a comparative discussion of the evidence for biogenic silica in wufeng longmaxi siliceous shale reservoir in the sichuan basin china abstract the siliceous wufeng longmaxi formation is the main shale gas play in china it contains a large amount of silica which has been reported to be of biogenic origin the previous evidences for a biogenic origin include the presence of siliceous skeletal debris resembling organisms such as sponge spicules various parameters such as the ratios of al al fe mn and si si fe al ca and a number of different correlations such as a positive relationship of silica content with total organic matter toc however these evidences especially various parameters and correlations become unpersuasive when comparing wufeng longmaxi formation siliceous shale with other shale in these parameters and correlations a series of petrographic thin section and scanning electron microscope sem observations elemental analysis toc analysis and mineral composition analysis were conducted to verify the unpersuasiveness of the existing evidences and then propose new evidences to demonstrate the abundance of biogenic silica in wufeng longmaxi siliceous shale it is shown that siliceous ellipsoids are a better mark of biogenic silica in wufeng longmaxi siliceous shale than sponge spicule radiolarian and foraminifera except for the barium ba concentration most elemental composition data cannot be used to distinguish biogenic silica from silica with an airborne volcanic ash origin furthermore the poor crystal morphology of the silica in wufeng longmaxi siliceous shale was a clear difference from the airborne volcanic ash derived silica in lucaogou formation and hydrothermal silica in nutitang and doushantuo formations hence the crystal morphology can be considered as a distinguishing feature for biogenic silica

role of nonlinear ocean dynamic response to wind on the asymmetrical transition of el nino and la nina to understand why el nino is frequently followed by la nina while the opposite occurs rarely we analyze the inherent asymmetry in a delayed negative feedback loop in the framework of delayed oscillator theory using observational data the asymmetrical response of the ocean wave to wind is much larger than that of the wind intensity to sst and that of the subsurface temperature to thermocline strong oceanic response during el nino compared to la nina is presumably due to the relatively shallow mean thermocline over the western pacific which efficiently traps the atmospheric momentum in the shallow upper ocean and the asymmetrical wind pattern response to sst a modified delayed oscillator model experiment verifies that the asymmetrical ocean wave response to wind is more important in the asymmetrical transition of el nino and la nina than asymmetrical wind intensity response to sst and asymmetrical subsurface temperature response to thermocline

a study on the regulation of the concentrations of some trace metals rb sr zn pb cu v cr ni mn and mo in saanich inlet sediments british columbia canada abstract bulk metal concentrations were measured in the sediments of saanich inlet in an attempt to establish the occurrence of trace metal enrichment in the anoxic central basin ba ni v cr zn pb cu and mo were found to be enriched in the anoxic ooze over the possible contributions from lithogenic sources spatial and seasonal variations in the chemical composition of the settling particulates collected with interceptor traps gave further indications of the mode of incorporation of these metals biogenic ba and cr appeared to be associated with opaline silica although alternative explanations are also possible particularly for ba zinc seemed to be added to the sediment essentially in association with planktonic materials while cu required an additional source directly linked to the anoxic environment similarly ni v and mo were added to the anoxic sediments by reactions occurring at the sediment water interface in the nearshore environment studied here these metals particularly ni and mo were not associated to any significant extent with planktonic materials of all the elements analyzed mo showed the largest enrichment in the anoxic sediments of saanich inlet

the characteristics and formation mechanism of a regional fault in shale strata insights from the middle upper yangtze china abstract shale is a type of fracture prone rock but few regional faults are observed in shale strata here we investigate a regional detachment fault in the middle upper yangtze muy to understand the formation mechanism of a special regional fault in shale strata based on a lithological mineralogical and mechanical study as well as semi quantitative model of displacement we found that the formation of this detachment fault is closely related to the lithological association and flexural slip processes the lithological association of this detachment fault is characterized by two thick competent layers separated by a thin weak interlayer at both the macroscopic and microscopic scales when these layers are folded the detachment fault zone is commonly present in a thin weak interlayer namely the wufeng formation at the macroscopic scale and primarily along interfaces in laminar siliceous shales lss and secondarily in k bentonite interlayers within the lss at the microscopic scale the regional fault zone is characterized by parallel to strata surfaces and abrupt contacts with the protolith the fabric of the fault core is obviously controlled by the flexural slip intensity and the number of slip events as well as their direction and structural position the natural shale gas obtained from well hd 1 has proven that this regional detachment fault in shale strata is not only a migration pathway for hydrocarbons but also acts as an adsorption state reservoir for free gas from other areas this regional detachment fault in shale strata is likely to advance the shale gas industry and to expand the exploration of conventional gas

geochemical compositions and depositional conditions of upper jurassic and lower cretaceous yorkshire clays england fifty three samples from the oxford kimmeridge and speeton clays of the yorkshire area have been analysed petrographically and geochemically by x ray diffraction x ray fluorescence atomic absorption and combustion toc major elements and the following trace elements have been determined rb sr ba cr v co ni cu zn and mo p 2 o 5 rb ba cr and v show positive correlation to the clastic fraction quartz feldspar and clay minerals cao mno and sr and to a lesser extent ni cu and zn seem to be positively correlated to calcite while fe 2 o 5 mno mgo and co are linked to siderite stratigraphical variations of element element ratios have been used to obtain sedimentological information from the petrographical and geochemical data the oxford clay with its coarse and immature clays was deposited in a regressive development an upwards shallowing with ventilated deposition of more mature and altered clastic material took place throughout the unit during deposition of the kimmeridge clay more reducing conditions existed and finer grained smectite rich sediments were formed the fine grained speeton clay was deposited during changing depositional conditions varying ventilation in a generally regressive development several sedimentological breaks characterize the unit

geochemical facies analysis of fine grained siliciclastics using th u zr rb and zr rb sr ratios abstract abundance of the trace elements zr rb sr th and u may provide insight into the sedimentological origin of fine grained siliciclastic sediments provided that the units are derived from similar source areas as demonstrated here with suites of the fine grained jurassic and cretaceous rocks from the barents sea and svalbard zr rb ratios can be interpreted to indicate grain size variations while zr rb sr values reflect variations in the siliciclastic versus carbonate contents the th u ratio can be applied as an indicator of the redox conditions in 3d plots such as presented here the interplay between these geochemical factors can be interpreted in terms of the sedimentological evolution of the depositional basin the geochemical facies analyses show that similar depositional conditions existed on the jurassic shelf in the two studied localities the succeeding prodeltaic cretaceous beds were generally coarser grained and deposited in ventilated depositional conditions

north pacific temperature and precipitation response to el nino like equatorial heating sensitivity to forcing location this study investigates the sensitivity of oceanic and atmospheric response in the extra tropics especially in the north pacific to the position of equatorial el nino like heating within a slab ocean climate model in a suite of numerical experiments we impose an idealized equatorial sea surface temperature sst anomaly in the pacific and systematically vary its longitudinal position along the equator to mimic different flavors of el nino we find that regardless of the forcing location the induced sst pattern closely resembles a positive phase of the pacific decadal oscillation with a characteristic warming along the north american coast as part of an arc shaped pattern accompanied by wind anomalies around the aleutian low however the extent and magnitude of the coastal warming vary nonmonotonically when the forcing shifts westward along the equator the strongest response is found when the equatorial forcing is located in the central pacific close to the dateline in contrast precipitation response over southern california is strongest for an eastern pacific warming centered at 150 w even though its magnitude is highly uncertain since the boundary between dry and wet precipitation anomalies passes through this region we repeat the experiments for cold i e la nina like anomalies and observe a significant asymmetry in the sst and atmospheric response between the warm and cold cases finally our experiments suggest that tropical heating or cooling over the western pacific warm pool generates the largest tropical rainfall response and hence the largest global mean sst anomaly

lack of organic matter accumulation on the upwelling influenced somalia margin in a glacial interglacial transition abstract monsoon induced upwelling has been operating off somalia for at least the last 160 000 years making the nw indian ocean one of the most productive oceanic areas in the world we have studied the sediments recovered during the indusom cruise of the r v marion dufresne from three different environments off this margin a core from the highly productive surface waters core md85 674 a core where the oxygen minimum intersects the slope core md85 664 and a reference core from the deep basin with normal bottom oxygen levels and moderate primary production core md85 668 though the first two environments are a priori favourable to organic matter om accumulation no marine om enrichment can be observed in the cores to understand this anomaly emphasis is placed upon the transition from isotopic stage 6 to stage 5 because the end of the glacial stage 6 is characterised by intensified upwelling and primary productivity in this region whereas stage 5 experienced a marked decrease in productivity various palaeoenvironmental markers such as om v ni cu zn ba and p have been used to identify periods of high productivity and or bottom water oxygen depletion the results suggest that 1 the lack of marine om in two settings favourable to organic carbon storage may be due to the nature of primary productivity coccolithophorid production would not be prone to om accumulation in contrast to the contribution of om by diatoms or particularly naked phytoplankton dinoflagellates or other peridinians 2 ba is not an accurate palaeoproductivity marker in this region although the oceanic environment would have been a priori suitable for the use of ba as a proxy indicator 3 the period of intensified upwelling in stage 6 as well as the stage 6 5 transition left no geochemical imprint on the sediments this means that some upwelling systems may not be accompanied by marked enrichments in marine organic matter within the underlying sediments in other words the somalia upwelling does not participate to the so called biological pump and has no positive effect upon long term carbon storage

a 10 15 yr modulation cycle of enso intensity abstract this study examines the slow modulation of el nino southern oscillation enso intensity and its underlying mechanism a 10 15 yr enso intensity modulation cycle is identified from historical and paleoclimate data by calculating the envelope function of boreal winter nino 3 4 and nino 3 sea surface temperature sst indices composite analyses reveal interesting spatial asymmetries between el nino and la nina events within the modulation cycle in the enhanced intensity periods of the cycle el nino is located in the eastern tropical pacific and la nina in the central tropical pacific the asymmetry is reversed in the weakened intensity periods el nino centers in the central pacific and la nina in the eastern pacific el nino and la nina centered in the eastern pacific are accompanied with basin scale surface wind and thermocline anomalies whereas those centered in the central pacific are accompanied with local wind and thermocline anomalies the el nino la nina asymmetries provide a possible m

the normality of el nino the amplitude of the el nino southern oscillation enso would be normally distributed if the coupled pacific ocean atmosphere were a linear system forced by gaussian weather noise moment estimates of skewness and kurtosis demonstrate that this is not the case for monthly mean anomalies in pacific sea surface temperatures during 1950 97 the noted predominance of el nino events compared to la nina events is related to the high skewness in the eastern pacific skewness and kurtosis both exhibit an intriguing geographical variation from positive in the eastern to negative in the western pacific we have also examined nino 3 indices generated by three climate models having widely different complexity these exhibit a wide range of skewness and kurtosis values rather different from those found for the observations skewness and kurtosis can be used to diagnose non linear processes and provide powerful tools for validating models and for testing observed sea surface temperatures for the presence of possible climate change

a tale of shales the relative roles of production decomposition and dilution in the accumulation of organic rich strata middle upper devonian appalachian basin abstract a new consensus on the processes responsible for organic carbon burial in ancient epeiric seas has emerged more firmly grounded in the uniformitarian framework of modern oceanography and biogeochemistry this consensus recognizes the interdependent roles of sedimentation primary production and microbial metabolism in favor of earlier end member models e g production vs preservation in this study one of the classic stratigraphic sequences upon which the preservation end member was based is re interpreted in light of this new consensus the study employs an extensive new sedimentological biogeochemical database from cores drilled in western new york the database spans over 500 m and 15 my of devonian deposition in the appalachian basin and provides a framework for comparative study of organic matter burial the major conclusions are 1 few organic rich units were deposited under pervasive anoxic sulfidic water columns 2 establishment and breakdown of seasonal thermoclines on annual or longer timescales were the predominant mode of stratification and 3 under such conditions remineralization of bio limiting nutrients may have played a key role in organic matter burial by creating a eutrophication pump this pump may have augmented an already rising nutrient inventory such that productivity levels exceeded the threshold required for development of suboxic to anoxic conditions in sediments and episodically in bottom waters a final conclusion asserts that the master variable for organic matter accumulation was relative sea level change which exerted influence on clastic dilution preservation and production processes sea level rise events led to sediment starvation and organic carbon concentration in distal basin sediments as well as to decreased effectiveness of seasonal mixing and thus longer build up intervals for remineralized nutrients episodic mixing of nutrient enriched bottom waters led to enhanced production ultimately increased clastic sediment delivery and water column mixing during relative sea level fall diluted surface sediment organic content such that respiratory demand could be met by increased oxygen supply thus terminating deposition of strata enriched in organic carbon

tropical sea surface temperatures for the past four centuries reconstructed from coral archives most annually resolved climate reconstructions of the common era are based on terrestrial data making it a challenge to independently assess how recent climate changes have affected the oceans here as part of the past global changes ocean2k project we present four regionally calibrated and validated reconstructions of sea surface temperatures in the tropics based on 57 published and publicly archived marine paleoclimate data sets derived exclusively from tropical coral archives validation exercises suggest that our reconstructions are interpretable for much of the past 400 years depending on the availability of paleoclimate data within and the reconstruction validation statistics for each target region analysis of the trends in the data suggests that the indian western pacific and western atlantic ocean regions were cooling until modern warming began around the 1830s the early 1800s were an exceptionally cool period in the indo pacific region likely due to multiple large tropical volcanic eruptions occurring in the early nineteenth century decadal scale variability is a quasi persistent feature of all basins twentieth century warming associated with greenhouse gas emissions is apparent in the indian west pacific and western atlantic oceans but we find no evidence that either natural or anthropogenic forcings have altered el nino southern oscillation related variance in tropical sea surface temperatures our marine based regional paleoclimate reconstructions serve as benchmarks against which terrestrial reconstructions as well as climate model simulations can be compared and as a basis for studying the processes by which the tropical oceans mediate climate variability and change

influence of sedimentary environment on organic matter enrichment in shale a case study of the wufeng and longmaxi formations of the sichuan basin china abstract as two essential controls on the formation of organic matter om enriched shales both paleoproductivity and preservation models remain controversial for the wufeng and longmaxi shales in the sichuan basin southwest china this study provides geochemical parameters as proxies for the paleoproductivity characteristics ba p al and ni cu al bottom water redox status u th v v ni v cr and mo and terrigenous clastic flux th and al of the wufeng longmaxi formations in the sichuan basin a back deep basin in a foreland basin system in southwest china combining these data with total organic carbon toc content and sedimentation rate data obtained from graptolite zones allowed us to discuss the validity of these popular indices and to identify the main factors that controlled om enrichment in the formations toc contents exceed 4 wt in the upper wufeng formation to the bottom part of the longmaxi formation lm1 3 which are the most om rich intervals the average p al ratio for well jy2 in the jiaoshiba area is 0 009 which is lower than those for well yy1 0 028 in the yongchuan area and well dy1 0 02 in the dingshan area indicating the lowest productivity levels were in the jiaoshiba area based on the redox proxies the samples from well dy1 reflect less reducing bottom water conditions than those from wells jy2 and yy1 the th and al indices increase upwards indicating that the terrigenous clastic input increased and that those in the yongchuan area were lower than those in the jiaoshiba and dingshan areas the sedimentation rate was too low to dilute the om in the sichuan basin especially during the depositional time of the om rich intervals such that the redox status of the water became more critical given the more strongly reducing conditions of the sedimentary environment and the high thermal maturity of the om in this formation the ba concentrations appeared anomalously low and became inaccurate as a paleoproductivity index as well as the validity of v v cr and v v ni anomalously decreased as redox indices

coral reefs of the turbid inner shelf of the great barrier reef australia an environmental and geomorphic perspective on their occurrence composition and growth investigations of the geomorphic and sedimentary context in which turbid zone reefs exist both in the modern and fossil reef record can inform key ecological debates regarding species tolerances and adaptability to elevated turbidity and sedimentation furthermore these investigations can address critical geological and palaeoecological questions surrounding longer term coral sediment interactions and reef growth histories here we review current knowledge about turbid zone reefs from the inner shelf regions of the great barrier reef gbr in australia to consider these issues and to evaluate reef growth in the period prior to and post european settlement we also consider the future prospects of these reefs under reported changing water quality regimes turbid zone reefs on the gbr are relatively well known compared to those in other reef regions they occur within 20 km of the mainland coast where reef development may be influenced by continual or episodic terrigenous sediment inputs fluctuating salinities 24 36 ppt and reduced water quality through increased nutrient and pollutant delivery from urban and agricultural runoff individually and in synergy these environmental conditions are widely viewed as unfavourable for sustained and vigorous coral reef growth and thus these reefs are widely perceived as marginal compared to clear water reef systems however recent research has revealed that this view is misleading and that in fact many turbid zone reefs in this region are resilient exhibit relatively high live coral cover 30 and have distinctive community assemblages dominated by fast growing acropora montipora and or sediment tolerant species turbinaria goniopora galaxea porites palaeoecological reconstructions based on the analysis of reef cores show that community assemblages are relatively stable at millennial timescales and that many reefs are actively accreting average 2 7 mm year where accommodation space is available despite recent anthropogenic pressures these turbid zone reefs challenge traditional views on the environmental conditions required for active reef growth but given their proximity to land and associated stresses current knowledge on these less well understood reefs should be synthesised to aid coastal management directives terrigenous sediments are a dominant influence on turbid zone reef occurrence composition and growth and therefore the assessment of their future prospects will require a detailed understanding of the sedimentary regimes under which they occur and of their differential response modes

nonlinear principal component analysis tropical indo pacific sea surface temperature and sea level pressure abstract nonlinear principal component analysis nlpca is a generalization of traditional principal component analysis pca that allows for the detection and characterization of low dimensional nonlinear structure in multivariate datasets the authors consider the application of nlpca to two datasets tropical pacific sea surface temperature sst and tropical indo pacific sea level pressure slp it is found that for the sst data the low dimensional nlpca approximations characterize the data better than do pca approximations of the same dimensionality in particular the one dimensional nlpca approximation characterizes the asymmetry between spatial patterns characteristic of average el nino and la nina events which the 1d pca approximation cannot the differences between nlpca and pca results are more modest for the slp data indicating that the lower dimensional structures of this dataset are nearly linear

the oceanic phosphorus cycle and continental weathering during the neogene little is known about the history of dissolved phosphorus p input to the ocean during the cenozoic an important factor in reconstructing global change because of the role of p in controlling net oceanic productivity and organic carbon burial we present p accumulation rates from the eastern neogene and western cenozoic equatorial pacific a region chosen to reflect oceanic p input trends because of its importance in global models of new production and biogenic sedimentation p accumulation rates range from 5 to 60 mol p cm 2 kyr 1 and exhibit a positive correlation with mass sediment accumulation rates calcium carbonate being the major sediment component the influences of surface productivity patterns site migration through time relative to equatorial upwelling and water depth are observed in the p accumulation rate records these site specific effects are relatively minor however compared to synchronous significant trends in p accumulation rates in these equatorial pacific sites the most notable event occurred in the late miocene when mean p accumulation rates exhibited a strong peak at 5 6 ma to the highest mean value of the neogene 37 mol p cm 2 kyr 1 followed by a sharp decrease to 1 2 ma 14 mol p cm 2 kyr 1 after which values increased slightly to the present these changes in p accumulation rates in the equatorial pacific translate into substantial changes in p burial the decrease from 5 6 to 1 2 ma signified a 62 decrease in p burial in the equatorial pacific and the difference is equivalent to 14 of the estimated modern p input rate to the oceans some of the late neogene change in the equatorial pacific p accumulation rate record may have been due to redistribution of p burial to high latitude regions however on the basis of p mass balance considerations redistribution alone cannot account for the bulk of the change in p accumulation and burial in the equatorial pacific the p accumulation rate record is markedly different from the unidirectional increases in continental weathering rates over the last 40 m y interpreted from the sr isotope record suggesting a decoupling of nutrient input fluxes from input fluxes of other dissolved constituents

decadal amplitude modulation of two types of enso and its relationship with the mean state in this study we classified two types of el nino southern oscillation enso events within the decadal enso amplitude modulation cycle using a long term coupled general circulation model simulation we defined two climate states strong and weak enso amplitude periods and separated the characteristics of enso that occurred in both periods there are two major features in the characteristics of enso the first is the asymmetric spatial structure between el nino and la nina events the second is that the el nino la nina asymmetry is reversed during strong and weak enso amplitude periods el nino events during strong weak enso amplitude periods resemble the eastern pacific central pacific el nino in terms of the spatial distribution of sea surface temperature anomalies ssta and physical characteristics based on heat budget analysis the spatial pattern of the thermocline depth anomaly for strong weak el nino is identical to that for weak strong la nina but for an opposite sign and slightly different amplitude the accumulated residuals of these asymmetric anomalies dominated by an east west contrast structure could feed into the tropical pacific mean state moreover the residual pattern associated with el nino la nina asymmetry resembles the first principal component analysis pca mode of tropical pacific decadal variability indicating that the accumulated residuals could generate the change in climate state thus the intensified enso amplitude yields the warm residuals due to strong el nino and weak la nina over the eastern tropical pacific this linear relationship between enso and the mean state is strong during the mature phases of decadal oscillation but it is weak during the transition phases furthermore the second pca mode of tropical pacific decadal variability plays an important role in changing the phase of the first mode consequently the feedback between enso and the mean state is positive feedback to amplify the first pca mode whereas the second pca mode is a negative feedback to lead the phase change of the first pca mode due to their lead lag relationship these features could be regarded as evidence that the decadal change in properties of enso could be generated by the nonlinear interaction between enso and the mean state on a decadal to interdecadal time scale

analysis of the southward wind shift of enso in cmip5 models abstractduring the mature phase of el nino southern oscillation enso events there is a southward shift of anomalous zonal winds sws which has been suggested to play a role in the seasonal phase locking of enso motivated by the fact that coupled climate models tend to underestimate this feature this study examines the representation of the sws in phase 5 of the coupled model intercomparison project cmip5 it is found that most models successfully reproduce the observed sws although the magnitude of the zonal wind stress anomaly is underestimated several significant differences between the models with and without the sws are identified including biases in the magnitude and spatial distribution of precipitation and sea surface temperature sst anomalies during enso multiple linear regression analysis suggests that the climatological meridional sst gradient as well as anomalous enso driven convective activity over the northwest pacific both might play a role in controlling the sws while the mode

intra skeletal calcite in a live collected porites sp impact on environmental proxies and potential formation process geochemical proxies measured in the carbonate skeleton of tropical coral porites sp have commonly been used to reconstruct sea surface temperature sst and more recently seawater ph nevertheless both reconstructed sst and ph depend on the preservation state of the skeleton here made of aragonite i e diagenetic processes and its related effects should be limited in this study we report on the impact of the presence of intra skeletal calcite on the skeleton geochemistry of a live collected porites sp the porites skeleton preservation state was analyzed using x ray diffraction and scanning electron microscopy sr ca mg ca u ca ba ca li mg and b ca ratios were measured at a monthly and yearly resolution using solution icp ms and multi collector icp ms the 11b signatures and the calcite percentages were acquired at a yearly timescale the coral colony presents two parts one with less than 3 calcite referred to as no calcite skeleton the other one corresponding to the skeleton formed during the last 4 yrs of growth with calcite percentages varying from 13 to 32 referred to as with calcite skeleton this intra skeletal calcite replaces partly or completely numerous center of calcification cocs all geochemical tracers investigated are significantly impacted by the presence of calcite the reconstructed sst decreases by about 0 1 c per calcite percent as inferred from the sr ca ratio such impact reaches up to 0 26 c per calcite percent for temperature deduced from the li mg ratio so less than 5 of such intra skeletal calcite does not prevent sst reconstructions using sr ca ratio but the percentage and type of calcite have to be determined before fine sst interpretation seawater ph reconstruction inferred from boron isotopes drop by about 0 011 ph unit per calcite percent such sensitivity to calcite presence is particularly dramatic for fine paleo ph reconstructions here we suggest that after being brought to shallow waters following a cyclone the studied coral was seasonally subjected to rainfall related water freshening that could have mimicked a vadose environment like can be encountered on raised fossil coral reefs nevertheless the process of calcite precipitation remains to be determined

quantifying the role of oceanic feedbacks on enso asymmetry the role of oceanic feedbacks in determining the asymmetry of el nino southern oscillation enso magnitude spatial structure and duration is quantified on the basis of a novel temperature variance budget results confirm previous studies that in the eastern pacific el nino warm temperature anomalies are larger in magnitude than la nina cold temperature anomalies mainly due to stronger positive oceanic feedbacks for el nino we find that la nina cold anomalies are typically stronger than el nino warm anomalies in the central pacific with a faster growth rate for cold anomalies due to a stronger positive thermocline feedback and weaker nonlinear damping the thermocline feedback related to recharge oscillator dynamics plays a dominate role and leads to asymmetry in the duration of el nino and la nina events in particular the thermocline feedback becomes significantly negative during the late decaying phase of el nino and speeds up its demise

compositional controls on early diagenetic pathways in fine grained sedimentary rocks implications for predicting unconventional reservoir attributes of mudstones diagenesis significantly impacts mudstone lithofacies processes operating to control diagenetic pathways in mudstones are poorly known compared to analogous processes occurring in other sedimentary rocks selected organic carbon rich mudstones from the kimmeridge clay and monterey formations have been investigated to determine how varying starting compositions influence diagenesis the sampled kimmeridge clay formation mudstones are organized into thin homogenous beds composed mainly of siliciclastic detritus with some constituents derived from water column production e g coccoliths s depleted type ii kerogen as much as 52 6 total organic carbon toc and others from diagenesis e g pyrite carbonate and kaolinite the sampled monterey formation mudstones are organized into thin beds that exhibit pelleted wavy lamination and are predominantly composed of production derived components including diatoms coccoliths and foraminifera in addition to type iis kerogen as much as 16 5 toc and apatite and silica cements during early burial of the studied kimmeridge clay formation mudstones the availability of detrital fe iii and reactive clay minerals caused carbonate and silicate buffering reactions to operate effectively and the pore waters to be fe ii rich these conditions led to pyrite iron poor carbonates and kaolinite cements precipitating preserved organic carbon being s depleted and sweet hydrocarbons being generated in contrast during the diagenesis of the sampled monterey formation mudstones sulfide oxidation coupled with opal dissolution and the reduced availability of both fe iii and reactive siliciclastic detritus meant that the pore waters were poorly buffered and locally acidic these conditions resulted in local carbonate dissolution apatite and silica cements precipitation natural kerogen sulfurization and sour hydrocarbons generation differences in mud composition at deposition significantly influence subsequent diagenesis these differences impact their source rock attributes and mechanical properties

a modern vs permian black shale the hydrography primary productivity and water column chemistry of deposition the sediment currently accumulating in the cariaco basin on the continental shelf of venezuela has an elevated organic carbon content of approximately 5 is accumulating under o2 depleted bottom water conditions so42 reduction is composed dominantly of foraminiferal calcite diatomaceous silica clay and silt and is dark greenish gray in color upon lithification it will become a black shale recent studies have established the hydrography of the basin and the level of primary productivity and bottom water redox conditions these properties are used to model accumulation rates of cd cr cu mo ni v and zn on the seafloor the model rates agree closely with measured rates for the uppermost surface sediment the model is applied to the meade peak phosphatic shale member of the phosphoria formation a phosphate deposit of permian age in the northwest united states it too has all of the requisite properties of a black shale although the deposit is a world class phosphorite it is composed mostly of phosphatic mudstone and siltstone chert limestone and dolomite it has organic carbon concentrations of up to 15 is strongly enriched in several trace elements above a terrigenous contribution and is black the trace element accumulation defines a mean primary productivity in the photic zone of the phosphoria basin as moderate at 500 g m 2 year 1 organic carbon comparable to primary productivity in the cariaco basin the source of nutrient enriched water that was imported into the phosphoria basin upwelled into the photic zone and supported primary productivity was an o2 minimum zone of the open ocean the depth range over which the water was imported would have been between approximately 100 and 600 m the mean residence time of bottom water in the basin was approximately 4 years vs 100 years in the cariaco basin the bottom water was o2 depleted but it was denitrifying or no3 reducing rather than so42 reducing

asymmetry in the duration of el nino and la nina abstract el nino and la nina are not a simple mirror image but exhibit significant differences in their spatial structure and seasonal evolution in particular sea surface temperature sst anomalies over the equatorial pacific cold tongue are larger in magnitude during el nino compared to la nina resulting in positive skewness of interannual sst variations the associated atmospheric deep convection anomalies are displaced eastward during el nino compared to la nina because of the nonlinear atmospheric response to sst in addition to these well known features an analysis of observational data for the past century shows that there is a robust asymmetry in the duration of el nino and la nina most el ninos and la ninas develop in late boreal spring summer when the climatological cold tongue is intensifying and they peak near the end of the calendar year after the mature phase el ninos tend to decay rapidly by next summer but many la ninas persist through the following year and often reintensify in

reversed spatial asymmetries between el nino and la nina and their linkage to decadal enso modulation in cmip3 models abstractthis study examines preindustrial simulations from coupled model intercomparison project phase 3 cmip3 models to show that a tendency exists for el nino sea surface temperature anomalies to be located farther eastward than la nina anomalies during strong el nino southern oscillation enso events but farther westward than la nina anomalies during weak enso events such reversed spatial asymmetries are shown to force a slow change in the tropical pacific ocean mean state that in return modulates enso amplitude cmip3 models that produce strong reversed asymmetries experience cyclic modulations of enso intensity in which strong and weak events occur during opposite phases of a decadal variability mode associated with the residual effects of the reversed asymmetries it is concluded that the reversed spatial asymmetries enable an enso tropical pacific mean state interaction mechanism that gives rise to a decadal modulation of enso intensity and that at least three cmip3 models realistically simu

the late frasnian kellwasser horizons of the harz mountains germany two oxygen deficient periods resulting from different mechanisms in the harz mountains germany three late devonian sections aeketal huhnertal and kellwassertal were analyzed for major and trace element concentration the inorganic geochemical data were used to determine the environmental conditions associated with the deposition of the two late frasnian black kellwasser horizons in a submarine rise environment low ti al and zr al values and slight enrichment in nutrient and organic matter related trace elements e g ba cu and ni suggest that the kellwasser horizons were deposited during two periods of minimum detrital input but relatively elevated primary production enrichments in u v and mo in both black kellwasser horizons and values of redox indices including u th v cr and ni co indicate oxygen restricted conditions prevailed during the late frasnian times under oxygen depleted conditions reductive diagenesis caused precipitation of iron sulphides such as pyrite that are observed with sem however variations in major and trace element concentrations are not similar in the two kellwasser horizons particularly regarding redox markers the lower kellwasser horizon seems to be more o2 depleted than the upper kellwasser horizon in some german sections on the basis of these results we propose that the two kellwasser horizons are not caused by identical conditions the lower kellwasser horizon results from increased primary productivity enhanced by land derived nutrient loading and which triggered the anoxic conditions recorded in drowned platform setting in contrast the upper kellwasser horizon results from the onset of oxygen impoverished bottom water in the deepest part of the ocean due to episodic water stratification during maximum frasnian flooding oxygen depleted water may have impinged shallower environment during the linguiformis transgressive pulse nutrients would have been released from organic matter decay under reducing conditions and brought up to the photic zone during episodic water mixing

contrasting eastern pacific and central pacific types of enso abstract surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of el nino southern oscillation enso in the tropical pacific an eastern pacific ep type and a central pacific cp type an analysis method combining empirical orthogonal function eof analysis and linear regression is used to separate these two types correlation and composite analyses based on the principal components of the eof were performed to examine the structure evolution and teleconnection of these two enso types the ep type of enso is found to have its sst anomaly center located in the eastern equatorial pacific attached to the coast of south america this type of enso is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical indian ocean in contrast the cp type of enso has most of its surface wind sst and subsurface anomalies confined in the central pacific and tends to onset develop and decay in situ

constraints on the accumulation of organic matter in upper ordovician lower silurian black shales from the lower yangtze region south china abstract the late ordovician to early silurian o s was an important period in which many significant geological events occurred during the o s transition organic rich black shales were widely deposited and became important unconventional energy sources paleoproductivity detrital input and redox conditions are the three major factors controlling organic matter om accumulation although the effect of each factor is relatively clear the complex influences of these factors remain poorly understood specifically the evolution of these factors and the corresponding influence on the accumulation of om during the o s transition has not yet been systematically investigated this paper investigates the constraints on om accumulation in o s transition black shales from the lower yangtze region based on graptolite fossil identification zircon u pb dating and geochemical analyses of a well sequenced drilling profile the results show that i the sy 1 core sequence was well constrained from graptolite zones wf2 447 62 ma to lm5 441 57 ma across the o s boundary with decreasing sedimentation rates srs in the upper katian wf2 to wf3 and increasing srs in the lower rhuddanian ii complementary volcanic inputs katian and rhuddanian and upwelling events hirnantian exerted strong control over paleoproductivity iii orogenic processes in south china controlled detrital inputs and redox conditions iv om accumulation in the lower yangtze area across the o s transition occurred in three stages in stage 1 wf2 wf3 strong volcanism boosted productivity whereas om preservation was not favored in the oxic environment in stage 2 wf4 lm3 upwelling and volcanism resulted in high productivity and provided the optimal configurations for om enrichment in stage 3 lm4 and later rare om was preserved due to terrestrial dilution and unfavorable preservation conditions eventually wf4 lm3 became the prominent om rich biozones due to the effective coordination of the controlling factors namely upwelling volcanism and redox conditions

coral boulders on melekeok reef in the palau islands an indicator of wave activity associated with tropical cyclones abstract waves generated by tropical cyclones and tsunamis cause various impacts such as coastal erosion and damage to infrastructure the intensity of tropical cyclones will probably increase in the near future as a result of global warming therefore predicting the likely impacts of these storms is a prime concern boulder deposits are one of the key proxies that assist our understanding of previous tropical cyclones and tsunamis and are important if we are to accurately project their future impacts in december 2012 typhoon bopha hit the palau islands and many boulders were probably deposited on the east coast of babeldaob island during the event this area is one of the few locations where it is possible to distinguish between deposits that were generated by tropical cyclone waves and tsunamis this study records the distribution of boulders from the shore to the reef crest at melekeok reef on babeldaob island and evaluates the relationship between the movement of boulders and the hydraulic forces generated by the waves using a hydrodynamic model and wave calculations in addition this study projects the coastal impacts of tropical cyclone waves in the near future many boulders have been deposited on the reef crest within 100 m of the reef edge and the maximum weight of the boulders is 2 2 tons the boulders are composed of massive corals e g platygyra and they originated from the upper reef slope the results of the hydrodynamic modeling indicate that these boulders were transported and deposited by the waves generated by typhoon bopha significant wave height 8 7 m or tcs with a similar intensity of typhoon bopha moreover there are no boulder deposits at the shore which implies that the reef has not been affected by tsunamis even if one or more tsunamis have inundated the reef the associated hydraulic forces appear to have been lower than those of typhoon bopha these findings indicate that typhoon bopha has probably generated the most intense wave event in recent times however it is likely that tropical cyclones more intense than typhoon bopha will affect the reef in the near future as the climate continues to warm through the 21st century consequently the study site will probably face an increased risk of coastal erosion and destruction of property if no plans are developed to reduce and manage such impacts

organic carbon accumulation and preservation in surface sediments on the peru margin concentrations and characteristics of organic matter in surface sediments deposited under an intense oxygen minimum zone on the peru margin were studied in samples from deck deployed box cores and push cores acquired by submersible on two transects spanning depths of 75 to 1000 m at 12 and 13 5 s the source of organic matter to the seafloor in these areas is almost entirely marine material as confirmed by the narrow range of of organic carbon obtained in the present study 20 3 to 21 6 pdb and the lack of any relationship between pyrolysis hydrogen index and carbon isotope composition organic carbon contents are highest up to 16 on the slope at depths between 75 and 350 m in sediments deposited under intermediate water masses with low dissolved oxygen concentrations 5 mol kg even at these low concentrations of dissolved oxygen however the surface sediments that were recovered from these depths are dominantly unlaminated strong currents up to 30 cm s associated with the poleward flowing peru undercurrent were measured at depths between 160 and 300 m on both transects the seafloor in this range of water depths is characterized by bedforms stabilized by bacterial mats extensive authigenic mineral crusts and or thick organic flocs constant advection of dissolved oxygen although in low concentrations active resuspension of surficial organic matter activity of organisms and transport of fine grained sediment to and from more oxygenated zones all contribute to greater degradation and poorer initial preservation of organic matter than might be expected under oxygen deficient conditions dissolved oxygen concentrations ultimately may be the dominant affect on organic matter characteristics but reworking of fine grained sediment and organic matter by strong bottom currents and redeposition on the seafloor in areas of lower energy also exert important controls on organic carbon concentration and degree of oxidation in this region

analysis of the non linearity in the pattern and time evolution of el nino southern oscillation in this study the observed non linearity in the spatial pattern and time evolution of el nino southern oscillation enso events is analyzed it is shown that enso skewness is not only a characteristic of the amplitude of events el ninos being stronger than la ninas but also of the spatial pattern and time evolution it is demonstrated that these non linearities can be related to the non linear response of the zonal winds to sea surface temperature sst anomalies it is shown in observations as well as in coupled model simulations that significant differences in the spatial pattern between positive el nino versus negative la nina and strong versus weak events exist which is mostly describing the difference between central and east pacific events central pacific events tend to be weak el nino or strong la nina events in turn east pacific events tend to be strong el nino or weak la nina events a rotation of the two leading empirical orthogonal function modes illustrates that for both el nino and la nina extreme events are more likely than expected from a normal distribution the bjerknes feedbacks and time evolution of strong enso events in observations as well as in coupled model simulations also show strong asymmetries with strong el ninos being forced more strongly by zonal wind than by thermocline depth anomalies and are followed by la nina events in turn strong la nina events are preceded by el nino events and are more strongly forced by thermocline depth anomalies than by wind anomalies further the zonal wind response to sea surface temperature anomalies during strong el nino events is stronger and shifted to the east relative to strong la nina events supporting the eastward shifted el nino pattern and the asymmetric time evolution based on the simplified hybrid coupled rechoz model of enso it can be shown that the non linear zonal wind response to sst anomalies causes the asymmetric forcings of enso events this also implies that strong el ninos are mostly wind driven and less predictable and strong la ninas are mostly thermocline depth driven and better predictable which is demonstrated by a set of 100 perfect model forecast ensembles

organic geochemical and mineralogical characterization of the lower silurian longmaxi shale in the southeastern chongqing area of china implications for organic matter accumulation abstract abundant in organic matter the lower silurian longmaxi shale in the upper yangtze platform south china has been demonstrated to play important roles in the petroleum system as both a good source rock and a shale gas reservoir in order to better understand the heterogeneous organic matter accumulation of such shales in the southeastern chongqing area the vertical variations of total organic carbon toc contents mineral concentrations and biomarker distributions were systematically analyzed in this study the longmaxi formation consists of fine grained siliciclastic rocks deposited in a restricted marine shelf environment and it can be further subdivided into two members the lower member is enriched in toc whereas a diminished toc content is documented in the upper member laterally the toc content gradually drops southeast ward in the study area the mineralogical compositions dominated by quartz and clay and to a lesser extent feldspar and carbonate show good correlations with toc contents vertically especially in the lower member saturated and aromatic hydrocarbon biomarkers indicate a dominant organic matter origin from lower hydrobionts algae and bacteria in a reducing marine environment negative correlation relationships between toc contents and terrigenous clastic minerals indicate the predominant role of dilution of terrigenous clastic materials in controlling the organic matter accumulation the sea level drop combined with the continuously active xuefeng uplift contributed to more terrigenous clastic inputs into the study area which resulted in a significant reduction of toc content in the upper longmaxi member

evidence for a mid holocene tsunami deposit along the andaman coast of thailand preserved in a mangrove environment abstract klong thap lamu a large mangrove fringed tidal channel along the northern andaman coast of thailand provides an ideal location to test the hypothesis that a paleotsunami record can be preserved in the sediments of a mangrove forest the 2004 indian ocean tsunami destroyed local swaths of mangrove forest with highly variable widths up to 300 m left in the wake of the tsunami is a thin mantling of laterally discontinuous sand macerated shells and localized coral rubble that is being mixed rapidly into the underlying mangrove peat transects across the channel s tsunami modified shore show that the sand layer thins abruptly at the border of the undisturbed mangroves suggesting that the energy of the wave dissipated quickly as it entered the forest the distribution and sedimentology of the 2004 tsunami deposit unit ti suggest that any paleotsunami deposit within this mangrove environment should be spatially restricted and thoroughly bioturbated sediment cores collected from within the 2004 tsunami zone penetrate a buried coral shell peat unit unit tiii that tapers inland unit tiii is strikingly similar to unit ti except for unit tiii s diffuse sedimentology which we attribute to extensive bioturbation unit tiii also cross cuts an identified facies boundary that is traceable across the width of the 2004 tsunami zone rather than a facies boundary associated with the regional early to late holocene sea level regression stratigraphic correlations suggest that unit tiii represents an event horizon i e tsunami ams 14 c dates on material from within unit tiii combined with an upper bracketing age suggest that the tsunami event occurred sometime between 2720 and 4290 cy bp if correct this tsunami predates the 3 4 tsunami events recognized to the north at koh phra thong unit tiii is however a potential far field equivalent of a recently recognized paleotsunami deposit on the southwestern indian coast ca 3 710 years before present nair et al 2010

scavenged excess aluminum and its relationship to bulk titanium in biogenic sediment from the central equatorial pacific ocean we present results from chemical analyses of al and ti in surface sediment sampled along two cross equator latitudinal transects at 135w and 140w in the central equatorial pacific ocean although traditionally both al and ti are considered to reside exclusively within terrigenous phases in marine sediment these sediments present extremely high al ti ratios that are several times that of average shale and other potential crustal sources a sharp maximum in al ti is observed slightly south of the equator where sedimentary bulk accumulation rate bar is also highest reflecting elevated productivity in the overlying water caused by surface water divergence bulk al ti decreases sharply away 2 latitude to near crustal values at 4 north and south the latitudinal profiles of al ti are entirely unrelated to the concentration of the biogenic components as well as to the absolute accumulation of al and ti these results indicate the presence of a significant scavenged component of al sourced directly from seawater during particle settling the data from the two transects analytically and oceanographically confirms our earlier work that was based on the single 135w transect calculations of alexcess indicate that the highest al ti ratios correspond to 50 of the total al being unsupported by the small amount of terrigenous phases present these results are consistent with previous and ongoing studies of biogenic sediment suspended particulate matter and sediment trap material quantitative use of al as an index of terrigenous material may therefore lead to an overestimation by a factor of two of the true terrigenous load in marine sediment sedimentary rock and settling particles because bulk al ti appears to respond to sedimentary bar which in biogenic regimes is linked to surface water productivity downcore records of al ti in biogenic sediment may track productivity changes through time such al ti proxy records may be applicable in sediment of all ages unlike radionuclide tracers which are limited by radioactive decay to use over the past hundreds of kyr

el nino and la nina sea surface temperature anomalies asymmetry characteristics associated with their wind stress anomalies 1 the asymmetric nature of el nino and la nina sea surface temperature sst anomalies is investigated by the use of national centers for environmental prediction reanalysis data and various ocean and atmosphere models it is demonstrated that the relatively weak sst anomalies during la nina compared with those of el nino are related to the westward shift of wind stress anomalies by 10 15 the asymmetric characteristics of atmospheric responses are confirmed by the general circulation model experiments with the two different sst anomalies which have equal amplitude but are of opposite sign from each other the experiments with an intermediate ocean model and a hybrid coupled model clearly show that the sst anomalies over the equatorial pacific become weaker as the zonal wind stress shifts to the west not only the amplitude but also the oscillation timescale of the sst anomaly is shown to be sensitive to the location of wind stress anomalies the duration of la nina which is rather shorter than that of el nino is also related to the longitudinal displacement of the wind stress anomaly

effect of sedimentary environment on the formation of organic rich marine shale insights from major trace elements and shale composition abstract sedimentary environment and redox conditions play a significant role in the formation of organic rich shale the vertical variations of major trace elements toc total organic carbon and mineral compositions were investigated for the lower silurian longmaxi typical marine shale in the upper yangtze platform south china to decipher sedimentary environment redox conditions detrital input sedimentation rate sr paleoproductivity and watermass restriction this gives insight to the effects of variations in sedimentary environment on the formation of organic rich shale the results show that the lower longmaxi formation is composed of three systems tracts tst transgressive systems tract ehst early highstand systems tract and lhst late highstand systems tract from tst to lhst the contents of toc quartz and pyrite decline steadily whereas clay minerals and carbonate show an increasing trend thus organic rich siliceous orss organic moderate mixed omms and organic lean argillaceous olas shales are dominant for tst ehst and lhst respectively due to a continues fall of the relative sea level a deep water shelf environment with anoxic condition high paleoproductivity and low detrital input in tst gradually evolves into a semi deep water environment with dysoxic oxic conditions moderate paleoproductivity and moderate detrital influx in ehst further to an environment of oxic condition low paleoproductivity and high detrital flux in lhst as evidenced by mo toc and mo u patterns orss was deposited in a moderately restricted watermass weaker than black sea which progressively evolved into an enhanced restriction degree during the deposition of omms and olas due to a fall of relative sea level major trace elements and excess silica ex sio2 concentrations illustrate that origins of quartz in the lower longmaxi shale are primarily terrigenous biogenic and authigenic smectite illitization the average proportions of ex sio2 biogenic and authigenic quartz are 52 34 24 86 and 6 57 for orss omms and olas respectively biogenic quartz is the dominant contributor to ex sio2 while the contribution of authigenic quartz is limited and the formation of the former is earlier than the latter according to the diagenetic transformation temperature as both biogenic quartz and organic matter are firmly related to the abundance and preservation of paleoorganisms anoxic condition high paleoproductivity low detrital flux and moderate restriction collectively control the high enrichment and preservation of organic matter and biogenic quartz while oxic condition low paleoproductivity high detrital flux and stronger watermass restriction are unfavorable for the enrichment of biogenic quartz and organic matter

catastrophic impact of typhoon waves on coral communities in the ryukyu islands under global warming 1 typhoon generated storm waves generally cause mechanical damage to coral communities on present day reefs and the magnitude and extent of damage is predicted to increase in the near future as a result of global warming therefore a comprehensive understanding of potential future scenarios of reef ecosystems is of prime interest this study assesses the current status of coral communities on ibaruma reef ryukyu islands on the basis of field observations engineering and fluid dynamic models and calculations of wave motion and predicts the potential effects of a super extreme typhoon incident wave height h 20 m wave period t 20 s on the reef on the present day reef massive corals occur in shallow lagoons and tabular corals occur from the reef crest to the reef slope the observed distribution of corals which is frequently attacked by moderate h 10 m t 10 s and extreme h 10 m t 15 s typhoons is consistent with the predictions of engineering models moreover this study indicates that if a super extreme typhoon attacks the reef in the near future massive corals will survive in the shallow lagoons but tabular corals on the reef crest and reef slope will be severely impacted the findings imply that super extreme typhoons will cause a loss of species diversity as the tabular corals are important reef builders and are critical to the maintenance of reef ecosystems consequently reef restoration is a key approach to maintaining reef ecosystems in the wake of super extreme typhoons

geochemical characteristics redox conditions and organic matter accumulation of marine oil shale from the changliang mountain area northern tibet china abstract the organic rich changliang mountain oil shale located in the north qiangtang depression northern tibet is considered to be excellent mineral resource in china the changliang mountain oil shale reported here was deposited in a tidal flat lagoon environment and is characterized by black thin layered oil shales intercalated with dark gray marls here we present geochemical data from the changliang mountain oil shale profile in order to investigate the mechanism of organic matter om accumulation and to establish the formation model for the marine oil shale deposition total organic carbon toc values range from 2 96 to 23 47 in the oil shale samples while the marl samples contains low toc contents ranging from 0 06 to 0 21 in the organic rich oil shale sediments many redox indicators including mo al ratios v cr ratios th u ratios ni co ratios and the relationship of mo to toc suggest a deposition under dysoxic to anoxic environments subsequently the bottom water evolved into an oxic water body when the organic poor marls were deposited however the negative and or weak relationship between toc and productivity indices p ti and ba al indicates that om accumulation was not controlled mainly by primary productivity but dysoxic anoxic bottom water environment a stratified water column may be initiated by the supply of fresh water from the continent nearby combining with warm and humid climate which is beneficial to the reproduction of marine organisms the death and bury of these organisms could lead to the formation of dysoxic anoxic bottom waters and enhance the preservation of om in this study a preservation model of the changliang mountain oil shale was established the model implies that excellent preservation is the major controlling factor for om enrichment in the oil shale layer in addition factors such as mixed deposition with clay minerals and detrital matter input cannot be ignored for their influence on om enrichment

productivity or preservation the factors controlling the organic matter accumulation in the late katian through hirnantian wufeng organic rich shale south china abstract the wufeng organic rich shale is widespread in the upper yangtze platform and it is one of the most advantageous shale gas producers in china its deposition commenced with the onset of the boda warming event in the late katian and terminated at the hirnantian glacial maximum the depositional mechanism of the wufeng formation was poorly understood owing to its relatively thin thickness being interpreted as the result of organic matter om accumulation in a shelf setting under anoxic conditions this study integrated detailed geochemical analyses based on the core samples from three boreholes which are located in the outer middle and inner shelf of the upper yangtze platform in order to investigate the depositional environments during the deposition of the wufeng formation geochemical redox proxies mo ef u ef and v cr and productivity proxies p baxs sixs indicate that the deposition of the wufeng formation was associated with four intervals wf1 to wf4 each characterized by its unique geochemical features related to sea level fluctuations black siliceous mudstones deposited during wf1 and wf2 are relatively organic lean due to low productivity less favorable preservation conditions and terrestrial dilution whereas black siliceous mudstone deposited during wf3 and wf4 is organic rich due to high paleoproductivity and conducive preservation conditions the geochemical proxies cd mo co x mn associated with the modern upwelling settings were replicated in the wufeng formation revealing that the outer shelf of the upper yangtze platform was dominated by persistent upwelling the upwelling driven primary productivity is considered as the first order control for the om enrichment at the outer shelf of the upper yangtze platform seasonal upwelling may influence the middle shelf of the upper yangtze platform where both primary productivity and preservation played essential roles in the om accumulation in contrast the om accumulation at the inner shelf was fundamentally driven by good preservation conditions

geochemistry of recent toc rich sediments from the gulf of california and the black sea major and minor elements incl ag as ba cd co cr cu mn mo ni pb sr v zn have been determined in recent sediments from the gulf of california upwelling area and black sea sapropels in order to reinterpret their chemical composition in view of reliable seawater and plankton data the chemistry of the gulf of california sediments reflects regeneration processes which occur in the water column i e only a small fraction 10 of elements like cd which in seawater are coupled to the labile nutrients c n p is buried in the sedimentary column in contrast elements like the more resistant nutrients si undergo a deeper regeneration cycle ba several trace metals which are present in comparatively higher concentrations in seawater as mo u v and at the same time are reactive under reducing conditions and or are able to form stable sulfides are fixed in the sediments during early diagenesis the early diagenetic behavior of ba is closely related to bacterial sulfate reduction the formation of barite concretions is discussed anoxic conditions in the water column act as ideal traps for a number of redox sensitive and or stable sulfide forming elements a simple trace metal balance calculation shows that the chemical composition of black sea sapropels is controlled by fluvial and mediterranean seawater element input and the accumulation rate of terrigenous detrital material

seawater as the source of minor elements in black shales phosphorites and other sedimentary rocks many of the minor elements in seawater today have a concentration depth profile similar to that of the biologically essential nutrients no 3 and po3 4 they show a relative depletion in the photic zone and enrichment in the deep ocean the difference between their surface and deep ocean values normalized to the change in po3 4 approaches the average of measured minor element p ratios in marine plankton although individual analyses of the latter show extreme scatter for a variety of reasons despite this scatter in the minor element analyses of plankton agreement between the two sets of data shows unequivocally that an important marine flux of many minor elements through the ocean is in the form of biogenic matter with a composition approaching that of plankton this interpretation is further supported by sediment studies particularly of sediments which accumulate in shelf slope environments where biological productivity in the photic zone is exceptionally high and organic carbon contents of the underlying sediment elevated the interelement relations observed for some of these sediments approach the average values of plankton these same interelement relations are observed in many marine sedimentary rocks such as metalliferous black shales and phosphorites rocks which have a high content of marine fractions e g organic matter apatite biogenic silica and carbonates many previous studies of the geochemistry of these rocks have concluded that local hydrothermal activity and or seawater with an elemental content different from that of the modern ocean was required to account for their minor element contents however the similarity in several of the minor element ratios in many of these formations to minor element ratios in modern plankton demonstrates that these sedimentary rocks accumulated in environments whose marine chemistry was virtually identical to that seen on continental shelf slopes or in marginal seas of the ocean today the accumulation of the marine fraction of minor elements on these ancient sea floors was determined largely by the accumulation of organic matter settling from the photic zone and with a composition of average plankton a second marine fraction of minor elements in these rocks accumulated through precipitation and adsorption from seawater the suite of elements in this fraction reflects redox conditions in the bottom water as determined by bacterial respiration for example high mn high cr v and high mo concentrations above those which can be attributed to the accumulation of planktonic matter characterize accumulation under bottom water oxidizing denitrifying and sulfate reducing conditions respectively

asymmetry and nonlinearity of the influence of enso on the northern winter stratosphere 1 observations the el nino southern oscillation enso has significant effects on the extratropical stratosphere this study explores the nonlinearity and the asymmetry of these influences by distinguishing the different effects of four types of enso moderate el nino strong el nino moderate la nina and strong la nina it is revealed that the moderate el nino and the strong la nina are much more efficient than the strong el nino and the moderate la nina respectively in modulating the northern winter stratospheric variability resulting in significant nonlinearity and asymmetry the tropical rainfall anomalies induced by a moderate el nino or a strong la nina are centered over the central equatorial pacific region near the dateline while the convection responses to a strong el nino or a moderate la nina are centered farther eastward accordingly the anomalous pacific north america wave train pattern is modulated by enso in a nonlinear and asymmetric way which leads the large nonlinear and asymmetric components of the vertical eliassen palm e p flux responses to enso the increase of planetary wave activity in the extratropical stratosphere in moderate el nino winters is thus greater than in strong el nino winters whereas a strong la nina gives a larger decrease in propagation than a moderate la nina the relatively strong weak e p flux responses to moderate strong el nino and strong moderate la nina explain the remarkable nonlinearity and asymmetry in the response of the extratropical stratosphere to enso

the simplest enso recharge oscillator 1 eastern pacific sea surface temperature sst and mean equatorial pacific thermocline depth are key variables in el nino southern oscillation enso a linear fit to observations leads to a remarkably simple picture enso can be represented by a classical damped oscillator with sst and thermocline depth playing the roles of momentum and position respectively an independent fit of observed relationships between western and eastern thermocline depth central wind stress and eastern pacific sst yields the same picture and supports a recharge oscillator interpretation the oscillation arises from the interaction between the recharge time of the warm pool and the time delay between east and west pacific both finite kelvin wave speed and sst dynamics contribute to the time delay including seasonality in the description we find two periods of relative instability boreal spring with a large phase progression and autumn with nearly stationary phase

pyrite geochemistry in the toarcian posidonia shale of south west germany evidence for contrasting trace element patterns of diagenetic and syngenetic pyrites authigenic pyrite grains from a section of the lower toarcian posidonia shale were analysed for their trace element contents and sulphur isotope compositions the resulting data are used to evaluate the relationship between depositional conditions and pyrite trace element composition by using factor analysis trace elements in pyrite may be assigned to four groups i heavy metals including cu ni co pb bi and tl ii oxyanionic elements as mo and sb iii elements partitioned in sub microscopic sphalerite inclusions zn and cd and iv elements related to organic or silicate impurities ga and v results indicate that trace element contents in pyrite depend on the site and mechanism of pyrite formation with characteristic features being observed for diagenetic and syngenetic pyrites diagenetic pyrite formed within anoxic sediments generally has a high heavy metals content and the degree of pyritization of these elements increases with increasing oxygen deficiency similar to the degree of pyritization of reactive fe the highest gradient in the increase of the degree of trace element pyritization with bottom water oxygenation was found for the elements ni cu mo as tl in contrast syngenetic pyrite formed within a euxinic water column typically is enriched in as mo and sb but is low in heavy metals and the geochemical variation reflects changes in sea water composition

multiple controls on the preservation of organic matter in devonian mississippian marine black shales geochemical and petrographic evidence geochemical and petrographic analysis of an interval of black shales between the huron shale member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian suggests that multiple controls influenced the accumulation of organic matter stratigraphic trends were determined following detailed analysis of a core from the central appalachian basin d6 montgomery county ky specifically c s fe relationships mo v v ni ni co and v cr were used to assess paleo redox conditions during sediment accumulation the role of clastic input was evaluated using ti al k al and si al and c p was used as a proxy for paleoproductivity the terrestrial to marine maceral ratio t m vitrinite plus inertinite alginite plus bituminite was used to evaluate changes in om source c s fe relationships and trace element ratios suggest anoxic conditions prevailed during deposition of much of the upper part of this interval however bottom water conditions were intermittently dysoxic during accumulation of the huron shale member and possibly dysoxic to marginally oxic during accumulation of the lowermost huron shale member productivity appears to have been an important factor in the accumulation of corg and high c p ratios are consistent with a productivity anoxia feedback mechanism in addition nutrients from increased terrestrial weathering may have contributed to enhanced productivity variations in sediment influx may also have influenced corg concentrations through sediment starvation one of the more significant observations in this work is an increase in terrestrial om inertinite and vitrinite up section which may reflect vegetative changes occurring on land during this time interval most of this increase is due to inertinite much of which appears to be fusinitic in origin and hence may be fossil charcoal this latter observation has implications for the expansion of land plants into drier niches and for late devonian atmospheric oxygen levels introduction of more resistant terrestrial om to anoxic basins may have been an important factor in the preservation of high carbon 10 intervals especially in the cleveland member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian

relationship between sedimentation rate and total organic carbon content in ancient marine sediments an analysis of deep sea drilling project dsdp cores indicates quantitative relations between sedimentation rate and total organic carbon content in fine grained ancient marine sediments of jurassic cretaceous and cenozoic ages these relations are largely independent of geographic setting geologic age and differential compaction but are strongly affected by lithology for any given sedimentation rate the total organic carbon content toc by weight percent increases from calcareous sediments to calcareous siliceous sediments to siliceous sediments to black shale the total organic carbon content also varies with the sedimentation rate for each lithology starting at low rates of sedimentation toc first increases with sedimentation rate owing to a more rapid passage of the sediment through the near surface zone of intense organic degradation above a critical sedimentation rate toc typically decreases with increasing sedimentation rate owing to clastic dilution of the organic input near surface organic degradation however continues to be less efficient at higher burial rates therefore the oil generation potential of oil prone organic constit ents should continue to increase with increasing sedimentation rate similar relations were also established between total organic carbon accumulation rate and grain accumulation rate and support both reduced near surface organic degradation and the clastic dilution effect by using the toc cutoff for a petroleum source rock these relations can be used to identify the presence of petroleum source rock formations in marine sedimentary basins the results of this study may have important implications for petroleum exploration in frontier regions sedimentation rate can be determined from seismic reflection records or seismic isopachs in basins where only limited well data are generally available seismic records can thus be used to identify potential petroleum source rocks and to estimate the relative oil generation potential of source rocks in various frontier sedimentary basins prior to and during the early phases of exploratory drilling

wind stress variations and interannual sea surface temperature anomalies in the eastern equatorial pacific abstract vertical advection of temperature is the primary mechanism by which el nino southern oscillation enso time scale sea surface temperature sst anomalies are generated in the eastern equatorial pacific variations in vertical advection are mediated primarily by remote wind forced thermocline displacements which control the temperature of water upwelled to the surface however during some enso events large wind stress variations occur in the eastern pacific that in principle should affect local upwelling rates the depth of the thermocline and sst in this study the impact of these wind stress variations on the eastern equatorial pacific is addressed using multiple linear regression analysis and a linear equatorial wave model the regression analysis indicates that a zonal wind stress anomaly of 0 01 n m 2 leads to approximately a 1 c sst anomaly over the nino 3 region 5 n 5 s 90 150 w due to changes in local upwelling rates wind stress variations of this magnitude occurred in the easte

disturbance gradients on inshore and offshore coral reefs caused by a severe tropical cyclone tropical storms cyclones hurricanes or typhoons are the most severe form of mechanical disturbance of coral reefs in 2005 severe tropical cyclone ingrid crossed the far northern great barrier reef a region that had not been affected by a major disturbance for several decades and where benthic data had been collected before the cyclone crossed this storm provided a unique opportunity to improve understanding of the extent and type of damage inflicted on inshore and offshore coral reefs along a gradient of wind speeds modeled maximum wind speeds ranged from 46 m s 1 equivalent to category 4 near the path to 22 m s 1 category 1 70 km to either side of the path surveys of 82 sites on 32 reefs along the wind gradient showed that the types and intensity of disturbance were well explained by local maximum wind speed and by spatial and biotic factors while offshore reefs had the deepest depth of damage inshore reefs had the greatest rates of coral breakage and dislodgement on a severely affected inshore reef hard coral cover decreased about 800 taxonomic richness decreased 250 the density of coral recruits decreased by 30 while massive coral cover remained unaltered maximum winds 33 m s 1 and 40 m s 1 caused catastrophic damage on inshore and offshore reefs respectively observations from this cyclone were used to predict potential changes in storm related coral loss under altered cyclone intensity scenarios

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

facies patterns and geography of the yangtze region south china through the ordovician and silurian transition abstract lithofacies and biofacies changes through the ordovician and silurian transition on the yangtze platform are coincident with stepwise mass extinctions recovery events global sea level changes and regional palaeogeographic configurations facies patterns through three intervals the late mid ashgill hirnantian and early rhuddanian indicate that black shale occupied most of the yangtze platform region during the late mid ashgill and early rhuddanian while the hirnantian possesses more diverse facies types the black shale was replaced by carbonate facies during the hirnantian coincident with a global sea level low stand biofacies changes from the late mid ashgill graptolitic to the hirnantian shelly facies were apparently signalled by gradual and diachronous existence of a mixed facies the manosia facies in the yangtze region however the biofacies change was abrupt from the hirnantian to the early rhuddanian when graptolitic facies occupied most areas on the yangtze platform leaving only a very narrow limited belt of shelly facies along the southern margin of the platform in northern guizhou the early rhuddanian unified biofacies pattern is a result of a global sea level rise which may be synchronized with a recovery bioevent of graptolites after hirnantian mass extinction

oceanic environment changes caused the late ordovician extinction evidence from geochemical and nd isotopic composition in the yangtze area south china the ordovician silurian o s transition was a critical interval in geological history multiple geochemical methods are used to explore the changes in oceanic environment the nd isotopic compositions in the yangtze sea are controlled by two sources the continental erosion and the panthalassa ocean high end t values during the katian late hirnantian and rhuddanian intervals are associated with the high sea level which resulted in less terrestrial input based on the low ti al and zr al ratios in contrast low end t values during the early hirnantian interval are related to the sea level fall in this case the exposure of submarine highs and the growth of yangtze oldlands could lead to more continental materials being transported into the yangtze sea based on high ti al and zr al ratios in addition the negative end t excursion can also be attributed to the weak circulation between the yangtze sea and panthalassa ocean when sea level was low furthermore the sea level eustacy plays a significant role in the changes in redox water conditions the redox indices mainly uef ce ce and corg pt across the o s transition show a predominance of anoxic ocean over the yangtze sea during the katian late hirnantian and rhuddanian intervals and an oxygenated episode was briefly introduced during the early hirnantian period because of the fall in sea level the late ordovician biotic crisis was marked by two phase extinction events and the change in sea level and redox chemistry may be the important kill mechanisms

effects of weathering on nickel and vanadyl porphyrins of a lower toarcian shale of the paris basin the effects of weathering on the organic matter within a narrow sediment interval from surficial to 10 m depth belonging to the lower toarcian shales of the paris basin were studied at a molecular level among the compositional changes observed the most striking feature is a severe breakdown of the metalloporphyrins ni and vo at the surface as evidenced by quantitative data in addition this degradation of the geoporphyrins is accompanied by substantial modification of their composition with preferential degradation of porphyrins with exocyclic rings over polyalkylporphyrins these quantitative and qualitative changes are thought to result from exposure of the sediment to weathering conditions more specifically abiotic oxidation is likely to be the main weathering process responsible for this superficial alteration of the sedimentary porphyrins this is particularly suggested by oxidation experiments carried out on a mixture of sedimentary nickel and vanadyl porphyrins where oxidation of the former complexes occurs at a faster rate thus geoporphyrins may be used as molecular indicators to evaluate the degree of oxidation of weathered geological samples containing this kind of molecule

glacial interglacial variability in the eastern tropical north pacific oxygen minimum zone recorded by redox sensitive trace metals 1 changes in the intensity of the oxygen minimum zone omz in the eastern tropical north pacific over the past 140 kyr are recorded as enrichments and depletions of redox sensitive metals in sediments of two piston cores one within and one below the modern omz from the continental margin off mazatlan mexico 22 41 n 106 28 w concentrations of al 7 7 0 6 ti 0 37 0 03 fe 3 1 0 25 mn 320 31 ppm and ba 560 82 ppm in core nh15p within the omz at 420 m water depth were relatively constant over the last 110 kyr in contrast concentrations of cd 4 8 2 ppm cu 29 8 9 1 ppm u 9 1 3 7 ppm mo 12 1 5 0 ppm v 138 2 51 9 ppm and re 45 8 25 5 ppb were all at least 30 higher in interglacial stages compared to glacial stages concentrations of al 7 4 0 3 ti 0 35 0 03 fe 3 5 0 4 and mn 385 77 ppm in core nh22p below the omz at 2025 m water depth were comparable to those in core nh15p while concentrations of ba 1662 292 ppm were about a factor of three higher in contrast concentrations of cd 0 9 0 3 ppm u 6 6 0 9 ppm mo 3 2 1 2 ppm v 81 8 10 1 ppm and re 25 4 12 ppb were lower in sediments of comparable age than the concentrations of these same metals in the omz core and the differences in their concentrations over glacial interglacial cycles were less pronounced than those in shallower core comparison of the nonlithogenic fraction of metals in the sediments with their estimated contribution from plankton suggests that organic matter is probably the major source of cu ba and perhaps cd to the sediment whereas the indirect effects of organic carbon and low bottom water oxygen concentrations on sediment redox state appear to be more important controls on the distributions u re mo and v changes in the depth at which re and mo precipitated in the sediments and in the re mo ratio suggest that the redox state of the surface sediment and overlying water at both core depths varied over time re and mo removal depths were shallower and re mo ratios were lower at the omz site than in deeper water suggesting that a more reducing environment prevailed over time at the shallower site although the redox state of the waters and sediment at both sites varied over glacial interglacial cycles the omz likely was never anoxic in the last 140 kyr this variability in redox state could be attributed to changes in regional export productivity changes in ocean circulation or a combination of both processes a paleoproductivity reconstruction from biogenic ba data suggests that glacial productivity was considerable lower than it was during interglacial stages model results suggest that the oxygen penetration depth an indicator of sediment redox state changed less than 1 cm as a result of the change in productivity changes in oxygen penetration depth estimated from re and u removal depths are significantly larger suggesting that changes in ventilation are a more important control on sediment redox state overall trace metal results confirm the tight coupling between ocean circulation marine productivity and global change

impact on the coral reefs at yongle atoll xisha islands south china sea from a strong typhoon direct sweep wutip september 2013 abstract relatively little is known about the extent and distribution of damage to coral reefs by typhoons in the south china sea especially in remote reefs where typhoons occur frequently a strong typhoon wutip jtwc category 3 directly struck the yongle atoll on 29 september 2013 causing 62 deaths and sinking dozens of ships in the yongle atoll maritime area xisha islands south china sea surveys on coral reefs at yongle atoll were conducted using scuba diving before july 2013 and after 8 days the typhoon sweep the results show that the effects of wutip on coral reefs were patchy as a result of varying coral reef geomorphology and depth the typhoon caused significant damage to reef associated depths on the passage of the atoll where currents generated by the typhoon produced the strongest energy coral destruction was most spectacular at the 2 m depth 46 living scleractinian corals were damaged at 6 m and 15 m depths damage to the coral reefs were minimal the shallow fore reef area on the steep slopes the upper region of the outer slopes with depths between 2 and 6 m were the principal zones of the typhoon effect however the vertical part of the steep slopes were mainly damaged indirectly waves rolling boulders or corals which were less severely affected than the shallow fore reef steep slope area on the low angle slopes the correlation between the typhoon damage to coral reefs and depth was low because the wave and current energy induced by the typhoon were homogenously attenuated along gentle slopes under the stress of global warming destructive damage to coral reefs on the xisha islands is expected to increase and will require frequent monitoring to determine trends in the near future

enso influence on the north atlantic european climate a non linear and non stationary approach el nino southern oscillation enso impact on the north atlantic european sector nae is still under discussion recent studies have found a non stationary feature of this teleconnection suggesting an effective modulating role of the ocean mean state nevertheless physical explanations about the underlying mechanisms have been little studied in the available literature in addition enso events show different sst spatial patterns phases and amplitudes which can also influence on the related remote impacts in view of all this in the present study a set of partially coupled experiments have been performed with a global atmospheric general circulation model in which different sst enso patterns are superimposed over distinct pacific and atlantic sst mean states these sst background conditions are constructed according to the observational difference between periods with a distinct impact of enso on the leading euro mediterranean rainfall mode in late winter early spring our results point to two distinct mechanisms associated with enso that can be modulated by the sst mean state 1 the thermally driven direct circulation walker and hadley cells connecting the atlantic and pacific basins and 2 the rossby wave propagation from the tropical pacific to the north atlantic the former elucidates that the positive nao like pattern usually related to la nina events could be only valid for selected decades the latter explains a reinforced signature of eastern pacific ninos on the euro mediterranean rainfall when the tropical pacific is warmer than usual and the north atlantic is colder than usual this feature is consistent with the changing enso impact identified in previous studies and demonstrates how the enso teleconnection with the nae climate at interannual timecales could be modulated by multidecadal changes in the sst according to our results the assumption of stationarity which is still common to many studies of enso teleconnections clearly has to be questioned

trace element behavior and redox facies in core shales of upper pennsylvanian kansas type cyclothems the black shale submember of core shales of pennsylvanian kansas type cyclothems is highly enriched in redox sensitive trace elements tes relative to the overlying gray shale submember as well as to many other modern and ancient organic rich deposits controls on trace element behavior in the black shale can be inferred from trace element enrichment factors efs relative to gray shale and the relationship of tes to total organic carbon toc most tes conformed to one of two patterns 1 mo u v zn and pb exhibited moderate efs and strong covariation with toc in samples having 10 wt toc and 2 cu ni cr and co exhibited low efs and moderate to strong covariation with toc in all samples these patterns are inferred to represent different responses to benthic redox conditions the first pattern is characteristic of tes of strong euxinic affinity i e those taken up in solid solution by fe sulfide or involved in other reactions catalyzed by free h2s and resident mainly in authigenic phases whereas the second pattern is characteristic of tes of weak euxinic affinity i e those not strongly influenced by the presence of free h2s and resident mainly in the organic carbon or detrital fractions of the sediment these inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples euxinic conditions were considered to have existed if at least two of four redox indicator trace elements mo u v zn showed euxinic levels of enrichment and nonsulfidic anoxic conditions were inferred otherwise the validity of the procedure is indicated by 1 agreement among all four redox indicators for a large majority of samples 69 of 185 2 among samples yielding a mixed redox signal a systematic sequence of te enrichment v zn mo u and 3 for tes of weak euxinic affinity reduced variance among samples representing each redox facies sequential enrichment may be a response to differential redox thresholds for accumulation e g v or postdepositional remobilization of trace elements e g u and may provide a basis for finer assessment of redox conditions in low oxygen paleoenvironments than permitted by simple classification schemes the multiproxy procedure for redox facies analysis developed in this study is likely to be more reliable than widely used single proxy indicators based on trace elements e g mo authigenic u or v v ni or c s fe systematics e g s toc or dop d 2004 elsevier b v all rights reserved

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

geochemical characteristics of the lower silurian longmaxi formation on the yangtze platform south china implications for depositional environment and accumulation of organic matters abstract the organic rich lower silurian longmaxi formation is now regarded as the favorable target for shale gas exploration and production however the mechanism of organic matter accumulation in these deposits remains highly controversial in this study we investigate the total organic carbon toc content and the major and trace element abundances of a newly recovered core from the yangtze platform to reconstruct the paleo environment and to elucidate the factors that control organic matter accumulation our results suggest that the greenhouse conditions during the early silurian were punctuated by several cooling events bottom water redox conditions improve gradually upsection with a transition from anoxic water conditions in the lower longmaxi formation to suboxic oxic water conditions in the upper longmaxi formation the primary productivity on the yangtze platform appears to have been high during deposition of the longmaxi formation especially in its lower part due to an enhanced phosphorus recycling the strong correlations between toc and copper and nickel imply that the productivity was especially critical to the organic matter accumulation in the lower longmaxi formation furthermore the rapid consumption of dissolved oxygen in bottom water favored the establishment of anoxic water conditions which facilitated organic matter preservation the poor correlations between toc and barium and phosphorus in the lower longmaxi formation likely reflect intense recycling of nutrients the evolution of water redox conditions and accumulation of organic matters in the longmaxi formation can be related to global fluctuations in sea level and regional tectonic uplift of the yangtze platform

organic matter accumulation of the wufeng longmaxi shales in southern sichuan basin evidence and insight from volcanism abstract the wufeng longmaxi formations wf lm fms in the sichuan basin are sets of graptolite bearing shale strata containing high frequency bentonite layers in order to investigate the influence of volcanism on the organic matter om accumulation in shales detailed observations of several typical profiles and wells were performed also analyses including total organic carbon toc contents and mineral compositions were conducted on 126 shale and 5 bentonite core samples major and trace element analyses were conducted on the selected 25 shale and 5 bentonite samples in the wf lm fms of well lu a results show that wf and lm1 4 members are the bentonites concentrated sections while lm5 6 are the bentonites relatively concentrated sections and no bentonite is found in lm7 9 members the high potassium k content of bentonites have the typical characteristics of intermediate acid calcium alkaline volcanic rocks such as andesite and dacite which probably originated from intraplate collision or volcanic arc structural backgrounds related to the collision belt of the cathaysia block to the yangtze block productivity indicators p content excess si p al cu al and ni al in the wf and lm1 3 members are all significantly higher than those in the lingxiang lx and lm4 5 members the higher biological productivity during the ordovician silurian o s transition was attributed to the massive and intensive volcanism the fertilization by volcanic ash brought abundant biologically relevant nutrient elements n p si fe and al into the ocean thus triggering the phytoplankton bloom and enhancing primary biological productivity all the redox condition indexes moef uef nief vef mo toc corg p and u th positively correlate with toc content during the o s transition the intensive and massive volcanic eruptions triggered global cooling sea level changes late ordovician mass extinction and primary productivity increases thus promoting anoxic and possibly intermittently euxinic bottom conditions in addition the deposited bentonite layers had a strong capacity for oxygen isolation volcanism should be considered when modeling the om accumulation of the wf lm shales

the behavior of redox sensitive metals across a laminated massive laminated transition in saanich inlet british columbia abstract holocene laminated sediments in saanich inlet british columbia are interrupted by frequent non laminated massive layers these layers may be debris flows released by earthquakes or bioturbated sediments deposited during periods of relatively high bottom water oxygen concentration and or low surface productivity or both we determined the organic carbon content and the concentration of a suite of redox sensitive metals in bulk sediments at approximately 1 cm resolution across a laminated massive laminated interval odp leg 169s site 1033 hole b 4h4 54 74 cm to determine the redox conditions under which the massive layer was deposited our results indicate that this massive interval was deposited under anoxic bottom waters manganese al ratios are consistently low throughout the massive section while mo al cd al re al and u al ratios are enriched relative to their metal al ratios in detrital material represented by cowichan river suspended sediments the concentration of organic carbon in the lower portion of the massive layer is higher than in the upper portion which has a concentration similar to that in the overlying and underlying laminated sediments well defined peaks in mo al cd al and re al and a broad peak in u al occur in the lower portion of the massive layer the positions of the cd al re al and mo al peaks as well as the increase in organic carbon content with depth in the massive layer are best explained by a process of diagenetic redistribution of metals that occurred after the massive layer was emplaced

late ordovician to earliest silurian graptolite and brachiopod biozonation from the yangtze region south china with a global correlation late ordovician to earliest silurian is an important geological period marked by large geological and biological events however the strata and fossils of this interval are not complete in many parts of the world based on studies of 43 sites in south china in particular the continuous sections on the yangtze platform we recognize a complete succession including seven graptolite zones and two shelly faunas in ascending order the graptolite zones are the dicellograptus complanatus dicellograptus complexus paraorthograptus pacificus including lower subzone tangyagraptus typicus subzone and diceratograptus mirus subzone normalograptus extraordinarius normalograptus ojsuensis normalograptus persculptus akidograptus ascensus and parakidograptus acuminatus zones the shelly faunas are the foliomena nankinolithus and hirnantia faunas which may be correlated with d complanatus zone and n extraordinarius n ojsuensis to part of n persculptus zones respectively the biozonation through this interval from the yangtze region can be correlated with that of other parts of the world such as dob s linn in scotland spain and portugal thuringia saxonia bavaria bohemia poland kazakhstan kolyma malaya peninsula yukon canadian arctic islands nevada argentina niger and victoria australia the hirnantian substage which has been proposed by us recently includes the n extraordinarius n ojsuensis zone hirnantia fauna and n persculptus zone the base of the hirnantian substage is marked by the first appearance data fads of n extraordinarius and n ojsuensis which have been determined to be synchronous on a global scale

spatial variation in sediment fluxes redox conditions and productivity in the permian triassic panthalassic ocean abstract two permian triassic boundary sections in central japan provide a rare window into environmental conditions within the panthalassic ocean which encompassed more than half the earth s surface at 252 ma integration of petrographic geochemical and time series data provides new insights regarding the fluxes of major and trace components to the sediment as well as environmental conditions in both the deep and intermediate water masses at each study site the ubara section was located in a high productivity peri equatorial location whereas the gujo hachiman section was located in a moderate productivity location at some distance from the paleoequator an upward transition from gray organic poor cherts to black siliceous mudstones at both sites occurred in conjunction with increased primary productivity intensified euxinia within the oxygen minimum zone omz and decimation of the radiolarian zooplankton community euxinia in the omz of the equatorial panthalassic ocean developed episodically for a 200 250 kyr interval during the late permian followed by an abrupt intensification and lateral expansion of the omz around the permian triassic boundary throughout the study interval bottom waters at both sites remained mostly suboxic a finding that counters hypotheses of development of a superanoxic permo triassic deep ocean as a consequence of stagnation of oceanic overturning circulation

a new model evaluating holocene sediment dynamics insights from a mixed carbonate siliciclastic lagoon bora bora society islands french polynesia south pacific abstract mixed carbonate siliciclastic lagoons of barrier reefs provide great potential as sedimentary archives focusing on paleoenvironmental and paleoclimatic changes as well as on event deposition sediment sources include lagoonal carbonate production the marginal reef and the volcanic hinterland mixed carbonate siliciclastic continent attached coastal lagoons have been intensively studied however their isolated oceanic counterparts have been widely disregarded here we present a new model of holocene sediment dynamics in the barrier reef lagoon of bora bora based on sedimentological paleontological geochronological and geochemical data the lagoonal succession started with a pleistocene soil representing the lowstand systems tract as the rising holocene sea inundated the carbonate platform peat accumulated locally 10 650 9400 years bp mixed carbonate siliciclastic sedimentation started ca 8700 5500 years bp and represents the transgressive systems tract during that time sediments were characterized by relatively coarse grain size and contained high amounts of terrestrial material from the volcanic hinterland as well as carbonate sediments mainly produced within the lagoon siliciclastic content decreases throughout the holocene after the rising sea had reached its modern level sand aprons formed between reef crest and lagoon creating transport pathways for reef derived material leading to carbonate dominated sedimentation ca 6000 3000 years bp during the highstand systems tract however mainly fine material was transported and accumulated in the lagoon while coarser grains were retained on the prograding sand apron from ca 4500 500 years bp significant variations in grain size total organic carbon as indicator for primary productivity ca and cl element intensities as qualitative indicators for carbonate availability and lagoonal salinity are seen such patterns could indicate event re deposition and correlate with contemporaneous event deposits found in the lagoon of nearby tahaa which are supposed to be induced by elevated cyclone activity correspondingly enhanced erosion and run off from the volcanic hinterland as well as lower lagoonal salinity would be associated with intense rainfall during repeated cyclone landfall increased amounts of coarse grained sediment from marginal reef areas would be transported into the lagoon however ti ca and fe ca ratios as proxies for terrigenous sediment delivery have incessantly declined since the mid holocene also benthic foraminiferal faunas do not validate reef to lagoon transport of sediment alternatively the apparent onset of higher hydrodynamic energy conditions can be explained by more permanent southeast trade winds and higher than present sea level which are supposed for the mid late holocene in the south pacific sustained winds would have flushed higher amounts of open ocean water into the lagoon enhancing primary productivity and the amount of pelagic organisms within the lagoon while lowering lagoonal salinity we propose the shift towards coarser grained sedimentation patterns during the mid late holocene to reflect sediment load shedding of sand aprons due to oversteepening of slopes at sand apron lagoon edges during times of stronger trades and higher than present sea level of the highstand systems tract which led to redeposition of sediment even within the lagoon center modern conditions including a sea level fall to modern level were reached ca 1000 years bp and lagoonal infill has been determined to a large part by fine grained carbonate dominated sediments produced within the lagoon and derived from the marignal reef infill of lagoonal accommodation space via sand aprons is estimated to be up to six times higher than infill by lagoonal background sedimentation and emphasizes the importance of the progradation of sand aprons contrary to the commonly supposed assumption that coarse grained sediment layers within fine grained lagoonal successions represent overwash events induced by storms or periods of higher storm activity we postulate a new model of long term lagoonal sediment dynamics including sea level climatic change and geomorphological variation of the barrier reef lagoon

factors controlling organic matter accumulation in the upper ordovician lower silurian organic rich shale on the northeast margin of the upper yangtze platform evidence from petrographic and geochemical proxies abstract organic rich shales are widespread in the upper ordovician lower silurian wufeng longmaxi formations on the northeastern margin of the upper yangtze platform and these shales have been recognized to be the hydrocarbon source rocks and shale gas reservoirs with the greatest development potential in china however organic matter accumulation in these shales needs further research especially in the areas which experienced an extensive upwelling and volcanism here this work integrates detailed petrographic and geochemical proxies namely redox sensitive trace elements rstes and ratios of si al ti al from two ordovician silurian sections on the northeast margin of upper yangtze platform in order to understand the depositional environment and identify the major factors controlling the organic matter accumulation during the ordovician silurian transition data of si al and ti al ratios indicate that the deposition of black gray siliceous mudstones in the lower wufeng formation commenced with a transgression triggered by the boda warming event which led to a reduced detrital input based on rstes the black carbonaceous shales of the upper wufeng formation are organic rich owing to an elevated primary productivity caused by seasonal upwelling driven by the vigorous thermohaline circulation abundant nutrients supplied by the post glacial transgression and a mass biotic recovery of marine microorganisms stimulated productivity and further strengthened the depletion of oxygen in the water column which lead to high concentrations of organic matter in lower longmaxi formation although the water column conditions were not conducive to the accumulation of organic matter it was possible that the increased productivity from upwelling resulted in relatively high organic matter contents in the middle longmaxi formation the rstes especially cd mo co mn reveal that the organic matter accumulation of the wufeng longmaxi formation during ordovician silurian transition may have been primarily controlled by the preservation conditions and also influenced by the marine primary productivity and the detrital input

characteristics of microorganisms and origin of organic matter in wufeng formation and longmaxi formation in sichuan basin south china abstract to evaluate the characteristics of microorganisms and the origin of organic matter of the wufeng formation and longmaxi formation wf lmx in sichuan basin south china the type and number of microorganisms were determined in this study using scanning electron microscope sem microphotographs and microbial extraction the contribution of various microorganisms to organic matter was analyzed in combination with the data of biomarkers and total organic carbon toc it can be deduced from the paleogeography and pristine phytane pr ph ratio that the microorganisms of wf lmx resided in 60 m 200 m deep shelf with anoxic bottom water from sem microphotographs and microbial microscopy analysis it was demonstrated that the microorganisms in the wf lmx can be divided into 3 types planktonic algae mainly including acritarchs and green algae fungi and benthic algae acritarchs were the most common microorganisms in the wf lmx with the average relative content of 60 5 the average relative contents of benthic algae fungi and green algae were 17 6 18 0 and 3 9 respectively since the acritarchs and green algae in the wufeng formation and the longmaxi formation basically belong to planktonic algae the relative content of planktonic algae in them is about 64 4 the strata of wf lmx can be divided into 3 sections based on the distribution characteristics of various microorganisms the relative content of acritarchs gradually decreased upwards while that of benthic algae gradually increased the multiple proxies of biomarkers proved that the planktonic algae was the main source of organic matter in the wf lmx combining the statistical data of microorganisms it was considered that the organic matter in wf lmx was mainly derived from acritarchs which might be the components of planktonic algae the fungi had a significant contribution to the organic matter in organic rich layers toc 2 0 rather than in organic poor layers while green algae and benthic algae made little contribution to the organic matters in wf lmx

el nino la nina and the nonlinearity of their teleconnections the paradigm of an atmospheric system varying linearly with respect to extreme phases of the el nino southern oscillation is questioned it is argued that the global response to tropical pacific sea surface temperature forcing will be inherently nonlinear a physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection climate statistics for warm and cold events of the tropical pacific are analyzed separately for the northern winter periods during 1950 96 composite analysis of 500 mb heights reveal planetary scale teleconnection patterns as noted in earlier studies a new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites and the two wave trains appear to have different tropical origins a large nonlinear component in north american surface climate anomalies is also found which is consistent with such a phase shift in teleconnections in the tropics rainfall anomalies also show evidence of nonlinear behavior the maximum rain anomalies along the equator are located east of the date line during warm events but west of the date line during cold events the interpretation of this behavior is complicated however by the fact that composite warm event sst anomalies are not the exact inverse of their cold event counterparts idealized atmospheric general circulation model agcm experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system the model is forced with a composite sst anomaly that undergoes a realistic seasonally varying enso life cycle as described by e rasmusson and t carpenter both positive and negative phases of the sst anomaly are used and a 40 member ensemble of warm and cold event model simulations is conducted a nonlinear climate response in the agcm is found that closely resembles the observed composites including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns

multi proxy analysis of organic matter accumulation in the upper ordovician lower silurian black shale on the upper yangtze platform south china abstract there is no doubt that organic matter plays an important role in shale gas accumulation and storage thus successful evaluation and production strategies of organic rich shale deposits require an understanding of the range of factors that contribute to the accumulation and preservation of organic matter in these deposits this paper reports results of a multi faceted study of two ordovician silurian transition sections of the upper yangtze platform of south china organic and inorganic geochemical data are used to reconstruct paleoenvironmental changes across this critical interval of earth history and to identify those factors that were most important to organic matter accumulation deposition of organic rich shale of the katian lower wufeng formation was favored by rising sea level and diminished clastic sediment content black shale of the upper wufeng preceded hirnantian glaciation whereas the overlying lower longmaxi formation accumulated in association with a post glacial rise of sea level as well as the peak of caledonian tectonism the carbonaceous deposits appear to reflect the combined effects of elevated primary productivity as suggested by si al and ti al ratios especially in the upper wufeng and consequent depletion of water column oxygen preservation consideration of the relationships of redox sensitive trace element concentrations and total organic carbon content suggest that bottom water conditions fluctuated between anoxic and euxinic during this period perhaps related to rapid oscillations of sea level moreover the basin appears to have remained connected with the global ocean in spite of caledonian uplift of bordering areas thus black shale sedimentation on the upper yangtze platform at the ordovician silurian boundary reflects the interplay of climate change and tectonism and their influences on sea level clastic sediment content and paleo productivity

relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas u s a analyses of 21 samples collected from a core of the 52 8 cm thick stark shale member of the dennis limestone in wabaunsee county kansas demonstrate four cycles with two orders of magnitude variations in contents of cd mo p v and zn and order of magnitude variations in contents of organic carbon cr ni se and u the observed variability in amounts and or ratios of many metals and amounts and compositions of the organic matter appear related to the cause and degree of water column stratification and the resulting absence presence of dissolved o2 or h2s high cd mo u v zn and s contents a high degree of pyritization dop 0 75 0 88 and high high v v ni 0 84 0 89 indicate the presence of h2s in a strongly stratified water column intermediate contents of metals and s intermediate dop 0 67 0 75 and intermediate v v ni 054 0 82 indicate a less strongly stratified anoxic water column whereas low metal contents and low v v ni 0 46 0 60 indicate a weakly stratified dysoxic water column high p contents at the top of the organic matter rich intervals within the stark shale member indicate that phosphate precipitation was enhanced near the boundary between anoxic and dysoxic water compositions relatively abundant terrestrial organic matter in intervals deposited from the more strongly stratified h2s bearing water column indicates a combined halocline thermocline with the fresher near surface water the transport mode for the terrestrial organic matter the predominance of algal organic matter in intervals deposited from a less strongly stratified water column indicates the absence of the halocline and the presence of the more generally established thermocline relatively low amounts of degraded hydrogen poor organic matter characterize intervals deposited in a weakly stratified dysoxic water column the inferred variability in chemistry of the depositional environments may be related to climate variations and or minor changes in sea level during the general phase of deeper water deposition responsible for this widespread shale member

analysis of the nonlinearity of el nino southern oscillation teleconnections abstractel nino southern oscillation enso has significant variations and nonlinearities in its pattern and strength enso events vary in their position along the equator with some located in the central pacific cp and others in the east pacific ep to study how these variations are reflected in global enso teleconnections both observations and idealized atmospheric general circulation model agcm simulations are analyzed clear nonlinearities exist in observed teleconnections of sea level pressure slp and precipitation however it is difficult to distinguish if these are caused by the different signs strengths or spatial patterns of events strong el nino events mostly being ep events and strong la nina events mostly being cp events or by combinations of these therefore sensitivity experiments are performed with an agcm forced with idealized ep and cp enso sea surface temperature sst patterns with varying signs and strengths the response is generally stronger for warm events than for c

pliocene holocene evolution of depositional conditions in the eastern mediterranean role of anoxia vs productivity at time of sapropel deposition a multiproxy geochemical study of nine sapropel layers from odp hole 964a odp leg 160 in the eastern mediterranean spanning the pliocene holocene time interval provides new insights into the evolution of sapropel deposition paleoenvironmental proxies were used for reconstruction of productivity ba derived from marine barite oxygen conditions trace metal ratios and sedimentary regime clay minerals detrital elements these proxies reveal a significant increase in river runoff relative to decreasing aeolian input during sapropel deposition over the whole time interval ba excess supports the argument that a significant increase in export productivity is the main triggering mechanism for sapropel deposition although preservation also played an important role furthermore major differences exist in depositional conditions including both oxygenation and productivity since the pliocene productivity fluctuated substantially and was higher during the pliocene and pleistocene than during the holocene at the same time decreasing oxygen availability parallels the enhanced productivity dysoxic to anoxic conditions appear to coincide with marine productivity maxima thus suggesting that oxygen depletion may be linked to greater consumption rather than restricted circulation this correspondence supports the hypothesis that productivity fluctuations resulting from climate oscillations were the main cause of enhanced organic matter contents and also a main controlling factor for reduced oxygen availability

enso regimes reinterpreting the canonical and modoki el nino 1 we propose that the first two empirical orthogonal function eof modes of tropical pacific sea surface temperature sst anomalies do not describe different phenomena i e el nino southern oscillation enso and el nino modoki but rather the nonlinear evolution of enso we introduce two new uncorrelated indices e and c based on the leading eofs that respectively account for extreme warm events in the eastern and cold moderate warm events in the central equatorial pacific corresponding to regimes with different evolution recent trends in enso can be described as an increase in the central pacific c variability that is associated with stronger cold events as well as a reduction in the eastern pacific e variability within the cold moderate warm regime consistent with model projections however little can be said observationally with respect to the extreme warm regime