westward propagation of latitudinal asymmetry in a coupled ocean atmosphere model abstract hemispheric asymmetries of continental geometry have long been speculated to be the cause of the northern hemisphere position of the intertropical convergence zone over the central and eastern pacific it is unknown however how the effects of continental asymmetries are transmitted to and felt by the central pacific thousands of kilometers away this paper proposes a transmitter mechanism by investigating the response of a coupled ocean atmospheric model to a symmetry breaking force by the american continents the model treats land forcing implicitly as an eastern boundary condition in the absence of oceanic feedback the model response to the eastern boundary forcing is tightly trapped and confined to a small longitudinal extent off the coast whereas the climate over the interior ocean is symmetric about the equator ocean atmosphere coupling greatly enhances the transmissibility of the effects of the land forcing establishing large latitudinal asymmetry over a great zonal extent a westwar

geoarchaeological investigations at the topper and big pine tree sites allendale county south carolina the topper and big pine tree sites are located along the central savannah river in south carolina both sites contain significant clovis horizons and the topper site is reported to contain a pre clovis assemblage characterized by a smashed core and microlithic industry the stratigraphic position of the early assemblage at topper is indeed below clovis and radiocarbon and luminescence ages support its pre clovis age however the human origin of the proposed artifacts has not been conclusively proven the late quaternary stratigraphic sequence developed for this segment of the savannah river provides support for a regional pattern of river metamorphosis over the last 50 000 years in southeastern u s streams

a geochemical study of oil migration at source rock reservoir contacts stable isotopes abstract whereas organic geochemical analyses of oils and potential source rocks have enabled correlations to be drawn and have been utilized to suggest modes of migration only limited data has been published relating a known source rock in contact with an oil filled reservoir this paper presents initial results from the examination of an approximately 100 m continuous core through the kimmeridge shale of the north sea the variability in extractable source rock hydrocarbon contents kerogen toc asphaltene and their carbon isotopic contents are documented nitrogen isotopic content of kerogens and asphaltenes as well as kerogen and asphaltene ton are relatively constant carbon isotopic compositions of kerogen extractable hydrocarbons and asphaltenes covaried significantly as did nitrogen isotopic compositions of kerogen and asphaltenes average isotopic compositions of the asphaltene free extracts and asphaltenes were nearly identical to the oil in the primary reservoir small chemical differences are noted among extracts

boiling sand springs dismal river nebraska agents for formation of vertical cylindrical structures and geomorphic change boiling motion not temperature sand springs fed by ground water moving upward along distinct conduits occur along the dismal river in the nebraska sand hills the cylindrical conduits are developed in alluvium and are as large as 10 m in diameter and 44 m deep sides of the spring conduits are firm boiling sand is overlain in several places by a clear layer of water in the spring time varying wave patterns and boils can be observed along the interface between these layers sediment within the conduits is generally well sorted although some debris is present because of their large size firm sides and persistence in time the conduits have the potential for preservation as vertical cylindrical structures comparable to those reported in sedimentary rocks of several ages the discovery of preserved structures is evidence of paleo ground water discharge and therefore the structures are a useful mapping tool for determining position in landscape evolution

biological marker distribution in coexisting kerogen bitumen and asphaltenes in monterey formation diatomite california organic rich 18 2 monterey formation diatomite from california was studied the organic matter consist of 94 bitumen and 6 kerogen biological markers from the bitumen and from pyrolysates of the coexisting asphaltenes and kerogen were analyzed in order to elucidate the relationship between the various fractions of the organic matter while 17 alpha h 18 alpha h 21 alpha h 28 30 bisnorhopane was present in the bitumen and in the pryolysate of the asphaltenes it was not detected in the pyrolysates of the kerogen a c40 isoprenoid with head to head linkage however was present in pyrolysates of both kerogen and asphaltenes but not in the bitumen from the diatomite the maturation level of the bitumen based on the extent of isomerization of steranes and hopanes was that of a mature oil whereas the pyrolysate from the kerogen showed a considerably lower maturation level these relationships indicate that the bitumen may not be indigenous to the diatomite and that it is a mature oil that migrated into the rock we consider the possibility however that some of the 28 30 bisnorhopane rich monterey formation oils have not been generated through thermal degradation of kerogen but have been expelled from the source rock at an early stage of diagenesis

interhemispheric thermal gradient and tropical pacific climate 1 we explore the impact of interhemispheric thermal gradients forcing on the tropical pacific ocean atmosphere climate in an intermediate coupled model the equatorial zonal sea surface temperature sst gradient strengthens with an increased northward interhemispheric thermal gradient the increase arising from earlier onset and later retreat of the seasonal cold tongue and intensification during the peak cold season when the mean interhemispheric thermal gradient is reversed the central equatorial pacific sst annual cycle abruptly reverses in phase with its cold season in mar may rather than sep nov while startling this response is consistent with a prevailing hypothesis that ties the cold tongue sst annual cycle phase to the hemispheric mean asymmetry of the intertropical convergence zone el nino southern oscillation activity is also sensitive to the interhemispheric thermal gradient with peak activity occurring when the mean gradient is small reducing rapidly as the mean gradient increases in either direction

a study of response of the equatorial pacific sst to doubled co2forcing in the coupled cam 1 5 layer reduced gravity ocean model abstractthe response of the equatorial pacific sst under co2 doubling is investigated using community atmosphere model version 3 1 cam3 1 1 5 layer reduced gravity ocean rgo coupled model a robust el nino like warming pattern is found in the equatorial pacific the surface heat budget analyses suggest the el nino like pattern results from a weakening of the walker circulation in the western equatorial pacific all the heat flux components are important to warm the ocean with the vast majority canceled by entraiment cooling related to increased stratification in the central eastern pacific the oceanic horizontal advections along with longwave radiation and latent heat flux act to warm the ocean with entrainment shortwave radiation and horizontal diffusion acting as damping terms an enhanced annual cycle of sst in the equatorial pacific is also found which is driven by the ocean dynamical adjustments to changing winds in the eastern ocean although the ocean model used here is a simple reduced

variations in the sterane carbon number distributions of marine source rock derived crude oils through geological time abstract the analysis of the sterane data of a large set of crude oils 414 derivedfrom marine carbonate 27 and siliciclastic source rocks 14 where influences of terrestrial or lacustrine derived organic matter can reasonably be excluded shows that there are increases in the relative content of c28 steranes and decreases in the relative content of c29 steranes through geological time there are no consistent variations in the relative content of c27 steranes through time with one major exception a proterozoic oil from oman palaeozolic and older crude oils are thus generally characterised by strong predominances of c29 steranes and low relative concentrations of c28 steranes significantly higher proportions of c28 steranes and lower proportions of c29 steranes occur in oils derived from jurassic and upper cretaceous source rocks these changes through time do not appear to reflect the chemical evolution of the sterols of one particular variety of marine organism the increase in c28 steranes may be related to the increased diversification of phytoplantonic assemblages in the jurassic and cretaceous possible sources of the c28 sterols necessary for the observed changes in crude oil steranes includes diatoms coccolithophores and dinoflagellates although the technique does not give an accurate means of determining the age of the source rock of a crude oil it is possible to distinguish younger crudes derived from the upper cretaceous and tertiary from palaeozoic and older crudes

migrated oil on novaya zemlya russian arctic evidence for a novel petroleum system in the eastern barents sea and the kara sea in this article we present evidence for the migration of cretaceous or younger oil into paleozoic strata on the islands of novaya zemlya russian arctic originating from the surrounding basins of the barents sea and the kara sea we thus suggest a novel petroleum system for the greater barents sea and kara sea regions organic geochemical data reveal that medium mature petroleum is hosted in overmature paleozoic rocks onshore novaya zemlya this petroleum likely migrated from the surrounding offshore sedimentary basins of the kara and barents seas into the onshore strata on a broad front covering 400 km 248 mi along the archipelago thus the findings describe the remnants of petroleum migration on a regional scale high maturities of the examined onshore strata vitrinite reflectance ro of 1 9 4 0 and conodont color alteration index values of 4 6 render the indigenous origin of the medium mature petroleum unlikely organic geochemical characteristics of the migrated hydrocarbons lead us to suggest the existence of a hitherto undescribed marine shale source rock with some contribution of terrigeneous organic matter the 13c isotope values varying within a range of 5 for bulk extracts as well as for individual n alkanes and isoprenoids suggest isotopic heterogeneity of the organic source facies the source rock units are inferred to have released hydrocarbons mostly at oil window maturities higher than 0 6 ro the occurrence of n alkanes and isoprenoids as well as abundant and partially degraded tricyclic terpanes indicates mixed undegraded and heavily biodegraded oil this suggests several petroleum charges with varying degrees of microbial degradation occurrences of oleanane high ratios of c28 to c29 steranes and elevated 24 norcholestane and 24 nordiacholestane ratios suggest cretaceous or tertiary source rocks

recognition and source correlation of migrated hydrocarbons in upper jurassic hareelv formation jameson land east greenland organic geochemical analysis of an interbedded shale sandstone sequence from the upper jurassic hareelv formation jameson land east greenland has revealed oil shows in the sandstones consistent with petroleum generation and migration a comparison of the molecular characteristics of extractable material from the sandstones with those of kerogen and bitumen from the shales indicates that the most likely origin of these shows is generation within the shales with expulsion and short range migration into the sandstones this conclusion is based on comparisons of biological marker distributions stable carbon isotopic compositions of extractable material and kerogen and pyrolysate compositions of kerogen and asphaltenes oil from a seep in the savoia halvo region south of jameson land can be correlated to the jurassic sandstone oil shows based on similar isotopic compositions and asphaltene pyrolysate distributions impregnation of both sandstones and shales throughout the sequence by products generated at higher maturities is considered unlikely but cannot be ruled out by the existing data the molecular characteristics of the sandstone hydrocarbons exhibit a striking similarity to those of oils from the mid norway region the similar geologic ages of the hareelv formation and the kimmeridge clay of northwestern europe which is the acknowledged source of the mid norway oils and the geographic proximity of the two regions at the time of early north atlantic rifting indicate that hydrocarbons from these present day distant regions have been generated from very similar organic facies deposited under similar environmental conditions these results are significant in that in addition to stratigraphic correlation of depositional sequences on both margins of the early rifted north atlantic the hydrocarbons generated from source rocks contained in these sequences now can als be geochemically correlated the results also suggest that jurassic hydrocarbon source facies deposited throughout the early north atlantic are geochemically similar a trait imparted to their generation products

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

late holocene eolian activity in the mineralogically mature nebraska sand hills abstract the age of sand dunes in the nebraska sand hills has been controversial with some investigators suggesting a full glacial age and others suggesting that they were last active in the late holocene new accelerator mass spectrometry radiocarbon ages of unaltered bison bones and organic rich sediments suggest that eolian sand deposition occurred at least twice in the past 300014c yr b p in three widely separated localities and as many as three times in the past 80014c yr at three other localities these late holocene episodes of eolian activity are probably the result of droughts more intense than the 1930s dust bowl period based on independent great plains climate records from lake sediments and tree rings however new geochemical data indicate that the nebraska sand hills are mineralogically mature eolian sands in nebraska have lower k feldspar and k2o rb and ba contents than most possible source sediments and lower k feldspar contents than dunes of similar age in colorado the most likely explanation for mineralogical maturity is reduction of sand sized k feldspar to silt sized particles via ballistic impacts due to strong winds over many cycles of eolian activity therefore dunes of the nebraska sand hills must have had a long history probably extending over more than one glacial interglacial cycle and the potential for reactivation is high with or without a future greenhouse warming

reconstruction of historical sea surface temperatures using empirical orthogonal functions abstract studies of climate variability often rely on high quality sea surface temperature sst anomalies although the high resolution national centers for environmental prediction formerly the national meteorological center optimum interpolation oi sst analysis is satisfactory for these studies the oi resolution cannot be maintained before november 1931 due to the lack of satellite data longer periods of ssts have come from traditional analyses of in situ ship and buoy sst observations alone a new interpolation method is developed using spatial patterns from empirical orthogonal functions e0fs that is a principal component analysis to improve analyses of sst anomalies from 1950 to 1981 the method uses the more accurate oi analyses from 1982 to 1993 to produce the spatial eofs the dominant eof modes which correspond to the largest variance are used as basis functions and are fit in a least squares sense to the in situ data to determine the time dependence of each mode a complete field

twentieth century tropical sea surface temperature trends revisited 1 this study compares the global distribution of 20th century sst and marine air temperature trends from a wide variety of data sets including un interpolated archives as well as globally complete reconstructions apart from the eastern equatorial pacific all datasets show consistency in their statistically significant trends with warming everywhere except the far northwestern atlantic the largest warming trends are found in the middle latitudes of both hemispheres two of the sst reconstructions exhibit statistically significant cooling trends over the eastern equatorial pacific in disagreement with the un interpolated sst and marine air temperature datasets which show statistically significant warming in this region twentieth century trends in tropical marine cloudiness precipitation and slp from independent data sets provide physically consistent evidence for a reduction in the strength of the atmospheric walker circulation accompanied by an eastward shift of deep convection from the western to the central equatorial pacific

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

large scale facies sequences in alluvial overbank environments abstract gradational coarsening upwards or fining upwards sequences order of meters thick in overbank environments can be produced by progressive crevasse splay levee progradation or abandonment while the channel belt remains unchanged in position in contrast meter scale facies sequences related to periodic channel bell avulsion may show relatively abrupt changes in facies and paleocurrent direction simulation models suggest that the number of such avulsion related facies changes in any overbank sequence bounded above and below by channel belt deposits is on the order of 1 to 10 this is confirmed using an ancient example in this example the average thickness of each avulsion bounded overbank facies sequence was 3 m assuming an average recurrence interval for avulsions of about 1 000 ye rs the mean overbank deposition rate was about 3 mm per year

transport direction of peoria loess in nebraska and implications for loess sources on the central great plains abstract in the midwestern united states large rivers draining the laurentide ice sheet lis were the most important sources of peoria loess deposited during the last glaciation loess deposition near those rivers may have responded primarily to ice sheet dynamics rather than direct effects of climatic change in contrast it has been proposed that thick peoria loess on the central great plains was derived mainly from unglaciated landscapes northwest of the main loess deposits in this study transport directions inferred from more than 600 measurements of peoria loess thickness in nebraska are used to test the hypothesis that much of the peoria loess on the great plains is nonglaciogenic a strong northwest to southeast thickness trend indicates that most peoria loess in nebraska was transported from one or more unglaciated northwestern source areas rather than from glacially influenced river floodplains the missouri river draining the lis the platte river draining alpine glaciers and the elkhorn river unglaciated basin were secondary sources their contribution is not detectable beyond a distance of 40 60 km peoria loess deposition on the central great plains was largely a direct response to climatic change in the unglaciated source region

short term biomarker variability in the monterey formation santa maria basin abstract forty eight samples of a 370 ft miocene monterey formation core from the union leroy 51 18 well santa maria basin california are examined for source rock potential and molecular distributions total organic carbon content rock eval pyrolytic yield vitrinite reflectance and distribution of regular steranes tricyclic and pentacyclic terpanes and aromatic steroids are measured the present day temperature range through the sampled interval is estimated to be less than 5 c maturity differences among samples are negligible source rock potential and molecular distribution differences are considered to arise entirely from the effects of source input diagenesis including lithologic effects and migration the sampled section is comprised of siliceous and phosphatic carbonate lithofacies and covariances between geochemical parameters source potential and biomarker distribution and lithofacies are recognized several molecular parameters change systematically with depth lithology including ethylcholestane ratios and c 20 and c 22 sterane and hopane epimer ratios the siliceous lithofacies possesses higher moretane hopane tricyclic pentacyclic terpane and sterane terpane ratios and lower mono mono tri aromatic steroid ratios bisnorhopane hopane ratios are up to 40 times higher in the phosphatic carbonate lithofacies than in the siliceous lithofacies increased relative concentrations of aromatic steroids are attributed to sulfur sterol reactions during very early diagenesis whereas increased relative bisnorhopane amounts are considered to result from massive input of specific anaerobic biota although kerogen elemental ratios change abruptly at the lithofacies boundary molecular distributions within the extractable organic matter change gradually beginning about 30 ft 9m above this interface this gradual change is tentatively attributed to upward migration of hydrocarbons originating in the phosphatic carbonate lithofacies probably through fractures within the lower part of the siliceous lithofacies interval

isotopic and rock magnetic expression of environmental change at the pleistocene holocene transition in the central great plains abstract in a region too dry for the effective use of the traditional palynological approach loess deposits of the central great plains offer a source of proxy information for the reconstruction of past climates the brady soil a ubiquitous feature developed within the uppermost late pleistocene peoria loess recorded the character of vegetation change associated with climate shifts during the pleistocene holocene transition stable carbon isotope ratio analysis and two room temperature magnetic parameters were used to examine the nature of the change during this period 13 c values derived from soil organic matter indicate that in the late pleistocene minor populations of drought tolerant c4 plants were interspersed among the dominant cool season grasses c3 in the west while c3 grasses were accompanied by trees in the east by the early holocene c4 grasses were the dominant vegetation in the west and contributed substantially to the 13 c signal in the east magnitude of the 13 c shift suggests an increase in july mean daily temperature of 8 10 c according to existing models magnetic susceptibility and frequency dependence signal the cessation of loess deposition and development of the brady soil and indicate a spatial pattern in the intensity of weathering across the region

lacustrine evidence for moisture changes in the nebraska sand hills during marine isotope stage 3 abstract in the central great plains of north america loess stratigraphy suggests that climate during the late pleistocene was cold and dry however this record is discontinuous and there are few other records of late pleistocene conditions cobb basin located on the northern edge of the nebraska sand hills contains lacustrine sediments deposited during marine isotope stage 3 beginning approximately 45 000 cal yr bp and continuing for at least 10 000 yr the lake was formed by a dune dam blockage on the ancient niobrara river and its deposits contain a diatom record that indicates changes through time in lake depth driven by changes in effective moisture during the earliest stages of lake formation the climate was arid enough to mobilize dunes and emplace dune sand into a blocking position within the niobrara streambed diatom assemblages suggest that lake level was shallow at formation increased substantially during a wet interval and then became shallow again as arid conditions resumed by about 27 000 cal yr bp the lake was filled and a shallow ephemeral river occupied the basin

geochemistry and origin of natural gas in the petroliferous mahu sag northwestern junggar basin nw china carboniferous marine and permian lacustrine gas systems abstract the mahu sag located in the northwestern junggar basin of nw china is a renowned carboniferous marine permian lacustrine hydrocarbon depocenter that in theory could host both oil and gas however as ongoing hydrocarbon exploration and production are focused solely on oil few gas prospects have been discovered in this paper we discuss the possible occurrence of natural gas deposits based on a comprehensive study of gas geochemistry including gas composition carbon isotopes and compositions of light hydrocarbons c5 c7 and biomarkers in retrograde condensates combined with geological information available for the study area our results indicate that three types of natural gas occur in the region a sapropelic type gas derived from the lower permian fengcheng formation p1f a humic type gas sourced from carboniferous strata c and the overlying lower permian jiamuhe formation p1j and a humic type gas derived from the middle permian lower wuerhe formation p2w the p1f sourced sapropelic type gas accumulated during at least two distinct periods of time yielding low maturity oil associated gases and mature to high maturity kerogen oil cracking gases the carboniferous and p1j sourced humic type gases are mainly high maturity to over mature kerogen oil cracking gases without obvious geochemical evidence for a multi stage accumulation the p2w sourced gas is a mature humic type gas of these three types of gas the former two have the potential to form significant gas deposits and constitute valid exploration targets making the mahu sag a prospective area for gas exploration favorable areas for gas occurrence include deep anticlines hosting both kerogen and oil cracking gases the inferred exploration targets occur at significant depths which is why little drilling has been undertaken in these areas and major gas discoveries have yet to be made

norwegian sea area permo triassic organic carbon rich deposits from seismic abstract seismic surveys of the permo triassic successions in norwegian sea sub basins have been studied to determine the distribution of organic carbon rich intervals in the deeper basinal areas upper permian to lower triassic organic carbon rich deposits had been described in cores from the margins of the basin but their distribution in the deeper parts of the basin was unknown the distribution of the organic carbon rich deposits in the deeper basin areas has been determined using a combination of amplitude versus angle offset ava avo analysis and an assessment of strata bound deformation structures ava avo anomaly class iv which has a negative normal incident reflection coefficient that decreases with angle offset has been used to predict the presence of organic carbon rich rocks in this work the intercept i and gradient g plots ig crossplots together with the near far angle amplitude comparison of the seismic surveys have been used to complement the interpretation the ig cross plotting was done by selecting small windows data probes along the intervals speculated to be organic carbon rich any data probe which displayed avo class iv elements on the ig crossplots and exhibited amplitude dimming with angle has been considered to indicate an organic carbon rich layer the results of this work show the presence of both upper permian and middle triassic organic carbon rich sediments in the deeper parts of sub basins within the froan and helgeland basins in the norwegian sea area two and one organic rich intervals are indicated in the froan and helgeland basins respectively the distribution of these organic rich rocks was partly tectonically controlled resulting in spatially limited deposits in the compartmentalized froan basin but more extensive deposits in the helgeland basin none of the lower triassic sections examined in this study showed ava avo characteristics indicative of organic carbon rich sediments on ig crossplots

optical and radiocarbon ages of stacked paleosols and dune sands in the nebraska sand hills usa abstract optical ages for eolian sands from the nebraska sand hills indicate periods of extensive eolian activity at ca 115 25 840 70 2300 240 and 3560 340 a activity was also noted at single sampling locations at ca 6180 370 8430 510 and 13110 800 a many of these ages are similar to those noted by earlier authors optical ages from samples collected within paleosols indicate shorter and possibly less extensive periods of eolian activity at approximately 1220 150 1590 110 and possibly 1950 150 a during which the paleosol sands accumulated what was originally interpreted as a single 1 2 m thick paleosol is shown by optical dating to consist of three or more welded soils developed within eolian sands with optical ages of ca 3800 240 2740 240 1560 110 and possibly 1930 140 a each of which match eolian pulses recognized elsewhere scatter in some optical ages is attributable to intersection of sand filled rodent burrows extending in outcrop 1 5 m below the contact between paleosol and overlying topset beds a 5310 360 a optical age for one probable intersected burrow provides evidence for upward or lateral transport of older sands

application of biological markers in the recognition of palaeohypersaline environments the hydrocarbon fractions of a marl sample from a messinian basin in the northern appenines and four oils rozel point oil utah and three seep oils from sicily were studied

depositional environment and organic geochemistry of the upper permian ravnefjeld formation source rock in east greenland the upper permian ravnefjeld formation in east greenland is composed of shales that laterally pass into carbonate buildups and platforms of the wegener halvo formation the ravnefjeld formation is subdivided into five units that can be traced throughout the upper permian depositional basin two of the units are laminated and organic rich and were deposited under anoxic conditions they are considered good to excellent source rocks for liquid hydrocarbons with initial average toc total organic carbon values between 4 and 5 and hi hydrogen index between 300 and 400 the cumulative source rock thickness is between 15 and 20 m the source rocks are separated and enclosed by three units of bioturbated siltstone with a toc of less than 0 5 and an hi of less than 100 the e siltstones were deposited under relatively oxic conditions the organic geochemistry of the source rocks is typical for marine source rocks with some features normally associated with carbonate evaporite environments low pr ph pristane phytane low cpi carbon preference index distribution of tricyclic and pentacyclic terpanes the establishment of anoxic conditions and subsequent source rock deposition was controlled by eustatic sea level changes the subenvironment paleogeographic setting influx of carbonate material water depth salinity has some influence on a number of bulk parameters toc hi relations toc ts total sulfur relations and in particular biomarker parameters such as pr ph and terpane ratios all the basal shales or shales in the vicinity of carbonate buildups or platforms are characterized by low pr ph high c23 tricyclic terpanes and high c35 and c33 hopanes

organic geochemical characterisation of depositional palaeoenvironments of source rocks and oils in brazilian marginal basins abstract an investigation of bulk isotopic and molecular features of a wide selection of source rocks and oils from brazilian marginal basins ranging from lower cretaceous to tertiary in age provides a number of organic geochemical criteria that characterise and distinguish their depositional palaeo environments the methods employed include evaluation of organic carbon contents rock eval pyrolysis vitrinite reflectance measurements determination of carbon isotope ratios elemental and visual kerogen analysis assessment of oils and solvent extracts by liquid and gas chromatography and quantitative biological marker investigations using gc ms for aliphatic hydrocarbons and uv vis spectrophotometry for metalloporphyrins selected data were evaluated using principal component analysis the results enable the recognition and differentiation of seven depositional regimes lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate marine deltaic marine highly anoxic with a predominance of calcareous mudstone lithology and marine anoxic with predominance of siliciclastic lithology diagnostic features in the biological markers from these depositional environments include the carbon number distributions of n alkanes pristane phytane ratios absolute concentrations of carotane higher acyclic isoprenoids c 30 hopane and steranes and the abundance of the latter relative to 4 methylsteranes the occurrence and abundance of particular biological markers such as gammacerane tricyclic and tetracyclic terpanes 18 h oleanane 28 30 bisnorhopane and 25 28 30 trisnorhopane and the relative abundances of nickel and vanadyl porphyrins

buried paleoindian age landscapes in stream valleys of the central plains usa abstract a systematic study of late quaternary landscape evolution in the central plains documented widespread deeply buried paleosols that represent paleoindian age landscapes in terrace fills of large streams 5th order in alluvial fans and in draws in areas of western kansas with a thick loess mantle alluvial stratigraphic sections were investigated along a steep bio climatic gradient extending from the moist subhumid forest prairie border of the east central plains to the dry subhumid and semi arid shortgrass prairie of the west central plains radiocarbon ages indicate that most large streams were characterized by slow aggradation accompanied by cumulic soil development from ca 11 500 to 10 000 14c yr b p in the valleys of some large streams such as the ninnescah and saline rivers these processes continued into the early holocene the soil stratigraphic record in the draws of western kansas indicates slow aggradation punctuated by episodes of landscape stability and pedogenesis beginning as early as ca 13 300 14c yr b p and spanning the pleistocene holocene boundary the development record of alluvial fans in western kansas is similar to the record in the draws slow aggradation was punctuated by multiple episodes of soil development between ca 13 000 and 9000 14c yr b p in eastern kansas and nebraska development of alluvial fans was common during the early and middle holocene but evidence shows fan development as early as ca 11 300 14c yr b p buried soils dating between ca 12 600 and 9000 14c yr b p were documented in fans throughout the region in stream valleys across the central plains rapid alluviation after ca 9000 14c yr b p resulted in deeply buried soils that may harbor paleoindian cultural deposits hence the paucity of recorded stratified paleoindian sites in the central plains is probably related to poor visibility i e deep burial in alluvial deposits instead of limited human occupation in the region during the terminal pleistocene and early holocene the thick dark cumulic a horizons of soils representing buried paleoindian age landscapes are targets for future archaeological surveys

modeling climate shift of el nino variability in the holocene a coupled ocean atmosphere general circulation model is used to investigate climatic shift of el nino in the holocene the model simulates a reduced enso intensity in the early and mid holocene in agreement with paleoclimate record the enso reduction is proposed to be caused by both an intensified asian summer monsoon and a warm water subduction from the south pacific into the equatorial thermocline

aromatic hydrocarbon biomarkers in terrestrial organic matter of devonian to permian age abstract this paper presents the results of a detailed study on the occurrence and distribution of alkylnaphthalenes and alkylphenanthrenes in 39 coal and sediment samples from the late palaeozoic containing predominantly terrestrial organic matter most of the samples represent the euramerian flora realm and originate from locations beyond the variscan front in eastern northern and central europe i e especially england and the moscow basin the samples are of relatively low maturity 0 32 to 1 80 rr and consist mainly of mixtures of type iii and ii kerogen quantification of the c0 to c4 naphthalenes and the c0 to c4 phenanthrenes showed that these compound classes were highly abundant in all samples aromatic hydrocarbon maturity parameters in general are in good agreement with measured vitrinite reflectance values 1 2 7 trimethylnaphthalene an assumed diagenetic product of oleanane type biomarkers was present in all investigated samples this observation provides evidence that oleanane type lipids were biosynthesised by organisms predating the evolution of angiosperms or that assumed formation pathways for 1 2 7 trimethylnaphthalene are insecure 1 2 8 trimethylphenanthrene was significantly enriched in samples from the permian and the one sample from the devonian investigated in this study the precursor s of 1 2 8 trimethylphenanthrene therefore may have been produced by organisms which were least abundant in the carboniferous depositional environments represented by our samples

geochemical effects of primary migration of petroleum in kimmeridge source rocks from brae field area north sea i gross composition of c15 soluble organic matter and molecular composition of c15 saturated hydrocarbons in mature oil prone source rocks of the upper jurassic kimmeridge clay in the brae field area north sea the yield and the gross composition of solvent extractabte pctroleum likc compounds as well as the molecular proportions of c15 saturated hydrocarbons are primarily controlled by the effects of hydrocarbon expulsion during primary migration within sample series extending from shale centres towards adjacent reservoir sandstones regular and pronounced yield decreases have been documented as well as marked compositional changes for c15 soluble organic matter and its compound class fractions saturated hydrocarbons aromatic hydrocarbons nso compounds and for normal and isoprenoid alkanes relative migration losses indicating relative expulsion efficiencies were determined for the c15 alkanes throughout the outer five meters of thick shales relative expulsion efficiencies increase regularly and drastically for all compounds considered e g exceeding 90 for the c15 n alkanes in the outermost shale samples samples from thin 5 50 cm shale layers interbedded between reservoir sandstones reveal similarly high expulsion efficiencies for n alkanes the degree of depletion remains uniform throughout the molecular range c15 to c30i e no compositional fractionation occurred during primary migration which is interpreted to reflect expulsion of oil as a single phase fluid a simple conceptual model is proposed to explain the mechanisms and relationships of generation and expulsion processes in time and space a geochemically relevant conclusion is that the c15 soluble organic matter recovered by solvent extraction of mature source rocks represents only a portion of the total non volatile petroleum like material originally generated

linking the pacific meridional mode to enso coupled model analysis abstract the occurrence of a boreal spring phenomenon referred to as the pacific meridional model mm is shown to be intimately linked to the development of el nino southern oscillation enso in a long simulation of a coupled model the mm characterized by an anomalous north south sst gradient and anomalous surface circulation in the northeasterly trade regime with maximum variance in boreal spring is shown to be inherent to thermodynamic ocean atmosphere coupling in the intertropical convergence zone itcz latitude and the mm existence is independent of enso the thermodynamic coupling enhances the persistence of the anomalous winds in the deep tropics forcing energetic equatorially trapped oceanic waves to occur in the central western pacific which in turn initiate an enso event the majority of enso events in both nature and the coupled model are preceded by mm events

marine ingressions into the middle late permian saline lake of the southern permian basin rotliegend northern germany possibly linked to sea level highstands in the arctic rift system abstract a huge saline lake existed in the southern permian basin spb of northwest europe during late wordian to early wuchiapingian more than 2500 m thick continental siliciclastics and evaporites of the upper rotliegend ii were deposited before the marine zechstein transgression flooded the basin marine deposition took place in the arctic rift system between east greenland and the fennoscandian shield at that time interval sediments of the foldvik creek group reflect relative sea level fluctuations short termed pre zechstein ingressions from the boreal realm into the spb are known by the marine lamellibranch liebea reichei however sedimentological analysis of different saline lake horizons show that the marine influenced saline lake horizon does not differ lithologically from other saline lake claystone layers in the rotliegend succession the 87 sr 86 sr ratios of anhydrite 0 7089 0 7100 reflect deposition in a continental setting in contrast to this s isotopic values more than 11 7 cdt reflect marine pre zechstein ingressions into the spb in the middle niendorf and munster members s isotopic values of anhydrite can be used as an indicator for marine influence in the spb the pre zechstein ingressions superimpose the climatic triggered lake level fluctuations of the rotliegend saline lake two marine ingressions can be integrated into a set of regularly recurring abnormities in the depositional evolution these important evolutionary steps the saline lake formation the garlstorf ingression the p ameland and bahnsen lake level highstands the niendorf ingression and the zechstein transgression show a periodicity of more or less 1 ma one million year cyclicity is also known from deposits of the arctic rift system in east greenland wegener halvo and ravnefjeld formations a correlation of the upper rotliegend ii deposits with the succession of east greenland is proposed based on the assumption that the marine ingressions as well as the exceptionally intensive saline lake expansions could be linked to sea level highstands in the arctic rift system the result is the first correlation of upper rotliegend ii deposits with marine strata

sources and paleoclimatic significance of holocene bignell loess central great plains usa abstract this paper reexamines the stratigraphy sources and paleoclimatic significance of holocene bignell loess in the central great plains a broadly similar sequence of loess depositional units and paleosols was observed in thick bignell loess sections up to 300 km apart suggesting that these sections record major regional changes in the balance between dust deposition and pedogenesis new optical ages together with previously reported radiocarbon ages indicate bignell loess deposition began 9000 11 000 yr ago and continued into the late holocene some bignell loess is

the potential role of redox reactions for the distribution of alkyl naphthalenes and their oxygenated analogues in terrestrial organic matter of late palaeozoic age abstract the occurrence and distribution of alkyl naphthalenes and alkyl phenanthrenes in 39 late palaeozoic coal and sediment samples containing predominantly terrestrial organic matter is related to thermal maturity and biological source input this study investigates the relationship between aromatic hydrocarbons and the corresponding aldehydes ketones carboxylic acids and dicarboxylic acids based on the naphthalene skeleton it is suggested that alkyl naphthalenes are oxygenated in the sediments the behaviour of alkyl phenanthrenes and their oxygenated analogues is discussed in this context alkyl naphthalenes and phenanthrenes were abundant in all samples the low polarity nitrogen sulfur and oxygen compound fraction was characterised by the presence of alkyl naphthaldehydes and naphthyl ketones for the majority of the samples the presence of naphthalene carboxylic acids and anthracene phenanthrene carboxylic acids was restricted to samples of relatively enhanced maturity vitrinite reflectance rr 0 67 1 26 with one exception the correlations between the different classes of compounds based on the naphthalene skeleton led to the hypothesis that within the maturity range investigated aldehydes and ketones were readily formed from the corresponding aromatic hydrocarbons while the carboxylic acids were formed at elevated maturity for alkyl naphthalene dicarboxylic acids two formation pathways are suggested because of two different distribution patterns a direct correlation of these dicarboxylic acids with the occurrence of other compounds having a naphthalene skeleton was not apparent

organic geochemistry of upper palaeozoic lacustrine shales in the east greenland basin abstract the devonian and carboniferous lower permian succession in east greenland includes three geochemically distinct groups of lacustrine shales with a possible petroleum potential 1 1 source rocks with 2 10 toc hydrogen index betwen 450 and 900 a high content of saturated hydrocarbons a high content of n alkanes extending into the waxy range and a distinct odd even predominance and low to moderate pr ph values occur in the upper carboniferous part of the succession 2 2 source rocks with 10 toc hydrogen index above 700 a high content of saturated hydrocarbons a complete dominance of n alkanes without odd even predominance low waxiness and virtual lack of isoprenoids appear to be restricted to the upper devonian 3 3 shales with a high content of saturated hydrocarbons higher contents of branched and cyclic compounds high pr ph values low waxiness and max of n alkanes at c 22 occur in the middle devonian

biomarker geochemistry of the miocene monterey formation west san joaquin basin california implications for petroleum generation abstract much of the miocene monterey formation of california is rich in biogenic sediment especially organic matter and silica because of the geologic structure the monterey in the subsurface near lost hills in the san joaquin basin forms a natural laboratory for the study of the diagenetic responses of these materials rocks of similar age and lithology are buried to depths ranging between 500 and 3500 m and are thus exposed to a temperature range of 45 130 c the diagenetic progression of silica from opal a to opal ct to microquartz is well documented in monterey burial history studies however diagenetic indicators need to be established below the depth of complete conversion of opal ct to quartz which may be very shallow 1500 m or less at lost hills conventional maturity indicators are problematic the scarcity of vitrinite in many monterey samples hampers reflectance measurements in addition values that are measured may be anomalously low maximum pyrolysis temperatures are depressed due in part to high heavy bitumen content biomarker geochemistry provides effective alternative maturity indicators of particular interest are the stereochemical variations observed in the assemblages of steranes and triterpanes extracted from oil well core samples for example the 20s 20r ratio of 5 h 14 h 17 h 24 ethylcholestane increases from 0 09 to 0 56 over the depth range cited samples from petroleum accumulation zones are distinguished by anomalously mature biomarker assemblages considering their depth of burial this indicates that these bitumens are as mature as the deepest non production zone sample 3430 m even though they are from much shallower depths 580 1572 m other maturity and or migration indicators confirm this such as the relative increases in amounts of 14 h 17 h steranes rearranged steranes and tricyclic terpanes thus it appears that any immature indigenous bitumen in production zone samples is overwhelmed by a mature component which presumably migrated updip from deeper warmer strata since much oil is produced from shallow organic rich fractured monterey shales early in situ generation has previously been hypothesized however while both source and reservoir rock are lithologically similar and lie within the same formation biomarker geochemistry indicates that substantial generation occurs only in deeply buried monterey shales

stable carbon isotopes of amorphous kerogens from phanerozoic sedimentary rocks amorphous kerogens from phanerozoic sedimentary rocks may be divided into two groups on the basis of their 13c values h amorphous kerogens have isotopic values in the range of 24 to 20 per mil and l amorphous kerogens have isotopic values in the range of 35 to 26 per mil the occurrence of amorphous kerogens in the intermediate isotopic range from one rock unit in the data set suggests a weak continuum may exist between these two groups phytoplankton and to a lesser extent zooplankton and bacteria are considered to be the precursors for both kerogen types a plausible explanation for this dichotomy may be found in the source of co2 utilized by phytoplankton which is considered to be controlled by environmental factors h amorphous kerogens are expected to occur in silled basins that are overlain by expansive well circulated deep 500 m water where the prevailing source of carbon in the photic zone is atmospheric derived co2 conversely l amorphous kerogens are expected to occur in restricted basins that are overlain by stratified shallow 200 m water where the prevailing source of carbon in the photic zone may be organic derived co2

upper permian as a new play model on the mid norwegian continental shelf investigated by shallow stratigraphic drilling a 750 m thick fully marine succession of sandstones coarse grained turbidites shales and reworked sabkha sediments has been cored on the eastern margin of the mid norwegian shelf the succession has been dated as upper permian lower triassic and is comparable to rocks of the same age exposed onshore east greenland these data demonstrate that the marine depositional basin between greenland and norway extended much farther east than previously thought reddish shallow marine sandstones in the lower 170 m of the cored succession probably represent reworking of older sedimentary rocks present to the east of the drill sites this suggests that upper devonian lower permian sediments were deposited on caledonian basement east of the present day limits of the basin the cored succession also contains source rocks that can be stratigraphically correlated with the oil prone source rocks of the upper permian ravnefjeld formation onshore east greenland some of the cored sandstone intervals were stained with light nonbiodegraded oil that most likely was sourced from upper permian or alternatively lower triassic mudstones reworked fragments of reef building organisms in upper permian turbidites and upper permian carbonates encountered in an exploration well on the nordland ridge indicate that carbonate deposition and reef building occurred on structural highs on the trondelag platform the observations from the cored successions are key elements in a new paleozoic play model on the mid norwegian continental shelf and include the first evidence for the existence of an upper permian source rock in the area with upper permian carbonates or sandstones or triassic jurassic sandstones as reservoir begin page 108

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

the role of ocean dynamical thermostat in delaying the el nino like response over the equatorial pacific to climate warming abstractthe role of ocean dynamics in the response of the equatorial pacific ocean to climate warming is investigated using both an atmosphere ocean coupled climate system and its ocean component results show that the initial response fast pattern to an uniform heating imposed on the ocean is a warming centered to the west of the date line owing to the conventional ocean dynamical thermostat odt mechanism in the eastern equatorial pacific a cooling effect arising from the up gradient upwelling in time the warming pattern gradually propagates eastward becoming more el nino like slow pattern the transition from the fast to the slow pattern likely results from 1 the gradual warming of the equatorial thermocline temperature which is associated with the arrival of the relatively warmer extratropical waters advected along the subsurface branch of the subtropical cells stcs and 2 the reduction of the stc strength itself a mixed layer heat budget analysis finds that it is the total ocean dynamic

floodplain sedimentation in the upper mississippi valley natural versus human accelerated abstract understanding the time scales and pathways for response and recovery of rivers and floodplains to episodic changes in erosion and sedimentation has been a long standing issue in fluvial geomorphology floodplains are an important component of watershed systems because they affect downstream storage and delivery of overbank flood waters and they also serve as sources and temporary sinks for sediments and toxic substances delivered by river systems here 14c and 137cs isotopic dating methods are used along with ages of culturally related phenomena associated with mining and agriculture to determine rates of sedimentation and morphologic change for a reach of the upper mississippi river and adjacent tributaries in southwestern wisconsin and northwestern illinois the most important environmental change that influenced fluvial activity in this region during last 10 000 years involved the conversion of a late holocene mosaic of prairie and forest to a landscape dominated by cropland and pastureland associated with euro american settlement results presented herein for the upper mississippi valley umv show that the shift from pre agriculture natural land cover to landscape dominance by agricultural land use of the last 175 200 years typically increased rates and magnitudes of floodplain sedimentation by at least an order of magnitude accelerated overbank flooding led to increased bank heights on tributary streams and in turn contributed to more frequent deep flows of high energy these high energy flows subsequently promoted bank erosion and lateral channel migration and the formation of a historical meander belt whose alluvial surface constitutes a new historical floodplain inset against the earlier historical floodplain the new historical floodplain serves as a flume like channel that provides efficient downstream transport of water and sediment associated with moderate and large magnitude floods floodplains on lower tributaries however continue to experience rates of overbank sedimentation that are of anomalously high magnitude given improved land cover and land conservation since about 1950 this lower valley anomaly is explained by minimal development of historical agriculture period meander belts because of relatively low stream power in these channel and floodplain reaches of relatively low gradient in general long term pre agriculture rates of vertical accretion between about 10 000 and 200 years ago averaged about 0 2 mm yr 1 in tributary watersheds smaller than about 700 km2 and about 0 9 mm yr 1 on the floodplain of the upper mississippi river where the contributing watershed area increases to about 170 000 km2 on the other hand rates of historical vertical accretion during the period of agricultural dominance of the last 200 years average between 2 and 20 mm yr 1 with short episodes of even higher rates during times of particularly poor land conservation practices significant hydrologic effects of mining and agricultural started by the 1820s and became widespread in the study region by the mid 19th century the hydrologic and geomorphic influences of mining were relatively minor compared to those related to agriculture high resolution dating of floodplain vertical accretion deposits shows that large floods have frequently provided major increments of sedimentation on floodplains of tributaries and the main valley upper mississippi river the relative importance of large floods as contributors to floodplain vertical accretion is noteworthy because global atmospheric circulation models indicate that the main channel upper mississippi river should experience increased frequencies of extreme hydrologic events including large floods with anticipated continued global warming instrumental and stratigraphic records show that coincident with global warming a shift to more frequent large floods occurred since 1950 on the upper mississippi river and these floods generally contributed high magnitudes of floodplain sedimentation

sensitivity of biomarker properties to depositional environment and or source input in the lower toarcian of sw germany abstract a sequence of lower toarcian sediments which are highly contrasting in their depositional environment over a 5 m depth interval has been investigated in detail for the variability of geochemical properties which are used for source characterization and oil to source correlation lower liassic marls are representative of a well aerated shallow water environment in contrast to the immediately overlying bituminous shales which are deposited under extremely reducing conditions various properties have been found to vary considerably within these two units amongst the most important are carbon isotopic composition of the kerogen the pristane phytane ratios nickel as opposed to vanadyl porphyrins and the c27 dia regular steranes although maturation within the profile does not change some of the maturation dependent biomarker properties such as the monoaromatic steroid side chain cracking and the tm ts ratio exhibit large changes which can be assigned to diagenetic processes another maturation dependent property the 20s 20r epimerization of c29 steranes exhibits smaller changes which could also be due to early diagenetic processes the study suggests that reducing and oxidizing conditions i e eh and ph in the sediment exert an influence on several biomarker precursor product pathways in maturation studies initial variations due to depositional conditions have therefore to be taken into account

stratigraphic evidence for millennial scale temporal clustering of earthquakes on a continental interior fault holocene mississippi river floodplain deposits new madrid seismic zone usa abstract the earthquake cycles that characterize continental interior areas that are far from active plate boundaries have proven highly cryptic and difficult to resolve we used a novel paleoseismic proxy to address this issue namely we reconstructed holocene mississippi river channels from maps of floodplain strata in order to identify channel perturbations reflective of major displacement events on the high hazard and mid plate reelfoot thrust fault new madrid seismic zone u s a only three discrete slip events are currently documented for the reelfoot fault ad 900 ad 1450 and ad 1812 this study extends this record and thus illustrates the utility of stratigraphic proxies as paleoseismic tools we concurrently offer here some of the first quantified response times for tectonically induced channel pattern changes in large alluvial rivers we identified at least two cycles of pervasive meandering that were interrupted by channel straightening responses occurring upstream of the reelfoot fault scarp these straightening responses initiated at 2244 bc 269 to 1620 bc 220 and ad 900 respectively and each records initiation of a period of reelfoot fault slip after millennia of relative tectonic quiescence the second or new madrid straightening response was triggered by the previously known ad 900 fault slip event and this initial low sinuosity has been protracted until the modern day by the latter ad 1450 and ad 1812 events the first or bondurant straightening response began a period of several hundred to 1400 years of low river sinuosity which evidences a similar period of multiple recurrent displacement events on the reelfoot fault these bondurant events predate the existing paleoseismic record for the reelfoot fault these data offer initial evidence that slip events on the reelfoot fault were temporally clustered on millennial scales and thus offers the first direct evidence for millennial scale clustering of earthquakes on a continental interior fault this carries additional ramifications namely faults that have been quiescent and non hazardous for millennia could re enter an enduring period of recurrent hazardous earthquakes with little warning likewise the reelfoot fault also reveals evidence of temporal clustering of earthquakes on short term cycles months as well as evidence for longer term reactivation cycles 10 4 10 6 years this introduces the possibility that temporal clustering could be hierarchical on some continental interior faults

properties of a 5500 year old flood plain in the loup river basin nebraska abstract flood plain aggradation within the loup river basin of central nebraska was episodic and alternated with incision throughout much of the holocene a widespread episode of flood plain stability however occurred about 5700 5100 cal year bp the purpose of this paper is to describe the properties of this buried flood plain at six sites in the basin to consider why the properties of the buried flood plain vary from site to site and to evaluate possible reasons why the loup river flood plains stabilized 5500 years ago episodic valley bottom aggradation was common during flood plain formation at five of the six sites the radiocarbon ages particle size data and organic carbon data for the buried flood plain reveal that valley bottom aggradation generally slowed between about 5700 and 5100 cal year bp erratic down profile changes in percentages of sand clay and organic matter indicate flood plain sedimentation and soil formation were often episodic sand and clay rarely show a steady fining upward trend organic matter fluctuates with depth at some sites multiple incipient a horizons were buried during waning valley bottom aggradation at two localities the buried flood plain is evident as a clay rich stratum that must have been deposited in a paleochannel flood plain stabilization between 5700 and 5100 cal year bp probably occurred in response to the effects of external climate forcing on vegetation and hydrologic changes flood plains of other rivers in the central great plains also stabilized at this time further supporting a climatic explanation for slowing of valley aggradation and formation of a flood plain at this time recognition of buried flood plains is important to both soil mapping in valleys and to the discovery of cultural resources in valleys

hot acidic late permian seas stifle life in record time abstract the end of permian time 252 251 ma hosts the largest mass extinction in earth history yet events heralding this global catastrophe remain intensely disputed we present a chemostratigraphic marker the 187re 188os ratio which soars to unprecedented levels approaching the permo triassic boundary these ratios are tied to profound trace element changes and a precise re os time record at 252 ma preserved in black shales from east greenland and the mid norwegian shelf within a 36 meter shale section an 80 fold increase in re concentrations two fold for os signals seawater conditions that became increasingly inhospitable to life unwavering initial 187os 188os ratios of 0 6 preclude mafic volcanism and meteorite impact as the direct cause of late permian anoxia we argue that extraordinarily high 187re 188os ratios are the hallmark of simultaneously rising ocean temperature and acidity leading to loss of oxygen and the stifling of life in latest permian time

a global oceanic data assimilation system abstract a global oceanic four dimensional data assimilation system has been developed for use in initializing coupled ocean atmosphere general circulation models and many other applications the data assimilation system uses a high resolution global ocean model to extrapolate the information forward in time the data inserted into the model currently consists only of conventional sea surface temperature observations and vertical temperature profiles the data are inserted continuously into the model by updating the model s temperature solution every timestep this update is created using a statistical interpolation routine applied to all data in a 30 day window centered on the present timestep large scale features in the sea surface temperature analyses are consistent with those from independent analyses subsurface fields created from the assimilation are much more realistic than those produced without the insertion of data furthermore information contained in the assimilation field is shown to be re

diagenetic trends in the siliceous facies of the monterey shale in the santa maria region california x ray diffraction and oxygen isotopic analyses of outcrop and subsurface samples of siliceous rocks were used to reconstruct thermal and diagenetic histories of the miocene monterey shale near santa maria california within many stratigraphic sections soft porous diatomaceous rocks change gradationally to underlying hard and brittle chert porcellanite and siliceous shale the accompanying silica mineral zones are in descending stratigraphic order 1 biogenic silica opal a 2 cristobalitic silica opal ct and 3 microcrystalline quartz boundaries between silica mineral zones and stratigraphic horizons are often discordant within the opal ct zone the d 101 spacing of opal ct decreases in a smooth non linear fashion from about 4 10 a to 4 04 a in the santa maria valley and bradley oil field areas the thicknesses of the opal ct zones are greater and the present thermal gradients less than in the adjacent orcutt oil field thin opal ct zones at shallow maximum burial depths apparently correlate with higher thermal gradients using present thermal gradients and reconstructed maximum burial depths from well data in the santa maria region the ranges in temperatures for the top and base of the opal ct zone are 38 54 c and 55 110 c respectively the temperature difference between these two boundaries ranges from 17 to 60 c in comparison temperature ranges for these two boundaries computed from oxygen isotopic compositions of opal ct and quartz extrapolated experimental quartz water fractionations and assuming o18 0 o for the isotopic composition of the equilibrating fluid are 18 56 c and 31 80 c for the top and base of the opal ct zone respectively the temperature difference between these boundaries is 11 36 c using this method thermal gradients and sedimentation rates strongly influence rates of silica transformations reconstructed thermal and diagenetic histories of siliceous rocks of the monterey shale at four well sites in the santa maria region demonstrate that most silica conversions probably occurred during the last 3 4 myr in response to accelerated rates of sedimentation and therefore burial heating during the pliocene

an optical age chronology of late pleistocene fluvial deposits in the northern lower mississippi valley the lower mississippi valley lmv contains many large braided channel belts that are preserved west of the holocene floodplain previous efforts to establish geochronologic control on channel belt construction have been hindered by the lack of organic material for radiocarbon dating luminescence techniques provide a burial date for the sediment itself and may prove useful in this context samples from three channel belts in the northern lmv were analyzed using the single aliquot regenerative technique on 90 125mm quartz optical ages 19 7 17 8 16 1 15 0 and 12 5 12 1 ka are consistent with geomorphic relationships and indicate that channel belts were formed in the late pleistocene under glacial conditions these optical ages provide the first detailed chronology of lmv channel belt formation and are the first step towards developing a chronology for the entire lmv r 2003 elsevier science ltd all rights reserved

molecular genetic markers and maturity indices in intermontane lacustrine facies kishenehn formation montana abstract molecular markers have considerable promise as thermal maturation indicators in source rocks having a well defined depositional environment this occurs in the kishenehn formation northwest montana and southeast british columbia an oligocene unit comprised of fluvial and lacustrine shales up to 3 km of these non marine sediments were deposited in a 900 sq km elongated half graben atop the precambrian rocks of the lewis thrust sheet specific outcrops of the coal creek member of the kishenehn formation are known to contain excellent potential source rocks including extensive oil shales the source rock potential and molecular marker geochemistry of most of the major kishenehn outcrops have now been investigated and regional results are presented in this paper source rock analysis of a regional suite of kishenehn samples indicates excellent petroleum potential immature type i kerogen throughout the basin several classes of distinctive diagenetic molecular markers occur within the coal creek member of the kishenehn formation including diasterenes spirosterenes methylspirosterenes b ring monoaromatic anthrasteroids hopanes and moretanes molecular markers indicative of non marine deposition include dehydroabietane conifer input and an onocerane recently identified in leaf fossils of miocene lacustrine beds in adjacent idaho triterpane ratios are significantly more sensitive than vitrinite reflectance methods in assessing thermal maturation in the kishenehn and are successfully used in this study to order outcrop locations according to thermal maturity level the systematic variation of specific markers with increasing thermal maturation suggests that molecular correlation is feasible and could provide a method of assessing stratigraphic continuity in the basin

chemical signals for oxidative weathering predict re os isochroneity in black shales east greenland abstract re and os isotopes in shales are increasingly used for precise and accurate geochronology and for tracking rates of continental weathering in the geologic past moreover trace element compositions of organic rich shales reveal paleoredox conditions and properties of shale organic matter om useful for lithostratigraphic correlations chemical weathering alters the original shale composition and hence may compromise geologic interpretations based on geochemical data here we compare re os isotopes trace elements and om properties in correlative shales from outcrops and nearby drillcore to quantify the effects of weathering we define chemical parameters that distinguish weathered from pristine shale in samples that are macroscopically identical black shale from the ravnefjeld formation in east greenland yields disturbed re os isotope systematics for outcrop samples and highly precise re os isochron ages for drillcore geochemical data show that re os and common os are hosted in the organic matter rather than sulfides re and os both show mobility during weathering combined use of rock eval pyrolysis indices and sulfur contents documents oxidation of both om and pyrite thereby providing a valuable chemical criterion to assess invisible shale weathering further studies on chemically diverse shales will test the widespread application of these criteria as weathering indicators systematic differences in major and trace element content and kerogen quality between weathered and fresh shale samples are used to characterize and quantify weathering effects the character of the om in shales is most telling ravnefjeld data are compared with data from time correlative shales from the mid norwegian shelf georgiev et al 2011 hot acidic late permian seas stifle life in record time earth planet sci lett 310 389 400 to present a strategy for identification of re os isochroneity in advance of re os analytical work our recent compilation and comparison of upper permian shales from widely separated sequences on pangea s margins reveal exceptionally high re os ratios on a global scale we suggest upper permian shales may have significantly influenced the cenozoic e g eocene 187os 188os ratio of seawater on their exposure and weathering

variation in radiocarbon ages of soil organic matter fractions from late quaternary buried soils radiocarbon dating of three organic matter fractions total humic acid and residue isolated from late quaternary buried soils of the central great plains reveals that there often are considerable differences among but no consistent order to the ages of fractions for late holocene soils the residue fraction or the total fraction generally produces the oldest age for late pleistocene soils however no fraction was consistently the oldest the absence of a consistent sequence of fraction ages is attributed to postburial contamination of soils when bulk samples from the same soil were split and sent to two laboratories different radiocarbon ages were usually obtained the variability in radiocarbon ages of soil organic matter confirms that caution should be taken when using radiocarbon ages obtained from different laboratories to make regional stratigraphic correlations

the occurrence of bisnorhopane trisnorhopane and 25 norhopanes as free hydrocarbons in some australian shales abstract the triterpenoid hydrocarbons of some west australian shales have been examined by gc ms in addition to the common 17 h 21 h hopanes 17 h 21 h hopanes and 17 h 21 h moretanes 28 30 bisnorhopane 25 28 30 trisnorhopane and 25 norhopanes were identified in the organic extracts in contrast pyrolysates of the solvent extracted sediments contained only the common hopane and moretane series indicating that 28 30 bisnorhopane 25 28 30 trisnorhopane and 25 norhopanes are not bonded to kerogen but rather are present in the sediments as free hydrocarbons

early holocene alluvial stratigraphy chronology and paleoindian early archaic geoarchaeology in the loup river basin nebraska u s a abstract the preservation of alluvium dictates the discovery of archaeological sites in valleys we address two questions in our study of the loup river basin in the midcontinent of north america 1 what is the alluvial chronology of the loup river basin between about 10 300 and 7700 bp and 2 what is the potential for preservation and exposure of paleoindian and early archaic sites cleaned cut banks walls of backhoe trenches and archaeological test units cores collected with a trailer mounted giddings soil probe and bucket auger samples were described buried a horizons organic enriched alluvial strata peat and charcoal were sampled for radiocarbon dating dating was supplemented by temporally diagnostic cultural materials we recognize the absence of 14 000 10 300 bp alluvium in the loup river basin floodplain stability very slow aggradation occurred from 10 300 10 000 bp rapid floodplain aggradation is inferred between 10 000 and 9450 bp between 9450 and about 9250 bp erosion initially produced the kilgore creek terrace the valley floor landscape stabilized from about 9250 to 9100 bp before an episode of rapid aggradation overwhelmed floodplains and alluvial colluvial fans the fans stabilized about 8600 8500 bp while floodplains in larger valleys 5th order stabilized shortly after about 8400 8200 bp renewed valley bottom aggradation after 8200 was interrupted at about 7750 the absence of alluvium dated between 14 000 and 10 300 bp in the loup river basin precludes discovery of early paleoindian sites in valleys and contrasts with the presence of alluvium and buried soils containing clovis and folsom paleoindian sites in other drainage basins in the u s central great plains although the distribution of the kilgore creek terrace is an excellent proxy of preservation of 10 300 9450 bp alluvium in the loup river basin and thus late paleoindian sites very few remnants of this terrace have been preserved two early holocene erosional episodes have been documented in the loup river basin at 9450 9250 bp and again immediately before 8300 8200 bp alluvium deposited between 10 300 and 9450 contains one archaeological site and alluvium deposited 9250 8200 contains five other paleoindian sites five early archaic sites are documented in three alluvial colluvial fans and on a terrace remnant in the north loup river valley but have not been discovered in an alluvial stratigraphic context outside of fans although stable surfaces are much more likely to accumulate a greater density of artifacts than sedimentary units that are deposited rapidly we document three paleoindian components that are in alluvium between buried soils

on the genesis of the equatorial annual cycle abstract a linear theory is proposed that can explain both the period and the westward propagation of the equatorial annual cycles in the sst and zonal wind a coupled model linearized about a mean state of the air sea system is used this model allows the surface winds to directly change the sst through surface evaporation and vertical mixing in contrast to the formulation of the conventional air sea coupling models that emphasize the effects of winds on ocean dynamics it is demonstrated that the characteristics of the equatorial seasonal cycle including its period phase and amplitude are determined to a large extent by the mean state of the air sea coupling system the meridional wind which is specified here is the most important forcing for the annual cycle in sst suggesting that the equatorial annual cycle is the response to an annual solar forcing in the off equatorial regions

el nino variability in simple ocean data assimilation soda 1871 2008 1 a new ocean reanalysis that covers the period from 1871 to 2008 is used to explore the time evolving characteristics of el nino the new reanalysis assimilates all available hydrographic and sea surface temperature data into a model of the global ocean forced with surface boundary conditions from an atmospheric reanalysis that also covers the period from 1871 through 2008 using traditional measures of el nino our reanalysis shows that the timing of el nino events is in agreement with sea surface temperature reconstructions but el nino in the reanalysis is stronger particularly from 1871 to 1920 a new index based on the first moment of the temperature anomaly is introduced the new index is used to characterize the strength and location of el nino events and has the advantage that it is independent of the location of el nino using the new index el nino in the reanalysis shows prominent decadal variability of strength but relatively little long term trend el nino events were strong in the last part of the 19th century and first part of the 20th century and again in the latter part of the 20th century with weak el nino events in the middle of the 20th century the location of el nino also varies considerably ranging from the western to the eastern pacific near the coast of south america however the null hypothesis that the location of el nino can be represented as a random distribution about a central longitude of about 140 w cannot be rejected

investigating biological nitrogen cycling in lacustrine systems by ft icr ms analysis of nitrogen containing compounds in petroleum abstract biological nitrogen cycling plays an important role in bio environmental and petroleum geochemistry until now most research has focused on marine environments using nitrogen isotopes and in contrast nitrogen cycling in lacustrine environments remains poorly understood to fill this knowledge gap we present a case study of crude oils from permian brackish and saline alkaline lacustrine rocks in the junggar basin northwestern china to complement the large variation in nitrogen isotope values in lacustrine sediments we analyzed the pyrrolic n containing compounds of crude oil using negative ion electrospray ionization fourier transform ion cyclotron resonance mass spectrometry esi ft icr ms our results show that pyrrolic compounds derived from biological sources are more abundant in oils from brackish lacustrine settings i e the jimusar sag oils of the junggar basin than in oils from alkaline lacustrine settings i e the mahu sag oils of the junggar basin which is mainly due to greater higher plant contributions to the latter higher plants provide abundant alkaloids and chlorophyll that are the biological precursors of pyrrolic n containing compounds in addition anoxic sulfate type brackish lacustrine settings provide abundant ferrous iron and sulfide that promote n fixation this study provides the first insights into biological n cycling in brackish and alkaline lacustrine systems which has significance for fossil fuel resources and their environmental impacts our data suggest that the n cycling in lacustrine systems might have an important role in entire earth system n budget

diagenetic history and hydrocarbon potential of upper permian carbonate buildups wegener halvo area jameson land basin east greenland 1 the upper permian of jameson land includes two carbonate sequences the karstryggen and wegener halvo formations the karstryggen formation contains hypersaline carbonates and localized evaporites that were heavily weathered and dissected prior to deposition of the overlying strata the overlying wegener halvo formation represents an abrupt and extensive marine inundation over the underlying karstified karstryggen surface bryozoan brachiopod algal cement buildups of the wegener halvo formation are localized on karstic highs and show up to 150 m of depositional relief in situ mound core deposits are flanked by allodapic limestones which pass laterally into intermound calcareous shales the diagenetic histories of the core and flank facies are very different core facies porosity was intially obliterated by marine cements but repeated meteoric exposure altered unstable core facies constituents this alteration produced extensive secondary porosity through grain and cement leaching with local collapse brecciation flank strata however underwent little sea floor diagenesis and low permeability and mineralogically stable grain composition protected these strata from meteoric alteration early cementation and stabilization of core strata led to minimal burial diagenetic porosity loss uncemented flank beds however underwent profound mechanical and chemical compaction during this stage thus at the time of hydrocarbon generation distal flank beds had less than 2 porosity coarse upper flank beds had 5 10 remnant primary porosity and core facies deposits had 8 12 secondary pore space hydrocarbons generated from surrounding marine shales charged many of the bioherms with oil subsequent fracturing and hydrothermal fluid flow however flushed hydrocarbons and filled pores with ferroan calcite barite fluorite galena and baroque dolomite this heating and flushing is thought to have been especially intense in the wegener halvo region thus more basinal areas may still have reservoirs containing significant oil in equivalent upper permian limestones if as is likely the sea level changes affecting the greenland permian were eustatic then this study may provide significant clues to porosity development throughout the largely unexplored northern zechstein basin and the arctic basin of the barent sea this study also provides some important connections to the probably time equivalent guadalupian carbonate reservoir rocks of west texas new mexico and wyoming

pacific meridional mode and el nino southern oscillation 1 we present intriguing evidence that the majority of el nino events over the past four decades are preceded by a distinctive sea surface warming and southwesterly wind anomaly in the vicinity of the intertropical convergence zone itcz during the boreal spring this phenomenon known as the meridional mode mm is shown to be intrinsic to the thermodynamic coupling between the atmosphere and ocean the mm effectively acts as a conduit through which the extratropical atmosphere influences enso modeling results further suggest that the mm plays a vital role in the seasonal phase locking behavior of enso the findings provide a new perspective for understanding the important role of thermodynamic ocean atmosphere feedback in enso and may have profound implications for enso prediction particularly the unresolved issue of the spring predictability barrier citation chang p l zhang r saravanan d j vimont j c h chiang l ji h seidel and m k tippett 2007 pacific meridional mode and el nino southern oscillation geophys res lett 34 l16608 doi 10 1029 2007gl030302

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

late holocene dune activity linked to hydrological drought nebraska sand hills usa dunee elds of the great plains contain stratigraphic records of episodic holocene aeolian activity potentially providing a valuable record of climatic change it has been dife cult to establish unambiguous links between activity at specie c sites and regional palaeoclimate however here we demonstrate that widespread late holocene aeolian activity in the nebraska sand hills the largest dunee eld on the great plains of north america occurred during a period of hydrological drought aeolian sand sheets are interbedded with peat that accumulated in interdunes throughout much of the holocene the youngest of these sand sheets was deposited between 950 and 650 cal bp about the same time as the most recent major episode of aeolian activity at upland sites up to 120 km apart sand sheets could only have advanced across the interdunes if the local groundwater e ow systems that maintain interdune wetlands were temporarily reduced or eliminated by a reduction in recharge both reduced recharge and upland aeolian activity are best explained by regional megadrought

holocene alluvial fills in the south loup valley nebraska abstract four holocene alluvial fills are present in nebraska s south loup river valley fill iv the oldest and thickest was deposited between 10 200 and 4800 14c yr b p fill iii has an age of about 3000 14c yr b p fill ii is younger than 2100 and older than 900 14c yr b p and fill i is younger than 900 14c yr b p regional contemporaneity of valley alluviation in the eastcentral great plains suggests that climate has controlled long term sediment storage in the south loup river valley

molecular thermal maturity indicators in oil and gas source rocks many detailed chemical parameters have been proposed as indicators of thermal maturity in oil and gas source rocks certain classical maturity parameters involving carbon preference indices and compound class ratios such as hydrocarbons extract yield and extract yield total organic carbon are less commonly used today having been complemented with detailed molecular parameters among these parameters the molecular distributions of metalloporphyrins cyclic hydrocarbons low molecular weight hydrocarbons and gases are most commonly used recent instrumental advances have allowed the routine measurement of molecular ratios in geochemical organic matter stimulating the development and use of biological markers such as steranes hopanes and metallated tetrapyrroles as thermal maturity indicators increased chromatographic resolution of source rock hydrocarbons has also led to the use of low molecular weight hydrocarbons methylphenanthrenes and aromatized steranes as maturity indicators in this paper we discuss these developments emphasizing the applications and the pitfalls of using molecular maturity indicators