abundant sr rich aragonite in eastern mediterranean sapropel s1 diagenetic vs detrital biogenic origin caco3 contents in eastern mediterranean sapropels are generally lower than in the enclosing marl sediments in sediments of a transect from 650 to 2100 m water depth at the sirte continental slope the opposite feature was observed although the increased sr ca ratios observed in these sediments agree with such feature observed in other eastern mediterranean s1 sediments their absolute magnitude is much higher the enhanced sr ca ratio in these sediments is associated with their aragonite content which for the sirte transect reaches levels of up to 40 wt the aragonite content and sr ca ratios in the s1 sediments of this transect decrease with increasing water depth and decrease with distance to the african coast for all eastern mediterranean cores in view of the lack of a coherent relationship with sedimentary reduced sulphur contents and porosity and considering the major amount of aragonite found specifically in the sediments of the sirte transect authigenic precipitation can contribute only a limited fraction at most sem observation and electron microprobe analyses showed that the needles and needle clusters are morphologically aragonite contain the highest sr ca ratio and are similar to skeleton fragments of the green alga halimeda consequently a detrital biogenic source is the likely mechanism for the major part of the aragonite enrichments found in s1 sediments possibly offshore directed surface water flows related to wind stress and or enhanced run off consistent with enhanced precipitation during sapropel s1 may have assisted in the transport of near coastal aragonitic organisms to more coast remote areas

an ichnological model for a deltaic depositional system new insights from the neogene siwalik foreland basin of darjeeling sikkim himalaya abstract trace fossils being almost always in situ yield information about the organism s behaviour in response to its ambient environment largely controlled by the hydrodynamic conditions salinity and bathymetry the neogene siwalik succession exposed in the tista valley the southern part of the darjeeling sikkim himalaya contains fifteen ichnogenera sporadically distributed generally in suites of low abundance although at places the bioturbation index is high three major ichnofacies namely scoyenia skolithos and cruziana have been recognised based on the association of different kinds of ichnogenera preserved in dominantly wave reworked delta front open marine bay fill and prodelta deposits the overall characters of the siwalik trace fossils are i low diversity ii low abundance iii diminutive size iv paucity of suspension feeding structures v co occurrence of both vertical and horizontal trace fossils and vi predominance of simple structures formed by trophic generalists a predominance of drifted plant litter synsedimentary deformation structures hyperpycnites and rare structures of suspension feeding organisms is consistent with a deltaic depositional environment the overall diminutive size of trace fossils their low diversities and low abundances are attributed to a stressful environment caused by freshwater influx these characteristics of siwalik ichnogenera probably mark the distinctions likely to be observed between trace fossils of deltaic and non deltaic shoreline deposits it thus appears that the riverine discharge during floods followed by post flood recovery of normal marine conditions might have been a key controlling factor in shaping the ichnological characteristics in the river wave interactive deltaic system of the siwalik sea the findings of ichnogenera typical of marine affinity unequivocally establishes a marine deltaic depositional environment negates the exclusively continent interior alluvial fan fluvial interpretation for this succession of earlier workers

simulating reef response to sea level rise at lizard island a geospatial approach abstract sea level rise will result in changes in water depth over coral reefs which will influence reef platform growth as a result of carbonate production and accretion this study simulates the pattern of reef response on the reefs around lizard island in the northern great barrier reef two sea level rise scenarios are considered to capture the range of likely projections 0 5 m and 1 2 m above 1990 levels by 2100 reef topography has been established through extensive bathymetric profiling together with available data including lidar single beam bathymetry multibeam swath bathymetry lads and digitised chart data the reef benthic cover around lizard island has been classified using a high resolution worldview 2 satellite image which is calibrated and validated against a ground referencing dataset of 364 underwater video records of the reef benthic character accretion rates are parameterised using published hydrochemical measurements taken in situ and rules are applied using boolean logic to incorporate geomorphological transitions associated with different depth ranges such as recolonisation of the reef flat when it becomes inundated as sea level rises simulations indicate a variable platform response to the different sea level rise scenarios for the 0 5 m rise the shallower reef flats are gradually colonised by corals enabling this active geomorphological zone to keep up with the lower rate of rise while the other sand dominated areas get progressively deeper in the 1 2 m scenario a similar pattern is evident for the first 30 years of rise beyond which the whole reef platform begins to slowly drown to provide insight on reef response to sea level rise in other areas simulation results of four different reef settings are discussed and compared at the southeast reef flat barrier reef coconut beach fringing reef watson s bay leeward bay with coral patches and mangrove beach sheltered lagoonal embayment the reef sites appear to accrete upwards at a rate commensurate with the rate of rise thereby maintaining their original profile and position relative to the sea surface and the leeward and lagoonal sites with a low accretion rate maintain a similar profile but slowly gain depth relative to sea level the result of this variable response is that elevated features of the reef platform such as reef patches and crests tend to become more pronounced

1982 sepm presidential address episodic sedimentation how normal is average how rare is rare does it matter abstract do sedimentary rocks record mainly average continuous day to day processes or relatively rare large magnitude ones separated by long nondepositional intervals subtle legacies from lyellian uniformitarianism may still impose a subconscious abhorrence of unique events discontinuities and large deviations from average magnitudes where repeated sharp changes of sedimentation are inescapable periodic cycles are commonly invoked to preserve uniform orderly variations from some supposed norm the sedimentary record rarely reflects such uniformity however as sedimentologists have gradually realized magnitude versus frequency of processes has long been debated in geomorphology but has received less attention in sedimentology recurrence interval recovery time and preservation potential are critical factors for evaluating their significance for the sedimentary record large magnitude processes which represent positive deviations from the norm and are rare on the human time scale must be significant over geologic time but how significant could not everyday processes have obliterated much of the evidence flood deposits have relatively low preservation potential because they lie above base level marine gravel layers dispersed by abnormal waves have greater preservation potential because most ordinary processes are not competent to modify them sandy or shelly de osits formed by large waves and displaying either hummocky cross stratification or graded bedding have a moderate preservation potential especially if too thick for burrowing animals to homogenize them turbidites which provide exceptional records of episodicity have excellent preservation potential because they lie well below base level many bedding planes are important records of episodicity too some are surfaces of erosion others of nondeposition these represent negative deviations from average process magnitudes the sedimentological importance of rare events is difficult to assess because the record of such events may be very subtle this is especially true if a deposit has been thoroughly bioturbated or if the record of an event is simply an erosional surface it has now become possible to evaluate quantitatively ancient episodic sedimentation using modern process rates as well as refined biostratigraphic and isotopic dating i predict that such evaluation will necessitate revision of our favorite depositional models which have become so important for exploration as well as for research

the relationship between sedimentary facies and faunal associations in the llandovery siliciclastic ross brook formation arisaig nova scotia the llandovery siliciclastic ross brook formation of arisaig nova scotia comprises three broadly defined sedimentary facies these are a mottled silty mudstone facies facies a a laminated shale facies facies b and a laminated siltstone facies facies c facies a consists of variably bioturbated silty mudstones muddy siltstones and fissile shales it developed in relatively shallow water conditions mudstones were presumably deposited from suspension and siltstone laminae and thin layers were formed by increased wave and current activity mottling resulted from bioturbation by epifaunal and particularly infaunal benthic organisms within facies a two subfacies are recognized a i is mudstone dominated and a ii is fine grained siltstone dominated facies b consists of alternating laminae of undisturbed mudstone and fine grained siltstone probably produced as a result of deposition from suspension during a temporary upward expansion of the oxygen minimum layer facies c consists of 0 5 30 c

shelf construction in a foreland basin storm beds shelf sandbodies and shelf slope depositional sequences in the upper cretaceous mesaverde group book cliffs utah the upper cretaceous campanian kenilworth member of the blackhawk formation mesaverde group is part of a series of strand plain sandstones that intertongue with and overstep the shelfal shales of the western interior basin of north america analysis of this section at a combination of small sedimentological and large stratigraphical scales reveals the dynamics of progradation of a shelf slope sequence into a subsiding foreland basin four major lithofacies are present in the upper mancos and kenilworth beds of the book cliffs a lag sandstone and channel fill shale lithofacies constitutes the thin basal transgressive sequence which rests on a marine erosion surface it was deposited in an outer shelf environment shale interbedded sandstone and shale and amalgamated sandstone lithofacies were deposited over the transgressive lag sandstone lithofacies as a wave dominated delta and its flanking strand plains prograded seaward analysis of grain size and primary structures in kenilworth beds indicates that there are four basic strata types which combine to build the observed lithofacies the fine to very fine grained graded strata of the interbedded facies are tempestites deposited out of suspension by alongshelf storm flows geostrophic flows there is no need to call on cross shelf turbidity currents density underflows to explain their presence very fine to fine grained hummocky strata are likewise suspension deposits created by waning storm flows but were deposited under conditions of more intense wave agitation on the middle shoreface cross strata sets in this region are bed load deposits that accumulated on the upper shore face in the surf zone lag strata are multi event bed load deposits that are the product of prolonged storm winnowing they occur on transgressive surfaces while the graded beds are tempestites in the strict sense all four classes of strata are storm deposits the distribution of strata types and their palaeocurrent orientations suggests a model of the kenilworth transport system driven by downwelling coastal storm flows and probably by a northeasterly alongshore pressure gradient the stratification patterns shift systematically from upper shoreface to lower shoreface and inner shelf lithofacies partly because of a reduction in fluid power expenditure with increasing water depth but also because of progressive sorting which resulted in a decrease in grain size in the sediment load delivered to successive downstream environments the kenilworth member and an isolated outlier the hatch mesa lentil constitute a delta prodelta shelf depositional system their rhythmically bedded lenticular sandstone and shale successions are a prodelta shelf facies and may be prodelta plume deposits major upper cretaceous sandstone tongues in the book cliffs are underlain by erosional surfaces like that beneath the blackhawk formation which extend for many tens of kilometres into the mancos shale these surfaces are the boundaries of upper cretaceous depositional sequences the sequences are large scale genetic stratigraphic units they result from the arranging of facies into depositional systems the depositional systems are in turn stacked in repeating arrays which constitute the depositional sequences the anatomy of these foreland basin sequences differs

long shelf sediment transport and storm bed formation by cyclone winifred central great barrier reef australia three major sediment facies belts occur on the great barrier reef shelf an inner shelf prism of holocene terrigenous sand and mud a patchy middle shelf veneer of palimpsest muddy shelly calcsand 1 m thick above a weathered pleistocene erosion surface and an apron of modern carbonate mud and sand around reefs of the main reef tract these sediments were mobilized and strongly affected by the passage of severe tropical cyclone winifred central pressure 958 hpa which traversed the central great barrier reef shelf on february 1 1986 re surveys after the passage of cyclone winifred showed that i a storm induced shell lag and or a normally graded bed of terrigenous fine sand mud had been deposited at depths down to 20 m ii middle shelf longitudinal bedforms were widespread at depths of 28 35 m and comprised a furrowed substrate of palimpsest muddy shell gravel surmounted by 40 150 m wide ribbons of quartzose and bioclastic sand up to 15 cm thick iii fields of northward facing 1 2 m wavelength megaripples were present adjacent to zones of ribbons and in the alleys between ribbons iv five days after the cyclone mud was still settling from suspension and large parts of the inner shelf were bathed in muddy hypopycnal river plumes some of which reached 30 km seaward to the inner edge of the reef tract and v suspended mud derived in part by unmixing of the seabed was present throughout the shelf water column and a seaward thinning mud drape up to 40 cm thick had accumulated on and seawards of the inshore sediment prism tapering seawards to a few mm thick only over most of the middle shelf it is inferred that storm waves and currents associated with the passage of cyclone winifred caused widespread unmixing of bottom sediments offshore long shelf transport of bedload sand ribbons and megaripples was affected by powerful shelf parallel currents of velocity 1 3 m s as the storm passed the graded seaward thinning sand mud bed was deposited over the inner middle shelf on the middle shelf bioturbation and downward mixing of the mud drape started immediately after the passage of the cyclone and was well advanced after 3 months in this way the ephemeral seabed features produced by passage of a cyclone are gradually degraded and the storm layer stratigraphy becomes incorporated within a thin middle shelf veneer of muddy shelly calcsand

reef accretion and coral growth rates are decoupled in holocene reef frameworks abstract a central assumption of holocene reef models is that reef accretion rates are directly related to coral growth rates with reefs dominated by faster growing corals having higher accretion rates yet few studies have explicitly tested this assumption particularly in indo pacific region through high precision u th dating and palaeoecological reconstructions of coral community structure this study explores patterns of reef accretion mm yr 1 among late holocene reef frameworks from the inshore central great barrier reef modern assemblages were dominated by either slow growing goniopora 9 6 2 mm yr 1 or rapid growing branching acropora 89 6 mm yr 1 framework building corals despite a nearly 10 fold difference in coral growth rates rates of reef accretion were comparable between frameworks dominated by slow growing goniopora 8 6 1 3 mm yr 1 and rapid growing branching acropora 7 1 1 4 mm yr 1 u th chronologies indicate that accretion rates were continuous throughout the past 750 years r2 0 96 0 98 despite a temporal shift in framework building corals from acropora to goniopora that occurred 250 years ago that coral growth rates are decoupled from reef accretion at holocene scales indicates that previous models of accretion in pacific coral reefs may be based upon inaccurate assumptions the finding that ecological processes are decoupled from geological processes has implications for the management of modern coral reefs and suggests that maintenance of living corals regardless of taxonomic identify is important for accretion of reef frameworks

ichnology and paleoecology of offshore siliciclastic deposits in the cardium formation turonian alberta canada the raven river member of the cardium formation upper cretaceous turonian was deposited in a storm dominated offshore setting in the western interior seaway of north america the ichnology of this unit can provide a useful model for further investigation of shelfal deposits a two fold approach to the ichnology has been utilized in this study first lithofacies are delineated which encompass the degree of bioturbation as part of the rock s sedimentary texture in addition ichnofossil assemblages are established which represent recurring groups of ichnogenera lithofacies comprise several coarsening upward sequences of sandstone and mudstone in which bioturbation tends to decrease upwards mudstone units represent deposition below fairweather wave base in a quiet water setting while sandstone beds are the result of storm generated deposition the sequence shows a punctuated aggradation of shelfal sediments in a storm dominated environment ichnofossil assemblages show a differentiation into pre and post storm ichnogenera with textural changes playing a minor role in assembly composition ichnogenera present include asterosoma bergaueria conichnus cylindrichnus chondrites helminthopsis ophiomorpha palaeophycus planolites rhizocorallium rosselia skolithos teichichnus thalassinoides terebellina and zoophycos

the importance of large benthic foraminifera to reef island sediment budget and dynamics at raine island northern great barrier reef low lying reef islands are among the most vulnerable environments on earth to anthropogenic induced climate change and sea level rise over the next century because they are low composed of unconsolidated sediment that is able to be mobilised by waves and currents and depend on sediments supplied by reef organisms that are particularly sensitive to environmental changes e g ocean temperatures and chemistry therefore the spatial and temporal links between active carbonate production and island formation and dynamics are fundamental to predicting future island resilience yet remain poorly quantified in this paper we present results of a detailed geomorphological and sedimentological study of a reef and sand cay on the northern great barrier reef we provide an empirical investigation of the temporal linkages between sediment production and reef island development using a large collection of single grain ams 14c dates large benthic foraminifera lbf are the single most important contributor to contemporary island sand mass 47 ranging from 36 to 63 at raine island reflecting rapid rates of sediment production and delivery standing stock data reveal extremely high production rates on the reef 1 8 kg m 2 yr 1 while ams 14c dates of single lbf tests indicate rapid rates of sediment transferral across the reef we also demonstrate that age is statistically related to preservation and taphonomic grade severely abraded tests moderately abraded tests pristine tests we construct a contemporary reef and island sediment budget model for raine island that shows that lbf baculogypsina marginopora and amphistegina contribute 55 of the sediment produced on the reef annually of which a large proportion 54 contribute to the net annual accretion of the island the tight temporal coupling between lbf growth and island sediment supply combined with the sensitivity of lbf to bleaching and ocean acidification suggests that islands dominated by lbf are likely to be very sensitive to short and long term climate change projections potential outcomes of this work relate to improving the understanding of the future change dynamics of reef islands in response to climate change

trace fossil evidence for restoration of marine ecosystems following the end permian mass extinction in the lower yangtze region south china abstract unlike the high abundance low diversity macrofaunas that characterize many early triassic benthic palaeocommunities ichnofossils were relatively common in the aftermath of the end permian mass extinction worldwide ichnofossils therefore are a good proxy for ecosystem recovery after the end permian biotic crisis this paper documents 14 ichnogenera and one problematic form from lower triassic successions exposed in the lower yangtze region south china post extinction ichnodiversity remained rather low throughout the griesbachian early smithian period and abruptly increased in the late smithian however several lines of evidence including extent of bioturbation burrow size trace fossil complexity and tiering levels indicate that diversification of ichnotaxa in the late smithian did not signal full marine ecosystem recovery from the permian triassic p tr mass extinction marine ichnocoenoses did not recover until the late spathian in south china the marginal sea provided hospitable habitats for tracemakers to proliferate in the aftermath of the end permian mass extinction

ichnology of a glacially influenced continental shelf and slope the late cenozoic gulf of alaska yakataga formation abstract the study of trace fossils in glaciomarine strata is important because of the low preservation potential of fauna but glaciomarine settings have received little attention from ichnologists widespread biological activity is recorded by ichnofossil assemblages in glaciomarine strata of the late cenozoic 6 ma to present yakataga formation alaska glacial sedimentation began in the gulf of alaska in the miocene along a deep water active margin basin dominated by turbidity currents and debris flows later strata record progradation of the continental slope by mass flow processes and the establishment of a broad shelf influenced by repeated glaciation ice rafting of coarse debris changes in water depth and salinity storms earthquakes and high sedimentation rates yakataga formation strata show overall a limited ichnological diversity and low degree of bioturbation in relation to comparable non glacial settings although certain beds are highly bioturbated twenty four ichnotaxa are identified and grouped into nine assemblages characteristic of different depositional settings and substrate types ichnogenera and body fossil evidence shows that polychaetes arthropods molluscs and echinoderms were the dominant infaunal benthic organisms with deposit feeding being the predominant feeding strategy poorly consolidated muddy sediments excluded suspension feeders and limited the development of the skolithos ichnofacies typical of non glacial shelves characterized by clean shifting sand substrates evidence of rapid sedimentation is given by escape structures fugichnia the presence of diplocraterion and by the mass mortality of bivalves firm ground burrows typical of the glossifungites ichnofacies are associated with erosional surfaces boulder pavements and coquinas diminutive feeding traces may reflect salinities lowered by glacial meltwater inputs the downslope transport of food by turbidity currents and mass flows may explain the development of a diverse cruziana ichnofacies in water depths where in non glacial settings the nereites ichnofacies is found an ichnological summary is presented for the late cenozoic gulf of alaska continental margin similar ecological conditions obtain in the modern setting and provide valuable supportive data ichnofacies identified from the yakataga formation are probably widespread in late paleozoic and late cenozoic glacially influenced marine strata

a new gravity survey of the lake district and three dimensional model of the granite batholith a new regional gravity survey of the lake district has defined the principal anomalies in considerably more detail than previous surveys and has formed the basis for a three dimensional interpretation of the sub surface shape of the lower palaeozoic 9granite9 batholith the gravitational effects of the surrounding low density permo triassic carboniferous and silurian sedimentary successions have been calculated and removed from the observed field the remaining residual gravity field due to the batholith has been interpreted on a 1 km square grid in terms of a generalized two density model extending to a depth of 9 km the interpretation shows that the skiddaw granite is a steep sided relatively flat topped intrusion the roof zone encompasses the grainsgill caldew and sinen gill outcrops and corresponds well with the mapped thermal aureole the southern part of the roof region of the shap granite coincides with the metamorphic aureole but a broad shoulder extends at about 1 km depth to the northwest beneath the haweswater igneous complex the eskdale granite is linked at shallow depth beneath the borrowdale volcanic group to the wasdale granite the central part of the lake district is underlain by granite at relatively shallow depth less than 2 km which appears to be a subsurface extension of the outcrops at eskdale and wasdale

cardium formation u cretaceous at seebe alberta storm transported sandstones and conglomerates in shallow marine depositional environments below fair weather wave base as a result of detailed mapping at seebe alberta we have defined five coarsening upward sequences in the turanian cardium formation the sequences begin with bioturbated mudstones and coarsen int

shallow water sclerosponges on jamaican reefs and a criterion for recognition of hurricane deposits we report here that excavation into the acropora palmata rubble on the reef crest at 4 m water depth on discovery bay reefs jamaica revealed the presence of numerous sclerosponges ceratoporella nicholsoni living attached directly to the coral branches 1 2 m below the rubble surface the coral branches excavated were deposited during a storm event in august 1980 and consequently lack the zoned crusts showing a succession from photophilic light loving to sciaphilic shade loving secondary frame builders which normally develop during slow steady incremental coral branch accumulation thus the nature and sequence of encrustations on coral rubble can indicate the speed of its accumulation

development of a pliocene mixed carbonate siliciclastic reef limon costa rica the miocene to pleistocene limon group of costa rica is a mixed carbonate siliciclastic succession that formed in association with the emergence of the central american isthmus our study focuses on a lower late pliocene reef unit the newly excavated contact cut which is located at the contact between the siliciclastic sediments of the rio banano formation and the mixed reefal and coral bearing deposits and siliciclastic sediments of the quebrada chocolate formation the siliciclastic sediments were deposited in a thick deltaic setting sourced by erosion of the cordillera de talamanca deposits of the limon group preserve a sequence of progressively shallowing near shore sediments that were exposed by uplift during the early to middle pleistocene the contact cut outcrop shows the first reef sequence in the stratigraphic sequence and thus illustrates the reestablishment of caribbean coral reef predominance in the neogene it shows extensive reef growth during a rise in sea level and a slight progradation during the succeeding sea level highstand three stages of reef evolution are recognized based on faunal diversity the contact cut reef complex is comparable to the time equivalent reef of the las islas roadcut situated west of limon which shows a rapid burial of the corals by siliciclastics both reefs document a distinct facies diversification during the final stages of the closing of the central american seaway the reefs developed in an environment stressed by siliciclastic input which ultimately caused a decrease in coral diversity and abundance followed by a temporary demise of the reefs the biotic composition of the patch reefs that occurred during the sea level rise las islas and contact cut did not differ from the reefs that developed during the final highstand in sea level the reefs of the overlying moin formation limon group differences in the position on the shelf relative to the source of the siliciclastics might have been the cause for the different response to the rise in sea level of the transgressive reefs with a very fast give up scenario for las islas reef and a catch up followed by a give up phase for contact cut reef

carbonate and terrigenous sediment budgets for two inshore turbid reefs on the central great barrier reef abstract inshore turbid zone reefs on the great barrier reef gbr occur within 20 km of the mainland coast under marine environmental conditions with respect to sedimentation rates turbidity and water quality that are generally considered marginal for reef growth despite this data from various benthic habitat assessments report high 30 coral cover in these environments and reef core records show them to be characterised by relatively rapid rates of vertical accretion 2 8 mm year a long term trend indicative of high net carbonate productivity and in situ carbonate framework accumulation however the lack of quantitative data on terrigenous sediment input and flux rates and on carbonate production rates has inhibited understanding of both ecological timescale rates of carbonate production and the aggregated long term net impacts of sediments on reef growth to address this knowledge gap a modern carbonate budget and terrigenous sediment model that quantified allochthonous sediment inputs onto within and off reef was developed at two inshore reefs middle reef and paluma shoals both are located within the central region of the gbr and are subjected to high terrigenous sediment load 11 000 tonnes year and fluctuating turbidity 5 to 100 mg l regimes based on sediment dynamic modelling over 81 of sediments delivered were transported off reef with net sediment accumulation limited to sheltered reef habitats net carbonate production was high 6 9 kg m2 year due to high coral cover 30 high coral calcification rates acropora average 6 3 g cm2 year and low bioerosion rates 0 3 to 5 kg m2 year but varied spatially with highest net carbonate production 10 kg m2 year within deep 2 m at lat windward reef zones high carbonate framework production has enabled middle reef and paluma shoals to vertically accrete rapidly middle reef establishing at depths of 4 m paluma shoals at 3 m depth and both reaching sea level in

palaeoecological effects of back arc spreading on miocene benthic communities sw japan arc abstract during the early to middle miocene rapid development of backarc basins now known as the sea of japan occurred in the ne margin of the asian continent then the entire sw japan arc the arc was rotated clockwise very rapidly such an event was associated with the opening of another backarc basin located to the south of the arc immediately after this opening the very young hot oceanic plate began to subduct underneath the arc this subduction caused rapid uplifting and enhanced the denudation of the arc in the post early miocene the lower to middle miocene misaki group is a 3 000 m thick siliciclastic forearc basin fill consisting of wave dominated shallow marine and overlying braid plain deposits its defining features are the low ichnodiversity and paucity of ichnofabrics for instance up to 96 of the total thickness of the measured offshore deposits are non or very slightly bioturbated despite the other normal offshore deposits are generally highly bioturbated although the less bioturbated sediments were previously considered as anoxic deposits anoxic water was unlikely to develop within the highly open wave dominated shallow marine settings the highly active tectonics associated with the spreading of the two backarc basins and the forced subduction most likely caused sediment mass production in the hinterland as evidenced by the sedimentological features of the coeval kuma group and over sedimentation highly frequent and rapid sedimentation that was taken place across the entire misaki basin this over sedimentation supported by a series of evidence such as the pervasive soft sediment deformation across the group estimated rate of net aggradation more than 136 to 230 cm kyr etc most likely induced the colonisation of depauperated fauna and diluted their ichnofabrics across the entire basin the extremely active tectono sedimentation played an important role in the development of the basin wide anomalous benthic ecosystems and ichnofabrics during the early to middle miocene

production and cycling of calcium carbonate in a shelf edge reef system st croix u s virgin islands applications to the nature of reef systems in the fossil record abstract geologic reefs are the end products of not only constructive processes that produce calcium carbonate but also of destructive processes e g bioerosion and wave action that reduce solid substrate to sediment and of physical processes that rework the reef fabric and transport sediment a study was conducted at cane bay on the island of st croix u s virgin islands to quantify the suite of processes that have influenced holocene reef development data on carbonate production reef accretion bioerosion and sediment transport were used to construct a detailed carbonate budget and to apply the findings of this study to the character of reefs observed in the fossil record total carbonate production on the reef ranged from 0 to 5 78 kg m2 per year with a reef wide average of 1 21 kg m2 per year 1 13 by corals 0 02 by coralline algae 0 06 by primarily molluscs forams and echinoderms based on 7 cores only 0 91 kg m2 per year of this have been retained within the reef interior the remaining 0 24 kg m2 per year of sediment along with the 0 06 kg m2 per year contributed directly by molluscs etc are deposited within reef channels and are probably flushed from the reef by major storms of the material recovered in the cores 58 was either loose sediment and rubble or open void space much of the recognizable coral material was demonstrably reworked and out of place accretion rates across the shelf generally increased with water depth as a result of active slumping along the steepening reef face over the past 2 000 3 000 years the importance of detrital material in the reef fabric and the major role played by secondary processes that constantly rework the substrate have resulted in a reef whose interior is more of a garbage pile than an in place assemblage of corals cemented together into a rigid framework the physical similarities between the detrital fabric of the reef at cane bay and those found in many ancient deposits imply that the general processes operating along the cane bay shelf have persisted during much of the evolution of ancient reefs it is proposed that our modern models overemphasize the importance of in place framework as a criterion for an ecologic reef

quaternary atoll development new insights from the two dimensional stratigraphic forward modelling of mururoa island central pacific ocean knowledge about the quaternary evolution of mid ocean atolls comes mainly from drilling and field observations carried out on a number of pacific carbonate islands however little is known about the early to mid pleistocene atoll development history especially at margin and foreslope settings using previous field and subsurface data from mururoa atoll and a process based modelling software dionisos a two dimensional forward stratigraphic model of atoll development is proposed for the past 1 8 million years myr observational data from vertical to inclined coring seismic and bathymetric surveys indicate that from approximately 0 45 to 0 40 million years before present ma carbonate deposition at mururoa atoll resulted in a series of mostly prograding reef units the model is first constrained at the base by the shape and topography of the pre quaternary basement a number of sensitivity tests were performed to define the respective influence of variant parameters the best fit development scenario that accounts for the overall geometry and stratigraphic architecture of the quaternary sediment packages is obtained by using the sea level curve by miller et al 2005 uniform subsidence rate of 105 m myr 1 and carbonate production rates gradually increasing from 0 50 to 8 mm yr 1 between 1 80 ma and the present additional controlling parameters include subaerial erosion at a constant rate of 0 25 m kyr wave energy and sediment transport processes the stratigraphic forward model predicts a succession of three distinct types of carbonate systems that have developed since the earliest pleistocene toe of slope systems from 1 80 ma to about 0 80 ma open platform systems from 0 80 ma to 0 50 ma and framework reef systems from about 0 50 ma to the present the development of these different systems is most likely to be controlled by climate and changes in sea level cycles during the low amplitude 41 kyr cycle periods of the earliest pleistocene ambient conditions were not conducive to framework reef growth shallow water carbonate sedimentation was dominantly gravity driven operating along the platform foreslopes only during the mid pleistocene climate transition narrow open platform units have developed at the upper parts of the pre quaternary basement flanks with the onset of the high amplitude 100 kyr sea level modes and climate restoration reef frameworks started to be generated these models from mururoa agree with a number of previous studies suggesting that most of the true framework reefs were not initiated prior to 0 50 ma mururoa atoll is demonstrated to be a robust analogue for providing more realistic interpretations of the development history of pacific atolls further modelling with three dimensional dionisos could generate better predictions by taking into account hydrodynamic and transport parameters more accurately

impacts of cyclone yasi on nearshore terrigenous sediment dominated reefs of the central great barrier reef australia tropical cyclone tc yasi category 5 was a large 700 km across cyclone that crossed australia s queensland coast on the 3rd of february 2011 tc yasi was one of the region s most powerful recorded cyclones with winds gusting to 290 km h and wave heights exceeding 7 m here we describe the impacts of tc yasi on a number of nearshore turbid zone coral reefs that include several in the immediate vicinity of the cyclone s landfall path king reef lugger shoal and dunk island as well as a more distally located reef paluma shoals 150 km to the south in halifax bay these reefs were the focus of recent between 2006 and 2009 pre yasi studies into their geomorphology sedimentology and community structure and here we discuss data from a recent august 2011 post yasi re assessment this provided a unique opportunity to identify and describe the impacts of an intense tropical cyclone on nearshore reefs which are often assumed to be vulnerable to physical disturbance and reworking due to their poorly lithified framework observed impacts of tc yasi were site specific and spatially highly heterogeneous but appear to have been strongly influenced by the contemporary evolutionary stage and ecological make up of the individual reefs with site setting i e exposure to prevailing wave action apparently more important than proximity to the landfall path the most significant ecological impacts occurred at king reef probably a result of freshwater bleaching and at paluma shoals where widespread physical destruction of branched acropora occurred new coral recruits are however common at all sites and colony re growth clearly evident at king reef only localised geomorphic change was evident mainly in the form of coral fracturing rubble deposition and sediment movement but again these impacts were highly site specific the dominant impact at paluma shoals was localised storm ridge shingle sheet deposition at lugger shoal major offshore fine sediment flushing and at dunk island major onshore coarse sand deposition there was little geomorphic change evident at king reef thus whilst small scale and taxa specific impacts from cyclone yasi are clearly evident geomorphological changes appear minor and ecological impacts highly variable between sites and there is no observed evidence for major reef structural change the study suggests that the vulnerability of reefs to major physical disturbance events can be extremely site specific and determined by interacting factors of location relative to storm path and pre event geomorphology and ecology

episodic sedimentation how normal is average how rare is rare does it matter where repeated sharp changes of sedimentation are inescapable periodic cycles are commonly invoked to preserve uniform orderly variations from some supposed norm the sedimentary record rarely reflects such uniformity however as sedimentologists have gradually realized magnitude versus frequency of processes has received little attention in sedimentology recurrence interval recovery time and preservation potential are critical factors for evaluating their significance for the sedimentary record large magnitude processes which represent positive deviations from the norm and are rare on the human time scale must be significant over geologic time everyday processes may have obliterated much of the evidence the sedimentological importance of rare events is difficult to assess because the record of such events may be very subtle this is especially true if a deposit has been thoroughly bioturbated or if the record of an event is simply an erosional surface it has now become possible to evaluate quantitatively ancient episodic sedimentation using modern process rates as well as refined biostratigraphic and isotopic dating i predict that such evaluation will necessitate revision of our favorite depositional models which have become so important for exploration as well as for research modified journal abstract

biogenic sedimentary fabrics associated with pioneering polychaete assemblages modern and ancient abstract organically enriched terrigenous marine sediments are commonly associated with near bottom waters containing low concentrations of dissolved oxygen as well as with sediment pore waters high in dissolved sulfides today such habitats are typically dominated by dense aggregations of opportunistic polychaetes which intensively pelletize surface sediments while deposit feeding laboratory study of one such species capitella sp i indicates that these polychaete aggregations and their associated agglutinated tubes have a low probability of direct preservation in the sedimentary column synthetic lutites prepared from these sediments however contain pelletal sedimentary fabrics indicative of the former presence of polychaetes to evaluate the effectiveness of these criteria for paleoecological reconstructions of omzs we undertook a study of the sonyea group upper devonian catskill shelf and basin wedge shaped thin sections of rocks from a range of environments in the upper devonian catskill shelf and basin complex were examined only sections from the slope facies fulfilled the necessary criteria for postulating the presence of an omz methods are given for the preparation of synthetic lutites in order to identify these cryptic yet paleocologically important sedimentary fabrics recognition of such fabrics in otherwise barren shales may allow for more detailed reconstructions of ancient hypoxic and anoxic basins

marine event beds and recolonization surfaces as revealed by trace fossil analysis turbidites and tempestites exhibit characteristic distributions of trace fossils to gain maximum advantage of the sedimentological and palaeoecological significance of these traces an attempt should be made to relate each trace to the associated colonization surface this approach allows traces initiated at the normal top of an event bed to be distinguished from traces that subsequently passed into the bed from a higher colonization level or were initiated on the eroded surface of the bed

the importance of quaternary records in reducing risk from tropical cyclones numerous late holocene records of tropical cyclones have been collected from north east queensland australia they are in the form of multiple sedimentary ridges paralleling the shore the ridges are composed of coral fragments or shell and sand or pure sand a method to determine the intensity of the tropical cyclone responsible for deposition of the ridges at each site has been applied and the results suggest that in the majority of cases these features were deposited by very high magnitude events the results suggest that extrapolations of long term cyclone magnitude and frequencies from the 30 to 40 year long instrumental record which is the method commonly used to assess risk from this hazard substantially underestimate the risk from this hazard this is confirmed for the cairns region by an 800 year long high resolution isotope record of tropical cyclones preserved in a limestone stalagmite together the sedimentary and isotope records suggest that tropical cyclone activity in north east queensland has been in a phase of quiescence since before european settlement of the region in approximately ad 1870 it is suggested that the incorporation of the palaeo record into risk assessments will provide a more realistic guide to the magnitude frequency relationship of tropical cyclones and help reduce risk from this hazard as a consequence

chondrites a trace fossil indicator of anoxia in sediments the trace fossil chondrites a highly branched burrow system of unknown endobenthic deposit feeders occurs in all types of sediment including those deposited under anaerobic conditions in some cases such as the jurassic posidonienschiefer formation of germany chondrites occurs in black laminated carbonaceous sediment that was deposited in chemically reducing conditions in other cases such as numerous oxic clastic and carbonate units throughout the geologic column chondrites typically represents the last trace fossil in a biotutbation sequence this indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters

from platform top to adjacent deep sea new source to sink insights into carbonate sediment production and transfer in the sw indian ocean glorieuses archipelago abstract over the past ten years a huge amount of source to sink studies have aimed to unravel the tectonic climatic and other processes that shape the landscape from mountains to the deep ocean interestingly these studies have been mainly dedicated to siliciclastic or mixed systems for which the connection between drainage basins continental shelves slope and basin environments are often well constrained here we present a study focusing on a source to sink study dedicated to a pure carbonate system located in the sw indian ocean glorieuses archipelago extensive field sampling and geophysical acquisition across the carbonate platform have allowed us to estimate the composition the lateral variability and volumes of neritic sands deposited on the platform top additional seismic and bathymetric surveys across the platform interior illustrate the presence of plurimetric sandy bodies deposited along the leeward platform edge corresponding to the export of carbonate sediments from the platform top toward the platform edge under the influence of dominant currents and wind driven processes high resolution seismic bathymetric data and sediment cores acquired along the leeward slope and basin adjacent to the carbonate platform highlight the presence of channel levee complexes and turbiditic lobes which have accumulated on the seafloor on top of a 250 m thick sedimentary basin at 2000 3400 m water depth our study points out that carbonate sands and aragonitic mud produced on the platform top during the holocene have been shed to the adjacent basin we also demonstrate that this routing system was active at least throughout the last three glacial interglacial cycles this study has important consequences for our understanding of carbonate sedimentation processes occurring in the vicinity of isolated carbonate platforms 1 it highlights the role of oceanographic conditions in the distribution of sediment on a platform top and its export along the platform edge and the adjacent basin 2 it contributes to quantify the productivity of a carbonate platform as well as its sediment storage capacity 3 a first estimate of a carbonate source to sink system is proposed demonstrating that 0 57 km3 of sediments have been produced during the holocene 0 3 km3 being presently stored on the platform and the remaining having been exported to the deep basin

the geochemistry metasomatism and petrogenesis of the granites of the english lake district new geochemical data for the carrock threlkeld ennerdale shap skiddaw and eskdale granites of the lake district are presented and discussed with particular reference to the metasomatism and petrogenesis of the intrusions the caledonian granites of the lake district have more associated hydrothermal activity and mineralization than their equivalents north of the iapetus suture in scotland pervasive high temperature metasomatism which affects the shap skiddaw and eskdale intrusions is accompanied by remobilization of the large ionic lithophile elements k rb sr u and li and b although high field strength elements including the rare earth elements remain unaffected except near greisen and mineral veins the threlkeld intrusion appears to have suffered loss of a ba and sr during a low temperature event however there is no consistent relationship between granite composition hydrothermal activity and mineralization which could be used to support the granite cupola model for mineralization in the province rather the episodic mineralization which affects the lake district may be related more to the broad geothermal field consequent upon the emplacement of the deeper lake district batholith identified from geophysical data despite the variable metasomatic perturbations of their primary chemistry three distinct groups of intrusions can be recognized on geochemical grounds the carrock granophyre is a product of tholeiitic fractionation and the threlkeld and ennerdale bodies are more typical calc alkaline intrusions whereas the eskdale shap and skiddaw plutons show a progressive evolution towards more complex geochemical patterns suggesting decreasing hornblende but increasing plagioclase control of fractionating processes the culmination of this trend may have been the emplacement of a large high heat production granite beneath the lake district at the end of the caledonian orogeny the suggestion made on geophysical grounds that the eskdale intrusion is a cupola of the lake district batholith cannot be simply reconciled with geochemical modelling none of the lake district granites has geochemical or isotopic characteristics which are convincingly s type i e formed by partial melting of a sedimentary protolith and a model of subcrustal magmagenesis beneath an evolving arc or continental margin appears to be more appropriate

a detrital sediment budget of a maldivian reef platform abstract sediment dynamics are an important control on the morphology and development of reef systems by actively removing and redistributing excess detrital sediment this study presents quantitative data from direct point measurements of sediment transport on the platform surface and fore reef slope of vabbinfaru reef north male atoll maldives a suite of sediment traps were used to construct actual rates of platform sediment fluxes and off reef export over different spatial and temporal seasonal scales to establish key sediment transport pathways findings showed that high sediment fluxes occur on vabbinfaru platform in the absence of major storm activity up to 1905 g m 1 d 1 with 95 of annual transport occurring during the southwest monsoon as a result of increased wave energy climate driven changes in the platform process regime caused a reversal of net sediment transport pathways between each monsoon season off reef export rates were high reaching a maximum of 12 58 kg m 1 y 1 for gravel and 407 g m 1 d 1 for sand sized sediment an estimated 127 120 kg is exported from the platform annually equating to a significant loss from the reef sediment budget and contributing to the long term geomorphic development of the fore reef slope and atoll basin detrital sediment reservoirs on vabbinfaru are not purely depositional carbonate sinks but rather temporary stores that are important in the transfer of sediment between reef zones

the effects of bioturbation on the fabric of shale abstract x radiography and scanning electron microscope analyses of shales from diverse sedimentary environments reveal wide variations in macro and microfabrics attributed to the degree of bioturbation these fabrics provide clues about the physical condition of the sediment substrate at the time of clay deposition and the relationship between bioturbation activity and the sedimentary environment organic rich shales from anoxic environments are unbioturbated and characterized by fine lamination and a microfabric of parallel clay flakes two fabric types were found in shales formed under oxic conditions highly bioturbated and indistinctly bedded fabric in shales subjected to considerable bioturbation is recognized by a homogeneous gray tone in an x radiograph and by a random microfabric in a scanning electron micrograph this fabric is also very similar to mudstones formed from lithified flocculated clay however it does not possess the stepped domains or stepped cardhouse fabric of the latter indistinctly bedded shale possesses remnant original lamination and preferred particle orientation indicative of less intense bioturbation the fabric types are useful in determining whether the sediment substrate was a soupground softground or firmground as well as indicating the amount and intensity of biogenic activity during sediment deposition

ichnology of a late palaeozoic ice marginal shallow marine succession talchir formation satpura gondwana basin central india abstract the late palaeozoic glaciomarine talchir formation in the satpura gondwana basin central india hosts sparse to profuse trace fossils of various kinds although sporadically among the three principal depositional systems that gave rise to the talchir succession deposits of the ice contact fan delta system and the glacial outwash braidplain delta system lack trace fossils of any kind on the other hand within the deposits of the storm wave dominated shoreface shelf system a variety of animal traces is present including simple locomotion traces and non descript bioturbation three trace fossil assemblages could be recognized within these deposits assemblage i is dominated by cylindrichnus of the skolithos ichnofacies that occurs in storm laid medium to fine sandstones deposited in shoreface and transitional shoreface inner shelf environments in contrast assemblage ii comprising dominantly horizontal grazing cum deposit feeding traces cochlichnus helminthopsis phycosiphon planolites archaeonassa and psammichnites occurs on decimeter thick sandstone beds interlayered with mudstones deposited in lower shoreface to inner shelf environments trace fossil assemblage iii is known from a 6 9 m thick outer shelf to lower shoreface progradational succession showing a vertical transition from dark gray mudstone to fine sandstone the middle part of this particular section shows rhizocorallium and flat type zoophycos whereas the upper part hosts profuse cylindrichnus along with rosselia and teichichnus in lesser proportions this assemblage is comparable to the marine ichnofacies succession combining elements of both skolithos and cruziana ichnofacies the characteristic features of the talchir trace fossil assemblages are i low ichnodiversity ii presence of forms typically found the in marine environment iii co occurrences of vertical and horizontal traces of skolithos and cruziana ichnofacies iv presence of simple structures formed by trophic generalists v abundance of certain forms and vi presence of monospecific suites these characters are akin to those of brackish water ichnofaunas in the talchir succession the transition from an ice contact fan delta system to a relatively ice free open marine system indicates an enormous flux of fresh water into the sea reducing its overall salinity predominance of annelid and worm traces and the rarity of crustacean burrows in the talchir strata also suggest a stressful environment due to the prevailing cold climate and a lower than normal marine salinity it thus appears that mixing of fresh water during deglaciation might be a key controlling factor in shaping the characters of ichnofaunas in glacially influenced shallow marine environments

off reef transport of coral fragments at lizard island australia abstract the generation and movement of coral rubble is important to the sedimentary budget of a reef in sediment facies development and in the promotion of reef growth this study examined the rate of down slope transport of live and dead coral fragments from shallow reef fronts at lizard island on the great barrier reef australia ten large 1 m2 collecting trays were deployed and cleared annually for 4 years at each of two sites at the base 8 12 m depth of the steeply sloping fringing reef the rate of export of coral fragments down the reef slope was very high an average of 132 fragments weighing 1 87 kg was recorded each year per meter of reef front a mean of 2 25 of the fragments representing 43 species was alive in the trays at each annual census yielding an average rate of colonization onto the reef slope of 2 7 live fragments per meter of reef front per year reworking of hard calcareous substrates towards the slope promotes reef growth by two mechanisms 1 passive dispersal of live coral fragments to peripheral soft sediment habitats that are unsuitable for larval settlement and 2 subsequent colonization of rubble by coral larvae there were no major storms during the course of the study indicating that significant down slope transport of fragments can occur even in the absence of cyclones

substrate control of lower cambrian trace fossils from bornholm denmark abstract a ten meter thick sequence within the lower cambrian succession from snogebaek harbour to broens odde bornholm contains abundant trace fossils throughout the systematics of some of the ichnogenera are briefly discussed in particular buthotrephis and a new form of diplocraterion the trace fossils can be subdivided into four associations the skolithos diplocraterion rhizocorallium and teichichnus buthotrephis associations the recurrence of these associations can be correlated with changes in substrate in particular the diplocraterion association in the middle and upper part of the broens odde member exposed here occurs only in storm deposits

global cretaceous paleogeography international geologic correlation program project 191 abstract five global cretaceous paleogeographic maps within a plate tectonic framework are illustrated based on the ten contributions in this special volume

carbonate sediment production transport and supply to a coral cay at raine reef northern great barrier reef australia a facies approach abstract coral cays are low lying typically 2 mm grain size and the relative abundances of foraminifera and coral grains gravelly coral dominated sediment is concentrated at the reef margins whereas facies on and around the leeward cay are dominated by the sand size tests of benthic foraminifera mud is absent in reef sediments and reflects the prevailing high energy wave dominated setting as well as a paucity of mud producers benthic foraminifera tests are the major sediment component constituting an average proportion of 39 range 2 77 sediment derived from the skeletal remains of corals 24 1 65 mollusks 15 3 30 halimeda 14 4 36 and coralline algae 6 0 20 are present in lesser volumes foraminifera content is highest 40 on tidally emergent algal pavement where they live in greatest abundance and on the cay shorelines where their tests are deposited and comprise the bulk of beach sand 36 63 a comparison of the raine island data with other exposed modern reefs and platforms of the central and western pacific shows that occurrence and distribution of facies types is broadly consistent beyond these sedimentological data the taphonomy of foraminifera at raine island indicates that tests are vulnerable to destruction due to abrasion when transport and reworking is prolonged therefore the foraminifera rich facies adjacent to and on the cay disjunct from the source zones as well as taphonomic evidence imply that transport from the outer reef flat to the cay must be relatively quick these short temporal links between ecological source zones and depositional landforms are likely to have important ramifications for the contemporary management of reef associated landforms e g cays in the future

coral indicators of past sea level change a global repository of u series dated benchmarks fossil corals provide valuable data for reconstructing past sea levels as they are often well preserved in the fossil record and can be dated with u series methods here we present a global and internally consistent database of usingle bondth dated fossil coral sea level indicators including full consideration of all known associated uncertainties both vertical and chronological we include carefully determined taxon specific depth distributions rather than blanket depth uncertainty terms as used in most previous work this is based on a synthesis of extensive modern ecological information on depth ranges these ranges are found to be spatially variable between ocean basins between regions and on sub regional scales because depth itself is not limiting instead depth distributions arise from complex physical chemical and biological interactions with coral reef growth distribution and composition one of the main causes for recognition of the greater depth variability of coral taxa has been the routine inclusion of deep diving and rov surveys in coral ecological studies over the past few decades which has broken through the shallow water bias of early surveys by adding frequent observations on deeper occurrences although more are needed it is also clear from our assessment that coral habitat depth distributions must be determined on the species level to reduce uncertainties in reconstructions of past sea levels and that application to sea level studies then requires these studies also to identify fossil corals to the species level samples identified only to the genus level give rise to wide uncertainties in habitat depth and hence sea level our database contains extensive metadata to assist evaluations of dating quality as well as geomorphic and stratigraphic metadata we demonstrate with examples how such metadata can help to evaluate sea level reconstructions for example by identifying outlier points one example discusses the last interglacial lig where we use the available data with their uncertainties to assess probabilistically the time at which local sea levels exceed that of the present which yields a mean age of 124 6 ka with 95 probability bounds at 118 5 and 129 5 ka we conclude with identification of key outstanding issues relating to i current incomplete understanding of tectonic setting including the current lack of independent verification of uplift subsidence rates and reliance of somewhat unsatisfactory and circular use of the elevation of last interglacial deposits ii the depth distributions of coral taxa and iii the complete documentation of stratigraphic geomorphological and other contextual information with suggestions for strategies to address these issues

late quaternary shedding of shallow marine carbonate along a tropical mixed siliciclastic carbonate shelf great barrier reef australia the north east australian margin is the largest modern example of a tropical mixed siliciclastic carbonate depositional system with an outer shelf hosting the great barrier reef gbr and an inner shelf dominated by fluvially sourced siliciclastic sediment wedges the long term interplay between these sediment components and sea level is recorded in the queensland trough a 1 2 km deep n s elongate basin situated between the gbr platform and the queensland plateau in this paper 154 samples from 45 surface grabs and six well dated piston cores were analysed for total carbonate content carbonate mineralogy and sr concentration to establish spatial and temporal patterns of carbonate accumulation in the queensland trough over the last 300 kyr surface carbonate contents are lowest on the inner shelf 5 and in the trough axis 60 because of siliciclastic dilution carbonate on the shelf is mostly sr rich aragonite and high mg calcite hmc whereas that in the basin is mostly low mg calcite once normalized to remove the effects of siliciclastic dilution surface sr rich aragonite and hmc abundances decrease linearly to background levels 100 km seaward of the shelf edge core samples show that over time normalized aragonite and sr abundances are greatest during periods of shelf flooding and lowest when sea level drops below the shelf edge this is consistent with changes in the production of coral and calcareous algae and the shedding of their debris from the shelf interestingly normalized hmc concentrations on the slope peak during periods of major transgression perhaps because of maximum off shelf transport from inter reef areas or intermediate water dissolution after accounting for siliciclastic dilution there are strong similarities in both spatial and temporal patterns of carbonate minerals between slopes and basins of the north east australian margin and those of pure carbonate margins such as the bahamas a limited set of basic processes including the formation and breakdown of carbonate on the shelf the transport of carbonate off the shelf and eustatic sea level probably controls carbonate accumulation in slope and basin settings of tropical environments irrespective of proximal siliciclastic sediment sources

characteristic trace fossils in nearshore to offshore sequences upper cretaceous of east central utah more than 20 trace fossil species occur in marine facies of the cretaceous star point and blackhawk formations in the book cliffs and wasatch plateau provinces of utah major genera include ancorichnus arenicolites aulichnites chondrites conichnus cylindrichnus medousichnus ophiomorpha palaeophycus planolites rosselia schaubcylindrichnus scolicia skolithos teichichnus teredolites and thalassinoides newly named taxa include ancorichnus capronus medousichnus loculatus and rosselia chonoides most trace fossils occur in characteristic albeit intergradational ichnofacies correlative with major lithofacies of regressive nearshore to offshore sequences the latter include foreshore foreshore shoreface transition shoreface and offshore facies landward facies are typified by clean well sorted well stratified sparsely burrowed sandstones seaward facies except where interrupted by hummocky bedded sandstones exhibit successively less pure less well sorted and stratified more intensely

animal substrate interactions in an early miocene wave dominated tropical delta delineating environmental stresses and depositional dynamics tacata field eastern venezuela abstract the miocene tacata reservoirs of the eastern venezuela basin contain deposits that accumulated as a result of the progradation of a wave dominated delta complex in a tropical setting integration of ichnologic and sedimentologic data helps to detect different stress factors allowing distinction between deltaic and associated along strike strandplain shoreface successions fluvial discharge was repeatedly interrupted by periods of storm wave reworking and suspension fallout leaving diagnostic ichnologic signatures in the deposits repeated storms rank among the most important controlling factors on the front of the tacata deltas lateral especially on the updrift side to the river mouths wave activity caused nearly continuous accretion of the associated strandplains evidence of tidal influence is essentially restricted to distributary channel and particularly interdistributary bay deposits although elements of the skolithos ichnofacies e g skolithos are present they tend to occur in subordinate numbers as a result of water turbidity distributary channel deposits are sparsely bioturbated but the presence of certain ichnotaxa e g ophiomorpha allows distinction from freshwater fluvial channels ichnofabrics from interdistributary bay deposits display all the characteristics expected from brackish water settings e g low ichnodiversity presence of monospecific suites and are also typically sparsely bioturbated teichichnus and planolites commonly associated with synaeresis cracks are dominant ichnotaxa in these fine grained low energy protected brackish water settings in contrast delta front and prodelta deposits contain some ichnotaxa that typically do not occur in brackish water settings such as chondrites and phycosiphon preservation of very thin storm layers is probably more common in wave dominated deltas than in strandplain systems because deltaic stresses preclude the establishment of an abundant infauna that otherwise would have completely reworked such thin sandstone layers amalgamated thick bedded storm deposits are typically unburrowed or contain deep vertical ophiomorpha scolicia ichnofabrics seem to be restricted to the fully marine parts of strandplain deposits and are therefore useful to detect possible delta asymmetry along depositional strike or vertical changes in degree of deltaic influence

the significance of isotopic dates from the english lake district for the ordovician saurian time scale the lower palaeozoic time scale is discussed in the light of a new date for the threlkeld microgranite and a reassessment of other published dates from the lake district which suggest ages of c 410 ma for the base of the devonian c 421 ma for the ashgill c 429 ma for the late caradoc c 439 ma for the early llandeilo and c 468 ma for the early llanvirn