3d stratigraphic forward modelling for analysis and prediction of carbonate platform stratigraphies in exploration and production abstract stratigraphic forward modelling sfm has been used to answer important questions in stratigraphic analysis this has been demonstrated through generic modelling of synthetic data and numerous two dimensional 2d real data case studies but the method has rarely been used to further our understanding of specific real three dimensional 3d carbonate data sets by quantitative comparison this paper applies carbonate 3d a sfm program to a hydrocarbon reservoir and outcropping carbonate platforms at both exploration and production scales we show the value of sfm in the exploration and production of hydrocarbons through predicting facies distributions and stratigraphic geometries between wells and by analysing and answering fundamental questions about the formation of specific carbonate strata first the model is tested using the 3d outcrops of a miocene attached carbonate platform at nijar se spain where 78 of mapped facies are matched in the simulations second sfm of an 80 000 km 2 jurassic ramp in ne spain exploration scale predicts new facies in areas without data leads to an improved understanding of ramp evolution modification of the interpreted sea level curve and re interpretation of the main sediment transport direction application to the isolated platform reservoir judy creek devonian canada exemplifies the advantages of applying sfm at reservoir scale the simulations yield information on platform geometries and facies distributions an improved understanding of the factors that control platform evolution and propose a revised sea level history wider applications of sfm in exploration include assessment of the possibilities and probabilities of facies distributions and evaluation and ranking of different interpretations of platform evolution at the reservoir scale facies probability distributions and layer geometries derived from sfm can serve as input into static reservoir models to guide geostatistical simulations

spherulites in calcrete laminar crusts biogenic caco 3 precipitation as a major contributor to crust formation abstract spherulites calcitic fibro radial spherulitic polycrystals are a major component of calcite layers in quaternary calcrete laminar crusts to explain the formation of spherulites petrographic and chemical studies were performed on pleistocene calcrete laminar crusts holocene biological crusts and laboratory in vitro cultures of cyanobacterial strains spherulites were found to be formed of acicular and radiating crystals either smooth and regular edged or twisted and irregular edged spherulites were composed of low mg calcite the concentration of mg in the spherulites increasing from nucleus to periphery the shape and chemistry of the in vitro spherulites and laminar crust spherulites were identical the structure elementary crystal shape and size of spherul tes can be used to differentiate them from microcodium with which they are commonly confused in the literature spherulite genesis can be linked to cyanobacterial activity involving photosynthetic uptake of hco 3 leading to caco3 precipitation the bicarbonate causing release of equivalent amounts of oh in the mucilaginous sheath the main steps in cyanobacteria biomineralization producing spherulites are 1 uptake of co2 and or hco 3 from the medium as the inorganic carbon source for photosynthesis 2 release of oh in the sheath 3 carbonate ion formation resulting from the reaction of oh and hco 3 followed by 4 caco3 precipitation this process involves two steps in desert environments during dry spells the cyanobacterial mat calcifies leading to spherulite production and the fo mation of thin clear microsparitic layers during wet periods a thin sedimentary deposit forms mixing micrite detrital particles and inherited or new tiny spherulites with the mucilaginous mat of cyanobacteria which traps all of this material an organo micritic layer forms during the following dry spell the process is repeated and the laminar crust is formed in conclusion the presence of spherulites in the laminar crust is indicative of subaerial exposure the crust being a terrestrial stromatolite

interactions between sediment production and transport in the geometry of carbonate platforms insights from forward modeling of the great bank of guizhou early to middle triassic south china abstract carbonate platforms grow through the precipitation transport and final deposition of carbonate sediment out of seawater quantifying the relative contributions of initial production versus subsequent transport in determining the growth rates and geometries of platforms remains a significant challenge in this study stratigraphic forward modeling is used to quantify the roles of sediment production transport and deposition during each growth stage of a permian triassic carbonate platform with a complex growth history parameter optimization and sensitivity analysis show that within the range of reasonable values the morphology of the platform is most sensitive to sediment transport moderately sensitive to maximum carbonate production rate and least sensitive to the productivity depth curve the ramp to high relief steep sloped platform transition during early triassic time can be explained by any factor that limits sediment transport from shallow water areas of high production to the slope and basin reefs may play a role in limiting sediment transport on many platforms but other processes such as early marine cementation or carbonate production along the slope may be equally capable of yielding this shift in platform geometry in this particular case early lithification of ooid and skeletal shoals on the platform margin perhaps facilitated by unusually high carbonate saturation state of seawater may have inhibited sediment transport into the basin prior to the development of a reef on the platform margin later anisian progradation of the platform margin can be explained by the development of a slope factory rather than requiring increased sediment transport from the platform top the development of an escarpment margin in the ladinian is mainly influenced by accommodation in the slope profile created by antecedent anisian topography a general implication from the model results is that the growth of steep sloped carbonate platforms lacking slope factories may often be limited by transport of sediment from the platform top to accommodation on the slope rather than by the intrinsic production capacity of the platform top factory

deep structure of the santos basin sao paulo plateau system se brazil the structure and nature of the crust underlying the santos basin sao paulo plateau system ssps in the se brazilian margin are discussed based on five wide angle seismic profiles acquired during the santos basin sanba experiment in 2011 velocity models allow us to precisely divide the ssps in six domains from unthinned continental crust domain cc to normal oceanic crust domain oc a seventh domain domain d a triangular shape region in the se of the ssps is discussed by klingelhoefer et al 2014 beneath the continental shelf a 100 km wide necking zone domain n is imaged where the continental crust thins abruptly from 40 km to less than 15 km toward the ocean most of the ssps domains a and c shows velocity ranges velocity gradients and a moho interface characteristic of the thinned continental crust the central domain domain b has however a very heterogeneous structure while its southwestern part still exhibits extremely thinned 7 km continental crust its northeastern part depicts a 2 4 km thick upper layer 6 0 6 5 km s overlying an anomalous velocity layer 7 0 7 8 km s and no evidence of a moho interface this structure is interpreted as atypical oceanic crust exhumed lower crust or upper continental crust intruded by mafic material overlying either altered mantle in the first two cases or intruded lower continental crust in the last case the deep structure and v shaped segmentation of the ssps confirm that an initial episode of rifting occurred there obliquely to the general opening direction of the south atlantic central segment

lithospheric extension from rifting to continental breakup at magma poor margins rheology serpentinisation and symmetry the symmetry or asymmetry of the process of continental breakup has been much debated over the last 20 years with various authors proposing asymmetric simple shear models others advocating more symmetric pure shear models and some combinations of the two the unroofing of vast expanses of sub continental mantle at non volcanic margins has led some authors to argue in favour of simple shear models but supporting evidence is lacking subsidence evidence from conjugate margin pairs is equivocal and the detailed crustal and lithospheric structure of such pairs not generally well enough known to draw firm conclusions in the porcupine basin where the final stages of break up are preserved the development of structural asymmetry is demonstrable and apparently related to late stage coupling of the crust to the mantle following the complete embrittlement of the crust this agrees with theoretical modelling results which predict that asymmetric models can develop only on a lithospheric scale when the crust and mantle are tightly coupled however whether such asymmetry is maintained during continued exhumation of the mantle is unclear

the geodynamics of lithospheric extension lithospheric extension is a fundamental plate tectonic process controlling the collapse of mountain belts the break up of continents and the formation of new oceanic basins this review summarises major advances on understanding a the nature of the ocean continent transition b the origin and evolution of detachment faults c the dynamic strength of continental lithosphere during extension and d the role of magmatism during extension major steps have been made in mapping out the complexities of the ocean continent transition zone particularly in magma poor rifted margins where extensional structures are not masked by voluminous magmatism the role of detachment faulting during rifting seems to be crucial and explains observations on depth dependent stretching of the lithosphere despite new insights into the dynamic behaviour of the lithosphere its rheological response remains a major uncertainty in modelling the evolution of extensional systems likewise the multiple roles that basaltic magmatism may have in modifying extension remain a key question future insights into the global behaviour of extensional systems will be gained by constraining lithospheric rheology through integrating structural evolution and magmatism in the field geodetic measurements of active extension thermochronology seismic surveys and drilling programs 2008 elsevier b v all rights reserved

combining sedimentary forward modeling with sequential gauss simulation for fine prediction of tight sandstone reservoir abstract a considerable number of tight sandstone gas fields are observed in the xihu depression east china sea the y gas field is at the stage of development it is necessary to describe the reservoir shape and permeability characteristics in detail to deploy development wells the seismic prediction effects of tight sandstone are not good sedimentary forward modeling technology can effectively predict the macroscopic characteristics of sedimentary sand bodies but this technique lacks micro details geostatistical modeling can depict reservoir details but this technique cannot easily reflect macro laws therefore taking h1 layer of the oligocene huagang formation in the y gas field as an example the combination of sedimentary simulation and geostatistical modeling is proposed geostatistical modeling is combined to describe reservoir details by using the sequential gauss simulation method under the control of sedimentary simulation results as macro laws first based on the test data and the sensitivity test results of the adjacent study area five parameters transport capacity of the river sand ratio maximum initial water depth lake level change and tectonic subsidence needed for the simulation are determined a sedimentary forward simulation is carried out and a sand ratio model reflecting macroscopic sedimentary law is obtained second in the geostatistical modeling stage the variogram which has a great influence on the results of geological modeling is discussed the results show that the larger the length and width of the variogram the larger the simulated reservoir scale then considering the characteristics of fewer wells in the study area a reliable variogram is obtained by using the sand ratio results of the sedimentary simulation 2538 m in length and 876 m in width and the main input parameters of geological modeling data probability distribution characteristics and variogram are determined subsequently under the trend of the sediment sand ratio simulation geological modeling research was carried out by using the sequential gauss simulation method and a high precision sand ratio prediction model was established finally the sand ratio model is transformed into a sedimentary microfacies model and the permeability characteristics of different sedimentary microfacies are calculated under the control of sedimentary facies the permeability model is established by the sequential gauss simulation method the model prediction results show that the simulation results can reflect the morphology distribution and permeability of sedimentary microfacies in detail and the macroscopic characteristics of delta sedimentary law the permeability of channels in the study area is 0 3 md and the distribution area is much larger than that of other types of sedimentary microfacies compared with other types of deposits the channel around well a area has better development potential in the front of the delta and is the most favorable oil and gas development area in the study area

facies classification and patterns of lacustrine carbonate deposition of the barra velha formation santos basin brazilian pre salt abstract the lacustrine carbonate rocks of the giant pre salt oil fields in the santos and campos basins differ in a number of important aspects from classic lake deposits prior work has described distinctive and unusual features of deposition early diagenesis and reservoir quality with in these rocks that defy classification using established schemes in addition to their unusual textures debate continues as to how to interpret the vertical stacking pattern of facies a new facies classification scheme is proposed based on the relative abundance of three end member components mud micrite and clay minerals calcite spherulites and fascicular calcite shrubs although focused on the main textural and mineralogical features of the rocks as seen today the proposed scheme takes into account the relative contribution of depositional and early diagenetic components sediment mineralogy and the degree of dissolution application of this scheme offers insight into depositional conditions whilst also linking to reservoir quality basic elementary cycles can be defined using this classification in combination with the variation in the abundance of detrital grains and the chemical composition three possible models are suggested to interpret the origin of the basic cycle within the barra velha formation in the context of variation in climate lake level and water chemistry integration of data from different sources including petrographic core description and chemical data for the basic cycle offers improved process based understanding of metre scale facies patterns and provides a foundation for understanding larger scale vertical variations within and between unconformity bound sequences

lower jurassic lower cretaceous belemnite biogeography and the development of the mesozoic boreal realm abstract the distribution of lower jurassic lower cretaceous belemnites is reviewed in the light of recent taxonomic and biogeographic studies and it is seen that belemnite provinciality developed in the late lower jurassic when distinct arctic taxa are first recognised in the middle jurassic boreal and tethyan belemnite realms are apparent the boreal realm being divisable into informal boreal atlantic and arctic provinces which can be recognised up into the lower cretaceous in the upper jurassic and lower cretaceous distinct arctic belemnites are found in association with tethyan ammonites in california and it is this factor in association with an observed increase in belemnite diversity northwards from the boreal atlantic to the arctic provinces that suggests that latitudinal temperature gradients were not the overall control influencing the development of boreal and tethyan belemnite realms instead the hostile environment of the boreal atlantic area the european archipelago is seen as an effective barrier to the migration of tethyan belemnites to the arctic and vice versa however high sea level stands may have helped blur these distinctions as in the late valanginian hauterivian when arctic taxa invaded europe and tethyan taxa the periphery of the arctic basin

the relationship between the geometry of normal faults and that of the sedimentary layers in their hanging walls abstract we derive an analytical expression that relates the shape of a fault in cross section to the shape of the bedding horizons in its hanging wall block the expression assumes that the hanging wall deforms by simple shear and that the footwall remains undeformed throughout although this paper concentrates on normal faults the expression is equally valid and applicable to thrust faults the direction of simple shear in the hanging wall block is arbitrary and has a dramatic effect on the predicted fault or bedding geometry there is no reason to believe that the simple shear occurs on vertical planes as is commonly assumed in graphical approaches to this problem and ignoring the presence of inclined simple shear is likely to lead to considerable underestimates of the amount of extension across normal faults and in the amount of shortening across thrusts similar though more complicated expressions can be obtained when compaction within the hanging wall block is taken into account for a planar normal fault such compaction may result in the development of a hanging wall syncline

the hydrochemical evolution of alkaline volcanic lakes a model to understand the south atlantic pre salt mineral assemblages abstract understand the origin of the exotic strontium rich calcite magnesium rich clay silica deposits formed during the early cretaceous in the south atlantic pre salt lakes is challenging our ability to comprehend the chemical evolution of alkaline volcanic lakes here we present a new hydrochemical model based on an open basin concept thermodynamic equilibrium and chemical data from lake baringo east african rift to shed light on the mechanisms facilitating carbonate clay silica precipitation this model explores the effects that the leakage to adjacent waterbodies the combination of lake evaporation and lake recharge with river hydrothermal and marine waters and the bathymetric effects of the partial co2 pressure have in the stationary precipitation of pre salt lacustrine mineral assemblages sediment thickness calculations suggest that the facies cyclicity in the pre salt and elsewhere are likely reflecting temporal fluctuations in the type of waters sourcing the lake and in the degree of leakage to aquifers over multiple evaporative freshening cycles a plausible link between enhanced strontium uptake into pre salt calcite allochems and ca2 co32 lake water stoichiometries allows to infer different scenarios for strontium rich calcite formation with or without magnesium clays our conceptual model allows to quantify the role that hydrology groundwater charge discharge to aquifers evaporation exert on carbonate clay silica precipitation providing with a refined framework to understand the basin scale chemical sedimentation in alkaline lakes furthermore this model represents a robust template upon which critically test the superimposed kinetic factors likely attached to the genesis of specific mineral factories such as those encountered in the south atlantic pre salt alkaline lakes

belemnite extinction and the origin of modern cephalopods 35 m y prior to the cretaceous paleogene event belemnites a very successful group of mesozoic cephalopods flourished in cretaceous oceans until the cretaceous paleogene event when they became globally extinct following this event the modern types of cephalopods squids cuttlefish octopus radiated in the cenozoic in all oceans in the north pacific however a turnover from belemnites to the modern types of cephalopods about 35 m y before the cretaceous paleogene event documents a more complex evolutionary history of cephalopods than previously thought here we show that the modern types of cephalopods originated and prospered throughout the late cretaceous in the north pacific the mid cretaceous cephalopod turnover was caused by cooling and the closure of the bering strait which led to a subsequent faunal isolation of this area in the late cretaceous the former niches of the fast swimming belemnites were taken over by the modern types of cephalopods which evolved endemically the cretaceous paleogene event only allowed the modern types of cephalopods to spread globally and to take over the niches previously held by belemnites

late holocene hydrological history of lake tanganyika east africa from isotopic data on fossil stromatolites abstract lake tanganyika situated in the western branch of the east african rift system shows a slightly positive water budget and generates a small outflow through the lukuga river dependent mainly on the ruzizi river inflow from lake kivu in the northern part of the basin conditions more arid than those presently observed closed the kivu basin from 3800 to 1300 yr b p previous studies esimated that the closure of the corresponding tanganyika basin lowered the lake level by 75 150 m in this paper we present the results of isotopic and morphologic analyses of fossil stromatolites the stromatolites formed as thick incrustations on hard substrates and are found at depths between 6 and 60 m below the modern lake level their isotopic composition 18o 13c 14c very precisely document late holocene water levels and hydrologic fluctuations in the lake tanganyika basin with reference to the actual situation a major low stand at 10 m below present level is identified from 3400 to 1900 yr b p with a rapid recession and gradual rise to modern levels maximum 18o values vs pdb in the stromatolites rose from ca 3 5 at 3400 yr b p to 6 at 2500 yr b p then decreased progressively to 1 6 at 1300 yr b p these values are interpreted as a maximum aridity episode culminating at ca 2500 yr b p at which time a negative precipitation evaporation p e ratio resulted in a much higher residence time of paleolake waters and thus a noticeable enrichment in 18o the observed decoupling of the isotopic ratio 18o 16o and water volume responses is thought to be linked to the inertia of the large rift aquifers which controlled the paleolake level

late holocene land surface change in a coupled social ecological system southern iceland a cross scale tephrochronology approach this work is supported by a uk natural environment research council nerc phd studentship ne f00799x 1

role of subaerial volcanic rocks and mantle plumes in creation of south atlantic margins implications for salt tectonics and source rocks abstract seaward dipping reflectors sdrs represent flood basalts rapidly extruded during either rifting or initially subaerial sea floor spreading evaporites can form on this basaltic proto oceanic crust as in the afar triangle today evidence for sdrs in south atlantic deep water regions comes from proximity to the uniquely large parana etendeka volcanic province onshore the tristan and gough hot spots drilled volcanic rocks and seismic profiles showing sdr provinces more than 100 km wide as much as 7 km thick and thousands of kilometers long sdrs are clearest adjoining the aptian salt basins however we speculate that sdrs are also present but seismically obscured below the salt basins we argue that the conjugate aptian salt basins are post breakup not pre breakup they were separated from the start by a mid oceanic ridge distal salt accumulated on proto oceanic crust not rift basins this hypothesis is supported by seismic stratigraphy and structure magnetic anomalies plate reconstructions and hydrothermal potash evaporites an important implication for exploration is that thick basalts rather than rift age source rocks may underlie distal parts of the salt basins

early jurassic belemnites from the gondwana margin of the southern hemisphere sinemurian record from south tibet abstract belemnites order belemnitida a very successful group of mesozoic coleoid cephalopods dominated fossil coleoid assemblages throughout the jurassic and cretaceous according to the current view the phylogenetically earliest known belemnites have been reported from the lowermost jurassic hettangian of northern europe the earliest belemnites are characterized by low diversity and small sized rostra their distribution has until recently been assumed to be restricted to northern europe until the pliensbachian early belemnites the sinobelemnitidae and the belemnitina are now also known from the late triassic of china and the hettangian sinemurian of japan and therefore from the eastern tethys and western paleo pacific oceans it has been suggested that the distribution of belemnites became more widespread and expanded to the southern hemisphere for the first time in the toarcian here we re describe a sinemurian belemnite from south tibet which was located at the gondwana margin at that time the specimen is characterized by a long rostrum with one deep and long alveolar groove with a splitting surface whose position cannot be determined as being either dorsal or ventral this morphological feature allows an assignment of the re described rostrum to either the sinobelemnitidae or the pachybelemnopseina the sinemurian belemnite from tibet represents the earliest firm record of the belemnitida from the southern hemisphere suggesting that the wide distribution and diversification of this order was established much earlier than previously thought

diversity and morphological evolution of jurassic belemnites from south germany abstract belemnites are extinct cephalopods whose evolutionary history is representative of successful adaptive radiations during the mesozoic nevertheless a detailed understanding of the dynamics and palaeoenvironmental drivers of this evolution is still lacking in order to fill this gap we analyze the diversity and morphological disparity of jurassic rostra from south germany and compare these patterns with other euro boreal trends we show that after an early apparition of few dissimilar groups during the hettangian sinemurian interval belemnites experienced four periods of diversification i e early pliensbachian middle late toarcian early bajocian and oxfordian marked by morphological disparifications of rostra towards forms potentially optimized for different hydrodynamic properties these adaptive radiations were interrupted at regional scale by four biological crises corresponding to morphological bottlenecks i e pliensbachian toarcian aalenian late bajocian and kimmeridgian most of them were morphoselective except the aalenian extinction which could be related to a prominent sea level fall by comparing our results to palaeoenvironmental data we show that warm temperate seawater temperatures might have favoured the diversification of belemnites potentially by accelerating their metabolic rates the population turnovers and the evolutionary rates on the long term conversely cooling or hyperthermal events correspond with biological crises migrations towards refuge areas located in the arctic and mediterranean domains could have been key factors for rapid post crisis recoveries finally the available data suggest a trend towards increased streamlining of the rostrum through the jurassic

quaternary atoll development new insights from the two dimensional stratigraphic forward modelling of mururoa island central pacific ocean knowledge about the quaternary evolution of mid ocean atolls comes mainly from drilling and field observations carried out on a number of pacific carbonate islands however little is known about the early to mid pleistocene atoll development history especially at margin and foreslope settings using previous field and subsurface data from mururoa atoll and a process based modelling software dionisos a two dimensional forward stratigraphic model of atoll development is proposed for the past 1 8 million years myr observational data from vertical to inclined coring seismic and bathymetric surveys indicate that from approximately 0 45 to 0 40 million years before present ma carbonate deposition at mururoa atoll resulted in a series of mostly prograding reef units the model is first constrained at the base by the shape and topography of the pre quaternary basement a number of sensitivity tests were performed to define the respective influence of variant parameters the best fit development scenario that accounts for the overall geometry and stratigraphic architecture of the quaternary sediment packages is obtained by using the sea level curve by miller et al 2005 uniform subsidence rate of 105 m myr 1 and carbonate production rates gradually increasing from 0 50 to 8 mm yr 1 between 1 80 ma and the present additional controlling parameters include subaerial erosion at a constant rate of 0 25 m kyr wave energy and sediment transport processes the stratigraphic forward model predicts a succession of three distinct types of carbonate systems that have developed since the earliest pleistocene toe of slope systems from 1 80 ma to about 0 80 ma open platform systems from 0 80 ma to 0 50 ma and framework reef systems from about 0 50 ma to the present the development of these different systems is most likely to be controlled by climate and changes in sea level cycles during the low amplitude 41 kyr cycle periods of the earliest pleistocene ambient conditions were not conducive to framework reef growth shallow water carbonate sedimentation was dominantly gravity driven operating along the platform foreslopes only during the mid pleistocene climate transition narrow open platform units have developed at the upper parts of the pre quaternary basement flanks with the onset of the high amplitude 100 kyr sea level modes and climate restoration reef frameworks started to be generated these models from mururoa agree with a number of previous studies suggesting that most of the true framework reefs were not initiated prior to 0 50 ma mururoa atoll is demonstrated to be a robust analogue for providing more realistic interpretations of the development history of pacific atolls further modelling with three dimensional dionisos could generate better predictions by taking into account hydrodynamic and transport parameters more accurately

the barremian aptian turnover of biota in northwestern europe evidence from belemnites abstract neocomian valanginian barremian and gault aptian albian are lithostratigraphic terms used in the last century to divide the sub chalk cretaceous of northern europe the division is based on significant palaeoceanographic and palaeogeographic changes in the early aptian these changes are linked to a major turnover of marine floras and faunas which occurred simultaneously in the boreal realm the tethys and the indo pacific ocean various floral and faunal elements became extinct in the aptian both in the tethys and in the boreal realm while on the other hand new genera and species evolved marked changes in the diversification rate were observed for organisms with a different mode of life plankton nekton benthos apart from calcareous nannofossils foraminifera and ammonites this turnover also occurs in belemnites and the suborder belemnitina was completely replaced by the suborder belemnopseina the northwestern european barremian is characterised by the very successful belemnite family oxyteuthididae belemnitina which was completely replaced by the genus neohibolites belemnopseina in early aptian times this aptian turnover which is expressed by a homogenisation of marine floras and faunas is best explained by significant palaeoceanographic changes occurring in the early aptian the sea floor spreading rate which increased at the barremian aptian boundary significantly peaked in the late early aptian a mantle plume in the pacific possibly caused an additional production of oceanic crust both processes caused a major sea level rise this in turn resulted in a major change of the palaeoceanographic setting and restricted marginal seas like the northwestern european basins in barremian times became drowned the more open oceanic setting of the aptian enabled cosmopolitan floras and faunas to spread worldwide the aptian saw the radiation of planktonic foraminifera which played only a minor role in pre aptian times these palaeoceanographic changes from restricted marginal seas to a more homogeneous pelagic setting are considered to be the main cause for the significant changes in the composition of belemnite faunas

application of stratigraphic sedimentological forward modeling of sedimentary processes to predict high quality reservoirs within tight sandstone abstract the prediction of high quality reservoirs within tight sandstone is presently a popular and challenging research topic many geophysical characteristics of tight sandstone reservoirs are similar to those of the surrounding rock making it difficult to predict the distribution of these reservoirs in this paper a stratigraphic sedimentological forward modeling is proposed to predict the distribution of high quality tight sandstone reservoirs in the xihu depression east china sea stratigraphic sedimentological forward modeling can evaluate the influences of different geological parameters on sedimentary processes and the results to reproduce the spatial distribution of sedimentary strata in a progradational delta and the overall stratigraphic stacking pattern different parameters were tested by numerical simulation according to the influence of the parameters on the sedimentary process the parameters can be divided into two types high sensitivity parameters transport capacity of the river and sand ratio and low sensitivity parameters maximum initial water depth lake level change and tectonic subsidence the analysis results are suitable for continental sedimentary basins with relatively high deposition rates in the process of optimizing the simulation parameters 236 simulations were carried out by adjusting the high sensitivity parameters and then the low sensitivity parameters an optimal model that can reflect the development characteristics of high quality tight sandstone reservoirs was obtained according to the characteristics of high quality reservoirs the product of the sand ratio and reservoir thickness from the sedimentary simulation results is used as the parameter for evaluating high quality reservoirs the ratio can effectively overcome the difficulties of insufficient amounts of data and seismic prediction and effectively predict the locations of high quality reservoirs in low exploration areas of tight sandstone reservoirs this method also provides a new idea for the prediction of high quality reservoirs in this kind of area in the future

non linear holocene climate evolution in the north atlantic a high resolution multi proxy record of glacier activity and environmental change from hvitarvatn central iceland abstract iceland is well situated to monitor north atlantic holocene climate variability terrestrial sites there offer the potential for well dated high resolution continuous records of environmental change and or glacier activity laminated sediments from the proglacial lake hvitarvatn provide a continuous record of environmental change and the development of the adjacent langjokull ice cap for the past 10 2 ka replicate lake sediment cores collected from multiple locations in the basin are placed in a secure geochronology by splicing a varve chronology for the past 3 ka with a tephra constrained paleomagnetic secular variation derived chronology for older sediments multiple proxies including sedimentation rate bulk density ice rafted debris sediment organic matter biogenic silica and diatom abundance allow annual to multi decadal resolution and reveal a dynamic holocene terrestrial climate following regional deglaciation of the main iceland ice sheet summer temperatures were high enough that mountain ice caps had already melted or were contributing insignificant sediment to the lake pronounced increases in sedimentation rate sediment density and the influx of terrestrial organic matter between 8 7 and 7 9 ka suggest early holocene warmth was interrupted by two distinct pulses of cold summers leading to widespread landscape destabilization and possibly glacier growth the holocene thermal maximum htm 7 9 to 5 5 ka was characterized by high within lake productivity and ice free conditions in the watershed neoglaciation is recorded as a non linear transition toward cooler summers landscape destabilization and the inception and expansion of langjokull beginning ca 5 5 ka with notable increases in ice cap size and landscape instability at 4 2 and 3 0 ka the past two millennia are characterized by the abrupt onset of sustained cold periods at ca 550 and 1250 ad separated by an interval of relative warmth from ca 950 to 1150 ad the greatest holocene extent of langjokull occurred in the nineteenth century and is coincident with peak landscape instability followed by ice recession throughout the twentieth century

reconstructing late holocene environmental change in iceland using high resolution tephrochronology high resolution records of sediment accumulation are necessary to evaluate subtle temporal and spatial variations in sediment flux especially in the context of decadal scale human environment inte

seismic stratigraphy and subsidence analysis of the southern brazilian margin campos santos and pelotas basins abstract the campos santos and pelotas basins have been investigated in terms of 2d seismo stratigraphy and subsidence the processes controlling accommodation space e g eustacy subsidence sediment input and the evolution of the three basins are discussed depositional seismic sequences in the syn rift barremian to the drift holocene basin fill have been identified in addition the subsidence uplift history has been numerically modeled including i sediment flux ii sedimentary basin framework iii relation to plate tectonic reconfigurations and iv mechanism of crustal extension although the initial rift development of the three basins is very similar basin architecture sedimentary infill and distribution differ considerably during the syn rift sag to the drift basin stages after widespread late aptian early albian salt and carbonate deposition shelf retrogradation dominated in the campos basin whereas shelf progradation occurred in the santos basin in the tertiary these basin fill styles were reversed since the paleogene shelf progradation in the campos basin contrasts with overall retrogradation in the santos basin in contrast long term cretaceous paleogene shelf retrogradation and intense neogene progradation characterize the pelotas basin its specific basin fill and architecture mainly resulted from the absence of salt deposition and deformation these temporally and spatially varying successions were controlled by specific long term subsidence uplift trends onshore and offshore tectonism in the campos and santos basins affected the sediment flux history distribution of the main depocenters and occurrence of hydrocarbon stratigraphic structural traps this is highlighted by the exhumation and erosion of the serra do mar serra da mantiqueira and ponta grossa arch in the hinterland as well as salt tectonics in the offshore domain the pelotas basin was less affected by changes in structural regimes until the eocene when the andean orogeny caused uplift of the source areas flexural loading largely controlled its development and potential hydrocarbon traps are mainly stratigraphic

palaeohydrology of the lower cretaceous pre salt lacustrine system from rift to post rift phase santos basin brazil abstract large oil accumulation discoveries in the last decade in the pre salt rock succession off the brazilian coast aroused renewed interest in carbonate reservoirs prompting several studies aiming at unravelling the conditions of formation of these rocks despite that there are still many gaps in the knowledge concerning environmental conditions of the deposition of the pre salt carbonates of santos basin located at the southeastern brazilian margin in this study we present and discuss a new suite of geochemical and biostratigraphic data of the lacustrine rift to post rift succession broadly correlated with itapema and barra velha formations of the santos basin whose deposition occurred in the aptian the integration of the petrographic biostratigraphic and geochemical data serves the ultimate purpose of the study which is to apply the new radiogenic strontium data as a proxy for the reconstruction of the evolution of the lake hydrology associated with the deposition of the carbonates of the itapema and barra velha formations these data are integrated into numerical models whose results bring new ideas on the general hydrologic conditions of the lake system and on its evolution through time the mass balance calculations indicate that two end members alone can account as potential sources of sr to the palaeolake a mafic and a felsic component respectively the latter likely contributed with significantly higher fluxes roughly one to two and up to four orders of magnitude higher than the former end member for most of the depositional history in order to generate the 87sr 86sr trends observed in the carbonate rocks finally the results obtained from the integration of the observations with the numerical models point to decreasing fluxes of water with time as contributed from both sources suggesting that the formation of the deposits became very likely constrained to progressively more evaporitic and alkaline lake waters these results also open up a new window into the environmental conditions of the interior gondwana continent immediately prior to the definitive opening of the south atlantic ocean

tectonic control of the oil rich large igneous carbonate salt province of the south atlantic rift abstract the early cretaceous south atlantic magmatic province samp which includes the parana etendeka lip produced about 8 million km 3 of tholeiitic basalt and diabase over an area of 4 million km 2 huge pre salt oil reserves discovered in 2007 by petrobras in non marine carbonates are estimated at more than 45 billion barrels here we show the close causal relationship of the southward increasing width of the wedge shaped south atlantic rift with the similarly southward increase in igneous activity in the thicknesses of non marine carbonate and salt and in the size of oil reserves all controlled mainly by south america s early clockwise rotation away from africa about a pole in its northeast large diabase dike swarms transversal to the rift witness to south america s rotation that opened in its wake the southward widening south atlantic rift westward increasing pressure on the equatorial margin by south america s clockwise rotation forced open the benue trough and created pre late aptian folds in the demerara plateau and in brazil s solimoes upper amazonas basin prerift and synrift volcanic activity increases southward culminating in the parana etendeka lip and in the offshore volcanic sdrss that continue southward to the cape basin berriasian valanginian rift sediments deposited from about 145 ma 10 ma before the flood basalts of the parana etendeka lip the largest transversal dike swarm continued in the proto walvis ridge that separated the central south atlantic endorheic rift basin from the sea in the south erosion and leaching of basalts supplied ca mg and sio 2 to the endorheic basin for the deposition of non marine carbonates and authigenic clays basalt flows intercalated with carbonates nearly until salt deposition about 113 ma hypogenic leaching of carbonates by mantle derived co 2 created optimal reservoirs supergiant oil deposits occur where the widest endorheic basin and the volcanic province overlap

cretaceous paleogeographic maps of brazil abstract thirty six paleographic maps covering the entire cretaceous record of brazil and all the brazilian basins are prepared for this paper each of the paleogeographic maps is accompanied with an explanation text the evolution of the country is seen in these maps such as 1 the early cretaceous rifting episode 2 first evidence of epicontinental and marginal seas with the conspicuous evaporite deposits 3 the albian cenomanian open seas and wide continental shelf 4 the turonian santonian transgressions onlap relationships and narrow continental shelves 5 the campanian maastrichtian onlap offlap relationships transitional to tertiary regressive deposits and 6 the evolution of the non marine interior basins some climatic observations are dealt with during the explanation of the maps

detachment faulting and the evolution of passive continental margins major detachment faults play a key role in the lithospheric extension process in the basin and range province and may also be important in other continental extension terranes such detachment faulting leads to an inherent asymmetry of extensional structure and of uplift subsidence patterns detachment models developed for the formation of metamorphic core complexes can also be applied to the formation of passive continental margins we therefore suggest the existence of upper plate and lower plate passive margins these give rise to a complementary asymmetry of opposing margins after continental breakup transfer faults offset marginal features and allow margins to switch from upper plate to lower plate characteristics along strike

a three dimensional high resolution reservoir model of napo formation in oriente basin ecuador integrating sediment dynamic simulation and geostatistics abstract with the rapid development of computer hardware and software technology 3d modeling technology of reservoirs has been widely applied in the exploration of oilfields however when modeling the reservoir with few wells due to the absence of efficient constraints in interwell areas the accuracy of the resulting 3d model is usually lacking in this paper we study the issue of model accuracy under the conditions of oil reservoir with few wells and propose a new 3d geological modeling method that is constrained by the multiple parameters based on sedimentary dynamics we carry out a series of sediment dynamic simulation by considering a number of key processes and parameters affecting the deposition of m1 member of napo formation in t oilfield oriente basin from 79 8 ma to 76 ma to constrain the lithofacies and properties models the proposed modeling method comprises two steps first the lithology distribution is obtained from a petrologic 3d model through the forward modeling of sedimentary processes second geostatistical method is applied to build the reservoir geological model with the constraints of sedimentary dynamics and logging information from work areas the distribution of sedimentary characteristics by using a coordination kriging modeling method as a result a high degree fit is obtained between the actual characteristics of the strata and the reservoir model with relative error of 4 6 indicating future application of this method for geological modeling of reservoirs with few wells

carbonate microbialites and hardgrounds from manito lake an alkaline hypersaline lake in the northern great plains of canada abstract manito lake is a large perennial na so 4 dominated saline to hypersaline lake located in the northern great plains of western canada significant water level decrease over the past several decades has led to reduction in volume and surface area as well as an increase in salinity the salinity has increased from 10 ppt to about 50 ppt tds this decrease in water level has exposed large areas of nearshore microbialites these organogenic structures range in size from several cm to over a meter and often form large bioherms several meters high they have various external morphologies vary in mineralogical composition and show a variety of internal fabrics from finely laminated to massive in addition to microbiolities and bioherms the littoral zone of manito lake contains a variety of carbonate hardgrounds pavements and cemented clastic sediments dolomite and aragonite are the most common minerals found in these shoreline structures however calcite after ikaite monohydrocalcite magnesian calcite and hydromagnesite are also present the dolomite is nonstoichiometric and calcium rich the magnesian calcite has about 17 mol mgco 3 ams radiocarbon dating of paired organic matter and endogenic carbonate material confirms little or no reservoir affect although there is abundant evidence for modern carbonate mineral precipitation and microbialite formation most of the larger microbialites formed between about 2300 and 1000 cal bp whereas the hardgrounds cements and laminated crusts formed about 1000 500 cal bp

quantitative seismic stratigraphic interpretation of the evaporite sequence in the santos basin abstract on the account of the absence of modern analogues the interpretation of evaporite bearing basins relies extensively on seismic and well data recent studies describe the intrasalt kinematic geometries and compositions relating the change of reflection patterns in seismic data to variations in evaporite sequences however these interpretations are only qualitative this study describes a step further in proceeding from qualitative to quantitative interpretation of an evaporite dominated interval it integrates geophysical and geological foundations by combining rock physics seismic inversion and statistical techniques to deliver seismic driven facies volume of the evaporite sequence in the santos basin offshore brazil synthetic seismogram demonstrate the ambiguities and uncertainties in relating the seismic amplitude to salt types rock physics analysis indicates that acoustic impedance is an effective differentiator of salt types in comparison to seismic amplitude therefore we perform seismic inversion to transform interface property into layer property the acoustic impedance volume mitigated significantly the risk of seismic interpretation in the salt sequence the bayesian classification integrates acoustic impedance and rock physics analysis to deliver the seismic driven facies volume which categorizes bittern salts halite and anhydrite this enables the refinement of the seismic stratigraphic interpretation of intrasalt sequences of the ariri formation based on the sedimentary cycles of evaporites additionally we calculate proportion maps to evaluate the spatial variability of salt deposition we observe an increase in bittern salts and anhydrite proportions from the bottom to the top of the sequence the comparison between well based and seismic based proportions testifies to the quantitative potential of seismic data the approach provides quantitative analysis of the evaporite sequence and can be applied to other salt bearing basins

stromatolites in precambrian carbonates evolutionary mileposts or environmental dipsticks stromatolites are attached lithified sedimentary growth structures accretionary away from a point or limited surface of initiation though the accretion process is commonly regarded to result from the sediment trapping or precipitation inducing activities of microbial mats little evidence of this process is preserved in most precambrian stromatolites the successful study and interpretation of stromatolites requires a process based approach oriented toward deconvolving the replacement textures of ancient stromatolites the effects of diagenetic recrystallization first must be accounted for followed by analysis of lamination textures and deduction of possible accretion mechanisms accretion hypotheses can be tested using numerical simulations based on modern stromatolite growth processes application of this approach has shown that stromatolites were originally formed largely through in situ precipitation of laminae during archean and older proterozoic times but that younger proterozoic stromatolites grew largely through the accretion of carbonate sediments most likely through the physical process of microbial trapping and binding this trend most likely reflects long term evolution of the earth s environment rather than microbial communities

kinematic keys of the santos namibe basins understanding the genesis of the very peculiar 600 km wide santos basin sa o paulo plateau system and its narrow conjugate namibe margin is a kinematic and structural problem several hypotheses have been proposed in order to explain the genesis of this system that imply the same amount of horizontal movement we investigate the consequences of the horizontal movement in the santos basin based in plate kinematic reconstructions the kinematic history of this system that we present here based on the interpretation of seismic profiles and kinematic constraints has the following consequences 1 there is no evidence of a ridge jump sensu stricto but rather a southwards propagation in the central segment of the south atlantic that starts in the northern part between the ne brazilian and gabonese margins 2 the namibe margin evolved as a transform passive margin 3 the opening direction of the santos basin sa o paulo plateau system is oblique to the general opening motions of the south american and african plates and 4 this opening is younger 6 ma than those of the other basins of the central segment of the south atlantic

stable isotope records from sepia officinalis a key to understanding the ecology of belemnites abstract the stable isotope ratios 1 8 o 1 3 c of the aragonite of cuttlebones of sepia officinalis were measured on a high resolution scale where every septum was measured our studies aim at understanding whether variations of the isotope signature are controlled by ontogenetic and or ecological factors five specimens were reared from eggs under known water temperatures a sixth specimen was caught in the german part of the north sea the data suggest that the oxygen isotope composition is in isotopic equilibrium with the surrounding seawater and reflects ambient temperature migration and seasonal temperature changes are visible in the acquired data set the carbon isotope signature shows signs of biofractionation and no direct correlation to the oxygen signature as far as ontogeny and ecology are concerned

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

three dimensional stratigraphic sedimentological forward modeling of an aptian carbonate reservoir deposited during the sag stage in the santos basin brazil abstract stratigraphic sedimentological forward modeling is a useful technique to test the role of parameters that may act in the depositional processes of sedimentary rocks the technique was applied to the santos basin brazil using the software program dionisos to test possible depositional scenarios for an aptian section of a lacustrine carbonate platform developed during the late sag stage uppermost pre salt section of the basin different parameters were tested in a set of numerical simulations with the aim of reproducing the carbonate facies spatial distribution and the overall stratigraphic stacking pattern of the platform as observed in the available well data several models were simulated and four of them are discussed in this paper based on the available descriptive data from 10 wells model 3 is considered to produce the best fit to explain the development of the 100 m thick aptian carbonate platform occurrences of grainstones and stromatolites as proximal and intermediate facies respectively and the overall carbonate stacking pattern thus based on 3d stratigraphic sedimentological forward modeling the best set of environmental conditions able to explain the pattern of carbonate deposition observed in the study area are 1 a slow carbonate depositional rate 0 08 mm y over an interval of 2 4 my which is indicative of a larger microbial contribution and 2 lake level oscillations which were essentially induced by arid climatic conditions these results also enable new perspectives for the application of stratigraphic sedimentological forward modeling as a predictive tool for hydrocarbon exploration in carbonates and for the development of depositional models of other sag carbonate platform settings

lake level and paleoenvironmental history of lake tanganyika africa as inferred from late holocene and modern stromatolites fossil and living stromatolites are abundant around the margins of lake tanganyika africa and provide a wealth of paleolimnologic and paleoclimatic information for the late holocene six lines of evidence show that stromatolites and cements are precipitating in the lake today 1 carbonate saturation state calculations 2 documentation of living stromatolites and their depth distribution 3 new stable isotope data showing the lake s present mixing state and ancient evaporation and inflow balance 4 new radiocarbon data and a reevaluation of apparent 14 c ages derived from lake tanganyika carbonates 5 the presence of modern mg calcite cements derived from lake waters and 6 the presence of modern biologically mediated mg calcite precipitates in the lake lake tanganyika s lake levels have been remarkably stable over the past 2800 yr fluctuating around the marginally open to marginally closed level through most of this time period lake lowstands and high 18 o values from the ninth century b c to the early fifth century a d indicate that the lake basin was comparatively dry during this time however the period prior to the most recent opening of lake kivu into the lake tanganyika basin ca a d 550 was not marked by major lake lowstands nor was this opening accompanied by a dramatic lakelevel rise the kivu opening was roughly coincident with a significant shift toward isotopically lighter 18 o and 13 c lake water which persists today the lake remained close to its outlet level between the sixth and thirteenth centuries a d lake levels rose between the fourteenth and sixteenth centuries at some time between the late sixteenth and early nineteenth centuries lake level fell to perhaps its lowest level in the past 2800 yr by the early nineteenth century lake level had begun to rise to the overflow level apparently the result of a regional increase in precipitation evaporation ratios weak 18 o 13 c covariance for late holocene carbonates suggests that the surface elevation of the lake has remained near the outlet level with only occasional periods of closure however there is no simple relationship between solute input from lake kivu isotope input from lake kivu and lake levels in lake tanganyika lake kivu waters are the primary source of major ions in lake tanganyika but are much less important in controlling the 18 o and the lake level of lake tanganyika because the ruzizi river s discharge into lake tanganyika is largely derived from sources other than lake kivu the overflow events in the two lakes have been uncoupled during the late holocene

presalt stratigraphy and depositional systems in the kwanza basin offshore angola the lower cretaceous presalt section in the kwanza basin contains an excellent petroleum system that includes synrift strata barremian overlain by a sag interval aptian and capped by the loeme salt the upper synrift is generally limestone with widespread mollusk packstones and grainstones coquinas deposited in a fresh to moderately saline alkaline lake the sag interval is characterized by carbonate platforms and silica rich isolated buildups formed in highly evaporated highly alkaline lakes shrubby dendritic microbially influenced boundstones and intraclast spherulite grainstones accumulated in shallow water on platform tops microbial cherts were deposited as organic buildups on large isolated structural highs basinward west of platforms and they apparently formed at low temperatures in very alkaline lake water shrubby boundstones and microbial cherts have vuggy pores that are primary and result in high permeability wackestones and packstones with calcitic grains mainly spherulites in dolomite or argillaceous dolomite were deposited in slightly deeper low energy sag environments in addition clays especially stevensite precipitated out of the silica rich highly alkaline lake waters during sag deposition calcite precipitated on the shallow lake floor with morphologies that ranged from spherulites to shrubs and included a continuum of intermediate forms spherulites probably precipitated just below the sediment water interface spherulites and shrubby calcites are commonly recrystallized spherulites floating in stevensite probably formed in deeper lacustrine environments organic rich mudstones were deposited in even deeper lacustrine environments in synrift and sag intervals and they are likely the source of most hydrocarbons in this system these interpretations are supported by seismic core petrographic and stable isotope data

stratigraphic simulation of sedimentary basins concepts and calibration a two dimensional stratigraphic simulation program based on semiempirical algorithms has been successfully applied to clastic carbonate and mixed clastic carbonate depositional regimes the program may be used to predict reservoir distribution to constrain interpretations of well and seismic data to test exploration scenarios in frontier basins and to evaluate the fundamental controls on basin stratigraphy applications to seismic and well log data sets from main pass u s gulf coast offshore sarawak malaysia and the baltimore canyon u s east coast demonstrate that the program simulates stratigraphy on a basin wide scale as well as on the scale of individual prospects the main pass section is an offlapping sequence of neogene clastics the model simulates 17 m y of geologic history at a 200 000 yr resolution and reproduces gross basin geometry major sequence boundaries depth and location of nearshore marine sands intervals of sediment bypass into deep water shelf margin positions and paleobathymetry three neogene carbonate buildups of central luconia offshore sarawak malaysia were simulated using a sea level history optimized to reproduce the carbonate growth anatomy the model reproduced observed seismic reflection geometries and transgressive aggradational progradational retrogradational and subaerial exposure phases the program has also simulated jurassic pleistocene basin and stratigraphic sequence geometries and mixed clastic carbonate facies distribution along a 300 km regional dip line of the baltimore canyon trough modeled features of interest include a progradational middle jurassic carbonate margin punctuated by clastic deposition during sea level lowstands and a late jurassic early cretaceous aggradational carbonate margin culminating in the development and subsequent drowning of isolated carbonate buildups simulated bathymetries facies relations and subaerial exposure surfaces for the early cretaceous aggradation margin are consistent with detailed petrographic paleontologic and seismic stratigraphic interpretations