satellite remote sensing of surface oceanic fronts in coastal waters off west central florida abstract two algorithms designed to detect deepwater oceanic features and arbitrary edge profiles were tuned to automatically delineate fronts in coastal waters off west central florida using satellite derived sea surface temperature sst chlorophyll a concentration chl normalized water leaving radiance nlw and fluorescence line height flh images during select periods in the spring and fall of 2004 and 2005 the dates correspond to recreational king mackerel scomberomorus cavalla tournaments a histogram based algorithm was useful to detect coastal surface sst nlw and flh fronts specifically a gradient based algorithm with a smaller kernel box of 3 3 pixels best identified nearshore

ice pumps and their rates an ice pump is a heat engine driven by the change of freezing point with pressure which will melt ice at depth in the ocean and deposit it at a shallower location it is self starting calculations of the maximum magnitude of this effect are made which show good agreement with field data available for sea and lake ice the discussion is applied to the general case of a moving pack ice sheet with a well mixed surface layer and to floating ice shelves the rate of melt from an 11 m deep pressure ridge keel due to ice pumping is estimated as 26 cm year and that from the front of the ross ice shelf at mcmurdo sound antarctica is estimated as 5 m year for the level of water movement noted in the authors field observations far from the ice front pumping between shelf areas of different thickness will still occur with tidal motion providing the necessary water exchange but its magnitude is now limited by the ability to remove the potentially stable layer of melt water out of the system it is important to realize that the pumping does not depend on the availability of sensible heat in the water column and its effects are additional to any melting caused by the advection of warmer water to the ice water interface

borehole imagery of meteoric and marine ice layers in the amery ice shelf east antarctica a real time video camera probe was deployed in a hot water drilled borehole through the amery ice shelf east antarctica where a total ice thickness of 480 m included at least 200 m of basal marine ice down looking and side looking digital video footage showed a striking transition from white bubbly meteoric ice above to dark marine ice below but the transition was neither microscopically sharp nor flat indicating the uneven nature at centimetre scale of the ice shelf base upstream where the marine ice first started to accrete marine ice features were imaged including platelet structures cell inclusions entrained particles and the interface with sea water at the base the cells are assumed to be entrained sea water and were present throughout the lower 100 150m of the marine ice column becoming larger and more prevalent as the lower surface was approached until near the base they became channels large enough that the camera field of view could not contain them platelets in the marine ice at depth appeared to be as large as 1 2 cm in diameter particles were visible in the borehole meltwater probably marine and mineral particles liberated by the drill but their distribution varied with depth

limited availability of sulfur promotes copper rich mineralization in hydrothermal pb zn veins a case study from the schwarzwald sw germany abstract mixing of compositionally contrasting fluids is widely accepted as the major ore forming process in unconformity related hydrothermal pb zn fluorite barite veins although the general process is relatively well understood the temporal evolution of such fluid systems which may result in distinct mineralogical changes of the ore and gangue minerals precipitating are insufficiently constrained one specific example is the occurrence of late stage siderite chalcopyrite gersdorffite mineralization in 28 hydrothermal veins of the schwarzwald sw germany post dating the major fluorite barite galena sphalerite phase which is very common in the whole area to investigate the underlying process for this late stage cu ni stage published fluid inclusion data have been complemented by detailed confocal raman micro spectroscopy of fluid inclusions petrographic observations and electron microprobe analyses petrography as well as mineral compositions of sphalerite gersdorffite pyrite arsenopyrite fahlore and galena record a gradual but significant influx of cu and ni into a prevailing pb zn hydrothermal system this influx caused a distinct shift towards lower fo2 and pb zn sb ag s in the hydrothermal system at the transition from the pb zn to the cu ni mineralization stage this transition in mineralogy and the related gradual change of the hydrothermal fluid can be explained by changes in the relative proportion of involved fluid components however the transition to the cu ni mineralization stage by fluid influx is significantly different compared to the common rapid fluid mixing from below which is thought to be responsible for the typical pb zn veins and probably records the gradual transition from long term stable deep fluid reservoirs with constant chemical compositions towards more shallow and perturbed fluid reservoirs during rifting and exhumation

structural characteristics of congelation and platelet ice and their role in the development of antarctic land fast sea ice ice cores were obtained in january 1990 from the land fast ice in mcmurdo sound for a study of variations in texture fabric sub structure composition and development two primary ice types were observed congelation and platelet with a minor amount of frazil ice congelation ice growth precedes platelet ice accretion congelation ice fabrics show frequent moderate to strong alignments a phenomenon believed to be due to water current control of selective ice crystal growth platelet ice originates at the base of the congelation ice initially as a porous latticework of tabular ice crystals which subsequently consolidate by congelation of the interstitial water interstitial congelation ice fabrics generally have little or no alignment indicating the reduced effect of currents within the platelet latticework prior to solidification platelet crystal textures range from small wavy edged forms to large blade like forms platelet crystal fabrics indicate that in addition to being randomly oriented the platelet latticeworks commonly include many crystals with their flat 0001 faces oriented both parallel and normal to the base of the overlying ice plate width data suggest that the interstitial congelation ice growth rates remain similar to those of the overlying congelation ice this effective increase in growth rates probably happens because the latticework of accumulating platelets ahead of the freezing interface ensures that the water within the platelet layer is at the freezing point and less heat has to be removed from platelet rich water than from platelet free water for a given thickness of congelation ice to grow the negative oceanic heat flux associated with platelet ice formation in mcmurdo sound explains why mcmurdo sound fast ice is thicker than ross sea pack ice and also why it reaches a greater thickness than arctic fast ice grown in a similar polar marine climate plate widths in the mcmurdo sound congelation ice suggest however that it grows no faster than arctic congelation ice

oil oil correlation and potential source rocks for oils in paleozoic reservoir rocks in the tataria and perm basins russia abstract we present a study of 45 oil samples from the tataria and perm basins in the volgo ural region russia crude samples were obtained from 30 oil fields across the two basins samples are from variable carbonate and sandstone reservoir rocks ranging in age between givetian devonian and kazanian permian at various present day depths oil oil correlation suggests that despite the diversity of the reservoir rocks and vast geographic distribution all oils studied are classified in general into a singular genetic oil family with possible indication for secondary subdivision into two subgroups the major characteristics of the oils i e low pr ph ratio cpi 1 relatively high c 27 sterane low proportions of rearranged steranes c 29 c 30 hopane low ratio of ts to tm hopanes high sulfur content and high ratio of v to ni all suggest a reducing and probably hypersaline depositional environment for the source rock which was likely carbonate rich thermal maturity indicated for all the oils is in the upper range of the main phase of oil generation furthermore the characteristics obtained for the light end normal alkanes and mono aromatics indicate no significant degradation for most of the samples hence the relatively high specific gravity of the oil samples is not attributed to either maturity or degradation effects difference recorded in pr ph ratio between samples from perm basin are tentatively attributed to spatial variations in depositional environment conditions differences in tricyclic terpanes content in samples from both basins possibly indicate some variations in input of specific tasmanites algae to their source rock preliminary examination of an extract of devonian domanic formation sample corroborates the possibility that this formation is a major source rock for the oils in both the tataria and perm basins

numerical model to determine the composition of h2o nacl cacl2 fluid inclusions based on microthermometric and microanalytical data natural fluids approximated by the h2o nacl cacl2 system are common in a wide range of geologic environments including sedimentary basins associated with hydrocarbon occurrences and mvt deposits submarine hydrothermal systems and other metamorphic magmatic and hydrothermal environments we present a comprehensive numerical model and microsoft excel based computer program to determine the compositions of fluid inclusions in the h2o nacl cacl2 system based on microthermometric and microanalytical data the model consists of six polynomial correlation equations that describe liquid salinity as a function of nacl cacl2 ratio and melting temperature on each of the ice hydrohalite halite antarcticite cacl2 4h2o and cacl2 2h2o vapor saturated liquidus surfaces the cotectic and peritectic boundaries are determined from the intersections of the liquidus surfaces the model is implicitly internally consistent and topologically correct the model expands upon the compositional range of applicability and the data types that can be used for compositional determination it reproduces experimental data for all compositions that lie within the h2o nacl cacl2 4h2o compositional triangle in the h2o nacl cacl2 system and yields accurate reproductions of the h2o nacl and h2o cacl2 binaries furthermore in comparison to previously published models the one presented here eliminates systematic errors wavy isotherms and cotectic and peritectic curves with local bumps

on the seasonal and interannual migrations of the transition zone chlorophyll front 1 high resolution satellite measurements of ocean color and surface winds along with historical in situ data are used to explore interannual variability in the annual migration of the transition zone chlorophyll front tzcf in the central north pacific ocean significant variations in frontal position and annual range were observed including a significant southerly displacement during el nino events this displacement apparently forced by enhanced surface convergence and vertical mixing in the transition zone creates vast regions of anomalously high wintertime surface chlorophyll in the north pacific subtropical gyre a remarkably close correspondence between the positions of the tzcf and the 18 c surface isotherm over a portion of the central north pacific allows historical temperature data to be used as a proxy for tzcf position this surface temperature proxy has revealed decadal scale variability in frontal position with greater lesser annual range and southerly extent following the large scale 1976 77 1998 99 climate shifts interannual variations in tzcf position could have important implications for the distribution and survival of a number of apex predators that utilize the tzcf as a migratory and foraging habitat

influence of multistage oil emplacement on carbonate cementation in the eocene shahejie formation dongying sag bohai bay basin china abstract the influence of multi stage oil emplacement on carbonate cementation was investigated on the basis of determining the sequence of oil emplacement and carbonate cementation in the clastic reservoirs of the upper part of the fourth member of the eocene shahejie formation es4s in the yanxie 229 area dongying sag the sequence of multistage oil emplacement and carbonate cementation was determined by projecting the homogenization temperatures ths of two phase aqueous inclusions on a burial and thermal history plot the ratio of the number of quartz grains with yellow fluorescent oil inclusions therein to the total number of quartz grains ygoi and the ratio of the number of quartz grains with blue fluorescent oil inclusions therein to the total number of quartz grains bgoi were calculated to analyze the paleo oil saturation of each stage of oil emplacement the ygoi and bgoi values reflect the relative level of the paleo oil saturation of the first stage yellow fluorescent fsyf oil and the second stage blue fluorescent ssbf oil respectively a large number of primary pores were preserved in the oil layers whereas only a small number of dissolution pores and micropores were developed in the oil bearing water layers and dry layers calcite dolomite ferrocalcite and ankerite cementation and two stage oil emplacement occurred in the es4s reservoirs the fsyf oil emplacement occurred earlier than the ankerite cementation and ferrocalcite cementation but later than the calcite cementation and dolomite cementation the ssbf oil emplacement occurred later than all phases of carbonate cementation the dolomite cementation was not influenced by the fsyf oil emplacement because it occurred earlier than the fsyf oil emplacement the ankerite cementation was dominantly inhibited by the fsyf oil emplacement in the oil layers and the degree of inhibition increased with the increase in paleo oil saturation of the fsyf oil the ssbf oil emplacement further increased the paleo oil saturation in the oil layers which enhanced the inhibition of the ankerite cementation and even stopped it the ankerite cementation in the dry layers and oil bearing water layers was slowed down or stopped due to the lack of pores and the low transportation rate of external material which was caused by the intense ankerite cementation prior to the ssbf oil emplacement

cement stratigraphy in triassic and jurassic limestones of the weserbergland northwestern germany abstract cement stratigraphy of the korallenoolith oxfordian and trochitenkalk upper muschelkalk formations southern lower saxony hills of germany is based on investigation of 232 carbonate samples by cathodoluminescence cl this enables subdivision of cements into four main generations generation 1 consisting of fine columnar equant and syntaxial cements with blotchy cl and or microdolomite inclusions that is interpreted as originally submarine mg calcitic precipitate generation 2 found in jurassic samples only these cements show intrinsic to non luminescent cl with thin bright orange subzones and they are interpreted as meteoric phreatic calcites generation 3 1 characterized by zoned calcites with variable cl colours these cements precipitated under shallow burial conditions in a phreatic environment during an incipient stage of late diagenesis generation 3 2 with relatively uniform orange cl indicative of precipitation in a stable chemical environment this cement generation is interpreted as late diagenetic deep burial calcites generation 3 3 partially strongly zoned and with a characteristically intense cl contrast it has been identified in only 17 of the 82 trochitenkalk samples deformation twins end within this generation indicating a post tectonic genesis for the subsequent younger cement zones the cements were probably precipitated in a near surface environment characterized by reducing or variable eh conditions generation 4 consisting of calcites that show intrinsic cl with bright orange subzones comparable to generation 2 but lacking deformation twins these cements are interpreted as post tectonic late diagenetic products of a meteoric phreatic environment based on detailed cl petrography fifteen diagenetic events three calcite cements three dolomite generations three fissure generations two stages of dedolomitization aragonite dissolution matrix recrystallization and two stages of hmc lmc transformation can be distinguished and timed relative to cement zonation the progressively decreasing 18o values for cement generations 1 to 3 2 likely reflect increasing temperatures caused by burial the low 18c values of cement generation 4 are probably a reflection of a meteoric diagenetic environment a time burial cementation pathway can be modelled combining cl patterns cement isotopic data and the subsidence history of the study area the main features of this model are 1 1 generation 1 cements are submarine precipitates and their age therefore coincides with sedimentation 2 2 cement generation 3 1 of the trochitenkalk commenced precipitation at a depth of about 120 m reached during late triassic time in case this minimum depth is also the formation depth of generation 3 1 in the korallenoolith formation then precipitation of these cements started during late jurassic time 3 3 cement generation 3 2 of both the trochitenkalk and the korallenoolith formation precipitated at assumed depths 1000 m reached during the doggerian and at the time of jurassic cretaceous transition respectively 4 4 cement generation 4 precipitated after the sediments had undergone telogenesis and must thus be younger than the intra senonian sub hercynian tectonic phase and possibly even younger than the paleocene tectonic pulse laramian phase

hydrocarbon water interactions during brine migration evidence from hydrocarbon inclusions in calcite cements from danish north sea oil fields abstract crude oils in primary and secondary fluid inclusions in calcite from fractures in seven offshore oil fields associated with diapiric salt structures in the danish sector of the north sea were analyzed by capillary column gas chromatography and compared with crude oils produced from the same reservoirs oils from fluid inclusions in all fields show evidence of biodegradation decreased n c17 pristane and n c18 phytane ratios and loss of n c7 2 methyl hexane and 3 methyl hexane relative to methyl cyclohexane and water washing absence of benzene and depletion of toluene some oils in inclusions are extremely enriched in c6 and c7 cyclic alkanes suggesting that these samples contain hydrocarbons exsolved from ascending hotter formation waters compared to inclusion oils the produced oils are less biodegraded but are water washed indicating that both types of oil interacted with large volumes of formation water the carbon isotopic composition of the calcite host of the fluid inclusions in the dagmar and skjold fields is as light as 16 5 pdb and the sulfur isotopic composition of pyrite in and adjacent to the calcite veins in the skjold field is as light as 39 6 cdt indicating that biodegradation of the oils was a source of some of the carbon in the calcite and sulfate reduction was the source of sulfur for the pyrite the evidence for microbial degradation of petroleum is consistent with present day reservoir temperatures 65 96 c but is not consistent with previous estimates of the temperatures of calcite vein filling 95 130 c which are much higher than the temperatures of known occurrences of biodegraded oil

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

cement distribution in a carbonate reservoir recognition of a palaeo oil water contact and its relationship to reservoir quality in the humbly grove field onshore uk abstract the distribution of mineral cements total porosity microporosity and permeability have been determined for the humbly grove oolitic carbonate reservoir middle jurassic great oolite formation weald basin onshore uk using a combination of optical petrography electron microscopy fluid inclusion analysis quantitative xrd wireline data analysis and core analysis data grainstone reservoir facies have porosities ranging between 5 and 24 but are mostly between 11 and 24 permeabilities vary from

diagenetic evolution of the carnian wetterstein platforms of the eastern alps the carbonate platforms of the wetterstein formation of the eastern alps drau range and northern calcareous alps show a distinct facies zonation of reefs and lagoons while some lagoonal areas were episodically emerged and formed lagoonal islands others remained permanently flooded the scale of near surface meteoric or marine diagenesis was related to this lagoonal topography at shallow burial depth cementation was dominated by altered marine solutions which additionally caused recrystallization of metastable constituents of the sediment and earlier marine cements high magnesian calcite aragonite connected with a carbon and oxygen isotopic change to more negative values deeper burial cementation shows a succession with two types of saddle dolomite and three types of blocky calcite carbon and oxygen isotopic values of these cements show a trend towards more negative values from the first to the last generation in the following succession clear saddle dolomite zoned blocky calcite cloudy saddle dolomite post corrosion blocky calcite replacive blocky calcite fluid inclusion studies of the carbonate cements are interpreted to indicate a deeper burial temperature development that first increases from 175 to 317 c followed by a temperature decrease to 163 260 c and subsequent increase up to 316 c whereby the samples of the drau range always show the lowest values calculations of the isotopic composition of the water from which the carbonate cements were precipitated yielded positive 18o values from 6 66 to 17 81 o smow which are characteristic for formation and or metamorphic waters also the isotopic compositions of the palaeofluids probably changed during deeper burial diagenesis following the temperature development

seasonal variations in the properties and structural composition of sea ice and snow cover in the bellingshausen and amundsen seas antarctica sixty three ice cores were collected in the bellingshausen and amundsen seas in august and september 1993 during a cruise of the r v nathaniel b palmer the structure and stable isotopic composition 18 o 16 o of the cores were investigated in order to understand the growth conditions and to identify the key growth processes particularly the contribution of snow to sea ice formation the structure and isotopic composition of a set of 12 cores that was collected for the same purpose in the bellingshausen sea in march 1992 are reassessed frazil ice and congelation ice contribute 44 and 26 respectively to the composition of both the winter and summer ice core sets evidence that the relatively calm conditions that favour congelation ice formation are neither as common nor as prolonged as the more turbulent conditions that favour frazil ice growth and pancake ice formation both frazil and congelation ice layers have an av erage thickness of 0 12 m in winter evidence that congelation ice and pancake ice thicken primarily by dynamic processes the thermodynamic development of the ice cover relies heavily on the formation of snow ice at the surface of floes after sea water has flooded the snow cover snow ice layers have a mean thickness of 0 20 and 0 28 m in the winter and summer cores respectively and the contribution of snow ice to the winter 24 and summer 16 core sets exceeds most quantities that have been reported previously in other antarctic pack ice zones the thickness and quantity of snow ice may be due to a combination of high snow accumulation rates and snow loads environmental conditions that favour a warm ice cover in which brine convection between the bottom and top of the ice introduces sea water to the snow ice interface and bottom melting losses being compensated by snow ice formation layers of superimposed ice at the top of each of the summer cores make up 4 6 of the ice that was examined and they increase by a factor of 3 the quantity of snow entrained in the ice the accumulation of superimposed ice is evidence that melting in the snow cover on antarctic sea ice floes ran reach an advanced stage and contribute a significant amount of snow to the total ice mass

calcite cement stratigraphy and cementation history of the burlington keokuk formation mississippian illinois and missouri abstract iron content and cathodoluminescence define six regionally extensive calcite cement zones over 100 000 sq km of study area in the burlington keokuk formation of illinois and missouri the regional cement stratigraphy is composed of mappable zones analogous to lithostratigraphic units which represent diagenetic episodes during which calcite with distinct cathodoluminescent properties precipitated in a given time interval relative to other diagenetic events such as cement fracturing and calcite dissolution individual cement zones may not be strictly isochronous throughout the study area but are not strongly diachronous two different but related cathodoluminescent sequences have been identified within pre pennsylvanian cements in the burlington keokuk formation 1 within lower strata early nonferroan cement consists of both nonluminescent and luminescent calcite zones ii iv 2 within upper strata early nonferroan cement consists of entirely luminescent calcite zone ii petrographic relationships indicate that zone ii is time equivalent with zones ii iv in lower burlington keokuk strata the occurrence of cement zones ii iv encased in pennsylvanian shale and quartz sand within pre pennsylvanian karst cavities constrains the age of early nonferroan calcite as pre pennsylvanian in ll cases pre pennsylvanian cements are followed by ferroan dull to moderately luminescing calcite zone v which in turn is overgrown by nonferroan moderate to brightly luminescing calcite zone vi cross cutting relations of burlington keokuk syntaxial calcite with mississippi valley type mineralization phases constrains the minimum age of cement zones v and vi as early permian pre pennsylvanian cements formed in a shallow meteoric aquifer characterized by vertically segregated chemical facies pre pennsylvanian cements within lower strata precipitated from waters of varying eh while those in upper strata formed from reduced waters post mississippian pre early permian cements precipitated under less than 1 km of overburden from reducing meteoric waters or subsurface brines

diagenesis by burial fluids middle ordovician platform to platform margin limestones east tennessee relationship to mississippi valley type deposits abstract we compare relative timing and geochemistry of different paragenetic phases in platform margin and platform interior limestones within a nearly 400 m thick succession of middle ordovician strata emphasis is on late stage cements that include ferroan coarse sparry calcite and ferroan baroque dolomite platform interior rocks contain two late cements clear sparry calcite and nonferroan dolomite not observed in platform margin rocks depleted 18o and high iron content of these four calcite and dolomite phases indicate a fluid that had interacted with siliciclastic material late stage diagenetic cements in the platform margin limestones generally have more lower values of 18o higher iron and manganese contents and more radiogenic 87sr than their counterparts from the platform multiple interpretations for the different diagenetic phases and geochemistry are possible we favor a water rock interaction hypothesis because it requires a single source and is therefore the simplest explanation ferroan coarse sparry calcite and ferroan baroque dolomite could have been generated from brines expelled from the sevier basin before the end of the middle ordovician ca 450 ma these fluids could have moved up dip into platform carbonates under pressures induced by burial alone this is based on an analysis of burial curves possible temperatures and an assumed range of likely brine compositions bitumen associated with some ferroan baroque dolomite may be synchronous with mississippi valley type main ore stage sphalerite the timing for fluid migration that we suggest here contrasts with conventional thinking which places the major fluid migration during the alleghenian orogeny 332 250 ma at the end of the late paleozoic

cement geochemistry of photozoan carbonate strata upper carboniferous lower permian finnmark carbonate platform barents sea the following figure was originally printed without the vertical axis labels the paper appeared in the

impact of antarctic ice shelf basal melting on sea ice and deep ocean properties 1 an approximation of antarctica s rocky and icy coastline normally forms the southern boundary in global climate models such a configuration neglects extensive ice shelf areas where ocean ice interaction initiates a net freshwater flux to the circumpolar continental shelf equal to 75 of the annual mean net precipitation in coastal seas the results of a numerical model for the southern ocean using two contrasting configurations with and without caverns beneath major antarctic ice shelves are compared they show that the freshwater flux due to deep basal melting significantly stabilizes the shelf water column in front of an ice shelf as well as downstream due to advection by the coastal current if the freshwater from the caverns is absent sea ice is thinner shelf waters are warmer and saltier and the southern ocean deep basins are flushed by denser waters

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

anomalous winter winds decrease 2014 transition zone productivity in the ne pacific wind driven transport from the north pacific in winter provides nutrients to a highly productive region in the transition zone between the subarctic and subtropics this region supports many species of fish marine mammals and seabirds in winter 2013 2014 anomalous winds from the south weakened nutrient transport in the eastern north pacific resulting in substantial decreases in phytoplankton biomass by january 2014 waters were warmer than usual by 3 5 c at the center of an affected area covering 1 5 106 km2 south of this area winter chlorophyll levels dropped to the lowest levels seen since the sea viewing wide field of view sensor satellite began taking measurements in 1997 it is anticipated that impacts will be felt in some fisheries and among migrating predators this coming year

the diagenesis of the late dinantian derbyshire east midland carbonate shelf central england carbonate cements in late dinantian asbian and brigantian limestones of the derbyshire carbonate platform record a diagenetic history starting with early vadose meteoric cementation and finishing with burial and localized mineral and oil emplacement the sequence is documented using cement petrography cathodoluminescence trace element geochemistry and c and o isotopes the earliest cements pre zone 1 are locally developed non luminescent brown sparry calcite below intrastratal palaeokarsts and calcretes they contain negligible fe mn and sr but up to 1000 ppm mg their isotopic compositions centre around 18o 8 5 13c 5 0 calcretes contain less 13c subsequent cements are widespread as inclusion free low mg low fe crinoid overgrowths and are described as having a dead bright dull cathodoluminescence the dead cements zone 1 are mostly non luminescent but contain dissolution hiatuses overlain by finely detailed bright subzones that correlate over several kilometres across dead bright subzones there is a clear trend in mg 500 900 ppm mn 100 450 ppm and fe 80 230 ppm zone 1 cements have isotopic compositions centred around 18o 8 0 and 13c 2 5 zone 2 cement is bright thin and complexly subzoned it is geochemically similar to bright subzones of zone 1 cements dull zone 3 cement pre dates pressure dissolution and fills 70 or more of the pore space it generally contains little mn fe and sr but can have more than 1000 ppm mg increasing stratigraphically upwards the 18o compositions range from 5 5 to 15 and the 13c range is 1 to 3 20 00 zone 4 fills veins and stylolite seams in addition to pores it is synchronous with pb ba f ore mineralization and oil migration zone 4 is ferroan with around 500 ppm fe up to 2500 ppm mg and up to 1500 ppm mn isotopic compositions range widely 15o 2 7 to 9 and 13c 3 8 to 2 50 unaltered marine brachiopods suggest a dinantian seawater composition around 15o 0 smow but vital isotopic effects probably mask the original 13c pdb value pre zone 1 calcites are meteoric vadose cements with light soil derived 13c and light meteoric 18o an unusually fractionated pluvial 15o smow value of around 6 is indicated for local dinantian meteoric water calcrete 18o values are heavier through evaporation zone 1 textures and geochemistry indicate a meteoric phreatic environment fe and mn trends in the bright subzones indicate stagnation and precipitation occurred in increments from widespread cyclically developed shallow meteoric water bodies meteoric alteration of the rock body was pervasive by the end of zone 1 with a general resetting of isotopic values zone 3 is volumetrically important and external sources of water and carbonate are required emplacement was during the namurian early westphalian by meteoric water sourced at a karst landscape on the uplifted eastern edge of the derbyshire east midland shelf the light 18o values mainly reflect burial temperatures and an unusually high local heat flow but an input of highly fractionated hinterland derived meteoric water at the unconformity is also likely relatively heavy 13c values reflect the less altered state of the source carbonate and aquifer zone 4 is partly vein fed and spans burial down to 2000 m and the onset of tectonism light organic matter derived 13c and heavy 18o values suggest basin derived formation water combined with textural evidence of geopressures this relates to local high temperature ore mineralization and oil migration low water to rock ratios with host rock buffering probably affected the final isotopic compositions of zone 4 masking extremes both of temperature and organic matter derived co2

development and properties of sea ice in the coastal regime of the southeastern weddell sea from october to december 1986 a program consisting of sea ice core analysis in combination with sea ice observations was carried out from the icebreaker r v polarstern as part of the winter weddell sea project the ship operated in the central and southeastern weddell sea with interests focusing on the ice shelf front between 70 s and 77 s where a system of coastal polynyas extended for several tens to hundreds of kilometers opened and maintained despite temperatures well below freezing by offshore wind forcing three wind controlled ice formation regimes may be distinguished 1 for wind speeds 10 m s the ice cover is heavily ridged and rafted 50 and formation of granular ice predominates of the total length of cores sampled in the coastal regime 32 consisted of columnar and 35 of granular ice in addition we observed two unique ice classes along the coast platelet ice formed through consolidation of underwater ice platelets underneath the solid ice cover contributed 11 to our core samples another 22 consisted of intermediate columnar granular ice which originates under the dynamic hydrographic conditions of the near ice shelf region

modeling the effects of frazil ice crystals on the dynamics and thermodynamics of ice shelf water plumes the seawater that comes into contact with the base of a floating ice shelf is modified as a result of the phase changes that occur melting is prevalent in the deepest parts of the subice cavity and this drives a buoyant flow of ice shelf water isw along the sloping ice shelf base the ascent of the isw toward the surface of the ocean causes supercooling because the freezing point rises with the falling pressure and this induces a change from melting to freezing assuming that seed crystals exist the isw now fulfills the condition for the rapid growth of disc shaped frazil ice crystals which may subsequently settle upward out of suspension under the action of gravity a simple numerical model of these processes has been developed based on the theory of inclined plumes the isw is treated as a turbulent particle laden gravity current ascending a reactive boundary and containing a suspended crystal load which evolves in response to the supercooling of the water and the inverted sedimentation of the crystals the frazil ice has two important effects on the behavior of the isw plume because the generation of crystals through out the plume provides such a large area over which phase changes can occur the conversion of supercooling into ice happens much more readily than is possible through turbulent transfer of heat and mass at the ice shelf base a suspended crystal load reduces the bulk density of the isw so that a growing suspension causes the plume to accelerate while deposition of crystals onto the ice shelf effects a deceleration there are positive feedbacks in that an acceleration of the plume induces more rapid crystal growth while a deceleration allows suspended crystals to settle out more easily

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

tracing deep fluids in the bozhong sag evidence from integrated petrography and geochemistry data abstract the bozhong sag is a mature exploration area for petroleum in the bohai bay basin china which is a typical oil bearing basin and hosts the penglai pl 19 3 and qinhuangdao qhd 32 6 giant oil fields xue 2018 despite 60 years of hydrocarbon exploration in the basin only few large gas fields have been discovered the discovery of the bozhong bz 19 6 gas field not only indicated that the bozhong sag has great potential for natural gas exploration but also raised questions regarding the formation of large scale natural gas fields in typical oil prone basins and in sapropelic source rocks the present study therefore performs a detailed investigation of the sources and migration pathways of the deep fluids in the bozhong sag area as a means of shedding light into this scientific challenge the bozhong sag is located in the thinnest crust and tectonic transition zone of the bohai bay basin intense extension and thinning of lithosphere led to the upward ejection of deep crust and mantle materials under diapirism improvements in this tectonic setting and the fluid migration path occurred as a result of early faults that were formed by compressive thrust in the indosinian yanshan orogenies in addition to a process of extensional development and reactivation of himalayan faults we obtained cores from 13 wells in the bozhong sag and subsequently observed their petrography and analyzed samples for fluid inclusions also volcanic rock samples were analyzed for major and trace elements and carbonate rock samples were analyzed for 13c 18o and 87sr 86sr previously reported 13cco2 and he isotopic data were are also discussed our results showed that petrography was characterized by thermal fading and hydrothermal breccia around fractures filled with quartz and calcite deep fluid activity was mainly reflected by petrographic assemblages of quartz ankerite pyrite plus calcite and volcanic eruptive rocks that were i enriched with large ion lithophile elements lile ii enriched with light rare earth elements lree iii relatively deficient in high field strength elements hfse and iv relatively deficient heavy rare earth elements hree thermal anomaly events were reflected by the homogenization temperature of fluid inclusions and characteristics of magmatic hydrothermal fluids were exhibited by 13c 18o and 87sr 86sr our findings indicated that deep fluids were mainly derived from the deep parts of the upper mantle and that they were slightly contaminated by crustal materials combining our results with those of previous studies on deep xenoliths and xenolithic fluid compositions in eruptive rocks of eastern china zhang et al 1999 han et al 2008 we interpreted that deep fluid properties in the study region were characterized by high h2 and low total volatile gases we conclude that the deep fluids in the bozhong sag was mainly derived from deep material in the upper mantle and that the fluid activity pattern was aided by the deep fracture fault systems in addition to central and fissure type wide area eruption activities

sea surface temperature gradients across blue whale and sea turtle foraging trajectories off the baja california peninsula mexico sea surface temperature sst fronts are integral to pelagic ecology in the north pacific ocean so it is necessary to understand their character and distribution and the way these features influence the behavior of endangered and highly migratory species here telemetry data from sixteen satellite tagged blue whales balaenoptera musculus and sea turtles caretta caretta chelonia mydas and lepidochelys olivacea are employed to characterize biologically relevant sst fronts off baja california sur high residence times are used to identify presumed foraging areas and sst gradients are calculated across advanced very high resolution radiometer avhrr images of these regions the resulting values are compared to classic definitions of sst fronts in the oceanographic literature we find subtle changes in surface temperature between 0 01 and 0 101c km across the foraging trajectories near the lowest end of the oceanographic scale between 0 03 and 0 31c km suggesting that edge detection algorithms using gradient thresholds 40 101c km may overlook pelagic habitats in tropical waters we use this information to sensitize our edge detection algorithm and to identify persistent concentrations of subtle sst fronts in the northeast pacific ocean between 2002 and 2004 the lower gradient threshold increases the number of fronts detected revealing more potential habitats in different places than we find with a higher gradient threshold this is the expected result but it confirms that pelagic habitat can be overlooked and that the temperature gradient parameter is an important one r 2006 elsevier ltd all rights reserved

chalk fluid interactions with glycol and brines abstract mechanical properties of high porosity chalks are strongly dependent on the type of fluid in the pores dry chalk is considerably stronger than water saturated chalk and this phenomenon is often referred to as the water weakening effect to address the problem of chalk fluid interactions several series of tests have been performed with glycol and high concentration brines as saturating fluids glycol is a fluid that in many aspects resembles oil except that glycol is miscible with water glycol saturated chalk turns out to have properties very similar to oil saturated chalk compared to dry chalk both oil and glycol make the chalk somewhat weaker but this weakening effect is much less than with water several series of tests with brines with high concentrations of calcium chloride or sodium chloride show that the water weakening effect is considerably reduced in high ionic strength solutions most tests were performed as quasi hydrostatic tests with a constant stress ratio of 0 9 in such tests the yield point marks the onset of accelerated pore collapse and the yield value is close to the hydrostatic yield stress in addition to these compressive tests a series of brazilian tests were performed revealing the same trend the variations in mechanical strength have been correlated with the activity of water in the brines within the experimental accuracy of the compressive tests there is a linear trend between reduction of water activity and the corresponding increase in strength this leads to the hypothesis that the water activity may be a key parameter in the water weakening mechanism but this conclusion also indicates that water weakening may be a special case of general chalk fluid interactions where the degree of weakening depends on the strength of adsorption of the fluid molecules to the calcite surfaces

the transition zone chlorophyll front a dynamic global feature defining migration and forage habitat for marine resources abstract pelagic ecosystem dynamics on all temporal scales may be driven by the dynamics of very specialized oceanic habitats one such habitat is the basin wide chlorophyll front located at the boundary between the low chlorophyll subtropical gyres and the high chlorophyll subarctic gyres global satellite maps of surface chlorophyll clearly show this feature in all oceans in the north pacific the front is over 8000 km long and seasonally migrates north and south about 1000 km in the winter this front is located at about 30 35 n latitude and in the summer at about 40 45 n it is a zone of surface convergence where cool vertically mixed high chlorophyll surface water on the north side sinks beneath warm stratified low chlorophyll water on the south side satellite telemetry data on movements of loggerhead turtles and detailed fisheries data for albacore tuna show that both apex predators travel along this front as they migrate across the north pacific the front is easily monitored with ocean color satellite remote sensing a change in the position of the tzcf between 1997 and 1998 appears to have altered the spatial distribution of loggerhead turtles the position and dynamics of the front varied substantially between the 1998 el nino and the 1999 la nina for example from may to july 1999 the transition zone chlorophyll front tzcf remained between about 35 n and 40 n latitude showing very little meandering whereas in 1998 during the same period the tzcf exhibited considerable meandering and greater monthly latitudinal movement catch rates for albacore were considerably higher in 1998 than in 1999 and we hypothesize that a meandering tzcf creates regions of convergence which enhances the foraging habitat for apex predators along the front

impact of basin burial and exhumation on jurassic carbonates diagenesis on both sides of a thick clay barrier paris basin ne france several diagenetic models have been proposed for middle and upper jurassic carbonates of the eastern paris basin the paragenetic sequences are compared in both aquifers to propose a diagenetic model for the middle and late jurassic deposits as a whole petrographic optical and cathodoluminescence microscopy structural fracture orientations and geochemical 18o 13c ree studies were conducted to characterize diagenetic cements with a focus on blocky calcite cements and their connection with fracturation events four generations of blocky calcite cal1 cal4 are identified cal1 and cal2 are widespread in the dominantly grain supported facies of the middle jurassic limestones about 90 of the cementation whereas they are limited in the oxfordian because grain supported facies are restricted to certain stratigraphic levels cal1 and cal2 blocky spars precipitated during burial in a reducing environment from mixed marine meteoric waters and or buffered meteoric waters the meteoric waters probably entered aquifers during the late cimmerian jurassic cretaceous boundary and late aptian early cretaceous unconformities the amount of cal2 cement is thought to be linked to the intensity of burial pressure dissolution which in turn was partly controlled by the clay content of the host rocks cal3 and cal4 are associated with telogenetic fracturing phases the succession of cal3 and cal4 calcite relates to the transition towards oxidizing conditions during an opening of the system to meteoric waters at higher water rock ratios these meteoric fluids circulated along pyrenean oligocene and alpine fractures and generated both dissolution and subsequent cementation in oxfordian vugs in mud supported facies and in poorly stylolitized grainstones however these cements filled only the residual porosity in middle jurassic limestones in addition to fluorine inputs fracturation also permitted inputs of sulphur possibly due to weathering of triassic or purbeckian evaporites or h2s input during paleogene times

resetting of mg isotopes between calcite and dolomite during burial metamorphism outlook of mg isotopes as geothermometer and seawater proxy abstract magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates calcite due to its ubiquitous occurrence and the large mg isotope fractionation associated with the mineral has attracted great interests in applications of mg isotope geochemistry however the fidelity of mg isotopes in geological records of carbonate minerals e g calcite and dolomite against burial metamorphism remains poorly constrained here we report our investigation on the mg isotope systematics of a dolomitized middle triassic geshan carbonate section in eastern china magnesium isotope analysis was complemented by analyses of sr c o isotopic compositions major and trace element concentrations and petrographic and mineralogical features multiple lines of evidence consistently indicated that post depositional diagenesis of carbonate minerals occurred to the carbonate rocks magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high 26mg dolomite end member and a low 26mg calcite end member irrespective of sample positions in the section and calcite dolomite ratio in the samples by fitting the measured mg isotope data using a two end member mixing model an inter mineral 26mgdolomite calcite fractionation of 0 72 was obtained based on the experimentally derived mg isotope fractionation factors for dolomite and calcite a temperature of 150 190 c was calculated to correspond to the 0 72 26mgdolomite calcite fractionation such temperature range matches with the burial thermal history of the local strata making a successful case of mg isotope geothermometry our results indicate that both calcite and dolomite had been re equilibrated during burial metamorphism and based on isotope mass balance of mg the system was buffered by dolomite in the section therefore burial metamorphism may reset mg isotope signature of calcite and mg isotope compositions in calcite should be dealt with caution in studies of carbonate rocks with thermal history by contrast mg isotopes of dolomite are less prone to post depositional resetting due to a number of properties including high mg abundance and high thermodynamic stability and mg isotopes in dolomite may be a more robust recorder for original carbonate precipitates

organic matter diagenesis in shallow water carbonate sediments muddy carbonate deposits near the dry tortugas florida are characterized by high organic carbon remineralization rates however approximately half of the total sedimentary organic matter potentially supporting remineralization is occluded in caco3 minerals intracrystalline while a portion of nonintracrystalline organic matter appears to cycle rapidly intracrystalline organic matter has an approximately constant concentration with depth suggesting that as long as its protective mineral matrix is intact it is not readily remineralized organic matter in excess of intracrystalline organic matter that is preserved may have a variety of mineral associations e g intercrystalline adsorbed or detrital in surface sediment aspartic acid contributed 22 mole and 50 mole to nonintracrystalline and intracrystalline pools respectively in deeper sediment 1 6 1 7m the composition of hydrolyzable amino acids in both pools was similar aspartic acid 40 mole like amino acids intracrystalline and nonintracrystalline fatty acids have different compositions in surface sediments but are indistinguishable at depth these data suggest that preserved organic matter in the nonintracrystalline pool is stabilized by its interactions with caco3 neutral lipids are present in very low abundances in the intracrystalline pool and are extensively degraded in both the intracrystalline and nonintracrystalline pools suggesting that mineral interactions do not protect these compounds from degradation the presence of chlorophyll a but absence of phytol in the intracrystalline lipid pool demonstrates that chloropigments are present only in the nonintracrystalline pool sedimentary chloropigments decrease with depth at similar rates in dry tortugas sediments as found in alumino silicate sediments from the long island sound suggesting that chloropigment degradation is largely unaffected by mineral interactions overall however inclusion and protection of organic matter by biominerals is a major pathway for organic matter preservation in this low organic carbon biomineral rich regime

the relationship between petroleum emplacement and carbonate reservoir quality examples from abu dhabi and the amu darya basin abstract the relative importance of petroleum emplacement in inhibiting diagenetic processes and preserving porosity and permeability in lower cretaceous thamama group kharaib formation carbonate reservoirs of abu dhabi uae and in callovian kimmeridgian carbonate reservoirs of the amu darya basin in uzbekistan and turkmenistan has been evaluated by combining geologic petrophysical and geochemical data when petroleum emplacement is synchronous with and prior to significant burial cementation in carbonates primary petroleum inclusions are trapped in the cements the process appears to be characterised by steep intra field porosity depth trends within a more gradual regional decline in porosity with depth this has profound implications for the prediction of porosity in carbonate reservoirs reservoir quality is better in grainstones and packstones compared to adjacent wackestones and lime mudstones in the kharaib formation because of preserved macroporosity intergranular vuggy mouldic the pore system in the finer units is dominated by micropores these features indicate a primary textural control on porosity and permeability within the grainstones and packstones macroporosity is variably filled by late equant sparry calcite cements porosity and permeability variations in grainstones and packstones at a reservoir scale are therefore controlled by the variation in amount of equant sparry calcite cement this in turn depends on the timing of the precipitation of this cement relative to petroleum emplacement as shown by fluid inclusion data where petroleum emplacement has occurred relatively early at migration foci prior to significant burial cementation by equant sparry calcite reservoir quality is preserved where it has occurred after significant burial cementation reservoir quality has been destroyed in the amu darya sequences primary macroporosity is commonly preserved down to depths of 11 000 ft 3 5 km with differences in the porosity and permeability characteristics of grainstones being controlled by variations in the amount of early probably freshwater cement and the extent of associated dissolution small volumes of burial cements do occur but they do not contain petroleum inclusions consequently there is no firm evidence that petroleum emplacement has inhibited diagenesis in this area this part of the study has shown that it is not always possible to obtain conclusive evidence from the diagenesis to pin down the processes responsible for the preservation of reservoir quality and that petroleum filling may not always be the primary cause the relationships documented here show that the race for space between diagenetic waters and petroleum is a major control on reservoir quality in the thamama group carbonate reservoirs but is not so important for the jurassic carbonates in the amu darya basin

the devonian and carboniferous of the moscow syneclise russian platform stratigraphy and sea level changes abstract the moscow syneclise is a vast sedimentary basin located in the centre of the east european platform the palaeozoic sequence of this syneclise and especially its devonian carboniferous part is most suitable for sea level fluctuation analysis the devonian and carboniferous sediments consist mainly of shallow marine carbonates containing several minor terrigenous intervals they attain total thicknesses of up to 1 5 km the modern stratigraphic scale includes 33 regional stages for the devonian and 32 for the carboniferous correlation of this scale with global scales is supported by conodont miospore and foraminifera zonations the new calibrated devonian and carboniferous relative sea level curves for the moscow syneclise reflect late eifelian mid frasnian early tournaisian late visean early serpukhovian and moscovian gzhelian transgressions several of these sea level changes which are particularly evident on the margins of the moscow syneclise originated in response to differential tectonic movements of the voronezh anteclise and the tokmovo uplift as well as to vertical oscillations of the entire east european craton

observation and modeling of platelet ice fabric in mcmurdo sound antarctica 1 during the annual growth of landfast ice in mcmurdo sound antarctica an episodic flux of platelet ice crystals from the ocean contributes to the build up of a porous subice platelet layer which is steadily incorporated into the sea ice cover as it thickens over winter in november 2007 we examined the spatial variability of these processes by collecting sea ice cores with simultaneous oceanographic observations along an east west transect in the sound previously identified draped and bladed platelet ice types were observed in addition we identify resumed columnar growth which appears to be a result of geometric selection from the subice platelet layer after the arrival of new platelet crystals from the ocean has ceased a numerical model of mechanical platelet ice processes is developed that predicts crystal texture and c axis distributions producing virtual incorporated platelet ice with known growth history this model demonstrates how a disordered subice platelet layer arises from an initially flat interface and suggests that such a layer is more likely to form later in the growth season the model also suggests how the grain boundary density in incorporated platelet ice responds to changes in the flux of loose platelet crystals from the ocean application of this result to our 2007 platelet ice observations indicates that sea ice in western mcmurdo sound is subject to larger and more persistent platelet fluxes than the ice in the east this is consistent with the pattern of in situ supercooling just beneath the ocean surface

the kuroshio extension bifurcation region a pelagic hotspot for juvenile loggerhead sea turtles satellite telemetry of 43 juvenile loggerhead sea turtles caretta caretta in the western north pacific together with satellite remotely sensed oceanographic data identified the kuroshio extension bifurcation region kebr as a forage hotspot for these turtles in the kebr juvenile loggerheads resided in kuroshio extension current kec meanders and the associated anti cyclonic warm core and cyclonic cold core eddies during the fall winter and spring when the kec water contains high surface chlorophyll turtles often remained at a specific feature for several months however in the summer when the kec waters become vertically stratified and surface chlorophyll levels are low the turtles moved north up to 600 km from the main axis of kec to the transition zone chlorophyll front tzcf in some instances the loggerheads swam against geostrophic currents and seasonally all turtles moved north and south across the strong zonal flow loggerhead turtles traveling westward in the kebr had their directed westward movement reduced 50 by the opposing current while those traveling eastward exhibited an increase in directed zonal movement it appears therefore that these relatively weak swimming juvenile loggerheads are not passive drifters in a major ocean current but are able to move east west north and south through this very energetic and complex habitat these results indicate that oceanic regions specifically the kebr represent an important juvenile forage habitat for this threatened species interannual and decadal changes in productivity of the kebr may be important to the species s population dynamics further conservation efforts should focus on identifying and reducing threats to the survival of loggerhead turtles in the kebr r 2006 elsevier ltd all rights reserved

diagenetic history of pipe creek jr reef silurian north central indiana u s a abstract calcite cements in the silurian ludlovian pipe creek jr reef north central indiana are compositionally zoned with characteristic minor element concentrations and stable isotope signatures and were precipitated in different diagenetic environments superposition and crosscutting relationships allow us to group cement zones and to relate them to the sequence stratigraphic evolution of the reef pipe creek jr reef grew in normal marine waters with the reef top high greater than 50 m above the platform floor flank facies are volumetrically important and are preserved largely as limestone in contrast to most dolomitized silurian reefs in the midcontinent syndepositional marine cements fill primary porosity and synsedimentary fractures and are interlayered with marine internal sediment now low magnesium calcite their isotopic compositions are similar to those of depositional grains and cements estimated to have precipitated from ludlovian sea waters depositional porosity was reduced by 75 by the precipitation of these syndepositional cements which stabilized the steeply dipping flank slope postdepositional clear calcite cements are interpreted as shallow phreatic and burial cements on the basis of their relationship to periods of karstification and fracturing shallow phreatic cements with concentric cathodoluminescent cl zonation precipitated in primary pores and are postdated by fractures and caves filled with middle devonian sandstone cl zonal boundaries are sharp and some near a major stratigraphic unconformity show evidence of dissolution the volumetric abundance of the individual cl zones varies in the reef indicating a complex superposition of waters of varying chemistry and rock water interaction that are probably related to relative sea level changes this important aspect of the reef stratigraphy is recorded only by the diagenetic succession because evidence of earlier sea level changes is removed by a major later regional unconformity burial cements are the youngest diagenetic feature recognized and they rest conformably or unconformably over older cements they exhibit both concentric cl zonation and sectoral zoning they are ferroan to nonferroan and they contain thin sulfide zones along growth band boundaries their isotopic compositions do not overlap with shallow phreatic or marine cement values degraded oil postdates burial cements and is composed of the same sterane class as the devonian age antrim shale the probable source rock this source contrasts with that of reef reservoirs in the michigan basin where silurian strata are commonly the hydrocarbon source

crystal structure stable isotopes δ18o and development of sea ice in the ross amundsen and bellingshausen seas antarctica the crystal structure and oxygen isotopic composition of ice cores obtained from floes at the end of summer in the eastern ross sea the amundsen sea and the western bellingshausen sea were investigated to determine the ice growth processes and conditions that contribute to sea ice development in the eastern pacific sector of the southern ocean the isotope data indicate that a moderate amount of snow contributes to the development of the sea ice however even the combined use of isotopes and crystal structure analysis does not unambiguously explain the means by which all of the snow is entrained in the ice nevertheless it seems clear that much of the snow is contained in granular snow ice that results from seawater flooding of floes and the base of the snow cover the snow cover in the ross amundsen region was as much as 2 m deep and supported by 7 to 8 m thick floes primarily composed of frazil ice in the bellingshausen region the snow cover and the floes were thinner than in the ross amundsen region the bellingshausen cores were composed primarily of multiple layers of frazil and congelation ice in addition in both regions there were numerous tipped or inclined blocks of congelation ice and layers of rafted nilas in the cores the data indicate that the sea ice develops by multiple mechanisms in a turbulent environment

changes in zooplankton habitat behavior and acoustic scattering characteristics across glider resolved fronts in the southern california current system abstract we report cross frontal changes in the characteristics of plankton proxy variables measured by autonomous spray ocean gliders operating within the southern california current system sccs a comparison of conditions across the 154 positive frontal gradients i e where density of the surface layer decreased in the offshore direction identified from six years of continuous measurements showed that waters on the denser side of the fronts typically showed higher chl a fluorescence shallower euphotic zones and higher acoustic backscatter than waters on the less dense side transitions between these regions were relatively abrupt for positive fronts the amplitude of diel vertical migration dvm inferred from a 3 beam 750 khz acoustic doppler profiler increased offshore of fronts and covaried with optical transparency of the water column average interbeam variability in acoustic backscatter also changed across many positive fronts within 3 depth strata 0 150 m 150 400 m and 400 500 m revealing a front related change in the acoustic scattering characteristics of the assemblages the extent of vertical stratification of distinct scattering assemblages was also more pronounced offshore of positive fronts depth stratified zooplankton samples collected by mocness nets corroborated the autonomous measurements showing copepod dominated assemblages and decreased zooplankton body sizes offshore and euphausiid dominated assemblages with larger median body sizes inshore of major frontal features

fluid inclusion petrography and tectonic burial history of the al ali no 2 well evidence for the timing of diagenesis and oil migration northern oman foredeep cores cut in shallow marine lower and middle cretaceous carbonates in the al ali no 2 well umm al qaiwain united arab emirates display a five stage sequence of calcite cementation fracturing and stylolitization these stages are correlated with the tectonic history of the northern oman orogeny occurrence of fluorescent hydrocarbon fluid inclusions is restricted to stage 2 and stage 3 fracture filling calcites that are crosscut by stylolites stylolite formation during rapid burial beneath abyssal campanian foredeep sediments restricts hydrocarbon migration to post mid cenomanian and pre mid campanian time

global patterns of ocean transparency implications for the new production of the open ocean climatological mean fields of ocean transparency derived from secchi depth measurements held by the national oceanographic data center are presented clearly evident are the major coastal upwelling regions off peru northwest and south africa as well as the coastally enriched areas globally the central gyre regions in both north atlantic and north pacific waters are separated by a sharp discontinuity in water clarity from the more northern waters the change in secchi depth across this subtropical front is equivalent to a difference of 1 mg chlorophyll a m 3 over meridional distances of 1000 km sufficient data exist in the western pacific to demonstrate that the front migrates approximately 1000 km seasonally from a northern extreme at 28 n in september november to a southern extreme at 18 n in march may a simple explanation for this feature which is also clearly evident in recent satellite ocean color images of the the northern ocean basins is offered in terms of the effective vertical upwelling and resulting new production associated with seasonal variations in deep convective mixing

development of sea ice in the weddell sea we report on the development and physical properties of sea ice in the central and eastern weddell sea the investigations were part of the winter weddell sea project 1986 which extended over the months of july through december major elements of the glaciological part of this study included continuous shipborne observations of sea ice conditions and occasional helicopter reconnaissance flights extensive measurements of snow and ice thicknesses at daily ice stations and detailed analyses of sampled ice cores from each ice station textural investigations of the sampled ice revealed the dominance of frazil ice in the central weddell sea and the occurrence of an additional ice class called platelet ice together with the commonly known frazil and congelation ice in the coastal region of the eastern weddell sea these results in combination with the visual ice observations reveal two major mechanisms for sea ice generation in the antarctic which were not sufficiently well accounted for in previous investigations in the central weddell sea a cycle of pancake ice formation and its growth into consolidated floes seems to be the dominant process of the advancing sea ice edge in the coastal waters the growing sea ice cover consists to a considerable degree of ice platelets which are formed in the underlying water column in front of the ice shelf edges thus congelation ice growth which is mainly controlled by atmospheric thermodynamic forcing seems to be of less importance in the central and south eastern weddell sea than for example in the arctic basin

diagenesis of the palaeo oil water transition zone in a lower pennsylvanian carbonate reservoir constraints from cathodoluminescence microscopy microthermometry and isotope geochemistry abstract oil water transition zones in carbonate reservoirs represent important but rarely studied diagenetic environments that are now increasingly re evaluated because of their potentially large effects on reservoir economics here data from cathodoluminescence and fluorescence microscopy isotope geochemistry microthermometry and x ray tomography are combined to decipher the diagenetic history of a 5 m long core interval comprising the oil water transition zone in a lower pennsylvanian carbonate reservoir the aim is to document the cementation dynamics prior during and after oil emplacement in its context of changing fluid parameters intergrain porosity mean values of 7 are present in the upper two sub zones of the oil water transitions zone but values sharply increase to a mean of 14 in the lower sub zone grading into the water saturated portions of the reservoir and a very similar pattern is observed for permeability values in the top of the water filled zone cavernous porosity with mean values of about 24 is found carbonate cements formed from the earliest marine to the late burial stage five calcite ca 1 through 5 and one dolomite dol phase are recognized with phase ca 4b recording the onset of hydrocarbon migration carbon and oxygen cross plots clearly delineate different paragenetic phases with ca 4 representing the most depleted 13c ratios with mean values of about 21 during the main phase of oil emplacement arguably triggered by far field alpine tectonics carbonate cementation was slowed down and eventually ceased in the presence of hydrocarbons and corrosive fluids with temperatures of 110 140 c and a micro hiatal surface formed in the paragenetic sequence these observations support the oil inhibits diagenesis model the presence an earlier corrosion surface between phase ca 3 and 4 is best assigned to initial pulses of ascending corrosive fluids in advance of hydrocarbons the short lived nature of the oil migration event found here is rather uncommon when compared to other carbonate reservoirs the study is relevant as it clearly documents the strengths of a combined petrographic and geochemical study in order to document the timing of oil migration in carbonate reservoirs and its related cementation dynamics

carbonate platform drowning in a foreland setting the mid carboniferous platform in western urals russia abstract the stratigraphic evolution through time of the mid carboniferous russian platform deposited on the distal margin of the west uralian prograding foredeep basin can be observed in the approximately 3000 m thick sedimentary cover that constitutes the upper paleozoic foreland mid carboniferous permian of the uralian fold belt it is composed of wave dominated low angle carbonate ramps of late visean to early moscovian age and carbonate platforms bordered by slope reef mounds from the kasimovian to the late artinskian early kungurian eastward in the foredeep the carbonate platforms pass into terrigenous deposits a complete transgressive progradational section at the transition between carbonate ramp and terrigenous deposits exhibits from base to top 1 deepening upward carbonate ramp deposits 2 a shaly condensed section with volcaniclastics glauconite and phosphorites of late moscovian to early asselian age the transgressive part and 3 a shallowing upward section of turbidites ending in coarse grained fan deltas evaporites and meandering river redbeds by the earliest triassic the progradational section this paper focuses on the uppermost part of the carbonate ramp deposits serpukhovian to early moscovian these ramp facies comprise peritidal channels and mud flats wave to storm dominated shoals and patch reefs that are overlain by channel attached sand lobes of turbidites black shales and radiolarites of the condensed section this large scale deepening upward trend from inner ramp to outer ramp environments reflects a change in the depositional profile from a tide and wave dominated flat ramp to a wave and storm dominated steepened ramp margin and then to foreslope turbidites correlation of sections dated by fusulinid faunas in southern urals shows that the ramp evolved from emergent in the north perm solikamsk area as evidenced by karstification and deepened to the south belaya area with emplacement of carbonaceous foreslope debris flows and turbidites capped by deep marine black shales and radiolarites the time gap increases northward and reaches a span including the siuransky pro parte the akavassky the askynbashky and the asatausky pro parte biohorizons the mapping of these facies belts across all the urals shows that carbonate ramps wedge out in the middle urals and give rise to widely distributed diversified and deeper marine facies belts not only to the south towards the precaspian depression but also to the north towards the polar urals the drowning of these carbonate ramps and the cutoff in carbonate production on the russian platform during the mid carboniferous is explained by a succession of low frequency flexure relaxation cycles in the foreland associated with dilution by siliciclastics outpouring of volcaniclastics and changes in the nature and direction of the sediment input and high frequency cycles mainly controlled by eustasy

dust and pollution a recipe for enhanced ocean fertilization 1 for fe contained in aeolian dust to act as a micronutrient for oceanic phytoplankton some fraction of it must first be transformed mobilized into a form soluble in ocean water fe solubilization in deliquesced mineral dust aerosols emanating from east asia during the springtime outflow conditions is investigated here with a lagrangian box model of the gas and aqueous phase chemistry the model simulates the scavenging of soluble and reactive gaseous species by mineral dust aerosols chemical reactions of these species and mineral dust ions in deliquesced solution and dissolution of fe iii oxides that occurs as a result of the acid mobilization the calculations indicate that mineral calcite caco3 strongly buffers deliquesced dust aerosols with a ph that remains close to 8 until the amount of acid added to the aerosol solution exceeds caco3 alkalinity so2 pollutant emissions are a potential source of acidity to advecting dust from east asia the model is used to simulate the chemical evolution of dust plumes formed from two contrasting documented gobi desert storms that advected dust to fe limited regions of the north pacific ocean npo these calculations indicate that only plumes with relatively high initial so2 to dust ratios are capable of delivering significant amounts of bioavailable fe to the npo the estimated change in phytoplankton population inferred from the model calculated inputs of bioavailable fe for these two episodes is consistent with the satellite measured chlorophyll a concentrations in the npo model simulations indicate that 1 large dust advection episodes that can export vast amounts of mineral dust to the open ocean should have insignificant dissolved iron fraction dif as the amount of so2 required to acidify such dust plumes is about an order of magnitude higher than what can typically be entrained in the plume during its advection 2 smaller dust plumes will generally have higher difs because they require lower amounts of so2 and even if such small plumes may not cause algae blooms they could still be important sources of dissolved fe to the npo the calculations suggest that future changes in so2 pollutant emissions from east asia either up or down may affect the productivity of the npo

quartz veins with associated sb pb ag au mineralization in the schwarzwald sw germany a record of metamorphic cooling tectonic rifting and element remobilization processes in the variscan belt a combination of textural observations from 38 permian sb pb ag au bearing quartz veins in the schwarzwald sw germany with isotopic fluid inclusion and geochemical data allows to refine genetic models for this common type of mineralization to understand the origin of mineralogical diversity and the correlation with large scale tectonic events textures record four main mineralization stages i fe as sb au ii pb zn cu iii pb sb and iv ag sb stage i sulfides dominated by pyrite and arsenopyrite formed due to cooling of low salinity metamorphic fluids during the permian with maximum homogenization temperatures of 400 c invisible gold in arsenopyrite pyrite marcasite and stibnite was remobilized and locally precipitated as electrum at the end of stage i minerals of stages ii and iii comprise a rich diversity of sb bearing sulfosalts including e g bournonite zinkenite and jamesonite this assemblage formed during jurassic times due to mixing of high salinity mid and upper crustal fluids up to 27 wt nacl cacl2 with homogenization temperatures between 50 and 250 c stage iii is marked by a rich variety of pb sb sulfosalts its local abundance is directly related to the presence of stage i mineralization and its extent of remobilization during a significant influx of pb in the jurassic cretaceous the formation of the upper rhine graben during the tertiary reactivated especially ne sw oriented veins percolating ag rich fluids reacted with earlier stage iii pb sb sulfosalts forming ag rich minerals stage iv such as miargyrite pyrargyrite and stephanite the transition from metamorphic fluids to basinal saline e g pb bearing brines over hundreds of millions of years as is shown in this study and present in other variscan occurrences indicates a possibly typical poly stage characteristic of sb deposits worldwide which has however not been investigated in detail so far

the relationship between petroleum exotic cements and reservoir quality in carbonates a review exotic minerals i e those that do not have an obvious source of components within the host rocks can be major porosity occluding cement and replacement phases in subsurface carbonate reservoirs here we present and discuss petrographic and fluid inclusion data from a number of petroleum systems these have had different geological histories but a common factor is the presence of exotic mineral cements and late stage dissolution the effect of these cements and late stage dissolution on reservoir quality is also considered petroleum filling does not appear to inhibit the precipitation of exotic cements in the way that it appears to inhibit the precipitation of calcite burial dolomite and anhydrite are the most important of these volumetrically but they are often accompanied by other late stage cements such as fluorite kaolin quartz barite celestite sphalerite and galena generally in much smaller quantities in accounting for the concentration of the material contained in these cements compared with the host rocks stylolitisation is a possible mechanism in some cases but in many others import from sources external to the reservoir is required

observations of platelet ice growth and oceanographic conditions during the winter of 2003 in mcmurdo sound antarctica 1 platelet ice is the name given to ice crystals that nucleate in the ocean and grow either at depth or loosely attached to the ice water interface related to the proximity of ice shelves it is known to form in supercooled seawater this study details the conditions for its growth during the austral winter of 2003 in mcmurdo sound antarctica a key finding is that the presence of platelet ice in the sea ice cover is conclusively linked to the time history of the appearance of ice crystals in the water column monitored using the strength of the backscattered signal from an acoustic doppler current profiler as a proxy generally these crystals appeared from mid may as water near the interface became supercooled this near surface supercooling appears to be related to a simultaneous abrupt change in the structure of the upper 250 m of the water column from one that behaved dynamically and contained both the warmest and coolest measured temperatures to one in which the water was essentially isothermal near its surface freezing temperature near surface ocean temperature was also affected by tidal mixing and by an increase in the thickness and density over the course of winter of the surface mixed layer created by salt rejection during ice growth these processes allowed cold water trapped by buoyancy in a band at the base of the mixed layer in early winter to gain access to the ice water interface by midwinter this band of cold water probably had its origin beneath the mcmurdo ice shelf

chemical evolution of ore forming brines basement leaching metal provenance and the redox link between barren and ore bearing hydrothermal veins a case study from the schwarzwald mining district in sw germany abstract six mineralogically exemplary barren and mineralized hydrothermal veins with pb and zn ores of jurassic cretaceous and cenozoic age in the schwarzwald mining district sw germany were chosen to shed light on the origin of their mineralogical diversity the selection of the veins was guided by the fact that they represent the largest number of veins in the region are very well known mineralogically and geochemically and they provide nice examples of barren and mineralized veins of similar age fluid inclusion data from the individual veins overlap implying their diverse mineralogy is not caused by different fluid compositions participating during fluid mixing la icpms data of single fluid inclusions indicate no systematic variations in major elements but significant changes in fluid mixing ratios which caused variable trace element concentrations of different fluid inclusion assemblages in one sample we suggest that different ore gangue assemblages can be produced by mixing of identical fluid endmembers but variable mixing ratios la icpms analyses of single fluid inclusions in barren and mineralized veins record similar base metal and sulfur concentrations hence sulfide mineralization in the veins appears not to be controlled by metal solubility thermodynamic modeling based on the fluid data indicates that the presence of a reducing phase during fluid mixing is required for sulfide mineralization to precipitate la icpms trace element analyses of feldspars biotites chlorites and clay minerals in granites and paragneisses which are the source of the metal content in the ore forming fluids demonstrate that the dominant provenance for pb zn as sb ba tl mo fe and mn are probably paragneisses while co cu and ni are probably sourced from s type granite a rough quantification indicates that

carbonate cement stratigraphy and timing of diagenesis in a miocene mixed carbonate clastic sequence offshore sabah malaysia constraints from cathodoluminescence geochemistry and isotope studies a mixed carbonate clastic sequence is one of several miocene hydrocarbon bearing reservoirs in the northwestern sabah basin this sequence consists of bioclast rich sandstones interpreted as prograding storm shoal deposits the sequence contains a complex variety of carbonate nodules the sequence has undergone nine stages of cementation that completely occluded pores each stage represents a distinctive cement texture precipitating at specific temperatures and burial conditions the diagenetic evolution began with a syndepositional iron free marine calcite ca1 followed by an early methane derived dolomite do1 bladed calcite ca2 blocky vein filling fe calcites ca3ca4 clay mineral associated dolomite do2 fe dolomite and ankerite do3do4 and late iron rich calcite ca5 each stage of cement has distinctive sr2 mn2 mg2 fe2 ca2 and na contents reflecting changes in the palaeo porefluid systems with time the cements are correlatable over the whole study area precipitation occurred from very early to late stages of diagenesis at near surface to 2 0 km depths with progressive burial and temperature increase oxygen isotope values become strongly negative stage ca4 13c 0 5 pdb 18o 5 7 pdb the cements were precipitated at 20 75 c the source of carbon varies from marine dissolved carbonates to fermentation of organic matter methane meteoric waters and possibly hydrothermal fluids strontium isotope dating of do1 with 13c 32 5 pdb 18o 2 60 pdb and do2 13c 3 0 pdb 18o 2 5 pdb dolomites indicates that these dolomitization events took place at 10 5 ma and 8 9 ma respectively assuming precipitation within a completely open seawater system the do1 dolomite was precipitated from a methane derived brine at the boundary between the serravallian and tortonian stages after major uplift and induced faulting at a sea level lowstand the do2 dolomite was precipitated during intermediate to deep burial diagenesis during smectite illite transformation before hydrocarbon emplacement

postaccumulation sandstone porosity evolution by mechanical compaction and the effect on gas saturation case study of the lower shihezi formation in the bayan aobao area ordos basin china abstract porosity evolution and reservoir quality are strongly affected by mechanical compaction however the compaction induced porosity reduction process in sandstone reservoirs during the postaccumulation period and its effect on gas saturation remain poorly understood by studying the sandstones in the bayan aobao area we were able to quantify the porosity evolution and gas saturation variations caused by mechanical compaction during the postaccumulation period through fluid inclusion analysis and mathematical modeling moreover we verified our findings by compaction experiments and geological statistics fluid inclusion microthermometry was employed to determine the hydrocarbon accumulation periods and the highest homogenization temperature of the two phase aqueous fluid inclusions coexisting with natural gas fluid inclusions i e 115 c with a corresponding geological age of 140 ma was regarded as the beginning of the postaccumulation stages with these data we constructed an inversion evolution model based on the geologic statistical model of sandstone mechanical compaction for the postaccumulation period and determined the gas saturation changes based on compaction porosity evolution the modeling results indicate that the sandstone porosity decreased greatly during postaccumulation subsidence and increased slightly during late stage uplift while the gas saturation increased with both the porosity decrease during the postaccumulation subsidence and the porosity increases during the later uplift the modeling results of subsidence are concordant with the compaction experiments which also show that the larger the initial porosity the greater the porosity reduction the uplift modeling results demonstrate that an erosion induced decrease in burial depth allowed the sandstone porosity to increase which is supported by some scholars findings e g neuzil and pollock 1983 jiang et al 2004 zhang 2013 and by the positive correlation between sandstone porosities and restored geologic unit thicknesses in the study area however the inversion modeling indicates that the reason for the porosity rebound in litharenites is that the increase in elastic porosity slightly exceeds the decrease in viscoplastic porosity which would have been different if the uplift induced erosion rate had been distinctly lower gas production test data and restored geologic unit thicknesses indicate that uplift and erosion may be able to enrich sandstone gas reservoirs to a certain extent consistent with the calculated gas saturation variation results but a full understanding of gas saturation evolution awaits further studies the inversion model can provide a powerful tool for quantitative analysis of the sandstone compaction process during the postaccumulation period which could be used for reference in other similar regions

estimating palaeo water depth from the physical rock record abstract palaeo water depth and its change with time is a key factor in environmental analysis and in sedimentology in general the literature published on this topic and on related subjects however is substantial albeit scattered within and between different communities geologists oceanographers engineers physicists etc here i focus on proxies for palaeo bathymetry as obtained from the physical rock record floral faunal and chemical evidence for palaeo water depth being equally important must be dealt with elsewhere an assessment of the main depth related parameters in actualistic settings is presented and their applicability to the fossil sedimentary record discussed the outcome reveals the full complexity of this topic there is for example no such thing as an average wave base depth applicable to a wide range of fossil case settings this because wave and current climates in general and particularly so in neritic and coastal settings are intriguingly complex furthermore observations from modern oceans are not a priori applicable to fossil ones acknowledging these problems and limitations critically evaluated quantitative proposals for depth indicative facies and features in the sedimentary record are presented and error bars discussed

dynamics of cementation in response to oil charge evidence from a cretaceous carbonate field u a e abstract oil charge is thought to inhibit the growth of cements within subsurface pore systems we explore this phenomenon in a giant cretaceous carbonate field from u a e where the oil filled crest porosity ranges from 10 to 50 and permeability from 0 08 to 830 md but coeval water leg porosity is reduced to 10 to 23 and permeability to 0 1 to 4 md only 5 of primary interparticle pores 30 m diameter in the crest are fully cemented compared to 99 of pores in the water leg syntaxial calcite burial cements 10 m diameter in the oil leg show 12 cathodoluminescence zones with oil inclusions n 27 occurring in four of the five final zones mean in situ ion microprobe 18ovpdb data from the oil leg cements range from 1 2 in the oldest zone decreasing to 10 3 in zone 11 returning to 7 7 in the final zone the oldest distinguishable cement zone in the water leg shows highly variable 18o from 3 6 to 9 3 with a mean of 7 3 and with subsequent zones decreasing to a mean value of 9 4 for the youngest cement zone decreasing 18o values are interpreted as indicating increasing temperature reflecting burial and the evolution of pore water composition broadly similar trends in the oil and water legs suggest precipitation under the same general conditions unlike the oil leg cements the final zone in the water leg occludes nearly all remaining pore space the 18ovpdb of bulk micrite from the water leg shows an average of 7 4 n 9 compared to 6 2 n 10 from the oil leg suggesting the precipitation of further micrite cement at greater burial depths we infer that burial cementation slowed in the presence of oil due to a reduction of potential nucleation sites as well as porewater and solute movement within weakly oil wet pores whereas continued flow and solute movement through all pores including the micropores

the geochemistry of carbonate diagenesis the past present and future stable carbon and oxygen isotopes 18o and 13c values and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years as valuable as these insights have been many problems regarding the interpretation of geochemical signals within mature rocks remain for example while the 18o values of carbonate rocks are dependent both upon the temperature and the 18o value of the fluid and additional information including trace element composition aids in interpreting such signals direct evidence of either the temperature or the composition of the fluids is required such information can be obtained by analysing the 18o value of any fluid inclusions or by measuring the temperature using a method such as the clumped isotope technique such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well known tendency for 18o values of carbonate rocks to decrease with increasing age unlike the 18o 13c values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time however many studies have not sufficiently emphasized the effects of diagenesis and other post depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored finally many additional proxies are poised to contribute to the interpretation of carbonate diagenesis although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods care should be taken to understand both old and new proxies before applying them to the ancient record

hydrocarbon inclusions in late calcite cements migration indicators in the great oolite group weald basin s england abstract the fluorescence responses of hydrocarbon inclusions in calcite and dolomite cements are used to indicate the timing and longevity of oil migration in great oolite reservoirs of the weald basin of southern england oil migration and late stage calcite cementation were penecontemporaneous processes the gravity of the included hydrocarbons increases towards the basin depocentre through the range of 20 to 40 api reflecting the maturity of the source rocks reservoirs with a spread in the gravity of oil within inclusions were charged throughout source rock maturation those reservoirs with oil inclusions of a single gravity were charged in a discrete event

carboniferous permian carbon isotope stratigraphy of successions from china yangtze platform usa kansas and russia moscow basin and urals abstract the pennsylvanian and early permian were times of extreme sea level changes of 100 to perhaps up to 200 m for example glacio eustatic sea level changes are well documented from the us midcontinent moscow basin and yangtze platform where more than 100 stacked subtidal to supratidal sequences have been described in contrast carbonates developed in the ural mountains and south guizhou of the yangtze platform were deposited in ramp and slope settings 13c values of whole rock samples from the us midcontinent and moscow basin were intensively affected by diagenesis only well preserved brachiopod shells maintained their original carbon isotope ratios in contrast limestones deposited in the deeper water slope environments were not affected by meteoric diagenesis and are interpreted to have mainly retained their carbon isotope ratios mean 13c values of slope carbonates of the yangtze platform increase from about 3 during the visean and serpukhovian to 5 at the carboniferous permian boundary and decrease to values around 2 in the early kungurian this positive 13c excursion coincides with low 13c values in the yangtze platform successions which were reset by meteoric diagenesis the highest 13c values recorded in the slope succession coincide with the inferred maximum glaciation that caused pronounced sea level lowstands short lived but significant negative 13c excursions in the chinese slope succession are interpreted to reflect changes in ocean circulation due to sea level rises which caused enhanced production and or preservation of organic matter which influenced the subsequent early diagenetic cementation

textural characteristics and impurity content of meteoric and marine ice in the ronne ice shelf antarctica the texture and physical properties of an ice core recovered to 215 m depth from the ronne ice shelf antarctica have been studied with regard to formation and transformation of the ice at a depth of 152 8 m a sharp discontinuity marks the transition between meteoric ice accumulated from above and marine ice accreted from below as testified by electrolytical conductivity and stable isotope measurements as well as geophysical field surveys automated image analysis of thin sections indicates that the decrease in grain boundary density and the increase in grain cross sectional area with depth is commensurate with though not necessarily caused bythermodynamically driven grain growth down to 120m depth corresponding to a vertical strain of roughly 65 as computed with a simple temperature history particle path model the observed increase of grain boundary density i e a decrease of grain size with age in the marine ice is in part explained by the thermal history of this layer sediment inclusions at the top of the marine ice layer affect the observed grain boundary density profile by inhibiting grain growth and dynamic recrystallization this may allow some conclusions on the role of temperature particulate inclusions stress and strain rate in controlling the grain size evolution of deforming ice supplementing earlier laboratory experiments conducted at much shorter time scales salinities 0 026 parts per thousand brine volumes 0 09 0 2 parts per thousand and solid salt concentrations have been computed from electrolytical conductivity measurements mean of 51 0 x 10 6 s cm 1 for the marine ice an assessment of salt incorporation and desalination rates shows that these low salinities can at present only be explained by a unique densification mechanism of under water ice crystals at the base of the ice shelf

the effect of oil saturation on the mechanism of compaction in granular materials higher oil saturations lead to more grain fracturing and less pressure solution abstract whether addition of oil to sandstones slows stops or has no influence upon pressure solution and quartz cementation has long been disputed despite having major implications for petroleum exploration and appraisal strategies to elucidate the effect of addition of oil to compaction pressure solution and cementation processes this study utilizes an experimental approach simulating isochemical volumetric compaction using granular halite in the presence of variable brine oil mixtures each experiment at 500 kpa effective stress lasted 48 hours and involved repeated measurements of volumetric strain the lithified products of experiments were examined using sem techniques after 30 hours approximately 4 volumetric strain occurs when the brine oil ratio is 100 0 pure brine fractures are rare in samples from experiments undertaken with pure brine so that pressure solution and concomitant cementation must be the compaction mechanism when the brine oil ratio is decreased from 100 0 to 40 60 the volumetric strain remains about 4 but there are more fractures as quantified from sem image analysis these observations suggest that although pressure solution has occurred some of the volumetric strain is the result of fracturing implying that pressure solution has been less effective in the presence of some oil than it is in the presence of pure brine when the brine oil ratio is decreased further from 40 60 to 5 95 the volumetric strain increases up to 7 3 sem image analysis reveals that the strain is predominantly due to grain fracturing this change from pressure solution to grain fracturing is likely due to heterogeneous pressure solution resulting from heterogeneous distribution of stresses brine coated grain contacts undergo pressure solution but oil coated grain contacts experience increasing stress up to the point of failure as the surrounding grain pack compacts when the brine oil ratio is decreased to less than 5 95 volumetric strain decreased to about 1 with few induced fractures and little pressure solution compaction is negligible when the brine oil ratio is 0 100 only oil in the pores and fractures are negligible halite is more water soluble and more hygroscopic than quartz so that water will cling to halite surfaces more tenaciously than to quartz since even halite has its mechanism of volumetric strain affected when the brine oil ratio is less than 40 60 quartz pressure solution and subsequent cementation is even more likely to be affected by oil filling this experimental study suggests that the mechanism and extent of compaction and subsequent cementation in sandstones is strongly affected by the addition of oil

amplitudes of late pennsylvanian glacioeustasy the late paleozoic is well documented as a time of significant continental glaciation but the extents of the glaciation and attendant glacioeustasy are not well constrained because precise amplitudes of eustasy are difficult to extract from the stratigraphic record in this paper we use preserved relief on ancient subaerial exposure surfaces of large algal bioherms to demonstrate directly that late pennsylvanian glacioeustasy reached minimum amplitudes of 80 m and probably exceeded 100 m upper paleozoic algal bioherms accreted predominantly during sea level falls but also during sea level rises and highstands and were capable of remarkably rapid growth rates eustatic amplitudes in excess of 100 m approach amounts documented for the pleistocene and place constraints on models for gondwanan ice volume climate dynamics and potential character and magnitude of glacioclimatic fluctuations

acoustic detection of ice crystals in antarctic waters during the voyage of the rsv aurora australis to the region of prydz bay antarctica in january march 1991 ice crystals were encountered at depths from the surface to 125 m in the western area of the bay on two occasions crystals were retrieved by netting and echo sounder records have been used to infer additional regions of occurrence acoustic target strength estimates made on the ice crystal assemblies encountered show significant spatial variation which may relate to crystal size and or aggregation data from a suite of conductivity temperature depth casts have been used to map regions of the study area where in situ water temperatures fell below the computed freezing point such regions correlate well with those selected on the basis of echogram type and imply that ice crystals occurred at depth over large areas of the bay during the cruise period the ice crystal distribution described is consistent with that expected from a plume of supercooled water emerging from under the amery ice shelf and forming part of the general circulation of the bay the magnitude of the supercooled water plume is greater than those reported previously in the prydz bay region if misinterpreted as biota on echo sounder records ice crystals could significantly bias biomass estimates based on echo integration in this and potentially other areas

microfacies diagenesis and oil emplacement of the upper jurassic arab d carbonate reservoir in an oil field in central saudi arabia khurais complex abstract the upper jurassic kimmeridgian arab d reservoir of the arab formation in the arabian peninsula is considered to be the largest hydrocarbon carbonate reservoir in the world despite a relative large number of studies dealing with lithofacies and depositional sequences there are still few studies dealing with diagenesis of this supergiant reservoir in this study petrographic cathodoluminescence and ultra violet light fluorescence microscopy analyses of the arab d reservoir in an oil field of saudi arabia khurais complex have been combined with isotope geochemistry 13c 18o and 87sr 86sr to decipher the sequence of diagenetic events affecting the reservoir before and during oil emplacements and the impact of depositional mineralogies and their modifications during the diagenesis on the reservoir quality and heterogeneity all the analyzed samples correspond to lithofacies that can be ascribed to nine microfacies types mft 1 to mft 9 three stages of carbonate dissolution d1 to d3 four stages of calcite cements c1 to c4 and 5 zones of replacive dolomite and dolomite cement d1 to d5 have been documented from diagenetic environments ranging from marine to late burial abundant oil fluid inclusions have been recognized in calcite c3 and c4 and dolomite d5 from wells located in the flanks of the structure group 2 of cements cements from wells located in the center of the structure are largely oil inclusions free group 1 of cements this distribution suggests that group 2 of cements formed within the oil water transition zone of the reservoir during the oil infilling of the structure allowing to constrain the timing of oil emplacement and suggesting at least two phases of oil charging porosity enhancement by corrosive dissolution d3 occurred during late burial and took place just before precipitation of dolomite d5 and calcite c4 and just before the second stage of hydrocarbon arrival suggesting the presence of aggressive fluids preceding the late phase of hydrocarbon migration cross plot of carbon vs oxygen stable isotopes shows a general trend toward decreasing 18o values with increasing burial depth whereas all 13c values remain positive except for group 2 of c3 and c4 calcites which exhibit negative up to 4 6 13c values the later suggest precipitation from pore waters with increased volumes of 12c as a by product of hydrocarbon maturation except for c4 all the 87sr 86sr values are within the range of the late jurassic seawater suggesting precipitation from jurassic marine or evolved marine pore waters in contrast the more radiogenic calcite c4 suggests a source from fluids that interacted with siliciclastics or clay rich sequences depositional mineralogy of the grainy lithofacies is interpreted to have had an impact on the effectiveness of cementation and dissolution controlling the reservoir heterogeneity due to excess of cementation reservoir quality is worse in grainstone microfacies rich in aragonitic components and better in grainstone and packstone microfacies poorer in aragonitic grains but affected by late dissolution of micrite the integration of all these data resulted in a more precise understanding of the reservoir quality and heterogeneity

textural elemental and isotopic characteristics of pleistocene phreatic cave deposits jabal madar oman abstract two main types of karst formation are commonly known the surficial meteoric one and the subsurface hypogenic karst which can be related to both carbonic h2co3 and sulfuric h2s acids this paper documents evidence for a third co2 regime related type of karst that is less commonly described petrographic and geochemical properties of exhumed pleistocene phreatic cave deposits from the diapiric jabal madar dome in northern oman are documented and discussed in a process oriented context these calcites form at the interface between two fundamentally different diagenetic and hydrogeological domains the deep seated hydrothermal and the near surficial meteoric vadose one four calcite phases are recognized i acicular ii blocky to stubby elongated iii proto palisade and iv macro columnar calcites the macro columnar calcites forming the last stage of precipitation are conspicuous due to their cyclical red zonation and they form the main geochemical focus of this study fluid inclusion data point to fluid temperatures of between 30 to 50 c monophase liquid inclusions and elevated salinities 1 6 to 7 3 wt nacl equivalent low carbon isotope data 8 to 9 are in agreement with the influx of soil zone co2 whereas decreasing 18o 15 values might point to mixing of saline hydrothermal and 18o depleted meteoric freshwater i e two fluid sources trace element and stable isotope data shift between the different cement phases and vary cyclically across the red zoning in macro columnar calcites with respect to the intra crystal variability these patterns are perhaps best explained in the context of redox potential two interpretations are presented the one favored here suggests that the cyclical red zoning in macro columnar calcites is controlled by pleistocene monsoonal climate patterns

diagenesis of middle devonian carbonate mounds of the mader basin eastern anti atlas morocco abstract in the mader basin of the eastern anti atlas middle devonian carbonate mounds were established on a gently sloping ramp at moderate water depths primary stromatactis cavities in these mounds exhibit early marine shallow burial and deeper burial cementation the mound matrix was affected by neomorphic alteration stylolitization and dolomitization earliest cementation occurred in the marine environment nonluminescent to blotchy luminescent cloudy radiaxial calcites of originally high mg calcite composition coat the walls of stromatactis cavities and take up more than 50 of the primary pore space the isotopic signature d18o 2 6 0 2 pdb d13c 2 7 0 5 pdb is close to that of nonluminescent fabric retentive brachiopod shells in the same mounds and taken as the nearly pristine stable isotopic signature of mader basin seawater the high d18o values compared with middle devonian data of north america are interpreted to result from the mid latitudinal ca 35 s temperate water settings of the mader basin carbonate mounds the transition to the shallow burial realm is indicated by a typical non bright dull luminescence sequence nonluminescent scalenohedral cements pass into bright luminescent and banded luminescent scalenohedral cements which are overgrown in turn by dull to moderate luminescent blocky spar meteoric influence on that cement sequence can be excluded deeper burial diagenesis is represented by stylolitization ferroan calcite cementation and neomorphic alteration of the fine grained mound carbonates pressure solution and or outgassing of co2 are possible ion sources for ferroan calcite precipitation in the remaining pore space 18o depletion d18o 6 8 to 8 9 pdb of these cements can be calculated to elevated precipitation temperatures of 21 33 5 c and burial depths of 420 670 m microspar making up the bulk of the mounds was formed by a one step transformation of a precursor calcitic micrite low d18o values 6 9 p 2 1 pdb mottled luminescence and high fe concentrations indicate that this transformation also took place in the deeper burial realm

the fate of co2 derived from thermochemical sulfate reduction tsr and effect of tsr on carbonate porosity and permeability sichuan basin china abstract this article discusses the role of methane in thermochemical sulfate reduction tsr the fate of tsr derived co2 and the effect of tsr on reservoir porosity and permeability and the causes of the anomalously high porosity and permeability in the lower triassic soured carbonate gas reservoirs in the northeast sichuan basin southwest china the lower triassic carbonate reservoirs were buried to a depth of about 7000 m and experienced maximum temperatures up to 220 c before having been uplifted to the present day depths of 4800 to 5500 m but they still possess porosities up to 28 9 and permeabilities up to 3360 md the present day dry gas reservoirs evolved from a paleo oil accumulation and experienced varying degrees of tsr alteration as evidenced from the abundant sulfur rich solid bitumens and varying h2s and co2 concentrations tsr occurred mainly within the oil and condensate wet gas windows with liquid hydrocarbons and wet hydrocarbon gases acting as the dominant reducing agents responsible for sulfate reduction sulfur rich solid bitumen and h2s generation and calcite precipitation methane dominated tsr was a rather late event and had played a less significant role in altering the reservoirs intensive h2s and co2 generation during tsr resulted in calcite cementation rather than carbonate dissolution which implies that the amount of water generated during tsr was volumetrically insignificant 13c depleted co2 derived from hydrocarbon oxidation preferentially reacted with ca2 to form isotopically light calcite cements and the remaining co2 re equilibrated with the 13c enriched water rock systems with its 13c rapidly approaching the values for the host rocks which accounted for the observed heavy and relatively constant co2 13c values the carbonate reservoirs suffered from differential porosity loss by tsr involved solid bitumen generation and tsr induced calcite and pyrite precipitation intensive tsr significantly reduced the porosity and permeability of the intervals expected to have relatively high sulfate contents the evaporative platform dolostones and the platform margin shoal dolostones immediately underlying the evaporative facies early oil charge and limited intensity of tsr alteration together with very low phyllosilicate content and early dolomitization accounted for the preservation of anomalously high porosities in the reservoirs above the paleo oil water contact a closed system seems to have played a special role in preserving the high porosity in the gas zone reservoirs below the paleo oil water contact the closed system which is unfavorable for deep burial carbonate dissolution and secondary porosity generation was favorable for the preservation of early formed porosity in deeply buried carbonates especially sucrosic and vuggy dolostones have a high potential to preserve such porosity

growth rate and salinity profile of first year sea ice in the high arctic this paper describes the growth of sea ice and the salinity profiles observed in eclipse sound near pond inlet baffin island canada during the winter of 1977 78 a numerical method of calculation has been developed to incorporate the variations in snow conditions and physical properties of ice and snow during the growth season it is shown that the growth rate can be predicted reasonably well it is also shown that the vertical salinity profile in the ice towards the end of the season provides a record of previous climatological conditions a dependence has been shown between the predicted growth rate and the measured salinity

northward migration dynamics of skipjack tuna katsuwonus pelamis associated with the lower thermal limit in the western pacific ocean abstract a new and comprehensive migration route of skipjack tuna katsuwonus pelamis in the western pacific ocean was observed from the results of a large scale tagging project conducted from 2010 to 2016 skipjack were implanted with archival tags in the peritoneal cavity and released from a subtropical area sta the nansei islands nsi and the kuroshio extension area kea individuals released around the nsi displayed strong residency in that area on the other hand individuals released around the sta and kea demonstrated seasonal northward movements three major potential routes were observed with strong skipjack residency along i the kuroshio in the nsi and with seasonal northward movements along ii the kyushu palau ridge and iii the izu ogasawara islands during northward migration the skipjack experienced several specific physical oceanographic structures such as the kuroshio recirculation area subtropical mode waters the kuroshio current near the coast of japan the kuroshio extension and the kuroshio oyashio transition area however during their journey the skipjack did not enter water with temperatures of 18 c defined as the lower thermal limit furthermore the depth of the lower thermal limit is progressively shoaled at higher latitudes due to the distribution of colder water masses below 18 c which further limits the vertical distribution of skipjack our findings are the first fishery independent observations on the degree of horizontal and vertical habitat of skipjack tuna in the western pacific ocean which can be strongly driven by behavioural responses to the lower thermal limit

mississippian carbonate ramp to basin transitions in south central new mexico sequence stratigraphic response to progressively steepening outer ramp profiles abstract the sequence stratigraphic architecture of mississippian strata from the sacramento and san andres mountains south central new mexico illustrates the combined effects of relative sea level change and progressively increasing depositional gradients on sedimentary processes and resultant stratal geometries along the outer parts of a carbonate ramp to basin transition mississippian strata can be subdivided into three progradational sequences sequences 1 3 and a fourth basin restricted onlapping sequence sequence 4 sequences 1 3 contain wackestone to mudstone dominated transgressive systems tracts that are overlain by packstone to grainstone dominated progradational systems tracts progradational systems tracts created distinct ramp to basin transitions outer ramp margin that are characterized by basinward stratal thinning and a concomitant change to muddy lithofacies sequence 4 consists of onlapping fining upward stratal packages of peloidal skeletal grainstone that grade upward to laminated spiculitic lime mudstone the outer ramp margin facies of sequences 1 through 3 gradually steepened the outer ramp profile until the cumulative effects of the steepening caused the depositional gradient to surpass an equilibrium grade i e the gradient at which deposition and erosion bypass are about equal once the depositional gradient exceeded the equilibrium grade for the caliber of sediment supplied to the outer ramp margin widespread submarine erosion and sediment bypass on the outer ramp was initiated resulting in deposition of basin restricted strata of sequence 4 similar relationships and inferred processes have been recognized in progradational siliciclastic shelf deposits and are collectively described by previous workers as slope readjustment the mississippian ramp to basin transition in south central new mexico illustrates how sediment deposition dispersal and erosion responded to evolving depositional gradients and in turn controlled resultant large scale stratal geometries

top marine predators track lagrangian coherent structures meso and submesoscales fronts eddies filaments in surface ocean flow have a crucial influence on marine ecosystems their dynamics partly control the foraging behavior and the displacement of marine top predators tuna birds turtles and cetaceans in this work we focus on the role of submesoscale structures in the mozambique channel in the distribution of a marine predator the great frigatebird using a newly developed dynamic concept the finite size lyapunov exponent fsle we identified lagrangian coherent structures lcss present in the surface flow in the channel over a 2 month observation period august and september 2003 by comparing seabird satellite positions with lcs locations we demonstrate that frigatebirds track precisely these structures in the mozambique channel providing the first evidence that a top predator is able to track these fsle ridges to locate food patches after comparing bird positions during long and short trips and different parts of these trips we propose several hypotheses to understand how frigatebirds can follow these lcss the birds might use visual and or olfactory cues and or atmospheric current changes over the structures to move along these biologic corridors the birds being often associated with tuna schools around foraging areas a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel

a comparative study of two mississippian dolostone reservoirs in the volga ural basin russia abstract a significant proportion of the remaining oil reserves worldwide is concentrated in dolostone rock bodies the present paper focuses on tournaisian and visean limestones and geologically younger diagenetic dolomite units in two mature oil fields of the volga ural basin russia in contrast to many dolostone hosted hydrocarbon reservoirs worldwide the tournaisian and visean dolostones in the demkinskoye and the onbiyskoye oil fields plot near the low end of the porosity permeability range replacive and porosity destructive burial dolomitization has deteriorated the reservoir properties of these units dolomitization is related to the ascent of hot 170 215 c and saline 22 24 wt fluids as based on fluid inclusion data this temperature range points to an abnormally high temperature background thermal regime of the volga ural basin the onset of burial dolomitization predates oil charge as documented by the fact that oil bearing inclusions are only present in the outermost zones of porosity occluding dolomite cements isotope geochemical data dolomite petrography and fluid inclusion data reveal important similarities between hydrothermal dolostone units in the demkinskoye and the onbiyskoye oil fields based on these data and the detailed cement stratigraphy presented here it is argued that dolomite bodies in both oil fields formed as the result of one main alpine tectonic event pushing hot and saline dolomitizing brines ahead of ascending hydrocarbons

sulfate brines in fluid inclusions of hydrothermal veins compositional determinations in the system h2o na ca cl so4 sulfate is among the most abundant ions in seawater and sulfate bearing brines are common in sedimentary basins among other environments however the properties of sulfate bearing fluid inclusions during microthermometry are as yet poorly constrained restricting the interpretation of fluid inclusion compositions where sulfate is a major ion the schwarzwald mining district on the eastern shoulder of the upper rhinegraben rift is an example of a geologic system characterized by sulfate bearing brines and constraints on the anion abundances chloride versus sulfate would be desirable as a potential means to differentiate fluid sources in hydrothermal veins in these regions here we use the pitzer type formalism to calculate equilibrium conditions along the vapor saturated liquidus of the system h2o na ca cl so4 and construct phase diagrams displaying the predicted phase equilibria we combine these predicted phase relations with microthermometric and crush leach analyses of fluid inclusions from veins in the schwarzwald and upper rhinegraben to estimate the compositions of these brines in terms of bulk salinity as well as cation and anion loads sodium versus calcium and chloride versus sulfate these data indicate systematic differences in fluid compositions recorded by fluid inclusions and demonstrate the application of detailed low temperature microthermometry to determine compositions of sulfate bearing brines thus these data provide new constraints on fluid sources and paleo hydrology of these classic basin hosted ore forming systems moreover the phase diagrams presented herein can be applied directly to compositional determinations in other systems