small scale waves encountered during aase variability on scales of 200 km or less in the lower stratosphere is examined using potential temperature data collected during the aase campaign enhanced variability is found over regions containing topography presumably due to gravity waves the effect of gravity wave critical levels on topographically induced variability is examined a significant reduction in variability is found when a critical level is present

explaining the weddell polynya a large ocean eddy shed at maud rise satellite observations have shown the occasional occurrence of a large opening in the sea ice cover of the weddell sea antarctica a phenomenon known as the weddell polynya the transient appearance position size and shape of the polynya is explained here by a mechanism by which modest variations in the large scale oceanic flow past the maud rise seamount cause a horizontal cyclonic eddy to be shed from its northeast flank the shed eddy transmits a divergent ekman stress into the sea ice leading to a crescent shaped opening in the pack atmospheric thermodynamical interaction further enhances the opening by inducing oceanic convection a sea ice ocean computer model simulation vividly demonstrates how this mechanism fully accounts for the characteristics that mark weddell polynya events

winter upper ocean stability and ice ocean feedbacks in the sea ice covered southern ocean abstractin this study under ice ocean data from profiling floats instrumented seals and shipboard casts are used to assess wintertime upper ocean stability and heat availability in the sea ice c

initial testing of a numerical ocean circulation model using a hybrid quasi isopycnic vertical coordinate abstract an ocean circulation model developed for the study of mesoscale to gyre scale circulation and heat transport is described and tested the model employs density as vertical coordinate except in the immediate vicinity of possible coordinate surface intersections with the ocean surface test simulations are carried out for a double gyre ocean basin of the type used by holland 1978 but with better resolution in the upper 1000 m of the model ocean the final state of a 5 year coarse mesh 50 km resolution on a 2400 km 1200 km domain spin up is used as the initial state for mesoscale experimentation on a 25 km mesh basin energetics as well as mean mass transport streamfunction and mean potential vorticity fields are given for three mesoscale experiments in which the magnitude and formulation of lateral dissipation are varied each of these experiments run for approximately five years exhibits vigorous mesoscale activity associated with western boundary current separation and the free jet

the western desert versus nile delta a comparative molecular biomarker study abstract the western desert and the nile delta are prolific petroleum producing basins the correlation and matching between their petroleum systems have been briefly studied overall geochemical and biological marker analyses of twelve crude oil and condensate samples taken from seven oil gasfields located in the nile delta and the western desert basins of egypt were effective in identifying and geographically defining two major oil families related by age and source rock depositional environment these samples were classified respectively as late cretaceous tertiary and jurassic early cretaceous the source rocks giving rise to the late cretaceous tertiary oils are associated with abundant terrestrial organic matter the source rocks giving rise to jurassic early cretaceous oil are presumably generated from a mixed terrestrial marine source meanwhile the western desert oil samples show prominent c 30 steranes elevated c 27 monoaromatic steroids and a distinct homohopane distribution suggesting this oil type is derived from a more marine influenced source rock than terrigenous sourced oil in the nile delta the most crucial geochemical fingerprinting biomarkers that have been used to differentiate between nile delta and the western desert oil are oleananes highly branched isoprenoids hbi sterane isomerization 24 norcholestanes aromatic steroid hydrocarbons and c 30 24 n propylcholestanes

transient sea ice polynya forced by oceanic flow variability abstract in the weddell sea during the winters of 1974 1976 a significant opening in the sea ice cover occurred in the vicinity of a large bathymetric feature the maud rise seamount the event is commonly referred to as the weddell polynya aside from such a large scale relatively persistent polynya in the weddell sea transient small scale polynya can also appear in the sea ice cover at various times throughout the winter and at various locations with respect to the maud rise the underlying causes for the occurrence of such transient polynya have not been unambiguously identified we hypothesize that variations in the mean ocean currents are one major contributor to such variability in the sea ice cover analysis of the sea ice equations with certain idealized patterns of ocean currents serving as forcing is shown to lead to ekman transports of sea ice favorable to the initiation of transient polynya aside from the actual spatial pattern of the idealized ocean currents many other factors need also be taken into account when looking at such transient polynya two other such factors discussed are variations in the sea ice thickness field and the treatment of the sea ice rheology simulations of a sea ice model coupled to a dynamical ocean model show that the interaction of dynamical oceanic currents with large scale topographic features such as the maud rise does lead to the formation of transient polynya again through ekman transport effects this occurs because the seamount has a dynamic impact on the three dimensional oceanic flow field all the way up through the water column and hence on the near surface ocean currents that are in physical contact with the sea ice further simulations of a sea ice model coupled to a dynamic ocean model and forced with atmospheric buoyancy fluxes show that transient polynya can be enhanced when atmospheric cooling provides a positive feedback mechanism allowing preferential open ocean convection to occur the convection which takes hold at sites where transient polynya have been initiated by sea ice ocean stress interaction has an enhancing effect arising from the convective access to warmer deeper waters to investigate all of these effects in a hierarchical manner we use a primitive equation coupled sea ice ocean numerical model configured in a periodic channel domain with specified atmospheric conditions we show that oceanic flow variability can account for temporal variability in small scale transient polynya and thus point to a plausible mechanism for the initiation of large scale sustained polynya such as the weddell polynya event of the mid 1970s

warming of deep and abyssal water masses along the greenwich meridian on decadal time scales the weddell gyre as a heat buffer abstract the southern ocean renders a significant contribution to the global overturning system through the formation of deep and bottom waters the weddell sea is one of the most prominent regions in this respect data obtained between 1984 and 2008 from eight repeat hydrographic sections moored instruments and profiling floats in the weddell gyre on the greenwich meridian almost all of them collected with rv polarstern were used to identify variations in the weddell system fluctuations in the water mass properties were detected in the warm deep water with a temperature maximum in the 1990s and a minimum in 2005 but also significant variations occurred in the weddell sea deep and bottom waters whereas the warm deep water is dominated by decadal variations the average temperature and salinity of the whole water column is subject to a positive trend over 24 years the variations of the water mass properties are induced by variations of the inflow of circumpolar deep water at the boundary due to asymmetric wind forcing at the northern and the southern limb of the gyre variable in and outflows occur at the open boundaries internal processes redistribute heat and salt in the gyre resulting in a long term increase of the temperature and salinity in the whole water column the transfer of heat to deeper layers assigns to the weddell gyre the role of a buffer with potential impact on the global climate

high resolution sea ice motions from amsr e imagery passive microwave remote sensing imagery has proven to be a useful source for sea ice motions because of its all sky capabilities however the low spatial resolution of the passive microwave sensors has not allowed the retrieval of small scale motion details such as lead and ridge formation the nasa earth observing system advanced microwave scanning radiometer amsr e has more than double the spatial resolution of previous passive microwave sensors allowing it to track the formation of moderate sized leads and yield much more detailed and more accurate ice motion estimates comparisons with buoys indicate that amsr e motions have errors 30 lower than ice motions derived from the previous passive microwave sensors while amsr e still cannot retrieve the same level of detail as synthetic aperture radars or visible infrared sensors amsr e s complete coverage can better capture the ephemeral motions of the sea ice cover on daily and potentially sub daily timescales

taylor proudman columns in non hydrostatic divergent baroclinic and barotropic flows the taylor proudman theorem states that the velocity of slow steady flow in a rotating incompressible fluid does not change along the direction of the rotation axis this fundamental result has been invoked to explain blocking phenomena observed over topographic features in oceanic and atmospheric flows on earth and atmospheric patterns observed in giant gas planets even in cases where the assumption of incompressibility fails the possible existence of taylor proudman columns is analyzed here for a less restrictive family of non hydrostatic divergent density stratified flows including situations where the stratification gradient and rotation axis are not parallel the results show that taylor proudman like constraints are possible in baroclinic inviscid and viscous nonlinear flows of constant vorticity beltrami flows and low rossby number flows it is found that 1 the baroclinic term is moderated by a factor of the order of the rossby number 2 a conservation law can be found for baroclinic flows and 3 taylor proudman columns will be eroded in viscous flows one particular result stressed in this note is its interpretation in equatorial regions where the rotation axis is perpendicular to the main stratification gradient and it is argued that taylor proudman columns could be difficult to discern with observational parameters from convective cells with only zonal and vertical transport copyright 2009 royal meteorological society

geostrophic wind fields in the stratosphere and mesosphere from satellite data 1 daily maps of horizontally resolved zonal and meridional geostrophic wind fields in the altitude range of 20 90 km were obtained from the cryogenic infrared spectrometers and telescopes for the atmosphere crista experiment during november 1994 and august 1997 results are compared with zonal mean zonal winds from climatological sources and with assimilated data from standard analyses correlative data from ground based and balloon and rocket borne measurements are used to validate the crista winds the comparisons show that geostrophic wind fields from high spatial resolution satellite borne temperature measurements are a good approximation for the winds in the middle atmosphere up to mesopause heights therefore they may be used as input for further modeling efforts particularly in the mesosphere where no wind data from standard analyses are available

relationship between petroleum composition and depositional environment of petroleum source rocks crude oils of nonmarine source can be distinguished from those of marine shale source and from oils originating in marine carbonate sequences by using a battery of geochemical parameters as demonstrated with a sample suite of nearly 40 oils a novel parameter based on the presence of c30 steranes in the oil was found to be a definitive indication of a contribution to the source from marine derived organic matter a second novel parameter based on monoaromatized steroid distributions was effective in helping to distinguish nonmarine from marine crudes and can be used to gauge relative amounts of higher plant input to oils within a given basin sterane distributions were similarly useful for detecting higher plant input but were less effective than monoaromatize steroid distributions for making marine versus nonmarine distinctions concentrations of high molecular weight paraffin can also be effective nonmarine indicators but are influenced by maturation and biodegradation processes certain algal derived nonmarine oils may show little high molecular weight paraffin response oils from carbonate sources with a few exceptions can be distinguished by having low pristane phytane ratios low carbon preference indexes and high sulfur contents gammacerane indexes and carbon isotope ratios of the whole crude are not effective in distinguishing these types of environmental differences on a global basis

oils and source rocks from pauls valley anadarko basin oklahoma u s a abstract thirty oils from the pauls valley area of the anadarko basin oklahoma have been analyzed for n alkane terpane and sterane distributions in an effort to classify genetically related oils ten rock samples from the area were also analyzed in an attempt to relate oil types to their possible source rocks the pauls valley area located near the southeast corner of the anadarko basin has producing formations ranging in age from middle ordovician to late pennsylvanian trapping mechanisms responsible for the accumulation of hydrocarbons vary from purely structural traps to fractured reservoirs to up dip truncations of reservoirs and up dip pinchouts of sandstones results show that 85 of oils in the area probably have a common source the woodford shale a group of oils reservoired in the viola group exhibit distinct geochemical characteristics and are thought to have a different source the differences between the oils from these two sources include enhanced c 24 tetracyclic terpane concentrations relative to c 26 tricyclic terpanes diminished c 28 30 tricyclic terpanes relative to t s and t m diminished c 30 steranes relative to their c 29 counterparts predominance of c 35 over c 34 extended hopanes and an even odd predominance of the normal alkane distribution extracts from the viola group generally exhibit the same qualities as the associated oils and the limestone is proposed as their probable source rock the predominance of c 29 steranes for oil samples which appear to have a marine source inferred by their n alkane distribution the presence of c 30 steranes and high levels of tricyclic terpanes suggests that caution be used in the interpretation of terrigenous sources based on the high abundance of c 29 steranes the deese group the springer formation the sylvan shale and the arbuckle group are not likely sources for the oils analyzed from the pauls valley area differences in api gravity and color previously used to classify oils in this region are not source related but are related to maturation and migration effects

a large amplitude gravity wave in the lower stratosphere detected by radiosonde temperature profiles in the lower stratosphere commonly show fluctuations typical peak to peak amplitude of a few degrees on a vertical scale of a few kilometres the routine operational radiosonde launched from shanwell 56 43 n 2 87 w at 2318 gmt on 12 december 1986 recorded very large amplitude excursions in temperature 15 9 k change over a vertical distance of 2 km in the lower stratosphere which were identified as being exceptional by the staff at the radiosonde station the temperature fluctuations were accompanied by strong shear in the horizontal wind and large variations in the rate of ascent of the balloon the disturbance is argued to be due to a quasi stationary gravity wave with vertical momentum flux about 3 or 4 n m 2 averaged over a horizontal scale of at least 20km these observations their meteorological context and their interpretation are described in detail

upstream effects of mesoscale mountains abstract the alpine experiment alpex has revealed that low level air is typically diverted around the alps without reaching the mountaintop in pursuit of an understanding of the physical basis of this phenomenon and of its generality we have explored the characteristics of orographic blocking of a rotating continuously stratified quid as revealed in a simple model problem retaining full nonlinear and transient effects hydrostatic dynamics is assumed and the obstacle is taken to be an infinitely long ridge with height h x the key questions treated are the strength of the upstream deceleration of cross mountain flow and the length scale over which the decelerated region extends by means of scale analysis the controlling parameters are found to be the rossby number ro u fl and the froude number fr nhm u where u is the speed of the oncoming flow f is the coriolis parameter l the mountain half width n the brunt vaisala frequency and hm is the maximum mountain height the scale analysis also

paleoenvironmental reconstruction of the late santonian songliao paleo lake the late cretaceous is often characterized as having a variable greenhouse climate however the relatively few continental sites preserving geologic records from this time exist limiting information on terrestrial climate and environments worldwide the songliao basin slb of northeastern china is one of the largest cretaceous age continental rift basins thus this well preserved lacustrine deposit provides a unique record of terrestrial paleoenvironmental conditions during the cretaceous here we report organic geochemical data from late cretaceous age lacustrine deposits lower nenjiang formation from the eastern side of the slb outcrop samples were collected from the houjingou section and the following analyses were performed 1 total organic carbon toc content and isotopic composition 2 biomarker distribution including the identification and determination of relative amounts of both aliphatic and aromatic hydrocarbons and steranes and 3 compound specific stable carbon and hydrogen isotopic compositions of n alkanes the biomarker distribution and stable carbon isotopic values 13c of the toc indicate organic matter om from the uppermost section of the first member of the nenjiang formation upper k2n1 was mainly sourced from aquatic macrophytes and land plants in the lower part of the second member of the nenjiang formation lower k2n2 the biomarker distribution and 13c of both the toc and n alkanes indicate that om was sourced from a mixture of algae bacteria and higher plants as a result of marine transgression seawater incursions indicated by the presence of 24 n propyl cholestanes and 24 iso propyl cholestanes occurred episodically in lower k2n2 the negative hydrogen isotopic composition 2h of short chain n alkanes in lower k2n2 indicates an extremely humid environment and it is likely that an influx of freshwater caused large scale flooding of the songliao paleo lake high resolution biomarker and stable isotope records from the houjingou section demonstrate abrupt environmental changes in the songliao paleo lake following seawater incursions during the late cretaceous

c30 steranes novel markers for marine petroleums and sedimentary rocks abstract a series of c30 steranes has been identified in petroleum through the application of metastable scanning gas chromatography mass spectrometry their chromatographic pattern in crude oil resembles an epimerized distribution of steranes it is proposed that the biological precursors for the c30 steranes are marine sterols which contain 30 carbon atoms hence c30 steranes are markers for input to sedimentary lipids from marine organisms

synoptic observations and theory of orographically disturbed wind and pressure abstract a survey of existing synoptic data from the vicinity of major mountain ranges indicates two common aspects of orographic influence on the atmosphere a hydrostatically generated pressure difference across the mountains and a leftward in the northern hemisphere deflection of the air as it approaches the mountain to explain these features the linear theory of queney is extended to include isolated mountains and the force balances implied by the model are clarified by using an expansion in inverse powers of the rossby number the validity of this expansion in the far field and the generation of inertial waves are discussed the results of the theory show that for typical values of the rossby number the pressure field and vertical motion field are unaffected by the coriolis force while the horizontal trajectories of air parcels are altered in agreement with observation the ability of an isolated range to block and deform a passing cold front is shown to depend on having a narrow enough range s

mixed marine and lacustrine input to an oil cemented sandstone breccia from brora scotland abstract a rounded cobble collected from a beach near brora scotland contains angular brecciated sandstone clasts cemented together by crude oil no oil occurs within the tight dolomite cemented clasts except along fractures provenance of the cobble is uncertain however the lithology and shape of the clasts suggests that they are fault gouge breccia composed of old red sandstone from the nearby helmsdale fault oil emplacement presumably along the fault cemented the breccia prior to transport and weathering of the cobble independent source and biodegradation parameters support mixing of two charges of oil like oil from the nearby beatrice field the oil cement contains 24 n propylcholestanes and carotane that indicate marine and lacustrine source rocks respectively the oil cement also contains pristane phytane residual n alkanes and a complete series of 25 norhopanes which indicate mild and heavy biodegradation respectively the first charge consisted of lacustrine devonian oil that was heavily biodegraded at shallow depth the origin of the second charge is unclear unlike beatrice oil the oil cement contains oleanane and shows a higher 24 24 27 nordiacholestane ratio suggesting input from a cretaceous or younger paralic marine shale source rock although cretaceous and paleocene source rocks are inferred to exist in various depocenters in the northeast atlantic margin subcrops of these rocks offshore brora are thermally immature alternately the second charge could originate from an effective middle jurassic source rock that contains oleanane this hypothesis is supported by mass spectrometric confirmation of oleanane in an extract from the marine equivalent of the middle jurassic brora coal in the nearby ukcs 11 30 2 well oleanane in crude oil is not positive proof of a cretaceous or younger source rock for the oil

structure and significance of c30 4 methyl steranes in lacustrine shales and oils abstract the structure of the abundant c 30 4 methyl steranes of ancient freshwater lacustrine sediments and derived oils is of interest as their precursors the 4 methyl and in particular 4 23 24 trimethyl sterols dinosterols are reported to be specific to dinoflagellates this study employs a novel liquid crystal gc phase combined with gc ms and gc ms ms to separate and characterise mixtures of c 30 4 methyl sterane standards not resolvable on non polar phases this technique is then applied to identify the c 30 4 methyl steranes in an ancient freshwater sediment a freshwater lacustrine and a marine derived oil a comparison is also made with the 4 methyl steranes in marine sediments containing varying amounts of dinoflagellate cysts the c 30 4 methyl steranes of the freshwater lacustrine samples have been shown to possess a 4 methyl 24 ethylcholestane structure while both 4 methyl 24 ethylcholestanes and 4 23 24 trimethyl 5 h cholestanes dinosteranes were found in the marine dinoflagellate rich sediments while still indicative of dinoflagellates 4 methyl 24 ethyl sterols are generally not the major dinoflagellate sterol and alternative explanations for the abundance of 4 methyl 24 ethylcholestanes in ancient lacustrine sediments should be considered possibly ancient freshwater dinoflagellates synthesised principally the 4 methyl 24 ethyl form alternatively a source from an unrecognized algal class is possible while a source from bacteria which are known to synthesise certain 4 methylsterols is discussed

mudstones and embedded concretions show differences in lithology related but not source related biomarker distributions abstract the mudstones of the western australian gogo formation harbour numerous carbonate concretions which often contain preserved fossils of lagerstatte like quality these are especially notable in places where the mudstone has eroded giving way to nodule fields which afford valuable paleobiological records it is however a challenge to determine their paleoenvironmental context here we analysed concretions from a core drilled in the canning basin gogo formation at two different depths concretions were compared to the surrounding mudstone found at the same depth electron microscopy and x ray spectroscopy showed that the concretions were carbonate rich and contained detrital fragments biomarker data showed that mudstone and concretions had very similar distributions and presented marine biosignatures including indicators of anoxic depositional conditions a stratified water column and photic zone euxinia the concretions contained higher amounts of c 27 steranes indicating that more labile organic matter such as animal remains could have triggered concretion formation statistical analyses of the results showed that concretions and shales differed p p 31 homohopanes and hopane sterane ratios p

biomarker signatures of the ediacaran early cambrian origin petroleum from the central sichuan basin south china implications for source rock characteristics abstract hydrocarbons with an ediacaran early cambrian origin from the central sichuan basin south china were investigated for biomarker compositions they were obtained by solvent extraction from the upper ediacaran reservoir core samples which contain abundant solid bitumen the solid bitumen is widely believed to be formed by thermal cracking of early charged oils in the reservoirs which have presumed source rocks of an ediacaran early cambrian age thermal maturity parameters based on phenanthrenes and aromatic steroids suggest a very high thermal maturity for the extracted hydrocarbons which is consistent with the severe maturation undergone by their host reservoirs age diagnostic biomarkers including c30 24 isopropylcholestanes and mid chain monomethyl alkanes support source rocks of an ediacaran early cambrian age the extracted hydrocarbons have very similar biomarker signatures which include high relative abundance of acyclic isoprenoids and pristane phytane 1 and the presence of c26 norcholestanes methyl and ethylsteranes the presence of hopanoids including extended series and methylhopanes indicates contributions from prokaryotic bacteria while the presence of various steroids including regular steranes and methylsteranes indicates contributions from the eukaryotic algae parameters based on tricyclic terpane and hopane dibenzothiophene phenanthrene ratios and c27 diasteranes diasteranes regular steranes ratios suggest a major shale source but a mixed shale carbonate source cannot be completely excluded presence of c30 demethylsteranes low pristane phytane ratios high gammacerane index and presence of 28 30 dinorhopane and 2 methyhopanes indicate that the source rocks were deposited in a stratified anoxic marine depositional environment with enhanced salinity conditions

rifted margin source rock deposition a carbon isotope and biomarker study of a west african lower cretaceous lacustrine section lower cretaceous passive margin sections penetrated in wells peripheral to the deep basinal development of pre salt sediments of the liawenda ponta vermelha troughs in the lower congo coastal basin revealed sustained source potential kerogen type kinetic ea a and carbon isotopic data plus rock extract biomarker signatures confirmed large systematic organofacies variations within these rift phase sediments an inverse correlation between 25 28 30 trisnorhopane and gammacerane abundances suggested three major depositional regimes reflecting salinity and water depth control 13c depleted basal sediments showing strong gammacerane 4 methyl sterane signatures were segregated by a major isotopic excursion this event represented the transition between saline playa lake to deeper water stratified conditions supporting a high level of anoxia for these intermediate sediments sterane and tricyclic diterpane abundances plus sterane hopane ratios had marine connotations and could be interpreted as the result of intermittent marine incursions fore shadowing irreversible oceanic ingression a resurgence of gammacerane abundance in the uppermost sediments typified littoral shallow marine depositional conditions recognition of a possible non ubiquity in lacustrine depositional conditions during the opening of a rifted margin provides further insight into the complexity and attendant controls on hydrocarbon generation in such habitats

preconditioning and formation of maud rise polynyas in a high resolution earth system model abstractopen ocean polynyas oops in the southern ocean are ice free areas within the winter ice pack that are associated with deep convection potentially contributing to the formation of antarct

effects of topography on fronts abstract the hydrostatic boussinesq equations are used to simulate the passage of fronts over a two dimensional mountain in a cyclic domain the fronts are forced by a confluent periodic deformation field that moves with the uniform mean flow over the mountain the initial conditions are selected to give a cold front confined to the lower part of the domain fourth order diffusion terms are included in the numerical model to control energy cascade to the grid size scale a numerical frontogenesis experiment with no topography produces a realistic surface front in about two days numerical solutions for flow over the mountain with no front are found by integrating the equations from the initial conditions which are semigeostrophic steady state solutions various mountains are considered that have the same height but different widths the numerical solutions for wide mountains remain close to the semigeostrophic initial conditions while for narrower mountains vertically propagating waves and a hydraulic

umir formation organic geochemical and stratigraphic assessment as cosource for middle magdalena basin oil colombia a detailed geochemical and stratigraphic study conducted on a sedimentary sequence of the upper cretaceous umir formation in a section outcropping on the eastern flank of middle magdalena basin mmb colombia identifies this formation as a new hydrocarbon source rock not previously considered as a source for mmb oil the umir formation is composed of coal coaly shale claystone siltstone and sandstone based on rock eval data the coal and coaly shale show good potential for oil generation certain biomarkers are characteristic of the depositional environment of the umir formation and related oil and contrast it with the la luna formation and related oil for example biomarkers of the umir formation show pristane phytane ratios greater than 1 predominance of c29 steranes low oleanane hopane ratios 0 08 diasteranes steranes ratios greater than 1 22 29 30 trisnor 18a neohopane trisnor 17a hopane ts tm ratios less than 0 46 and relatively low c35 c34 hopane values 0 94 values of the bicadinane index of 0 15 0 25 in umir samples sharply contrast with those of la luna samples which are in the range 0 0 07 oleanane hopane ratios do not show a good correlation with other plant indicators for example c29 sterane percentages and bicadinane indices low oleanane hopane may reflect a predominately conifer rather than angiosperm contribution to the depositional system which is also supported by observations of abundant resinite in thin sections the diasteranes steranes ratio displays an inverse correlation with total organic carbon toc content and hydrogen index hi from rock eval pyrolysis suggesting that this parameter strongly depends on oxic depositional conditions the biomarker results of the umir formation show two main sources of organic matter in competition marine algal vs higher plant a detailed biomarker comparison of santos 31 oil reservoired in the middle upper eocene esmeralda and la paz formations sampled in a field located in the eastern area of the middle magdalena basin shows it to be sourced from the umir formation establishing a new umir esmeralda la paz petroleum system in the mmb this contrasts with a good correlation of suerte oil in the same geographic area with la luna source rocks

sea ice motion from satellite passive microwave imagery assessed with ers sar and buoy motions observing the motion of sea ice from space is analogous to observing wind stress over the wet oceans both provide surface forcing for modeling ocean dynamics ice motion also directly provides the advective component of the equations governing the mass balance of the sea ice cover thus its routine observation from space would be of great value to understanding ice and ocean behavior to demonstrate the feasibility of creating a global multidecadal ice motion record from satellite passive microwave imagery and to quantitatively assess the errors in the estimated ice motions we have tracked ice every 3 days in the arctic ocean and daily in the fram strait and baffin bay during the 8 winter months from october 1992 to may 1993 and daily in the weddell sea during the 8 winter months from march to october 1992 the method which has been well used previously involves finding the spatial offset that maximizes the cross correlation of the brightness temperature fields over 100 km patches in two images separated in time by from 1 to 3 days the resulting ice motions are compared with contemporaneous buoyand sar derived ice motions the uncertainties in the displacement vectors between 5 and 12 km are better than the spatial resolution of the data both 85 ghz data with 12 km spatial resolution and 37 ghz data with 25 km resolution are tracked these trials with the 37 ghz data are new and show quite surprisingly that the error is only about 1 km larger with these data than with the 12 km 85 ghz data errors are typically larger than average in areas of lower ice concentration in the most dynamic regions particularly near the ice edge in the barents and greenland seas and in zones of high shear these passive microwave ice motions show a large increase in spatial detail over motion fields optimally interpolated from buoy and wind observations especially where buoy data are virtually absent such as near coasts and in some passages between the arctic ocean and its peripheral seas the feasibility of obtaining ice motion from the 37 ghz data in addition to the 85 ghz data should allow an important record of ice motion to be established for the duration of the scanning multichannel microwave radiometer smmr special sensor microwave imager ssm i and future microwave sensors that is from 1978 into the next millenium

a case study of the mountain lee wave event of january 6 1992 a mountain wave event observed at the southern tip of greenland on january 6 1992 was corroborated by three experiments the meteorological measurement system mms the microwave temperature profiler mtp and the reactive nitrogen instrument no noy gravity wave signatures with classical phase relationship between wind and temperature were observed on both the outbound and inbound legs at different altitudes the waves showed both vertically propagating and evanescent properties characteristics of the dominant wave mode are wavelength 35 km vertical displacement 0 8 km and peak to peak vertical wind 6 ms 1 with the prevailing wind at 37 ms 1 the stratospheric temperature was reduced by 6k to 195 5k within 8 minutes the implication and potential impact of mountain lee waves on the formation of polar stratospheric clouds psc s are discussed

the petroleum geochemistry of canadian beaufort tertiary non marine oils abstract molecular isotopic and elemental data for a set of 28 paleogene and 3 cretaceous oils from the mackenzie delta and offshore canadian beaufort sea have been evaluated the depositional environment and organic matter characteristics of the source units for these oils have been predicted the paleogene oils of the canadian beaufort are molecularly distinctive and clearly contain a major land plant component oleanane and the 17 h and 17 h 24 28 bisnorlupanes are present as well as the following compound types 24 norlupanes and possibly higher homologues de a lupane noroleanenes norursene dehydroabietane 28 30 bisnorhopanes several molecular and isotopic characteristics are useful in assessing and ordering the extent of biodegradation and thermal maturation of these oils the cretaceous oils are separately sourced from the paleogene oils the latter oils comprise two distinct land plant derived genetic families distinguished by the presence absence of 24 28 bisnorlupanes 24 norursene 24 norlupane and 24 noroleanenes the kugmallit richards family contains each of these compound types and is considered to originate from the eocene richards formation in contrast lupanoids and noroleanenes are absent in oils of the reindeer moose channel family the occurrence of 28 30 bisnorhopane and or oleanane in these oils suggests a paleocene origin although these source rock predictions are supported by the available data they must be considered speculative until detailed molecular isotopic and elemental compositional data are available regionally for potential source rocks of the eocene and paleocene source units in the canadian beaufort

orographically forced stratospheric waves over northern scandinavia simulations were carried out using the two dimensional version of a non hydrostatic numerical model in order to calculate the mesoscale response to flow across the scandinavian mountain range the initial conditions were deduced from an upstream sounding of 27 january 1992 during the easoe campaign over and to the east of the mountain crest regions of mesoscale extent developed which experienced cooling up to 7 k air parcel trajectories passed these areas in approximately 10 min

flow over mountains coriolis force transient troughs and three dimensionality some issues concerning uniform stratified flow over a three dimensional mountain that have not been fully explored are studied using primitive equation models when the froude number fr is small e g fr 0 5 we find that the coriolis force cannot be neglected for flow over small scale mountains characteristic length l 50 km even though the rossby number ro is large when the coriolis force is neglected a pair of symmetric vortices is induced on the lee side irrespective of the scale of the mountain as long as fr lies roughly between 0 1 and 0 5 the major effect of the coriolis force is to modify or diminish the lee vortices due to the leftward deflection on the upstream side of the mountain the coriolis deflection also reduces the upstream propagation when fr is 1 most of the flow goes over the mountain and the coriolis effect is small for the same ro therefore the importance of the coriolis effect is determined by both ro and fr as the scale of the mountain increases from small scale to mesoscale 100 km l 300 km the upstream flow is deflected more to the left by the coriolis effect and a trough develops on the lee side the length scale of the trough depends on the scale of the mountain in the along flow direction for smaller scale mountains small vortices can be generated within the lee side trough when fr is small when the mountain scale is increased the lee side vortices disappear and only a lee side trough remains depending on the mean wind speed and the mountain scale the lee side trough can be advected by the anticyclonic flow over the mountain to the south and remain attached to the mountain for a long time a train of troughs is generated on the lee side of an elliptic mountain associated with the lee side gravity waves simulations of flows over mountains in two dimensional and three dimensional models with the same cross sectional profile are compared for small scale mountains l 100km the two dimensional model overestimates the amount of airflow over the mountain and also the lee side downslope wind

a three dimensional mountain wave imaged in satellite radiance throughout the stratosphere evidence of the effects of directional wind shear swath scanned thermal radiances from the advanced microwave sounding units amsu a on the noaa and aqua satellites are used to image the horizontal temperature structure of a long wavelength mountain wave that formed over southern scandinavia on 14 january 2003 data from all six stratospheric channels show this wave propagating through the full depth of the stratosphere in channels 9 11 altitudes 20 90 hpa the imaged wave has a phase structure broadly consistent with a stationary wave radiated by the southeastward flow over and above the quasi elliptical terrain of southern norway channel 12 radiances at 10 hpa however show a remarkable abrupt change in imaged wave structure the horizontal wavelength contracts phase lines rotate anticlockwise by 30 40 and peak activity migrates to the south to lie over denmark and northern germany similar structure persists in channels 13 and 14 at 2 5 hpa with progessively increasing radiance amplitudes these features are stable over the 10 hours of amsu a measurements from five separate overpasses and are validated against independent radiances acquired by the atmospheric infrared sounder airs and retrieved airs amsu a temperature profiles from the aqua overpass this change at the channel 11 12 interface coincides with an onset of anticlockwise rotation backing and intensification of background stratospheric winds with height fourier ray and spatial ray modelling incorporating these directionally sheared winds and simplified orographic forcing reproduce the salient features of the observations but only after wave induced temperature perturbations have been converted to channel radiances using a forward model the differential visibility of various components of this three dimensional mountain wave to the amsu a channel weighting functions has a first order impact on the observations at heights above 10 hpa once that is factored in the combined observations and modelling provide direct experimental support for the shutts model s predictions of how backing wind vectors affect the vertical evolution of three dimensional mountain waves implications of these observations for orographic gravity wave drag parametrization are briefly discussed copyright 2007 royal meteorological society

a convective model for the weddell polynya abstract mechanisms are considered which may induct the large over 105 km2 area of open water or polynya which frequently occurs within the weddell sea winter sea ice we propose that when surface cooling and ice formation decrease the temperature and increase the salinity of the surface water the latter by salt rejection during ice formation in a preconditioned area static instability with intense vertical mixing can occur the upwelled warm salty deep water can then supply enough heat to melt the ice or prohibit its formation even in the middle of winter a simple two level model is derived to test this theory and is found to agree well with observations the process is found to be irregular due to different times of ice onset from one year to the next and to a lesser extent from variations in surface heating and cooling further it is shown that unless the freshwater input exactly balances the increased salinity from the overturn each year the system will either gain or lose salt yearly an

impact of the tropopause on upward propagation of mountain waves the vertical propagation of mountain waves into the stratosphere is investigated with reference to the scorer parameter profile in the troposphere and the change in brunt vaisala frequency at the tropopause vhf radar provides data on the vertical and horizontal wind velocities and echo power while radiosondes supply temperature profiles in studies of four large amplitude mountain wave events where the wave phase remains nearly constant throughout the troposphere partial reflection at a sharp tropopause offers a better explanation than wave trapping below a minimum in the scorer parameter

origin of nama basin bitumen seeps petroleum derived from a permian lacustrine source rock traversing southwestern gondwana abstract biodegraded bitumens associated with quartz and calcite veins in the cambrian fish river subgroup sediments of the nama group of southern namibia have a geochemical signature diagnostic for organic matter that was deposited in a saline lacustrine palaeoenvironment in particular they contain abundant gammacerane carotane and 3 methylhopanes while 24 isopropyl cholestanes and dinosteroids are not detectable sealed tube hydrous pyrolysis of asphaltene and polar fractions yielded saturated hydrocarbons amenable to c isotopic analysis and these analyses show unusually low 13 c values these combined characteristics are also present in immature bitumens from the permian irati formation of brazil and a saline lacustrine facies of the whitehill formation in the karoo basin south africa we conclude that the bitumens originated from whitehill equivalent strata of the kalahari basin deposited in what was an extensive saline lacustrine basin in southwestern gondwana during the early permian in southern africa source rocks of the whitehill formation are generally immature for petroleum generation and it is therefore likely that the nama bitumens were expelled by contact metamorphism during emplacement of karoo dolerite sills and dykes in the jurassic

depositional environments of late cretaceous gongila and fika formations chad bornu basin northeast nigeria abstract organic geochemical and palynofacies studies of 172 ditch cuttings samples of possible source rock shales from the late cretaceous gongila and fika formations in the chad basin of ne nigeria were carried out to determine their paleoenvironments of deposition although dominated by amorphous organic matter c s ratios and molecular parameters suggest the mostly organic lean shales toc contents typically below 1 5 were deposited in a normal marine environment levels of oxygenation influenced by water depth in the depositional environment appear to control organic richness and quality of the dark grey shales the organic rich toc 2 0 upper part of the fika formation was deposited under anoxic conditions during the late cretaceous and could represent an oceanic anoxic event mature intervals where such conditions prevailed would have generated liquid hydrocarbon although none were sampled here a trend of increasing organic richness towards the central part of the larger chad basin observed in this and other studies supports the development of organic rich marine shales average toc contents of 2 3 of equivalent age in the termit basin where water depth would have been deeper and oxygen conditions at levels that permitted preservation of marine organic matter

halo of low ice concentration observed over the maud rise seamount 1 a distinctive halo of low sea ice concentration has been observed above the maud rise seamount in the eastern weddell sea the 300 km circular halo is seen most clearly in the monthly mean ice concentration for the months july through november the mean was computed from satellite based passive microwave measurements over a 23 year period the halo is most distinct in october even then however the mean ice concentration in the halo is just 10 less than in the center where it is very near 100 the halo may reflect the existence of a taylor cap circulation over the seamount or other topographically induced mechanisms

cassini imaging of jupiter s atmosphere satellites and rings the cassini imaging science subsystem acquired about 26 000 images of the jupiter system as the spacecraft encountered the giant planet en route to saturn we report findings on jupiter s zonal winds convective storms low latitude upper troposphere polar stratosphere and northern aurora we also describe previously unseen emissions arising from io and europa in eclipse a giant volcanic plume over io s north pole disk resolved images of the satellite himalia circumstantial evidence for a causal relation between the satellites metis and adrastea and the main jovian ring and information on the nature of the ring particles

global measurements of stratospheric mountain waves from space temperatures acquired by the cryogenic infrared spectrometers and telescopes for the atmosphere crista during shuttle mission sts 66 have provided measurements of stratospheric mountain waves from space large amplitude long wavelength mountain waves at heights of 15 to 30 kilometers above the southern andes mountains were observed and characterized with vigorous wave breaking inferred above 30 kilometers mountain waves also occurred throughout the stratosphere 15 to 45 kilometers over a broad mountainous region of central eurasia the global distribution of mountain wave activity accords well with predictions from a mountain wave model the findings demonstrate that satellites can provide the global data needed to improve mountain wave parameterizations and hence global climate and forecast models

sources and preservation of organic matter in the cretaceous toolebuc formation eastern australia abstract the organic matter rich toolebuc formation of eastern australia was deposited in a lower cretaceous epicontinental sea parameters from biological marker studies indicate that the organic matter is immature to marginally mature for hydrocarbon generation the occurrence of abundant coccoliths and the distribution of alkane biomarkers suggest that the organic matter type ii is largely of planktonic origin and only in the southeastern part of the depositional area can a terrestrial influence be discerned variations in kerogen composition can be attributed to the extent of the oxidation of the source materials and the degree of incorporation of sulphur the atomic h c ratios c 1 1 are remarkably constant for most of the toolebuc formation atomic o c ratios vary from 0 1 and 0 4 and can be related both to depth and paleogeographic position kerogen sulphur contents range up to 7 and the highest values occur in the most carbonate rich sediments total sulphur inorganic organic to carbon ratios in the sediments vary from 1 to

origin of beatrice oil by co sourcing from devonian and middle jurassic source rocks inner moray firth united kingdom commercial hydrocarbons in the moray firth area of the north sea occur in reservoirs ranging in age from devonian to tertiary with the bulk of the reserves located in upper jurassic and lower cretaceous clastic rocks most hydrocarbon discoveries in this area have been made in the outer moray firth primarily in the witch ground graben a single oil field beatrice has been developed in the inner moray firth area the unusual location and chemical composition of beatrice compared to piper and other north sea oils generated from the kimmeridge clay have contributed to the longstanding controversy on its origin oil source potential in the inner moray firth has been recognized in lacustrine devonian dolomitic siltstones middle jurassic paralic coals upper jurassic marine shales and other rocks however prior to this study only the upper jurassic kimmeridge clay was recognized as a significant effective source rock in the main graben area of the north sea biomarker and stable carbon isotope analyses conclusively show that beatrice oil could not have been generated from the classic kimmeridge clay source rock but is a mixture of products derived from effective devonian and middle jurassic source rocks this work demonstrates the power of a multiparameter geochemical approach in solving this difficult oil to source rock correlation problem use of this approach can lead to the recognition of new exploration plays in previously well explored basins

petroleum geochemistry and depositional setting of lacustrine source rocks abstract lacustrine sequences are increasingly being recognised as hosts for commercial reserves of petroleum petroleum source rocks in lacustrine sequences have organic carbon contents ranging from 20 and kerogen types range from type i to type iii the organic matter can be of land plant algal or bacterial origin most undegraded lacustrine oils are extremely paraffinic and waxy but a few are asphaltic and rich in sulphur the crude oils and source rocks contain a wide diversity of biological marker compounds reflecting different source inputs the diversity of chemistries displayed by lacustrine source rocks and crude oils reflect the wide variety of organic source materials and depositional conditions operative in lakes lacustrine sequences preserved in the geological record represent sediments deposited in fluvial lakes on humid flood plains and tectonic lakes in humid semi arid and arid environments preservation of organic matter in lakes is dependent on the formation of anoxic or micro oxic bottom waters this is favoured by stratification of lake waters brought about by temperature and salinity contrasts organic material preserved in oligotrophic lakes is largely of land plant origin which has been extensively modified by bacteria under mildly oxidizing conditions and supplemented by the bacterial remains source rocks of this type are found in 1 fluvial lacustrine settings e g jurassic of eromanga basin australia and 2 the oligotrophic phase of larger tectonic lakes e g early stages of green river formation uinta basin usa as these freshwater lakes become productive algal remains are contributed to the sediment and anoxic bottom waters can become more firmly established the green algae pediastrum and botryococcus appear to be particularly important although land plant detritus is still significant e g cretaceous source rocks songliao basin china saline lakes conditions tend to restrict the diversity of the source biota although preservation may be enhanced through anoxia brought about by salinity stratification and inhibition of bacterial decay e g later stages green river formation uinta basin usa sulphate rich and hypersaline lacustrine systems result in the formation of sulphur rich sources and oils e g jianghan basin china because of the diversity of organic matter types maturation criteria for hydrocarbon generation in lacustrine sequences also vary however in most cases higher maturation levels are required for significant hydrocarbon generation at present it is uncertain the extent to which algal and bacterial organic matter contribute to the source for the waxy hydrocarbons which are characteristic of lacustrine oils organic rich rocks formed in large freshwater and saline lakes are the most productive type of lacustrine source rock although sources formed in lakes of flood plains and deltas are also widespread

heterocyclic aromatic hydrocarbon distributions in petroleum a source facies assessment tool abstract this study reports a novel source facies assessment application from distributions of heterocyclic aromatic hydrocarbons in petroleum i e dibenzothiophene dbt dibenzofuran dbf and fluorene f to illustrate the approach initially a large set of crude oils from global petroleum basins are geochemically characterized based on source facies organic matter type and environment of deposition variation petroleum bulk properties and molecular distributions of isoprenoids terpanes steranes and related parameters are applied to demonstrate the source facies and maturity of the entire oil suite and to delineate the oil suite into marine carbonate marine shale marine shale with terrigenous organic matter om coaly and lacustrine source facies families from within this interpretive context the relative percentages of hetercyclic aromatic hydrocarbons are reported and discussed from each of these source facies families a triplot drawn from the percentages of dbt dbf and f is shown to effectively differentiate the oils source facies classifications marine carbonate oils show highest dbt plotted in the dbt vertex freshwater lacustrine sourced oils positioned near to 100 f vertex coaly sourced oils revealed highest dbf the marine shale and marine shale with terrigenous om oil families plotted away from three vertices and represent a distinctive position with in the triplot these results establish an effective source facies assessment tool triplot based on heterocyclic aromatic hydrocarbon distributions these novel signatures which are derived from variations in the chemical composition of source rocks hence kerogen lead to the occurrence of kerogen catalysis in sedimentary reaction like carbon catalysis for the formation of heterocyclic aromatic hydrocarbons

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

geochemistry of selected oils and rocks from the central portion of the west siberian basin russia six analyzed oils produced from middle jurassic to upper cretaceous strata in the middle ob region of the west siberian basin show biomarker and stable carbon isotope compositions indicating an origin from the upper jurassic bazhenov formation the chemical compositions of these oils are representative of more than 85 of the reserves in west siberia kontorovich et al 1975 bazhenov sourced oil in cenomanian strata in the van egan field underwent biodegradation in the reservoir resulting in a low api gravity an altered homohopane distribution and the appearance of 25 norhopanes without alteration of the steranes high api gravity oil from the salym field has surpassed the peak of the oil window consistent with abnormally high temperatures and pressures in the bazhenov source rock from which it is produced the remaining oils are very similar including samples from valanginian and bathonian callovian intervals in a sequence of stacked reservoirs in the fedorov field bazhenov rock samples from the study area contain abundant oil prone marine organic matter preserved under anoxic conditions organic matter in a bazhenov core from the pokachev 58 well was compared with the oils because it is thermally mature and shows total organic carbon toc 13 8 wt and hydrogen index values hi 489 mg hc g toc representative of the average for the formation 10 7 wt for 840 samples 420 mg hc g toc for 75 samples other rocks in the middle ob region are far less likely to have generated these oils than the bazhenov formation no prospective source rocks older than middle jurassic were available geochemical analyses indicate a lack of thermally mature hauterivian or younger source rocks in the study area core samples from the lower cretaceous frolov formation either are thermally immature hauterivian or show little oil generative potential berriasian valanginian the upper jurassic vasyugan formation shows lower oil generative potential than the bazhenov formation the average toc for vasyugan rocks is 3 20 wt 240 samples average atomic h c ratios for vasyugan and bazhenov kerogens are 0 90 10 samples and 1 13 25 samples respectively the vasyugan formation cannot be excluded as a source rock because insufficient sample was available for biomarker analysis core from the lower to middle jurassic tyumen formation in the yemyegov 15 well was compared with the oils because it is thermally mature and shows toc and hi values 2 78 wt and 137 mg hc g toc respectively indicating slightly more favorable oil generative characteristics than the average for the formation 2 75 wt for 720 samples 95 mg hc g toc for 25 samples the core contains terrigenous gas prone organic matter that shows no relationship with the analyzed oils

halo of ice deformation observed over the maud rise seamount 1 a distinctive halo of sea ice deformation was observed above the maud rise seamount in the eastern weddell sea in the winter of 2005 the deformation halo is coincident with a halo of low mean ice concentration that is often observed in the region monthly mean ice vorticity estimates for the months july through november reveal the deformation zone most clearly in an arc about 100 km northwest of the seamount where there is a strong gradient in the bathymetry at depths of 3000 5000 m the deformation was computed from satellite based ice motion vectors derived from envisat synthetic aperture radar backscatter images the deformation halo is evidence of a taylor cap circulation over the seamount which has been described and analyzed with modeling studies and concurrent oceanographic observations obtained during an extensive field campaign

petroleum geochemistry of oil and gas from barbados implications for distribution of cretaceous source rocks and regional petroleum prospectivity petroleum produced from the barbados accretionary prism at woodbourne field on barbados is interpreted as generated from cretaceous marine shale deposited under normal salinity and dysoxic conditions rather than from a tertiary source rock as previously proposed barbados oils correlate with some oils from eastern venezuela and trinidad that are positively correlated to extracts from upper cretaceous la luna like source rocks three distinct groups of barbados oils are recognized based on thermal maturity suggesting petroleum generation occurred at multiple levels within the barbados accretionary prism biodegradation is the most significant process affecting barbados oils resulting in increased sulfur content and decreased api gravity barbados gases are interpreted as thermogenic having been co generated with oil and show mixing with biogenic gas is limited gas biodegradation occurred in two samples collected from shallow reservoirs at the woodbourne field the presence of cretaceous source rocks within the barbados accretionary prism suggests that greater petroleum potential exists regionally and perhaps further southeast along the passive margin of south america likewise confirmation of a cretaceous source rock indicates petroleum potential exists within the barbados accretionary prism in reservoirs that are deeper than those from woodbourne field

constraining causes of fish mass mortality using ultra high resolution biomarker measurement lamina by lamina measurement of biomarkers at a sub millimetre resolution within the achanarras limestone member has helped to resolve the changing environmental conditions associated with a fish mass mortality horizon an anomalous proportion of c30 sterane 24 n propylcholestane marks the beginning of the horizon and likely corresponds to an influx of marine water this appears to have been short lived and was likely analogous to a modern day storm tide the subsequent laminae record an increased incidence of water column stratification and hypoxic bottom waters in the form of an elevated gammacerane index the mass mortality horizon studied was from an upper interval of the achanarras limestone member with a fossil fish assemblage comprising mostly dipterus an early dipnoan lungfish however lower intervals of the achanarras limestone member have greater assemblage diversity including species associated with marine conditions such as coccosteus and evidence higher proportions of c30 sterane indicating better connection to the marine environment therefore it appears that ingressing seawater in and of itself was not responsible for creating a stressed environment rather disconnection of the lake from marine waters stranded fish in a lake that when perturbed by storm tides killed en masse by exposing fish to hypoxic conditions in a similar way to modern water bodies affected by storm tides generated during hurricanes

laboratory experiments with tilted convective plumes on a centrifuge a finite angle between the buoyancy force and the axis of rotation author posting cambridge university press 2004 this article is posted here by permission of cambridge university press for personal use not for redistribution the definitive version was published in journal of fluid mechanics 506 2004 217 244 doi 10 1017 s0022112004008572

scarcity of the c30 sterane biomarker 24 n propylcholestane in lower paleozoic marine paleoenvironments abstract 24 n propylcholestane 24 npc a c30 sterane compound derived from sterol precursors which are the major sterol constituents of modern pelagophyte microalgae occurs in certain neoproterozoic rocks and oils and throughout the phanerozoic rock record this broad distribution leads 24 npc to be widely considered a reliable indicator of open to partially restricted marine depositional conditions for source rocks and oils here we report two significant hiatuses in the occurrences of 24 npc in the lower paleozoic marine rock record the first in the middle late cambrian and the second in the late ordovician early silurian transition for a range of lithofacies carbonates and siliciclastic rocks organic carbon contents both organic lean and organic rich and paleoceanographic environments shelf and deeper water marine settings and observed offshore of two paleocontinents laurentia and baltica the ordovician silurian gap is at least 9 million years and possibly up to 20 million years in duration robust older occurrences of 24 npc steranes in some neoproterozoic rocks and oils suggest that oceanographic conditions in our intervals of lower paleozoic time were unfavorable for the proliferation of pelagophyte algae as phytoplankton caution should therefore be applied when interpreting a lacustrine versus marine depositional environmental setting for source rocks and oils in these intervals of early paleozoic time using lipid biomarker assemblages

nonorographic generation of arctic polar stratospheric clouds during december 1999 1 during december 1999 polar stratospheric clouds pscs were observed in the absence of conditions conducive to generation by topographic gravity waves the possibility is explored that pscs can be generated by inertia gravity waves igw radiating from breaking synoptic scale rossby waves on the polar front jet the aerosol features on 7 and 12 december are selected for comparison with theory and with simulations using the university of wisconsin nonhydrostatic modeling system uwnms consistent with rossby adjustment theory a common feature in the uwnms simulations is radiation of igw from the tropopause polar front jet especially from sectors which are evolving rapidly in the rossby wave breaking process packets of gravity wave energy radiate upward and poleward into the cold pool while individual wave crests propagate poleward and downward causing mesoscale variations in vertical motion and temperature on 12 december the eastbound dc 8 lidar observations exhibited a fairly uniform field of six waves in aerosol enhancement in the 14 20 km layer consistent with vertical displacement by a field of igw propagating antiparallel to the flow with characteristic horizontal and vertical wavelengths of 300 and 10 km uwnms simulations show emanation of a field of igw upward and southwestward from a northward incursion of the polar front jet the orientation and evolution of the aerosol features on 7 december are consistent with a single psc induced by an igw packet propagating from a breaking rossby wave over western russia toward the northeast into the coldest part of the base of the polar vortex with characteristic period 9 hours vertical wavelength 12 km and horizontal wavelength 1000 km linear theory shows that for both of these cases igw energy propagates upward at 1 km hour and horizontally at 100 km hour with characteristic trace speed 30 m s the spatial orientation of the psc along igw phase lines is contrasted with the nearly horizontal filamentary structures in the psc which are indicative of flow streamlines it is suggested that vertical displacement is a crucial factor in determining whether a psc will form and that most pscs are relatable to specific synoptic and mesoscale motions

semigeostrophic flow over orography in a stratified rotating atmosphere part i steady three dimensional solutions over finite ridges abstract three dimensional steady and inviscid flow over orography is examined by means of a semigeostrophic model a constant coriolis parameter f uniform potential vorticity and a uniform basic flow characterize this model first used by merkine and kalnay rivas it is demonstrated that the neglect of ageostrophic accelerations which characterize a semigeostrophic model essentially requires low rosssby number flow ro 0 3 and relatively small values of the nondimensional mountain height d 0 5 where d 3 103 m is the deformation depth in this parameter range the disturbance potential is a solution of laplace s equation the atmosphere is semi infinite and the finite amplitude lower boundary is an isentropic surface the basic solution expressed in prolate spheroidal coordinates provides disturbance flows over an isolated mountain finite ridges and the limiting flow over a two dimensional ridge a comparison between the quasi geostrophic and semigeostrophic responses to flow over the isola

multiple oil families in the west siberian basin two major oil families are identified in the west siberian basin twenty six of 32 analyzed oils occur in jurassic and cretaceous reservoirs and are derived from anoxic marine upper jurassic bazhenov source rock based on geochemical comparison of oils and source rock extracts these oils are widely distributed both north and immediately south of the ob river and their biomarker ratios indicate a wide range of source rock thermal maturity from early to middle oil window van egan russkoye samotlor sovninsko sovyet olyenye ozynornoye and kogolym to peak oil window srednekhulym yem yegov vostochno surgut khokhryakov fedorov and urengoi to late oil window salym some of these oils have been mildly e g fedorov 75 to heavily e g russkoye biodegraded n the reservoir the bazhenov sourced oils show different compositions that support regional variations of organic facies in the source rock for example the anoxic marine bazhenov facies which generated the oils in the samotlor fedorov and nearby fields was particularly clay poor and sulfur rich six nonbiodegraded highly mature oils show geochemical characteristics that suggest they were derived from clastic rich lacustrine or nearshore marine source rocks dominated by terrigenous higher plant input like those in the lower to middle jurassic tyumen formation although no correlation was observed between the oils and a single rock sample yem yegov 15 from the formation the six oils occur in the tyumen taitym geologiche and cheremshan and fractured basement paleozoic gerasimov yagyl yakh and verchnekombar reservoirs in positions readily accessible to any oil migrating from the tyumen source rock for example at the gerasimov location the tyumen formation lies unconformably on weathered basement paleozoic reservoir rocks most of the probable tyumen sourced oils ar from south of the ob river but the occurrence of geologiche oil to the north suggests that related oils may be widespread in the basin

stratified semigeostrophic flow over two dimensional topography in an unbounded atmosphere abstract we obtain simple closed form expressions describing stratified rotating flow over an infinite ridge in the semigeostrophic regime the results are used to discuss the degree to which air parcels slow down as they approach a steep mountain the critical burger number for the appearance of infinite velocities at the mountain crest is calculated for several mountain profiles 1t is shown that for gaussian and bell shaped mountains the breakdown occurs in a range in which the upstream deceleration is not pronounced

norcholestane in miocene onnagawa siliceous sediments japan abstract a significant amount of 24 norcholestane with 20r 5 h 14 h 17 h stereochemistry is often found in marine siliceous sediments of the middle miocene onnagawa formation japan some onnagawa siliceous sediments are abnormally abundant in 24 norcholestane the primary production in the northeastern japan sea during the middle miocene was markedly increased due to the invasion of nutrient rich cold seawater from the north accompanied by the tectonic opening of the japan sea 24 norcholestane in high relative abundance is derived mainly from the marine diatoms which were enhanced during this event the drastic ecological change caused by rapid tectonic opening of the japan sea and global climatic deterioration during middle miocene time is suggested to be influential in the formation of 24 norcholestane rich onnagawa siliceous sediments

internal waves and vertical mixing in the storfjorden polynya svalbard 1 latent heat polynya are preferential sites for dense water formation through brine release the combined action of winds and heat loss leading to sea ice fracture followed by the reactivation of sea ice formation drives this process of dense water formation the impact of high frequency dynamics and especially internal wave breaking on this process is investigated here with the analysis of hydrographic observations collected from a drifting mooring in storfjorden svalbard the main frequency components of the barotropic tide are first revealed by the analysis of a 23 day time series of pressure data interestingly the same frequency peaks are isolated by a spectral analysis of isopycnal displacements suggesting a tidal forcing for these baroclinic waves the hypothesis of local generation in the storfjorden is next examined and numerous sites of potential generation are identified specifically for semi diurnal and sixth diurnal frequencies diurnal baroclinic waves however do not appear to be locally generated but rather popagate cyclonically along the shelf as internal kelvin waves the characteristic of these waves and their energy flux are then inferred a parameterization of dissipation based on the potential energy of the internal wavefield is next proposed and an upper bound for dissipation rate within overturning regions is provided the most vigorous mixing is associated with brine release events i e strong vertical mixing through thermohaline convection with eddy diffusivities of up to 10 3 m2 s 1 the background mixing likely associated with internal wave breaking however displays values within 10 6 10 4 m2 s 1 this background mixing contributes about o 0 1 w m 2 to the vertical heat flux with a net heating in the bottom layer and cooling in the upper layer local heating and cooling rates of the order of 0 025 c month 1 are obtained which is significant with respect to the 0 1 c temperature difference between the bottom and surface layers

a molecular and isotopic study of the organic matter from the paris basin france thirteen liassic sedimentary rocks of increasing depth and three petroleums from the paris basin were studied for 13c 12c isotopic compositions and biological markers including steranes sterenes methylphenanthrenes methylanthracenes and triaromatic steroids the isotopic compositions of n alkanes from mature sedimentary rocks and petroleums fall in a narrow range 2 except for the deepest hettangian rock and the trias petroleum for which the short chain n alkanes are enriched and depleted in 13c respectively most of the molecular parameters increase over the 2000 2500 m depth range reflecting the transformation of the organic matter at the onset of petroleum generation in this zone carbonate content and carbon isotopic composition of carbonates as well as molecular parameters are distinct for the toarcian and hettangian source rocks and suggest a migration of organic matter from these two formations two novel molecular parameters were defined for this task one using methyltriaromatic steroids from organic extracts the other using 1 methylphenanthrene and 2 methylanthracene from kerogen pyrolysates the anomalous high maturity of the dogger petroleum relative to the maturity depth trend of the source rocks is used to estimate the minimal vertical distance of migration of the organic matter from the source rock to the reservoir

geochemical characterization of source rocks crude oils and gases of northwest cuba abstract in order to characterize the cuban petroleum system we analyzed source rocks as well as crude oils and gases from carbonate producing reservoirs from northwest onshore cuban fields the geochemical oil and gas characterizations were based on bulk analyses chromatography liquid and gas mass spectrometry and mass spectrometry coupled to stable carbon isotope ratio determination analyses of sampled source rocks intervals were performed with rock eval 6 and provided valuable data for the appraisal of the active petroleum system in northwest cuba our paper focused on the genetic semblance between carbonate reservoired crude oils and source rocks to assess the offshore extension of the onshore cuban carbonate petroleum system crude oils source rocks and crude oils offshore dsdp source rocks were correlated to a common type of carbonate depositional environment an understanding of the geochemical compositions of carbonate crude oils grouped in families including heavy sulphur rich oils light or mixed and biodegraded fluids helped to underline the different processes operating in the reservoirs today the high degree of anoxicity during the organic matter deposition in the upper jurassic and lower cretaceous was confirmed we observed low hydrocarbon cracking levels and non biodegraded fluids of type ii iis organic matter in upper jurassic and lower cretaceous reservoirs while shallower tertiary reservoirs although more mature were altered by microbial biodegradation there reservoirs with temperatures below 80 c provided a good habitat for aerobic anaerobic bacteria and the possibility of hydrocarbon biodegradation

some effects of a seamount on oceanic flows abstract to demonstrate some effects of a seamount an oceanic flows we have considered a uniform two layer flow passing a right circular cylinder of arbitrary height in a rotating fluid in the case of vanishing stratification we first generalize previous results of low obstacles to an obstacle of finite height and then show how the frictional regime provides a transition from partial to total blocking as the obstacle top approaches the surface in the case of general stratification we have discerned various dynamical regimes according to blockage of the flows characterized by distinctive interface signatures for example as the obstacle top rises through the water column the axisymmetric doming of the interface first gives way to a reduced fore and aft symmetry when the lower layer is partially blocked then becomes a net depression when the lower layer is totally blocked and finally returns to its unperturbed level as both layers become totally blocked we have derived the critical stratificati

paleoenvironmental implications of novel c30 steranes in precambrian to cenozoic age petroleum and bitumen petroleums and bitumens from early proterozoic 1800 ma to miocene 15 ma age marine strata contain 24 isopropylcholestanes a novel group of c30 steroids the abundance of these compounds relative to 24 n propylcholestanes varies with source rock age late proterozoic vendian and early cambrian oils and or bitumens from siberia the urals oman australia and india have a high ratio of 24 isopropylcholestanes to 24 n propylcholestanes 1 while younger and older samples have a lower ratio 0 4 temporal changes in this parameter may reflect the relative abundance of certain porifera sponges and certain marine algae through time geochemical indicators such as this which can constrain the source rock age of a migrated oil are useful in source rock identification during petroleum exploration

ocean heat flux in the central weddell sea during winter abstract seasonal sea ice which plays a pivotal role in air sea interaction in the weddell sea a region of large deep water formation with potential impact on climate depends critically on heat flux from the deep ocean during the austral winter of 1994 an intensive process oriented field program named the antarctic zone flux experiment measured upper ocean turbulent fluxes during two short manned ice drift station experiments near the maud rise seamount region of the weddell sea unmanned data buoys left at the site of the first manned drift provided a season long time series of ice motion mixed layer temperature and salinity plus a truncated high resolution record of temperature within the ice column direct turbulence flux measurements made in the ocean boundary layer during the manned drift stations were extended to the ice ocean interface with a mixing length model and were used to evaluate parameters in bulk expressions for interfacial stress a rossby similarity drag law and ocean to

organic matter geochemistry and petrography of late cretaceous cenomanian turonian organic rich shales from the belle fourche and second white specks formations west central alberta canada abstract organic rich mudstones with up to 10 wt toc from the upper portion of the belle fourche formation and the lower part of the second white specks formation in the western canada sedimentary basin were evaluated as source rocks both geochemistry and organic petrography indicate an open marine paleoenvironment with deposition of type ii kerogen based on the predominance of marine alginite and amorphous organic matter om limited amounts of terrigenous vitrinite and inertinite macerals the presence of marine fossils and the low ratio of toc to total sulfur 1 26 the prevalence of short chain n alkanes n c13 to n c19 a predominance of c28 h 20s steranes and small concentrations of oleanane confirm the dominantly algal and planktonic origin of om alternating oxic to anoxic paleoenvironmental sedimentary conditions are proposed based on common bioturbation abundant inoceramid prisms and good organic richness biomarker distributions are consistent with intermittent anoxia without unequivocal evidence for water column stratification or hypersalinity the thermal maturity measured in seven sediment cores by different methods consistently indicates a westward increase in maturity according to vitrinite reflectance tmax and hopane and sterane biomarkers two cores are thermally immature 0 42 ro one is early mature 0 65 ro and four cores are within the oil window 0 78 to 0 89 ro all thermally mature cores retain good to very good hydrocarbon potential 248 mg hc g rock and are dominantly oil prone and minor gas prone based on their maceral compositions the upper belle fourche and lower second white specks formations represent potential targets for unconventional light shale oil production

depositional and organofacies influences on the petroleum potential of an unusual marine source rock waipawa formation paleocene in southern east coast basin new zealand abstract the paleocene waipawa formation is a widespread 2 80 m thick marine mudstone that occurs in several new zealand basins it is relatively enriched in organic matter om and is the inferred source of a sub commercial oil discovery and several correlated oil seeps to determine the organofacies and depositional influences on the petroleum potential of the formation we have undertaken a high resolution multidisciplinary study of the taylor white section in the central east coast basin this section is the thickest stratigraphically coherent surface exposure of the formation and includes contacts with the bounding whangai and wanstead formations bathymetric indicators within the foraminiferal assemblages indicate a slope setting for the section deepening from middle to lower bathyal through the waipawa wanstead succession significantly the whangai formation in this section is barren of foraminifera dinoflagellate and calcareous nannofossil biostratigraphy provides somewhat conflicting age control but a resulting age model indicates a tenfold increase in compacted sediment accumulation rate during waipawa deposition from 1 to 10 cm ky our multivariate statistical analysis of geochemical and paleontological data reveals systematic variation in paleoenvironmental and source rock parameters within the section with samples forming four distinct clusters or organofacies om rich and om poor waipawa organofacies whangai and wanstead organofacies the two waipawa organofacies are distinguished by enrichments in total organic carbon toc and organic 13c dominance of phytoclasts mainly degraded woody plant matter 66 98 and low amounts of amorphous organic matter whangai and wanstead organofacies are characterised by a greater proportion of marine om but are distinguished from each other by differences in om preservation om is well preserved with indications of hypoxia in the whangai organofacies but is poorly preserved in the wanstead organofacies geochemical fingerprinting identifies an interval of whangai organofacies that separates two phases of waipawa organofacies deposition the lower phase comprises four alternations between om rich and om poor waipawa organofacies and the upper phase comprises a single pulse of om rich waipawa facies bounded by om poor intervals overall waipawa formation in this section has toc and pyrolysable hydrocarbon s2 values of 0 2 4 6 mean 2 2 wt and 0 1 12 4 mean 3 9 mg hc g rock respectively one third of s2 values exceed 5 mg hc g rock indicating good very good bulk petroleum potential with the remainder having poor fair potential petroleum potential s2 increases with increasing toc r2 0 85 hydrogen index hi values range from 21 to 295 mg hc g toc averaging just 147 mg hc g toc in line with these modest hi values quantitative pyrolysis gas chromatography confirms that the petroleum potential is primarily for gas or gas condensate with relatively little oil potential of the total paraffinic petroleum yield gas n c1 5 contributes 80 100 whilst total n c6 and non volatile n c15 paraffinic oil contribute 20 and 6 respectively despite the low paraffinic oil potentials n c6 and n c15 correlate relatively strongly with hi and less strongly with toc the overall gas condensate prone nature of the waipawa organofacies at taylor white reflects the predominance of woody phytoclasts which are unlikely to produce paraffinic oil the small paraffinic oil component is instead more likely to be associated with the marine algal component although this component is volumetrically subordinate the higher paraffinic oil potential appears to result from the combination of high productivity of specific marine algae i e pelagophytes hypoxic depositional conditions and most importantly increased preservation of om including through sulfurisation this raises the possibility of more algal rich oil prone facies existing within the waipawa formation in areas with higher toc or alternatively in areas beyond the direct reach of the terrestrial influxes yet still sufficiently influenced by low water column oxygen levels and high sulfur contents that promote enhanced om preservation

the occurrence of isorenieratane and 24 n propylcholestanes in paleogene lacustrine source rocks from the dongying depression bohai bay basin implications for bacterial sulfate reduction photic zone euxinia and seawater incursions abstract lacustrine organic rich source rocks shales and mudstones were examined to assess the depositional environment and organic input sources of the third and fourth members of the eocene shahejie formation bohai bay basin china major organic contributions to the shahejie formation from dinoflagellates diatoms botryococcus and marine pelagophyte chrysophyte algae were determined using n alkane distributions gammacerane index and diagnostic steranes traces of higher plant biomarkers suggest that terrigenous organic inputs were limited the pervasive presence of carotane aryl isoprenoids paleorenieratane renieratane isorenieratane 2 methylhopanes and crocetane indicate significant organic contributions from bacterial communities including cyanobacteria purple sulfur bacteria chromatiaceae green sulfur bacteria chlorobiaceae and sulfate reducing bacteria the extent of h2s content bacterial sulfate reduction and photic zone euxinia pze were evaluated by determining the aryl isoprenoids ratio air 0 7 9 0 the presence of isorenieratene derivatives and the fate of sulfur in the water column there was a decrease of pze extent and duration from the northeast to the southwest of the palaeo lake and there was a decrease of water body salinity and bottom water anoxia from the fourth to the third member of the shahejie formation abrupt environmental perturbations in the third member of the shahejie formation are indicated not only by significant changes in parameters such as the pristane phytane and carotane n c20 alkane ratios the gammacerane index the isorenieratane c18 aryl isoprenoid and the air but also by the time lag in the expansion of cyanobacterial lineages after the expansion of purple green sulfur bacteria as well as seawater incursions the unexpected occurrence of intact c30 4 desmethylsteranes 24 n propylcholestanes in the shahejie formation is first reported here after very careful checking and provides unambiguous biological evidence for at least two marine transgression events reaching the eocene dongying palaeo lake the organic enrichment of the petroleum source rocks in the shahejie formation is a consequence of combined indigenous lacustrine algal production the constrained and favourable preservation conditions and significant bacterial contributions and marine organic matter inputs to the lake

depositional environment of the late santonian lacustrine source rocks in the songliao basin ne china implications from organic geochemical analyses abstract the songliao basin slb located in northeastern china is one of the largest cretaceous continental sedimentary basins in the world the slb is filled with sediments deposited in the upper jurassic the lower cretaceous and the upper cretaceous epochs the nenjiang formation k2n is subdivided into five members where member 2 k2n2 was deposited in the late santonian in the lower part of the nenjiang formation this member is characterized by a thick succession of organic rich source rocks however the complexity of the depositional environment raises questions about the specific factors that drove this accumulation of organic material here we present data on the total organic carbon toc contents and their stable carbon isotope values 13corg as well as biomarker data from 50 outcrop samples collected from the yuewangcheng ywc section in the southeastern slb according to the variations of the bulk organic parameters toc and 13corg and biomarker indices the profile could be divided into three stages stages i iii the distribution of biomarkers n alkanes steranes and hopanes and 13corg values indicate that the organic matter om in the lower k2n2 is derived largely from algae and macrophytes with a minor input from bacteria and land plants the water column was stratified as indicated by the presence of gammacerane variations in the pristane phytane pr ph and aryl isoprenoids relative to phenanthrene ratio a i p suggest that bottom waters were anoxic during stage i 31 5 26 0 m and stage ii 26 0 16 3 m with the anoxic layer impinging on the euphotic zone and a relative oxic environment at stage iii 16 3 0 m this brackish environment persisted in the water over the interval represented by the section as reflected by methytrimethyltridecyl chromans mttcs index mttci and mttc mttc ratios marine transgressions with subsequent seawater incursions can be detected with the presence of 24 n propyl cholestanes and 24 isopropyl cholestanes in the lower k2n2 sediments especially during stage i these seawater incursions are closely correlated with anoxic conditions and the deposition of organic rich source rocks

the denver cyclone part i generation in low froude number flow abstract a numerical model is used to study the denver cyclone a mesoscale vortex that develops in eastern colorado under southerly to southeasterly flow diurnal effects e g surface heating cooling have been excluded from these simulations but are discussed in part ii of this study simulations are first performed with a southerly ambient wind i e parallel to the continental divide if the froude number of the flow based on the height of the palmer divide an east west ridge to the south of denver is small then a vortex forms over the denver region this circulation then propagates northward at just over half the upstream flow velocity leaving essentially stagnant air in the lee of the palmer divide it is shown that coriolis turning has a negligible effect on the flow when the ambient wind is from the south however when the ambient wind is at an angle to the continental divide northerly winds can develop along the foothills due to coriolis turning of the flow as it approaches the divid

petroleum migration and mixing in the potiguar basin brazil regional studies of petroleum samples from both offshore and onshore reservoirs of the potiguar basin brazil reveal compositional differences with discernible landward trends attributable to oil mixing these chemical discrepancies can be related to a combination of source rocks maturity and migration history the source rocks are classified in two groups based on their geochemical and molecular characteristics 1 neocomian and aptian lacustrine freshwater shales and 2 aptian marine evaporitic shales and marls both lie in an offshore structural low the geochemically contrasting oils derived from these source beds migrated updip constrained by a monoclinal structure through aptian carrier beds to thermally immature strata evaluation of compositional heterog neities in the oils and an investigation of migration effects on their compositions reveal trends related to the amount of mixing which in turn reflects the timing of both oil generation and migration and the direction of migration the more migrated oils contain greater contributions from freshwater sources whereas the less migrated oils display more pronounced contributions from the younger and shallower hypersaline source beds biomarker maturity parameters indicate that the most migrated oils are less mature consistent with their early generation from the deeper lacustrine freshwater source beds and migration to fill the shallower reservoirs first the results suggest that drainage of the basin evolved from lateral to vertical and enable prediction of the distribution of petrol um types within the basin

stratospheric temperature anomalies and mountain waves a three dimensional simulation using a multi scale weather prediction model a non hydrostatic weather prediction model with an interactive grid nesting facility mm5 is used to infer the three dimensional mesoscale temperature field over the scandinavian mountains during 23 january 1991 six hours after the initialization from operational analyses warm and cold anomalies of mesoscale extent developed on isentropic surfaces at stratospheric heights over the windward slope of the mountains and further downstream mean mesoscale temperature fluctuations along isentropes amount to more than 4 k while minima and maxima can differ by more than 30 k consistent with height variations exceeding 3 km taking into account the three dimensional motion field cooling rates up to 20 k h are estimated

the effect of possible taylor columns on the summer ice retreat in the chukchi sea the chukchi sea topography consists of a broad flat 50 m deep plain with two prominent shoals herald and hanna which have horizontal dimensions of about 100 km and rise to depths of about 30 m herald shoal in particular is a prominent isolated seamount which because of the warm water flux in summer through bering strait has a warm 0 1 m s 1 flow incident upon it examination of active and passive microwave imagery of the region for 1992 1994 shows that as the general ice cover recedes the ice remains preferentially over herald shoal for 3 4 weeks after the surrounding ice has melted a scale analysis suggests that the cause of the ice persistence is the formation of a taylor column over the shoal which traps cold water and ice above it a similar trapping of ice occurs over hanna shoal and on its eastern slope but the response is complicated by a very different topography and the northward flow down barrow canyon

high resolution organic record of bridge creek deposition northwest new mexico abstract organic and inorganic geochemical data are presented and interpreted for a high resolution sample set from the uppermost portion of a transgressive systems tract condensed interval spanning the cenomanian turonian boundary at red wash northwest new mexico source potential toc rock eval yields thermal maturity vr elemental ca th and u in whole rock and molecular n alkanes steranes terpanes data are presented for a 64 sample 12 4 m composite section of limestones marlstones and shales of the bridge creek member of the greenhorn formation vertical sampling resolutions of 1 spl 19 cm spatial and 1 spl 33 ka temporal are used to monitor the progress of the transgression from the uppermost cenomanian up to the beginning of the highstand systems tract the section is thermally immature and maturity fluctuations are absent indicating that organic parameters are a function of organic matter production and preservation including diagenesis the rhythmic lithologic fluctuation within the bridge creek is not reflected in the source potential elemental or molecular data which show either no obvious pattern e g carbonate content toc or a unidirectional trend toward development of anoxia upsection e g hydrogen index sterane distributions homohopane index the distribution of the triaromatic steroid hydrocarbons c 20 21 26 28 according to side chain length also varies significantly despite the absence of maturity differences all of the unidirectional trends in the data are interpreted as related to either productivity differences e g sterane hopane ratios and changes in the relative concentration of r c 28 and r c 30 desmethylsteranes or the development of anoxia in the lower water column e g decreases in the diasterane regular sterane ratio increases in the homohopane index westward movement of the paleoshoreline during bridge creek time is also monitored by upsection decreasing th u ratios at red wash

error analysis and assimilation of remotely sensed ice motion within an arctic sea ice model new sea ice motion fields available from remotely sensed data are potentially useful for assessing and improving models of the polar ice pack here we investigate the error characteristics of the observed ice motions relative to drifting buoys and a dynamic thermodynamic ice model a data assimilation approach is then used to assess the potential of the motion data for reducing model biases as well as the potential of the model to serve as an interpolation tool to generate improved ice motion data sets special sensor microwave imager ssm i derived and model simulated ice motions for the years 1988 through 1993 are compared with ice displacement observations from drifting buoys variability and biases are summarized for seasonal and regional means ssm i motions are assimilated into the model using an optimal interpolation method that accounts for the modeled and ssm i motion error variances and the number and distribution of the ssm i motions modeled and ssm i derived motions are found to have comparable mean errors with some notable regional and seasonal differences assimilation substantially reduces the error standard deviation and improves the correlation of the simulated motions relative to the buoy observations but some biases remain in the model framework used here assimilation of the ssm i data substantially alters average ice thickness in some regions of the arctic and affects ice mass outflow through the fram strait but has a small effect on mean ice concentration the assimilation yields an increase in the spatial and temporal variability in ice deformation the observations are particularly suited for improving the simulation of specific synoptic events where substantial differences can occur between simulated and observed ice transport

relationships between porosity organic matter and mineral matter in mature organic rich marine mudstones of the belle fourche and second white specks formations in alberta canada abstract this study presents approaches for evaluating hybrid source rock reservoirs within tight rock petroleum systems the emerging hybrid source rock reservoir shale play in the upper cretaceous second white specks and belle fourche formations in central alberta canada is used as an example to evaluate organic and inorganic compositions and their relationships to pore characteristics nineteen samples from a 77 5 m long core were analyzed using organic petrography organic geochemistry several methods of pore characterization and x ray powder diffraction xrd the lower part of the studied section includes quartz and clay rich mudrocks of the belle fourche formation with low carbonate content whereas the upper portion contains calcareous mudrocks of the second white specks formation strata are mineralogically composed of quartz plus albite 18 56 wt carbonates calcite dolomite ankerite 1 65 wt clays illite kaolinite chlorite 15 46 wt and pyrite 2 12 wt petrographic examinations document that organic matter represents marine type ii kerogen partly biodegraded with limited terrestrial input vitrinite reflectance r o 0 74 0 87 t max values 438 446 c and biomarkers indicate mid maturity within the oil window the relatively poor remaining hydrocarbon potential expressed as an s2 value between 2 1 and 6 5 mg hc g rock may result from an estimated 60 83 of the original kerogen having been converted to hydrocarbons with the bulk having migrated to adjacent sandstone reservoirs however the present day remaining total organic carbon toc pd content remains relatively high 1 7 3 6 wt compared with the estimated original toc o of 2 4 5 0 wt the calculated transformation ratio of 60 83 suggests that the remaining 17 40 wt of kerogen is able to generate more hydrocarbons the studied section is a tight reservoir with an average swanson permeability of 3 37 10 5 md measured on two samples and total porosity between 1 7 and 5 0 vol 3 vol on average the upper part of the sandy belle fourche formation with slightly elevated porosity values 3 5 5 vol likely represents the interval with the best reservoir properties in the studied core interval total pore volume ranges between 0 0065 and 0 0200 cm 3 g measured by a combination of helium pycnometry and mercury immersion mesopores 2 50 nm are the most abundant pores and occupy 34 67 of total porosity or a volume of 0 0030 0 0081 cm 3 g in comparison micropores 3 g and macropores 50 nm reach up to 57 with the exception of some samples failing to indicate the presence of this pore fraction volume 0 0000 0 0107 cm 3 g macroporosity is mostly responsible for variations in total porosity as suggested by macroporosity s strongest correlation with total porosity within the section the relatively narrow ranges of toc and minerals contents among measured samples limit our ability to further deconvolute factors that influence changes in total porosity and pore size distribution