pleistocene multiple growth lacustrine oncoids from the poacher s point formation etosha pan northern namibia the poacher s point formation is located within the etosha pan northern namibia it contains pleistocene stromatolites ooids and silica nodules the stromatolites were constructed by cyanobacteria in very lowenergy lacustrine conditions the internal structure of the oncoids is complex and subdivided into shells by unconformities each unconformity bounded shell probably represents stromatolite growth during a distinct lacustrine event shallower conditions are represented by colloform growth and deeper water by smooth oncoid mat morphology the unconformities represent hiatuses of unknown duration at least six stromatolite growth shells are recognized silica concretions which may have developed during shallowing lake stages are also present the lack of clastic material in the carbonate lithologies suggests that the lake waters may have accumulated from collecting rainwater or have been spring fed the lowest bed of the succession is a saline clay which represents a seasonally flooded salt pan deposited in an arid to semi arid climate similar to that of today the overlying carbonates represent sedimentation during a series of transient lacustrine events representing intermittent wetter periods finally due to progressive aridity the lacustrine succession was terminated by calcrete development

sedimentary architecture of a prograding oolitic siliciclastic wedge response to changes in wave base oscillation kimmeridgian iberian basin abstract a detailed facies and sequential architectural analysis has been carried out along the wedge shaped shallow marine cross bedded oolitic siliciclastic ricla member kimmeridgian northern iberian basin the obtained results are based on fieldwork along the 4 1 km continuous outcrops with the use of high resolution photomosaics and drone made videos which have led to a precise and extensive facies reconstruction three main facies that are laterally related a to b to c in down dip direction have been differentiated which correspond to the topset foreset and bottomset parts of a sloping depositional surface sedimentation was controlled by sweeping drift and downwelling storm induced currents causing avalanching processes with the deep action of oscillatory currents the sedimentary architecture consists in 5 successive units composed by several sub units arranged according to different stacking patterns which reflect the sedimentary response to wave base oscillations superimposed to the regressive part of a third order transgressive regressive cycle the sedimentological features indicate that this unit which has been previously interpreted as a dune complex fit with an infralittoral prograding wedge model as it is observed in geographically close and stratigraphically similar units the ricla member is therefore regarded as an example of a well exposed grain supported unit with broad potential application to other prograding grain dominated lithosomes that do not conform to the traditional sand shoal model

middle and late jurassic radiolarian palaeoecology versus carbon isotope stratigraphy abstract jurassic radiolarians are sensitive to palaeoclimatic palaeoceanographic changes recorded by the stable carbon isotope curve carbon isotopic variations have been linked to changes in ocean structure productivity and concentrations of greenhouse gases in the atmosphere in the middle upper jurassic terminilletto section of the umbria marche sabina apennines central italy well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform derived carbonates the 13 c curve in the aalenian kimmeridgian interval indicates three main positive 13 c events in the lower bajocian late bathonian lower callovian and middle oxfordian the positive 13 c shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea water spumellaria nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with 13 c and chert abundance values and seem to be related to episodes of high nutrient mobilisation from the base of the bajocian the radiolarian associations show a slight tendency towards diversification coincident with increasing 13 c values in the upper part of the middle bajocian last appearances prevail over first appearances associated with the peak of the 13 c event this may indicate maximum eutrophic conditions coincident with the late bathonian early callovian positive 13 c shift the radiolarian associations record a different trend with respect to the bajocian event when the 13 c values are increasing to a maximum radiolarian associations tend to be reduced in species diversity followed by a small diversification trend when the 13 c values are decreasing we speculate that during the callovian a more stressful palaeoenvironment due to high level of eutrophication is indicated by the combination of high productivity of biogenic silica and low carbonate input although varying preservational conditions may have influenced the observed trends in the radiolarian associations the good correlation between changes of sedimentation patterns radiolarian assemblages and 13 c positive anomalies open interesting avenues for further investigations concerning the palaeoecology of mesozoic radiolarians

continuity and facies heterogeneities of shallow carbonate ramp cycles sinemurian lower jurassic north east spain the lateral continuity and facies heterogeneities of metre scale cycles in a greenhouse lower jurassic sinemurian carbonate ramp from the northern iberian basin spain was evaluated from extensive field analysis carried out on a well exposed 12 km long outcrop eleven high frequency continuous cycles and their bounding surfaces are traceable laterally through the entire outcrop however three of these cycles are found to split laterally into discontinuous cycles of more limited distribution up to 3 to 5 km of lateral extent the continuous and discontinuous cycles have a similar field expression in one dimensional logs as a consequence the number of cycles that can be differentiated is variable along the logged sections i e from 11 to 16 cycles have variable facies heterogeneities and sedimentary trends depending on the environment of formation shallowing upward and symmetrical cycles occur in protected lagoon tidal flat areas and in the open marine high energy domain these cycles show significant facies heterogeneities which were controlled mainly by lateral migration of a mosaic of facies over an irregular topography deepening upward and aggradational cycles are generated in low energy sub wave base open marine areas facies are laterally homogeneous reflecting low potential for carbonate accumulation and inability to fill the created accommodation space in this low relief and relatively deep area cycle boundaries are generated by stages of rapid accommodation gain involving the flooding of the carbonate ramp they are more likely to originate from regional tectonic pulses related to the extensional tectonics operating in the northern iberian basin rather than greenhouse low amplitude eustacy discontinuous cycles tend to occur in thickened areas and are interpreted as originating from the infill of wedge shaped accommodation space resulting from differential subsidence i e local tectonic pulses in conclusion where thickness variations occur in extensional settings lateral continuity of cycles should not be expected in less well exposed or in one dimensional sections and in wells it would not be possible to distinguish continuous from discontinuous cycles or to understand such two dimensional heterogeneities identification of unique cycle forming mechanisms or attempting cyclostratigraphic long distance correlation of cycles is unrealistic without a detailed analysis of the architecture of cycles in laterally continuous outcrops

microbial deposits in the aftermath of the end permian mass extinction a diverging case from the mineral mountains utah usa the lower triassic mineral mountains area utah usa preserves diversified smithian and spathian reefs and bioaccumulations that contain fenestral microbialites and various benthic and pelagic organisms ecological and environmental changes during the early triassic are commonly assumed to be associated with numerous perturbations productivity changes acidifica tion redox changes hypercapnia eustatism and temperature changes post dating the permian triassic mass extinction new data acquired in the mineral mountains sediments provide evidence to decipher the relationships between depositional environments and the growth and distribution of microbial structures these data also help to understand better the controlling factors acting upon sedimentation and community turnovers through the smithian early spathian the studied section records a large scale depositional sequence during the dienerian spathian interval during the transgression depositional environments evolved from a coastal bay with continental deposits to intertidal fenestral microbial limestones shallow subtidal marine sponge microbial reefs to deep subtidal mud dominated limestones storm induced deposits microbialite sponge reefs and shallow subtidal deposits indicate the regression three microbialite associations occur in ascending order i a red beds microbialite association deposited in low energy hypersaline supratidal conditions where microbialites consist of microbial mats and poorly preserved microbially induced sedimentary structure ii a smithian microbialite association formed in moderate to high energy tidal conditions where microbialites include stromatolites and associated carbonate grains oncoids ooids and peloids and iii a spathian microbialite association developed in low energy offshore conditions that is preserved as multiple decimetre thick isolated domes and coalescent domes data indicate that the morphologies of the three microbialite associations are controlled primarily by accommodation hydrodynamics bathymetry and grain supply this study suggests that microbial constructions are controlled by changes between trapping and binding versus precipitation processes in variable hydrodynamic conditions due to the presence of numerous metazoans associated with microbialites throughout the smithian increase in accommodation and spathian decrease in accommodation the commonly assumed anachronistic character of the early triassic microbialites and the traditional view of prolonged deleterious conditions during the early triassic time interval is questioned

jurassic evolution of the arabian carbonate platform edge in the central oman mountains the jurassic sahtan group exposed in northern oman was deposited in shallow marine environments at the edge of the arabian platform facing the neo tethys hamrat duru basin the upper sahtan group is made up of a mixed siliciclastic carbonate unit overlain by pure carbonate deposits assigned to a bathonian and early callovian age on the basis of brachiopods and foraminifers these carbonate depositional systems were composed of outer oolitic shoals that underwent subaerial exposure and a deeper somewhat restricted gently dipping shelf interior oolitic material was shed off the platform edge into the deep sea depositional complex of the guweyza formation the sahtan group is affected by an important thickness reduction towards northeastern jabal akhdar the angular unconformity 0 2 at the top of the sahtan group is shown to result from tilting and top truncation of genetic sequences this unconformity is overlain by the rayda formation a veneer that shows an onlap pattern including a gradual deepening upwards facies evolution the minimal time span of the stratigraphic hiatus is mid callovian kimmeridgian oxfordian and kimmeridgian sequences were probably never deposited in this area because of lack of accommodation space and or because of subaerial exposure it is proposed herein that the unconformity was shaped by subaerial carbonate dissolution during a steady tectonically driven exhumation of the platform edge during the tithonian a major eustatic sea level rise caused transgression of the rayda formation upon the platform edge and normal shelf marine conditions resumed in the eastern arabian peninsula

freshwater carbonates within a late triassic siliciclastic fluvial system in a gondwana rift basin the maleri formation india abstract spring related carbonates are valuable repositories for information on physical and biotic environments of the past however for mesozoic and earlier records their use is limited due to their low preservation potential and difficulties in accurate identification of the carbonate type this study aims to characterise the source of carbonate clasts preserved as thin beds of cross bedded grainstones in late triassic siliciclastic fluvial deposits the maleri formation pranhita godavari rift basin india the microfabric and stable isotopic compositions of the grainstones and thin and discontinuous beds of impure limestones of this formation are presented here these features help in identifying the freshwater carbonate precipitating environments that existed in an ancient continental rift basin though such deposits are not primarily preserved in this case the microfabric of the carbonate grains provides evidence for carbonate precipitation in aquatic environment related to karstic springs taking together the microfabric stable isotopic compositions as well as the associated geological and palaeontological information it could be shown that the calcium carbonate precipitation took place in palustrine pools related to tufa like spring systems and in alluvial swamps under a pluvial climatic setting this research thus demonstrates that carbonate grains derived from spring related carbonate deposits formed mainly near the margins of rift basins can be incorporated into nearby siliciclastics if interpreted correctly they can be used in reconstructing ancient karstic carbonate environments even when in situ primary record is not preserved therefore making it possible to access the information stored in freshwater carbonates

an oscillating trend in phanerozoic non skeletal carbonate mineralogy textural and compositional data on ancient ooids and cements suggest the existence of an oscillating phanerozoic temporal trend in non skeletal carbonate mineralogy the trend shows good correlation with eustatic climatic oscillations proposed by others the most likely mechanism appears to be plate tectonically influenced oscillations in pco2 the vapour pressure of co2 rather than change in oceanic mg ca ratio

calcitic aragonitic and mixed calcitic aragonitic ooids from the mid proterozoic belt supergroup montana a great variety of ooid types occurs within the siyeh and snowslip formations of the mid proterozoic belt supergroup montana cortical layers are inferred to have been composed either of calcite in a radial concentric or radial with dark rays fabric or aragonite in a radial or concentric fabric the calcitic cortical layers record their original fabrics but the originally aragonitic cortical layers have been replaced by calcite in a range of textures and by quartz and dolomite some formerly aragonitic cortical layers are replaced by calcite spar which contains relics of the original cortical structure others consist of calcite spar without inclusions or columnar calcite which grew radially from the nucleus commonly a calcitic ooid some ooids were wholly composed of calcite others were of aragonite but two phase ooids were common mostly consisting of an inner calcitic part and an outer aragonitic part probable microdolomite inclusions suggest a high mg content of the calcitic cortical layers the depositional environment of these oolites was probably analogous to baffin bay texas where a similar range of ooid types is forming today

spatial variation in carbonate carbon isotopes during the cambrian spice event across the eastern north china platform abstract the cambrian spice steptoean positive carbon isotope excursion event is widely reported from the late miaolingian to the early furongian but recent studies imply that the synchroneity and magnitude of the spice may be controversial in order to test the spatial variation of the spice here we present 367 carbonate 13c data from six outcrop sections across a 700 km transect along the eastern north china platform the spice is present in all the studied sections but showing different features regarding the duration and magnitude an abrupt increase in 13c from 1 5 to 3 5 occurs in three shandong sections with maximum value present only in a thin 0 5 1 2 m thick transgressive lag deposit crudely wave stratified bioclastic grainstone in contrast the 13c record of the baijiashan and shashan sections in the liaoning region displays a gradual increase 20 m thick from 1 5 to the maximum value of 4 7 both facies analysis and trilobite collections suggest that the spatial variation of the spice in the north china platform most likely resulted from missing of sedimentary record with high 13c values in the shandong sections as a result of erosion and non deposition during sea level lowstand a possible coeval hiatus prior to the sauk iii transgression in the laurentian basins further high resolution integrated studies of sedimentology biostratigraphy and sedimentary geochemistry on the spice event are required to better understand its nature

controls on the distribution of deep sea sediments deep sea sediments represent the largest geological deposit on earth and provide a record of our planet s response to conditions at the sea surface from where the bulk of material originates we use a machine learning method to analyze how the distribution of 14 400 deep sea sediment sample lithologies is connected to bathymetry and surface oceanographic parameters our probabilistic gaussian process classifier shows that the geographic occurrence of five major lithologies in the world s ocean can be predicted using just three parameters sea surface salinity and temperature provide a major control for the growth and composition of plankton and specific ranges are also associated with the influx of non aerosol terrigenous material into the ocean while bathymetry is an important parameter for discriminating the occurrence of calcareous sediment clay and coarse lithogenous sediment from each other we find that calcareous and siliceous oozes are not linked to high surface productivity diatom and radiolarian oozes are associated with low salinities at the surface but with discrete ranges of temperatures reflecting the diversity of planktonic species in different climatic zones biosiliceous sediments cannot be used to infer paleodepth but are good indicators of paleotemperature and paleosalinity our analysis provides a new framework for constraining paleosurface ocean environments from the geological record of deep sea sediments it shows that small shifts in salinity and temperature significantly affect the lithology of seafloor sediment as deep sea sediments represent the largest carbon sink on earth these shifts need to be considered in the context of global ocean warming

oxfordian ramp system la manga formation in the bardas blancas area mendoza province neuquen basin argentina facies and depositional sequences abstract the outcrops of the oxfordian la manga formation at bardas blancas neuquen basin west central argentina allow the recognition of six different depositional facies a to f on the basis of sedimentological analysis taphonomic attributes and microfacies studies these depositional facies correspond to outer ramp a middle ramp b inner ramp oolitic shoal c inner ramp margin patch reef d lagoon deposits e and a paleokarst surface f outer ramp deposits which are not completely represented consist of greyish carbonate beds where the fabric of the shell beds gryphaeids reflects the action of waves and currents middle ramp deposits consist of a packstone grainstone lithofacies indicating the importance of storm processes and is dominated by ooids intraclasts pelecypods echinoderms and gastropods which accumulated on a middle ramp storm dominated shoreface trace fossils belong to the skolithos and cruziana ichnofacies characterizing the upper lower and middle shoreface setting respectively the inner ramp deposits consist of oolitic grainstones and subordinate packstones shoal with a small sponge bioherm at the base different types of ooids peloids and coated grains are abundant as well as skeletal fragments of molluscs echinoderms and corals lithofacies and microfacies studies suggest a high energy and shallow water depositional setting the inner ramp margin deposits consist of reef core facies fore and back reef facies characterized by a scleractinian community of relatively low generic diversity the rich associated fauna consists of bivalves echinoids serpulids bryozoans dasycladacean algae and cyanophytes as well as foraminifers and ostracods the growth forms of the corals are indicative of shallow well illuminated water both the back and fore reef deposits suggest intensive reworking by storm waves or currents the lagoon deposits consist of bioclastic and peloidal wackestones as well as bioclastic intraclastic packstones which accumulated on a lagoon under intermittently agitated water in a shallow subtidal to intertidal settings a stratiform breccia with both matrix and clasts supported fabrics is interpreted as paleokarst the clasts are derived from the rocks of oolitic shoal and inner ramp margin patch reef the six depositional facies are included into a major organizational framework of three third order depositional sequences ds 1 ds 2 ds 3 mainly represented by transgressive and highstand systems tracts stages with sequence boundaries of regional importance the general depositional evolution is here related to the slow subsidence experienced during the oxfordian earliest kimmeridgian time related to tectonic inversion in the neuquen basin a four step architectural and sedimentary schematic model of the response of the platform to sea level changes is proposed

soft sediment deformation structures in cambrian siliciclastic and carbonate storm deposits shandong province china differential liquefaction and fluidization triggered by storm wave loading abstract this paper focuses on soft sediment deformation structures ssds in both siliciclastic and carbonate storm deposits of the cambrian mantou and chaomidian formations shandong province china in order to understand their deformation mechanisms and possible triggers siliciclastic ssds e g sand volcanoes and pillows and carbonate ssds e g sedimentary dykes grainstone matrix breccias deformed cross beddings and marlstone matrix breccias occur exclusively in hummocky cross stratified fine sandstone and peloidal grainstone respectively the siliciclastic ssds formed in porous and permeable surface sediment whereas the carbonate ssds formed under shallow burial conditions when early marine cementation prevailed the various deformation structures resulted mainly from differences between siliciclastic and carbonate sediment conditions and resulting deformation mechanisms sand volcanoes formed by upward extrusion of over pressured fluidized sandy sediment whereas sand pillows resulted from upward injection of lower density muddy sediment into overlying liquefied sandy sediment sedimentary dykes and grainstone matrix limestone breccias formed as a result of differential liquefaction and fluidization of heterogeneously cemented carbonate sediment whereas deformed cross beddings and marlstone matrix limestone breccias developed by the thixotropic liquidization and injection of clayey sediment and further disruption of thin peloidal layers sedimentary facies analysis and analysis of the physical processes indicate that the ssds were most likely caused by cyclic loading of storm waves

automated mineralogical methodology to study carbonate grain microstructure an example from oncoids oncoids collected from an arid intertidal embayment of the gulf of aqaba saudi arabia were examined for their morphology and mineralogical composition this study tested a methodological approach for studying oncoid microstructure and chemical mineralogical composition in detail the method was applied to more than 30 oncoid samples and examined internal morphology and composition via automated mineralogy and petrographic methods deploying quantitative evaluation of minerals by scanning electron microscopy qemscan the qemscan analysis system gathers x ray and backscattered electron data from predefined points on a sample and interprets it in mineralogical terms by comparisons with a spectral library volumetric modal analysis a function of the cumulative data obtained is then used to quantify the mineral species present in the sample the most abundant minerals in this study consist of calcium carbonate 60 70 quartz dominates the detrital trapped grains 19 5 potassium feldspar and albite constitute 5 6 and 3 4 respectively minerals such as illite chlorite biotite muscovite smectite kaolinite apatite and ilmenite and siderite individually make up less than 1 of the overall oncoid composition unlike traditional light microscope petrography x ray fluorescence and x ray diffraction methods the proposed technique has several advantages including but not limited to preservation of the oncoid microstructure porosity and pore size estimation elemental distribution of major minerals determination of the chemical composition of grains as well as the cement and relatively high accuracy of elemental compositional data taken from polished sections this study shows that qemscan can provide an effective and robust tool in analyzing different components of oncoids and other carbonate grains

lithofacies and cyclicity of mohilla evaporite basins on the rifted margin of the levant in the late triassic makhtesh ramon southern israel marine connected basins with evaporites occur beneath most extensional continental margins that originated at low latitudes and often are of major economic significance cyclicity in the evaporite lithofacies reflects the degree of restriction of the basin overprinted by sea level changes and caused by structural movements in the barrier region whether by fault block rotation footwall uplift or hanging wall subsidence in both extensional and compressional basins the upper triassic evaporites of the ramon section in southern israel model cyclic sedimentation in such environments the mohilla formation is a carbonate evaporate siliciclastic succession of carnian age that fills a chain of basins extending along the levant margin from southern israel to jordan and syria the basins developed in half grabens adjacent to normal faults that formed during a period of regional extension evaporites of this formation are well exposed in outcrops at makhtesh ramon the southernmost of these basins the m2 member of the mohilla formation is composed of 42 sub metre cycles of alternating dolostone gypsum and calcareous shales field and microfacies analysis showed these cycles to conform mostly to restricted shallow and marginal marine environments spatially limited by the uplifted shoulders of the half graben systems a total of 10 facies types belonging to six depositional environments have been identified from stacking patterns and analysis of bed to bed change cycles can be categorized into three groupings i low frequency exposure to exposure cycles that developed under eustatic or climate control ii high frequency deepening shallowing upward cycles characterized by gradual transitions due to short term sea level or runoff event oscillations possibly referable to orbital forcing and iii high frequency shallowing upward cycles characterized by abrupt transitions attributable to sporadic tectonic events affecting accommodation space or barrier effectiveness the way facies and cycling of the sedimentary environments was deciphered in the mohilla evaporite basin can be used to unravel the genesis of many other evaporite basins with barriers of tectonic origin

paleoenvironmental framework of dinosaur tracksites and other ichnofossils in early cretaceous mixed siliciclastic carbonate deposits in the neuquen basin northern patagonia argentina abstract the study of the uppermost section of the early cretaceous agrio formation in northern patagonia neuquen basin where dinosaur tracks assigned to cf therangospodus pandemicus are exposed tracksites i and ii evidence mixed marginal marine siliciclastic carbonate deposits the succession was divided in two intervals a lower one containing theropod tracks recorded on top of subtidal oolithic limestones with tiny wave ripples suggesting shoreline fluctuations and subaerial exposure tidal influence is recognised by fining upward and prograding cycles starting with subtidal carbonates and ending with fine grained siliciclastic deposits at the top or rarely laminites dolomitization affects subtidal deposits generated in an alkaline media stressful for tracemakers intertidal facies include abundant heterolithic deposits coquinas composed of gastropods encrusted by multilayered bryozoans and muddy levels with incipient mud cracking invertebrate ichnofossils recognized from tidally dominated deposits include arenicolites kouphichnium and rhizocorallium the upper interval is a transgressive regressive cycle that starts with dark shales deficiently oxygenated and covered by prograding sandstones and finally sand flat deposits this interval contains gyrochorte hillichnus and ophiomorpha documented in wave influenced sandstones dinosaur tracks as well as hillichnus attributed to tellinoid bivalves and kouphichnium assigned to xiphosurans imply the activity of producers rarely recorded previously as body fossils in marginal marine deposits of southern south america previous paleogeographic schemes are questioned by our analysis which shows evidence of extremely shallow and tide controlled sedimentation sometimes with subaerial exposure with high cyclicity related to a marginal marine depositional setting and lack of significant erosion by the overlying unit as traditionally was suggested

permian oolitic carbonates from the baoshan block in western yunnan china and their paleoclimatic and paleogeographic significance marine carbonate ooids are environment sensitive and hence valuable for paleoclimatic and paleogeographic reconstructions this paper describes permian ooids from the baoshan block in western yunnan china in order to offer a new means to refine the uncertain paleogeographic details of this gondwana derived block four major types of ooids micritic ooids compound ooids leached ooids and half moon ooids are documented from the hewanjie formation in the northern and the shazipo formation in the southern baoshan block these ooids are dated via biostratigraphic analysis to be wordian early wuchiapingian and signify an ameliorated shallow marine temperature for the guadalupian strata of the baoshan block results of this study coupled with literature data reveal diachronous debut of permian ooids among the gondwana derived blocks mostly sakmarian in central taurides of turkey central iran central pamir and karakorum block versus wordian capitanian in baoshan block peninsular thailand and south qiangtang in contrast asselian sakmarian strata of baoshan block as well as peninsular thailand and south qiangtang are characterized by glaciomarine diamictites these observations suggest that the baoshan block was probably situated at a considerably higher paleolatitude under distinct influence of gondwana glaciation during the asselian sakmarian than those blocks yielding sakmarian ooids moreover marine ooids are virtually absent nearby the equator within the permian tethys similar to the modern situation the baoshan block is accordingly interpreted to drift to warm water southern mid latitudes during the wordian capitanian and remain to the south of central iran karakorum block and south china which were equatorially located in the capitanian

facies and depositional sequence evolution controlled by high frequency sea level changes in a shallow water carbonate ramp late kimmeridgian ne spain the outcrops of the sierra de albarracin ne spain allow a precise reconstruction of the shallow sedimentary domains of a late kimmeridgian carbonate ramp developed in western marginal areas of the iberian basin the sedimentary record shows a hierarchical sequence stratigraphic organization which implies sea level changes of different frequencies the studied succession is arranged in a long term transgressive regressive sequence which is likely to reflect local variation in the subsidence rates this sequence includes four higher order sequences a to d which have variable thickness from 3 to 21 m the similar sedimentary evolution observed in distant localities suggests the existence of high frequency sea level fluctuations controlling the sequence development the average amplitude of these cycles would range from 5 to 10 m the precise estimation of their duration some few hundreds of kyr and their possible assignment to any of the long term orbital cycles the 100 or the 400 kyr eccentricity cycles is uncertain sequences a and b formed during the long term transgressive interval are relatively thin from 3 to 9 m give up sequences that were never subaerially exposed these sequences are locally formed by five shallowing upward elementary sequences sequences c and d are catch down sequences with evidence of emersion of subtidal facies sequence c formed during the stage of maximum gain of long term accommodation is the thickest sequence from 13 to 21 m and includes coral microbial reefs pinnacles up to 16 m in height the increased production rates were able to fill part of the accommodation created during the early stage of high frequency sea level rise and the shallow platform was eventually exposed to subaereal erosion and meteoric cementation

oncoid distribution in the shallow domains of a kimmeridgian carbonate ramp late jurassic ne spain abstract the distribution and abundance of oncoids in the shallow domains of a latest kimmeridgian carbonate ramp was accomplished on the basis of a detailed sedimentological and petrographic analysis of the lower part of the higueruelas formation iberian basin northeastern spain six types of oncoids are recognized based on the internal structure of the cortex and show a preferential distribution on the carbonate ramp which record from intertidal lagoon backshoal shoal sand blanket foreshoal to offshore domains spherical type i oncoids composed of continuous micritic laminae occur in all the subenvironments in low proportions sub spherical type ii oncoids constituted by micritic laminae and discontinuous organism bearing laminae of mostly bacinella irregularis dominate in the higher energy shoal sand blanket domain type iii oncoids with alternating micritic and organism bearing laminae of mostly bacinella irregularis lithocodium aggregatum association include two varieties type iiia oncoids with micritic and organism bearing laminae of similar thickness preferentially formed in the foreshoal domain and type iiib oncoids with thinner micritic laminae formed in a low energy sheltered lagoon irregular type iv oncoids characterize the low energy settings and include two varieties type iva oncoids mainly consisting of a bacinella lithocodium meshwork which occur abundantly in the lagoon and less abundant type ivb oncoids composed of a continuous organism bearing laminae of lithocodium which are found in the offshore domain water energy and platform morphology played an important role in formation and distribution of the oncoids in these shallow domains where normal marine water and oligotrophic conditions are highlighted by the high diversity of light dependant micro encrusters in type iii and iv oncoids comparable oncoid distribution patterns of diverse late jurassic shallow carbonate platforms enhance their potential use as reliable palaeoenvironmental proxies

insights into a million year scale rhenohercynian carbonate platform evolution through a multi disciplinary approach example of a givetian carbonate record from belgium in this paper we formulate answers to three important questions related to givetian carbonate records and their use for reconstructing million year scale past palaeoenvironmental changes first we provide detailed illustrations of the fascinating diversity that shaped a significant shallow reefal platform during early to late givetian time in the rhenohercynian ocean secondly we improve the sedimentological model of the extensive givetian carbonate platform in the dinant basin and thirdly we evaluate the application of magnetic susceptibility as a tool for long term trend correlations and palaeoenvironmental reconstructions these goals are reached by making a sedimentological geophysical and geochemical study of the la thure section through the early late givetian interval we discerned 18 microfacies ranging from a homoclinal ramp to a discontinuously rimmed shelf and then a drowning shelf the comparison of these sedimentological results with those published for the south of the dinant syncline allowed us to provide an up to date model of the vertical and lateral environmental development of one of the largest givetian carbonate platforms in europe this comparison also increased the knowledge on the distribution of facies belts in the dinant basin and allowed us to highlight the taghanic event palaeoredox proxies reveal a substantial change in the oxygenation level from oxygen depleted to more oxic conditions between middle and late givetian time we demonstrated the relationship between variation in magnetic susceptibility values and proxies for siliciclastic input such as si al the la thure section is considered a key section for the understanding of internal shelf settings bordering laurussia9s southeastern margin

limestone pseudoconglomerates in the late cambrian gushan and chaomidian formations shandong province china soft sediment deformation induced by storm wave loading this paper focuses on the formative processes of limestone pseudoconglomerates in the gushan and chaomidian formations late cambrian of the north china platform shandong province china the gushan and chaomidian formations consist mainly of limestone and shale marlstone interlayers wackestone to packstone grainstone and microbialite as well as numerous limestone conglomerates seventy three beds of limestone pseudoconglomerate in the gushan and chaomidian formations were analysed based on clast and matrix compositions internal fabric sedimentary structures and bed geometry these pseudoconglomerates are characterized by oligomictic to polymictic limestone clasts of various shapes i e flat to undulatory disc blade and sheet marlstone and or grainstone matrix and various internal fabrics i e intact thrusted edgewise and disorganized as well as transitional boundaries limestone pseudoconglomerates formed as a result of soft sediment deformation of carbonate and argillaceous interlayers at a shallow burial depth differential early cementation of carbonate and argillaceous sediments provided the requisite conditions for the formation of pseudoconglomerates initial deformation i e burial fragmentation liquefaction and injection and subsequent mobilization and disruption of fragmented clasts are two important processes for the formation of pseudoconglomerates burial fragmentation resulted from mechanical rupture of cohesive carbonate mud whereas subsequent mobilization of fragmented clasts was due to the injection of fluid materials liquefied carbonate sand and water saturated argillaceous mud under increased stress storm wave loading was the most probable deformation mechanism as an external triggering force subsequent re orientation and rounding of clasts were probably prolonged under normal compactional stress eventually disrupted clasts along with matrix materials were transformed into pseudoconglomerates by progressive lithification soft sediment deformation is prevalent in alternate layers of limestone and mud marl stone and or grainstone regardless of their depositional environments

facies distribution and coral microbialite reef development on a low energy carbonate ramp chay peninsula kimmeridgian western france abstract the chay peninsula western france succession corresponds to a kimmeridgian shallow and low energy ramp system that developed in the northeast of the aquitaine basin the sedimentation shows a transition from a carbonate dominated to a mixed carbonate siliciclastic depositional environment that takes place at the base of a major third order sea level transgression facies partitioning and coral microbialite reef levels i e reef windows suggest higher frequency fourth order sea level oscillations reef growth phases i e high frequency reef windows are interpreted to have been controlled by fifth order sea level oscillations in the mixed siliciclastic carbonate system successive prograding units of shoreface sediments pass into thick marl limestone alternations over a distance of tens of metres such remarkable short distance lateral facies variations suggest a complex sedimentary system made of juxtaposed deposits that rapidly shift through time terrigenous fluxes in modifying the light intensity and the nutrient level in the water column strongly controlled the facies distribution and notably the reef composition and growth identified coral genera suggest mixed photo heterotrophic mode of nutrition and low mesotrophic conditions in marine waters for each reef growth phase nutrient increase favoured large amounts of microbialites to develop forming a crust that entirely capped the coral reef surface thus high frequency fluctuations in nutrient input in tune with fifth or higher order sea level fluctuations controlled the reef development at a millennial scale the chay peninsula reef distribution and development provide insight into understanding the response of reef communities under climatically induced environmental changes

structural diversity of biogenic carbonate particles in microbial mats non skeletal carbonate particles in microbial mats were studied using thin sections and scanning electron microscopy the microbial mats form biolaminated units so called potential stromatolites in salterns this study emphasizes the coexistence of different particle forms and makes a genetic connection between the heterogeneity of the organic substrate built by bacteria and diatoms and their extracellular polymeric substances eps whereas allochthonous particles are scarce lanzarote microbial mats provide various autochthonous surfaces for the attachment of cells and eps including sheaths and capsules of cyanobacteria frustules of diatoms metabolic products such as gas bubbles liquid globules and faecal pellets as well as the carbonate precipitates themselves morphologically different carbonate precipitates are i calcified organic clumps peloids ii particles composed of concentric aragonite and biofilm laminae ooids and oncoids hi isolated particles floating in gel supported mats and coated by rims of fibrous cement cortoids iv particles bound by cryptocrystalline matrices or cement resulting in aggregate grains and v lobate cement which fills out spaces and pores and fixes the particles peloids are suggested to represent faecal pellets although microbial systems also generate cell clumps by non faecal processes ooid and oncoid constructions clearly record alternating processes of biofilm accumulation and aragonite encrustation further characteristic features of carbonate particles generated within a microbial mat are i an irregular distribution ranging from isolated particles floating within the gel like matrix to closely packed particles ii the amalgamation of different particle types e g peloids and ooids in aggregate grains iii the heterogeneous nature of nuclei comprising bacterial clumps intraclasts individual cells cell colonies and bubbles iv the enrichment of remains casts and imprints of cells within precipitates and v deformation e g truncated cortices of particles

birth and demise of a middle jurassic isolated shallow marine carbonate platform on a tilted fault block example from the southern iberian continental palaeomargin abstract subbetic middle jurassic oolitic limestones of the jabalcuz formation crop out in san cristobal hill near jaen city andalucia spain between hemipelagic limestone and marl successions the jabalcuz limestones range in facies from calcareous breccias and micritic limestones to white cross bedded oolitic limestones recent erosion has exhumed a jurassic isolated shallow water carbonate platform on the san cristobal hill this shallow platform developed on a tilted fault block an almost continuous laterally extensive outcrop reveals tectono sedimentary features distinctive of block tilting in the different margins of the fault block the studied sections represent various palaeogeographic positions in the ancient shallow water carbonate platform and basin transition this exceptional outcrop allows to decipher the triggering mechanisms of the birth evolution and drowning of this jurassic isolated shallow water carbonate platform two shallowing upward depositional sequences separated by flooding surfaces can be distinguished on two different sides of the fault block in the southeastern part of the outcrop proximal sections grade vertically from distal talus fault breccias with bivalve and serpulid buildup intercalations to white cross bedded oolitic limestones defining the lowermost depositional sequence upwards overlying a flooding surface the second sequence with oolitic limestones prograding over micritic deposits is recorded in the southwest oolitic peloidal and more distal micritic facies alternate with notable southeastern progradation of oolitic facies in the upper part of the section which represents the upper depositional sequence the top of this second depositional sequence is another flooding surface recorded by the sedimentation of marls with radiolarians from the overlying formation in the northwestern outcrops the two depositional sequences are also almost completely preserved and can be differentiated a 100 m thick succession composed of a basal slumped unit of micritic and peloidal limestones overlain by cross bedded oolitic limestones represents the lowermost sequence the superposition of a newer slumped unit of micritic and peloidal limestones on the cross bedded oolitic limestones defines the lower part of the uppermost depositional sequence finally the central sections are less thick and comprise a facies succession consisting almost entirely of oolitic limestones locally oolitic limestones often show cross bedding and prograding clinoforms the cross bedding has centrifugal directions around the perimeter outcrops of san cristobal hill whereas in the centre palaeocurrents are highly variable the sense of the palaeoslopes as deduced from slumps also fits with a centrifugal pattern finally in the southwestern outcrops the demise of the carbonate platform is marked by backstepping oolitic facies the presence of lumachelle facies and onlapping hemipelagic facies all the data point to the birth evolution and drowning of an isolated shallow water carbonate platform that developed on a tilted fault block the fault block tilting controlled the development of talus breccias in the southeastern part and of slumps in the northwest dipping hangingwall ramp in the shallowest environments produced by the tilting uppermost part of the fault block a shallow marine carbonate platform developed carbonate production mainly oolitic kept up with relative sea level fluctuations and extended the platform at least to the northwest southeast and southwest based on observable data finally tectonics and sea level fluctuations drowned this carbonate platform

carbon isotope anomalies and demise of carbonate platforms in the sinemurian early jurassic of the tethyan region evidence from the southern alps northern italy despite its global impact on ecosystems the triassic jurassic boundary event had only a modest effect on the carbonate depositional systems of the southern alps whereas a fundamental reorganization of the same palaeogeographic area took place during the sinemurian age this paper investigates whether or not the well documented demise of sinemurian carbonate platforms in the tethyan region was a response to a global event by examination of carbon isotope anomalies in successions of different facies that record this interval of time a chemostratigraphic transect from lake garda up to the eastern italian border is illustrated by four stratigraphic sections high resolution 20 cm over key intervals chemostratigraphic sampling allowed detection of a major negative 13 c anomaly of 1 5 preceded by a positive excursion both in shallow and deep water successions over the stratigraphical range of the ammonite genus arnioceras a comparison with sections from the uk suggests that the positive excursion belongs to the turneri zone and the succeeding negative excursion falls within the obtusum zone in the deep water belluno basin the negative anomaly occurs in a biogenic chert rich unit recording the onset of mesotrophic conditions in the basin in the platform carbonate successions this major negative carbon isotope excursion is developed within a calcarenitic unit corresponding to the lowest occurrence of the foraminifer paleomayncina termieri this evidence for deepening and transgression across the carbonate platform suggests pre conditioning for drowning hence rather than tectonic subsidence alone environmental factors may have aided the demise of tethyan carbonate platforms during the early jurassic sinemurian age

the western edge of the mediterranean pelagian platform a messinian mixed siliciclastic carbonate ramp in northern tunisia the marine messinian deposits of tunisia cover a narrow littoral strip some 300 km long between the northern bizerte and cap bon areas and the central eastern sahel region litho and biofacies analysis of six stratigraphic sections reveals the distinctive features of these deposits the lower messinian deposits are characterized by ubiquitous siliciclastics and abundant oolitic bioclastic limestones organized in an eastward facing ramp westward landward this ramp changes into coastal lagoons sometimes containing evaporites eastward the ramp passes to the reefal pelagian platform extending as far as lampedusa two main sedimentary cycles are distinguished 1 an early messinian siliciclastic retrogradational then oolitic bioclastic progradational cycle beni khiar formation and lower oued bel khedim formation 2 a late messinian brackish to continental cycle that probably accumulated in rapidly subsiding lagoons cued el bir formation and upper oued bel khedim formation the tunisian early messinian cycle is partly eustatically controlled but the late messinian cycle cannot be confidently correlated to other well known messinian series because of tectonic movements the lower messinian deposits of tunisia are also characterized by abundant suspension feeding organisms molluscs and bryozoans and rare corals calcareous algae echinoids and larger benthic foraminifers the proposed palaeoenvironmental model shows that the lower messinian ramp of tunisia was located on a current protected margin and subjected to continent derived sediment and nutrient supply eastward nutrient influx diminished and a shallow water isolated carbonate platform with coralgal facies developed between the western and the eastern mediterranean basins the main hydrological connection between these two basins occurred through a narrow seaway situated to the northeast of the pelagian platform south of sicily and malta

laboratory analysis of dissolution effects on southern ocean polycystine radiolaria abstract laboratory analyses were conducted on siliceous microfauna in holocene and older interglacial samples from the southern ocean to determine dissolution effects on their skeletons examination of siliceous skeletons was made at regular intervals throughout the experiment no major differential dissolution was detected among the dominant southern ocean radiolarian species as only minor variations in relative abundance occurred with increasing degrees of silica dissolution dissolution rate is a function of age of the polycystine radiolaria with higher holocene rates than those registered in the interglacial sample these results serve to strengthen the premise that information about past southern ocean conditions can be reliably acquired from analysis of polycystine radiolarian assemblages preserved in marine sediments

the sedimentology and development of a modern sandspit miankaleh peninsula and a lacustrine lagoon gorgan bay caspian sea iran abstract gorgan bay is a 240 km 2 lacustrine lagoon on the southeastern margin of the caspian sea from which it is separated by the 48 km long barrier beach sandspit of the miankaleh peninsula to the north the northern windward side of the sandspit displays an eroded berm the bulk of the sandspit is characterized by the presence of beach ridges and transverse nebkha and parabolic dunes the southern leeward side of the sandspit faces the muddy low energy lagoon of gorgan bay the shore sediments are well sorted negatively skewed very fine to fine sands the sand dunes are composed of well sorted positively skewed fine sand grain types of the shore and dune sediments are very similar with quartz grains and small superficial ooids being the major constituents these similarities suggest the dune deposits represent windblown shore sediments in contrast the gorgan bay sediments are poorly sorted positively skewed very fine to coarse sands with abundant bivalves gastropods ostracods and charophyte oogonia clay minerals include chamosite illite and chlorite all of volcanic origin the presence of pyroxenes and amphiboles may suggest a provenance from the gorgan metamorphic complex the study shows that the growth of the miankaleh peninsula sandspit is a result of predominantly eastward longshore transport of littoral fine sands which has been thrown by storm waves above the mean spring tide waterline in the form of slightly curved beach ridges this has allowed the development of dry beach conditions backshore and the growth of vegetation the beach ridges have been successively accreted in an eastern direction younging to the east the formation of superficial ooids is mainly linked to low energy conditions however occasional high energy events existed and long hot summers may also have played also a role in ooid formation the sand was reworked by the prevailing northwesterly winds dune formation spit formation facilitated the infilling of the sheltered lagoon by the trapping of sediment derived from the gorgan metamorphic complex to the south

shallowing upward sequences in purbeckian peritidal carbonates lowermost cretaceous swiss and french jura mountains purbeckian carbonates in the swiss and french jura goldberg formation lower berriasian comprise shallow subtidal intertidal supratidal low energy high energy marine brackish freshwater and hypersaline facies these facies are arranged in small 0 2 1 5 m thick sequences which display a dominant shallowing upward component and which form the fundamental units of the highly structured purbeckian sedimentary record six types of small scale sequences can be recognized a intertidal to supratidal overprinting of shallow lagoonal facies b algal marsh sequence with frequent dolomitization c sabkha sequence often associated with collapse breccia d tidal flat sequence with desiccation features e lacustrine sequence f terrestrial overprinting of subtidal or intertidal facies episodic event deposits such as tempestites are superimposed thin transgressive beds which rework elements of the underlying facies are frequently found at the base of the sequences green marls and black pebbles are common at the top and indicate long subaerial exposure the sequences are often incomplete as subtidal facies may be absent or their upper part can be eroded lateral facies changes are common which is due to the very shallow and partly emergent purbeckian platform where various depositional environments were juxtaposed however many sequence boundaries are well developed and can be correlated over large parts of the study area the purbeckian shallowing upward sequences were generated by climatically controlled sea level changes autocyclic processes occurred locally but were overprinted by drops of sea level affecting the entire platform the small scale sequences are most probably related to the 20 000 year cycle of the precession of the equinoxes larger sequences with usually well developed emersion surfaces are attributed to the 100 000 and 400 000 year eccentricity cycles of the earth s orbit identification and correlation of sequence boundaries makes it possible to set up a framework of isochronous surfaces which often cut across facies boundaries and thus to interpret in detail the palaeogeographic sedimentological and diagenetic evolution of the purbeckian peritidal carbonate environments

depositional environment diagenetic evolution and their impact on the reservoir quality of the carboniferous kt ii carbonate in the zhanazhol reservoir pre caspian basin kazakhstan abstract the carboniferous kt carbonate unit late serpukhovain to early moscovian of the zhanazhol reservoir in the pre caspian basin is a giant condensate reservoir with great heterogeneity although the depositional characteristics and their impact on reservoir quality have been well documented by previous studies few studies have focused on diagenesis the interplay between depositional environment and their controls on reservoir heterogeneity in this study combining sedimentological petrographic and geochemical analyses we reconstructed the depositional settings and diagenetic history of the kt carbonate and assess their impacts on reservoir quality according to the vertical and lateral distribution of 12 observed microfacies types we proposed a depositional model of a northward deepening ramp consisting of tidal flat inner ramp and middle ramp which has played a critical role in controlling the reservoir quality mainly through grain types and matrix content fusulinidal grainstones packstones have the best reservoir quality because of its porous fusulinidal fragments and low micritic matrix content the major diagenetic events including cementation eight cement types dissolution fabric and non fabric selective dissolution compaction pressure dissolution and microfracturing early and late were grouped into six diagenetic environments marine meteoric shallow burial epigenic karstification intermediate burial and deep burial marine cementation and compaction are the main reason for porosity decreasing in upper inner ramp and middle ramp respectively the minor moldic pores created by fabric selective dissolution during meteoric stage were enlarged by freshwater leaching during epigenic karstification and its associated cementation occluded pores in the underlying bioclastic grainstones packstones late non fabric selective dissolution and cementation likely resulted in local porosity rearrangements without net porosity gain or loss but certainly reduced reservoir heterogeneity the interaction between depositional environment and diagenetic evolution played a vital role in the formation of two types of vertical distribution patterns of porosity types and understanding this interaction and its impacts on reservoir quality within a sequence stratigraphic framework can more reliably predict the distribution of reservoir properties and provides insights for adjacent fields with similar settings

complexity of the 2009 l aquila earthquake causative fault system abruzzi apennines italy and effects on the middle aterno quaternary basin arrangement abstract an mw 6 1 devastating earthquake on april 6 2009 struck the middle aterno valley abruzzi apennines italy due to the activation of a poorly known normal fault system structural analysis of the fault population and investigation of the relationships with the quaternary continental deposits through integrated field and laboratory techniques were conducted in order to reconstruct the long term tectono sedimentary evolution of the basin and hypothesize the size of the fault segment a polyphasic evolution of the middle aterno valley is characterized by a conjugate e w and n s striking fault system during the early stage of basin development and by a dip slip nw striking fault system in a later phase the old conjugate fault system controlled the generation of the largest sedimentary traps in the area and is responsible for the horst and graben structures within the basin during the early pleistocene the e w and n s system reactivated with dip slip kinematics this gave rise to intra basin bedrock highs and a significant syn tectonic deposition causing variable thickness and hiatuses of the continental infill subsequently since the end of the early pleistocene with the inception of the nw striking fault system several nw strands linked into longer splays and their activity migrated toward a leading segment affecting the paganica san demetrio basin the paganica san demetrio fault alignment the findings from this work constrain and are consistent with the subsurface basin geometry inferred from previous geophysical investigations notably two major elements of the e w and n s striking faults likely act as transfer to the nearby stepping active fault systems or form the boundaries as geometric complexities that limit the paganica san demetrio fault segment overall length to 19 3 km the resulting size of the leading fault segment is coherent with the extent of the 6 april 2009 l aquila earthquake causative fault the positive match between the geologic long term and coseismic images of the 2009 seismogenic fault highlights that the comprehensive reconstruction of the deformation history offers a unique contribution to the understanding faults seismic potential

in situ dissolution experiment of radiolaria in the central north pacific ocean abstract monospecific phaeodarian radiolarian assemblages of castanidium longispinum were suspended in plastic cages built with 225 m nylon mesh at different water depths from 378 to 5582 m in the central north pacific weight losses of these samples after a suspension period of 61 days were used to determine dissolution rates the highest weight losses were observed at 378 m where samples lost 90 of their initial weight through the main thermocline weight losses decreased from 90 to 60 and reached a constant value of 40 below it these weight losses are roughly an order of magnitude higher than those reported by earlier workers the higher weight losses can be attributed in part to the more soluble nature of the phaeodarian radiolarian skeletons and in part to the improved experimental technique kinetic considerations show that temperature is the major factor that controls silica dissolution rates in the ocean using an arrehnius plot for the apparent rate constants it can be shown that in surface water dissolution rats should be two orders of magnitude higher than in deep water below the main thermocline

experimental evidence that ooid size reflects a dynamic equilibrium between rapid precipitation and abrasion rates ooids are enigmatic concentrically coated carbonate sand grains that reflect a fundamental mode of carbonate sedimentation and inorganic product of the carbon cycle trends in their composition and size are thought to record changes in seawater chemistry over earth history substantial debate persists concerning the roles of physical chemical and microbial processes in their growth including whether carbonate precipitation on ooid surfaces is driven by seawater chemistry or microbial activity and what role if any sediment transport and abrasion play to test these ideas we developed an approach to study ooids in the laboratory employing sediment transport stages and seawater chemistry similar to natural environments ooid abrasion and precipitation rates in the experiments were four orders of magnitude faster than radiocarbon net growth rates of natural ooids implying that ooids approach a stable size representing a dynamic equilibrium between precipitation and abrasion results demonstrate that the physical environment is as important as seawater chemistry in controlling ooid growth and more generally that sediment transport plays a significant role in chemical sedimentary systems

oligo miocene lacustrine microbial and metazoan buildups from the limagne basin french massif central the limagne basin french massif central is an extensive continental lacustrine system accommodating microbial and metazoan buildups from chattian to aquitanian age a description of these buildups and their associated biotic components in grand gandaillat and crechy quarries provides insights into their spatio temporal distribution patterns flats cauliflowers domes cones and coalescent columnar morphologies have been identified with a main laminated mesofabric and laminated columnar filamentous and caddisfly coated microfabrics two low gradient margin models emerged based on the changes in the distribution morphology and size of the microbial and metazoan rich deposits through time the first model applies to the chattian deposits in the grand gandaillat quarry and the second to the aquitanian deposits in the crechy quarry this study emphasizes the heterogeneity of marginal lacustrine carbonate siliciclastic cycles the lacustrine palustrine cycles of the limagne basin record i lacustrine deposits composed of microbial and metazoan buildups and organic matter rich marls indicating periods of high accommodation and ii palustrine deposits composed of mudstone and clayey paleosoils indicative of periods of low accommodation the cycles differ with thin and symmetrical deposits that dominate the chattian cycles whereas thicker and asymmetrical deposits mark the aquitanian cycles in addition the chattian buildups are exclusively microbial and only a few centimeters thick whereas the aquitanian ones are multiple meters in height and are composed of both microbes and metazoans climatic tectonism volcanic and local parameters are involved in the deposition of buildups and their organization in each different cycle climate may control the long term arid humid sedimentary succession tectonic may explain the difference in the deposit thickness between two cycles of different ages and localizations as well as the specific distribution of the buildups throughout the basin volcanism may control the chemical lacustrine conditions and local physiography may impact the soil removal ability of the lake margin

decoding the mechanism of formation in marine ooids a review abstract ooid shoals sedimentary structures consisting of carbonate grains are often used as proxies to explore changes in seawater chemistry over earth history despite their importance as contributors to the global carbonate budget and as paleo environmental indicators for water depth ph temperature and water energy the mechanism of formation of these concentric sub spherical concretions of tangentially or radially arranged aragonite or calcite crystals is still the subject of intense debate unlike oncoids whose microbial origins are well acknowledged ooids are traditionally viewed as abiotic grains mainly produced in suspension by agitated warm waters that are supersaturated with respect to caco3 yet there is considerable evidence including geochemical bio signatures and detection of viable microbes capable of mineralization and biofilm production and degradation to suggest otherwise the emergence of new and sophisticated technologies reveals that the level of microbial diversity of these sedimentary grains exceeds that of some microbialite systems these findings have refined our understanding of ooid genesis and ooid accretion processes and argue toward microbial mediation both as a direct result of metabolic activities inducing changes in the environment conducive to precipitation and by a passive mechanism in which mucilaginous extracellular polymeric substances eps act as a template for mineral nucleation furthermore new developments in the field indicate that carbonate mineralization in marine ooids occurs through sequential precipitations that involve an amorphous calcium carbonate phase acc which some argue are of biotic origins herein we discuss the most relevant theories of ooid formation including some of the early pioneering studies that laid the groundwork for new theories attempting to decode the origins of these controversial grains

the vertical distribution of radiolaria in the waters surrounding japan abstract geographic and vertical distribution patterns of living radiolaria are closely related to the characters of the water column we studied living radiolaria in samples collected at closely spaced depth intervals in the waters surrounding japan in order to understand their vertical distribution and its controlling factors such information is needed to reconstruct past vertical water mass structure the japanese islands are surrounded by the marginal japan sea and the north pacific ocean and from approximately 46 n to 26 n they thus extend across a large latitudinal range and are exposed to a similarly wide range of environmental conditions inducing the warm kuroshio tsushima and tsugaru currents and the cold oyashio current we performed plankton tows mesh size 63 mm from late may to early june 2002 at eight sites sampling the upper 200 m of the water column at seven depth intervals we recognized five radiolarian assemblages the upper surface assemblage 0 40 m the lower surface assemblage 40 80 m the surface assemblage 0 80 m the subsurface assemblage 80 200 m and the lower surface subsurface assemblage 40 200 m groups pseudodictyophimus gracilipes and tetrapyle octacantha juvenile show tropical submergence i e they live at the surface in high latitudes and at greater depth in low latitudes four taxa live at specific temperature and salinity acrosphaera spinosa larcopyle butschlii challengeron diodon and stichocorys seriata four taxa are associated with characteristic temperatures neosemantis distephanus arachnocorys umbellifura antarctissa sp 1 and saccospyris conithorax

basin analysis in the southern tethyan margin facies sequences stratal pattern and subsidence history highlight extension to inversion processes in the cretaceous panormide carbonate platform nw sicily abstract in the mediterranean the south tethys paleomargin experienced polyphased tectonic episodes and paleoenvironmental perturbations during mesozoic time the cretaceous shallow water carbonate successions of the panormide platform outcropping in the northern edge of the palermo mountains nw sicily were studied by integrating facies and stratal pattern with backstripping analysis to recognize the tectonics vs carbonate sedimentation interaction the features of the requienid limestone including geometric configuration facies sequence lithological changes and significance of the top unconformity highlight that at the end of the lower cretaceous the carbonate platform was tectonically dismembered in various rotating fault blocks the variable trends of the subsidence curves testify to different responses both uplift and downthrow of various platform blocks impacted by extensional tectonics physical stratigraphic and facies analysis of the rudistid limestone highlight that during the upper cretaceous the previously carbonate platform faulted blocks were subjected to vertical movements in the direction opposite to the displacement produced by the extensional tectonics indicating a positive tectonic inversion comparisons with other sectors of the southern tethyan and adria paleomargins indicate that during the cretaceous these areas underwent the same extensional and compressional stages occurring in the panormide carbonate platform suggesting a regional scale significance in time and kinematics for these tectonic events

an extensive erosion surface of a strongly deformed limestone bed in the gushan and chaomidian formations late middle cambrian to furongian shandong province china sequence stratigraphic implications abstract in order to understand sequence development and sea level fluctuations during the late middle cambrian to early furongian on the north china epeiric platform the present study focuses on a unique subtle erosion surface of an extensive approx 100 km strongly deformed limestone bed in the uppermost part of the gushan formation shandong province china the gushan formation and the overlying chaomidian formation consist mainly of shales and a variety of carbonates that were deposited in subtidal environments e g deep subtidal shallow subtidal shoreface shoal subtidal microbial flat and restricted platform interior three third order depositional sequences s1 3 are identified each of which comprises a thin transgressive systems tract tst and a relatively thick highstand systems tract hst each sequence is bounded by a drowning unconformity sb1 a subaerial unconformity sb2 or a surface of submarine erosion sb3 the upper sequence boundary sb2 of sequence 1 s1 is represented by a subtle erosion surface of an extensive deformed limestone bed with a wide variety of soft sediment deformation structures e g lime mudstone breccias chaotic wacke packstone laminae and fragments homogenized oolites and clastic dykes and is overlain by small sporadic microbial buildups and an extensive bioclastic grainstone bed the deformed limestone was formed during early diagenesis by differential deformation processes brecciation liquefaction fluidization and injection which were most likely induced by pore water overpressure during the period of rapid sea level fall despite the lack of subaerial exposure features e g paleokarst paleosol etc the characteristics of the erosion surface cutting well lithified sediment below the missing of a significant geological record the prochuangia biozone and the worldwide correlatable positive carbon isotope excursion collectively indicate that the erosion surface developed under conditions of subaerial exposure after contemporaneous marine cementation of the deformed sediment the missing of the prochuangia biozone is most likely due to non deposition at a subaerial hiatal surface the erosion surface was submerged as a result of subsequent rise in sea level where sporadic microbial buildups formed under suitable conditions freshly deposited winnowed shell dominated transgressive lag deposits containing chuangia trilobite fragments brachiopod shells and abundant glauconite grains formed with continued rise in sea level which became in turn overlain by shale dominated facies the unique combination of the subtle erosion surface sensu stricto a subaerial unconformity and the underlying deformed limestone bed provides an important criterion for recognizing the subtle changes in relative sea level on shallow epeiric platforms

the late jurassic tithonian a greenhouse phase in the middle jurassic early cretaceous cool mode evidence from the cyclic adriatic platform croatia well exposed mesozoic sections of the bahama like adriatic platform along the dalmatian coast southern croatia reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding late jurassic tithonian shallow platform interior over 750 m thick ca 5 6 myr duration facies within parasequences include dasyclad oncoid mudstone wackestone floatstone and skeletal peloid wackestone packstone shallow lagoon intraclast peloid packstone and grainstone shoal radial ooid grainstone hypersaline shallow subtidal intertidal shoals and ponds lime mudstone restricted lagoon fenestral carbonates and microbial laminites tidal flat parasequences in the overall transgressive lower tithonian sections are 1 4ae5 m thick and dominated by subtidal facies some of which are capped by very shallow water grainstone packstone or restricted lime mudstone laminated tidal caps become common only towards the interior of the platform parasequences in the regressive upper tithonian are dominated by peritidal facies with distinctive basal oolite units and well developed laminate caps maximum water depths of facies within parasequences estimated from stratigraphic distance of the facies to the base of the tidal flat units capping parasequences were generally 4 m and facies show strongly overlapping depth ranges suggesting facies mosaics parasequences were formed by precessional 20 kyr orbital forcing and form parasequence sets of 100 and 400 kyr eccentricity bundles parasequences are arranged in third order sequences that lack significant bounding disconformities and are evident on accommodation fischer plots of cumulative departure from average cycle thickness plotted against cycle number or stratigraphic position modelling suggests that precessional sea level changes were small several metres as were eccentricity sea level changes or precessional sea level changes modulated by eccentricity supporting a global hot greenhouse climate for the late jurassic tithonian within the overall cool mode of the middle jurassic to early cretaceous

depositional environments and diagenesis of the kuldhar and keera dome carbonates late bathonian early callovian of western india abstract this paper describes 11 microfacies types in late bathonian early callovian carbonates of the kuldhar member of the jaisalmer formation rajasthan and the keera golden oolite member of the chari formation kachchh mainland western india the different microfacies associations reported in this study reflect an ideal shallowing upward sequence representing a system of bioclastic bars developed on the lower ramp evolving into an oolitic bar to bank system separating restricted lagoonal from lower ramp environment four main types of cements i e bladed fibrous syntaxial overgrowth and blocky cement characterized in a few cases by ferroan calcite and anhydrite ii occur in these carbonates the study also reveals that chemical compaction followed the two phases of early mechanical compaction that largely governed porosity of these limestones however micritization and neomorphism also contributed significantly in this respect diagenetic signatures in these carbonates suggest that marine phreatic and fresh water phreatic environments dominated but deep burial diagenesis also played its role in shaping these rocks the early and late diagenetic changes have been controlled by the depositional facies evolving in a basin riddled with rifting in an extensional tectonic regime forcing regional scale sea level fluctuations

outcrop analog for an oolitic carbonate ramp reservoir a scale dependent geologic modeling approach based on stratigraphic hierarchy considerable effort has been devoted to the development of simulation algorithms for facies modeling whereas a discussion of how to combine those techniques has not existed the integration of multiple geologic data into a three dimensional model which requires the combination of simulation techniques is yet a current challenge for reservoir modeling this article presents a thought process that guides the acquisition and modeling of geologic data at various scales our work is based on outcrop data collected from a jurassic carbonate ramp located in the high atlas mountain range of morocco the study window is 1 km 0 6 mi wide and 100 m 328 1 ft thick we describe and model the spatial and hierarchical arrangement of carbonate bodies spanning from largest to smallest 1 stacking pattern of high frequency depositional sequences 2 facies association and 3 lithofacies five sequence boundaries were modeled using differential global position system mapping and light detection and ranging data the surface based model shows a low angle profile with modest paleotopographic relief at the inner to middle ramp transition facies associations were populated using truncated gaussian simulation to preserve ordered trends between the inner middle and outer ramps at the lithofacies scale field observations and statistical analysis show a mosaiclike distribution that was simulated using a fully stochastic approach with sequential indicator simulation this study observes that the use of one single simulation technique is unlikely to correctly model the natural patterns and variability of carbonate rocks the selection and implementation of different techniques customized for each level of the stratigraphic hierarchy will provide the essential computing flexibility to model carbonate settings this study demonstrates that a scale dependent modeling approach should be a common procedure when building subsurface and outcrop models

capturing and modelling metre scale spatial facies heterogeneity in a jurassic ramp setting central high atlas morocco each simulation algorithm including truncated gaussian simulation sequential indicator simulation and indicator kriging is characterized by different operating modes which variably influence the facies proportion distribution and association of digital outcrop models as shown in clastic sediments a detailed study of carbonate heterogeneity is then crucial to understanding these differences and providing rules for carbonate modelling through a continuous exposure of bajocian carbonate strata a study window 320 m long 190 m wide and 30 m thick was investigated and metre scale lithofacies heterogeneity was captured and modelled using closely spaced sections ten lithofacies deposited in a shallow water carbonate dominated ramp were recognized and their dimensions and associations were documented field data including height sections were georeferenced and input into the model four models were built in the present study model a used all sections and truncated gaussian simulation during the stochastic simulation for the three other models model b was generated using truncated gaussian simulation as for model a model c was generated using sequential indicator simulation and model d was generated using indicator kriging these three additional models were built by removing two out of eight sections from data input the removal of sections allows direct insights on geological uncertainties at inter well spacings by comparing modelled and described sections other quantitative and qualitative comparisons were carried out between models to understand the advantages disadvantages of each algorithm model a is used as the base case indicator kriging model d simplifies the facies distribution by assigning continuous geological bodies of the most abundant lithofacies to each zone sequential indicator simulation model c is confident to conserve facies proportion when geological heterogeneity is complex the use of trend with truncated gaussian simulation is a powerful tool for modelling well defined spatial facies relationships however in shallow water carbonate facies can coexist and their association can change through time and space the present study shows that the scale of modelling depositional environment or lithofacies involves specific simulation constraints on shallow water carbonate modelling methods

secular variation of calcium carbonate mineralogy an evaluation of ooid and micrite chemistries three ooid types are recognized from the lower tournaisian kohlenkalk shelf facies at velbert germany ooids from this unit have a predominantly concentric laminae fabric radial concentric and small radial fibrous ooids are minor components to this oolite the diagenetic response of kohlenkalk ooid chemistry is significantly different from that observed in contemporaneous crinoid and brachiopod material fabric evidence suggests that radial concentric and radial fibrous ooids were probably originally aragonite high mg calcite and high mg calcite respectively fabric and trace elemental chemistries of the concentric fabric ooids suggests that they were originally precipitated as aragonite and subsequently altered to low mg calcite

comparison of radiolarian vertical distributions in the okhotsk sea near the kuril islands and in the northwestern north pacific off hokkaido island abstract the vertical distribution of radiolarians was investigated by using a closing type net with 63 m mesh in the okhotsk sea station nu 2 near bussol strait down to 1000 m depth and in the northwestern north pacific oyashio region station x down to 500 m depth both stations were sampled in september 1995 radiolarian standing stocks were high between 50 and 200 m at both stations and generally decreased with depth the depth integrated living total radiolarian standing stock from 0 to 500 m at station nu 2 was more than three times higher than that at station x the maximum standing stocks of polycystine radiolarians occurred in the 50 100 m depth interval but there were also significant abundance peaks of phaeodarian radiolarians in the 100 200 m interval at both stations the radiolarian production is likely to be associated with not only phytoplankton production in upper waters but also with microbial production in intermediate waters a total of 79 taxa were encountered 25 spumellaria 41 nassellaria and 13 phaeodaria five radiolarian groups were obtained based on r mode cluster analysis group a lower intermediate water dwellers 300 1000 m group b taxa with different distributions in the okhotsk sea 300 1000 m and in the oyashio region 0 100 m group c upper intermediate water dwellers 200 500 m group d surface subsurface water dwellers 0 200 m and group e taxa with pronounced 200 m

sequence stratigraphy of the upper jurassic mixed siliciclastic carbonate deposits in the north german basin lower saxony hildesheimer wald the wendhausen 6 core drilled in the hildesheimer wald 30 km se of hannover provides an insight into the oxfordian deposits of the north german basin consisting of the ornatenton heersum and korallenoolith formations eight facies are recognized based on the different fossil combinations sedimentary structures and the carbonate content a facies model of a mixture of a deltaic system and a carbonate ramp is presented based on the interpretation of these facies which helps the understanding of the facies and sequence stratigraphic evolution in the mixed system in the north german basin and could be applied to other shallow water mixed depositional systems sequences of three hierarchies are delimited small scale sequences are defined by the changes in components grain size and the vertical facies stacking patterns medium scale sequences are bounded by distinctive exposure surfaces these surfaces are characterized either by the enrichment of iron minerals or by irregular base of the lowstand channel fill sandstones overlying on them large scale sequences are derived from the facies proportion statistics of each medium scale sequence the similar trend between the regional sea level curve and the facies statistic curve implies that sea level fluctuations have a great control on the large scale sequence evolution during the oxfordian age sequence stratigraphic correlation was achieved at the medium scale sequence level and four surfaces of oxfordian age were correlated across the north german basin

paleoenvironmental implications of an extensive maceriate microbialite bed in the furongian chaomidian formation shandong province china abstract this study focuses on the unique occurrence of an extensive microbialite bed 10 20 m thick in the chaomidian formation furongian in shandong province china in order to understand its paleoenvironmental implications the microbialite bed can be traced for over 6000 km2 in area the microbialites are characterized by centimeter to decimeter scale branching maze like constituents maceriae of microbial and muddy sediments with chaotic texture including tabular maceriate microbialite type 1 columnar maceriate microbialite type 2 and columnar chaotic microbialite type 3 within the bed each microbialite unit is generally well correlated for tens of kilometers the entire bed is bounded by limestone marlstone alternation at the base and an erosional surface at the top that is subsequently overlain by a grainstone bed of various thicknesses the microbialite bed formed when the seafloor reached suitable water depth for the microbial growth during sea level rise accompanied with carbonate production the maze like maceria structures formed to acquire a larger surface area under a relatively large input of lime mud the tabular maceriate microbialites initially formed in relatively deep water environments and flourished on broad and flat seafloor whereas the columnar microbialites types 2 and 3 developed under the influence of strong waves and currents the microbialite bed was eroded and terminated by frequent storm events and buried under the reworked grainstone further rise in sea level and increased metazoan activities afterwards limited the resurgence of microbes in the late furongian

carbonate platform drowning in a foreland setting the mid carboniferous platform in western urals russia abstract the stratigraphic evolution through time of the mid carboniferous russian platform deposited on the distal margin of the west uralian prograding foredeep basin can be observed in the approximately 3000 m thick sedimentary cover that constitutes the upper paleozoic foreland mid carboniferous permian of the uralian fold belt it is composed of wave dominated low angle carbonate ramps of late visean to early moscovian age and carbonate platforms bordered by slope reef mounds from the kasimovian to the late artinskian early kungurian eastward in the foredeep the carbonate platforms pass into terrigenous deposits a complete transgressive progradational section at the transition between carbonate ramp and terrigenous deposits exhibits from base to top 1 deepening upward carbonate ramp deposits 2 a shaly condensed section with volcaniclastics glauconite and phosphorites of late moscovian to early asselian age the transgressive part and 3 a shallowing upward section of turbidites ending in coarse grained fan deltas evaporites and meandering river redbeds by the earliest triassic the progradational section this paper focuses on the uppermost part of the carbonate ramp deposits serpukhovian to early moscovian these ramp facies comprise peritidal channels and mud flats wave to storm dominated shoals and patch reefs that are overlain by channel attached sand lobes of turbidites black shales and radiolarites of the condensed section this large scale deepening upward trend from inner ramp to outer ramp environments reflects a change in the depositional profile from a tide and wave dominated flat ramp to a wave and storm dominated steepened ramp margin and then to foreslope turbidites correlation of sections dated by fusulinid faunas in southern urals shows that the ramp evolved from emergent in the north perm solikamsk area as evidenced by karstification and deepened to the south belaya area with emplacement of carbonaceous foreslope debris flows and turbidites capped by deep marine black shales and radiolarites the time gap increases northward and reaches a span including the siuransky pro parte the akavassky the askynbashky and the asatausky pro parte biohorizons the mapping of these facies belts across all the urals shows that carbonate ramps wedge out in the middle urals and give rise to widely distributed diversified and deeper marine facies belts not only to the south towards the precaspian depression but also to the north towards the polar urals the drowning of these carbonate ramps and the cutoff in carbonate production on the russian platform during the mid carboniferous is explained by a succession of low frequency flexure relaxation cycles in the foreland associated with dilution by siliciclastics outpouring of volcaniclastics and changes in the nature and direction of the sediment input and high frequency cycles mainly controlled by eustasy

facies heterogeneity at interwell scale in a carbonate ramp upper jurassic ne spain abstract the well exposed upper kimmeridgian carbonate ramp near arroyo cerezo iberian basin eastern spain provides an excellent analog to stratigraphically equivalent subsurface reservoirs such as the carbonate ramps of the arab d of the middle east and the smackover of the gulf of mexico critical questions regarding interwell scale heterogeneity and correlation motifs for low angle ramp systems can be addressed using continuous exposures that encompass a full range of inner to outer ramp facies outcrops in this area provide a complete exposure of the ramp succession in depositional dip direction at arroyo cerezo a 40 m thick and 1 3 km long dip oriented continuous outcrop has been studied lithofacies and bounding surfaces have been mapped on a continuous photomosaic to build a detailed 2d cross section complemented by five stratigraphic sections 300 m apart and petrographic analysis the reconstructed section shows the facies transition from relative proximal to distal carbonate ramp settings carbonate facies associations are grouped according to the dominant carbonate types buildup dominated systems and coated grain dominated systems detailed mapping of facies and bounding surfaces documents distinct ramp depositional units with downdip facies changes occurring within the 1 3 km length of the outcrop the arroyo cerezo outcrop indicates that the ramp facies continuity when based on a 5 10 km distance well log correlation is mostly apparent use of detailed spatial and temporal analysis of high quality outcrop analogs promotes more realistic models for understanding the interwell meter scale heterogeneity and the scale of these depositional heterogeneities although being below resolution of subsurface tools governs in fact along with diagenetic modifications the fluid flows within a reservoir the scale of these stratigraphic heterogeneities needs to be considered in order to optimize and enhance hydrocarbon production and last recovery

temporal and spatial flux changes of radiolarians in the northwestern pacific ocean during 1997 2000 abstract in order to examine the radiolarian fluxes and evaluate their relationship to the physical and biological environments time series sediment traps were deployed at three stations stations 50n knot and 40n in the northwestern north pacific from 1997 to 2000 station 50n 50 n 165 e 3260 m is located in the center of western subarctic gyre wsag station knot 44 n 155 e 2957 m is located toward the margin of wsag and station 40n 40 n 165 e 2986 m is located in the subarctic boundary total radiolaria fluxes at station 40n showed higher values than those at the other two stations and were mainly attributed to the influence of relatively high temperature and high salinity subtropical gyre waters correlation coefficients between total mass fluxes mainly composed of diatoms and radiolarian fluxes at three stations were relatively low this is primarily because of the wide vertical distribution of radiolarians and various trophic patterns corresponding to their niche radiolarian species were classified according to their geographic water mass and vertical distributions based on previous studies using sediment samples as a result seasonal changes of radiolarian fluxes in each water mass showed patterns corresponding to particular controlling factors such as physical hydrography and food conditions among these patterns temporal changes in radiolarian taxonomic composition in the upper layer 0 100 m seemed to reflect well the sea surface temperature anomaly ssta changes affected by el nino and la nina events at station 40n therefore radiolarian assemblages can be used to reconstruct past ssta changes and to understand the past el nino and la nina teleconnection in the kuroshio oyashio extension region

styles of interaction between aeolian fluvial and shallow marine environments in the pennsylvanian to permian lower cutler beds south east utah usa the pennsylvanian to permian lower cutler beds comprise a 200 m thick mixed continental and shallow marine succession that forms part of the paradox foreland basin fill exposed in and around the canyonlands region of south east utah aeolian facies comprise i sets and compound cosets of trough cross bedded dune sandstone dominated by grain flow and translatent wind ripple strata ii interdune strata characterized by sandstone siltstone and mudstone interbeds with wind ripple wavy and horizontal planar laminated strata resulting from accumulation on a range of dry damp or wet substrate types in the flats and hollows between migrating dunes and iii extensive near flat lying wind rippled sandsheet strata fluvial facies comprise channel fill sandstones lag conglomerates and finer grained overbank sheet flood deposits shallow marine facies comprise carbonate ramp limestones tidal sand ridges and bioturbated marine mudstones during episodes of sand sea construction and accumulation compound transverse dunes migrated primarily to the south and south east whereas south westerly flowing fluvial systems periodically punctuated the dune fields from the north east several vertically stacked aeolian sequences are each truncated at their top by regionally extensive surfaces that are associated with abundant calcified rhizoliths and bleaching of the underlying beds these surfaces record the periodic shutdown and deflation of the dune fields to the level of the palaeo water table during episodes of aeolian quiescence fluvial systems became more widespread forming unconfined braid plains that fed sediment to a coastline that lay to the south west and which ran approximately north west to south east for at least 200 km shallow marine systems repeatedly transgressed across the broad low relief coastal plain on at least 10 separate occasions resulting in the systematic preservation of units of marine limestone and calcarenite between units of non marine aeolian and fluvial strata to form a series of depositional cycles the top of the lower cutler beds is defined by a prominent and laterally extensive marine limestone that represents the last major north eastward directed marine transgression into the basin prior to the onset of exclusively non marine sedimentation of the overlying cedar mesa sandstone styles of interaction between aeolian fluvial and marine facies associations occur on two distinct scales and represent the preserved expression of both small scale autocyclic behaviour of competing coeval depositional systems and larger scale allocyclic changes that record system response to longer term interdependent variations in climatic and eustatic controlling mechanisms the architectural relationships and system interactions observed in the lower cutler beds demonstrate that the succession was generated by several cyclical changes in both climate and relative sea level and that these two external controls probably underwent cyclical change in harmony with each other in the paradox basin during late pennsylvanian and permian times this observation supports the hypothesis that both climate and eustasy were interdependent at this time and were probably responding to a glacio eustatic driving mechanism

alternation of microbial mounds and ooid shoals middle jurasssic morocco response to paleoenvironmental changes abstract the occurrence of neritic microbial carbonates is often related to ecological refuges where grazers and other competitors are reduced by environmental conditions or to post extinction events e g in the late devonian early triassic here we present evidence for middle jurassic bajocian microbial mounds formed in the normal marine shallow neritic setting of an inner ramp system from the high atlas of morocco the microbial mounds are embedded in cross bedded oolitic facies individual mounds show low relief domal geometries up to 3 m high and 4 5 m across but occasionally a second generation of mounds exhibits tabular geometries

phaeodarian skeletons their role in silica transport to the deep sea the skeletons of phaeodarian radiolaria transport and redistribute silica to the tropical deep oceans by dissolving in the water column and on the sea floor the skeletons are initially solid but within a few days to months become progressively more porous while settling through the water column phaeodarian radiolaria are rarely preserved in the bottom sediments in contrast polycystine radiolaria are the dominant radiolaria preserved in the fossil record this preservational difference may be due to differences in skeletal constituents

late quaternary paleoceanographic changes in the bering sea and the western subarctic pacific based on radiolarian assemblages seven piston cores were obtained from the bering sea and the western subarctic pacific during cruise kh99 3 of r v hakuho maru in august 1999 cores bow 8a bow 9a bow 12a ab umk 3a gat 3a in the bering sea and core es in the western subarctic pacific the quantitative high resolution analyses of radiolarians in the cores revealed significant variations in both their faunal assemblages and accumulation rates ar a trend of conspicuous turn over of the surface dwellers and intermediate dwellers increase of one at expense of the other after the last glacial maximum lgm is clearly visible in the bering sea data set however this turn over is not present at site es in the western subarctic pacific core these changes in radiolarian assemblages around the lgm suggest that the surface waters had extremely low temperature and low salinity and that the subsurface dichothermal layer temperature minimum layer was thickened all the way across the entire east west span of the bering sea furthermore sea ice coverage extended to the central aleutian basin around the lgm this suggests that the water mass structure in the western subarctic pacific around the lgm was basically the same as that of the eastern bering sea based on the species composition of the surface dwellers however the detailed development of intermediate water masses differed from that of the eastern bering sea during marine isotope stage mis 5 to 3 such species turn over events did not occur and species abundance stayed relatively uniform in the studied cores therefore the present water mass structure is interpreted to have been formed after the lgm based on the relative abundances of cycladophora davisiana the most dominant species dwelling in the intermediate water and a useful tracer of cold and well oxygenated intermediate water in the north pacific the past north pacific intermediate water npiw had the following source regions during the last 100 kyr 1 both the okhotsk sea and the bering sea during mis 5 to 3 2 the bering sea around the lgm and 3 shifting from the bering sea to the okhotsk sea after the lgm relatively low radiolarian ar at site bow 8a which is the shallowest site studied here present water depth 884 m were observed during the glacial periods this is due to decrease of radiolarian production in the thinned upper water layer above the dicothermal layer caused by sea level drop cycladophora davisiana probably lived deeper during the glacials than today as it was absent in the shallow piston core r 2005 elsevier ltd all rights reserved

facies and stratigraphic architecture of the korallenoolith formation in north germany lauensteiner pass ith mountains abstract during the oxfordian bahamian type shallow water carbonates formed in the lower saxony basin of north germany the outcrop of the korallenoolith formation in a quarry in the ith mountains lauensteiner pass contains a series of well exposed coral and coral microbial reefs intercalated with oolites six different facies are distinguished which can be assigned to the inner part of a carbonate ramp based on textural variations and facies stacking patterns accommodation space to sediment supply and or sediment production cycles of different hierarchies were defined in this succession a multispectral outcrop gamma ray log was measured as additional tool to separate facies and to identify the cyclicity a good correlation between fluctuations in the gamma ray log and the lithological changes exists generally coral and coral microbial reefs reflect times of higher available accommodation space oolites indicate sedimentation in shallower waters we thus show how based on sequence stratigraphy the succession of the korallenoolith fm can be subdivided into genetic packages this approach may contribute in providing a tool for a firm high resolution correlation of the different outcrops of this formation which is presently only poorly constrained the good correlation between gamma ray log and the cyclicity may also be helpful for subsurface correlations in the lower saxony basin

composite micrite envelopes in the lagoon of abu dhabi and their application for the recognition of ancient firm to hardgrounds abstract micrite envelopes are common early diagenetic features in marine carbonates throughout the phanerozoic this paper documents a continuum of sub recent constructive and destructive composite micrite envelopes and discusses their application for the recognition of ancient marine firm to hardgrounds in the modern subtropical carbonate depositional environment of the abu dhabi coastal lagoon micrite envelopes are actively forming and are directly assigned to a range of processes and depositional environments i in the outer high energy lagoon bioclasts and ooids typically contain empty microendolithic borings ii in the unconsolidated sediments of the inner to middle lagoon destructive micrite envelopes yield fragments of their host grains that result from boring etching activity and are bound and covered by biofilms iii constructive envelopes are formed by high mg calcite micrite cements and coat destructive envelopes in the inner to middle lagoon or may nucleate on aragonite needle cements in the outer lagoon micrite cements that form constructive envelopes are typical early marine diagenetic features and are among the main fabrics of firm to hardgrounds calcitic skeletal grains such as benthic foraminifera and coralline red algae are less affected by microbioeroders compared to aragonitic ooids gastropods and bivalves high mg calcite constructive envelopes have a higher preservation potential relative to aragonite host particles and aragonite cements hence the presence and recognition of constructive micrite envelopes in the rock record may be instrumental to identifying ancient aragonitic as well as unconventional firm to hardgrounds that may otherwise be difficult to recognise

transgressive oversized radial ooid facies in the late jurassic adriatic platform interior low energy precipitates from highly supersaturated hypersaline waters dark gray oolitic units characterized by oversized ooids with primary radial calcite fabrics occur in the interior of the late jurassic late tithonian adriatic platform a large mesozoic tethyan isolated platform in croatia they differ from open marine platform margin ooid grainstones in their dark color cerebroid outlines broken and recoated grains abundant inclusions highly restricted biota and lack of cross stratifithey have been interpreted as being of vadose origin vadoids at tops of upward shallowing parasequences however detailed sections show that most oolitic units occur at bases of precessional parasequences overlying erosional surfaces on fenestral carbonates the oolitic units are similar to quiet water ooids that form today in low energy settings they developed in an arid climate during initial transgression of supratidal fl ats along lowenergy shores seaward of tidal fl ats and along the margins of restricted lagoons and intertidal ponds superimposed fenestral fabrics meniscus micrite cements and grain breakage occurred as they aggraded to high tide level and were subjected to wetting and drying thermal expansion and contraction and wind transport they migrated landward with transgression forming extensive sheets and were overlain by subtidal lagoonal facies that shallow up into fenestral carbonates these distinctive facies may have been overlooked in the geological record or their geological distribution requires juxtaposition of calcite seas high calcite supersaturation states arid climate and presence of fl at topped carbonate platforms in a greenhouse world

subaerial exposure and deposition of shallowing upward sequences evidence from stable isotopes of purbeckian peritidal carbonates basal cretaceous swiss and french jura mountains purbeckian lowermost cretaceous peritidal carbonates are characterized by open marine lagoonal intertidal and lacustrine facies arranged in milankovitch type shallowing upward sequences shallowing upward sequences typically consist of 2 6 individual beds the sequences may be i complete ii incomplete or ii pedogenetically overprinted reflecting the duration of subaerial exposure and or the extent of erosion and pedogenetic modification at the cycle tops the stable isotopic composition of the peritidal micrites reveals homogenous 6 o values attributed to diagenetic stabilization in a meteoric water buffered system carbon isotopes show three distinctly different carbon isotope patterns dependent on the completeness of the shallowing upward sequences complete shallowing upward sequences consist of l6 individual carbonate beds the carbon isotope values show a facies dependent pattern open marine carbonate muds record enriched 6i3c values of 0 28 while lagoonal 0 82 intertidal 2 46 10 and lacustrine micrites 2 96 are increasingly depleted this distinct pattern is explained by carbonate mud deposition in environments of differing salinity and marine influence incomplete sequences 2 5 carbonate beds are characterized by depleted 6 c values below subaerial exposure surfaces that become progressively enriched in c with increasing depth pedogenetically overprinted sequences 1 3 carbonate beds show strong i3c depletion throughout the sequence with little variation in the carbon isotopic composition the depleted values 4 51 10 of the pedogenetically altered micrites suggest that modification during subaerial exposure was associated with equilibration with meteoric solutions enriched in isotopically light soil gas coz the duration of subaerial exposure is the most crucial factor determining the extent of pedogenetic alterations the completeness of the shallowing upward sequences and the carbon isotope pattern the recorded patterns clearly illustrate that micrites have a good potential for the preservation of their primary carbon isotopic composition if the duration of subaerial exposure is rather brief otherwise the recorded carbon isotope patterns may support sequence stratigraphic analysis by providing a refinement of the time stratigraphic interpretation

sedimentary evolution of a shallow carbonate ramp kimmeridgian ne spain unravelling controlling factors for facies heterogeneities at reservoir scale abstract the facies evolution of a late jurassic latest kimmeridgian shallow carbonate ramp was reconstructed after the analysis and correlation of 21 logs in a 20 30 km outcrop area located south of zaragoza northeast spain the studied succession belongs to the higueruelas formation which is of potential use as an analogue for understanding facies heterogeneities in certain hydrocarbon carbonate reservoirs e g the arab formation persian gulf the studied succession is arranged in nine sedimentary units bounded by discontinuity surfaces that can be traced over kilometres facies analysis permitted the reconstruction of two sedimentary models showing the transition from inner ramp subenvironments i e intertidal lagoon backshoal washover shoal sand blanket to the mid ramp foreshoal and offshore domains an oncolitic peloidal oolitic and an oolitic peloidal dominated ramp the oncolitic peloidal oolitic dominated ramp is characterized by peloidal oolitic and oncolitic dominated shoal sand blankets that developed in higher energy inner areas protecting peloidal oolitic backshoal and oncolitic lagoon domains including a mosaic of stromatoporoid carpets peloidal facies with fenestral porosity accumulated in an intertidal belt or as patches on top of the shoal sand blankets and washover deposits offshore from the shoal sand blankets chaetetid stromatoporoid coral rich buildups grew on the more proximal mid ramp surrounded by peloidal and peloidal bioclastic grain to mud supported facies an oolitic peloidal dominated ramp developed in a second stage of the evolution of the platform characterized by the presence of a wide restricted peloidal bioclastic oolitic lagoon on the inner ramp grading into a backshoal area dominated by storm related intraclastic peloidal deposits stromatoporoid carpets disappeared and oncolitic dominated deposits were constrained to the foreshoal and backshoal domains and locally to local ponds that developed in the intertidal belt or the restricted lagoon internal and external factors controlling facies heterogeneity and the sedimentary evolution of the carbonate ramp include resedimentation topographic relief and long to short term sea level fluctuations

radiolarians under the seasonally sea ice covered conditions in the okhotsk sea flux and their implications for paleoceanography abstract four time series sediment traps at two stations and three piston cores from the okhotsk sea were quantitatively examined for coarse sized radiolarian shells 63 m traps were deployed at 300 m and 1550 m at station m4 53 01 n 145 30 e and at 300 m and 700 m at station m6 49 30 n 146 28 e during august 1998 through may 2000 the chronologies of the piston cores were established applying 18 o and paleomagnetic intensity variations they provide records extending back to marine isotope stage mis 5 51 the modern and past changes in radiolarian assemblages are associated with environmental and productivity changes radiolarian fluxes in the sediment traps exhibited significant summer to autumn flux peaks with suppressed values during the winter when sea ice covered the sea surface at the trap sites total radiolarian accumulation rate rar variations in each core tended to correspond to glacial interglacial cycles and increased during the last deglaciation in particular the temporal rar variation in core xp98 pc1 off kamchatka showed a similar trend with the climatic changes expressed by 18 o values during the glacial interglacial cycles for the last 125 kyr regional differences were also apparent rars showed extremely low values during 12 40 kyr and 63 70 kyr in core xp98 pc2 central okhotsk sea indicating the enhanced sea ice impact the sea ice coverage might have continued for a significant part of the year during the intervals since radiolarians did not appear to increase even during the summer to autumn rar variations in core xp98 pc4 off sakhalin showed higher values than xp98 pc2 during mis 2 and 4 thus in eastern sakhalin around site xp98 pc4 sea ice coverage might have been seasonal but not perennial even during mis 2 and 4 among the radiolarian taxa cycladophora davisiana was the most abundant species at the lower traps and in all cores the fluxes of c davisiana at lower traps showed much higher values than those of upper traps and also showed similar temporal patterns with the fluxes of aluminum and terrigenous materials therefore c davisiana fluxes may be associated with terrigenous organic materials increased nutrient supply from the continental shelves presumably transported by seasonal sea ice and released by sea ice melting might be mainly responsible for the high production of c davisiana in the okhotsk sea especially during the last deglaciation

tectonic controls of phanerozoic sedimentary rock cycling the cyclic nature of the phanerozoic sedimentary rock distribution carbon sulphur coupling and material transfer among sedimentary reservoirs appears to be controlled by tectonic factors the distribution of preserved sedimentary mass in terms of rock mass remaining u geologic age shows a minimum c 300 350 ma ago which separates two subcycles of erosion and deposition of sedimentary rocks the older subcycle was interrupted because of the major continental collisions of the devonian and late carboniferous these collisions resulted in a reduction of outcrop areas of rocks of the older cycle relative to their masses leading to a decline in the probability of destruction and an increase in half life of these older sediments a strong correlation exists between the long term cyclicity in the phanerozoic global sea level curve and the distribution of carbon and sulphur among their major exogenic reservoirs this correlation is related to two principal tectonic modes of the phanerozoic oscillatory and submergent it is postulated that the submergent mode of active plate convergence obduction and subduction of sediments large ridge volume and high sea level gave rise to low erosion and sedimentation rates less restricted environments of carbonate deposition and relatively high atmospheric co 2 levels high temperatures resulting from an increased rate of production of co 2 from diagenetic and metamorphic reactions at subduction zones as sea level rose carbon was transferred from the sedimentary reservoir of reduced organic carbon to that of oxidized inorganic carbon in limestones whereas sulphur moved from the oxidized sulphate reservoir to the reduced sulphide reservoir as sea level fell reservoir transfers were opposite to those above culminating in the oscillatory mode of generally elevated continental interiors these reservoir transfers are consistent with secular changes observed in the distribution of 13 c and 34 s in sedimentary materials during the phanerozoic petrographic examination of phanerozoic oolite formations shows that ooids with preserved calcitic relict textures are characteristic of pre carboniferous carbonate rocks whereas ooids with relict textures indicative of initial aragonite mineralogy are dominant in rocks of younger age these changes in ooid mineralogy may be interpreted as reflecting changes in co 2 levels of the ocean atmosphere system consistent with the above tectonic considerations atmospheric co 2 levels were higher prior to carboniferous time favouring formation of calcitic ooids and skeletal parts after the carboniferous co 2 levels fell and aragonite and mg calcites of greater than 8 mol mg increased in abundance as precipitates

three orders of regional sea level changes control facies and stacking patterns of shallow platform carbonates in the maestrat basin tithonian berriasian ne spain middle tithonian berriasian shallow platform carbonates of the maestrat basin salzedella and montanejos sections ne spain are stacked in sequence stratigraphic units of different orders higher order sequences parasequences and subunits have a shallowing or deepening shallowing evolution they have been related to the short term eccentricity and precession cycles major facies changes and stacking pattern of parasequences reveal the presence of two 2nd order sequences the lower sequence is middle tithonian mid early berriasian in age the upper sequence extends up to the mid late berriasian it is suggested that local subsidence changes along with regional sea level changes controlled the long term evolution of accommodation in the maestrat basin facies evolution stacking pattern and sharp lithological changes have allowed the definition of five 3rd order sequences in the lower sequence in montanejos the transgressive deposits are characterised by the progressive absence of the restricted lagoon facies and the presence of deepening upward intervals in the parasequences the highstand deposits display an increase in siliciclastics and a progressive predominance of restricted lagoon facies some of the 3rd order sequence boundaries match the sequence boundaries identified in other european basins and may be related to sea level falls induced by the long term eccentricity cycle enhanced during periods of long term loss of accommodation

cretaceous evolution of the central asian proto paratethys sea tectonic eustatic and climatic controls the timing and mechanisms of the cretaceous sea incursions into central asia are still poorly constrained we provide a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy together with detailed paleoenvironmental analyses of cretaceous records of the proto paratethys sea fluctuations in the tajik and tarim basins the early cretaceous marine incursion in the western tajik basin was followed by major marine incursions during the cenomanian ca 100 ma and santonian ca 86 ma that reached far into the eastern tajik and tarim basins these marine incursions were separated by a turonian coniacian ca 92 86 ma regression basin wide tectonic subsidence analyses imply that the early cretaceous sea incursion into the tajik basin was related to increased pamir tectonism we find that thrusting along the northern edge of the pamir at ca 130 90 ma resulted in increased subsidence in a retro arc basin setting this tectonic event and coeval eustatic highstand resulted in the maximum observed geographic extent of the sea during the cenomanian ca 100 ma the following turonian coniacian ca 92 86 ma major regression driven by eustasy coincides with a sharp slowdown in tectonic subsidence during the late orogenic unloading period with limited thrusting the santonian ca 86 ma major sea incursion was likely controlled by eustasy as evidenced by the coeval fluctuations in the west siberian basin an early maastrichtian cooling ca 71 70 ma potentially connected to global late cretaceous trends is inferred from the replacement of mollusk rich limestones by bryozoan and echinoderm rich limestones

ooids in purbeck limestones lowermost cretaceous of the swiss and french jura ooids occurring in the shallow water purbeckian carbonate sediments of the jura mountains can be grouped into six types gradations from one type to another and coexistence of the various types are common type 1 ooids are small and well rounded they display fine concentric micritic laminae in many cases their cortices are dissolved and replaced by void filling spar microsparitic neomorphic replacement occurs locally type 2 ooids are large and have irregular shapes they show fine micritic laminae and occasional layers of fine radial crystals they commonly evolve into oncoids ooids of type 3 display many fine radial cortical laminae and are patchily micritized they are medium in size and mostly well rounded this type of ooid may pass into large irregularly shaped coated grains type 4 ooids have 1 to 4 cortical laminae with a fine radial structure and patchy micritization they are medium in size and well rounded type 5 ooids have only one lamina with a coarse radial structure they are small and well rounded associated are spherical grains containing bundles of elongate crystals ooids of type 6 show superpositions of two or more different radial and or fine micritic laminae the cortical structure may also change laterally in the same lamina the preferential dissolution of type 1 ooid cortices to form oomoulds indicates a primary composition of unstable carbonate sedimentological features and comparison with modern ooid occurrences point to formation on high energy sandbars in normal marine waters type 2 ooids grew in marine lagoonal environments with quiet water and abundant cyanobacteria the radially structured ooid cortices of types 3 4 and 5 show no dissolution features this implies that they were originally composed of stable carbonates or that an unstable carbonate phase was transformed into a stable one at an early stage of diagenesis type 3 ooids occur together with marine faunas and indicate high water energy ooids of type 4 and type 5 originated probably from relatively quiet water of variable salinity coexistence of different ooid types and mixed forms of type 6 implies gradual or rapid changes in hydrodynamic geochemical and microbiological conditions which were a feature of the purbeckian depositional environments

microfabric and origin of cambrian carbonate ooids examples from the cambrian oolite of carteret northeastern armorican massif france abstract the oolite at carteret cambrian atdabanian in age is composed of purely radial radial concentric and composite ooids the close resemblance between the cortex of purely radial ooids and the innermost cortex of radial concentric ones suggests that the latter ooids may originate from purely radial ones with an accretion of envelopes with a radial fabric the appearance of a concentric texture is the result of phenomena of abrasion undergone by purely radial ooids with diameters over 0 600 0 680 mm when transported as bed load the abrasion resulting from this transport stops the radial growth of crystals formerly developing in a low energy environment then in a high energy environment laminae of small equant crystals are formed it is due to an alternation between a low energy environment and a high energy environment that ooids acquire their concentric texture when compared to similar present day ooids it appears that radial ooids may have been formed in algal mats interbedded with carteret oolite

milankovitch cyclicity in purbeck peritidal limestones of the prebetic berriasian southern spain peritidal carbonate rinks purbeck facies of the uppermost portlandian to berriasian in the type section of the sierra del pozo formation in the prebetic zone southern spain are divisible into 141 shallowing upward cycles averaging 2 m in thickness the subtidal facies in these cycles consist of micritic or marly limestones with dasycladacean algae and lituolids the intertidal facies are micritic limestones containing birdseyes and miliolids the supratidal facies comprise laminated algal limestones the tops of which display desiccation cracks and rhizocretions or more locally palaeosols calcretes or palaeokarst surfaces a statistical study using power spectra of the fast fourier transform demonstrates that the periodicity of these cycles is in the milankovitch frequency band

la presence de fossiles marins dans le cretace terminal des andes centrales et ses consequences paleogeographiques abstract the maastrichtian deposits late campanian to early danian of the central andes comprise three transgressive regressive sequences in bolivia el molino formation they have yielded diverse terrestrial brackish water or marine fossils which make it possible to define the depositional environments at their exact stratigraphic position marine influenced transgressive facies are by far the best developed in the first sequence among the vertebrates five groups of fishes are restricted with some rare exceptions to marine environmentsl some other fish families genera or species are known to occur both in freshwater brackish and marine environments and therefore provide no precise environmental indications among the invertebrates echinoids serpulids foraminifera and some pelecypods and gastropods attest to a marine influenced environment which may however have experienced periodic salinity variations the other pelecypods and gastropods generally indicate freshwater environments the ostracods often ubiquitous only provide paleoecologic indications when they constitute oligospecific shell beds suggesting abnormally low salinity values calcispheres and dinoflagellates indicate a stronger marine influence charophytes especially when abundant suggest a lacustrine environment because of their stratigraphic and paleogeographic positions stromatolites may indicate intertidal to supratidal environments the fossils most likely of marine generally occur in the transgressive lower parts of the three sequences where marine oolites and glauconite are also observed the often endemic nature of the marine assemblages the common occurrence of dwarfism and the lack of true nektonic forms suggest that most part of the basin was permanently rather shallow and subjected to important frequent and or local salinity variations the freshwater fishes appear to be reworked and dissociated in the marine levels but are better preserved in the mainly continental upper parts of the sequences marine fossils are rare in the upper sequence these data contradict with interpretations which suggest that the central andean senonian deposits are exclusively terrestrial given other paleogeographic constraints we propose that maastrichtian sedimentation took place in a wide elongated subsident basin forming the eastern foreland of the paleo andes and showing a cul de sac shape in the south this restricted basin was periodically connected with the open sea through present day venezuela the salinity of its southern part situated far from the basin mouth was shallow and affected by fresh water from inflowing rivers

a facies distribution model controlled by a tectonically inherited sea bottom topography in the carbonate rimmed shelf of the upper tithonian valanginian southern tethyan continental margin nw sicily italy the upper tithonian valanginian shallow water carbonates outcropping in the palermo mts nw sicily consist of several facies associations reflecting different depositional environments of a carbonate rimmed shelf pertaining to the southern tethyan continental margin the reconstructed depositional model based on the sedimentological features cyclic facies arrangement and biota distribution shows that a wide protected lagoon dominated by algae molluscs and scattered patch reefs was bordered landward by a tidal flat where stromatolitic algal mats were cyclically subaerial exposed and seaward by a marine sand belt and reef complex oolitic packstone grainstone lithofacies cyclically subjected to subaerial exposure suggests the occurrence of a barrier island located nearly to the lagoonal carbonate shoreline allowing the development of narrow embayments with restricted circulation in the outer platform the oolitic lithofacies of the marine sand belt pass landward into the protected lagoon where washover oolite sands occur and seaward into a high energy zone back reef apron gradually merging in the reef complex in the latter coral framestone occupied the inner sector reef flat while the facies association dominated by boundstone with ellipsactinia sp developed in the outer sectors reef wall adjacent to the fore reef and upper slope environments stratigraphic evidence associated with the recognized facies associations helped to reconstruct the geo tectonic setting of the carbonate platform where the distribution of the depositional facies along the shelf and their extension were influenced by the tectonically inherited sea bottom topography in a regime of extensional tectonics localized and thin succession of high energy prograding oolite sand belt depositional facies occupied structural highs footwall uplift while the largely diffused and thick low energy aggrading peritidal to lagoonal depositional facies developed in subsiding hanging wall the reef complex and the fore reef depositional facies exhibiting lateral migration and prograding geometries with clinoforms and downlap stratal terminations developed on a subsident stepped margin adjacent to a faulted shelf break this morphostructural setting can be comprised in a model where the tilted and faulted blocks inner platform and stepped margin outer platform paleo topography inherited from the rifting tectonics was the most important factor controlling the geometry and depositional architecture of a carbonate platform growing on the southern tethyan passive margin

microfacies biofacies and depositional environments of the bajocian bathonian middle dhruma carbonates central saudi arabia three cliff forming outcrops of the dhruma formation representing the carbonate platform in the hafirat nisha district west of riyadh saudi arabia were investigated to identify and understand the microfacies variability in a carbonate ramp setting an integrated approach including detailed field investigations petrographic biofacies and micropaleontological analyses was used to construct a model of the depositional environments of the investigated outcrop sections the depositional model indicates that the identified lithofacies were predominantly deposited in outer ramp middle ramp inner ramp and lagoonal settings the presence of the benthic foraminifera redmondoides lugeoni and nautiloculina oolithica and the trace fossil thalassinoides indicates deposition in shallow water environments and the prevalence of warm climatic conditions during the middle jurassic the occurrences of calcareous and agglutinated benthic foraminiferal species pseudomarssonella maxima siphovalvulina variabilis timidonella sarda n oolithica r lugeoni praekurnubia crusei paleopfenderina salernitana haurania deserta siphovalvulina spp lenticulina sp textulariopsis sp and amijella amiji imply that our studied sections are situated within the dm 2 to dm 5 biozones bajocian to early bathonian this is also supported by the calcareous nannofossil assemblages that show a bajocian to early bathonian age the depositional sequences indicate a shift in the depositional environment from low energy lagoonal with intermittent shoal complexes in the d2 and d3 units to predominantly shoal complex and open marine settings in the d4 unit suggesting a seaward shift towards the top of the d4 unit the interpreted depositional settings are similar to those previously documented in the subsurface equivalent faridah reservoir this indicates that the investigated d2 d4 units outcrops are excellent analogues of the subsurface reservoir

uplifted marine terraces of the akamas peninsula cyprus evidence of climatic conditions during the late quaternary highstands an outcrop study of uplifted marine terraces provides information on the climate of past sea level maxima supplementing existing palaeoclimatological archives the western coast of the akamas peninsula shows several uplifted and intricately stacked quaternary marine terraces this study focuses on the sedimentology petrography and sequence stratigraphy of the last three recent terraces and provides palaeoclimatological reconstruction and chronological framing all three terraces display basically the same stratigraphic succession which consists of regressive sequences ranging from bioturbated storm influenced subtidal high energy sands to subaerial exposure and aeolian deposition each sequence differs in petrography reflecting contemporaneous climatic conditions the first studied sequence marine isotope stage 9 or 11 was deposited in a warm arid climate with oligotrophic water favouring ooid formation the second sequence marine isotope stage 7 displays colder but humid conditions with lower carbonate production and strong detrital input the third sequence marine isotope stage 5e records warm humid conditions with high carbonate production combined with significant detrital input these littoral terraces offer high quality outcrops of glacioeustatic dominated littoral sedimentology together with evidence indicative of the regional climate during the late pleistocene

facies cycles and controls on the evolution of a keep up carbonate platform kimmeridgian swiss jura during the late jurassic accelerated ocean floor spreading and associated sealevel rise were responsible for a worldwide transgression which reached its maximum in the late kimmeridgian in many western european basins this major sea level rise led to the formation of marly and condensed sections in the swiss jura however a shallow carbonate platform kept growing and only subtle changes in the stratigraphic record suggest an increasingly open marine influence field observations and thin section analyses reveal that the central swiss jura was at that time occupied by tidal flats and by more or less open marine lagoons where shoals and bioherms developed the evolution through time of sedimentary facies and bed thicknesses permits the definition of small medium and large scale depositional sequences the diagnostic features of these sequences are independent of scale and seem largely controlled by the kimmeridgian second order transgression a high resolution sequencestratigraphic correlation with biostratigraphically well dated hemipelagic and pelagic sections in the vocontian basin in france reveals that i the most important increase in accommodation recorded in the kimmeridgian of the central swiss jura occurs in the eudoxus ammonite zone late kimmeridgian and corresponds to the second order maximum flooding recognized in many sedimentary basins ii the small and medium scale sequences have time durations corresponding to the first and second orbital eccentricity cycle i e 100 and 400 ka respectively suggesting that sedimentation on the platform and in the basin was at least partly controlled by cyclic environmental changes induced by insolation variations in the milankovitch frequency band the comparison of the high resolution temporal framework defined in the swiss jura and vocontian basin with the sequencestratigraphic interpretation realized in other western european basins shows that the large scale sequence boundaries defined in the kimmeridgian of the swiss jura appear in comparable biostratigraphic positions in most western european basins discrepancies that occur are probably because of local or regional tectonics

a high resolution opal and radiolarian record from the subpolar north atlantic during the mid pleistocene transition 1069 779ka palaeoceanographic implications abstract a high resolution record of radiolarian assemblages from site u1314 was studied to reconstruct hydrographic and climatic changes in the north atlantic ocean during the mid pleistocene transition period 1069 779 ka besides the faunal record absolute accumulation of radiolarians and total biogenic opal are used to determine changes in surface water productivity results show that the north atlantic arctic front shifted back and forth repeatedly at a glacial interglacial timescale bringing the site under the influence of both cold arctic glacial and much warmer atlantic interglacial waters during glacial intervals and ice rafted debris ird events the deep dwelling taxon cycladophora davisiana was the greatest contributor of the radiolarian assemblage suggesting cold surface conditions melt water discharge and changes in deep and intermediate circulation interglacial intervals were characterized by abundant shallow dwelling taxa like pseudodyctiophimus gracilipes and lithomelissa setosa increased opal accumulation and higher radiolarian diversities indicating a northward flow of warm atlantic surface waters to the site u1314 area a marked change in the structure of the radiolarian assemblage occurred after mis 22 860 ka with large taxa differences between warm and cold periods probably in response to changing ocean conditions due to the higher amplitude of glacial interglacial changes as the dominant periodicity of high latitude climate oscillations shifted from 41 kyr to 100 kyr thus we conclude that the radiolarian assemblage from the north atlantic have changed drastically along with variations in ocean circulation in response to orbital and millennial scale climatic variations that occurred in the early and mid pleistocene

variations in stratigraphic and reservoir properties adjacent to the mid paleocene sequence boundary campo section pyrenees spain abstract the paleocene of the campo section spain has different sedimentological characteristics above and below the mid paleocene unconformity beneath the unconformity sediments are dominated by evaporitic carbonates and collapse breccias above it they are characterized by continental detrital beds alternating with paleosols different subaerial features are observed and correspond to different porosity values pore throat sizes and micrite morphologies unexposed or intertidal facies have low porosity low throat pore size mesoporosity and well preserved rhombic crystals intermediate exposed facies paleosols possess medium porosity medium pore throat size microporosity and mainly micro rhombic crystals finally the facies corresponding to high exposure intensity and to evaporitic original facies presents high porosity permeability large pore throat size and rounded micritic crystals these observations show that the emersion phase caused important dissolution especially when associated with an easily dissolved original lithofacies