de glauconiarum origine the glauconitic facies is widespread on present day continental shelves from 50 s to 65 n and at water depths between 50 and 500 m and is in particularly great abundance on the upper slope and outer shelf between 200 and 300 m it is also common in many ancient rocks of post late precambrian age it occurs as sand to pebble sized essentially green particles granular facies but also as a surface coating on particles and hardgrounds and as a diffuse impregnation film and diffuse facies we suggest the replacement of the term glauconite which has been interchangeably used to designate a morphological form and a specific mineral by glaucony facies and glauconitic smectite and glauconitic mica as end members of the glauconitic mineral family the widely accepted model of burst and hower for glauconitization requires a degraded micaceous 2 1 layer lattice structure parent clay mineral however detailed analysis of numerous samples of recent glaucony reveals that such a parent substrate is exceptional the model therefore requires modification generally the parent material is carbonate particles argillaceous kaolinitic faecal pellets infillings of foraminiferal tests various mineral grains and rock fragments that pass gradually into the commonly occurring green grains we show that the process of glauconitization is achieved by de novo authigenic growth of automorphous crystallites in the pores of the substrate accompanied by progressive alteration and replacement of the substrate it is this two fold evolution that causes the verdissement of granular substrates macrofossils and hardgrounds the authigenic mineral is an iron rich and potassium poor glauconitic smectite while new smectites are growing into the remaining pore space the earlier smectites are modified by incorporation of potassium producing decreasingly expandable minerals with a non expandable glauconitic mica as the end member this mineralogical diversity of the glauconitic mineral family explains the highly variable physical and chemical properties of glaucony four categories nascent little evolved evolved and highly evolved glaucony are distinguished glauconitization appears to be controlled by a delicate balance between degree of physical confinement of a particle and the amount of ionic exchange between the micro environment and ambient open marine sea water the optimum conditions for glauconitization are those of semi confinement as a result the interior of a grain is more glauconitized than its less confined periphery similarly for identical substrate types large grains 500 m provide more favourable substrates for glauconitization than lesser confined small grains on a larger scale the formation of glaucony is governed by the availability of iron and potassium and the balance between detrital influx and winnowing low accumulation rates expose grains to the open marine environment for sufficiently long times 105 106 years for highly evolved glaucony

spirit mars rover mission to the columbia hills gusev crater mission overview and selected results from the cumberland ridge to home plate this paper summarizes the spirit rover operations in the columbia hills of gusev crater from sols 513 to 1476 and provides an overview of selected findings that focus on synergistic use of the athena payload and comparisons to orbital data results include discovery of outcrops voltaire on husband hill that are interpreted to be altered impact melt deposits that incorporated local materials during emplacement evidence for extensive volcanic activity and aqueous alteration in the inner basin is also detailed including discovery and characterization of accretionary lapilli and formation of sulfate silica and hematite rich deposits use of spirit s data to understand the range of spectral signatures observed over the columbia hills by the mars reconnaissance orbiter s compact reconnaissance imaging spectrometer crism hyperspectral imager 0 4 4 m is summarized we show that crism spectra are controlled by the proportion of ferric rich dust to ferrous bearing igneous minerals exposed in ripples and other wind blown deposits the evidence for aqueous alteration derived from spirit s data is associated with outcrops that are too small to be detected from orbital observations or with materials exposed from the shallow subsurface during rover activities although orbital observations show many other locations on mars with evidence for minerals formed or altered in an aqueous environment spirit s data imply that the older crust of mars has been altered even more extensively than evident from orbital data this result greatly increases the potential that the surface or shallow subsurface was once a habitable regime

an integrated model of extrusive sand injectites in cohesionless sediments clastic injection and surface expression of subsurface sediment remobilization is a phenomenon which is becoming increasingly recognized however understanding of the physical mechanisms that control these features remains limited dominated by inference from outcrop and seismic studies here this limitation is addressed through a set of experiments focused on the development and evolution of fluidization features in non cohesive bedded sequences fluidization and the onset of piping are shown to occur progressively through a sequence of discrete phases with initial void formation development of infiltration horizons rupture and finally pipe formation critically the style of piping the stability of piping and the temporal evolution of venting are shown to exhibit considerable variability in particular pipes may either be stable or very mobile migrating laterally over large distances these produce deposits that are typically interpreted in outcrop as being the product of en masse liquefaction rather than localized dynamic fluidization these differing elements are synthesized to produce a model of sand extrudites in addition the implications of this model are explored

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

alternative biological sources for 1 2 3 4 tetramethylbenzene in flash pyrolysates of kerogen pyrolysates of kerogens isolated from indian ocean surface sediments and from black sea unit ii contain abundant 1 2 3 4 tetramethylbenzene 1 2 3 4 tmb suggesting the presence of macromolecularly bound isorenieratane skeletons derived from isorenieratene biosynthesized by green sulphur bacteria cf hartgers et al 1994c however the 13c content of 1 2 3 4 tmb is identical to that of algal lipids excluding an origin from green sulphur bacteria the presence of 1 2 3 4 tmb in pyrolysates of stable residues of several marine algae indicates that it can also have an algal origin therefore the assessment of photic zone anoxia on the basis of the abundant presence of 1 2 3 4 tmb in the pyrolysate is not possible without determination of its stable carbon isotopic composition and comparison with those of algal lipids

the glauconite fe illite fe smectite problem a critical review iron silicate minerals are a significant component of sedimentary systems but their modes of formation remain controversial our analysis of published data identifies end member compositions and mixtures and allows us to recognize controls of formation of different mineral species the compositional fields of glaucony fe illite fe al smectites are determined in the m 4si vs fe sum of octahedral cations m interlayer charge solid solutions could exist between these phases the fe al and fe rich clay minerals form two distinct solid solutions the earliest phases to be formed are fe al smectites or berthierine depending on the sedimentation rate reductive microsystems appear in the vicinity of organic debris in unconsolidated sediments the fe is incorporated first in pyrite and then in silicates after oxidation potassium ions diffuse from the sea water sediment interface if not interrupted the diffusion process is active until reaction completion is reached i e formation of fe illite or glauconite or a mineral assemblage berthierine nontronite according to the available al ion amounts in the microsystem mixed layer minerals are formed when the diffusion process is interrupted because of sedimentation compaction or cementation despite the common belief of their value as palaeoenvironment indicators these minerals can form in a variety of environments and over a period of millions of years during sediment burial

mud flow levitation on mars insights from laboratory simulations sediment mobilisation occurring at depth and ultimately manifesting at the surface is a process which may have operated on mars however the propagation behaviour of this mixture of water and sediments hereafter simply referred to as mud over the martian surface remains uncertain although most of the martian surface is below freezing today locally warmer surface temperatures do occur and our current knowledge suggests that similar conditions prevailed in the recent past here we present the results of experiments performed inside a low pressure chamber to investigate mud propagation over a warm 295 k unconsolidated sand surface under martian atmospheric pressure conditions 7 mbar results show that the mud boils while flowing over the warm surface the gas released during this process can displace the underlying sand particles and hence erode part of the substrate this entrenched flow can act as a platform for further mud propagation over the surface the escaping gas causes intermittent levitation of the mud resulting in enhanced flow rates the mud flow morphologies produced by these phenomena differ from those produced when mud flows over a frozen martian surface as well as from their terrestrial counterparts the intense boiling removes the latent heat both from the mud and the subsurface meaning that the mud flow would eventually start to freeze and hence changing again the way it propagates the diverse morphology expressed by our experimental mudflows implies that caution should be exercised when interpreting flow features on the surface of mars and other celestial bodies

formation processes of framboidal pyrite abstract pyrite framboid formation may be the result of four consecutive processes 1 nucleation and growth of initial iron monosulfide microcrystals 2 reaction of the microcrystals to greigite fe 3 s 4 3 aggregation of uniformly sized greigite microcrystals i e framboid growth and 4 replacement of greigite framboids by pyrite the uniform morphology uniform size range and ordering of the microcrystals in individual framboids as well as the range of observed framboid structures from irregular aggregates to densely packed spherical aggregates and polyframboids are consequences of these processes using dlvo theory derjaguin landau verwey and overbeek we have evaluated the stability of colloidal iron monosulfide suspensions with ionic strengths typical of marine and lacustrine waters in addition to van der waals attractive and double layer repulsive forces a term is included to account for the ferrimagnetic properties of greigite numerical models predict that magnetically saturated greigite particles 0 1 m in diameter will rapidly aggregate in either marine or fresh water the aggregation model is in agreement with the sequence of greigite formation followed by pyrite framboid formation established in a previous experimental study sweeney and kaplan 1973 and is consistent with the occurrence of framboids composed of other magnetic minerals e g greigite magnetite and magnesioferrite based on the temperature dependent magnetic properties of greigite and aging experiments in hydrothermal solutions this mechanism for framboid formation via precursor greigite could operate to temperatures of 200 c consistent with the occasional occurrence of pyrite framboids in the paragenesis of metalliferous ore deposits

molecular isotopic characterisation of hydrocarbon biomarkers in palaeocene eocene evaporitic lacustrine source rocks from the jianghan basin china immature organic matter in lacustrine source rocks from the jianghan basin eastern china was studied for distributions and stable carbon isotopic compositions 13 c of hydrocarbon biomarkers all of the bitumens contain isorenieratane 13 c ca 17 indicating the presence of chlorobiaceae and thus periods of euxinic conditions extended into the photic zone aliphatic hydrocarbon fractions are dominated by pristane and phytane and contain relatively low amounts of 4a and 4 methylsteranes c 30 13 c ca 16 believed to originate from 4 methylsterols in dinoflagellates 13 c values of gammacerane ca 24 and c 30 17 21 h hopane ca 23 are consistent with an origin from bacterivorous ciliates that fed on chlorobiaceae the bitumens contain low relative amounts of organo sulphur compounds one rock contains c 37 and c 38 n alkanes 13 c ca 36 derived from alkadienes and alkenones of prymnesiophytes the distributions of hydrocarbon biomarkers suggest that they were initially sulphurised during early diagenesis and later released during early thermal maturation

geomorphic knobs of candor chasma mars new mars reconnaissance orbiter data and comparisons to terrestrial analogs high resolution imaging science experiment hirise imagery and digital elevation models of the candor chasma region of valles marineris mars reveal prominent and distinctive positive relief knobs amidst light toned layers three classifications of knobs types 1 2 and 3 are distinguished from a combination of hirise and thermal emission imaging system themis images based on physical expressions geometries spatial relationships and spectral data from compact reconnaissance imaging spectrometer for mars crism type 1 knobs are abundant concentrated topographically resistant features with their highest frequency in west candor which have consistent stratigraphic correlations of the peak altitude height these type 1 knobs could be erosional remnants of a simple dissected terrain possibly derived from a more continuous resistant capping layer of pre existing material diagenetically altered through recrystallization or cementation types 2 and 3 knobs are not linked to a single stratigraphic layer and are generally solitary to isolated with variable heights type 3 are the largest knobs at nearly an order of magnitude larger than type 1 knobs the variable sizes and occasional pits on the tops of type 2 and 3 knobs suggest a different origin possibly related to more developed erosion preferential cementation or textural differences from sediment water injection or intrusion or from a buried impact crater enhanced color hirise images show a brown coloration of the knob peak crests that is attributable to processing and photometric effects crism data do not show any detectable spectral differences between the knobs and the host rock layers other than albedo these intriguing knobs hold important clues to deducing relative rock properties timing of events and weathering conditions of mars history

origin and hydrology of a large intact early cambrian paleocave system and its role in overlying fluidisation structures arctic canada abstract paleokarst is most commonly expressed as subtle stratigraphic surfaces rather than large void systems penetrating deeply into the paleo subsurface in contrast a regional precambrian cambrian unconformity on victoria island nwt canada is associated with exceptional exposure of large intact cambrian paleocaverns 100 m diameter tens of m high the paleocaves are distributed along a paleo horizontal plane and an associated gryke network is present in the 30 60 m of neoproterozoic dolostone between cave rooves and the base of overlying cambrian sandstone both are filled by cambrian sandstone the formation and preservation of such karst features require aggressive dissolution along a stable paleo water table shortly before transgression and deposition of shallow marine sand over the dolostone during the transgression the karst network acted as a conduit for flowing groundwater that was discharged through overlying unconsolidated cambrian shallow marine sand producing water escape structures sand volcanoes and their conduits the conduits are preserved as cylindrical remnants of the sand volcanoes feeder pipes sediment fluidisation was probably caused by variations in the hydraulic head gradient in a meteoric lens near the cambrian coastline under a tropical climate with abundant probably seasonally variable rainfall that caused pulses in subsurface fluid flow spatial distribution of the paleocaves and sand volcanoes suggests their formation on the southeast side of a recently faulted horst of proterozoic carbonate bedrock that formed a nearshore island during early cambrian sea level rise fluidisation structures such as those reported here have generally been difficult to interpret owing to a lack of data on the fluid hydraulics of the underlying aquifer this is the first report linking the hydraulics of a well characterised paleokarst to development of fluid escape structures such structures are widely known from sandstones overlying the sub cambrian unconformity around the circumference of laurentia

calcium sulfate veins characterized by chemcam curiosity at gale crater mars the curiosity rover has analyzed abundant light toned fracture fill material within the yellowknife bay sedimentary deposits the chemcam instrument coupled with mastcam and chemcam remote micro imager images was able to demonstrate that these fracture fills consist of calcium sulfate veins many of which appear to be hydrated at a level expected for gypsum and bassanite anhydrite is locally present and is found in a location characterized by a nodular texture an intricate assemblage of veins crosses the sediments which were likely formed by precipitation from fluids circulating through fractures the presence of veins throughout the entire similar to 5 m thick yellowknife bay sediments suggests that this process occurred well after sedimentation and cementation lithification of those sediments the sulfur rich fluids may have originated in previously precipitated sulfate rich layers either before the deposition of the sheepbed mudstones or from unrelated units such as the sulfates at the base of mount sharp the occurrence of these veins after the episodes of deposition of fluvial sediments at the surface suggests persistent aqueous activity in relatively nonacidic conditions

formation of fluidization pipes during liquefaction examples from the uratanna formation lower cambrian south australia usually well preserved fluidization pillars and sand filled fluidization pipes occur within submarine channel sands of the basal uratanna formation lower cambrian in the adelaide geosyncline of south australia the morphology of these structures reflects complex lateral and vertical movement of fluids during liquefaction and dewatering fluidization pipes acted as conduits for highly concentrated upward directed fluid flow the formation and maintenance of these pipes was dependent upon the development of a pipe wall composed of clay plugged fine sand formed during initial fluidization this lining acted as a permeability barrier confining and concentrating fluidized flow within the pipe each of the pipes is surrounded by a cylindrical fluidization halo in which leakage through the pipe lining produced partial fluidization of the surrounding sediment fine scale structures within these haloes indicate that fluids flowed radially and upward out of the fluidization pipes at an acute angle these fluids merged with and influenced the orientation and size of adjacent fluidization pillars the fluidization pipes of the uratanna formation may represent unusual preservation of the unstable fluid flow conditions that occur during incipient fluidization of sand beds

on the origin mixing and alteration of crude oils in the tarim basin abstract the origin of oil in the tarim basin northwestern china has been debated for decades here we present new insights into this challenging issue based on data from the bachu maigaiti area combined with a synthesis of data from other oil fields in the basin results of the organic geochemical characterization of 39 oil samples from various fields using gc fid py gc gc ms and gc ms ms revealed that the oils in the tarim basin can be generally classified into three families the oils of the first family whose representatives in our study come from the luntaibei condensate field are terrigenous as indicated by highest pristane phytane 2 8 and methylcyclohexane n heptane 1 8 and lowest dibenzothiophene phenanthrene 28 regular steranes and gammacerane a relatively high abundance of c 31 c 35 homohopanes as well as the presence of 1 2 3 4 tetramethylbenzene and aryl isoprenoids from c 13 to c 22 providing evidence for a contribution from green sulfur bacteria thriving under euxinic conditions the occurrence of these two marine oil families implies hitherto unknown organic facies for the respective source rocks family 2 oils may have been generated from cambrian shales deposited under suboxic conditions while family 3 oils could have been generated from cambrian to ordovician sources deposited in euxinic environments in addition biodegradation and mixing is quite common for the oils from the tarim basin mixing is evident not only by the coexistence of an unresolved complex mixture and c 7 c 36 n alkanes in certain oils but also by seemingly conflicting oil maturity parameters the results presented in this communication confirm the complexity of tarim basin petroleum systems in terms of ages and organofacies of the source rocks mixing of migrating and or accumulating petroleum and concomitant biodegradation

diagenetic constraints on the use of cerium anomalies as palaeoseawater redox proxies an isotopic and ree study of cambrian phosphorites seawater rare earth element ree distributions show heavy ree enrichment and cerium depletion but these characteristics are only rarely found in ancient marine authigenic minerals such as carbonate fluorapatite and calcite this enigma may be due to changing ree distributions in seawater through time or to post depositional redistribution of ree differentiating between these two factors is however far from straightforward as their relative importance is likely to vary and evidence is often ambiguous in this article we present ree as well as strontium and sulphur isotope data for basal cambrian phosphorites of south china which confirm the emerging rule of thumb that granular phosphorites seldom reveal extreme departures from the seawater norm and tend to undergo therefore less diagenetic alteration of ree spectra than skeletal apatites and other phosphate types this study reveals stratigraphic trends in ce anomalies ce ce that could be taken to imply the preservation of a palaeoenvironmental signal however further investigation of our data shows that such trends in phosphorites can also be caused by post depositional alteration which tends to 1 increase ree contents 2 reverse ce depletion 3 alter eu anomalies and 4 concentrate preferentially the middle ree mree further alteration which may be due to weathering has led to hree depletion and positive la and y anomalies tetrad effect this is the first study where ceanom and phosphate bound sulphate s isotope values could be compared for one particular stratigraphic section which provides us with an additional tool for the interpretation of diagenetic redox conditions least altered phosphorites from meishucun that yield a strongly negative ceanom constrain early cambrian seawater 34s to about 33 we conclude that phosphorite ceanom primarily records variations in the local conditions of diagenesis while outlining some special cases in which diagenetic redox conditions may broadly reflect local bottom water redox conditions

multiple phases of hydrocarbon generation and migration in the tazhong petroleum system of the tarim basin people s republic of china abstract organic petrology organic geochemical analysis and fluid inclusion methods were employed to investigate a series of core samples from the tazhong uplift bitumens and organic inclusions were found to occur widely in paleozoic rocks especially carbonates and both can be subdivided into three groups the reflectance ranges of the three bitumen groups are 1 30 1 60 i 0 50 0 80 ii and 0 15 0 40 iii respectively and the corresponding organic inclusion groups are dark yellow fluorescence organic inclusions with a homogenization temperature of 200 240 c blue green fluorescence organic inclusions with a temperature of 160 200 c and the strong yellow fluorescent organic inclusions with a temperature of 80 130 c the wide occurrence of the three group bitumens and organic inclusions in the tazhong uplift reveals that there were three periods of large scale oil migration and accumulation in this area the analysis of hydrocarbon generating history based on paleotemperature and burial history of source rocks shows that they underwent three oil generating peaks in early ordovician triassic and cenozoic respectively which led to three phases of hydrocarbon generation and migration it is believed that the tazhong uplift is an old uplift rich in oil and gas and has been fed with oil and gas from nearby source areas during a long geological history and also that it has great hydrocarbon potential

distinguishing cambrian from upper ordovician source rocks evidence from sulfur isotopes and biomarkers in the tarim basin abstract the reported source rocks for the abundant petroleum in the tarim basin china range from cambrian to lower ordovician and or upper ordovician in age however the difference between the two groups of source rocks is not well characterized in this study pyrite was removed from eleven mature to over mature kerogen samples from source rocks using the method of crcl 2 reduction and grinding the kerogen and coexisting pyrite samples were then analyzed for 34 s values results show that the kerogen samples from the cambrian have 34 s values between 10 4 and 19 4 the values are significantly higher than those from the lower ordovician kerogen 34 s of between 6 7 and 8 7 which in turn are generally higher than from the upper ordovician kerogen samples 34 s of between 15 3 and 6 8 the associated pyrite shows a similar trend but with much lower 34 s values this stratigraphically controlled sulfur isotope variation parallels the evolving contemporary marine sulfate and dated oil 34 s values from other basins suggesting that seawater sulfate and source rock age have an important influence on kerogen and pyrite 34 s values the relatively high 34 s values in the cambrian to lower ordovician source rocks are associated with abundant aryl isoprenoids gammacerane and c 35 homohopanes in the extractable organic matter indicating that these source rocks were deposited in a bottom water euxinic environment with water stratification compared with the upper ordovician the cambrian to lower ordovician source rocks show abundance in c 28 20r sterane c 23 tricyclic terpanes 4 23 24 trimethyl triaromatic dinosteroids and depletion in c 24 tetracyclic terpane c 29 hopane thus 34 s values and biomarkers of source rock organic matter can be used for distinguishing the cambrian and upper ordovician source rocks in the tarim basin

a euxinic southern north atlantic ocean during the cenomanian turonian oceanic anoxic event abstract during mid cretaceous times large amounts of organic carbon corg became sequestered in black shales possibly due to oceanic anoxic events characterized by the development of an extended oxygen minimum zone omz here we provide the first direct evidence for an open ocean omz in the cenomanian turonian c t southern north atlantic and in fact show that the base of the photic zone was euxinic as revealed by molecular fossils from photosynthetic green sulfur bacteria in c t black shales this together with evidence for bottom water anoxia and accumulation of redox sensitive trace metals and hydrogen rich organic matter indicates a continuously euxinic water column concurrent with the high corg accumulation rates which are 15 150 times greater in the southern than in the northern north atlantic and the low biological productivity this suggests that preservation controlled the accumulation of corg in c t black shales

ancient impact and aqueous processes at endeavour crater mars the rover opportunity has investigated the rim of endeavour crater a large ancient impact crater on mars basaltic breccias produced by the impact form the rim deposits with stratigraphy similar to that observed at similar sized craters on earth highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits gypsum rich veins cut sedimentary rocks adjacent to the crater rim the gypsum was precipitated from low temperature aqueous fluids flowing upward from the ancient materials of the rim leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate rich sandstones of the meridiani region

molecular and isotopic compositions of bitumens in silurian tar sands from the tarim basin nw china characterizing biodegradation and hydrocarbon charging in an old composite basin abstract biodegradation and oil mixing in silurian sandstone reservoirs of the tarim basin one of the largest composite basins in china were investigated by analyzing the molecular characteristics and stable carbon isotopic signatures of low molecular weight lmw saturated hydrocarbons and high molecular weight hmw asphaltenes detection of 25 norhopanes and 17 nortricyclic terpanes in most silurian tar sands from the tabei uplift in the tarim basin suggests a much greater degree of biodegradation here than in the tazhong uplift this explains the relatively more abundant tricyclic terpanes gammacerane pregnane and diasteranes in tar sands from the tabei uplift than in those from the tazhong uplift hence care must be taken when assigning oil source correlations using biomarkers in tar sands because of the biodegradation and mixing of oils derived from multiple sources in such an old composite basin asphaltenes in the tar sands seem to be part of the oil charge before biodegradation depending on the relative anti biodegradation characteristics of asphaltenes the similarity in carbon isotopic signatures for asphaltenes and their pyrolysates and the consistent product distribution for flash pyrolysis and for regular steranes in asphaltene pyrolysates regardless of whether the tar sands were charged with fresh oil according to the relative distributions of regular steranes and the relatively abundant 1 2 3 4 tetramethylbenzene significantly enriched in 13 c the oil sources for asphaltenes in the tar sands might be related to lower paleozoic marine source rocks formed in euxinic conditions nevertheless the relatively low abundance of gammacerane and c 28 regular steranes observed in asphaltene pyrolysates and residual hydrocarbons within limited samples investigated in this work made a direct correlation of oils originally charged into silurian tar sands with those cambrian source rocks reported so far seem not to be possible comparison of carbon isotopic signatures of n alkanes in asphaltene pyrolysates with those of lmw saturated hydrocarbons is helpful in determining if the abundant n alkanes in tar sands are derived from fresh oil charges after biodegradation the limited carbon isotopic data for n alkanes in lmw saturated hydrocarbons from the tar sands can be used to classify oils charged after biodegradation in the composite basin into four distinct groups

paleozoic oil source rock correlations in the tarim basin nw china we studied a suite of 40 oils and extracts of purported source rocks from the tarim basin in nw china the main group of oils comes from tazhong and tabei wells which sample the largest known petroleum accumulations in the basin these oils can be statistically correlated with extracts of ordovician rocks based upon high relative concentrations of 24 isopropylcholestanes and low relative concentrations of dinosteranes triaromatic dinosteroids and 24 norcholestanes in contrast extracts from cambrian rocks have low relative concentrations of 24 isopropylcholestanes with high relative concentrations of dinosteranes triaromatic dinosteroids and 24 norcholestanes although some tarim basin cambrian rocks yield high total organic carbon contents we see little evidence in the analyzed oil samples to suggest that they came from cambrian source rocks

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

a habitable fluvio lacustrine environment at yellowknife bay gale crater mars the curiosity rover discovered fine grained sedimentary rocks which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy this aqueous environment was characterized by neutral ph low salinity and variable redox states of both iron and sulfur species carbon hydrogen oxygen sulfur nitrogen and phosphorus were measured directly as key biogenic elements by inference phosphorus is assumed to have been available the environment probably had a minimum duration of hundreds to tens of thousands of years these results highlight the biological viability of fluvial lacustrine environments in the post noachian history of mars

source of 1 2 3 4 tetramethylbenzene in asphaltenes from the tarim basin 1 alkyl 2 3 6 trimethylbenzenes and a high relative amount of 1 2 3 4 tetramethylbenzene ttmb have been previously detected in the marine oils and asphaltenes in the oils from the tarim basin in the present study the stable carbon isotopic compositions of ttmb and n alkanes in the pyrolysates of asphaltenes in the marine oils from the northern tarim basin and silurian tar sands from the tarim basin were determined ttmb has stable carbon isotopic compositions in the range from 23 to 24 and are about 12 more enriched in 13c than concomitant n alkanes 35 to 37 in the pyrolysates the results indicate a contribution from green sulfur bacteria chlorobiaceae to ttmb thus the depositional environments of the source rocks for the marine oils and the bitumen in tar sands from the tarim basin are characterized by periods of euxinic conditions within the photic zone

seismogenically induced fluidization of jurassic erg sands south central utah large bodies of fluidized sandstone occur in the jurassic entrada carmel page and navajo formations at several locations in south central utah they are most abundant in the entrada sandstone where they commonly occur in clusters have a cylindrical form and have a sharp contact with their cross bedded host rock these clastic pipes are as wide as 75 m and have exposed heights of as much as 100 m some of the entrada pipes extend well into the underlying carmel redbeds other clastic pipes in the entrada sandstone are less deformed and display various degrees of brittle to hydroplastic deformation and liquefaction clastic pipes in the page and navajo sandstones are less common but are similar in size and form to those in the entrada and carmel and probably have a similar origin some massive sandstone bodies are irregular in form and have tongue like projections into the host rock implying forcible injection of fluidized sand several pipe host contacts in the entrada sandstone display small scale ring faults where relative displacement can be clearly demonstrated pipe sandstones are invariably down faulted locally as much as 5 m at two sites carmel host rock is upwarped around the entrada pipes stratified and cross bedded breccia blocks occur in many entrada pipes and preliminary petrographic analysis indicates that at least some of these breccia blocks are derived from the host rock homogeneous pipe sandstones are also petrographically similar to their entrada host rock suggesting that some pipes originate through fluidization of the fine grained entrada fluidization of the entrada must have occurred in a water saturated environment during early diagenesis but before complete lithification most probably under considerable porewater pressure although there are no known modern analogues to these huge masses of structureless sandstone they may have a small scale modern counterpart in earthquake induced sandblows these features were most probably caused by large magnitude seismic events during the middle jurassic although other possibilities cannot be ruled out at this point

recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach study of organic matter in immature sediments from a messinian evaporitic basin shows that consideration of structures modes of occurrence and carbon isotopic compositions of free and sulfur bound carbon skeletons allow identification of biochemical precursors detailed information concerning biotic communities present during deposition of sediments can be retrieved in this way moreover unprecedented biochemicals were recognized these extend the horizon of biomarker geochemistry

geochemistry of alkylbenzenes in the paleozoic oils from the tarim basin nw china a b s t r a c t monoaromatic hydrocarbons alkylbenzenes in paleozoic oils condensates from the tarim basin were quantitatively analyzed using gas chromatography mass spectrometry their relative abundances and distributions show large variation which are most likely controlled by the temperature and duration of the catagenesis stage of petroleum maturation relatively high abundance of long chain linear substituted alkylbenzenes and alkyltoluenes in the studied samples implies that source rocks of these oils condensates contain high contents of algal material the dominance of dodecylbenzene in these n alkylbenzenes suggests the formation of alkylbenzenes from fatty acids via lactone formation dehydration the 1 2 3 4 tetramethylbenzene temb 1 methyl 3 phytanylbenzene 1 m 3 pyb and aryl isoprenoids are mainly derived from carotenoids produced by chlorobiaceae and their occurrence may indicate a highly reducing depositional environment however the concentration of these compounds diminishes significantly at high maturity with increasing thermal maturity the prominent trend of demethylation of alkylbenzenes is accompanied by shortening of alkyl side chains large variation in the c4 alkylbenzene isomer distribution is also controlled by thermal maturity the 1 2 3 5 temb and 1 2 4 5 temb isomers are more stable than other temb isomers and the overall thermodynamic stability of tembs is lower than that of dimethylethylbenzenes therefore several maturity parameters can be derived based on alkylbenzene stability absolute concentrations of alkylbenzenes generally increase with increasing thermal maturity but concentrations of 1 m 3 pyb and aryl isoprenoids decrease significantly at high maturity maturity parameters obtained from alkylbenzenes are especially useful for highly mature oils and condensates when most biomarkers are depleted caution is advised when interpreting the paleoenvironment and thermal maturity of an oil from the alkylbenzene signatures because they are affected by various other processes such as evaporative fractionation thermal cracking and biodegradation as well

grain coatings diagenesis of jurassic sandstones in south central utah and implications for targeting fossil microbes on mars abstract clusters of large scale decameters to 100 m dia fluidization pipes have been identified at several locations in jurassic navajo and entrada sandstones in south central utah these typically cut the cross bedded aeolian sabhka host rock at right angles similar pipe like structures have been tentatively identified on mars and the question of the diagenesis of host rock has important implications for the genesis of pipe structures current thinking regarding the genesis of host rock structures is that the grains were derived from wet aeolian sabkha environments eds of all samples indicates a si al ratio of 2 1 suggesting smectite clay minerals are to be expected in a dry mid latitude climatic zone and unlike the pipe structures which contain hyphopodium like structures fungal filaments similar in morphology to modern tropical leaf parasites the host rock is relatively bereft of microbes entombed in grain coatings moreover microtextural data from host rock grains in these wet aeolian wet sabkha environments suggest a lack of volatility judging from infrequent observation of percussion crack evidence of grain collision presumably during the time of formation a microfeature commonly found within the pipe structures the diagenesis process can be reconstructed from the composition of the coatings on recovered grains of quartz feldspar mica and occasional calcite as imaged with the sem and studied by eds xrd of the coatings provides confirmation of the clay mineralogy and inaa is used to cross check the chemistry obtained by eds if similar microfeatures exist on grains from both earth and mars materials transported by similar aeolian processes one would not expect to find fossil evidence of life on grains in host rocks while martian pipe structures may be the optimum target for the astrobiological exploration of the red planet host rock might be relatively devoid of fossil microbes if diagenesis of sandstones on mars is anything like earth

ancient aqueous environments at endeavour crater mars opportunity has investigated in detail rocks on the rim of the noachian age endeavour crater where orbital spectral reflectance signatures indicate the presence of fe 3 rich smectites the signatures are associated with fine grained layered rocks containing spherules of diagenetic or impact origin the layered rocks are overlain by breccias and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the endeavour impact compositional data for fractures in the layered rocks suggest formation of al rich smectites by aqueous leaching evidence is thus preserved for water rock interactions before and after the impact with aqueous environments of slightly acidic to circum neutral ph that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate rich rocks at meridiani planum

volumetric estimates of ancient water on mount sharp based on boxwork deposits gale crater mars while the presence of water on the surface of early mars is now well known the volume distribution duration and timing of the liquid water have proven difficult to determine this study makes use of a distinctive boxwork rich sedimentary layer on mount sharp to map fluid based cementation from orbital imagery and estimate the minimum volume of water present when this sedimentary interval was formed the boxwork structures on mount sharp are decameter scale light toned polygonal ridges that are unique compared to previous observations of martian fractured terrain because they are parallel sided ridges with dark central linear depressions this texture and the sedimentary setting strongly imply that the ridges are early diagenetic features formed in the subsurface phreatic groundwater zone high resolution orbital imagery was used to map the volume of light toned cemented ridges based on the cemented volume a minimum of 5 25 105 m 3 of cement was deposited within the fractures using a brine composition based on observations of other martian cements and modeling the degree of evaporation each volume of cement requires 800 6700 pore volumes of water so the mapped boxwork ridge cements require a minimum of 0 43 km 3 of water this is a significant amount of groundwater that must have been present at the 3620 m level 1050 m above the current floor of gale crater providing both a new constraint on the possible origins of mount sharp and a possible future science target for the curiosity rover where large volumes of water were present and early mineralization could have preserved a once habitable environment

molecular organic geochemistry of the tarim basin northwest china we conducted organic geochemical analyses on the largest suite of oils and source rock extracts from the tarim basin northwest china currently available statistical cluster analysis of the entire suite of tarim oils distinguishes at least seven genetic groups of oils the largest group of oils was collected from the tazhong and tabei uplifts and originated from marine middle upper ordovician anoxic marls that mark slope facies at the margins of structural uplifts two other genetic groups most likely originated from marine middle upper ordovician source rocks but of distinct facies with one an oxic shale rich source west of the bachu uplift and the other an anoxic shale source at tazhong

clastic pipes and mud volcanism across mars terrestrial analog evidence of past martian groundwater and subsurface fluid mobilization abstract clastic pipes are cylindrical injection features that vertically crosscut bedding with sharp contacts terrestrial pipes have cylindrical morphologies massive or radially graded interiors and raised outer rims increased grain size and subsequent cementation along the more porous edges makes the rims more resistant to weathering pipes have crosscutting relationships with other pipes due to multiple formation events or migrating eruption centers and are associated with other soft sediment deformation features terrestrial clastic pipes form via liquefaction and fluidization which require a near surface groundwater system to initiate i e sand sized sediments must be saturated for pipes to form clastic pipes cm to 1000 m diameters occur on mars across multiple time periods and terrains and are recognized in both rover and orbital imagery a conical or cylindrical geometry and massive interior core characterize these features the pipes on mars show various geomorphic expressions and are classified into five types by the presence or absence of a raised outer rim or a central pit these types are interpreted to represent the erosional evolution of pipes at different stages from their initial surface eruptive structures to their weathered remnants eroded conical hills martian pipes formed via fluidization as evidenced by 1 raised outer rims possibly indicating textural differences along the pipe edges from traction interactions of fluid suspended sediment 2 crosscutting relationships with other pipes suggesting reactivated fluidization pathways or migrating eruptive vents and 3 close spatial association between pipes and other features thought to form by soft sediment deformation e g contorted bedding integration of terrestrial analog data with the mars observations provides evidence for past martian groundwater and subsurface fluid mobilization

physical properties of petroleum formed during maturation of lower cambrian shale in the upper yangtze platform south china as inferred from phasekinetics modelling abstract lower cambrian shale in the upper yangtze platform uyp south china is an important source rock of many conventional petroleum fields and was recently recognized as a promising unconventional shale reservoir in this paper hydrocarbon generation kinetics and petroleum physical properties were investigated using the phasekinetics approach di primio and horsfield 2006 and a cambrian shale sample from the georgina basin north territory australia nta as similar paleogeological and sedimentary environments in cambrian are found for the uyp and nta the source rock comprises type ii kerogen and belongs to an organofacies generating paraffinic naphthenic aromatic low wax oil bulk petroleum generation can be described by a single frequency factor a 8 43e 14 1 s and a dominant activation energy at 56 kcal mol which is characteristic for sulphur poor organic matter deposited in an anoxic marine environment onset transformation ratio tr 10 and end tr 90 of bulk hydrocarbon generation was calculated to take place at 120 c and 165 c respectively for an assumed average geological heating rate of 1 5 c ma based on the thermal history of a local model well onset temperature was not reached until the middle triassic 241 ma when sediments were buried more than 2000 m and basalt eruptions caused enhanced heat flows the main generation stage of primary petroleum took place during the middle late triassic and ended in the early jurassic 187 ma for burial depths exceeding 4000 m tr 90 165 c temperatures increased to more than 200 c in the middle late jurassic leading to secondary cracking of primary products hydrocarbons formed at the onset tr 10 of petroleum generation can be characterized by a gas oil ratio gor of 63 sm3 sm3 a saturation pressure psat of 101 bar and a formation volume factor bo of 1 2 m3 sm3 those parameters stay low during primary petroleum generation before 203 ma at temperatures 10 000 sm3 sm3 psat 250 bar and bo 2 0 m3 sm3 during secondary cracking starting roughly at 200 ma 152 c and 3500 m burial assuming zero expulsion the shale reservoir position within the sedimentary basin indicates that bubble point pressure was always below reservoir pressure and fluids in the shale reservoir occurred only as a single undersaturated phase throughout maturation history black oil and volatile oil phases dominated during the primary cracking period whereas wet gas and dry gas phases dominated during the secondary cracking period

chemical variations in yellowknife bay formation sedimentary rocks analyzed by chemcam on board the curiosity rover on mars the yellowknife bay formation represents a similar to 5m thick stratigraphic section of lithified fluvial and lacustrine sediments analyzed by the curiosity rover in gale crater mars previous works have mainly focused on the mudstones that were drilled by the rover at two locations the present study focuses on the sedimentary rocks stratigraphically above the mudstones by studying their chemical variations in parallel with rock textures results show that differences in composition correlate with textures and both manifest subtle but significant variations through the stratigraphic column though the chemistry of the sediments does not vary much in the lower part of the stratigraphy the variations in alkali elements indicate variations in the source material and or physical sorting as shown by the identification of alkali feldspars the sandstones contain similar relative proportions of hydrogen to the mudstones below suggesting the presence of hydrous minerals that may have contributed to their cementation slight variations in magnesium correlate with changes in textures suggesting that diagenesis through cementation and dissolution modified the initial rock composition and texture simultaneously the upper part of the stratigraphy similar to 1m thick displays rocks with different compositions suggesting a strong change in the depositional system the presence of float rocks with similar compositions found along the rover traverse suggests that some of these outcrops extend further away in the nearby hummocky plains

compositional variation of glauconites in upper cretaceous paleogene sedimentary iron ore deposits in south eastern western siberia abstract glauconite occurs either as unaltered greenish or as altered brownish variety in upper cretaceous palaeocene sediments in the southeastern corner of western siberia studied section within the bakchar iron ore deposit includes ipatovo slavgorod gan kino and lyulinvor formations which are represented by sandstones siltstones claystones and oolitic ironstones of coastal marine facies the origin of unaltered glauconite is explained by the verdissement theory transgressions during lower coniacian santonian and campanian favored the formation of unaltered glauconites in dysoxic to anoxic conditions subaerial exposure of glauconite resulted in leaching of potassium oxidation of iron and formation of iron hydroxides in upper coniacian maastrichtian and palaeocene glauconite ultimately converts to leptochlorite and hydrogoethite by this alteration abundant microscopic gold inclusions besides sulphides sulphates oxides and silicates characterize this glauconite mineral inclusions include precious rare metals and non ferrous metals the concentration of gold in glauconite may be as high as 42 9 ppb abundant inclusions of various compositions in glauconites indicate enrichment of marine sediments in precious and non precious metals while major element composition of glauconites is affected by subaerial exposure the broadly similar micro inclusions in both altered and unaltered varieties are possibly related to the comparatively immobile nature of ree and trace elements

changes in palaeoenvironmental conditions during deposition of the permian kupferschiefer lower rhine basin northwest germany inferred from molecular and isotopic compositions of biomarker components abstract biomarker distributions based on gc and gc ms data supplemented by stable carbon isotopic compositions based on irm isotope ratio monitoring gc ms data have been used to investigate changes in depositional conditions in a number of samples from a 2 m core rheinberger heide covering the entire deposition of the permian kupferschiefer lower rhine basin northwest germany compound classes investigated are aliphatic and aromatic hydrocarbons and maleimides 1h pyrrole 2 5 diones the core has been previously divided into four sections ti tiia tiib and tiii based on lithology the biomarker distributions and the 13c values of components indicate contributions from cyanobacteria algae green sulphur bacteria and higher plants minor throughout kupferschiefer deposition all of the phytoplanktonic components show 13c enrichment in the lowest section suggesting a greater productivity the occurrence of components derived from green sulphur bacteria chlorobiaceae indicates that the entire deposition was characterised by periods of photic zone anoxia such conditions were rapidly established after the initial transgression of the zechstein sea and may have been productivity driven but were less prevalent during deposition of the upper core sections

chlorobiaceae in palaeozoic seas revealed by biological markers isotopes and geology biomarker hydrocarbons in oils and sediments have considerable potential for assessing the nature of biological processes in the past but only a few can be uniquely related to particular organisms reef hosted oils in the silurian of the michigan basin canada and the devonian of western canada have high abundances of 1 alkyl 2 3 6 trimethylbenzenes their precise structures suggest that they are diagenetic products of aromatic carotenoids of the green sulphur bacteria individual components are enriched in 13c by 7 8 relative to the saturated hydrocarbons of the same oil an isotopic anomaly of this magnitude and direction correlates with a component of photosynthetic carbon assimilation by the reductive tricarboxylic acid cycle these results together with data on palaeoenvironments provide compelling evidence for the existence in ancient restricted seas of microbial communities containing chlorobiaceae organisms with distinctive biochemistry which leave morphologically identifiable remains

molecular indicators of palaeoenvironmental conditions in an immature permian shale kupferschiefer lower rhine basin north west germany from free and s bound lipids a study of the distributions of free and s bound biomarkers and their 13c values in the extract of a bulk sample of the permian kupferschiefer from the lower rhine basin has been carried out to provide a more detailed characterization of the biological inputs the distributions and isotopic compositions of selected components released from nickel boride desulphurization have been compared with those of components in the free fraction the free biomarkers occur in greater abundance than their s bound counterparts the distribution and carbon isotopic composition of both free and bound components in the extract indicate a major cyanobacterial and algal input likewise the free and bound aromatic hydrocarbons contain components which reveal an origin from the carotenoids of chlorobiaceae green sulphur bacteria providing molecular evidence for the occurrence of photic zone anoxia in the water column most of the components in the complex mixture of mono di tri and tetra aromatics in the free aromatic hydrocarbon fraction result from cyclization and aromatization reactions

episodic euxinia in the changhsingian late permian of south china evidence from framboidal pyrite and geochemical data abstract a multiproxy study of a new upper permian lower triassic section xiaojiaba in sichuan province china documents large changes in marine productivity redox conditions and detrital input prior to the latest permian mass extinction marine productivity as proxied by total organic carbon content toc biogenic sio 2 and excess barium displays a long term decline through most of the changhsingian stage late late permian culminating in very low values around the permian triassic boundary concurrently redox proxies including pyrite framboid 34 s py mo auth and u auth and c org p document a shift from suboxic to dysoxic oxic conditions that was interrupted by several episodes of benthic euxinia and detrital siliciclastic proxies al hf nb and rees suggest an increased flux of weathered material from land areas the long term changes in productivity redox conditions and terrigenous detrital fluxes were probably caused by a regional sea level fall across the south china craton on the other hand the brief euxinic episodes occurring during the late permian had oceanographic causes probably related to the transient upward expansion of the chemocline at the top of the oceanic oxygen minimum zone these euxinic episodes may have been harbingers of the more widespread anoxia that developed concurrently with the latest permian mass extinction and that may have played a major role in triggering the largest biotic crisis of the phanerozoic

aryl isoprenoids and diaromatic carotenoids in paleozoic source rocks and oils from the western canada and williston basins abstract aryl isoprenoids in the range c13 c31 have been identified in source rock bitumens and oils from several paleozoic age petroleum systems in the western canada and williston basins the principal compounds possess the 2 alkyl 1 3 4 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria two c40 perhydrodiaromatic carotenoids which are structurally related to the presumed precursors of the aryl isoprenoids have also been identified in oils and source rock bitumens of the duvernay late devonian petroleum system pyrolysis gas chromatograms of kerogens isolated from several paleozoic source rocks show an unusual abundance of 1 2 3 4 tetramethylbenzene it is proposed that this compound arises from cleavage of diaromatic carotenoid moieties which have been incorporated into the kerogen structure with increasing maturation concentrations of the aryl isoprenoids in duvernay source rock bitumens increase to a point whereas the c40 perhydrodiaromatic carotenoids decrease steadily previous studies have suggested that aryl isoprenoids may be indicators of enhanced salinity environments this is not supported by the present work which shows high concentrations in source rocks associated with presumed normal marine salinities there is however a general association with intervals of condensed clastic or mixed clastic carbonate sedimentation within carbonate depositional systems from the association found and from parallels to modern habitats of photosynthetic bacteria it can be inferred that these biomarkers indicate prolific bacterial growth in a stratified water column at and below the oxic anoxic boundary layer in sub tropical to tropical marine environments

characteristics of selected petroleum source rocks xianjiang uygur autonomous region northwest china 1 the sedimentary basins of xinjiang uygur autonomous region china are moderately to poorly explored for petroleum volumetric adequacy of petroleum source rocks is a critical exploration risk in these basins particularly because source rock data are limited this study provides new source rock data and speculatively assesses the source rock potential of xinjiang basins the junggar zhungaer basin the best explored of the xinjiang basins and containing a giant oil field is underlain in many areas by an upper permian lacustrine oil shale sequence remarkable for its organic richness and oil source quality depending on its position in the basin the permian section ranges from immature to overmature and is inferred to be the principal source of oil in the basin upper triassic middle jurassic coal measures including lacustrine rocks constitute a secondary source rock sequence in the basin the smaller intermontane turpan tulufan basin contains a very similar upper triassic middle jurassic sequence which where sufficiently buried probably comprises the only significant oil source sequence in the basin the vast tarim talimu basin offers the greatest variety of potential source rocks of all xinjiang basins but remains the least well documented from limited but geologically planned and focused sampling cambrian carboniferous and permian strata are not considered major oil contributors in the dominantly shallow marine paleozoic section of the northern tarim basin only ordovician black shales appear to have significant potential the upper triassic middle jurassic sequence of the northern tarim basin is similar to that of the junggar and turpan basins a section rich in coal and lacustrine shale that constitutes another potentially significant oil source due to the size stratigraphic packaging and structural relief of the northern tarim basin paleozoic and mesozoic potential il source beds range from immature to overmature

fluidized sediment pipes in gale crater mars and possible earth analogs since landing in gale crater the mars science laboratory rover curiosity has traversed fluvial lacustrine and eolian sedimentary rocks that were deposited within the crater 3 6 to 3 2 b y ago here we describe structures interpreted to be pipes formed by vertical movement of fluidized sediment like many pipes on earth those in gale crater are more resistant to erosion than the host rock they form near other pipes dikes or deformed sediment and some contain internal concentric or eccentric layering these structures provide new evidence of the importance of subsurface aqueous processes in shaping the near surface geology of mars

reconstruction of δ13c of chemocline co2 aq in past oceans and lakes using the δ13c of fossil isorenieratene abstract high abundances of the diaromatic carotenoid isorenieratene derived from photosynthetic green sulfur bacteria chlorobiaceae were found just below the chemocline in an anoxic fjord in norway throughout the annual cycle the stable carbon isotope composition of this carotenoid co varied with the 13c of co2 aq and is independent of the co2 and isorenieratene concentration this constant isotopic fractionation p of isorenieratene versus co2 4 1 was subsequently used in the reconstruction of 13c of co2 at the chemocline in ancient oceans and lakes these reconstructions indicate that 13c of co2 at the chemocline is often influenced by isotopically light co2 formed by remineralization of organic matter this process can depending on the depth and stability of the chemocline also effect the isotopic composition of the phytoplankton and thus isotopic records of sedimentary inorganic and organic carbon

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time

source facies of the paleozoic petroleum systems in the tabei uplift tarim basin nw china implications from aryl isoprenoids in crude oils abstract aryl isoprenoids have been detected for the first time in crude oils from paleozoic petroleum systems in the tabei uplift tarim basin northwestern china the principal compounds possess the 1 alkyl 2 3 6 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria with a predominance of c13 c23 homologues in these samples flash pyrolysates of the asphaltene fractions isolated from crude oils show an unusual abundance of 1 2 3 4 tetramethylbenzene an indicator for a significant contribution of diaromatic carotenoids to the source kerogen of these oils the wide distribution of these compounds in crude oils reveals that penetration of the photic zone by sulfidic waters during deposition enabled prolific growth of photosynthetic green sulphur bacteria chlorobiaceae this suggests that the source rocks for the paleozoic petroleum systems in the tabei uplift were likely deposited under euxinic conditions with sulfate and sulfide rich water bodies which doesn t support previously published conclusions of a middle upper ordovician source that marks the slope facies at the margins of structural uplifts

centimeter to decimeter hollow concretions and voids in gale crater sediments mars voids and hollow spheroids between 1 and 23 cm in diameter occur at several locations along the traverse of the curiosity rover in gale crater mars these hollow spherical features are significantly different from anything observed in previous landed missions the voids appear in dark toned rough textured outcrops most notably at point lake sols 302 305 and twin cairns island sol 343 point lake displays both voids and cemented spheroids in close proximity other locations show one or the other form the spheroids have 1 4 mm thick walls and appear relatively dark toned in all cases some with a reddish hue only one hollow spheroid winnipesaukee sol 653 was analyzed for composition appearing mafic fe rich in contrast to the relatively felsic host rock the interior surface of the spheroid appears to have a similar composition to the exterior with the possible exceptions of being more hydrated and slightly depleted in fe and k origins of the spheroids as martian tektites or volcanic bombs appear unlikely due to their hollow and relatively fragile nature and the absence of in place clearly igneous rocks a more likely explanation to both the voids and the hollow spheroids is reaction of reduced iron with oxidizing groundwater followed by some re precipitation as cemented rind concretions at a chemical reaction front although some terrestrial concretion analogs are produced from a precursor siderite or pyrite diagenetic minerals could also be direct precipitates for other terrestrial concretions the gale sediments differ from terrestrial sandstones in their high initial iron content perhaps facilitating a higher occurrence of such diagenetic reactions

sources of alkylbenzenes in lower cretaceous lacustrine source rocks west african rift basins abstract we conducted molecular biomarker and compound specific carbon isotope analyses of off line pyrolyzates from lacustrine samples recovered by onez 1 well the kissenda formation in the gabon basin and well a the maculungo formation in the kwanza basin in west africa pyrolyzates from onez 1 well contain isotopically depleted 1 2 3 4 tetramethylbenzene 1 2 3 4 tetramb 26 1 to 29 4 and 1 2 4 trimethylbenzene 1 2 4 trimb 26 4 to 29 7 which are isotopically similar to aryl isoprenoids 29 9 and 31 2 and carotane 28 5 to 31 3 identified in the bitumen fractions pyrolyzates from 3 samples in the lower sections of well a contain isotopically enriched 1 2 3 4 tetramb ca 16 and 1 2 4 trimb ca 14 consistent with an origin from diagenetic products of isorenieratene chlorobactene biosynthesized by green sulfur bacteria chlorobiaceae pyrolyzates from five samples in the upper sections of well a are characterized by the presence of intermediate carbon isotope values of 1 2 3 4 tetramb 20 7 to 22 8 and 1 2 4 trimb 19 3 to 21 2 and isotopically enriched isorenieratane ca 14 5 off line pyrolyzates from these lacustrine source rocks represent two distinct end members 13 c depleted diagenetic products of carotene derived from a lacustrine algal source and 13 c enriched diagenetic products of isorenieratene chlorobactene derived from green sulfur bacteria organic matter om from onez 1 well shows a significant proportion of algal biomass with a 13 c depleted composition the presence of 13 c enriched biomarkers derived from carotenoids of chlorobiaceae from samples in the lower part of well a indicates the development of photic zone euxinia and a significant biogeochemical role of sulfur in the upper section of well a the 1 2 3 4 tetramb and 1 2 4 trimb have 13 c values indicative of contributions from both chlorobiaceae and algae to the om

oligocene to holocene glauconite phosphorite grains from the head of the cape canyon on the western margin of south africa abstract glauconite and carbonate fluorapatite cfa are significant components of the condensed upper oligocene to holocene sediment succession recovered from the western margin of southern africa the detailed texture and geochemistry of these glauconite phosphorite grains are reported here within the stratigraphic framework established on the outer continental shelf in the head of the cape canyon area three texturally and stratigraphically distinct glauconite grain types are recognised oligo miocene infilled foraminiferal tests mio pliocene green and quaternary dark green to black grains most of these glauconitic grains include a minor to significant amount of cfa the upper oligocene to lower miocene sediment succession is dominated by fine sand sized benthic and planktic foraminifera glauconite grains constitute 20 50 of the sediment and represent tests infilled by variable proportions of glauconite and cfa cement with the test wall replaced by cfa only glauconite cfa formation during the late oligocene to early miocene was associated with warm water upwelling coupled with third order marine transgressions rare earth element ree chemistry indicates that sub oxic conditions prevailed during diagenesis mio pliocene green and quaternary dark green to black medium sand sized glauconite grains constitute between 20 and 95 of these predominantly siliciclastic sediments the green to black glauconite grains are texturally different but have similar major and ree chemistry since the mid miocene formation of glauconite cfa grains is associated with cold water upwelling and detrital fe rich terrigenous mud deposition in oxic to suboxic bottom waters analogous to the holocene coast parallel organic rich mudbelt on the shelf the texture of these grains indicates repeated cycles of glauconite and cfa authigenesis during marine transgressions and winnowing and reworking during marine regressions

high iron glaucony from the continental shelf of the yellow sea off the southwestern korean peninsula abstract massive fractured and porous types of glauconies are found in subtidal sand and semi consolidated sand mud deposits from the continental shelf of the southeastern yellow sea thermal treatments on powdered glaucony increase the x ray intensity near 10 a suggesting the presence of some expandable layers ferric iron and mg 0 35 0 54 atoms progressively substitute for al from porous to massive glauconies a higher proportion of expandable layers is also observed with apparent increases from porous to massive type the clay preserved is ordered disordered massive to fractured type and interstratified illite smectite porous type containing 7 27 expandable layers glauconies from the yellow sea apparently form after deposition in reducing environments at the interface between dissolving clay minerals and degrading biogenic debris