carbonate factories a conundrum in sedimentary geology abstract describing characterizing and interpreting the nearly infinite variety of carbonate rocks are conundrums intricate and difficult problems having only conjectural answers that have occupied geologists for more than two centuries depositional features including components rock textures lithofacies platform types and architecture all vary in space and time as do the results of diagenetic processes on those primary features approaches to the study of carbonate rocks have become progressively more analytical one focus has evolved from efforts to build reference models for specific phanerozoic windows to scrutinize the effect of climate and long term oscillations of the ocean atmosphere system in influencing the mineralogy of carbonate components this paper adds to the ongoing lively debates by attempting to understand changes in the predominant types of carbonate producing organisms during the mesozoic cenozoic while striving to minimize the uniformitarian bias our approach integrates estimates of changes in ca2 concentration in seawater and atmospheric co2 with biological evolution and ecological requirements of characteristic carbonate producing marine communities the underlying rationale for our approach is the fact that co2 is basic to both carbonates and organic matter and that photosynthesis is a fundamental biological process responsible for both primary production of organic matter and providing chemical environments that promote calcification gross photosynthesis and hypercalcification are dependent largely upon sunlight while net primary production and e g subsequent burial of organic matter typically requires sources of new nutrients n p and trace elements our approach plausibly explains the changing character of carbonate production as an evolving response to changing environmental conditions driven by the geotectonic cycle while identifying uncertainties that deserve further research with metazoan consumer diversity reduced by the end permian extinctions excess photosynthesis by phytoplankton and microbial assemblages in surface waters induced by moderately high co2 and temperature during the early mesozoic supported proliferation of non tissular metazoans e g sponges and heterotrophic bacteria at the sea floor metabolic activity by those microbes especially sulfate reduction resulted in abundant biologically induced geochemical carbonate precipitation on and within the sea floor for example with the opening of tethyan seaways during the triassic massive sponge microbe boundstones the benthic automicrite factory formed steep massive and thick progradational slopes and locally mud mounds as tectonic processes created shallow epicontinental seas photosynthesis drove lime mud precipitation in the illuminated zone of the water column the resulting neritic lime mud component of the shallow water carbonate factory became predominant during the jurassic paralleling the increase in atmospheric pco2 while the decreasing importance of the benthic automicrite factory parallels the diversification of calcifying metazoans phytoplankton and zooplankton with atmospheric pco2 declining through the cretaceous the potential habitats for neritic lime mud precipitation declined at the same time peak oceanic ca2 concentrations promoted biotically controlled calcification by the skeletal factory with changes produced by extinctions and turnovers at the cretaceous tertiary boundary adaptations to decreasing ca2 and pco2 coupled with increasing global temperature gradients i e high latitude and deep water cooling and strategies that efficiently linked photosynthesis and calcification promoted successive changes of the dominant skeletal factory through the cenozoic larger benthic foraminifers protist protist symbiosis during the paleogene red algae during the miocene and modern coral reefs metazoan protist symbiosis since late miocene

changes in coral reef structure through the miocene in the mediterranean province adaptive versus environmental influence well documented mediterranean examples of miocene carbonate platforms with complete exposures from shallow water to basinal facies provide evidence for temporal changes in reef building capacity of zooxanthellate corals in pre late tortonian platforms small coralgal patches and mounds occur from platform top to the toe of slope but they did not build to sea level in contrast barrier reefs with unequivocal reef crest structures that reached sea level are documented in late tortonian early messinian platforms we suggest that a change in both calcification rates and bathymetric zonation was the result of coevolution of corals and symbiodinium zooxanthellae coeval to global cooling and at least at a regional scale a geochemical change that supported widespread aragonite precipitation through the late miocene

synchronous detachment folds and coeval sedimentation in the prepyrenean external sierras spain a case study for a tectonic origin of sequences and systems tracts this paper reports on the structural and sedimentary evolution of the middle to late eocene of the prepyrenean external sierras southern pyrenees spain the initiation duration and kinematics of a set of growth structures that developed in a shallow marine depositional setting is documented the detailed analysis of the syntectonic marine sediments not only confirms the already known east to west progression of deformation but also reveals the continued growth of the early formed structures as later ones propagate towards the foreland the sedimentary units coevally deposited with these growth structures are arranged in four depositional sequences their boundaries correspond to flooding surfaces which grade basinwards into correlative conformities they are also indicated by the presence of both angular unconformities and onlap geometries each depositional sequence generally consists of two systems tracts the lower one or transgressive systems tract is formed by up to 400 m of azoic marls deposited in outer ramp areas the upper one or highstand systems tract mainly consists of shallow siliciclastic and carbonate facies up to 200 m thick deposited in middle to inner ramp areas these depositional sequences are interpreted to be controlled by regional tectonic pulses an increase of tectonic activity resulted in the flooding of the basin and in the subsequent deposition of a thick succession of nearly azoic blue marls i e transgressive systems tract the overlying highstand systems tract developed following periods of diminished tectonism with the consequent growth and progradation of shallow carbonate platform facies

paleogeographic and sedimentary evolution of the south pyrenean foreland basin abstract during the paleogene and neogene the ne iberian plate underwent significant paleogeographic changes driven by the iberian and european plate collision and the resulting formation of the pyrenean orogen and its corresponding foreland basin shortening resulted in the advance of the orogenic wedge emplacement of allochthonous units and progressive basin partitioning sediment transfer systems reacted to the evolving paleogeographic scenario shifting from forebulge to foredeep and wedge top settings critical reorganizations included successive shifts from open to close drainage conditions which had an strong impact on accommodation and the stratigraphic architecture of the basin infill overfill and later erosion the aim of this work is to synthesize the paleogeographic and sedimentary evolution of the south pyrenean foreland with emphasis on the reconstruction of sediment routing the evaluation of sedimentation rate trends the timing of sedimentary shifts and the analysis of their causes stratigraphic data are compiled in a comprehensive magnetostratigraphy based chronostratigraphic framework besides sedimentary and structural data are put together to produce a series of palinspastically restored paleogeographic maps which reflect five key stages in the evolution of the region these stages include 1 the late cretaceous tectonic inversion of the extended iberian margin 2 the early eocene formation of the southern pyrenean foredeep 3 the middle eocene widening and overfilling 4 the late eocene shift into an internal drainage and 5 the late miocene drainage opening and erosion in the light of these results the variable role of tectonics climate and eustacy at different time scales are discussed

structure and composition of organic reefs and carbonate mud mounds concepts and categories defined here as essentially in place calcareous deposits created by sessile organisms organic reefs are diverse and complex structures with a long geological history their classification has been the subject of fierce debate often characterized by reliance on subjective features such as wave resistance and qualitative attempts to discriminate between first and second class reefs in contrast emphasis is here placed on the objective characteristic of the type of sedimentary support which largely determines the sedimentary composition of the deposit constructional and depositional processes result in three principal sedimentary components matrix m essentially in place skeletons s and cavity cement c whose proportions can be represented on msc triangular plots separately or together these components also provide the structural support for the reef on these compositional and structural bases three main categories of organic reef are recognized 1 matrix supported reefs agglutinated microbial reefs cluster reefs segment reefs 2 skeleton supported reefs frame reefs 3 cement supported reefs cement reefs agglutinated microbial reefs possess laminated clotted or aphanitic fabrics created by microbial trapping of particulate sediment in place skeletons and large primary cavities are rare early cementation may provide added support topographic relief is limited by the need for currents to provide sediment to accreting surfaces cluster reefs skeletal reefs in which essentially in place skeletons are adjacent but not in contact resulting in matrix support characterized by relatively high matrix skeleton ratios and low volumes of extra skeletal early cement sediment trapping is an important corollary of skeletal growth and cluster reef organisms are tolerant of loose sediment absence of framework limits the topographic relief that cluster reefs can attain relative to spatial extent and may permit bedding to develop within the reef close cluster reefs have skeletons up to 1 unit distance apart spaced cluster reefs have skeletons more than 1 and up to 2 unit distances apart with increasing separation of skeletons they grade to level bottom communities segment reefs matrix supported reefs in which skeletons are adjacent and may be in contact but are mostly disarticulated and mainly parauthochtonous matrix abundance is high and early cement relatively low moderate relief can develop in response to intense on reef sediment production frame reefs skeletal reefs in which essentially in place skeletons including calcified microbes are in contact characterized by relatively high skeleton matrix ratio skeletal support enables them to raise themselves above the substrate independently of cementation and particulate sedimentation simultaneously by creating partly open shelter cavities skeletal support may facilitate early cementation both relief and early lithification promote marginal talus formation skeletal shape and orientation distinguish conical stick like dendritic domical and laminar frames each of these may be open or filled open frame reefs

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

mixing of siliciclastic and carbonate sediments in shallow shelf environments the inhibiting effect that siliciclastic material has on carbonate secreting organisms has lead to the generalization that sediments composed of mixtures of carbonate and siliciclastic material should rarely form however many modern and ancient shelf deposits contain a spectrum of sediments that are of mixed composition the processes responsible for this mixing can be grouped into four categories 1 punctuated mixing where sporadic storms and other extreme periodic events transfer sediments from one depositional environment to another 2 facies mixing where sediments are mixed along the diffuse boundaries between contrasting facies 3 in situ mixing where the carbonate fraction consists of the autochthonous or parautochthonous death assemblages of calcareous organisms that accumulated on or within siliciclastic substrates and 4 source mixing where admixtures are formed by the uplift and erosion of nearby carbonate source terranes the allochemical constituents of mixed sediments are both coralgal and foram mollusc in composition the foram mollusc assemblage is the most common because of the effects of increased turbidity unstable substrates and the clogging of filter feeding mechanisms associated with a siliciclastic influx

the submarine delta of the ganges brahmaputra cyclone dominated sedimentation patterns the ganges brahmaputra belongs to the world s largest rivers in terms of sediment discharge but little is known yet about the processes controlling sediment distribution on the shelf and the documentation of these processes in large and small scale sedimentary structures for this study the submarine delta of the river system was investigated by high resolution seismic reflection profiles and piston and gravity coring logged physical properties of the cores were combined with visual core description grain size analysis and radiography sedimentation rates were estimated by 210pb and 137cs gamma spectrometry and cross checked with evaluation of seismic profiles the data reveal that the broad delta topset 20 m waterdepth is formed by a thick layer of sand silt highest sedimentation rates about 10 cm a 1 occur at the centre of clinoform delta foreset beds where about 20 of the total riverine sediment load is deposited and thus cause an annual progradation of the subaqueous delta front by about 15 m the foreset beds consist of graded sand silt layers which are thought to be deposited by sediment laden flows generated during the surge of tropical cyclones tempestites interbedded with silty clay layers the head of a canyon the swatch of no ground that deeply incises into the shelf forms a sediment trap along the westward cyclonic transport path where sedimentation rate increases to about 50 cm a 1 episodically earthquakes or storms destabilize especially the rapidly accumulated foreset beds in the eastern delta creating up to 8 m thick mass flows on the outer shelf in water depth beyond 80 m no holocene sediment is deposited

dynamics of tethyan carbonate platforms tethyan carbonate platforms are relatively short lived depositional systems which were born developed died and sometime resurrected in a tectonically active area in contrast with pericratonic platforms which are generally huge in size hundreds of kilometers across and show wide facies belts very gentle slopes ramps and transitional boundaries tethyan carbonate platforms are smaller tens of kilometers and have steep slopes generally faulted boundaries and abrupt facies changes it appears clear that the overall control on these two contrasting systems is the geodynamic milieu relatively stable in the first case where eustatic oscillations and long term subsidence are probably the main dictators quite dynamic and aggressive in the second one where carbonate platforms developed through the entire geodynamic spectrum rifting transtension transpression and collision of the wilson cycle primary controls on tethyan carbonate platforms appear to be tectonics most important and eustatic sea level oscillations which determine their emplacement growth and decay their overall shape and architecture are a function of these factors secondary factors affecting tethyan carbonate platform evolution are physiography oceanographic conditions and biology as a function of geologic time especially across the mesozoic tertiary boundary facies and facies distribution and to a lesser extent their shape are controlled by thesemore variables less

terrigenous sedimentation and coral reef growth a conceptual framework abstract the role of terrigenous and non framework carbonate sedimentation has not been prominent in models of coral reef growth and evolution we derive and discuss a semi quantitative model which relates coral reef growth to sedimentation the model is independent of coral biology and is based upon the relative net rates of framework and non framework sediment accumulation and or removal the model might enable some forecasting of long term responses to changes in sedimentation regime and other environmental factors the occurrence of turbid zone reefs is successfully explained in regions of very high turbidity but with little or no net sediment accumulation potential future use of the model may include aiding prediction of the effects of other geological and oceanographic factors on the growth or demise of coralline communities

internal waves as controlling factor in the development of stromatoporoid rich facies of the apulia platform margin upper jurassic lower cretaceous gargano promontory italy abstract during the late jurassic stromatoporoid rich buildups were developed in south and intra tethys realms these stromatoporoid buildups are mainly characterized by the high percentage of intraclastic bioclastic debris as main components of buildup bodies however the source of hydrodynamic energy resulted in debris production is still a matter of debate this study examines the upper jurassic lower cretaceous stromatoporoid rich buildups of monte sacro limestones msl apulia carbonate platform acp in order to describe the main carbonate facies along the study area as well as the possible source of turbulence three main lithofacies have been distinguished lf1 stromatoporoid rich facies with two subfacies lf1 s1 floatstone with wackestone to fine grained packstone lf1 s2 rudstone floatstone with intraclastic bioclastic packstone grainstone lf2 stromatoporoid coral facies distributed in wackestone to packstone matrix lf2 s1 and tabular stromatoporoid corals surrounded by wackestone matrix lf2 s2 and lf3 stromatoporoid microbial facies these facies were deposited along the mid part of a distally steepened ramp the in situ form of stromatoporoids was developed in a mud dominated matrix lf1 s1 under low energy conditions while the intraclastic bioclastic rich facies lf1 s2 were deposited under a high energy condition the distribution of lf2 and lf3 in muddy matrix suggests occurrence of these lithofacies in quiet environments the biotas were influenced by several factors including nutrient and light availability as well as by hydrodynamism the stromatoporoid rich buildups in acp can be categorized as phototrophic heterotrophic reefs generated in a pure carbonate environment the light penetration was confined resulted in the high development of light independent micro encrusters tubiphytes morronensis in a mesophotic condition where the environment was not ideal for light dependent microencrusters lithocodium bacinella to grow we suggest that debris dominated stromatoporoid rich lithofacies lf1 thrived in meso oligophotic setting along the nutricline and were affected by more than episodic high energy events in a context where the surface waves were not effective in such environments internal waves can be an effective candidate to explain the episodic turbulences to produce the debris rich facies of lf1 s2 moreover internal waves can pump the nutrient rich waters to the buildups and create an ideal setting where these metazoan communities thrived

similarities between planktonic and larger foraminiferal evolutionary trends through paleogene paleoceanographic changes abstract the paleogene evolutionary records of planktonic foraminifera and larger benthic foraminifera show parallel patterns in development that may in part reflect changes in nutrient flux to surface waters following the terminal cretaceous extinctions faunas were dominated by a few cosmopolitan opportunistic species more specialized k strategists in both groups diversified during the paleocene dominating into the early eocene consistent with he globally mild climatic regime and probable limited rates of nutrient flux to surface waters high latitude cooling intensified in the middle eocene promoting diversification of less specialized taxa characteristic of cooler and deeper waters higher latitudes meridional upwelling zones and boundary currents geographic ranges of warm water taxa diminished and fragmented yet many species survived thus global diversities during the middle eocene were the highest in the cenozoic as cooling and increased rates of nutrient flux further intensified in the late eocene extinction rates of warm water planktonic and larger benthic species exceeded origination rates of cooler water and less specialized forms so diversity dropped to intermediate levels where it remained through the late eocene and oligocene previous observations that planktonic foraminiferal faunas dominated by warm water taxa are often replaced by cool water faunas even though oxygen isotopes only recorded relatively minor cooling can be reconciled by the explanation that the biotic communities responded to changes in trophic resources and euphotic habitats that accompany the temperature reduction as well as to temperature change itself

the dagpazari carbonate platform mut basin southern turkey facies and environmental reconstruction of a coral reef system during the middle miocene climatic optimum abstract plate tectonics and climate change have deeply influenced the evolution of coral reef systems of the mediterranean during the miocene most of this information is based on studies of coral reefs from the western and central sectors of the mediterranean this study reports facies analyses sr isotope stratigraphy and environmental reconstructions of the dagpazari coral reef system located within the mut basin in southern turkey stratigraphic correlations and sr isotope ratios on several oyster shells date the dagpazari reef to the early langhian ten different facies have been recognized and their arrangement has led to the identification of two main depositional units interpretation of the biotic associations indicates that the dagpazari depositional system developed constantly within the euphotic zone the reef framework was mainly built by massive faviid and poritid zooxanthellate corals whereas loose grain sediments were essentially produced by halimeda coralline red algae or influenced by the presence of seagrass colonizations this study highlights for the first time the great importance of halimeda as sediment producer in the eastern mediterranean coral reef systems this role is related to the common occurrence of halimeda plates within almost all the reef facies but especially to the presence of large in situ bioherms dominated by the algal segments dagpazari langhian halimeda bioherms also represent the oldest of these structures so far recorded in the fossil record the development of the dagpazari platform was mainly controlled by eustatic fluctuations of the sea level and by the morphology of the antecedent substrate in particular the occurrence of a pre existent topographic high promoted the constant presence of shallow water environments throughout the depositional history of the reef system with the production of euphotic carbonates both landward and basinward and the consequent formation of a small elliptical platform 87sr 86sr ages place the dagpazari reef system exactly within the middle miocene climatic optimum phase the most recent warm phase of the earth this suggests that zooxanthellate corals were able to exert their reef building capacity in shallow water settings even during periods of global warming thus being not exclusively an adaptation to cooling climates as proposed in the recent debates

global change and modern coral reefs new opportunities to understand shallow water carbonate depositional processes human activities are impacting coral reefs physically biologically and chemically nutrification sedimentation chemical pollution and overfishing are significant local threats that are occurring worldwide ozone depletion and global warming are triggering mass coral bleaching events corals under temperature stress lose the ability to synthesize protective sunscreens and become more sensitive to sunlight photo oxidative stress also reduces fitness rendering reef building organisms more susceptible to emerging diseases increasing concentration of atmospheric co2 has already reduced caco3 saturation in surface waters by more than 10 doubling of atmospheric co2 concentration over pre industrial concentration in the 21st century may reduce carbonate production in tropical shallow marine environments by as much as 80 as shallow water reefs decline worldwide opportunities abound for researchers to expand understanding of carbonate depositional systems coordinated studies of carbonate geochemistry with photozoan physiology and calcification particularly in cool subtropical transition zones between photozoan reef and heterotrophic carbonate ramp communities will contribute to understanding of carbonate sedimentation under environmental change both in the future and in the geologic record cyanobacteria are becoming increasingly prominent on declining reefs as these microbes can tolerate strong solar radiation higher temperatures and abundant nutrients the responses of reef dwelling cyanobacteria to environmental parameters associated with global change are prime topics for further research with both ecological and geological implications

the future of coral reefs in an age of global change coral reefs are the only ecosystem that is strongly defined by a geological component most definitions require that the biological community produces its own build up of calcium carbonate in terms of reef building the geological record reveals that coral reefs have flourished over the past few million years particularly during interglacial periods based on our observations of modern day reefs which are limited to the past few centuries we tend to link coral reef health to carbonate production however reef ecosystems face future global scale environmental changes that may decrease their reef building capacity in contrast to past discussions of the factors which determine reef building potential by a coral reef community the essential question that arises from this review is how important is reef building to a coral reef community

flocculation and sedimentation on the po river delta with the goal of improving understanding of the effect of flocculation on the formation of fine grained deposits on continental shelves hydrographic profiling in situ imaging of suspended matter and collection of surficial sediment samples were conducted at the po river delta in june 2001 these data show that during medium flow conditions 1920 m3 s sedimentation occurs rapidly immediately offshore of the main distributary po della pila rapid sedimentation is promoted by large rapidly sinking flocs forming in the river well upstream of the mouth the delivery of fine sediment to the seabed at the mouth of the po is sufficient to overwhelm the erosive effects of waves and currents leading to accumulation of mud in water depths as shallow as 4 m on cross shelf transects 2 km north and south of the mouth however suspended sediment supply from the river is reduced to the point that mud accumulates only seaward of the 8 m isobath along the central transect suspended sediment concentration decreases rapidly seaward of the 6 m isobath where the emergence of a more organic rich population of flocs along a mid water density interface is suggested energetic activity along the 15 m isobath likely promotes resuspension with the potential for removal of material from the delta further investigation of floc properties namely the relationship of floc size to settling velocity is necessary to establish the degree to which the suspension is flocculated during transport and deposition

late holocene evolution of the mekong subaqueous delta southern vietnam abstract as asia s third largest river with regard to sediment load the mekong river delivers approximately 160 million tons of sediment per year to the south china sea high resolution seismic profiling and coring during 2006 and 2007 cruises revealed a low gradient subaqueous delta system up to 20 m thick surrounding the modern mekong river delta mrd in the west of the south china sea based on clinoform structure grain size 210pb ams 14c and 13c results the subaqueous delta is divided into four zones defined by different sedimentary processes and depositional features over the past 3000 yr the evolution of the mrd has shown a morphological asymmetry indicated by a large down drift area and a rapid progradation around cape camau 200 km downstream from the river mouth this asymmetric feature is consistent with increased wave influence the strong southwestward coastal current strengthened by the strong ne monsoon plays an important role locally in longshore transport of resuspended sediments into the gulf of thailand a late holocene sediment budget for the mrd has been determined based on the area and thickness of deltaic sediment approximately 80 of mekong delivered sediment has been trapped within the delta area which together with a falling sea level resulted in a rapidly prograding mrd over the past 3000 yr

marine biota response to clastic sediment influx a quantitative approach abstract there have been few quantitative studies of the effects of siliciclastic and volcaniclastic sediment influx on carbonate producing organisms from the geological record this study presents the results of quantitative field petrographic and acid digestion analyses of samples from three cenozoic shallow water mixed carbonate volcani siliciclastic depositional environments the miocene wonosari formation of south java the miocene batu putih limestone of east borneo and the eocene collsuspina limestone of northeast spain carbonate production in these systems is dominated by larger benthic foraminifera coralline algae and corals analyses of the quantity grainsize and type of volcani siliciclastic sediment within these mixed successions have allowed assessment of the influence of these factors on shallow water carbonate producers larger benthic foraminifera and coralline algae exhibit the greatest tolerance to siliciclastic sediment influx abundant up to 55 and 38 wt respectively at a range of grain sizes to coarse sand platy corals are also present within sediments containing a large proportion of insoluble material geologically averaged rates of clastic accumulation and their potential influences on carbonate producers inferred herein may be difficult to compare directly with the daily and seasonal fluctuations experienced by modern clastic influenced systems however this study may aid our understanding of the likely effects of increased clastic influx today commonly anthropogenically related to marine carbonate environments over longer time periods

development of equatorial delta front patch reefs during the neogene borneo abstract miocene patch reefs formed in turbid waters associated with high siliciclastic input at the seaward margin of the equatorial mahakam delta in eastern borneo se asia patch reefs were initiated on unstable substrates on localized low relief bathymetric highs associated with delta front channels or distributary mouthbars in the process of abandonment patch reefs developed only in shallow waters formed low relief buildups lacked rigid frameworks and had gently sloping margins although the biodiversity of the patch reefs may be comparable with that of clear water systems all the organisms present were adapted to turbid water areas associated with siliciclastic and sometimes nutrient influx the patch reefs were transient features and their demise was influenced by increased siliciclastic and nutrient input perhaps at times associated with deepening carbonate production and bioherm or patch reef development can occur in turbid water delta front areas as localized or more regionally extensive units during any phases of eustatic sea level however development and preservation of turbid water carbonates is most likely during relative transgression or perhaps late lowstand periods this is in contrast with common highstand carbonates from clear water shelves where nearly pure carbonates interdigitate with siliciclastics it is the interplay between factors such as tectonics eustasy delta lobe switching shelf currents and amount and size fraction of siliciclastic influx that ultimately controlled carbonate development and preservation

global and regional influences on equatorial shallow marine carbonates during the cenozoic abstract the se asian carbonate record allows insight into the poorly known response of equatorial marine systems to regional and global change during the cenozoic there is a marked change from larger benthic foraminifera to corals as dominant shallow marine carbonate producers in se asia around the oligo miocene boundary the early miocene acme of coral development in se asia lags oligocene coral development in the caribbean and mediterranean despite local tectonics providing apparently suitable habitable areas regional and global controls including changing co2 oceanography nutrient input and precipitation patterns are inferred to be the main cause of this lag in equatorial reefs it is inferred that moderate although falling level of co2 ca2 and ca mg when combined with the reduced salinities in humid equatorial waters all contributed to reduced aragonite saturation hindering reefal development compared with warm more arid regions during the oligocene by the early miocene atmospheric co2 levels had fallen to pre industrial levels although this was a relative arid phase globally in se asia palynological evidence indicates that the early miocene experienced everwet but more stable and less seasonal conditions than periods before or after tectonic convergence truncated deep throughflow of cool nutrient rich currents from the pacific to indian ocean around the beginning of the miocene thereby directly and perhaps indirectly though less seasonal conditions reducing nutrients it is inferred that aragonitic reefs were promoted where previously the waters had been more acidic more mesotrophic more turbid and less aragonite saturated extensive reefal development resulted in an order of magnitude expansion of shallow carbonate areas through buildup and pinnacle reef formation in the early miocene tectonics via increased habitat partitioning and reducing distances to other coral rich regions may also have contributed to enhanced reefal development declining reefal importance at the end of the early miocene resulted from uplift of land areas enhanced oceanic ventilation through thermohaline circulation and narrowing of oceanic gateways as well as increased seasonal runoff at least in se asia through initiation intensification of the monsoons implications of this study are that with current anthropogenically induced environmental changes it will be the diverse reefs of se asia that are likely to be amongst the first and hardest hit as oceanic aragonite saturation decreases and terrestrial nutrient runoff increases

coral reef diagenesis records pore fluid evolution and paleohydrology of a siliciclastic basin margin succession eocene south pyrenean foreland basin northeastern spain an integrated field petrographic and geochemical study has determined the fluid rock interaction history in part of an eocene reef complex on the margins of the siliciclastic dominated catalan sector of the south pyrenean foreland basin results show that at least four distinct fluid systems influenced the basin margin and demonstrate the sensitivity of reef rocks as paleohydrological archives in siliciclastic environments the earliest calcite cements precipitated from meteoric waters at shallow burial depths and mineralogical stabilization of reef carbonate was mostly completed during this episode textural and isotope trends typical of paleo exposure surfaces are lacking and trace element results suggest that meteoric waters were transmitted laterally and or upward into the reef via delta lobe sandstone paleoaquifers the distribution of late cements is highly variable and fracture fed demonstrating the importance of deformation in controlling fluid flow subsequent to reef lithification isotopic and elemental compositions of burial calcites plus their paragenetic association with barite and dolomite show that fluids of marine parentage were expelled from compacting basinal marls into the basin margin paleoaquifers the calders reef also records an episode of extrabasinal fluid circulation probably associated with faulting of the basin margin ferroan saddle dolomite contains fluid inclusions with elevated homogenization temperatures indicating thermal disequilibrium with the surrounding strata hydrothermal activity was possibly related to neogene extensional tectonics the final cement stage in the reef records the influence of telogenetic meteoric water possibly reflecting the present day basin margin hydrology

the descriptive nomenclature and classification of growth fabrics in fossil scleractinian reefs abstract framework sensu stricto is a concept originally relating to modern reefs and is defined by structural ecological and sedimentological criteria however in the geological literature the term framework has come to be applied to almost any organically influenced in situ accumulation including non calcareous non rigid facies associated with sea grasses this drastic departure from the original meaning is misleading and scientifically unhelpful the concept of wave resistance is integral to that of framework but in the geological record it is not easy to evaluate and the term may be of little comparative use between reef environments it is suggested that the term growth fabric be generally applied as a descriptive term for the presence of aggregated in situ corals or other organisms in growth position within a facies the term growth fabric should be used as an alternative to framework as a purely descriptive term the term framework should be restricted to its original definition and used only where the criteria for framework can be clearly demonstrated two end member types of scleractinian growth fabric genesis are recognised termed superstratal and constratal terms adapted from gili e masse j p skelton p w 1995 rudists as gregarious sediment dwellers not reef builders on cretaceous carbonate platforms palaeogeogr palaeoclimatol palaeoecol 118 245 267 in a superstratal growth fabric the constituent organisms collectively projected decimetres to metres above the substratum creating positive topographic relief in contrast constratal growth is where vertical organic accretion occurred at a similar rate to sediment accumulation hence the majority of the skeletal material remained continuously embedded in the sediments and only a small proportion of the skeleton projected centimetres above the sediment surface the architectural palaeoecological sedimentological and diagenetic implications of different types of growth fabric genesis is discussed a review of the classification of reef fabrics suggests that there is currently no adequate system to describe fossil scleractinian growth fabrics the most commonly used classification of reefal fabrics is that of embry and klovan 1971 embry a f klovan j e 1971 a late devonian reef tract on northeastern banks island northwest territories bull can pet geol 33 730 781 there are a number of shortcomings in this scheme which may be grouped into three categories 1 the interpretative nature of the classification 2 problems in interpreting biological effect from form and 3 insufficient categories to adequately describe mesozoic and cenozoic growth fabrics moreover there appears to be a lack of a standardised nomenclature for growth fabrics which has hindered meaningful comparisons of scleractinian growth fabrics through time and space a descriptive system based on a modification and expansion of the embry and klovan system 1971 is proposed and a revised nomenclature for growth fabrics presented the system is designed to be flexible in its application it can be used simply to describe a growth fabric or through the use of genetic and non genetic modifiers to imply types of reef building processes and growth fabric heterogeneity although the concepts and terminology discussed in this paper relate to scleractinian growth fabric they are equally applicable to fabrics comprising other organisms

architecture of the tectonically influenced sobrarbe deltaic complex in the ainsa basin northern spain abstract the syn tectonic sobrarbe deltaic complex eocene of the ainsa basin spanish pyrenees is confined by lateral thrust ramps and influenced by intra basinal growth anticlines six facies associations have been distinguished within the deltaic complex i slope marls and turbidite sandstones ii distal delta front silty and bioturbated sandstones iii proximal delta front and delta plain deposits tidal inlet tidal flat mouth bar bay distributary channel and floodplain environments iv biogenic deposits at flooding surfaces v collapse zone sediments and vi nummulite dominated shallow marine carbonates the deltaic complex comprises four composite sequences which each contain a number of minor sequences of the genetic maximum flooding surface bounded type regressive unconformities and their correlative surfaces separate the composite sequences cs and each cs can be divided into lowstand transgressive and highstand components at the base the comaron cs is a wnw prograding deltaic complex containing six minor sequences characterized by basinward stepping sandstone wedges separated by transgressive mudstones double regressive unconformities are often associated with these sandstone wedges proximally in the basin growth of the intra basinal arcusa anticline caused gentle folding of the comaron cs and syn growth strata at the base of the overlying las gorgas cs contain a prominent forced regressive sandstone wedge the las gorgas sandbody and display thinning of bedsets onto the crest of the anticline moreover it can be demonstrated that relative sea level rise took place in the growth synclines at the same time as a fall in relative sea level occurred on the growth anticlines the tectonic deformation caused a shift in the direction of deltaic progradation towards the north northwest as demonstrated by the well developed clinoforms in the highstand sequence set of the las gorgas cs a second phase of tectonic activity this time triggering large scale collapse of the delta front occurred at the transition between the las gorgas and barranco el solano cs tilting of the basin floor led to the development of coeval transgressive and regressive strata separated by a fulcrum line of zero net vertical movement of the shoreline in the post tilt phase reduced sediment supply and accelerated subsidence led to widespread transgression and a change from clastic to carbonate dominated sedimentation this phase was terminated by a gradual increase in sediment supply causing progradation of a mixed clastic carbonate system dominated by large nummulite banks and bioturbated shoreface marls and sandstones finally a pronounced fall in relative sea level associated with the transition to the buil cs triggered slope instabilities and eventually established fluvial conditions all over the study area with the exception of the anticline crests the relatively high rate of tectonic subsidence in the study area suppressed relative sea level falls resulting in development of discontinuous lowstand strata and bounding surfaces the segmented nature of many regressive unconformities may be related to incremental growth of thrust related structures and each segment is separated from neighbouring segments by gaps of limited vertical and lateral displacement precursors of progressive unconformities are seen in the upper proximal part of the comaron cs by downdip fanning and updip convergence of minor sequences these differentially tilted stratal units provide reliable indicators of syn sedimentary tectonism

synchronous extension and contraction in frontal thrust sheets of the spanish pyrenees the ainsa marine foreland basin of the southern pyrenees contains eocene deltaic and turbidite sequences that were deformed synchronously by both thrusting and extensional faulting during sedimentation two basin scale extensional truncation surfaces developed within a prograding imbricate thrust wedge in the footwall of the cotiella thrust sheet detailed mapping and analysis have shown that these features are major extensional detachment faults that produced complex sedimentological and stratal relations

evidence for the episodic turn on and turn off of turbid zone coral reefs during the late holocene sea level highstand terrigenous sediment accumulation within nearshore marine environments is regarded as a major factor inhibiting carbonate production and coral reef accretion while recent ecological and geological research into reef development under long term terrigenous sediment influence questions the overly simplistic nature of such views understanding of the time scales of reef initiation and growth and the morphodynamics of reef accretion in these settings remains limited here we present evidence to support recent suggestions that once established rapid reef accretion and progradation is possible but that the restricted accommodation windows in which such reefs develop often result in short lived ephemeral phases of reef building specifically we describe two discrete periods of reef growth within one small 600 m wide coastal embayment around a high island on the terrigenous sediment dominated inner shelf of the central great barrier reef australia these reef building phases occurred at either end of the holocene sea level highstand the first during the late postglacial marine transgression and early highstand 6900 4500 calibrated cal yr b p the second following the late holocene regression and stillstand 1600 cal yr b p to present an 3000 yr hiatus occurred between these events probably as a function of subtle changes in sea level and associated shoreline morphodynamics

coral reefs in coarse terrigenous sedimentary environments upper tortonian granada basin southern spain abstract during the upper tortonian coral reefs developed on fan deltas and braid deltas along the active eastern edge of the granada basin the corals grew in environments characterized by deposition of coarse sands and conglomerates frequency of sedimentation together with sea level rises controlled reef development and determined the architecture and composition of the carbonate deposits in direct contrast to these reefs others flourished at the same time along stable coastal margins of the basin their structure was influenced mainly by periodic rises in sea level the mapping of all these reefs serves as an accurate guide to the upper tortonian geography of the granada basin

influences of temperature and mg ca ratio on caco3 precipitates from seawater the mg ca ratio at which the calcium carbonate mineral that has pseudohomogeneously precipitated from seawater changes from calcite to aragonite was experimentally determined as a function of temperature results indicate a dramatic change in the critical mg ca ratio over a relatively small temperature range for example in normal seawater with a mg ca of 5 1 the critical temperature is 6 3 c at a temperature of 25 c however mg ca must be less than 1 4 0 1 for calcite to form these data indicate that paleoclimatic conditions at the time of carbonate deposition must be considered when attempting to make inferences about variation in other factors such as paleo p co 2 p pressure and paleo mg ca ratios that may control carbonate mineral formation by abiotic processes however the inverse relation between inferred global paleoclimatic conditions and the dominant type of caco 3 polymorph being abiotically deposited i e warm conditions and low mg calcite versus cool conditions and aragonite suggest that substantial changes must have taken place in ocean chemistry over phanerozoic time

platy corals from the middle triassic of upper silesia poland implications for photosymbiosis in the first scleractinians abstract coral patch reefs from middle triassic upper pelsonian lower illyrian strata in the upper silesia region of southern poland germanic domain of the peri tethys are rare examples of the first scleractinian buildups the shallowing upward succession in the tarnow opolski quarry records a transition from sponge to coral patch reefs interbedded with bioclastic limestones coral pillarstones built by thin branching volzeia szulci are succeeded by platy pamiroseris silesiaca constructing two platestone layers each up to 50 cm thick serial sections through platestones revealed flat to undulose growth form of p silesiaca the maximum observable dimension of the coral plates is 24 cm wide typically up to 12 cm while thickness of most plates is 1 1 5 cm coral plates are interlayered with crinoidal wacke to packstone and microbialites which are locally important component of the platestone platy corals grew in a shallow turbid water environment with changing but dominantly moderate hydrodynamics net sedimentation was low as indicated by the epibionts encrusted to the undersides of the coral plates and locally common microbial fabrics growth interruptions of p silesiaca record events of storm induced sediment input and resuspension of carbonate mud based on the euphotic floor model the flattened morphology of p silesiaca is interpreted as an optimal growth form in a turbid low light environment platy scleractinian assemblages from silesia are the oldest occurrences of this ecological coral group mostly representing deeper mesophotic habitats and support the hypothesis that some of the earliest scleractinians had photosymbionts like modern zooxanthellae

the role of nutrient availability in bioerosion consequences to carbonate buildups abstract zooxanthellate organisms which are among the major carbonate producers on coral reefs are highly adapted to nutrient deficient conditions and tend to be outcompeted by filamentous or fleshy algae if nutrients are abundant reef dwelling bioeroding organisms on the other hand seem to increase in abundance with increasing availability of nutrient and food resources maximum rates of calcium carbonate production in a reef system are comparable in magnitude to maximum rates of bioerosion the dynamic interplay between accretion destruction of coral reefs is therefore likely to be strongly influenced by nutrient availability nutrient availability may also influence development of carbonate facies in reef systems that develop in oligotrophic waters skeletal sands and framework should dominate carbonate buildups in systems that develop in mesotrophic waters enhanced bioerosion should reduce much of the skeletal material to carbonate muds increasing the prevalence of mud rich facies eutrophic conditions should result in bioeroded hardgrounds and carbonate depositional hiatuses when carbonate accumulation rates fail to equal or exceed rates of local relative sea level rise reefs drown bored and lithified pavements with crusts of ferromanganese oxides phosphates or glauconite often separate shallow reef from overlying deeper water deposits nondeposition bioerosion and evidence for low redox potentials at the sediment water interface all implicate excess nutrient availability as a factor in reef drowning some carbonate depositional hiatuses and bioerosional surfaces are local phenomena evidence of responses to local increases in nutrient availability resulting from submergence of soils runoff or topographic upwelling others appear to reflect regional or worldwide events because many carbonate producing organisms have life history strategies specialized to nutrient deficient conditions they are unable to compete when nutrients become plentiful events that triggered ocean turnover or sharp increases in the rate of deep ocean circulation would have increased sea surface nutrient availability worldwide such eutrophication could have caused widespread extinctions in reef communities because eutrophication promotes bioerosion details of the fossil records of those events are probably lost in bioerosional hiatuses

mesophotic coral buildups in a prodelta setting late eocene southern pyrenees spain a mixed carbonate siliciclastic system lower priabonian coral bioherms and biostromes encased in prodelta marls clays occur in the ainsa jaca piggyback basin in the south central pyrenean zone detailed mapping of lithofacies and bounding surfaces onto photomosaics reveals the architecture of coral buildups coral lithosomes occur either isolated or amalgamated in larger buildups isolated lithosomes are 1 to 8 m thick and a few hundred metres wide clay content within coral colonies is significant stacked bioherms form low relief buildups commonly 20 to 30 m thick locally up to 50 m these bioherms are progressively younger to the west following progradation of the deltaic complex the lowermost skeletal rich beds consist of bryozoan floatstone with wackestone to packstone matrix in which planktonic foraminifera are abundant and light related organisms absent basal coral biostromes and the base of many bioherms consist of platy coral colonies floating in a fine grained matrix rich in branches of red algae corals with domal or massive shape locally mixed with branching corals and phaceloid coral colonies dominate buildup cores these corals are surrounded by matrix and lack organic framework the matrix consists of wackestone to packstone locally floatstone with conspicuous red algal and coral fragments along with bryozoans planktonic and benthonic foraminifera and locally sponges coral rudstone and skeletal packstone with wackestone to packstone matrix also occur as wedges abutting the buildup margins integrative analysis of rock textures skeletal components buildup anatomy and facies architecture clearly reveal that these coral buildups developed in a prodelta setting where shifting of delta lobes or rainfall cycles episodically resulted in water transparency that allowed zooxanthellate coral growth the bathymetric position of the buildups has been constrained from the light dependent communities and lithofacies distribution within the buildups the process product analysis used here reinforces the hypothesis that zooxanthellate corals thrived in mesophotic conditions at least during the late eocene and until the late miocene comparative analysis with some selected upper eocene coral buildups of the north mediterranean area show similarities in facies components and textures and suggest that they also grew in relatively low light mesophotic and low hydrodynamic conditions

architectural stacking patterns of the ebro delta controlled by holocene high frequency eustatic fluctuations delta lobe switching and subsidence processes abstract during the late pleistocene and holocene 125 ka b p to present a type 1 4th order depositional sequence comprising regressive lowstand transgressive and highstand system tracts formed worldwide the holocene 10 ka b p to present part of this contains the latest and present highstand systems tract hst within this and the underlying transgressive systems tract tst of the ebro delta in northeastern spain higher frequency 5th to 6th order sea level fluctuations are recognised these form retrogradational and progradational high frequency depositional sequence sets within the tst and hst respectively each high frequency sequence comprises 1 a basal highly reflective shell lag associated with an erosional transgressive surface 2 aggradational deposits which seawards consist of a wedge of marine clays with transparent seismic facies but inland are represented by thick peats 3 progradational deposits composed of sandy delta front facies displaying slope clinoforms these pass seawards into prodeltaic grey silts and landwards into red silts and pebbly sands of delta plain facies the progradational deposits downlap towards their bases the aggradational deposits formed in response to a period of rising sea level and a rapid increase in accommodation space progradation began when sediment supply to the delta exceeded accommodation space as a result of relative sea level fall the relative sea level curve for the delta has a stepped character caused by the punctuation of the 4th order sea level trend by higher frequency eustatic fluctuations as well as by high subsidence rates of about 1 75 mm per year the tst comprises retrogradational parasequences that onlap the underlying pleistocene gravels the maximum flooding surface separating the tst from the hst was formed about 6900 yrs b p on the basis of14c dating of peats the hst comprises progradational deltaic and aggradational units stacked as progradational high frequency parasequence sets the hst of the ebro delta is compared with other deltaic sequences around the world in particular with that of the mississippi delta a tentative chronology of the high frequency climatic and eustatic oscillations influencing deltaic sedimentation globally over the last 7000 years is presented

the hydrodynamic and sedimentary setting of nearshore coral reefs central great barrier reef shelf australia paluma shoals a case study the great barrier reef gbr shelf contains a range of coral reefs on the highly turbid shallow inner shelf where interaction occurs with terrigenous sediments the modern hydrodynamic and sedimentation regimes at paluma shoals a shore attached turbid zone coral reef and at phillips reef a fringing reef located 20 km offshore have been studied to document the mechanisms controlling turbidity at each reef waves currents and near bed turbidity were measured for a period of 1 month bed sediments were sampled at 135 sites on the inner shelf muddy sands are widespread with admixed terrigenous and carbonate gravel components close to the reefs and islands except on their relatively sheltered sw side where sandy silty clays occur at paluma shoals the coral assemblage is characteristic of inner shelf or sheltered habitats on the gbr shelf dominated by galaxea fascicularis up to 50 coral cover and is broadly similar to that at phillips reef further offshore and in deeper water the sediments of the paluma shoals reef flats consist of mixed terrigenous and calcareous gravels and sands with intermixed silts and clays whereas the reef slope is dominated by gravelly quartz sands the main turbidity generating process is wave driven resuspension and turbidity ranges up to 175 nephelometric turbidity units ntu in contrast at phillips reef turbidity is 40 ntu probably occurs for a total of 40 days each year and relatively little time is spent at intermediate turbidities 15 50 ntu the extended time spent at either low or high turbidities is consistent with the biological response of some species of corals to adopt two alternative mechanisms of functioning autotrophy and heterotrophy in response to different levels of turbidity sedimentation rates over periods of hours may reach the equivalent of 10 000 times the mean global background terrigenous flux btf of sediment to the sea floor i e 10 000 btf over three orders of magnitude greater than the holocene average for halifax bay of 3 btf as elsewhere along the nearshore zone of the central gbr dry season hydrodynamic conditions form a primary control upon turbidity and the distribution of bed sediments the location of modern nearshore coral reefs is controlled by the presence of suitable substrates which in halifax bay are pleistocene and early holocene coarse grained and relatively stable alluvial deposits

structure and development of detrital reef deposits in turbid nearshore environments inhaca island mozambique coral communities are intermittently developed along the seaward margins of wide up to 500 m intertidal flats that fringe the western margins of inhaca island southern mozambique the coral communities occur in an environment that can be considered as marginal for coral growth in the sense that they are subject to high turbidity levels which results in rapid light attenuation and to the effects of periodic smothering and burial associated with a mobile siliciclastic dominated sediment substrate these constraints limit coral community development both spatially and bathymetrically in addition historical evidence suggests that the main sites of coral growth shift over decadal timescales due to periodic sediment remobilisation such rapid rates of turnover restrict the development of rigid framework deposits and in contrast the main depositional product of coral growth is an abundance of branched mainly acropora sp coral rubble rubble production is aided both by intense internal bioerosion sponge bivalve and worm traces and by periodic storm damage much of this rubble accumulates along the channel margins and provides a substrate for subsequent coral recruitment the deposits can be distinguished from those associated with clear water reef environments by 1 the lack of a rigid reef framework either comprising of in situ coral or encrusted coral rubble 2 the distinct lack of rubble encrustation syn depositional cementation and 3 the predominance of a siliciclastic rich sediment matrix the deposits indicate however a long term history of coral community occurrence in sites dominated by siliciclastic sedimentation cores recovered from a transect across the tidal flats identify a coral rubble floatstone facies extensively developed along the western margins of the island it comprises mainly branched coral rubble often heavily bioeroded but sparsely encrusted along with spheroidal rhodoliths and molluscan fragments set within a poorly sorted mixed siliciclastic carbonate sediment matrix 14c dating indicates that most of the rubble deposits date from the period 6500 4700 years bp which corresponds to a period of regional sea level highstand a detailed growth chronology cannot be established due to the lack of in situ coral but rapid rubble deposition and reef flat progradation around 350 m can be inferred for this period equivalent to an average progradation rate of around 0 2 m year 1 over the subsequent 4700 years progradation of only around 25 m has occurred this may be attributed to reworking and erosion of the seaward margin of the deposits during periods of fluctuating sea level between 4700 and 900 years bp or to a lack of seaward accommodation space

siliciclastic and volcaniclastic influences on equatorial carbonates insights from the neogene of indonesia in active tectonic areas of humid equatorial regions nearshore shallow water environments are commonly sites of near continuous siliciclastic influx and or punctuated volcaniclastic input despite significant clastic influence neogene carbonates developed in se asia adjacent to major deltas or volcanic arcs and are comparable with modern mixed carbonate clastic deposits in the region research into delta front patch reefs from borneo and fore arc carbonate platform development from java is described and used to evaluate the effects of siliciclastic and volcaniclastic influx on regional carbonate sedimentation local changes in carbonate producing biota and sequence development regional carbonate development in areas of high siliciclastic or volcaniclastic input was influenced by the presence of antecedent highs changes in the amounts or rates of clastic input delta lobe switching or variations in volcanic activity energy regimes and relative sea level change a variety of carbonate producing organisms including larger benthic foraminifera some corals coralline algae echinoderms and molluscs could tolerate near continuous siliciclastic or volcaniclastic influx approximately equal to their own production rates these organisms adopted various strategies for coping with clastic input including a degree of mobility morphologies adapted to unstable substrate inhabitation or shedding sediment and shapes adapted to low light levels local carbonate production was also affected by energy regime clastic grain sizes and associated nutrient input clastic input influenced the inhabitable depth range for photoautotrophs the zonation of light dependent assemblages and the morphology and sequence development of mixed carbonate clastic successions this study provides data on the dynamic interactions between carbonate and non carbonate clastic sediments and when combined with information from comparable modern environments allows a better understanding of the effects of siliciclastic and volcaniclastic influx on carbonate production

late holocene evolution of the mahakam delta east kalimantan indonesia abstract the late holocene mahakam delta located along the tropical eastern shore of kalimantan indonesia is considered to be a textbook example of a mixed tide fluvial dominated delta system the delta prograded about 60 km during the past 5000 years which led to the development of a distinct network of distributary and tidal channels wave action is low due the limited fetch in the narrow strait of makassar mahakam river discharge is about a quarter of the mississippi river discharge and is characterized by absence of flood surges therefore natural levees crevasse splays and avulsions are absent in the delta plain for the past four decennia both modern and ancient mahakam delta deposits have been studied in detail in order to better understand subsurface miocene and tertiary mahakam deposits which host large volumes of hydrocarbons this study focuses on the dynamics and stratal patterns of delta plain delta front platform deposits and suspended sediments due to the predominance of semi diurnal tides and the associated flow reversals depositional patterns are highly variable which has resulted in the formation of characteristic sand mud couplets the distribution of the sand mud couplets found in this study differs from previously proposed conceptual models they are limited to the fluvial domain and form in the distributary channels lateral channel bar or at the fluvial dominated delta front platform which flanks the mouth bar deposits in offshore direction the sand mud couplets which formed as delta front platform and lateral channel bar deposits are similar and can only be identified based on their 14 c age the sand content decreases significantly towards the tidal dominated areas due to limitation in transport capacity turbidity measurements taken in front of the river mouth also show rapid settlement of river plume sediments some 22 new ams 14 c dates show that late holocene sea level history resembles the eustatic sea level curve giving a first approximation of the late holocene sea level history for east kalimantan the dates suggest that the progradational delta system evolved under conditions of slowly rising sea level which compares well to the eustatic sea level curve in addition calculated averaged deposition rates of the sand mud couplets indicate that deposition is driven by the spring neap tide cycles instead of the daily tidal cycle

secular oscillations in the carbonate mineralogy of reef building and sediment producing organisms driven by tectonically forced shifts in seawater chemistry the primary mineralogy of oolites and early marine carbonate cements led sandberg nature 305 1983 19 22 to divide the phanerozoic eon into three intervals of aragonite seas and two intervals of calcite seas hardie geology 24 1996 279 283 has shown that these oscillations together with synchronous oscillations in the mineralogy of marine potash evaporites can be explained by secular shifts in the mg ca ratio of seawater driven by changes in spreading rates along mid ocean ridges the hardie model also predicts that high mg calcite should precipitate along with aragonite as it does in today s aragonite sea we have uncovered oscillations in the carbonate mineralogy of hypercalcifying organisms ones that have produced massive skeletons large reefs or voluminous bodies of sediment that correspond to sandberg s aragonite seas and calcite seas and that are predicted by the hardie model particular groups of corals sponges and algae appear to have been dominant reef builders only when favored by an appropriate mg ca ratio in seawater in early and middle paleozoic calcite seas calcite i reefs were dominated by calcitic tabulate heliolitid and rugose corals and calcitic stromatoporoids in contrast during the period of late paleozoic early mesozoic aragonite seas aragonite ii aragonitic groups of sponges scleractinian corals and phylloid algae as well as high mg calcitic red algae were principal reef builders during late cretaceous time at the acme of calcite ii massive rudists displaced aragonitic hermatypic corals in today s aragonite sea aragonite iii scleractinian corals are again dominant reef builders along with high mg calcitic coralline algae major sediment producing algae exhibit temporal patterns similar to those of reef builders calcitic receptaculitids flourished during calcite i whereas aragonitic dasycladaceans did not become dominant rock formers until aragonite ii during calcite ii calcitic nannoplankton formed massive coccolith chalks in warm shallow seas of the late cretaceous after the mg ca ratio of seawater had reached a very low value and calcium concentration a very high value as the mg ca ratio of seawater rose and calcium concentration fell during the cenozoic era individual coccoliths on average became less massive and encrusted cells less thickly by pliocene time during aragonite iii the prominent genus discoaster secreted only narrow rayed coccoliths that covered less than 25 of the cell surface also during aragonite iii the aragonitic green alga halimeda emerged as the dominant skeletal sediment producer in reef tracts the influence of seawater chemistry on skeletal secretion appears to have been especially strong for morphologically simple taxa that exert relatively weak control over their own calcification such groups include algae sponges corals and bryozoans morphological simplicity also permits these groups to adopt vegetative or colonial modes of growth that confer success in competition for space on reefs this linkage in addition to the basic chemical demands of hypercalcification has given the mg ca ratio of seawater strong control over the success of individual reef building taxa more generally this ratio appears to have strongly influenced evolutionary changes in the skeletal mineralogy of sponges and cheilostome bryozoans throughout their history we conclude that throughout phanerozoic time a chain of causation has extended from mid ocean ridge processes via seawater chemistry to the mineralogical and biological composition of reef communities and bioclastic carbonate deposits

quantifying the kinematics of detachment folds using three dimensional geometry application to the mediano anticline pyrenees spain the kinematics of detachment folds have been described by three different models 1 hinge migration is responsible for fold amplification 2 fold amplification is due to limb rotation and 3 both hinge migration and limb rotation cause fold amplification a numerical method is proposed to determine which of these mechanisms is responsible for the formation of natural detachment folds this procedure consists of measuring and plotting geometric data collected from cross sections constructed across the termination of a fold where shortening dies out laterally or in an area with a lateral shortening gradient assuming that observed spatial variations in fold geometry reflect temporal geometric evolution the procedure allows determination of equations that govern the kinematics of the particular detachment fold analyzed to validate the results obtained from the application of this technique to natural examples they must be contrasted with other indicators of fold amplification mechanisms such as microstructures mesostructures and syntectonic sediment patterns this analysis is applied to an asymmetric growth fold the mediano anticline in the southern pyrenees of spain and shows that it grew due to limb rotation and minor hinge migration these data coupled with analysis of the growth stratal patterns using reverse and forward modeling techniques are used to derive deformation rates and to display the kinematics of this fold

environmental reconstruction of a late burdigalian miocene patch reef in deltaic deposits east kalimantan indonesia abstract most studies of cenozoic shallow water mixed carbonate siliciclastic depositional systems have focused on their sedimentology to date however comprehensive analyses of biotas and biofacies of indo west pacific reefs that developed in mixed carbonate siliciclastic systems are lacking this study describes the palaeoenvironment and biodiversity of a late burdigalian patch reef that developed in a mixed carbonate siliciclastic depositional system the studied exposure is located at the northeast margin of the kutai basin near bontang indonesia and is approximately 80 m wide and 25 m thick multi taxon analysis of the most abundant fossil groups including larger benthic foraminifera corals coralline algae and bryozoans aims to provide a model for environmental interpretation that will allow comparison with similar deposits of indo west pacific region based on fossil content and lithology five different facies types have been distinguished foraminiferal packstone fp bioclastic packstone with foralgal communities bp thin platy coral sheetstone cs platy tabular coral platestone cp and shales s among larger benthic foraminifera smaller and more robust forms dominate in the fp and bp facies while larger and flatter forms are the most abundant in the cs and cp facies thin platy corals are dominant in the cs facies and gradually change into thicker platy tabular forms in the cp facies assemblages and growth forms of coralline algae show no major differences between the facies types and are dominated by melobesioids and sporolithon the majority of bryozoan species are encrusting and were found only in the cs facies light dependent organisms occurring in the reef indicate low light conditions typical for mesophotic reefs the relatively small size of this reef complex and quite distinct vertical changes in the facies types combined with the high siliciclastic content in most of the units points to strong terrigenous input affecting water transparency as the main factor controlling the reef growth

application of a diffusion erosion model to alluvial channels which degrade due to base level lowering the applicability of a diffusion erosion model that predicts transient longitudinal profiles of degrading alluvial channels has already been demonstrated in laboratory experiments and is here applied to some field examples by fitting simulated longitudinal profiles to measured ones for several streams with discharge 0 04 q5 680 m3s 1 diffusion erosion coefficients k were determined which are well correlated to discharge and drainage area headward knickpoint migration which results from base level lowering was also treated through the diffusion erosion model theoretically the distance of a knickpoint from the mouth of a tributary should be proportional to the square root of the time that elapsed since the base level was lowered field observations are in accordance with these theoretical considerations use of the model is discussed for prediction of erosion and for assessment of the age of alluvial fault scarps crossed by streams

benthic carbonate factories of the phanerozoic marine carbonate precipitation occurs in three basic modes abiotic or quasi abiotic biotically induced and biotically controlled on a geologic scale these precipitation modes combine to form three carbonate production systems or factories in the benthic environment 1 tropical shallow water factory dominated by biotically controlled mainly photo autotrophic and abiotic precipitates 2 cool water factory dominated by biotically controlled mainly heterotrophic precipitates and 3 mud mound factory dominated by biotically induced mainly microbial and abiotic precipitates sediment accumulations of the factories differ in composition geometry and facies patterns and some of these differences appear prominently in seismic data thus facilitating subsurface prediction the characteristic accumulation of the tropical factory is the flat topped often reef rimmed platform in cool water systems reefs in high energy settings are scarce and hydrodynamic influence dominates producing seaward sloping shelves and deep water sediment drifts often armored by skeletal framework the typical accumulation of the mud mound factory is groups of mounds in deeper water where the mud mound factory expands into shallow water it forms rimmed platforms similar to the tropical factory the tropical factory is most productive the mud mound factory reaches 80 90 and the cool water factory 20 30 of the tropical growth rate the three factories represent end members connected by transitions in space transitions in time are linked to biotic evolution

estimating palaeo water depth from the physical rock record abstract palaeo water depth and its change with time is a key factor in environmental analysis and in sedimentology in general the literature published on this topic and on related subjects however is substantial albeit scattered within and between different communities geologists oceanographers engineers physicists etc here i focus on proxies for palaeo bathymetry as obtained from the physical rock record floral faunal and chemical evidence for palaeo water depth being equally important must be dealt with elsewhere an assessment of the main depth related parameters in actualistic settings is presented and their applicability to the fossil sedimentary record discussed the outcome reveals the full complexity of this topic there is for example no such thing as an average wave base depth applicable to a wide range of fossil case settings this because wave and current climates in general and particularly so in neritic and coastal settings are intriguingly complex furthermore observations from modern oceans are not a priori applicable to fossil ones acknowledging these problems and limitations critically evaluated quantitative proposals for depth indicative facies and features in the sedimentary record are presented and error bars discussed

a model for the palaeoenvironmental distribution of larger foraminifera based on late middle eocene deposits on the margin of the south pyrenean basin ne spain abstract on the margin of the south pyrenean basin the late middle eocene sediments represent a well preserved regressive system permitting determination of the distribution of larger foraminifera along the depth gradient eocene deposits are compared with distribution patterns of recent larger foraminifera based on taxa occupying comparable positions along similar ecological gradients eocene taxa reveal by their test morphology a similar response to specific ecological conditions to that recorded for recent foraminifera four assemblages characterise an open marine shelf they range from the lower limit of the photic zone to the lower part of the upper photic zone two assemblages characterise the upper part of the upper photic zone and indicate respectively two different substrates firm or soft below the photic zone no larger foraminifera exist and the foraminiferal assemblages are dominated by smaller benthic foraminifera

sand beach ridges record 6000 year history of extreme tropical cyclone activity in northeastern australia sand beach ridges are considered to be derived either from aeolian processes and or waves but their deposition by individual or multiple storms has not been investigated in any detail we use numerical meteorological and oceanographic models to determine the origin of a sequence of 29 shore parallel sand beach ridges in northeastern australia the results suggest that the ridges were constructed by waves and that the final form or height of the ridges is a function of high energy tropical cyclone generated waves plus storm tides hence these landforms archive a nearly 6000 year long history of intense tropical cyclones the record implies that these extreme tempests occur considerably more frequently than that suggested by the short historical record for this region the genesis of this sand beach ridge plain has implications for the interpretation of similar sequences elsewhere along the northeast coast of australia and in comparable environments globally if other similar sand beach ridge plains have also been deposited by like processes it stands to reason that these long term records of high intensity tropical cyclones can be used to ascertain a regional scale risk assessment from this hazard

sediment facies and late holocene progradation of the mekong river delta in bentre province southern vietnam an example of evolution from a tide dominated to a tide and wave dominated delta abstract the mekong river delta southern vietnam is a typical mixed tide and wave energy delta with a wide delta plain formed during the last 6 ka and is one of the largest deltas in the world three cores were taken from bentre province in the lower delta plain with the objective to describe the sediment facies and to clarify the changes from tide dominated to tide wave dominated delta of the mekong river delta during the late holocene three cores bt1 bt2 and bt3 were obtained in 1997 holocene sediments in bt1 and bt3 with thickness ranging from 10 to 20 m were mainly composed of deltaic sediments unconformably overlying the late pleistocene sediments the bt2 core however consisted of transgressive estuarine sediments covered by deltaic sediments infilling the paleo mekong river incised valley which is more than 70 m deep and was formed during the last glacial period the deltaic sediment facies and succession in the bt2 and bt3 cores taken from the outer delta plain with beach ridges were different from those of the bt1 core taken from the inland delta plain the bt2 and bt3 cores provide a good example of tide and wave dominated delta sediments and were characterized by a coarsening upward delta front facies covered by a fining upward subtidal to intertidal flat facies followed by a coarsening upward foreshore dune facies these changes from the inland delta plain to the beach ridge delta plain were accompanied by changes in progradation rates and subaqueous delta topography caused by increased wave influence

the transition between sheet like lobe and basin plain turbidites in the hecho basin south central pyrenees spain genetic facies analysis based on bed by bed correlations from sheet like lobes to the basin plain in some hecho turbidite systems demonstrates that at least 50 of the flows building the sheet like lobes kept moving downcurrent to the closely related basin plain and underwent flow transformations interpreted to have resulted from interaction with topography at the basin margin s that gave rise to specific facies these facies form a new facies tract that replaces the fine grained group of turbidite facies very fine sand to mud and characterizes the basin plain beds beds in the sheet like lobes evolve downcurrent in a way that is predictable by the existing turbidite facies tract models whereas 36 of basin plain beds which account for 78 of the basin plain volume do not the latter have deposits from high density turbidity currents at their bases and typically complete basin floor coverage the new facies tract developed when the flows obliquely encountered the southern foreland margin ramp at the ramp the lower sand laden and high density part of the larger flows was deflected evolving downcurrent along the ramp trend the upper part of the flow more dilute and thicker was reflected from the foreland margin as a train of declining undular bores moving hydraulic jumps subsequent reflections generated against the flanking margins in the closed basin led to ponding which resulted in an overall sheet like stacking pattern across sheet like lobes and the basin plain and is the diagnostic feature of the distal element in the lower sand rich stages of the turbidite systems calcilutites on top of beds interpreted until now as hemipelagites show field evidence of having a turbiditic origin hemiturbidites thus forming the facies capping the new facies tract

paleogene propagation of the southern pyrenean thrust wedge revealed by finite strain analysis in frontal thrust sheets implications for mountain building abstract to better evaluate the sequence of shortening and estimate shortening rates associated with the propagation of the southern pyrenean front we propose an original approach based on the reconstruction of finite displacement and finite vertical axis rotations this study is based on the quantitative analysis of published datasets including balanced cross sections paleomagnetic and thermochronologic data we distinguish three main episodes of shortening between 41 and 37 ma 37 and 30 ma and between 30 and 16 ma they are associated with a decrease of accretionary rates from 3 km ma to 0 39 0 27 km ma on the pro wedge side of the pyrenean orogenic wedge based on the comparison between frontal accretionary flux and outcoming fluxes in the axial zone of the pyrenees we show that the period ranging from 37 to 30 ma recorded a remarkable increase in erosion that is not compensated by accretion in the wedge in the context of the overall decrease in the iberia eurasia plate convergence we suggest that the main cause of the acceleration of erosion on top of the growing pyrenean orogen is related to climate changes that occurred at the eocene oligocene boundary

mesophotic bioerosion variability and structural impact on u s virgin island deep reefs abstract mesophotic reef corals found 30 150 m below sea level build complex structures that provide habitats for diverse ecosystems whereas bioerosion is known to impact the development and persistence of shallow reef structures little is known regarding the extent of mesophotic bioerosion or how it might affect deeper reef geomorphology and carbonate accretion originally pristine experimental coral substrates and collected coral rubble were both used to investigate the variation and significance of mesophotic coral reef bioerosion south of st thomas u s virgin islands bioerosion rates were calculated from experimental coral substrates exposed as framework for 1 and 2 years at four structurally distinct mesophotic coral reef habitats between 30 and 45 m as well as at a mid shelf patch reef 21 m and a shallow fringing patch reef 9 m the long term effects of macroboring were assessed by examining coral rubble collected at all sites overall differences in bioerosional processes were found between shallow and mesophotic reefs increases in bioerosion on experimental substrates amount of weight lost were related to both decreasing seawater depth and increasing biomass of bioeroding parrotfish significant differences in coral skeleton bioerosion rates were also found between the transitional mesophotic reef zone 30 35 m and the upper mesophotic reef zone 35 50 m after 2 years of exposure ranging from 19 6 to 3 7 g year total coral rubble macroboring was greater at most deep sites compared to shallower sites bioerosional grazing was found to dominate initial substrate modification in reefs 30 7 m and shallower but sponges are believed to act as the main time averaged long term substrate bioeroders in reefs between 35 and 50 m although initial substrate bioerosion rates of a uniform substrate were relatively homogeneous in the 35 50 m depth zone comparison of site composition suggests that mesophotic bioerosion will vary depending on the amount location and type of available substrate and the duration both coral rubble and in situ coral framework are exposed on the seafloor these variations may exaggerate pronounced structural differences in mesophotic reef habitats that experience few other methods of erosion

connecting large scale coastal behaviour with coastal management of the rhone delta abstract the aim of this paper is to connect the large scale coastal behaviour lscb of the rhone delta shoreface sediment budget river sediment input to the beaches climatic change with the impact and efficiency of hard engineering coastal structures the analysis of the 1895 to 1974 bathymetric maps as well as 2d modelling of the effect of wave blocking on longshore transport allows us to draw up a conceptual model of the lscb of the rhone delta the river sand input settled in the mouth area prodeltaic lobe favours the advance of adjacent beaches there is however a very weak alongshore sand feeding of the non adjacent beaches farther off the mouth after a mouth shift the prodelta is eroded by aggressive waves and the sand is moved alongshore to build spits this conceptual model suggests that there is a timeshift between the input of river sediments to the sea and the build up of a beach nonadjacent to the mouth nowadays as the river channels are controlled by dykes and human interventions a river shift is not possible it thus appears unlikely that the river sediments can supply the beaches of the rhone delta coast under these conditions we must expect that the problems of erosion will continue at saintes maries de la mer and on the faraman shore in areas with chronic erosion where the shoreline retreat has been partially stopped by hard engineering practices in the 1980s therefore these artificially stabilised sectors remain potentially under threat because of profile steepening and downdrift erosion evidenced in this paper by bathymetric profile measurements in the long term 1905 to 2003 the temporal analysis of the storm surges and the sea level show very weak but reliable increasing trends thus these climatic agents will be more aggressive on the beaches and on the coastal structures calling their efficiency into question we also evidence that the hard engineering structures were built in a favourable climatic context during the 1980s meanwhile the storm surges and the sea level rise are stronger since the 1990s regarding to the lscb of the rhone delta and the impact of hard engineering coastal structures we suggest that classical hard coastal protections are not the best option to protect the coast

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

scleractinian assemblages under sediment input their characteristics and relation to the nutrient input concept abstract in the geological record scleractinian dominated turbid water bioconstructions that accumulated under substantial terrigenous input along with shallow neritic marls rich in well preserved corals are common these occurrences indicate that beyond some threshold the ecologic and taphonomic effects of sedimentation prevail over the effects of nutrification field data and experiments on recent corals show that some taxa cope well with terrigenous turbidity and sedimentation and acclimate to increased heterotrophy colonial corals resilient to sediment input commonly are massive to platy forms of high skeletal plasticity and with large polypars to effectively reject sediment or are branched species providing a very small sedimentation area cleaned by feeble currents or small polyped massive taxa that tolerate intermittent veneering by sediment these corals may comprise siltation assemblages of recent turbid water reefs and level bottoms in siliciclastic environments conversely excess input of even low amounts of dissolved inorganic nutrients into clear waters adversely affects many coral species fossil turbid water bioconstructions twb were situated in inner shelf to shore zone settings or near storm wave base on shelves or ramps did not stack into reef complexes mostly show a cluster to segment fabric are scarce in or devoid of frame pores with marine cement and lacked a high carbonate slope relative to fossil clear water buildups preserved in pure limestone successions fossil twb contain moderately diverse coral assemblages with an increased proportion of sediment resistant forms aside from coral behaviour that is elusive in fossils the sediment resistance of corals was mainly determined by colony shape and polypar size but small polyped sediment tolerant corals became common since the early cretaceous late jurassic to cretaceous turbid water coral assemblages are dominated by plocoid or thamnasterioid forms corresponding cainozoic assemblages consist mainly of cerioid and plocoid taxa in fossil twb bioerosion and encrustation are similar or higher than in contemporaneous clear water buildups under higher sediment input accumulation of discrete twb was quenched and level bottoms of both corals and soft substrate biota formed in the resulting coral marls depending on turbidity sedimentation and substrate stability the coral fauna consists largely of both solitary corals and mainly sediment resistant pseudocolonial colonial forms or is dominated by solitary corals many corals show growth anomalies resulting from partial mortality due to episodic rapid sedimentation and unstable substrate in coral marl environments because of terrigenous input nutrient levels probably were elevated yet macroboring and encrustation are very scarce beyond some threshold of terrigenous sediment input and accumulation the ecologic and taphonomic effects of sedimentation and unstable substrate prevail over the effects of nutrient enrichment during the meso cainozoic evolution of scleractinians increasing photoautotrophy and progressive invasion of oligotrophic environments is in contrast to a late cretaceous to cainozoic increase in the relative number of reefs in marginal marine siliciclastic settings this trend may be explained by second order sea level fall and shrinking of epicontinental carbonate seas and isolated platforms driving corals to more narrow attached shelves and by a wider total trophic range in which distinct coral assemblages can thrive as a result of coral evolution and diversification

meco and alpine orogenesis constraints for facies evolution of the bartonian nummulitic and solenomeris limestone in the argentina valley ligurian alps

reverse modelling of detachment folds application to the pico del aguila anticline in the south central pyrenees spain abstract a simple method to estimate fold amplification and thrust movement rates for detachment folds is documented and illustrated by its application to a symmetrical detachment fold in the southern pyrenees spain the technique provides a complete record of the kinematic evolution of detachment folds and is based on the application of equations for detachment folds involving limb rotation the method uses the stratal pattern of the syntectonic sediments and assumes that these growth strata were deposited horizontally that the folds involve a homogeneous competent unit detached over a ductile horizon and that the folds can be represented by chevronkink bands the procedure is applicable to any detachment fold with associated growth strata that display wedge geometries progressive unconformities indicating limb rotation through time this method can be used for both detachment folds formed with constant limb length or variable limb length and it can also accommodate undecompacted or decompacted growth strata

the modern po delta system lobe switching and asymmetric prodelta growth the modern po delta system comprising five main delta lobes has been investigated by integrating vhr seismic surveys recorded offshore from water depths as shallow as 5 m to the toe of the prodelta in about 30 m with accurate historical cartography extending back several centuries previous studies give sedimentological and geochronological information from precisely positioned sediment cores this combined historical and stratigraphic reconstruction of the modern po prodelta allows volumetric reconstructions indicating an average sediment load of 9 4 10 6 ty r 1 for po di pila and po di goro gnocca lobes this estimate is remarkably consistent with the total sediment load of 11 5 10 6 ty r 1 available for parts of the last century from a gauge station at the apex of the delta plain in pontelagoscuro these integrated stratigraphic studies allow to explain the key characters of the po delta system a the marked asymmetry of the whole delta prodelta system reflecting prevailing sediment dispersal to the south of each individual delta outlet b the shoreparallel overlapping of successive prodelta lobes fed by distinct river outlets of ever changing relative importance c the delta outlets being artificially forced in a fixed position so that natural avulsion is prevented and delta lobes undergo headland retreat leaving a marked erosion on the prodelta d the presence of prodelta lobes showing widespread bcut and fillq features ranging from 100 to 300 m and depths up to 4 5 m filled with massive silt to very fine sand offshore of short lived very active distributary channels e g po di tolle lobe and suggesting that in some particular interval short lived episodes of submarine erosion are induced by catastrophic increases in river discharge of natural origin or induced by human maintenance the seismic stratigraphy of the modern po delta documents that markedly distinct prodelta architectures form when a newly activated lobe is located updrift north in this case or downdrift south of the one that is retreating in the first case the abandoned lobe becomes sheltered by the new rapidly advancing one in the opposite case the retreating lobe is updrift and a substantial portion of the sediment is cannibalized and transported to the new lobe downdrift d 2005 elsevier b v all rights reserved

paleoenvironmental reconstruction of a downslope accretion history from coralgal coralline sponge rubble to mud mound deposits eocene ainsa basin spain abstract in the lutetian intraslope ainsa sub basin small sub spherical carbonate mud mounds occur associated with hemipelagic marls and mixed gravity flow deposits the studied mud mounds consist of a mixture of allochthonous parautochthonous and autochthonous components that show evidences of reworking bioerosion and accretion by different fossil assemblages at different growth stages the crusts of microbial lithistid sponges played an important role stabilizing the rubble of coralgal coralline sponges and formed low relief small benthic patches in a dominant marly soft slope environment these accidental hard substrates turned into suitable initiation nucleation sites for automicrite production dense and peloidal automicrites on which the small mud mounds dominated by opportunistic epi and infaunal heterozoan assemblages grew a detailed microfacies mapping and paleoenvironmental analysis reveals a multi episodic downslope accretion history starred by demosponges coralline and lithistid sponges agariciid corals calcareous red algae putative microbial benthic communities and diverse sclerobionts from the upper slope to the middle slope the analyzed mud mound microfacies are compared with similar fossil assemblages and growth fabrics described in many fossil mud mounds and with recent deep water fore reefs and cave environments

holocene evolution of the song hong red river delta system northern vietnam abstract the song hong red river delta located on the western coast of the gulf of bac bo tonkin in the south china sea formed as a result of the song hong sediment discharge throughout the holocene the river s sedimentary basin upstream from the delta plain is not large the delta plain comprises emerged tidal mangrove flats formed during the sea level highstand at 2 3 m 6 4 cal kyr bp and a beach ridge strandplain with straight to lobate beach ridges on the landward and seaward sides of the delta plain respectively the delta affords us the opportunity to examine river mouth morphodynamics comprehensively in relation to sediment discharge and sea level changes in this paper we describe the holocene evolution of the song hong delta system and the river mouth morphodynamics on the basis of seven sediment cores each 30 70 m long taken from the delta plain during 1999 2001 and 101 radiocarbon dates obtained from the core sediments sediments from the seven cores consisting of incised valley fills since the last glacial maximum can be divided in ascending order into fluvial sediments composed of gravelly sand and mottled clay tide influenced estuarine sediments containing shell and wood fragments and deltaic sediments composed of tide influenced sand and mud deposits in which the contents of sand and wood fragments increase upward by applying sequence stratigraphic concepts a transgressive surface can be identified at the gravelly sand mottled clay boundary and the maximum flooding surface can be identified at the estuarine deltaic sediments boundary the lowstand systems tract transgressive systems tract and highstand systems tract record 15 15 9 and 9 0 cal kyr bp respectively during the past 9 kyr the majority of the sediment discharged by the song hong accumulated in the incised valley and enhanced progradation at the river mouth the river mouth prograded from the bay head toward the gulf and its morphology changed from funnel shaped 9 6 cal kyr bp to straight 6 2 cal kyr bp and finally to lobate 2 0 cal kyr bp the morphological change from a funnel shaped to straight coast is interpreted to have been closely related to a hydrologic regime shift from a tide dominated bay head setting to a wave influenced open coast setting the cessation of the sea level rise at 6 cal kyr bp may have played only a small role in the change of river mouth morphology because the progradation rate decelerated from 22 to 4 m yr instead of accelerating at that time the river mouth morphodynamic change from straight to lobate was largely caused by an increase in the song hong sediment discharge from 17 27 9 2 cal kyr bp to 49 million t yr 2 0 cal kyr bp as a result of anthropogenic deforestation along the upper reaches of the song hong