the influence of surface and tectonic processes on landscape evolution of the iberian chain spain quantitative geomorphological analysis and geochronology abstract in tectonically active areas the landscape response to tectonic forcing is described and possibly quantified by regional topographic and hydrographic features as well as by spatial variation in rates of surface processes we investigated the recent landscape evolution of the iberian chain ne spain an intraplate thrust belt formed in cenozoic times and characterized by a dome shaped topography in its central sector the landscape is dominated by low relief surfaces late neogene in age presently standing at an average altitude of 1300 m a recent regional uplift controlled the organization of the present fluvial network and dissection of the landscape in this framework we investigated the geomorphic responses to tectonic forcing by the calculation of morphometric parameters focusing on topography map of local relief swath profiles and hydrography basin hypsometric curve and integral basin asymmetry factor river longitudinal profiles and relative indices and using srtm dem the results of morphometric analysis have been coupled with radiometric uranium series dating of calcareous tufas lying on fluvial strath terraces the obtained ages allow the estimation of incision rate along the high tajo and martin rivers our results indicate that uplift and rock type erodibility are the main factors influencing landscape evolution of the study area the incision rates are very similar throughout the central sector of the range indicating that despite subtle local variation the rivers are responding to a main tectonic input the regional uplift in conclusion the iberian chain landscape is in a transient state in response to a recent dome like uplift indeed the fluvial processes that weakly incised this landscape at a rate of 0 6 mm yr are approaching a radial pattern on the basis of geological and geomorphic constraints we hypothesize that the uplift started around or after 3 ma

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

microbial carbonates the geological record of the calcified bacterial algal mats and biofilms summary deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the archaean geologically best known in seas and lakes microbial carbonates are also important at the present day in fluviatile spring cave and soil environments the principal organisms involved are bacteria particularly cyanobacteria small algae and fungi that participate in the growth of microbial biofilms and mats grain trapping is locally important but the key process is precipitation producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation various metabolic processes such as photosynthetic uptake of co2 and or hco3 by cyanobacteria and ammonification denitrification and sulphate reduction by other bacteria can increase alkalinity and stimulate carbonate precipitation extracellular polymeric substances widely produced by microbes for attachment and protection are important in providing nucleation sites and facilitating sediment trapping microbial carbonate microfabrics are heterogeneous they commonly incorporate trapped particles and in situ algae and invertebrates and crystals form around bacterial cells but the main component is dense clotted or peloidal micrite resulting from calcification of bacterial cells sheaths and biofilm and from phytoplankton stimulated whiting nucleation interpretation of these texturally convergent and often inscrutable fabrics is a challenge conspicuous accumulations are large domes and columns with laminated stromatolite clotted thrombolite and other macrofabrics which may be either agglutinated or mainly composed of calcified or spar encrusted microbes stromatolite lamination appears to be primary but clotted thrombolite fabrics can be primary or secondary microbial precipitation also contributes to hot spring travertine cold spring mound calcrete cave crust and coated grain deposits as well as influencing carbonate cementation recrystallization and replacement microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water and thus relies uniquely on a combination of biotic and abiotic factors this overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas and in the past by temporal variation in abundance of marine microbial carbonates patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry stromatolites appeared at 3450 ma and were generally diverse and abundant from 2800 to 1000 ma inception of a proterozoic decline variously identified at 2000 1000 and 675 ma has been attributed to eukaryote competition and or reduced lithification thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the palaeozoic and reappeared in the late devonian microbial carbonates retained importance through much of the mesozoic became scarcer in marine environments in the cenozoic but locally re emerged as large agglutinated domes possibly reflecting increased algal involvement and thick micritic reef crusts in the late neogene famous modern examples at shark bay and lee stocking island are composite coarse agglutinated domes and columns with complex bacterial algal mats occurring in environments that are both stressed and current swept products of mat evolution ecological refugia sites of enhanced early lithification or all three

timing of post glacial reinhabitation and ecological development of two new england usa drainages based on trace fossil evidence abstract trace fossils as paleoecological and paleobiogeographical tools in pleistocene glaciolacustrine sediments have been largely ignored combining high resolution varve stratigraphy with trace fossil data can lead to refined paleoenvironmental interpretations during times of rapid climate change based on trace fossils from glaciolacustrine varves in the connecticut and merrimack river valleys a new timeline for the reinhabitation of new england by fish and associated invertebrates has been constructed in addition it appears that colonization of the recently deglaciated environments occurred in at least four successional stages if these stages can be recognized elsewhere it may be possible to accurately model other postglacial migrations using trace fossils and varve chronostratigraphy

early history of scleractinian corals and its geological consequences conventional views have implied that scleractinian corals were hermatypic and thus were potentially reef building from the onset of their appearance in early mesozoic time in shallow shelf carbonate environments however for almost 25 m y they held rather subordinate positions and generally did not participate in extensive ecologic reef framework evidence from both north america and europe demonstrates that triassic corals had ecologic preferences quite different from those in the cenozoic a key step in the evolutionary success of these corals may have been the advent of a symbiotic association with algae this association believed to have developed at the end of the triassic could have been responsible for thrusting scleractinians into prominent positions as reef builders and may account for their dramatic radiation in mesozoic time

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

facies analysis and palaeoenvironmental interpretation of the late oligocene attard member lower coralline limestone formation malta the oligocene represents a key interval during which coralline algae became dominant on carbonate ramps and luxuriant coral reefs emerged on a global scale so far few studies have considered the impact that these early reefs had on ramp development consequently this study aimed at presenting a high resolution analysis of the attard member of the lower coralline limestone formation late oligocene malta in order to decipher the internal and external factors controlling the architecture of a typical late oligocene platform excellent exposures of the lower coralline limestone formation occurring along continuous outcrops adjacent to the victoria lines fault reveal in detail the three dimensional distribution of the reef associated facies a total of four sedimentary facies have been recognized and are grouped into two depositional environments that correspond to the inner and middle carbonate ramp the inner ramp was characterized by a very high energy shallow water setting influenced by tide and wave processes this setting passed downslope into an inner ramp depositional environment which was colonized by seagrass and interfingered with adjacent areas containing scattered corals the middle ramp lithofacies were deposited in the oligophotic zone the sediments being generated from combined in situ production and sediments swept from the shallower inner ramp by currents compositional characteristics and facies distributions of the attard ramp are more similar to the miocene ramps than to those of the eocene an important factor controlling this similarity may be the expansion of the seagrass colonization within the euphotic zone this expansion may have commenced in the late oligocene and was associated with a concomitant reduction in the aerial extent of the larger benthonic foraminifera facies stacking pattern analysis shows that the depositional units parasequences at the study section are arranged into transgressive regressive facies cycles this cyclicity is superimposed on the overall regressive phase recorded by the attard succession furthermore a minor highstand correlated with the ru4 ch1 sequence and subsequent minor lowstand ch2 sequence have been recognized the biota assemblages of the attard member suggest that carbonate sedimentation took place in subtropical waters and oligotrophic to slightly mesotrophic conditions the apparent low capacity of corals to form wave resistant reef structures is considered to have been a significant factor affecting substrate stability at this time the resulting lack of resistant mid ramp reef frameworks left this zone exposed to wave and storm activity thereby encouraging the widespread development of coralline algal associations dominated by rhodoliths

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

conflicting isotopic and biotic evidence for tropical sea surface temperatures during the tertiary abstract the biotic evidence from a varied group of shallow water organisms including mangroves zooxanthellate corals mainly reefal and larger foraminifera suggests that sea surface temperatures at low latitudes during the tertiary from at least the early eocene to the middle miocene were subtropical to tropical in nature and similar to temperatures prevailing at low latitudes at the present day 20 28 c in a recent paper shackleton 1984 the suggestion is made on the basis of oxygen isotope studies of foraminiferal shells that low latitude sea surface temperatures during the palaeogene and much of the neogene were invariably lower than those in similar regions today with a stable temperature of around 18 c this paper discusses the conflicting evidence for sea surface temperatures obtained from palaeontological and isotopic sources and suggests that palaeotemperatures derived from some isotopic studies are too low to account for the distribution and diversity of many tertiary tropical and subtropical biotas

the paradox of drowned reefs and carbonate platforms shallow water carbonate platforms and reefs are drowned when tectonic subsidence or rising sea level outpaces carbonate accumulation and benthonic carbonate production ceases drowned platforms are common in the geologic record but they present a paradox if one considers rates of processes involved during the early holocene when sea level rose at rates of 6 000 to 10 000 m yr mm 1 000 yr most reefs and platforms were outpaced by the rising sea during the late holocene with sea level rising 500 to 3 000 m yr in the atlantic caribbean area reefs and platforms started to recover built to sea level and prograded seaward 1 000 m yr is thus a conservative estimate of the average growth potential of modern reefs and platforms independently accumulation rates of prograding platforms in the geologic record suggest growth potential in excess of several hundred microns per year the growth potential of 1 000 m yr exceeds any relative rise of sea level caused by long term processes in the geologic record newly formed ocean crust subsides at a maximum of 250 m yr basin subsidence averages 10 to 100 m yr and sea level rises due to increased sea floor spreading amount to less than 10 m yr rapid pulses of relative rise of sea level or reduction of benthic growth by deterioration of the environment remain the only plausible explanations of drowning the geologic record shows examples of both of these processes global mass extinctions of reefs and platforms occurred in the middle cretaceous eustatic rise due to submarine volcanism or desiccation of a small ocean basin and the late devonian global crisis of ocean environment extraterrestrial cause drowning controlled by regional tectonics prevailed in the jurassic and early cretaceous of the tethyan realm and the drowning of mesozoic platforms in the western north atlantic seems to have been dictated by plate tectonic drift to higher latitudes

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

subtropical carbonates in a temperate realm modern sediments on the southwest australian shelf the southwestern continental margin of australia 19 degrees s 22 degrees s in the western indian ocean is transitional between cool water and warm water carbonate realms it comprises the incipiently rimmed flat topped steep fronted rottnest shelf in the south the uniform subtropical starved carnarvon ramp off shark bay and the ningaloo fringing reef in the north the margin is strongly influenced by the poleward flowing warm nutrient poor leeuwin current which promotes overall downwelling and strong summer equatorward blowing winds which generate local seasonal upwelling the structurally quiescent northern part of the rottnest shelf with minimum accommodation is characterized by luxuriant stands of sea grasses and macrophytes growing on coralline encrusted hardgrounds and rooted in sediments rich in coralline algae and larger symbiont bearing foraminifers together with abundant cool water elements such as bryozoans molluscs and small foraminifers halimeda is poorly calcified and does not contribute to the sediment azooxanthellate corals although present are not common such a sediment pattern has many analogs in the geologic record especially the early cenozoic the incipient rim is a morphologically complex linear ridge system interpreted to be a buried mid pleistocene barrier reef or beach dune complex the northern part of the ridge complex is capped by the houtman abrolhos reef platforms subphotic sediments on the deep outer shelf and upper slope affected by seasonal upwelling are typical cool water poorly sorted bryozoan dominated deposits rich in small foraminifers and sponge spicules the inner part of the more structurally active carnarvon ramp ranges from steep eolianite cliffs to hypersaline environments of shark bay to the ningaloo fringing reef mid ramp sediment especially off shark bay is mostly relict or stranded and foraminifer dominated sand with abundant mg calcite cemented intraclasts these sediments accumulating on a relatively barren seafloor likely represent attenuated carbonate production brought about by downwelling and episodic incursions of saline shark bay derived waters onto the ramp the outer ramp is either planktic foraminiferal sand sorted by strong bottom currents or spiculitic mud such sedimentation patterns should typify the western margins of large ocean basins during those periods in geologic history when circumglobal equatorial circulation was active and equatorial gateways narrow in contrast to eras of supercontinents when cool water carbonate sedimentation and upwelling prevailed in similar settings furthermore because low latitude trade winds relax during glacial epochs and the cool water upwelling belt moves equatorward into otherwise tropical realms temperate and subtropical sedimentation patterns in these regions should oscillate at the 100 ky scale in the stratigraphic record

dynamic response of the shallow marine benthic ecosystem to regional and pan tethyan environmental change at the paleocene eocene boundary the indus basin of pakistan preserves a record of a late paleocene early eocene shallow marine carbonate ecosystem in the east tethys and of its response to an interval of marked climate change and regional tectonic reconfiguration local palaeoecological conditions and or the tethyan latitudinal temperature gradient favoured meso oligotrophic biotic assemblages of mainly larger benthic foraminifera lbfs and dasycladacean algae in the late paleocene early thanetian of east tethys whereas coral algal assemblages dominated west tethys the appearance of oligotrophic lbfs miscellanids and ranikothalids in the indus basin during latest paleocene late thanetian time is comparable with west tethys and suggests a pan tethyan response to long term early paleogene warming however the response of the shallow marine biota to profound earliest eocene environmental change in east tethys was remarkably different from that apparent in the west the larger foraminifer turnover lft and rapid radiation of typical eocene lbfs e g alveolina nummulites and orbitolites seen in the west does not occur in the east during the earliest eocene a relict late paleocene fauna mainly miscellanids and ranikothalids persisted in east tethys but this shows profound morphological and ecological modifications with palaeo depth ranges compressed to shallower environments the delayed lft in the indus basin indicates the complex response of the shallow marine biota to the earliest eocene climate perturbation in the east india asia collision at the paleocene eocene boundary may have produced local biogeographic barriers increased seasonal runoff and altered oceanic gateways and oceanic circulation delaying the lft later in the early eocene pan tethyan environmental conditions were restored and alveolina and nummulites migrated east

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

reef drowning during the last deglaciation evidence for catastrophic sea level rise and ice sheet collapse elevations and ages of drowned acropora palmata reefs from the caribbean atlantic region document three catastrophic metre scale sea level rise events during the last deglaciation these catastrophic rises were synchronous with 1 collapse of the laurentide and antarctic ice sheets 2 dramatic reorganization of ocean atmosphere circulation and 3 releases of huge volumes of subglacial and proglacial meltwater this correlation suggests that release of stored meltwater periodically destabilized ice sheets causing them to collapse and send huge fleets of icebergs into the atlantic massive inputs of ice not only produced catastrophic sea level rise drowning reefs and destabilizing other ice sheets but also rapidly reduced the elevation of the laurentide ice sheet flipping atmospheric circulation patterns and forcing warm equatorial waters into the frigid north atlantic such dramatic evidence of catastrophic climate and sea level change during deglaciation has potentially disastrous implications for the future especially as the stability of remaining ice sheets such as in west antarctica is in question

rapid cenozoic glaciation of antarctica induced by declining atmospheric co2 the sudden widespread glaciation of antarctica and the associated shift towards colder temperatures at the eocene oligocene boundary 34 million years ago refs 1 4 is one of the most fundamental reorganizations of global climate known in the geologic record the glaciation of antarctica has hitherto been thought to result from the tectonic opening of southern ocean gateways which enabled the formation of the antarctic circumpolar current and the subsequent thermal isolation of the antarctic continent5 here we simulate the glacial inception and early growth of the east antarctic ice sheet using a general circulation model with coupled components for atmosphere ocean ice sheet and sediment and which incorporates palaeogeography greenhouse gas changing orbital parameters and varying ocean heat transport in our model declining cenozoic co2 first leads to the formation of small highly dynamic ice caps on high antarctic plateaux at a later time a co2 threshold is crossed initiating ice sheet height mass balance feedbacks that cause the ice caps to expand rapidly with large orbital variations eventually coalescing into a continental scale east antarctic ice sheet according to our simulation the opening of southern ocean gateways plays a secondary role in this transition relative to co2 concentration

evolution of late oligocene early miocene attached and isolated carbonate platforms in a volcanic ridge context maldives type yadana field offshore myanmar this study investigates the stratigraphic evolution of the late oligocene early miocene carbonate platforms of the yadana area offshore myanmar well data regional 2d and local 3d seismic surveys allow the identification of three shallow water carbonate platforms yadana 3df and 3de showing various morphologic and stratigraphic patterns influenced by the presence of a paleohigh the identification of seven seismic sequences in the yadana area constrains the stratigraphic evolution in three stages 1 development of aggrading attached and isolated platforms during the chattian 2 a period of platform emersion during the oligocene miocene transition 3 drowning of the smaller buildup 3de associated with km scale backstepping on the large platforms 3df and yadana during the aquitanian the aquitanian marks the onset of renewed volcanic activity associated with the development of fringing carbonate reefs during the burdigalian the rapid similar to 6 my development of these wide similar to 5 70 km and thick similar to 300 850 m carbonate platforms has been mainly controlled by the subsidence however the results highlight a strong overprint of eustatic fluctuations on the rates of change in accommodation and hence on the stratigraphic architecture of the carbonate platforms based on an alternative model for the cenozoic geodynamic evolution of the yadana area our results suggest that the platforms developed on a volcanic ridge of hotspot origin located in the indian ocean and not on a volcanic arc subduction jump processes are interpreted to have played a key role in the demise of all platforms by drastically changing the paleoenvironmental conditions during the early miocene and led to the present day location of the yadana ridge in a back arc setting the carbonate platforms from the yadana area are thus a representative example of the interplay between global mechanisms and local paleoenvironmental parameters on carbonate platform initiation growth and demise c 2017 elsevier ltd all rights reserved

calcification generates protons for nutrient and bicarbonate uptake abstract the biosphere s great carbonate deposits from caliche soils to deep sea carbonate oozes precipitate largely as by products of autotrophic nutrient acquisition physiologies protons constitute the critical link calcification generates protons which plants and photosynthetic symbioses use to assimilate bicarbonate and nutrients a calcium atpase based trans mechanism underlies most biological calcification this permits high calcium carbonate supersaturations and rapid carbonate precipitation the competitive advantages of calcification become especially apparent in light and nutrient deficient alkaline environments calcareous plants often dominate the lower euphotic zone in both the benthos and the plankton geographically and seasonally massive calcification concentrates in nutrient deficient environments including alkaline soils coral reefs cyanobacterial mats and coccolithophorid blooms structural and defensive uses for calcareous skeletons are sometimes overrated

the structure of the easter platform houtman abrolhos reefs pleistocene foundations and holocene reef growth abstract seismic reflection profiles have been used to expand an evolutionary model developed from a drilling and dating program of the easter platform one of three shelf edge coral reef platforms on the western margin of australia the houtman abrolhos reefs are surrounded by an open shelf which is mantled by cool water carbonate sediments and exist in a temperate tropical transition zone in conditions which are close to the limits for coral reef development the easter platform has distinct windward and leeward reefs and a lagoon divided by a central platform consisting of several small islands reef limestones of the central platform are calcretised and are last interglacial in age whilst the windward and leeward reefs and associated blue hole and reticulate reef terrains are holocene features seismic investigations indicate that holocene reef growth was strongly asymmetrical about the antecedent last interglacial reef platform the windward reef front is dominated by relict reef morphology and relatively thin ca 9 m or less holocene reefs have recolonised the windward margin of the antecedent platform at the site of the present day windward reef most holocene reef growth took place on the lee side of the antecedent platform and colonised an essentially flat surface at sl 40 m which has been seismically identified as the last interglacial surface up to 40 m of interpreted holocene reef overlies this monotonous surface throughout the leeward reef and associated blue hole and reticulate reef terrains demonstrating that the antecendent surface has had little influence on the processes and morphology of holocene reef construction in addition to the last interglacial reflector three deeper subparallel reflectors at sl 46 m 52 m and 60 m interpreted to represent calcrete horizons are present beneath the leeward lagoon and leeward reef terrains and are traceable to beneath the adjacent shelf surface the unconformity bound sequences so defined are thin 6 8 m and blanket like and are likely to be shelfal equivalents of pre holocene reef buildup phases found within the central platform

holocene growth history of a reef complex on a cool water carbonate margin easter group of the houtman abrolhos eastern indian ocean the houtman abrolhos reefs situated on the western continental margin of australia occupy a transitional position between cool water shelf carbonate sediments to the south and more tropical environments to the north their existence at the outer limits of the geographical range for coral reef growth is a result of the warm poleward flowing leeuwin current though the modern reefs differ ecologically from tropical reefs their geological characteristics have been little known until recently each of the three island groups in the abrolhos consists of a central platform of last interglacial reefs about which windward and leeward holocene reefs have developed asymmetrically in the easter group the subtidal windward reef in the west is ca 10 m thick and is backed by a leeward prograding lagoon sand sheet which is 0 3 m thick the emergent parts of the leeward reefs in the east consist of an upward shallowing sequence comprising reef facies peritidal rudstone facies and coral rubble storm ridges this is underlain by over 26 m of holocene reef facies coring and dating of the holocene reefs using both u th tims and 14 c methods in the easter group has shown significantly different lithofacies in the windward and leeward reefs and has allowed reconstruction of holocene reef growth and sea level history coralline algal bindstones and interbedded coral framestone facies characterise the relatively slow growing windward holocene reefs whereas the fast growing leeward reefs consist of coral framestone facies which are dominated by acropora the leeward reefs commenced growth about 10 000 u th years ago and the morley reef grew to 0 3 m above present sea level by 6400 u th years b p recording a relative high sea level event this generated holocene constructional topography characterised by blue hole terrain windward holocene reef growth commenced after 8200 u th years b p following erosion of the windward part of the last interglacial platform high wave energy and competition with macroalgae limited coral growth and the coralline algal dominated windward reefs grew more slowly to sea level the holocene sea level record provided by dates from the 26 m core of the morley reef a keep up reef is the first such record from the western continental margin of australia

stratigraphic restriction of stromatolites in a middle and upper ordovician foreland platform succession ottawa embayment eastern ontario stromatolites are abundant and widely distributed within two narrow stratigraphic intervals in middle darriwilian and upper lower turinian ordovician strata of the laurentian foreland interior in the ottawa embayment eastern ontario these lithostratigraphic markers coincide with rapid tectonically driven flooding of the foreland interior and may identify an opportunistic microbial response to nutrient loading with shallow peritidal subtidal marine reworking of terrestrial or nutrient rich coastal systems the remaining chatfieldian edenian foreland platform succession represents deeper water deposition in response to elevated subsidence rates along the laurentian margin stromatolites are absent in this higher energy setting but microbial calcite is preserved as coccoid like microencrustations on skeletal debris stromatolites of darriwilian age are dolomitic occur in the carillon formation and are part of a regional 200 km onlap of peritidal sediment during onset of taconic orogenesis

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

heterozoan carbonates in subtropical to tropical settings in the present and past water temperature has received considerable attention as steering factor for the genesis of different types of marine carbonate sediments however parameters other than temperature also strongly influence ecosystems and consequently the carbonate grain associations in the resulting carbonate rock among those factors are biological evolution water energy substrate water chemistry light penetration trophic conditions co2 concentrations and mg ca ratios in the seawater increased nutrient levels in warm water settings for example lead to heterotrophic dominated associations that are characteristic of temperate to cool water carbonates failure to recognize the influence of such environmental factors that shift the grain associations towards heterotrophic communities in low latitudes can lead to misinterpretation of climatic conditions in the past modern analogues of low latitude heterozoan carbonates help to recognize and understand past occurrences of heterozoan warm water carbonates careful analysis of such sediments therefore is required in order to achieve robust reconstructions of past climate

ecological control of sedimentary accommodation evolution from a carbonate ramp to rimmed shelf upper miocene balearic islands abstract stratal patterns and facies architecture develop in response to sediment flux and the available space for sediment accumulation accommodation in siliciclastic systems these two parameters are independent in carbonates however they are highly interdependent 1 sediment input production highly depends on biological systems and consequently on intrabasinal conditions nutrients temperature salinity etc 2 sediment dispersal depends on the production loci and on the interaction between the amount and type of sediment being produced and the hydraulic energy additionally biological processes binding baffling framework construction and even cementation frequently modify it 3 accommodation is not an independent factor with respect to sediment input type efficiency and area of the carbonate factory depend on sea level changes and sea floor morphology the base level for sediment to accumulate accommodation depends on the type and locus of sediment being produced the upper miocene carbonate platforms of the balearic islands illustrate how changes in intrabasinal environmental conditions nutrients and or temperature produce changes in stratal patterns and facies architecture if they affect the biological system during early tortonian carbonate production occurred both in the shallow euphotic zone foramol and in the deeper oligophotic zone rhodalgal originating a distally steepened ramp during late tortonian and early messinian carbonate production mainly occurred in the euphotic zone where framework producing biota coral reefs formed a rimmed platform although deposited under similar conditions of high frequency sea level fluctuations these two types of platforms exhibit different internal facies architecture and distribution of heterogeneities because of differences in base level in carbonates base level for sediment accumulation depends on the type and amount of sediment being produced on the production loci and on the processes controlling sediment dispersal base level for the loose foramol rhodalgal sediment associations of the ramp was controlled by wave and storm base and the associated currents whereas base level for the framework dominated reef complex was sea level furthermore the increase on effective accommodation space to allow the reef rimmed shelf to prograde onto the distally steepened ramp both platforms being depositional sequences resulted from an ecological change rather than significant relative sea level change namely by the shift from grain to framework producing biota the euphotic framework producing biota was able to fill the accommodation space existing between wave and storm base level and sea level that was not previously filled by the loose bioclasts

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

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

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

shallow water marl limestone alternations in the late jurassic of western france cycles storm event deposits or both abstract the contribution of event deposits to various basin fills can be very significant higher than 90 in some cases events may lead to the formation of marl limestone alternations which can also result from cyclic changes in sea level or climate for example the marl limestone alternations of the late jurassic of western france contain abundant coarse grained accumulations that resemble storm deposits described in other western european successions the detailed analysis of facies evolution and hierarchical high frequency stacking pattern of depositional sequences of the phare de chassiron section ile d oleron western france allows the controls on marl limestone formation to be defined this section contains nearshore and shallow marine mud deposits that were exposed to high energy events elementary small and medium scale depositional sequences are defined the stacking pattern and the duration of these sequences suggest an orbital control on sedimentation precession 20 ka cycles notably controlled the formation of elementary sequences that correspond to marl limestone alternations the deposition of marly or carbonate mud occurred in this storm dominated system because of muddy sea beds the gentle slope of the shelf and the great amount of particles in suspension which reduced water energy resulting from storms sediment supply was also sufficient to limit bioturbation and favour the preservation of numerous storm deposits the production of carbonate mud was localised on positive structures and partly controlled by milankovitch scale sea level cycles transport by storms of carbonate mud to the adjacent marly depressions during high carbonate production periods led to the formation of calcareous beds marl limestone alternations in the late jurassic of western france therefore result from the combined effects of cyclic changes in carbonate production and high energy episodic events

corals to rudists an environmentally induced assemblage succession abstract corals and rudist bivalves commonly coexisted on the shallow carbonate platforms of the cretaceous tethyan realm usually the carbonate platforms show lateral and vertical biotic zonations in general the vertical biotic zonation relates directly to a consistent lateral biofacies pattern coral or coral rudist assemblages occupy more open zones of the platform and rudist dominated assemblages the more restricted zones several corresponding coral to rudist assemblage successions in carbonate platforms have previously been widely interpreted as ecological successions we document some coral to rudist assemblage successions in a well preserved upper cretaceous section in the tremp area of the south central pyrenean unit which are interpreted by contrast as environmentally induced faunal replacements a repeated assemblage succession in the eastern part of the section begins with a coral dominated assemblage and passes up gradually to a mixed coral and rudist assemblage that is succeeded by a paucispecific unit of hippuritid elevator congregations the lower coral rudist units of such successions represent relatively more open marine conditions and the uppermost hippuritid unit relatively more restricted marine conditions this assemblage succession was formed in response to a change in the depositional setting caused by sediment accumulation two consecutive coral dominated assemblages overlain by mixed coral and rudist assemblages constitute a second kind of a sedimentary coral to rudist assemblage succession discussed in this paper its regular recurrence makes up the uppermost part of the section in the east the predominance of platy to low domal coral colonies in the lower units suggests that conditions were initially favourable for horizontal coral growth as the habitat changed these coral assemblages were replaced by massive tabular to large domal coral colonies with the large hippuritid vaccinites and were sometimes succeeded in turn by clustered hippuritid elevators the most important factor causing the replacement was probably the increase in sediment flux associated with turbidity this change in the depositional environment eventually favoured the establishment of rudist elevators well adapted to moderate and intermittent to continuous accumulation of sediment

late quaternary structure and development of the northern ningaloo reef australia ningaloo reef situated on the central west coast is australia s largest fringing reef system extending southward from 22 s for over 200 km its narrow lagoon is backed by a coastal plain which is largely composed of an emergent last interglacial reef on the flank of folded tertiary limestones the west facing reef is exposed to strong oceanic swells across a narrow 8 km continental shelf climatic aridity cyclones tsunamis and the poleward flowing leeuwin current all influence the reef system seismic profiling and a coring and dating program along a transect through a reef pass indicate two periods of reef development in the northern part of the reef holocene and last interglacial seaward of the crest the holocene reef forms either a prominent 500 m wide bulge with 10 m of relief and an abrupt seaward slope or a series of discrete patch reefs holocene reef development is limited to depths of less than 30 m and reaches a maximum thickness of ca 10 15 m below the reef crest u th tims dates from distal parts of the last interglacial section between 18 and 36 m give ages toward the end of the high stand 120 115 ka last interglacial reef growth was more extensive of the two filling much of the available accommodation space perhaps as a result of a stronger leeuwin current this substrate subsequently provided an antecedent foundation for holocene reef development

the first microbialite coral mounds in the cenozoic uppermost paleocene from the northern tethys slovenia environmentally triggered phase shifts preceding the petm abstract upper thanetian microbialite coral mounds from the adriatic carbonate platform sw slovenia are described herein for the first time representing an important case study of extensively microbially cemented boundstones in the early paleogene the mounds are constructed primarily by microbialites associated to small sized coral colonies forming metric bioconstructions in a mid ramp setting detailed macroscopic and microscopic studies show that microbes are the major framework builders playing a prominent role in the stabilization and growth of the mounds with corals being the second most important component microbial carbonates represent up to 70 of the mounds forming centimetric thick crusts alternating with coral colonies the microbial nature of the crusts is demonstrated by their growth form and internal microfabrics showing accretionary binding and encrusting growth fabrics often with gravity defying geometries thin sections and polished slabs reveal a broad range of mesofabrics with dense structureless micrite leiolite laminated crusts stromatolites and clotted micritic masses thrombolites a first layer of micro encrusters including leiolites and thrombolites occurs in cryptic habitats whereas discontinuous stromatolites encrust the upper surface of corals a second encrustation the major mound construction phase follows and is dominated by thrombolites encrusting corals and other micro encrusters this sequence represents the basic constructional unit horizontally and vertically interlocked in an irregular pattern to form the mounds the processes which favored the deposition of these microbial carbonates were mainly related to in situ precipitation with minor evidences for grain agglutination and trapping processes scleractinian corals comprise moderately diversified community of small centimetric colonial massive platy encrusting and branching forms coral colonies are distributed uniformly throughout the mounds without developing any ecological zonation these features indicate that coral development remained at the pioneer stage throughout the mound growth the spatial relationships between corals and microbialites as well as the characteristics of microbial crusts and coral colonies indicate a strong ecological competition between corals and microbes a model for the evolution of the trophic structures during the mound growth is proposed with changes in the paleoecology of the main bioconstructors triggered by frequent environmental perturbations turbidity and nutrient pressure interpreted here as related to frequent recurrences of wet phases during the warm humid climate of the uppermost thanetian might have promoted temporary dominance of microbes over corals causing rapid environmentally driven phase shifts in the dominant biota