berriasian aptian black shales of the maiolica formation lombardian basin southern alps northern italy local to global events the lower cretaceous maiolica formation represents the classic pelagic succession of the apulian margin of the tethys ocean in the southern alps it consists of white calcilutites with minor marly layers and black shales a multidisciplinary study including lithostratigraphy nannofossil assemblage composition and organic geochemistry was performed on two composite sections in order to characterise the marl shale layers that record production and storage of organic matter om and terrigenous input in the berriasian aptian interval such layers are associated with turbidite deposition and bottom current activity in the late berriasian earliest valanginian late valanginian and early aptian the uppermost hauterivian barremian black shales alternate with pelagic calcilutites forming an interval barren of redeposited layers the quantity of organic carbon increases from the berriasian to the barremian the background composition of the kerogen is continental dominated with varying proportions of marine derived om preservation of om did not necessarily occur under anoxic conditions on the contrary storage of om probably resulted from enhanced terrestrial input of nutrients siliciclastics woody and herbaceous fragments inducing mesotrophic conditions and increased primary productivity higher fertility of surface waters during the late valanginian and early aptian is reflected by distinctive decreases in abundance of oligotrophic nannoconids and increase in abundance of mesotrophic diazomatholithus in the valanginian during the barremian the rhythmic establishment of eutrophic conditions documented by the highest amounts of marine om determined high frequency fluctuations in nannoconid abundance the early aptian nannoconid crisis is interpreted as the result of a major climate change and enhanced primary productivity variations of calcareous nannofloras as well as changes of lithology and om which we describe in the lower cretaceous maiolica formation of the lombardian basin can also be recognised in coeval units from other sites of the apulian side of the tethys similar episodes of siliciclastic and terrestrial om accumulation and major changes in calcareous nannofossils are also recorded in the upper valanginian and lower aptian pelagic sediments of the tethys atlantic and partly pacific oceans such nannofossil variations are coeval with positive excursions of the 13c curve and suggest perturbations of the bio geochemical cycles at a global scale additional minor changes in siliciclastic and terrestrial om accumulation as well as in nannofloras are probably the result of local events strictly related to the physiography and evolution of the tethyan margin

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

barents sea seasonal ice zone features and processes from ers 1 synthetic aperture radar seasonal ice zone experiment 1992 sea ice features and processes in the barents sea were studied during the seasonal ice zone experiment 1992 sizex92 a dedicated ers 1 satellite synthetic aperture radar sar field campaign carried out in march 1992 sizex92 was based around the research vessels polarsyssel and hakon mosby in situ oceanographic meteorological and ice measurements were made coordinated with low altitude aerial observations and ers 1 sar data acquired in near real time fifty eight low and full resolution sar scenes were obtained during sizex92 which provided a validation data set for ers 1 sar backscatter under winter conditions in the barents sea analysis of sizex92 data has provided geophysical insights including a better understanding of barents sea ice edge freezing processes and ice edge development in response to atmospheric forcings in particular areas of new ice formation were found to be related to bathymetric features through their influence on the circulation of arctic and atlantic water masses ers 1 sar image sequences revealed rapid mesoscale variations in new ice areas and the ice edge in response to wind conditions in addition to geophysical insight sizex92 demonstrated some of the technical capabilities and limitations of ers 1 sar to identify new ice areas the ice edge ice floes and ice types mapping new ice areas using satellite sar data may be considered the most promising new application the limitations of ers 1 sar derived ice classification and ice motion estimates in the marginal ice zone are identified

high resolution chemo and biostratigraphic records of the early aptian oceanic anoxic event in cantabria n spain palaeoceanographic and palaeoclimatic implications abstract during the early aptian major palaeoenvironmental changes occurred leading to an oceanic anoxic event oae 1a and a perturbation of the global carbon cycle new detailed litho bio and chemostratigraphic toc 13ccarb 13corg records of two superbly exposed and expanded lower aptian sections in cantabria la florida and cuchia allow to recognize the expression of the oae 1a in shallow shelf environments of northern spain the succession consists of shallow platform limestones that include a marly unit patrocinio formation the deposition of which occurred mostly at the onset of the oae 1a 120 5 ma this study presents a new integrated biostratigraphy based on ammonites planktonic foraminifera calcareous nannofossils and palynomorphs that allows an accurate age resolution of the succession the marly unit records an abrupt negative 13c excursion in both bulk organic matter up to 5 and carbonate up to 6 mean 3 as has been already observed at the onset of the oae 1a in other lower aptian deposits worldwide in detail however the negative excursion presents two minima in the studied sections this negative spike is confidently attributed to the upper half of the hayesites irregularis nannofossil zone to the upper part of the blowiella blowi foraminiferal zone and to the middle upper part of the deshayesites weissi ammonite zone a third negative excursion occurs at the base of the rhagodiscus angustus nannofossil zone which may be correlatable with the dufrenoyia furcata ammonite zone this data set refines the age of the oae 1a and reveals the existence of a stratigraphic gap in the westernmost margin of the basque cantabrian basin that covers at least a portion of the upper part of the early aptian sedimentary facies and quantitative analysis of palynomorphs and nannofossils document significant environmental changes associated with the oae 1a compositional changes of neritic carbonates and calcareous nannofossils data indicate the occurrence of a biocalcification crisis inferred to have been related to co2 induced changes in seawater chemistry and palynomorphs identify a thermal maximum followed by a cooling phase the latter show a classopollis maximum during the oae 1a which is followed by a decrease in classopollis and an increase of bisaccate pollen after the event

topographic control of thermohaline frontal structure in the barents sea polar front on the south flank of spitsbergen bank a combination of observations and process oriented numerical modeling is used to investigate the thermohaline structure of the barents sea polar front on the south flank of spitsbergen bank the polar front is the boundary between warm saline north atlantic water and cool fresh arctic water located over the outer edge of the bank observations from the barents sea polar front experiment in august 1992 show that north atlantic water was present in waters of 250 m or deeper with little vertical structure beneath the upper 50 m of the water column the mean velocity field over the south flank of the bank shows a westward flow of roughly 0 1 m s 1 in the north atlantic water and weak mean velocities over the outer edge of the bank a primitive equation model is used with idealized bathymetry to show that the inflow of north atlantic water into the barents sea via the bear island trough bifurcates at the sill between nordkapp bank and sentral bank at the eastern edge of the bear island trough one branch of the north atlantic water recirculates westward out of the barents sea and back into the norwegian sea the flow of north atlantic water is barotropic and linear following the bathymetry the recirculating branch is sheared off at the sill such that the core of recirculating flow is concentrated between the isobath coincident with the sill depth 260 m and the center of the trough 500 m both the cross bank structure of the model thermohaline fields as well as the along bank velocity are very similar to the observations at a depth of 80 m thus the frontal structure is controlled by the interaction of the barotropic inflow with the sill at the eastern edge of the bear island trough and is not controlled by processes occurring over the bank

late valanginian barremian early cretaceous palaeotemperatures inferred from belemnite stable isotope and mg ca ratios from bersek quarry gerecse mountains transdanubian range hungary abstract a high resolution stable isotope study of upper valanginian barremian early cretaceous belemnites from bersek quarry gerecse mountains transdanubian range hungary is presented over 190 belemnite rostra including hibolithes subfusiformis duvalia dilatata and conohibolites gladiiformis have been analysed for oxygen and carbon isotopes and for trace element geochemistry the obtained carbon isotope curve shows a long term decrease from 1 2 in the upper valanginian to 0 5 in the upper hauterivian followed by more variable values in the early barremian superimposed on this trend are a number of possible shorter term peaks this pattern broadly follows published carbon isotope curves for the same interval and is therefore thought to reflect a global rather than a regional signal the oxygen isotopes show the most positive values in the uppermost valanginian and become increasingly more negative through the hauterivian into the barremian such changes are interpreted as an increase in marine temperatures through the section the mg ca data paralleling the oxygen isotope trend confirms our temperature interpretation the oxygen isotope ratios are generally more negative and therefore allow us to infer warmer temperatures than those derived from belemnites from time equivalent sections in germany and speeton uk consistent with the more southerly latitudinal position of the gerecse mts within the tethys ocean the oxygen isotope and mg ca data also reveal habitat differences for the different belemnite groups analysed vaunagites pistilliformis belemnites pistilliformis and hibolithes typically have more negative oxygen isotope values than pseudobelus and duvalia and are therefore interpreted to have lived in warmer and or shallower parts of the water column consistent with previous interpretations

rupture process of the 2001 may 7 mw 4 3 ekofisk induced earthquake summary on 2001 may 7 following unintentional water injection a moderate size induced earthquake struck the ekofisk oil field north sea despite of its relatively moderate magnitude clear low frequency waveforms could be recorded up to more than 2000 km epicentral distance suggesting a slow rupture at very shallow depth and wave propagation through low velocity shallow structures the event poses a rare opportunity to constrain rupture velocity duration and rise time of a superficial m 4 event occurring on a horizontal plane in soft water saturated sediments two previous studies discussed the earthquake point source finding vertical dip slip focal mechanisms with opposite senses of p and t axes a further investigation was thus required to provide a basis for a deeper discussion of the failure dynamics we significantly improve the used data set test different earth models and derive a point source as well as a kinematic rupture model we carefully discuss parameter uncertainties and effects related to shallow sources and wave propagation through different crustal structures to resolve the previous controversy we additionally provide a kinematic rupture model based on apparent source times derived from rayleigh and love waves the waveforms resolve a predominant unilateral rupture along a horizontal plane at about 2 km depth we derive an unusually slow rupture consequence of a slow rupture velocity of about 500 m s 1 and a long rise time of about 7 s an independent modelling of gps based static displacements allows to confirm the focal mechanism polarity and to locate the centroid at the eastern side of the field resulting in a much larger seismic moment in comparison with dynamic seismic moment the rupture directivity is confirmed by the relative location of the centroid with respect to the epicentre which is set at the site of water injection

forcing mechanisms for mid cretaceous black shale formation evidence from the upper aptian and lower albian of the vocontian basin se france calcareous nannoplankton palynomorph benthic foraminifera and oxygen isotope records from the supraregionally distributed niveau paquier early albian age oceanic anoxic event 1b and regionally distributed niveau kilian late aptian age black shales in the vocontian basin se france exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid cretaceous low latitudes to quantify surface water productivity and temperature changes nutrient and temperature indices based on calcareous nannofossils were developed the nutrient index strongly varies in the precessional band whereas variations of the temperature index reflect eccentricity since polar ice caps were not present during the mid cretaceous these variations probably result from feedback mechanisms within a monsoonal climate system of the mid cretaceous low latitudes involving warm humid and cool dry cycles a model is proposed that explains the formation of mid cretaceous black shales through monsoonally driven changes in temperature and evaporation precipitation patterns the lower albian niveau paquier which has a supraregional distribution formed under extremely warm and humid conditions when monsoonal intensity was strongest bottom water ventilation in the vocontian basin was diminished probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes surface water productivity in the vocontian basin was controlled by the strength of monsoonal winds the upper aptian niveau kilian which has a regional distribution only formed under a less warm and humid climate than the niveau paquier low latitude deep water formation was reduced to a lesser extent and or on regional scale only the threshold for the formation of a supraregional black shale was not reached the intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale at least in the vocontian basin the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity

paleoclimate and extensional tectonics of short lived lacustrine environments lower cretaceous of the panormide southern tethyan carbonate platform nw sicily abstract subaerial erosion and continental sedimentation interbedded with shallow water carbonates are unequivocal stratigraphic records to evaluate paleoenvironmental and paleoclimate evolution of emerged landmass stratigraphic analysis of the cretaceous monte gallo section of the mesozoic panormide carbonate platform in the northern side of the palermo mountains nw sicily records a peculiar continental derived clays that interrupted the shallow water carbonate sedimentation these clays rest with lenticular geometries above the tectonically enhanced subaerial erosional unconformity of the barremian lower aptian requienid limestones and are covered by the upper cretaceous rudistid limestone sedimentological investigation combined with mineralogical and petrographic results reveal the occurrence of alkaline to saline lake clays deposition in pond filling depositional environment recording stressed conditions evaporation especially in its final living phase they were formed when a half graben tilted block tectonics produced footwall uplift of the gallo faulted blocks carbonate platform paleoclimate evaluations of the continental derived clays highlighted that a period of warm humid conditions which favoured their formation interrupted the uniform warm climate conditions highlighting a greenhouse climate phase

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

a comparison of gcm simulated cretaceous greenhouse and icehouse climates implications for the sedimentary record abstract two general circulation model simulations of mid cretaceous climate are presented one representing a greenhouse and the other representing an icehouse world through a comparison of greenhouse and icehouse palaeoclimates differences in processes which are intrinsically linked with climate such as continental weathering and snow and ice accumulation may be observed a number of conspicuous and discrete climatic differences can be seen between the two simulations which may be translated into a number of identifiable signatures in the sedimentary record the climate at mid high latitudes in the icehouse simulation was more arid than the greenhouse simulation and could result in deposition of smectite dominated clay suites in contrast the climate of low latitudes of the icehouse simulation resulted in a moister climate than the greenhouse simulation which could affect the weathering regimes and result in deposition of kaolin dominated clay suites thus cool climate episodes do not necessarily result in a global increase in aridity the icehouse simulation predicts a small permanent icecap at high latitudes which could account for the origin of dropstones in marine sediments furthermore a sea level fall as a consequence of an accumulation of ice at high latitudes may also increase continentality and surface albedo which may also contribute to the causes of the drier climate at high latitudes hurricanes are likely to be more frequent in greenhouse than icehouse climates mid latitude depressions also important for generating storms are likely to be both intense and frequent during icehouse and greenhouse periods of the middle cretaceous

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

paleoenvironmental changes during the valanginian new insights from variations in phosphorus contents and bulk and clay mineralogies in the western tethys paleoenvironmental and paleoclimatic changes during the valanginian carbon isotopic excursion cie have been investigated in the western tethys for this purpose bulk rock and clay mineralogies as well as phosphorus p contents were evaluated in a selection of five sections located in the vocontian basin angles se france alvier e switzerland malleval e france and the lombardian basin capriolo n italy breggia s switzerland within the cie interval bulk rock and clay mineralogies are inferred to reflect mostly climate change the onset of the cie busnardoites campylotoxus ammonite zone is characterized by higher detrital index di sum of the detrital minerals divided by calcite contents values and the presence of kaolinite in their clay mineral assemblages in the late valanginian from the saynoceras verrucosum zone up to the end of the valanginian the samples show relatively variable di and lower values or the absence of kaolinite the variation in the mineralogical composition is interpreted as reflecting a change from a climate characterized by optimal weathering conditions associated with an increase in terrigenous input on the southern european margin during the cie towards an overall unstable climate associated with drier conditions in the late valanginian this is contrasted by a dissymmetry proximal vs distal along the studied transect the northern tethyan margin being more sensitive to changes in continental input compared to the distal environments p accumulation rates par present similar features in the vocontian basin p content variations are associated with changes in terrigenous influx whereas in the lombardian basin i e capriolo and breggia par values are less well correlated this is mainly because the deeper part of the tethys was less sensitive to changes in continental inputs the onset of the cie top of the b campylotoxus zone records a general increase in par suggesting an increase in marine nutrient levels this is linked to higher continental weathering rates and the enhanced influx of nutrients into the ocean in the period corresponding to the shift itself p contents show a dissymmetry between the vocontian and lombardian basins proximal vs distal for the sections of malleval alvier and angles a decrease in p concentrations associated to a decrease in detrital input is observed in capriolo and breggia par show maximum values during the plateau indicating a more complex interaction between different p sources the time interval including the top of s verrucosum zone up to the end of the valanginian is characterized by variable par values suggesting variable nutrient influxes these changes are in agreement with an evolution towards seasonally contrasted conditions in the late valanginian

effects of mackenzie river discharge and bathymetry on sea ice in the beaufort sea mackenzie river discharge and bathymetry effects on sea ice in the beaufort sea are examined in 2012 when arctic sea ice extent hit a record low satellite derived sea surface temperature revealed warmer waters closer to river mouths by 5 july 2012 mackenzie warm waters occupied most of an open water area about 316 000 km2 surface temperature in a common open water area increased by 6 5 c between 14 june and 5 july 2012 before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the mackenzie delta in 2012 melting by warm river waters was especially effective when the strong beaufort gyre fragmented sea ice into unconsolidated floes the mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the arctic ocean constituting a stark contrast to the antarctic that has no such rivers to affect sea ice

middle and late albian geography oceanography and climate and the setting of the kirchrode i and ii borehole sites abstract the paper reviews the literature on the geography oceanography and climate belts during the middle and late albian emphasis is placed on the northern hemisphere and the lower saxony basin the middle and late albian represents a time with a greenhouse climate the n s temperature gradient and the temperature gradient between the shallow and deep waters of the oceans were lower than at present meaning higher temperatures especially at middle and high latitudes a more sluggish ocean circulation than today and the absence of polar ice caps warming from the early to late albian is documented in the marine sediments by oxygen isotope studies and the poleward expansion of rudist dominated carbonate platforms in the terrigenous sediments of the northern hemisphere it is documented by northward migration of low latitude relatively arid flora the opening north atlantic was still narrow at the beginning of the albian it widened and deepened through the albian a shallow seaway between the south atlantic and the western tethys developed during the late albian wide shelf seas existed on the continental plates with rising sea level the basins of the western epicontinental seas of eurasia became increasingly connected and sedimentation gradually became more calcareous nevertheless these basins received a large clastic input from the land documenting the weathering conditions on the surrounding land masses they received also a considerable biogenic particle flux from the surface waters documenting productivity of the marine plankton because of these different origins of the sediment components as well as the connections with neighbouring seas the sediments in these shelf basins were expected to document changes in climate as well as palaeo oceanographic changes earlier interpretations based on ammonite studies that indicate changing connections between the arctic ocean and the tethys during the albian can thus be tested the lower saxony basin was a shelf sea in the southern part of the warm humid climate belt at mid latitudes in the northern hemisphere in which thick deposits of hemipelagic sediments accumulated mapping previous to our study indicated that a complete undisturbed albian basinal sequence ca 400 m thick is present below a thin quaternary cover in a sub basin between the nne ssw trending benthe and lehrte salt structures in the central part of the lower saxony basin the boreholes at the kirchrode i and ii sites 52 22 35 n 9 49 87 e and 52 22 16 n 9 49 12 e respectively in hannover were drilled into this sub basin the high sedimentation rates known for the albian of the lower saxony basin are ideal for studying climatic changes with a cyclicity of a few ten thousand to a few hundred thousand years milankovitch cyclicity

coral reefs and growth dynamics of a low angle carboniferous platform records from tianlin southern china abstract metazoan reef building receded globally during the carboniferous after the late devonian extinction events shallow water bioconstructions were generally small and scarce and corals played a minor role in their construction however in southern china one large 50 m high and three small 6 16 m high coral reefs dating from the late visean serpukhovian have recently been discovered in two localities in guangxi to understand the occurrence of these coral reefs and to constrain the factors that controlled their growth three sections around langping guangxi were measured and selected samples were analysed using petrography biostratigraphy and chemostratigraphy the depositional environment of these exceptional mississippian reefs was interpreted as a low angle platform 1 2 5 recording oligotrophic conditions and normal salinity the three small reefs have grown around the fair weather wave base whereas the large coral reef has grown in a deeper environment between the fair weather and storm wave base during carboniferous the global temporal reef distribution can be partly ascribed to paleoclimate changes however in southern china the growth of extended mississippian coral reefs is restricted to a short time window the late visean serpukhovian which coincides with high amplitude and high frequency sea level fluctuations most likely related to glacial pulses recent studies revealed that several rugose coral species survived the mid carboniferous glaciation event thanks to the persistence of warm water ocean currents maintaining tropical conditions on the platform due to the scarcity of extended coral reefs elsewhere it cannot be excluded that tianlin provided an ecological refuge for corals related to oceanic currents another potential favorable factor could be the mid ramp depositional setting the deep water platform areas could potentially provide more stable conditions less affected by global stress events however the deep reef refugia hypothesis remains debatable as only very few studies have explored its validity at the community level even if the causes of the occurrence of an extended coral reef in southern china cannot be fully constrained the existence of this large coral framework in the late visean serpukhovian provides additional evidence that coral communities did build reefs after the late devonian extinction events

phosphorites glass ramps and carbonate factories the evolution of an epicontinental sea and a late palaeozoic upwelling system phosphoria rock complex this is the peer reviewed version of the following article matheson e j and frank t d 2020 phosphorites glass ramps and carbonate factories the evolution of an epicontinental sea and a late palaeozoic upwelling system phosphoria rock complex sedimentology doi 10 1111 sed 12731 which has been published in final form at https doi org 10 1111 sed 12731 this article may be used for non commercial purposes in accordance with wiley terms and conditions for use of self archived versions

depletion of perennial sea ice in the east arctic ocean 1 the extent of perennial sea ice in the east arctic ocean 0 180 e decreased by nearly one half with an abrupt reduction of 0 95 106 km2 while the west arctic ocean 0 180 w had a slight gain of 0 23 106 km2 between 2004 and 2005 as observed by satellite scatterometer data during november december the net decrease in the total perennial ice extent is 0 72 106 km2 about the size of texas perennial ice in the east arctic ocean continued to be depleted with an areal reduction of 70 from october 2005 to april 2006 with the east arctic ocean dominated by seasonal sea ice a strong summer melt may open a vast ice free region with a possible record minimum ice extent largely confined to the west arctic ocean simultaneous scatterometer measurements of sea ice and winds will be crucial for sea ice monitoring and forecasts

sea ice thickness from field measurements in the northwestern barents sea the barents sea is one of the fastest changing regions of the arctic and has experienced the strongest decline in winter time sea ice area in the arctic at 23 4 per decade sea ice thickness in the barents sea is not well studied we present two previously unpublished helicopter borne electromagnetic hem ice thickness measurements from the northwestern barents sea acquired in march 2003 and 2014 the hem data are compared to ice thickness calculated from ice draft measured by uls deployed between 1994 and 1996 these data show that ice thickness varies greatly from year to year influenced by the thermodynamic and dynamic processes that govern local formation vs long range advection in a year with a large inflow of sea ice from the arctic basin the barents sea ice cover is dominated by thick multiyear ice as was the case in 2003 and 1995 in a year with an ice cover that was mainly grown in situ the ice will be thin and mechanically unstable as was the case in 2014 the hem data allow us to explore the spatial and temporal variability in ice thickness in 2003 the dominant ice class was more than 2 years old and modal sea ice thickness varied regionally from 0 6 to 1 4 m with the thinner ice being either first year ice or multiyear ice which had come into contact with warm atlantic water in 2014 the ice cover was predominantly locally grown ice less than 1 month old regional modes of 0 5 0 8 m these two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic or have a different impact on heat transport from ocean to atmosphere

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

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

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

multistratigraphic records of the lower cretaceous valanginian cenomanian puez key area in n italy abstract we present a stratigraphic investigation of a hauterivian to cenomanian hemipelagic succession from col puez in the dolomites southern alps northern italy a composite section of seven segments was studied with bio magneto and chemostratigraphy which enabled detailed and robust age calibration of the puez succession it also revealed the paleoceanographic history and helped identify the important global climatic events of that period the age of the lower cretaceous puez formation in the dolomites is refined as late hauterivian to early cenomanian ammonoids provide a detailed biostratigraphic subdivision that forms the basis for analyses of the faunal distribution and the paleoenvironmental evolution of basins and plateaus across the tethys the succession consists of facies similar to those of coeval units in the tethys apart from the late barremian to late aptian interval which is marked by a major hiatus followed by a few meters thick redbed of late aptian age the lower cretaceous was characterized by a weak 1 positive 13c trend punctuated by a positive shift in the late hauterivian corresponding to the faraoni level oxygen isotope values show a decreasing trend from the hauterivian to the albian cenomanian which mirrors a long term increasing trend in paleotemperatures from 15 18 c to 25 30 c this is in agreement with global paleotemperature reconstructions for this period representing the onset of mid cretaceous super greenhouse conditions nonetheless no black shale occurs at the intervals equivalent to aptian albian oceanic anoxic events oae suggesting unique paleoceanographic conditions enhanced current activity on a submarine height on the trento plateau area during the mid cretaceous

palaeoenvironmental and palaeoceanographic controls on black laminated mudrock deposition example from devonian carboniferous strata alberta canada abstract sedimentological palaeontological and ichnological analyses indicate that heightened episodes of equatorial upwelling in tandem with an expanded and intensified oxygen minimum zone promoted deposition of upper famennian to lower tournaisian laminated organic rich mud rocks of the exshaw formation on the alberta cratonic platform exshaw mud rocks represent the culmination of an upper devonian transgression that commenced with deposition of open marine carbonates of the big valley formation the transgression was abruptly halted at the devonian carboniferous boundary by a rapid eustatic sea level fall and the consequent deposition of near shore marine to shelfal bioturbated siltstones and sandstones of the exshaw formation the siltstones grade into laminated organic lean mud rocks to the north in more distal offshore shelf settings these mudrocks reflect a period of low primary production but continued anoxia of bottom waters continuation of anoxic conditions resulted from development of restricted circulation in the epicontinental sea due to the establishment of a westward located physical barrier following this event was a relative sea level rise that led to deposition of black laminated mudrocks of the banff formation

paleoceanographic constraints on precambrian phosphorite accumulation baraga group michigan usa abstract the palaeoproterozoic baraga group ca 1850 1 ma of northern michigan is a 1200 m thick sedimentary succession of marine clastic iron formation chert and phosphatic sedimentary rocks that accumulated at the peak of the world s first major phosphogenic episode lithofacies stacking patterns are interpreted to record the flooding of the nuna continental margin during two sea level cycles the base of the first sequence is marked by a transgressive lag on archean basement that is transitional into a highstand accumulation of sandstones deposited in peritidal environments the bottom of the second sequence is characterized by a chert and carbonate unit with numerous subaerial exposure surfaces deposited in intertidal to supratidal environments this chert grades upward into subtidal deposits composed of interbedded organic rich mudstone and sandstone the highstand and falling stage systems tracts are composed of progradational deltaic deposits sequences were framed using the newly discovered sudbury impact ejecta horizon as a datum its emplacement approximately coincides with unrelated environmental changes that increased the delivery of river borne sediment to the nuna margin iron bearing minerals ankerite siderite and pyrite show that ferrous iron was present in peritidal to deep marine environments ankerite dominates nearshore settings where pyrite is absent pyrite occurs in deeper progradational deltaic deposits where sulfide was produced by bacterial sulfate reduction phosphorite is restricted to shallow water sediments of the first sequence and the lowstand of the second sequence precipitation is interpreted to be the result of fe redox pumping just below the sediment water interface where photosynthetically produced nearshore oxygen oases impinged on the seafloor such shallow water phosphorite accumulation is in stark contrast to many phanerozoic depositional systems in which phosphogenesis occurs across the shelf this difference likely reflects the dissimilarity in the oxygenation state of the seafloor in the precambrian fe redox pumping and thus phosphogenesis was restricted to shallow water settings with a suboxic seafloor in the phanerozoic phosphorite forms in the full spectrum of shelf environments because the entire seafloor is generally well oxygenated the concentration of bioavailable p in neritic environments during the proterozoic may have played a major role in the development of benthic microbial ecosystems and evolving eukaryotes

aalenian carbon isotope stratigraphy calibration with ammonite radiolarian and nannofossil events in the western tethys abstract in this study a detailed carbon isotope stratigraphy of four aalenian sections well dated with ammonites from the median subbetic palaeogeographic domain external zones of the betic cordillera southern spain is presented two of these represent the most complete aalenian sections of the southern iberian palaeomargin western tethys these sections are rhythmic sequences made of marls and marly limestones containing rich ammonite fauna and nannofossils that enable an accurate biostratigraphic control at the subzone level moreover the lower and upper aalenian boundaries are well defined in these sections and therefore represent optimal sites to link the carbon isotope curves to ammonite zones and subzones and nannofossil events the uppermost toarcian lowermost bajocian 13 c values of bulk carbonates show evident fluctuations the values are low 1 in the upper toarcian mactra subzone increase slightly to 2 in lower aalenian comptum subzone fall to a relative minimum 1 1 5 in the middle aalenian bradfordensis zone reach a marked positive peak of 2 5 2 7 in the upper aalenian concavum subzone and then the values decrease again to 1 5 1 7 near the aalenian bajocian boundary marine carbonate 13 c curves in subbetic and the apennines shows similar variations but higher 13 c values in the apennines sections a slight offset is also present between the sections from the same basin this drift is interpreted by variations in carbon isotopic composition of sea water dic associated with different palaeoceanographic settings comparison of the 13 c values of bulk carbonates and biotic events ammonite diversity and nannofossil and radiolarian abundances reveals relationships between the carbon cycle and biotic evolution the latest toarcian aalenian turnovers toarcian aalenian boundary and middle late aalenian follow low 13 c values where extinct taxa are replaced by new ones radiation episodes are associated with increasing 13 c values and with sea level rise in the earliest late aalenian concomitantly with a major 13 c positive excursion and with the transgressive cycle it is noted a major increase of the eutrophic calcareous nannofossil genus biscutum and a sharp peak in radiolarian abundance although the aalenian interval seems not to be characterized by major large amplitude negative or positive excursions as observed in other phanerozoic intervals these data point to a close connection between perturbations in the global carbon cycle and the palaeoenvironmental changes that occurred which in turn had important interactions with the evolution of pelagic biota

condensation and phosphatization of the middle and upper ordovician limestones on the malopolska block poland response to paleoceanographic conditions abstract the growth fault activity in the late middle ordovician resulted in the establishment of a horst like submarine paleohigh in the northern malopolska block this topographic submarine swell was the site of carbonate deposition characterized by a low overall net sediment accumulation rate the sedimentary and ecological conditions on this paleohigh were controlled by a paleocurrent that flowed along the northern margin of the malopolska block however seasonal intense storms associated with the mid latitude location of this terrane cannot be excluded the paleocurrent induced seasonal upwelling of nutrient rich waters from deeper parts of the current system that shifted onto the paleohigh and caused phosphatization of the sediment the winnowing and reworking of sediment together with slow carbonate production by a temperate water biota and relatively long periods of omission resulted in low accumulation rates and sediment condensation the cessation of the paleocurrent and associated phosphatization coincides with changes in the oceanic circulation system due to the late ordovician collision of avalonia with baltica and gradual closure of the tornquist sea

the madotz urgonian platform aralar northern spain paleoecological changes in response to early aptian global environmental events abstract sudden addition of carbon dioxide to the atmosphere can reduce the caco3 saturation and weaken the biocalcification potential of marine organisms in shallow water and in open marine settings in this study the response of an aptian neritic carbonate environment to sudden addition of carbon dioxide at the beginning of oceanic anoxic event 1a is investigated the beginning of the oae1a was coupled with a major perturbation on the carbon cycle as indicated by a negative carbon isotope excursion in the sedimentary record this isotope anomaly is regarded as a proxy for massive addition of volcanic or methane derived co2 to the atmosphere within only a few 104 years the impact of a rapid change in atmospheric pco2 on biocalcifiers in low latitude shallow water settings can be studied in a well preserved aptian carbonate shelf succession cropping out today in the aralar mountains ne spain the madotz section n spain preserves a continuous shallow water record that was deposited on a mid latitude atlantic oriented mixed siliciclastic carbonate ramp lower aptian sediments consist of two neritic limestone successions separated by orbitolinid rich marlstone enriched in organic matter the lower neritic limestone succession ends with a submarine hardground and the transition from the lower neritic limestone to the orbitolinid marlstone coincides with a negative spike in the organic carbon isotope record this negative spike can be correlated with the negative carbon isotope anomaly marking the base of oae1a the paleoecological change coinciding with the base of oae1a occurred at a time of sea level rise and it coincided with a demise of heavily calcified nannoconids in the tethys and pacific oceans the paleoecological change observed in the madotz section corresponds to a comparable change seen in the more distal and more expanded carbonate ramp section igaratza at the aralar mountains ocean acidification caused by sudden increase in pco2 may explain reduced calcification potential of some shallow water calcifiers calcification crisis was amplified by rising sea level increasing temperatures and increased flux of detrital material and nutrients from continents into coastal seas

fractal nature of stratigraphic sequences orders of stratigraphic sequences are being used loosely and with widely varying definitions the orders seem to be subdivisions of convenience rather than an indication of natural structure it is proposed that at least at time scales of 103 106 yr sequences and systems tracts are scale invariant fractal features in which units bounded by exposure surfaces and units bounded by flooding surfaces are about equally likely support for this conceptual model derives from the well known facts that 1 sediment architecture is largely scale invariant over a wide range of scales in time and space 2 first order trends of sea level movements and sedimentation rates are fractal on all geologically relevant time scales and 3 detailed studies in carbonates indicate approximately equal abundance of flooding surfaces and demonstrable exposure surfaces among unit boundaries finally traces of prograding shelf edges that step up and step down in response to sea level changes are demonstrated in this study to have a fractal nature

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

arctic reappraisal of global carbon cycle dynamics across the jurassic cretaceous boundary and valanginian weissert event abstract late jurassic early cretaceous global carbon cycle dynamics have mainly been inferred from tethyan atlantic and pacific carbon isotope 13c records these records indicate a steady deceleration of the carbon cycle in late jurassic and jurassic cretaceous j k boundary times followed by a major mid valanginian carbon cycle perturbation demarcated by the well documented positive excursion named the weissert event however this model remains to be confirmed in boreal records which are rare and typically difficult to correlate with the global 13c signal in this study the first continuous and biostratigraphically calibrated organic carbon isotope 13corg stratigraphy is established for the bathonian lower barremian representing 30 myr of the boreal realm based on high resolution sampling of bulk rock marine shale from four time equivalent sections in arctic svalbard supplemented by existing 13corg data the 13corg stratigraphy displays several distinctive trends notably i a kimmeridgian positive excursion followed by a large negative excursion 6 4 in the upper kimmeridgian middle volgian consistent with existing boreal 13c records ii an upper volgian ryazanian overall positive recovery across the j k boundary and iii a prominent positive excursion 5 5 in the valanginian interpreted to represent the weissert event followed by steady high values into the lower barremian with no apparent excursion decay time calibrated correlation of the observed trends with existing 13c records representative of the entire exchangeable carbon reservoir reflects major global carbon cycle adjustments including i boreal decoupling from the global carbon reservoir during late jurassic and j k boundary times due to basinal isolation and ii global carbon cycle recoupling at the onset of the weissert event coinciding with incipient oceanographic connectivity boreal carbon cycling was inherently controlled by the basin configuration the new 13corg stratigraphy provides a well calibrated tool for boreal and boreal tethyan correlations and confirms that the weissert event represents an important perturbation of the global carbon cycle

mercury anomalies volcanic pulses and drowning episodes along the northern tethyan margin during the latest hauterivian earliest aptian abstract the latest hauterivian earliest aptian time interval includes three episodes of significant environmental change faraoni late early barremian and taxy episodes this time interval appears to partially overlap with large scale volcanic activity related to the tristan da cunha plume along the rio grande rise high arctic large igneous province volcanism and the early phase in the formation of the greater ontong java lip in the pacific the establishment of exact temporal relationships between volcanic activity and environmental change remains however a major challenge due to the scarcity of numerical ages for the early cretaceous we report mercury hg contents in uppermost hauterivian lowermost aptian marl limestone alternations from seven sections along a n s transect in the western tethys the hg contents in marl samples display rather scattered records which are generally well correlated with the total organic carbon toc records in associated limestone beds five distinct spikes in hg concentrations occur in three intervals latest hauterivian early barremian and latest barremian the small amounts of organic matter

cyclostratigraphy and high frequency carbon isotope fluctuations in upper cretaceous shallow water carbonates southern italy a detailed carbon isotope study has been carried out on a santonian upper cretaceous carbonate platform succession that crops out at monte sant erasmo southern italy previous centimetre scale studies on this succession have shown that high frequency eustatic changes resulting from the earth s orbital fluctuations controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles bundles groups of three to five elementary cycles and superbundles groups of three or four bundles the elementary cycles which correspond to single beds suggest a control caused by earth s precession the bundles and superbundles record the short 100 kyr and long 400 kyr eccentricity periodicity respectively the 1 3 c signal of the monte sant erasmo succession is cyclic in nature and may be considered to be a reliable proxy for the sedimentary evolution and related sea level history of the analysed sequence the carbon isotope cyclicity is recorded at bundle and superbundle level but it is not evident at the scale of the elementary cycles at least with the sampling interval used in this study spectral analysis of the 1 3 c record shows two main peaks corresponding to the short and long eccentricity periodicity whereas the precession signal is not evident in the power spectrum in addition lithofacies analysis shows that in each bundle and superbundle higher c isotope values occur in sediments characterized by marine cements whereas lower values are normally found in more restricted deposits overprinted by early meteoric diagenesis early diagenesis driven by periodic sea level fluctuations developed in either shallow subtidal marine diagenesis or subaerial exposed meteoric overprint sedimentary environments and directly influenced the carbon isotope signature as a consequence the 1 3 c record at monte sant erasmo reflects high frequency climatic oscillations controlling both environmental and early diagenetic changes the long term isotopic record is similar to that of contemporaneous pelagic sections in england and elsewhere in italy it is concluded that the 1 3 c signature of shallow water carbonates such as those of monte sant erasmo offers great potential for correlation with coeval sections including those of the pelagic realm

decoupling of p and corg burial following early cretaceous valanginian hauterivian platform drowning along the nw tethyan margin during the hauterivian three important phases of platform drowning phosphogenesis and mesotrophic carbonate deposition along the northern margin of the tethys are not mirrored by positive n 13 ccarb excursions such as during the valanginian and aptian but rather by decreasing to stable trends the aim of this study is to understand the decoupling of organic carbon and phosphorus burial during the hauterivian for this purpose po4 concentrations were determined from biogenic limestones from eight sections along a platform to basin transect integration with a previously obtained dataset for the valanginian leads to a biostratigraphically calibrated high resolution phosphorus accumulation rate mg cm 2 kyr curve based on 575 data points from the late valanginian to early hauterivian phosphorus accumulation rates increased nearly threefold from 0 75 mg cm 2 kyr to 2 1 mg cm 2 kyr the phosphorus accumulation rate increase obtained in this study correlates well with a compilation based on odp and dsdp records indicating that phosphorus accumulation rates along the northern margin of the tethys reflect global changes in p in and output a global rise in continental p input is thought to have resulted from intensified greenhouse climate conditions leading to increased riverine runoff coeval sea level rise led to re arrangement of circulation and oxygenation of bottom waters which meant that p was increasingly well retained by means of fe and mnoxyhydroxides furthermore the nw margin of the tethys may have been especially susceptible to phosphogenesis as it was influenced by cold water exchange with the boreal realm and prone to coastal upwelling the late hauterivian witnessed sea level fall more sluggish circulation along the nw tethyan margin and also globally lower weathering and erosion rates leading to generally lower phosphorus accumulation rates increased regeneration of phosphorus might have occurred as circulation stagnated and bottom water oxygen levels decreased increased phosphorus input into early hauterivian oceans did not lead to the production of organic carbon rich rocks but rather to increased carbonate carbon burial also seen in a decoupling between the n 13 ccarb record decreasing and phosphorus accumulation rates increasing decoupling of these records reflects the ecological recovery of the carbonate system after a prolonged phase of reef destruction during the late early and late valanginian carbonate production in the

halocline water formation in the barents sea hydrographic data from the first phase of the coordinated eastern arctic experiment cearex are analyzed the data consist of temperature and salinity measurements made by a ship based conductivity temperature depth ctd instrument and by a drifting salargos buoy these data were collected in the autumn and early winter of 1988 1989 in the northern barents sea mostly in ice covered conditions and then across the marginal ice zone miz the data show that relatively warm salty water of atlantic origin is modified by air cooling and ice melting to produce lighter water that has properties identical to lower halocline water found in the arctic ocean this occurs mostly at the miz and to a lesser degree within the ice pack itself at the miz the halocline water subducts underneath the lighter meltwater that resides directly under the ice pack geostrophic velocity calculations indicate that it then turns eastward and flows toward the kara sea in keeping with previous chemical tracer analyses a rough calculation reveals that the amount of halocline water formed in this way in the barents sea and fram strait is 30 50 of that formed by ice growth in eastern arctic polynyas

water mass distribution and polar front structure in the western barents sea the water mass distribution in the western barents sea the thermohaline structure of the western barents sea polar front and the local formation of a dense water mass are described on the basis of an analysis of historical hydrographic data this study concentrated on the frontal region between bjornoya and hopen island where arctic water is found on the spitsbergen bank and atlantic water in the bear island trough and hopen trench the distributions of atlantic and arctic waters in relation to topography were consistent with the hypothesis that the location of the polar front is fixed at about the 250 m isobath by the barotropic circulation of atlantic water within the bear island trough and hopen trench in winter vertical gradients of temperature and salinity were weak throughout the frontal region consistent with a barotropic topographically controlled front in summer vertical gradients remained weak below 100 m depth but increased in the upper layer as a result of the presence of fresh warm surface water produced by melting ice the topographic control of thermohaline properties at the surface was disrupted by the meltwater pool and the meltwater contributed to water mass modification in the frontal region the following seasonal cycle of water mass formation was hypothesized summer heating melts the sea ice on the spitsbergen bank and produces the surface meltwater pool this meltwater not only increases vertical thermohaline gradients on the bank but also crosses the front and freshens the surface layer throughout the western barents sea subsequent winter cooling which creates ice over the bank also forms dense water in the bear island trough and hopen trench by convective mixing of atlantic water and the overlying meltwater

wind driven shelf basin exchange on an arctic shelf the joint roles of ice cover extent and shelf break bathymetry 1 the efficiency of shelf basin exchange sbe in polar regions during summer is strongly moderated by the location of the ice edge relative to underlying topography numerical model calculations suggest that upwelling favorable winds generate very little sbe so long as the ice edge remains shoreward of the shelf break but an abrupt onset of shelf break upwelling takes place when the ice edge retreats beyond the shelf break a climatology 1968 2000 of ice conditions from the canadian shelf of the beaufort sea shows large interannual variability in ice edge extent and duration of ice free conditions in summer similarly available hydrographic data reflect a corresponding variability in water mass properties under scenarios of climate warming associated with greenhouse gas build up both the extent and duration of summer melt back are predicted to increase and this may have dramatic impacts on sbe and biological productivity

carbon isotope analysis of fossil wood and dispersed organic matter from the terrestrial wealden facies of hautrage mons basin belgium pedogenic nodules calcitic shells dispersed organic carbon and bulk rocks affected by low diagenesis are judged to be reliable tools for carbon isotope chemostratigraphy up to now no systematic study has been carried out to check the reliability of fossil wood material for carbon isotope chemostratigraphy in terrestrial settings the 235 m thick wealden facies sediments of the danube bouchon quarry at hautrage hautrage clays formation mons basin belgium encompass dark to grey clays and sands rich in organic matter and coalified charcoalified fragments of fossil wood deposited in an alluvial plain during middle barremian to earliest aptian we measured and compared the carbon isotope ratios of 110 levels of the stratigraphic succession for dispersed organic carbon delta c 13 doc and fossil wood delta c 13 wood collected in the same geological level in the whole succession the averages of delta c 13 doc and delta c 13 wood have a significant difference of about 0 9 the delta c 13 wood is usually heavier than the delta c 13 doc which is consistent with measurements on different constituents of modern trees branches versus leaves and tissues in one single stratigraphic level the variability of delta c 13 wood is much higher up to 7 3 parts per thousand than that of delta c 13 doc 0 4 parts per thousand four main causes may explain these results firstly the delta c 13 doc averages the isotopic signal of different compounds and tissues such as leaves seeds cuticles as they become mixed and dispersed the delta c 13 wood reflects the carbon isotope ratio of a small part only of one single tree which is a complex system with delta c 13 variations over a range of 4 parts per thousand secondly there is strong delta c 13 variability between different species of plants in hautrage several gymnosperm genera were collected including podocarpoxylon taxodioxylon brachyoxylon and thujoxylon and numerous fern taxa thirdly coalification and charcoalification can affect the delta c 13 of the doc and the various kinds of woods in a different way fourthly the wood fragments may be reworked several times from more ancient geological levels especially in the alluvial plain environment of hautrage where thick levels of fluviatile coarse sand deposits are observed however in the whole succession both delta c 13 wood and delta c 13 doc curves show similar trends this suggests that carbon isotope curves on fossil wood can be matched to carbon isotope curves on doc for the whole trend fossil wood is a relatively good chemostratigraphic tool when sufficient samples are measured in the succession whenever possible both control of the wood taxa and estimation of degree of char coalification are however recommended in one single level charcoal has more stable delta c 13 wood values than delta c 13 wood of coalified fragments the delta c 13 positive trend can be due to several causes including global pco 2 variations and or regional changes and or local environmental conditions in the alluvial plain if global the dating of the hautrage succession may be refined to the late early barremian early late barremian by matching palynological and carbon isotope chemostratigraphical data c 010 elsevier b v all rights reserved

the influence of terrestrial run off on marine biotic communities an example from a thrust top carbonate ramp upper pennsylvanian foreland basin picos de europa nw spain article i nfo high diversity marine biotic communities characterize the lower kasimovian upper pennsylvanian carbonates of the las llacerias formation in the andara massif picos de europa province cantabrian mountains spain the carbonates accumulated on a small thrust top ramp system within the shallow low energy and euphotic realms biotic communities were characterized by abundant photozoans calcareous algae and cyanobacteria and heterozoans including filter and suspension feeders calcareous and siliceous sponges bryozoans brachiopods crinoids diverse other metazoans rugose solitary and colonial corals tabulate corals bivalves gastropods and echinoids benthic foraminifers including very abundant small incrusting tubiforms and conspicuous swarms of cement filled spheres calcispheres or penella small sized buildups of chaetetid sponges syringoporids branching rugose corals anthracoporella and phylloid algae commonly developed in these shallow water environments meanwhile mud mounds formed at greater water depths mostly below the lower limit of the phothic zone the occurrence of such diverse biotic communities and the grain composition of the shallow water deposits not recorded in the platform top successions of the antecedent bashkirian moscovian carbonate shelf valdeteja and picos de europa formations are interpreted as linked to increased nutrient levels mesotrophic to mildly eutrophic conditions in the actual sea surface water the nutrients are inferred to have resulted from land derived fluxes from the rivers draining the adjacent growing variscan orogenic chain nutrients were subsequently transported into the narrowed marine shallowing foreland basin located in the eastern side of pangea within the palaeoequatorial humid belt comparison to the pennsylvanian auernig group in the carnic alps allows the discrimination between the influence of land derived versus upwelling derived nutrients providing a useful tool in the interpretation of biotic assemblages in the fossil rock record

seafloor control on sea ice abstract the seafloor has a profound role in arctic sea ice formation and seasonal evolution ocean bathymetry controls the distribution and mixing of warm and cold waters which may originate from different sources thereby dictating the pattern of sea ice on the ocean surface sea ice dynamics forced by surface winds are also guided by seafloor features in preferential directions here satellite mapping of sea ice together with buoy measurements are used to reveal the bathymetric control on sea ice growth and dynamics bathymetric effects on sea ice formation are clearly observed in the conformity between sea ice patterns and bathymetric characteristics in the peripheral seas beyond local features bathymetric control appears over extensive regions of the sea ice cover across the arctic ocean the large scale conformity between bathymetry and patterns of different synoptic sea ice classes including seasonal and perennial sea ice is identified an implication of the bathymetric influence is that the maximum extent of the total sea ice cover is relatively stable as observed by scatterometer data in the decade of the 2000s while the minimum ice extent has decreased drastically because of the geologic control the sea ice cover can expand only as far as it reaches the seashore the continental shelf break or other pronounced bathymetric features in the peripheral seas since the seafloor does not change significantly for decades or centuries sea ice patterns can be recurrent around certain bathymetric features which once identified may help improve short term forecast seasonal outlook and decadal prediction of the sea ice cover moreover the seafloor can indirectly influence the cloud cover by its control on sea ice distribution which differentially modulates the latent heat flux through ice covered and open water areas

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

microbial foraminiferal episodes in the early aptian of the southern tethyan margin ecological significance and possible relation to oceanic anoxic event 1a two regionally significant microbial foraminiferal episodes 150 kyr each occur within the early aptian shallow marine platform in oman and throughout eastern arabia the stratigraphically lower of these two intervals is characterized by isolated or coalescent domes that share similarities with modern open marine stromatolites from the exuma cays bahamas the upper interval is predominantly built by a problematic lithocodium bacinella consortium in buildup and massive boundstone facies based on highresolution chemostratigraphy these shoalwater intervals are coeval with oceanic anoxic event 1a oae1a livello selli field evidence demonstrates that the buildup episodes alternate with stratigraphic intervals dominated by rudist bivalves this biotic pattern is also recognized in other coeval tethyan sections and is perhaps a characteristic shoalwater expression of the oae1a the short lived regional expansions of this microbial foraminiferal out ofbalance facies cannot be explained by local environmental factors salinity and oxygen level alone and the buildup consortia do not occupy stressed refugia in the absence of grazing metazoans judging from recent analogues the main fossil groups i e microbial assemblages macroalgae larger sessile foraminifera and rudist bivalves all favoured elevated trophic levels but with different tolerance limits the implication of this is that the influence of palaeofertility events possibly related to oae1a on carbonate platform community structures must be investigated the observations made in these coastal sections are a significant first step for the improved understanding of the early aptian period of biotic oceanic and climatic change

rapid formation of a sea ice barrier east of svalbard 1 daily seawinds scatterometer images acquired by the quikscat satellite show an elongated sea ice feature that formed very rapidly 1 2 days in november 2001 east of svalbard over the barents sea this sea ice structure called the svalbard sea ice barrier spanning approximately 10 in longitude and 2 in latitude restricts the sea route and poses a significant navigation hazard the secret of its formation appears to lie in the bottom of the sea a comparison between bathymetry from the international bathymetric chart of the arctic ocean data and the pattern of sea ice formation from scatterometer data reveals that the sea ice barrier conforms well with and stretches above a deep elongated channel connecting the franz josef victoria trough to the hinlopen basin between svalbard and franz josef land historic hydrographic data from this area indicate that this sea channel contains cold arctic water less than 50 m below the surface strong and persistent cold northerly winds force strong heat loss from this shallow surface layer leading to the rapid formation of the sea ice barrier heat transfer rates estimated from european centre for medium range weather forecasts temperature and wind data over this region suggest that the surface water along the deep channel can be rapidly cooled to the freezing point scatterometer results in 1999 2003 show that sea ice forms in this area between october and december understanding the ice formation mechanisms helps to select appropriate locations for deployment of buoys measuring wind and air sea temperature profile and to facilitate ice monitoring modeling and forecasting

a mechanism for brief glacial episodes in the mesozoic greenhouse 1 the mesozoic perhaps the longest period of warmth during the phanerozoic earth history has been repeatedly affected by short lived cold interludes lasting about one million years while the origin of these cold snaps has been classically attributed to a temporary atmospheric co2 drawdown quantified mechanisms explaining these instabilities of the carbon cycle are still lacking based on a climate carbon cycle model we show that the general demise of carbonate platforms accompanying these short lived cold interludes is a powerful mechanism capable of generating a fast atmospheric co2 decrease and a moderate sea level drop associated with ice sheet buildup the temporary nature of the carbonate production decline explains the relative short time of these cold events but makes it possible to account for ice sheet waxing and waning

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

response of proto north atlantic carbonate platform ecosystems to oae1a related stressors abstract integrated biostratigraphic chemostratigraphic studies provide evidence that the proto north atlantic realm witnessed major changes in carbonate platform production in the run up of the early aptian oceanic anoxic event oae 1a whereas pervasive growth of lithocodium microencrusters represents an early harbinger of oae1a related environmental perturbation the subsequent replacement of oligotrophic rudist coral nerineid by mesotrophic orbitolinid oyster communities was clearly associated with the event itself in order to test the supra regional relevance of this major community replacement two shallow water sections in the southern lusitanian basin portugal are investigated by means of geochemistry carbon and oxygen isotopes cement petrography and detailed sedimentological analysis the focus is on a regional prominent discontinuity surface s4 at the transition between oligotrophic and mesotrophic carbonate platform production which might indicate that the major biotic change could have been associated with a phase of non sedimentation and possibly erosion the studied sections sao juliao crismina provide evidence that the major early aptian biotic turnover was preceded by numerous subordinate but significant changes in platform ecology which mirrored a series of progressive short term environmental changes in the course of oae1 several transient mass occurrences of orbitolinids indicate repeated phases of ecological stress arguably due to enhanced nutrient input and deepening small scale sea level changes at parasequence level below the major discontinuity surface are revealed by alternations of rudist assemblages dominated by clinger or recumbent forms as well as intercalated hardground and subaerial exposure stages expanded phases of subaerial exposure however can be largely ruled out following the geochemical and cement petrographic data presented here enhanced continent derived siliciclastic input characterising the lower orbitolinid oyster dominated limestones is in support of a shift to more humid conditions during the middle early aptian this is in line with palaeoclimatic data which propose a southward movement of the mid latitude arid climate belt during this time the documented rapid replacement of oligotrophic assemblages by various environmental stress adapted carbonate platform communities might be seen as explanation for ongoing early aptian proto north atlantic carbonate production during a time of widespread platform demise and drowning in the northern tethyan realm

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

paleoceanographic changes during the early cretaceous valanginian hauterivian evidence from oxygen and carbon stable isotopes we investigated valanginian hauterivian bulk rock and belemnite samples from vocontian basin sections in southeastern france for their stable carbon and oxygen isotope signature firstly because these sections permit calibration with high resolution biostratigraphy based on ammonites and secondly because detailed isotope studies for the hauterivian are lacking the results show that 13c values for bulk rock decrease during the late valanginian early hauterivian with 1 and increase again during the late hauterivian with 1 the 18o signal for bulk rock samples is mostly disturbed by diagenesis the belemnites show carbon and oxygen isotope values that are lower and higher than bulk rock samples respectively we explain this as the result of the belemnites recording a deeper water signal with lighter 13c values and heavier 18o values implicating colder water at greater depth the overall preservation of the belemnites is very good and permits the construction of a paleo temperature trend this trend shows warm deeper water temperatures during the late early valanginian 15 c and progressively cooler temperatures during the late valanginian and early hauterivian 11 c during the late hauterivian temperatures increase again 13 c we relate this cooling trend for deeper water to a second order sea level rise which allowed for the exchange of cold boreal and warm tethyan water masses the influx of cold nutrient rich water had a profound effect on carbonate producing biota along the northern margin of the tethys during the hauterivian leading to prolonged phases of condensation and platform destruction during the early hauterivian the carbonate system along the northern tethyan margin shifted into a green water mode of carbonate production high rates of carbonate production under mesotrophic conditions also observed in other parts of the world meant that the global carbon cycle became buffered shown by the stable trends in carbon isotopes

upper cretaceous campanian phosphorites in jordan implications for the formation of a south tethyan phosphorite giant a record of sedimentary authigenic and biological processes are preserved within the upper cretaceous campanian alhisa phosphorite formation ap in central and northern jordan the ap formed near the eastern extremity of the south tethyan phosphorite province stpp a carbonate dominated upper cretaceous to eocene phosphorite giant that extends from colombia north africa to the middle east multidisciplinary research of the ap and associated cherts chalks and oyster buildups indicate that phosphatic strata formed on a highly productive storm dominated east west trending epeiric platform along the south tethyan margin the onset of phosphogenesis and the accumulation of economic phosphorite coincided with a rise in relative sea level that onlapped peritidal carbonates of the ajlun group pristine phosphates are associated with well developed micrite concretionary horizons and contain abundant non keeled spiral planktic foraminifera and a low diversity benthic assemblage of buliminacean foraminifera suggesting that pristine phosphates are a condensed facies and phosphogenesis was stimulated by the effects of a highly productive surface ocean and the suboxic diagenesis of sedimentary organic matter the bulk sediment composition and absence of fe bearing authigenic phases such as glauconite pyrite including pyrite molds siderite and goethite within pristine phosphates suggests that deposition and authigenesis occurred under conditions of detrital starvation and that iron pumping played a minimal role in phosphogenesis authigenic precipitation of phosphate occurred in a broad array of sedimentary environments herein termed a phosphorite nursery that spanned the entire platform this is a non uniformitarian phenomenon reflecting precipitation of sedimentary apatite across a wide depositional spectrum in a variety of depositional settings wherever the conditions were suitable for phosphogenesis sedimentologic data indicate that pristine phosphates were concentrated into phosphatic grainstones through storm wave winnowing and storm generated shelf parallel geostrophic currents economic phosphorites formed through the amalgamation of storm induced event beds stratigraphic packaging of phosphatic strata indicates that temporal variations in storm frequency were a prerequisite for the formation of economic phosphorite syndepositional phosphogenesis reworking and amalgamation to form phosphorites contrasts sharply with the principles of baturin cycling a transgressive systems tract coupled with high surface productivity created detritally starved settings favourable for phosphogenesis storm reworking of pristine

evolution and demise of a mid cretaceous carbonate shelf the altamira limestones cenomanian of northern cantabria spain abstract in northern cantabria the cenomanian transgression is pulsatory in character and progressively onlaps onto deltaic siliciclastics of latest albian to earliest cenomanian age this pronounced 2nd order sea level rise can be subdivided into an earlier constructive phase and a later destructive phase separated by a significant low sea level stand at the early mid cenomanian boundary in the first phase the flooding of the north iberian continental margin in the early early cenomanian caused the sources of terrigenous sediments located on the iberian meseta to retreat thus promoting the development of a carbonate ramp this ramp evolved into a shelf attached platform altamira platform during the course of the early cenomanian pronounced sea level fall in the early mid cenomanian boundary interval exposed the platform increased fluvial input and terminated the constructive phase the destructive phase started in the early mid cenomanian and lasted until the late cenomanian carbon and oxygen stable isotopes microfacies analysis palaeontological criteria and sequence stratigraphy are used to elucidate the complex interplay of climatic changes sea level history nutrient supply and platform drowning three 3rd order sea level rises early and late mid cenomanian early late cenomanian resulted in a westward backstepping and final drowning of the altamira platform the drowning succession is accompanied by a negative shift of 18 o and a positive 13 c excursion interpreted to reflect progressive climatic warming and elevated nutrient levels the resulting eutrophication is represented by the biotic community of the drowning succession and negatively influenced the carbonate budget of the depositional system as a result the stressed platform was readily drowned during the mid and earliest late cenomanian 3rd order sea level rises