geochemical evidence of secondary microbial methane from very slight biodegradation of undersaturated oils in a deep hot reservoir a rare finding of early mature undersaturated oils with low gas oil ratios enables us to document secondary microbial methane generation during very slight biodegradation in a deep hot reservoir in the ultradeep water of the gulf of mexico in three studied gas samples methane is enriched in 13 c 13 c is from 63 to 64 relative to pure thermogenic methane estimated 13 c is from 71 to 67 and pure primary microbial methane 13 c is 68 carbon dioxide in gases has 13 c values that negatively correlate with 13 c values of pure thermogenic methane methane is unusually enriched in heavy isotope 2 h relative to associated ethane some extracted oils are depleted in long chain alkyl aromatics these lines of geochemical evidence suggest anaerobic microbial degradation of oil and subsequent reduction of resulting carbon dioxide to methane although specific geobiological details of secondary microbial methane generation are unclear this process may be partially responsible for charging some of the largest gas and gas hydrate fields in the world

a comparative study of interior layered deposits on mars interior layered deposits ilds of the eastern valles marineris and adjacent chaos regions were analysed using high resolution imagery topography and spectral data in order to detect possible correlations we find that ilds are susceptible to erosion and weathering as proven by their shapes mesa buttes surface structures pitted fluted yardangs stair stepped morphologies at different scales and metre sized boulders and talus ilds bear hydrated sulphates consequently we conclude that aqueous conditions dominated during their formation subhorizontal layering and parallel bedding of the ilds could then indicate that deposition took place under low energy aquatic conditions their superposition on chaotic terrain suggests that they are younger than chaotic terrain and hence younger than late hesperian for the hydrated ilds which show polyhydrated on top of monohydrated sulphates we think that formation within an evaporative body is not conceivable and we assume instead that a conversion of sulphates by post formational humidity changes took place as hydrated ilds correlate well with rock fragmentation we suppose that volume changes due to water content are responsible for rock fragmentation despite the different ild settings the basic conditions during sedimentation and erosion of ilds could not have varied greatly because comparable mineralogies and morphologies are found among ilds

three dimensional normal faulting models of the valles marineris mars and geodynamic implications inversion of martian topography using a three dimensional boundary element model permits revised estimates of fault dip angle depth of faulting paleogeothermal gradient and extensional strain in the valles marineris region the major normal faults dip at 40 55 to depths of 60 75 km with comparatively small footwall uplifts 500 m for throws to 10 km implying that paleogeothermal gradients during faulting were 10 k km 1 or less assuming relatively rapid strain rates appropriate to the extending martian crust accumulation of dip slip offsets along the main normal faults likely was associated with anticlinal flexure and deformation of preexisting strata within the troughs the magnitudes of the predicted vertical and horizontal displacements outside the troughs as well as extensional strains are spatially variable depending on both cross and along strike position relative to the troughs the predicted displacements and strains attain maximum values at the troughs and decay to background values at cross strike distances of 250 km corresponding to 3 4 times the depth of faulting with an average province wide strain of 4 15 by implication the aggregate strain field surrounding tharsis is a highly variable spatial and temporal composite of the inhomogeneous strain fields each associated and scaling in size with an individual graben from the smallest structures through the largest valles marineris troughs

application of backscattered electron imaging to the study of source rocks microtextures abstract scanning electron microscope sem used in backscattered electron bse mode is a powerful tool for the sedimentological study of source rocks owing to its spatial and chemical resolutions ease and speed of operating the obtained imaging is dependent on atomic number contrasts between the different constituents of the sample using the bse mode combined with energy dispersive x ray spectrometry minerals and organic matter can be distinguished more clearly than with the light microscope classically used by organic petrologists in order to describe microtextures of organic rich sediments particularly the disposition of the organic matter this technique has been tested on source rocks having various sedimentological and geochemical characteristics accordingly two patterns of organic matter disposition have been recognized laminated and particulate these dispositions can be put back into their sedimentary context by considering the depositional environment and diagenesis the organic matter disposition suggests the existence of organic networks which are suspected to be a major control for hydrocarbon expulsion

spectral and geological study of the sulfate rich region of west candor chasma mars sulfates have been discovered by the omega spectrometer in different locations of the planet mars they are strongly correlated to light toned layered deposits in the equatorial regions west candor chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates a detailed study coupling mineralogy derived from omega spectral data and geology derived from hrsc imager and other datasets leads to some straightforward issues the monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material it likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments or during hydrothermal alteration at depth because it is typically found on outcrops that are eroded and steep polyhydrated sulfates that match any ca na fe or mg sulfates with more than one water molecule are preferentially present on less eroded and darker outcrops than outcrops of kieserite these variations can be the result of a diversity in the composition and or of the rehydration of kieserite on surfaces with longer exposure the latter possibility of rehydration in the current or recent atmosphere suggests the low surface temperatures preserve sulfates from desiccation and also can rehydrate part of them strong signatures of iron oxides are present on sulfate rich scarps and at the base of layered deposits scarps they are correlated with tes gray hematite signature and might correspond to iron oxides present in the rock as sand size grains or possibly larger concretions that are eroded and transported down by gravity at the base of the scarp pyroxenes are present mainly on sand dunes in the low lying terrains pyroxene is strongly depleted or absent in the layered deposits when mixed with kieserite local observations favor a spatial mixing with dunes over layered deposits sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation either in an intermittent lacustrine environment or by hydrothermal fluid circulation both possibilities require the presence of sulfur rich groundwater to explain fluid circulation the elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2 5 km above datum only 1 km below the plateau surface

microbial alteration of subsurface natural gas accumulations bacterial alteration of subsurface reservoired hydrocarbon accumulations extends into the range of the c1 c4 gaseous hydrocarbons preferentially attacking the wet gas components in most instances during the initial stages of bacterial gas alteration propane seems to be selectively attacked resulting in anomalous propane carbon isotopic compositions as well as unusual carbon isotopic distributions among the wet gas components extensive bacterial alteration appears to be capable of removing all but traces of the wet gas components resulting in a dry gas that could be confused with overmature dry gas whose wet components have undergone extensive thermal cracking recognition of microbial alteration in subsurface reservoired hydrocarbon gas accumul tions is important for both correlation purposes and maturity estimates

geochemistry of petroleum systems in the niuzhuang south slope of bohai bay basin part 1 source rock characterization detailed mapping of the tertiary strata of the dongying depression bohai bay basin reveals that oil shales and dark mudstones in the es4 and es3 members of the eocene oligocene shahejie formation have excellent potential as petroleum source rocks regional distributions of total organic carbon content kerogen type and thermal maturation indicate that abundant mature source rocks are present in the niuzhuang sag whereas source rocks along the niuzhuang south slope are currently immature or marginally mature for the generation of conventional oils this study examined the molecular characteristics for a number of biomarker compound classes and related these to either source facies change or different burial and thermal maturation an important observation made during this study is the significant variation in the relative distributions and absolute concentrations of a wide range of aliphatic and aromatic hydrocarbon markers in the rock extracts as a function of burial depth this variation may potentially explain the uncertainty associated with the maturity assessment and genetic modeling for so called immature oils that are usually defined on the basis of alkane biomarker isomerization ratios and the presence of biomarkers with biological configurations

composition and stable isotope geochemistry of natural gases from kansas midcontinent u s a abstract more than 28 1012 ft 3 79 1010 m3 of natural gas and 5 3 109 bbl 8 4 108 m3 of oil have been produced in kansas u s a from paleozoic carbonate and sandstone reservoirs on structural uplifts and shallow embayments along the northern margin of the anadarko basin a heavily explored geologically well characterized state kansas is an excellent place to study hydrocarbon migration and to test geochemical models for the origin of natural gases immature to marginally mature rocks of eastern kansas cherokee and forest city basins produce mixed microbial and thermogenic gases gases in this region have wetness 0 03 51 methane 13c 65 to 43 and methane d 260 to 150 gases from central and western kansas nemaha uplift to hugoton embayment are entirely thermogenic and have wetness 4 51 methane 13c 48 to 39 and methane d 195 to 140 ethane and propane 13c values throughout kansas vary from 38 to 28 and from 35 to 24 respectively mature thermogenic gas generated from source rocks in southwestern kansas and the anadarko basin with 1 0 ro 1 4 is recognized throughout the state lateral migration into shallow reservoirs on the central kansas and northern nemaha uplifts and in the cherokee basin probably occurred along basal pennsylvanian conglomerates and weathered lower paleozoic carbonates at the regional sub pennsylvanian unconformity early thermogenic gas generated by local source rocks with ro 0 7 is recognized in isolated fields in the salina and forest city basins in ordovician reservoirs beneath the sub pennsylvanian unconformity in the cherokee basin and in reservoirs generally above the unconformity in the cherokee and sedgwick basins the eastern central kansas uplift and the hugoton embayment

new models for the origin of valles marineris closed depressions current models for the formation of the abundant large closed depressions of valles marineris have serious shortcomings purely tectonic mechanisms are inconsistent with the morphology of many depressions and removal of large quantities of ground ice from the canyon walls is inconsistent with the observed strength of the walls accordingly we offer some alternatives one possibility involves decay of ice rich bodies occupying partially sediment choked ancient graben that predated the overlying cratered and ridged plains other possibilities involve the removal of massive equatorial carbonate deposits storing much of the planet s co2 inventory generated during greenhouse conditions on early mars solution by carbonic acid derived from the atmosphere analogous to terrestrial karst requires extensive recycling of the available water supply solution by various groundwater acids possibly derived from the tharsis magmas requires less water especially if only the smaller closed depressions are due to carbonate decay alternatively volume loss due to decarbonation of carbonate during early high heat flow or a later tharsis related heat pulse can produce extensive collapse especially if the carbonates have high silica content

efflorescence as a source of hydrated sulfate minerals in valley settings on mars abstract a distinctive sulfur cycle dominates many geological processes on mars and hydrated sulfate minerals are found in numerous topographic settings with widespread occurrences on the martian surface however many of the key processes controlling the hydrological transport of sulfur including sulfur sources climate and the depositional history that led to precipitation of these minerals remain unclear in this paper we use a model for the formation of sulfate efflorescent salts mg ca na sulfates in the rio puerco watershed of new mexico a terrestrial analog site from the semiarid southwest u s to assess the origin and environmental conditions that may have controlled deposition of hydrated sulfates in valles marineris on mars our terrestrial geochemical results s 34 of 36 0 to 11 1 show that an ephemeral arid hydrological cycle that mobilizes sulfur present in the bedrock as sulfides sulfate minerals and dry wet atmospheric deposition can lead to widespread surface accumulations of hydrated sulfate efflorescences repeating cycles of salt dissolution and reprecipitation appear to be major processes that migrate sulfate efflorescences to sites of surface deposition and ultimately increase the aqueous so 4 2 flux along the watershed average 41 273 metric tons yr we suggest that similar shallow processes may explain the occurrence of hydrated sulfates detected on the scarps and valley floors of valles marineris on mars our estimates of salt mass and distribution are in accord with studies that suggest a rather short lived process of sulfate formation minimum rough estimate 100 to 1000 years and restriction by prevailing arid conditions on mars

formation of martian outflow channels by catastrophic dewatering of evaporite deposits geological mapping based on topographic analysis of mars orbiter laser altimeter mola data together with photointerpretation of mars orbiter camera moc images and thermodynamic and heat flow considerations frame a new hypothesis for the formation of martian outflow channels through catastrophic dewatering of evaporite deposits mola transects across valles marineris show that the valley is located at the crest of a 3 km high topographic bulge on the flank of the much larger tharsis rise interpretation of moc images showing layered deposits within valles marineris as unconformably underlying hesperian age lava flows means that these thick deposits thought to contain hydrous sulfates were heated by an increased geothermal gradient due to development of tharis increased temperatures adequate to dehydrate hydrous evaporites would trigger significant volumetric expansion and catastrophically release tremendous amounts of overpressured water

hematite bearing materials surrounding candor mensa in candor chasma mars implications for hematite origin and post emplacement modification abstract the valles marineris canyon system on mars is of enduring scientific interest in part due to the presence of interior mounds that contain extensive layering and water altered minerals such as crystalline gray hematite and hydrated sulfates the presence of hematite and hydrated sulfate minerals is important because their host rock lithologies provide information about past environments that may have supported liquid water and may have been habitable this work further defines the association and relationship between hematite bearing materials and low albedo presumably aeolian deposits and layered materials identifies physical characteristics that are strongly correlated with the presence of hematite and refines hypotheses for the origin and post emplacement modification including transport of these hematite bearing and associated materials there are only three regions surrounding candor mensa where hematite has been identified even though morphologic properties are similar throughout the entire mensa three possible explanations for why hematite is only exposed in these regions include 1 the topographic structure of the mensa walls concentrates hematite at the base of the layered deposits influencing the ability to detect hematite from orbit 2 the presence of differing amounts of dark mantling material and hematite free erosional sediment 3 the potential fracturing of the mensa and the influence of these structures on fluid flow and subsequent digenesis the observations of hematite bearing materials in this work support the hypothesis that hematite is eroding from a unit in the candor mensa interior layered deposits ild and is being concentrated as a lag deposit adjacent to the lower layers of candor mensa and at the base in the form of dark aeolian material due to the similar geologic context associated with hematite bearing and ild materials throughout the valles marineris canyon system the insight gained from studying these materials surrounding candor mensa can likely be applicable to similar layered deposits throughout valles marineris

the formation of valles marineris 1 tectonic architecture and the relative roles of extension and subsidence 1 the formation of the valles marineris troughs on mars is widely held to involve some combination of horizontal extension and vertical subsidence or collapse but the specific tectonic mechanism is poorly understood this study uses boundary element models of valles marineris formation to evaluate a range of fault dip angles for two end member models of trough formation simple extensional tectonism and extension together with vertical accommodation at the base of the lithosphere representing either viscous lower crustal flow or some other form of deep seated collapse the models are constrained by the lack of footwall uplift on the plateau surface outside the troughs and the lack of significant tectonic failure of the plateau in response to the stress changes induced by valles marineris formation the results demonstrate that trough formation by extensional tectonism alone generates large surface uplifts in the surrounding plateau and enormous stresses in the lithosphere in conflict with the observations the only mechanism that is compatible with both the observed topography and the limitations imposed by the finite strength of the lithosphere is trough formation through displacement along steeply dipping to subvertical border faults together with vertical accommodation at the base of the subsiding fault block fault dips are constrained to be greater than or equal to 85 leading to a ratio of vertical subsidence to horizontal extension exceeding 5 7 and a maximum extension of less than 4 6 km these results confirm earlier studies suggesting that trough formation involved a substantial component of vertical subsidence or collapse with only modest amounts of total extension

tectonic history of the tharsis region mars the faults of the tharsis region of mars have been mapped and delineated on the basis of age the orientation of each group of faults was analyzed to determine if they were radial to a point the results indicate that there are at least four discrete centers of faulting within the tharsis area which are of significantly different age the four centers proposed are from oldest to youngest 1 in the thaumasia highlands 2 in northern syria planum and finally 3 and 4 near pavonis mons while episodes 3 and 4 occupy the same geographic position they are separated in time by the development of the tharsis lava plains and shields each episode of tectonism was separated from the next by a period of major basaltic volcanism the tectonic features of the tharsis area are thus viewed as being the cumulative result of the superposition of several discrete episodes of faulting rather than the result of one episode about a single point

fill and spill of giant lakes in the eastern valles marineris region of mars the existence of hesperian age 3 7 3 4 ga surface water bodies on mars is a contentious issue often conflicting with favored climate models extensive lakes are proposed to have filled parts of valles marineris during this period yet evidence for their presence and temporal continuity is poorly constrained here we report geomorphic and chronologic evidence for the initiation and demise of a voluminous lake system within the basins of eastern valles marineris we find that independent kilometer deep lakes were present here well after the wetter global climate optimum that characterized the previous noachian epoch 4 1 3 7 ga relative and impact crater chronologies of flood channels emerging from lake basins indicate relatively late lake spillover in the early amazonian ca 3 0 ga drawdown of the lake and cessation of interbasin sedimentation may be recorded by a similar early amazonian ca 3 1 ga crater retention age on the surface of capri mensa a 4 km tall sulfate bearing interior layered deposit the topography data demonstrate that incision of the bedrock barriers between the basins during spillover was driven by a dramatic local base level difference between the lake surface and downstream basin floors we postulate that the lake spillover process created an integrated drainage routing system between a voluminous equatorial water supply and the northern plains basin

topography of valles marineris implications for erosional and structural history compilation of a simplified geologic geomorphic map onto digital terrain models of the valles marineris permitted an evaluation of elevations in the vicinity of the troughs and the calculation of depth of troughs below surrounding plateaus thickness of deposits inside the troughs volumes of void spaces above geologic geomorphic units and volumes of deposits the central troughs north ophir north and central candor and north melas chasmata lie as much as 11 km below the adjacent plateaus in ophir and candor chasmata interior layered deposits reach 8 km in elevation if the deposits are lacustrine and if all troughs were interconnected lake waters standing 8 km high would have spilled out of coprates chasma onto the surrounding plateaus having surface elevations of only 4 5 km in this case interior deposits above about 4 km in the central troughs would not be lacustrine they could be volcanic on the other hand the troughs may not have been interconnected at the time of interior deposit emplacement they may have formed isolated ancestral basins the existence of such basins is supported by independent structural and stratigraphic evidence the ancestral basins may have eventually merged perhaps through renewed faulting to form northern subsidiary troughs in ophir and candor chasmata and the coprates north melas ius graben system the peripheral troughs are only 2 5 km deep shallower than the central troughs they may have formed from a combination of erosional collapse and structural activity chaotic terrain is seen in the peripheral troughs near a common contour level of about 4 km on the adjacent plateaus which supports the idea of release of water under artesian pressure from confined aquifers the layered deposits in the peripheral troughs may have formed in isolated depressions that harbored lakes and predated the formation of the deep outflow channels if these layered deposits are of volcanic origin they may have been emplaced beneath ice in the manner of table mountains areal and volumetric computations show that erosion widened the troughs by about one third and that deposits occupy one sixth of the interior space even though the volume eroded is larger than the volume deposited topographic and geologic considerations imply that material eroded from trough walls was probably part of the interior layered deposits but not their sole source additional material may have come from subterranean piping from reworking of local disintegration products on the floors such as chaotic materials or from eolian influx but overall it is likely that the additional material is volcanic and that it forms mostly the upper more diversely bedded layers of the interior deposits

high resolution thermal inertia derived from the thermal emission imaging system themis thermal model and applications 1 thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the thermal emission imaging system themis on the mars odyssey spacecraft producing the highest resolution thermal inertia data set to date themis thermal inertia values have an overall accuracy of 20 a precision of 10 15 and are consistent with both thermal emission spectrometer orbital and miniature thermal emission spectrometer surface thermal inertia values this data set enables the improved quantification of fine scale surface details observed in high resolution visible images in the tharsis region surface textures and crater rims observed in visible images have no corresponding variation in the themis thermal inertia images indicating that the dust mantle is pervasive at themis scales and is a minimum of a few centimeters and up to 1 2 m thick the thermal inertia of bed form material indicates particle diameters expected for aeolian sediments and these materials are likely currently saltating variations in the thermal inertia within interior layered deposits in hebes chasma can be distinguished and the thermal inertia is too low to be consistent with bedrock or a lava flow thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation higher resolution themis thermal inertia enables the identification of exposed bedrock on the martian surface in nili patera and ares vallis bedrock material corresponds to distinct compositional and morphologic surfaces indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes

fault fracture mesh petroleum plays in the zhanhua depression bohai bay basin part 2 oil source correlation and secondary migration mechanisms abstract the chemical compositions of crude oils from over 20 oilfields in the zhanhua depression bohai bay basin were studied in order to understand their genetic relationships thermal maturity and biodegradation ranking molecular geochemical parameters indicate the presence of three possible oil families in reservoirs ranging from paleozoic basement to neogene a number of biomarker features support deposition of the source rocks for these oils under a wide range of depositional environments the majority of the oils discovered in the depression belong to the fl family and display characteristics consistent with a dominantly freshwater to slightly brackish water lacustrine source rock in the es 3 member of the shahejie formation the somewhat geographically restricted sl family oils are apparently linked to saline lacustrine carbonate evaporite source rocks distributed mostly in the upper es 4 member of the shahejie formation from the bonan gubei sag areas the thermally less mature bl family oils occur mostly within the es 1 es 2 or dongying formation reservoirs near the central sag areas and show close affinities to the interbedded or intercalating es 1 calcareous mudstones and oil shales deposited in a slightly saline to dominantly brackish water lacustrine setting the sl and fl family oils are generally mature whereas most of the bl family oils usually show low maturity oil source correlation demonstrates strong genetic relationships between the mature es 4 and es 3 source rocks of the eocene oligocene shahejie formation in the sag areas and the oils accumulated in the shallow neogene petroleum plays the geochemical data provide strong support for two sharply contrasting hydrocarbon migration scenarios 1 short distance lateral migration is dominant in the central sag areas and 2 the fault fracture mesh facilitated vertical migration and coupled with the regional porous guantao formation sand sheets makes the structural stratigraphic and lithological features over basement high blocks the focal points for petroleum accumulation therefore further exploration in this highly mature petroleum province should focus on heavy oils in the shallow neogene strata and light oils in the tight sandstones of the deep sag areas

sources and mechanisms of formation of gaseous hydrocarbons in sedimentary rocks abstract accepted concepts of principal stages of hydrocarbon formation fail to satisfactorily explain the accumulation of supergiant gasfields in west siberia u s s r such as for example urengoy which comprise 30 of the proven gas reserves of the world a new mathematical model has been developed which applies the concept of activation energy distribution to the formation of gases characteristic differences in the molecular structure of humic and sapropelic source organic matter are expressed in different activation energy distributions the model allows the calculation of isotope values for different types of organic matter and their dependence on maturity application of the model to west siberia suggests that the supergiant gas accumulations in urengoy are more likely formed from terrestrial organic matter through thermochemical reactions at moderate depths and are not the result of either deep overmature or bacteriogenic processes the new mathematical model suggests that humic organic matter in general has a high methane generating capacity at comparably low maturities of organic matter equivalent to 0 5 0 7 on the vitrinite reflectance scale

hydrated minerals in the deposits of aureum chaos abstract hydrated minerals have been detected in many martian chaos regions and chasmata playing a major role in its past aqueous activity based on short wave infrared data from crism imagery and elevation data we identified and mapped hydrated minerals in aureum chaos to shed light on their stratigraphy and geological context the interior layered deposits ilds display three stratigraphic units the lowest unit shows massive and also layered high albedo monohydrated sulfate mhs best matching kieserite 20 650 m thick with intercalated hydroxylated ferric sulfates hfss best matching jarosite and ferric oxides the overlying polyhydrated sulfate phs is commonly layered 20 40 m thick smooth to heavily fractured of lower albedo and partially contains ferric oxides spectrally neutral distinctly layered and bumpy cap rock 40 300 m thick forms the top we found spectral and morphological similarities to aram chaos phs mhs ferric oxides texture of ild and cap rock and juventae chasma hfs besides the phyllosilicate nontronite was found attributed to chaotic terrain as light toned fractured exposure and within dark smooth mantling the coexistence of sulfates and phyllosilicates indicates changes in the geochemistry of the aqueous environment since sulfates and phyllosilicates could be alteration products the observed mineralogy presumably is not the original conversions between phs and mhs mhs or phs into jarosite jarosite into iron oxides are considered due to its occurrence along mantling edges and on flat surfaces of mhs without textural differences it appears that phs is an alteration product of mhs e g due to surface exposure the facies and relative timing of sulfate formation remains undefined however two different formation models are considered the first implies contemporaneous ild and phs deposition and diagenetic sulfate conversion into mhs iron oxides due to overburden later on this model is less conclusive than groundwater evaporation the second model due to the lack of a sharp phs mhs boundary that would indicate a diagenetic formation alternatively the second model suggests subsequent sulfate formation groundwater would have penetrated into pre existing sulfate free ild the permeability and porosity of ild material would have defined the rate of water absorption and sulfate precipitation low in cap rock resulting in cementation of probably aeolian deposited ilds we think this model is more consistent and could explain ild stratigraphy with the potential anhydrous cap rock on top the surface age of chaotic terrain late hesperian and mantling deposits mid to late amazonian limit the ild age and possibly the emplacement of sulfates phyllosilicates in the mantling are presumably allochthonous limiting the timing of in situ phyllosilicates is more complicated they could be noachian excavated material following the phyllosian era or instead syn or post chaotic a close spatial and temporal association of sulfates and phyllosilicates in which nontronite represents the deep facies and sulfates the evaporitic facies is known from earth and is also possible and would combine groundwater alteration with the observed mineralogy the preservation of nontronite hfs and mhs probably reflects a relatively dry environment with intermittent aqueous activity since their emplacement

strength of faults on mars from mola topography the stresses which must be maintained on faults bounding the rift topography at tempe fossae the north tempe rift ntr and valles marineris vm on mars are estimated using a simple elastic model and topographic data from the mars orbiter laser altimeter mola the absence of rift flank uplift at the ntr is consistent with an elastic thickness te of 20 km or greater at the time of rift formation the maximum resolved shear stresses on bounding faults due to this topography do not therefore exceed 20 mpa similar to the inferred strength of terrestrial faults elastic thickness estimates at vm are mostly around 50 km or greater therefore for canyon widths of 400 km the bounding faults of vm if present must be able to withstand stresses of up to approximately 100 mpa however if the fault controlled sections of the canyons do not exceed 150 km in width as suggested by geomorphological analysis the fault strength required is only 20 mpa although the maximum resolved shear stresses required to support the topography at vm may need to be greater than the stresses which terrestrial faults can support at least some faults on mars are no stronger than similar features on earth this observation is consistent with the existence of liquid water in the shallow subsurface of mars at the time the faults were active on venus plate tectonics is probably prevented by the frictional resistance to motion across strong faults on mars it is more likely that the large thickness of the elastic layer of the lithosphere and the possible positive buoyancy of the crust are responsible for the observed lack of plate tectonics c 2002 elsevier science usa

related magma ice interactions possible origins of chasmata chaos and surface materials in xanthe margaritifer and meridiani terrae mars abstract we examine here the close spatial and temporal associations among several unique features of xanthe and margaritifer terrae specifically the valles marineris troughs or chasmata and their interior deposits chaotic terrain the circum chryse outflow channels and the subdued cratered material that covers xanthe margaritifer and meridiani terrae though previous hypotheses have attempted to explain the origin of individual features or subsets of these we suggest that they may all be related all of these features taken together present a consistent scenario that includes the processes of sub ice volcanism and other magma ice interactions results of intrusive events during late noachian to early amazonian times

recognition and quantification of the effects of primary migration in a jurassic clastic source rock from the norwegian continental shelf a detailed quantitative geochemical study was made of a mature jurassic clastic source rock sequence in order to attempt to recognize and quantify petroleum migration effects two different quantitative approaches were followed to monitor primary migration effects on both the bitumen 1 e g whole rock extract and the bitumen 2 e g isolated kerogen extract fractions these methods were a comparisons of toc normalized extract yields and quantified molecular compositions of petroleums from both tightly carbonate cemented zones and those from less cemented zones and b comparison of petroleums from shale laminae vs those from interbedded siltstone laminae on this basis it was possible to assess apparent primary migration efficiency relative expulsion efficiencies in certain shale samples and relative import efficiencies in siltstone bands ranged from 11 total extract to 85 saturated hydrocarbons and individual n alkanes no carbon number dependent fractionation effects were observed for n alkanes of bitumen 1 in the c15 to c35 range i e expulsion efficiencies were independent of carbon number suggesting bulk oil flow with chromatographic modification as the predominant transport mechanism

discontinuities in the shallow martian crust at lunae syria and sinai plana detailed photoclinometric profiles across 125 erosional features and 141 grabens in the western equatorial region of mars indicate the presence of three discontinuities within the shallow crust pits troughs and wall valleys tributary canyons within noctis labyrinthus and valles marineris and escarpments within the fretted terrain of sacra fossae and kasei valles show distinct erosional base levels at depths of 0 3 0 6 km 1 km and 2 3 km the shallowest discontinuity corresponds to thickness estimates for the ridged plains unit in this region and thus the discontinuity probably is the contact between a sequence of layered rock making up this unit and the underlying megaregolith the 1 km discontinuity is reflected in the base levels of erosion of all the features studied and it may correspond to the base of the proposed layer of ground ice model calculations using photoclinometric profiles of simple grabens corrected for the effects of mass wasting and the 60 dip of bounding faults measured from the exposed traces of faults on trough walls show that graben bounding faults consistently intersect at the mechanical discontinuity at about 1 km depth this discontinuity may represent an interface between ice laden and dry regolith ice laden and water laden regolith or pristine and cemented regolith a correlation between wall valley head depth and local thickness of the faulted layer suggests that the 1 km discontinuity also controlled the depth of the heads of sapping canyons there is no apparent relation between the pit and trough depths and the local thickness of the faulted layer which can be explained if pits and troughs developed by subsidence into underlying tension cracks that disrupted the 1 km discontinuity the data do suggest however that erosion of shallow pits and troughs was influenced by the 1 km discontinuity the third discontinuity at a depth of 2 3 km corresponds to the proposed base of the martian megaregolith and is probably the interface between overlying ejected breccia and in situ fractured basement rocks

paleoreconstruction by biological markers abstract during diagenesis and conversion of the original lipid fraction of biological systems to petroleum hydrocarbons the following four basic events needed for paleoreconstruction can be monitored by biological markets 1 sourcing 2 maturation 3 migration and 4 biodegradation actual cases of applying biological markers to petroleum exploration problems in different parts of the world are demonstrated cretaceous and phosphoria sourced oils in the wyoming thrust belt can clearly be distinguished from one another by high quality source fingerprinting of biomarker terpanes using gas chromatography mass spectrometry identification of recently discovered biological markers head to head isoprenoids allows subtle source differentiation between oils from sumatra the degree of crude oil maturation in basins from california alaska russia wyoming and louisiana can be assessed by specific novel biomarker ratios 20s 20r sterane epimers field evidence from such interpretation is confirmed by laboratory pyrolysis of the rock an example of immature sumatra rock is given extensive migration is documented by biomarkers in several oils the effect of biodegradation on biomarker steranes and terpanes is exemlified in a california basin all biological marker results are consistent with the geological setting and add a new dimension in assisting the petroleum explorationist toward paleo reconstruction

did the martian outflow channels mostly form during the amazonian period simud tiu and ares valles comprise some of the largest outflow channels on mars their excavation has been attributed variously to or a combination of erosion by catastrophic floods glaciers and debris flows numerous investigations indicate that they formed largely during the late hesperian 3 61 3 37 ga however these studies mostly equate the ages of the outflow channel floors to those of the flows that generated mesoscale several hundred meters to a few kilometers bedforms within them to improve the statistical accuracy in the age determinations of these flow events we have used recently acquired high resolution image and topographic data to map and date portions of simud tiu and ares valles which are extensively marked by these bedforms our results which remove the statistical effects of older and younger outflow channel floor surfaces on the generation of modeled ages reveal evidence for major outflow channel discharges occurring during the early 3 37 1 23 ga and middle 1 23 0 328 ga amazonian with activity significantly peaking during the middle amazonian stages we also find that during the documented stages of middle amazonian discharges the floor of tiu valles underwent widespread collapse resulting in chaotic terrain formation in addition we present evidence showing that following the outflow channel discharges collapse within northern simud valles generated another chaotic terrain this younger chaos region likely represents the latest stage of large scale outflow channel resurfacing within the study area our findings imply that in southern circum chryse the martian hydrosphere experienced large scale drainage during the amazonian which likely led to periodic inundation and sedimentation within the northern plains

structural development of coprates chasma and western ophir planum valles marineris rift mars a portion of valles marineris was mapped in detail in order to clarify the dominant processes responsible for the formation of coprates chasma new crater counts indicate that the caprock on western ophir planum plateau has a late hesperian crater age whereas trough floor preserved in western coprates chasma has an early to late hesperian crater age caprock on western ophir planum correlates in relative age with the syria planum formation and the caprock may overlie lower hesperian ridged plains material the conspicuous absence of wrinkle ridges on ophir planum may reflect burial by this later material trough floor material in coprates chasma correlates in relative age with ridged plains material on the adjacent lunae planum and coprates plateaus and represents a structurally coherent block displaced downward by normal faulting the crater counts and detailed structural relationships demonstrate the commonly accepted view that coprates chasma occupies a graben the floor of this graben is only thinly mantled by intratrough deposits and is relatively intact the trough shows no evidence for a chaotically broken and jumbled floor as required by genesis models of collapse and subsurface drainage formation of coprates chasma by keystone collapse of locally elevated topography is not supported by available topographic data but a general association between the trough and volcanotectonic activity in the tharsis region is considered to be a likely explanation for the trough forming stresses subtle asymmetries in topography and boundary fault development across coprates chasma may imply a gentle down to the north half graben geometry for the trough normal faults that define the northern margin of western coprates chasma and those that deform the adjacent ophir planum plateau change trend systematically with position implying a 30 rotation of the local horizontal principal stresses in this region during trough growth faulting on ophir planum appears related to the faulting that created the coprates chasma trough the geology and structure of coprates chasma are comparable to those of other troughs such as melas ius and perhaps candor chasmata suggesting that these troughs may also have formed as grabens the revised crater age for western ophir planum indicates that the initiation of trough faulting and subsidence in the valles marineris system is early late hesperian and may have been synchronous across the system relative to the prevailing cratering rate

recent advances in petroleum isotope geochemistry abstract organic matter is isotopically heterogeneous lipids tend to be depleted in the heavy carbon and hydrogen isotopes as compared to carbohydrates and lignite the c and h isotopic composition of kerogens is determined by many factors such as environmental conditions during formation and deposition and variability of sources of organic matter stable isotope concentrations in mature kerogens are not significantly altered during maturation and hence reflect the variability of the organic matter during deposition isotope variations in kerogens therefore reflect to some extent the paleogeographic situation and can be used for paleoreconstruction a basin facies with anoxia and a marginal facies with detrital input can be differentiated isotopically in the toarcian of central europe coals are isotopically heterogeneous due to different isotopic composition of macerals inertinite and vitrinite tends to be enriched in deuterium as compared to exinite also boghead coals tend to be depleted in dueterium which possibly reflects various lipid contents of respective precursor materials petroleums can be genetically classified through the patterns of covariance of their compound classes carbonate and shale sourced petroleums may be additionally differentiated through their deuterium content the general world wide applicability of such genetic differentiations needs still to be proved carbon and hydrogen isotope variations in methane are genetically controlled bacterial methane in freshwater environments is characteristically depleted in deuterium even complex origins of natural gases can be unraveled using compositional and isotopic variations new analytical developments led to the application of carbon isotope analyses of gaseous hydrocarbons desorbed from sediments for geochemical surface exploration a discussion reveals that processes such as isotope effects during degassing and bacterial oxidation as well as indigenous formation of hydrocarbons may completely obscure the results

hydrated mineral stratigraphy of ius chasma valles marineris new high resolution spectral and morphologic imaging of deposits on walls and floor of ius chasma extend previous geomorphic mapping and permit a new interpretation of aqueous processes that occurred during the development of valles marineris we identify hydrated mineralogy based on visible near infrared vnir absorptions we map the extents of these units with crism spectral data as well as morphologies in ctx and hirise imagery three cross sections across ius chasma illustrate the interpreted mineral stratigraphy multiple episodes formed and transported hydrated minerals within ius chasma polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma they may have been precipitates in a closed basin or diagenetically altered after deposition fluvial or aeolian processes then deposited layered fe mg smectite and hydrated silicate on the chasma floor postdating the sulfates the smectite apparently was weathered out of noachian age wallrock and transported to the depositional sites the overlying hydrated silicate is interpreted to be an acid leached phyllosilicate transformed from the underlying smectite unit or a smectite jarosite mixture the finely layered smectite and massive hydrated silicate units have an erosional unconformity between them that marks a change in surface water chemistry landslides transported large blocks of wallrock some altered to contain fe mg smectite to the chasma floor after the last episode of normal faulting and subsequent landslides opal was transported short distances into the chasma from a few m thick light toned layer near the top of the wallrock by sapping channels in louros valles alternatively the material was transported into the chasma and then altered to opal the superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential distinct aqueous environments characterized by alkaline then circum neutral and finally very acidic surface or groundwater chemistry

interior trough deposits on mars subice volcanoes widespread several kilometer thick successions of layered deposits occur as mounds that partly fill the troughs or chasmata that compose the valles marineris on mars like terrestrial subice volcanoes the layered deposits occur in a volcano tectonic setting within basins that may have held ponded water or ice on the basis of their dimensions morphologies and associated catastrophic floods and other geologic events as shown in viking and new mars global surveyor mgs data sets we suggest that the interior deposits are volcanic in origin and possibly generated by subice eruptions a tuya origin for the mounds can explain the lack of external sediment mound heights that can rival the plateau local flat topped mesas morphologically distinct mounds of different ages horizontal to steep dips fine grained materials indications of rare volcanic vents and lava flows and spectral composition the extremely diverse layering of west candor chasma and possible volcanic cones in melas may have formed by related subaerial eruptions consistent with the suggestion that interior deposits are eroding out of the wall rock some deposits could have been erupted from sites along the walls

are there carbonate deposits in the valles marineris mars the thick sequences of layered deposits found in the valles marineris have recently been determined by s s nedell s w squyres and d w andersen 1987 icarus 70 409 441 to contain a minimum of 105 km3 of material we suggest that this material could be derived from the precipitation of 30 mbar of atmospheric co2 as carbonates in lakes as surface temperatures fell on mars the presence of an insulating ice cover would have allowed liquid water to exist fed by transitory surface melting atmospheric co2 would have accumulated in such lakes enhancing carbonate precipitation support for this hypothesis comes from processes that occur in the perennially frozen lakes in the dry valleys of antarctica where the mean temperature is 253 k and the lake water is supersaturated with atmospheric gases a search of the recently reissued mariner 6 7 infrared spectrometer data in the wavelength region between 2 and 6 m failed to confirm the presence of carbonates due to the fact that no spectral footprints appear to directly overlie the layered deposits and that deposits may be blanketed by an eolian mantle this negative result is inconclusive we feel that the canyon deposits are still a prime site for future searches for carbonates on mars

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

origin of the neogene shallow gas accumulations in the jiyang superdepression bohai bay basin natural gas resources occur extensively along the east coast of china with a number of large and medium sized gas fields being discovered in recent years gas reservoirs include neogene paleogene and the underlying mesozoic and paleozoic basement of the total proven natural gas reserves in the jiyang superdepression bohai bay basin almost 89 7 is present in the shallow neogene gas pools in traps formed on top of the paleotopographic highs and along the margin of the secondary depressions these gases are closely associated with heavy oils occurring as gas caps or associated gases within the heavy oil pools or in separate gas pools above or updip from the heavy oil pools the gases contain over 95 methane and small quantities of c 2 alkanes nitrogen and carbon dioxide the stable carbon isotopes of methane in these gases are up to 10 more positive than those of the thermogenic gases in the deep paleogene reservoirs with propane more enriched in 13 c than butane this study demonstrated that the majority of the petroleum source rocks in the jiyang superdepression tend to be oil prone and are currently within or shallower than the conventional oil window 0 45 1 0 ro the chemical and carbon isotopic compositions of the gases together with the moderate to severe biodegradation of the associated heavy oils in the shallow neogene strata clearly suggest that the formation of the shallow natural gases in the jiyang superdepression result from the anaerobic degradation of accumulated oils in reservoir

reconciling channel formation processes with the nature of elevated outflow systems at ophir and aurorae plana mars 1 many hesperian outflow channels head at elevations compatible with aquifer recharge beneath the martian south polar cap and such channels are widely interpreted as the products of this recharge some outflow channels head at greater elevations that are inconsistent with southern recharge including three systems located in aurorae planum and eastern ophir planum these three systems have previously been interpreted as having formed through aqueous outbursts from local aquifers recharged by the meltwaters of ancient upland glaciers to the west however the viability of this interpretation is weakened by the lack of a geomorphic record supportive of past meltwater flow from western uplands inconsistencies between hypothesized processes and the nature of regional topography and mineralogy and the absence of satisfactory analog processes for catastrophic aqueous flow from the subsurface in contrast a volcanic origin for the ophir and aurorae systems appears to be in accord with the basic characteristics of constituent channels and associated landforms the volcanotectonic nature of the valles marineris system and adjacent upland plains and the nature of available analog landforms and processes though numerous uncertainties remain a volcanic interpretation of these outflow systems can more simply account for the existence of component channels the attributes of other elevated outflow systems on mars similarly appear to be most consistent with volcanic origins if the ophir and aurorae systems formed volcanically thermal considerations imply minimum erupted lava volumes of 6 4 103 km3 for allegheny vallis and 6 2 104 km3 for elaver vallis

formation mechanisms of secondary hydrocarbon pools in the triassic reservoirs in the northern tarim basin abstract the northern tarim basin tabei is a rich composite hydrocarbon accumulation region with multi layers of oil and gas reservoirs in the ordovician carboniferous and triassic strata in the triassic the tabei region was dominated by non marine sedimentation that developed deltaic sandstone reservoirs with favourable petrophysical properties for hydrocarbon accumulations hydrocarbons in the triassic hydrocarbon pools are dominated by oil and condensate gas analysis of the hydrocarbons in combination with well testing and drilling data reveals that oils in the triassic hydrocarbon pools are commonly biodegraded and originated mainly from the middle upper ordovician source rocks the predominant dry gases in the reservoirs are cracked from oils derived from the cambrian source rocks the origin of hydrocarbons in the triassic pools is similar to those in the underlying reservoirs fluid inclusions and k ar dating confirm that the hydrocarbons were accumulated during the himalayan orogenic movement because the middle upper ordovician source rocks already experienced peak hydrocarbon generation in the late hercynian orogeny late permian the triassic hydrocarbon pools are from secondary adjustment of earlier oil and gas pools from the underlying ordovician and carboniferous reservoirs due to the rapid subsidence of the kuqa foreland basin to the north of the tabei region since the beginning of the himalayan orogenic movement the triassic reservoir strata was changed from south dipping to north dipping resulting in the formation of plunging anticlines and hydrocarbon migration toward the south at the same time fault reactivation occurred in the area causing the hydrocarbons from the deeper reservoirs to migrate into the triassic structural traps through faults and unconformities and thus formed the widespread secondary hydrocarbon pools the structure inversion during the triassic and the formation of nose structures since the himalayan orogeny 250 290 ma permian controlled the secondary accumulation in the triassic reservoirs the reformation process of the hydrocarbon pools continued until the late himalayan orogeny when the gas was charged and developed condensate pools in the eastern area

a non extensive statistics of the fault population at the valles marineris extensional province mars a non extensive statistical physics approach is formulated and tested for the fault length distribution in the valles marineris extensional province mars the approach is composed of the following parts 1 the tsallis entropy 5 defined as s q k b 1 sigma w i 1 p i q q 1 2 maximization of the tsallis entropy under appropriate constraints 3 derivation of the cumulative distribution function cdf of the fault length population in testing the model a non extensive q parameter equal to 1 10 for independent non interacting faults and q 1 75 for linked faults are estimated the latter supports the conclusion that the fault system in the valles marineris extensional province mars is a sub extensive one and verifies with statistical physics terms the geological criteria introduced by schultz 2000 to classify the faults in independent and linked respectively c 2011 elsevier b v all rights reserved

origins of partially reversed alkane δ13c values for biogenic gases in china with increasing molecular weight 13c values of hydrocarbon gases change in two different manners the normal order would be 13c1 13c2 13c3 13c4 partially reversed order is common in gas samples from sedimentary basins in china which can be attributed to one or several of the following four mixing processes a mixing of biogenic and abiogenic gases b mixing of sapropelic and humic sourced gases c mixing of gases from the same types of source rocks with different maturity and d mixing of gases from the same source rock interval of varying maturity

underlying structural control of small scale faults and fractures in west candor chasma mars 1 orientations of small scale faults and fractures within the interior layered deposits of west candor chasma were measured to investigate what information about the geologic history of valles marineris they can contribute deformational features were separated into six categories based on morphology and their orientations were analyzed the elevations at which the deformational features formed are recorded as a proxy for stratigraphic level deformational features occur over a continuous range of elevations and display regionally consistent preferred orientations indicating their formation was controlled by a regional stress regime the two most abundant preferred orientations of 35 and 110 are approximately parallel to the chasma walls and the inferred underlying normal faults the alignment of three populations of small faults at 140 consistent with the morphology of release faults indicates a large scale fault underlying the southeastern border of ceti mensa the preferred orientations imply these small scale deformational features formed from a continuation of the same imposed stresses responsible for the formation of valles marineris indicating these stresses existed past the formation of the interior layered deposits the origins of a fourth preferred orientation of 70 is less clear but suggests the study area has undergone at least two periods of deformation

the formation of valles marineris 2 stress focusing along the buried dichotomy boundary 1 although valles marineris is widely regarded as an extensional tectonic feature the source of stress responsible for its formation remains unknown this study argues that the tensile stresses that triggered valles marineris tectonism are a result of its location south of and subparallel to the buried crustal dichotomy boundary beneath tharsis the emplacement of the tharsis volcanic load straddling the pre existing topographic step of the crustal dichotomy boundary would have resulted in an abrupt change in the thickness of the load causing differential subsidence and extension across the boundary thin shell flexural models predict a narrow belt of focused tensile stresses south of the buried dichotomy boundary coinciding with the location of present day valles marineris the interaction of these boundary generated stresses with the competing stress fields associated with tharsis loading can explain the formation of noctis labyrinthus in the west and the deflection of the valles marineris troughs away from the buried boundary toward the east finite element models demonstrate that the magnitudes and vertical variations of stress at valles marineris are sensitive to the timing of loading and flexure in tharsis the incremental loading and flexure expected for a large volcanic rise results in the maximum tensile stress at valles marineris occurring at depth with tensile stresses through the majority of the lithospheric column dikes forming within this tensile stress belt would propagate through the full vertical extent of the lithosphere due to the stress release associated with the dilation of the dikes playing a crucial role in the formation of the valles marineris troughs

composition and structures of the subsurface in the vicinity of valles marineris as revealed by central uplifts of impact craters abstract despite recent efforts from space exploration to sound the martian subsurface with radar the structure of the martian subsurface is still unknown major geologic contacts or discontinuities inside the martian crust have not been revealed another way to analyze the subsurface is to study rocks that have been exhumed from depth by impact processes the last martian mission mro mars reconnaissance orbiter put forth a great deal of effort in targeting the central peaks of impact craters with both of its high resolution instruments crism compact reconnaissance imaging spectrometer for mars and hirise high resolution science experiment we analyzed the composition with crism and the physical characteristics on hirise of the rocks exhumed from depth from 31 impact craters in the vicinity of valles marineris our analyses revealed the presence at depth of two kinds of material massive light toned rocks and intact layers exhumed light toned massive rocks are enriched in low calcium pyroxenes and olivine hydrated phases such as smectites and putative serpentine are present and may provide evidence of hydrothermal processes some of the rocks may represent portions of the volatile rich pre noachian martian primitive crust in the second class of central peaks exhumed layers are deformed folded and fractured visible near infrared vnir spectra suggest that they are composed of a mixture of olivine and high calcium pyroxene associated with hydrated phases these layers may represent a noachian volcanic accumulation of up to 18 km due to tharsis activity the spatial distribution as well as the in depth distribution between the two groups of rocks exhumed are not random and reveal a major geologic discontinuity below the tharsis lava plateau the contact may be vertical over several kilometers depth suggesting the pre existence of a steep basin early giant impact or subsidence basin or sagduction processes

geochemistry of petroleum systems in the niuzhuang south slope of bohai bay basin part 2 evidence for significant contribution of mature source rocks to immature oils in the bamianhe field the chemical compositions of 28 representative crude oils and oil sand samples collected from the bamianhe region of the bohai bay basin eastern china were studied in detail in order to understand their genetic relationships biodegradation ranking and thermal maturity level molecular geochemical parameters indicate the presence of one single oil family in the cenozoic reservoirs a number of biomarker features support deposition of the source rocks for these oils under conditions of enhanced salinity stratified water columns the extremely low maturity levels of these immature oils as indicated by sterane isomerization ratios were not supported by other maturity parameters the genetic relationship between the oils and the es4 and es3 members of the eocene oligocene shahejie formation present in the deeper part of the niuzhuang sag but not those along the niuzhuang south slope was suggested using a wide range of molecular parameters variation in the sterane concentrations observed from potential source rocks with different maturity levels in the study area suggests a high probability of migration contamination of mature oils by immature bitumens along migration pathways or from intra reservoir shales variation in the level of oil biodegradation could also create anomalies in the use of gross oil compositions as an indicator of oil maturity although the recent rapid subsidence of the bohai bay basin and the saline depositional environment of one of the potential source rocks favor oil generation at relatively low maturity levels most of the economic oils discovered in the bamianhe region appear to have derived from conventionally mature source rocks but contain lower maturity fluids admixed with them

rheological constraints on martian landslides we use a dynamic finite difference model to simulate martian landslides in the valles marineris canyon system and olympus mons aureole using three different modal rheologies frictional bingham and power law the frictional and bingham modes are applied individually fluidized rheology is treated as a combination of frictional and power law modes general fluidization can include pore pressure contributions whereas acoustic fluidization does not we find that general fluidization most often produces slides that best match landslide geometry in the valles marineris this implies that some amount of supporting liquid or gas was present in the material during failure the profile of the olympus mons aureole is not well matched by any landslide model suggesting an alternative genesis in contrast acoustic fluidization produces the best match for a lunar slide a result anticipated for dry crust with no overlying atmosphere the presence of pressurized fluid during valles marineris landsliding may be due to liquid water beneath a thin cryosphere 1 2 km or flash sublimation of co2

light toned layered deposits in juventae chasma mars abstract we examine hypotheses for the formation of light toned layered deposits in juventae chasma using a combination of data from mars global surveyor s mars orbiter camera moc mars orbiter laser altimeter mola and thermal emission spectrometer tes as well as mars odyssey s thermal emission imaging system themis we divide juventae chasma into geomorphic units of i chasm wall rock ii heavily cratered hummocky terrain iii a mobile and largely crater free sand sheet on the chasm floor iv light toned layered outcrop llo material and v chaotic terrain using surface temperatures derived from themis infrared data and slopes from mola we derive maps of thermal inertia which are consistent with the geomorphic units that we identify llo thermal inertias range from 400 to 850 j m 2 k 1 s 1 2 light toned layered outcrops are distributed over a remarkably wide elevation range 5 8 km from the chasm floor to the adjacent plateau surface geomorphic features the absence of small craters and high thermal inertia show that the llos are composed of sedimentary rock that is eroding relatively rapidly in the present epoch we also present evidence for exhumation of llo material from the west wall of the chasm within chaotic and hummocky terrains and within a small depression in the adjacent plateau the data imply that at least some of the llo material was deposited long before the adjacent hesperian plateau basalts and that juventae chasma underwent and may still be undergoing enlargement along its west wall due to wall rock collapse chaotic terrain evolution and exposure and removal of llo material the new data allow us to reassess possible origins of the llos gypsum one of the minerals reported elsewhere as found in juventae chasma llo material forms only at low temperatures 60 c and thus excludes a volcanic origin instead the data are consistent with either multiple occurrences of lacustrine or airfall deposition over an extended period of time prior to emplacement of hesperian lava flows on the plateau above the chasm

mars exploration rover candidate landing sites as viewed by themis the analysis of six landing sites that were candidates for the two nasa mars exploration rovers mer benefited from recently available image data from the thermal emission imaging spectrometer themis onboard the 2001 mars odyssey spacecraft the combination of daytime and nighttime thermal infrared images from themis supplemented by additional data sets has lead to new or expanded insights into the nature of each landing site in meridiani planum a layer of lighter toned higher thermal inertia material is observable just below the hematite bearing layer gusev crater displays a more complex stratigraphy than previously observed including an upper layer with lobate margins the highest inertia unit of southern isidis planitia is confined to topographic lows in the rim basin margin and does not appear to be due to highland material transported onto the basin floor the enigmatic ovoid blocky terrain on the floor of melas chasma displays higher thermal inertia than its surroundings an indication that it contains coarser or more indurated material than the adjacent aeolian bedforms the myriad channels of athabasca valles display distinctive thermal signatures despite the presence of a bright layer of dust covering the region the presence of alluvial fans produced from spur and gulley erosion of the walls of eos chasma demonstrates that mass movements have occurred following the canyon scouring floods

ages of valles marineris mars landslides and implications for canyon history the chronology of landslides of valles marineris the equatorial trough system of mars has been investigated by a crater population study valles marineris landslides have widespread debris aprons which offer a remarkable opportunity to study the crater population with high resolution images from mars orbiter camera moc and from mars odyssey thermal emission imaging system themis sixty six ages were determined within valles marineris including 56 landslide ages and 10 ages of the previous termcanyonnext term floor results reveal that landslides of valles marineris system of previous termcanyonsnext term occurred during a widespread period of time between 3 5 gy and 50 my in some locations the previous termcanyonnext term floor has an apparent age of 3 5 gy suggesting that at least locally within valles marineris no major refreshing processes have occurred for 3 5 gy the temporal repetitivity of landslides implies that the triggering mechanisms of the landslides are reproducible in time landslides have the same features whatever their age the dynamic of these landslides is probably the same either with intervention of water up to recently the last 100 my or without water since 3 5 gy

thick shell tectonics on one plate planets applications to mars a theory for stress distributions in thick lithospheric shells on one plate planets is developed based on the zero frequency equations of a self gravitating elastic spherical shell overlying a strengthless fluid stress distributions in lithospheres are reviewed for both the compensated and flexural modes in the former case surface stresses only depend on surface topography while for the latter case it is shown for long wavelengths that stress trajectories are mainly dependent on the lithospheric lateral density distribution and not on elastic properties computational analyses are carried out for mars and it is found that isostatically compensated models correctly predict the graben structure in the immediate tharsis region and a flexural loading model is satisfactory in explaining the graben in the regions surrounding tharsis a three stage model is hypothesized for the evolution of tharsis isostasy with north south graben formation on tharsis followed by flexural loading and radial graben formation on the perimeter of tharsis followed by a last stage of loading with little or no regional deformation this model is consistent with the martian lithosphere monotonically thickening over geologic time

testing evidence of recent hydration state change in sulfates on mars the east candor interior layered deposit ild has signatures of mono and polyhydrated sulfate in alternating layers that give insight into the processes which formed these layered deposits and on the environmental conditions acting on them since then we use orbital data to explore multiple hypotheses for how these deposits formed 1 sulfate bearing ilds experience hydration changes on seasonal to a few years timescales under current mars environmental conditions 2 the deposits experience hydration under recent mars conditions but require the wetter climate of high obliquity and 3 the kieserite could be an original or diagenetic part of a complex evaporite mineral assemblage modeled climatology shows recent mars environmental conditions might pass between multiple sulfate fields however comparison of observatoire pour la mineralogie l eau les glaces et l activite omega and compact reconnaissance imaging spectrometer crism observations of the same ild do not show changes in hydration over 2 mars years low temperatures might slow the kinetics of that transition it is likely that more clement conditions during periods of high obliquity are needed to overcome mineral metastability and hydrate kieserite bearing deposits we find the alternate model that the deposit is a cyclic evaporite sequence of mono and polyhydrated sulfates also plausible but with an unexplained dearth of fe sulfates

study of phyllosilicates and carbonates from the capri chasma region of valles marineris on mars based on mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars mro crism observations abstract spectral reflectance data from the mro crism mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars of capri chasma a large canyon within valles marineris on mars have been studied results of this analysis reveal the presence of minerals such as phyllosilicates illite smectite montmorillonite and carbonates ankerite and manganocalcite these minerals hint of the aqueous history of noachian time on mars phyllosilicates are products of chemical weathering of igneous rocks whereas carbonates could have formed from local aqueous alteration of olivine and other igneous minerals four different locations within the capri chasma region were studied for spectral reflectance based mineral detection the study area also shows the spectral signatures of iron bearing minerals e g olivine with carbonate indicating partial weathering of parent rocks primarily rich in ferrous mineral the present study shows that the minerals of capri chasma are characterized by the presence of prominent spectral absorption features at 2 31 m 2 33 m 2 22 m 2 48 m and 2 52 m wavelength regions indicating the existence of hydrous minerals i e carbonates and phyllosilicates the occurrence of carbonates and phyllosilicates in the study area suggests the presence of alkaline environment during the period of their formation results of the study are important to understand the formation processes of these mineral assemblages on mars which may help in understanding the evolutionary history of the planet

formation and evolution of the chaotic terrains by subsidence and magmatism hydraotes chaos mars the origin of the martian chaotic terrains is still uncertain and a variety of geologic scenarios have been proposed we provide topographic profiles of different chaos landscapes notably aureum and hydraotes chaos showing that an initial shallow ground subsidence occurred at the first step of the chaos formation we infer that the subsidence was caused by intrusion of a volcanic sill which could have produced consequent melting as well as release of ground water from disrupted aquifer signs of a volcanic activity are observed on the floor of hydraotes chaos a complex and deep depression located at the junction of three channels the volcanic activity is represented by small 0 5 to 1 5 km diameter rounded cones with summit pits the cone s size and morphology as well as the presence of possible surrounding lava flows suggest that they are primary volcanic cones similar to terrestrial cinder cones the identification of volcanic activity on the deepest chaos where the lower crustal thickness and the faults fractures system contributed to the magma rising reveals that magmatic activity proved by the cones and possibly help by structural activity has been a major factor in the formation of chaotic terrains

layering stratigraphy of eastern coprates and northern capri chasmata mars abstract distinct competent layers are observed in the slopes of eastern coprates chasma part of the valles marineris system on mars our observations indicate that the stratigraphy of coprates chasma consists of alternating thin strong layers and thicker sequences of relatively weak layers the strong competent layers maintain steeper slopes and play a major role in controlling the overall shape and geomorphology of the chasmata slopes the topmost competent layer in this area is well preserved and easy to identify in outcrops on the northern rim of coprates chasma less than 100 m below the southern ophir planum surface the volume of the topmost emplaced layer is at least 70 km 3 and may be greater than 2100 km 3 if the unit underlies most of ophir planum the broad extent of this layer allows us to measure elevation offsets within the north rim of the chasma and in a freestanding massif within coprates chasma where the layer is also observed rim outcrop morphology and elevation differences between ophir and aurorae plana may be indicative of the easternmost extent of the topmost competent layer these observations allow an insight into the depositional processes that formed the stratigraphic stack into which this portion of the valles marineris is carved and they present a picture of some of the last volcanic activity in this area furthermore the elevation offsets within the layer are evidence of significant subsidence of the massif and surrounding material

dark materials in valles marineris indications of the style of volcanism and magmatism on mars rifting on the equatorial canyon system of valles marineris provides a unique view of the interior of the martian crust to depths reaching 7 km exposing several in situ bedrock units which testify to past volcanic and magmatic processes on mars a thick regionally extensive deposit observed in coprates and juventae chasmata is interpreted on the basis of spectral reflectance erosional morphology and tendency for eolian mobilization to be composed of mafic glass possibly an ancient martian analogue of the lunar terra mantling deposits spectral mapping suggests that the dark floor covering materials in the lower canyons are derived from this unit a series of cliffs in the ophir chasma wall rock is interpreted to be exposures of resistant bedrock the spectral signature of this massive and uniform unit most closely resembles that of terrestrial mafic rocks altered to or coated by crystalline hematite application of computer mapping techniques to probable young volcanic materials in the central troughs yields an inferred distribution of volcanic activity consistent with the interpretation of extrusion along faults near the margins of the canyon floors this result supports the hypothesis that the valles originated through tectonic extension

correlated relative and absolute geomagnetic paleointensities from a pliocene n r polarity reversal record in basaltic lava flows on kauai hawaii

lithospheric scale buckling and thrust structures on mars the coprates rise and south tharsis ridge belt detailed photogeologic mapping documents for the first time the deformation sequence of the coprates rise materials of middle noachian through perhaps early hesperian age were involved in the horizontal shortening of crustal and lithospheric rocks that produced uplift and asymmetric east vergent folding of these layers during the late noachian and perhaps early hesperian previous suggestions of normal faulting as the deforming mechanism are not supported by the new mapping or by dislocation models of rise topography the most likely mechanism for producing the coprates rise is folding due to buckling instability and perhaps thrust faulting an extensive ridge belt concentric to south tharsis is defined by a newly recognized system of approximately coeval long wavelength topographic ridges and swales that include the coprates rise horizontal shortening of crust and lithosphere is manifested by periodically spaced structures at two different scales wrinkle ridges spaced tens of kilometers apart and the south tharsis system of ridges spaced hundreds of kilometers apart both types of structures may be associated with early volcanotectonic activity and crustal thickening in south tharsis these and other large ridges indicate that lithospheric buckling and thrust faulting may have been common on early mars

the controls on the composition of biodegraded oils in the deep subsurface part 1 biodegradation rates in petroleum reservoirs abstract biodegradation rates in oilfields have been assessed conservatively using whole oil column minimum rate estimates diffusion controlled oil column compositional gradient modelling and mixed oil kinetic models biodegradation rate constants first order are around 10 6 10 7 yr 1 for hydrocarbons in the degradation zones these corresponding well with zero order field wide minimum rate estimates of about 10 8 kg hydrocarbons kg oil year for the whole oil column with biodegradation induction times of around 1 2 ma to perturb an entire oil column for light oil reservoirs and 10 20 ma for heavy oil reservoir degradation the results indicate that where we see continuous gradients in the oil columns degradation must have been occurring episodically for many millions of years to remove the n alkanes from an oil i e about 10 of an oil around ca 15 ma is needed for a heavy oil ca 5 ma for a light n sea oil the timescales of oilfield degradation and filling are thus very similar and consequently the degree of biodegradation will be substantially controlled by oilfield charge history assessment of mixed degraded non degraded oil occurrence provides an independent confirmation that these rates are realistic and that timescales of degradation and field charging are similar the maximum effective rate constant of degradation ultimately controlled by the limiting effect of diffusion of alkanes to the oil water contact owc ca 10 4 yr 1 for a 130 m thick oil column first order rate constant is well above the estimated rate constants indicating oil biodegradation rate is not limited by electron donor supply i e hydrocarbons but by supply of nutrients or oxidants this suggests that diffusive transport of nutrients and electron acceptors in the aquifer to the site of biodegradation may be adequate to maintain the low rate biosphere

relative age of interior layered deposits in southwest candor chasma based on high resolution structural mapping high resolution topography generated from stereo hirise high resolution imaging science experiment imagery reveals the meter scale structure of interior layered deposits ild in southwest candor chasma this study seeks to determine the age of the local ild relative to any normal faults that can be attributed to chasma formation the study area is located near the contact of these ild and the wall rock and is in an area where chasma forming normal faults have been proposed we find that while normal faults are found in the study area these faults are not sufficiently large nor appropriately located or oriented to accommodate the roughly northeast southwest extension that is required for normal faults that can be attributed to chasma formation additionally bedding exposed in the local ild generally dips toward the center of candor chasma consistent with sediment deposition in a preexisting basin further pit craters of tithonia catena presumed to predate or be contemporaneous with the formation of west candor chasma do not cut into the ild within the study area these independent lines of evidence support a postchasma age for the ild exposed within the study area chasma related normal faults may exist within these ild at depth but are not exposed at the surface approximately 2 km of conformable stratigraphy is exposed in the study area and therefore at least several kilometers of the local ild were deposited subsequent to any chasma related normal faulting that may have occurred in this part of candor chasma

correlation of natural gas by use of carbon isotopic distribution between hydrocarbon components the natural distribution of carbon isotopes between hydrocarbon gas components is used for 1 determining a gas s maturity 2 correlating a reservoired gas to its source 3 correlating one reservoired gas with another and 4 recognizing gas mixtures calculated separations of carbon isotopes between the normal alkane components of a natural gas have been related to source rock maturity by use of a single continuous diagram independent of source type actual data from a wide variety of geologic settings and geologic ages confirm this relationship and demonstrate its applicability to the source rock levels of organic metamorphism ranging from 8 to 13 covering the entire range of oil and wet gas generation at greater maturities the wet gas components are found to undergo thermal degradation losing their usefulness for correlation three examples showing indigenous gas west texas non indigenous gas gippsland basin australia and gas mixtures from multiple sources southeastern alberta illustrate exploration applications

stratigraphy and erosional landforms of layered deposits in valles marineris mars the complex stratigraphy of layered deposits suggests a diversity of origins ages and post depositional modification histories the complexities within some layered deposits indicate changes in the dominant source materials in space and time the stratigraphy of layered deposits in the isolated martian chasmata hebes juventae and gangis is not well correlated this indicates that at least these chasmata had isolated depositional environments resulting in different stratigraphic sequences separated layered deposits in ophir candor and melas chasmata might have been a single continuous deposit in each chasma chaotic terrains are found in conjunction with layered deposits in juventae gangis and capri eos chasmata in these chasmata layered deposits unconformably overlie chaotic terrains chaotic terrain formation may have provided water to form paleolakes and lacustrine deposition of thick layered deposits may have occurred if the canyons were closed a very thick sequence of the layered deposits has been exposed by erosion a combination of gradual processes such as evaporation of ice and eolian and fluvial transport in addition to structural processes may be responsible for this erosion another alternative is that catastrophic water release under the layered deposits disrupted and initiated erosion of the layered deposits newly identified units of anomalous color are confined to the depressions or reentrants in western candor chasma the difference in color between these units and the surrounding terrain is most consistent with a somewhat greater content of bulk crystalline hematite in these anomalous units the presence of the candor units is a result of original and or secondary deposition which is different from the primary and dominant formation of the layered deposits

spatiotemporal evolution mineralogical composition and transport mechanisms of long runout landslides in valles marineris mars abstract long runout landslides with transport distances of 50 km are ubiquitous in valles marineris vm yet the transport mechanisms remain poorly understood four decades of studies reveal significant variation in landslide morphology and emplacement age but how these variations are related to landslide transport mechanisms is not clear in this study we address this question by conducting systematic geological mapping and compositional analysis of vm long runout landslides using high resolution mars reconnaissance orbiter imagery and spectral data our work shows that 1 a two zone morphological division i e an inner zone characterized by rotated blocks and an outer zone expressed by a thin sheet with a nearly flat surface characterizes all major vm landslides 2 landslide mobility is broadly dependent on landslide mass and 3 the maximum width of the outer zone and its transport distance are inversely related to the basal friction that was estimated from the surface slope angle of the outer zone our comprehensive compact reconnaissance imaging spectrometer for mars crism compositional analysis indicates that hydrated silicates are common in landslide outer zones and nearby trough floor deposits furthermore outer zones containing hydrated minerals are sometimes associated with longer runout and increased lateral spreading compared to those without detectable hydrated minerals finally with one exception we find that hydrated minerals are absent in the inner zones of the investigated vm landslides these results as whole suggest that hydrated minerals may have contributed to the magnitude of lateral spreading and long distance forward transport of major vm landslides

mineralogical and chemical distribution of the es3l oil shale in the jiyang depression bohai bay basin e china implications for paleoenvironmental reconstruction and organic matter accumulation abstract the es3l lower sub member of the third member of the eocene shahejie formation shale in the jiyang depression is a set of relatively thick and widely deposited lacustrine sediments with elevated organic carbon and is considered to be one of the most important source rocks in east china we can determine the mineralogy organic and inorganic geochemistry of the es3l shale and calculate paleoclimate indexes by using multiple geochemical proxies based on organic chemistry total organic carbon toc and rock eval pyrolysis major and trace elements x ray diffraction and carbon and oxygen isotope data from key wells alongside ecs elemental capture spectroscopy well log data these indicators can be used to analyze the evolution of the paleoenvironment and provide a mechanism of organic matter om accumulation the es3l oil shale has high toc abundance most samples 3 0 and is dominated by type i kerogens additionally the organic rich shale is rich in cao and enrichment in some trace metals is present such as sr ba and u the positive 13c and negative 18o values high sr ba b ga and ca ca fe ratios and low c s ratios indicate that the es3l shales were mainly deposited in a semi closed freshwater brackish water lacustrine environment the consistently low ti al and si al ratios reflect a restricted but rather homogeneous nature for the detrital supply many redox indicators including the th u v v ni and u ratios pyrite morphology and toc ts fe diagrams suggest deposition under dysoxic to suboxic conditions subsequently the brackish saline bottom water evolved into an anoxic water body under a relatively arid environment during which organic lean marls were deposited in the early stage later an enhanced warm humid climate provided an abundant mineral nutrient supply and promoted the accumulation of algal material om input from algal blooms reached a maximum during the deposition of the organic rich calcareous shale with seasonal laminations high p ti ratios and a strongly positive relationship between the p and toc contents indicate that om accumulation in the oil shale was mainly controlled by the high primary productivity of surface waters with help from a less stratified water column factors such as the physical protection of clay minerals and the dilution of detrital influx show less influence on om enrichment

diagenetic haematite and sulfate assemblages in valles marineris abstract previous orbital mapping of crystalline gray haematite ferric oxides and sulfates has shown an association of this mineralogy with light toned layered deposits on the floor of valles marineris in chaos terrains in the canyon s outflow channels and in meridiani planum the exact nature of the relationship between ferric oxides and sulfates within valles marineris is uncertain the observatoire pour la mineralogie l eau les glaces et l activite omega spectrometer initially identified sulfate and ferric oxides in the layered deposits of valles marineris the thermal emission spectrometer tes has also mapped coarse gray haematite in or at the base of these deposits we use compact reconnaissance imaging spectrometer for mars crism spectra and context camera ctx and high resolution imaging science experiment hirise imagery from the mars reconnaissance orbiter mro to explore the mineralogy and morphology of the large layered deposit in central capri chasma part of the valles marineris canyon system that has large clear exposures of sulfate and haematite we find kieserite mgso 4 h 2 o and ferric oxide often crystalline red haematite in the lower bedrock exposures and a polyhydrated sulfate without ferric oxides in the upper bedrock this stratigraphy is duplicated in many other basinal chasmata suggesting a common genesis we propose the haematite and monohydrated sulfate formed by diagenetic alteration of a sulfate rich sedimentary deposit where the upper polyhydrated sulfate rich haematite poor layers either were not buried sufficiently to convert to a monohydrated sulfate or were part of a later depositional phase based on the similarities between the valles marineris assemblages and the sulfate and haematite rich deposits of meridiani planum we hypothesize a common evaporite and diagenetic formation process for the meridiani planum sediments and the sulfate bearing basinal interior layered deposits

natural gas constituent and carbon isotopic composition in petroliferous basins china abstract there are abundant gas resources in petroliferous basins of china large to midsize gas fields are found in eastern central and western of china however origin constituents and isotopic composition of natural gas in different gas fields are varied distinctly and some present strong chemical secondary alteration and show variation both in age and space based on the systematic analysis of constituents and carbon isotope of a large number of gas samples combined with the geological characteristics this paper classifies the origins of the gases explores the gas isotope characteristics and evolutionary regulation with the variation time and space and further discusses the distinctive geochemistry of the gases in china these gases are dominated by dry gas its methane carbon isotope values range from 10 to 70 ethane from 16 to 52 propane from 13 to 43 and butane from 18 to 34 the carbon isotopes of most gases show the characteristics of humic derived gas and crude oil cracked gas in addition large primary biogenic gas fields have been discovered in the qaidam basin inorganic derived alkane gases have been discovered in deep of the songliao basin half of these gas fields are characterized by the alkane carbon isotope reversal in different degrees research indicates there are several reasons can result in carbon isotope reversal firstly gas charge of different genetic types or different source in one gas reservoir may cause carbon isotope reversal besides high over mature evolution of gas can also lead to the carbon isotopic reversal of alkanes thirdly secondary alteration of hydrocarbons may also result in abnormal distribution of carbon isotope isotope transforms to unusual light and heavy

displacement length scaling for terrestrial and martian faults implications for valles marineris and shallow planetary grabens the displacement length ratio for the central composite graben in valles marineris inferred from topography and likely stratigraphic offsets to be d max l 4 6 x 10 3 is consistent with the scaling relations derived from terrestrial faults and grabens that also demonstrate a systematic variation in displacement with position along the structure the large 10 km depth in central valles marineris is therefore not unusual but rather should be expected for a fault system 2240 km long in contrast existing measurements of throw along the numerous shallow radial grabens in tharsis while apparently inconsistent with the scaling relations demonstrate the importance of recognizing mechanical segment length along linked or echelon graben sets faults on other planetary surfaces should scale with their terrestrial counterparts as long as they extend substantially deeper than the gravity dependent near surface rock mass zone 1 km for earth 2 5 km for mars

origin of deep strata gas of tazhong in tarim basin china abstract tazhong is located in the interior of the taklamakan desert in the tarim basin deep carbonates are targeted exploration areas with abundant gas and the largest ordovician gas condensate field has been discovered the hydrocarbon is mainly distributed in the reef shoal complex of the upper ordovician lianglitage formation and in the interbedded weathered reservoirs of the lower middle ordovician yingshan formation despite the deep burial depth of the reservoirs and strong heterogeneity the reservoir bodies are large multiple layered and enrichment in hydrocarbons indicates a great exploration potential the ordovician gas condensate reservoir in the tazhong consists mainly of methane with a gas dryness coefficient of 0 91 0 98 the ordovician gas in the tazhong belongs to secondary oil cracking gas the comprehensive analysis of natural gas composition stable carbon isotopes and adamantane content showed that the natural gas was from paleo reservoir cracking at depth basin geothermal history burial history fluid inclusion data and geological analysis show that the gas accumulation occurred 5 ma ago the sulfur isotope of sulfides the presence of 2 thia adamantane and existence of light co 2 carbon isotopes indicate that the h 2 s was formed via tsr the natural gas accumulated through migration along faults

mitigative anthropogeomorphology a revived plan for the mediterranean sea basin and the sahara since at least 1964 macro engineering has proposed solutions for earth biosphere problems affecting mankind and its infrastructures from 1929 1948 herman sorgel put forth his atlantropa macroproject which was designed to lower the mediterranean sea by 1 m every year by natural evaporation and to irrigate the sahara with diverted zaire river freshwater the present author has slightly modernized sorgel s gift to homo sapiens construction of atlantropa would provide macro engineering and terraforming with a much needed practice run for the remaking of our solar system s planets

surficial geologic surveys of gale crater and melas chasma mars integration of remote sensing data abstract remote sensing observations of gale crater and melas chasma are synthesized to better understand the present surface layer in these two scientifically interesting regions data sets analyzed include geologic maps mars orbiter laser altimeter mola elevation thermal emission spectrometer tes albedo tes thermal inertia mola residual pulse width tes rock abundance and viking and mars orbiter camera images using these data sets we constrain the properties of and processes acting on the present surface and create self consistent models for the surface layer surface properties within gale crater are variable and complex and interpreting the surface layer is not straightforward observations indicate that aeolian processes have shaped some of the intracrater surface but other areas do not comply with this model and have counterintuitive surface characteristics in contrast aeolian activity appears to have played a large role in shaping the present day physical structure of all surfaces in melas chasma and is reflected in the remote sensing data sets here we summarize our analysis and discuss the surface attributes as determined from these data sets

fault fracture mesh petroleum plays in the zhanhua depression bohai bay basin part 1 source rock characterization and quantitative assessment abstract in the prolific zhanhua depression of the bohai bay basin eastern china over 76 of the proven petroleum reserves occur in the neogene guantao and minhuazhen formations detailed geological and geochemical mapping of the phanerozoic strata in this area reveals that oil shales and dark mudstones in the es4 es3 and es1 members of the eocene oligocene shahejie formation have excellent potential as petroleum source rocks regional distributions of total organic carbon content kerogen type and thermal maturation indicate that abundant mature source rocks are present in several discrete sag areas bounded by extensive basement related fault networks in contrast source rocks along the paleo topographic highs are currently immature with respect to the generation of conventional oils this study examined the key molecular characteristics for the common isoprenoid hopanoid and steroid biomarkers in relation to source facies variations in lacustrine sediments the hydrocarbon source potential and expulsion efficiency for each of the source rock units were evaluated which integrated the source rock characteristics with regional thermal subsidence and sediment burial an important observation made during this study is the striking contrast between the source potential and proven oil reserves within each stratigraphic section illustrating how significant the migration of hydrocarbon fluids derived from deep mature source kitchens through over 2000 m of fine grained formations must have been to form several giant oil accumulations in the shallow strata these results support the concept of the neogene fault fracture mesh petroleum plays proposed by zhang et al 2004 marine petroleum geology 21 651 668 and the vital role that the faults and fracture systems have in controlling hydrocarbon migration conduits and accumulation habitat in this rift basin

fault length statistics and implications of graben sets at candor mensa mars abstract the lengths of individual martian grabens from three spatially and temporally distinct regional sets are analyzed by a two dimensional window sampling method length distributions are influenced by fault growth and coalescence processes image resolution window size and the post faulting geologic history of the region cumulative length frequency distributions can be linear for graben lengths between 30 and 100 km with slopes on the area plot of 2 suggesting self similar growth of the graben array post faulting geologic processes contribute to concave cumulative length distributions on the log log plot with curtailment and truncation biases producing strongly non linear distributions for smaller and longer lengths respectively recent evidence for a positive correlation between stratigraphic throw and graben length from analogous terrestrial grabens implies that the magnitudes of throw and extensional strain may also be dependent on relative position along the martian grabens

generation accumulation and resource potential of biogenic gas biogenic gas is generated at low temperatures by decomposition of organic matter by anaerobic microorganisms more than 20 of the world s discovered gas reserves are of biogenic origin a higher percentage of gases of predominantly biogenic origin will be discovered in the future biogenic gas is an important target for exploration because it occurs in geologically predictable circumstances and in areally widespread large quantities at shallow depths in rapidly accumulating marine sediments a succession of microbial ecosystems leads to the generation of biogenic gas after oxygen is consumed by aerobic respiration sulfate reduction becomes the dominant form of respiration methane generation and accumulation become dominant only after sulfate in sediment pore water is depleted the most important mechanism of methane generation in marine sediments is the reduction of co2 by hydrogen electrons produced by the anaerobic oxidation of organic matter co2 is the product of either metabolic decarboxylation or chemical decarboxylation at slightly higher temperatures the factors that control the level of methane production after sediment burial are anoxic environment sulfate deficient environment low temperatu e availability of organic matter and sufficient space the timing of these factors is such that most biogenic gas is generated prior to burial depths of 1 000 m in marine sediments most of the biogenic gas formed can be retained in solution in the interstitial pore waters because of higher methane solubility at the higher hydrostatic pressures due to the weight of the overlying water column under certain conditions of high pressures and or low temperatures biogenic methane combines with water to form gas hydrates biogenic gas usually can be distinguished from thermogenic gas by chemical and isotopic analyses the hydrocarbon fraction of biogenic gas consists predominantly of methane the presence of as much as 2 of heavier hydrocarbons can be attributed to admixture of minor thermogenic gas due to low temperature degradation of organic matter the amounts of hydrocarbon components other than methane generally are proportional to temperature age and organic matter content of the sediments biogenic methane is enriched in the light isotope 12c dgr13c1 lighter than 55 ppt owing to kinetic isotope fractionation by methanogens the variations in isotopic composition of biogenic methane are controlled primarily by dgr13c of the original co2 substrate which reflects the net isotopic effect of both addition and removal of co2 the methane isotopic composition also can be affected by mixing of isotopically heavier thermogenic gas the possible complicating factors require that geologic chemical and isotopic evidence be considered in attempts to interpret the origin of gas accumulations accumulations of biogenic gas have been discovered in canada germany italy japan trinidad the united states and ussr in cretaceous and younger rocks at less than 3 350 m of burial and in marine and nonmarine rocks other gas accumulations of biogenic origin have undoubtedly been discovered however data that permit their recognition are not available

ground ice on mars inventory distribution and resulting landforms abstract most 90 of the estimated original volume of outgassed water on mars cannot be satisfactorily accounted for by exospheric escape or storage in the atmosphere as frost or in the permanent north polar ice cap the balance may be stored as ground ice in the martian cryosphere a zone of permanently frozen ground that is protected from the atmosphere by a debris cover ground ice can exist throughout the entire cryosphere but it need not fill it if the ground ice does fill the cryosphere then excess water can exist in a confined aquifer the theoretical distribution of ground ice can be tested by identification of forms on the martian surface that may be related to the presence of subsurface ice the observed features that are most likely to reflect ground ice are thermokarst like pits and debris flows landforms with ambivalent origins include polygonally patterned ground lobate ejecta blankets craters with central pits and curvilinear features the most persuasive morphologic evidence for ground ice is thermokarst pits and debris flows the thermokarst pits are primarily located in the volcanic regions of tharsis and elysium the association of ice related features with these volcanic areas suggests that these forms are not directly latitude dependent activation by orbital variations could produce periodic multiple episodes of melting that are dependent upon latitude the presence of ice related features in both hemispheres and the equatorial region of mars indicates that ground ice may be or have been present over the entire planet as predicted by the cryosphere model

young volcanic deposits in the valles marineris mars abstract a study of the interior deposits of the central valles marineris has led to the discovery of a sequence of deposits that cover the chasma floors and range in thickness from that of thin dust to several kilometers the emplacement of the deposits was the last major event in the history of the valles marineris following deposition of older layered interior beds warping faulting erosion and landslide emplacement the young deposits are of three major types 1 dark patches typically occurring along faults 2 light colored deposits locally associated with craters and 3 rugged mottled deposits with in places light colored lobate fronts these young materials may be of volcanic origin as suggested by the low albedo and spectrally gray colors of some their association with faults and possible volcanic craters and calderas and their embayment relations and lobate margins no other mechanism explains all the observed features and relations as well as volcanism if these deposits are volcanic implications are that 1 volcanism was associated with rifting in the valles marineris 2 the volcanism was explosive in places and 3 the volcanism may be as young as the late tharsis volcanism and locally may well be recent

origin and evolution of the layered deposits in the valles marineris mars abstract thick sequences of layered deposits are found in the martian valles marineris they exhibit fine nearly horizontal layering and are present as isolated plateaus of what may have once been more extensive deposits individual sequences of layered deposits are as thick as 5 km the greatest total thicknesses of deposits are found in candor ophir and melas chasmata individual layer thicknesses range from about 70 to 300 m some tilting of sequences is observed but at the best image resolutions no angular unconformities are detectable in the layers the sequences of events in the canyons as deduced from morphologic and stratigraphic evidence was 1 graben formation in response to the tharsis uplift 2 canyon wall retreat and canyon enlargement roughly contemporaneous with formation of the layered deposits 3 deep erosion of the layered deposits 4 landsliding of the canyon walls and 5 eolian erosion of the layered deposits perhaps continuing up to the present we consider four hypotheses for the origin of the layered deposits they are eolian deposits they are remnants of the material that makes up the canyon walls they are deposits of explosive volcanic eruptions or they were deposited in standing bodies of water the rhythmic nature of the layers and their lateral continuity horizontality great thickness and stratigraphic relationships with other units in the canyons all appear most consistent with deposition in an aqueous environment if standing bodies of water existed in the valles marineris they were almost certainly ice covered there are three ways in which sediment could have entered an ice covered lake down through the ice cover up from the lake bottom or in from the lake margins layers of sediment could have been transported downward through an ice cover by foundering or rayleigh taylor instabilities but it is not clear whether there was a viable mechanism for repeatedly accumulating thick sediment layers on top of the ice cover subaqueous volcanic eruption on the lake bottom does not suffer from many of the morphologic arguments that make origin by subaerial volcanism seem improbable while this mechanism is attractive there are no eruptive centers observed and there is no other direct evidence to support it because canyon enlargement took place at roughly the same time as layer deposition debris from the canyon walls is an obvious and likely source for some of the material in the layered deposits however the volume of material removed from the canyon walls may be insufficient to account for all of the presently observed material we conclude that there are several geologically feasible but as yet unproven mechanisms that could have led to formation of thick deposits in ice covered paleolakes in the valles marineris present data are insufficient to choose conclusively among the various possibilities several types of data from the mars observer mission will be useful in further characterizing the deposits and clarifying the process of their origin the deposits should be considered important targets for a future mars sample return mission

three dimensional forward stratigraphic modelling of the gravel to mud rich fan delta in the slope system of zhanhua sag bohai bay basin china abstract an important hydrocarbon reservoir is hosted by the third member of the shahejie formation es 3 in the zhanhua sag bohai bay basin seismic stratal slices reveal different characteristics of channels and fan delta lobes between the south slope break belt and southwest gentle slope areas combined with lithology wire line logs and three dimensional 3 d seismic data in the southern slope of zhanhua sag and an excellent analogue has been provided for understanding various key depositional evolution of fan deltas in the slope system from base to top es 3 l es 3 m and es 3 u the sedsim a three dimensional stratigraphic forward modelling programme is applied to simulate the evolution of fan deltas in the southern slope break systems and southwestern gentle slope systems of the zhanhua sag by considering a number of key processes and parameters affecting the fan deltaic deposition from 43 ma to 38 2 ma modelling results indicate that depositional types and scales evolved from the thickest medium scale gravel or sand rich fan deltas 43 ma 41 4 ma es 3 l to the thinnest small scale mud rich fan deltas and lacustrine mud 41 4 ma 39 8 ma es 3 m and lastly to less thicker larger scale mixed sand mud fan deltas 39 8 ma 38 2 ma es 3 u the types of slope system sediment supply and lake level change are three controlling factors for determining the source to sink architecture of the gravel to mud rich fan deltas and sediment dispersal characteristics this study has demonstrated that the process based modelling approach can be effectively used to simulate complex geological environments and quantify controlling factors

geochemical characterization of secondary microbial gas occurrence in the songliao basin ne china abstract a suite of natural gases from the northern songliao basin in ne china were characterized for their molecular and carbon isotopic composition gases from shallow reservoirs display clear geochemical evidence of alteration by biodegradation with very high dryness c1 c2 100 high c2 c3 and i c4 n c4 ratios high nitrogen content and variable carbon dioxide content isotopic values show wide range variations 13 c ch 4 from 79 5 to 45 0 13 c c 2 h 6 from 53 7 to 32 2 13 c c 3 h 8 from 36 5 to 20 1 13 c n c 4 h 10 from 32 7 to 24 5 and 13 c co 2 from 21 6 to 10 5 a variety of genetic types can be recognized on the basis of chemical and isotopic composition together with their geological occurrence secondary microbial gas generation was masked by primary microbial gas and the mixing of newly generated methane with thermogenic methane already in place in the reservoir can cause very complicated isotopic signatures system openness also was considered for shallow biodegraded gas accumulations gases from the daqing anticline are relatively wet with 13c enriched methane and 13c depleted co2 representing typically thermogenic origin gases within the longhupao da an terrace have variable dryness 13c enriched methane and variable 13c of co2 suggesting dominant thermogenic origin and minor secondary microbial methane augment the puqian ao nan uplift contains relatively dry gas with 13c depleted methane and 13c enriched co2 typical for secondary microbial gas with a minor part of thermogenic methane gas accumulations in the western slope are very dry with low carbon dioxide concentrations some gases contain 13c depleted methane ethane and propane indicating low maturity primary microbial origin recognition of varying genetic gas types in the songliao basin helps explain the observed dominance of gas in the shallow reservoir and could serve as an analogue for other similar shallow gas systems

identification distribution and possible origins of sulfates in capri chasma mars inferred from crism data crism is a hyperspectral imager onboard the mars reconnaissance orbiter mro nasa 2005 which has been acquiring data since november 2006 and has targeted hydrated minerals previously detected by omega mars express esa 2003 the present study focuses on hydrated minerals detected with crism at high spatial resolution in the vicinity of capri chasma a canyon of the valles marineris system crism data were processed and coupled with mro and other spacecraft data in particular hirise high resolution science experiment mro images detections revealed sulfates in abundance in capri especially linked to the interior layered deposits ild that lie in the central part of the chasma both monohydrated and polyhydrated sulfates are found at different elevations and are associated with different layers monohydrated sulfates are widely detected over the massive light toned cliffs of the ild whereas polyhydrated sulfates seem to form a basal and a top layer associated with lower albedo deposits in flatter areas hydrated silicates phyllosilicates or opaline silica have also been detected very locally on two mounds about a few hundred meters in diameter at the bottom of the ild cliffs we suggest some formation models of these minerals that are consistent with our observations

methanogenic biodegradation of petroleum in the west siberian basin russia significance for formation of giant cenomanian gas pools approximately 1700 tcf 48 trillion m3 of dry gas 99 methane reserves and resources occur in western siberia mostly in shallow 1500 m 4921 ft cenomanian pools in the northern part of the basin this dry gas constitutes about 11 of the world s conventional gas endowment and about 17 of the annual gas production the origin of the dry gas has been debated extensively over the last 45 yr but remains controversial widely discussed hypotheses on the origin include early mature thermogenic gas from coal primary microbial gas from dispersed organic matter or coal and thermogenic gas from deep source rocks however all these hypotheses are in some ways inconsistent with the molecular or isotopic composition of the gases or the results of basin and petroleum systems modeling here i present geochemical and geological evidence that a significant although yet not quantified part of the shallow dry gas in the northern west siberian basin originated from methanogenic biodegradation of petroleum circumstantial evidence includes the occurrence of heavily biodegraded oil legs and residual oil in many cenomanian gas pools as well as geochemical evidence of heavy to slight biodegradation in jurassic albian reservoirs commonly underlying the cenomanian pools direct evidence includes most importantly 13c enriched co2 in pools with biodegraded oil although data are limited which indicates 40 70 wt conversion of oil derived co2 to secondary microbial methane distinctive hydrocarbon molecular and isotopic compositions of most gases in cenomanian pools average dryness c1 sum c1 c5 is 0 9976 average 13c of methane is 51 8 suggest that they represent mixtures of biodegraded thermogenic gases from deep mainly jurassic source rocks and secondary microbial methane with an occasional small addition of primary microbial methane contribution of early mature coal derived gas is possible in areas with the most significant thermal stress of hauterivian aptian sediments but remains speculative review of petroleum habitats of five representative oil gas condensate fields in western siberia including the world s second largest gas field urengoyskoe suggests that methanogenic biodegradation may best explain the observed distribution and properties of fluids in the shallow reservoirs of those fields recognition of secondary microbial gas in western siberia helps explain the observed dominance of gas in the shallow cool northern part of the basin where conditions were more favorable for prolonged petroleum biodegradation than in the central and southern parts of the basin secondary microbial gas has been recognized worldwide and may 1 represent a volumetrically significant exploration target in shallow reservoirs perhaps more significant than primary microbial gas and 2 indicate effective thermogenic petroleum systems in the deeper sections large volumes up to 66 500 tcf 1884 trillion m3 of secondary microbial methane could have been generated from biodegraded petroleum accumulations worldwide although a part of that gas accumulated as oil dissolved free and hydrate bound gas most gas apparently escaped into the overburden atmosphere and ocean and could have affected global climate in the geologic past