microbial biomass a catalyst for caco3 precipitation in advection dominated transport regimes microorganisms have long been thought to impact caco3 precipitation but determining the extent of their influence on sediment formation has been hampered by our inability to obtain direct experimental evidence about mineral formation processes in natural environments we address this problem by conducting kinetic experiments within a modern terrestrial carbonate spring to determine aragonite precipitation rates and to quantify the relative influences of aragonite saturation state a microbial biomass concentration and microbial viability on caco3 mineralization in advection dominated transport regimes at an a value consistent with modern seawater 3 63 0 09 our controlled in situ kinetic experiments show that 1 the natural steady state aragonite precipitation rate is more than twice that determined when microbial biomass on the aragonite mineral surface is depleted by 0 2 m filtration and 2 inhibiting microbial viability with ultraviolet uv irradiation has no significant effect on the mean precipitation rate furthermore our modeling of the caco3 precipitation process which uses the empirical crystal growth rate expression and additional in situ kinetic measurements reveals that reducing biomass concentrations by 45 can decrease the empirical rate constant by more than an order of magnitude these findings strongly suggest that microorganisms catalyze caco3 precipitation in advection dominated systems and imply that changes in carbonate mineralization rates may have resulted from changes in local microbial biomass concentration throughout geologic history

carbonate platform evolution from a bioconstructed platform margin to a sand shoal system devonian guilin south china the depositional organization and architecture of the middle late devonian yangdi rimmed carbonate platform margin in the guilin area of south china were related to oblique extensional faulting in a strike slip setting the platform margin shows two main stages of construction in the late givetian to frasnian with a bioconstructed margin evolving into a sand shoal system in the late givetian the platform margin was rimmed with microbial buildups composed mainly of cyanobacterial colonies mostly renalcis and epiphyton these grew upwards and produced an aggradational locally slightly retrogradational architecture with steep foreslope clinoforms three depositional sequences s3 s5 are recognized in the upper givetian strata which are dominated by extensive microbialites metre scale depositional cyclicity occurs in most facies associations except in the platform margin buildups and upper foreslope facies in the latest givetian at the top of sequence s5 relative platform uplift subaerial exposure and associated rapid basin subsidence probably a block tilting effect caused large scale platform collapse and slope erosion to give local scalloped embayments along the platform margin and the synchronous demise of microbial buildups subsequently sand shoals and banks composed of ooids and peloids and a little later stromatoporoid buildups on the palaeohighs developed along the platform margin from which abundant loose sediment was transported downslope to form gravity flow deposits another strong tectonic episode caused further platform collapse in the early frasnian at the top of sequence s6 leading to large scale breccia release and the death of the stromatoporoid buildups siliceous facies banded cherts and siliceous shales were then deposited extensively in the basin centre as a result of the influx of hydrothermal fluids the platform margin sand shoal bank system possibly with gullies on the slope persisted into the latest frasnian until the restoration of microbial buildups four sequences s6 s9 characterized by abundant sand shoal deposits on the margin and gravity flow and hemipelagic deposits on the slope are distinguished in the frasnian strata smaller scale depositional cyclicity is evident in all facies associations across the platform slope basin transect the distinctive depositional architecture and evolution of this yangdi platform are interpreted as having been controlled mainly by regional tectonics with contributions from eustasy environmental factors oceanographic setting biotic and sedimentary fabrics

the lefkada barrier and beachrock system nw greece controls on coastal evolution and the significance of extreme wave events abstract the lefkada preveza coastal zone nw greece is characterised by an active barrier system and related extensive beachrock sequences besides the gradual coastal processes of longshore drift and spit evolution the presence of active tectonics and the occurrence of tsunamis have been documented in previous studies and are part of the coastal geomorphological system in this paper we present the results of detailed multi proxy sedimentological and geomorphological investigations carried out along the northern part of the barrier system and in back beach positions our findings suggest that extreme wave events contributed to coastal and environmental changes and involved temporary breakdown of the barrier system sedimentary findings suggest that one generation of event deposits may be related to the 365 ad crete earthquake and associated tsunami according to our results the lefkada coastal system formed by the interaction of both long term gradual and sudden impulsive littoral geomorphodynamics extreme wave events are assumed to have played a significant role in the evolution of the present coastline acting as recurrent impulsive disturbances of the coastal system subsequently the onset of long term gradual coastal processes such as longshore drift re established a state of natural coastal balance by re arranging the coastal sediments

fabric transitions from shell accumulations to reefs an introduction with palaeozoic examples one unresolved conceptual problem in some palaeozoic sedimentary strata is the boundary between the concepts of shell concentration and reef in fact numerous bioclastic strata are transitional coquina reef deposits because either distinct frame building skeletons are not commonly preserved in growth position or skeletal remains are episodically encrusted by stabilizer reef like organisms such as calcareous and problematic algae encrusting microbes bryozoans foraminifers and sponges the term parabiostrome coined by kershaw can be used to describe some stratiform bioclastic deposits formed through the growth and destruction by fair weather wave and storm wave action of meadows and carpets bearing frame building archaeocyaths bryozoans corals stromatoporoids etc and or epibenthic non frame building e g pelmatozoan echinoderms spiculate sponges and many brachiopods organisms this paper documents six palaeozoic examples of stabilized coquinas leading to pseudo reef frameworks some of them formed by storm processes generating reef soles aborted reefs or being part of mounds on ramps and shelves and were consolidated by either encrusting organisms or early diagenesic processes whereas others bioclastic dominated shoals in barrier shelves were episodically stabilized by encrusting organisms indicating distinct episodes in which shoals ceased their lateral migration a paramount quantity of information characterizes the formation and distribution of shell concentrations and reefs in modern and cenozoic strata but the knowledge of phanerozoic shell concentrations and reefs is decreasing when increasing in age the palaeozoic is a key time span in the history of life owing to the wide occurrence of skeletonized metazoans the so called cambrian explosion zhuravlev riding 2000 and the successive biodiversifications related to i major extinctions such as the end ordovician cooper 2004 the frasnian famenian boundary buggisch 1991 copper 2002 racki house 2002 and the endpermian extinction wignall hallam 1992 and ii major community replacements such as the lower middle cambrian transition 2 j j alvaro et al remains webb 1996 following wood s 1998 definition reefs develop due to the aggregation of sessile epibenthic marine organisms with the resultant higher rate of in situ carbonate production than in surrounding sites although the relative capacity of some gregarious epibenthic organisms bearing mineralized skeletons to be preserved in living position is a common characteristic of reef organisms this character is also shared with other non reef metazoans adapted to soft substrates and forming bundles like clusters one group of these organisms named secondary soft bottom dwellers by seilacher 1984 differs from mud stickers e g non encrusting pelmatozoans and sponges in the heavy weight of their shells these metazoans mainly brachiopods and molluscs develop common cup boulderand fan shaped convergent morphologies favouring recliner strategies seilacher 1984 savazzi 1999 skeletal concentrations can be subdivided according to their biostratinomic features into biogenic sedimentary diagenetic and mixed concentrations kidwell et al 1986 biogenic concentrations can be intrinsic or extrinsic in character the former generated by the organisms that produce the hard parts resulting from intrinsic gregarious behaviours of autochthonous and parautochthonous skeletal organisms e g preferential colonization by larvae and single colonization events of opportunistic species and the latter produced by other organisms that interact with skeletonized organisms on their discarded hard parts leading to the formation of parautochthonous and allochthonous concentrations e g hard part rich fecal masses and shell filled pits sedimentary concentrations result from physical usually hydraulic processes of concentration in which hard parts behave as sediment particles and non bioclastic matrix is either reworked or fails to accumulate e g shelly storm lags aeolian beach pavements channel lags in fluvial intertidal and subtidal environments or shell paved turbidities diagenetic concentrations form or are significantly enhanced by processes acting after burial such as compaction or selective dissolution of matrix and finally mixed concentrations form by the interplay of two or more kinds of the aforementioned processes and can display both autochthonous parautochthonous and allochthonous shell

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

texture of microbial sediments revealed by cryo scanning electron microscopy abstract textures of modern lacustrine stromatolites on kiritimati line islands central pacific ocean and of buried layers in the stromatolitic carbonate sediments from french polynesian atoll lakes kopara have been studied using cryo scanning electron microscopy sem equipped with a freeze drying sample preparation device this study confirms that microscopic three dimensional organic networks built through reorganization of polysaccharide fibers inherited from sheaths of dead cyanobacteria and from other extracellular polymer secretions are common components of microbial sediments of which they may form the framework in addition to this role in sediment cohesion and formation of microstructure the organic framework appears to be involved in carbonate precipitation with n the stromatolites through chemical nucleating steric and hydrodynamical controls the role of the dead organic constituents of the stromatolites is not only confirmed in micrometer size crystal precipitation but extended to the post mortem internal mineralization of cyanobacterial filaments and to the formation of peloids that evolve into spherulites bacterial including nannobacterial carbonate bodies and carbonate impregnated cyanobacterial sheaths are also shown to form in the stromatolites studied all these carbonate precipitation processes may cooperate in lithification of a given sediment

bonaire s boulder fields revisited evidence for holocene tsunami impact on the leeward antilles abstract supralittoral boulders and blocks are prominent sedimentary features along rocky shorelines worldwide in most cases their deposition is attributed to high energy wave events tsunamis severe storms even though tsunami waves are expected to have higher transport capacities compared to storm waves megaclasts of up to 100 t were observed to have been moved laterally by the latter waveform the deduction of certain extreme wave events tsunamis severe storms from the boulder record thus remains a major challenge in palaeo event research the debate on their differentiation is ongoing at the eastern coast of bonaire leeward antilles in the southern caribbean numerous limestone blocks and boulders up to c 130 t are distributed on top of a 3 6 m a s l above mean sea level palaeo reef platform disagreement exists among a number of authors concerning the transport processes involved in the formation of the boulder fields in this paper state of the art modelling approaches of coastal boulder entrainment and transport were applied in order to provide new and more reliable data to support challenge the working hypothesis of tsunami deposition to improve the reliability of the boulder transport model more realistic input parameters were provided by new dgps measurements of the boulder dimensions and the calculation of bulk densities by taking into account the heterogeneity of the reef rock boulders existing hydrodynamic equations were modified to allow for the irregular shape and real dimensions of the boulders the results indicate that i boulder weight and dimension and thus ii calculated wave energy and wave heights were overestimated in most of the previous studies where calculations of boulder volume were based on multiplication of the main axes the results of this study and wave heights observed during recent severe tropical cyclones seem to rule out storm generated waves for the dislocation of the largest blocks however the majority of coarse clast deposits may have been generated by periodic hurricane swells the results underline the significance of more realistic field data in modelling boulder transports by waves

high frequency of super cyclones along the great barrier reef over the past 5 000 years understanding long term variability in the occurrence of tropical cyclones that are of extreme intensity is important for determining their role in ecological disturbances1 2 3 4 5 for predicting present and future community vulnerability and economic loss6 and for assessing whether changes in the variability of such cyclones are induced by climate change7 our ability to accurately make these assessments has been limited by the short less than 100 years instrumented record of cyclone intensity here we determine the intensity of prehistoric tropical cyclones over the past 5 000 years from ridges of detrital coral and shell deposited above highest tide and terraces that have been eroded into coarse grained alluvial fan deposits these features occur along 1 500 km of the great barrier reef and also the gulf of carpentaria australia we infer that the deposits were formed by storms with recurrence intervals of two to three centuries8 9 10 11 and we show that the cyclones responsible must have been of extreme intensity central pressures less than 920 hpa our estimate of the frequency of such super cyclones is an order of magnitude higher than that previously estimated which was once every several millennia12 13 14 and is sufficiently high to suggest that the character of rainforests and coral reef communities were probably shaped by these events

tsunami imprints on the leeward netherlands antilles aruba curacao bonaire and their relation to other coastal problems abstract tsunami are one of the major natural hazards in the caribbean the historical record lists 88 tsunami from local events to teletsunami in the time period from 1489 to 1998 this study focuses on the spatial distribution and geomorphologic evidence related to coarse littoral sediment and boulder deposition by tsunami events of holocene age in the southern caribbean at a worldwide scale these debris deposits represent the most extensive and impressive records of holocene paleo tsunami so far studied hitherto the leeward lesser antilles consisting of the islands of aruba curacao and bonaire were not known to have had tsunami affecting their coastlines the possible contribution of tsunami to configuring coastlines e g the questions of embayment development the coastal environment changes and the absence of holocene fringing reefs along the windward coasts is discussed

ice 5g and ice 6g models of postglacial relative sea level history applied to the holocene coral reef record of northeastern st croix u s v i investigating the influence of rotational feedback on gia processes at tropical latitudes abstract fossil coral reefs along the northeastern coast of st croix in the caribbean sea provide an 8000 year record of dated and interpreted holocene sea level change we herein compare this record with the predictions of models of glacio hydro isostatic adjustment for st croix and for additional sites at similar latitudes in the greater and lesser antilles region rsl predictions are based upon the model ice 5g vm2 and with a modified model ice 6g vm5a both including and excluding the influence of rotational feedback misfits between the modeled sea levels and the local geologic data are most apparent for models without rotational feedback particularly in the prediction of a 2 to 4 m unsupported mid holocene misfit at 4 ka as well as a small amplitude highstand that extends from 2 5 to 1 5 ka incorporation of the influence of rotational feedback provides the best fit to the data largely eliminating the unsupported mid holocene misfit between the data field and the sea level histories predicted by the models without rotational feedback and fitting data older than 5 kyr more closely than a previously published latitudinally averaged sea level curve for the western atlantic the st croix data therefore demonstrate that rotational influence extends at least 27 further south from its 45 n mid latitude extremum along the us east coast and identifies tropical latitudes as influenced by proglacial forebulge collapse implications for reef based sea level reconstruction include the ability to accurately model sea levels at specific tropical sites with partial holocene chronologies using the ice 6g vm5a model with rotational feedback latitudinally averaged sea level curves are therefore of limited use in understanding the relative importance of contributing physical influences on postglacial sea level history

carbonate mounds from paradox to world heritage the recent marine carbonate world comprises two major compartments 1 the surface domain of the photozoan carbonates confined in space by water depth and by the penetration of light and 2 a deep domain where heterozoan mound builder guilds directly forage on fluxes of nutrients which primarily percolate from the photic zone and or are generated by in situ benthic processes locally giant cold water coral mounds tower up to heights of 150 to 250 m above the sea floor in general between 500 and 1300 m water depth and within sharply delineated provinces some 15 years of research on these giant mound provinces conveys a picture of their distribution in space and possibly sheds light on controls acting in concert globally there is no counterpart for the prolific north atlantic mound basin namb a chemical control is seen by an overlay of the mound provinces on a map of the aragonite saturation horizon ash an external physical control is inferred fromthe position of themound provinces girdling a vigorous north atlantic subtropical gyre systemand clustering close to the roof of the intermediate to deep water masses of a dynamically stratified ocean on the eastern boundary of the namb nutrient fluxes are enhanced by mixing processes driven either by internal waves between galicia and the shetlands or by the vast and heterogeneous eastern boundary upwelling system along the iberian african margins down to 10 n early diagenesis by carbonate dissolution and re precipitation driven by convecting or advecting internal fluids can contribute to stabilize such constructions facilitating an exuberant vertical accretion it is speculated that in thenorth atlantic ocean the deep water carbonate factory outclasses in size the shallow water coral reefs giant mound formation is a recurrent play of life since the dawn of the metazoans nama group upper neoproterozoic however with actors and plots varying from act to act remarkably literature reports only three occurrences of deep water mounds in the phanerozoic the modern ocean possibly the danian and the carboniferous some striking parallelisms in the development of the atlantic and the paleo tethys oceans combined with the developing insights in the controls on deep watermounds in the present ocean invite for a comparative study this has the potential to eventually shed light on the full circulation pattern of the paleo tethys ocean surface and deep comparative studies will build upon 1 modeling of ocean circulation constrained by the record of deep water carbonate systems and supported by advances in tracer and proxy tools and 2 field studies on representative and accessible continental locations the mound route that develops in morocco under the auspices of ioc unesco will provide tomulti disciplinary teams with marine and continental experience opportunities for confronting observations from the modern ocean and on key records of past oceanic basins it has the potential to eventually qualify for a unesco recognition as world heritage

coastal stratigraphies of eastern bonaire netherlands antilles new insights into the palaeo tsunami history of the southern caribbean abstract a sediment record of three alluvial sites along the east and northeast oriented shore of bonaire netherlands antilles provides evidence for the recurrence of several extraordinary wave impacts during the holocene the interpretation of onshore high energy wave deposits is controversially discussed in recent sedimentary research however it represents a powerful tool to evaluate the hazard of tsunami and severe storms where historical documentation is short and or fragmentary a facies model was established based on sedimentary and geochemical characteristics as well as the assemblage and state of preservation of shells and shell fragments radiocarbon data and the comparison of the facies model with both recent local hurricane deposits and global tsunami signature types point to the occurrence of three major wave events around 3300 2000 1700 and shortly before 500 bp since i the stratigraphically correlated sand layers fulfill several sedimentary characteristics commonly associated with tsunamis and ii modern strong hurricanes left only little or even no sediment in the study areas they were interpreted as tsunamigenic however surges largely exceeding the energy of those accompanying modern hurricanes in the southern caribbean cannot entirely be ruled out the results are partially consistent with existing chronologies for holocene extreme wave events deduced from supralittoral coarse clast deposits on aruba bonaire and curacao as well as overwash sediments from cayo sal venezuela

comments to dawson a g and stewart i 2007 tsunami deposits in the geological record sedimentary geology 200 166 183

spatial geochemistry of a carboniferous platform margin to basin transect balancing environmental and diagenetic factors abstract conventional one dimensional chemostratigraphy of marine carbonates assesses the chemical archive of individual stratigraphic sections and their correlation in space and time whereas this approach has shown to be of value when linking isobathymetric domains usually characterised by similar facies more caution is needed when correlations are extended across different physiographic settings and hence different facies belts here the spatial geochemical record of pennsylvanian platform margin to basin transects across a bathymetric range of about 800 m is documented and discussed in a process oriented context particularly the presence of layered palaeo water masses and their potential control on slope facies distribution and geochemical properties requires attention whereas carboniferous thermo and or chemo clines most likely affected depth related slope facies zonation it was facies change and hence variances in porosity permeability properties that controlled differential early burial diagenetic alteration specifically the lower slope related breccia facies is characterised by higher volumes of early burial carbonate cements this implies that these sediments entered the shallow burial domain with a considerable open pore space and gave way to an increased rock fluid ratio whereas the 13 c record is invariant with bathymetry the more diagenesis sensitive 18 o proxy records pronounced shifts observed across major facies boundaries from this it is concluded that although the primary controlling factor of slope facies distribution with depth is probably palaeoceanographic in nature it is differential rock fluid ratios that control the first order spatial shifts in 18 o composition these findings show that one dimensional chemostratigraphy will severely underestimate the complexity of three dimensional bathymetric data sets across platform margins this is of relevance for the interpretation of the geochemical archive of fossil carbonate platforms in general

the role of porosity in discriminating between tsunami and hurricane emplacement of boulders a case study from the lesser antilles southern caribbean coastal boulder deposits are a consequence of high energy wave impacts such as storms hurricanes or tsunami parameters useful for distinguishing between hurricane and tsunami origins include distance of a deposit from the coast boulder weight and inferred wave height in order to investigate the role of porosity on boulder transport and elucidate the distinction between tsunami and hurricane impacts we performed archimedean and optical 3d profilometry measurements for the determination of accurate physical parameters for porous reef and coral limestone boulders from the islands of aruba bonaire and curacao abc islands netherlands antilles leeward islands subsets of different coral species and lithotypes constituting the boulders were sampled the physical parameters of boulders were analyzed and each boulder component was attributed to a certain range of porosity and density lowest porosities were observed in calcarenite 5 8 whereas highest porosities were measured for serpulid reef rock 47 68 porous serpulid reef rock 0 8 1 2 g cm 3 and the coral diploria sp 0 6 1 0 g cm 3 possess the lowest bulk densities while less porous calcarenite 2 0 2 7 g cm 3 and the coral montastrea cavernosa yield the highest bulk density values 1 6 2 7 g cm 3 the obtained physical parameters were used to calculate boulder weights and both hurricane and tsunami wave heights necessary to initiate transport of these boulders boulders are up to 5 6 times lighter than given in previously published data and hence required minimum hurricane or tsunami waves are lower than hitherto assumed the calculated wave heights the high frequency of tropical storms and hurricanes in the southern caribbean and the occurrence of boulders exclusively on the windward sides of the islands implicate that for boulders on the abc islands a hurricane origin is more likely than a tsunami origin 2008 elsevier b v all rights reserved

burial cementation is it important a case study stuart city trend south central texas the stuart city trend is a shelf edge buildup of lower cretaceous bioclastic and reefal carbonates that is currently buried to depths of between 3 300 and 5 000 m 11 000 and 16 000 ft compaction and cementation have generally reduced rock porosities to less than 9 sediments were cemented in the marine environment by finely crystalline bladed isopachous cement and volumetrically important 14 volume coarse to very coarsely crystalline fibrous to bladed isopachous mg calcite cement these cements have been neomorphically altered end page 536 to low mg calcites forming an unusual radiaxial texture observed in the coarse to very coarsely crystalline bladed calcite cement evidence of their marine origin consists of a relative 1 mole mg memory a marine like isotopic character dgr18o approx 2 5 and dgr13c approx 2 0 and early relative timing of precipitation diagenetic alteration of these carbonate sediments by the interaction with meteoric water in lenses that formed within topographic highs along the shelf margin changed the initial marine chemical isotopic and textural character of the sediments secondary porosity formation mineral stabilization aggrading neomorphism and equant spar calcite cementation are the important products of meteoric diagenesis the equant spar calcite cements make up approximately 16 by volume of the limestones studied they are iron and manganese poor the majority have a dgr13c composition which falls in the range of modern marine carbonates i e 0 9 to 3 5 pmil the dgr18o compositions range from 1 3 to 6 6 pmil relative to the pdb standard oxygen stable isotopic and petrographic data suggest that over 50 of the equant spar calcite cements were formed in a near surface meteoric environment a large percentage of the remaining equant spar calcite cements formed at shallow burial depths in a water limited system where mass transfer was dominated by diffusional processes thermally induced dgr18o depletion of the equant spar calcites indicating significant fluid flow was of minimal importance pyrobitumen pore fillings and inclusions in the outer 1 0 mm thick rims of the very coarsely crystalline equant spar calcite cements indicate that only minor amounts of cementation have occurred since the introduction of hydrocarbons deep burial diagenesis i e post hydrocarbon migration consisted of the precipitation of minor amounts of galena fluorite and sr rich equant spar calcites these diagenetic products can be directly related to the present day formation water the chemical isotopic and textural characteristics of the stuart city trend limestones contain the imprints of their initial marine composition and shallow diagenetic alterations in a hydrodynamic system burial diagenesis has not significantly altered these limestones fault and fracture control on the movement of formation waters in this system determine the location and intensity of late stage diagenetic events end of article last page 537

230th u dating of last interglacial brain corals from bonaire southern caribbean using bulk and theca wall material abstract we compared the suitability of two skeletal materials of the atlantic brain coral diploria strigosa for 230th u dating the commonly used bulk material comprising all skeletal elements and the denser theca wall material eight fossil corals of presumably last interglacial age from bonaire southern caribbean sea were investigated and several sub samples were dated from each coral for four corals both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232th content and 230th 238u ratios the bulk material samples of another coral show younger ages and lower 230th 238u ratios than the corresponding theca wall samples this coral also contains a considerable amount of 232th the application of the available open system models developed to account for post depositional diagenetic effects in corals shows that none of the models can successfully be applied to the bonaire corals the most likely explanation for this observation is that the assumptions of the models are not fulfilled by our data set comparison of the theca wall and bulk material data enables us to obtain information about the open system processes that affected the corals the corals showing apparently older ages for their bulk material were probably affected by contamination with a secondary detrital phase the most likely source of the detrital material is carbonate sand the higher 230th 232th ratio of this material implies that detrital contamination would have a much stronger impact on the ages than a contaminant with a bulk earth 230th 232th ratio and that the threshold for the commonly applied 232th reliability criterion would be much lower than the generally used value of 1 ng g 1 the coral showing apparently younger ages for its bulk material was probably influenced by more than one diagenetic process a potential scenario is a combination of detrital contamination and u addition by secondary pore infillings our results show that the dense theca wall material of d strigosa is generally less affected by post depositional open system behaviour and better suited for 230th u dating than the bulk material this is also obvious from the fact that all ages of theca wall material reflect a last interglacial origin 125 ka whereas the bulk material samples are either substantially older or younger however for some corals the 230th u ages and activity ratios of the bulk material and the theca wall samples are similar this shows that strictly reliable 230th u ages can also be obtained from bulk material samples of exceptionally well preserved corals however the bulk material samples more frequently show elevated activity ratios and ages than the corresponding theca wall samples our findings should be generally applicable to brain corals mussidae that are found in tropical oceans worldwide and may enable reliable 230th u dating of fossil corals with similar skeletal architecture even if their bulk skeleton is altered by diagenesis the 230th u ages we consider reliable 120 130 ka along with a recently published age of 118 ka provide the first comprehensive dating of the elevated lower reef terrace at bonaire 118 130 ka which is in agreement in timing and duration with other last interglacial records

exploring the impact of diagenesis on isotope geochemical and microstructural alteration features in biogenic aragonite for the quaternary and neogene aragonitic biogenic and abiogenic carbonates are frequently exploited as archives of their environment conversely pre neogene aragonite is often diagenetically altered and calcite archives are studied instead nevertheless the exact sequence of diagenetic processes and products is difficult to disclose from naturally altered material here experiments were performed to understand biogenic aragonite alteration processes and products shell subsamples of the bivalve arctica islandica were exposed to hydrothermal alteration thermal boundary conditions were set at 100 degrees c 175 degrees c and 200 degrees c these comparably high temperatures were chosen to shorten experimental durations subsamples were exposed to different o 18 depleted fluids for durations between two and twenty weeks alteration was documented using x ray diffraction cathodoluminescence fluorescence and scanning electron microscopy as well as conventional and clumped isotope analyses experiments performed at 100 degrees c show redistribution and darkening of organic matter but lack evidence for diagenetic alteration except in delta 47 which show the effects of annealing processes at 175 degrees c valves undergo significant aragonite to calcite transformation and neomorphism the delta o 18 signature supports transformation via dissolution and reprecipitation but isotopic exchange is limited by fluid migration through the subsamples individual growth increments in these subsamples exhibit bright orange luminescence at 200 degrees c valves are fully transformed to calcite and exhibit purple blue luminescence with orange bands the delta o 18 and delta 47 signatures reveal exchange with the aqueous fluid whereas delta c 13 remains unaltered in all experiments indicating a carbonate buffered system clumped isotope temperatures in high temperature experiments show compositions in broad agreement with the measured temperature experimentally induced alteration patterns are comparable with individual features present in pleistocene shells this study represents a significant step towards sequential analysis of diagenetic features in biogenic aragonites and sheds light on reaction times and threshold limits the limitations of a study restricted to a single test organism are acknowledged and call for refined follow up experiments

tsunami geomorphology erosion and deposition from the 15 november 2006 kuril island tsunami the 15 november 2006 kuril earthquake mw 8 1 8 4 and tsunami enabled us to collect a compelling data set of coastal geomorphic change in the kuril islands from 3 months before to 9 and 21 months after the tsunami our pre tsunami and post tsunami surveys of the islands including four topographic profi les measured in 2006 and reoccupied in 2007 allow us the confi dence to attribute many changes to the tsunami in spite of an absence of eyewitness accounts in the central islands areas with low runup 15 m underwent massive erosion that dramatically altered the coastline tsunami deposits roughly corresponded with the extent of tsunami runup and inundation the amount of sediment eroded by the tsunami far outweighed the amount deposited on land in all cases studied the tsunami was dominantly erosive in the kuril islands because the high relief topography of the coastline accelerated tsunami outfl ow

mid to late holocene changes in tropical atlantic temperature seasonality and interannual to multidecadal variability documented in southern caribbean corals proxy reconstructions of tropical atlantic sea surface temperature sst that extend beyond the period of instrumental observations have primarily focused on centennial to millennial variability rather than on seasonal to multidecadal variability here we present monthly resolved records of sr ca a proxy of sst from fossil annually banded diploria strigosa corals from bonaire southern caribbean sea the individual corals provide time windows of up to 68 years length and the total number of 295 years of record allows for assessing the natural range of seasonal to multidecadal sst variability in the western tropical atlantic during snapshots of the mid to late holocene comparable to modern climate the coral sr ca records reveal that mid to late holocene sst was characterised by clear seasonal cycles persistent quasi biennial and prominent interannual as well as inter to multidecadal scale variability however the magnitude of sst variations on these timescales has varied over the last 6 2 ka the coral records show increased seasonality during the mid holocene consistent with climatemodel simulations indicating that southern caribbean sst seasonality is induced by insolation changes on orbital timescales whereas internal dynamics of the climate system play an important role on shorter timescales interannual sst variability is linked to ocean atmosphere interactions of atlantic and pacific origin pronounced interannual variability in the western tropical atlantic is indicated by a 2 35 ka coral possibly related to a strengthening of the variability of the el nino southern oscillation throughout the holocene prominent inter to multidecadal sst variability is evident in the coral records and slightly more pronounced in the mid holocene we finally argue that our coral data provide a target for studying holocene climate variability on seasonal and interannual to multidecadal timescales when using further numerical models and high resolution proxy data

nature and origin of organic matter in carbonates from speleothems marine cements and coral skeletons organic matter in speleothem calcite marine carbonate cements and aragonitic coral skeletons was studied to determine its location molecular structure functionality and effect on mineral growth sem analyses showed that inorganically precipitated carbonates incorporate during growth adsorbed organic matter between submicroscopic subunits of the crystals whereas biologically secreted carbonates incorporate biogenic tissue between the crystals molecular fluorescence spectroscopy indicated that low molecular weight fulvic acids are the most important constituents of the organic matter the fulvic acids are probably derived from soils speleothem calcite dissolved organic matter marine carbonates and biological decay products aragonitic coral skeleton

coral boulders gravel tongues and sand sheets features of coastal accretion and sediment nourishment by cyclone tomas march 2010 on taveuni island fiji abstract tropical cyclone tc tomas in march 2010 was a category 4 storm that struck the northern and eastern islands of fiji in the southwest pacific with the coast of taveuni island in particular experiencing a significant surge and high waves as the eye passed within 30 km post storm field investigations of the coastal geomorphic impacts concentrated on an area in central taveuni s16 50 179 52 w where protected fringing reefs and coastlines form part of the bouma national heritage park bnhp here a range of cyclone constructional imprints were found to have supplemented existing coastal sediments fresh coral boulders strewn across reef platforms indicate that tc tomas had sufficient power to deliver new coral blocks but that this material comprises a relatively minor component 20 of pre existing boulder fields comparison between the dimensions of fresh max 4 9 m 3 and older blocks max 40 m 3 reveals that unknown earlier events storms or tsunamis produced much larger debris and therefore presumably generated much stronger flow velocities across the fringing reefs than tc tomas analysis of calcarenite slabs quarried from in situ beachrock exposures was particularly useful for calculating storm surge flow velocities at the shoreline giving mean values of 3 4 and 1 9 m s for run up and backwash respectively several elongate tongues max length 75 m of fresh coral gravel were also constructed perpendicular to the reef crest a conceptual model of debris accretion based on wave refraction across a crescent shaped reef front is developed to explain their formation but which does not rely on the simultaneous existence of a reef parallel rubble rampart overall the patchy and discontinuous nature of cyclogenic accretionary features across reef beach and back beach locations indicates the potential challenges for identification and interpretation of palaeo cyclone events within the sedimentary record on affected coastlines in the south pacific islands

influence of local sedimentary conditions on development of microbialites in the oxfordian carbonate buildups from the southern part of the krakow czestochowa upland south poland abstract during the late jurassic the krakow czestochowa upland area was situated on a shelf that linked a shallow epicontinental basin with the tethys ocean locally carbonate buildups of differentiated size and structure developed on this shelf the buildups comprise different varieties of microbialites leiolites thrombolites and stromatolites of variable properties negative ce anomalies and distinct enrichment in heavy rare earth elements present in all studied microbialites indicate that on the entire late jurassic shelf in the krakow region the sea water was generally well oxygenated and comparable as far as alkalinity is concerned to the recent one differentiated development of microbialites was controlled by local sedimentary conditions unrelated to distinct changes of sea water chemistry it is likely that formation of microbialites was mainly dependent on the content of dissolved amino acids colloidal organic matter or fine grained nutrient suspension and the energy of sedimentary environment

microbial biomineralization processes forming modern ca mg carbonate stromatolites abstract modern ca mg carbonate stromatolites form in association with the microbialmat in the hypersaline coastal lagoon lagoa vermelha brazil thestromatolites although showing diversi ed fabrics characterized by thin orcrude lamination and or thrombolitic clotting exhibit a pervasive peloidalmicrofabric the peloidal texture consists of dark micritic aggregates of veryhigh mg calcite and or ca dolomite formed by an iso oriented assemblage ofsub micron trigonal polyhedrons and organic matter limpid acicular crystalsof aragonite arranged in spherulites surround these aggregates unlike thearagonite crystals organic matter is present consistently in the dark micriticcarbonate comprising the peloids this organic matter is observed as sub micron at and lamentous mucus like structures inside the interspaces of thehigh mg calcite and ca dolomite crystals and is interpreted as the remains ofdegraded extracellular polymeric substances moreover many fossilizedbacterial cells are associated strictly with both carbonate phases these cellsconsist mainly of 0ae2to4lm in diameter sub spherical rod like and lamentous forms isolated or in colony like clusters the co existence offossil extracellular polymeric substances and bacterial bodies associated withthe polyhedrons of ca mg carbonate implies that the organic matter andmicrobial metabolism played a fundamental role in the precipitation of theminerals that form the peloids by contrast the lack of extracellular polymericsubstances in the aragonitic phase indicates an additional precipitationmechanism the complex processes that induce mineral precipitation in themodern lagoa vermelha microbial mat appear to be recorded in the studiedlithi ed stromatolites sub micron polyhedral crystal formation of high mgcalcite and or ca dolomite results from the coalescence of carbonatenanoglobules around degraded organic matter nuclei sub micron polyhedralcrystals aggregate to form larger ovoidal crystals that constitute peloids subsequent precipitation of aragonitic spherulites around peloids occurs asmicro environmental water conditions around the peloids change keywords bacterial fossils biomineralization microbialite nanoglobules peloids stromatolites

middle late cambrian rankenella girvanella reefs of the mila formation northern iran following the collapse of the early cambrian archaeocyathan calcimicrobial reef consortium the middle late cambrian furongian was an interval dominated by purely microbial dendrolite and stromatolite reefs however among these latter a few exceptional occurrences of metazoan reefs are known one such reef complex occurs in the late middle early late cambrian furongian portion of the mila formation of northern iran in the otherwise low energy interval of this formation the anthaspidellid demosponge rankenella hamdii sp nov is associated with encrusting girvanella eocrinoid plates rhynchonelliformean brachiopod valves and subordinate hyoliths and trilobites in tempestite shell beds these beds underwent synsedimentary cementation on the seafloor to form hardgrounds in the succeeding higher energy interval a complex of metre scale bioherms and or taphoherms incorporates toppled or transported rankenella hamdii in association with brachiopods echinoderm plates trilobites and some red arg

a pennsylvanian microbial boundstone dominated carbonate shelf in a distal foreland margin picos de europa province nw spain abstract a pennsylvanian bashkirian moscovian high rising microbial boundstone dominated carbonate platform 12 000 km2 developed in the external margin of a variscan foreland basin intensely studied in the northern domain cuera area the stratigraphy and sedimentology of the southern domain the picos de europa province is here revisited distribution of the bashkirian facies valdeteja formation defines a ramp low angle platform with an internal zone central and eastern sectors of the picos de europa province consisting of huge amounts of massive cement rich microbial boundstones surrounded by an external zone comprising lower slope boundstone derived breccias and basinal lime mudstones from the bashkirian moscovian transition to the early kasimovian picos de europa formation the carbonate platform moderately aggraded acquiring a high rising and flat topped geometry and then prograded rapidly into the external zone where platform derived carbonate sediment and clay sourced from the orogen were deposited seismic scale exposures of the western margin of the shelf show angular bedding relationship between basin toe of slope slope and platform top stratal domains with slope inclination up to 32 and a topographic relief of 550 m the platform evolution above described for the picos de europa province significantly differs with respect to the cuera area where platform mostly prograded during the bashkirian and subsequently aggraded during early moscovian the evolutionary differences between these two carbonate domains which are geographically close are interpreted as changes in tectonic subsidence distribution acting as the major factor controlling the large scale platform geometries in the active foreland basin context finally the tectonic overload due to the emplacement of the cuera thrust sheets during the moscovian kasimovian transition changed the platform growth style from progradational to aggradational and consequently the stacking pattern of the platform top cycles in the picos de europa province

multiple dating approach 14c 230th u and 36cl of tsunami transported reef top boulders on bonaire leeward antilles current achievements and challenges abstract dating the transport deposition time of supratidal coarse clast deposits is difficult limiting their value for inferring frequency magnitude patterns of high energy wave events on bonaire leeward antilles caribbean these deposits form prominent landforms and transport by one or several holocene tsunamis is assumed at least for the largest clasts although a large dataset of 14c and electron spin resonance esr ages is available for major coral rubble ridges and ramparts it is still debated whether these data reflect the timing of major events and how these datasets are biased by the reworking of coral fragments as an attempt to overcome the current challenges for dating the dislocation of singular boulders three distinct dating methods are implemented and compared i 14c dating of boring bivalves attached to the boulders ii 230th u dating of post depositional secondary calcite flowstone and subaerial microbialites at the underside of the boulders and iii surface exposure dating of overturned boulders via 36cl concentration measurements in corals approaches ii and iii have never been applied to coastal boulder deposits so far the three 14c age estimates are older than 40 ka i e most probably beyond the applicability of the method which is attributed to post depositional diagenetic processes shedding doubt on the usefulness of this method in the local context the remarkably convergent 230th u ages all pointing to the late holocene period 1 0 1 6 ka are minimum ages for the transport event s the microbialite sample yields an age of 1 23 0 23 ka and both flowstone samples are in stratigraphic order the older onset of carbonate precipitation and younger flowstone layers yield ages of 1 59 0 03 and 1 23 0 03 ka respectively four coral samples collected from the topside of overturned boulders yielded similar 36cl concentration measurements however the computed ages are affected by large uncertainties mostly due to the high natural chlorine concentration after correction for the inherited component and chemical denudation since platform emergence inducing additional uncertainty the calculated 36cl ages cluster between 2 5 1 3 and 3 0 1 4 ka for three of four boulders whilst the fourth one yields an age of 6 1 1 8 ka probably related to a higher inheritance these 230th u and 36cl age estimates are coherent with a suggested tsunami age of

electron spin resonance and radiocarbon dating of coral deposited by holocene tsunami events on curacao bonaire and aruba netherlands antilles abstract electron spin resonance esr dating of coral has become an efficient geochronological tool for studying the last 500 000 years this study presents results of esr dating of holocene coral from curacao bonaire and aruba leeward netherlands antilles the coral accumulated in rubble ridges and ramparts onshore and the depositional process is attributed to a series of tsunami events in addition to the calculation of equivalent dose d e values it is crucial for esr dating to obtain the correct d 0 value for each sample the annual dose rate d 0 estimation of the samples in this study is uncertain as the timing of the tsunami event and the residence time of a component of the dated sediment in different environments marine versus terrestrial is difficult to quantify assuming that the tsunami event deposited coral shortly after death the esr and 14 c ages of 22 samples reaching from 3650 to 128 years correspond well with each other this confirms the idea that the living coral reef was partly destroyed by tsunami events the esr dating uncertainties coincide with the variability of 14 c ages caused by the marine reservoir effect the local marine reservoir effect was estimated using four recent samples from 1920 and provided values between 375 and 595 yr bp

was phanerozoic reef history controlled by the distribution of non enzymatically secreted reef carbonates microbial carbonate and biologically induced cement throughout most of the phanerozoic reef rigidity resulted as much or more from early lithification by microbial carbonates and biologically induced cements non enzymatic carbonates than from biological encrustation of or by large enzymatically secreted metazoan skeletons reef framework is divided into four categories 1 skeletal metazoan 2 non skeletal microbialite stromatolite and thrombolite 3 calcimicrobe and 4 biocementstone in which small or delicate organisms serve as scaffolds for rigid cement crusts the last three categories are dominated by non enzymatic carbonates skeletal framework and non skeletal microbialite framework were the most abundant framework types through the phanerozoic the composition and abundance of skeletal framework was controlled largely by mass extinction events but most reefs consisted of both microbialite and skeletal organisms in a mutually beneficial relationship microbialite framework was abundant throughout the palaeozoic and early mesozoic but declined after the jurassic calcimicrobe framework was important during the cambrian early ordovician and devonian and biocementstone framework was important from the late mississippian to the late triassic the phanerozoic history of reefs does not correlate well with the stratigraphic distribution of large skeletal reef builders or with a variety of physicochemical parameters including sea level history wilson cycle or global climate cycles because non enzymatic carbonates result from induction by non obligate calcifiers and not enzymatic precipitation by obligate calcifiers the distribution of these carbonates was controlled to a larger extent by temporal changes in physicochemical parameters affecting the saturation state of sea water with respect to carbonate minerals changes in pco ca mg ratios cation concentrations and temperature may have affected the abundance of non enzymatic carbonates and hence reefs independently from the effects of these same parameters and mass extinction events on skeletal reef biota the decline in abundance of reefal microbialite and absence of calcimicrobe and biocementstone reef framework after the jurassic may be a result of relatively low saturation states of sea water owing to increased removal and sequestration of finite marine carbonate resources by calcareous plankton since the jurassic reef history is difficult to correlate with temporal changes in specific global parameters because these parameters affect skeletal biota and biologically induced carbonate precipitation independently hence reef history was regulated not just by skeletal reef biota but by parameters governing non enzymatic carbonates

hurricane signatures and landforms toward improved interpretations and global storm climate chronology abstract the correct understanding of the geological and geomorphic evolution of paralic basins and coastal barriers is a prerequisite for establishing holocene hurricane archives worldwide detection and documentation of hurricane signatures in coastal deposits are becoming instrumental in attempts to reconstruct mid and late holocene storm climate history subsurface exploration and field studies on the ne gulf coast and data gleaned from the literature suggest the need for a complex approach that provides well documented details of coastal landscape evolution until recently prehistoric hurricanes and their intensity levels have been automatically interpreted from the frequency and thickness of sand layers in muddy paralic deposits however in addition to wind velocity several hydro aerodynamic and other factors a wide range of stratigraphic conditions topographic setting and sand sources also determine variations in the extent and intensity of storm flooding erosion transfer and deposition of sand layers in small paralic basins inherent limitations in these sedimentary records and their interpretation must be overcome in order to improve local hurricane chronologies and establish interregional correlations before sedimentary and chemical signatures are accepted as diagnostic indicators of overwash especially by catastrophic hurricanes alternative causes must also be considered a parallel scale of storm flood level stages should supplement the saffir simpson hurricane categories the relationship between storm intensities and flooding elevations is highly complex changes in sea level shore positions formation and extinction of preexisting incised valley networks the impact of transgression and regression processes on estuaries and their deposits play determining roles in setting the stage for overwash processes strandplain progradation followed by erosive shore retreat played a key role in framing certain paralic lakes without overwash sand layers and marine microfossils may be also emplaced by storm driven currents that enter unobstructed estuaries inlets and storm breaches bioturbation also distorts the storm record significant lateral variations in the number and thickness of intercalated sand layers at closely adjacent sites suggest the importance of local differences in sources transport and preservation processes in the dimensions relative positions and accessibility of sand resources inside and adjacent to coastal basins variations in the number thickness and ages of sand laminae may not be related to the number of storms and their intensities this may impair correlations between regionally interpreted calm and intensive phases in partial overlap with an assumed quiescent storm phase stable isotope ratios in lacustrine muds impacted by salt water influx reveal frequent hurricane activity during the last 1 5 ka as well by mimicking effects of reduced storminess the fewer and thinner sand laminae deposited between 7 0 and 3 4 ka b p may be attributed to greater distances of estuarine landward transport by storm tidal currents at times of lower sea levels

shallow water mud mounds of the early devonian buchan group east gippsland australia abstract the lower devonian rocky camp member of the murrindal limestone buchan group of southeastern australia consists of a series of carbonate mud mounds and smaller lagoonal bioherms the rocky camp mound is the best exposed of the mud mounds and has many characteristics in common with waulsortian carboniferous mounds detailed paleoecological and sedimentological studies indicate that the mound initially accumulated in the photic zone in contrast to most of the previously recorded mud mounds five facies are present in the mud mound a dasycladacean wackestone facies at the base of the mound represents a moderate energy shallow water bank environment within the photic zone a crinioidal wackestone facies was deposited in a laterally equivalent foreslope setting a poriferan crinoidal mudstone facies developed in a quiet deeper water lee side mound setting associated with a minor relative sea level rise a stromatoporoid coralline packstone facies in the upper part of the mound deposited in a high energy fair weather wave base mound front environment the crest of the mound is represented by a crinoidal receptaculitid packstone facies indicative of a moderate energy mound top environment in the photic zone sheltered by the mound front stromatoporoid coral communities a mound flank facies is present on the southern side of the mound and this consists of high energy crinoidal grainstones mud mound deposition was terminated by a transgression that deposited dark gray fossil poor marl of the overlying taravale formation the rocky camp mound appears to have originated in shallow water photic zone conditions and grew into a high energy environment with the mound being eventually colonized by corals and stromatoporoids the indications of a high energy environment during later mound growth growth form of colonial metazoans and grainstones of the flanking facies suggest that the micrite in the mound was autochthonous and implies the presence of an energy damping mechanism probably biological at the mound surface

are reefs and mud mounds really so different although both ecologic reefs and mud mounds are demonstrably rigid framework reefs they are still considered to be distinct in terms of their dominant processes of formation and preferred environmental settings this distinction has rested largely upon the assumption that ecologic reefs are dominated by skeletal metazoans growing in shallow waters in contrast to the complex autochthonous micrite supported cavity systems that characterise deep water mud mounds now considered to represent either organomineralic deposits where carbonate precipitation has taken place in association with nonliving organic substrates to form automicrite or various types of microbialite where carbonate forms as a direct result of the physiological activity or decay of benthic microorganisms yet such autochthonous micrite is increasingly recognised as an important component of many ancient shallow ecologic reefs as well as some modern coral reefs and indeed may contribute locally up to 80 of the reef rock these observations raise doubts as to the validity of current fabric based definitions used to distinguish between mud mounds and ecologic reefs whether the autochthonous micrite in mud mounds proves to be dominated by either automicrite or microbialite both require particular environmental conditions for their formation automicrites form where surplus organic matter from metazoans has degraded to release quantities of acidic amino acids with a significant ability to bind ca 2 and microbialite formation also often requires either unusual marine chemistries or ecological conditions such conditions might include changes in terrigenous influx ground water seepage local anoxia and increases in the ph of interstitial reef waters or in nutrient concentration d 2001 elsevier science b v all rights reserved

jurassic septarian concretions from nw scotland record interdependent bacterial physical and chemical processes of marine mudrock diagenesis septarian concretions in the staffin shales formation kimmeridgian isle of skye allow controls on concretion rheology and septarian cracking to be investigated stratabound concretions consist of anhedral ferroan calcite microspar enclosing clay and minor pyrite intergranular volumes range from 77 to 88 and calcite 13c and 18o values in most concretion bodies range from 10 0 to 17 3 and 0 3 to 0 6 respectively consistent with rapid and pervasive cementation in marine pore fluids septarian rupture occurred during incipient cementation with a sediment volume reduction of up to 43 crack lining brown fibrous calcite records pore fluid re oxygenation during a depositional hiatus followed by increasing fe content and 13c related to bacterial methanogenesis brown colouration results from an included gel like polar organic fraction that probably represents bacterially degraded biomass a new hypothesis for concretion growth and septarian cracking argues that quasi rigid proto concretions formed via binding of flocculated clays by bacterial extracellular polysaccharide substances eps this provided rheological and chemical conditions for tensional failure subcritical crack growth volume contraction calcite nucleation and incorporation of degraded products into crack lining cements bacterial decay of eps and syneresis of host muds provided internal stresses to initiate rupture at shallow burial development of septarian shrinkage cracks in muds is envisaged to require pervasive in situ bacterial colonization and to depend on rates of carbonate precipitation versus eps degradation and syneresis subsequent modification of septarian concretions included envelopment by siderite and calcite microspar hydraulic fracturing associated with cretaceous shallow burial or palaeogene uplift and cementation by strongly ferroan yellow sparry calcite that records meteoric water invasion of the host mudrocks an abundance of fatty acids in these spars indicates aqueous transport of organic breakdown products and 13c data suggest a predominantly methanogenic bicarbonate source however the wide 18o range for petrographically identical cement 1 3 to 15 6 is difficult to explain

oxfordian reef architecture of the la manga formation neuquen basin mendoza province argentina abstract the neuquen back arc basin is located on the west margin of the south american platform between latitudes 36 and 40 s the basin is famous for its continuous sedimentary record from the late triassic to cenozoic comprising continental and marine clastic carbonate and evaporitic deposits up to 2 600 m in thickness the stratigraphical and paleontological studies of the outcrops of the la manga formation argentina located near the bardas blancas region mendoza province 35 s and 69 o allow the reconstruction of the sedimentary environments of an oxfordian carbonate ramp where outer ramp middle ramp inner ramp oolitic shoal inner ramp margin patch reef lagoon and paleokarst were differentiated the reefs consist of back reef facies and in situ framework of coral boundstones that was formed at the top of shallowing upward succession coral reefs were analyzed by defining coral colonies shapes paleontological content coral diversity and taphonomy studies in some studied sections abundant fragments of gryphaeids encrusting bryozoans and isolated sponges provided a suitable substrate for coral colonization however other sections show an increase in the proportions of ooids peloidal and coral intraclasts the core reef facies is composed of white grey unstratified and low diversity scleractinian coral limestone dominated by robust and thinly branching corals with cerioid phocoid growths and massive coral colonies with meandroid thamnasteroid growth forms the assemblage is characterized by actinastraea sp australoseris sp thamnasteria sp and garateastrea sp internal facies organization and different types of coral colonies allow to recognize the development of varying framework as well as intercolony areas a superstratal growth fabric characterizes the coral assemblage on the basis of coral growth fabric branche and domal types the reef of la manga formation is considered a typical mixstones the intercolony areas consist of biomicrites and biomicrorudites containing abundant coral fragments parautochthonous gryphaeids and another bivalves ctenostreon sp gastropods harpagodes sp natica sp echinoderms test and spines plegiocidaris sp miliolids cayeuxia sp acicularia sp salpingoporella sp intraclasts ooids peloids and coated grains the domal growth forms are probably more protected against biological and physical destruction meanwhile delicate branching growth forms with very open and fragile framework were more affected and fragmented due to wave action and bioerosion the reef fabric shows different intervals of truncation as consequence of erosion resulting from coral destruction by storm waves or currents the maximum flooding surface separates oolitic shoal facies below from the aggradational and progradational coralline limestones facies above subsequent sea level fall and karstification 148 ma affected reef and oolitic facies

more light on photosymbiosis in fossil mollusks the case of mercenaria tridacnoides abstract several morphological paleoecological and life history criteria have been traditionally employed when testing for possible cases of photosymbiosis among fossil mollusks recently another criterion has been proposed based upon the offset observed in stable isotope patterns particularly 13c in a modern photosymbiotic bivalve this study combines stable isotope and growth increment analyses with traditional criteria for recognizing molluscan photosymbiosis in an investigation of the important but peculiar bivalve mercenaria tridacnoides from the neogene of the southeastern united states m tridacnoides as its name might hint has been proposed as a possible photosymbiotic host however the geochemical and paleontological data presented here reinforce each other and suggest otherwise this case illustrates the increased predictive power obtained by combining geochemical with more traditional paleontological approaches

a revised morpho and chronostratigraphy of the late and middle pleistocene coral reef terraces on southern barbados west indies the barbados coral reef terraces are one of the few type localities worldwide that provide insights into interglacial sea level change during the late and middle pleistocene several sea level estimates have been established since the late 1960s and each has contributed to the barbados model of sea level change this paper presents new morpho and chonostratigraphic data from the barbados coral reef terraces developed over the last 12 years the work is based on significant advances in electron spin resonance esr dating of fossil coral air photo interpretation and a greatly improved geomorphic map of preserved fossil beach formations and reef terraces above present sea level the need for a revision of past published morpho and chronostratigraphies is best demonstrated on the southern part of the island the morpho and chronostratigraphic sequence in this region is both more complex and diverse than has been assumed so far the revised morphostratigraphy presented here includes a differentiation of coral reef terraces wave cut platforms and other erosive features such as notches and cliffs our study of these geomorphic features combined with new numeric dating results esr u th enable a revised estimate of the spatial and temporal variation in tectonic uplift rate within south barbados these new rates are an essential requirement for more precise glacio eustatic sea level reconstructions during the late and middle pleistocene from this region

neoproterozoic reef microstructures from the little dal group northwestern canada basinal facies in the neoproterozoic little dal group contain large reefs up to 300 m in height and 8 km in diameter in contrast to the stromatolitic composition typical of earlier proterozoic buildups little dal reefs consist mainly of three different calcareous microfossils a tubule thread microfossil analogous to the calcimicrobe girvanella in paleozoic reefs formed laminar reticulate structures like those in ordovician bioherms a clotted to saccate microfossil comparable morphologically to paleozoic renalcis constructed botryoidal to encrusting masses an enigmatic component of multicellular appearance that has attributes of an early calcified metaphyte exhibits the encrusting sheetlike habit characteristic of middle to late paleozoic algae these reefs represent an intermediate stage between proterozoic stromatolitic buildups and paleozoic metazoan calcimicrobial reefs and biogenic mounds

competing mechanisms for boulder deposition on the southeast australian coast this study investigates the role of late holocene sea level change large storms and possible pre historic tsunami in the deposition of boulder features on an exposed headland and sheltered rock ramp large accumulations of boulders are found on coastal rock platforms cliff tops and ramps in the jervis bay region of southeastern australia these deposits are elevated above sea level and in places exhibit obvious signs of imbrication as a response to flow in a landward direction the event history of these features is controversial and holocene sea level change storms and tsunami can be considered as possible non mutually exclusive mechanisms of deposition it is apparent that even if the detachment site transport distance elevation and final orientation of a boulder can be identified deciphering the event history remains a difficult task

high energy coralgal stromatolite frameworks from holocene reefs tahiti french polynesia drill cores from holocene reefs on tahiti french polynesia reveal a framework composed of massive branching acroporids encrusted by coralline algae associated with sessile vermetid gastropods and arborescent foraminifers laminated micritic crusts form coatings over coral branches or more commonly over related encrusting organisms throughout the cored reef sections these crusts appear as a major structural and volumetric component of the reef framework the microbial nature of these micritic crusts is inferred from their typical organic growth forms and geometry the occurrence of microbial remains and stable isotope measurements the reef communities accumulated at depths less than 5 m below mean sea level in a high energy environment throughout vertical growth from 7140 170 yr bp to the present the nature of the involved benthic communities stable isotope data and high calcification rates of microbially encrusted corals strongly suggest that local environmental conditions have been optimal for reef development for the last 7000 years the causes of the predominance of microbial communities over actual encrusters red algae foraminifers remain problematic and could be related to short term fluctuations in ecological parameters microbial micritic crusts seemingly played a prominent role in protecting the coralgal colonies from bioeroders and grazers and possibly in strengthening the framework due to rapid lithification the record of similar microbial crusts in other quaternary reef tracts suggests that microbial communities may have played a more prominent role in quaternary reefs than presently recognized

spatial and temporal distribution of microbial carbonates skeletal and non skeletal grains in a pennsylvanian carbonate platform valdorria northern spain abstract the valdorria carbonate platform in northern spain features a well preserved and continuous outcrop of a bashkirian platform to basin transect during the asatauian late bashkirian the platform growth changed gradually from a progradational to an aggradational mode recording 10 most likely short eccentricity controlled cyclothems the facies of the platform top and slope have been mapped and the architecture of each cyclothem schematically reconstructed the distribution of microbial carbonates microbially mediated precipitates skeletal grazers burrowers corals filter feeders algae foraminifera osagia like oncoids and thartarella terebella worm tubes and non skeletal grains faecal pellets has been quantified for the transgressive regressive periods of deposition transgressive maximum flooding early and late regressive intervals of each cyclothem this study shows that the distribution of microbial carbonates skeletal and non skeletal grains along a carbonate platform transect is variable through time and mainly governed by a set of measurable interconnected factors regulating the local palaeoenvironments the water depth and the wave energy facies along the platform profile inner outer break slope during periods of sea level fluctuations transgressive to regressive intervals of deposition auloporid corals siliceous sponges phylloid algae and osagia like oncoids are characteristic of a low energy environment situated from estimated palaeo water depths of 25 to 80 metres below sea level mbsl onward that formed in the outer platform during the maximum flooding intervals anthracoporella archaeolithoporella boundstone is characteristic of the moderate energy environments created in the horizontal inner platform during the transgressive intervals microbially mediated precipitates are reliable indicators of the slope and masloviporidium indicator of low energy environments of the upper slope on the platform top ungdarella and donezella are more abundant during the early regressive intervals than during any other interval stacheoids are mainly present in the water depth range of 10 to 60 mbsl tournayellids from 15 to 35 mbsl and archaediscids from 15 to 75 mbsl all in low to moderate energy conditions rugose corals are common in the water depth range of 5 to 35 mbsl either during the transition from the early to the late regressive intervals as solitary forms or forming boundstone or during periods of higher sea level stand as solitary forms in floatstone fenestellids fistuliporids and trilobites occur mainly in the slope but are also common in the platform top during the maximum flooding and or the early regressive intervals archaeolithoporella is a reliable indicator of the platform top deposits but its abundance is closely linked to the presence of adequate substrates a high abundance in the assemblage of gastropods endothyrids palaeotextulariids bradyinids and fusulinids characterizes the platform top shallow water coated grain grainstones formed under high energy currents during the late regressive intervals tetrataxids act as encrusters on microbial precipitates of the slope or on phylloid algae and archaeolithoporella of the platform top but are also observed as nuclei of coated grains brachiopods are more abundant in low to moderate energy and 35 to 55 mbsl environments that prevailed during the transgressive intervals faecal pellets were commonly observed in low energy environments from 50 to 325 mbsl at the platform break and in the slope and the same applies for thartarella terebella worm tubes that are virtually absent in high energy deposits finally crinoids lasiodiscids and tuberitinids are randomly distributed and are not indicative of any specific environment the here well constrained distribution patterns of microbial carbonates skeletal and non skeletal grains in valdorria outcrop hold the potential to serve as a reference for interpretation of depositional environments of other platforms using biota associations and depositional texture particularly in regions where the platform geometry is not preserved or is not fully exposed

the role of microbialitic facies in the micro and nano pore system of dolomitized carbonate platforms upper triassic southern italy abstract the pore system of two dolomitized triassic carbonate platforms named lower and upper unit and cropping out in southern italy has been investigated through mercury porosimetry and electron microscopy despite their variability all facies show micro to nano pores systems composed of intra and inter crystal pore types this is due to the prevalence of microbialites in the inner platform margin settings together with an homogenous diagenetic history porosity and permeability are generally very low 60 the porosity derived from nanopores is significant in all facies and particularly in the shallow water environments a positive correlation between nanopores volume and porosity is present in the whole upper unit and in the shallow water facies of the lower unit moreover different sub environments of the platforms show separated amount of nanopores and porosity on the contrary permeability does not seem to be influenced by the nanopores distribution regardless a wide spectrum of fabric and morphologies microbialitic facies of both units show a confined range of porosity average 1 0 standard deviation 0 6 and permeability average 0 4 standard deviation 0 2 most probably because composed of syn sedimentary microbial dolomite which presents a high resistance to compaction during the burial history finally despite the complete dolomitization porosity and permeability ratio varies in function of the main depositional environments and less of the precursor sedimentary facies suggesting a control of the final pore size distribution mainly linked with the presence absence of the microbial primary dolomitic facies instead of the native fabrics of the other sedimentary facies

stable isotope sclerochronology of rudist bivalves growth rates and late cretaceous seasonality the almost complete translation of shell accretion to vertical growth was a successful morphogenetic adaptation of rudist bivalves which replaced coral algal hydrozoan communities in most tethyan shallow marine environments during the cretaceous growth rates of rudist shells are therefore important in reconstructions of cretaceous shallow marine benthic communities carbon and oxygen isotopic compositions were analyzed in sclerochronological profiles through the shells of two late cretaceous rudist bivalves from greece and turkey values of 13 c vary between 0 8 and 2 2 in the hippuritid vaccinites ultimus and between 0 8 and 2 6 in the radiolitid gorjanovicia cf costata ranges in 18 o are 5 3 to 2 9 and 4 6 to 2 1 respectively a distinct cyclicity of 13 c and 18 o in both shells reflects late cretaceous seasonality and indicates annual vertical growth increments of 45 mm in v ultimus and 54 mm in gorjanovicia the concentrations of minor elements are similar to those of extant bivalves with low mg calcite shells

tsunami probability in the caribbean region we calculated tsunami runup probability in excess of 0 5 m at coastal sites throughout the caribbean region we applied a poissonian probability model because of the variety of uncorrelated tsunami sources in the region coastlines were discretized into 20 km by 20 km cells and the mean tsunami runup rate was determined for each cell the remarkable 500 year empirical record compiled by o loughlin and lander 2003 was used to calculate an empirical tsunami probability map the first of three constructed for this study however it is unclear whether the 500 year record is complete so we conducted a seismic moment balance exercise using a finite element model of the caribbean north american plate boundaries and the earthquake catalog and found that moment could be balanced if the seismic coupling coefficient is c 0 32 modeled moment release was therefore used to generate synthetic earthquake sequences to calculate 50 tsunami runup scenarios for 500 year periods we made a second probability map from numerically calculated runup rates in each cell differences between the first two probability maps based on empirical and numerical modeled rates suggest that each captured different aspects of tsunami generation the empirical model may be deficient in primary plate boundary events whereas numerical model rates lack backarc fault and landslide sources we thus prepared a third probability map using bayesian likelihood functions derived from the empirical and numerical rate models and their attendant uncertainty to weight a range of rates at each 20 km by 20 km coastal cell our best estimate map gives a range of 30 year runup probability from 0 30 regionally

lithified and unlithified mg calcite precipitates in tropical reef environments abstract push cores from the branching coral framework of lagoonal reefs in belize and panama indicate that the micritic mg calcite in the unlithified mud matrix is similar in composition to the well documented submarine lithified micritic crusts and infillings found in open reef framework the sediment matrix of the lagoonal framework contains significant concentrations of 12 to 13 mole mgco3 calcite that shows almost no signs of skeletal origins as indicated by a fairly consistent mineralogy and independent distribution patterns in sand silt and clay size fractions its sedimentological and mineralogical similarity to cemented micritic crusts and infillings suggests that the precipitation of micritic mg calcite is widespread in tropical reef waters and becomes lithified when precipitated in open frameworks but remains unlithified when trapped in impermeable lagoonal muddy sediments

sedimentology of a mid late ordovician carbonate mud mound complex from the kathmandu nappe in central nepal abstract this sedimentological study of the godavari quarry is the first relating to the palaeozoic tethyan sedimentary rocks of the kathmandu nappe central nepal sedimentological analyses led to the identification of six microfacies belonging to a large carbonate mud mound complex which can be divided into mound flank and off mound main depositional settings identification of two dasycladaceans dasyporella cf silurica stolley 1893 and vermiporella sp in the mound facies gives a mid late ordovician age to this newly discovered godavari carbonate mud mound which makes this mound one of the oldest ever described in the asian continent the mound microfacies are characterized by a high micritic content the presence of stromatactis and the prevalence of red coloured sediments the red pigmentation probably being related to organic precipitation of iron the flank microfacies are characterized by a higher crinoid and argillaceous content and the presence of bio and lithoclasts concentrated in argillaceous lenses finally the off mound microfacies show very few bioclasts and a high argillaceous content palaeoenvionmental interpretation of microfacies in terms of bathymetry leads us to infer that the godavari mud mound started to grow in a deep environment setting below the photic and wave action zones and that it evolved to occupy a location below the fair weather wave base cementation of cavities within the mound facies underlines a typical transition from a marine to a burial diagenetic environment characterized by 1 a radiaxial non luminescent feroan calcite cement marine showing a bright orange luminescent band in its middle part 2 a bright zoned orange fringe of automorphic feroan calcite meteoric phreatic 3 a dull orange xenomorphic feroan calcite cement in the centre of cavities burial and 4 a saddle dolomite within the centre of larger cavities the faunal assemblage diversity and relative proportion of the godavari mound facies is dominated by crinoids and ostracods which makes this carbonate mud mound comparable to the meiklejohn peak mounds nevada

microbial carbonates as indicators of environmental change and biotic crises in carbonate systems examples from the late devonian alberta basin canada microbial precipitation of calcium carbonate has played a vital role in the development of carbonate platforms since their initiation in the proterozoic we report here the varied roles that microbial carbonates played in late devonian carbonate platforms in the alberta basin canada we recognize microbial carbonates as important contributors within the carbonate system during times of major environmental change including transgressive events in platform environments and the recovery interval following the frasnian famennian mass extinction detailed sequence stratigraphic analysis of two isolated platforms in the canadian rockies was used to document their evolution from a regional ramp to isolated platforms with phases of progradation aggradation and backstepping and renewed progradation related to rates of second order and third order sea level change and basin infill the carbonate system was reorganized following annihilation of many carbonate producing biota during the frasnian famennian mass extinction microbial carbonates figure prominently in both frasnian platform development and the famennian recovery of the carbonate system following the frasnian famennian mass extinction during transgressive platform phases deeper water facies with a crinoid rugose coral and microbe dominated biota abruptly overlie prograding stromatoporoid framestones microbial carbonates consist of abundant girvinellid oncoids that nucleated around other fossil clasts the temporary replacement of stromatoporoid communities during transgression implies a shift from oligotrophic to mesotrophic conditions and the microbes likely capitalized on the change in nutrient supply microbes played a significant role in highstand reef margin facies where renalcis was a binder and cementer in stromatoporoid framestones and downslope rugose coral stromatoporoid mounds microbially laminated carbonates also form stromatolitic mats in peritidal shallowing upward cycles and repetitive stromatolitic intervals commonly indicate sea level lowstands associated with the development of sequence boundaries stromatoporoid reefs and their associated reef interior facies indicate an oligotrophic ecosystem where microbial carbonates were relegated mainly to cryptic or stressed marine habitats an end frasnian sea level lowstand exposed the isolated carbonate platforms transgression and mass extinction characterize the frasnian famennian boundary event and microbial carbonates occur at this horizon in western canada stromatolites oncoids and large scale microbial thrombolites appear to be

potential and limits of combining studies of coarse and fine grained sediments for the coastal event history of a caribbean carbonate environment the coastal deposits of bonaire leeward antilles are among the most studied archives for extreme wave events ewes in the caribbean here we present more than 400 electron spin resonance esr and radiocarbon data on coarse clast deposits from bonaire s eastern and western coasts the chronological data are compared to the occurrence and age of fine grained extremewave deposits detected in lagoons and floodplains both approaches are aimed at the identification of ewes the differentiation between extraordinary storms and tsunamis improving reconstructions of the coastal evolution and establishing a geochronological framework for the events although the combination of different methods and archives contributes to a better understanding of the interplay of coastal and archive related processes insufficient separation superimposition or burying of coarse clast deposits and restricted dating accuracy limit the use of both fine grained and coarse clast geoarchives to unravel decadal to centennial scale events at several locations distinct landforms are attributed to different coastal flooding events interpreted to be of tsunamigenic origin coastal landforms on the western coast have significantly been influenced by sub recent hurricanes indicating that formation of the coarse clast deposits on the eastern coast is likely to be related to past events of higher energy

microbial mediated pre salt carbonate deposition during the messinian salinity crisis calcare di base fm southern italy abstract a multi scale analysis of sedimentary carbonate facies and post sedimentary diagenetic features of the calcare di base formation the precursor to evaporites in upper messinian successions of northern calabria and central sicily has revealed their microbial bio mediated origin massive to laminated microbial boundstones represent the most common sedimentary facies forming flat to low relief cm to m scale stromatolitic and thrombolitic bodies the fabric of the micrite varies from peloidal to aphanitic and almost always preserves filamentous bacteria which characterized the original microbial mat the mat was dominated by sulphur oxidizing bacteria belonging to the thiotrichaceae but there is evidence for a more complex community with sulphate and or nitrate reducing bacteria all being responsible for the mediation of the carbonate precipitation microbial boundstones are rich in pseudomorphs of ca sulphate and halite which formed during the deposition of the microbial carbonate layers of primary gypsum are interbedded locally with carbonates suggesting the presence of restricted marine conditions the stable o and c isotopic composition of the carbonates that vary from dolomite to aragonite and calcite suggests a complex interplay between arid to humid climatic changes expressed cyclic interbedding of the carbonate with marl marlstone later diagenetic events mainly consist of phreatic meteoric recrystallization and cementation although considered as diachronous the microbial carbonates can be mapped out over a distance of more than 500 km across southern italy this indicates near constant environmental conditions upon the central mediterranean shelf at the beginning of the salinity crisis deposition of the extensive subaqueous microbial deposit that largely comprises the calcare di base is envisaged to have taken place across a shallow to moderate depth platform with local slopes into deeper water areas where some resedimentation occurred

lithofacies and depositional processes on a high steep margined carboniferous bashkirian moscovian carbonate platform slope sierra del cuera nw spain the depositional slope of the sierra del cuera a carboniferous bashkirian moscovian high steep margined carbonate platform provides excellent cross sections of lithofacies zonations and associated stratal geometries the steep 30 40 and nearly planar upper slope is dominated by massive sheet like layers of microbial cement rich boundstone which alternate with intercalations of red stained bryozoan cementstone with crinoids and brachiopods the slightly gentler 20 26 and concave upward lower slope is characterized by clast supported resedimented deposits the upper slope extended from platform break to ca 300 m water depth whereas lower slope sediments were deposited in water depths up to 600 700 m at which level the slope beds flatten to a few degrees toe of slope and interfinger with spiculitic and argillaceous basinal sediments between 250 and 450 m water depth boundstones and breccias alternated in a transitional zone the lower slope sediments include clast supported breccias with radiaxial fibrous cement in interparticle space mud to clast supported breccias with red stained carbonate mud matrix and packstone to grainstone and rudstone beds most of the clasts comprise boundstone reworked from an upper slope setting and smaller grains are platform and slope derived a pervasive submarine cementation occurs along the upper two thirds of the flank and this stabilized the slope slope deposition is interpreted as follows during active boundstone accretion microbial boundstone layers slid off and formed breccia tongues extending from the lower upper slope down to the toe of slope rock falls and avalanches were generated whenever the shear strength of the substrate of loose or partly lithified sediment was exceeded upper slope boundstone accretion and shedding independent of the depth of light penetration controlled most of the depositional processes on the slope cement dominated intervals are considered to be related to early highstand and or flooding phases relative sea level fluctuations and or associated changes in the water conditions are believed to be responsible for intervals of low boundstone production or cement precipitation whether the in situ boundstone and breccia are preferentially related to lowstand or highstand periods is as yet unclear

the mystery of boulders moved by tsunamis and storms abstract boulders are moved differently in storm and tsunami and produce different characteristics of the boulder deposits this contribution is motivated by two observations one by bourgeois and macinnes 2010 which described that boulders were moved selectively due to different bed roughness during 15 november 2006 tsunami on the island of matua the second topic is motivated by the boulder lines on ishigaki island by goto et al 2010 both topics are approached with linear wave theory and stability analysis from both the safety factor is derived for a spherical boulder with bed roughness and exposure as moment arms with which we are able to quantify the influence of bed roughness on the incipient motion of boulders for constant forces a bed roughness of about 30 of the boulder radius will prevent boulder transport furthermore the comparison between storm and tsunami waves in terms of the amplitude necessary to move boulders revealed that amplitude of storm waves is smaller than tsunami which we ascribe to the contribution of both velocity components to lift forces the comparison of total energy and number of waves revealed that storms have a larger total energy and a much larger number of waves which lead us to the conclusion that tsunamis produce unorganized boulder deposits whereas storms are capable of organizing boulders along lines and in clusters

a thin layer of phytoplankton observed in the philippine sea with a synthetic moored array of autonomous gliders 1 a synthetic moored array composed of five buoyancy propelled autonomous underwater gliders was used to characterize mesoscale variability and phytoplankton distribution in a 100 km 100 km domain in the philippine sea east of luzon strait for 10 days in may 2004 the study area located east of the kuroshio near the subtropical front is dominated by strong internal tides by energetic westward propagating mesoscale eddies with azimuthal velocities exceeding 50 cm s and by a deep 130 m maximum in chlorophyll fluorescence each glider in the array was instructed to maintain geographic position while repeatedly profiling to 200 m depth good station keeping performance enabled the resulting series of vertical profiles to be interpreted in the same manner as a physically moored chain of instruments although organized primarily as a demonstration of glider capabilities this field exercise provides a unique data set for examining biological physical interactions in the open ocean here we report on the evolution of a thin layer of phytoplankton observed near the deep chlorophyll maximum coincident observations of fine structure in temperature and salinity suggest that the thinning process of this layer was driven primarily by physical forcing most probably vertical shear associated with energetic diurnal internal waves as opposed to a biological mechanism such as convergent swimming grazing or spatial variation in growth rate

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

electron spin resonance esr dating abstract esr dating has been systematically applied in earth sciences and archaeology since 1975 when ikeya dated a stalactite from the akiyoshi cave in japan in the meantime this new technique has been successfully applied to the dating of materials such as speleothems spring deposited travertines mollusc shells corals and tooth enamel the present research focuses on the dating of quartz which allows the age assessment of heated ceramics volcanic rocks intrafault material or windblown sediments esr dating is based on the measurement of the number of paramagnetic centers in a mineral these centers are generated by alpha beta and gamma radiation of the matural radioelements such as u th and k and have accumulated over time two parameters have to be determined the accumulated dose ad and the dose rate d to which the sample was exposed this review comprises three major parts a introduction into esr dating b application of the method and c appendices giving detailed description of dose rate calculation physical basis of electron spin resonance the esr spectrometer and esr lines the major emphasis lies on the outline of the application of esr dating this includes the discussion of the esr signals of the various materials sampling sample preparation and measurement techniques

why is stromatactis so rare in mesozoic carbonate mud mounds the sedimentary diagenetic structure stromatactis is widespread in palaeozoic spiculitic carbonate mud mounds but occurs only sporadically in mesozoic sponge carbonate mud mounds comparative analysis of palaeozoic and mesozoic stromatactis limestones suggests that this variation results from the degree of siliceous sponge skeletal rigidity and the amount of internal sediment accumulation in the original cavity network partial to entire filling by internal sediment resulted in a continuum from a small amount of internal sediment and large amount of cement stromatactis common in the palaeozoic to only internal sediments aborted stromatactis common in the mesozoic these observations match independent lines of evidence concerning the siliceous sponge evolution and sediment recycling e g bioerosion across the palaeozoic to mesozoic biotic revolution

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

paleoenvironmental implications of novel c30 steranes in precambrian to cenozoic age petroleum and bitumen petroleums and bitumens from early proterozoic 1800 ma to miocene 15 ma age marine strata contain 24 isopropylcholestanes a novel group of c30 steroids the abundance of these compounds relative to 24 n propylcholestanes varies with source rock age late proterozoic vendian and early cambrian oils and or bitumens from siberia the urals oman australia and india have a high ratio of 24 isopropylcholestanes to 24 n propylcholestanes 1 while younger and older samples have a lower ratio 0 4 temporal changes in this parameter may reflect the relative abundance of certain porifera sponges and certain marine algae through time geochemical indicators such as this which can constrain the source rock age of a migrated oil are useful in source rock identification during petroleum exploration

messinian stromatolite thrombolite associations santa pola se spain an analogue for the palaeozoic stromatolite thrombolite associations are the dominant facies forming large portions of the santa pola carbonate platform se spain during deposition of the terminal carbonate complex tcc the tcc the last period of marine sedimentation in the western mediterranean associated with the messinian salinity crisis comprises a ne sw trending thrombolite reef with occasionally interlayered stromatolite horizons and a predominantply stromatolite and oolite facies in the back reef area the stromatolites are mainly dome shaped but fine columnar or wavy undulose forms can occur the stromatolites form huge bioherms extending tens to hundreds of metres they are finely laminated with alternating layers of dolomicrite and dolomicrospar the dolomicrite layers appear to be a primary dolomite precipitate whereas the dolomite crystals in the dolomicrospar layers apparently formed around a meta stable nuclei which was subsequently dissolved or degraded the low content of sand sized particles in the stromatolitic layers indicates formation under low energy conditions possibly on a tidal flat as reported from other areas in the western mediterranean deposition of the tcc at santa pola was apparently cyclic whereby stromatolites generally terminate each depositional cycle subtidal conophyton stromatolites possibly the only known occurrence younger than palaeozoic are however found on the reef slope at the base of the first tcc depositional cycle the dolomitic nature of the unadulterated stromatolitic laminations and the association of stromatolites and thrombolites as platform builders were a common feature in the early palaeozoic but are unusual in post ordovician carbonate facies we propose that the conditions during tcc deposition were very restricted possibly reflecting an environment similar to that of the early palaeozoic

questioning the microbial origin of automicrite in ordovician calathid demosponge carbonate mounds calathid demosponge carbonate mounds are a feature of early to middle ordovician shallow marine carbonate depositional environments of tropical to subtropical palaeolatitudes these mounds contain an important amount of autochthonous non skeletal microcrystalline calcium carbonate automicrite conventionally considered microbial in origin here the automicrite of calathid demosponge carbonate mounds tarim basin north west china is broken down into five distinct fabrics an in situ peloidal spiculiferous fabric am 1 an in situ peloidal fabric am 2 an aphanitic microtubular fabric am 3 a minipeloidal fabric am 4 and a laminoid cerebroid fabric am 5 type am 1 occurs with am 2 being succeeded by an assemblage of am 3 and am 4 types am 4 and am 5 are separated by an erosional disconformity a good correlation of fluorescence and cathodoluminescence of automicrites indicates that induced and supported organomineralization produced automicrite probably via the permineralization of non living organic substrates adsorbing dissolved metal humate complexes using a spreadsheet with six parameters and 17 characters am 1 to am 4 turn out to be non microbial in origin instead these automicrites represent relics of calcified metazoan tissues such as siliceous sponges non spiculate sponges or the basal attachment structures of stalked invertebrates fabric am 5 is a microbial carbonate but is post mound in origin forming a drape within a reefal framework established by am 4 the five automicritic fabrics individually or as an assemblage are a common element of ordovician calathid demosponge carbonate mounds in general the reassessment of the origins of these automicritic fabrics holds consequences for understanding of the great ordovician biodiversification event in terms of community structure reef ecology and reef evolution episodically these fabrics are also present in other carbonate build ups stretching from the neoproterozoic over the entire phanerozoic eon the massive calcification of metazoan soft tissue am 1 to am 4 characterizes episodes and conditions of enhanced marine calcification and might be of value to refine secular trends of pco2 ca concentration and mg ca ratio at the scale of individual sedimentary basins

progress in esr dating of pleistocene corals a new approach for de determination abstract esr dating has been widely applied for dating of corals of the age up to 500 000 to 600 000 years ago many studies have yielded promising results but the accurate determination of the equivalent dose d e remains a major limitation inflexion points in the dose response curve are shown to hinder correct fitting and limit the reliability of d e values here we present a new approach to obtain more reliable d e values

microscopic calcite dendrites in cold water tufa implications for nucleation of micrite and cement dendritic calcite forms in an active cold water tufa system in association with extracellular polymeric substances eps that discontinuously coat bryophytes and cyanobacteria dendrites consist of 100 200 nm thick calcite fibres that form 3d lattice like domains in each dendrite domain fibres have three structurally equal orientations which correspond in disposition to radii from the centre of a calcite unit cell to the convex triple face junctions on its surface fibres do not form in the orientation of the c axis the external form of each dendrite has the shape of half of a shortened octahedron with an upper triangular surface parallel to the substrate dendrite nucleation takes place on or in microbial eps whether microbial cells are present or not and is probably effected by attraction of ca 2 cations to negatively charged eps together with co2 degassing and concomitant ph increase of supersaturated spring water in stream splash zones ensuing dendrite growth is abiogenic and controlled by diffusion dendrite c axes are perpendicular to the substrate probably because the negative charge of eps forces the orientation of ca 2 and co 2 planes within the developing dendrite crystal to be parallel to the eps film surface dendrites are eventually filled and overgrown by solid syntaxial calcite which gradually and completely obliterates the dendrites as more familiar calcite crystal forms develop no trace of the dendritic nucleus remains in the rock record calcite crystal nucleation may take place by this mechanism in many marine and meteoric settings given that microbial eps is now assumed to be virtually ubiquitous in these environments this phenomenon could contribute to the development of familiar fabrics such as marine micrite cement and fibrous calcite cement radial ooids peloids abiogenic stromatolites sea floor precipitates microbialites tufa travertine speleothems and some meteoric cements it may also contribute to the substrate normal orientation of c axes of common cement fabrics

petrology of lower cretaceous carbonate mud mounds albian n spain insights into organomineralic deposits of the geological record the process of organomineralization is increasingly well understood with respect to modern carbonate sediments accumulating adjacent to tropical reef atolls and reef caves mineralization related to non living organic substrates results in autochthonous micrite production automicrites automicrites are the main constructive element of lower cretaceous albian carbonate mud mounds in northern spain these slope mud mounds occur within transgressive and early highstand system tracts encompassing several macrobenthic ecological zones they are clearly separated from the biocalcifying carbonate factory urgonian carbonate platforms in both space and time within these build ups most automicrites were initially indurated and accreted to form a medium relief growth framework automicrites have a uniform presumably high mg calcite precursor mineralogy they show an inorganic stable isotope signature 13c around 3 3 within the range of early marine cements and skeletal compounds lacking major vital effects epifluorescence microscopy shows that they have facies specific fluorescence which is similar to skeletal compounds of acanthochaetetes but clearly different from allomicritic sediment and cements which are mostly non fluorescent the edta soluble intracrystalline organic fraction siof of albian automicrites shows an amino acid spectrum that is similar to shallow subsurface samples from their modern counterparts gel electrophoresis of the siof demonstrates an exclusively acidic character and a mean molecular size range between 20 and 30 kda experiments in vitro inhibition tests indicate that the siof has a significant ca2 binding capacity fluorescence and chemical characteristics of siof point to a main substance class such as humic and fulvic acids compounds that form from pristine organic matter during early diagenesis biomarker analyses provide evidence for the crucial role of biodegradation by heterotrophic microorganisms but no biomarker for cyanobacteria has been found primary sources of organic material should have been manifold including major contributions by metazoans such as sponges it is concluded that many carbonate mud mounds are essentially organomineralic in origin and that the resulting fabric of polygenetic muds polymuds may represent ancestral metazoan reef ecosystems which possibly originated during the neoproterozoic

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

the world s most spectacular carbonate mud mounds middle devonian algerian sahara abstract in the southern ahnet basin of algeria a unique middle devonian underwater scenery is revealed which consists of 191 mud mounds 15 mud ridges and 2 mud atolls distributed over nine discrete areas of a shallow pelagic carbonate shelf all the buildups are totally exhumed thus perfectly exhibiting their original morphologies slope angles elevations and the pattern of the onlapping strata as well as their relationship to the surrounding off buildup sequences types of buildups include 1 small mud mounds 1 5 m high 10 20 m diameter 2 large mud mounds up to 40 m high up to 200 m diameter 3 lens shaped mounds 1 30 m thick 10 15 slopes 4 mud ridges up to 100 m high 150 8500 m long and 5 semicircular mud atolls 2500 2800 m long 20 30 m high the buil ups were constructed during a short time span in the early givetian part of the lower varcus zone probably not exceeding a few hundred thousand years sedimentation rates in coeval off buildup areas were at least 3 10 times lower the lithology of the buildups is a massive boundstone with a high proportion of irregular spar filled cavities stromatactis but only very scattered potential frame builders the carbonate mud is considered to be an in situ cyanobacterial precipitate although evidence of such is poor organic components of the buildups are not significantly different from those of the off buildup lithologies and include numerous crinoid ossicles some tabulate and solitary rugose corals brachiopods mollusc debris trilobites and very rare sponge spicule and bryozoans the total absence of stromatoporoids large tabulate and colonial rugose corals green algae and micritic envelopes around grains suggests growth of the buildups in the lower part of the photic zone 100 200 m they are onlapped by a discontinuous sequence a few meters thick of skeletal packstones and grainstones and locally orthoceratid floatstones that were deposited later in the givetian a widespread rise of sea level in the early frasnian buried both buildups and adjacent areas under shales and siltstones postdepositional alteration of the mud buildups includes 1 formation of stromatactis cavities probably by dewatering and internal erosion 2 cementation of stromatactis cavities and interparticle pore spaces by early high mg calcite and late blocky low mg calcite 3 neomorphic transformation of mg calcitic mud and aragonitic skeletal debris 4 occasional formation of neptunian dikes 5 slight erosion of buildup surfaces 6 compaction and slumping of onlapping capping beds and 7 local dolomitization the formation and growth of the mud build ups is envisaged as a sequence of stages starting with patchy coral thickets evolving into small mud mounds that coalesced into larger mounds by continuous vertical and lateral growth closely spaced mounds amalgamated into mud ridges and mud atolls regular nw se and n s patterns of some mound rows and ridges show a relationship of buildup formation to rejuvenated late precambrian tectonic lineaments which reappear in the hercynian orogeny the isotopic signature of matrix and early ements of mound rocks however does not support the idea of fluid migration and hydrothermal co2 supply during buildup growth

an extreme wave event in eastern yucatan mexico evidence of a palaeotsunami event during the mayan times the yucatan peninsula mexico has typically been considered a tectonically stable region without significant seismic activity in contrast the region is one that is regularly affected by hurricanes a detailed survey of ca 100 km of the eastern yucatan and cozumel coast identified the presence of ridges containing boulders measuring 1 m with up to three ridges at some locations the ridges reach five metres in height and their origin is associated with extreme wave event ewe activity previously modelled tsunami waves from known seismically active zones in the region muertos thrust belt and south caribbean deformed belt are not of sufficient at the yucatan peninsula to have produced the boulder ridges recorded in this study the occurrence of hurricanes in this region is more common but two of the most destructive hurricane gilbert 1988 and hurricane wilma 2005 produced coastal waves too small to have created the ridges recorded here in this paper a new tsunami model has been generated that indicates a tsunami event may have caused the ewe that resulted in the deposition of the boulders ridges

chenier type ridges in giralia bay exmouth gulf western australia processes chronostratigraphy and significance for recording past tropical cyclones abstract past coastal flooding events may be inferred from geomorphic and sedimentary archives including particular landforms e g beach ridges washover fans deposits e g washover sediments in lagoons or erosional features e g erosional scarps within strandplains in giralia bay southern exmouth gulf western australia sandy ridge sequences in supratidal elevations form the landward margin of extensive mudflats the formation of these ridges is assumed to be mainly driven by tropical cyclones tcs although their depositional processes need to be clarified we investigated the supratidal sandy ridge sequence in giralia bay by carrying out process monitoring geomorphological mapping by means of an unmanned aerial vehicle survey as well as sedimentological and geochronological investigations and multivariate statistics based on the resulting data this study aims at i identifying the most important driving processes to form the sandy ridges ii establishing their chronostratigraphy and iii understanding their significance for recording past tc activity trench excavations revealed sandy units that are interbedded with mud layers at the base similar to the present distal mudflat sediments on top mud intercalations recede and sand layers of varying grain size distribution dominate in the upper part of the trenches younger sediment layers onlap older ones documenting the stepwise seaward accretion of the ridges onto the mudflat while our data suggests that tidal processes have only limited effects on ridge activity sediment transport erosion and deposition seems to be driven by both tc induced storm surges and high magnitude precipitation events causing surface discharge most accretionary sand units are thus assumed to represent events of morphodynamic activity during tc induced flooding since the mid holocene ridge activity is recorded in a roughly decadal resolution and over historical as well as prehistorical holocene time scales while the ridges do not represent beach or chenier ridges sensu stricto they may be described as chenier type ridges due to their stratigraphical architecture ridge evolution however over a millennial time scale seems to be indicated by the landward rise of the sequence possibly corresponding to the mid holocene sea level highstand of western australia of at least 1 2 m above present mean sea level

origin and significance of isotope shifts in pennsylvanian carbonates asturias nw spain abstract the primary variability of the composition and properties of seawater is much greater in the shallow coastal zones than in the main body of ocean water an inadequate understanding of this variability as well as different diagenetic environments severely limit the interpretation of the stable isotope record of shoalwater carbonates in order to investigate this primary and diagenetic variability along a bashkirian moscovian platform to basin transect 13c and 18o analyses have been performed on more than 1000 matrix micrite carbonate cement and brachiopod shell samples in isotope analysis these different carbonate materials tend to complement each other inasmuch as they have different advantages and shortcomings the resulting data reveal spatial trends in 13c and 18o signatures from platform top lower values to basin higher values in the case of 13c from pristine brachiopods this trend can be explained by the long residence time aging of platform top water masses in the case of brachiopod 18o this variance is interpreted to reflect temperature differences between warm surface and colder bottom water separated by a permanent thermocline at about 150 to 200 m beneath the shelf break micrite and marine cement isotopic values from the platform interior were reset lowered during pervasive early meteoric diagenesis in contrast micrite and marine cement isotopic values from the outer platform slope and basin show higher values close to the assumed pennsylvanian seawater isotopic composition this implies that isotopic data from shoalwater carbonates including pristine brachiopod shells might not necessarily reflect paleoceanographic trends of the open ocean water masses because of changes in coastal water mass isotope signature and interaction with early meteoric fluids

internal precipitation of microcrystalline carbonate a fundamental problem for sedimentologists abstract recent studies of submarine lithification have shown that microcrystalline carbonate or carbonate mud traditionally thought to represent ooze deposited in quiet water commonly forms as an internal precipitate below the sediment water interface this internally precipitated micrite alters the mud grain ratio of pre existing sedimentary deposits and invalidates classifications that relate the amount of micrite matrix in limestones to the degree of water energy associated with the environment of deposition

late jurassic climate and its impact on carbon cycling abstract the climate of the late jurassic has been characterized by high atmospheric co2 levels and by a monsoonal rainfall pattern in this study we traced the evolution of the global carbon cycle through the late jurassic with the help of carbonate carbon isotope stratigraphy the oxfordian tithonian 13c curve is marked by one major positive carbon isotope excursion with an amplitude 13 c 1 0 middle to late oxfordian and a second minor positive excursion with an amplitude 13 c late kimmeridgian the early kimmeridgian and early tithonian 13c values fluctuate around 13 c 2 0 3 and contrast with the less positive 13c values of early oxfordian and late tithonian age 13 c 1 0 5 a comparison of the late jurassic carbonate carbon isotope curve with the occurrence of organic rich sediments suggests that not only fluctuations in organic carbon burial but also in carbonate carbon burial had an impact on the c isotope record the oxfordian c isotope excursion appears to correspond to a time of overall increased organic carbon burial triggered by increased nutrient transfer from continents to oceans during a time of rising global sea level however episodes of enhanced organic carbon burial during the kimmeridgian and early tithonian are not reflected by prominent spikes in the c isotope record favourable conditions for carbonate platform growth at a time of high global sealevel may have resulted in the stabilisation of the c org c carb burial ratio and hence maintained the 13c record at steady but relatively positive values the middle and late tithonian c isotope values drop below 13 c 1 5 a similar shift to less positive c isotope values was recognized in other c isotope records from the tethys and atlantic oceans and reflects a decrease in the c org c carb burial ratio possibly related to a reorganisation of the global climate system globally widespread marine black shale mature quartzose sandstone assemblages suggest that the relative efficiency of the late jurassic carbon pumps was controlled by weathering erosion and runoff causing widespread marine eutrophication eutrophication favoured the organic carbon pump but it diminished the carbonate platform growth potential the monsoonal rainfall distribution pattern may explain why late jurassic carbonate platforms experienced less severe growth crises than early cretaceous carbonate platforms

holocene marine 14c reservoir age variability evidence from 230th dated corals in the south china sea the south china sea scs is well connected with the western pacific and influenced by the east asian monsoon we have examined temporal variations in radiocarbon marine reservoir ages r and regional marine reservoir corrections delta r of the scs during the holocene using paired measurements of ams c 14 and tims th 230 on 20 pristine corals the results show large fluctuations in both r and delta r values over the past 7500 years yrs with two distinct plateaus during 7 5 5 6 and 3 5 2 5 thousand calendar years before present cal ka bp the respective weighted mean delta r values of these plateaus are 151 85 and 89 59 yrs which are significantly higher than its modern value of 23 52 yrs this suggests that using a constant modern delta r value to calibrate c 14 dates of the scs marine samples will introduce additional errors to the calibrated ages our results provide the first database for the holocene r and delta r values of the scs for improved radiocarbon calibration of marine samples we interpret the two delta r plateaus as being related to two intervals with weakened el nino southern oscillation enso and intensified east asian summer monsoon easm this is because the c 14 content of the scs surface water is controlled by both the c 14 concentration of the pacific north equatorial current nec which is in turn influenced by enso induced upwelling along the pacific equator and vertical upwelling within the scs as a result of moisture transportation to midlatitude region to supply the easm rainfall

the frasnian famennian mass extinction insights from high resolution sequence stratigraphy and cyclostratigraphy in south china two sequences sfr sfa each 1 1 2 myr in duration are recognised in the strata across the frasnian famennian f f transition both in carbonate platform and interplatform basinal successions in south china the sequence boundary between the two sequences is placed a little below the top of the frasnian the sequences are basically composed of coarsening upward bed thickness increasing upward cycles and shallowing upward cycles parasequences in basinal and platform deposits respectively which stack into cycle sets typically six to eight cycles 10 and 12 cycle sets are identified in sequences sfr and sfa respectively these cycle sets can be further grouped into larger scale composite cycle sets herein termed mesocycle and megacycle sets with two and four cycle sets respectively this vertical cycle stacking pattern and the hierarchy of cyclicity suggest a milankovitch style of forcing such that the cycles and cycle sets were formed in response to the orbital perturbations of precession 16 18 kyr and eccentricity v100 kyr in duration respectively in the basinal cycles smaller scale rhythmic stratification beds typically six to eight beds in a cycle are extensive and were likely caused by millennial scale climatic forcing in the lower sequence sfr the latest highstand deposits consist of calciturbidites and debrites in deep water strata and fenestral limestones in shallow water strata representing a major third order sea level fall within these deposits four cycle sets are further identified in both coeval deep water and platform successions succeeding deeper water organic rich facies within which three cycles occur are the transgressive deposits of the overlying famennian sequence sfa these cycles represent three higher frequency 16 18 kyr sea level fluctuations and accompanying anoxia superimposed on a major third order sea level rise the f f boundary is placed at the top of the first cycle based on conodont data thus a major sea level fall and then a rise occurred in the f f transitional period faunal and sedimentological data reveal a massive biotic decline in concert with the major sea level fall and a further biotic demise coinciding with the major sea level rise and its three superimposed higher frequency sea level fluctuations and accompanying anoxia the f f biotic crisis was therefore characterised by two episodes of step down extinction on the basis of milankovitch orbital rhythms the first major biotic extinction took place over v400 kyr and the subsequent event was v50 kyr in duration i e v450 kyr for the entire event at the same time as the massive decline of normal marine fossils during the latest frasnian sea level fall there was widespread cyanobacterial growth and a thriving of planktonic calcispheres suggesting eutrophic conditions this situation could have caused a severe biotic loss as a result of the deterioration of surface water clarity and formation of anoxic bottom waters due to over

microbial carbonates as contributors to upper permian guadalupian lopingian biostromes and reefs in carbonate platform margin setting ziyun county south china permian guadalupian and lopingian reefs in ziyun county southern guizhou southwestern china occur in a carbonate platform margin setting guadalupian reefs maokouan are characterized by sponges calcimicrobes microbialites as microencrusters and syndepositional calcite cement global sea level falling in the latest guadalupian changed the reef biotopes lower lopingian wuchiapingian deposits reflect a rapid transgressive regressive cycle reefs were not developed during that time although coral biostromes are common however microbial carbonates occur commonly in these biostromes including dark coloured homogeneous microbialite free growing microbes shamovella and archaeolithoporella interpreted to be problematic microbial deposits upper lopingian changhsingian reefs were formed by sponges microbialites shamovella archaeolithoporella automicrite and syndepositional calcite cement common primary encrustations consist of thin homogeneous subparallel layers of archaeolithoporella which is an important reef builder particularly throughout the lopingian reef succession secondary encrustations are characterized by dark coloured homogeneous microbialite containing thin thalli that alternate with light coloured microspar pseudospar reef building organisms e g sponges archaeolithoporella calcimicrobes and hydrozoans were bound lithified and preserved by syndepositional calcite cement and microbially precipitated micrite automicrite in changhsingian reefs of the shitouzhai limestone microbial carbonate e g micritic peloidal crusts and automicrite layers encrusted the top sides and undersides of in situ organisms and also grew on their upper surface as thick accumulations radiaxial fibrous calcite cement is present but is not common abundant microbial carbonates in the guadalupian to lopingian reefs in ziyun indicate that microbial precipitation of calcium carbonate played a vital role in the development of permian reefs in this platform margin setting c 2004 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

soluble humic substances from in situ precipitated microcrystalline calcium carbonate internal sediment and spar cement in a cretaceous carbonate mud mound albian carbonate mud mound limestones exposed near iraneta northern spain show a fabric and particle specific fluorescence intense fluorescence is restricted to in situ precipitated microcrystalline automicritic fabrics calcified demosponges and coralline sponges intermediate intensity derives from micritized bioclasts pellets and a rim of marine bladed cement most invertebrate skeletons late diagenetic equant cement and crosscutting zones of dolomitization are weakly to nonfluorescent internal microcrystalline sediment allomicrite and red algae debris have variable fluorescence correlation between rock fluorescence and soluble humic substances was evaluated from 3 g of automicrite allomicrite and cement time resolved laser induced fluorescence spectroscopy trlfs with ultra short pulses on two extracrystalline fractions naoh soluble and two intracrystalline fractions hcl soluble and naoh soluble showed that most of the soluble humic substances of automicrite are within the crystals but conversely are significantly enriched on outer surfaces of allomicrite spar cement is close to detection limits fluorescence lifetimes are in the range of 0 5 2 ns and 3 5 6 ns we conclude that precipitation of automicrite took place during oxidative organic matter diagenesis i e during condensation reactions of degradation products of marine biopolymers by contrast allomicrite formed by skeletal breakdown followed by ingestion organic coating and reingestion during deposit feeding a humic substance based model of marine polymer gels represents a new approach for the understanding of ancient polygenetic carbonate muds so typical of phanerozoic mud mounds in deeper water settings

reconstruction of storm tsunami records over the last 4000 years using transported coral blocks and lagoon sediments in the southern south china sea large transported coral blocks on reef flats and elevated sedimentation rates in atoll lagoons were demonstrated to be excellent proxies for past strong storms tsunamis in the southern south china sea here we introduce another important proxy coarse fraction contents of lagoon sediments this proxy is based on the principle that coarse fractions of enclosed lagoon sediments are usually controlled by strong sedimentary dynamics on the surrounding reef flat and thus increases in the weight percentages of coarse grained fractions of the lagoon sediments should also reflect strong storm tsunami events or increases in storminess with the size of the content peak as the proxy for the degree of storminess bearing this in mind we measured the contents of the 1 mm grain size fractions referred to as coarse fraction content in an undisturbed lagoon core precisely dated to cover the last 4000 years the decadal resolution data show a systematic variation with some peaks strongly correlated with in timing with strong storm tsunami events dated at ad 1872 15 1685 8 similar to 1680 6 1443 9 1336 9 1210 5 similar to 1201 4 and 1064 30 using wave transported coral blocks using the mean coarsefraction content 9 2 for the entire core as a reference line a total of 77 peaks were identified for the past 4000 years twenty of these peaks are higher than 23 the mean value for peaks that are correlated in age with the six strong storm events identified using independently dated coral blocks among these 23 peaks 13 occurred within the last 1000 years the concentration of contentpeaks in the last millennium could be partially due to higher deposition rates and sampling resolution over the last similar to 4000 years there appears to be a weakly increasing trend in coarse fraction contents towards present time but this trend is not obvious within the last millennium this long term variation may be related to changes in both storminess and reef lagoon morphology however the data do suggest three extremely stormy periods centring around ad similar to 1200 similar to 400 bc and similar to 1200 bc respectively overall this study demonstrates that combined use of transported coral blocks and coarse fraction contents of lagoon sediments provides an excellent means for comprehensive reconstruction of past storm tsunami activity c 2008 elsevier ltd and inqua all rights reserved

controls on the evolution of carbonate mud mounds in the lower cretaceous cupido formation northeastern mexico abstract the lower cretaceous cupido formation in northeastern mexico represents part of an extensive post rift carbonate platform system that stretched across much of the gulf of mexico passive margin numerous sponge microbial mud mounds are found within the lower part of the cupido formation four mound types were identified at bustamante canyon and other localities in the state of nuevo leon mexico type 1 siliceous sponge microbial mounds contain boundstone core facies are the oldest mounds and are associated with adjacent deep ramp to basinal lime mudstone facies type 2 sponge microbial mounds also have boundstone core facies are associated with outer ramp wackestone packstone facies and overlie strata that contain type 1 mounds type 3 sponge microbial coral mounds contain only 40 50 boundstone core facies and overlie or are locally interstratified with type 2 mound bearing strata although type 3 mounds are associated with outer ramp packstone facies type 4 calcisponge microbial coral biodetrital dominantly skeletal packstone mounds are the youngest mounds and are associated with outer ramp packstone and ramp crest rudist packstone facies both the length and height i e synoptic relief of individual types 1 2 and 3 mounds range from a few meters to tens of meters only type 4 mounds reach several hundred meters in length and are up to 90 m thick although synoptic relief on type 4 mounds was minor systematic changes in the biota morphologies dimensions abundance stratigraphic distribution and facies associations of the lower cupido mounds were largely controlled by the initial ramp like depositional profile of the lower cupido platform and the long term second order accommodation trends that affected ramp evolution during early cretaceous time the ramp like profile was not conducive to transport of large volumes of allochthonous sediment from updip source areas to mound locations on the outer ramp this allowed slowly accumulating types 1 2 and 3 mounds to build synoptic relief because adjacent outer ramp facies accumulated at even slower rates in contrast type 4 mound cores contain abundant coarse grained skeletal sediment and also developed the least synoptic relief of all lower cupido mounds because of higher accumulation rates associated with adjacent grain rich ramp crest lithofacies we suggest that these systematic changes in mound attributes largely reflect long term second order accommodation loss and regional progradation of the lower cupido ramp during early cretaceous time accordingly the upward transition from type 1 to types 2 and 3 mounds and ultimately to type 4 buildups can be explained by the progressive shallowing of outer ramp environments as more updip facies tracts prograded eastward from late hauterivian to early aptian time there are few stratigraphic successions in the rock record that provide better evidence for the links between large scale stratigraphic relationships and mound evolution along low gradient carbonate ramps