upheavals during the late maastrichtian volcanism climate and faunal events preceding the end cretaceous mass extinction abstract the late maastrichtian was a time of major climate evolution and extinction extremes rapid climate warming of 2 3 c in intermediate waters between 69 5 and 68 ma top c31r to base c30n accompanied maximum evolutionary diversification 43 increase zone cf5 to low cf4 in planktic foraminiferal history followed immediately by a cluster of extinctions during the last 250 ky of the maastrichtian c29r zones cf2 cf1 rapid warming of 4 c in intermediate waters and 8 c on land resulted in high stress environments ending in the mass extinction the end cretaceous mass extinction is recorded in sediments between massive deccan lava flows in india and attributed to so 2 and co 2 outgassing leading to ocean acidification the early late maastrichtian climate and faunal upheavals are not well known here we document the faunal similarities of both events from the indian ocean through the tethys and gulf of mexico results show that both extreme warm events are marked by high stress environments characterized by decreased abundance and diversity of large specialized species and dwarfing high abundance of low oxygen tolerant species and disaster opportunist surface dweller guembelitria blooms the similarity in faunal response with the deccan warming of c29r cf2 cf1 suggests that volcanism was also responsible for the warming and faunal upheaval of the early late maastrichtian major volcanic activity at this time included the onset of deccan eruptions and ninetyeast ridge volcanism the role of the chicxulub impact appears to have been a contributing rather than causal factor in the mass extinction

paleoclimate and paleoceanography over the past 20 000 yr in the mediterranean sea basins as indicated by sediment elemental proxies abstract marine sediments record paleoenvironmental changes over time through variations in major and trace element concentrations the main objective of this paper is to review such changes in the mediterranean sea basins over the last 20 ka using the inorganic chemistry and mineralogy of marine sediment records elemental ratio proxies that are mostly used are discussed and the uncertainties involved in using them for paleoclimate and paleoceanographic reconstructions are evaluated the focus on the mediterranean region is based on the sensitivity of this region to global climate changes due to its semi enclosed nature the elemental ratios that have been particularly useful for reconstructing terrigenous inputs into the mediterranean have been ti al and zr al ratios as proxies for eolian dust input and mg al k al and rb al ratios as proxies for fluvial input redox sensitive elements e g u mo v co ni cr have provided reliable reconstructions of oxygen conditions at the time of deposition some of these elements are also particularly susceptible to post depositional remobilization and record diagenetic processes instead of the original environmental signatures regarding productivity fluctuations most of the paleoproductivity reconstructions are based on the abundance of barite and ba excess algorithms the biogeochemistry of ba is however not fully understood and mechanisms for barite precipitation in the water column are not yet known two case studies are presented the eastern mediterranean sapropel s1 deposited between 10 8 and 6 1 cal ka bp and the westernmost mediterranean paleoclimate record over the last 20 ka

maastrichtian oil shale deposition on the southern tethys margin egypt insights into greenhouse climate and paleoceanography abstract a comprehensive set of organic and inorganic geochemical proxies clay mineralogy and molecular fossils are presented from two biostratigraphically well dated oil shale horizons of egypt within the upper cretaceous duwi and dakhla formations the studied oil shales were deposited within intracratonic sedimentary basins in a broad northern african epeiric sea calcareous nannofossil biostratigraphy indicates that the oil shales range from early to late maastrichtian in age covering nannofossil zones uc18 uc19 and uc20 the oil shales contain smectite and kaolinite as the main clay minerals that formed by weathering of precursor basement rocks the relative abundances of clay minerals and several geochemical proxies e g c value cia ga rb rb sr and sr cu along with the occurrence of warm water nannofossil taxa demonstrate that the maastrichtian oil shales accumulated under a warm arid to humid greenhouse climate during a general maastrichtian cooling trend this episode of oil shale deposition in egypt coincided with the first potential imprint of the global warming that has been recorded during early to late maastrichtian times 70 6 67 7 ma elevated eolian terrigenous input was recorded within the duwi formation oil shales shown by high ti al si al zr al and low la lu ratios the duwi formation environment was characterized by enhanced salinity and a stratified water column compared to that of the dakhla formation shown by elevated values of the gammacerane index tetracyclic terpane carotene and sr ba ratio the caco3 content and carbonate siliciclastic ratio indicate that the dakhla formation oil shales were deposited during a relative sea level rise in a deeper marine setting than the duwi formation oil shales the data further imply a wind driven upwelling scenario of nutrient input s that simulated primary production and increased organic matter fluxes thus paleoclimate and paleoceanography had a considerable impact on organic matter enrichment

depositional environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china abstract the non marine santanghu basin in northwest china hosts one of the richest and thickest permian lacustrine source rock intervals in the world conventional oil in jurassic sandstone reservoirs and tight oil in the tuffaceous permian tiaohu formation were sourced from mudrocks in the underlying second member of lucaogou formation which also have tight oil potential proved by recent commercial discoveries based on inorganic and organic geochemistry organic petrography and stable isotope geochemistry the depositional environment and the tight oil potential of the second member of permian lucaogou formation were investigated the data imply a gradual evolution of the depositional environment from a stratified saline to a freshwater lake the succession can be subdivided into a lower middle and an upper unit each characterized by decreasing water salinity high bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria water column stratification accelerated the activity of methanothrophs as indicated by low 13c values of hopanes biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of prasinophytae compared to other algae with decreasing salinity enhanced terrigenous organic matter input appeared during periods of high freshwater inflow low total organic carbon toc contents in the lower unit are most likely caused by rapid sedimentation rate high bioproductivity and excellent preservation conditions resulted in high toc contents in the middle unit terrigenous organic matter input increased together with fresh water inflow in the upper unit resulting in high toc values during periods of possibly low sedimentation rates in a deep water column the samples of the second member exhibit a good to very good potential to generate conventional oil high toc and extractable organic matter yields together with the thickness of the fine grained sediments show that the middle and upper units of the second member of lucaogou formation hold significant tight oil potential mineralogical composition of this dolomite rich shale with respect to abundance of brittle minerals including quartz and carbonates and rare clay testifies a good tight oil potential

coal and oil shale of early carboniferous age in northern canada significance for paleoenvironmental and paleoclimatic interpretations abstract lower carboniferous mississippian coal beds and oil shale occur at several locations in northern canada in the northern yukon territory coal of semi anthracite anthracite rank r 0 max 2 72 4 03 occurs in the kayak formation in the british mountains and at hoidahl dome near the headwaters of blow river farther south in the liard basin northwest territories coals of high volatile bituminous rank r 0 max 0 67 0 80 are known to occur in the mattson formation in the arctic islands thicker beds of the emma fiord formation the oldest unit in the sverdrup basin contain thin coal seams and oil shale on devon island near the southern edge of the basin and on axel heiberg and ellesmere islands on the north side of the basin organic matter in the devon island section is at a low maturity level r 0 m 0 26 0 50 whereas that from ellesmere and axel heiberg has reached the level of meta anthracite r 0 max 5 0 depositional environments for these carbonaceous sediments were different the coal bearing kayak strata accumulated in a coastal plain setting overlain transgressively by younger marine beds the mattson coal beds appear to have formed in a prograding delta but coal and oil shale in the emma fiord were deposited in lacustrine environments in a rift basin these canadian occurrences resemble penecontemporaneous deposits in svalbard and elsewhere adjacent to the present day arctic ocean they formed at low latitudes where conditions were favourable for the preservation of carbonaceous matter prior to the opening of the arctic ocean basin in mesozoic times sites of the mainland were undoubtedly closer to sites in the arctic islands than they are today

interannual and decadal cycles in river flows of southeastern south america abstract the time series of annual streamflow of four rivers in southeastern and south central south america the negro paraguay parana and uruguay rivers for the period 1911 93 are analyzed application of the multitaper method shows that the following features are significant at the 95 level 1 a nonlinear trend 2 a near decadal component and 3 interannual peaks with enso timescales the trend and near decadal components are most marked in the two more central rivers the paraguay and parana with enso timescale variability most pronounced in the negro and uruguay rivers in the southeast composites of sst are made for each of the statistically significant oscillatory components of river flow by reconstructing each component using singular spectrum analysis these composites confirm the influence of enso on the streamflow variability of the negro and uruguay rivers with el nino associated with enhanced streamflow on the decadal timescale high river runoff is associated with anomalously coo

daytime heat transfer processes related to slope flows and turbulent convection in an idealized mountain valley abstract the mechanisms governing the daytime development of thermally driven circulations along the transverse axis of idealized two dimensional valleys are investigated by means of large eddy simulations in particular the impact of slope winds and turbulent convection on the heat transfer from the vicinity of the ground surface to the core of the valley atmosphere is examined the interaction between top down heating produced by compensating subsidence in the valley core and bottom up heating due to turbulent convection is described finally an evaluation of the depth of the atmospheric layer affected by the slope wind system is provided

an objective methodology for identifying oceanic provinces an objective methodology for identifying oceanic provinces in hydrographic data is presented although the technique is sufficiently general so as to be applicable to a variety of data sets the sub and near surface temperature t and salinity s of the atlantic ocean were measured on two atlantic meridional transect amt cruises covering approximately 100 of latitude and 50 of longitude the cruises covered the boreal autumn and austral spring amt 1 and the boreal spring and austral autumn amt 2 during 1995 and 1996 respectively there are distinct patterns of change in t s from 50 n to 50 s for both sub and near surface measurements although this study concentrates primarily on the latter near surface density t encapsulates the variations in t s the position of localized extrema in the t first spatial derivative locates the change in bulk t s properties and hence the extent of a physical province the province identification methodology is validated by comparing the results obtained using in situ density a mixed layer depth space series constructed from expendable bathythermograph profiles and climatological density additional validation of the methodology is achieved by intercomparing different in situ data sources between the two cruise periods the comparisons show the near surface measurements are indicative of the mixed layer and that the amt 1 and amt 2 cruises are representative of the corresponding climatological months a simple scheme for investigating how far a province extends away from the cruise track uses the climatological data in concert with a t s description of each province from the amt along track observations to produce a two dimensional map of the geographical extent of each province although exceptions between the province extents and the basic circulation of the atlantic ocean occur the majority of the provinces have the correct shape and extent that is their edges follow the flow fields associated with the currents that bound them and they extend over an appropriate area the province identification methodology is sensitive and reliable enough to investigate temporal differences in oceanic provinces which means it might be useful for parameterizing global budget calculations in numerical models

a high resolution holocene record on the southern brazilian shelf paleoenvironmental implications abstract a high resolution multi proxy record has been used to determine the environmental changes during theholocene on the southern brazilian shelf present oceanographic conditions reveal wind and freshwaterinput as the determinants of short term productivity changes in the study area magnetic susceptibilityand grain size variations together with proxies of productivity organic carbon carbon accumulationrate ba sr and ca content ba al ba ti and al ti ratios were analyzed and compared with proxies ofredox condition v ti ratio terrigenous input fe ca and ti ca ratios as well as other element ti ratios to evaluate the paleoceanographic and paleoclimatic changes over the period the core covers a time interval of about 7650 years with sedimentation rates varying from 0 025 to0 250 cma 1 which represent time intervals of between 8 and 80 a per sample there is a clear change inthe sedimentation rate at about 2800 b p all grain size and elemental results indicate the occurrence of conspicuous changes between 5200 and5000 cal b p as well as between 3000 and 2800 cal b p a comparison of the results with the palyno logical information available from the adjacent continental areas suggests that the sedimentary changesin this last interval may be correlated with the onset of modern climatic conditions in south america andespecially with the onset of the plata plume water a water mass that carries cold less saline waterstowards the north however minor changes are observed at ca 1500 b p and are correlated with anincrease in the atmospheric humidity furthermore a time series analysis undertaken using severalproxies indicated the occurrence of sub milankovitch cycles which may be compared with thosereported worldwide 2008 elsevier ltd and inqua all rights reserved

brazil malvinas frontal system as seen from 9 years of advanced very high resolution radiometer data 1 surface thermal fronts in the southwestern atlantic swa ocean are examined using 9 years 1987 1995 of advanced very high resolution radiometer data fronts are detected considering a gradient based edge detector sea surface temperature gradients are calculated from 4 km resolution 5 day composite images covering the western argentine basin south of 30 s variability in the position and intensity of the fronts from seasonal to interannual timescales is characterized in six regions including different parts of the brazil current front bcf and the subantarctic front saf shelf break brazil sb b brazil malvinas collision bm c brazil current overshoot bc o shelf break malvinas sb m malvinas return flow mrf and falkland escarpment fe fronts in the sb b sb m mrf and fe regions are controlled by the bathymetry in the bm c region the bcf and saf appear to merge as a single front this front does not present large seasonal north south excursions as previously described though it pivots seasonally around a fixed point located approximately at 39 5 s 53 5 w changing its orientation from n s in winter to nw se in summer consequently on average the front intersects the 1000 m isobath at 38 30 s in summer and north of 37 s in winter in the bc o region the bcf has a u shape centered at 53 w the intensity of the fronts in each region except in the fe region presents large seasonal variability in the sb b bm c and bc o regions the frontal intensity is highest 0 35 c km during austral winter the annual components explain 83 67 and 71 of the total variance respectively in the sb m and mrf regions the saf is most intense 0 25 c km in summer and fall the annual component of the intensity fluctuations explains 29 and 38 of the total variance respectively in the fe region the annual component of frontal intensity explains only 17 of the variability in the six regions important interannual variability is found the zapiola rise centered at 45 s 43 w appears as a gradient free region closed planetary potential vorticity contours in this area suggest it is dynamically isolated

the antarctic dipole and its predictability this study investigates the nature of interan nualvariability ofantarcticseaiceanditsrelationshipwith the tropical climate we nd that the dominant interan nual variance structure in the sea ice edge and surface air temperature elds is organized as a quasi stationary wave which we call the antarctic dipole adp it is charac terized by an out of phase relationship between the ice and temperature anomalies in the central eastern pacic and atlantic sectors of the antarctic the dipole consists of a strong standing mode and a weaker propagating motion within each basin s ice eld it has the same wavelength as the antarctic circumpolar wave acw and dominates the acw variance the dipole is clearly associated with tropical enso events it can be predicted with moderate skill using linear regression involving surface temperature two to four months ahead the prediction performs better in extreme warm cold years and best in la ni na years

geochemical disturbance and paleoenvironmental changes during the early toarcian in nw europe the early toarcian oceanic anoxic event oae is associated with a rapid and severe environmental change whose causes are still a matter of debate a new paleoenvironmental interpretation is proposed based on a multidisciplinary dataset chemical mineralogical and paleontological obtained from a borehole drilled by andra french national radioactive waste management agency in the lower toarcian of the eastern paris basin france during the earlymost toarcian tenuicostatumzone the presence ofwell oxygenated sea water is reflected by an abundant and diverse fauna alongwith paleoredox proxies u al mo al and v al typical of oxidizing conditions associated with predominant mechanical weathering on the continent at the base of the serpentinum zone an important paleoenvironmental change is marked by an initial phase of organic matter enrichment 12 toc during the negative shift of 13c carbon isotope excursion cie euxinic anoxic conditions indicated by cobalt enrichment and the development of framboidal pyrite lead to the disappearance of the benthic and pelagic fauna and alloworganic matter to be preserved in the sediments at this time the lowconcentration of paleoproductivity proxies cd p ni and zn suggests weak chemical weathering on the continent due to a rather arid climate low concentrations of sr and coccoliths are due to an input of fresh water probably coming from the arctic through the laurasian seaway thus the isolation of the paris basin from the tethyan realm and the influx of freshwater favour haline stratification and the preservation of organic matter following the cie oxygen concentration gradually increases up to amaximumflooding surface dated as coevalwith the serpentinum zone elegantulum subzone paleoproductivity proxies indicate a weak primary productivity the top of the lower toarcian is characterized by a second enrichment in organic matter 12 toc due to an important input of nutrients this enhanced primary production generates euxinic anoxic conditions in the sediment and in part of the water column leading to a high enrichment in paleoredox proxies mo u v co and causing the sudden disappearance of the benthic fauna and a progressive decline of the pelagic fauna the metal enrichment is related to intense chemical weathering on the continent due to a more humid climate

changes in the water column structure and paleoproductivity in the western south atlantic ocean since the middle pleistocene evidence from benthic and planktonic foraminifera abstract based on an integrated approach planktonic and benthic foraminifera and stable isotopes carried out in two cores collected on continental slope of santos basin central brazil the paleoceanographic oscillations of the last 570 ka are documented benthic foraminiferal isotopic records coupled with foraminiferal assemblages analyses show 100 ky long term oscillation in the superficial productivity along the middle pleistocene these long term oscillations are interrupted by 30 ky short term changes that mark the transition periods of higher productivity 425 400 ka and 190 160 ka and lower 290 260 ka the planktonic foraminifera species allowed the recognition of changes in the water column structure and in the superficial productivity observed in the area those changes in the superficial waters promoting different organic matter export to the sea floor might have resulted in changes on the more abundant and phytodetritus opportunist benthic taxa epistominella exigua and alabaminella weddellensis

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

vertical structure of mesoscale eddies in the eastern south pacific ocean a composite analysis from altimetry and argo profiling floats 1 the mean vertical structure of mesoscale eddies in the peru chile current system is investigated by combining the historical records of argo float profiles and satellite altimetry data a composite average of 420 526 profiles acquired by argo floats that surfaced into cyclonic anticyclonic mesoscale eddies allowed constructing the mean three dimensional eddy structure of the eastern south pacific ocean key differences in their thermohaline vertical structure were revealed the core of cyclonic eddies ces is centered at 150 m depth within the 25 2 26 0 kg m 3 potential density layer corresponding to the thermocline in contrast the core of the anticyclonic eddies aes is located below the thermocline at 400 m depth impacting the 26 0 26 8 kg m 3 density layer this difference was attributed to the mechanisms involved in the eddy formation while intrathermocline ces would be formed by instabilities of the surface equatorward coastal currents the subthermocline aes are likely to be shed by the subsurface poleward peru chile undercurrent in the eddy core maximum temperature and salinity anomalies are of 1 c and 0 1 with positive negative values for aes ces this study also provides new insight into the potential impact of mesoscale eddies for the cross shore transport of heat and salt in the eastern south pacific considering only the fraction of the water column associated with the fluid trapped within the eddies each ce and ae has a typical volume anomaly flux of 0 1 sv and yields to a heat and salt transport anomaly of 1 3 1011 w and 3 8 103 kg s 1 respectively

palaeoclimatic evolution during eocene and its influence on oil shale mineralisation fushun basin china the fushun basin is a small explored coal and oil shale bearing cenozoic fault basin in the liaoning province northeast china the basin mainly consists of eocene swamp to lacustrine deposits of the guchengzi to xilutian formation and contains the biggest opencast oil shale mine in asia this mine has provided an ideal opportunity to undertake palaeoclimate reconstruction in this basin based on a single geological profile and the analyses of 93 samples using various approaches namely field geological observation clay mineralogical and geochemical sr ba sr cu stable c and o isotope analyses all of which were compared with palaeobotanical data the eocene climate of fushun basin evolved from warm temperate to north subtropical and generally changed from warm humid to subhumid semiarid paleoclimatic and geochemical parameters shows that the very warm and humid climate during jijuntun formation increased the initial productivity of lake water and caused a steady stratification of the lake water then caused oxygen lack in the bottom of water productivity of the lake provides the mean origin of organic matters for oil shale formation and steady anoxic environment is beneficial for the conservation of organic matters

statistics of brazil current rings observed from avhrr 1993 to 1998 1 a 6 year time series of sea surface temperature fields derived from noaa polar orbiter avhrr 5 day composites is used to estimate the lifetime size and trajectory of 43 warm core rings shed by the brazil current at the southwestern atlantic region in a consistent fashion for the first time ring lifetimes range from 11 to 95 days and are not bi modal as is the case for the gulf stream anticyclones translational speeds range from 4 2 to 27 2 km day with a mean value of 13 1 km day after formation rings are mostly elliptical with a mean major radius of 126 50 km and a minor radius of 65 22 km none of the rings seem to last more than four months in the region an attempt to explore possible connections between ring shedding variability and the antarctic dipole is also addressed

eddy train encounters with a continental boundary a south atlantic case study satellite altimetry suggests that large anticyclonic eddies rings originating from the agulhas current retroflection occasionally make their way across the entire south atlantic ocean what happens when these rings encounter a western boundary current in this work interactions between a train of nonlinear lenslike eddies and a southern hemisphere continental boundary are investigated analytically and numerically on a b plane the train of eddies is modeled as a steady double frontal zonal current with the same vorticity and transport as the eddies themselves the continental boundary is represented by a vertical wall which is purely meridional in one case and is tilted with respect to the north in another case it is demonstrated analytically that the eddy wall encounter produces an equatorward flow parallel to the continental wall thus suggesting a weakening of the transport of the associated poleward flowing western boundary current upstream of the encounter zone and unchanged transport downstream a large stationary eddy is established in thecontactzonebecauseitsb inducedforceisnecessarytobalancetheotherforcesalongthewall thesizeof this eddy is directly proportional to the transport of the eddy train and the meridional tilt of the wall these scenarios are in good agreement with results obtained numerically using an isopycnal bleck and boudra model

late cretaceous winter sea ice in antarctica the late cretaceous is considered to have been a time of greenhouse climates although evidence from maastrichtian sediments for rapid and significant sea level changes suggests that ice sheets were growing and decaying on antarctica at that time there is no direct geological evidence for glaciation but we present palynomorph records from seymour island antarctica that may suggest maastrichtian sea ice the dinoflagellate cyst impletosphaeridium clavus is dominant we propose that its profusion may signify the accumulation of resting cysts from dinoflagellate blooms related to winter sea ice decay prior to the cretaceous paleogene transition i clavus decreased dramatically in abundance we link this with climate warming terrestrial conditions inferred from pollen and spore data are consistent with our climate interpretations based on i clavus together with 18 o values from macrofossils these data and our interpretation support the presence of ephemeral ice sheets on antarctica during the latest cretaceous highlighting the extreme sensitivity of this region to global climate change

contrasting compositions of saharan dust in the eastern atlantic ocean during the last deglaciation and african humid period abstract during the african humid period ahp much of the modern hyperarid saharan desert was vegetated and covered with numerous lakes in marine sediments off northwestern africa the ahp is represented by markedly reduced siliciclastic sediment flux between 12 3 and 5 5 ka changes in the origin of this terrigenous sediment fraction can be constrained by sediment chemistry and radiogenic isotope tracers at ocean drilling program odp site 658 hole c 20 44 95 n 18 34 85 w 2263 mbsl the neodymium nd isotope composition of terrigenous detritus shows little variability throughout the last 25 kyr indicating that the contributing geological terranes have not changed appreciably since the last glacial period in contrast there were large and abrupt changes in strontium sr isotope ratios and chemical compositions associated with the ahp during which 87 sr 86 sr ratios were markedly less radiogenic and sediments show higher chemical indices of alteration we show that sediment geochemical changes during the ahp cannot be attributed to changes in the source terranes physical sorting or intensity of chemical weathering the low 87 sr 86 sr and high sr concentrations of ahp age samples also conflict with the interpretation of increased fine grained fluvially derived sediments we propose that the most significant compositional changes at odp 658c are due to the addition of an aluminosilicate component that has a highly altered major element signature but is enriched in soluble elements like sr and magnesium mg compared to aluminum al and has low 87 sr 86 sr relative to local terrigenous source areas we interpret these characteristics to reflect authigenic sediment supply from extensive north african paleolake basins that were prevalent during the ahp

early to late maastrichtian environmental changes in the indian ocean compared with tethys and south atlantic abstract planktic foraminiferal analysis including species populations diversity trends high stress indices and stable isotopes of the latest campanian through maastrichtian in the south atlantic tethys and indian oceans reveal four major climate and faunal events that ended with the cretaceous paleogene k pg formerly cretaceous tertiary k t mass extinction the prelude to these events is the late campanian cooling that reached minimum temperatures in the earliest maastrichtian base c31r correlative with low primary productivity and species diversity event 1 begins during the persistent cool climate of the early maastrichtian lower c31r when primary productivity rapidly increased accompanied by rapid species originations attributed to increased nutrient influx from increased upwelling erosion during the sea level fall 70 6 ma and ninety east ridge volcanism during event 2 upper c31r to lower c30n climate rapidly warmed by 2 3 c in deep waters and peaked at 22 c on land primary productivity remained high and diversification reached maximum for the entire cretaceous we attribute this climate warming to intense ninety east ridge volcanic activity beginning 69 5 ma accompanied by rapid reorganization of intermediate oceanic circulation enhanced greenhouse conditions due to the eruption of deccan phase 1 in india resulted in detrimental conditions for planktic foraminifera marking the end of diversification global cooling resumed in event 3 c30n species diversity declined gradually accompanied by dwarfing decreased large specialized species increased small ecologically tolerant taxa and ocean acidification event 3 is mainly the result of enhanced weathering and volcanogenic co2 adsorption by the oceans during the preceding warm event 2 that led to cooling and lower ph in the surface ocean event 4 marks the last 250 kyr of the maastrichtian c29r which began with the largest deccan eruptions phase 2 that caused rapid climate warming of 4 c in deep waters and 8 c on land acid rain and ocean acidification leading to a major carbonate crisis preceding the k t mass extinction

climate model predictions for the latest cretaceous an evaluation using climatically sensitive sediments as proxy indicators to date many general circulation model gcm experiments have failed to reproduce the warm high latitude temperatures suggested for the cretaceous by geological proxy climate indicators especially for the northern hemisphere and within continental interiors the vast majority of these proxies are biologically based and it is important to determine whether alternative sedimentologically based proxies indicate similar cold biases in models therefore we have performed an evaluation of the very latest generation of climate model predictions for terrestrial sites using climatically sensitive sediments as palaeoclimate indicators evidence from the geological record comprising coal peat evaporites bauxite and laterite deposits are portrayed on a series of palaeoclimate data maps these are then compared with the global distributions of potential deposits generated from model simulations of the maastrichtian using versions of the hadley centre climate model the maastrichtian was chosen because of the greater range and sophistication of gcms adapted for its climate simulation and sediment prediction than for other cretaceous stages this thus represents the first attempt at comparing such state of the art models to lithological climate indicators and quantifying their relative performances for peat coal there is generally good correspondence between maastrichtian model predictions for predicted potential deposits and the observed record for evaporites there is also very close agreement between predictions by the models and the geological record minor differences between the individual model versions resulting from their differing levels of atmospheric co2 and the different palaeogeographical representations of intracontinental seaways in the northern hemisphere for bauxites and laterites the models predict less than half of the documented deposits successfully portraying equatorial accumulations but omitting the majority of mid to high latitude deposits the main discrepancy is therefore identified as the failure of all models to predict bauxite and laterite deposits corresponding with recorded accumulations within the mid to high latitudes of europe and asia in many cases the effects of co2 have minimal impact on the skill of model prediction however for evaporite distributions the low co2 model is appreciably worse in general the best match across the geological data and models is achieved by the simulation with open northern hemisphere seaways overall these results confirm those inferred from biological proxies showing that climate models have a serious cold bias in high latitudes and continental interiors during the cretaceous and that the latest generation of climate models still produces results which are incompatible with the geological data levels of atmospheric co2 and uncertainties in palaeogeography cannot explain the discrepancy the cold bias is common to many climate models and suggests that a process or mechanism is poorly represented or omitted in the current generation of climate models or that we are failing to recognise a major boundary condition change in the cretaceous if the former this implies that we may be underestimating the extent of extreme future climate change at high latitudes and in continental interiors

the trace metal content of recent organic carbon rich sediments implications for cretaceous black shale formation organic carbon rich sediments are enriched in several redox sensitive and stable sulfide forming trace metals tm and form an important sink in global tm cycles in today s ocean such sediments are deposited in coastal upwelling areas like those in the gulf of california off peru or off the namibian coast and euxinic basins like the black sea in an attempt to distinguish both environments by their specific tm patterns some important conclusions may be drawn 1 the tm enrichment seen in both environments broadly is rather similar 2 upwelling sediments are often enriched in cd and p and depleted in co and mn 3 sapropels have a tendency towards higher enrichments in ba and mo s re as cu ni sb and fe reflecting the strong sulfidation in an anoxic water column 4 upwelling systems cover a broad range of environmental settings where the steepness of the slope the proximity of h2s to the sediment seawater interface and the intensity of bio accumulation and regeneration play an important role for tm accumulation 5 the tm content of anoxic basins is mainly controlled by tm availability in the water column and sedimentation rate 6 enhanced bio productivity is the main switch turning an oxygenated into an anoxic environment cretaceous black shales oae 2 exhibit tm signatures of both coastal upwelling areas and sapropels the strong enrichments in cd mo tl v cu ni bi and sb demonstrate that bio accumulation and presence of h2s in the water column and associated sulfidation processes persisted during this time interval in large parts of the proto atlantic the usefulness of ba as a paleoproductivity proxy is obscured by diagenesis the extreme accumulation in ag and zn requires either an additional tm source for instance hydrothermal input or a different tm seawater composition during the cretaceous the geochemical data suggest that the major driving force for the widespread occurrence of c t black shales seems to be the increase in volcanic activity and associated co2 input throughout the cretaceous the ocean atmosphere system operated in a mode different from today during this time interval after conversion of the nutrient co2 into organic matter the system switched back into the normal operational mode

latitudinal temperature gradients and high latitude temperatures during the latest cretaceous congruence of geologic data and climate models a major challenge in paleoclimatology is disagreement between data and models for periods of warm climate data generally indicate equable conditions and reduced latitudinal temperature gradients while models generally produce colder conditions and steeper latitudinal gradients except when using very high co2 here we show congruence between temperature indicators and climate model output for the cool greenhouse interval of the latest cretaceous maastrichtian using a global database of terrestrial and marine indicators and fully coupled simulations with the community climate system model version 3 in these simulations we explore potential roles of greenhouse gases and properties of pre anthropogenic liquid clouds in creating warm conditions our model simulations successfully reproduce warm polar temperatures and the latitudinal temperature gradient without overheating the tropics best fits for mean annual temperature are simulations that use 6 preindustrial levels of atmospheric co2 or 2 preindustrial levels of atmospheric co2 and liquid cloud properties that may reflect pre anthropogenic levels of cloud condensation nuclei the siberian interior is problematic but this may relate to reconstructed elevation and the presence of lakes data and models together indicate tropical sea surface temperatures 5 c above modern an equator to pole temperature difference of 25 30 c and a mid latitudinal temperature gradient of 0 4 c per 1 latitude similar to the eocene modified liquid cloud properties allow successful simulation of maastrichtian climate at the relatively low levels of atmospheric co2 indicated by proxies and carbon cycle modeling this supports the suggestion that altered properties of liquid clouds may be an important mechanism of warming during past greenhouse intervals

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

sedimentary corg p ratios paleocean ventilation and phanerozoic atmospheric po2 the corg p ratios of organic rich facies tocn1 exhibit considerable variation through the phanerozoic from b10 1 in the permian phosphoria formation to n1000 1 in some devonian black shales relative to the composition of phytoplankton c p 106 1 which provide the bulk of organic c and p to organic rich marine sediments the range of phanerozoic sedimentary corg p ratios largely reflects the influence of benthic redox conditions on diagenetic pathways of c and p remobilization enhanced preservationoforganiccatlowerredoxpotentials combinedwithenhancedsedimentaryretentionofremineralizedorganicpathigher redox potentials results in a strong relationship between benthic redox conditions and sedimentary corg p ratios the strong secular coherence of the phanerozoic corg p record i e limited variation within narrow time slices suggests that these ratios are controlled primarily by factors influencing benthic redox conditions on a global scale such as atmospheric po2 inversion and scaling of the phanerozoic corg p record yields a new atmospheric po2 model that has strong similarities to existing models based on elemental and isotopic mass balances yet differs in some potentially significant respects in particular the new model suggests that atmospheric po2 wasmarkedlylowerduringtheearlytomiddlepaleozoicthanpreviouslyinferred duringmostofthedevonian atmospherico2levels mayhavebeensufficientlylow b13 astopreventthesustainedcombustionofplantmaterial thisfeatureofthemodelmayaccount for ananomalous gapinthefossilcharcoalrecordduringthedevonian theredox dependentburialofpintheoceanresults inpositive and negative feedback mechanisms that tend to stabilize atmospheric oxygen concentrations on geologic timescales temporal variations in the burial of p relative to c suggest that the strength of these feedback mechanisms varied over the phanerozoic 2007 elsevier b v all rights reserved

interannual variability of south atlantic circulation from 4 years of topex poseidon satellite altimeter observations variability of large scale and regional south atlantic circulation is investigated using topex poseidon sea level observations interannual variations are identified from empirical orthogonal functions of gridded sea level fields year to year fluctuations of root mean square sea level variability and variability of agulhas eddies evaluated from the along track data two modes of variability are identified a basin scale mode indicates that sea level in the eastern south atlantic underwent a transition from a state of high sea level and enhanced gyre scale geostrophic circulation in 1993 and 1994 to a state of lower sea level and more sluggish circulation in 1996 the dominant mode of basin scale zonal wind has the same temporal signature suggesting a link between the observed variation of gyre scale circulation and the regional wind forcing time variations of this mode also coincide with a transition from a broad agulhas eddy corridor observed in 1993 and 1994 to a narrower corridor observed in 1996 the input of salt and vorticity to the south atlantic subtropical gyre via agulhas eddies may therefore be partially controlled by interannual variations of the wind forced large scale circulation a second mode isolates interannual variations in the brazil malvinas confluence region during 1993 eddy variability along the brazil current extension was relatively strong and variability along the continental slope was weak the opposite pattern was observed in 1995 these variations may be related to interannual variations of the latitude of the confluence while variations associated with both modes are smaller than those observed on seasonal timescales these interannual variations contribute significantly to the total south atlantic variability

geochemistry of permo triassic mudstone of the satpura gondwana basin central india clues for provenance abstract major and trace element data of the permo triassic mudstones from the intracratonic satpura gondwana basin central india have been used to investigate provenance the satpura succession 5 km thick unconformably overlies the precambrian basement sediment dispersal pattern suggests that the precambrian rocks straddling the southern margin of the satpura basin were the most probable source for the sediments the lowermost unit of the satpura succession comprises glacio marine and glacio fluvial deposits the rest of the succession largely represents a variety of fluvial depositional systems with some records of fluvio deltaic and fluvio lacustrine sedimentation under a climatic spectrum of temperate humid to warm semi arid the present study is confined to the lower six formations namely talchir barakar motur bijori pachmarhi and denwa arranged in that order from bottom to top the oldest rocks of this sequence the talchir formation are enriched in mobile elements such as na ca and mg depleted in alumina and have high icv 0 93 1 29 and lower cia values 61 82 74 89 compared to those of the younger mudstones k 2 o al 2 o 3 ratios of the talchir mudstones 0 24 0 28 are higher than the younger mudstones in this sequence these results suggest that the talchir mudstones were weathered less intensely and are thus more immature than the younger mudstones this is consistent with the prevailing cold climate and relatively higher rate of basin subsidence in contrast the majority of the mudstones from the younger formations are depleted in mobile elements have relatively low icv 0 18 0 87 and k 2 o al 2 o 3 values 0 07 0 26 higher cia values 76 99 92 86 and appear compositionally more mature reflecting moderate to high intensity source rock weathering among them the barakar mudstones likely have been more intensely weathered than mudstones from any of the other formations the trace element compositions and ratios are consistent with most mudstones being derived from a felsic source with some mudstones being derived from a more mafic source for example la sc 0 805 and 0 114 la th 6 245 5 072 7 418 6 245 and 5 072 and eu eu 1 431 0 868 and 0 805 of some mudstones indicate mafic source bivariate plot of th sc and zr sc indicates considerable enrichment of zircon that suggests recycling from meta sedimentary rocks prominent negative eu anomaly high lree hree and flat hree pattern reflect sediment derivation from predominantly felsic rocks of the old upper continental crust sio 2 al 2 o 3 versus k 2 o na 2 o plot for the mudstones suggests that they formed in a passive margin also total ree content of most of the mudstones is conformable with passive margin tectonic setting and craton interior type of provenance plotting in la th sc th sc zr 10 and la sc versus ti zr diagrams largely indicates continental margin settings for majority of the mudstones but fails to differentiate between active and passive continental margins

kaolinized potassium leached zones at the contacts of the garn formation haltenbanken mid norwegian continental shelf abstract the middle jurassic garn formation consists mainly of subarkosic arenite in which potassium feldspar is several times as abundant as plagioclase in cores from eight wells the top of the formation upper 6 12 m appears to have undergone relatively intense alteration of potassium feldspar to kaolinite with the resulting loss of bulk postassium content this could be explained as a result of subaerial weathering of the top of the sandstone body except for the fact that in two of the wells the same pattern of alteration is observed at the base of the formation an alternative explanation is that alteration resulted from the introduction of acid released by the maturation of organic matter in adjacent shales in all instances the altered zones display a gradual increase in kaolinite content and a decrease in the ratio of bulk rock potassium aluminium over a distance of several metres approaching the formation boundary this pattern indicates that the active species responsible for the alteration entered vertically from the formation contacts rather than being introduced by lateral flow along the sandstone bed the cores studied are tentatively interpreted as recording different stages in the following depth related sequence of diagenetic events 1 early kaolinization throughout the formation by meteoric water flushing 2 formation of additional kaolinite near the formation contacts by the influx of acid from surrounding shales at approximately 2 7 km depth below the sea floor and 3 extensive alteration of kaolinite to illite at approximately 3 7 km depth illitization has been impeded in the leached zones near the formation contacts due to a local deficiency in reactive potassium here kaolinite survives unaltered whereas kaolinite throughout the rest of the formation has been extensively replaced by illite this implies that the illitization of sandstone can occur by short range diffusion in a chemically closed system solely in response to increasing thermal exposure at greater depth

high resolution sequence stratigraphy of the maastrichtian ypresian succession along the eastern scarp face of kharga oasis southern western desert egypt a thick maastrichtian ypresian succession dominated by marine siliciclastic and carbonate deposits of the regionally recognized nile valley and garra el arbain facies associations is exposed along the eastern escarpment face of kharga oasis located in the western desert of egypt the main objectives of the present study are i to establish a detailed biostratigraphic framework ii to interpret the depositional environments and iii to propose a sequence stratigraphic framework in order to constrain the palaeogeographic evolution of the kharga sub basin during the maastrichtian ypresian time interval the biostratigraphic analysis suggests the occurrence of 10 planktonic zones two in the early maastrichtian cf8b and cf7 four in the palaeocene p2 p3 p4c and p5 and four in the early eocene e1 e2 e3 and e4 recorded zonal boundaries and biostratigraphic zones generally match with those proposed elsewhere in the region the stratigraphic succession comprises seven third order depositional sequences which are bounded by unconformities and their correlative conformities which can be correlated within and outside egypt these depositional sequences are interpreted as the result of eustatic sea level changes coupled with local tectonic activities each sequence contains a lower retrogradational parasequence set bounded above by a marine flooding surface and an upper progradational parasequence set bounded above by a sequence boundary parasequences within parasequence sets are stacked in landward stepping and seaward stepping patterns indicative of transgressive and highstand systems tracts respectively lowstand systems tracts were not developed in the studied sections presumably due to the low relief ramp setting the irregular palaeotopography of the dakhla basin which was caused by north east to south west trending submerged palaeo highs and lows together with the eustatic sea level fluctuations controlled the development and location of the two facies associations in the kharga oasis the nile valley open marine and garra el arbain marginal marine

an alternative scaling for unsteady penetrative free convection 1 the daytime evolution of the atmospheric boundary layer under high pressure anticyclonic synoptic systems over a homogeneous terrain can be successfully described by a penetrative free convection model evolving from an initially stably stratified environment in this article dimensional analysis has been employed to derive a new set of scaling parameters which are functions of external time dependent fluid properties and boundary conditions this novel theoretical framework has been adopted to compare laboratory scale experiments performed using a thermally controlled water tank and a large eddy simulation les numerical model both these have been developed for the characterization of the instabilities associated with the development of the convective boundary layer cbl the characteristic length and time scales of the thermal plumes their spatial distribution and interaction with the overlying stable layer are analyzed the proposed scaling parameters appear to be representative of the bulk and turbulent properties of the cbl as confirmed by both numerical and laboratory results

nd and pb isotope signatures on the southeastern south american upper margin implications for sediment transport and source rocks abstract neodymium and lead isotope values in sediment samples were used to interpret sediment transport and source rocks on the southeastern south american upper margin the sediments of the argentinian margin exhibit an average nd value of 1 9 indicating the influence of the andean rocks as sediment sources sediments from the rio de la plata estuary show an average nd value of 9 6 which is similar to that of the southern brazilian upper margin finally sediments of southeastern brazil which are associated with the transport of the brazil current exhibit an average nd of 13 0 the pb isotope signatures also confirm the differentiation of source rocks in the sedimentation of the study area in addition pb isotopes helped to establish the extent of the influence of the rio de la plata on the sedimentation of the southern brazilian margin in terms of pb isotopes the sediments from the rio de la plata estuary and southern brazil are more radiogenic than those of southeastern brazil and the argentinian margin

late cretaceous to early paleocene climate and sea level fluctuations the tunisian record abstract climate and sea level fluctuations across the cretaceous tertiary k t transition in tunisia were examined based on bulk rock and clay mineralogies biostratigraphy and lithology in five sections el melah el kef elles ain settara and seldja spanning from open marine to shallow inner neritic environments late campanian to early danian trends examined at el kef and elles indicate an increasingly more humid climate associated with sea level fluctuations and increased detrital influx that culminates at the k t transition this long term trend in increasing humidity and runoff in the tethys region is associated with middle and high latitude cooling results of short term changes across the k t transition indicate a sea level lowstand in the latest maastrichtian about 25 100 ka below the k t boundary with the regression marked by increased detrital influx at el kef and elles and a short hiatus at ain settara a rising sea level at the end of the maastrichtian is expressed at elles and el kef by deposition of a foraminiferal packstone a flooding surface and condensed sedimentation mark the k t boundary clay which is rich in terrestrial organic matter the p0 p1a transition is marked by a sea level lowstand corresponding to a short hiatus at ain settara where most of p0 is missing and a period of non deposition and erosion in the lower part of p1a 64 95 ma at seldja p0 and possibly the topmost part of cf1 are missing these sea level fluctuations are associated with maximum humidity these data suggest that in tunisia long term environmental stresses during the last 500 ka before the k t boundary and continuing into the early danian are primarily related to climate and sea level fluctuations within this long term climatic trend the pronounced warm and humid event within the latest maastrichtian zone cf1 may be linked to greenhouse conditions induced by deccan volcanism the absence of any significant clay mineral variations at or near the k t boundary and ir anomaly suggests that the bolide impact had a relatively incidental short term effect on climate in the tethys region

trace element budgets in the ohio sunbury shales of kentucky constraints on ocean circulation and primary productivity in the devonian mississippian appalachian basin abstract the hydrography of the appalachian basin in late devonian early mississippian time is modeled based on the geochemistry of black shales and constrained by others paleogeographic reconstructions the model supports a robust exchange of basin bottom water with the open ocean with residence times of less than forty years during deposition of the cleveland shale member of the ohio shale this is counter to previous interpretations of these carbon rich units having accumulated under a stratified and stagnant water column i e with a strongly restricted bottom bottom water circulation a robust circulation of bottom waters is further consistent with the palaeoclimatology whereby eastern trade winds drove upwelling and arid conditions limited terrestrial inputs of siliciclastic sediment fresh waters and riverine nutrients the model suggests that primary productivity was high 2 g c m 2 d 1 although no higher than in select locations in the ocean today the flux of organic carbon settling through the water column and its deposition on the sea floor was similar to fluxes found in modern marine environments calculations based on the average accumulation rate of the marine fraction of ni suggest the flux of organic carbon settling out of the water column was approximately 9 of primary productivity versus an accumulation rate burial of organic carbon of 0 5 of primary productivity trace element ratios of v mo and cr mo in the marine sediment fraction indicate that bottom waters shifted from predominantly anoxic sulfate reducing during deposition of the huron shale member of the ohio shale to predominantly suboxic nitrate reducing during deposition of the cleveland shale member and the sunbury shale but with anoxic conditions occurring intermittently throughout this period

alluvial sandstone composition and paleoclimate i framework mineralogy abstract systematic variations in compositional maturity of first cycle fluvial sandstones are found in the cutler formation permian and fountain formation permian pennsylvanian in colorado and in the gondwana supergroup permian triassic of peninsular india these variations reflect changing climate during deposition climate is considered to be the critical factor affecting maturity because source rocks granite granite gneiss and tectono environmental setting alluvial systems associated with basement cored block uplifts were similar and remained relatively unchanged throughout deposition of all three of the units the roughly 3 200 m thick gondwana succession consisting of five sandstone petrofacies is characterized by the following sequence of change oldest to youngest in compositional maturity expressed in q f r percentages 54 42 4 88 10 2 62 34 4 82 16 2 99 1 0 this sequence is a function of the changing paleoclimate glacial arid temperate humid warm semiarid warm semihumid warm humid associated with the overall global limatic change and the changing latitudinal location of india as it moved from a location close to the south pole northward during the interval of time represented by gondwana deposition lithologic and fossil evidence indicates that during deposition of the fountain formation climate gradually changed from relatively wet and warm to at least semiarid and warm this climatic change is the main factor responsible for the difference in compositional maturity of the older fountain sandstone q f r 65 26 9 relative to the younger q f r 54 36 10 cutler sandstone was deposited in an arid climate and has maximum compositional immaturity q f r 49 44 7 a log log plot of the ratio of total quartz to total feldspar plus rock fragments against the ratio of total polycrystalline quartz to to al feldspar plus rock fragments is a sensitive discriminator of first cycle sandstones with differing climatic heritage bulk chemical composition data support interpretation of climate from framework mineralogy but by themselves are not sensitive enough to be unequivocal indicators the same is true for the ztr index and observations of degree and abundance of solution pits embayments on detrital quartz results of this study support the conclusion of earlier empirical and theoretical analyses which suggest that the optimum conditions for the production and preservation of a distinctive climatic signature on sand composition are met in extensional plate tectonic settings such settings are characterized by coarse grained crystalline parent rocks short transport distances in low order streams deposition in nonroutine environments and shallow burial diagenesis however even in such optimum settings only rarely will climate be a more important determinant of sandstone composition than the tectonic setting itself

multi sensor satellite and in situ measurements of a warm core ocean eddy south of the brazil malvinas confluence region abstract a warm core eddy was detected south of the brazil malvinas falkland confluence bmc region in satellite images of the southwestern atlantic ocean in late 2002 the structure was also sampled by in situ instruments deployed by a ship in 2 days of november 2002 an analysis of satellite data was performed to account for the lifecycle dimension surface temperature surface chlorophyll concentration surface height anomaly and displacement of the eddy since it was detached from the brazil current in september 2002 satellite data were derived from several sources such as the amsr e modis and radar altimeter the structure lasted 64 days at south of the brazil malvinas confluence region later being re assimilated by the brazil current return flow in situ data collected during 2 days showed that the eddy was about 150 m deep 5 5 c warmer and 1 practical salinity unit saltier than adjacent waters the salt anomaly associated to the eddy was estimated as 1 37 10 12 kg while its heat content was 4 24 10 18 j these are typical estimates for eddies present at the bmc region sea surface temperature sst chlorophyll concentration and sea surface height anomaly time series were analyzed for the eddy s center along its trajectory path throughout its lifetime mean translational velocities for the eddy during its lifetime were computed from visual interpretation and by using an adaptation of the maximum cross correlation mcc method on amsr e sst images the overall deviation between the two methods was 26 this suggests that the mcc method has a potential to be applied in monitoring programs to automatically account for the translational velocities of eddies in the bmc region

on the boundary layer structure over highly complex terrain key findings from map within map one of the scientific projects was devoted to boundary layers in complex terrain in a number of subprojects boundary layer issues were addressed and detailed high resolution multi sensor observations were combined with simulation by models allowing for adequate parametrization of turbulence processes in this contribution the projects are briefly introduced and an attempt is made to summarize their key findings and to put them into a joint perspective spatial variability is found to be large but strictly related to topography and therefore allowing for possible parametrization traditional boundary layer scaling approaches cannot simply be applied over highly complex topography but some of the map findings suggest the potential for suitable extensions of those scaling relations to cover various cases of complex terrain the mean boundary layer structure and thermally driven flows in narrow valleys are found not to be generally in line with previous results from larger valleys elsewhere furthermore local circulations are reported to contribute considerably to exchange between valley and free troposphere in particular the range of their effects on the lower atmosphere seems to be larger than just turbulent transport within the planetary boundary layer would suggest thus in larger scale numerical models where the topography is not resolved possible sub grid parametrizations for local exchange seem to be in order copyright 2007 royal meteorological society

water tank studies of atmospheric boundary layer structure and air pollution transport in upslope flow systems 1 heated mountain slopes sometimes vent air pollutants out of the boundary layer over the slope top and at other times trap pollutants in closed circulations field numerical and water tank studies of fair weather atmospheric conditions over complex terrain have shown more complicated vertical distributions of temperature moisture and aerosols than over horizontal terrain to study these phenomena we analyze flow fields densities and dye distributions in a bottom heated salt stratified water tank over a 19 slope with adjacent plain and plateau and compare with field and numerical model data vertical layering of dye results from upslope and plain plateau circulations the thermal boundary layer tbl the bottom layer up to neutral buoyancy height coincides with the lower branches of these circulations the return flow branches form elevated layers el with properties intermediate between the tbl and environmental background as heating continues the tbl rapidly entrains the els leading to deeper circulations with new els at greater heights field data suggest that successive formation and entrainment of els occurs at multiple scales in the atmosphere if the aerosol loading of an el is too high to distinguish it from the underlying tbl on lidar backscatter scans then both layers and the associated closed circulation appear embedded in one deep backscatter boundary layer the findings suggest defining the atmospheric boundary layer in complex terrain on the diurnal heating timescale rather than the commonly used 1 hour timescale which is more appropriate for flat terrain we discuss conditions leading to venting versus trapping of air pollutants

middle late holocene caribbean aridity inferred from foraminifera and elemental data in sediment cores from two cuban lagoons abstract coastal lagoons are rarely used as paleoclimate archives because of their complex geomorphic histories which can be affected by both climate and sea level change combined foraminiferal and xrf element analysis of sediment cores from punta de cartas and playa bailen cuba isolated the effects of climate change wet vs dry on the lagoon environments foraminiferal assemblages from both punta de cartas and playa bailen show increasing diversity over the past 4000 yr bp with a prominent increase at 1400 1100 yr bp assemblages were initially dominated by ammonia spp e g ammonia tepida and elphidium spp e g elphidium excavatum indicating brackish conditions but increased miliolid species e g triloculina spp quinqueloculina spp indicate a shift to more marine conditions up core correspondingly terrigenous input to the lagoon fe ti ti ca and k declined over the past 4000 yr bp with a flexion at 1200 1100 yr bp that is likely a consequence of decreasing precipitation fe ti and k have been used as proxies for detrital erosion and transport rates in tropical and sub tropical basins with greater input during wet periods but have rarely been applied to shallow lagoon systems coincident changes in the xrf and foraminiferal data indicate decreased freshwater input to the lagoon and support an inference for the onset of drier climate conditions similar temporal patterns in the foraminifera and xrf records from the two lagoons which are 10 km apart suggest a regional climate influence with increasingly arid conditions developing since the middle holocene 4 kyr bp a pronounced drying over the last 1200 years agrees with other climate records from the caribbean

analysis of second order moments in surface layer turbulence in an alpine valley the paper presents the analysis of field measurements in the atmospheric surface layer over the floor of the adige valley near the city of bolzano in the alps turbulence quantities such as drag coefficient displacement height and roughness length appear similar to those reported in the literature concerning surface layer turbulence over flat uniform terrain the analysis of the non dimensional standard deviations u v w legitimates the adoption for all the wind components of the same monin obukhov similarity relationship in the form originally proposed only for flat uniform terrain under steady state conditions and the extension of this expression to the case of winds over a valley floor in slowly varying situations the coefficients i are very similar for along valley and cross valley winds as are the i ones moreover the u values are only slightly larger than the v contrary to what is reported in the literature conversely shows distinctly different behaviour in the stable and unstable regimes in particular in the latter case a large scatter in the data is observed however since the most scattered data turn out to occur in transition periods i e sunrise and sunset after a specific data selection the best fit parameters are more accurately estimated in addition emphasis is laid on the relevance of an appropriate formulation and use of a suitable recursive filter to separate the low frequency unsteadiness of the mean flow from the turbulence signal copyright 2009 royal meteorological society

wintertime convection in warm core rings thermocline ventilation and the formation of mesoscale lenses large heat losses from warm core ring 82b during february march and april 1982 formed a 400 m thick thermostad in the center of the ring two different models were constructed to simulate the formation of the thermostad water mass properties a one dimensional vertical model forced with a meteorological time series and a volumetric mixing model with climatological input both models indicate that a flux of slope water into the ring is necessary to yield the observed thermostad salinities the subsequent slow decay of the ring core in the slope water suggests that such winter convected rings can easily maintain the warm band water identified by wright and parker 1976 the large loss of core water during interactions with the gulf stream suggests that the reabsorption of such winter cooled warm rings is an important source of high salinity high oxygen anomalies in the main thermocline of the sargasso sea the volume of water in a typical ring reabsorption is sufficient to generate many 20 intrathermocline eddies with t s properties close to those of recently reported lenses this suggests that many of these small eddies are much more local in origin and may be more highly dissipative than has previously been suggested an estimate of the flux of high salinity high oxygen water into the main thermocline by this mechanism leads to ventilation at a rate that is a significant fraction of the ekman pumping at these density levels thus the reabsorption of winter cooled warm core rings by the gulf stream is an important eddy ventilation mechanism for the sargasso sea

geochemical characteristics redox conditions and organic matter accumulation of marine oil shale from the changliang mountain area northern tibet china abstract the organic rich changliang mountain oil shale located in the north qiangtang depression northern tibet is considered to be excellent mineral resource in china the changliang mountain oil shale reported here was deposited in a tidal flat lagoon environment and is characterized by black thin layered oil shales intercalated with dark gray marls here we present geochemical data from the changliang mountain oil shale profile in order to investigate the mechanism of organic matter om accumulation and to establish the formation model for the marine oil shale deposition total organic carbon toc values range from 2 96 to 23 47 in the oil shale samples while the marl samples contains low toc contents ranging from 0 06 to 0 21 in the organic rich oil shale sediments many redox indicators including mo al ratios v cr ratios th u ratios ni co ratios and the relationship of mo to toc suggest a deposition under dysoxic to anoxic environments subsequently the bottom water evolved into an oxic water body when the organic poor marls were deposited however the negative and or weak relationship between toc and productivity indices p ti and ba al indicates that om accumulation was not controlled mainly by primary productivity but dysoxic anoxic bottom water environment a stratified water column may be initiated by the supply of fresh water from the continent nearby combining with warm and humid climate which is beneficial to the reproduction of marine organisms the death and bury of these organisms could lead to the formation of dysoxic anoxic bottom waters and enhance the preservation of om in this study a preservation model of the changliang mountain oil shale was established the model implies that excellent preservation is the major controlling factor for om enrichment in the oil shale layer in addition factors such as mixed deposition with clay minerals and detrital matter input cannot be ignored for their influence on om enrichment

analysis of satellite sea surface temperature time series in the brazil malvinas current confluence region dominance of the annual and semiannual periods we study the dominant periodic variations of sea surface temperature sst in the brazil malvinas confluence region from a satellite derived data set compiled by olson et al 1988 this data set is composed of 202 sea surface temperature images with a 4 4 km resolution and extends over 3 years from july 1984 to july 1987 each image is a 5 day composite the dominant signal as already observed by podesta et al 1991 has a 1 year period we first fit a single frequency sinusoidal model of the annual cycle in order to estimate mean temperature amplitude and phase at 159 points uniformly distributed over the region the residuals are generally small less than 2 c the largest departures from this cycle are located either in the brazil malvinas frontal region or in the southeastern part of the region other periods in sst variations are identified by means of periodograms of the 159 residual time series in which the annual cycle has been substracted the periodograms show that a semiannual frequency signal is present at almost every location the ratio of the semiannual amplitude to the annual amplitude increases southward from 0 at 30 s to reach up to 45 at 50 s in the south the semiannual signal creates an asymmetry and the resulting total annual cycle has a cold period winter longer than the warm one summer in the frontal region the annual and semiannual signals have an important interannual variation this semiannual frequency is associated with the semiannual wave present in the atmospheric forcing of the southern hemisphere differential heating over the mid latitude oceans and the high latitude ice covered antarctic continent has been suggested as the cause of this semiannual wave van loon 1967

daytime development of the boundary layer over a plain and in a valley under fair weather conditions a comparison by means of idealized numerical simulations abstractthe daytime thermal structures of the valley boundary layer vbl and of the convective boundary layer cbl above a plain as revealed by idealized large eddy simulations are compared simulations in the two environments consider similar thermal forcing thus allowing an analysis of the atmospheric heating processes in the vbl and cbl in light of the volume effect theory traditionally invoked to explain the larger diurnal temperature ranges observed in valleys it is found that after an equal input of thermal energy the atmospheric volumes affected by thermal perturbations in the cbl and in the vbl are comparable although the boundary layer top is higher in the vbl than in the cbl the average vbl depth is approximately equal to the cbl depth since the ground elevation is nonuniform in the valley accordingly the volume averaged potential temperature increments in the cbl and vbl are comparable nevertheless surface air temperature variations are larger in the vbl while differences in th

trace elements stable isotopes and clay mineralogy of the elles ii k t boundary section in tunisia indications for sea level fluctuations and primary productivity abstract trace elements and stable isotopes in bulk rocks and foraminifera bulk rock and clay mineral compositions are used as palaeoproxies to evaluate sea level fluctuations climatic changes and variations in primary productivity across the k t transition at elles ii in tunisia from 1 m 33 kyr below to 1 m 70 kyr above the k t boundary results on clay minerals major and trace elements stable isotopes in bulk rock samples e g ca cu zn rb sr zr ba 13c and 18o and in foraminifera sr ca 13c 18o indicate that the latest maastrichtian last 33 kyr in tunisia was marked by a relatively warm but humid climate and a rising sea level the transgressive surface is marked by deposition of a foraminiferal packstone just below the k t boundary followed by maximum flooding across the k t boundary red layer and black clay layer humid warm conditions accompanied the maximum flooding along with increased total organic carbon values and rapidly decreasing primary productivity at the k t boundary an impact event ir anomaly ni rich spinels spherules exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera increasingly more humid conditions prevailed within the lowermost danian zone p0 50 kyr culminating in a sea level lowstand near the top of p0 a slow recovery of the ecosystem in zone p1a coincided with a rising sea level and gradually less humid climatic conditions

tectonic and climate control of oil shale deposition in the upper cretaceous qingshankou formation songliao basin ne china oil shales were deposited in the songliao basin ne china during the upper cretaceous period representing excellent hydrocarbon source rocks high organic matter om contents a predominance of type i kerogen and a low maturity of om in the oil shales are indicated by bulk geochemical parameters and biomarker data a major contribution of aquatic organisms and minor inputs from terrigenous land plants to om input are indicated by n alkane distribution patterns composition of steroids and organic macerals strongly reducing bottom water conditions during the deposition of the oil shale sequences are indicated by low pristane phytane ratios high c14 aryl isoprenoid contents homohopane distribution patterns and high v ni ratios enhanced salinity stratification with mesosaline and alkaline bottom waters during deposition of the oil shales are indicated by high gammacerane index values low mttc ratios high carotene contents low toc s ratios and high sr ba ratios the stratified water column with anoxic conditions in the bottom water enhanced preservation of om moderate input of detrital minerals during the deposition of the oil shale sequences is reflected by titanium concentrations in this study environmental conditions in the paleo lake leading to om accumulation in the sediments are related to sequence stratigraphy governed by climate and tectonics the first member of the qingshankou formation k2qn1 in the songliao basin containing the oil shale sequence encompasses a third order sequence that can be divided into three system tracts transgressive system tract tst highstand system tract hst and regressive system tract rst enrichment of om changed from low values during tst i to high moderate values during tst ii iii and hst i ii low om enrichment occurs during rst i and rst ii therefore the highest enrichment of om in the sediments is related to stages of mid late tst and early hst

daytime heat transfer processes over mountainous terrain abstractthe daytime heat transfer mechanisms over mountainous terrain are investigated by means of large eddy simulations over idealized valleys two and three dimensional topographies corresponding to infinite and finite valleys are used in order to evaluate the influence of the along valley wind and the valley surroundings on the heat transfer processes the atmosphere is coupled to an interactive land surface allowing for dynamic feedback on the surface fluxes the valley heat budget is analyzed both from a local and bulk perspective and the flow is reynolds decomposed into its mean and turbulent component the analysis clarifies recent issues of contention regarding the heating of the valley atmosphere the flow decomposition allows one to clearly distinguish between the different heating processes those associated with the mean flow such as advection induced cooling by the upslope flows and the warming induced by the compensating subsidence and those associated with the turbulent motions the

novel cyclised and aromatised diagenetic products of β carotene in the green river shale abstract a suite of novel diagenetic products of carotene has been identified in an extract of a sample from the green river shale identification is mainly based on comparison of mass spectra with those of diagenetic products of another carotenoid isorenieratene these compounds were formed by i cyclisation and aromatisation of the polyene isoprenoid chain ii explusion of toluene and m xylene from the polyene isoprenoid chain and iii aromatisation of the 1 1 5 trimethylcyclohex 5 enyl moieties resulting in 1 2 dimethylbenzene end groups reduction of the double bonds of carotene is the most important diagenetic process however as judged from the high relative amount of carotane 63 of quantified diagenetic products of carotene these results indicate that the fossilisation potential of carotenoids is greater than previously thought

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

distribution of major elements in atlantic surface sediments 36 n 49 s imprint of terrigenous input and continental weathering 1 numerous studies use major element concentrations measured on continental margin sediments to reconstruct terrestrial climate variations the choice and interpretation of climate proxies however differ from site to site here we map the concentrations of major elements ca fe al si ti k in atlantic surface sediments 36 n 49 s to assess the factors influencing the geochemistry of atlantic hemipelagic sediments and the potential of elemental ratios to reconstruct different terrestrial climate regimes high concentrations of terrigenous elements and low ca concentrations along the african and south american margins reflect the dominance of terrigenous input in these regions single element concentrations and elemental ratios including ca e g fe ca are too sensitive to dilution effects enhanced biological productivity carbonate dissolution to allow reliable reconstructions of terrestrial climate other elemental ratios reflect the composition of terrigenous material and mirror the climatic conditions within the continental catchment areas the atlantic distribution of ti al supports its use as a proxy for eolian versus fluvial input in regions of dust deposition that are not affected by the input of mafic rock material the spatial distributions of al si and fe k reflect the relative input of intensively weathered material from humid regions versus slightly weathered particles from drier areas high biogenic opal input however influences the al si ratio fe k is sensitive to the input of mafic material and the topography of andean river drainage basins both ratios are suitable to reconstruct african and south american climatic zones characterized by different intensities of chemical weathering in well understood environmental settings

mechanisms of up valley winds abstract the basic physical mechanisms governing the daytime evolution of up valley winds in mountain valleys are investigated using a series of numerical simulations of thermally driven flow over idealized three dimensional topography the three dimensional topography used in this study is composed of two two dimensional topographies one a slope connecting a plain with a plateau and the other a valley with a horizontal floor the present two dimensional simulations of the valley flow agree with results of previous investigations in that the heated sidewalls produce upslope flows that require a compensating subsidence in the valley core bringing down potentially warmer air from the stable free atmosphere in the context of the three dimensional valley plain simulations the authors find that this subsidence heating in the valley core is the main contributor to the valley plain temperature contrast which under the hydrostatic approximation is the main contributor to the valley plain pressure differe

precipitation anomalies in southern brazil associated with el nino and la nina events the impact of el nino and la nina events warm and cold phases of the southern oscillation on rainfall over southern brazil is investigated through the use of a large dataset of monthly precipitation from 250 stations this region is partly dominated by rough orography and presents different climatic regimes of rainfall as previous global studies on southern oscillation precipitation relationships used data from only two stations in southern brazil this region was not included in the area of consistent southern oscillation related precipitation in southeastern south america the present analysis is based on the method by ropelewski and halpert the sensitivity of which is assessed for this region the spatial structure of the rainfall anomalies associated with warm cold events is analyzed and subregions with coherent anomalies are determined their distribution indicates the influence of relief latitude and proximity to the ocean these areas are subjected to further analysis to determine the seasons of largest anomalies and assess their consistency during warm cold events the whole of southern brazil was found to have strong and consistent precipitation anomalies associated with those events their magnitude is even larger than in argentina and uruguay all of the subregions have consistent wet anomalies during the austral spring of the warm event year with a pronounced peak in november the southeastern part also shows a consistent tendency to higher than average rainfall during the austral winter of the following year there is also a consistent tendency to dryness in the year before a warm event during the spring of cold event years strong consistent dry anomalies prevail over the whole region also with maximum magnitude in november they are even stronger and more consistent than the wet anomalies in warm event years consistent anomalies do not occur over large areas in the years before and after cold events the wet anomalies during the austral spring of the warm event year weaken and even reverse during the following january the same tendency though not so clear is observable in the dry anomalies of cold events the seasons of largest anomalies disclosed by this study differ from those found by previous global studies for other regions in southeastern south america this study expands the area of consistent warm cold event related precipitation defined by previous studies in southeastern south america by including a region of larger anomalies and provides a spatial and temporal refinement to the warm cold event precipitation relationship

a sediment nutrient oxygen feedback responsible for productivity variations in late miocene sapropel sequences of the western mediterranean abstract cyclic sediments observed throughout the mediterranean during the late miocene have been related to precessional forcing of ocean stratification individual couplets typically 2 m thick sequences of sapropels and diatom rich marls can be reliably traced from western spain to crete and were formed in restricted marginal basins micropaleontological evidence indicates paradoxically that the organic carbon rich sapropels were formed under low productivity conditions marked by surface water stratification and deep anoxia whereas the diatom rich marls were formed under high productivity conditions marked by upwelling here we present geochemical evidence mainly from detailed phosphorus determinations and paleo redox proxies indicating that a sediment nutrient oxygen feedback herein dubbed the sno effect is in part responsible for driving the observed productivity variations during stratification anoxic conditions in these basins cause the release of the limiting nutrient phosphorus from reducible oxide phases in the sediments basin stagnation causes the buildup of phosphorus below the photic zone subsequent overturn driven by precessionally driven winds injects phosphorus rich bottom waters into the photic zone the biotic response to this overturn is high productivity in marls directly overlying the sapropels culminating in diatom mat formation exhaustion of the stored excess phosphorus results in lower productivity marls which grade back into sapropels due to lower wind stresses and the return of stagnant basin conditions these findings indicate that the sno effect may in part be responsible for precessional scale productivity variations observed in parts of the mediterranean and perhaps present in other restricted ocean basins like the miocene monterey formation and the modern santa barbara basin

slow oceanic teleconnections linking the antarctic circumpolar wave with the tropical el nino southern oscillation a case study for the period 1982 1994 shows that a major source for the antarctic circumpolar wave is in the western subtropical south pacific where interannual anomalies in sea surface temperature sst and precipitable water prwat form once established these interannual anomalies in tandem with anomalies in sea level pressure slp move south toward the southern ocean the system then migrates east around the globe through a combination of oceanic advection with the antarctic circumpolar current and ocean atmosphere coupling the coincidence of interannual anomalies in sst slp and prwat indicates the extratropical ocean and atmosphere are tightly linked on these timescales large portions of the interannual sst anomalies branch advectively northward into the south atlantic and indian oceans ultimately reaching the tropics in each basin some 6 8 years after appearing in the low latitude pacific this constitutes a slow oceanic teleconnection that is unique in climate dynamics made possible by the continuity of earth s oceans via the southern ocean in the tropical indian ocean these interannual anomalies move east and arrive at the indo pacific transition in advance of the trans pacific propagation of the respective el nino southern oscillation enso phases the interannual sst and prwat anomalies that appear in the subtropical south pacific are directly linked with the enso cycle on the equator through anomalous vertical convection and a regional overturning cell in the troposphere the same cell that initiates fast planetary waves in the atmosphere that carry enso signals around the southern hemisphere on much shorter timescales

lagrangian drifter dispersion in the southwestern atlantic ocean abstractin the framework of monitoring by ocean drifters mondo project a set of lagrangian drifters were released in proximity of the brazil current the western branch of the subtropical gyre in the south atlantic ocean the experimental strategy of deploying part of the buoys in clusters offers the opportunity to examine relative dispersion on a wide range of scales adopting a dynamical systems approach the authors focus their attention on scale dependent indicators like the finite scale lyapunov exponent fsle and the finite scale mean square relative velocity fsrv between two drifters as a function of their separation and compare them with classic time dependent statistical quantities like the mean square relative displacement between two drifters and the effective diffusivity as functions of the time lag from the release the authors find that dependently on the given observable the quasigeostrophic turbulence scenario is overall compatible with their data analysis with discrepancies fr

history of the south java current over the past 80 ka a sediment core located below the present south java current sjc was used to reconstruct paleoclimate and paleoceanography on the basis of biogenic and terrigenic proxy records the core spans the past 80 ka of environmental change and shows considerable contrasts from the glacial to the holocene presently the core site is situated beneath a seasonally varying low salinity tongue which is advected from the java sea via the sunda strait it carries terrigenous matter of a characteristic signature during the last glacial period stage 4 2 when sea level was lower than during the holocene the sunda strait was closed and the terrigenous supply from that source ceased as the core site is close to the equator our results indicate that atmospheric and oceanographic circulation was alternatively dominated by the northern hemisphere east asian monsoon system and the southern hemisphere australian monsoon system between 20 and 12 ka the australian se winter monsoon reached its maximum and intensified the westward flowing sjc increased mixing of the surface waters led to a slight rise in paleoproductivity a similar but much weaker situation prevailed from 74 to 70 ka during most of the glacial period from 70 to 20 ka strong northeasterly winds associated with the east asian winter monsoon intensified the indian monsoon current and the eastward flowing sjc and may have also carried dust across the equator to our core site during this glacial phase populations of the giant diatom ethmodiscus rex were thriving and may indicate a reduced deep and intermediate thermohaline circulation at the site the monsoonal system as we know it today with distinct dry and wet seasons may not have been active before v12 ka 2002 elsevier science b v all rights reserved

tracking oceanic currents by singularity analysis of microwave sea surface temperature images in the recent years the power of employing singularity analysis of scalar variables to perform pattern recognition in complex images has been evidenced this approach is particularly useful when the image under study corresponds to a scalar variable submitted to a turbulent flow because in that case the arrangement of singularity manifolds corresponds to the multifractal hierarchy from the underlying turbulent flow in this paper we will show how this intimate connection between image processing and physics when applied to microwave sea surface temperature images allows to uncover global circulation patterns in the ocean at a daily basis with the resolution of 1 4 of degree using this technique details not evidenced in the non processed image are revealed the emerging patterns provide a description of the global oceanic currents much richer than the usual global circulation scheme in particular instabilities eddy generation and filamentation are distinctly identified a pattern extraction of this kind is useful in order to measure and track mesoscale oceanic phenomena opening the way to many operational and reanalysis applications

review short term sea level changes in a greenhouse world a view from the cretaceous abstract this review provides a synopsis of ongoing research and our understanding of the fundamentals of sea level change today and in the geologic record especially as illustrated by conditions and processes during the cretaceous greenhouse climate episode we give an overview of the state of the art of our understanding on eustatic global versus relative regional sea level as well as long term versus short term fluctuations and their drivers in the context of the focus of unesco iugs igcp project 609 on cretaceous eustatic short term sea level and climate changes we evaluate the possible evidence for glacio eustasy versus alternative or additional mechanisms for continental water storage and release for the cretaceous greenhouse and hothouse phases during which the presence of larger continental ice shields is considered unlikely increasing evidence in the literature suggests a correlation between long period orbital cycles and depositional cycles that reflect sea level fluctuations implying a globally synchronized forcing of eustatic sea level fourth order depositional sequences seem to be related to a 405 ka periodicity which most likely represents long period orbital eccentricity control on sea level and depositional cycles third order cyclicity expressed as time synchronous sea level falls of 20 to 110 m on 0 5 to 3 0 ma timescales in the cretaceous are increasingly recognized as connected to climate cycles triggered by long term astronomical cycles that have periodicity ranging from 1 0 to 2 4 ma future perspectives of research on greenhouse sea level changes comprise a high precision time scale for sequence stratigraphy and eustatic sea level changes and high resolution marine to non marine stratigraphic correlation

geochemistry of the miocene oil shale hancili formation in the cankiri corum basin central turkey implications for paleoclimate conditions source area weathering provenance and tectonic setting abstract the geochemistry of oil shale units of hancili formation in the cankiri corum basin central turkey was studied using various chemical analyses the mineralogical composition of the samples were preliminarily investigated using pearson s correlation coefficients of selected elements indicating that the samples contain abundant clay minerals as well as k feldspar and carbonate the k 2 o al 2 o 3 and sio 2 al 2 o 3 ratios indicate that the major proportion of clay minerals is composed of smectite si al ti k na and fe reside in clay minerals while ca mg and mn are mostly associated with carbonates e g calcite and dolomite and phosphorous p is present as apatite the total ree content of the oil shale range from 19 to 113 ppm the chondrite normalized patterns of the oil shale show lree enrichments hree deficits negative eu anomalies and negligible ce anomalies in general major trace and rare earth element abundances suggest that the studied oil shale in the cankiri corum basin are mainly from the intermediate rocks mixed with small amounts of basic rocks and that their source rocks are mostly deposited in the continental collision setting the ree geochemistry of the oil shale suggests that these samples were derived from a consistent terrigenous source and the eu anomaly was inherited from the source rocks the paleoclimate index c value varies between 0 07 and 1 22 reflecting a generally semi arid to humid conditions in addition rb sr 0 22 and sr cu 9 09 ratios support the idea that warm and humid conditions prevailed during deposition of the hancili formation sr ba ratios 0 54 3 7 of the studied samples suggest a paleoenvironment with variable salinity the co variation among this factor and paleoclimate indicators suggest that variations in climatic conditions exerted a primary control on salinity the substantially low c value and rb sr ratio and significantly high ratios of sr cu and sr ba and also elevated carbonate content of four samples indicate that these samples were deposited during hot and arid periods and that the paleoclimate controlled the terrigenous sediment flux to the lake basin the chemical index of alteration cia a cn k ternary diagram and high th u ratios indicate that the parent rocks of the oil shale experienced moderate chemical weathering steady state

mineralogical and chemical distribution of the es3l oil shale in the jiyang depression bohai bay basin e china implications for paleoenvironmental reconstruction and organic matter accumulation abstract the es3l lower sub member of the third member of the eocene shahejie formation shale in the jiyang depression is a set of relatively thick and widely deposited lacustrine sediments with elevated organic carbon and is considered to be one of the most important source rocks in east china we can determine the mineralogy organic and inorganic geochemistry of the es3l shale and calculate paleoclimate indexes by using multiple geochemical proxies based on organic chemistry total organic carbon toc and rock eval pyrolysis major and trace elements x ray diffraction and carbon and oxygen isotope data from key wells alongside ecs elemental capture spectroscopy well log data these indicators can be used to analyze the evolution of the paleoenvironment and provide a mechanism of organic matter om accumulation the es3l oil shale has high toc abundance most samples 3 0 and is dominated by type i kerogens additionally the organic rich shale is rich in cao and enrichment in some trace metals is present such as sr ba and u the positive 13c and negative 18o values high sr ba b ga and ca ca fe ratios and low c s ratios indicate that the es3l shales were mainly deposited in a semi closed freshwater brackish water lacustrine environment the consistently low ti al and si al ratios reflect a restricted but rather homogeneous nature for the detrital supply many redox indicators including the th u v v ni and u ratios pyrite morphology and toc ts fe diagrams suggest deposition under dysoxic to suboxic conditions subsequently the brackish saline bottom water evolved into an anoxic water body under a relatively arid environment during which organic lean marls were deposited in the early stage later an enhanced warm humid climate provided an abundant mineral nutrient supply and promoted the accumulation of algal material om input from algal blooms reached a maximum during the deposition of the organic rich calcareous shale with seasonal laminations high p ti ratios and a strongly positive relationship between the p and toc contents indicate that om accumulation in the oil shale was mainly controlled by the high primary productivity of surface waters with help from a less stratified water column factors such as the physical protection of clay minerals and the dilution of detrital influx show less influence on om enrichment

rings in the ocean certain robust long lived eddy features in t he world s ocean have come to be k nown as rings the nomenclature stems from fuglister 1 1972 who c oined t he name based on the c ircle or ring of gulf stream waters t hat surrounded a class of eddies formed from t he g ulf stream through the pinch off of meanders here it s uffices to define rings as intense eddies or vortices that represent a wrapped up piece of a major ocean c urrent they t ranslate over space scales of hundreds to thousands of k ilometers and exist for periods lasting from months to years rings move t hrough the ocean carrying anomalies s imilar to the contrasts in physical biological and chemical properties observed across the major ocean c urrents while the term ring is t ied to fuglister t he existence ofthese features was evident at least as early as t he 1930s when iselin 2 1936 1940 encountered strong cold anomalies in the region south of the gulf stream that we would identify as c old corc cyclonic rings today iselin fully rec ognized these features as part of the highly time dependent eddy motion in the ocean later iselin fuglister 1948 were the first to survey what is now k nown as a warm core anticyc lonic ring there are tw o types of rings cold core rings are made up of w aters from the poleward s ide of c urrents like the gulf stream that are introduced to

end triassic calcification crisis and blooms of organic walled disaster species the triassic jurassic t j mass extinction event is marked by isotope anomalies in organic 13 corg and carbonate carbon 13 ccarb reservoirs these have been attributed to a rapid 4 fold rise in pco2 as a result of massive flood basalt volcanism and or methane hydrate dissociation here we examine the response of marine photosynthetic phytoplankton to the proposed perturbation in the carbon cycle our high resolution micropalaeontological analysis of t j boundary beds at st audrie s bay in somerset uk provides evidence for a bio calcification crisis that is characterized by 1 extinction and malformation in calcareous nannoplankton and 2 contemporaneous blooms of organic walled green algal disaster species which comprise in one case n70 of the total palynomorph fraction blooms of prasinophytes and acritarchs occur at the onset and in association with a prominent negative shift in 13 corg values close to the first appearance of the early jurassic ammonite psiloceras planorbis across the same interval we obtained palaeotemperature and palaeosalinity estimates from oyster low mg calcite based on mg ca sr ca and 18 o records the results of our palynological and geochemical analyses strongly suggest that shallow marine basins in nw europe during this period became salinity stratified inducing anoxic conditions the t j boundary event shows similarities with the permian triassic p t mass extinction event which was also marked by extensive flood basalt volcanism negative excursions in carbon isotope records a bio calcification crisis the development of shallow marine anoxia and mass abundances of acritarchs in the early triassic this leads us to suggest that the proliferation of green algal phytoplankton may be symptomatic of elevated carbon dioxide levels in the atmosphere and oceans during mass extinction events 2007 published by elsevier b v

climatic control on the composition of carboniferous permian gondwana sediments khalaspir basin bangladesh abstract late paleozoic or permo carboniferous gondwana successions world wide are marked by widespread and lengthy glaciation 67 ma and multiple transitions from icehouse to greenhouse state mineralogical and compositional changes in sandstones and mudstones of the gondwana succession in drill hole gdh 45 from the khalaspir basin of bangladesh are interpreted in a climatic framework using the proxies of the mineralogical index of alteration mia and the chemical index of alteration cia low mia

vortices of the mediterranean sea an altimetric perspective the presence of coherent vortices makes observed mesoscale fields of the ocean resemble twodimensional turbulence using this analogy a common definition of a coherent structure has been used to study the statistical properties of mediterranean sea vortices observed by satellite altimeters over a 7 yr period a vortex has been defined as the simply connected region with values of the okubo weiss parameter w 0 2w where w is the spatial standard deviation of w and the same sign of vorticity this definition is shown to be appropriate to detect and characterize statistically properties such as size mean kinetic energy and amplitude of vortices in the mediterranean basin from sea level anomaly maps corresponding to the period from october 1992 to october 1999 the distribution of such properties for the mediterranean vortices suggests a heuristic criterion to extract and select very coherent and long lived vortices from the whole set of structures identified in altimetric maps such coherent vortices appear to be selected for amplitudes greater than 2w where the amplitude has been defined in terms of the okubo weiss parameter rather than vorticity and strongly correspond to those reported from observations with independent data systematic locating and tracking of such vortices provide for the first time a general picture of their preferential paths in the mediterranean basin which are characterized by complex but rather well defined patterns

global climate change and planktic foraminiferal response in the maastrichtian 1 the lengthy warm stable climate of the cretaceous terminated in the campanian with a cooling trend interrupted in the early and latest maastrichtian by two events of global warming at 70 68 ma and at 65 78 65 57 ma these climatic oscillations had a profound effect on pelagic ecosystems especially on planktic foraminiferal populations here we compare biotic responses in the tropical subtropical tethyan open ocean and mesotrophic zin valley israel and oligotrophic tunisia slopes which correlate directly with global warming and cooling the two warming events coincide with blooms of guembelitria an extreme opportunist genus best known as the main survivor of the cretaceous paleogene k pg catastrophe in the maastrichtian guembelitria bloomed in the uppermost surface water above shelf and slope environments but failed to reach the open ocean as it did at k pg the coldest interval of the late maastrichtian 68 65 78 ma is marked by an acme of the otherwise rare species gansserina gansseri a deep dwelling keeled globotruncanid the g gansseri acme event can be traced from the deep ocean even onto the tethyan slope marking copious production and circulation of cold intermediate water this acme is abruptly terminated by extinction of the species a dramatic reversal attributed to a short term global warming episode this extinction corresponds precisely with the second bloom of guembelitria that began 300 kyr prior to the k pg event the antithetical relationship between blooming of guembelitria and the g gansseri acme reflects planktic foraminiferal sensitivity to warm cool warm cool climatic oscillations marking the end of the cretaceous

chlorophyll variability and eddies in the brazil malvinas confluence region abstract ocean color data from sea viewing wide field of view sensor seawifs have been used to investigate temporal and spatial variability of chlorophyll a concentration in the brazil malvinas confluence bmc region 30 50 s and 30 70 w our analysis is based on 60 monthly averaged and 230 weekly averaged images 9 9 km 2 resolution that span from october 1997 to september 2002 in the southwestern atlantic ocean a nonlinear model was used to fit the annual harmonic of the chlorophyll concentration anomalies in the region analysis of the spatial variability of model parameters has shown the existence of a marked annual cycle at several locations in the study region we also have observed shorter period oscillating features on smaller spatial scale associated with the bmc dynamics these mesoscale features have periods of about 9 12 weeks and have a marked northward propagation with higher chlorophyll values relative to the surrounding waters further investigation of these mesoscale features with an advanced very high resolution radiometer thermal infrared and topex poseidon t p altimeter data has unveiled interesting eddy like surface structures in the bmc region these multiple eddies are clearly visible on both thermal and color imagery off southern brazil furthermore the seawifs images have shown a decrease in chlorophyll a concentration as these eddies propagate northward due to mixing with chlorophyll poor tropical waters carried southward by the brazil current several rings along the shelf region which are probably generated by shear instabilities also have been detected by the ocean color images

structure of the entrainment zone capping the convective atmospheric boundary layer the authors use large eddy simulation les to investigate entrainment and structure of the inversion layer of a clear convectively driven planetary boundary layer pbl over a range of bulk richardson numbers ri the les code uses a nested grid technique to achieve fine resolution in all three directions in the inversion layer extensive flow visualization is used to examine the structure of the inversion layer and to illustrate the temporal and spatial interaction of a thermal plume and the overlying inversion it is found that coherent structures in the convective pbl that is thermal plumes are primary instigators of entrainment in the ri range 13 6 ri 43 8 at ri 5 13 6 strong horizontal and downward velocities are generated near the inversion layer because of the plume interface interaction this leads to folding of the interface and hence entrainment of warm inversion air at the plume s edge at ri 5 34 5 the inversion s strong stability prevents folding of the interface but strong horizontal and downward motions near the plume s edge pull down pockets of warm air below the nominal inversion height these pockets of warm air are then scoured off by turbulent motions and entrained into the pbl the structure of the inversion interface from les is in good visual agreement with lidar measurements in the pbl obtained during the lidars in flat terrain field experiment a quadrant analysis of the buoyancy flux shows that net entrainment flux or average minimum buoyancy flux wu min is identified with quadrant iv w2u1 0 motions that is warm air moving downward plumes generate both large negative quadrant ii w1u2 0 and positive quadrant iii w2u2 0 buoyancy fluxes that tend to cancel the maximum vertical gradient in potential temperature at every x y grid point is used to define a local pbl height zi x y a statistical analysis of zi shows that skewness of zi depends on the inversion strength spectra of zi exhibit a sensitivity to grid resolution the normalized entrainment rate we w where we and w are entrainment and convective velocities varies as ari21 with a 0 2 in the range 13 6 ri 43 8 and is in good agreement with convection tank measurements for a clear convective pbl the authors found that the finite thickness of the inversion layer needs to be considered in an entrainment rate parameterization derived from a jump condition

physical mechanisms of the thermally driven cross basin circulation the physical mechanisms responsible for the formation of a thermally driven cross basin circulation in a basin with asymmetric heating of opposite mountain sidewalls are investigated a large eddy simulation is performed with the weather research and forecasting model for an idealized basin based on the topography of arizona s meteor crater the individual components of the horizontal momentum and thermodynamic balance equations are analyzed to determine their respective contributions in forcing the cross basin circulation a cross basin pressure gradient with higher pressure on the less irradiated sidewall leads to the development of a cross basin flow near the basin floor a weak opposing return flow develops above this cross basin flow as a result of a reversed cross basin pressure gradient the reversed cross basin pressure gradient is caused by cold air advection by upslope winds in the stable morning atmosphere on the sunlit sidewall and warm air advection by downslope winds on the still shaded sidewall as this reverses the cross basin temperature gradient producing a higher temperature on the less sunlit sidewall

distributions and stable carbon isotopic compositions of biomarkers in torbanites from different palaeogeographical locations abstract the relative distributions and stable carbon isotopic compositions of certain aliphatic and aromatic biomarkers from 11 botryococcus braunii rich torbanites from scotland south africa and australia covering the late carboniferous to late permian were investigated the data was scrutinised for any evidence of molecular features which may be characteristic of palaeogeography the torbanites studied were selected to cover a range of age and palaeoclimatic conditions e g permian and late carboniferous when gondwana was covered by an extensive ice sheet the late permian when the climate warmed from glacial to cool to temperate and the carboniferous when laurasia was located within the equatorial zone all torbanites are composed of abundant n alkanes and novel macrocyclic alkanes which based on similar 13c values are ascribed a common origin all samples are also characterised by a high cyanobacterial input as indicated by abundant hopanoids other biomarker distributions and stable carbon isotopic compositional differences separated the torbanites into three groups which also correlate to three different palaeogeographical palaeoclimatic precincts i group a southern africa and eastern australia temi torbanites which are characterised by a high relative abundance of cyanobacterial and methylotrophic hopanoids abundant branched hydrocarbons and 13c enriched homologous series of monomethylakanes ii group b eastern australia newnes and glen davis torbanites contain relatively high amounts of drimanes and abundant 13c enriched homologous series of monomethylakanes and iii group c scottish torbanites torbane hill and westfield contain high relative amounts of cyanobacterial hopanoids methylotrophic hopanoids and abundant branched aliphatics but no 13c enriched homologous series of monomethylakanes

circulation on the western south atlantic continental shelf 2 spring and autumn realistic simulations 1 buoyancy driven currents are here investigated in a complex scenario where two river plumes the la plata river and the patos lagoon plumes occur in the vicinity of two opposing western boundary currents the malvinas and the brazil currents the study addresses the contrasting scenarios found during the austral spring and fall seasons due to variations in river discharge in wind stress and in the boundary current transport the winds blow preferably from the northeast during the spring and from the southwest during the fall the brazil current transport is stronger during the spring when the brazil malvinas confluence is displaced southward and weaker during the fall when the confluence moves northward the study is conducted as a series of numerical simulations which consider the river discharges the tides variable wind stress and thermohaline fields which are realistic in terms of the brazil malvinas confluence our discussion focuses on the riverine water distribution in each season the austral fall scenario shows coastally trapped plumes and the spring scenario shows significant offshore removal but our fall plumes are not too elongated and narrow as other authors found in the presence of constant winds no tides and no boundary currents and our spring offshore removal is not as strong as found by others

spatial and temporal variability of the brazil malvinas confluence and the la plata plume as seen by seawifs and avhrr imagery 1 ocean color octs seawifs and sea surface temperature avhrr images were used to evaluate spatial and temporal variability of the brazil malvinas confluence and la plata plume 20 to 45 s and 40 to 65 w the data set covers the period from january 1997 to june 2003 chlorophyll and sst data were combined using principal component analysis pca the results yielded were used to identify and follow front displacements pca maps showed a close relationship with previous observations of currents behavior and the la plata plume firstly the analysis was performed on data retrieved from a monthly climatology and the results show three remarkable features a gradual increase of the northward intrusion of the la plata plume throughout the period lasting from summer to winter the summer shape of the la plata plume showed a stronger penetration over the shelf on the argentinean side of the estuary mouth and the seasonal migration of the brazil malvinas confluence monthly composites were then used and compared with discharge and wind data from scatterometers the results show that increases on discharge led to a greater influence of the la plata plume over the continental shelf although during 1998 el nino it did not penetrate farther north because of the unfavorable wind pattern northerly on the other side during 2002 high discharge rates were associated with strong southerly winds leading to a northern penetration of the plume the same analysis was applied to daily images to show its application on locating the front s position this analysis showed the same patterns

a multiproxy approach to the climate and marine productivity variations along mis 5 in se brazil a comparison between major components of calcareous nannofossil assemblages and geochemical records abstract in this study changes in terrigenous input based on geochemical elementary ratios e g fe ca ti ca ba ca fe k and on marine primary productivity based on calcareous nannofossil assemblages from the southeastern brazilian continental margin are analyzed for the time interval 140 to 55 ka mis 6 to mis 4 variation in the terrigenous input follows the continental paleoclimate records based on speleothems from se brazil and the summer insolation curve from low latitudes for the southern hemisphere in turn marine productivity shows a high correlation with terrigenous input terrigenous input maxima correlate to increased marine productivity during sub stages 5d and 5b both terrigenous input and marine productivity would be strongly controlled by changes in the intertropical convergence zone and winds associated with the south atlantic convergence zone thus ne winds would have prevailed promoting humidity and precipitation rates over se brazil as well as an intensified wind driven upwelling and eddies associated with the brazil current which favored the presence of a shallow nutricline our results are consistent with that of different proxies presented in other studies providing estimates of changes on the precipitation rate of se brazil and changes on marine productivity in the south atlantic ocean during mis 5

the thermally driven diurnal wind system of the adige valley in the italian alps the adige valley is one of the major corridors connecting the po plain with the inner alps a series of permanent weather stations and one wind profiler provide a regular monitoring of air temperature atmospheric pressure global solar radiation wind speed and direction over the 140 km valley length and in the adjacent plain data from these stations are analysed for a subset of days on which weather conditions favoured a full development of diurnal valley winds in the period 2012 2014 the analysis highlights typical features in the alternating patterns of diurnal up valley winds and nocturnal down valley winds in particular the wind intensity depends linearly on the along valley pressure gradient supporting the concept of a quasi steady balance between pressure gradient and surface friction also in agreement with previous investigations the amplitude of the surface pressure cycle increases in the up valley direction causing the reversal of the horizontal pressure gradient twice per day in contrast no appreciable along valley variation in the diurnal temperature range is found the analysis of surface temperature and pressure measurements suggests that the larger pressure perturbations found far into the valley are caused by the increased depth of the atmospheric layer subject to heating and cooling local inhomogeneities in the valley cross section in particular in the vicinity of a large basin cause temperature and pressure perturbations that are strong enough to alter the typical cycle of down and up valley winds similarly local wind convergence over the major cities during the night are explained in terms of the urban heat island effect

climate change driven black shale deposition during the end triassic in the western tethys abstract several new triassic jurassic boundary sections from the eiberg basin northern calcareous alps austria have been studied at high resolution we present integrated geochemical and biological proxy data from this western tethys shelf basin high resolution correlation of kuhjoch the global boundary stratotype section and point gssp for the base of the jurassic hochalplgraben and tiefengraben shows that the initial and main carbon isotope excursions cie are contemporaneous with first and last occurrences of boundary defining macro and microfossils we focus on the end triassic initial cie at the transition from the limestones of the kossen formation to the marls of the kendlbach formation this change coincides with a dramatically increased influx of conifer cheirolepidiaceae pollen and increased total organic carbon toc values succeeded by an acme of green algae cymatiosphaera we present a model in which increased terrestrial organic matter influx is related to enhanced seasonality and increased erosion of the hinterland reduced salinity of the surface waters led to the mass occurrence of green algae stratification of the water column may have caused anoxic bottom water conditions and black shale deposition during the initial cie at the base of the kendlbach fm