classification of huminite iccp system 1994 abstract in the new classification iccp system 1994 the maceral group huminite has been revised from the previous classification iccp 1971 int handbook coal petr suppl to 2nd ed to accommodate the nomenclature to changes in the other maceral groups especially the changes in the vitrinite classification iccp 1998 the new vitrinite classification iccp system 1994 fuel 77 349 358 the vitrinite and huminite systems have been correlated so that down to the level of sub maceral groups the two systems can be used in parallel at the level of macerals and for finer classifications the analyst now has according to the nature of the coal and the purpose of the analysis a choice of using either of the two classification systems for huminite and vitrinite this is in accordance with the new iso coal classification that covers low rank coals as well and allows for the simultaneous use of the huminite and vitrinite nomenclature for low rank coals

eddy resolving observation of the north pacific subtropical mode water abstracthydrographic data obtained by high resolution shipboard observations and argo profiling floats have been analyzed to study the mesoscale structure and circulation of the north pacific subtropical mode water stmw the float data show that in the late winter of 2008 stmw having a temperature of approximately 18 8 17 7 and 16 6 c formed west of 140 e at 140 150 e and east of 150 e respectively in the recirculation gyre south of the kuroshio extension after spring the newly formed stmw gradually shift southward decreasing in thickness simultaneously the stmws of 16 6 and 17 7 c are gradually stirred and then mixed in terms of properties in late fall they seem to be integrated to form a single group of stmws having a temperature centered at 17 2 c such stmw circulation in 2008 is much more turbulent than that in 2006 which was investigated in a previous study the difference between the two years is attributed to the more variable state of the kuroshio extension in 2008 associate

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

early diagenetic silica deposition in algal cysts and spores a source of sand in black shales abstract devonian black shales deposited on the north american craton contain abundant tasmanites cysts although these are typically flattened because of compaction a small proportion are filled with diagenetic silica the latter are spherical to ellipsoidal 0 1 0 5 mm and filled with chalcedony microquartz and megaquartz and single quartz crystals chalcedonic cyst fillings are preserved best in cheat and phosphate nodules whereas megaquartz and single quartz crystals are most common in shale matrix together with colloform textures this suggests that the various silica types originated from recrystallization of early diagenetic silica deposits thin sandstone beds in the chattanooga shale e g bransford sandstone contain abundant quartz sand that is much coarser than the detrital quartz component of the underlying black shales because of this their quartz component is thought to have been transported over considerable distances from the basin margin however because certain shale horizons contain as much as 10 silicified cysts that upon reworking could have yielded quartz grains of fine to coarse sand size the quartz component of these sandstone beds may actually have formed in situ indeed petrographic examination of the sandstone beds shows them to contain quartz grains with morphological and textural features of cyst quartz e g rounding sphericity chalcedony pyrite inclusions lobate grain margins thus silica deposition in algal cysts may provide a significant component of intrabasinal quartz sand in shale sequences distinction of this type of quartz from extrabasinal detrital quartz is important to the reconstruction of the depositional history of shale sequences

extension controls quaternary tectonics geomorphology and sedimentation of the n appennies foothills and adjacent po plain italy abstract in the middle pleistocene thrusting in the n apennine fold and thrust belt came to an end and foredeep sedimentation in the adjacent po plain basin ceased a new tectono sedimentary regime was installed extensional faults were activated in the foothills and are limited to the northeast by a major sw dipping normal fault the bologna fault for which a vertical displacement of 1000 m is estimated the region northeast of the fault i e its footwall was progressively tilted towards the po plain the sw sectors of the tilting region were progressively uplifted above sea level subjected to erosion thereby feeding a deltaic system which prograded towards the northeast in the subsiding regions compressional structures without major deformation are recorded in the zone of maximum curvature all these features are explained by the onset of extensional deformation along the bologna fault and consequent flexural unloading of its footwall the evidence therefore shows that the transition region between the n apennine foothills and po plain has been under a tensional stress regime since the middle pleistocene

geochemical and isotopic evidence for paleoredox conditions during deposition of the devonian mississippian new albany shale southern indiana the upper part of the new albany shale is divided into three members in ascending order these are 1 the morgan trail member a laminated brownish black shale 2 the camp run member an interbedded brownish black and greenish gray shale and 3 the clegg creek member also a laminated brownish black shale the morgan trail and camp run members contain 5 to 6 total organic carbon toc and 2 sulfide sulfur isotopic composition of sulfide in these members ranges from 5 0 to 20 0 c s plots indicate linear relationships between abundances of these elements with a zero intercept characteristic of sediments deposited in a non euxinic marine environment formation of diagenetic pyrite was carbon limited in these members the clegg creek member contains 10 to 15 toc and 2 to 6 sulfide sulfur isotopic compositions of sulfide range from 5 0 to 40 the most negative values occur in the uppermost clegg creek member and are characteristic of syngenetic pyrite formed within an anoxic water column abundances of carbon and sulfur are greater and uncorrelated in this member consistent with deposition in as euxinic environment in addition dop degree of pyritization values suggest that formation of pyrite was generally iron limited throughout clegg creek deposition but sulfur isotopes indicate that syngenetic water column pyrite becomes an important component in the sediment only in the upper part of the member at the top of the clegg creek member a zone of phosphate nodules and trace metal enrichment coincides with maximal toc values during euxinic deposition phosphate and trace metals accumulated below the chemocline because of limited vertical circulation in the water column increased productivity would have resulted in an increased flux of particulate organic matter to the sediment providing an effective sink for trace metals in the water column phosphate and trace metals released from organic matter during early diagenesis resulted in precipitation of metal rich phosphate nodules

multicore structure of the north pacific subtropical mode water from enhanced argo observations seventeen argo profiling floats with enhanced vertical and temporal sampling were deployed in the kuroshio recirculation gyre in the western north pacific in late march 2014 the subtropical mode water stmw observed in many profiles displays a multicore structure with more than one minima in potential vorticity pv corroborated by vertical covariations in apparent oxygen utilization aou these cores are classified into four submodes according to density and aou the submode waters are typically 100 m thick in which pv varies by 1 10 10 m 1 s 1 and aou by 10 mole kg the stmw multicore structure is most frequently observed in spring gradually taken over by single core profiles into summer the seasonal evolution is suggestive of vertical mixing especially in stmw of lower density

formation and spreading of subtropical mode water in the north pacific a time averaged description of the formation and spreading of north pacific subtropical mode water npstmw is presented the formation of npstmw is studied using transpac expendable bathythermograph data the data are transformed into a stream coordinate system and averaged the coordinate system uses the position of the kuroshio front as its origin maps are presented of the temperature structure and mixed layer distribution in winter relative to the kuroshio front the formation of npstmw occurs in two separate stages cooling and thickening as water flows at the surface in the kuroshio in winter the water is cooled by the intense ocean atmosphere heat flux taking place in the area when water leaves the kuroshio to the south the thermocline underneath becomes deeper convection is able to penetrate deep into the water column and the heat flux acts more to thicken the surface mixed layer rather than reduce the temperature the area south of the kuroshio where relatively homogeneous waters are found is the source region for npstmw at the end of the winter the thick mixed layers are assumed to be covered over by a seasonal thermocline and become npstmw the levitus 1982 data are used to study the way in which npstmw is spread away from its source region by the subtropical circulation the distribution of potential vorticity pv on four npstmw isopycnals is studied with low pv used as a tracer for npstmw the pv reveals a pattern of differential spreading whereby npstmw formed in the western part of the source region is advected to the west after its formation npstmw formed farther east is advected more to the south or east after formation differential spreading allows npstmw to be found in a large part of the northwestern subtropical gyre well away from its source region the distribution of npstmw described by masuzawa 1969 with npstmw getting colder from west to east is explained as a combination of the distribution of npstmw at its source and the way it is spread after it is formed

high resolution carbon isotope records of the aptian to lower albian from se france and the mazagan plateau dsdp site 545 a stratigraphic tool for paleoceanographic and paleobiologic reconstruction high resolution carbon isotope stratigraphy is established for the aptian to lower albian of the vocontian basin se france and correlated to the carbon isotope record of the mazagan plateau dsdp site 545 the carbon isotope stratigraphy of the vocontian basin is proposed as a standard reference curve for the aptian to lower albian due to the completeness and high temporal resolution of the stratigraphic succession the good biostratigraphical time control and the frequent occurrence of regional to global black shale horizons including oceanic anoxic events 1a oae 1a of the lower aptian and oae 1b of the lower albian the carbon isotope record appears better suited for long distance short term correlation of different marine and terrestrial environments than biostratigraphy because of the synchroneity of carbon isotope signals in a range of sediment types however the combination of both biostratigraphy and carbon isotope stratigraphy provides an effective tool to reconstruct biotic change and paleoceanography and to correlate regional to global black shale horizons in different marine environments this combined approach allows us to ascertain the synchroneities or diachroneities of first and last appearances of biostratigraphic marker species based on the demonstrated diachroneity of important biostratigraphic markers of the aptian albian boundary the globally observed break point between the end of the uppermost aptian positive carbon isotope excursion and the onset of the pronounced negative shift of 13c values is an alternative criterion the distinctive structure and amplitudes of the carbon isotope record are observed in both the inorganic and organic carbon and can therefore be recognized in all marine and terrestrial environments of the aptian to lower albian

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

benthic foraminifera from the necop study area impacted by the mississippi river plume and seasonal hypoxia abstract benthic foraminifera influenced by the mississippi river plume and seasonal hypoxia were assessed from louisiana inner continental shelf sediment samples surface foraminifera assemblages were representative of in situ populations as established by staining techniques community diversity and richness evenness analyses indicate three regimes high stress sediment dominated intermediate stress hypoxia dominated and low stress low sediment accumulation high oxygen epistominella vitrea and buliminella morgani are useful tracers of rapid sediment accumulation rate and hypoxia a bottom water productivity signal west of the mississippi river plume is indicated by benthic and planktic foraminifera abundance peaks surface benthic foraminifera trends are utilized to interpret changes in historical community structure from hypoxic area sediments deposited since the turn of the century the hypoxia tolerant species buliminella morgani increases markedly upcore while hypoxia intolerant species decrease or disappear diversity and dominance trends temporally correspond to a dramatic increase in u s fertilizer application the results of this study have application to paleoenvironmental research spanning longer geologic timescales the documented relationships between population structure and stressors in river dominated marine systems may provide a useful analog for recognition of these conditions in the fossil record

tertiary tectonic evolution of the external south carpathians and the adjacent moesian platform romania depth interpreted seismic sections of the getic depression foredeep paleostress indicator data and analysis of outcrop to regional scale structures are integrated to derive the tectonic evolution of the south carpathians moesian platform area following late cretaceous and older orogenic phases the south carpathians moesian platform area underwent strike slip deformation with ne sw oriented compression and nw se tension in paleogene to early burdigalian times tensional deformation is recorded which led to the opening of wsw ene to e w trending extensional basins in the late burdigalian ne sw oriented contraction took over causing the oblique inversion of preexisting extensional structures during sarmatian times nw se and slightly younger n s trending compression caused the activation of mainly nw se dextral strike slip faults and in the frontal areas south directed thrusting the nw se direction of extension determined for paleogene to early burdigalian times is hardly compatible with presently accepted models of substantially continuous dextral wrenching between the intra carpathians units to the north of the south carpathians and the moesian platform to the south in contrast we have demonstrated dextral transpressive to transtensional movements within an e w trending corridor from the late burdigalian to late sarmatian which are compatible with available models

climatology and decadal variations in multicore structure of the north pacific subtropical mode water the pycnostad of the north pacific subtropical mode water stmw often displays multiple vertical minima in the potential vorticity profile argo profile data from 2004 to 2015 are used to investigate inter annual to decadal variations of the multicore structure climatologically about 24 pycostads of stmw have multicore structure and most of them distribute in the region west of 150 e stmw cores are classified into three sub modes the cold middle and warm ones with potential temperatures of 16 0 17 c 17 18 c and 18 19 5 c respectively the kuroshio extension ke varies between stable and unstable states the unstable ke with large meanders increases the subsurface stratification and shoals the winter mixed layer east of 150 e with warmer temperatures there the dominant stmw type varies from the cold single type in stable ke years making up 72 of the profiles with stmw to the middle single one 53 in unstable years the variation of the dominant stmw type in the region east of 150 e subsequently affects the multicore structure of stmw west of 150 e in a broad region between 130 e and 180 e profiles with stmw are fewer in unstable years but the proportion of multicore profiles increases among stmw profiles this might be due to the split recirculation gyre with a chaotic ke

extension of berner s new geochemical classification of sedimentary environments to ancient sediments using stable isotopes of carbon and oxygen in siderite nodules and lithology of host shales one can recognize geochemical environments proposed by berner in devonian carboniferous sediments of the appalachian basin his oxic post oxic and sulfidic diagenetic environments are well represented sediments of the methanic environment may be present but the evidence is equivocal the sulfidic sediments can be further subdivided into well laminated and bioturbated corresponding to the presence of h 2 s in the overlying water in the first case but confined to the sediment pore waters in the second journal abstract

organic petrology of source rocks history and state of the art abstract the development of organic source rock petrology depended on the methods applied a procedure derived from coal petrology is the study of polished sections of the untreated rock under incident light this method combined with the fluorescence techniques is best suited to characterize and identify the discrete organic matter macerals and permits the most reliabble maturity measurements on the basis of vitrinite reflectance and of various fluorescence parameters another common method treats the rock with acids and studies strew slides of organic matter concentrates this destroys the natural texture of the rock and often some of the individual macerals as well but on the other hand it allows recognition of extremely fine particles which are not resolvable in polished sections maturity studies based on maceral colour changes as observed in strew slides are rapid and practical although they are rather subjective the relative merits of the various methods are discussed the individual organic constituents as seen in the whole rock and in organic matter concentrates are described and illustrated in two colour plates some classification systems are compared in tabular form finally the history of microscopic observations and measurements with respect to the generation of petroleum like substances in coal is briefly reviewed

subtropical mode water variation in the northwestern part of the north pacific subtropical gyre temporal variations of the north pacific subtropical mode water npstmw are studied with the proper temporal resolution for describing seasonal variation using monthly hydrographic data taken near the ogasawara islands npstmw is formed south of the kuroshio and the kuroshio extension in late winter and advected to the ogasawara site by the southwestward westward return flow of the kuroshio recirculation while npstmw is seen at the ogasawara site in almost all seasons npstmw with a higher core temperature is advected to this site in april and one with a colder core follows in and after june until january or february furthermore the npstmw core temperature shows considerable interannual variation this variation is very similar to that found in other regions away from the ogasawara site suggesting that it reflects the larger scale variation of npstmw and that this site would be suitable for monitoring the npstmw core temperature a significant correlation between the npstmw core temperature and the monsoon index which is defined as the difference in the sea level pressure between nemuro japan and irkutsk russia as an indicator of wintertime cooling indicates that npstmw contains a memory of wintertime cooling in the preceding winter

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

c s fe relationships and the isotopic composition of pyrite in the new albany shale of the illinois basin u s a the relationship between pyritic sulfur content spyr and organic carbon content corg of shales analyzed from the new albany group depends upon corg for samples of 6 wt no spty corg correlation is apparent the degree of fe pyritization dop shows similar relationships to corg these c s fe relationships suggest that pyrite formation was limited by the availability of metabolizable organic carbon in samples where corg 6 wt apparent sulfur isotope fractionations relative to contemporaneous seawater sulfate 34s for pyrite formation average 40 for non calcareous shales and 25 for calcareous shales 34s values become smaller with increasing corg spyt and dop for all corg poar 6 wt and some corg nch 6 wt shales these trends suggest that pyrite formation occurred in a closed system or that instantaneous bacterial fractionation for sulfate reduction decreased in magnitude with increasing organic carbon content the isotopic trends observed in the new albany group are not necessarily representative of other shales having a comparable range of organic carbon content e g cretaceous shales and mudstones from the western interior of north america gautier 1986 34s values in the remainder of the corg rich new albany group shales are relatively large 38 to 47 and independent of corg spyr and dop which suggests that pyrite in these shales formed mostly at or above the sediment water interface by precipitation from an isotopically uniform reservoir of dissolved h2s

mesoscale eddy effects on the subduction of north pacific mode waters mesoscale eddy effects on the subduction of north pacific mode waters are investigated by comparing observations and ocean general circulation models where eddies are either parameterized or resolved the eddy resolving models produce results closer to observations than the noneddy resolving model there are large discrepancies in subduction patterns between eddy resolving and noneddy resolving models in the noneddy resolving model subduction on a given isopycnal is limited to the cross point between the mixed layer depth mld front and the outcrop line whereas in eddy resolving models and observations subduction takes place in a broader zonally elongated band within the deep mixed layer region mesoscale eddies significantly enhance the total subduction rate helping create remarkable peaks in the volume histogram that correspond to north pacific subtropical mode water stmw and central mode water cmw eddy enhanced subduction preferentially occurs south of the winter mean outcrop with an anticyclonic eddy to the west and a cyclonic eddy to the east the outcrop line meanders south and the thermocline mld shoals eastward as eddies propagate westward the mld shoals shielding the water of low potential vorticity from the atmosphere the southward eddy flow then carries the subducted water mass into the thermocline the eddy subduction processes revealed here have important implications for designing field observations and improving models

tertiary tectonic and sedimentological evolution of the south carpathians foredeep tectonic vs eustatic control abstract a detailed seismic sequence stratigraphy study based on a dense network of seismic profiles is integrated with structural observations from interpreted geological sections to derive a tectonic and sedimentological model for the miocene pliocene evolution of the south carpathians foredeep getic depression following paleogene and older orogenic phases the first tectonic event which affected the studied area was characterised by early miocene large scale extension to transtension which is responsible for the opening of the getic depression as a dextral pull apart basin further middle miocene contraction caused wnw ese oriented thrusts and associated piggy back basins the last tectonic episode recognised in the studied area relates to general transpressive deformations during the late miocene early pliocene interval a first nw se oriented dextral episode is followed by second n s sinistral deformations the detailed sequence stratigraphy study allows for the definition of the dominant tectonic control of the sedimentary sequences in foreland basins a eustatic control may be associated but has a clear subordinated character

early diagenetic pyrite morphology in a mudstone dominated succession the lower jurassic cleveland ironstone formation eastern england abstract diagenetic pyrite in the mudstones and ironstones of the lower jurassic cleveland ironstone formation of eastern england exhibits two distinct morphologies framboidal pyrite commonly associated with organic matter and euhedral pyrite associated with detrital clay pellets these two morphologies are mutually exclusive in occurrence framboidal pyrite is present in clay rich mudstones ooidal ironstones apatite rich units and some silt rich mudstones euhedral pyrite is present in silt rich and sand rich mudstones 34s isotopic analysis of six samples of pyrite suggests that both types of pyrite morphology precipitated during early diagenesis from porewaters with open access to overlying sea water although both probably acted as sites for continued pyrite precipitation during burial it is proposed that framboidal pyrite precipitated from iron dominated porewaters at sites of sulfide supply i e in the region of organic matter as a result of bacterial sulfate reduction where locally sulfide production rates were high enough for porewaters to reach supersaturation with respect to fes euhedral pyrite also precipitated from iron dominated porewaters but sulfide production rates from organic matter was such that fes saturation was not reached at the sites of sulfide production instead euhedral pyrite was precipitated directly from porewater when fes2 saturation was reached the control over pyrite morphology was probably the amount and reactivity of the organic matter within the deposited sediments the sand rich mudstones contained less reactive organic matter due to clastic dilution and deposition in shallower environments with o2 rich bottom waters the ironstones and apatite rich units were deposited under very low sedimentation rates and as a result organic matter contents were very low and iron reduction dominated early diagenesis which inhibited sulfate reduction the presence of minor framboidal pyrite within these units however suggests that sulfide reduction took place in micro environments during early diagenesis

organic geochemistry and organic petrology of a potential source rock of early eocene age in the beaufort mackenzie basin abstract the biological marker compounds 17 h and 17 h 23 28 bisnorlupane have been identified in a coaly interval at about 3300 3320 m depth within the lower taglu sequence early eocene in the immiugak a 06 well in the beaufort mackenzie basin these biomarkers were previously only known to occur in the lower part of the richards formation and were thus used to infer that the richards was the source for most of the tertiary oils and condensates in the basin the discovery of bisnorlupanes in older much more organic rich rocks indicates that the previous oil source rock correlations may not have been correct and that the coals in the lower taglu sequence are likely the dominant effective source rock especially for the paleocene and early eocene reservoirs in the southern part of the mackenzie delta petrographic and rock eval analyses indicate that the lower taglu sequence coaly section should be mainly a source for gas but with some potential to expel liquids the level of thermal maturity inferred from rock eval tmax 432 438 c equivalent to about 0 65 0 75 ro vitrinite is slightly higher than that inferred from the measured reflectance fluorescence and foraminiferal colouration index which all indicate that the maturity at 3300 m is about 0 60 0 65 ro vitrinite equivalent at the gulf et al immiugak a 06 well site

differential formation and circulation of north pacific central mode water abstract a repeat hydrographic section along 165 e was analyzed to verify a westward extension of the formation region of the north pacific ocean central mode water cmw suggested by previous synoptic observations and to investigate the relation between the formation region and thermohaline fronts the cmw formation region extends at least as far west as 155 e much farther than recognized in a previous study based on climatology it is located in two interfrontal regions between the kuroshio extension front and the kuroshio bifurcation front kbf and between the kbf and the subarctic front where two types of cmw namely the lighter variety with potential density of 25 8 26 2 kg m 3 and the denser one of 26 3 26 4 kg m 3 are formed how this differential formation of cmw is reflected in its gyrewide distribution was examined using one time sections of the world ocean circulation experiment woce hydrographic program in the north pacific the main circulation paths of the two types of cmw diverge eas

transport and reduction of sulfate and immobilization of sulfide in marine black shales in fine grained sediments in which the amount of reduced sulfur retained in stable phases substantially exceeds that present initially in pore waters rates of sulfate reduction may have equaled or exceeded rates of sulfate transport resulting in enrichment of sup 34 s in pore waters and reduction products abundance and isotopic compositions of reduced sulfur compounds can be used to calculate the extent of sulfide retention and improve reconstructions of carbon sulfur oxidation reduction redox budgets the miocene monterey formation and upper devonian new albany shale represent distinct types of black shales that accumulated under different conditions of sulfate reduction our results suggest that the rate of sulfate reduction was controlled largely by mass transport in the monterey and by the reduction process itself in the new albany sulfide was more efficiently retained in the monterey thus each mole of sulfide in the new albany represents a greater amount of sedimented organic carbon removed during sulfate reduction 30 refs 4 figs 1 tab

deciphering the upper famennian hangenberg black shale depositional environments based on multi proxy record abstract presented for the first time in this paper are the results of a detailed multi proxy investigation conducted on the hangenberg black shale hbs from the polish part of the laurussian shelf which provide details about the environmental conditions in existence during deposition of the shale and the role played by anoxic conditions in the mass extinction events that occurred at the end of the devonian times inorganic and organic redox indicators indicate that bottom water redox conditions changed periodically from being mainly anoxic euxinic to oxic or being partially depleted in oxygen u th values above 1 25 ni co values above 7 and v v ni values above 0 8 recorded from the lower part of the hbs all point to anoxic euxinic conditions being present as do high total organic carbon contents toc above 10 and degree of pyritisation dop values around 0 75 however the presence of benthic fauna over the lower part of the hbs attests to opportunistic colonisation of the seafloor during oxic episodes evidence for similar episodes has also been recognised over the middle part of the hbs e g u th values below 1 25 ni co values below 4 v v ni values below 0 8 toc values of 3 to 5 5 and dop values of 0 4 to 0 75 plus the common occurrence of benthic fauna anoxic conditions returned during the deposition of the upper part of the hsb though they were not as well developed as when the lower part of the shale was laid down of interest is the presence of small pyrite framboids and isorenieratene biomarkers in all the analysed samples which suggest that euxinic conditions persisted in the photic zone of the water column a twenty centimetre thick layer of volcanogenic deposits tuffites is present in the middle part of the hbs the geochemical characteristics of which are typical of ocean floor basalts the occurrence of volcanogenic material below and within the hbs together with an absence of calcium carbonate over its upper part the presence of abundant tetrads just above the black shale and a drastic decrease in faunal frequency in the upper part of the hbs imply that volcanism may have caused oceanic acidification or hypercapnia that in turn potentially may have influenced the hangenberg mass extinction event

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

hydrographic conditions of the devono carboniferous north american seaway inferred from sedimentary mo toc relationships abstract deepwater anoxia developed widely within a series of silled intracratonic basins in north america during the middle devonian to early carboniferous but the hydrographic factors contributing to this development are virtually unknown the present study demonstrates that the degree of enrichment of strongly hydrogenous elements such as molybdenum mo in the organic rich shales that accumulated in these basins has the potential to provide information about paleohydrographic conditions most of the study units 49 of 55 exhibit significant positive covariation between elemental mo and toc concentrations yet there is substantial variation in the statistical parameters that define these relationships specifically the regression lines characterizing mo toc covariation have slopes m ranging from 2 to 65 10 4 although a majority of the study units yield m values between 10 and 25 10 4 the parameter m exhibits systematic stratigraphic variation within individual basins and geographic variation among basins suggesting that mo toc relationships were controlled by slowly evolving watermass characteristics of the devono carboniferous north american seaway a recent study of modern anoxic silled basins algeo t j lyons t w 2006 mo total organic carbon covariation in modern anoxic marine environments implications for analysis of paleoredox and paleohydrographic conditions paleoceanography 21 pa1016 doi 10 1029 2004pa001112 demonstrated that m is closely linked to the degree of restriction of the subpycnoclinal watermass as reflected in aqueous mo concentrations mo aq and deepwater renewal times dw these relationships reflect control of sedimentary mo enrichment by both the amount of sedimentary organic matter i e host phase availability and the concentration of aqueous mo i e source ion availability when applied to black shales of the devono carboniferous north american seaway these relationships permit both qualitative and quantitative inferences regarding the degree of restriction of deepwaters in cratonic basins and the evolution of hydrographic conditions through time black shales associated with early stages of sea level rise commonly exhibit low m values 1000 yr higher sea level stands resulted in more open marine conditions and enhanced deepwater renewal leading to deposition of black shales with m values up to 65 equivalent to mo aq 70 of the normal seawater concentration and dw

a new geochemical classification of sedimentary environments because of the relative constancy of ph in most subaqueous sediments and the general lack of measurability of eh these parameters are not practically useful for classifying sedimentary environments in their place a new classification is offered which derived from studies of modern sediments is based on the presence or absence of dissolved oxygen and dissolved sulfide in the sediments at the time of authigenic mineral formation sedimentary environments are first of all divided into oxic and anoxic depending upon the presence or absence of measurable dissolved oxygen anoxic environments in turn are divided into sulfidic and non sulfidic depending upon the presence of measurable dissolved sulfide anoxic nonsulfidic environments are further divided into postoxic or resulting from oxygen removal without sulfate reduction weakly reducing and methanic or resulting from complete sulfate reduction with consequent methane formation strongly reducing the environments are shown to succeed one another during early diagenesis in the order oxic post oxic sulfidic methanic iron and manganese minerals characteristic and stable in each environment are listed and discussed so that they may be used to distinguish the environments when studying the ancient geological record

characteristics of collisional orogens with low topographic build up an example from the carpathians sequence stratigraphy in the hinterland kinematic analysis of thin skinned thrusting in the foreland and thermochronological tracking of exhumation in the orogenic core are combined to quantify the mechanics of an orogen with low topographic build up the carpathian system demonstrates that collisional deformation can couple and thicken the lower orogenic plate along reverse faults that dip more steeply than the subduction zone defining a foreland coupling type of collision near the surface this is expressed by wide antiforms in the upper plate and the thin skinned orogenic wedge a sequence stratigraphic analysis of the back arc transylvanian basin demonstrates that the sedimentary architecture records orogenic uplift pulses with both short and long wavelengths these correspond to the activation of individual thrust sheets in the thin skinned wedge and to lower plate coupling events respectively

assessment of the oil source rock potential of the pedregoso formation early miocene in the falcon basin of northwestern venezuela abstract the early miocene pedregoso formation is one of the numerous formations rich in organic matter within the stratigraphic record of the urumaco trough in the central area of the falcon basin due to its lithological characteristics and stratigraphic position this formation is of great interest regarding the basin s petroliferous systems the evaluation of various inorganic and organic geochemical parameters indicates that the organic matter is primarily of marine origin deposited in a marine carbonate environment typical of reefal systems under oxic to dysoxic conditions the low variability in the toc concentrations and in the distributions of the biomarkers extracted from the samples suggests that the paleoenvironmental conditions and the organic matter supply remained approximately constant throughout the sedimentation of this unit the pedregoso type ii organic matter marine origin and initial organic richness value 1 8 suggest that this unit has probably generated hydrocarbons within the urumaco trough however present day thermal maturity parameters reveal that the pedregoso organic matter is overmature dry gas window indicating that this unit is only capable to generate gas in addition the geothermal gradient maturity parameters and the maximum paleotemperature estimated in this study suggest that the pedregoso formation reached a maximum burial depth the 6 5 km consistent with the value obtained from data of stratigraphic thickness in the urumaco trough this implies that the thermal anomaly that affected the basin during the late eocene early miocene did not reach the central part of the basin and therefore the organic matter maturation in this unit is due to the sedimentary burial

orogen parallel extension in the southern carpathians a structural study including a kinematic analysis based on sense of shear criteria recorded in fault rocks is combined with fission track dating a two stage alpine tectonic evolution is proposed for the major tectonic units which constitute the southern carpathians of the parang mountains area upper cretaceous top to the sse nappe stacking was followed by wsw ene orogen parallel extension in the eocene top to the ene shearing in lower greenschist facies mylonites from the eastern part of the danubian window parang mountains is associated with a low angle detachment at the base of the brittlely deformed getic nappe the getic detachment below the dome shaped getic detachment east dipping at the eastern termination of the danubian window the danubian units were rapidly exhumed hence the eastern part of the danubian window represents a greenschist facies core complex as a working hypothesis it is proposed that this orogen parallel stretch was originally n s oriented and that it formed when the rhodopean fragment which includes the getic and supragetic nappes moved northward into an oceanic embayment past the western margin of moesia this eocene extension was part of a process of oroclinal bending in the area of the southern carpathians and their continuation into the balkan mountains extension was followed by about 50o clockwise rotation of the southern carpathians associated with dextral wrenching along the northern boundary of moesia and compression in the moldavides of the eastern carpathians 1998 elsevier science b v all rights reserved

lateral variations in mechanical properties of the romanian external carpathians inferences of flexure and gravity modelling we present the results of two dimensional flexure and gravity modelling of the subsidence of the romanian carpathian foreland based on twenty profiles through the southern and eastern carpathians the narrow spacing of the grid of profiles allows us to investigate the lateral tectonic variations transverse to the belt but also along strike the topographic elevation of the romanian carpathian mountain belt is modest and the minimum in the bouguer gravity anomaly characteristic for flexural control of subsidence is located relatively far towards the foreland in respect to the mountain belt as the contribution of topographic loading to the evolution of the romanian carpathian foreland system is small a subduction underplating dominated tectonic regime controlled the nappes emplacement and basin shortening in the external flysch and molasse basins during the late tertiary the modelling results support the existence of important variations in effective elastic thicknesses te and plate boundary forces high flexural bending stresses in the western part of the southern carpathians can explain low te values whereas the increase of te to the east can be explained by changes in rheological properties of the moesian platform field observations indicate that variations in deflection along strike are probably also related to basement unregularities stress field rotations and strike slip movement along lateral ramps during the tertiary in the eastern carpathians the model results indicate a n s trend of lateral back stepping of the subduction system a distinct back step in the vicinity of the seismically active vrancea area supports the involvement of the e w crustal scale trotus fault which forms the transition from the east european platform to the scythian and moesian platforms development of a possible n s migration of plate boundary activity or slab detachment and successive intersection with the trotus fault can explain the large pliocene subsidence in the focsani depression and relative uplife of the east european platform north of the mentioned fault

a global transition to ferruginous conditions in the early neoproterozoic oceans eukaryotic life expanded during the proterozoic eon1 2 5 to 0 542 billion years ago against a background of fluctuating ocean chemistry2 3 4 after about 1 8 billion years ago the global ocean is thought to have been characterized by oxygenated surface waters with anoxic and sulphidic waters in middle depths along productive continental margins and anoxic and iron containing ferruginous deeper waters5 6 7 the spatial extent of sulphidic waters probably varied through time5 6 but this surface to deep redox structure is suggested to have persisted until the first neoproterozoic glaciation about 717 million years ago8 9 10 11 here we report an analysis of ocean redox conditions throughout the proterozoic using new and existing iron speciation and sulphur isotope data from multiple cores and outcrops we find a global transition from sulphidic to ferruginous mid depth waters in the earliest neoproterozoic coincident with the amalgamation of the supercontinent rodinia at low latitudes we suggest that ferruginous conditions were initiated by an increase in the oceanic influx of highly reactive iron relative to sulphate driven by a change in weathering regime and the uptake of sulphate by extensive continental evaporites on rodinia we propose that this transition essentially detoxified ocean margin settings allowing for expanded opportunities for eukaryote diversification following a prolonged evolutionary stasis before one billion years ago

carbon sulfur iron systematics of the uppermost deep water sediments of the black sea box cores recovered during leg 4 of the 1988 r v knorr black sea oceanographic expedition from deep water regions of the basin were dominated by coccolith rich microlaminated unit 1 sediment and muddy gray turbidite layers both organic carbon oc and pyrite sulfur values for unit 1 display narrow ranges with mean concentrations of 5 3 1 1 1 wt and 1 3 0 3 wt respectively unit 1 is not enriched in pyrite s relative to sediments deposited under oxygenated bottom waters normal marine sediments with comparable oc concentrations carbon sulfur relationships evaluated on a calcium carbonate free basis to avoid spurious correlations resulting from dilution effects demonstrate that oc and pyrite s are essentially decoupled these observations combined with the persistence of elevated pore water sulfide to depth and a strong correlation between pyrite s and the detrital fe component argue strongly for limitation of pyrite formation in unit 1 by the availability of reactive fe unit 1 fe limitation is further indicated by degree of pyritization dop studies a measure of the extent to which the original potentially reactive fe has been transformed to pyrite these studies show sulfidation of reactive fe ranging from 57 to 78 with dop values independent of oc concentration unit 1 dop profiles suggest that the majority of the pyrite is formed in the sulfidic water column and or very close to the sediment water interface pyrite s concentrations of unit 1 when compared with the particulate reduced sulfur fluxes measured in time series sediment traps are compatible with predominantly water column pyrite formation because of the limitations in the supply of reactive fe associated with the comparatively high supply of oc the microlaminated sediment is characterized by c s ratios greater than those typical of holocene oxically deposited sediments the turbidite muds of the deep basin display high reduced s values relative to holocene normal marine sediments in samples with low oc concentrations low c s ratios this reflects pyrite formation under anoxic sulfidic bottom water conditions in a probable upper slope source region as well as during transport and final deposition intermediate dop values for the turbidites in part a product of their rapid rate of deposition reveal that fe limitation is ultimately not a factor and that further pyrite should form during burial however the very rapid rate at which unit 1 pyrite forms suggests fundamental differences between the overall reactivities of the fe phases associated with the microlaminated and turbiditic sediments the signature of water column anoxia with regard to sedimentary pyrite formation is clearly indicated by the high dop values of unit 1 and the comparatively high levels of s associated with the low concentrations of oc of the turbidite muds this agrees with similar conclusions based on studies of ancient sedimentary rocks

sterane biomarkers as indicators of palaeozoic algal evolution and extinction events abstract algae are among the oldest organisms known to inhabit the earth s biosphere with a record dating back some 2 7 ga only few marine algae produce hard parts that can be preserved over geologic time and consequently their fossil record is incomplete molecular fossils or biomarkers add complementary information to the fossil palynomorph record steroids are important constituents of eukaryotic cell membranes and are preserved in sediments as steranes c28 and c29 steranes are indicators for the presence of green and c27 steranes for the presence of red algae respectively the relative abundance of steranes allows the investigation of the fossil record for palaeozoic algal diversification and evolution in this study 500 palaeozoic rock samples representing a broad facies variety from the upper ordovician to the p t boundary were investigated for sterane compositions in addition three profiles covering the hirnantian the f f and the hangenberg event were analyzed for possible shifts in the sterane distribution associated with extinction events a sharp increase of the c28 c29 sterane ratio from 0 70 at the devonian carboniferous boundary implies a fundamental change in the green algae assemblage from more primitive mainly c29 sterane producing algae to modern c28 sterane producing algae for all investigated extinction events a pronounced but short lived rise in the c28 sterane content occurs that is attributed to an episodic increase in prasinophytes the gradual radiation of algae may have been triggered by frequent mass extinctions in the upper devonian culminating with the massive decline of acritarchs at the d c boundary the coeval rise in the c28 c29 sterane ratio indicates the presence of an non encysting algal group and coincides with the global augmentation of numerous filamentous codiacea siphonales and the rise of euspondyle and metaspondyle dasycladales

a subsurface pathway for low potential vorticity transport from the central north pacific toward taiwan island 1 analysis of the simple ocean data assimilation product reveals that the central north pacific 28 n 35 n 150 e 170 w is one of the main formation regions for low potential vorticity water of density between 25 4 and 25 8 it is found that the low potential vorticity water is transported from the central north pacific toward the east of taiwan island along a subsurface pathway following the subtropical gyre circulation and it takes approximately 12 years propagation of pycnocline thickness anomalies is detected along the pathway in association with the decadal variability of the subduction rate

a role of eddies in formation and transport of north pacific subtropical mode water 1 hydrographic data acquired during 2001 by argo profiling floats deployed in the kuroshio recirculation region are used to verify the inference that mesoscale eddies prevailing in the recirculation region play an important role in the formation and transport of north pacific subtropical mode water npstmw that is the deeper winter mixed layer is formed preferentially where the thermocline is deeper in association with anticyclonic eddies in the succeeding seasons mesoscale eddies retain npstmw during their southwestward movement from the npstmw formation region so that anticylonic eddies contribute substantially to the npstmw transportation the spatial distributions of the mixed layer depth in winter and the npstmw thickness in the succeeding seasons based on the float data suggest that they are affected by mesoscale eddies the float data also provide the statistical relations of these quantities against the thermocline depth which are consistent with our inference

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

diagenetic origin of quartz silt in mudstones and implications for silica cycling mudstone the most abundant sedimentary rock type1 composed primarily of clay or silt sized particles contains most of the quartz found in sedimentary rocks2 these quartz grains which are chemically and mechanically resistant and therefore preserve their characteristics well have long been considered to be derived from the continental crust1 here we analyse quartz silt from black shales in the eastern usa dating back to the late devonian period about 370 million years ago using backscattered electron and cathodoluminescence imaging and measure oxygen isotopes with an ion probe our results indicate that up to 100 of the quartz silt in our samples does not originate from the continental crust instead it appears to have precipitated early in diagenesis in algal cysts and other pore spaces3 with silica derived from the dissolution of opaline skeletons of planktonic organisms such as radiolaria and diatoms transformation of early diatoms into in situ quartz silt might explain the time gap between the earliest fossil occurrences of diatoms about 120 myr ago4 and molecular evidence for a much earlier appearance between 266 or even 500 myr ago5 6 moreover if many other mudstone successions show similarly high proportions of in situ precipitated rather than detrital quartz silt the sedimentary record in mudstones may have been misinterpreted in the past with consequences for our estimates of palaeoproductivity as well as our perceptions of the dynamics and magnitude of global biogeochemical cycling of silica

pyrite and organic matter in phanerozoic normal marine shales data have been obtained from our own chemical analyses and from the literature for the concentrations of organic carbon c and pyrite sulfur s in over 600 samples of cambrian to recent normal marine shales normal marine refers to deposition in oxygenated bottom water as evidenced by the presence of benthic fossils and or indicators of bioturbation all samples were selected to minimize 1 1 loss of c and or s due to weathering at the outcrop by emphasizing the use of drill core material 2 2 analytical errors and non diagenetic effects by avoiding sediments low in c or s content such as sandstones 3 3 fe limitation of pyrite formation by avoiding limestones cherts and euxinic shales 4 4 metamorphic loss of c relative to s by avoiding rocks obviously subjected to even low grade metamorphism our results indicate that 1 there is generally a good positive linear correlation between organic c and pyrite s for normal marine shales of all ages and 2 the mean cs ratio for normal marine shales has varied over time devonian to tertiary shales exhibit mean cs weight ratios 1 8 0 5 somewhat lower than quaternary sediments meancs 2 8 this we believe is due to preferential c loss relative to s during biogenic methanogenesis plus diagenetic heating distinctly lower mean c s values for the cambrian and ordovician 0 5 0 1 cannot be explained solely in terms of diagenetic c loss and instead must represent low original ratios the low original ratios we suggest were due mainly to the absence of bacterially refractory organic matter added to the marine environment by rivers at that time because the major source of such material vascular land plants had not yet evolved this along with a possibly lower degree of bioturbation contributed to enhanced pyrite formation and preservation and thus lower early paleozoic cs ratios

observations of the subtropical mode water evolution from the kuroshio extension system study abstract properties and seasonal evolution of north pacific ocean subtropical mode water stmw within and south of the kuroshio extension recirculation gyre are analyzed from profiling float data and additional hydrographic and shipboard adcp measurements taken during 2004 the presence of an enhanced recirculation gyre and relatively low mesoscale eddy variability rendered this year favorable for the formation of stmw within the recirculation gyre stmw formed from late winter convection that reached depths greater than 450 m near the center of the gyre the lower boundary of stmw corresponding to 25 5 kg m 3 was set by the maximum depth of the late winter mixed layer properties within the deep portions of the stmw layer remained largely unchanged as the season progressed in contrast the upper boundary of the stmw layer eroded steadily as the seasonal thermocline deepened from late april to august vertical eddy diffusivity responsible for this erosion was estimated from a budget analysis of

climate response to orbital forcing across the oligocene miocene boundary spectral analyses of an uninterrupted 5 5 million year my long chronology of late oligocene early miocene climate and ocean carbon chemistry from two deep sea cores recovered in the western equatorial atlantic reveal variance concentrated at all milankovitch frequencies exceptional spectral power in climate is recorded at the 406 thousand year ky period eccentricity band over a 3 4 million year period 20 to 23 4 my ago ma as well as in the 125 and 95 ky bands over a 1 3 million year period 21 7 to 23 0 ma of suspected low greenhouse gas levels moreover a major transient glaciation at the epoch boundary approximately 23 ma mi 1 corresponds with a rare orbital congruence involving obliquity and eccentricity the anomaly which consists of low amplitude variance in obliquity a node and a minimum in eccentricity results in an extended period approximately 200 ky of low seasonality orbits favorable to ice sheet expansion on antarctica

evolution of the north pacific subtropical mode water in anticyclonic eddies anticyclonic eddies aes trap and transport the north pacific subtropical mode water stmw but the evolution of the stmw trapped in aes has not been fully studied due to the lack of eddy tracking subsurface observations here we analyze profiles from special designed argo floats that follow two stmw trapping aes for more than a year the enhanced daily sampling by these argo floats swirling around the eddies enables an unprecedented investigation into the structure and evolution of the trapped stmw in the aes the upper lower thermocline domes up concaves downward and this lens shaped double thermocline encompasses the thick stmw within the eddy core the lighter stmw 25 0 25 2 trapped in aes dissipates quickly after the formation in winter because of the deepening seasonal thermocline but the denser stmw 25 2 25 4 remains largely unchanged except when the ae passes across the izu ridge the enhanced diapycnal mixing over the ridge weakens the denser stmw appreciably while many aes decay upon hitting the ridge some pass through a bathymetric gap between the hachijojima and bonin islands forming a cross ridge pathway for stmw transport by contrast the north pacific intermediate water npiw underneath is deeper than the eddy trapping depth 600 m and hence left behind east of the izu ridge in argo climatology the shallow stmw 400 m intrudes through the gap westward because of the eddy transport while the npiw 800 m is blocked by the izu ridge

late holocene climate and ecosystem history from chesapeake bay sediment cores usa palaeoclimate records from late holocene sediments in chesapeake bay the largest estuary in the usa provide evidence that both decadal to centennial climate variability and european colonization

petrography and geochemistry of dispersed organic matter in the oligocene source rocks of the central western part of the getic depression romania abstract the aims of this study include the evaluation and interpretation of oligocene source rocks from the central western part of the getic depression romania and the identification of their maturation and their hydrocarbon potential 24 argillite samples belonging to the source rocks were studied using organic petrography and geochemistry methods including rock eval pyrolysis and the following sets of results were obtained maceral diversity values of vitrinite reflectance thermal alteration index and organic geochemical values the oligocene disperse organic matter contains both humic and terrestrial organic matter as well as sapropelic marine algal matter represented by telalginite and lamalginite several anoxic deep marine water intervals were recorded in the getic depression the samples are immature with tmax values ranging between 415 c and 434 5 c and random vitrinite reflectance of 0 32 and 0 53 the samples yield a total organic content between 0 55 and 5 71 with a hydrogen index between 9 and 379 mg g showing two types of kerogen a mixed type ii iii kerogen indicating a generative potential for hydrocarbon and gas and b type iii kerogen indicating a gas generative potential

evaluation of high frequency paleoenvironmental variation using an optimized cyclostratigraphic framework example for c s fe analysis of devonian mississippian black shales central appalachian basin u s a abstract stratigraphic successions are rarely sampled at sufficiently dense spacing to permit evaluation of paleoenvironmental variation at the shortest fundamental frequency operative in the depositional system of interest often because that frequency remains undetermined here we provide an example of a sampling strategy optimized for recovery of high frequency paleoenvironmental signals based on 1 full core analysis using a continuous survey tool such as x radiography followed by 2 fine sampling of selected small scale cycles that record significant short term paleoenvironmental variation we show that this strategy results in recovery of high frequency paleoenvironmental signals that are completely missed by low density sampling protocols permitting key insights into depositional and early diagenetic processes that may otherwise by overlooked the present case study is based on c s fe systematics of the cleveland and sunbury shales which belong to the upper devonian lowermost carboniferous black shale succession of the central appalachian basin in eastern north america in these units the fundamental scale of paleoenvironmental variation is recorded by pervasive decimeter scale 5 to 20 cm thick compositional cycles that are readily visible in outcrop in which high organic layers weather out as resistant ledges we identified these cycles in drillcores using x radiography which proved to be an effective proxy for compositional variation owing to control of bulk density primarily by total organic carbon toc content we then sampled selected dm scale cycles n 21 at a centimeter spacing generating short high resolution multiproxy chemostratigraphic records including toc sulfur and fe concentrations fepy fehr a redox proxy 34spyrite and organic maceral content this analysis yielded the novel insight that all proxies related to authigenic iron sulfides e g stotal and spyrite fetotal and fepyrite fepy fehr and 34spyrite covary negatively with toc within the dm scale cycles we interpret the unusual pattern of negative toc pyrite covariation in the cleveland and sunbury shales to have resulted from differential distributions of labile organic matter om which drove h2s production via microbial sulfate reduction msr and reactive fe which controlled pyrite formation labile om was concentrated in high toc layers whereas reactive fe was concentrated in low toc layers possibly as fe oxyhydroxide coatings on silt grains as a consequence of which part of the h2s generated in the high toc layers diffused upward into the low toc layers before becoming fixed as pyrite this process is evidenced by several contrasts between high toc and low toc layers 1 higher spyrite concentrations and fepy fehr values in the latter 2 concentration of pyrite in the lower part of low toc layers immediately above high toc layers and 3 higher 34spyrite values in the latter reflecting late diagenetic formation of the h2s that diffused upward into the low toc layers to our knowledge this process has not been documented previously in ancient marine shales probably owing to insufficiently high resolution analysis in earlier studies

effects of mesoscale eddies on subduction and distribution of subtropical mode water in an eddy resolving ogcm of the western north pacific abstract the effects of mesoscale eddies on the subduction and distribution of the north pacific subtropical mode water stmw are investigated using an eddy resolving ocean general circulation model ogcm first the subduction rate is calculated and the contribution of eddies to the subduction of stmw is estimated it is found that eddy subduction significantly contributes to the total subduction of stmw second eddy thickness transport and diapycnal flux are directly diagnosed to investigate the large scale eddy induced transport process of stmw the large southward eddy thickness transport in the stmw core density is consistent with eddy subduction the eddy transport on the isopycnal surface of stmw is directed down the thickness gradient and traverses the mean flow the meridional eddy transport streamfunction indicates two eddy circulation cells south of 30 n associated with the circulation of stmw these cells flatten density surfaces similar to the effect of the gent and mcwilliams gm schem

effect of mesoscale eddies on subtropical mode water variability from the kuroshio extension system study kess abstract forty eight profiling floats have been deployed in the kuroshio extension ke region since may 2004 as part of the kuroshio extension system study kess project by combining the float temperature salinity measurements with satellite altimetry data this study investigates the role played by mesoscale eddies in controlling the property changes in north pacific subtropical mode water stmw following a 3 yr period of low eddy activity in 2002 04 the ke showed a transition to a high eddy kinetic energy state in 2005 this transition is the result of delayed oceanic response to the 2002 shift in the basin scale surface wind forcing in connection with the pacific decadal oscillation the high eddy kinetic energy state of the ke is characterized by successive shedding of strong cold core rings into the recirculation gyre resulting from the interaction of the ke jet with the shatsky rise or the preexisting cutoff rings by transporting northern origin high potential vorticity pv ke water into t

discovery of agglutinated benthic foraminifera in devonian black shales and their relevance for the redox state of ancient seas abstract agglutinated foraminifera are benthic organisms that occur in marginal marine to bathyal environments though some taxa can live in oxygen deficient environments they require at least some oxygen in order to persist at the seafloor the discovery that they occur widely in late devonian black shales has a bearing on the boundary conditions required for episodes of extensive carbon sequestration in marine sediments and their connection to atmospheric composition and global climate devonian black shales of the eastern us have been studied extensively to determine the fundamental controls on carbon burial and a range of mechanisms has been proposed finding agglutinated benthic foraminifera in these black shales refocuses the debate about their origin and points to limitations of earlier models

redox dynamics in the chesapeake bay the effect on sediment water uranium exchange the effect of seasonal variations in productivity and redox dynamics on the sediment water exchange of uranium was investigated on a twelve cruise time series in the chesapeake bay the deep waters of the bay undergo seasonal anoxia in response to high primary productivity and water column stratification from late spring to early fall dissolved oxygen was used to monitor water column redox conditions and dissolved iron manganese and sulfide were measured to monitor sediment redox conditions dissolved 238u was measured in the water column and sediment porewaters to monitor water column sediment exchange uranium incorporation in bay sediments results from two distinct processes productivity dependent scavenging from the water column and redox dependent cycling of uranium between sediments and bottomwater uranium is removed from surface waters of the bay by scavenging with biodetritus during periods of high primary productivity bottomwater and sediment redox conditions determine whether this particle bound uranium is buried or released to overlying water particulate uranium is released to bottomwaters and porewaters during the degradation of biodetritus and oxidation of authigenic uranium low oxygen in bottomwaters in the summer results in minimal exchange of uranium between the sediments and bottomwater due to the stability of reduced u iv high bottomwater oxygen concentrations associated with bay turnover in the fall results in release of authigenic uranium by oxidation to the soluble vi form enrichment of uranium in fall bottomwater suggests that authigenic uranium is very labile when exposed to oxic environmental conditions this process is enhanced by physical mixing when anoxic sediments are resuspended into the oxic bottomwaters