holocene reef growth in torres strait the platform and fringing reefs of torres strait are morphologically similar to reefs of the northern great barrier reef to the south except that several are elongated in the direction of the strong tidal currents between the coral sea and the gulf of carpentaria surface and subsurface investigations and radiocarbon dating on yam warraber and hammond islands reveal that the initiation and mode of holocene reef growth reflect antecedent topography and sea level history on the granitic yam island fringing reefs have established in some places over a pleistocene limestone at about 6 m depth around 7000 years bp emergent holocene microatolls of porites sp indicate that the reefs have prograded seawards while sea level has fallen gradually from at least 0 8 m above present about 5800 years bp on the warraber island reef platform drilling near the centre indicated a pleistocene limestone foundation at a depth of about 6 m over which reefs established around 6700 years bp reef growth lagged behind that on yam island microatolls on the mature reef flat indicate that the reef reached sea level around 5300 years bp when the sea was around 0 8 1 0 m above present on the reef flat on the western side of hammond island bedrock was encountered at 7 8 m depth overlain by terrigenous mud a progradational reef sequence of only 1 2 m thickness has built seaward over these muds as sea level has fallen over the past 5800 years reef flat progradation on these reefs is interpreted to have occurred by a series of stepwise buildouts marked by lines of microatolls parallel to the reef crest marking individual coalescing coral heads detrital infill has occurred between these this pattern of reef progradation is consistent with the radiocarbon dating results from these reefs and with seismic investigations on the torres reefs

evidence for extended hercynian basement and a preserved jurassic basin margin tract in northern calabria southern italy the longobucco basin abstract in the longobucco basin northeastern calabria southern italy a mesozoic succession covers the hercynian basement documenting the evolution of a continental margin during the early jurassic extensional tectonic phase correlated with the western tethys rift the basin evolved from continental red beds around the rhaetian hettangian boundary to shallow marine and eventually deep sea siliciclastic turbidites in the late pliensbachian toarcian to dominantly pelagic deposits middle jurassic onwards around the sinemurian pliensbachian boundary following a prominent phase of normal faulting sedimentation took different paths in either hangingwall block or footwall block settings this study based on geological mapping focuses on the southwestern boundary of the longobucco basin and in particular on the mutual relationships existing between the deeper water basin fill units fiume trionto and fosso petrone formations the basement and the shallow water limestone of the caloveto formation which forms a narrow strip running parallel to the rift shoulder the contacts among the above mentioned units are generally all stratigraphic unconformities of various types onlap downlap nonconformity these characteristics separate the study area from the depocentral parts of the basin in terms of vertical stratigraphy nature of contacts among stratigraphic units unconformable vs conformable and impact of synsedimentary tectonics the signature of early jurassic extension occurs in the form of 1 laterally continuous clastic bodies interpreted as products of catastrophic basin margin collapse and avalanching 2 exhumation of the pre rift units which are otherwise deeply buried and 3 neptunian dykes of at least two generations our new data provide evidence for the presence of a 20 km long nw se trending preserved paleoescarpment where the basinal units onlap either the basement or the caloveto formation which forms a fringing carbonate body with intriguing facies and bio sedimentological features the paleoescarpment was the submarine morphological expression of a sinemurian pliensbachian fault as testified by the age of the clastic body that seals it another pulse of synsedimentary extension took place in the latest pliensbachian toarcian overprinting the existing rift architecture and reviving the production of megaclastic deposits

holocene fringing reefs and sea level change in mangaia island southern cook islands abstract holocene relative sea levels in oceanic islands that are situated sufficiently far from glaciated regions provide basic information for the study of the melting histories of the continental ice sheets and of the rheological structure of the earth we have studied mangaia island south cooks as one such oceanic island located in the middle pacific ocean in addition to the usual geological and geomorphological observations of geomorphic features associated with former shorelines we have used a portable drilling sampler for shallow borings of coral reefs geological and geomorphological studies of the coast of mangaia island have revealed that there was a higher sea level than the present in the mid holocene the heights and ages of emerged microatolls on the emerged bench indicate that the sea reached a maximum level of 1 7 m around 4000 3400 yr b p and then emergence is considered to have occurred between 3400 and 2900 yr b p at the same time the reef crest formed in the period from 5000 to 3400 yr b p emerged above the sea and suffered erosion as a result of this change in sea level upward reef growth from the fore reef slope began to form a new reef crest by 2000 yr b p to seaward of the old reef crest the reef margin of mangaia grew outward intermittently with seaward jump of the reef front in accordance with a fall of sea level in the late holocene the presence of fossil reef crests or eroded algal ridges on modern reef flats is a rather common feature in the south pacific the geomorphic development of such features on reef flats can be explained by the effect of the late holocene fall in sea level

post glacial sea level rise from a coral record at huon peninsula papua new guinea dating of coral reef terraces can provide a record of changes in sea level which should be pronounced during the transition between glacial and interglacial periods cores drilled from coral reefs at barbados in the equatorial west atlantic1have revealed the sea level changes that occurred during the younger dry as event at the end of the last glacial maximum 11 000 yr bp it has not been known however whether pacific coral reefs can grow at a rate sufficient to keep up with the rise in sea level during such a transition here we report results obtained from a 52 m drill core from the post glacial reef at huon peninsula papua new guinea spanning the interval from 7 000 to 11 000 14c yr bp which show that coral growth kept pace while the relative sea level rose by 50m although the tectonic environment is very different from that at barbados the two records compare well when corrections are made for local tectonic uplift showing that sea level rise was similar at both locations the rate of rise was greatest between 9 000 and 10 00014c yr bp corresponding to the time of the younger dryas

the morphology and distribution of submerged reefs in the maui nui complex hawaii new insights into their evolution since the early pleistocene reef drowning and backstepping have long been recognised as reef responses to sea level rise on subsiding margins during the late pleistocene 500 14 ka hawaiian reefs grew in response to rapid subsidence and 120 m 100 kyr sea level cycles with recent work on the submerged drowned reefs around the big island of hawaii and in other locations from the last deglacial providing insight into reef development under these conditions in contrast reefs of the early pleistocene 1 8 0 8 ma remain largely unexplored despite developing in response to significantly different 60 70 m 41 kyr sea level cycles the maui nui complex mnc forming the islands of maui molokai lanai and kahoolawe provides a natural laboratory to study reef evolution throughout this time period as recent data indicate the reefs grew from 1 1 to 0 5 ma we use new high resolution bathymetric and backscatter data as well as sub bottom profiling seismic data and field observations from rov and submersible dives to make a detailed analysis of reef morphology and structure around the mnc we focus specifically on the south central region of the complex that provides the best reef exposure and find that the morphology of the reefs varies both regionally and temporally within this region barrier and pinnacle features dominate the steeper margins in the north of the study area whilst broad backstepping of the reefs is observed in the south within the au au channel in the central region between the islands closely spaced reef and karst morphology indicates repeated subaerial exposure we propose that this variation in the morphology and structure of the reefs within the mnc has been controlled by three main factors the subsidence rate of the complex the amplitude and period of eustatic sea level cycles and the slope and continuity of the basement substrate we provide a model of reef development within the mnc over the last 1 2 ma highlighting the effect that the interaction of these factors had on reef morphology

coral reefs of the turbid inner shelf of the great barrier reef australia an environmental and geomorphic perspective on their occurrence composition and growth investigations of the geomorphic and sedimentary context in which turbid zone reefs exist both in the modern and fossil reef record can inform key ecological debates regarding species tolerances and adaptability to elevated turbidity and sedimentation furthermore these investigations can address critical geological and palaeoecological questions surrounding longer term coral sediment interactions and reef growth histories here we review current knowledge about turbid zone reefs from the inner shelf regions of the great barrier reef gbr in australia to consider these issues and to evaluate reef growth in the period prior to and post european settlement we also consider the future prospects of these reefs under reported changing water quality regimes turbid zone reefs on the gbr are relatively well known compared to those in other reef regions they occur within 20 km of the mainland coast where reef development may be influenced by continual or episodic terrigenous sediment inputs fluctuating salinities 24 36 ppt and reduced water quality through increased nutrient and pollutant delivery from urban and agricultural runoff individually and in synergy these environmental conditions are widely viewed as unfavourable for sustained and vigorous coral reef growth and thus these reefs are widely perceived as marginal compared to clear water reef systems however recent research has revealed that this view is misleading and that in fact many turbid zone reefs in this region are resilient exhibit relatively high live coral cover 30 and have distinctive community assemblages dominated by fast growing acropora montipora and or sediment tolerant species turbinaria goniopora galaxea porites palaeoecological reconstructions based on the analysis of reef cores show that community assemblages are relatively stable at millennial timescales and that many reefs are actively accreting average 2 7 mm year where accommodation space is available despite recent anthropogenic pressures these turbid zone reefs challenge traditional views on the environmental conditions required for active reef growth but given their proximity to land and associated stresses current knowledge on these less well understood reefs should be synthesised to aid coastal management directives terrigenous sediments are a dominant influence on turbid zone reef occurrence composition and growth and therefore the assessment of their future prospects will require a detailed understanding of the sedimentary regimes under which they occur and of their differential response modes

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

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

growth and structure of fringing reefs in a muddy environment south thailand abstract most fringing reefs of the se coast of phuket thailand have wide up to 300 m intertidal reef flats and narrow 2 5 m reef fronts that abut the muddy forereef only a few meters deep these reefs prograde by splitting toppling and regeneration of reef front massive corals notably porites lutea splitting of massive corals is greatly aided by the boring action of upogebia sp shrimps and by planes of weakness developed within the colony skeleton by nestling bivalves the large size of toppled blocks ensures that some of the uppermost polyps are viable above the soupy forereef sediment surface cores indicate that the reefs are essentially tabular features consisting of mainly massive reef front corals grown on muddy foundations that have shallowing upwards sediment haracteristics 14c ages and leveling data of fossil former reef front corals exposed on the reef flat suggest that reef growth started in the mid holocene when sea level was at least 0 8 m higher than now since then the rate of lateral reef progradation has averaged 40 mm yr the preservation potential of these reefs is low because of the combination of a lack of organic or inorganic binding of the corals into a rigid frame and the unconsolidated nature of the underlying sediments

modern coral reefs of western atlantic new geological perspective contrary to popular belief of the late 1960s western atlantic holocene reefs have a long history and are not feeble novice nearshore veneers that barely survived postglacial temperatures rather the growth of these reefs kept pace with the rising seas of the holocene transgression and their development was for the most part controlled by offshore wave energy conditions and the relationship between changing sea levels and local shelf topography thus the outer shelves of the eastern caribbean in areas of high energy have relict reefs consisting predominantly of acropora palmata a robust shallow water coral the flooding of adjacent shelves during the postglacial transgression introduced stress conditions that terminated the growth of these reefs when about 7 000 r ago shelf water conditions improved scattered deeper water coral communities reestablished themselves on these stranded shelf edge reefs and fringing and bank barrier reefs began to flourish in shallow coastal areas at the same time the fragile and rapidly growing acropora cervicornis and other corals flourished at greater depths on the more protected shelves of the western caribbean and the gulf of mexico as a result late holocene buildups more than 30 m thick developed in those areas

holocene coral reef growth and sea level in a macrotidal high turbidity setting cockatoo island kimberley bioregion northwest australia abstract the inshore kimberley bioregion of northwest australia is a macrotidal low wave energy frequent cyclones and high turbidity setting with abundant fringing coral reefs here we describe the holocene development of a sheltered fringing reef at cockatoo island in the kimberley using data from reef cross sections subaerially exposed in an iron ore mining pit seismic profiles across the adjacent contemporary reef and gis and ground truth mapping of contemporary reef habitats subsidence since the last interglacial has provided accommodation for 13 20 m of holocene reef accretion upon an older probably last interglacial reef in the pit cross sections the reef initiated at 9000 cal y bp and accreted in a catch up mode reaching sea level at 3000 cal y bp and reef accretion rates varied from 26 8 mm year to 0 8 mm year averaging 2 mm year the catch up interpretation is supported by the predominance of branching acropora throughout the holocene section and the absence of contemporary intertidal indicators such as porites cylindrica and millepora intricata this pattern differs from the otherwise similar mud rich but mostly microtidal inshore fringing reefs of the great barrier reef which initiated in the late holocene on shallow substrates under a stable sea level the study provides the first holocene reef growth history for an inshore kimberley reef within a biodiversity hotspot

large earthquakes kill coral reefs at the north west gulf of aqaba down faulting at the north west margins of the gulf of aqaba is inferred to have triggered a catastrophic sedimentary event at 2 3 ka that killed the elat fringing coral reef whereas segments of the holocene reef were perfectly fossilized and preserved beneath a veneer of siliciclastic sediments other segments were abraded settled by nomads and later re submerged under 4 m of water repeated damage triggered by down throwing earthquakes degenerate the fringing reefs of the north west end of the gulf conversely on the north eastern and southern parts of the gulf where earthquakes uplift the margins modern reefs are thriving attached to uplifted fossil reef terraces therefore coastal subsidence moderates the development of fringing coral reefs during the late holocene sea level stand still

the holocene drowned reef of les saintes plateau as witness of a long term tectonic subsidence along the lesser antilles volcanic arc in guadeloupe abstract resulting from the interplay between tectonics and eustatism reef terraces are powerful markers of vertical movements at a scale of 1000 to 100 000 years in the lesser antilles they grow around every island of the archipelago and record both local and subduction related tectonics the recent acquisition and interpretation of very high resolution bathymetry of les saintes submarine plateau french west indies together with seismic reflection profiles are a unique opportunity to study one of these submarine structures at metric to kilometric scales addressing the questions of its nature age and growth environment but also of the control of active tectonics on its formation the 20 km wide les saintes reef plateau lies at about 45 mbsl it is crosscut by nw se striking north dipping normal faults that belong to les saintes fault system and graben which produced a mw 6 3 earthquake in 2004 the plateau is composed of four 20 m thick reef units piled up in layer cake morphology down to 110 mbsl the upper unit has a fresh morphology and presents typical reef features like barrier and lagoon spurs and grooves pinnacles etc from its morphology we propose that it grew during the holocene last transgression below the three other units likely formed during pleistocene sea level highstands and were eroded during the low stands as evidenced in seismic reflection profiles this scenario would imply that les saintes plateau formed in a context of subsidence with a rate we evaluate to be of the order of tenths of mm yr probably linked to local tectonics we believe that this deformation is also related to plate scale subduction processes similarly to deformations occurring on the other islands of the guadeloupe archipelago

fringing reef growth on a terrigenous mud foundation fantome island central great barrier reef australia the leeward fringing reef at fantome island central great barrier reef province is a carbonate body which has developed under the influence of terrigenous sedimentation the reef flat is up to 1000 m wide and is surfaced by mobile sand and gravel with almost all live corals restricted to the seaward rim the reef slope has coral columns and heads on the upper part but below 5 m water depth it is a muddy substrate with scattered mounds of branching corals three high recovery cores show the reef is up to 10 m thick and developed over a gently sloping terrace of weathered pleistocene alluvium three post glacial stratigraphic units are recognised i carbonate reef top unit of coral rudstone and framestone including sinuluriu spiculite 2 lower slope unit of coral floatstone in a terrigenous muddy matrix and 3 transgressive basal unit of skeletal arkosic sand the acid insoluble content of matrix and of individual corals increases downwards coral growth rates decrease downwards reflecting slower growth in muddier environments radiocarbon dating shows that the reef prograded seaward at almost stable sea level an average vertical accumulation rate of 6 7 mm yr is indicated two age reversals are interpreted as material transported by storms or by erosion in response to a late holocene sea level fall the carbonate reef top unit has developed adjacent to and is environmentally compatible with a muddy terrigenous lower slope unit terrigenous influx has not changed during the holocene and terrigenous content of sediments is controlled by deposition on the reef slope of fine sediment winnowed from the reef flat and concentration of coarse sediment in the transgressive basal sheet

evidence for smoothly falling sea level relative to north queensland australia during the past 6 000 yr post glacial sea level curves are expected to differ between different parts of the world as a result of global isostatic changes1 or perhaps other forms of geoidal changes2 i report here results from the inner part of the northern great barrier reef which seem to show a pattern of smoothly falling sea level during the past 6 000 yr the results are consistent with stratigraphical results from prograded mangrove coasts on the nearby north queensland mainland the region is remote from the tectonically active margin of the south west pacific ocean and the results contribute to the global data set relevant to isostatic changes being assembled by the international sea level project igcp project no 61 they also provide a baseline relevant to holocene coral reef growth in the inner great barrier reef

development of an inshore fringing coral reef using textural compositional and stratigraphic data from magnetic island great barrier reef australia the stratigraphy of fringing coral reef environments and platforms provides unique insights into reef development and evolution this study used twelve sediment cores from three transects across a reef flat in nelly bay magnetic island ne australia to examine its development over the holocene the maximum thickness of the holocene reefal material based on seismic and bore log data was around 5 m and comparable to other fringing reefs in the great barrier reef gbr six different sedimentary facies were identified in the cores and two coincided with reef accretion the lower muddy sand with coral rubble and the upper siliciclastic sand with coral rubble radiocarbon and u series dates show that the nelly bay fringing reef initiated around 6300 yr bp on a gently sloping unconsolidated or weakly cemented pleistocene alluvial sedimentary facies the ages of four massive coral heads range between 5790 and 6290 calibrated c 14 yr bp were almost contemporaneous with reefal initiation indicating that conditions were favourable for reef growth around this time vertical accretion rates for the nelly bay fringing reef were on average about 0 5 mm yr over the last 6000 yr although rates were as high as 5 mm yr during initiation average lateral accretion rates varied from 98 to 120 mm yr which are comparable to rates of other fringing reefs in the region the age structure of the lower muddy sedimentary facies was consistent with the classic seaward prograding model of fringing reef development in contrast the upper siliciclastic sand with coral rubble facies was much younger in age 1100 yr bp than the models and appears to represent an erosional unconformity between the upper and lower reefal facies possibly linked to late holocene sea level fall this younger facies extends laterally across the reef flat and has no obvious prograding symmetry our integrated approach using multi proxy analyses of sediment cores from the nelly bay reef flat highlights the complex development of this reef which include changes in coral composition and rubble preservation reef evolution in response to sea level change and changes in reef accretion rates

coral reef records of quaternary changes in climate and sea level abstract although coral reefs have long been regarded as documenting climate change largely through its effects on sea level the temporal continuity and sensitivity to disturbance of their records appears to fall short of those provided by ice cores deep sea sediments and similar proxies the reasons for this anomaly relate principally to shifts in the loci of deposition the temporal windows in which accretion has been able to occur in a given place reflecting sea level at a particular height relative to the present datum are severely constrained where it has been possible coral growth and reef accretion have been and are sensitive to the signals provided by the environment in the form of changes in water depth temperature salinity nutrient supply turbidity and ph acidity concomitant with changes in sea level itself changes in these environmental parameters are directly or indirectly controlled by climate however because the responses of corals to stimuli are commonly site specific and the nature of the changes evoked so disparate it is likely that only major sea level cycles will provide evidence of a consistent global response in what has been a segmented record

relative sea levels and coastal sedimentation in southeast australia in the holocene abstract in recent years australian studies of relative sea level change have shown reasonable consistency on the termination date of the postglacial marine transgression at c 6 500 14c years bp the following stillstand period has been characterized in some regions by a slight falling trend from a high stand or in other areas by a level not easily distinguished from the present the latter situation occurs on the embayed coast of new south wales here studies of depositional environments and sequences within bed rock embayments have linked the holocene sea level history to patterns of sedimentation on the inner shelf in bay barriers and in estuaries deposition of quartz rich sand in shoreface flood tidal delta and backbarrier environments occurred during the marine transgre sion and the subsequent stillstand shell fragments from these deposits have been radiocarbon dated shoreline displacement continues to the present day partly in response to changes in availability of sand in the shoreface zone and partly in response to variations in regional storminess patterns a nd the great shroud of the sea rolled on as it rolled five thousand years ago herman melville moby dick

holocene sea level change and evolution of a mixed coral reef and mangrove system at iriomote island southwest japan abstract exposed fossil microatolls and core samples from a coral reef and a mangrove forest at the yutsun river mouth iriomote island southwest japan reveal the internal structure and temporal changes in the sedimentary processes of a mixed reef mangrove system evidence from the core samples and fossil microatolls suggests sea level reached its present position before 5100 cal yr b p and a relative sea level highstand of 1 1 1 2 m above the present sea level occurred from 5100 to 3600 cal yr b p this was followed by a gradual fall in relative sea level the tectonically corrected sea level curve indicates a stable sea level after 5100 cal yr bp with a sea level highstand of up to 0 4 m between 5100 and 3600 cal yr b p a nearshore reef dominated by massive porites and arborescent acropora initially developed at 6500 3900 cal yr b p reef development was potentially terminated by relative sea level fall and sediment discharge from the yutsun river that affected the backreef environment an offshore coral reef reached present day sea level by 1000 cal yr b p forming a wave break that enabled the foundation of mangrove forest on the fringing reef after 1000 cal yr b p the reef development was significantly delayed compared with other coral reefs in the region with similar medium to high energy conditions but it provided a calm environment in the backreef area that allowed the development of mangroves these features demonstrate the chronology and causal relationship between coral reef and mangrove development under the influence of holocene sea level change and river discharge

melting ice sheets 400 000 yr ago raised sea level by 13 m past analogue for future trends abstract marine isotope stage mis 11 was possibly the longest 423 000 362 000 yr ago and warmest interglacial of the entire quaternary period this resulted from a special arrangement of earth s orbital parameters similar to the present interglacial mis 1 suggesting that mis 11 provides an analogue for future natural climate forcing and sea levels although precise documentation of mis 11 sea level history is therefore crucial especially considering additional impetus from anthropogenic warming the maximum mis 11 sea level remains highly contentious estimates from onshore indicators have ranged from below present sea level to about 20 m resulting from uncertainties in reliability of sea level indicators estimates of their subsequent displacement by vertical crustal motion and in dating we used a clear and unambiguous sea level indicator interface between subtidal and intertidal deposits in well exposed regressive raised shoreline deposits along south africa s southern coast the coast is stable in terms of tectonic setting and falls within a zone of low predicted glacio isostatic adjustment gia and low sensitivity for plausible model parameters the sea level indicators were directly dated using thermally transferred optically stimulated luminescence tt osl which gave a mean age of 390 ka corresponding with mis 11 we determined a precise maximum elevation of 14 m for the mis 11 sea level indicator which corrected for minor crustal uplift and gia yielded a eustatic sea level of 13 m 2 m the complete mis 11 transgressive regressive shoreline succession is preserved and the wave cut platform extends 950 m inland from the present shoreline indicating a prolonged highstand we have also documented sea level fluctuations during mis 11 including an earlier lower highstand close to present sea level which may explain the lower elevation range of some previous estimates at one locality mis 11 deposits form a sea cliff against which mis 5e sediments at an elevation of 6 2 m abut the 13 m mis 11 sea level tallies with total melting of the greenland and west antarctica ice sheets regarded as most susceptible to melting our data predict notably higher sea levels in the future regardless of anthropogenic influence on climate

response of reef coral communities to sea level rise a holocene model from mauritius western indian ocean the fringing reef at pointe au sable mauritius indian ocean was used to examine the effects of holocene sea level rise on coral growth this reef is about 1000 m wide and comprises a forereef slope 30 m maximum depth a narrow reef crest and a very shallow backreef 1 5 m maximum depth four major coral communities were recognized which developed within relatively narrow depth ranges a pachyseris oulophyllia community deeper than 20 m an acropora tabulate faviid community 20 6 m a robust branching acropora community less than 6 m and a pavona community less than 10m three high recovery cores show the holocene reef sequence is a maximum of 19 3 m thick and comprises four coral biofacies which are similar to counterparts identified in modern communities robust branching tabular branching robust branching domal and foliaceous coral facies a minimum sea level curve for the past 7500 years was constructed using distribution patterns of coral biofacies and radiocarbon dates from corals reconstruction of reef growth history indicates that both offshore and onshore reef zones were developing coevally aggrading at rates of 4 3 mm year 1 from 6900 years b p the reef caught up with sea level only after sea level stabilized changes in coral community and reef growth rates were driven principally by increasing water agitation due to the decrease in accommodation space based on the composition of the successive coral assemblages the reef appears to have grown through successive equilibrium stages

seismic stratigraphy and development of the shelf edge reefs of the great barrier reef australia extensive shelf edge reefs sers and terraces are common along the seaward margin of the great barrier reef gbr we aim to better understand the architecture of the sers deposited during a poorly constrained period the last glacial maximum lgm and early postglacial a dense array of topas seismic lines was interpreted at hydrographers passage in the southern central gbr following a seismic stratigraphic approach ground truthed against integrated ocean drilling program expedition 325 iodp exp 325 sediment core data we interpreted two prominent sub bottom reflectors an upper r1 and a lower r2 that separate three seismic units according to our borehole to seismic correlation in a representative location r1 corresponds to a downward increase of impedance which is also reflected in lithological and diagenetical changes r2 is poorly constrained but likely also represents a lithological contrast seismic velocities were also estimated in the same borehole location for inter reef deposits and reef framework together with the geomorphic interpretation we reconstructed velocity maps for the study area leading to the generation of a 3d geomorphic model of the antecedent topography or substrate and volumetric calculations geomorphic and thickness trends suggest a strong relationship between the antecedent topography and the morphology of the sers the distribution of seismic facies identified in the dataset coupled to geomorphic trends and published sea level curves allowed us to reconstruct the lgm to postglacial depositional history of these deposits our interpretation suggests significant regressive reefal accumulations formed on top of a marine flooding surface represented by reflector r2 during the sea level fall to the lgm r1 is the distal equivalent of an unconformity previously identified in the gbr inner and mid shelf widely affected by subaerial exposure on top of which a postglacial transgressive mainly reefal unit 1 was deposited two zones are distinguished 1 a distal zone below 80 mbsl with thick deposits displaying fringing reef morphologies influenced by the late lgm fall and subsequent early postglacial rise in sea level and by the updip availability of substrate and 2 a proximal zone above 80 mbsl of enhanced vertical growth with unfilled lagoons resulting from the lack of lateral substrate and the rapid sea level rise our seismic stratigraphic model of the development of the sers sediment volumetrics and 3d reconstruction of the antecedent topography provides a foundation for future forward modeling stratigraphic studies

the role of fringing coral reefs on beach morphodynamics article i nfo this paper examines the degree of energy dissipation provided by a fringing coral reef and its role on the morphodynamics of adjacent beaches in terms of volumetric sediment transport morphological data were collected from the microtidal mexican caribbean beaches of puerto morelos fringed by a reef and cancun without a reef from september 2007 to may 2011 being exposed to the same offshore wave conditions the morphodynamics of the coral reef fronted beach were compared with those of the adjacent beach without a coral reef spatio temporal changes in beach morphology were determined applying empirical orthogonal functions eof to the shorelines extracted from the topographic data and it was concluded that puerto morelos was considerably less dynamic than cancun the longshore energy fluxes were larger in cancun and the subaerial morphological differences in both beaches and under the same offshore conditions demon strated that puerto morelos was particularly stable under shore normal easterly waves a calibrated phase averaged wave model was implemented to determine the amount of wave energy dissipation across the coral reef for energetic shore normal waves the model determined that the semi emerged coral reef was ca pable of reducing up to 85 of the incident wave height the reef crest height controlled the amount of wave energy dissipation and the distance between the reef crest and the shore determined the vulnerability of the beach to morphological changes reef crest degradation by 1 m resulted in a 10 increase in incoming wave energy which resulted in 0 9 m 3 h m of sand being mobilised along the beaches closer to the reef

nearshore circulation in a tropical fringing reef system 1 the role of waves tide and wind on the circulation of a fringing reef system was investigated using data collected during a 6 week field experiment in a section of ningaloo reef off western australia the high correlation observed between current velocities and wave height throughout the system revealed the dominant role wave breaking plays in driving the overall reef lagoon circulation whereas the modulation of the currents at tidal frequencies suggested that the wave driven currents responded to tidal variations in the mean water level over the reef the influence of the various forcing mechanisms on the current field was investigated for both high and low frequency bands wave breaking was found to be the dominant forcing mechanism for the low frequency subtidal currents with the subtidal flow pattern consisting of a cross reef flow over the reef alongshore flow in the lagoon and water exiting back to the ocean through the main channel the tides controlled the high frequency current variability via two mechanisms one associated with the ebb flood cycle of the tides and the second associated with tidal modulations of the wave driven currents wind forcing and buoyancy effects were both found to be negligible in driving the circulation and flushing of the system during the observation period flushing time scale estimates varied from as low as 2 h to more than a day for the wide range of observed incident wave heights the results suggest that the circulation of ningaloo reef will be strongly influenced by even a small mean sea level rise

fringing reef growth over a shallow last interglacial reef foundation at a mid shelf high island holbourne island central great barrier reef fringing reefs are rare on the mid shelf of the central great barrier reef with holocene development histories established for a few examples the paucity of reef growth records from mid shelf fringing reefs has limited opportunities for comparisons with inshore fringing reef growth records to better understand the influence of changes in environmental conditions on reef growth with distance offshore the long term development of the mid shelf fringing reef at holbourne island was reconstructed using nine percussion and drill cores that captured the entire holocene period of reef growth the cores were chronologically constrained by 16 high precision th 230 ages a weathered pleistocene reef substrate was u th dated as last interglacial open system age of 131 100 1000 cal ybp and this provides the underlying foundation upon which the holocene reef initiated prior to similar to 7520 20 cal ybp the last interglacial reef was encountered 5 9 m below the present reef surface and is the shallowest confirmed last interglacial reef in the central gbr region to date most of the holocene reef structure was emplaced within 1000 years of initiation the chronostratigraphy and contemporary geomorphology of the fringing reef at holboume island preserve evidence of re working and stripping of the reef structure by cyclones this evidence includes 1 an age hiatus in core data of similar to 3500 years 6238 18 to 2683 10 cal ybp 2 the abundance of detrital branching coral rubble material within the core facies 3 the surface elevations and ages of fossil microatolls which reveal that storm induced ponding of water during low tidal stages up to 55 cm deep has been active but intermittent across the reef flat for at least 600 years and is still active today and 4 long standing shingle ridges onshore and modern shingle ridges on the reef flat

morphological indicators of structural control relative sea level fluctuations and platform drowning on present day and miocene carbonate platforms abstract the morphology of carbonate platforms may be influenced by tectonic activity and eustatic variations 3d seismic data and satellite imagery are used in order to investigate the morphological similarities between present day carbonates platforms east of borneo island and miocene carbonate platforms of the south china sea the morphological similarities exhibit platform fragmentation that could be caused by subtle faulting sufficient to drown reef rims platform contraction which is a result of back stepping of the reef margin during a relative sea level rise and polygonal patterns in internal lagoons described as mesh reefs in modern platforms and possibly interpreted as karst in miocene platforms vertical movements may trigger the formation of new geomorphological conditions that modify the distribution of coral growth with respect to the new hydrodynamic conditions in space and time these movements uplift and tilting reduce and localize the space necessary for the coral ecosystem explaining the contraction leading to drowning of parts of and ultimately the whole platform

fringing reef growth and morphology a review abstract fringing reefs are generally not simple veneers of coral growth along tropical shorelines extensive research over the past few decades based on radiocarbon dating of holocene reef deposits has indicated that they can develop in a complex variety of ways even though the surface morphology may appear relatively simple the principal factor that appears to determine the growth and morphology of fringing reefs is the available accommodation space sea level fluctuations are important primarily because the sea surface determines the absolute accommodation space for a given reef this means that a reef established during a period of sea level rise will be able to accrete vertically as space is created above it if however the reef establishes at or grows to the sea surface thereby occupying all the available accommodation space it can no longer accrete vertically and begins to build laterally the morphology and chronostratigraphy of a range of holocene fringing reefs are described on the basis of which six fringing reef growth models are identified in model a the fringing reef is established at depth and primarily accretes vertically towards the sea surface reef growth in model b initiates at sea level and due to the lack of vertical accommodation space grows laterally model c has a similar morphology to model b however the reef progrades over a non reefal sediment wedge episodic lateral and vertical growth occurs in model d with a stepwise progradation of the reef front the remaining models are characterised by seaward reef framework behind which unconsolidated sediments accumulate in model e reef crest growth forms a barrier leading to the development of a backreef lagoon model f has a similar morphology to model e except that the reef crest is formed by hurricane rubble accumulation rather than framework accretion and is periodically reworked

contradicting barrier reef relationships for darwin s evolution of reef types the darwinian progressive subsidence model for the evolution of fringing reefs barrier reefs and atolls has been generally accepted following the indisputable proof of subsidence provided by drilling results in the pacific nonetheless there are data that do not fit the expectations of the model such as the similar lagoon depths of barrier reefs and atolls as opposed to the subsidence theory s implicit prediction that atolls should have significantly greater depths in contrast a great deal of evidence supports the influence of meteoric solution on barrier reef morphology for example the maximum lagoon depth of 56 modern barrier reefs is statistically correlated with the lagoon catchment area for modern annual rainfall these modern rainfall patterns would seem to be a reasonable proxy for relative geographic differences in glacial lowstand rainfall even though the absolute amounts of such rainfall are unknown the correlation therefore suggests the importance of pleistocene subaerial solution in contributing to barrier reef morphology further support for antecedent influence occurs in the form of barrier reef passes in which the depth of the reef pass is correlated with onshore drainage volumes on a larger scale the cook island of mangaia provides evidence that solution can produce barrier reef morphology independent of reef development in contrast there are no examples of the subsidence predicted lagoon transition of fringing reefs to barrier reefs to atolls moreover the common occurrence of fringing reefs within barrier reefs negates subsidence as a causal factor in their presumed progressive evolutionary development consequently the evidence to date suggests that a solution morphology template has been accentuated by reef construction to produce the diagnostic barrier reef morphology we see today the importance of subsidence would seem to be in accounting for the overall thickness of the resulting carbonate caps of oceanic examples and in contributing to lagoon depth variation among the larger continental entities

foraminiferal biofacies in a silica rich neritic sediment late eocene south australia abstract the highly siliceous blanche point formation accumulated during the late eocene zones p15 p16 in the st vincent basin when the climate was warm it differs from shelly neritic carbonates above it and below it by higher but fluctuating numbers of benthonic foraminifera of the family uvigerinidae and by high dominance in different horizons of infaunal crustacean traces and of infaunal gastropods within the blanche point formation changes from a banded siliceous opal ct sediment to a homogeneous spongolite are paralleled by biofacies changes high numbers of uvigerinidae and in part of the formation high numbers of robertinacea bolivinidae sphaeroidina cassidulina are more consistent with generally lowered levels of oxygen at the sediment surface than with other forms of environmental stress the study is consistent with a recent conclusion based on mineralogy that the abundant silica came from volcanic ash it suggests too that restricted circulation permitted biogenic and other mechanisms of fix the silica in the st vincent basin whilst silica was being flushed away from more open environments facing the nascent southern ocean

origins and development of holocene coral reefs a revisited model based on reef boreholes in the seychelles indian ocean until recently concepts of coral reef growth and accumulation have been predominantly based on a darwinian model in this the upwards and outwards growth of a reef core a coral framework takes place over a foreslope consisting of reef talus with the simultaneous filling of the back reef lagoon by reef derived debris the principal adaptations of this pattern relate to the influence of relative changes in sea level and commonly ignore oceanographic factors such as storm frequency and severity boreholes through the outer edge of a fringing reef in the seychelles western indian ocean reveal a record of holocene sediment accumulation first established approximately 8 ka ago faunal and floral associations show that growth of this body began in relatively deep water but that this shallowed to 5 m within 1 ka subsequent accumulation was of keep up style but as the rate of sea level rise slowed shoaling became more frequent and aggradation was limited by reducing accommodation space constructional facies are characterised either by massive corals including leptastrea porites and faviids or by branching corals typically acropora of the danai robusta group coral surfaces may be encrusted by red algae foraminifera and vermetids and are commonly bored by filamentous algae clionids and molluscs however detrital facies are volumetrically dominant and the paucity of a constructional framework requires a re evaluation of models of reef accretion new models relate the geometry of accretion to the interplay between extreme storm events and fairweather hydrodynamic conditions these suggest that a contiguous framework forms in areas of moderate fairweather energy without extreme storm events severe storms destroy the continuity of reef structures and generate increasing volumes of coarse detritus low storm severity coupled with low fairweather hydrodynamic energy may promote the accumulation of fine grained reef derived sediments that inhibit framework growth while ecology reflects year by year sea conditions lithology and structure are controlled by exceptional storms with the effects of changing sea level superimposed

modern fringing reef carbonates from equatorial se asia an integrated environmental sediment and satellite characterisation study abstract fringing reefs of se asia may conservatively comprise 30 of the world s coral reef area but remain almost unstudied white 1987 tomascik et al 1997 this study provides insights into the primary sedimentological and early alteration characteristics of an isolated fringing reef system kaledupa hoga from the tukang besi archipelago se asia a combined multispectral satellite imagery field and petrographic study allowed for the generation of an environmental facies map which acts as a model for the distribution of primary sedimentological characteristics in relation to the primary environmental facies the islands of the tukang besi archipelago are mesotidal 71 accuracy when compared with field and sedimentary data with the exception of the reef crest and reef slope that commonly have widths on a sub imaging resolution although field and satellite imagery observations reveal ten environmental facies sedimentological characterisation results in a lower number of distinctive categories due to the similarity of many deposits foreshore backshore and bare intertidal deposits are distinctive and are composed of reef derived material that has been reworked shorewards seagrass associated facies all show some fine silt clay sized material

distinct relict fringing reefs in the northern shelf of the gulf of elat aqaba markers of quaternary eustatic and climatic episodes quaternary reef development and demise have been shown to correspond to worldwide sea level fluctuations and related environmental changes yet the mechanisms and rates affecting this relationship are not well resolved a set of high resolution seismic reflection and multibeam bathymetric data were interpreted six distinct systems of relict fringing reefs embedded within the sedimentary cover of the northern shelf of the gulf of elat aqaba were identified the two uppermost relict fringing reefs are also exposed on the sea floor in water depths of ca 20 m and ca 60 m along the north western corner of the northern gulf of elat aqaba and sub parallel to the current northern coast respectively two other relict fringing reefs are laterally correlated to each of the last two transgressive cycles and are inferred to have formed during decelerations in sea level rise during the last two deglaciations these reefs and the units to which they are laterally correlated portray a repeating stratigraphic pattern of reef development during deposition of seismically homogeneous sediment and an ensuing demise during deposition of heterogeneous sediment correlation of the reef stratigraphy with rates of late quaternary sea level rise and a sediment accumulation rate from one shelf core provide age estimations for the seismic stratigraphy two phases of fringing reef generation occurred during the last deglaciation since ca 18 ka the older reef probably developed between 12 8 ka and 11 5 ka at ca 60 m below present sea level and the younger reef after 8 4 to 8 0 ka at ca 20 m below present sea level these last two phases of reef generation are separated by a lobate seismic unit that is interpreted as fluvial deltaic deposits that backstepped across the shelf during the early holocene transgression results suggest that fringing reefs evolved along the northern shelf of the gulf of elat aqaba only during relative decelerations in sea level rise contemporaneous with low input of terrigenous sediment and probably during a period of aridity at present no fringing reef grows along the northern coast of the gulf of elat aqaba suggesting that these relatively arid periods may have been drier than recent the pattern of slowdown in sea level rise contemporaneous with conditions of increased aridity seems to have repeated during the last two sea level rises approximately at the same sea levels suggesting a common mechanism of short millennium scale phases of eustatic and climatic alteration during deglaciations

acidification mediated by a river plume and coastal upwelling on a fringing reef at the east coast of hainan island northern south china sea we investigated the dynamics of carbonate system which was greatly modulated by a river plume and coastal upwelling in july 2014 and july 2015 at the east coast of hainan island where a fringing reef distributes inshore by using a three end member mixing model we semi quantitatively estimated the removal of dissolved inorganic carbon dic mediated by biological production in the river plume and upwelled water to be 13 17 mol kg 1 and 15 16 mol kg 1 respectively the enhanced organic production was mainly responsible for these dic consumptions in both two regimes however nearly a half of dic removal was attributed to biocalcification in the plume system while it was negligible in the upwelling system furthermore the modeled results over reefs revealed that river plume and coastal upwelling were two major threats of acidification to coral communities at the east coast of hainan island during cruises in comparison the biological contribution to acidification was limited for balancing between organic production and biocalcification during july 2014 cruise whereas the acidification was greatly intensified by organic degradation during july 2015 cruise it was verified that naturally local acidification physical and biological processes played a major role in great ph decreases on a short term scale leading to coastal waters more vulnerable to anthropogenic ocean acidification uptake of atmospheric co2 by reducing buffering capacity of waters finally effects of acidification associated with other local threats on a fringing reef was further depicted with a conceptual model

anatomy of a fringing reef around grand cayman storm rubble not coral framework abstract our fair weather perception of modern reefs has led to the implicit assumption that their development is controlled by processes that govern the siting of in place coral growth yet more ephemeral processes such as storms and hurricanes assume much greater importance over longer time scales because few reefs escape their influence to discover the importance of storms on reef development we analyze the zonation anatomy and architecture of a fringing reef complex around grand cayman we find that the surface zonation of in place corals is merely a facade and the reef core is in fact composed of meter thick layers of coral cobble rudstone capped by crusts of coralline algae the large size and abraded condition of the rudstone clasts shows that these layers are not the product of f ir weather processes but the result of destruction and deposition during hurricanes as hurricane waves cross coral mantled zones of the inner shelf they destroy live coral stands and deposit the clasts as a rubble layer covering the entire reef complex between storms this rubble foundation is stabilized by coralline algal crusts and recolonized by rapidly growing corals leading eventually to full reef regeneration before the next hurricane this cyclic pattern of destruction and regeneration consequently produces a fringing reef complex with a core composed of hurricane generated rubble not coral framework as previously assumed in addition to explaining reef anatomy hurricane control also explains the variation in reef architecture along shelf uniform reef location across shelf and reef absence along certain shelf sections as hurricane waves cross a mid shelf scarp they start to break and destroy coral growth over most of the inner shelf coral rubble generated by these waves is deposited 350 50 m from the mid shelf scarp on margins exposed to the largest waves but only 250 50 m on semi protected margins that experience smaller fetch limited waves in areas where the width of the inner shelf is 250 m hurricane waves throw rubble ashore and a fringing reef does not develop during sea level rise this influence of shelf width on rubble deposition controls the timing of reef nitiation and that in turn controls reef architecture reefs initiate first on low gradient coasts with wide shelves and gradually extend around higher gradient coasts as sea level rises and shelf width increases thus older reefs are located farther offshore front deeper lagoons and have thicker and narrower profiles than younger reefs

sea level highstand recorded in holocene shoreline deposits on oahu hawaii abstract unconsolidated carbonate sands and cobbles on kapapa island windward oahu are 1 4 2 8 0 25 m above present mean sea level msl agreeing with stearns 1935 we interpret the deposit to be a fossil beach or shoreline representing a highstand of relative sea level during middle to late holocene time calibrated radiocarbon dates of coral and mollusc samples and a consideration of the effect of wave energy setup indicate that paleo msl was at least 1 6 0 45 m above present msl prior to 3889 3665 cal yr b p possibly as early as 5532 5294 cal yr b p and lasted until at least 2239 1940 cal yr b p hence the main phase of deposition on kapapa island lasted a minimum of c 1400 yr and possibly as long as c 3400 yr no modern samples have been recovered from the fossil beach on kapapa island and samples from potential source sites offshore of the island show modern ages indicating that sediments on the island are not deposited by modern era storm and tsunami overwash because antecedent sediments are uncommon offshore but common on the island deposition must have been time transgressive rather than related to a single event radiocarbon ages of coral and mollusc clasts from a breccia lining an emerged 1 4 0 25 m msl intertidal notch cut into emerged coralline algal carbonate of presumed last interglacial age on south mokulua island 15 km to the southeast of kapapa island correlate to the history recorded on kapapa island calibrated ages range from 2755 2671 to 3757 3580 cal yr b p averaging c 3100 cal yr b p suggesting that a higher than present sea level formed the notch prior to 3757 3580 cal yr b p a storm or tsunami origin for the features on kapapa and south mokulua islands is highly unlikely their age and elevation indicate instead a history of higher relative sea level and subsequent fall on windward oahu during the middle to late holocene this history is consistent with geophysical models of postglacial geoid subsidence over the equatorial ocean first predicted by walcott 1972 and later refined by clark et al 1978 and mitrovica and peltier 1991

geomorphological changes in the coastal area of farasan al kabir island saudi arabia since mid holocene based on a multi proxy approach abstract the geomorphological evolution of the southeastern coastal area of farasan al kabir island saudi arabia is revealed by the mapping of modern landforms and a multi proxy and high spatial resolution study including grain size particulate organic carbon mineralogy element geochemistry benthic foraminifera analysis and radiocarbon dating of a 3 3 m long sediment core the modern geomorphological features comprise a variety of arid landforms such as plateau cliffs and pediments of pleistocene coral limestones playa depressions located on plateau surfaces alluvial fans butte and sandy beaches the mid holocene evolution of the borehole area is resulted from the detailed analysis of five sedimentary units detected along the core matar 1 and includes three distinct stages a from 5253 223 y cal bp to 3138 223 y cal bp carbonate coarse grained material consisting of coral fragments molluscs calcareous algae and benthic foraminifera are deposited on a shallow marine fringing reefal platform which becomes progressively a nearshore backreef around 3675 215 y cal bp and later around 3138 223 y cal bp a reef ramp b since 3040 220 y cal bp the borehole area obtains the characteristics of a high energy beach that receives increasing inputs of terrigenous material c subsequently a supratidal backshore setting is established influenced mostly by terrestrial processes and occasionally by marine processes as it is indicated by the decreasing and sometimes sporadic presence of benthic foraminifera and recently a sedimentary veneer consisting of terrigenous carbonate and evaporite material is formed by terrestrial mainly wadi and aeolian processes

lagoon shelf sediment exchange by storms evidence from foraminiferal assemblages east coast of grand cayman british west indies abstract the abundance and size distribution of ecologically diagnostic foraminiferal species are ideal tracers of sediment transportation and storm processes on the windward shelf of grand cayman during storm peak sediment in the lagoon and fore reef is suspended by large storm waves sediments of sand size and finer including forereef foraminifera species are moved shoreward by wind driven currents and deposited in a blanket behind the reef the fore reef foraminiferal assemblage is winnowed and the mean and median sizes of amphistegina gibbosa progressively decrease from the shelf edge into the inner lagoon as the storm wanes water piled in the lagoon drains via channels and sediment is transported offshore consequently lagoonal sediment that includes lagoonal foraminiferal t sts is carried out of the lagoon and deposited on the fore reef terrace and down the shelf escarpment this process produces winnowed lagoonal sediments because suspended fine sediments are preferentially transported during the long inter storm periods tranquil conditions are once again established and sediment exchange between the lagoon and on the fore reef terrace ceases during this time lagoonal organisms once again colonize the lagoon and bioturbation causes mixing of surface and subsurface sediments

on the interpretation of shallow shelf carbonate facies and habitats how much does water depth matter abstract many stratigraphic studies of ancient shallow water carbonate platforms focus interpretation on the primacy of changes in accommodation inferred by assuming a direct and deterministic link between depositional facies and water depth the purpose of this study is to test this assumption explicitly and quantitatively by exploring relations between substrate type classified on the basis of both habitats and facies and the water depth at which they occur on a modern well studied shallow rimmed shelf margin gis analysis of digital benthic habitat and bathymetry maps of the shallow 8 m south florida shelf illustrate that most substrate types occur across a range of water depths similarly at greater water depths habitats and facies are more constrained more dominance of one class more deterministic with generally decreasing dominance more diversity at shallower water depths at a scale of shelf to basin transects facies and habitats clearly are related to water depth yet on this narrower 10 km shallow shelf margin at the scale of this study water depth and habitats and facies are not uniquely related or linked this general lack of correspondence between bottom type and water depth may be a manifestation of landscape disequilibrium a state in which habitats and facies do not fully reflect ambient environmental conditions perhaps recording the influence of rapid change in sea level alternatively it may reflect the impact of variables other than water depth although more general consequences of these results for other depositional settings remains to be evaluated they do emphasize the fact that variables other than bathymetry may significantly influence the ecological and sedimentologic attributes of depositional surfaces they do allow for the quantification of some of the potential uncertainties inherent in the interpretation of analogous ancient platforms and can serve to focus future observations on the causes and consequences of vertical and lateral heterogeneity in ancient stratigraphic sequences

holocene lagoonal sedimentation at the latitudinal limits of reef growth lord howe island tasman sea abstract the southernmost limit to coral reef growth occurs on lord howe island 33 30 s 159 05 e where a discontinuous fringing reef flanks the western side of the island coring and radiocarbon dating indicate that carbonate sediments were first deposited within the lagoon around 6500 radiocarbon years bp coincident with sea level reaching close to its modern level high energy conditions dominated the reef with robust branching corals dominating the developing reef growth of the reef crest between 6000 and 5000 yr bp is inferred to have caused a reduction in the energy conditions within the lagoon resulting in mud deposition during this period sedimentation occurred at average rates of around 5 mm yr though locally up to 10 mm yr which infilled almost all the available accommodation space in the lagoon by 4000 yr bp most of the lagoon had accreted to a level very close to the modern lagoon floor having accumulated over 11 m of sediment in the northern part of the lagoon and possibly up to 30 m in the south sediments younger than 3000 yr bp form a thin veneer over these older units with the main deposition being confined to embayments the coastal plain and the infilling of blue hole depressions the reef and lagoon fringing lord howe island appear to have developed their present form primarily during a phase of luxuriant growth in the mid holocene

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

reef coralgal assemblages as recorders of paleobathymetry and sea level changes in the indo pacific province the coralgal framework within the outer reef margin of many indo pacific reefs exhibits three main shallow water communities the environmental significance of which can be inferred by comparison with their modern counterparts a community dominated by tabular acropora gr hyacinthus cytherea with branching pocillopora damicornis p eydouxi montipora digitata occasional domal faviids and mm thick crusts of the coralline algae lithophyllum and mesophyllum mainly typical of the 6 15 m paleodepth range a community including robust branching acropora gr danai robusta a humilis a digitifera and subordinate favia stelligera echinopora gemmacea associated to vermetid gastropods and thick coralline crusts of hydrolithon cf onkodes and neogoniolithon cf fosliei flourishing in depths less than 6 m in medium to high water energy settings a community composed of domal porites cf lutea and p cf lobata with occasional acropora gr danai robusta and cm thick crusts of coralline algae in sheltered habitats in depths less than 10 m these biological assemblages allow us to determine relationships between reef growth and paleobathymetry and consequently to reconstruct regional relative sea level curves high water energy reefal assemblages provide stronger evidence for reconstructing sea level curves than low energy buildups because they have generally been controlled by a keep up growth mode subsiding reef sites seem to be more reliable indicators of sea level variations because they usually present expanded reef sequences

growth history of stromatolites in a holocene fringing reef stocking island bahamas abstract a stromatolite and algal ridge reef complex 2 1 m thick fringes the east coast of stocking island exuma cays bahamas this reef was established on a pleistocene calcarenite terrace about 4500 yr b p stromatolites which occur in back reef and reef flat zones are up to 1 m thick and were constructed by cyanobacterial dominated communities study of the growth history of these stromatolites ranging in scope from facies analyses to details of microfabric construction presents new perspectives on stromatolite formation lithologies identified in eight cores from across the stocking island reef complex together with plots of 13 radiocarbon dates in relation to a bahamian sea level curve indicate that this reef began as an intertidal vermetid gastropod buildup subsequent flooding of the pleistocene terrace allowed the branching coralline alga neogoniolithon strictum to overgrow the vermetids and eventually form an emergent algal ridge about 1500 years ago shifting sands accumulated in the lee of this ridge and excluded most benthic communities and herbivores thereby promoting growth of cyanobacterial mats that formed stromatolite buildups with a decrease in wave energy over the last 500 years possibly due to the growth of offshore patch reefs the urchin echinometra lucunter coloni ed the algal ridge resultant bioerosion by this urchin destroyed the emergent part of the ridge and is now undercutting the seaward edge of the stromatolite buildups lamination in the stocking island stromatolites results from early lithificafion processes in cyanobacterial mats possibly in response to biogeochemical changes in the mats during hiatuses in sediment accretion these processes which create partially indurated laminae with a distinct microstructure involve precipitation of thin micrite crusts intense microboring along a surface below this crust micritization of sediment grains and precipitation of point contact cement between micritized grains introduction of turf algae to the cyanobacterial mat community disrupts formation of the lithified laminae thereby inhibiting stromatolite development

regional extraction of flexural toppled slopes in epicentral regions of subduction earthquakes along the nankai trough using dems in the epicentral region of subduction earthquakes large scale landslides are triggered by strong shaking of slopes weakened by flexural toppling the distribution of flexural toppled slopes is the primary information for predicting and mitigating landslide damage beforehand this study proposes and tests a simple algorithm for extracting flexural toppled slopes on a regional basis from a 10 m resolution digital elevation model by windows of two sizes local relief is extracted with a large window 200 200 pixels and microtopography is extracted with a small window 3 3 pixels the algorithm was derived from the region of the kanagi kuzure landslide in shikoku and tested at aka kuzure landslide in honshu in japan both areas are underlain by strongly tilted sedimentary rocks in epicentral regions of subduction earthquakes along the nankai trough

hurricane control on shelf edge reef architecture around grand cayman rimming the outer shelf of grand cayman is a submerged 87 km long shelf edge reef that rises to within 12 m of mean sea level it consists of an array of coral armoured buttresses aligned perpendicular to shore and separated by steep sided sediment floored canyons individual buttresses have a diverse coral dominated biota and consist of three architectural elements a shield like front wall colonized by platy corals a dome shaped crown colonized by head corals and a shoreward projecting spur covered by varying amounts of branching coral buttresses are commonly fronted by coral pinnacles that in some areas have amalgamated with buttress walls to produce pinnacle and arch structures as margin orientation changes shelf edge reef architecture shows systematic variations that are consistent with changes in fetch and height of hurricane waves along margins exposed to fully developed storm waves shelf edge reef buttresses are deep have large amplitudes and are dominated by robust head corals these characteristics are consistent with hurricane induced pruning of branching corals and the flushing of significant quantities of sand from buttress canyons by return flows along margins impacted by fetch limited storm waves reef buttresses are shallower have intermediate amplitudes and have a significantly higher proportion of branching corals these characteristics are consistent with less coral pruning and sand flushing by weaker hurricane waves along margins fully protected from storm waves the buttresses canyon architecture of the shelf edge reef breaks down producing a series of shallow undulating branching coral dominated ridges that merge laterally into an unbroken belt of coral these characteristics correspond with negligible amounts of pruning and flushing during hurricanes in addition to differences between margins local intra marginal changes in shelf edge reef architecture are consistent with changes in the angle of hurricane wave approach open sections of the shelf edge reef which face directly into storm waves are pruned of branching corals and the fragments swept back onto the shelf producing extensive spurs by contrast on more sheltered obliquely orientated sections storm waves sweep debris along and off shelf producing little or no spur development instead the debris shed seawards accumulates in front of the buttress walls and initiates the development of coral pinnacles over time repeated buttress pruning and canyon flushing during hurricanes not only controls reef architecture but may also influence accretion patterns vertical accretion is limited by the effective depth of storm wave fragmentation once this hurricane accretion threshold is reached the reef moves into a shedding phase and accretes laterally via pinnacle growth amalgamation and infilling consequently the reef steps out over its own debris in a kind of balancing act between lateral growth and slope failure a pattern widely recognized in ancient reefs

reef talus a popular misconception reef fronts have traditionally been regarded as comprising debris derived by contemporaneous erosion of the reef however evidence from wave transport indicates that on present day reefs the bulk of the debris generated in this way accumulates in the back reef area with only finer grained sediment carried off reef by retreating flows or by overwash nevertheless in contrast to this observation fore reef debris slopes are commonly considered characteristic of phanerozoic reefs this apparent error reflects the conflation of processes defining contemporary growth and accretion of the reef and the corresponding long term accretion of the carbonate platform on which it rests present day reefs are commonly although not exclusively additions to long lived carbonate platforms growth of the latter is intermittent and has been moderated by changes in sea level that for recent reefs have been on time scales of less than 100 ka during low sea level stands growth ceases or is translated downslope and earlier deposits are subject to lithification and subaerial erosion similar changes are applied on a larger scale to the aggrading growth of carbonate platforms but the bulk accretion of these includes quite different processes and reflects far longer timescales during low sea level stands the margins of platforms commonly become unstable with instability reflected in slope failure and in the shedding of blocks ranging from metres to kilometres in diameter associated with the generation of debris flows and turbidites it is argued that these are the materials that are commonly described as reef talus in ancient structures although their formation is largely independent of any contemporary reef growth difficulties arise where the reef and the platform are treated as a single functional entity it is important to recognize the conceptual distinction between them reef talus is a misleading description of the debris predominantly generated by platform erosion and slope failure

reconciliation of late quaternary sea levels derived from coral terraces at huon peninsula with deep sea oxygen isotope records a major discrepancy between the late quaternary sea level changes derived from raised coral reef terraces at the huon peninsula in papua new guinea and from oxygen isotopes in deep sea cores is resolved the two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka ka 1000 yr before present but between 70 and 30 ka the isotopic sea levels are 20 40 m lower than the huon peninsula sea levels derived in earlier studies new high precision u series age measurements and revised stratigraphic data for huon peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 18o data using the sea level and deep sea isotopic data oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from greenland ice cores the record of ice volume changes through the last glacial cycle now appears to be reasonably complete