development and demise of a fringing coral reef during holocene environmental change eastern ningaloo reef western australia abstract reefs lining the western exmouth gulf located at the northern limit of the 300 km long ningaloo reef in western australia represent modern incipient coral reefs and veneers of non reef building coral algal communities on exposed pleistocene or give up holocene reef surfaces acquisition of sixteen cores alongside u series tims dates were used to confirm the nature of the pleistocene foundation and characterise holocene reef development three calcretised pleistocene units were identified as 1 the last interglacial mis 5e reef directly underlying holocene units 2 a mid pleistocene mis 7 bioclastic conglomerate unit and 3 a pleistocene alluvial fanglomerate eight holocene reef facies total thickness of 1 8 5 3 m included coral framework facies domal arborescent mixed tabulate and encrusting and detrital facies carbonate sand skeletal rubble and alluvial fan deposits holocene ages range from 7 93 to 5 8 ka bp with vertical accretion ranging from 1 46 to 9 88 mm year avg 4 11 mm year highest rates of accretion and thickest accumulation occurred in the most seaward and deepest cores composed of massive coral framestone and coralline algal crusts a six stage holocene chronology is proposed including 1 coastal inundation from 8 to 8 5 ka bp 2 initiation start up from 8 to 7 5 ka bp 3 rapid growth catch up and back step from 7 5 to 7 ka bp 4 rapid aggradational growth catch up from 7 to 6 5 ka bp 5 reef decline give up and detrital buildup from 6 5 to 5 8 ka bp and 6 detrital buildup and progradation from 5 8 ka bp to present changes in reef facies and the ultimate demise of the holocene reef probably involved a combination of increased sea level coastal flooding and erosion during the mid holocene highstand with associated increase in sedimentation turbidity and decline in water quality burial by sediment buildup during the mid holocene highstand and detrital progradation during the mid to late holocene regression and the introduction of alluvial sediment during cyclones and other severe storms to an already stressed community modern communities have thus shifted from coral dominated to bored macroalgal pavements this study shows that integration of reef development processes with response to environmental change can be used to assess future pressures on coral reef ecosystems globally

deciphering methane s fingerprint massive releases of methane from the ocean floor are increasingly being implicated in global climate perturbation in the past the latest example comes from an episode of severe climatic and oceanic change that occurred around 180 million years ago

patterns in the distribution of aptian rudists and corals within a sequence stratigraphic framework maestrat basin e spain abstract the ecological zonation of and environmental controls on rudist and coral assemblages on carbonate platforms of the old world have received more attention for late cretaceous examples than for their early cretaceous counterparts this study accordingly investigates the vertical and lateral distribution of aptian rudist bivalves and scleractinian corals on a carbonate platform succession from the western maestrat basin e iberian peninsula here colonial corals grew profusely on an isolated platform top environment during an earliest highstand stage of a long term trend of relative sea level as well as on marly slope settings during higher frequency transgressive pulses during the later highstand stage within a longer term relative sea level cycle a facies belt dominated by autochthonous rudist bivalves overlaid the coral meadow that had developed on the isolated platform top the internal part of this carbonate platform with rudists is dominated by slender elevator caprinids such as caprina parvula whereas requieniids and polyconitids predominate in the external zone the abundance of caprinids in the internal platform is remarkable given that caprinid lithosomes of late early aptian age are usually rare in the northern margin of the tethys the proliferation of caprinids in this case was probably favoured by the apparently more isolated nature of the carbonate platform on the slopes the coral communities that flourished during higher frequency transgressive pulses are overlain by carbonates with rudists mainly requieniids shed from the platform top during normal and forced regressive higher frequency changes of relative sea level accordingly the vertical change from coral dominated to rudist dominated facies in both platform top and slope settings records progradation to decipher the long term relative sea level changes that controlled the deposition of this carbonate succession a sequence stratigraphic analysis was performed two depositional sequences including a late early aptian intra dufrenoyia furcata zone forced regressive stage of relative sea level which subaerially exposed and incised the early aptian succession to a depth of 21 m were recognised the incisions were back filled with peritidal deposits during the subsequent marine onlap the rudist and coral bearing carbonates were deposited along platform top to slope profiles lacking a barrier margin and hence lagoon environments

sedimentology palaeoenvironments and biostratigraphy of the pliocene pleistocene carbonate platform of grande terre guadeloupe lesser antilles forearc pliocene and pleistocene deposits from grande terre guadeloupe archipelago french lesser antilles provide a remarkable example of an isolated carbonate system built in an active margin setting with sedimentation both controlled by rapid sea level changes and tectonic movements based on new field sedimentological and palaeontological analyses these deposits have been organized into four sedimentary sequences s1 to s4 separated by three subaerial erosion surfaces sb0 sb1 and sb2 sequences s1 and s2 calcaires inferieurs a rhodolithes deposited during the late zanclean to early gelasian planktonic foraminiferal zones pl2 to pl5 in low subsidence conditions on a distally steepened ramp dipping eastward red algal rich deposits which dominate the western part of grande terre change to planktonic foraminifer rich deposits eastward vertical movements of tens of metres were responsible for the formation of sb0 and sb1 sequence s3 formation volcano sedimentaire calcaires superieurs a rhodolithes and calcaires a agaricia was deposited during the late piacenzian to early calabrian zones pl5 to pt1a on a distally steepened red algal dominated ramp that changes upward into a homoclinal coral dominated ramp deposition of sequence s3 occurred during a eustatic cycle in quiet tectonic conditions its uppermost boundary the major erosion surface sb2 is related to the cala1 eustatic sea level fall finally sequence s4 calcaires a acropora probably formed during the calabrian developing as a coral dominated platform during a eustatic cycle in quiet tectonic conditions the final emergence of the island could then have occurred in late calabrian times

palaeoenvironmental and palaeoecological change on the northern tethyan carbonate platform during the late barremian to earliest aptian a major shift from urgonian oligotrophic carbonate accumulation to orbitolinid rich mixed siliciclastic carbonate deposition is observed near the barremian aptian boundary in many sections both within and outside the shallow marine tethyan realm this important facies change in the swiss helvetic alps is documented here and interpreted in the context of general palaeoenvironmental change to achieve this a detailed micropalaeontological sedimentological mineralogical and geochemical study has been carried out on six sections across the upper part of the lower schrattenkalk member late barremian the rawil member formerly lower orbitolina beds earliest aptian and the lowermost part of the upper schrattenkalk member early aptian the sediments of the rawil member exhibit inner platform facies with rudists miliolids orbitolinids and dasycladals to outer platform facies characterized by small benthic foraminifera orbitolinids crinoids and bryozoans stratigraphic trends in microfacies environments and the composition of microfossil assemblages indicate that the rawil member includes a transgressive systems tract and the base of a highstand systems tract which are composed of an increasing number of parasequences in distal directions five to nine in the sections studied here the sea level rise discerned in the rawil member is coeval with increased detrital input and phosphorus burial with maximum values up to 80 times and 21 times the background values in the subjacent part of the lower schrattenkalk member respectively furthermore the rawil member records the appearance of kaolinite indicating a change towards tropical and more humid climate conditions this change may have led to an increase in continental weathering rates and an associated increase in detrital and nutrient fluxes towards the ocean the phase of climate change observed near the barremian aptian boundary may have been triggered by a phase of intensified volcanic activity linked with the onset of the ontong java large igneous province and the rawil member may be the expression of a precursor episode to oceanic anoxic event 1a in the shallow marine environment

correlation of early cretaceous carbon isotope stratigraphy and platform drowning events a possible link the early cretaceous carbonate carbon isotope record is marked by three positive high amplitude 1 5 excursions each covering time spans of more than 106 years they are of late valanginian hauterivian and early and late aptian age in a case study along a transect across the western tethys ocean we identified a coincidence between 13c excursions black shale formation and widespread carbonate platform drowning events we conclude that the 13c excursions reflect a change in partitioning of carbon between the organic and carbonate carbon sinks which was triggered by climate induced ecological changes in cretaceous pelagic and neritic environments episodes of intensified greenhouse climate conditions led to an increase in weathering erosion and runoff rates and to elevated nutrient transfer rates from continents into oceans the resulting increase in oceanic nutrient levels favoured marine phytoplankton production and black shale deposition while conditions for carbonate producing biotas became unfavourable partial choking of carbonate production along river influenced coasts resulted in widespread carbonate platform drowning during times of sea level rise in the valanginian and aptian widespread contemporaneous black shale deposits and drowned carbonate platforms therefore reflect the contrasting response of the marine organic and carbonate carbon pumps to nutrient enhanced phytoplankton productivity the change in marine carbon partitioning is mirrored in a shift of the 13c record towards more positive values the transition to the 13c peak values lasted up to several hundred thousand years the peaks of the excursions also covering a time span of up to several hundred thousand years reflect a new stabilisation of the carbon partitioning between carbonate and organic carbon sinks a renewed intensification of carbonate sedimentation under mesotrophic conditions was facilitated by stabilisation of the sea level rise at a high level decreasing 13c values record increasing carbonate carbon burial rates at constant or decreasing organic carbon accumulation rates these changes contributed to the stabilisation of the marine carbon budget and the global carbon cycle up to millions of years after its initial perturbation

geochemical and paleoenvironmental record of the early to early late aptian major episodes of accelerated change evidence from sierra del rosario northeast mexico abstract the lower to lower upper aptian succession of northern mexico documents the drowning of the shallow water cupido cupidito carbonate platform system followed by deposition of the deep water sediments of the la pena formation using 13 c stratigraphy geochemical and mineralogical information coupled with previous microfacies paleontological and total organic carbon toc data from a stratigraphic section which includes such lithological change this study identifies distinctive episodes of accelerated global environmental change and determines the paleoenvironmental conditions conducive to the deposition of toc rich intervals within the cupidito unit the oceanic anoxic event 1a oae 1a is recorded near the base of the section and the intra furcata negative excursion in the topmost beds of the unit the upper part of the section within the la pena formation is correlatable with the noire level organic carbon rich intervals occur in the lower and middle part of the oae 1a upper part of the cupidito unit base of the la pena formation and in the noire level equivalent reducing conditions within the sediment and oxic dysoxic at the seafloor locally controlled persisted both before and during oae 1a interval in the cupidito lagoon oxygen depleted conditions dysoxic anoxic were more permanent and stronger during the deposition of the base of the la pena formation and the noire equivalent level it is proposed here that deposition of the lower middle part of the oae 1a and the base of the la pena formation was influenced by climate controlled increases in detrital and accompanying nutrient influx that supplied especially biolimiting nutrients fe p fostering marine productivity and toc burial upwelling of nutrient rich deeper waters and minor arrival of nutrients from runoff both account for the domination of radiolaria and organic carbon burial during the noire level equivalent record of the oae 1a time equivalent facies in the cupidito lagoonal sediments confirms the diachronism of the cupidito la pena flooding heterozoan carbonate production in the cupidito ramp was uninterrupted during and after oae 1a periodic arrival of detrital components and nutrients during warmer humid periods accelerated platform drowning which peaked during the diachronic deposition of the la pena formation

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

biogeochemical assessment of sources of organic matter and paleoproductivity during the early aptian oceanic anoxic event at shatsky rise odp leg 198 this study investigates organic rich sedimentary sequences deposited during the early aptian oceanic anoxic event oae1a at sites 1207 and 1213 on shatsky rise odp leg 198 in the west central pacific biomarker analyses provide evidence of the algal and bacterial origin of organic matter om in these sediments where the abundance of steroidal components particularly sterenes and sterones suggests that the om includes major contributions from eukaryotic sources in an environment characterized by high phytoplankton productivity the presence of alkenones at site 1213b is diagnostic of om derived from representatives of haptophyte algae among the calcareous nannoplankton and their 13c values average 31 6 are consistent with those expected during elevated pco2 the occurrence and prominence of 2 methylhopanes and 2 methylhopanones indicates significant contributions to the om from cyanobacteria which are also likely contributors of hopanoids based on their 13c compositions these biomarker data suggest that oceanic conditions perhaps nitrate or iron limited were conducive to cyanobacteria production during oae1a which appears to distinguish this event from other cretaceous oae

carbon isotope stratigraphy of the upper kharaib and shuaiba formations implications for the early cretaceous evolution of the arabian gulf region the carbon isotope profiles of shallow marine carbonates from the barremian aptian kharaib and shuaiba formations of the arabian gulf region range between 0 5 and 7 pmil dgr13c pdb peedee belemnite systematic variations can be correlated with isotope profiles reported from tethyan pelagic limestone sequences the detailed correspondence between the isotopic signature of the relatively well dated pelagic limestones and the poorly dated shallow water limestones from the arabian gulf region suggests that global marine carbon isotope changes apparently affected deep sea and shallow water carbonate sediments similarly and at a similar time resolution although oxygen isotopes have been reset during diagenesis carbon isotopes appear to have maintained their primary marine signature through time no evidence has been found to connect carbon isotope trends to subaerial exposure or later meteoric diagenesis in combination with other data the investigated carbon isotope profiles can be used for basin to platform and regional correlations beyond the current resolution of biostratigraphy in shallow water limestones carbon isotope stratigraphy confirms significant hiatuses in the investigated shallow water carbonate sequences using carbon isotope trends as a proxy for sea level fluctuations the carbon isotope cycles of the late early cretaceous of the arabian gulf region may represent four cycles of rising and falling sea level with a duration corresponding to that of third order sea level fluctuations regional correlations derived from isotope trends provide a scenario for the larger scale stratigraphic evolution of the arabian peninsula during the end of the early cretaceous differential rates of aggradation between realms influenced by siliciclastics and those characterized by siliciclastic poor clean carbonate deposition apparently caused the development of a pronounced basin platform topography during the early aptian shuaiba intrashelf basin and platform

modern changes of the high mountain landscapes and glaciation in southern siberia russia by the example of the eastern sayan mountains the period of observations of glaciation of the munku sardyk mountain massif in siberia is one of the longest i e 155 years however the data obtained are scattered and not systematic the paper presents an integrated analysis of the materials collected since the first description by the explorer of siberian mountains g i radde istoriy 1896 and extended by peretolchin 1908 and komarov 1953 as well as by glaciologists maksimov 1965 arefiev and mukhametov 1996 the authors considered the current state of the glaciers and interaction of natural geosystems of the massif taking into account the nival glacial processes since the beginning of the current millennium regular observations have been conducted on the munku sardyk massif by the v b sochava institute of geography sb ras limnological institute sb ras and east siberian state academy of education the studies revealed the leading landscape forming factors and examined the landscape structure of the surroundings of the contemporary nival glacial geosystems with due regard for the manifestations of altitudinal zonation a medium scale landscape typological mapping was carried out presented are the quantitative parameters of the dynamics of the nival glacial geosystems obtained on the basis of modern remote sensing instruments gps measurements and surface laser scanning using gis analysis the stump and stem of larch detected in the valley of the bugovek river 300 m above the contemporary upper forest limit and 1330 m up the valley show that most likely there was no glaciation during the atlantic period 7000 7300 years ago the modern glacier complex has formed only during the last 4000 5000 years the trend of shrinkage of glaciers since the end of the little ice age can be traced especially in recent years the length and area of the open part of the glaciers have decreased by half from 0 68 to 0 34 km2 the presence of small forms of glaciation on the southernmost limit of the siberian glaciation 1500 m below the theoretical climate boundary suggests that this area can be considered a unique key site to identify trends in development of the mountain and nival glacial geosystems and provides an opportunity to built reconstructive and predictive models of development of mountain landscapes under the conditions of ever increasing anthropogenic influence

carbon isotope stratigraphy in shallow water carbonates implications for cretaceous black shale deposition a barremian to albian succession on mount kanala part of a tethyan isolated carbonate platform was investigated for its 13c variations the limestone sequence is composed of a series of peritidal shallowing upward cycles with clear petrographic evidence for strong early diagenetic overprinting related to repeated subaerial exposure despite significant impact of diagenesis the observed changes in 13c can be very well correlated with deep water sections from different ocean basins and shallow water carbonate platforms in the middle east this lends further support to the applicability of 13c variations for stratigraphic purposes in shallow water limestones using the 13c signal time resolution in lower cretaceous platform carbonates can be significantly increased independent of bio zonations often hampered by ecological variability cyclostratigraphic analysis of the aptian part of the section shows that strong positive excursions of the cumulative departure from mean cycle thickness of the peritidal shallowing upward cycles coincide with global positive 13c excursions this and the fact that positive shifts in the 13c record are preserved within shallow water limestones provide evidence that black shale accumulation in the ocean basins occurred during sea level rise and flooding of platform tops integration of carbon isotope cyclo and sequence stratigraphic results from different carbonate platforms indicate that strong positive global 13c shifts and concurrent organic carbon burial during black shale deposition are ultimately caused by rapid rises of eustatic sea level hence the rate of change of eustatic sea level is considered to play a crucial role in black shale accumulation in the global ocean basins during the cretaceous

palaeobathymetric reconstruction of peritidal carbonates late barremian urgonian sequences of provence se france abstract peritidal platform carbonates of late barremian age early cretaceous cropping out in the marseille region provence se france tend to be arranged stratigraphically in deepening up or shallowing up sequences seven facies types lithofacies were defined in the studied stratigraphic interval ranging from supratidal to shallow subtidal settings there is a good correspondence between the inferred relative water depth of facies and their average bed thickness cumulative thickness of facies types expresses quantitatively their palaeobathymetric range and provides an estimate of their average water depth calculations show that the palaeobathymetry of supratidal intertidal facies types is from 0 to 40 cm i e a pertaining to a palaeotidal microtidal range the average palaeobathymetry of rudist facies ascribed to subtidal settings fluctuates between 40 cm and nearly 160 cm measuring a large number of beds belonging to both shallowing up and deepening up sequences and averaging the results appear relevant to minimise the effect of compaction pressure solution and synsedimentary progressive or abrupt changes in accommodation which are expected to modify bed thickness and its original palaeobathymetric significance the method proposed here has a good potential for palaeobathymetric reconstruction of ancient peritidal carbonates

impact of glacier changes on ecosystem of proglacial lakes in high mountain regions of east siberia russia mountain lakes in east siberia have been studied for recent changes in water chemistry turbidity and diatom assemblages preserved in bottom sediments we performed a regional analysis of the relative effect of climate and glacier changes on change in diatom diversity and supply of meltware in proglacial lakes we analysed sediment records from east siberian glacier lakes using geochemical and diatoms proxies we found that dramatic changes in communities and abundance of diatoms and biogenic proxy could be induced by low nutrient concentrations in glacial lakes and high turbidity due to active degradation of glaciers and snow patches as a result of the global increase in temperature in the northern hemisphere our evidences show that diatoms have been gradually decreased since ca the 1880s a significant tendency towards diatom reducing occurred at high summer regional temperatures this tendency may be attributed to the fact that glaciers and snow patches thawed actively in east siberia during ca 1880 1958 which was induced by the beginning of the recent warming ca 1850 1860 and a long period of relatively warm regional climate from ca 1900 to 1960

development patterns and controlling factors of tertiary carbonate buildups insights from high resolution 3d seismic and well data in the malampaya gas field offshore palawan philippines abstract the comprehensive subsurface database of the malampaya buildup late eocene to early miocene offshore nw palawan provides a rare insight into the development of south east asian cenozoic carbonate systems and their controlling factors the newly acquired high resolution three dimensional seismic survey combined with facies and well log analysis allowed a better understanding of the internal architecture of a carbonate platform whose development was largely controlled by tectonic deformation the malampaya carbonate system was initiated in the late eocene as an attached shelf influenced by significant clastic input the late eocene early oligocene shelf was subject to syn depositional extensional tectonics eastward tilting and block faulting that favoured the development of small size buildups on structural highs after a stage of eastward reef progradation an aggrading carbonate shelf frequently affected by subaerial exposure developed from the earliest late oligocene to the early miocene during this period recurrent reactivation of highs along the western and northeastern buildup margins determined the asymmetric morphology and internal architecture of the carbonate system the final demise of the carbonate buildup occurred in the late early miocene it resulted from an increase in subsidence rate and or a sharp increase in nutrient input additional parameters like eustacy oceanographic conditions and the type of carbonate producers played a subordinate role in the buildup development and ultimate demise

extreme 13c depletions in seawater derived brines and their implications for the past geochemical carbon cycle extreme depletions in the 13c content of the total dissolved inorganic carbon ct were found in brines overlying microbial mat communities total alkalinity at and ct in the brines suggest that intense photosynthetic activity of the microbial mat communities depletes the ct from the brine we suggest that this depletion drives a large kinetic negative fractionation of carbon isotopes similar to that observed in highly alkaline solutions in brines of extreme salinity where microbial mat communities no longer exist the 13c content of the ct increases probably because photosynthesis no longer dominates the gas exchange processes this mechanism explains light carbon isotope compositions of carbonate rocks from evaporitic sections and bears on the interpretation of 13c values in bedded stromatolitic limestones that are ca 3 5 b y old

nature and distribution of diagenetic phases and petrophysical properties of carbonates the mississippian madison formation bighorn basin wyoming usa abstract the purpose of this study is to characterize factors controlling the nature and distribution of the diagenetic phases that gave rise to carbonate reservoirs to do so a pluridisciplinary approach was carried out integrating sedimentologic and diagenetic studies on the madison formation lower carboniferous 357 340 my which is a carbonate reservoir in subsurface the madison formation outcropping in the bighorn basin wyoming usa is a 340 m thick carbonate series composed of four to seven 3rd order depositional sequences s1 to s7 depending of the palaeogeographic location the first three sequences s1 to s3 were deposited under arid and warm conditions during tournaisian times which favoured high accumulation of carbonates leading to a morphological change from a quite flat ramp s1 to s2 to a wide platform s3 it also probably favoured the early calcite cementation isopachous and syntaxial calcite cements of the subtidal deposits and the early dolomitization d1 of the supratidal to intertidal sabkha ones in addition the very flat profile occurring during s3 was also responsible for the postponed dolomitization d2 of s1 s2 due to reflux of brines at various degrees depending on the palaeogeographic location the deposition of s4 to s7 under humid conditions during visean times were associated with 1 a decrease of the carbonate accumulation and of the dolomitization 2 dissolution processes at micro pores network and macro scales karst collapse breccia and calcite cementation c1 the spatial distribution of all these first diagenetic phases acts as a controlling factor on the distribution of the later burial diagenetic phases thus the mesogenetic calcite cements are mostly observed in the secondary porosity created by dissolution karsts collapse breccias or dolomitization the burial diagenesis of the madison formation was characterized by 1 a dolomitization phase d3 in proximal parts of the platform leading to an increase of porosity and permeability and 2 calcite cementations c2 c3 in the distal parts of the platform leading to a decrease of these properties the madison formation provides a good spatial representation of sedimentary and diagenetic heterogeneities that may occur in the carbonate reservoirs due to various palaeogeographic locations climates burial history and structures

indications of long term episodic suspension transport of sand across the norfolk banks north sea abstract predicted 50 year maximum storm surge currents and the currents resulting from their combination with strong tidal currents are veered and amplified as they pass over the norfolk banks they therefore drive sand off the crest of well bank in a wide arc of directions between north east and south southwest this arc corresponds to that seen in the cross bedding dip directions known from the lee slope of well bank and to the northeasterly growth of the well bank the strength of these currents is such that some sand may even pass from bank to bank in the series this is facilitated by the proximity of the upper part of the sand banks to the sea surface such that their crests act as stepping stones where sand suspensions originate during storm surge episodes it is postulated that this new sand transport path oblique to the path of the peak tidal currents probably commences at the coast of east anglia and provides a route for transporting sand for up to about 100 km seaward

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

tidal and residual currents around a norfolk sandbank currents on either side of well bank were recorded for 41 days in may june 1981 in order to distinguish locally tidally generated asymmetries pertinent to maintenance of the bank from larger scale and wind driven flows semi diurnal currents were dominant nearly rectilinear and slightly inclined to the bank axis fourth diurnal currents were consistent with previously observed and computed fourth diurnal tides for the area overall amplitudes varied as the square of the semi diurnal amplitude hence they appear to be generated by tides but only a small part locally residual currents average over a tidal cycle were always in the sense of clock wise circulation around the bank consistent with simple models and giving strong evidence of local generation by tides this circulation combines with the semidiurnal currents to maintain the bank the slow increase of the residuals with the semi diurnal amplitude is interpreted as an effect of strong semi diurnal currents a persistent component onto the bank 7 m above the bottom at one position may indicate distortion of the frictional layer by the sloping bottom or by bank curvature

new oxygen isotope evidence for long term cretaceous climatic change in the southern hemisphere a new composite 18 o record generated from calcareous fine fraction and bulk sediments from the exmouth plateau details long term cretaceous climatic change at mid latitudes in the southern hemisphere assessment of new and previously published 18 o data indicates that a mid cretaceous global climatic optimum was achieved sometime between the time of the cenomanian turonian boundary and the middle turonian when surface ocean paleotemperatures were the highest of the past 115 m y periods of cooling and warming that reversed the general patterns were superimposed on long term aptian turonian warming and turonian maastrichtian cooling trends respectively extrapolation of southern hemisphere paleotemperature trends to maastrichtian paleotemperature data from a low latitude pacific guyot implies that maximum mid cretaceous low latitude paleotemperatures could have been in excess of 33 c

chemostratigraphic correlation of barremian and lower aptian ammonite zones and magnetic reversals based on carbon isotope stratigraphy we correlate the ammonite dated barremian reference section near angles se france with the magneto and biostratigraphically dated succession at cismon northern italy the results confirm the previous correlation of the lower barremian ammonite and magnetostratigraphy by channell et al 1995 and show that the base of cm0 selected as the stage boundary between the aptian and the barremian coincides with the stage boundary defined by ammonite stratigraphy the upper barremian carbon isotope record of the cismon section displays two positive 13c excursions whereas the data from angles show only one shift towards more enriched values the absence of the second upper barremian 13c excursion at angles indicates that up to 50 of the barremian stage is missing in the selected reference section the gap occurs most probably within the giraudi ammonite zone and is related to the 12d maximum flooding surface of jacquin et al 1998

glacier fluctuation in northern and high asia historical and methods perspective glaciers in asia occupy nowadays much smaller extents than those of the pleistocene but they still play an important role in alpine ecosystems e g shahgedanova 2002 glaciers also pose hazards to society and infrastructure with avalanches and glacial lake outburst floods being the most destructive of glacier related natural events richardson and reynolds 2000 jansk et al 2010 nie et al 2013 wang and zhang 2014 since the end of the little ice age lia glaciers have been retreating almost everywhere around the world and this process has dramatically accelerated during the recent decades fig 1 wgms 2013 however individual glaciers are behaving differently and some have advanced while most have been in retreat ipcc 2013 yao et al 2012 mountain glaciers are sensitive indicators of climate change e g dyurgerov and meier 2000 haeberli et al 2004 and to fully understand the connection between changing climate and glacier fluctuations all the variables of the glacier mass balance need to be assessed at the local and regional scale dowdeswell et al 1997 oerlemans 2005 one of the regions where information about glacier changes is still scarce is northern and high asia fig 1 largely because glaciers of the region are located relatively far from human settlements and some have only been found after the 1940s for example ivanov et al 2015 have provided the first inventory of glaciers in the barguzinsky ridge east of lake baikal russia in this issue at the same time continental glaciers of northern and high asia are located far from the main sources of moisture and are thus sensitive to climate change fujita 2008 kaser et al 2010 in this issue we have collected information about glaciers situated along a southwestnortheast transect from 77 e 32 n the western himalaya india to 128 e 65 n the orulgan range russia fig 2 and fed from different sources of moisture the north atlantic the arctic and the indo pacific air masses because glaciers in our focus area belong to different climate systems their systematic study across the whole region has the potential not only to assess the climate change at local and regional scales but also to reveal climate change patterns at a larger continental scale the papers of this issue cover a variety of glacier related topics methods studies glacier inventories current glacier dynamics and paleo reconstructions and are based on a range of data such as satellite imagery synoptic maps biogeochemical proxies from proglacial lake bottom sediments and meltwater streams pollen and oxygen isotope records from snow ice cores and high resolution seismic reflection data

early aptian paleoenvironmental evolution of the bab basin at the southern neo tethys margin response to global carbon cycle perturbations across ocean anoxic event 1a 1 lower aptian carbonates in the bab basin at the southern neo tethys margin record significant environmental changes across oceanic anoxic event 1a oae1a a long lasting negative shift of carbon isotope ratios 13c associated with a distinct decrease in oxygen isotope ratios 18o in orbitolinid rich carbonates characterizes the onset of oae1a livello selli supporting a hypothesis that a long lasting volcanic co2 emission is the main cause of oae1a inducing global warming a bloom of microencrusters lithocodium and bacinella across the proto bab basin occurred synchronously at the beginning of the subsequent positive 13c excursion responding to the global carbon cycle perturbations the carbonates formed during the oae1a show higher strontium isotope ratios 87sr 86sr compared with those of global seawater this was likely caused by a local influx of isotopically heavier strontium along with nutrients into the proto bab basin these biotic proliferations were triggered by an increased nutrient supply induced by intensified continental weathering due to the global warming suggested by the increase in 18o values spatial variations in the 13c values among sites in the bab basin and its surrounding platform are related to local environmental factors such as the degree of mixing of basin water with ocean water and local removal of 12c by metabolic activity at the platform top the 13c profile of the studied core indicates global removal of organic carbon of oae1a began during the early stage of the second order transgression and lasted until the early stage of the highstand after the oae1a the livello selli corresponds to the early stage of this transgression

an upper bound for the tidally rectified current at one location on the southern flank of georges bank abstract long term current observations at 45 and 75 m at one location on the southern flank of georges bank in water 85 m deep were examined for evidence of tidal rectification loder has shown analytically that rectification of the strong semidiurnal tidal current can cause a mean along bank flow and thus may partially drive the observed clockwise circulation around georges bank the amplitude of the tidally rectified along bank flow is proportional to the squared amplitude of the cross bank tidal current a simply extension of loder s model to include the weaker n2 and s2 tidal components suggests that fortnightly 354 h and monthly 661 h variations of the square of the cross bank tidal current should cause a modulation of the subtidal along bank flow the predicted ratio r of the fortnightly and monthly modulation of the along bank flow to the mean along bank flow on the southern flank was a function of position and ranged from 0 1 0 5 the amplitude of modulation of the along bank flow at 360

phosphogenesis carbon isotope stratigraphy and carbonate platform evolution along the lower cretaceous northern tethyan margin we distinguish three different stages in the evolution of the tithonian late jurassic to aptian early cretaceous northern tethyan carbonate platform 1 carbonate production in the coral oolite mode late tithonian to early valanginian early barremian to early aptian 2 carbonate production in the crinoid bryozoan mode early valanginian haute rivian late aptian and 3 platform retrogradation and destruction condensation and phosphogenesis that is platform drowning early valanginian to early hauterivian middle hauterivian late hauterivian to early barremian early to early late aptian and latest aptian to earliest albian transitions from the coral oolite mode to the crinoid bryozoan mode and consequently to platform drowning may have been driven by increases in nutrient levels on the shelf phases of relative sea level rise in times of carbonate production in the coral oolite mode are named constructive because of the observed platform regeneration following phases of widespread emersion during late sea level highstands in contrast phases of relative sea level rise in times of platform drowning are termed destructive the 13 c stratigraphies obtained from valanginian hauterivian and aptian albian hemipelagic successions beyond the platform correlate well with the early cretaceous pelagic 13 c record positive excursions in the pelagic 13 c record correspond in time to episodes of platform drowning this suggests the existence of a coupling mechanism between changes in the global carbon cycle and platform drowning in our view the early cretaceous crises in carbonate platform growth were the consequence of reinforced greenhouse conditions which may have been triggered by episodes of extensive flood basalt volcanism strong greenhouse conditions may have induced the following chain of feedback mechanisms enabling the biosphere to return to normal conditions climate warming sea level rise accelerated water cycle intensified weathering nutrient mobilization platform destruction increased productivity increased phosphogenesis and carbon burial weakened greenhouse conditions

morphology and evolution of drowned carbonate terraces during the last two interglacial cycles off hilo ne hawaii abstract the eastern side of hawaii island is a rapidly subsiding margin dominated by drowned carbonate platforms we present detailed bathymetric and backscatter data remotely operated vehicle and submersible observations sedimentological and 14c accelerator mass spectrometry and u th age data from seven submerged terraces h7 h2a d h1a b in water depths between 1100 and 25 m off hilo north eastern hawaii the main carbonate deposits on these terraces are coral deposits rhodolith beds coralline algal mounds crusts pavements and tabular sheets we identified five previously described sedimentary shallow to deep water facies and one new facies type that are consistent with reef drowning on a rapidly subsiding margin we used palaeobathymetric data derived from the sedimentary facies age versus depth relationships and published sea level curves to estimate a uniform long term subsidence rate of 2 80 0 36 m ky for the eastern side of hawaii over the last 150 ky terrace h7 developed about 380 ka based on data from the western side of the island active coral growth on terrace h2d occurred during the marine isotope stage mis 6 to 5 transition and the terrace drowned during the peak of mis 5e when sea level rose faster than reefs could grow favoured by the gentle platform gradient reefs established progressively landwards with a backstepping pattern during mis 5e to form the terraces h2c and h2b 122 ka final turn off of shallow water carbonate production on terraces h2b d coincided with the relative sea level rise of the interstadial mis 5a bathymetry and submersible data suggest that carbonate sediments on terraces h2a and h1b were deposited over an antecedent topography of local lava deltas emplaced during rising sea levels at ca 85 and 65 ka while terrace h1a established on lava delta substrates of the mauna loa volcano ca 11 ka we conclude that the initiation growth and drowning of coral reef terraces off hilo differ in some ways from the pattern observed in the submerged terraces in the western side of hawaii and that the platform evolution off hilo is more strongly influenced by emplacement of offshore lava flows

mechanisms underlying the regional morphological differences between the northern and southern radial sand ridges along the jiangsu coast china abstract radial sand ridges rsrs spread in a fan shaped pattern over the seabed of the southern yellow sea along the jiangsu coast china with pronounced differences between the northern and southern channel shoals indicated as ncs and scs respectively a depth averaged nested numerical model is employed to analyze the tidal hydrodynamics and sediment dynamics of the rsrs model results show considerable regional differences in terms of tidal current vector ellipses eight shaped ellipses are typical in the ncs where rotational tidal waves dominate while the scs are characterized by egg shaped ellipses because of the dominance of progressive tidal waves sand ridges tend to be elongated and straight in the ncs while short and dincontinuous in the scs numerical lagrange particles released near the ridges in the ncs tend to travel across the crest of the ridges rather than move around them as observed in the scs consistently the patterns of sediment convergence and divergence indicate that suspended sediments converge over the whole xiaoyinsha ridge located in the ncs while converge to the two sides of the hetunsha ridge located in the scs model results also highlight the importance of initial sediment compositions in determining patterns of the net sediment fluxes the suspended sediment concentration ssc time series during one tidal cycle may show single or double peaks depending on the grain size and the related lag effect bed load transport is much smaller than suspended load so sediment compositions should be carefully considered when simulating the ssc field and the hydrodynamic of the morphological evolution of the rsrs at the regional scale overall this study suggests that the ncs and scs may be treated as two relatively independent geomorphological systems characterized by different tidal flows and sediment compositions

the impact of early cretaceous gateway evolution on ocean circulation and organic carbon burial in the emerging south atlantic and southern ocean basins abstract organic carbon burial is an important driver of carbon cycle and climate dynamics on geological and shorter time scales ocean basins emerging during the early cretaceous break up of gondwana were primary sites of organic carbon burial implying that their tectonic and oceanographic evolution may have affected trends and perturbations in global climate via changes in local organic carbon burial assessing the role of individual ocean basins in the global carbon climate context requires a sound understanding of the processes that induced large scale changes in carbon burial and the timing of these changes here we reconstruct the oceanographic evolution and its links to organic carbon burial in the barremian to albian south atlantic and southern ocean basins which may have acted as carbon sinks of global importance our reconstruction is based on combined seawater neodymium isotope and sedimentological records obtained from multiple deep sea drill sites and a new general circulation model deep water circulation within and between those basins was primarily controlled by the opening of the shallow falkland plateau gateway between 118 ma and 113 ma and the deep georgia basin gateway by 110 ma for which we provide new age constraints based on biostratigraphic and carbon isotope data the opening of these gateways was accompanied by local to basin wide decreases in organic carbon burial suggesting that ocean circulation affected the oxygenation state via changes in deep water ventilation although our data do not provide quantitative information on the impact of changes in regional organic carbon burial on the global carbon cycle the synchronicity between the reduction of organic carbon burial in the south atlantic basin and global warming during the early albian points to a strong causal relationship

conditions for shallow geothermal energy utilization in dinaric karst terrains in croatia hydrogeological and thermogeological properties of the shallow subsurface in the dinaric karst area of croatia were investigated in the context of its utilization for ground and water source heat pumps gshps and wshps the research encompassed four 100 m deep boreholes with gshp installations in both coastal and inland dinaric karst different limestones and evaporitic rocks at one location and a set of six exploratory boreholes abstraction and reinjection wells for wshp heating and cooling using seawater on the coast fractured and karstified limestones it was determined that rock thermal conductivities are favourable for gshp utilization but dependent on the wider rock mass characteristics which are hard to predict size of karst voids and their saturation status in addition wells with high enough yield and stabile seawater or groundwater temperatures for wshp utilization can be designed in appropriate structural settings tensional fractures and fracture set intersections advantages and disadvantages of the utilized methodology have been pointed out as well as methods which should prove useful in the future especially if larger systems are planned hydrogeological geotechnical and thermal risks expected during the drilling installation and operational phases have also been identified presented case studies have given the insight into heat pump installation options and conditions in croatian part of the dinarides but can be useful to other researchers and engineers both in the dinarides and in similar karst regions

progressive palaeoenvironmental change during the late barremian early aptian as prelude to oceanic anoxic event 1a evidence from the gorgo a cerbara section umbria marche basin central italy abstract during oceanic anoxic event 1a oae 1a 120 ma li et al 2008 organic carbon rich layers were deposited in marine environments under anoxic conditions on a global scale in this study palaeoenvironmental conditions leading to this event are characterised by studying the upper barremian to the lower aptian succession of the gorgo a cerbara section central italy for this an integrated multi proxy approach 13ccarb 13corg 18o phosphorus total organic carbon toc bulk rock mineralogy as well as redox sensitive trace elements rstes has been applied during the late barremian thin organic rich layers occur episodically and associated corg ptot ratios indicate the presence of intermittent dysoxic to anoxic conditions coarse correlations are observed between toc p and biogenic silica contents indicating links between p availability productivity and toc preservation however the corresponding 13ccarb and 18o records remain quite stable indicating that these brief periods of enhanced toc preservation did not have sufficient impact on the marine carbon reservoir to deviate 13c records around the barremian aptian boundary toc enriched layers become more frequent these layers correlate with negative excursions in the 13ccarb and 13corg records possibly due to a warming period as indicated by the 18o record during the earliest aptian this warming trend is reverted into a cooling trend which is then followed by an important warming step near the onset of oceanic anoxic event 1a oae 1a during this time period organic rich intervals occur which are characterised by the progressive increase in rste the warming step prior the onset of oae 1a is associated with the well known negative spike in 13ccarb and 13corg records an important peak in p accumulation rste enrichments and corg ptot ratios indicating the prevalence of anoxic conditions the selli level itself may document a cooling phase rste enrichments and corg ptot ratios confirm the importance of anoxic conditions during oae 1a at this site the gorgo a cerbara section is interpreted to reflect the progressive impact of palaeoenvironmental change related to the formation of the ontong java plate basalt plateau which started already around the barremian aptian boundary and culminated into oae 1a

carbonate production by rudist bivalves the record of late barremian requieniid communities from provence se france abstract rudist bearing sediments from platform carbonates of late barremian age early cretaceous cropping out in the marseille region provence se france were investigated on a 46 km wide transect after seven stratigraphic sections to quantify the role of rudists in the corresponding stratigraphic system by using various proxies the regional stratigraphic contribution of total thickness of rudist beds is relatively high 43 1 each rudist community type possesses a specific skeletal contribution of skeletal content in the range of 19 2 to 31 5 at a stratigraphic scale including rudist rich and rudist free beds the skeletal contribution drops to 13 8 this value is derived from the standard skeletal contribution obtained for each community type combined with the stratigraphic contribution of rudist beds in vertical successions and horizontal stratigraphic units a closely related value 12 8 is obtained from calculations using specific lateral dimensions of rudist bodies and their spacing i e modules depending on community types each community has a particular potential quantitative contribution to the overall regional stratigraphic system rudist production is deduced from the cyclostratigraphic approach of accumulation rates for each community type estimates of caco 3 net production are in the range of 19 to 50 kg m 2 ka 1 these values are very low when compared with those obtained at a biological scale for modern bivalves late cretaceous rudists and recent coral reefs the geological scale used for our estimates may partly account for this difference whereas low accommodation rates linked to cretaceous greenhouse conditions appear a potential important factor in this respect the low net production of requieniid dominated communities sediment dwellers not framework builders also reflects their limited sedimentogenetic power

carbonate ramp depositional systems abstract the classification tectonic settings stratigraphy and early diagenesis of carbonate ramp systems are reviewed carbonate ramps are common in all geological periods but were dominant at times when reef constructing organisms were absent or inhibited ramps can be subdivided into inner mid and outer ramp environments the mid ramp zone extends from fair weather wave base to normal storm wave base although the water depths which these boundaries represent vary an additional outer slope environment occurs on distally steepened ramps as with siliciclastic shelves a range of wave storm and tide dominated ramps can be recognised and this forms the most convenient basis for ramp classification the carbonate productivity profile of ramps differs from that of rimmed shelves with the inner ramp showing lower production rates than comparable shallow water facies on rimmed shelves the zone of greatest organic carbonate sediment production appears to have shifted from the mid ramp to the inner ramp since the late jurassic carbonate ramps occur in most types of sedimentary basin but are best developed where subsidence is flexural and gradients are slight over large areas as in foreland and cratonic interior basins and along passive margins the featureless depositional profiles of many ramps means that sequence geometries are best observed on regional seismic lines some show low angle sigmoidal or shingled clinoforms suggesting that ramps may seldom be homoclinal but possess subtle slope geometries which reflect depositional environments because of their low angle slopes ramps respond differently to rimmed shelves during relative sea level changes although results seem to be strongly dependent on the rate of relative sea level change during a minor fall shallow ramp facies belts will simply shift basinwards in a forced regression in contrast the whole surface of a steep sloped flat topped rimmed shelf may be exposed so that sediment production ceases or is drastically reduced during a major fall shallow ramp bounded basins may empty completely conversely ramps also flood gradually whereas rimmed shelves do so more rapidly homoclinal ramps develop no resedimented lowstand deposits rimmed shelves and distally steepened ramps in contrast may develop lowstand talus or turbiditic wedges distally steepened ramps may behave more like homoclinal ramps during minor base level falls and like rimmed shelves during major base level falls many ramps consist of layered successions of several ramp sequences stacked one upon the other ramp stacks of this sort may show gross vertical accretion but individual ramp sequences seldom appear to develop in a keep up style apart from minor organic buildups as with many rimmed shelves steepening of the outer ramp margin due to tectonism slope inheritance or differential sedimentation may promote the development of a distally steepened ramp or rimmed shelf a wide variety of organisms have constructed buildups in mid and outer ramp environments isolated buildups may seed early in ramp development accrete to wave base or sea level and continue growth by stacking through successive ramp sequences so that depositional and diagenetic features within them are in concert with those of the shallow ramp the location of isolated buildups on ramps is governed by tectonism halokinesis antecedent topography or by the subtle slope geometry of the previous ramp sequence diagenesis on ramps shows some major variations compared with diagenesis on steep sloped flat topped carbonate platforms ramp bounded basins may form prolific petroleum sourcing and reservoiring systems and offer a range of subtle stratigraphic play types and lateral facies variations which determine reservoir quality and distribution isolated buildups in the mid and outer ramp environments represent one of the commonest petroleum reservoirs in ramp systems and tend to have their foundations in transgressive systems tracts grainstone and packstone reservoirs are widespread and range from shoreline carbonate sandbodies to major detached shoal complexes or shoals over offshore highs grainstone sandbodies occur in both highstand systems tracts and in prograding lowstand wedges

the role of sea surface temperature as a control on carbonate platform development in the western coral sea the derivation of a detailed sea surface paleotemperature curve for the middle miocene holocene 10 0 ma from odp site 811 on the queensland plateau northeast australia has clarified the role of sea surface temperature fluctuations as a control on the initiation and development of the extensive carbonate platforms of this region this curve was derived from isotopic analyses of the planktonic foraminifer globigerinoides ruber and converted to temperature using the surface water paleotemperature equation accounting for variations in global ice volume the accuracy of these data were confirmed by derivation of paleotemperatures using the water column isotopic gradient 13o corrected for salinity and variations in seafloor water mass temperature results indicate that during this period surface water temperatures were on average greater than the minimum required for tropical reef growth 20 c veron 1986 with the exception of the late miocene and earliest early pliocene 10 4 9 ma when there were repeated intervals of temperatures between 18 20 c tropical reef growth on the queensland plateau was extensive from the early to early middle miocene 21 13 ma after which reef development began to decline a lowstand near 11 ma probably exposed shallower portions of the plateau after re immersion near 7 ma the areal extent of reef development was greatly reduced 50 paleotemperature data from site 811 indicate that decreased sea surface temperatures were likely to have been instrumental in reducing the area of active reef growth on the queensland plateau reduced reefal growth rates continued until the late pliocene or quaternary despite the increase of average sea surface paleotemperatures to 22 23 c studies on modern corals show that when sea surface temperatures are below 24 c as they were from the late miocene to the pleistocene off northeast australia corals are stressed and growth rates are greatly reduced consequently when temperatures are in this range corals have difficulty keeping pace with subsidence and changing environmental factors in the late pliocene sedimentation rates increased due to increases in non reefal carbonate production and falling sea levels it was not until the mid quaternary 0 6 0 7 ma that sea surface paleotemperatures increased above 24 c as a result of the formation of a western coral sea warm water pool because of age discrepancies it is unclear exactly when an effective barrier developed on the central great barrier reef the formation of the warm water pool was likely to have either assisted the formation of this barrier and or permitted increased coral growth rates fluctuations in sea surface temperature can account for much of the observed spatial and temporal variations of reef growth and carbonate platform distribution off northeast australia and therefore we conclude that paleotemperature variations are a critical control on the development of carbonate platforms and must be considered an important cause of ancient platform drowning

eustatic curve for the middle jurassic cretaceous based on russian platform and siberian stratigraphy zonal resolution we have used the stratigraphy of the central part of the russian platform and surrounding regions to construct a calibrated eustatic curve for the bajocian through the santonian the study area is centrally located in the large eurasian continental craton and was covered by shallow seas during much of the jurassic and cretaceous the geographic setting was a very low gradient ramp that was repeatedly flooded and exposed analysis of stratal geometry of the region suggests tectonic stability throughout most of mesozoic marine deposition the paleogeography of the region led to extremely low rates of sediment influx as a result accommodation potential was limited and is interpreted to have been determined primarily by eustatic variations the central part of the russian latform thus provides a useful frame of reference for the quantification of eustatic variations throughout the jurassic and cretaceous the biostratigraphy of the russian platform provides the basis for reliably determining age and eustatic events the mesozoic section of the central part of the russian platform is characterized by numerous hiatuses in this study we filled the sediment gaps left by unconformities in the central part of the russian platform with data from stratigraphic information from the more continuous stratigraphy of the neighboring subsiding regions such as northern siberia although these sections reflect subsidence the time scale of variations in subsidence rate is probably long relative to the duration of the stratigraphic gaps to be filled so the subsidence rate can be calculated and filtered from the stratigraphic data we thus have compiled a more complete eustatic curve than would be p ssible on the basis of russian platform stratigraphy alone relative sea level curves were generated by backstripping stratigraphic data from well and outcrop sections distributed throughout the central part of the russian platform for determining paleowater depth we developed a model specifically designed for this region based on paleoecology sedimentology geochemistry and paleogeography the curve describes a series of high frequency eustatic events superimposed on longer term trends many of the events identified from our study can be correlated to those found by haq et al 1988 and other sea level studies from other parts of the world but there are significant differences in the relative magnitudes of events because the eustatic curve resulting from this study is based on a stable reference frame the curve can be used in sedimentary basin modeling and as a tool for quantifying subsidence history from the stratigraphy of passive margins basins and other active regions

tide and wave dynamics on a sand bank from the deep shelf of the western channel approaches abstract the sedimentary response of deep shelf sediments to the interplay of tides and waves based on the example of the celtic sea sand banks is described grab samples and 1500 km of multibeam and side scan data have been collected from the 300 km2 densely surveyed kaiser bank area the bank is 140 170 m deep 30 m high and 60 km long oriented perpendicular to the shelf edge and nearly parallel to the major axis of the tidal ellipse surficial sediments of the bank consist of medium to gravely biolithoclastic sands they are swept by tidal currents that reach 0 9 m s 1 m above the seabed and under the occasional influence of waves the mobile sands are commonly bedformed and rest on a highly backscattering lag the flanks below 140 m mainly exhibit transverse tidal dunes and sand ribbons whereas the top of the bank mostly displays discontinuous sand patches and wave ripples the sand patches are interpreted as the remnants of tidal bedforms reworked by waves calculations of the threshold of motion of four modal grain sizes under various conditions at the seabed show that tidal bedforms are active during spring tides sometimes associated with waves whereas only the largest annual waves may explain the observed wave ripples as in active tidal banks there is a reversal of tidal bedload transport from one bank side to the other the sedimentation rate is very low on the kaiser bank in addition there is a loss of sediment at both bank extremities and the tidal bedload cross bank transfer is very small probably controlled by shelf residual currents and long term drift of sediment resuspended by waves however the present day action of waves at the bank top is less intense than it was at lower sea levels during the holocene as evidenced by seismic studies

glacial history of the kuznetsky alatay mountains field investigations showed that the leeward slopes across the kuznetsky alatay mountains also the windward slopes in the tigertysh ridge are intensively eroded by glaciers and represent the classical type of alpine type landscape accumulative glacial landforms are developed in all types of glacial valleys study of five valleys the karatas the lower and the upper tayzhasu perekhodnya the right source of the small kazyr rivers showed that four stadial moraine complexes can be identified these moraines are very different by their morphology they indicate the change of glaciation from large ancient valley glaciers to modern small cirque and slope glaciers in this article the first data are assessed about evolution of glaciers and climate in the kuznetsky alatay mountains from the last glacial maximum of late pleistocene between 26 500 and 19 000 20 000 years bp to nowadays on the basis of studies of glacial landforms sedimentology and biostratigraphy in the glacier inventory complied in 1970s early 1980s 91 glaciers were recorded in the kuznetsky alatay however some were erroneously identified as glaciers the review of the current changes of modern glaciation of the kuznetsky alatay is made on the basis of repeated photographs and direct field measurements of 30 glaciers 18 out of the 30 studied glaciers melted away completely their area decreased from 1 4 to 0 5 0 3 km2 not all glaciers strongly degraded large cirque glaciers have not changed significantly over the past 110 years the area of perennial snowfields in the kuznetsky alatay mountains had reduced by 90 over the century the timberline has risen by about 50 m and is currently located at 1220 1200 m a s l

nannofossils and superplumes the early aptian nannoconid crisis a group of calcareous nannoplankton named nannoconids experienced a crisis in the early aptian and recovered only later in the late aptian after a period of virtual absence although no extinctions occurred the widespread nature of the nannoconid crisis suggests a global causal factor this crisis is recorded within the chiastozygus litterarius nannofossil and globigerinelloides blowi planktonic foraminiferal zones postdates magnetic chronozone m0 by approximately 300 kyr and precedes the oceanic anoxic subevent 1a and associated 13c anomaly by some 40 100 kyr selective dissolution and anoxia cannot explain the crisis because nannoconids are dissolution resistant forms and their crisis clearly precedes the deposition of anoxic sediments at least 1 m y prior to the nannoconid crisis the onset of a nannoplankton speciation event may be the response of nannofloras to a major rise in relative sea level the nannoconid crisis seems to be synchronous with the early aptian volcanic eruptions in the pacific ocean hence calcareous nannoplankton were severely affected by the superplume volcanic episode the coccolithophorid bloom nannoconid crisis was possibly induced by the excessive co2 levels in the atmosphere and or caused by changes in nutrient content of oceanic surface waters fertility was enhanced by rapid turnover of nutrients due to the abnormal volcanic activity and accelerated transfer of nutrients from the continents into the oceans under warm and humid conditions of the mid cretaceous greenhouse climate the nannoconid crisis may represent a competition between phytoplankton groups for nutrients or more likely competition between different calcareous nannoplankton the biologic affinity and mode of life of nannoconus are unknown because there is no modern analog of this genus however comparison of lower cretaceous nannofossil assemblages with modern nannoplankton cummunities suggests that nannoconids like extant florisphaera profunda possibly inhabited the lower photic zone concentrations of nutrients in the upper euphotic zone may have triggered blooms of coccolithophorids and nannoconid depletion this model implies that the nannoconid crisis is the result of an abrupt major change in the structure of surface waters caused directly or indirectly by the superplume the adjustments of the biosphere to the new paleoceanographic and climatic conditions required some 40 100 kyr before changing into abnormally high primary productivity and deposition of organic carbon rich sediments with dinoflagellates outcompeting nannoplankton

the response of two tethyan carbonate platforms to the early toarcian jurassic oceanic anoxic event environmental change and differential subsidence chemostratigraphic analyses 87 sr 86 sr d 13 ccarb of limestones from two jurassic platform carbonate sequences in italy trento and campania lucania platforms illustrate previously established trends found in pelagic sediments and skeletal carbonates from biostratigraphically well calibrated sections elsewhere in europe chemostratigraphic correlations between the platform carbonate successions and appropriate intervals from well dated reference sections allow the application of high resolution stratigraphy to these shallow water peritidal carbonates and furthermore elucidate the facies response to the early toarcian oceanic anoxic event oae lower jurassic toarcian levels of the western trento platform southern alps northern italy contain spiculitic cherts that appear where rising carbon isotope values characterize the onset of the oae a palaeoceanographic phenomenon interpreted as driven by increased nutrient levels in near surface waters there is a facies change to more clay rich facies at the level of the abrupt negative carbon isotope excursion also characteristic of the oae higher in the section the campania lucania platform southern apennines southern italy records a change to more clay rich facies where carbon isotope values begin to rise at the beginning of the oae but the negative excursion higher in the section occurs within oolitic facies although in both examples the early toarcian oae can be recognized by a change to more clay rich lithologies this facies development is diachronous and in neither case did the platform drown although the trento platform in the south west sector studied here was adversely affected by the oae it did not drown definitively until late aalenian time the campania lucania platform persisted throughout the jurassic and cretaceous differential subsidence rates which can be calculated using comparative chemostratigraphy are identified as a crucial factor in the divergent behaviour of these two carbonate platforms relatively fast in the case of the trento platform relatively slow in the case of the campania lucania platform it is proposed that where water depths remained as shallow as a few metres during the oae campania lucania platform dissolved oxygen levels remained high nutrient levels relatively low and conditions for carbonate secretion and precipitation remained relatively favourable whereas more poorly ventilated and or more nutrient rich waters trento platform adversely

the lower cretaceous mesogean benthic ecosystems palaeoecologic aspects and palaeobiogeographic implications abstract douville s mesogee was based on an organismic assemblage and therefore defined mainly as a palaeobiogeographic entity the palaeoecologic analysis of douville s lower cretaceous reference taxa as well as that of a lot of other taxonomic groups and the discussion on their palaeobiogeographic meaning according to the concepts of modern marine biogeography especially the bathymetric thermic relationships result in the definition of three main organismic assemblages whose mesogean significance is discussed the key reference taxa and associated biota indicate that the definition of the lower cretaceous mesogee implies characteristic palaeoenvironmental conditions this definition substantial for the whole cretaceous means that mesogee is not simply a palaeobiogeographic entity but also an ecosystem corresponding to the area of distribution of warm shallow water carbonate platforms

mechanisms for linear sandbank formation and maintenance in relation to dynamical oceanographic observations abstract theories associated with flow in the vicinity of headlands and sandbanks together with proposed mechanisms for sandbank formation and maintenance are reviewed to exemplify water and sand movement around a sandbank on a tidally dominated shelf tidal currents in the vicinity of a headland associated linear sandbank are described these data are integrated with sedimentological information on bedforms and grain size distributions the sandbank under detailed investigation the scarweather sands is located along the northern coastline of the bristol channel uk which is an area susceptible to high energy inputs the maximum spring tidal range here is around 10m and a 6000km fetch is available for storm wave approach from the atlantic ocean but the area is 460km from the shelf break detailed observations are presented from 11 long term current meter stations located within 10km of the sandbank currents are described in terms of residual water circulation shallow water harmonics and tidal ellipse characteristics bedload transport paths are inferred from the distribution of bedforms grain size and m2 m4 tidal current interactions transport vectors are predicted from near bed current meter observations combined with empirically derived formulae it is demonstrated that water circulation and sand transport paths form part of a clockwise eddy system around the sandbank mechanisms controlling the location and the characteristics of this particular sandbank are shown to be explicable in terms of a combination of models for sandbank formation and maintenance the results of the present study are thought to be applicable directly to headland associated sandbanks elsewhere it is shown on the basis of theoretical considerations that the pattern of residual water movement and possibly sand transport around this sandbank could be extended to continental shelves on a global basis

massive dissociation of gas hydrate during a jurassic oceanic anoxic event in the jurassic period the early toarcian oceanic anoxic event about 183 million years ago is associated with exceptionally high rates of organic carbon burial high palaeotemperatures and significant mass extinction heavy carbon isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon which is isotopically light in contrast examples of light carbon isotope values from marine organic matter of early toarcian age have been explained principally in terms of localized upwelling of bottom water enriched in 12c versus 13c refs 1 2 5 6 here however we report carbon isotope analyses of fossil wood which demonstrate that isotopically light carbon dominated all the upper oceanic biospheric and atmospheric carbon reservoirs and that this occurred despite the enhanced burial of organic carbon we propose that as has been suggested for the late palaeocene thermal maximum some 55 million years ago the observed patterns were produced by voluminous and extremely rapid release of methane from gas hydrate contained in marine continental margin sediments

depletion of 13c in seawater σc02 on modern carbonate platforms significance for the carbon isotopic record of carbonates seawater co2 from modern carbonate platforms bahama banks and florida is depleted in 13c by as much as 4 relative to open ocean water depletion in 13c is caused by isotopically light co2 input from respiration of marine and terrestrial organic matter during water mass residence on the bank as such depletion in 13c is related to changes in water chemistry driven by evaporation freshwater discharge and caco3 withdrawal deviation of modern platform seawater 13c values away from those of surface seawater suggests that 13c values of ancient cratonic carbonate must be cautiously interpreted initial depositional environment as well as alteration during diagenesis must be considered in extracting valid secular trends for oceanic 13c variation

environmental setting morphology and volumetric evolution of the middelkerke bank southern north sea abstract the middelkerke bank a tidal sandbank located in the southern north sea on the belgian continental platform has been the object of a multidisciplinary and international research project the morphological and hydrodynamical setting of the study area is presented a complete side scan sonar coverage of the bank allowed a detailed analysis of the morphology of the bank and of its superimposed bedforms large dunes cover the flanks and summit of the middelkerke bank they have a constant orientation a height ranging from 0 5 to 5 m a wavelength from 75 to 150 m and in most cases an asymmetrical profile the slopes of both lee and stoss flanks are very low small and medium dune fields occur on the entire bank and in the adjacent swales they are 2 d and present a wavelength ranging from 1 to 15 m flood and ebb oriented small dunes cover respectively the western and eastern flank of the bank bathymetric surveying of the middelkerke bank was carried out to assess the importance of volumetric variations of the bank mass caused by seasonal factors results show that changes in the bank volume can be quite important the bank s volume decreases in periods of heavy weather after which the process of sand uppiling acting during long periods of fair weather conditions causes the bank to restore itself volumetric variations of the total bank volume in a winter summer period can range along certain sections of the bank from 21 to 26 despite these large seasonal volumetric variations the bank shows a long term dynamic equilibrium as proven by the obtained evolution trend

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

carbonate platform facies models various types of carbonate platforms are characterized by distinctive profiles facies and evolutionary sequences ramps may be homoclinal or distally steepened and may have fringing or barrier shoal water complexes of ooid pellet sands or skeletal banks homoclinal ramps pass seaward into deeper water without major break in slope and lack deep water breccias distally steepened ramps may be low energy and characterized by widespread shallow subwave base mud blankets or high energy with coastal beach dune complexes and widespread skeletal sand blankets slope facies may contain abundant breccias of slope derived clasts rimmed shelves have relatively flat tops and marked break in slopes at the high energy shallow shelf edge where they pass into deep water such shelves may be aggraded with peritidal facies extending over much of the shelf or incipiently drowned depending on magnitude of sea level fluctuations they may be accretionary or bypass types that include gullied slope escarpment and high relief erosional forms intrashelf basins occur on some shelves controlling distribution of reservoir and source beds isolated platforms are surrounded by deeper water and may be located on rifted continental margins or on submarine volcanoes most have high relief rimmed margins platforms that have been subjected to rapid sea level rise may be incipiently drowned and characterized by raised rims elevated patch or pinnacle reefs and widespread subwave base carbonate or fine clastic blankets completely drowned shelves develop where the shelf is submerged to subphotic depths terminating shallow water deposition and commonly resulting in blanketing of the shelf by deeper water facies some margins show extensive down to basin faulting that is contemporaneous with carbonate deposition or associated with thick prograding clastic sequences the various types of platforms change in response to variations in sedimentation subsidence or sea level rise and may form distinctive evolutionary sequences the relatively few models presented appear to accommodate most geological examples some of which contain major reservoir facies

holocene glacier fluctuations and climate changes in the southeastern part of the russian altai south siberia based on a radiocarbon chronology abstract this study investigates glacier dynamic and climatic variations in the southeastern part of the russian altai se altai during the last 7000 years recent glacier retreats and ice melting in moraines has led to exhumation of organic material allowing the possibility of radiocarbon dating we report here 57 new radiocarbon dates from wood remains buried by moraines and from proglacial forefields from peat layers and lacustrine sediments that cover moraines from dead trees at the upper tree limit and from rock glaciers on trough slopes from six glacial valleys in the north chuya range se altai such a numerous dataset for the vast but unified in neotectonic and climatic conditions area is presented for the first time the history of research in the altai together with 62 previously published radiocarbon ages mainly of fossil soils and peat layers in the foot of the ranges in se altai they form the basis for understanding the relative magnitudes and timing of the most important glacial and climatic events of se altai new data refute the traditional concept of the russian altai holocene glaciations as a consecutive retreat of the late wurm glaciers and argue their complete degradation at the head of trough valleys at least 7000 cal years bp moraine complexes of three holocene glacial stages are morphologically expressed in trough valleys of the north chuya range they correlate with three identified periods of glacial advances from 4900 to 4200 cal years bp akkem stage from 2300 to 1700 cal years bp historical stage and in the 13th 19th centuries little ice age lia or aktru stage the coincident extremes of lowering temperature and increasing precipitation during the akkem stage led to abrupt glacier advances and forming of the most remote moraine complexes downstream in the valleys following glacier advances had distinctly smaller magnitudes in addition to the radiocarbon data the time limits of the historical stage were defined more precisely using dendrochronological and archaeological data from scythian burials of pazyryk culture in se altai repeated forest regrowth in the presently glaciatiated area indicates significant retreat or even complete glacier degradation during interstage warming the decreases of glacier length in the following stages argues for intensification of aridity in the se altai during the second half of the holocene the thermal minimum in the middle of 19th century the greatest in the last millennium did not positively influence the mass balance of glaciers which also supports this conclusion

early aptian algal bloom in a neritic proto north atlantic setting harbinger of global change related to oae 1a pervasive growth of microencrusters lithocodium bacinella characterizes short lived stratigraphic intervals in lower aptian shallow water carbonate platform settings of the central and southern tethys although a causal relationship between this peculiar shallow water facies and the early aptian oceanic anoxic event oae 1a seems likely the temporal and spatial distributions of lithocodium and bacinella mass occurrences in the rock record point to a rather complex pattern possible controls include various global and regional drivers expressed in environmental perturbation of neritic ecosystems microencruster blooms have hitherto been reported to occur at the onset and in the aftermath of oceanic anoxic event oae 1a slightly pre or postdating the deposition of dark organic rich black shales in pelagic basins this study presents evidence for a punctuated and well expressed early aptian bloom of the ulvophycean green algae lithocodium aggregatum observed at the proto north atlantic margin lusitanian basin portugal similar to southern and central tethyan sections a lithocodium dominated interval temporally replaces the rudist dominated platform ecosystem this lithocodium rich horizon is composed of oncoidal floatstones and boundstones including a well exposed biohermal level and reaches a thickness of up to 6 m high resolution carbon isotope stratigraphy shown here clearly argues for lithocodium to represent a biotic harbinger of environmental change in the run up of oae 1a chemostratigraphy provides evidence that the subsequent carbonate platform breakdown in the proto north atlantic was coeval with an early aptian carbonate platform drowning episode observed in the northern tethys prior to oae 1a a regionally enhanced nutrient level and a relative sea level rise are suggested to have triggered the transient mass occurrence of lithocodium microencrusters which also may have been influenced by elevated atmospheric co2 concentrations related to the emplacement of the ontong java large igneous province upwelling water masses and enhanced terrigenous runoff due to increased weathering may have served as possible sources of the required nutrients which tentatively diminished and finally interrupted the metazoan carbonate platform factory

onset of the mid cretaceous greenhouse in the barremian aptian igneous events and the biological sedimentary and geochemical responses basalts and biostratigraphy dated at 125 120 ma from the ontong java and manihiki plateaus in the western pacific evidence the largest volcanic event in earth history in at least the past 160 m y the intervening nova canton trough rifted at about 121 118 ma and a number of guyots and seamounts formed concurrently or slightly later geological events that probably were responses to these volcanic tectonic events occurred in the following chronostratigraphic order biotic fluctuations began at about 122 5 ma at about 122 0 ma 87sr 86sr began to decline slowly metal concentrations of co mn pb yb and cu in sediments peaked at about 121 5 121 2 ma changes in planktonic communities and sedimentation culminated in a nannoconid crisis just prior to 120 5 ma and in the selli black shale oae la at about 120 5 119 5 ma a sharp drop in 13c occurred at the beginning of the selli event and rebounded into a longer positive excursion that reached a peak after the selli event at about 119 5 118 5 ma at 120 5 ma 87sr 86sr declined rapidly and reached a minimum at about 116 113 ma we speculate that the intensity of these latter responses suggests a corresponding peak in volcanic tectonic activity at about 121 119 ma

terrestrial record of methane hydrate dissociation in the early cretaceous reconstruction of changing c isotopic composition of early cretaceous atmospheric co2 from fossilized c3 vascular land plant tissue revealed a brief and striking negative excursion d 25 in atmospheric d 13 c followed by a rapid positive compensation d 15 during the aptian ca 117 ma mass balance calculations show that dissociation of a small amount of methane gas hydrate is the most tenable cause of the negative excursion this would also result in an increased co2 o2 mixing ratio as o2 is consumed during ch4 oxidation to co2 spurring the exponential phase of angiosperm biogeographic expansion

a model for atmospheric co 2 over phanerozoic time a new model has been constructed for calculating the level of atmospheric co sub 2 over phanerozoic time which is much simpler mathematically than the blag model but more complex geologically and biologically results suggest that there has been a notable pattern of varying atmospheric co sub 2 level over the past 570 my with high levels during the mesozoic and early paleozoic and low levels during the permo carboniferous and late cenozoic sensitivity analysis shows that within reasonable limits of the principal governing parameters this qualitative trend of varying co sub 2 is relatively insensitive to the actual values chosen for these parameters causes of the co sub 2 variation are multiple and no single geological or biological process can be called upon to explain all co sub 2 variation for all time the calculated trend of co sub 2 over time agrees well with independent estimations of paleoclimates thus the greenhouse theory of paleoclimate on a long geological time scale is supported by the results of the present study

glaciers of the levaya sygykta river watershed kodar ridge southeastern siberia russia modern morphology climate conditions and changes over the past decades kodar ridge 57 n 118 e southeastern siberia is a glaciarized mountain area of inner asia here we have studied areal changes of glaciers and mid summer snow cover in the levaya sygykta river watershed area 650 km2 60 of total ice cover we used 1 50 000 1 100 000 topographic maps landsat tm 1995 etm 2001 2002 high resolution cartosat 1 2009 and worldview 2 2013 imagery two digital elevation models dems and field survey data to quantify the areal changes of the glaciers since the end of the little ice age lia to 2013 in 2013 the exposed area of 18 small glaciers from 0 02 to 0 88 km2 in the study area was 3 917 0 064 km2 and volume 255 106 m3 between the lia maximum and 2013 the area has been decreased by 61 with rate of 0 377 a 1 the data available today suggest the areal shrinkage of kodar glaciers from the lia seems to be larger than elsewhere in siberia the rate of area decrease in 1995 2001 was five times greater than in 1850 2013 and in 1850 1995 1 7 times less than in 1850 2013 using regional climatic data we have found that climate conditions obviously stimulated glacier mass loss over the past at least 60 years the increased variability of absolute and relative changes in 1995 2013 was due to influence of local factors on the overall climate driven deglaciation trend comparison of two dems has showed that between 1970 and 2009 ice surfaces of 12 tested glacier tongues have been lowered on average by 29 15 m with a rate of 0 75 m a 1

pollen based reconstructions of vegetation and climate changes during the late holocene in the southern altai mountains we here preset a result of high resolution pollen data of a lacustrine peat sediment core from yushenkule yskl peat southern altai mountains northwestern china we aim to reconstruct the palaeo

growth history of shallow water carbonates control of accommodation on ecological and depositional processes we explore the role played on the growth of shallow water carbonates by changes in accommodation using case studies from late quaternary to modern carbonate environments i e coral reefs and carbonate platforms and ramps accommodation appears not to influence either primary productivity or community structure k versus r strategists as these are directly governed by nutrient supply but it does control submarine depositional profiles and their stratigraphic expression i e volumetric sedimentary partitioning the growth of communities from incipient to senescent stages is dictated by relative rates of sea level variations although ambient temperatures and trophic conditions may modify the community response a decrease or stabilization of accommodation favours lateral migration thus generating ecological and sedimentary innovations organic carbon production tends to be positively correlated to that of carbonate both declining as accommodation decreases shallow water carbonates develop as a result of the interplay of factors including the types and rates of biological and physical processes applying depositional models of recent shallow water carbonates to the interpretation of ancient carbonate platforms first needs to acknowledge the respective role of the two contrasting phases that operated during the post glacial sea level rise an earlier fast rising phase versus a later slowly rising to stabilizing phase the period of relative sea level stabilization i e the past 6 000 years appears a relevant reference for still stand related carbonate systems furthermore the oligotrophic nutrient model a dominant feature of the modern shallow water tropics can be used as an analogue in reconstructing carbonate growth histories during greenhouse episodes of earth history

plate tectonic control on the evolution of cretaceous platform carbonate production carbonate producing biota on cretaceous carbonate platforms changed from early cretaceous aragonitic coral algal and coral rudist associations to turonian maastrichtian calcite dominated rudist associations abundance patterns of rudist bivalves examined from a large database show a shift from barremian cenomanian aragonite dominated to post cenomanian calcite dominated shells these skeletal mineral changes agree with a decrease in the mg ca ratio of seawater owing to high rates of production of oceanic crust during the barremian early turonian and its effect on seawater saturation with respect to aragonite and calcite increasing sr concentrations in biotic calcite from the barremian to the maastrichtian reflect the shift from aragonite dominated to calcite dominated platform sedimentation because aragonite precipitation is a major sink for seawater sr it is speculated that a particularly low mg ca ratio and the corresponding low supersaturation of seawater with respect to aragonite during the middle cretaceous was a major cue for the radiation of calcite dominated rudist bivalves which became important carbonate producers on turonian maastrichtian carbonate platforms changing mg ca ratios of seawater are not considered to have caused middle cretaceous crises in the evolution of carbonate platforms but seawater composition could have selected for calcite dominated biota when carbonate production resumed

inventory of nival glacial geosystems in lake baikal area east siberia russia glaciers in lake baikal area were plotted on topographic and tourist maps but often big perennial snow patches were designated as glaciers a special study of these entities to classify them in one group or another was necessary recently published data of remote sensing satellite images of high resolution allow distinguishing a variety of snow and ice objects accurate to 0 5 m in identifying sustainable nival glacial formations it was necessary to measure the characteristic parameters of these objects and their boundaries using topographic maps satellite images and gps devices the gis project and the database of nival glacial formations for the quantitative analysis of the accumulated information have been created the glaciers of mountain ridges of east siberia significantly reduced in thickness for the last decades and their abrupt degradation is manifested in the last 5 10 years the main glaciers of the barguzinskiy ridge decreases with 0 002 km2 year 1 that is comparable with the reduction rate of the glaciers of the eastern sayan ridge but is less than of the representative of the kodar ridge the azarovoy glacier

deciphering the message of early cretaceous drowning surfaces from the helvetic alps what can be learnt from platform to basin correlations drowning unconformities are a frequent feature of carbonate platforms and generally express the incapacity of shallow marine ecosystems to adapt to abrupt sea level rise and or palaeoenvironmental change during the late hauterivian and early barremian the helvetic carbonate platform experienced a major drowning phase documented by the phosphate and glauconite rich altmann member it has been shown that a drowning unconformity in the form of a hardground at the base of the altmann member on the pilatus summit central switzerland results from a complex polyphased diagenetic history that includes two main phases of phosphogenesis using carbon isotope stratigraphy biostratigraphy and sequence stratigraphy the correlation of this drowning unconformity from the helvetic domain with more distal and more complete sedimentary archives allows reconstruction of the sequence stratigraphic context of the drowning surface and also an estimation of the amount of time represented by the episodes of condensation unconformities associated with the altmann member drowning phase developed during transgressive episodes when strong currents arrived onto the previously subaerially exposed platform and periods of phosphogenesis may have lasted up to 2 8 myr variations in trophic levels and hitherto less well known intervening emersion phases played an essential triggering role for the altmann drowning phase high resolution studies of drowning unconformities unravel the diversity of palaeoenvironmental parameters involved in the unfolding of such crises during the evolution of carbonate platforms

carbon isotope stratigraphy a tool for basin to carbonate platform correlation the early cretaceous carbonate carbon isotope stratigraphy established in pelagic limestones is marked by several pronounced excursions towards positive 13c values we investigated a biostratigraphically and palaeomagnetically calibrated aptian section to see whether c isotope stratigraphy could be recognized in shallow water carbonates the chosen carbonate platform sections are located in southern italy and have been dated by biostratigraphy bulk samples chosen from the barremian albian part of the sequence were analysed for their o and c isotope compositions the c isotope curve established shows two major positive excursions which can be correlated with the synchronous and globally recognized aptian c isotope events the data provide evidence that c isotope stratigraphy can be used as a powerful correlation tool between pelagic and shallow water limestone sequences

morphodynamics of a tidal ridge system in the southwestern yellow sea hf radar study abstract a radial tidal ridge system is present throughout the coastal waters of the southwestern yellow sea china with varied and complicated ridges and channels between them a newly designed ground wave high frequency hf radar with full coverage and high spatial temporal resolution was employed in this study to measure the surface currents and bathymetric features correlated wave celerity in the study area from july 17 to august 6 2011 we found that the spatial distribution pattern of the tidal channels is generally stable with periodic adjustments during a spring neap tidal cycle and with higher degree of spatial orderliness from neap to spring tides than from spring to neap tides the nearshore part of the channels is most stable in lateral the middle part is relatively lateral unstable and the offshore part changes complicatedly flood dominated channels and ebb dominated ridges are identified using hf radar signals the horizontal kelvin number k eh is workable in lateral stability evaluation this study reveals the potential of hf radar in morphodynamic studies on shallow coastal waters

impact of early aptian carbon cycle perturbations on evolution of a marine shelf system in the basque cantabrian basin aralar n spain abstract the aptian oceanic anoxic event 1a oae1a ca 120 ma ago is one of the most prominent of a series of geologically brief intervals in the cretaceous reflecting a major perturbation in the global carbon cycle this carbon cycle perturbation is recorded in the c isotope stratigraphy in this study we present a new carbonate and organic carbon isotope record across oae1a from expanded shallow marine sections igaratza and iribas in the basque cantabrian basin n spain the sediments studied were accumulated on a mixed carbonate siliciclastic and carbonate shelf the 13 c carb and 13 c org curves obtained show a pronounced negative spike in the deshayesites weissi zone and a subsequent positive excursion within the newly described d deshayesi d furcata transition zone approximately equivalent to the upper d deshayesi zone of other sections specific changes in facies patterns and a reduction in neritic carbonate production predate the negative c isotope perturbation these changes coincide with global carbonate crises in neritic and pelagic environments corresponding with the beginning of oae1a selli level a condensed interval rich in ammonites is observed this horizon is linked to a major transgression with high biodiversity the ammonite bloom suggests enhanced primary productivity in the surface waters of the basque cantabrian basin at improving environmental conditions for selected biocalcifiers the ultimate recovery of shelf carbonate deposition occurred after oae1a and it coincided in time with the most positive values of the carbon isotope excursion based on carbon isotope stratigraphy it has been deduced that black shales corresponding to selli level are missing in aralar so that anoxia is not recorded in the studied sections of the marine shelf environment an organic rich interval aparein level postdates the early aptian major positive excursion the aparein event should be considered in the future research of oaes

relation between stratigraphic architecture and multi scale heterogeneities in carbonate platforms the barremian lower aptian of the monts de vaucluse se france abstract understanding the relationship between multi scale sedimentary heterogeneities and the stratigraphic architectures of carbonate platforms improves the interpretation of paleoenvironmental evolution in time and space such an approach improves the prediction of the spatial distribution of reservoir properties within carbonate stratigraphic units the reservoir scale stratigraphic anatomy and the growth history of a barremian aptian carbonate platform monts de vaucluse se france was based on 1 high resolution measured sections on outcrops 2 detailed microfacies analyses 3 paleoenvironmental interpretations 4 biostratigraphy using rudist bivalves foraminifera calcareous algae and locally echinoderm and ammonites and 5 sequence stratigraphic interpretations with a special focus on the identification of discontinuity surfaces with a significant stratigraphic correlation potential and critical environmental meaning the platform succession consists of subtidal mainly infralittoral with rare inter to supratidal deposits thirty types of elementary facies grouped in 12 facies associations have been defined the vertical and lateral changes in paleoenvironments together with the development of remarkable stratigraphic surfaces such as subaerial exposures marine erosional surfaces and drowning surfaces allow the definition of five stratigraphic sequences ranging from the late barremian to the earliest aptian these depositional sequences can be grouped into two distinct carbonate sedimentary systems characterized by specific sedimentary profiles and skeletal and non skeletal components 1 a carbonate platform with stronger hydrodynamic gradients rimmed by a narrow belt of high energy deposits with corals and rudistid rudstone facies and 2 a carbonate ramp dominated by orbitolinids fine grained facies including an elongated high energy oolitic shoal the two dimension architecture of the depositional sequences dimensioned geometries thickness and facies variations and the morphology of the shelf reflect a strong interaction between tectonic differential subsidence sediment production and global environmental conditions at the km scale the gorges de la nesque stratigraphic motif could represent a nested stratigraphic structure within the large scale model which could be implemented for up scaling petrophysical properties from the well to a full field model the association of coral facies to the rudist dominated system in the provence platform is a very clear proxy of the polarity of the carbonate platform and is critical for subsurface facies property modeling based on well data finally at the global scale the stratigraphic architecture and the step wise drowning events of the provence platform confirm and document the precursor events associated with environmental perturbations that affected the carbonate factory prior the oceanic anoxic event 1a oae1a

response of early cretaceous carbonate platforms to changes in atmospheric carbon dioxide levels during the late barremian and early aptian about 120 million years ago intense volcanic degassing and extremely rapid release of methane hydrates contained in marine sediments added high amounts of carbon to the ocean and atmosphere and resulted most probably in rising atmospheric carbon dioxide pressure in order to document the response of the shallow water carbonate producing communities to this pronounced disturbance of the carbon cycle we studied a late barremian to early aptian neritic carbonate succession deposited on the northern tethyan shelf swiss alps the sedimentological and stable carbon and oxygen isotope records of two sections located along a n s transect from proximal to more distal shelf environments were investigated the sediments correspond to outer mid and inner ramp deposits of a homoclinal carbonate ramp vertical facies variations within the two studied sections feature three progradation phases of the platform a highly resolved correlation of the shelf sediments with a pelagic succession from the southern alps northern italy is based on both 13c stratigraphy and biostratigraphy and indicates that the drowning of the helvetic carbonate platform coincided with a pronounced calcification crisis of calcareous nannofossils the biocalcification crisis started before but culminated during the aptian methane event recorded in a negative carbon isotope spike we propose that increased carbon dioxide concentrations in oceans and atmosphere related to volcanic activity and to sudden methane release reduced the marine calcium carbonate oversaturation and the calcification potential of benthic and planktonic organisms carbonate producing shallow water communities on platforms and ramps suffering from additional environmental stress such as extreme temperatures or high nutrient levels could not survive during times of rising sea level and as a consequence carbonate platforms drowned

carbon isotope composition of lower cretaceous fossil wood ocean atmosphere chemistry and relation to sea level change the carbon isotope composition of fossil wood fragments collected through a biostratigraphically well constructed aptian lower cretaceous shallow marine siliciclastic succession on the isle of wight southern britain shows distinct variations with time the results indicate that the stratigraphic signature of delta sup 13 c sub wood through the aptian was influenced primarily by fluctuations in the isotopic composition of co sub 2 in the global ocean atmosphere system as registered in marine carbonates elsewhere and was not governed by local paleoenvironmental and or paleoecological factors negative and positive excursions in delta sup 13 c sub wood through the lower aptian occur in phase with inferred transgressions and regressions respectively a pattern that contrasts with that observed in many previous studies for different time intervals the relationship between delta sup 13 c variations and relative sea level change is tentatively interpreted as a response to various climatic and eustatic factors relating to rapid sea floor spreading thermal uplift of ocean floor emplacement of plateaus volcanic co sub 2 emissions weathering and sedimentary rate

influence of hydrodynamic energy on holocene reef flat accretion great barrier reef the response of platform reefs to sea level stabilization over the past 6 ka is well established for the great barrier reef gbr with reefs typically accreting laterally from windward to leeward however these observations are based on few cores spread across reef zones and may not accurately reflect a reef s true accretional response to the holocene stillstand we present a new record of reef accretion based on 49 u th ages from heron and one tree reefs in conjunction with re analyzed data from 14 reefs across the gbr we demonstrate that hydrodynamic energy is the main driver of accretional direction exposed reefs accreted primarily lagoon ward while protected reefs accreted seawards contrary to the traditional growth model in the gbr lateral accretion rates varied from 86 3 m ka 42 4 m ka on the exposed one tree windward reef and 68 35 m ka 15 7 m ka on the protected leeward heron reef suggesting that wind wave energy is not a dominant control on lateral accretion rates this represents the most comprehensive statement of lateral accretion direction and rates from the mid outer platform reefs of the gbr confirming great variability in reef flat growth both within and between reef margins over the last 6 ka and highlighting the need for closely spaced transects

carbon isotope stratigraphy of cenomanian turonian platform carbonates from the southern apennines italy a chemostratigraphic approach to the problem of correlation between shallow water and deep water successions the carbon isotope record of three sections of shallow water carbonates from the upper cretaceous sequences of the southern apennines italy shows a pronounced positive excursion of about 4 5 using the upper cenomanian cisalveolina fraasi level as a biostratigraphic tie point we correlate this excursion to the oae 2 isotopic event comparison with the standard reference 13 c curve of eastbourne england shows that the overall character of the excursion is clearly reproduced in the shallow water curves chemostratigraphic correlation allows definition of the age of some important shallow water biostratigraphic events to the precision of an ammonite zone using the well established bio chronostratigraphic framework defined in the eastbourne section the onset of the cenomanian turonian isotopic excursion coincides with a transgressive trend recorded by the occurrence of more open marine facies and culminating with an incipient drowning in one of the sections studied our data suggest that the open ocean isotopic signal is most faithfully recorded and preserved in shallow water platform carbonates during transgressive periods when the effects of meteoric diagenesis and seawater ageing are less severe

holocene reef accretion on the rodrigues carbonate platform an alternative to the classic bucket fill model carbonate platform evolution around the island of rodrigues southwestern indian ocean is reconstructed from cores recovered across the platform9s windward margin in contrast to the classic bucket fill model of carbonate platform evolution whereby platform filling occurs predominantly as a function of the lagoonward transport of sediment from the reef rim data from rodrigues demonstrate that the primary mode of platform filling was through reef progradation from the platform interior seaward indeed radiocarbon dates indicate that much of the platform interior had filled by 2000 cal calibrated yr b p data also indicate that the reef rim probably caught up with sea level only in the past 1000 yr and subsequent export of sediment from those areas into the lagoon has probably only become important during the final stages of the platform9s evolution we interpret this as a function of the platform margin reef9s catch up growth mode this would have allowed significant marine circulation within the platform interior thus promoting active reef growth prior to sea level being attained given that such catch up growth modes are widely recognized on many reef platform margins we suggest that this novel platform evolutionary model may have widespread applicability sounder resolution 10 cm were made at each core site and water depths were normalized to the tide curves and corrected to mean sea level msl is 1 872 m above chart datum all core depth measurements were uncompacted and were normalized to msl

morphodynamic behaviour of a nearshore sandbank system the great yarmouth sandbanks u k offshore sandbanks provide a major source of sediment and may have a significant impact on the evolution of the nearby shoreline the prediction of sandbank evolution is extremely important for coastal engineers and managers however it is evident from the existing literature that additional investigations into the evolution of offshore sandbanks are needed the present paper describes qualitative and quantitative investigations of the evolution of the great yarmouth sandbanks a depth integrated tidal model has been used to calculate the residual currents arising from the sequence of sandbank configurations observed from historic charts over a 150 year period tidal simulations were performed with a nested model covering the southern north sea and great yarmouth zone east coast of the uk simulations were carried out for a period corresponding to several spring neap cycles to calculate residual currents and were compared directly with field measurements model calibration and validation was performed against published tidal elevation charts based on many observations tidal predictions and field measurements these detailed comparisons have been used to determine the errors in the model predictions overall the performance of the model is considered good the model output has been analysed to investigate qualitative links between the sandbank configuration and the residual flow statistics the results demonstrate that the long term changes in sandbank morphology can be explained from the pattern of tidal residual currents

controls on cyclostratigraphy of lower cretaceous carbonates and evaporites cupido and coahuila platforms northeastern mexico the lower cretaceous cupido barremian aptian and coahuila albian carbonate platforms of northeastern mexico exhibit thick successions of meter scale cycles deposited in three unique paleoenvironmental settings 1 the cupido shelf lagoon is composed of peritidal carbonate cycles deposited in the protected lee of a reef rimmed to barrier shoal margin 2 the restricted coahuila ramp interior consists of cyclic alternations of subtidal evaporites and peritidal carbonates 3 the deep water parts of both the cupido and coahuila platforms are composed of foraminiferal wackestones and lime mudstones interspersed with firmgrounds and hardgrounds in a cyclic arrangement vertical successions of meter scale evaporitic cycles and peritidal cycles exhibit systematic stacking patterns that build into intermediate scale high frequency sequences tens to hundreds of meters thick and large scale composite sequences hundreds of meters thick that can be correlated across the cupido and coahuila platforms these large scale stacking patterns are interpreted to reflect longterm accommodation events and when combined with the scale independent architecture of all genetic units permit the inference that all three meter scale cycle types on the cupido and coahuila platforms are also governed by relative sea level change the composition thickness and number of meter scale cycles within individual high frequency sequences can be highly variable across the cupido and coahuila platforms however even though the overall upward shallowing patterns are evident the lateral complexity of cycle architecture and distribution is interpreted to be a natural response to fluctuations in regional climate interacting with autogenic processes such as variations in carbonate production and dispersal intensity and frequency of tropical storms and monsoons thermohaline circulation patterns and ambient ocean chemistry and temperature these interacting processes created laterally variable physiographic and oceanographic conditions across the cupido and coahuila platforms complicating the sedimentary record generated by the composite sea level signal well documented evidence from barremian cenomanian pelagic cycles throughout the tethyan seaway strongly indicates that milankovitch driven climatic changes operated during the early cretaceous contemporaneous shallow marine cyclicity in several locations suggests that these climatic changes may have had globally widespread effects in an effort to link the shallow water and deep water realms we propose a model whereby milankovitch driven global climatic changes generated low amplitude high frequency eustatic fluctuations through some combination of thermal expansion and contraction of ocean water waxing and waning of small ice caps and alpine glaciers and changes in the storage capacity of aquifers and lakes to produce meter scale cycles across lower cretaceous shallow marine platforms

reconstruction of glacier fluctuations in the east sayan baikalsky and kodar ridges east siberia russia during the last 210 years based on high resolution geochemical proxies from proglacial lake bottom sediments we have presented results of study of bottom sediments of the proglacial lakes enriched with meltwater of peretolchin glacier the east sayan ridge chersky glacier the baikalsky ridge and glaciers of the kodar ridge bottom sediments formed from the end of the little ice age to 2013 were investigated with time resolution in year season using x ray fluorescence with synchrotron radiation and inductively coupled plasma mass spectrometry depth age models of the cores were estimated from year laminate layers using 210pb and 137cs chronology intense glacier thawing was calculated from the amount of clastic matter supplied by glacier meltwater into proglacial lakes a high content of some elements was closely associated with clastic material e g rb zr nb y or th in bottom sediments and most likely these elements affected the intensity of glacier melting we have defined three periods in significant increase of glacier flow melting during the last 210 years the first period ca 1800 1890 supply of suspended material by meltwater into lake ekhoy the east sayan ridge and lake preobrazhenskoe the kodar ridge was not intense until 1850 and 1875 respectively however the rate of meltwater supply into lake izumrudnoe the baikalsky ridge was high during the little ice age and it is likely attributed to local moisture from lake baikal the regional glacier water balances were most likely positive during the second period ca 1890 1940 the third period ca 1940 till present was characterised by moderate melting rate of glaciers located on the kodar and baikalsky ridges in contrast to peretolchin glacier that demonstrated the highest rate of melting and changes in outlines during this period

water and sediment movement in the vicinity of linear sandbanks the norfolk banks southern north sea geophysical surveys current meter measurements and fluorescent sand tracer experiments were undertaken in the vicinity of the broken bank the data are used to establish localised and regional patterns of water and sediment movement the results obtained confirm mechanisms proposed previously for sandbank growth with particular reference to the north sea these include the clockwise circulation of water and sand with convergence at the crestline secondary helical water circulations do not appear to be a dominant process influencing sandbank maintenance however such circulation may still be important in the initial formation of linear sandbanks and or at some stages in the bank development on a regional basis residual currents bedform asymmetries and tracer dispersion indicate an offshore sediment transport component this observation supports the hypothesis of other investigators formed on the basis of geomorphological observations and numerical model predictions concerning the movement of sand under extreme conditions moreover these transport pathways may persist under low wave and tidally dominated conditions as opposed to being restricted to storm activity

late early triassic climate change insights from carbonate carbon isotopes sedimentary evolution and ammonoid paleobiogeography the late early triassic sedimentary facies evolution and carbonate carbon isotopemarine record 13ccarb of ammonoid rich outer platform settings show striking similarities between the south china block scb and the widely distantnorthern indianmargin nim the studied sections are located within the triassic tethyshimalayan belt losar section himachal pradesh india and the nanpanjiang basin in the south china block jinya section guangxi province respectively carbon isotopes from the studied sections confirm the previously observed carbon cycle perturbations at a time of major paleoceanographic changes in the wake of the end permian biotic crisis this study documents the coincidence between a sharp increase in the carbon isotope composition and the worldwide ammonoid evolutionary turnover extinction followed by a radiation occurring around the smithian spathian boundary based on recent modeling studies on ammonoid paleobiogeography and taxonomic diversity we demonstrate that the late early triassic smithian and spathian was a time of a major climate change more precisely the end smithian climate can be characterized by a warm and equable climate underlined by a flat pole to equator sea surface temperature sst gradient while the steep spathian sst gradient suggests latitudinally differentiated climatic conditions moreover sedimentary evidence suggests a transition froma humid and hot climate during the smithian to a dryer climate fromthe spathian onwards by analogywith comparable carbon isotope perturbations in the latedevonian jurassic andcretaceouswe propose that high atmosphericco2 levels could have been responsible for the observed carbon cycle disturbance at the smithian spathian boundary we suggest that the end smithian ammonoid extinction has been essentially caused by a warm and equable climate related to an increased co2 flux possibly originating froma short eruptive event of the siberian igneous province this increase in atmospheric co2 concentrations could have additionally reduced the marine calcium carbonate oversaturation and weakened the calcification potential of marine organisms including ammonoids in late smithian oceans

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