambrian then rising back to 4 in the end of the early cambrian organic carbon and nitrogen contents widely varied with a relatively constant c n ratio in each stratigraphic unit and do not apparently control the carbon and nitrogen isotopic trends these observations suggest that the 15ntn and c n trends mainly reflect secular changes in nitrogen cycling in the yangtze platform onset of the observed negative n isotope excursion coincided with a global carbon isotope excursion event shuram excursion before the shuram event the high 15n probably reflects denitrification in a nitrate limited oceanic condition also degradation of dissolved and particulate organic matter could be an additional mechanism for the 15n enrichment and may have been significant when the ocean was rich in organic matter at the time of the shuram event both 13ccarb and 15ntn values were dropped probably due to massive re mineralization of organic matter this scenario is supported by an anomalously low c n ratio implying that enhanced respiration resulted in selective loss of carbon as co2 with recycled organic nitrogen after the shuram event the 15n value continued to decrease despite that 13ccarb rose back to 4 the continued 15n drop appears to have coincided with a decreasing phosphorus content in carbonate this suggests that ocean oxygenation may have generated a more nitrate rich condition with respect to phosphorus as a limiting nutrient similar to the shuram event another negative 13ccarb event in the canglanpuan stage of the early cambrian is also characterized by carbon isotopic decoupling as well as the low c n ratio the results strongly support that the two stages of the decoupled negative 13ccarb excursions reflect a disappearance of a large organic carbon pool in the ocean the two events appear to relate with the appearance of new metazoan taxa with novel feeding strategies suggesting a link between ocean oxygenation nutrient cycling and the appearance and adaptation of metazoans the nitrogen isotope geochemistry is very useful to understand the link between the environmental ecological and biological evolutions

irreversible change of the oceanic carbon cycle in the earliest cambrian high resolution organic and inorganic carbon chemostratigraphy in the three gorges area south china the terminal neoproterozoic and its transition into the cambrian witnessed major evolutionary and geochemical changes large fluctuations in the carbon isotope ratio for inorganic carbon 13ccarb across the precambrian cambrian boundary pc c boundary indicate a significant change in the oceanic carbon cycle at that time this work presents the first high resolution 13corg chemostratigraphy of drill core samples across the pc c boundary in the three gorges area south china and discusses carbon cycles based on the relation between 13corg and 13ccarb we found that changes of 13corg and 13ccarb values were decoupled during the significant negative excursion of 13ccarb across the pc c boundary suggesting the presence of a huge organic carbon pool ocp previously the large ocp was inferred to have been established in the terminal proterozoic and to have disappeared at the end of the mid ediacaran shuram excursion in contrast our study suggests that the large ocp lasted until the early nemakit daldynian stage on the other hand in the middle nemakit daldynian to atdabanian the 13ccarb and 13corg changed in parallel as observed normally in the phanerozoic in order to evaluate these scenarios quantitatively we performed numerical simulations and calculated the time evolution of the 13ccarb masses of the inorganic and organic carbon pools and the fluxes between them as a result we show that the observed negative 13ccarb excursion with steady 13corg can be produced by enhanced primary productivity and remineralization of the large ocp if the rate constant for removal of organic carbon was considerably lower than that of today the end of the decoupled negative 13ccarb excursion is attributable to an increase in the removal rates of inorganic and organic carbon from the ocean the enhanced flux of organic carbon burials eliminated the large ocp so that the modern style carbon cycle was established by the early nemakit daldynian stage the inferred rapid increases of both organic and inorganic carbon burial rates in the middle nemakit daldynian stage were likely caused by the appearance of planktonic metazoans with guts making fecal pellets and by the first skeletal animals the biological innovations may have changed the oceanic carbon cycle irreversibly just after the pc c boundary

oxygenation variations in the atmosphere and shallow seawaters of the yangtze platform during the ediacaran period clues from cr isotope and ce anomaly in carbonates abstract the late neoproterozoic era witnessed a significant oxygenation in earth s surface in line with the naissance and diversity of early animals however detailed variations of the oxygenation during this period remain controversial chromium isotope in ancient carbonates has shown its ability to trace the oxygenation history of the atmosphere hydrosphere system in this study we analyzed cr isotope and ce anomaly data of carbonates from the ediacaran doushantuo and dengying formations in the yangtze gorges area south china in order to reconstruct oxygenation variations in the atmosphere and shallow seawaters of the yangtze platform during the ediacaran period after evaluating and excluding detrital and diagenetic effects well preserved 53crauth signatures were obtained post marinoan carbonates record slightly positive 53crauth values 0 18 0 43 and slightly negative ce anomaly suggesting generally oxidizing conditions in the atmosphere with po2 over 1 pal and in shallow seawaters of the yangtze platform during the post marinoan phase which may have been related to the diversity of early ediacaran organisms shuram wonoka correlative carbonates are characterized by the fluctuations of 53crauth values 0 25 to 0 97 and a significant negative 13c excursion which may have resulted from partial oxidation of the large deep water doc reservoir under enhanced oxidative weathering conditions this process released 13c depleted carbon into dic pool and isotopically unfractionated cr iii into water columns the latter of which immediately precipitated by adsorption onto the detrital materials meanwhile an increase in local anoxia and even euxinia in the intrashelf basin of the yangtze platform driven by enhanced microbial sulfate reduction and the resultant h2s possibly limited regional biological evolution during this phase late ediacaran carbonates record elevated 53crauth values 0 40 0 96 together with the decreasing trend in ce ce values indicating a more oxygenated environment in the atmosphere and shallow seawaters of the yangtze platform during the late ediacaran phase which may have been beneficial to the diversification of late ediacaran animals

carbon isotope excursions and the oxidant budget of the ediacaran atmosphere and ocean a possible global drop in marine carbon isotope values to as low as 12 peedee belemnite pdb recorded in the ediacaran shuram formation of oman has been attributed to the non steady state oxidation of oceanic dissolved organic carbon doc resulting from the rise in atmospheric oxygen to near modern values at the end of the precambrian geologic constraints indicate that the excursion lasted between 25 and 50 m y requiring a doc pool thousands of times to 10 000 times the modern inventory to conform with carbon isotope mass balance calculations for a 12 excursion at the consequent rates of doc oxidation oceanic sulfate and oxygen in the atmosphere and oceans are exhausted on a time scale of 800 k y oxidant depletion is incompatible with independent geochemical and biological indicators that show oceanic sulfate and oxygen levels were maintained or increased during the shuram excursion furthermore a doc driven excursion does not explain strong covariation between the carbon and oxygen isotope record these indicators show that negative isotope excursions recorded in the shuram and other ediacaran sections are unlikely to represent a global ocean signal

physical and stochastic models of earthquake clustering abstract the phenomenon of earthquake clustering i e the increase of occurrence probability for seismic events close in space and time to other previous earthquakes has been modeled both by statistical and physical processes from a statistical viewpoint the so called epidemic model etas introduced by ogata in 1988 and its variations have become fairly well known in the seismological community tests on real seismicity and comparison with a plain time independent poissonian model through likelihood based methods have reliably proved their validity on the other hand in the last decade many papers have been published on the so called coulomb stress change principle based on the theory of elasticity showing qualitatively that an increase of the coulomb stress in a given area is usually associated with an increase of seismic activity more specifically the rate and state theory developed by dieterich in the 90s has been able to give a physical justification to the phenomenon known as omori law according to this law a mainshock is followed by a series of aftershocks whose frequency decreases in time as an inverse power law in this study we give an outline of the above mentioned stochastic and physical models and build up an approach by which these models can be merged in a single algorithm and statistically tested the application to the seismicity of japan from 1970 to 2003 shows that the new model incorporating the physical concept of the rate and state theory performs not worse than the purely stochastic model with two free parameters only the numerical results obtained in these applications are related to physical characters of the model as the stress change produced by an earthquake close to its edges and to the a and parameters of the rate and state constitutive law

interpreting carbon isotope excursions strangelove oceans large negative excursions in marine carbonate delta sup 13 c are commonly associated with period boundaries and mass extinctions explanations for these events must be consistent with limitations imposed by carbon isotope mass balance at steady state i e for excursions lasting more than 10 sup 5 yr the surface ocean delta sup 13 c is set by the organic fraction of the total carbon burial rate and the magnitude of the photosynthetic isotope effect the delta sup 13 c of the deep ocean and the surface to deep isotope gradient are set by both the organic fraction of the ocean s remineralized particulate flux and the magnitude of the isotope effect thus it is the carbon isotope composition of the deep ocean that is most reflective of internal oceanic processes the surface ocean records changes in the longer term throughput of carbon in the system the cessation of organic export from the surface ocean such as is presumed to have caused the strangelove ocean condition of the cretaceous tertiary k t boundary leads to an isotopically homogeneous ocean in decades to centuries if this condition persists the ocean s isotopic composition approaches that of the riverine weathering input in 10 sup 5 yr failure to approach this value during the k t event suggests continued production andmore burial of organic carbon dominantly in either terrestrial or shallow marine environments less

trace element and stable c o and radiogenic sr isotope geochemistry of stromatolitic carbonate rocks of the mesoarchaean pongola supergroup implications for seawater composition abstract the mesoarchaean pongola supergroup hosts one of the oldest well preserved stromatolitic carbonate successions major and trace element geochemistry along with c o and sr isotopic analyses of three stratigraphic sections of stromatolitic carbonate rocks were undertaken in order to infer the depositional environment and to unravel the chemical characteristics of contemporaneous seawater the carbonate rocks consist mainly of dolomite and to a lesser extent ankerite their variable sr concentrations of 95 to 450 mg kg are interpreted as resulting from early to late dolomitization of metastable carbonates aragonite and or high mg calcite facies control and calcitization during meteoric diagenesis 18o values range from 19 6 to 12 0 vpdb and reflect recrystallization of carbonates caused by high water rock interactions during diagenesis and metamorphism a 13c value of 2 5 vpdb was measured in carbonate samples least affected by alteration and we suggest that it approximates the composition of dissolved inorganic carbon in coeval seawater the samples display variable 87sr 86sr isotopic ratios from as low as 0 708 to 0 777 these ratios are considerably higher than those expected in archaean open ocean water masses buffered by hydrothermal interaction with the mantle we interpret the highly radiogenic sr isotopic ratios in some carbonate samples to reflect isotopic exchange with radiogenic sr from siliciclastic volcaniclastic components in the samples and fluids from clay rich layers intercalated with the carbonates the least radiogenic sr isotopic ratio may approximate the mixed isotopic composition of seawater in the epicontinental basin and of riverine freshwater draining the kaapvaal craton the dolomitic carbonate samples show shale normalized rare earth element and yttrium distribution patterns that resemble those of modern ocean water with positive lasn gdsn and ysn anomalies superchondritic y ho ratios a small negative cesn anomaly and depleted light rare earth elements relative to the heavy rare earth elements these anomalies are not as pronounced as expected for an open marine setting which together with the sr isotopic results support a more restricted setting with riverine input and fluctuations in marine ingressions a convex upward shale normalized rare earth element and yttrium pattern is probably a result of several factors including organic matter complexation and element fractionation during estuarine mixing the small negative cesn anomaly may suggest small amounts of free oxygen in shallow waters due to local oxygenic microbial activity

biogeochemical changes across the ediacaran cambrian transition in south china abstract the late neoproterozoic successions of south china comprise some of the most complete and well preserved records of the ediacaran cambrian transition the articles in this special issue provide a snapshot of ongoing research that is helping us to understand early stages in the development of the modern earth system these studies illustrate the transitional character of the ediacaran cambrian interval from the evolution and early extinctions of the first bilaterian metazoans during the ediacaran period to their dominance of pelagic and benthic realms by the end of the early cambrian geochemical data reveal a noisy transition of increasing baseline 13c values punctuated by extreme isotopic oscillations it is evident that highly negative 13c values and large amplitude 13c swings ceased once modern marine ecosystems had become firmly established by 520 ma we postulate that sub surface bioturbation helped to strengthen the relationship between benthic oxidation state and p retention thus tightening an important negative feedback that helps to stabilize productivity climate and oxygen levels in the modern earth system the disappearance of negative excursions after 520 ma might also suggest a key role for methanogenesis which would have declined following the rise of in sediment sulphur cycling due to bioturbation further insight into this fascinating interval is needed before we can disentangle the complex interactions between biological evolution and biogeochemical cycling during the emergence of the modern earth system

ca and mg isotope constraints on the origin of earth s deepest δ13c excursion abstract understanding the extreme carbon isotope excursions found in carbonate rocks of the ediacaran period 635 541 ma where 13 c of marine carbonates 13 c carb reach their minimum 12 for earth history is one of the most vexing problems in precambrian geology known colloquially as the shuram excursion the event has been interpreted by many as a product of a profoundly different ediacaran carbon cycle more recently diagenetic processes have been invoked with the very negative 13 c values of ediacaran carbonates explained via meteoric alteration late stage burial diagenesis or growth of authigenic carbonates in the sediment column thus challenging models which rely upon a dramatically changing redox state of the ediacaran oceans here we present 257 44 40 ca and 131 26 mg measurements along with mg mn and sr data from carbonates of the ediacaran aged wonoka formation fm of south australia to bring new isotope systems to bear on understanding the shuram excursion data from four measured sections spanning the basin reveal stratigraphically coherent trends with variability of 1 5 in 26 mg and 1 2 in 44 40 ca this ca isotope variability dwarfs the 0 2 0 3 change seen coeval with the permian triassic mass extinction the largest recorded in the rock record and is on par with putative changes in the 44 40 ca value of seawater seen over the phanerozoic eon changes in both isotopic systems are too large to explain with changes in the isotopic composition of ca and mg in global seawater given modern budgets and residence times and thus must be products of alternative processes relationships between 44 40 ca and sr and 26 mg and mg are consistent with mineralogical control e g aragonite vs calcite limestone vs dolostone on calcium and magnesium isotope variability the most pristine samples in the wonoka dataset preserving sr concentrations in the 1000s of ppm range and 44 40 ca values inherited from an originally aragonitic polymorph have 13 c carb of 8 to 7 thereby providing strong geochemical evidence that extremely negative 13 c carb values are primary products of the ediacaran surface environment

geochemical evidence for lacustrine microbial blooms in the vast permian main karoo parana falkland islands and huab basins of southwestern gondwana early permian black pyritic shale units i e the whitehill irati and huab formations and black rock member in southwestern gondwana basins have elevated 13c values of total organic carbon up to 17 pdb hydrogen indices between 300 and 1000 mg co2 g c and oxygen indices 30 mg co2 g c these data suggest a manifestation of a microbial bloom event values for 13c between 26 and 22 pdb hydrogen 100 mg co2 g c and oxygen indices of total organic carbon above and below these rock units are typical for palaeozoic terrestrial type iii organic matter carbon 13 isotope stratigraphy concur with palaeontological evidence that these formations are stratigraphical equivalents and therefore that the microbial blooms covered a vast area 5 million km2 possibly earth s most expansive microbial bloom the palaeoenvironment of the rock units preceding and including the black shales was most likely lacustrine with fresh to brackish water as shown by stable isotope c o and s evidence from organic matter carbonates and pyrite the implication is that a broad tectonic belt which formed as a result of compressional tectonics during the late carboniferous to early permian from the palaeo west must have been sufficiently well developed to cut off any contact with seawater earlier than predicted late permian from previous stratigraphic and sedimentological studies stable isotope data supported by mineralogical evidence indicate that conditions particularly in the upper portions of the lacustrine oil shales were brackish and locally may have been evaporitic we envisage that the microbial blooms possibly botryococcus peaked in the upper half of the black shale units conditions rapidly became unfavourable for microbial blooms across the entire basin in the overlying formations manifested by a change from oil shales type i organic matter to organic poor type iii shales this may possibly have been a consequence of tectonic activity and interrelated causes stable isotope data of carbonates in the overlying sediments indicate that in the palaeo north the basin became evaporitic drying up and in the palaeo southern part of the basin high latitude altitude water flooded the basin and so brought to a close the microbial blooms

the eepas forecasting model and the probability of moderate to large earthquakes in central japan abstract the eepas every earthquake a precursor according to scale model is a space time point process model based on the precursory scale increase phenomenon and associated predictive scaling relations it has previously been fitted to the new zealand earthquake catalogue and applied successfully in quasi prospective tests on the cnss catalogue for california for forecasting earthquakes with magnitudes above 5 75 and on the jma catalogue of japan for magnitudes above 6 75 here we test whether the scaling relations extend to lower magnitudes by applying eepas to depth restricted subsets of the nied catalogue of the kanto area central japan for magnitudes above 4 75 as in previous studies the eepas model is found to be more informative than a quasi static baseline model based on proximity to past earthquakes and much more informative than the stationary uniform poisson model the information that it provides is illustrated by maps of the earthquake occurrence rate density covering magnitudes from 5 0 to 8 0 for the central japan region as at the beginning of year 2004 using the nied and jma catalogues to mid 2003

renewal models and coseismic stress transfer in the corinth gulf greece fault system 1 we model interevent times and coulomb static stress transfer on the rupture segments along the corinth gulf extension zone a region with a wealth of observations on strong earthquake recurrence behavior from the available information on past seismic activity we have identified eight segments without significant overlapping that are aligned along the southern boundary of the corinth rift we aim to test if strong earthquakes on these segments are characterized by some kind of time predictable behavior rather than by complete randomness the rationale for time predictable behavior is based on the characteristic earthquake hypothesis the necessary ingredients of which are a known faulting geometry and slip rate the tectonic loading rate is characterized by slip of 6 mm yr on the westernmost fault segment diminishing to 4 mm yr on the easternmost segment based on the most reliable geodetic data in this study we employ statistical and physical modeling to account for stress transfer among these fault segments the statistical modeling is based on the definition of a probability density distribution of the interevent times for each segment both the brownian passage time bpt and weibull distributions are tested the time dependent hazard rate thus obtained is then modified by the inclusion of a permanent physical effect due to the coulomb static stress change caused by failure of neighboring faults since the latest characteristic earthquake on the fault of interest the validity of the renewal model is assessed retrospectively using the data of the last 300 years by comparison with a plain time independent poisson model by means of statistical tools including the relative operating characteristic diagram the r score the probability gain and the log likelihood ratio we treat the uncertainties in the parameters of each examined fault source such as linear dimensions depth of the fault center focal mechanism recurrence time coseismic slip and aperiodicity of the statistical distribution by a monte carlo technique the monte carlo samples for all these parameters are drawn from a uniform distribution within their uncertainty limits we find that the bpt and the weibull renewal models yield comparable results and both of them perform significantly better than the poisson hypothesis no clear performance enhancement is achieved by the introduction of the coulomb static stress change into the renewal model

the 2009 l aquila central italy seismic sequence as a chaotic process abstract in this paper we demonstrate that the seismic sequence of foreshocks culminating with the recent m w 6 3 main shock on april 6 2009 in l aquila central italy evolved as a chaotic process to do this we apply a nonlinear retrospective prediction to this seismic sequence and look at the temporal behaviour of the error between predicted and actual occurrence of the main shock when gradually increasing parts of the sequence are considered this is a generalisation of the typical nonlinear approach which is quite powerful to detect chaos in relatively short time series the method of prediction is based on the accelerated strain release asr analysis in time and on the nonlinear forecasting approach in a reconstructed phase space we find that i the temporal decay of the prediction error is consistent with an exponential function with a time constant of about 10 days and ii at around 6 days before the main shock asr analysis is quite powerful for anticipating the time of occurrence with an uncertainty of about a day due to its retrospective characteristics the latter result could be affected by changes on some a priori parameters used in the application of the asr technique however we consider these findings together with those obtained from the phase space analysis to be strong evidence that the studied sequence of foreshocks was produced by a physical process dominated by a significant chaotic component characterised by a k entropy 1 of about 0 1 day 1 this result could have important implications for the predictability of the possible main shock for those seismic sequences showing analogous nonlinear chaotic properties

50 myr recovery from the largest negative δ13c excursion in the ediacaran ocean sedimentary rocks deposited during the ediacaran period 630 542 ma contain carbonates whose carbon isotopic ratios show a marked negative excursion consisting of a precipitous drop from 5 to 12 followed by a sub linear recovery to positive 13c values isotopic ages u pb and thermal subsidence modelling are combined to constrain the excursion in time and indicate an onset at 600 ma and duration of recovery of approximately 50 myr the excursion is widely recognized in oman and has potential correlatives in ediacaran strata elsewhere and may thus represent a characteristic feature of the ediacaran period the amplitude of this carbon isotope excursion far exceeds those of other neoproterozoic anomalies the isotopic trend of negative excursion and long term recovery spanned at least one short lived glacial episode at 580 ma but appears unrelated to glaciation which indicates that negative anomalies in the neoproterozoic marine carbon isotope record are not directly or uniquely linked to ice ages

likelihood analysis of earthquake catalogues summary we apply several classes of stochastic multidimensional models to statistical analysis of earthquake catalogues using likelihood methods we investigate the importance of including different earthquake parameters in the model epicentral coordinates hypocentral depth time limits for interearthquake interaction and especially spatial distribution of earthquakes as well as spatial aftershock patterns results of this study combined with other investigations suggest that most distributions controlling earthquake interaction have a fractal or scale invariant form developed models are used for statistical analysis of several earthquake catalogues to evaluate parameters of earthquake occurrence these parameters are shown to be similar for shallow earthquakes of different magnitude ranges and seismogenic regions confirming self similarity of the earthquake process whereas intermediate earthquakes seem to emulate the pattern of shallow earthquake occurrence albeit at a much smaller aftershock rate deep earthquakes differ significantly in their properties predictability of standard shallow earthquake catalogues has been analysed we present evidence that for the best availabfe catalogues the predictability is close to 10 bits per earthquake several synthetic earthquake catalogues have been created and processed through the likelihood inversion scheme the results from likelihood analysis of these catalogues confirm our approach

ediacaran growth of the marine sulfate reservoir abstract the sulfur isotope record as preserved in sedimentary sulfate and sulfide minerals reflects the progressive oxidation of earth s surface environment the latest proterozoic to early paleozoic marine sulfur isotope record is distinguished by unusually high 34 s values in marine sulfates and sulfides geological considerations and sulfur isotopic data indicate that the 34 s enrichment of the marine sulfate reservoir was the result of a rapid increase in the net fractionation between sedimentary sulfate and pyrite 34 s without a compensatory decline in the fractional burial rate of pyrite f pyr a simple one box model in which 34 s is linked non linearly to marine so 4 is used to explore the response in sedimentary sulfur isotope records 34 s sulf and 34 s pyr to an increasing marine sulfate reservoir the model results when compared with a compilation of existing 34 s sulf and 34 s pyr data suggest that the marine sulfate reservoir grew rapidly to roughly phanerozoic levels in the middle ediacaran period before the gaskiers glaciation and prior to the onset of the shuram wonoka negative 13 c anomaly it is further hypothesized that p o 2 levels rose prior to the onset of this extreme perturbation to the global carbon cycle permitting the oxidation of a previously euxinic deep ocean and appearance of the first ediacaran fauna by ca 575 ma despite the enormous demand on oxidants implied by this large magnitude and long duration carbon isotope anomaly

natural enrichment of arsenic in loch lomond sediments abstract concentrations of arsenic in surface or near surface sediment in 12 of 13 cores from the three major basins of loch lomond are substantially enhanced up to 675 mg kg compared with background values of 15 50 mg kg sedimentary as profiles are attributed to post depositional enrichment processes since there are no recent significant sources of environmental as contamination anthropogenic or natural in the loch lomond area the enrichments can be interpreted in terms of post depositional diagenetic remobilization processes in sediment reducing zones followed by upward migration of as through interstitial waters and oxidation adsorption precipitation reactions in near surface oxidizing layers confirmation of the diagenetic adsorption hypothesis is provided directly by the analysis of as species 1 5 81 g l in pore water and indirectly via comparison with sedimentary phosphorus

carbon isotope variability across the ediacaran yangtze platform in south china implications for a large surface to deep ocean δ13c gradient new isotope data obtained from relatively conformable carbonate rich strata of the ediacaran yangtze platform in south china reveal substantial 13 c variability in platform sections four negative 13 c anomalies with a nadir down to 8 pdb are present in the interval between the cap carbonate level 635 ma and the precambrian cambrian boundary 542 ma while in slope and basinal sections 13 c values are negative through the entire doushantuo formation 635 551 ma if these 13 c values are close to their primary seawater signature they imply a strong 10 surface to deep ocean 13 c gradient that is consistent with long term deep ocean anoxia and the presence of a large dissolved organic carbon doc reservoir the two prominent negative 13 c excursions within the doushantuo formation above the cap carbonate level are associated with shoaling and local exposure of the platform the anomalies may thus record remineralization of a large oceanic doc pool via sulfate reduction that transferred 13 c depleted carbon from the oceanic doc reservoir to the surface ocean during regression inconsistencies in ediacaran 13 c profiles globally and variations in south china in particular highlight the need for further evaluation of local departures in 13 c from an inferred average seawater signature

retrospective forecasting of m 4 0 earthquakes in new zealand we have applied a variation of the epidemic type aftershock sequence etas model which is a stochastic triggering epidemic model incorporating short term clustering to data collected by the new zealand seismological observatory wellington geonet for forecasting earthquakes of moderate and large magnitude in the new zealand region the model uses earthquake data only with no explicit use of tectonic geologic or geodetic information in this epidemic type model every earthquake is regarded at the same time as being triggered by previous events and triggering following earthquakes a maximum likelihood estimate of the model parameters has been performed on the learning period from 1960 to 2005 for earthquakes of magnitude 4 0 and larger forecast verification procedures have been carried out in a forward retrospective way on the january 2006 to april 2008 data set making use of statistical tools as the log likelihood ratio the relative operating characteristics roc diagrams the molchan error diagrams the probability gain and the r score these procedures show that the clustering epidemic model achieves a log likelihood ratio per event of the order of some units and a probability gain up to several hundred times larger than a time independent spatially uniform random forecasting hypothesis the results show also that a significant component of the probability gain is linked to the time independent spatial distribution of the seismicity used in the model

comparative performance of time invariant long range and short range forecasting models on the earthquake catalogue of greece 1 time invariant long range and short range forecasting models were fitted to the earthquake catalogue of greece for magnitudes 4 0 and greater to optimize their ability to forecast events of magnitude 6 0 and greater in the period 1966 1980 the models considered were stationary spatially uniform and spatially varying poisson models a long range forecasting model based on the precursory scale increase phenomenon with every earthquake regarded as a precursor according to scale and epidemic type short range forecasting models with spatially uniform and spatially varying spontaneous seismicity each of the models was then applied to the catalogue for 1981 2002 and their forecasting performance was compared using the log likelihood statistic the long range forecasting model performed substantially better than the time invariant models and the short range forecasting models performed substantially better again the results show that the information value to be gained from modeling temporal and spatial variation of earthquake occurrence rate at both long and short range is much greater than can be gained from modeling spatial variation alone

beyond methane towards a theory for the paleocene eocene thermal maximum abstract extreme global warmth and an abrupt negative carbon isotope excursion during the paleocene eocene thermal maximum petm have been attributed to a massive release of methane hydrate from sediments on the continental slope 1 however the magnitude of the warming 5 to 6 c 2 3 and rise in the depth of the ccd 2 km 4 indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis additional carbon sources associated with methane hydrate release e g pore water venting and turbidite oxidation are also insufficient we find that the oxidation of at least 5000 gt c of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the petm for which there are several potential mechanisms production of thermogenic ch4 and co2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments 5 is capable of supplying large amounts of carbon but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments as well as the abrupt onset and termination of carbon release during the petm a global conflagration of paleocene peatlands 6 highlights a large terrestrial carbon source but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky in addition this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat the isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of co2 in addition to the oxidation of the underlying marine sediments the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands

the stratigraphic expression of a large negative carbon isotope excursion from the ediacaran johnnie formation death valley the rainstorm member of the ediacaran johnnie formation of the southern basin and range us records a large negative excursion in carbon isotope ratios of carbonate strata 13 c vpdb 6 the character of the excursion raises fundamental questions about whether this isotopic pattern is accurately capturing the time series behavior of marine dissolved inorganic carbon dic or is a product of diagenesis to explore this issue we examined the expression of this isotopic excursion within the johnnie oolite a 2 m thick marker bed which records the highest rate of change in 13 c sedimentologically the oolite unit is thought to be time transgressive if the isotopic excursion reflects time series behavior of the carbon cycle its expression in the oolite across the basin should systematically align the sections according to their slight diachroneity detailed carbon and oxygen isotopic stratigraphy of the oolite at seven different locations indicates the magnitude of the excursion at the base of the oolite is spatially variable such that after a palinspastic reconstruction the sections align along a systematic north to south gradient in the isotopic data the oolite preserved in the old dad mountains the most southerly section measured is an outlier to this trend and the most difficult to ordinate accurately in the reconstruction showing the largest isotopic range between the onset of carbonate deposition and top of the oolite several hypotheses are congruent with these data but the sum of observations is best explained by a scenario wherein the oolite is time transgressive and deposited in a north to south manner throughout the onset of the isotopic excursion if correct this implies that the stratigraphic 13 c pattern reflects time series behavior of marine dic

isotope stratigraphy of the ediacarian neoproterozoic iii of the adelaide rift complex australia and the overprint of water column stratification abstract this study establishes a high resolution 13c chemostratigraphic framework for the type ediacarian terminal proterozoic section in the adelaide rift complex a framework that contributes to the emerging global chronostratigraphic synthesis of a period that saw momentous changes in the earth s surface environment only 15 m of the 3 5 km thick type section consists of shallow water carbonates of the kind that have formed the basis of most previous studies of neoproterozoic chemostratigraphy however the organic 13corg record reveals a surprising richness of information and shows excellent utility in correlation between sections in the adelaide rift complex lateral variations in 13corg profiles correspond to expected diachronous patterns of basin fill with the addition of 87sr 86sr data correlation can also be made to the officer and amadeus basins consistent with known lithostratigraphic and sequence stratigraphic constraints sublittoral micritic carbonates of the upper nuccaleena formation cap dolostone and lower and middle wonoka formation show strong basinwide 13c depletion 13ccarb 3 to 10 despite compelling evidence for preservation of depositional 13ccarb such as good textural preservation evidence for sea floor lithification and in the wonoka formation pristine 87sr 86sr and low mn sr associated with the depleted carbonates are rare subaqueous evaporite relatively heavy 13corg and anomalously 13c depleted organic carbon of benthic microbial mat origin and a common cause salinity stratification of the water column is postulated the indicated palaeogeographic setting an evaporative mediterranean like basin tenuously connected to the world ocean is entirely consistent with previous suggestions of one or more messinian type desiccation events to explain very deep 1 km incised valleys or canyons in the adelaide rift complex and officer basin at horizons within the wonoka formation and correlates positive excursions in 13corg during basin stratification may in part be due to 12c depletion of surface waters by photosynthetic carbon fixation despite the proposed semi isolation of australian ediacarian basins from the world ocean major 13c excursions which can to some extent be differentiated by the monotonic rise in ediacarian marine 87sr 86sr appear to be correlatable to the upper windermere supergroup northwest canada

marine carbon reservoir corg ccarb coupling and the evolution of the proterozoic carbon cycle the post 2 0 ga proterozoic c isotope record reveals two distinct yet interrelated trends a stepwise increase in average 13c from 0 calculated with respect to the peedee belemnite isotope standard prior to ca 1 3 ga to 5 in the neoproterozoic and a concomitant increase in the magnitude of isotopic excursions steady state and non steady state models suggest that these fundamental changes are best explained by a combination of evolving burial fluxes and a secular decrease in the size of the marine dissolved inorganic carbon dic reservoir the dic reservoir size affects the sensitivity of the isotopic system to biogeochemical perturbation major rearrangements of carbon cycling during the proterozoic in part related to the evolving marine carbon reservoir permit elevated 13c values to be sustained for geologically long time spans recognition of this dependence on dic reservoir size provides for the first time a direct link between changing carbonate precipitation styles and the marine c isotope record and may help constrain estimates of proterozoic p co2

searching for an oxygenation event in the fossiliferous ediacaran of northwestern canada abstract late neoproterozoic ediacaran strata from northwestern canada provide a thick and rich sedimentological record preserving intercalated carbonates and shale extending from the 635 million year old marinoan glacial deposits up through the 541 million year old precambrian cambrian boundary this region also holds one of the classic localities for the study of early animal life with the ensuing suggestion that this temporal interval captures a gross change in the o 2 content of the earth s atmosphere to test this hypothesis and bring records of northwestern canada into line with other ediacaran fossil bearing basins we provide a detailed geochemical reconstruction from the wernecke mountains of the yukon where possible we also extend these records to the ogilvie mountains to the west and previously published data from the mackenzie mountains to the east our work in the wernecke mountains is set against a composite 13 c record for carbonate that preserves three distinct ediacaran isotope excursions the lowermost of which preserved in the gametrail formation is a putative shuram excursion equivalent what emerges from a multi proxy fe speciation sulfur isotopes major and trace element analyses reconstruction is a picture of a persistently anoxic and ferruginous ediacaran ocean notably absent is geochemical evidence for a prominent oxygenation event an expectation given the appearance of animals and large swings in 13 c the new insight gained through these data challenges the idea of an ediacaran jump in atmospheric oxygen which in turn muddles the link between animal evolution and local geochemical environments

testing earthquake prediction methods the west pacific short term forecast of earthquakes with magnitude mwhrv 5 8 in his paper kossobokov investigates the e ciency of our short term forecast for two western paciflc regions although we agree with the basic results of his evaluation that the forecast statistics is much better than a random guess we have reservations about his deflnition of earthquake prediction some of his tests and his interpretation of the test results we distinguish between deterministic earthquake predictions and statistical forecasts we argue that some techniques used by kossobokov may not be appropriate for testing our forecasts and discuss other testing methods based on the likelihood function we demonstrate that kossobokov s null hypothesis may be biased and this bias can in uence some of his conclusions we show that contrary to kossobokov s statement our algorithm predicts mainshocks when they are preceded by foreshocks

carbon sulfur and oxygen isotope evidence for a strong depth gradient and oceanic oxidation after the ediacaran hankalchough glaciation in order to understand spatial variations of stable isotope geochemistry in the quruqtagh basin northwestern china in the aftermath of an ediacaran glaciation we analyzed carbonate carbon isotopes 13ccarb carbonate oxygen isotopes 18ocarb carbonate associated sulfate sulfur 34scas and oxygen isotopes 18ocas and pyrite sulfur isotopes 34spy of a cap dolostone atop the ediacaran hankalchough glacial diamictite at four sections the four studied sections ykg mk h and zbs represent an onshore offshore transect in the quruqtagh basin our data show a strong paleobathymetry dependent isotopic gradient from the onshore to offshore sections 13ccarb values decrease from 2 to 16 vpdb whereas 18ocarb values increase from 4 to 1 vpdb both 34scas and 34spy show stratigraphic variations in the two onshore sections mk and ykg but are more stable in the two offshore sections h and zbs 18ocas values of onshore samples are consistent with terrestrial oxidative weathering of pyrite we propose that following the hankalchough glaciation seawater in the quruqtagh basin was characterized by a strong isotopic gradient the isotopic data may be interpreted using a three component mixing model that involves three reservoirs deep basin water surface water and terrestrial weathering input in this model the negative 13ccarb values in the offshore sections are related to the upwelling of deep basin water where anaerobic oxidation of dissolved organic carbon resulted in 13c depleted dic whereas sulfur isotope variations are strongly controlled by surface water sulfate and terrestrial weathering input derived from oxidative weathering of pyrite the new data provide evidence for the oceanic oxidation following the hankalchough glaciation

fault delineation and regional stress direction from the analysis of background microseismicity in the southern apennines italy abstract the present active faults and stress field acting in the southern apennines italy a structurally complex area characterized by high seismic potential are studied by analyzing the background microseismicity m 3 we used a microearthquake data set consisting of 1312 events that occurred from august 2005 to april 2011 by integrating the data recorded at 42 seismic stations of various networks the refined seismicity locations and focal mechanisms delineate a system of northwest southeast striking normal faults along the apenninic chain and an approximately east west oriented strike slip fault transversely cutting the belt the seismicity along the chain does not occur on a single fault but in a volume delimited by the faults activated during the 1980 irpinia m 6 9 earthquake on subparallel predominantly normal faults results show that the recent low magnitude earthquakes belong to the background seismicity and they are likely generated along the major fault segments activated during the most recent earthquakes suggesting that they are still active today 30 years after the mainshock occurrences the stress inversion from the whole data set suggests that a unique anti apenninic extensional regional stress field could explain the two different faulting styles characterizing the earthquakes that occur along the chain and the east west fault dissecting the belt on the other hand the results obtained by separately inverting the irpinia and the potenza clusters indicate a more complex model that would predict a change from a normal faulting regime acting in the inner sector of the chain to a strike slip regime moving eastward and down depth in the potenza area online material seismicity maps and focal mechanisms

a carbon isotope challenge to the snowball earth the snowball earth hypothesis contends that most of the planet was covered with thick ice for millions of years about three quarters of a billion years ago a dramatic warming event thought to have been fuelled by high atmospheric carbon dioxide levels eventually defrosted earth a new isotopic analysis of rocks that were laid down after the initial glaciation challenges the idea of a hard snowball earth the data are consistent with a rather low partial pressure of atmospheric co2 not the orders of magnitude above current levels that would provide the extreme warming necessary for escape from snowball earth this supports the idea that the initial glaciation was much less severe than has been proposed the snowball earth hypothesis postulates that the planet was entirely covered by ice for millions of years in the neoproterozoic era in a self enhanced glaciation caused by the high albedo of the ice covered planet in a hard snowball picture the subsequent rapid unfreezing resulted from an ultra greenhouse event attributed to the buildup of volcanic carbon dioxide co2 during glaciation1 high partial pressures of atmospheric co2 from 20 000 to 90 000 p p m v in the aftermath of the marinoan glaciation 635 myr ago have been inferred from both boron and triple oxygen isotopes2 3 these values are 50 to 225 times higher than present day levels here we re evaluate these estimates using paired carbon isotopic data for carbonate layers that cap neoproterozoic glacial deposits and are considered to record post glacial sea level rise1 the new data reported here for brazilian cap carbonates together with previous ones for time equivalent units4 5 6 7 8 provide estimates lower than 3 200 p p m v and possibly as low as the current value of 400 p p m v our new constraint and our re interpretation of the boron and triple oxygen isotope data provide a completely different picture of the late neoproterozoic environment with low atmospheric concentrations of carbon dioxide and oxygen that are inconsistent with a hard snowball earth

simulating meteoric and mixing zone carbonate diagenesis with a two dimensional reactive transport model meteoric and mixing zone diagenesis can dramatically alter the geochemical signatures of shallow marine carbonates most preserved pre cretaceous carbonates were deposited in shallow marine environments and thus may have been susceptible to meteoric and mixing zone diagenesis however a quantitative understanding of how the geochemical composition of carbonates changes during diagenesis still requires further development here we present a new two dimensional 2d reactive transport model coupled with a 2d coastal hydrology model to simulate carbonate diagenesis and provide insights into its impact on the isotopic and elemental compositions of carbonates in the geological record using this model we have simulated the stratigraphic trends and relationship between isotopic records for example 13c and 18o values observed in modern recent miocene sections where the impact of meteoric diagenesis has been clearly characterized our model can also reproduce anomalous neoproterozoic carbonate geochemical profiles where the effects of meteoric diagenesis have been debated further our model indicates that linear carbonate c o isotope co variations can either be generated in the mixing zone between freshwater and marine pore waters or in the freshwater phreatic zone with a downward decrease in recrystallization with no net carbonate dissolution or precipitation rate in addition numerous processes were observed to decouple 18ocarb values from other isotopic and elemental signatures during carbonate diagenesis indicating that a lack of linear correlation between 18ocarb values and other geochemical variables does not necessarily suggest limited meteoric alteration sensitivity analyses show that the steady state timescale is controlled by compositional differences between fluid endmembers the calcite water element distribution coefficient the recrystallization rate porosity and the groundwater discharge rate given that reactive transport models have proven to be powerful theoretical tools in many disciplines of earth sciences our hope is that this model will promote a more quantitative understanding of meteoric and mixing zone diagenesis of marine carbonates

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

enigmatic nature of thick sedimentary carbonates depleted in 13c beyond the canonical mantle value the challenges to our understanding of the terrestrial carbon cycle carbon and oxygen isotope measurements of 66 samples from the 60 m thick variegated marble in the upper allochthon of the norwegian caledonides have a mean 13ccarb of 8 4 0 9 v pdb and a mean 18o of 20 2 2 2 v smow the variegated marble is overlain by 150 m thick pale grey marble characterised by mean 13ccarb of 6 5 0 8 n 25 and underlain by dark grey marbles with a mean 13ccarb of 4 8 1 1 n 61 this tripartite unit of an poorly constrained age but between neoproterozoic and early silurian discontinuously developed over a distance of 500 km is likely to represent one of the largest isotopically anomalous sedimentary carbonate formations yet reported the marbles depleted in 13c beyond the canonical mantle value of 6 show no obvious evidence of post sedimentary repartitioning of carbon isotopes several other carbonate formations deposited within approximately 680 540 ma time interval chenchinskaya nikolskaya and torginskay in siberia ingta in nw canada shuram in central oman trezona and wonoka in south australia are several hundred meters thick developed over a distance of hundreds of kilometres and all show a similar depletion in 13c beyond the mantle value for reasons that are not well understood the existence of these carbonates represents a challenging problem for our current understanding of global carbon geodynamics changes in the ratio of reduced oxidised carbon sequestered in sediments a methane hydrate release or zero biological productivity if applied separately cannot explain carbon isotope characteristics and formation of these carbonates we tentatively propose that several factors associated with unusual geodynamic and palaeoclimatic scenarios developed between 600 and 540 ma might have been involved in the extreme lowering of the isotopic composition of carbon entering the global earth surface environment this period was marked by the retreat of neoproterozoic glaciers and break up of the supercontinent rodinia the late postglacial warming might have induced a massive release of methane hydrates extremely enriched in 12c the death of rodinia was marked by unusually rapid approximately 20 cm year motion of newly formed continental plates suggesting vigorous mantle convection and an enhanced restructuring of the lowest compartments of the earth this could provide a flux of 12c rich material from the isotopically light asthenosphere mantle source 13c 25 to 15 to the surface considerable reconfiguration of the continental and sea areas of the earth might have triggered enhanced weathering of previously deposited 12c rich organic matter in presenting this working hypothesis we also question the completeness of our understanding of the terrestrial carbon cycle and the popular assumption that the isotopic composition of carbon entering the global earth surface environment was always around 6

dynamic changes in sulfate sulfur isotopes preceding the ediacaran shuram excursion large excursions in 13 c and 34 s are found in sedimentary rocks from the ediacaran period that may provide detailed mechanistic information about oxidation of earth s surface however poor stratigraphic resolution and diagenetic concerns have thus far limited the interpretation of these records here we present a high resolution record of carbon and sulfur isotopes from the khufai formation leading up to and including the onset of the shuram carbon isotope excursion we document large coherent excursions in the sulfur isotope composition and concentration of carbonate associated sulfate cas that occur both independently and synchronously with the carbon isotope excursion isotopic changes appear decoupled from major stratigraphic surfaces and facies changes suggesting regional or global processes rather than local controls our data suggest that very low marine sulfate concentrations are maintained at least through the middle khufai formation and require that the burial fraction of pyrite and the fractionation factor between sulfate and pyrite necessarily change through deposition reconciliation of simultaneous up section increases in marine sulfate concentration and 34 s cas requires the introduction of strongly 34 s enriched sulfate possibly from weathering of cryogenian and earlier ediacaran 34 s enriched pyrite our analysis of the onset of the shuram carbon isotope excursion observed in stratigraphic and lithologic context is not consistent with diagenetic or authigenic formation mechanisms instead we observe a contemporaneous negative excursion in sulfate 34 s suggesting linked primary perturbations to the carbon and sulfur isotope systems this work further constrains the size isotopic composition and potential input fluxes of the ediacaran marine sulfate reservoir placing mechanistic constraints on possible drivers of extreme isotopic perturbations during this critical period in earth history

210pb dating of a loch lomond sediment core by conventional and particle track methods and some geochemical observations 210pb dating of a short mackereth core from a suite characterised previously by palaeomagnetic and radiocarbon dating has been performed using both conventional radiochemical and particle track methods the latter involves total and u assay using plastic detectors and untreated sediment pellets sedimentation rates determined by the two techniques are in good agreement 22 mg cm 2 y 1 suggesting that the simpler particle track method has much to offer in routine sediment dating the radiometric time scale is totally consistent with heavy metal profiles and the known industrial history of the surrounding area

testing earthquake forecast hypotheses abstract this paper outlines methodological aspects of the statistical evaluation of earthquake forecast hypotheses the recent debates concerning predictability of earthquakes clearly show how this problem is centred on the difficulty of systematically testing the numerous methodologies that in the years have been proposed and sustained by the supporters of prediction this difficulty starts sometimes from the lack of a quantitative and rigorous definition of the concerned precursor and other times from the lack of continuous observations upon which statistical analyses could be based the application of rigorous statistical methods with the aim of verifying any prediction method requires a univocal definition of the hypothesis or the model characterising the concerned anomaly or precursor so as it can be recognised objectively in any circumstance and by any observer a simple definition of an earthquake forecasting hypothesis could consist of the identification of particular sub volumes of the total time space volume usually named alarm volumes within which the probability of occurrence of strong earthquakes is higher than the average the test of a similar model needs the observation of a sufficient number of past cases upon which to carry out a statistical analysis aimed to determine the rate at which the precursor has been followed success rate or not followed false alarm rate by the target seismic event or the rate at which a target event has been preceded alarm rate or not preceded failure rate by the precursor a valid forecast hypothesis is expected to maximise success and minimise false alarms with regard also to the maximisation of the probability gain some geophysicists prefer a statistical approach such as the bayes criterion based on the computation of the likelihood of an observed realisation of seismic events and on the comparison of the likelihood obtained under different hypotheses this method can be extended as it has recently been the case for models of earthquake clustering to algorithms that allow the computation of the density distribution of the conditional probability of earthquake occurrence in space time and magnitude another approach to assess the validity of an earthquake forecast hypothesis could be that of estimating the total cost that the community has to pay in relation to earthquakes and choosing the model that minimise such cost whatever method is chosen for building up a new hypothesis the final assessment of its validity should be carried out by a test on a new and independent set of observations the implementation of this test could however be problematic for seismicity characterised by long term recurrence

synchrony and causal relations between permian triassic boundary crises and siberian flood volcanism the permian triassic boundary records the most severe mass extinctions in earth9s history siberian flood volcanism the most profuse known such subaerial event produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less analysis of 40 ar 39 ar data from two tuffs in southern china yielded a date of 250 0 0 2 million years ago for the permian triassic boundary which is comparable to the inception of main stage siberian flood volcanism at 250 0 0 3 million years ago volcanogenic sulfate aerosols and the dynamic effects of the siberian plume likely contributed to environmental extrema that led to the mass extinctions

comment on testing earthquake prediction methods the west pacific short term forecast of earthquakes with magnitude mwhrv 5 8 by v g kossobokov in his paper kossobokov investigates the efficiency of our short term forecast for two western pacific regions although we agree with the basic results of his evaluation that the forecast statistics is much better than a random guess we have reservations about his definition of earthquake prediction some of his tests and his interpretation of the test results we distinguish between deterministic earthquake predictions and statistical forecasts we argue that some techniques used by kossobokov may not be appropriate for testing our forecasts and discuss other testing methods based on the likelihood function we demonstrate that kossobokov s null hypothesis may be biased and this bias can influence some of his conclusions we show that contrary to kossobokov s statement our algorithm predicts mainshocks when they are preceded by foreshocks

an organodiagenetic model for marinoan age cap carbonates abstract the nuccaleena formation cap carbonate is the global stratotype for the marinoan glaciation and ediacaran gssp a designation that emphasises the importance of cap carbonates to our current understanding of global neoproterozoic biogeochemistry sedimentology and stratigraphy however to date there is no agreed depositional model for cap carbonates and there remains minimal detailed paragenetic data for developing process based depositional models here an early diagenetic organodiagenetic dolomite cementation model for marinoan cap carbonate formation is hypothesised and explored it is demonstrated how this process based model can explain the three main atypical sedimentary structures that are the basis for correlation of marinoan age cap carbonates giant tepee like structures sheet veins and tubestones these features are interpreted to be products of fluid overpressure deformation induced by organodiagenetic expansive cementation giant tepee like structures the hallmark of marinoan cap carbonates conform to a simple structural analysis that is consistent with the predicted stress field induced by expansive cementation driven fluid overpressure the undeformed to highly deformed gradient of deformation features in cap carbonates is consistent with the range of rheologies in a shallowly buried cementing carbonate modification of matrix textures and bedding surfaces also conforms to the range of expected textures within this model overall it is hypothesised that the aggradational condensed section architecture of cap carbonates was the primary control over the generation of these atypical sedimentary features the available paragenetic analysis suggests that the geochemical data particularly the c isotopic data can be reinterpreted as supportive of the organodiagenetic model and that the neoproterozoic ocean was perhaps similar to that of today the proposed model indicates that the current criteria for the placement of the ediacaran gssp are non unique and potentially non isochronous perhaps the most important aspect of this model is that it is testable and is a call for focused research on the much overlooked paragenesis of cap carbonates

comparison of short term and time independent earthquake forecast models for southern california we have initially developed a time independent forecast for southern california by smoothing the locations of magnitude 2 and larger earthquakes we show that using small m 2 earthquakes gives a reasonably good prediction of m 5 earthquakes our forecast outperforms other time independent models kagan and jackson 1994 frankel et al 1997 mostly because it has higher spatial resolution we have then developed a method to estimate daily earthquake probabilities in south ern california by using the epidemic type earthquake sequence model kagan and knopoff 1987 ogata 1988 kagan and jackson 2000 the forecasted seismicity rate is the sum of a constant background seismicity proportional to our time independent model and of the aftershocks of all past earthquakes each earthquake triggers aftershocks with a rate that increases exponentially with its magnitude and decreases with time following omori s law we use an isotropic kernel to model the spatial distribution of aftershocks for small m 5 5 mainshocks for larger events we smooth the density of early aftershocks to model the density of future aftershocks the model also assumes that all earthquake magnitudes follow the gutenberg richter law with a uniform b value we use a maximum likelihood method to estimate the model parameters and test the short term and time independent forecasts a retro spective test using a daily update of the forecasts between 1 january 1985 and 10 march 2004 shows that the short term model increases the average probability of an earthquake occurrence by a factor 11 5 compared with the time independent forecast

exceptional preservation of expandable clay minerals in the ca 2 1 ga black shales of the francevillian basin gabon and its implication for atmospheric oxygen accumulation abstract clay minerals are exceptionally well preserved in marine black shale of the ca 2 1 ga francevillian group in southeastern gabon the fb formation of the francevillian group is characterized by smectite rich clay minerals including randomly ordered r0 type and ordered r1 type mixed layer illite smectite i s the preservation of r0 type clay minerals suggests unexpectedly slow mineral transformation and a moderate degree of diagenesis which is unique considering the paleoproterozoic age of the sedimentary rocks r0 and r1 type smectite rich particles occur in stratigraphic intervals with high organic carbon content and are associated with carbonaceous filamentous structures suggesting formation of clay organic matter complexes our data suggests that clay minerals may have enhanced organic matter preservation providing the oldest example where a link between clay minerals and organic matter sequestration can be established our findings are consistent with the hypothesis that clay minerals enhanced organic carbon burial and aided in atmospheric oxygen accumulation through time

time dependent earthquake occurrence rates along the hellenic arc seismicity rate changes in the hellenic subduction zone southern aegean sea were studied by applying the dieterich 1994 rate state dependent friction model combined with static coulomb stress changes cff the coseismic slip of the strongest earthquakes with moment magnitude m w 6 0 was considered to contribute to the stress field evolution along with the continuous tectonic loading stress changes were calculated just after each strong event and their influence was examined in connection with the smaller magnitude earthquake occurrence rates qualitative and quantitative comparison between the observed seismicity rates smoothed by the means of a probability density function and the expected ones as they were forecasted by the rate state model were investigated for the interseismic periods study periods between subsequent strong earthquakes the calculations aim to identify areas of expected increased seismicity rates as candidates to accommodate enhanced seismic activity results strongly depend on the determination smoothing of the unperturbed reference seismicity rates and data adequacy seismicity rate results were filtered by certain criteria and constraints in an attempt to overcome model uncertainties epicentral errors rupture models parameter values and to provide reliable results for specific areas of major interest that is in areas with increased positive coulomb stress changes values the modeling approach resulted in satisfactory correlation between observed and synthetic seismicity rates and in particular the two strong m w 6 earthquakes that occurred in 2013 are located in areas of increased expected seismicity rates

importance of direct and indirect triggered seismicity in the etas model of seismicity 1 using the simple etas branching model of seismicity which assumes that each earthquake can trigger other earthquakes we quantify the role played by the cascade of triggered seismicity in controlling the rate of aftershock decay as well as the overall level of seismicity in the presence of a constant external seismicity source we show that in this model the fraction of earthquakes in the population that are aftershocks is equal to the fraction of aftershocks that are indirectly triggered and is given by the average number of triggered events per earthquake previous observations that a significant fraction of earthquakes are triggered earthquakes therefore imply that most aftershocks are indirectly triggered by the mainshock

secular variations in precambrian seawater chemistry and the timing of precambrian aragonite seas and calcite seas an extension of the seawater secular variation model that successfully predicted the observed timing of phanerozoic mgso 4 vs kcl marine evaporites and aragonite seas vs calcite seas has been applied to the prediction of the secular variations in the major ion chemistry of seawater and aragonite seas vs calcite seas during the precambrian testing of the predictions was based on those precambrian seafloor carbonate precipitates that have been interpreted by others to have formed originally as aragonite of 16 examples of precambrian seafloor aragonite 14 fall within the 6 periods of aragonite seas predicted for the late archean proterozoic by the model 1 falls on the transition between an aragonite sea and calcite sea and 1 falls in a period of calcite seas this strong correlation supports the following predictions of the model 1 precambrian seawater was a saline nacl water with ca hco 3 since at least the late archean 2 the major ion compositions of precambrian seawater chemistry and their secular variations are in the same ranges as those of phanerozoic seawater 3 the mg ca mole ratio in seawater has controlled the types of caco 3 polymorphs that have precipitated from earth9s oceans throughout the phanerozoic and most if not all of the precambrian

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

the effect of rising atmospheric oxygen on carbon and sulfur isotope anomalies in the neoproterozoic johnnie formation death valley usa abstract carbonates within the rainstorm member in the terminal neoproterozoic johnnie formation of death valley california record a remarkable negative carbon isotope anomaly to a nadir of near 11 that accompanies a dramatic rise in trace sulfate abundance and fall of carbonate associated sulfate 34 s values the carbonates including the laterally extensive johnnie oolite were deposited during marine flooding atop a sequence boundary best observed in cratonward sections the 12 c rich alkalinity delivered to the seawater pool was likely associated with a dramatic rise in atmospheric o 2 which resulted in 1 the oxidation of exposed continental shelf sediments rich in fossil organic matter and sulfides and 2 the ventilation of the oceans similar carbon isotope anomalies are recorded in broadly equivalent successions that post date known marinoan glacial deposits and pre date the precambrian cambrian boundary in oman india china australia and namibia supporting the view that the oxygenation event was global thus the biogeochemical anomaly post dates the last widely recognized neoproterozoic ice age but is nonetheless associated with sea level drawdown that is likely to be eustatic in origin the radiation of a high diversity microbiota and the first appearance of large metazoan fossils ediacaran animals follow this carbon isotope anomaly suggesting that a critical threshold with respect to atmospheric o 2 had been crossed by this time a negative excursion of similar magnitude occurs in overlying strata at the precambrian cambrian boundary which likely reflects similar processes