the apparent paradox of abundant foramol facies in low latitudes their environmental significance and effect on platform development recent studies of low latitude carbonates from se asia and australia have revealed deposits and platform types that do not fit easily into the perceived view of warm water tropical carbonates the sediments are classified as a foramol or foralgal facies and are dominated by non framework building light dependent biota such as perforate larger benthic foraminifera coralline algae and sometimes halimeda although ancient foramol deposits are often interpreted as an indication of non tropical conditions foramol facies have long been known from the tropics yet the environmental conditions in which they form are poorly known the aims of this paper are to evaluate how these deposits are best classified and more importantly whether there are any overriding controls that influence their common development in low latitude areas and if resultant platform development is affected the deposits are all best grouped within the photozoan association james n p 1997 the cool water depositional realm in james n p clarke j a d eds cool water carbonates sepm special publication 56 1 20 an assignment synonymous with warm water conditions the facies were also found to develop in conditions of limited light or oligophoty all the platforms described are characterised by having extensive areas of oligophotic facies generally in water depths extending down from 20 m but sometimes in shallower waters platforms types vary from land attached rimmed shelves homoclinal and distally steepened ramps to isolated banks and platforms but all have extensive moderate to deep photic zone development of oligophotic facies some workers might assign these platforms to the incipiently drowned platform type read j f 1985 carbonate platform facies models american association of petroleum geologists bulletin 69 1 21 however a morphological assignment is preferred here to signify that many of the deposits did not or may not form through drowning limited light in moderate to deeper depths of the photic zone often in regions with a reduced depth euphotic high light zone is seen as key to the extensive development of these deposits and the resultant platforms these conditions are often developed in humid low latitude areas of high terrestrial runoff and therefore regions of reduced water salinity or in areas of nutrient upwelling reduced water clarity due to nutrients plankton blooms suspended particulate matter upwelling and strong currents all promote the development of oligophotic conditions and facies on a regional scale time periods of relative rises in sealevel can also promote oligophotic facies development the findings of this study have broader implications for the development of low latitude platforms beyond australasia and during time periods when non framework building oligophotic biota are dominant sediment contributors the reconstruction of past climatic conditions based on study of foramol grain assemblages requires careful study to distinguish warm water deposits from those formed in cool waters

microstructures and c axis fabrics indicative of quartz dissolution in sheared quartzites and phyllonites abstract quartzites sheared in low metamorphic grade shear zones that extend along the contact with migmatitic gneissic complexes in the quadrilatere ferifero region southeastern brazil show quartz microstructures indicating deformation by dissolution dissolution occurred adjacent to the foliation planes preferentially in quartz porphyroclasts oriented with their 0001 planes parallel to the foliation dissolution worked as an efficient mechanism to remove porphyroclast edges smoothing foliations and enabling strain accommodation both dissolution and crystal plasticity were competitive crystallographically controlled processes operating in different domains of the evolving microstructure dissolution occurred along the foliation planes while isovolume crystal plasticity and accompanying recrystallization operated essentially in the quartzose domains between folia phyllonites formed in the most strained domains of the shear zones fine grained quartz grains in phyllonites show uncommon c axis fabrics c axis oriented at low angles to the stretching lineation which were interpreted to form either by direct reprecipitation or by residual concentration of grains unfavourably orientated to undergo dissolution domainal c axis fabrics reflect a deformation partitioning path with increasing participation of solution transfer strengthening c axis maxima at low angles with the stretching lineation at the expense of crystal plastic processes during progressive phyllonitization

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

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

a facies model for internalites internal wave deposits on a gently sloping carbonate ramp upper jurassic ricla ne spain abstract internal waves are waves that propagate along the pycnocline the interface between two density stratified fluids even though internal waves are ubiquitous in oceans and lakes their impact in the sedimentary record has remained largely unrecognized internal waves can remobilize the sediment from the depth at which the internal waves break onto the sea floor in shelf or ramp settings internal wave deposits internalites have to be distinguished from tempestites while in slope and deeper settings internalites require distinction from turbidites the upper kimmeridgian carbonate ramp succession cropping out near ricla ne spain provides some key evidence to differentiate the depositional processes induced by breaking internal waves from those related to surface storm waves sandy oolitic grainstone eventites previously interpreted as tempestites contain evidence of reworking by turbulent events related to breaking internal waves underlying rationale are 1 they occur in distal mid ramp position detached from the coeval shallow water successions 2 they do not have the characteristic coarsening and thickening upward trend of storm deposits 3 they gradually thin out to disappear both up dip and down dip interbedded with mid ramp lime mudstones and 4 they show little or no erosion towards the shallower areas a facies model for internalites produced by two sediment populations sand and mud on a gently sloping carbonate ramp is proposed the individual internalites occurring at ricla include several architectural elements sequentially organized in dip direction which can be related to the flows associated with breaking internal waves erosion in the breaker zone swash run up and tractive backwash flow individual internalites stack with down and up slope shingling configuration in dm thick packages thought to reflect the up slope and down slope migration of the breaker zone in turn related to depth variations of the palaeo pycnocline packages occur in dm to m thick clusters suggested to reflect changes in sediment supply and or variations in water stratification affecting the energy of internal waves

the ellipsactinia limestones of the marsica area central apennines a reference zonation model for upper jurassic intra tethys reef complexes abstract this study presents a new and innovative distribution model of the main reef builders that thrived on bioconstructed margins of upper jurassic intra tethys platforms the proposed model is based on the zonation of an upper jurassic reef complex presently exposed in the central apennines excellent exposures allow the reconstruction of the reef profile across the platform margin biota are mainly represented by corals and calcified demosponges distributed with different amounts and aggregating structures along the reef complex microencrusters represent a secondary but important component that actively contributes to the reef construction process reef builders are distributed in variable quantities and with variable aggregating structures along the reef complex revealing a strong reef zonation like the biota the sedimentary features grain size sorting and reworking degree bioerosion cement crusts and cavities show a distinctive distribution along the reef complex three main zones have been recognized along the studied reef complex an internal more protected and deeper zone corresponding to a relatively deep back reef lagoon is dominated by corals and chaetetids a central zone reef flat where well preserved coral bioconstructions give rise to a true but discontinuous framework and a more external zone corresponding to the reef crest characterized by the shallowest depths recorded across the reef complex and dominated by stromatopores the latter forms mound shaped structures playing a role essential for the zoned character of the reef complex these structures actively contribute to the construction of a moderately high topographic relief in the reef crest

integrating facies and structural analyses with subsidence history in a jurassic cretaceous intraplatform basin outcome for paleogeography of the panormide southern tethyan margin nw sicily italy abstract we illustrate the tectono sedimentary evolution of a jurassic cretaceous intraplatform basin in a fold and thrust belt present setting cala rossa basin detailed stratigraphy and facies analysis of upper triassic eocene successions outcropping in the palermo mts nw sicily integrated with structural analysis restoration and basin analysis led to recognize and describe into the intraplatform basin the proximal and distal depositional areas respect to the bordered carbonate platform sectors carbonate platform was characterized by a rimmed reef growing with progradational trends towards the basin as suggested by the several reworked shallow water materials interlayered into the deep water succession more the occurrence of thick resedimented breccia levels into the deep water succession suggests the time and the characters of synsedimentary tectonics occurred during the late jurassic the study sections involved in the building processes of the sicilian fold and thrust belt were restored in order to obtain the original width of the cala rossa basin useful to reconstruct the original geometries and opening mechanisms of the basin basin analysis allowed reconstructing the subsidence history of three sectors with different paleobathymetry evidencing the role exerted by tectonics in the evolution of the narrow cala rossa basin in our interpretation a transtensional dextral lower jurassic fault system wnw ese present day oriented has activated a wedge shaped pull apart basin in the frame of the geodynamic evolution of the southern tethyan rifted continental margin the cala rossa basin could have been affected by jurassic transtensional faults related to the lateral westward motion of africa relative to europe

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

origin of the rudstone floatstone beds in the upper jurassic arab d reservoir khurais complex saudi arabia abstract detailed description and analysis of cores from more than 50 wells through the kimmeridgian arab d reservoir arab d member and upper part of the jubaila formation in khurais abu jifan and mazalij oil fields are used to establish a consistent depositional model that represent a shift in the conceptual understanding of the upper jurassic carbonates of saudi arabia the jubaila fm and arab d mb conform to a shallowing upward carbonate evaporite succession in which three main carbonate facies belts occur capped by anhydrite the lower facies belt corresponds to the jubaila formation and consists of a series of eventites triggered by breaking internal waves interbedded peloidal wackestones represents the background sedimentation where neritic lime mud was churned by pellet producing benthonic fauna eventites consist of a lower intraclastic rudstone floatstone interval a middle grainstone packstone interval and an upper barren mudstone interval the middle facies belt is made of microbial coral stromatoporoid buildups the upper facies belt consists of the following shallow water lithofacies with cladocoropsis green algae foraminifers peloids and oolitic grainstones and oolitic cryptomicrobial mudstone to grainstone the stacking patterns of the internalites internal wave deposits in the jubaila fm suggests alternating periods with different internal waves activity namely different strength and bathymetric position of the pycnocline and intermittent production and accumulation of the neritic lime mud this interpretation represents a change to previous interpretations turbidites and tempestites and has important implications in both the perceptions of depositional processes in play and the criteria behind stacking lithofacies into parasequences and sequences

deformation induced silica redistribution in banded iron formation hamersley province australia abstract the formation of banded iron formations bif remains controversial despite their potential to provide key information on precambrian atmospheres and hydrospheres it is widely agreed that bif are chemical sedimentary rocks comprising alternating layers of iron oxides and chert formed from poorly known precursor phases many models address the chemical transformation of such precursor iron oxide phases into bif during compaction and diagenesis however the formation of chert and the influence of physical forces in this process have received less attention microstructural analysis of bif from the hamersley province western australia reveals that significant amounts of silica were redistributed by dissolution precipitation creep during both diagenesis and regional scale deformation this physicochemical process led to silica remobilisation and volume loss by stress induced dissolution of microcrystalline quartz in an aqueous fluid the dissolved solid phase was transported by diffusion and fluid flow along grain boundaries or within available porosity and then reprecipitated in low pressure zones leading to local volume increase these processes were further enhanced by rheological contrasts between different minerals resulting in significant variations of chert band thickness microstructural observations combined with quantitative microfabric analysis reveal domains of crystallographic preferred orientations cpo in quartz grains within chert layers the cpo fabrics record strain regimes e g pure and simple shear extension and shortening that modified quartz aggregates by dissolution precipitation creep providing new insights into the metamorphic and deformation history of bif we document microstructures that indicate that non coaxial deformation was active during diagenesis and subsequent deformation of the hamersley province bif further relatively undeformed chert layers may have been similarly affected by significant amounts of dissolution precipitation creep providing a possible explanation for the destruction of primary features we show that different generations of chert alternate on a micro scale suggesting that the role of deformation has been underestimated in many aspects of bif research the discovery of dissolution precipitation creep in low grade metamorphic bif provides a potential link between the physical and chemical processes that occur within these rocks after deposition in the hamersley province dissolution precipitation creep was active from the compaction or diagenesis stage and probably operated during all major extensional and compressional deformation events we also suggest that chert layers without cpo record the least overprint by diagenesis and as the most pristine form of bif should be targeted for future paleo environmental research

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

the use of syntectonic fibres to determine strain estimates and deformation paths an appraisal abstract fibrous pressure shadows developed adjacent to rigid brittle inclusions are familiar features in many tectonites belief that these structures reflect the deformation path as once adjacent grains move apart has led to the derivation of a variety of techniques to determine both incremental and finite strain estimates these methods which can be divided into rigid fibre models e g durney and ramsay and deformable fibre models e g ellis display potentially serious problems when applied to field examples recent studies of microstructures within veins and pressure shadows support the concept that syntectonic fibre complexes can reflect deformation paths and are therefore useful markers of incremental and finite strain the problems mentioned therefore stem directly from the application of the techniques worked examples using these techniques give a variety of strain values dependent upon the extent to which a particular technique allows for volume change or fibre deformation this is useful locally however if the results are to be meaningful on a regional scale then it is imperative that the same technique be applied in the analysis of all fibres regardless of the local deformation path in such studies the merits of a particular technique in determining a correct strain value come second to allowing the spatial distribution of strain to be determined semi quantitatively and thus allowing comparison of similarly derived results with one another

carbonate systems along nutrient and temperature gradients some sedimentological and geochemical constraints research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems changes in climate ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry including carbonate saturation state and nutrient availability and thereby have determined boundary conditions for the biota that form carbonate platforms in turn the biota determine accumulation rates and facies zonations thus controlling platform geometry and facies dynamics in the first section of this paper we examine how nutrient availability influences carbonate facies associations we first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations then we discuss how carbonate sedimentation can be characterized along nutrient gradients in the second section we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems we highlight the variety of existing proxies and their limitations and suggest that multiple lines of evidence are needed for valid interpretations our short review discusses sedimentological biogenic and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations however it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs nutrient supplies changes and facies in ancient carbonate sequences

fluctuations in the trophic resource continuum a factor in global diversity cycles the trophic resource continuum trc in euphotic zones of the world s oceans is the spectrum of conditions from the richest runoff and upwelling areas to the most nutrient deficient subtropical seas that spectral range has likely varied through geologic history as more efficient phytoplankton taxa evolved as oceanic circulation rates changed and in response to oceanic mixing events reduced rates of oceanic turnover should produce regionally intensified eutrophy and oligotrophy that is trc expansion because oceanic waters as a whole are relatively nutrient rich increased rates of oceanic turnover should prevent extremely eutrophic and extremely oligotrophic conditions from developing causing trc contraction global biotic diversities in the oceans are strongly influenced by communities in oligotrophic environments nutrient deficient waters are more stable and more transparent than richer waters permitting higher degrees of specialization sparse nutrient supplies necessitate smaller phytoplankton and longer more complex food chains preservation potential of oligotrophic biotas is also greater because calcareous taxa are more prevalent and because calcium carbonate is less apt to be bioeroded or dissolved fluctuations in the trc should profoundly affect diversity of habitats within the euphotic zone of the oceans the evolutionary response to a trc expansion diversification would occur in a geologic time frame of millions of years while evolutionary responses to a trc contraction including extinction could occur in a biological time frame of generations a simple model indicates that a reduction in the trophic resource continuum from expansion during a major marine transgression down to modern levels could result in loss of 40 of the euphotic habitats how fluctuations in the trc control diversity of euphotic habitats in the oceans provides an hypothesis by which to interpret global taxonomic diversity cycles as well as taxonomically selective extinctions changes in species dominance and some morphologic trends

fractal vein distributions within a fault fracture mesh in an exhumed accretionary melange chrystalls beach complex new zealand a well developed fault fracture mesh is observed in the chrystalls beach complex an accretionary melange within the otago schist on the south island of new zealand in this study an analysis of vein thicknesses and clustering of veins is presented both shear and extension veins have a power law thickness distribution measures of vein spacing best fit a power law distribution but a small data set limits this interpretation to a small fractal range vein clustering varies from random to moderately clustered between outcrops and is the greatest where a large proportion of relatively competent blocks occurs within the melange fractures are distributed within the melange matrix and this localized deformation requires heterogeneity in rheology and or fluid pressure distribution whereas pervasive distributed deformation occurs in relatively homogeneous rock the overall trend of this deformation being mainly accommodated by thin veins required that new fractures formed preferentially over refracturing existing veins which highlights the distributed nature of deformation within a fault fracture mesh the predominance of new fractures may result from vein material being stronger than the cleaved wall rock such that wall rock failure occurred instead of reopening of pre existing shear and extension veins

oxfordian upper jurassic coral reefs in western europe reef types and conceptual depositional model comparative sedimentology and palaeoecology of oxfordian upper jurassic coral dominated reefs of england france italy and switzerland has been used to 1 identify and characterize different types of late jurassic coral reefs with regard to their litho and biofacies and 2 develop a depositional model for these reefs relating different reef types to each other within a palaeoenvironmental framework eight generic reef types and one associated reef facies are recognized these are i biostromal units dominated by platy microsolenids developed within clean limestone facies ii biostromal units dominated by platy microsolenids developed within marly facies iii reefal thickets dominated by tall dense phaceloid colonies developed within pure carbonate muds iv microbial coral reefs dominated by massive branching ramose and phaceloid colonies v large high diversity reefal units associated with large volumes of bioclastic material vi small species poor reefs developed within mixed carbonate siliciclastic facies vii microbial coral reefs dominated by massive colonies viii reefal thickets dominated by branching ramose colonies with widely spaced branches developed amongst sand shoals and coral debris channels and ix conglomerates rich in rounded coral fragments the reef associated facies the development of these different constructional and compositional reef types is interpreted as being primarily a function of light intensity hydrodynamic energy levels and sediment balance a conceptual depositional model based on these parameters can be used to predict the spatial and temporal distribution of different reefal carbonates and highlight sedimentological and palaeoecological trends in reef development

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

structurally controlled growth of fibrous amphibole in tectonized metagabbro constraints on asbestos concentrations in non serpentinized rocks the nucleation and concentration of asbestos in rocks are mostly associated with mechanisms of fibre formation combined with the water dependent mineralogical alteration produced during the serpentinization of ultramafic masses very little is known about the structural settings and tectonic histories that influence and control the occurrence of asbestos in non serpentinized rocks diffusely embedded within tectonized ophiolitic suites focusing on a case history provided by a tectonized metagabbro from the ligurian alps northern italy a multiscale structural petrographic approach is used to investigate the relationships between rock fabric and fibrous amphibole growth within the metagabbro meso to microstructural observations are used to document the role of structurally controlled fluid rock interactions in localizing the growth of fibrous amphibole during ductile to brittle shearing mylonitic foliation to shear veins a qualitative structural scenario is provided to illustrate the growth of asbestos amphiboles in shear veins during the progression of shear deformation towards semi brittle rheological conditions the mechanisms of the structurally controlled growth of fibrous amphibole in non serpentinized rocks imply an examination of the tectonic boundary conditions that are at the origin of the concentration of asbestos in ophiolitic rocks involved in orogenic belt construction

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

sedimentation rates and growth potential of tropical cool water and mud mound carbonate systems carbonate fixation in the ocean proceeds in three basic modes abiotically biotically induced with organic trigger and biotically controlled where organisms determine timing location and composition of the product the three modes combine in a variety of ways to produce carbonate sediment when viewed on the scale of formations and global facies belts three benthic carbonate production systems or factories emerge 1 the tropical shallow water system dominated by biotically controlled mainly photoautotrophic and abiotic precipitates 2 the cool water system dominated by biotically controlled mainly heterotrophic precipitates and 3 the mud mound system dominated by abiotic and biotically induced mainly microbial precipitates the sedimentation rates of all three factories decrease as the time span of observation increases this scaling trend is not just an artifact of ratio correlation it is almost certainly related to the episodic pulsating nature of sedimentation the growth potential of the three systems can be estimated by drawing the envelope of the maximum observed rates of aggradation the tropical system shows the highest rates 10

computer simulation of reef growth light is one of the major controls on reef growth and carbonate production the growth of present reef builders depends largely upon the amount of light available for photosynthesis as light decreases with water depth so does reef growth the computer model presented extends this principle by combining two functions one for photosynthesis and the other for the extinction of light in water the model is used to simulate the growth of alacran reef mexico two reefs of the great barrier reef and the reefs of the windward platform of st croix us virgin islands the model also gives an accurate simulation of the growth of fore reef walls in belize in agreement with the accretion hypothesis developed for this feature

dinosaurs re write the geodynamics of the eastern mediterranean and the paleogeography of the apulia platform abstract evidence of a sizeable population of large dinosaurs on the apulia carbonate platform calls for a revision of the current paleotectonic and paleogeographic scenario of the eastern mediterranean area a review of geophysical and geological data of the ionian sea and surrounding areas leads to envisage the late jurassic early cretaceous ionian sea region as a cul de sac type basin enclosed by shallow water carbonate banks connecting the apulia carbonate platform to peloponnesus northern cyrenaica cyrene seamount and medina ridge these banks were repeatedly and periodically exposed to subaerial conditions and offered vast land areas for migration of dinosaurs as regards the nature of the mesozoic ionian basin interpretations are quite controversial the continental vs oceanic crust debate will likely be solved only when the ionian basin crust will be reached by drilling the conclusion of the present review leads to consider adria as a true african promontory and the apulia platform as a sort of florida peninsula attached to north africa cyrenaica spur subdividing the oceanic mesozoic mediterranean into a western ionian basin and an eastern levantine basin

extensional failure and hydraulic valving at minas da panasqueira portugal evidence from vein spatial distributions displacements and geometries abstract at panasqueira portugal exceptional exposure and demonstrable vein connectivity allow robust characterisation of brittle elastic failure mechanisms in intrusive related environments extensional failure was driven by cycles of fluid injection hydraulic valving and vein growth under conditions with v 1 and differential stress

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

transport by breaking internal gravity waves on slopes we use the results of a direct numerical simulation dns with a particle tracking model to investigate three dimensional transport by breaking internal gravity waves on slopes onshore transport occurs within an upslope surge of dense fluid after breaking offshore transport occurs due to an intrusion of mixed fluid that propagates offshore and resembles an intermediate nepheloid layer inl entrainment of particles into the inl is related to irreversible mixing of the density field during wave breaking maximum onshore and offshore transport are calculated as a function of initial particle position and can be of the order of the initial wave length scale for particles initialized within the breaking region an effective cross shore dispersion coefficient is also calculated and is roughly three orders of magnitude larger than the molecular diffusivity within the breaking region particles are transported laterally due to turbulence that develops during wave breaking and this lateral spreading is quantified with a lateral turbulent diffusivity lateral turbulent diffusivity values calculated using particles are elevated by more than one order of magnitude above the molecular diffusivity and are shown to agree well with turbulent diffusivities estimated using a generic length scale turbulence closure model based on a favourable comparison of dns results with those of a similar two dimensional case we use two dimensional simulations to extend our cross shore transport results to additional wave amplitude and bathymetric slope conditions

rheology of the plate interface dissolution precipitation creep in high pressure metamorphic rocks abstract subduction zone models invoke deformation to be concentrated along the plate interface in a region of particularly low temperature geophysical observations do not provide constraints on temperature stress and deformation patterns with desired resolution in contrast the record of high pressure metamorphic rocks exhumed from subduction zones provides details on p t history deformation mechanisms and stress state albeit not readily correlated with the former dynamic situation on larger scale here we review available information on dissolution precipitation creep dpc in high pressure metamorphic rocks which if representative for subduction zones in general can pose constraints on conditions rheology and flow patterns along the plate interface the key observations and conclusions are that 1 deformation is typically highly inhomogeneous and localized into shear zones 2 stresses are generally too low to drive crystal plastic deformation 3 microfabrics suggest dissolution precipitation creep to be the predominant deformation mechanism 4 an aqueous fluid at quasi lithostatic pressure is available throughout allowing for tensile fracturing and crack healing or sealing 5 low stress combined with high strain rates required for localized deformation at typical subduction rates implies low viscosity and 6 contribution of shear heating to the thermal budget of subduction zones should be moderate the dominant deformation mechanism dpc is reviewed in some detail including experimental and theoretical approaches various examples of dpc in high pressure metamorphic rocks are illustrated emphasizing the role of interphase boundaries as sites of dissolution rheology governed by dpc is proposed to control interplate coupling and development of a subduction channel with return flow being a likely candidate for rapid exhumation of high pressure metamorphic rocks

paleoclimatic control of biogeographic and sedimentary events in tethyan and peri tethyan areas during the oxfordian late jurassic abstract the paleobiogeographical distribution of oxfordian ammonites and coral reefs in northern and central europe the mediterranean area north and east africa and the middle east and central asia is compared with the distribution in time and space of the most important lithofacies interest in the oxfordian is focused on changes in facies and in biogeographical patterns that can be interpreted as the results of climatic events paleotemperature trends inferred from oxygen isotopes and paleoclimatic simulations are tested against fossil and facies data a late callovian early oxfordian crisis in carbonate production is indicated by the widespread absence of lower oxfordian reefal formations there is a gap hiatus in deposition on epicontinental platforms with middle oxfordian deposits resting paraconformably on upper callovian while shales accumulated in adjacent intracratonic basins simultaneously in mediterranean tethys radiolarites accumulated in deep troughs while rosso ammonitico facies formed on pelagic swells however deposition on swells was also discontinuous with numerous gaps hiatuses and sequences that are much reduced in thickness middle callovian deposits are generally overlain by middle oxfordian limestones the dearth of carbonates is consistent with a cooling event lasting about 1 my by the middle oxfordian a warming leading to greenhouse type conditions is suggested on the basis of both biogeographical mostly coral reef distribution and geochemical data carbonates spread onto an extensive european platform while radiolarites reached a maximum development in the mediterranean tethys two distinct latitudinal belts with seemingly different accumulation regimes are therefore inferred similar latitudinal belts were also present in the late oxfordian when carbonates were widespread the distribution of reefal facies in the late oxfordian early kimmeridgian fits relatively well with gcms simulations that imply low rainfall in the tethyan mediterranean area and slightly higher precipitation in central and northern europe local salinity variations reflecting more arid or humid conditions may bias the paleotemperature signal inferred from 18o values biogeographical and facies distributions combined with 18o values unravel the ambiguity and support a late callovian early oxfordian cooling followed by warming in the later oxfordian

the stratigraphic and structural setting of the mt lyell volcanic hosted sulfide deposits volcanic hosted sulfide deposits at mt lyell are confined to a complex silicic volcanic unit mine sequence which is up to 800 m thick and includes laterally impersistent lavas ash flow and ash fall deposits as well as abundant open framework volcanic mass flow breccias pervasive hydrothermal alteration involving na depletion is associated with the sulfide mineralization and persists with minor disseminated pyrite mineralization over a strike length of 8 km within the mine sequence stratigraphic relations together with lithofacies and thickness variations in volcanic units suggest that the sulfide mineralization and hydrothermal alteration occurred at a major eruptive center and that ore deposition occurred over an extended time interval during the accumulation of the mine sequence two orientation groups of middle devonian folds are present in the area first generation d 1 folds are closed to tight and upright north northwest trending structures which largely control the distribution and orientation of rock units in the volcanic sequence but have not been associated with significant microstructural modification of the ores or host rocks open west to west northwest trending upright second generation d 2 folds are well developed in sedimentary sequences overlying the volcanic sequence but are poorly developed in the volcanic sequence itself d 2 strain has been accommodated in the volcanic sequence largely by the development of a mesoscopically penetrative west to west northwest trending upright foliation s 2 and associated downdip lineation l 2 shortenings of up to 60 percent perpendicular to s 2 and elongations of up to 150 percent parallel to l 2 have modified primary sulfide microstructures and are responsible for many of the sulfide deposits in the area being elongate in the l 2 direction

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

genesis of natural hydraulic fractures as an indicator of basin inversion abstract satin spar fibrous gypsum veins which occur in evaporite basins worldwide provide significant insights into host rock deformation and fluid flow although the genetic mechanism remains obscure satin spar veins in the red marls of the triassic mercia mudstone of the bristol channel basin were characterized in the context of regional and local setting the vein network in the keuper marl lower mercia exhibits a lack of systematic cross cutting between three distinct vein sets two sets of veins are observed in the overlying tea green marl with one set clearly crossing the other the gypsum veins commonly contain a blocky median zone of multiple thin bands of host rock inclusions and alabastrine gypsum crystals exhibiting crack seal patterns fibrous zones on either side of the median zone consist of pure parallel aligned gypsum fibres that are oblique to vein walls indicating a hybrid shear extensional mode of vein widening veins developed within reverse reactivated faults contain fibre lineations in the median zones and also on vein surfaces suggesting a minimum of two phases of fault slip the veins are interpreted to have formed as a result of overpressure in the low permeability mudstones by tectonic compression during basin inversion giving rise to the median zone growth of gypsum fibres commenced when the initial fractures were completely sealed the timing of vein formation is suggested to be miocene based on cross cutting relationships with folds formed during the latest phase of basin inversion because the fractures initiated in response to fluid overpressures they provide a useful analog to subsurface hydraulic fracture systems in low permeability rocks subjected to tectonic compression the fibrous widening of the veins post dates their initiation and led to continued propagation and increased connectivity

the apulia carbonate platform gargano promontory italy upper jurassic eocene the upper jurassic to eocene carbonate rocks of the gargano promontory belong to the apulia carbonate platform acp and provide a spectacular and complete succession of slope and base of slope resedimented gravity flow carbonates with preserved reservoir properties and with its coeval carbonate platform displaying various tectonostratigraphic architectures the acp margin is characterized by an overall aggrading architecture and different geometric and depositional features facies types and sedimentary dynamics of the carbonate slope and gravity deposits can be analyzed with respect to the stratigraphic architecture of the platform to basin transition these outcrops are the only analogs of some important oil reservoirs and plays present in the equivalent slope to basin succession in the adriatic offshore and elsewhere

reef building and carbonate production modes in the west central tethys during the cenozoic abstract changing components rock textures lithofacies platform types and architecture throughout time are unique characteristics of carbonate rocks characterizing these attributes has been approached by 1 building reference models for specific phanerozoic intervals 2 recognizing the climatic impact in modulating carbonate production and 3 analyzing the influence of changing bio geochemical conditions the reference model approach is mostly based on biological evolution the climatic impact approach emphasizes temperature and the bio geochemical approach considers the changes in mg ca ratios and ca concentrations in the oceans to date however an analysis integrating all of these factors is still missing the analysis presented here includes all these factors but also co 2 which is fundamental for both photosynthesis and caco 3 precipitation here we analyze the waxing and waning of cenozoic reef limestones from the central tethys region through several steps 1 on the basis of rock volume rock textures associated sediments and light dependent skeletal components as records of light penetration and wave energy depth 2 on global environmental conditions 13 c 18 o p co 2 temperature and 3 on the basis of functionality nutritional requirements and available resources through the cenozoic water motion whether induced by surface or internal waves or by currents increased as the thermal gradients strengthened both with depth and with latitude active water motion is essential for plankton catchers such as corals but less so for many larger benthic foraminifers lbf pycnoclines in the meso oligophotic zone would then favor the benthic plankton catchers such as corals but would be detrimental for many lbf warm temperatures favored lbf the eocene lbf families predominated during lowering of atmospheric p co 2 by using respiratory co 2 to enhance the symbiont production of photosynthates under oligotrophic conditions and limited turbulence whereas the miocene families had to adapt to a progressive increase in turbulence the eurythermal coralline red algae however became preponderant producers in the mesophotic zone during times when the 13 c was relatively high this explains two apparent paradoxes 1 corals thrive best when the earth s high latitudes cool and 2 the dominance of corals and lbf is inversely correlated despite they both require tropical conditions and have similar trophic strategies mixotrophy

the upper cretaceous carbonates of the gargano murge region southern italy a model of platform to basin transition the outcrops in gargano murge region are good examples of the upper cretaceous carbonate systems of the peri adriatic area they enable the architecture and the processes of the platform to basin transition to be studied in detail the platform carbonates are juxtaposed to the deeper marine carbonates by the intermediary of a faulted scarp the base of slope is characterized by bioclastic and conglomeratic aprons interbedded with pelagic mudstones the outer shelf domain which was the prolific source of rudistid bioclastic aprons is not preserved the platform is mainly built of mud dominated transgressive systems tracts whereas highstand systems tracts are developed as bioclastic base of slope aprons the volume of the resedimented bioclasts largely exceeds the volume of missing outer shelf indicating that carbonate production and sediment bypass are more critical for this stratigraphic response than carbonate erosion the lowstands which were controlled by tectonic deformations are characterized by base of slope breccia and blocks eroded from the shelf edge this erosion resulted in the progressive retreat of the shelf edge the best potentials for hydrocarbon reservoir are found in the bioclastic base of slope aprons formed during the cenomanian and maastrichtian highstands this model is considered as an analog for the hydrocarbon reservoirs formed by the deep marine deposits of cretaceous tamabra limestone in the gulf of mexico

upper jurassic microsolenid biostromes of northern and central europe facies and depositional environment abstract microsolenid biostromes are a common and important reef type in many upper jurassic reefal sections comparative study of these biostromes in western europe allows the characterisation of this distinct biostrome type in terms of its taxonomic composition palaeoecology and sedimentary regime the biostromes are characterised by a coral community of relatively low generic diversity being dominated by the microsolenidae family of corals the coral skeletal biovolume is generally high and is overwhelmingly dominated by platy ecomorphotypes sedimentologically these biostromes developed in low energy marl and limestone regimes which were subject to low sedimentation rates and varying degrees of siliciclastic influx in contrast to the coral fauna the associated fauna shows a high generic diversity in particular a rich assemblage of echinoids and bivalves in addition the coral plates provide an ideal habitat for a well developed and strongly polarised encrusting and boring fauna top surfaces show limited post mortem encrustation by serpulids and cementing bivalves and are also bored by lithophagan bivalves the undersides of the plates show a highly developed and diverse cryptic fauna of serpulids thecidean brachiopods bryozoans calcareous sponges and sclerosponges it is concluded that the main control on the development of these biostromes was low light intensities though low energy level and low background sedimentation rates were also important it is suggested that relatively high nutrient levels may have also played a significant role the conditions for microsolenid biostrome development prevail in relatively deep water environments and hence these are the first coral dominated reefal structures to have developed in deeper water shallowing upward sequences the corals in these biostromes have adapted to these conditions by developing a strongly platy growth form but also reducing their growth rates substantially the microsolenids are particularly adapted to these environments in two ways 1 they secreted an extremely porous calcium carbonate skeleton which in environments where calcification rates are slow such as deep water environments is a distinct advantage 2 in response to the limited potential of phototrophy in these environments the microsolenids have developed a pennular septal structure which is suggested to be a means of improving heterotrophic feeding trophic analysis of the reef fauna reveals that the nutrient limitation model developed for present day coral reefs cannot be applied to these biostromes it is demonstrated that the microsolena and the present day agariciid leptoseris show a number of significant morphological and ecological similarities

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

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

regional implications of heat flow of the snake river plain northwestern united states abstract the snake river plain is a major topographic feature of the northwestern united states it marks the track of an upper mantle and crustal melting event that propagated across the area from southwest to northeast at a velocity of about 3 5 cm yr the melting event has the same energetics as a large oceanic hotspot or plume and so the area is the continental analog of an oceanic hotspot track such as the hawaiian island emperor seamount chain thus the unique features of the area reflect the response of a continental lithosphere to a very energetic hotspot the crust is extensively modified by basalt magma emplacement into the crust and by the resulting massive rhyolite volcanism from melted crustal material presently occurring at yellowstone national park the volcanism is associated with little crustal extension heat flow values are high along the margins of the eastern and western snake river plains and there is abundant evidence for low grade geothermal resources associated with regional groundwater systems the regional heat flow pattern in the western snake river plains reflects the influence of crustal scale thermal refraction associated with the large sedimentary basin that has formed there heat flow values in shallow holes in the eastern snake river plains are low due to the snake river plains aquifer an extensive basalt aquifer where water flow rates approach 1 km yr below the aquifer conductive heat flow values are about 100 mw m 2 deep holes in the region suggest a systematic eastward increase in heat flow in the snake river plains from about 75 90 mw m 2 to 90 110 mw m 2 temperatures in the upper crust do not behave similarly because the thermal conductivity of the plio pleistocene sedimentary rocks in the west is lower than that in the volcanic rocks characteristic of the eastern snake river plains extremely high heat loss values averaging 2500 mw m 2 and upper crustal temperatures are characteristic of the yellowstone caldera

the shifting biogeography of reef corals during the oxfordian late jurassic a climatic control until recently the jurassic was thought to have been a period characterised by a predominantly warm and equable climate during the oxfordian a time span of six million years in the late jurassic the distribution of tropical coral reefs was limited to about 35 n and near to 25 s however in middle oxfordian time coral reefs were abundant only at higher latitudes and almost entirely missing near the equator during that time the area of maximum reef development had shifted poleward to a belt lying between 20 n and 35 n leaving hardly any coral formations at the lower inner tropical latitudes after demise towards the end of middle oxfordian time the low latitude reefs recovered during the late oxfordian accompanied by a southward migration of reef corals in the northern hemisphere as suggested by stable isotope and palynological data the faunal migration can be correlated with a significant rise in seawater temperature during the middle oxfordian

long term event stratigraphy of the apulia platform margin upper jurassic to eocene gargano southern italy abstract the upper jurassic to eocene apulia platform margin and the eastward transition to the adjacent basinal deposits are well exposed in the gargano promontory southern italy a carbonate block that is part of the slightly deformed foreland of the southern apennine thrust belt the long term stratigraphy of this margin and slope transect is punctuated by five major dynamic phenomena that subdivide the succession into six second order sequences these events include 1 a valanginian drowning unconformity 2 an early aptian albian drowning and demise of the platform 3 late albian cenomanian platform margin failures 4 a santonian campanian retreat of the platform margin and 5 eocene uplift and platform margin collapse the first event is documented worldwide and is probably eustatic in origin the second is concomitant with some oceanic anoxic events oae the last three processes are probably related to foreland reaction to subduction and collision in the dinarides and hellenides thrust belts the ultimate cause of the albian cenomanian failures is more problematic a worldwide eustatic regression is documented at this time but regional geology seems to favor tectonic uplift

heterozoan carbonates when where and why a synthesis on parameters controlling carbonate production and occurrences abstract in modern and phanerozoic times heterozoan carbonates group a large array of depositional environments from the poles to the tropics this global assessment reviews the critical parameters and controlling factors of heterozoan carbonates i stratigraphic and global distributional trends ii oceanographic and trophic relationships and iii biological and sedimentary processes well documented case studies n 129 have been investigated when facies and stratigraphic attributes were available and when environmental settings such as oceanography climate and paleogeography were clearly identified these case studies occur during specific periods of time in the sedimentary record e g late ordovician early carboniferous early permian and neogene while they are absent during others e g triassic and jurassic periods during greenhouse to icehouse transitions and those with active thermohaline circulation are particularly conducive for heterozoan carbonates based on global oceanographic patterns and existing ecological and hydrodynamic regime classifications hallock 2001 pedley and carannante 2006 james and jones 2015 a process based classification scheme is proposed that distinguishes two main heterozoan carbonate systems i a highly productive system characterized by suspension feeding biota and ii an oligo mesotrophic warm temperate system characterized by red algal and seagrass derived biota eight depositional models are proposed that combine i the source of energy for metabolic activities that allow the carbonate producing biota to thrive and ii hydrodynamics and physiography of the depositional system that control the sediment accumulation the local and platform scale based profiles can be used to complement the facies approach of james and jones 2015

ecological controls on devonian stromatoporoid dominated and coral dominated reef growth in the mackenzie basin northwest territories canada the horn plateau formation composed of isolated reefs is part of the devonian strata that formed in the mackenzie basin in the northwest territories canada the reefs stretch over a 350 m north

microfacies diagenesis and oil emplacement of the upper jurassic arab d carbonate reservoir in an oil field in central saudi arabia khurais complex abstract the upper jurassic kimmeridgian arab d reservoir of the arab formation in the arabian peninsula is considered to be the largest hydrocarbon carbonate reservoir in the world despite a relative large number of studies dealing with lithofacies and depositional sequences there are still few studies dealing with diagenesis of this supergiant reservoir in this study petrographic cathodoluminescence and ultra violet light fluorescence microscopy analyses of the arab d reservoir in an oil field of saudi arabia khurais complex have been combined with isotope geochemistry 13c 18o and 87sr 86sr to decipher the sequence of diagenetic events affecting the reservoir before and during oil emplacements and the impact of depositional mineralogies and their modifications during the diagenesis on the reservoir quality and heterogeneity all the analyzed samples correspond to lithofacies that can be ascribed to nine microfacies types mft 1 to mft 9 three stages of carbonate dissolution d1 to d3 four stages of calcite cements c1 to c4 and 5 zones of replacive dolomite and dolomite cement d1 to d5 have been documented from diagenetic environments ranging from marine to late burial abundant oil fluid inclusions have been recognized in calcite c3 and c4 and dolomite d5 from wells located in the flanks of the structure group 2 of cements cements from wells located in the center of the structure are largely oil inclusions free group 1 of cements this distribution suggests that group 2 of cements formed within the oil water transition zone of the reservoir during the oil infilling of the structure allowing to constrain the timing of oil emplacement and suggesting at least two phases of oil charging porosity enhancement by corrosive dissolution d3 occurred during late burial and took place just before precipitation of dolomite d5 and calcite c4 and just before the second stage of hydrocarbon arrival suggesting the presence of aggressive fluids preceding the late phase of hydrocarbon migration cross plot of carbon vs oxygen stable isotopes shows a general trend toward decreasing 18o values with increasing burial depth whereas all 13c values remain positive except for group 2 of c3 and c4 calcites which exhibit negative up to 4 6 13c values the later suggest precipitation from pore waters with increased volumes of 12c as a by product of hydrocarbon maturation except for c4 all the 87sr 86sr values are within the range of the late jurassic seawater suggesting precipitation from jurassic marine or evolved marine pore waters in contrast the more radiogenic calcite c4 suggests a source from fluids that interacted with siliciclastics or clay rich sequences depositional mineralogy of the grainy lithofacies is interpreted to have had an impact on the effectiveness of cementation and dissolution controlling the reservoir heterogeneity due to excess of cementation reservoir quality is worse in grainstone microfacies rich in aragonitic components and better in grainstone and packstone microfacies poorer in aragonitic grains but affected by late dissolution of micrite the integration of all these data resulted in a more precise understanding of the reservoir quality and heterogeneity

microbialite morphology structure and growth a model of the upper jurassic reefs of the chay peninsula western france abstract during the early kimmeridgian the northern margin of the aquitaine basin western france is characterised by a significant development of coral reefs the reef formation of the chay peninsula comprises two main reefal units in which the microbial structures can contribute up to 70 of framework the microbial crusts which played an important role in the stabilisation and growth of the reef body show the characteristic clotted aspect of thrombolitic microbialites corals are the main skeletal components of the build ups the bioconstructions of the chay area are thus classified as coral thrombolite reefs four main morpho structural types of microbial crusts are distinguished 1 pseudostalactitic microbialites on the roof of intra reef palaeocaves 2 mamillated microbialites found either on the undersides or on the flanks of the bioherms 3 reticular microbialites in marginal parts of the reefs and between adjacent bioconstructed units and 4 interstitial microbialites in voids of bioclastic deposits thrombolitic crusts developed on various substrates such as corals bivalves or bioclasts the thrombolites formed a dense clotted and or micropeloidal microbial framework in which macro and micro encrusters also occur variations in accumulation rate strongly influenced the reef morphology in particular its relief above the sediment surface the coalescence of the coral microbialite patches created numerous intra reef cavities of metre scale dimensions the direction of microbial growth which defined the macroscopic microbialite forms strongly depended on the position within the reef framework but was also controlled by water energy accumulation rate and light availability

mica beards in three slates morphology formation and bearing on the strain history beards are intergrowths of mica chlorite and quartz or feldspar on detrital grains in weakly metamorphosed sedimentary rocks the three samples studied contain beards of mica and quartz or feldspar their internal morphology shows a variation in mica orientation related to the external foliation matrix formation occurred during foliation development with a syntaxial growth history in three dimensions the beards have oblate shapes so that they are present in all planes cut parallel to the shortening direction this indicates flattening strain conditions around the detrital grains during the beard formation

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

crack seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstructures abstract an analysis of crack seal fibre growth mechanisms has shown two important implications of the crack seal process for the interpretation of microstructures in low grade metamorphic rocks 1 1 the ability of fibre growth to track the incremental separation history of crack walls depends on details of the nucleation and growth mechanisms 2 2 fibrous crystals may develop cristallographic preferred orientations in certain crack seal situations the microstructures of layer silicates and associated phases developed in several examples of syntectonic intragranular microfracture sites and veins indicates that layer silicate 001 and grain shape preferred orientation can develop during crack seal deformation by oriented growth mechanisms during successive crack seal increments preferred orientation may develop in response to an interaction between anisotropic growth kinetics and the displacement history resulting in preferential rejoining by syntaxial overgrowth of pulled apart grains having fast growth directions parallel to the incremental displacement direction across a microcrack preferred orientation may also be developed and enhanced in crack seal growth sites by overgrowth of previously oriented layer silicates in the microcrack walls in this case the crystallographic preferred orientation need not be simply related to the displacement history during crack seal fibre growth since crack seal processes may operate on all scales down to the minimum size of a microfracture in a deforming rock such mechanisms of layer silicate preferred orientation development are expected to be very significant in developing and enhancing foliation during deformation involving microfracture and solution transfer processes

the initiation and development of metamorphic foliation in the otago schist part 1 competitive oriented growth of white mica the 3d shape size and orientation data for white mica grains sampled along two transects of increasing metamorphic grade in the otago schist new zealand reveal that metamorphic foliation as defined by mica shape preferred orientation spo developed rapidly at sub greenschist facies conditions early in the deformation history the onset of penetrative strain metamorphism is marked by the rapid elimination of poorly oriented large clastic mica in favour of numerous new smaller grains of contrasting composition higher aspect ratios and a strong preferred orientation the metamorphic mica is blade shaped with long axes defining the linear aspect of the foliation and intermediate axes a partial girdle about the lineation once initiated foliation progressively intensified by an increase in the aspect ratio size and alignment of grains although highest grade samples within the chlorite zone record a decrease in aspect ratio and reduction in spo strength despite continued increase in grain size these trends are interpreted in terms of progressive competitive anisotropic growth of blade shaped grains so that the fastest growth directions and blade lengths tend to parallel the extension direction during deformation the competitive nature of mica growth is indicated by the progressive increase in size and resultant decrease in number of metamorphic mica with increasing grade from c 1000 relatively small mica grains per square millimetre of thin section at lower grades to c 100 relatively large grains per square millimetre in higher grade samples reversal of spo intensity and grain aspect ratio trends in higher grade samples may reflect a reduction in the strain rate or reduction in the deviatoric component of the stress field

microcracks in rocks a review abstract in the past decade the number of studies about microcracks in rocks has rapidly increased this review of recent work concentrates on microcracks in rock as separate entities emphasizing microcrack morphogenesis kinematics dynamics population statistics and observational techniques cracks are produced when the local stress exceeds the local strength the local stress may be augmented by twin lamellae interactions kink bands and deformation lamellae stress concentrations at grain boundary contacts and around intracrystalline cavities local strength may be reduced along cleavage planes along grain boundaries and along any internal surface as a result of corrosion by chemically active fluids dislocations appear not to be a significant factor for crack nucleation below about 500 c in silicates spatial and temporal changes in temperature can also induce microcracking as a result of differential thermal expansion between grains with different thermoelastic moduli and thermal conductivities the amount of quartz in the rock has a significant effect on thermally induced microcracks because of its large and variable thermal expansivity the application of hydrostatic pressure between 100 and 200 mpa effectively closes most cracks but the closure may not be uniform if crack wall asperities exist hydrostatic pressure appears to stabilize cracks and make crack growth more difficult the number and average size of mechanically induced microcracks is greater in rock deformed at higher pressures the application of a deviatoric stress field on the boundaries of a rock mass results on a microscopic scale in a very complex stress system which greatly affects nucleation and propagation paths the relative amount of intragranular and intergranular cracking appears to depend upon mineralogy rock type and stress state the vast majority of stress induced microcracks in rocks appear to be extensional statistically they are predominantly oriented within 30 of the macroscopic maximum stress direction crack densities increase as macroscopic deviatoric stress increases above a threshold level crack size distributions may be either lognormal or exponential fracture in rock under compressive boundary loads is a result of the coalescence of many microcracks not the growth of a single crack some crack configurations are more favorable for coalescence than others as deviatoric stress increases and rock failure is approached the microcrack population changes spatially from random to locally intense zones of cracking away from the fault the crack density dies off rapidly to the background level a few grains away under lesser deviatoric stresses slow subcritical microcrack growth can occur as a result of stress aided corrosion at the crack tip the rate governing mechanism may be either the chemical reaction rate or the rate at which water can get to the crack tip important details still remain to be worked out