microstructure measurements along a quasi meridional transect in the northeastern atlantic ocean 1 this study presents vertical profiles of turbulence parameters obtained in the upper 100 m of the northeastern atlantic ocean along a transect from tropical permanently stratified waters to subpolar seasonally stratified waters in july august 2009 the focus is to fully characterize the vertical mixing along this transect for further studies related to phytoplankton and nutrient distributions derived values of temperature eddy diffusivity kt of temperature variance dissipation rate t and of turbulent kinetic energy dissipation rate e indicate a northward increase of turbulent mixing below the mixed layer in the northern stations where the wind stress is sufficiently high the vertical distributions of e in the mixed layer follow the wind stress scaling the related low wind scaling factors and the low values of e encountered at this cruise are in agreement with a strongly stratified upper water column at midday in summer

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

the diurnal cycle of surface divergence over the global oceans the diurnal cycle of surface divergence over the oceans is examined using 4 daily data from the tandem seawinds satellite missions during april september 2003 a statistically significant diurnal cycle of surface divergence is observed over a large fraction of the tropical and subtropical oceans the highest amplitudes are found adjacent to tropical landmasses and decrease exponentially with distance away from the coast with a representative e folding distance of approximately 200 km in most of these near coastal regions the surface divergence peaks at 15 20 h locally and there is evidence of offshore propagation of the signal there are regions however where strong cycles persist for much greater distances offshore over the southeast pacific ocean there is evidence of a diurnal subsidence wave that propagates for over 2000 km away from the south american coast at approximately 25 m s 1 a cloud response to the subsidence wave moving westward from the andes mountains is detected using passive microwave observations of liquid water path over the remote tropical pacific significant diurnal amplitude is found in and around regions of strong mean surface convergence with a phase suggesting a surface response to the early morning diurnal maximum in precipitation and propagation away from these sources consistent with gravity waves forced by deep tropospheric heating european centre for medium range weather forecasts ecmwf model simulations of 850 hpa subsidence show a diurnal cycle that is largely consistent with the seawinds divergence observations copyright c 2009 royal meteorological society

sequence stratigraphy and carbon isotope stratigraphy of an aptian mixed carbonate siliciclastic platform to basin transition galve sub basin ne spain

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

surface wave effects on high frequency currents over a shelf edge bank abstractseveral acoustic doppler current profilers and vertical strings of temperature conductivity and pressure sensors deployed on and around the east flower garden bank efgb were used to examine surface wave effects on high frequency flows over the bank and to quantify spatial and temporal characteristic of these high frequency flows the efgb about 5 km wide and 10 km long is located about 180 km southeast of galveston texas and consists of steep slopes on southern and eastern sides that rise from water depths over 100 m to within 20 m of the surface three dimensional flows with frequencies ranging from 0 2 to 2 cycles per hour cph were observed in the mixed layer when wind speed and stokes drift at the surface were large these motions were stronger over the bank than outside the perimeter the squared vertical velocity w2 was strongest near the surface and decayed exponentially with depth and the e folding length of w2 was 2 times larger than that of stokes drift the 2 h averaged w2 i

alternative interpretations for microstructure patches in the thermocline abstract two interpretations of microstructure patches measured in the main thermocline of the north pacific by gregg 1980 are questioned he concludes that the observed microstructure is not fossil temperature turbulence and that the observed cox numbers imply vertical diffusivities by turbulent mixing which am about 10 2 times smaller than canonical values of order 10 4 m2 s 1 the first conclusion that the micro structure is not fossil depends on an unnecessary assumption that in order to be fossil the microstructure must not be moving actually fossil turbulence microstructure must always have internal wave and laminar restratification motions the second conclusion depends on the first the pattern of thorpe displacement scales for the patches containing zero temperature gradients implies they were produced by turbulence with vertical scales as large as several meters however the large distances separating the zero gradient points implies that the microstructure is fossil at all scales at the ti

ecological succession palaeoenvironmental change and depositional sequences of barremian aptian shallow water carbonates in northern oman barremian and aptian shallow water carbonate facies uppermost lekhwair kharaib and shuaiba formations are described from outcrops in northern oman based on facies analysis and bedding pattern three orders of depositional sequences are defined third to fifth order and correlated between sections over the course of three third order sequences covering the barremian to lower aptian a third order depositional pattern is documented that consists of a succession of three distinct faunal assemblages discoidal orbitolinids and calcareous algae were deposited during early transgression microbialites and microencrusters dominate the late transgressive to early highstand facies and a rudist and miliolid dominated facies is typical of the highstand this ecological succession was controlled largely by palaeoenvironmental changes such as trophic level and clay influx rather than sedimentological factors controlled by variations in accommodation space orbitolinid beds and carbonates formed by microbialites and microencrusters seem to be the shallow water carbonate response to global changes affecting late barremian to aptian palaeoclimate and palaeoceanography

turbulence and entrainment in a buoyant surface plume in winter tidal outflow from the leschenault estuary forms a buoyant sheared stratified plume in koombana bay on each outgoing tide the turbulence in the plume and the local entrainment into the plume are examined based on measurements collected in an intensive field program coherency measurements between horizontally separated sensors are used to examine the anisotropy of the turbulence the effects of viscosity and buoyancy on the turbulence are studied using an activity diagram which is also an indicator of the mixing efficiency and total mixing the osborne cox model is tested and found to be valid in the plume

turbulent large eddy momentum flux divergence during high wind events abstractmomentum transport by energy containing turbulent eddies in the oceanic mixed layer were investigated during high wind events in the northern gulf of alaska off kayak island sixteen high wind events with magnitudes ranging from 7 to 22 m s 1 were examined winds from the southeast prevailed from one to several days with significant wave heights of 5 9 m and turbulent langmuir numbers of about 0 2 0 4 surface buoyancy forcing was much weaker than the wind stress forcing the water column was well mixed to the bottom depth of about 73 m spectral analyses indicate that a major part of the turbulent momentum flux was concentrated on 10 30 min time scales the ratio of horizontal scale to mixed layer depth was from 2 to 8 turbulent shear stresses in the mixed layer were horizontally asymmetric the downwind turbulent stress at 10 20 m below the surface was approximately 40 of the averaged wind stress and was reduced to 5 10 of the wind stress near the bottom turbulent kinetic energy in the cros

anatomy of turbulence in thermally stratified lakes turbulence within the thermocline of two thermally stratified lakes lake biwa japan and lake kinneret israel was investigated using a portable flux profiler this instrument provided high resolution profiles of temperature conductivity and two components of velocity within a measuring volume of approximately 8 mm 3 each data profile was segmented into statistically stationary segments a range of properties of the turbulence including direct estimates of the vertical mass flux were then calculated for each segment it was found that turbulence in the thermocline was generally patchy but within a patch dissipation levels were relatively high the turbulent motions were found to be fine grained with small thorpe scales and a large skewness of the distribution of the displacement scale this is distinct to that found in the ocean where shear instability produces large overturns the measurement showed that the net vertical mass flux in the thermocline was negligible and less than that predicted by osborn 1980 this is explained by noting that the net buoyancy flux consisted of two opposing parts a down gradient irreversible flux due to turbulent mixing and an up gradient reversible flux due to restratification that often cancel each other within a segment the low measured net buoyancy flux within the interior of the lakes suggested that other processes such as gravitational adjustments and benthic boundary layer processes should be responsible for the basin averaged vertical transport in these lakes

stratocumulus cloud top height estimates and their climatic implications a depth dependent boundary layer lapse rate was empirically deduced from 156 radiosondes released duringsixmonth longresearchcruisestothe southeastpacificsamplingavarietyofstratocumulusconditions thelapse ratedependenceonboundarylayerheightisweak decreasingfromabestfitof7 6to7 2k km 21 as theboundarylayerdeepensfrom800mto2km ship basedcloud baseheightsupto800mcorrespondwellto liftingcondensationlevels indicatingwell mixedconditions withcloud bases 800moften 200 600m higher than the lifting condensation levels the lapse rates were combined with moderate resolution imaging spectrometer 11 mm derived cloud top temperatures and satellite microwave derived sea surface temperatures to estimate stratocumulus cloud top heights the october mean cloud top height structure of the southeast pacific was then spatially and diurnally characterized coastal shoaling is apparent but so is a significant along coast cloud top height gradient with a pronounced elevation of the cloud top heights above thearicabightat 208s diurnalcloud topheightvariations inferredfromirregular4 times dailysampling can locally reach 250 m in amplitude and they can help to visualize offshore propagation of free tropospheric vertical motions a shallow boundary layer associated with the chilean coastal jet expands to its north and west in the afternoon cloud top heights above the arica bight region are depressed in the afternoon which may mean that increased subsidence from sensible heating of the andes dominates an afternoon increase in convergence upward motion at the exit of the chilean coastal jet in the southeast atlantic during october thestratocumuluscloud topheightsaretypicallylowerthanthoseinthesoutheastpacific acoastaljetregion can also be identified through its low cloud top heights coastal shoaling of the south atlantic stratocumulus region is mostly uniform with latitude in keeping with the more linear namibian angolan coastline the southeast atlantic shallow cloudy boundary layer extends farther offshore than in the southeast pacific particularly at 158s

convectively driven mixing in the bottom boundary layer closely spaced vertical profiles through the bottom boundary layer over a sloping continental shelf during relaxation from coastal upwelling reveal structure that is consistent with convectively driven mixing parcels of fluid were observed adjacent to the bottom that were warm by several millikelvin relative to fluid immediately above on average the vertical gradient of potential temperature in the superadiabatic statically unstable bottom layer was found to be 21 7 3 1024 km 21 or 6 0 3 1025 kg m24 in potential density turbulent dissipation rates increased toward the bottom but were relatively constant over the dimensionless depth range 0 4 1 0z d where d is the mixed layer height the rayleigh number ra associated with buoyancy anomalies in the bottom mixed layer is estimated to be approximately 1011 much larger than the value of approximately 10 3 required to initiate convection in simple laboratory or numerical experiments an evaluation of the data in which the bottom boundary layer was unstably stratified indicates that the greater the buoyancy anomaly is the greater the turbulent dissipation rate in the neutral layer away from the bottom will be the vertical structures of averaged profiles of potential density potential temperature and turbulent dissipation rate versus nondimensional depth are similar to their distinctive structure in the upper ocean during convection nearby moored observations indicate that periods of static instability near the bottom follow events of northward flow and local fluid warming by lateral advection the rate of local fluid warming is consistent with several estimates of offshore buoyancy transport near the bottom it is suggested that the concentration of offshore ekman transport near the bottom of the ekman layer when the flow atop the layer is northward can provide the differential transport of buoyant bottom fluid when the density in the bottom boundary layer decreases up the slope

effects of the andes on eastern pacific climate a regional atmospheric model study abstract a regional atmospheric model is used to study the effects of the narrow and steep andes on the eastern pacific climate in the southern hemisphere cold season i e august october 1999 the model reproduces key climatic features including the intertropical convergence zone itcz north of the equator and an extensive low level cloud deck capped by a temperature inversion to the south blocking the warm easterly winds from south america the andes help maintain the divergence and temperature inversion and hence the stratocumulus cloud deck over the southeast pacific off south america in an experiment where the andean mountains are removed the warm advection from the south american continent lowers the inversion height and reduces the low level divergence offshore leading to a significant reduction in cloud amount and an increase in solar radiation that reaches the sea surface in march and early april 1999 the model simulates a double itcz in response to the seasonal warming on and south

lagrangian evolution of the northeast pacific marine boundary layer structure and cloud during cset abstractflight data from the cloud system evolution over the trades cset campaign over the pacific stratocumulus to cumulus transition are organized into 18 lagrangian cases suitable for study an

expression of the late aptian cold snaps and the oae1b in a highly subsiding carbonate platform aralar northern spain abstract cretaceous climate records provide evidence that major volcanic pulses with duration of 103 to several 105 yr triggered changes in climate and oceanography black shales of oceanic anoxic event 1b ca 113 109 ma are regarded as signatures of late aptian greenhouse pulses associated with volcanic episodes new tex86 paleotemperature record indicates that warm aptian climate was interrupted by repeated cold snaps alternating with described greenhouse pulses an extraordinary thick shallow water carbonate succession of the aralar platform from the southeastern basque cantabrian basin in spain provides a unique opportunity to test the hypothesis that cold phases interrupted warm climate in the aptian platform evolution is traced through time of the proposed aptian cold snaps alternating with greenhouse episodes new high resolution c isotope records established in the studied upper aptian platform carbonates serve as chemostratigraphic tool providing a link between carbonate platform evolution basinal black shale formation and associated changes in open ocean palaeotemperatures the late aptian cold snaps find their expression in a remarkably reduced neritic succession punctuated by several emersion horizons formed during sea level lowstands the studied section bears evidence for several episodes of choked carbonate production related to increased runoff at times of sea level rise during which orbitolinids bloomed in a sediment loaden lagoonal setting these intervals coincide with the deposition time of organic rich kilian and leenhardt levels belonging to oae1b

the mid cretaceous carbonate system of northern israel facies evolution tectono sedimentary configuration and global control on the central levant margin of the arabian plate

observations of upper ocean boundary layer dynamics in the marginal ice zone 1 vertical profiles of turbulent kinetic energy dissipation and small scale hydrography were collected in the upper ocean boundary of both ice covered and ice free stations in the marginal ice zone of the barents sea in spring 2005 together with shipboard wind measurements and current profiles the mixed and mixing layer dynamics are studied during the survey shear production by the stress at the surface or under the ice dominated large upward turbulent heat fluxes 300 500 w m 2 were calculated for the mixing layers overlying the warm atlantic water which compared well with those obtained from an independent parameterization at the top of the pycnocline corresponding heat fluxes were 10 20 w m 2 significant stabilizing buoyancy fluxes were estimated for ice drift stations owing to the melting of ice in response to the large heat fluxes the mean dissipation profile in the ice free reference station agreed with the constant stress wall layer scaling within 30 on the contrary the observed dissipation profiles were enhanced in the upper half of under ice mixing layer or within 2 5 times the assessed pressure ridge keel depth deeper in the mixing layer the profiles relaxed toward the wall scaling the variability of dissipation in the mixed layer was better captured by the shear production profile when local friction speed was used together with a mixing length profile modified by buoyancy fluxes significant correlations were found between dissipation integrated over the mixing layer and work done by stress under the ice and the wind work at 10 m height the low correlation between the mixed layer depth and length scale for neutral conditions significantly increased when the reduction in the mixing length due to buoyancy fluxes was accounted for the mixing depth is observed to be strongly correlated with the outer neutral planetary length scale

sedimentology rhythmicity and basin fill architecture of a carbonate ramp depositional system with intermittent terrigenous influx the albian kharfot formation of the jeza qamar basin dhofar southern oman abstract the albian kharfot formation is preserved in the eastern margin of the jeza qamar basin which straddles across the oman yemen border this study addresses the sedimentological attributes of the formation and deduces its depositional setting cyclicity and relative sea level changes in local within the basin and regional arabian contexts the interaction among siliciclastic influxes in situ carbonate production and tectono climatic controls on the stacking nature of the various lithofacies that build up the formation is discussed in the study area the formation lies unconformably over barremian aptian qishn formation and conformably under late albian turonian dhalqut formation the kharfot formation thickens from 140 m in the eastern side of the study area to 300 m at the oman yemen border it consists of eight lithofacies orbitolina rich marls peloidal bioclastic packstone bioclastic mudstone to wackestone argillaceous bioclastic floatstone to rudstone bioclastic rudstone sandy peloidal bioclastic mudstone to packstone peloidal bioclastic grainstone and dolostone the vertical arrangement of these lithofacies defines recurring meter to decameter scale shallowing upward units deposited on a westward deepening inner to outer ramp setting tectonic rejuvenation of the siliciclastic source area was accompanied by warm humid climatic conditions as suggested by high kaolinitic marls of the kharfot fm and coeval quartz rich sandstone units harshiyat fm the shallowing upward rhythmic sedimentation of the formation has close resemblance with cycles of the nahr umr formation in northern oman and partially comparable with the global sea level changes the kharfot basin was an intrashelf depression that was part of the much larger arabian epeiric platform the latter is defined by a rimmed margin in northern oman where al hassanat formation represents platform margin deposits and nahr umr formation representing back rim intrashelf depression which received fine grained siliciclastic influx from the land westward in southern oman where kharfot formation accumulated the platform was unrimmed ramp type basin with high fine clastic influx along with elevated carbonate production

application of the wigner ville distribution to temperature gradient microstructure a new technique to study small scale variations the wigner ville distribution a new tool in the time frequency analysis of signals is applied to temperature gradient microstructure records in particular the wigner ville distribution is used to compute the local instantaneous and maximum frequencies of the signal as a function of depth and these frequencies are then related to the dissipation of turbulent kinetic energy the method is applied to two temperature gradient microstructure records from the wellington reservoir it is shown that a high resolution estimate of the dissipation is obtained that provides insight into the patchiness the wavenumber content and the reynolds froude number variability of the integral scales of motion in a strongly stratified water column

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

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

major palaeoenvironmental perturbation in an early aptian carbonate platform prelude of the oceanic anoxic event 1a the early aptian oceanic anoxic event oae 1a was characterized by intensified greenhouse climate conditions widespread accumulation of organic deposits in open marine settings major perturbations in the c cycle and a generalized increase in terrestrial runoff sedimentological diagenetic and chemostratigraphic analyses of lower aptian platform carbonates from the north cantabrian basin n spain illustrate the regional impact and effects of those global conditions on shallow marine environments the studied interval outlines four stages of platform evolution stage 1 earliest bedoulian is defined by an initial rapid marine transgression that led to deposition of shallow water oligotrophic photozoan skeletal assemblages and by a later interval of subaerial exposure stage 2 early bedoulian starts with a rapid transgression followed by deposition of grainstones that yield heterozoan assemblages more typical of mesotrophic conditions along with ferruginized oolites stage 3 early bedoulian is defined by the drowning of the carbonate platform and subsequent deposition of open marine marls which are thought to represent the local expression of the oae 1a finally stage 4 shows the return of shallow water photozoan carbonate sedimentation the carbonate o and c stable isotope records have revealed prominent negative excursions during deposition of the marly interval of the stage 3 which may be associated with the important global changes that occurred at the onset of the oae 1a the change in skeletal assemblages that preceded the isotopic excursions and the platform drowning documents conditions of environmental stress caused by a combination of local and global factors the global change coupled with increased basin subsidence triggered the drowning of the platform by progressive reduction of the growth potential of the carbonate factory

internal tide dissipation mixing and vertical nitrate flux at the shelf edge of ne new zealand an internal tide on the ne shelf of new zealand was observed with a combination of moored temperature loggers and current meters and vertical profiling with a microstructure probe internal tide energy flux across the shelf edge was calculated to be 400 w m with considerable variability driven by the passage of a storm through the region energy associated with the internal tide was significantly greater than the energy of the barotropic tide or of inertial shear dissipation of the internal tide calculated from the energy loss between two of the moorings was estimated to be 15 10 mw m 2 the associated vertical eddy diffusivity was 4 3 x 10 4 m 2 s 1 the microstructure observations indicated internal tide driven vertical diffusivities at the nitracline of 7 x 10 4 m 2 s 1 the observations of vertical eddy diffusivities are combined with measurements of the vertical nitrate gradient to suggest that mixing driven by the internal tide is the dominant mechanism for driving diapycnal nutrient supply during summer the calculated flux of about 12 mmol n m 2 d 1 into the photic zone is suggested to drive significant new subsurface production throughout the summer amounting to a possible contribution to annual new production on the shelf of 100 g c m 2

cascading of water down the sloping sides of a deep lake in winter during winter the temperature of the water overlying the shallow typically 2 5 m deep shelf region around the edge of the 310 m deep lake geneva falls more rapidly than that over deeper areas this causes the spilling or cascading of relatively dense water from the shallows down the sloping sides of the lake in the form of gravity currents 2 15 m thick and typically 0 1 c cooler than the ambient the flow is intermittent with slugs of cold water lasting on average for 8 hrs with mean downslope speeds of 5 2 cms 1 the temperature and thickness of the slugs is however variable with pulses of colder water lasting for 1 3 hrs each preceded by a front in which thickness increases and temperature falls by about 0 01 c per min the net volume flux carried by the slugs is 18 5 times the mean winter flow into the lake from rivers

integration of subsidence and sequence stratigraphic analyses in the cretaceous carbonate platforms of the prebetic jumilla yecla region spain abstract an integrated analysis of subsidence and sequence stratigraphy of the cretaceous successions of the jumilla yecla region betics se spain is supported by abundant stratigraphical sedimentological and palaeontological data with the aim to document and explain the accommodation changes that controlled the evolution and architecture of the carbonate platforms generated during that time on the southern continental margin of iberia the cretaceous shallow marine carbonates and clastics that extensively crop out in the jumilla yecla region are divided into 11 sequence sets major stratigraphic units bounded by tectonically induced unconformities which can be subdivided into several third order depositional sequences and their constituent system tracts all these genetic units build up a regional chronostratigraphic framework which is herein used to support subsidence calculations from the results of the subsidence analysis seven intervals with characteristic tectonosedimentary patterns were distinguished for cretaceous time from these intervals the first three respectively early tithonian early late berriasian late berriasian late hauterivian and latest hauterivian to earliest late albian were controlled by extensional tectonics strong enough to mask during most part of the time the long term thermal subsidence inherent to the continental margin this tectonism was related to the iberia africa divergence and the opening of the north atlantic later the fourth interval late albian mid cenomanian and the sixth interval late coniacian to late santonian were characterised regionally by overall homogeneous subsidence patterns controlled by thermal subsidence sediment loading and a relative tectonic quiescence finally the fifth and the seventh intervals respectively latest cenomanian early coniacian and campanian maastrichtian were characterised by strong tectonic movements and complex subsidence patterns which were related to changes in intraplate stresses related to the onset of the convergence between africa and iberia and with the evolution of the bay of biscay

morphological patterns of aptian lithocodium bacinella geobodies relation to environment and scale lithocodium aggregatum and bacinella irregularis are now extinct shallow marine life forms of unknown taxonomic origin forming part of the tropical platform biota during much of the mesozoic these organisms experienced bloom periods and temporarily replaced rudist coral assemblages during parts of the early aptian within the limitations of time resolution this out of balance facies is coeval with the oceanic anoxic event 1a related black shale deposition in oceanic basins but the triggering factors remain poorly understood here a platform wide comparison of lithocodium bacinella geobodies and morphotypes from the sultanate of oman is presented and placed in its environmental bathymetric and physiographic context lithocodium bacinella geobodies reach from kilometre scale superstructures to delicate centimetre sized growth forms clearly scale matters and care must be taken when drawing conclusions based on spatially limited observational data whilst the factors that cause lithocodium bacinella expansion should probably be considered in a global context regional to local factors affected growth patterns in a more predictable manner here the unresolved taxonomic relationship remains the main obstacle in any attempt to unravel the response of lithocodium bacinella to specific or interlinked environmental parameters as different organisms respond differently to changing environment acknowledging these limitations the following tentative patterns are observed i lithocodium bacinella tolerated a wide range of hydrodynamic levels and responded to differences in energy level or physiographic settings margin intrashelf basin inner platform by obtaining characteristic growth forms ii lithocodium bacinella favoured low sediment input but had the ability to react to higher sedimentation rates by enhanced upward growth a feature perhaps pointing to a phototrophic metabolism circumstantial evidence for continuous growth within the upper sediment column is debated iii the availability of accommodation space had a direct influence on the maximum size of geobodies formed iv fluctuating nutrient levels and sea water alkalinity may have affected the growth potential of lithocodium bacinella understanding the relationship between lithocodium bacinella morphogenesis on a wide range of scales and local environmental parameters allows for better prediction of the spatial distribution of reservoir properties and also results in an improved interpretation of palaeoenvironments this study might represent a useful first step in this direction

paleoenvironmental distribution patterns of orbitolinids in the lower cretaceous deposits of eastern rafsanjan central iran abstract the lower cretaceous orbitolinid rich deposits in eastern rafsanjan central iran were studied for analysis and interpretation of paleoenvironmental distribution patterns of orbitolinids based on detailed studies a total of seven microfacies were determined from the microfacies and paleontological studies the continental shelf with a relative water depth of 0 to 20 m can be separated into supralittoral littoral sublittoral transitional and sublittoral includes proximal and distal sublittoral paleoenvironmental zones orbitolinids with diverse test shapes were the main inhabitants of the sublittoral zone the orbitolinids in this zone commonly represent nutrient rich shallow warm waters of the photic zone with normal marine salinity ca 30 40 psu in a depth range of approximately 10 to 20 m the general abundance or richness of orbitolinids in the sublittoral zone resulted from a nutrient driven transgression the studies showed that the conical orbitolinids were the most abundant forms in the sublittoral zone reflecting their better adaptation to different water depths turbulence light levels and substrate stability however the almost discoidal and discoidal orbitolinids were dominant in the middle part of the proximal sublittoral zone with a muddy substrate deeper depth lower water energy and decreased light intensity all discoidal orbitolinids slightly discoidal almost discoidal and discoidal were very rare and sparsely distributed in the distal sublittoral zone and the middle outer part of the proximal sublittoral zone and generally reflect the highest sea level rise or transgression deepening maximum nutrient enrichment and increased water cloudiness that can be correlated with a transgressive systems tract tst and probably maximum flooding surface mfs the lowest diversity and abundance of orbitolinids in the outer part of the proximal sublittoral zone commonly co occurred with the presence of algal and sparse coral associations reflecting increased water temperature also the absence of in situ orbitolinids in the littoral sublittoral transitional zone resulted from high siliciclastic input and very high wave energy

strontium and carbon isotope chronostratigraphy of barremian aptian shoal water carbonates northern tethyan platform drowning predates oae 1a abstract a widely accepted hypothesis proposes that the early aptian demise of carbonate platforms in the northern tethyan realm reflects the impact of environmental changes that eventually led to the deposition of organic rich basinal sediments during oceanic anoxic event oae 1a in fact the temporal correlation of oceanic anoxia and platform drowning has not been rigorously tested and evidence indicating causality is debated the present paper provides a high resolution carbon and strontium isotope chronostratigraphy combined with detailed sedimentological analysis applied to the barremian aptian urgonian carbonate platform development at the northern rim of the tethys subalpine chains haute savoie ese france a characteristic barremian aptian carbon and strontium isotope pattern below the onset of oae 1a interval permits precise platform to basin correlation with the barremian stratotype locality of angles se france this chemostratigraphic pattern equally allows for a correlation with well studied shoal water and pelagic records of the northern and central tethys strontium isotope stratigraphy provides a high resolution numerical age data set indicating an earliest aptian age

sequence stratigraphy and architecture of a late early middle aptian carbonate platform succession from the western maestrat basin iberian chain spain abstract the attributes of a four systems tract sequence are at times difficult to identify in outcrop scale carbonate successions poor exposure conditions variable rates of sediment production erosion and or superposition of surfaces that are intrinsic to the nature of carbonate systems frequently conceal or remove its physical features the late early middle aptian platform carbonates of the western maestrat basin iberian chain spain display facies heterogeneity enabling platform platform margin and slope geometries to be identified and provide a case study that shows all the characteristics of a quintessential four systems tract based sequence five differentiated systems tracts belonging to two distinct depositional sequences can be recognized the highstand systems tract hst and forced regressive wedge systems tract frwst of depositional sequence a and the lowstand prograding wedge systems tract lpwst transgressive systems tract tst and subsequent return to a highstand stage of sea level hst of depositional sequence b an extensive carbonate platform of rudists and corals stacked in a prograding pattern marks the first hst the frwst is constituted by a detached slightly cross bedded calcarenite situated at the toe of the slope in a basinal position the lpwst is characterized by a small carbonate platform of rudists and corals downlapping over the frwst and onlapping landwards the tst exhibits platform backstepping and marly sedimentation resumed carbonate production in shelf and slope settings characterizes the second hst a basal surface of forced regression a subaerial unconformity a correlative conformity a transgressive surface and a maximum flooding surface bound these systems tracts and are well documented and widely mappable across the platform to basin transition area analyzed moreover the sedimentary succession studied is made up of four types of parasequence that constitute stratigraphic units deposited within a higher frequency sea level cyclicity ten lithofacies associations form these basic accretional units each facies assemblage can be ascribed to an inferred depositional environment in terms of bathymetry hydrodynamic conditions and trophic level the architecture of the carbonate platform systems reflects a flat topped non rimmed depositional profile furthermore these carbonate shelves are interpreted as having been formed in low hydrodynamic conditions the long term relative fall in sea level occurred during the uppermost early aptian which subaerially exposed the carbonate platform established during the first hst and resulted in the deposition of the frwst is interpreted as one of global significance moreover a possible relationship between this widespread sea level drop and glacio eustasy seems plausible and could be linked to the cooling event proposed in the literature for the late early aptian because of the important implications in sequence stratigraphy of this study the sedimentary succession analyzed herein could serve as an analogue for the application of the four systems tract sequence stratigraphic methodology to carbonate systems

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

mean structure and diurnal cycle of southeast atlantic boundary layer clouds insights from satellite observations and multiscale modeling framework simulations abstractthe mean structure and diurnal cycle of southeast se atlantic boundary layer clouds are described with satellite observations and multiscale modeling framework mmf simulations during austral spring september november hourly resolution cloud fraction cf and cloud top height ht are retrieved from meteosat 9 radiances using modified clouds and the earth s radiant energy system ceres moderate resolution imaging spectroradiometer modis algorithms whereas liquid water path lwp is from the university of wisconsin microwave satellite climatology the mmf simulations use a 2d cloud resolving model crm that contains an advanced third order turbulence closure to explicitly simulate cloud physical processes in every grid column of a general circulation model the model accurately reproduces the marine stratocumulus spatial extent and cloud cover the mean cloud cover spatial variability in the model is primarily explained by the boundary layer decoupling strength whereas a boundary layer

evolution of the urgonian shallow water carbonate platform on the helvetic shelf during the late early cretaceous abstract urgonian platform carbonate cretaceous barremian aptian forms an important lithostratigraphic unit in the helvetic fold and thrust unit of the northern swiss alps its widespread distribution and ubiquity allow for an integrated high resolution study of macro and microfacies benthic foraminiferal biostratigraphy sequence stratigraphy and carbon isotope and phosphorus records the resulting data confirm the importance of environmental forcing and sea level change on the style of carbonate production and accumulation along the margin of the northern tethys during the late early cretaceous stratal geometries the succession of microfacies the identification of major emersion surfaces and biostratigraphy observed and analysed in twelve sections through the inner middle and outer platform and in the panorama of the churfirsten range permit subdivision of the analysed succession into eight depositional sequences the succession starts with a phase of sedimentary condensation altmann member mb late hauterivian late early barremian sequences h7 h8 and b1 followed by the deposition of hemipelagic sediments drusberg mb restricted to sequence b2 of the late early barremian on the inner platform and covering the late early barremian to the middle late barremian on the outer platform and to the early aptian on the outer shelf thereby showing an important diachroneity of its upper boundary related to the inception and progradation of the urgonian platform and the development of predominantly lagoonal carbonate schrattenkalk formation fm early late barremian early aptian sequences b3 b4 b5 and a1 the schrattenkalk fm documents important progradation and aggradation of the carbonate platform and the change from a ramp like to flat topped geometry the oldest allochthonous remains of the shallow water carbonate platform were identified intercalated in and on top of the lower barremian drusberg mb sequence b2 sequence boundary sb b3 resulted from an important regressive phase near the early late barremian boundary which led to the emersion of the hemipelagic sediments of the drusberg mb in the inner part of the shelf and to the deposition of a lowstand systems tract at the base of the lower schrattenkalk mb late barremian sequences b3 5 in intermediate and distal domains deposition of in situ platform carbonate started during the following transgressive phase in the middle late barremian which flooded the entire investigated area the associated faunal assemblages and phosphorus contents indicate a concomitant increase in nutrient input which led to a mixed photozoan heterozoan platform association dominated by annelids and flat orbitolinids and the formation of a condensed phosphate rich bed on the outer shelf chopf bed middle late barremian the subsequent sea level highstand allowed for the deposition of the first typical urgonian carbonates rich in corals and rudists this depositional sequence b3 terminated by the important infilling of accommodation space combined with sea level fall of at least 15 m later on close to the barremian aptian boundary a further major emersion phase sb a1 was triggered by sea level fall estimated here as at least 16 m which terminated this first phase in the deposition of rudist and coral rich platform carbonates covering the middle late to latest barremian b3 b5 the overlying rawil mb lowermost aptian transgressive systems tract a1 resulted from progressive deepening and document a phase of increasing eutrophication of the depositional environment resulting in a mixed siliciclastic carbonate platform build up characterized by sea grass facies and the massive occurrence of palorbitolina lenticularis the overlying upper schrattenkalk mb lower aptian highstand systems tract a1 records recovery of the rudist rich photozoan urgonian platform its subsequent demise occurred well before the selli oceanic anoxic episode oae 1a it was initiated by emersion of the platform due to high amplitude sea level fall sb a2 followed by eutrophication during the subsequent transgressive phase the carbon isotope records show an increase towards more positive values during the lower schrattenkalk mb and the base of the rawil mb interrupted in most sections by an excursion to lower values near the barremian aptian boundary a shift to lower values occurred also in the uppermost part of the rawil mb followed by variable trends in the upper schrattenkalk mb these long term trends are well correlated with the basinal record angles la bedoule deviations in the correlations are related to the influence of facies and microfacies primary mineralogy emersion phases and post depositional alteration

convectively driven turbulent mixing in the upper ocean abstract two experiments were performed to study the characteristics of turbulence in convective mixed layers in the upper ocean in the first a diurnal convective mixed layer developed in the bahamas under the influence of the cycle of daytime solar heating and nighttime evaporative cooling the mixed layer reached as deep as 100 m each night and restratified each day in the second the mixed layer of a warm core gulf stream ring deepened from less than 50 m to more than 150 m in a little more than a day when subjected to rapid cooling during a cold air outbreak although individual profiles of the rate of viscous dissipation of turbulent kinetic energy had considerable spatial and temporal variability the mean dissipation profiles were similar to those in convecting atmospheric boundary layers the is established by the surface buoyancy flux jb0 jb0 0 61 and 0 72 in the bahamas and ring data respectively compared with 0 64 in convecting atmospheric mixed layers the mean profiles decre

impact of dynamic sedimentation on facies heterogeneities in lower cretaceous peritidal deposits of central east oman this study based in the haushi huqf area of central east oman aims to characterize the controls on facies distribution and geometries of some of the best preserved examples of lower cretaceous tidal flat facies within the tethyan epeiric platform field petrographic and geochemical data were acquired from the barremian aptian jurf and qishn formations that crop out in a 500 1000 m2 butte thus allowing for pseudo three dimensional quantitative data acquisition of the dimensions and spatial distributions of discontinuity surfaces and sedimentary bodies the interpretation presented here suggests that the main processes impacting sedimentation in the lower cretaceous peritidal environment of the haushi huqf were transport and erosion processes related to storm waves and currents the vertical evolution of the carbonate system is organized into six types of metre scale depositional sequences from subtidal dominated sequences to supratidal capped sequences which are bounded by regional discontinuity surfaces at subaerial exposure and submarine erosion surfaces associated with a base level shift sedimentary horizons along the entire depositional profile are cut by scours possibly created by storm events chemostratigraphy allows correlation between the haushi huqf and the age equivalent sections logged in the interior of the platform in oman the correlation suggests that the change from subtidal to intertidal depositional sequences during the late highstand is coeval with the development of rudist dominated shoals on the shelf this study is the first to discuss the controls on lower cretaceous peritidal carbonate cyclicity of the arabian epeiric platform the results presented here also offer a unique quantitative dataset of the distribution and dimensions of peritidal carbonate shoals and storm scours in a regional sequence stratigraphic context

bubble clouds and the dynamics of the upper ocean this is a review of turbulence in the upper ocean close to the sea surface particularly of the information that has been obtained from sonar observations of bubble clouds produced by breaking wind waves these clouds provide tracers of the turbulent motions and are important especially at high wind speeds in the process of air sea gas transfer the observations of bubble clouds are here related to other measurements of turbulence particularly to direct measurements of currents and temperatures in lakes or at sea and to laboratory studies some novel observations of bubble clouds and breaking waves their frequency and relation to langmuir circulation are presented there is now emerging a pattern of clues that point to the dominance of breaking surface gravity waves as a source of turbulence to a depth below the surface of 0 04 to 0 2 times the wavelength of the dominant breaking waves although the effect of swell has yet to be clarified the relative depth appears to increase with increasing values of w 1 c where w10 is the wind speed and c the phase speed of the dominant waves below this region the generation of turbulence may be dominated by shear stress or convection here turbulence is generally similar to that in the atmospheric boundary layer there are however coherent motions on the scale of the mixing layer that persist for periods of a few minutes to an hour or so to which the transport of a large part of the momentum and heat fluxes can be attributed and which strongly affect the dispersion of buoyant particles or bubbles these motions deserve special study to establish their contribution to heat and momentum transport and hence to determine if or when they should be specifically represented in models of the upper ocean devised for example to describe the dispersion of passive and non passive tracers or the air sea transfer of gases

observations of mixing near the sides of a deep lake in winter the dissipation rate of turbulent kinetic energy per unit mass vertical eddy diffusivity kz and the rate of dissipation of temperature variance x are estimated over the sloping sides of lake geneva both far from and near the bed using temperature data from horizontal tracks of a submarine during periods of winter cooling the estimated values are about one order of magnitude greater near the slope than those distant from it the mean dissipation rate per unit mass averaged over the epilimnion varies between o 10 210 m 2 s 23 in calm weather to o 10 28 m 2 s 23 in winds of 8 m s 21 for surface buoyancy fluxes of 6 3 10

the subtropical stratocumulus topped planetary boundary layer a climatology and the lagrangian evolution abstractprior work has shown that deeper planetary boundary layers pbls are associated with cloud breakup and reduced droplet concentration in subtropical stratocumulus cloud decks motivating a need for a thorough understanding of pbl mechanics here 169 000 boundary layer trajectories are calculated in four eastern subtropical ocean basins following reanalysis winds at 925 mb 1 mb 1 hpa these trajectories combined with a twice daily cloud top height inferred pbl depth product allow for a comprehensive lagrangian analysis of the stratocumulus sc topped pbl as the cloud deck transitions from sc to trade cumulus cu month to month variations of this pbl product are strongly positively correlated with an independent pbl product derived from gps radio occultation a climatology shows the pbl deepening offshore in every region the yearly cycle of pbl depth varies in opposition to the yearly cycle of lower tropospheric stability lts but high frequency variation between lts and pbl depth is more

large eddy simulation of the diurnal cycle in southeast pacific stratocumulus abstract this paper describes a series of 6 day large eddy simulations of a deep sometimes drizzling stratocumulus topped boundary layer based on forcings from the east pacific investigation of climate epic 2001 field campaign the base simulation was found to reproduce the observed mean boundary layer properties quite well the diurnal cycle of liquid water path was also well captured although good agreement appears to result partially from compensating errors in the diurnal cycles of cloud base and cloud top due to overentrainment around midday at all times of the day entrainment is found to be proportional to the vertically integrated buoyancy flux model stratification matches observations well turbulence profiles suggest that the boundary layer is always at least somewhat decoupled model drizzle appears to be too sensitive to liquid water path and subcloud evaporation appears to be too weak removing the diurnal cycle of subsidence had little effect on simulated liquid water path simulations

seismic reflection imaging of shallow oceanographic structures 1 multichannel seismic mcs reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure however the shallowest layers of the water column z 150 m have remained unexplored by this technique until recently in order to explore the feasibility of shallow seismic oceanography so we reprocessed and analyzed four multichannel seismic reflection sections featuring reflectors at depths between 10 and 150 m the influence of the acquisition parameters was quantified seismic data processing dedicated to so was also investigated conventional seismic acquisition systems were found to be ill suited to the imaging of shallow oceanographic structures because of a high antenna filter effect induced by large offsets and seismic trace lengths and sources that typically cannot provide both a high level of emission and fine vertical resolution we considered a test case the imagery of the seasonal thermocline on the western brittany continental shelf new oceanographic data acquired in this area allowed simulation of the seismic acquisition sea trials of a specifically designed system were performed during the aspex survey conducted in early summer 2012 the seismic device featured i four seismic streamers each consisting of six traces of 1 80 m ii a 1000 j sig sparker source providing a 400 hz signal with a level of emission of 205 db re 1 pa 1 m this survey captured the 15 m thick 30 m deep seasonal thermocline in unprecedented detail showing images of vertical displacements most probably induced by internal waves

physical properties of turbulent benthic boundary layers generated by internal waves physical properties of active turbulent benthic boundary layers tbbl generated by basin scale internal waves were studied within a northern hemisphere thermally stratified lake a microstructure profiler was used to measure the nature of the turbulence within the tbbls while a series of thermistor chains were used to monitor the thermal structure of the lake it was observed that a wind driven anticlockwise diurnal period vertical mode one kelvin wave generated large scale motions within the water column and that the interactions between this wave and the sloping lakebed induced tbbls a simple model based on potential energy change and boundary shearing was shown to describe the mean tbbl thickness

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

gravity wave induced perturbations in marine stratocumulus we discuss the role of atmospheric gravity waves in modulating cloud radiative and dynamical properties over the southeast pacific satellite imagery and satellite retrieved cloud properties during october 2008 illustrate three distinct episodes of horizontal propagation of gravity wave trains across the large scale stratocumulus sc cloud deck capping the local marine boundary layer in one period 79 october 2008 the waves modulated cloud top height by up to 400 m peak to trough propagating perpendicular to the synoptic boundary layer flow with phase speed 15 3 m s1 period approximate to 1 h and horizontal wavelength 55 km the gravity waves were observed to be non dispersive these waves were first evident in the cloud deck near 30 degrees s 85 degrees w during a 24 h period beginning at midday on 7 october 2008 and propagated northeastward toward the peruvian coast for the following 48 h during this time they induced both reversible and non reversible changes in cloud radiative and cloud dynamic properties such that areas of clear sky developed in the troughs of passing wave fronts these pockets of open cells persisted long after the passage of the gravity waves advecting northwestward with the background wind using the analysis fields of the european centre for medium range weather forecasts in conjunction with infrared and microwave satellite imagery we show that these gravity waves emerged from a disturbed subtropical jet stream the radiant of the waves was coincident in all cases with centres of large negative residuals in nonlinear balance suggesting that geostrophic readjustment of sharply divergent flows associated with the disturbed jet provided a source for the wave energy conversely gravity waves were not observed in more quiescent jet conditions this case study highlights the important and irreversible effects that gravity waves propagating in the troposphere can have on cloud radiative properties and hence surface radiation budgets over a very wide area it also highlights the importance of synoptic influence on sc covered marine boundary layers copyright c 2012 royal meteorological society

observations of a quasi shear free lacustrine convective boundary layer stratification and its implications on turbulence 1 convection due to surface cooling has been investigated in the surface boundary layer of a small lake under near ideal conditions undisturbed by wind large scale currents and differential cooling successive temperature microstructure profiles revealed a stable stratification in the lower bulk of the convective boundary layer despite strong cooling over the entire layer lateral heat fluxes as well as heat exchange with the thermocline could be excluded as driving mechanism of the observed stratification acoustic doppler current profiler adcp measurements indicated an asymmetric pattern of vertical velocities strong downward plumes were observed upon a background of slow upflow we suggest that this asymmetry allows cold water from the super adiabatic surface layer to intrude at the base of the convective layer thus causing the observed stratification this in particular involves downward plumes that feature a relatively low entrainment rate in the center bulk of the convective layer corresponding large eddy simulation studies as well as thermistor string and adcp data were found consistent with this scenario the dissipation rate of turbulent kinetic energy tke was estimated on the basis of the temperature microstructure profiles and from the adcp data mean dissipation rates of only about 20 of the surface buoyancy flux were typically identified this finding is attributed to respectively low buoyant production rates of tke attenuated by strong convective plumes penetrating through the stable stratification in the lower bulk of the convective layer into the thermocline index terms 4568 oceanography physical turbulence diffusion and mixing processes 4524 oceanography physical fine structure and microstructure 4572 oceanography physical upper ocean processes 4239 oceanography general limnology keywords convection temperature microstructure adcp stratification turbulent kinetic energy convective boundary layer

dynamical processes of transfer at the sea surface abstract this review describes the dynamical processes of transport from and immediately below the sea surface particularly those which involve convergence and the separation of flow and which result in the renewal of surface water at horizontal scales ranging from millimeters to hundreds of meters turbulence at or near the sea surface derives from several processes breaking waves and the bubbles they may produce precipitation and spray langmuir circulation and thermal convection and turbulence which is internally generated by shear interest in the subject derives from the requirements to predict air sea fluxes of heat momentum and gases to develop climate models to interpret satellite images of the sea surface including those of ship wakes and to predict upper ocean structure including mixing layer depth in models of phytoplankton blooms and acoustic propagation the general effect of subsurface turbulence on the sea surface and the effects of surfactants is described and each process is discussed in turn laboratory experiments and theoretical studies have contributed particularly to the understanding of the interaction of vortices and turbulence with the surface and to the consequences of breaking waves they point to the development of instability in the flow ahead of steep waves carrying parasitic capillary waves which may contribute to the onset of flow separation on the leading face of the waves and the development of a rotor or roller below the wave crest shown most clearly in the pattern of streamlines in a frame of reference moving forward with the wave the conditions near the flow separation line on the wave surface ahead of the rotor may be similar to those produced by vortices approaching a free surface detailed observation of breaking waves at sea is lacking but some progress has been made using acoustics to detect the clouds of subsurface bubbles formed by the larger breakers and the depth to which they penetrate the possible importance of three dimensional effects in breaking waves is discussed and a conjectural sketch of the surface flow field and the surface separation and reattachment pattern following a plunging breaker is described recent observations show elevated levels of turbulence close to the sea surface the depth of the layer in which this occurs is shown to be consistent with information derived from sonar studies of the depth of bubble clouds the observed frequency of breaking waves and laboratory observations of breaking waves rain is known to knock down the sea reducing the frequency and intensity of breaking waves the precise mechanics of the phenomena are uncertain but an enhancement of near surface turbulence and the damping of short surface gravity waves has been observed in laboratory experiments langmuir circulation temperature ramps and convection all associated with coherent structures are processes which mix the upper ocean although their relative importance is unknown connections between studies with quite disparate motivations are found to help provide descriptions of the upper ocean processes and estimates of the time scale of surface renewal associated with each of the processes identified many quantities being transferred across the sea surface appear to be transported by dynamical processes of scale much smaller than that of the dominant surface waves although their subsequent diffusion in the mixing layer may be strongly influenced by the larger scale processes further careful measurements in the laboratory and at sea are required to quantify the fluxes associated with the processes and to relate them to external parameters such as wind speed

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

an estimate of albian sea level amplitudes and its implication for the duration of stratigraphic hiatuses abstract carbonate platform tops are reliable but incomplete recorders of past sea level fluctuations as they are riddled with hiatuses of various durations basinal sections represent a more complete record but fail to register regressive transgressive events with small to moderate amplitudes we seek to avoid these problems by combining information on past sea level fluctuations from coeval platform top slope and basinal sections the outcome of this study is a semiquantitative albian sea level curve from the southern tethyan margin in oman in subaerial exposure surfaces the northern oman margin recorded 4 high amplitude 50 m 6 intermediate amplitude 30 m and 26 low amplitude 10 m regressive transgressive cycles hiatuses that cap the platform top depositional sequences might account for between 30 to 70 of the cycle duration the resulting platform top depositional sequences have frequencies in the order of 230 20 kyr i e they are in the time range of orbital eccentricity cycles it appears that at least some of these albian regressive transgressive cycles were rapid and punctuated as opposed to sinus shaped milankovitchian sea level oscillations

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

the diurnal cycle of cloud top height and cloud cover over the southeastern pacific as observed by goes 10 the diurnal cycles in cloud top height htop and cloud fraction cf in the southeastern pacific stratocumulus region were determined for october november 2008 by analyzing data from geostationary operational environmental satellite 10 goes 10 according to a diurnal semidiurnal harmonic fitting technique the value of htop was obtained by applying a formula based on a linear regression of the differences between goes 10 cloud top temperature and tropical rainfall measuring mission trmm microwave imager tmi satellite sea surface temperature with a common 0 25 83 0 258 spatial resolution a satellite liquid water path lwp climatology complemented this dataset southwestward transects ofhtopandlwpanomaliesreveala coherentpropagatingsignalfrom thecoast in the afternoon with a typical phase speed of 25ms 21 this pattern is preceded by a subsidence wave that reaches its peak a few hours before the maximum in htop and lwp anomalies coincident increases in lwp and htop after the subsidence wave passes suggest that the boundary layer deepening promotes cloud thickening and increased lwp which are likely maintained through a well mixed boundary layer and sufficient moisture fluxes that can counteract the effect of dry air entrainment the interference between the radiatively and subsidence wave driven cycles gives rise to a semidiurnal cycle in htop along the coast while thesemidiurnalamplitudeisnear80m closetothecoastwithafractionofexplainedvariancegreaterthan0 4 it decreases to 30m offshore 808w similar to htop cf also exhibits contrasting zonal differences but with a smaller semidiurnal component the phase of the semidiurnal harmonic resembles the subsidence propagation westward and the noticeable land sea breeze circulation at 268s that extends 200km offshore

similarity structure in the convective boundary layer of a lake natural convection influences a variety of geophysical phenomena including daily mixing cycles in the atmosphere and in surface waters the seasonal overturn of lakes and global climate variability conceptual models of convection in water are primitive and based on very limited data particularly at small dissipative scales here i present an analysis of microscale data from the convective boundary layer of a lake indicating a complex depth dependence in the rate at which temperature fluctuations are dissipated suitably scaled this vertical structure is remarkably similar to that found in the atmospheric convective boundary layer1 2 stirred by rising thermals of buoyant air heated at the earth s surface this comparison consistent with recent documentation of similarity in the more uniform vertical structure of energy dissipation3 5 suggests another unifying link in the structure and dynamics of convection in boundary layers of lakes oceans and the atmosphere6

orbitolina episodes in carbonate platform evolution the early aptian model from se spain abstract among the orbitolininae palorbitolina lenticularis blumenbach is a common facies marker in upper barremian lower aptian shallow water mesogean deposits and was hitherto ascribed to specific but contrasting paleoenvironments within the carbonate platform facies suites the albacete prebetic area se spain illustrates a model in which the palorbitolina facies spread over the whole platform system the development of the palorbitolina sediments coincided with a transgressive trend at the end of an important terrigenous period this model could also be applied to similar middle crotaceous orbitolina facies

residual circulation due to internal waves shoaling on a slope we describe the residual circulation induced in a two layer system when internal waves with a wave length equal to or longer than the slope length propagate over a sloping bottom and either reflect or break for the case of no wave breaking scaling is used to derive boussinesq type equations the solution of which leads to an expression for the residual circulation adjacent to the sloping bottom this residual circulation is maintained by a weak slope on the density interface for breaking waves laboratory experiments and numerical modeling were used to ascertain the details of the residual circulation arising from the formation of gravitational intrusions results from these three investigative tools were used to determine as a function of bottom slope and incident wave amplitude the internal wave reflection coefficient and the strength of the residual circulation pattern with and without wave breaking the ocean and most lakes are thermally stratified for at least part of the year in stratified fluids the density anomaly associated with the thermal stratification supports internal waves with a range of vertical modal structures antenucci et al 2000 antenucci and imberger 2001 antenucci and imberger 2003 the gravest or first vertical mode induces a large current over the lake or ocean bottom and when the bottom slopes the waves shoal causing them to break and lose energy to dissipation the associated currents and turbulence can often lead to sediment resuspension and mixing of the water column gloor et al 1994 pierson and weyhenmeyer 1994 steinman et al 1997 the gravitational motions in turn induced by the mixing may combine with secondary internal wave motions to drive a residual circulation that may transport resuspended and dissolved material to the central area of a lake hakanson 1982 ostrovsky et al 1996 inall 2009 also demonstrated mass transport due to intrusion caused by internal wave breaking in the fjord loch etive by using a fluorescent dye tracer such intrusions have been observed but their dynamics do not seem to have received any attention in this paper the processes leading to residual circulation are described when a continuous train of internal waves with an individual wavelength equal to or longer than the slope length supported by a two layer stratification impinges perpendicularly onto a sloping bottom two cases were investigated when the waves break and when they are reflected perfectly without breaking internal waves and their associated mass transport in lakes fjords and coastal oceans are reviewed in ostrovsky and stepanyants 1989 and huthnance 1989 whereas solitary internal waves are reviewed by brown and christie 1998 lamb 2002 and grue et al 2000 regarding mass transport lamb 2002 investigated shoaling of largeamplitude internal waves and demonstrated that trapped

changes in sedimentary patterns of coastal and deep sea successions from the north atlantic portugal linked to early cretaceous environmental change coastal mixed carbonate siliciclastic and carbonate deposits of late barremian to early aptian age from the lusitanian basin portugal are compared with a deep sea succession odp 641 off the coast of portugal the coastal deposits show an abrupt cessation of rudist dominated carbonate deposition marked by an emersion horizon and followed by the deposition of orbitolinid rich marls during the early aptian the subsequent development of the carbonate platform during the late aptian is masked by a hiatus for this time interval shallow water debris deposits of the deep sea succession odp 641 indicate that carbonate production in shallow water areas resume in the early late aptian carbon isotope stratigraphy in combination with available biostratigraphic data is used for intrabasinal correlation and for the correlation of the portuguese with shallow water successions from switzerland france oman and the pacific the correlation reveals that during the early aptian similar changes in their sedimentary patterns occur at the beginning of a marked negative shift of carbon isotope values associated with the global deposition of organic rich black shales in the deep sea oae 1a in all compared sections rudist dominated carbonate deposition is stopped and followed either by orbitolinid rich deposits the deposition of microbial carbonates or by the drowning of the carbonate platform the comparison shows that the deterioration for carbonate platform growth conditions during the early aptian occurred essentially simultaneously at the various localities during this episode the ocean waters were in a preconditioned state of acidification stressing biocalcifying organisms sea level change combined with local effects like elevated nutrient levels and higher temperatures were probably determining the nature of sedimentary change in shallow water environments during the carbonate crisis in the sections studied in portugal the high abundance of orbitolinids overlying rudist limestones indicates that increased nutrient input may have played an important local role among the factors that caused an overall deterioration for carbonate producers during the late early aptian

orographic influences on subtropical stratocumulus the impact of south american orography on subtropical stratocumulus clouds off the peruvian coast is investigated in the context of an atmospheric general circulation model it is found that stratocumulus incidence is significantly reduced when south american orography is removed key to this behavior is a decrease in lower tropospheric stability lts that allows for more frequent stratocumulus destruction through the model s cloud top entrainment instability mechanism the role of orography in enhancing peruvian stratocumulus is as follows within the pbl orography deflects the midlatitude westerly winds equatorward in association with cold air advection and blocking of the low level flow from the continent above the pbl the steep and high south american orography deflects a significant portion of the midlatitude westerlies equatorward this flow sinks along the equatorward sloping isentropes thus promoting subsidence both processes increase lts over the stratocumulus region in further agcm experiments the sensitivity of peruvian stratocumulus to the use of unsmoothed orographic boundary conditions is assessed the results show no significant differences to the control simulation which uses smoothed orography this suggests that in the context of gcms a representation of south american orography more detailed than is generally used has little potential for improving the performance of coupled ocean atmosphere models in the eastern tropical pacific

carbon isotope stratigraphy of early cretaceous urgonian shoal water deposits diachronous changes in carbonate platform production in the north western tethys abstract carbonate platforms are highly sensitive ecological systems that typically show rapid and characteristic response modes to environmental and climatic changes acting both on a regional scale and global scale a widely accepted hypothesis proposes that the late barremian stepwise establishment of the urgonian carbonate platform on the northern tethyan shelf was related to a gradual change from predominantly humid towards more arid greenhouse conditions this climate change resulted in the reorganisation of the carbonate platform ecosystem from heterozoan towards photozoan dominated assemblages and a decrease of organic matter burial in tethyan and boreal basins in order to decipher the palaeoenvironmental and climatic boundary conditions of these major changes in neritic and pelagic settings a precise chronostratigraphy of urgonian carbonate platform evolution is needed here we provide an integrated stratigraphic framework of lower barremian to lower aptian urgonian carbonate platform sections cluses forclaz located at the northern rim of the tethys subalpine chains ese france with special focus on sedimentological analyses and high resolution carbon isotope stratigraphy a characteristic barremian aptian carbon isotope pattern permits precise platform to basin correlation with cyclostratigraphic and ammonite dated pelagic and hemipelagic tethyan sections in the vocontian trough angles combe lambert glaise and umbria marche basin gorgo a cerbara similar to helvetic shoal water settings the carbonate platform in the subalpine chains experienced a gradual transition from heterozoan to photozoan dominated ecosystems this biogenic pattern points to a gradual change of the carbonate platform after the so called early barremian crisis towards an oligotrophic rimmed platform system urgonian limestone formation according to the chronostratigraphy of urgonian carbonate platform evolution in the subalpine chains established here the installation of a photozoan dominated rudist rich platform ecosystem referred to as urgonian limestones sensu stricto occurred at the early late barremian transition the onset of changes in the carbonate production mode heterozoan versus mixed heterozoan photozoan versus photozoan clearly predates the onset of similar lithological changes in the helvetic realm by about 1 0 to 1 2 myr the established chronostratigraphic framework points to a link between the change towards photozoan dominated limestones and fading palaeoenvironmental perturbations related to the mid barremian event which is associated with major faunal turnovers and the onset of cyclic black shale deposition in the central tethyan realm judging from palaeoenvironmental proxies including kaolinite phosphorus and black marl limestone ratios oscillating predominantly humid and relatively arid greenhouse conditions modulated the observed pattern in urgonian carbonate platform production mode and the varying frequencies of black shale deposits in the tethyan and boreal realms transient blooms of the orbitolinid foraminifera palorbitolina lenticularis at the onset of a marked upper barremian positive carbon isotope shift are interpreted to reflect increasing nutrient influx most probably related to accelerated hydrological cycling and or sea level rise these strata do not represent an over regional correlatable lithostratigraphic unit but likely an expression of progressive northern tethyan environmental and oceanographic change possibly related to ontong java large igneous province volcanism in the prelude of oceanic anoxic event 1a oae

variations in apparent mixing efficiency in the north atlantic central water abstract microstructure data from the north atlantic tracer release experiment natre are presented providing detailed profiles of the thermal variance in the upper 360 m of the canary basin for the fall and spring seasons the osborn cox model is used to compute the diffusivity kt the diffusivity for the depth range 240 340 m is found to be 1 0 0 04 10 5 m2 s 1 in the fall and 2 2 0 1 10 5 m2 s 1 in the spring in good agreement with dye inferred diffusivities at similar depths measured turbulent kinetic energy tke dissipation rates were found to be contaminated by hydrodynamic noise so the osborn dissipation method was not used to compute k however data segments for which the tke dissipation rate e was large enough to be unaffected by noise were used to compute the apparent mixing efficiency d the computed d values are used to investigate variations in apparent mixing efficiency with respect to density ratio r and turbulence reynolds number e n2 in an attempt to eluci

coherent structures at the ocean surface in convectively unstable conditions the turbulent boundary layer at the ocean surface has some dynamical similarities to the atmospheric boundary layer1 4 the atmospheric turbulent boundary layer may exhibit not only random fluctuations but also spatially coherent organized motion5 6 thorpe1 conjectured that such organized motion should also be found in the upper ocean boundary layer in convectively unstable conditions here i report on observations made in the tropical atlantic ocean which confirm this view horizontal temperature profiles obtained at a depth of 2 m at night revealed ramp like structures vertical velocity profiles in the upper few metres of the ocean was determined using a free rising profiler and exhibited abrupt changes corresponding to sudden changes in temperature these features are known5 6 to be characteristic of spatially coherent organized motions in turbulent boundary layers

stratigraphy and tectonosedimentary evolution of a late aptian albian carbonate margin the northeastern jebel akhdar sultanate of oman abstract upper aptian albian shallow water carbonates with rudists large foraminifera and calcareous algae are described from northern oman in the northeastern part of the parautochton of jebel akhdar the corresponding lithostratigraphic unit the al hassanat formation is partly a time equivalent of the nahr umr shales of albian p p age which have a wide extent on the arabian craton the al hassanat platform developed in two main phases first during the late aptian early albian the platform was fringing an emerged area central jebel akhdar with a limited extent basinward then during the middle albian the flooding of the central jebel akhdar resulted in an extensive development of the platform and a connection with the nahr umr shelf this sedimentary evolution and its palaeogeographic expressions were mainly controlled by structural patterns extensive uplift and block faulting to the edge of the antecedent early aptian platform with a significant differential subsidence then a sag of the arabian promontory this tectonosedimentary dynamics was related to the migration of the oceanic adjacent tethyan plate and took place during the global geodynamic albian revolution

increased terrigenous influx but no drowning palaeoenvironmental evolution of the tunisian carbonate platform margin during the late aptian during the aptian some carbonate platforms of the sub tropical realm for example on the northern tethys margin or in the gulf of mexico were affected repeatedly by severe perturbations in the carbonate production factory and drowning preferentially during global warming events such as the early aptian oceanic anoxic event 1a and a prominent mid late aptian warming interval these platform growth crises have been explained mainly by strongly increased coastal runoff for example siliciclastics and nutrients in combination with pronounced eustatic sea level rises in the last few years increasing evidence suggests that carbonate platforms of lower latitudes were generally less or even not affected by environmental perturbations during these events this raises the question as to the responsible factors that promoted platform growth or decline in different latitudinal areas in this study upper aptian middle gargasian to uppermost clansayesian inner tropical carbonate ramp deposits of the serdj formation at djebel serdj north central tunisia are studied in detail with regard to microfacies lithology biostratigraphy and chemostratigraphy these data allow reconstruction of the palaeoenvironmental evolution of the tunisian carbonate platform margin and investigation of its response to the prominent mid late aptian warming interval the unusually expanded 600 m thick serdj formation consists of limestones marlstones and siltstones suggesting deposition within mid ramp to inner ramp palaeoenvironments deposits of the mid late aptian are represented by quartz rich platform carbonates and siltstones probably resulting from increased coastal runoff on the tunisian shelf as a response to global warming and accelerated water cycling the siliciclastic input was accompanied by elevated nutrient levels as indicated by a partial decline in the abundance of oligotrophic biota and mass occurrences of orbitolines and green algae carbonate platform drowning during the mid late aptian as reported from the sub tropical realm has not been identified a comparison with other tropical river influenced platforms suggests that none of them drowned during the mid late aptian one important reason might be widespread arid to semi arid climatic conditions within lower latitudes during that time promoting platform growth due to comparably low nutrient runoff

rudists and carbonate platforms in the aptian a case study on biotic interactions with ocean chemistry and climate variations in aptian carbonate platform growth and associated turnover among rudists are reviewed and the results synthesized with evidence for climate change to yield an explanatory model extensive platform growth throughout the atlantic tethys low palaeolatitude pacific seamount belt in the earliest aptian was accompanied by prolific rudist diversification especially among the predominantly aragonitic caprinids occupying platform margins it was ubiquitously interrupted in the mid early aptian in tandem with major perturbations of the global carbon cycle that culminated in oceanic anoxic event 1a although the causal linkages remain contentious platform growth terminated along most of the northern tethyan margin and maybe also in the new world meanwhile lithocodium bacinella or similar microbial encrustations became widespread in lower palaeolatitudes recovery of tethyan platforms in the late early aptian was limited to lower palaeolatitudes caprinid rich platform margin facies again prevailed in central and southern tethyan areas but gave way to those dominated by rudists with a thickened calcitic outer shell layer polyconitids and requieniids in marly successions around iberia the end of the early aptian saw the lazarus style disappearance of caprinids and renewed tethyan platform growth in the late aptian was dominated by calcite rich rudists although rudists remained scarce in the new world until the terminal aptian this study postulates that sea water acidification influenced both the mid early aptian platform debacle and the subsequent late early aptian geographical restriction of platform recovery although in contrasting atmospheric regimes at first it was forced by the increasing atmospheric levels of volcanically derived co2 with mitigation in low latitudes from thermal expulsion of aqueous co2 here termed the kettle effect due to greenhouse warming however subsequent cooling due to drawdown of atmospheric co2 by organic carbon burial could have sustained acidification of platform waters in higher latitudes by reducing the protective kettle effect there caprinid susceptibility to such assaults may have been as much due to exposure on their preferred outer platform habitats as to their mineralogy the increased calcite aragonite ratio among rudists through the aptian resulted largely from this taxonomic turnover

drowning events development and demise of carbonate platforms and controlling factors the late barremian early aptian record of southeast france abstract in provence and languedoc se france four drowning events were identified in platform carbonates of late barremian bedoulian age their timing referred to ammonite zones or subzones is as follows 1 late barremian d1 at the gerhardtia sartousiana imerites giraudi boundary 2 middle bedoulian d2 at the deshayesites weissi deshayesites deshayesi boundary 3 mid late bedoulian d3 in correspondence with the roloboceras hambrovi subzone and 4 late bedoulian d4 at the deshayesites grandis dufrenoya furcata transition notwithstanding their relatively wide regional lateral continuity the depositional hiatus linkage with exposure paleobathymetric range and offset and geographical extent of drowning discontinuities are not uniform the late barremian drowning d1 is marked either by the development of a permanent intra shelf basin with ammonites associated with the re organization of platform basin relationships or by the wide extent of palorbitolina heteraster facies which develops to the detriment of the antecedent rudist facies the drowning event is followed by platform recovery during the early bedoulian but the corresponding development of shallow water carbonates is subsequently interrupted by the emergence of an uplifted bulge trending sub parallel to the provence languedoc margin the middle bedoulian drowning d2 is concurrent with the sealing of the antecedent paleotopography and the wide development of palorbitolina facies then bioclastic and coral facies tend to recover the mid late bedoulian drowning d3 is characterized by an overall deepening phase with ammonite bearing marly facies or cherty limestones shallow bioclastics being locally present the late bedoulian drowning d4 records the deposition of deep water marls evidence is lacking that global sea level changes or transgressive regressive cycles had a significant impact on drowning events and some evidence that changes in temperature and productivity of the ocean may have contributed to these phenomena in conjunction with other factors though distension fault activity is regarded as a major controlling factor for the origin of the late barremian deepening event its associated paleogeographic re organization ensuing emergence of the provence languedoc marginal bulge and its subsequent detumescence coeval with the middle bedoulian drowning associated changes in facies types from rudist to palorbitolina reflect sea water deepening coupled with trophic modifications as agents of differential subsidence tectonic phenomena are also testified by the contrasting regional patterns of paleobathymetric offsets combined with drowning events they are a clue for understanding thickness changes and coeval modifications in the overall orientation of the progradational polarity of the platform system towards the adjacent basinal areas environmental changes essentially the two main oae1a subevents are regarded as significant agents of the mid late and late bedoulian drownings whereas tectonic processes are also involved in the corresponding deepening however the effects of the oae events on the functioning of the shallow carbonate factory are poorly understood and still need to be investigated the rise in atmospheric carbon dioxide pressure and as a consequence the reduction of the calcification potential of benthic organisms both reported in the literature are not clearly reflected in the composition of the biota aragonite dominated organisms such as caprinid rudists thrive throughout the bedoulian the role of acidification in platform demise is therefore questionable

improved time control on cretaceous coastal deposits new results from sr isotope measurements using laser ablation sr isotope measurements of unaltered oyster shell calcite using laser ablation multi collector icpms techniques represent a powerful tool capable of establishing a chronostratigraphic framework for fossil near shore deposits this approach is tested on two shoal water successions from the portuguese algarve and lusitanian basins covering late barremian to albian strata 87 sr 86 sr values derived from low mg calcite of oyster shells fluctuate between 0 70717 0 00001 and 0 70746 0 00002 absolute values as well as stratigraphic trends match well with the global open marine seawater signal the new sr isotope results in combination with existing bio and chemostratigraphic records allow for identification of an early aptian biocalcification crisis at both studied localities and show that this event has severely affected coastal environments along the evolving atlantic siliciclastic intervals in the algarve section are interpreted as near shore equivalents of enhanced detrital shedding into shelf and deep sea environments as a consequence of increased chemical weathering rates during humid climate episodes

entrainment and turbulence in saline underflow in lake ogawara under certain tidal conditions a saline underflow originating in the pacific ocean moves into lake ogawara japan the underflow consists of a uniform saline bottom layer that is slightly warmer than the ambient and an interfacial shear layer in which the velocity and density are decreased within the experimental area the underflow is confined to a channel approximately 1 km wide and is essentially two dimensional the underflow had a bulk richardson number defined in terms of the mean properties between 1 and 2 the rate of entrainment into the bottom layer was calculated using two distinct methods the first method used the change in the maximum salinity of the underflow measured at two stations along the path of the underflow to infer the amount of ambient water entrained the second method made direct measurements of vertical mass fluxes with a profiler the agreement between the two methods was excellent the measured entrainment coefficients were consistent with the derived entrainment law the turbulent structure of the flow was mapped for a 3 h quasi steady period of the flow turbulence is predominantly generated on the bottom boundary and is transported vertically to the density interface where it leads to mixing

diurnal cycle of surface winds over the subtropical southeast pacific 1 the diurnal variability of surface winds over the se pacific is characterized with quikscat data for years 2000 2006 the twice daily satellite passes occur around 0600 and 1800 lt referred to as am and pm respectively the pm am wind difference maximizes in a region between 20 s and 30 s extending from the chilean coast up to 75 w this difference is mostly meridional along the coast with seasonal variation characterized by summertime weakening of the morning winds the observational analysis is supplemented with mesoscale model results for december 2003 they show that the coastal zonal flow increases between 0600 and 1200 local time lt but then decreases in the next 6 hours which explains the absence of an onshore component in the quikscat pm am difference additional model diagnostics show that in this region the diurnal cycle hodographs are more simple and larger above the marine boundary layer mbl than at the surface evaluation of the momentum and temperature budgets reveals the importance of the diurnal cycle of vertical velocity coupled with the thermal structure in controlling the diurnal cycle of the low level winds around 1300 lt coastal subsidence maximizes in a layer sloping from 1000 m at 36 s to 3000 m at 22 s inducing the development of a coastal trough at the surface during the night the passage of a high pressure perturbation reverses the surface meridional pressure gradient force inducing the decrease of the coastal meridional winds these results stress the important role played by the dynamics of the low troposphere above the mbl e g the heating of the andes cordillera to the east in controlling the wind diurnal cycles near the surface