wrinkle ridge assemblages on the terrestrial planets the wrinkle ridge assemblage is a group of associated features that have been observed on the moon mars and mercury members of the wrinkle ridge assemblage are classified as either arches or ridges based on morphology and ridges are subdivided into first second or third order ridges on the basis of dimensions the ridge assemblages described in this study are known to occur in mare basalts on the moon and smooth plains units that may be volcanic in origin on mars and mercury the structures that occur in the continental flood basalts of the columbia plateau in the northwestern united states are morphologically and dimensionally similar to features in the ridge assemblages on the terrestrial planets the anticlinal ridges of the columbia plateau and many first order ridges on the moon mars and mercury are interpreted to be folds with reverse or thrust faulting developed as a result of buckling flexure fracture or buckling as a consequence of reverse or thrust faulting fracture flexure estimates of the unit shortening across first order ridges using simple geometric forms to approximate the ridge morphology are lower than those determined for the anticlines of the columbia plateau where displacements are the results of folding and reverse to thrust faulting evidence of layer parallel extension that often accompanies folds developed by fracture flexure mechanisms i e drape or fault bend folds is not found in the anticlinal ridges of the columbia plateau and has only been observed in one ridge on the moon a kinematic model involving buckling followed by reverse to thrust faulting flexure fracture is favored for the origin of the anticlinal ridges of the columbia plateau and many of the first order ridges on the moon mars and mercury

discrepancies between different organic maturity indicators in a coal series affected by an abnormal thermal event visean niger abstract classical petrographical and geochemical approaches have been used to study visean coal seams sampled in two areas 50 km apart in northern niger t max values given by rock eval pyrolysis and individual molecular ratios determined on hopanes and steranes are in agreement with the burial history of the two sets of samples studied the difference of maturity of the two sample sets revealed by these various parameters is consistent with their current difference in burial depth 400 m only small changes of these parameters with depth were observed owing to the small depth interval sampled at both sites 15 and 40 m these variations also appear to be related to normal burial diagenesis no maturity differences between the two sample sets are revealed by vitrinite reflectance data and atomic h c ratios which are in the same range at both sites but display very large variations with depth r v 0 60 1 40 and h c at 0 80 0 90 to 0 55 these data indicate rapid entrance into the oil window this conclusion also being supported by microspectrofluorimetric observations showing oil production and expulsion and by the presence of pyrobitumens containing large devolatilization vacuoles in the deepest samples the abnormally high maturity gradient could have been caused by a hydrothermal event the present observations on coals confirm and supplement previous conclusions drawn from the study of organic materials disseminated in zn pb sulfide ore bearing sedimentary rocks the difference in sensitivity shown by the various maturity indicators is considered very likely to be due to differences in the kinetics of the transformations on which they each depend

a fault related coalification anomaly in the blanzy montceau coal basin massif central france abstract the stephanian intramontane blanzy montceau coal basin is situated along a variscan fault complex bordering the upper paleozoic blanzy le creusot bert graben the deposition of coal bearing strata was controlled by a complex of early faults known as the faille de bordure fb border fault another complex of permian faults known as the faille de l est fe eastern fault is situated along the more central part of the coal basin coalification in the basin follows three main trends 1 increasing rank from upper to lower coal seams in accordance with a general vertical trend hilt 1873 the gradient of volatile matter is higher than normal ranging from 3 to i i vdaf per 100 m or from 0 09 0 16 to 0 7 r per 100 m 2 increasing rank within each seam towards the fb fault an anomaly which cannot be explained by differences in lithology present day seam geometry or paleocover thickness the fb fault complex controlled the paleoheat flow the anomaly can be explained by means of convective circulation descending and ascending waters were presumably the main agents negative and positive respectively of heat transfer the fe fault complex was relatively cold because of rapid permian sedimentation which may have acted as a cooling factor 3 increasing rank towards the extensionally up lifted crystalline basement blocks coalification in the blanzy montceau basin started during the stephanian and was probably completed prior to the stephanian fault tectonics convective and conductive heat flow transfer played an important role during the permian convective circulation probably had a cooling effect

orientation relative age and extent of the tharsis plateau ridge system the tharsis ridge system is roughly circumferential to the regional topographic high of northern syria planum and the major tharsis volcanoes however many of the ridges have orientations that deviate from the regional trends normals to vector means of ridge orientations calculated in 10 boxes of latitude and longitude show that the tharsis ridges are not purely circumferential intersections of vector mean orientations plotted as great circles on a stereographic net show that the ridges are not concentric to a single point but to three broad zones these data indicate either that the tharsis ridge system did not form in response to a single regional compressional event with a single stress center or that the majority of the ridge system did form in a single event but with locally controlled deflections in the generally radially oriented stress field superposition relationships and relative ages suggest that the compressional stresses that produced the ridges occurred after the emplacement of the ridged plains volcanic units early in the hesperian period but did not extend beyond the time of emplacement of the syria planum formation units or the basal units of the tharsis montes formation during the latter half of the hesperian period comparison of topographic data with the locations of ridges demonstrates a good correlation between the topographic edge of the tharsis rise and outer extent of ridge occurrence compressional deformation related to tharsis is present out to about 5100 km from the regional topographic center located near northern syria planum the innermost extent cannot be determined because the ridged plains units have been buried by more recent volcanic units although ridge formation appears to have extended farther inward than is presently observed models involving a combination of isostatic stresses and stresses resulting from flexural loading appear to explain best the observed tensional features topography gravity and to a first approximation the locations and orientations of the compressional ridges

heterogeneities in the thickness of the elastic lithosphere of mars constraints on heat flow and internal dynamics derived values of the thickness of the effective elastic lithosphere on mars are converted to estimates of lithospheric thermal gradients and surface heat flow by finding the thickness of the elastic plastic plate having the same bending moment and curvature subject to assumed strain rates and temperature dependent flow laws for crustal and mantle material local thermal gradients and heat flow values so estimated were 10 14 k km 1 and 25 35 mw m 2 respectively at the time of formation of flexurally induced graben surrounding the tharsis montes and alba patera while gradients and heat flow values of less than 5 6 k km 1 and 17 24 mw m 2 respectively characterized the lithosphere beneath the isidis mascon and olympus mons at the time of emplacement of these loads on the basis of the mean global thickness of the elastic lithosphere inferred to support the tharsis rise and estimates of mantle heat production obtained from snc meteorites it is suggested that the present average global heat flux on mars is in the range 15 25 mw m 2 approximately 3 5 of this heat flux during the amazonian epoch has been contributed by excess conducted heat in the central regions of major volcanic provinces most likely this excess heat flux has been delivered to the base of the lithosphere by mantle plumes the fractional mantle heat transport contributed by plumes during the last 2 b y on mars is therefore similar to that at present on earth

comparative mineralogy organic geochemistry and microbial diversity of the autun black shale and graissessac coal france there is growing evidence that microbial populations associated with rocks may be involved in weathering processes in particular they may play a role in the degradation of fossil organic carbon widely present in sedimentary rocks in this study we investigate the microbial diversity associated with two organic rich rocks exhibiting contrasted organic chemical structure a typical type i aliphatic carbon rich kerogen autun shale and a coal rich in aromatic carbon graissessac coal in both rocks the mineralogy and the geochemistry of the organic matter were investigated moreover the microbial diversity associated with these rocks was characterized using bacterial 165 rrna gene analysis in the autun shale one dominant species is observed ralstonia whereas a larger microbial diversity is retrieved from the graissessac coal altogether we conclude that potential hydrocarbonoclastic microorganisms detected by the presence of nag like genes potentially encoding dioxygenase may be associated with a possible biodegradation of fossil organic carbon in the two samples we conclude that under favorable conditions aerobic biodegradation could occur and oxidize a minor fraction of these two different kerogens using a similar enzymatic process c 2014 elsevier b v all rights reserved

global and regional ridge patterns on mars abstract over 16 000 wrinkle ridges on mars have been classified mapped and digitized to provide a large computer accessible data base for analyzing regions subjected to possible compressive stresses the survey has revealed major compressive structures that occur well beyond the tharsis dominated hemisphere the large variety of affected geologic terrains indicate stresses not simply localized in the intercrater plains one major area of inferred compression occurs in the southern cratered highlands near longitude 180 w where major ridges and scarps extend over 3000 km the occurrence and orientation of many ridges are locally controlled by ancient impact basins the chryse basin in particular has an important effect on ridges in northern lunae planum the removal of all basin concentric ridges reveals however a complex global pattern although such patterns may yet be controlled by heavily degraded impact basins major regional trends also emerge that appear to require broader scale global stresses most ridges in the western hemisphere are shown to be orthogonal to three centers corresponding to tharsis 1 n 122 w syria 12 s 104 w and chryse 19 n 47 w ridges not included in these three sets are generally more random and highly localized most but by no means all ridges in the eastern hemisphere are controlled by the hellas and isidis basins a simple global grid is not yet identifiable and may not be recognizable owing to the large number of regional patterns

determination of maximum paleotemperatures of burial mptb of sedimentary rocks from pyrolysis data on the associated organic matter basic principles and practical application the balazuc 1 borehole drilled in the frame of the geologie profonde de la france programme and the work carried out by various specialists provided the samples and the independent paleotemperature assessment data both needed to check a model aiming to the straightforward determination of maximum paleotemperatures of burial mptb from rock eval pyrolysis data basically the model supposes that laboratory e g rock eval pyrolysis resumes the successive elimination of kerogen moieties of increasing thermal stability where it had stopped during burial diagenesis then the temperature tmin determined at the onset of the s2 rock eval pyrolysis peak supposed to correspond to a peculiar kerogen moiety which was just undergoing cracking when maximum burial depth was reached might be used to calculate the corresponding mptb taking into account the different values of the experimental and natural thermal gradients the good agreement between calculated mptb values and results of fission track and fluid inclusion studies carried out on balazuc 1 borehole samples supports the validity of the model according to fundamental considerations the application of this approach is limited to samples having at least reached the onset of the metagenetic stage other possible limitations and the causes of uncertainty on the obtained results are discussed a detailed operating procedure is presented

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

evidence and effects of fluid circulation on organic matter in intramontane coalfields massif central france abstract recent evidence for a late carboniferous hydrothermal event responsible for au as mineralization within the variscan belt of the french massif central adds a supplementary episode to the already rather complex thermal history of this area to better understand this history 45 coal samples from various sites in the massif central were studied petrographically reflectance analysis and geochemically rock eval pyrolysis the results of this study suggest that the studied coal was buried to 1500 m and that the coalification took place within 25 ma probably ending at the boundary between the early and late permian marked by the saalic orogeny two thermal end members basins were identified i the carboniferous of bosmoreau les mines limousin and west graissessac montagne noire showing geothermal paleoflow values between 150 and 180 mw m 2 and ii the stephanian of argentat and detroit de rodez sw massif central with values estimated at between 100 and 120 mw m 2 by plotting the t max and r o values on a diagram the samples were grouped into two populations the first showing a positive correlation between r o and t max and the second with higher t max values than expected after r o values selected samples of the second group are also characterized by a high oxygen index oi that increases with t max these divergence between r o and t max associated with a high oi may be the result of the circulation of slightly oxidizing hot fluids subsequent to coalification the other kind of r o t max divergence seems to be linked to local particularly high thermal activity especially in graissessac and bosmoreau basins it is interpreted as being due to a difference in response of these two maturity indicators respectively to the intensity and duration of the thermal events e g short lived hydrothermal circulation and thermal domes of regional extent

age determination of linear surface features using the buffered crater counting approach case studies of the sirenum and fortuna fossae graben systems on mars buffered crater counting bcc offers a possibility to determine ages of linear curvilinear surface features that provide no or only very limited surface areas for the conventional crater counting approach in this study we applied the bcc analysis to two tectonic fault systems fortuna fossae and a subsection of sirenum fossae we compared bcc results with age estimates derived from conventional crater counting on the surrounding geologic units and investigated to what extent crater ejecta blankets can be used for determining the stratigraphic placement of craters pre or post dating the formation of linear features furthermore we introduce a new functionality of the cratertools software for arcgis which allows for a user friendly semi automatic application of the otherwise time consuming procedure of bcc analysis the software provides the resulting crater size frequency data in a standard format which can be read and analyzed in the craterstats analysis software our case studies showed that the bcc approach provides equivalent or even more precise age results compared to the conventional stratigraphic approach here we found that the investigated section of sirenum fossae is younger than previously thought the derived formation age from the bcc analysis is 3 44 0 25 0 1ga which corresponds to late instead of early hesperian fortuna fossae formed shortly after the emplacement of its now fractured geologic host unit late hesperian ages derived from bcc analysis vary between 3 53 0 11 0 06ga and 3 50 0 11 0 07ga furthermore we recommend the use of crater ejecta blankets to position them in the stratigraphic sequence in order to improve crater statistics however the accuracy of the results depends on the extent and preservation state of the continuous ejecta blankets in the region of interest thus the applied buffer width has to be chosen carefully according to investigated crater sizes and local observations

petroleum generation simulation over six years of hydrocarbon formation from torbanite and brown coal in a subsiding basin abstract dry samples of torbanite and soft brown coal from which mineral matter and material soluble in chloroform have been removed have been artificially matured in an attempt to simulate conditions in a subsiding sedimentary basin with a constant geothermal gradient sealed tubes were increased in temperature by 1 c per week beginning at 100 c a tube containing each source material was opened and analysed at yearly intervals for six years olefins and carbon monoxide were not significant products at any stage at less than 300 c torbanite generated a paraffinic crude oil in 35 yield while the brown coal gave a wet co2 rich natural gas in most respects these experiments which are possibly as slow as can be realistically planned within a human time scale appear to have duplicated geochemical hydrocarbon generation

the formation of floor fractured craters in xanthe terra floor fractured craters ffc are a peculiar form of degradation of impact craters defined by the presence of crevice networks and mesas affecting crater floors they are preferentially distributed near chaotic terrains and outflow channels the scope of this paper is to present a detailed systematic analysis of ffc at xanthe terra ffc morphologies in this region are classified into five types making a picture of different stages of the same degradation process ffc are geographically intermixed with un fractured normal craters non ffc young craters are less prone to show this type of degradation as suggested by fresh ejecta layer with preserved crater floor size distributions of ffc and non ffc indicate that larger craters are preferentially fractured careful examinations of the crater floor elevations reveal that the crevices often extend deeper than the original crater cavity furthermore an onset depth for the formation of ffc is evidenced from the difference of spatial distributions between ffc and non ffc roof collapsed depressions observed in the same region have been also documented and their characteristics suggest the removal of subsurface material at depth from about 1200 to 4000 m these observations taken together suggest a subsurface zone of volume deficit at depth from 1 to 2 km down to several kilometers responsible for ffc formation then a scenario of ffc formations is presented in the context of groundwater discharge events at the late hesperian this scenario involves two key processes earth fissuring and piping erosion known to occur with rapid groundwater migrations on earth

crosscutting relations and relative ages of ridges and faults in the tharsis region of mars abstract observations of ridge fault crosscutting relationships on the ridged plains units surrounding the tharsis region of mars have led to the development of a classification scheme involving three distinct types of intersections ridges crosscut by faults are designated type c and account for 81 of the observed intersections ridges terminated at one end by a fault type t as well as those superposed on grabens type s are less numerous interpretation of the morphology of these intersections and the angles of intersection between ridges and faults with radial trends to major topographic features in the tharsis region have led to the following conclusions 1 the major ridge forming events in the tharsis region were roughly coincident with and in some cases possibly prior to the extensional events that produced the faulting of the tempe and mareotis regions the coprates and memnonia regions and the rifting of valles marinrris 2 the compressional events that formed most of the ridges are restricted in time both by the irrelationship to regional extensional events and by the age of the units on which they formed the suggestion that compressional ridges are a result of a single long term viscoelastic response of the lithosphere to loading of the crust is not supported by this study a model involving one or more isostatically compensated uplifts and subsequent relaxation of the crust after the emplacement of the ridged plains volcanic units is favored

martian wrinkle ridge topography evidence for subsurface faults from mola mars orbiter laser altimeter mola topography shows distinct elevation offsets across wrinkle ridges that can be explained simply by subsurface thrust faults mola has provided the first reliable topographic data of wrinkle ridges to test models for their origin although previous work has shown that wrinkle ridges result from compressional folding and faulting of near surface units the role of thrust faulting and its depth penetration have been argued topographic profiles across wrinkle ridges in solis planum lunae planum tempe terra xanthe terra arcadia terra sirenum thaumasia planum arabia terra syrtis major and hesperia planum show characteristic features such as superposed hills crenulations and elevation offsets between the plains on either side of the ridge the characteristic elevation offsets between plains surfaces on either side of the ridges shown by mola are easily explained by subsurface thrust faults that underlie the ridges and produce the offset in solis dorsa wrinkle ridges are 10 20 km wide well resolved by the 300 m spaced mola elevations have a total relief of 80 250 m and have elevation offsets of 50 180 m well above the uncertainty in the mola elevations mola topography shows that the plains decrease in elevation toward the southeast and are deformed into folds or arches not visible in images that are parallel to and in between the ridges the elevations of the plains on either side of the ridges in solis and lunae plana are characteristically down to the southeast and east respectively suggesting that faults beneath the wrinkle ridges offset the plains this offset indicates underlying thrust faults that dip to the northwest and west respectively and systematically lower the southeast side of the plains the observation that the elevation offsets across the ridges are maintained to the next ridge implies that the thrust fault penetrates to depths of tens of kilometers and thus well into the mechanical lithosphere small foreland basement uplifts on earth in which slip on shallowly dipping thrust faults in the crystalline basement is accommodated by folding in the overlying sedimentary rocks appear to be broadly analogous to these groups of wrinkle ridges and suggest that they are examples of thick skinned compressional deformation on mars these observations are not consistent with models for the formation of wrinkle ridges that involve folding of near surface layers only or subsurface thrust faults that flatten into decollements at shallow depths

origin of periodically spaced wrinkle ridges on the tharsis plateau of mars ridged plains are a major geologic unit on mars and are a predominant unit on the tharsis plateau a region that has undergone uplift extension and extensive shield and flood volcanism these units probably flood volcanic in origin are characterized by landforms classed as wrinkle ridges wrinkle ridges are interpreted to be folds resulting from buckling followed by reverse to thrust faulting flexure fracture a prominent characteristic of many of the wrinkle ridges on mars particularly those in the tharsis ridge system is the periodic nature of their spacing the periodic spacing has been evaluated in six major provinces on the tharsis plateau with regions further divided into domains based largely on variation in ridge orientation the average spacing of the tharsis ridges based on 2934 measurements is 30 km in an effort to account for the periodic nature of the wrinkle ridges the ridged plains material is modeled as both a single member and a multilayer with frictionless contacts that has buckled at a critical wavelength of folding free slip between layers is assumed based on the possible existence of mechanically weak interbeds in the ridged plains sequence separating groups of flows the near surface mechanical structure in the area of ridged plains is approximated by a strong layer or layers overlying a weak megaregolith of finite thickness overlying a strong basement buckling of the ridged plains is assumed to be decoupled from the basement by the weak megaregolith decoupling is enhanced if the megaregolith were water or ice rich at the time of deformation the rheologic behavior of the ridged plains and megaregolith is approximated by a linear elastic and linear viscous material the models are examined for a range in 1 the strength contrast between the ridged plains material and the underlying megaregolith 2 thickness of the ridged plains material 3 thickness of the megaregolith and 4 number of layers the elastic model can explain the observed ridge spacing only if the ridged plains are relatively thick 2400 m with multiple layers n 1 and relatively high contrasts in young s modulus e e0 100 the high e e0 required is possible only if the megaregolith was water rich at the time of deformation over the same range in values of the parameters viscous buckling is much less restricted the viscous model can explain the observed ridge spacing over a wide range in ridged plains thickness 250 m to several kilometers megaregolith thickness number of layers n 1 to 8 and contrasts in viscosity 0 10 in addition viscous buckling is viable if the megaregolith were dry water rich or ice rich at the time of deformation the absence of folds with a cross sectional geometry in the shape of a sinusoid anticline syncline pairs may be the result of initial deformation of the ridged plains material into low amplitude folds in infinitesimal strain followed by plastic yielding in the cores of the anticlines in finite strain initial elastic or viscous buckling coupled with plastic yielding confined to the hinge area followed by the development of reverse to thrust faulting could account for the asymmetric fold geometry of many of the wrinkle ridges

evidence for extensive olivine rich basalt bedrock outcrops in ganges and eos chasmas mars 1 several localized outcrops of olivine enriched bedrock have been previously identified in the ganges and eos chasma area on the eastern end of valles marineris with the thermal emission imaging system multispectral images these outcrops form a layer in the walls of ganges chasma and appear to be the remnants of a once continuous unit which was mapped over 100 km in this study we further characterize the composition forsterite content of 0 68 olivine abundance 10 to 15 thermal inertia 600 jk 1 m 2 s 1 2 consistent with in place rocky material vertical dimension 60 to 220 m extent 1100 km laterally volume 9 9 104 km3 dip 0 013 ne and continuity of this layer utilizing thermal emission spectrometer hyperspectral thermal emission imaging system multispectral and mars orbiter laser altimeter elevation data morphologic data from high resolution imagery display a relatively unmantled rough and pitted surface associated with the olivine enriched material consistent with thermal inertia data four possibilities for the origin of the olivine enriched unit are 1 volcanism associated with tectonic rifting of the valles marineris system 2 a volcaniclastic flow deposit 3 an intrusive mafic sill or 4 a discrete episode in martian history during which flood lavas were erupted onto the surface the most likely origin is an eruptive event consisting of compositionally uniform flood lavas originating from a primitive mantle source region possibly associated with the initiation of tharsis volcanism this unit is one of the largest continuous compositional units found on mars and is strikingly similar to other olivine enriched deposits identified in previous studies where compositional morphologic and thermophysical similarities are observed these similarities may indicate that there was a period in early martian history where compositionally uniform and extensive olivine enriched flood basalts were erupted on the martian surface

thrust fault vergence directions on mars a foundation for investigating global scale tharsis driven tectonics 1 insight into the mechanical and thermal structure of the martian lithosphere and the character of tharsis driven tectonics is gained from detailed mapping of the global distribution of thrust fault vergence directions with respect to the center of the tharsis tectono volcanic province our results reveal sub equal frequencies of thrust faults that verge away from and toward tharsis based on the observed distribution of thrust fault vergence directions we conclude that the base of the tharsis load was effectively welded by frictional and cohesive strength to the subjacent noachian crust throughout its periods of sustained volcanism and faulting during the late noachian to early hesperian rather than being detached along a ductile layer at its base

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

coal rank distribution and implications for structural and geothermal controls on coalification case study from the cevennes basin massif central france abstract a detailed study of the coalification and paleogeothermal evolution of the stephanian cevennes basin in southeastern france is presented in this paper this study includes several parameters 1 the geometry of the basement the base of the coal measures and the unconformity beneath the overlying mesozoic series 2 the lateral and vertical distribution of the content of volatile matter in the coal beds 3 the relationship between these parameters and the geological boundaries this study also addresses qualitative and semi quantitative parameters of the degree of coalification of organic matter in the same basin the parameters investigated are 1 the relief of the basement 2 the nature and thickness of the overlying mesozoic series and 3 the faulting in the basin in the cevennes basin two coalification episodes were recognized early pre folding and late post folding and their ages and intensities have been estimated the results suggest that coalification was strongly influenced by the faulting and the thickness of the strata overlying the coal seams the early coalification episode during the pennsylvanian basin filling stage was closely related to the syndepositional faulting and the later coalification episode was affected by subsequent rapid subsidence during the mesozoic the ultimate maturity level of the oldest stephanian coal was achieved by the polyphase and multiformity coalification

caloris basin mercury history of deformation from an analysis of tectonic landforms abstract the 1640 km diameter caloris basin is the largest impact basin on mercury and hosts three distinct suites of tectonic structures in its substantially deformed smooth plains indicative of the basin s complex history these structures i e radial graben comprising pantheon fossae concentric graben troughs arranged in an irregular pattern and wrinkle ridges are found at various regions throughout the basin and occasionally interact we document the locations orientations and cross cutting relationships of these structures using high resolution messenger images we suggest that caloris shows a history of continuous deformation resulting from the contemporaneous formation of sets of strain compatible tectonic structures rather than discrete stages of deformation producing each suite independently in temporal sequence we propose that radial graben formed continuously in the basin s early deformational history following initial wrinkle ridge formation possibly representative of a multi ring basin structure overlapping with continued wrinkle ridge formation and persisting with the formation of concentric graben after contraction ceased

geology of the central sulawesi belt eastern indonesia constraints for geodynamic models sulawesi island located at the junction of the asian australian and pacific plates is geologically important for unraveling the cenozoic tectonics of south east asia this island situated on the active margin of the asian plate suffered at least four major tectonic events in mid cretaceous oligo miocene middle miocene and early pliocene times the present paper is focused on the oligo miocene event which formed the main orogenic belt of this island several geodynamic models have been proposed for this belt our structural and stratigraphic investigations in the central area of sulawesi lead us to favor an eastward obduction of an ophiolitic nappe of asian origin onto a continental gondwana block while a west dipping slab was subducting underneath the western asiatic margin collision between this fragment of gondwana and the active asiatic margin in late oligocene or early miocene time produced the central metamorphic belt of sulawesi

erroneous coal maturity assessment caused by low temperature oxidation previous work carried out on different outcrop coals from the french massif central revealed abnormally high tmax values which initially were attributed to high temperature oxidising fluids this increase in tmax which was exclusively observed for medium to low volatile bituminous coals rr 1 5 was accompanied by a very clear exponential like decrease of the hydrogen index hi together with an increase in the oxygen index oi with the aim of checking the possibility that this rise in tmax could simply be caused by weathering a few mature coal samples rr 1 4 were experimentally oxidised at rather low temperatures 110 125 and 150 c and for durations of up to 6 5 month then the oxidation residues were subjected to rock eval 6 pyrolysis and to vitrinite reflectance measurements these experiments effectively reproduce the geochemical changes displayed by the naturally altered coals thus supporting the hypothesis that the previously studied natural alteration process could have been ultimately caused by weathering the observed artificial oxidation path could be divided into two stages i a strong decrease in hi and an increase in oi and ii a constant hi value and a slow rise in oi the increase in tmax seems related to the transition between the first and the second stages this behaviour of hi and oi during artificial oxidation suggests that these two rock eval derived indices can be practically used to detect a moderate and even a low oxidation degree finally if one ignores the constancy of the vitrinite reflectance values all along the oxidation path the decrease of hi and the concomitant increase of tmax mimic a thermal evolution pathway

effect of igneous intrusion on the organic geochemistry of a siltstone and an oil shale horizon in the midland valley of scotland abstract the effect of rapid thermal stress on the organic geochemistry of a siltstone intruded by a quartz dolerite dyke and an oil shale intruded by an alkali dolerite sill has been studied using optical petrography rock eval pyrolysis gas chromatrography and gas chromatography mass spectrometry maturity dependent ratios derived from both the aliphatic and aromatic hydrocarbon fractions corroborate the observation of raymond and murchison 1988b that the alkali dolerite sills which were intruded soon after sedimentation had a lesser effect than the later quartz dolerite intrusions the maturity parameters based on the alkylnaphthalene and alkylphenanthrene isomer ratios are more suitable for studying maturity variations in heat affected samples than those based on the commonly used aliphatic biological markers these aromatic compounds survive to higher ranks and the isomer ratios continue changing

oblique rifting at tempe fossae mars this work shows the results of a structural study of the faults observed at the tempe rift northeastern tharsis region mars a new detailed map of faults and fault systems was used to geometrically characterize the fracture architecture of the tempe rift and to measure fault length displacement and spacing data to analyze the spatial distribution of fault centroids and to investigate the fractal nature of fault trace maps a comparison with analog models and the use of conventional techniques of fault population analysis show that the tempe rift was most probably generated under sinistral oblique rifting processes which highlights the importance of the presence of inherited fractures in the tectonic evolution of the noachian crust the angle between the extension direction and the rift axis varies along the tempe rift ranging from 50o 60o at its central southern part to 66o 88o to the southwest fault scaling relationships are similar to those found at midocean ridges on earth with exponential fault length frequency distributions localized inhomogeneous deformation generated weakly interacting faults spanning the entire thickness of the mechanical layer this thickness decreased from southwest to northeast along the rift along with distance from the central part of the tharsis dome

magnitude of global contraction on mars from analysis of surface faults implications for martian thermal history faults provide a record of a planet s crustal stress state and interior dynamics including volumetric changes related to long term cooling previous work has suggested that mars experienced a pulse of large scale global contraction during hesperian time here we evaluate the evidence for martian global contraction using a recent compilation of thrust faults fault related strains were calculated for wrinkle ridges and lobate scarps to provide lower and upper bounds respectively on the magnitude of global contraction from contractional structures observed on the surface of mars during the hypothesized pulse of global contraction contractional strain of 0 007 to 0 13 is indicated by the structures corresponding to decreases in planetary radius of 112 m to 2 24 km respectively by contrast consideration of all recognized thrust faults regardless of age produces a globally averaged contractional strain of 0 011 to 0 22 corresponding to a radius decrease of 188 m to 3 77 km since the early noachian

a prediction of mars seismicity from surface faulting the shallow seismicity of mars has been estimated by measurement of the total slip on faults visible on the surface of the planet throughout geologic time seismicity was calibrated with estimates based on surface structures on the moon and measured lunar seismicity that includes the entire seismogenic lithosphere results indicate that mars is seismically active today with a sufficient number of detectable marsquakes to allow seismic investigations of its interior

tharsis dome mars new evidence for noachian hesperian thick skin and amazonian thin skin tectonics a photogeological reconnaissance of viking mosaics and images of the tharsis dome has been carried out fifteen new areas of transcurrent faulting have been located which together with other structures previously detected support a model in which the thaumasia plateau the southeastern part of the tharsis dome is proposed to be an independent lithospheric block that experienced buckling and thrust faulting in late noachian or early hesperian times as a result of an e w directed compression evidence is presented that this stress field rather than the tharsis uplift was decisive in the inception of valles marineris which we consider a transtensive dextral accident the buckling spacing permits us moreover to tentatively reconstruct a martian hesperian lithosphere similar in elastic thickness to the mean present terrestrial oceanic lithosphere thus supporting the possibility of a restricted lithospheric mobility in that period tharsis lithosphere was again subjected to shear stresses in amazonian times a period in which important accidents such as strike slip faults wrinkle ridges and straight and sigmoidal graben were formed under a thin skin tectonic regime while the lithosphere as a mechanical unit had become too thick and strong to buckle the possible causes of those stresses and especially their relationships to a putative period of plate tectonics are discussed

compressional structures on mars abstract wrinkle ridges accommodate very low amounts of shortening strain around immense volcanic constructs and within impact basins on mars they originate from stresses distributed uniformly throughout the brittle lithosphere and are consistently located in stratified deposits including lava flows and sediment most recent models interpret wrinkle ridges as the surface manifestation of folding above underlying blind thrusts that accommodate similarly low strain and likely penetrate tens of kilometers into the brittle crust alternative models suggest shortening accommodated by some wrinkle ridges is confined to only the upper few kilometers of the crust the interpretation of the geometry of blind thrusts on mars appears to be quite varied and remains controversial although some models suggest they may ultimately flatten into the brittle ductile transition in the middle to lower crust small scale crenulations superposed on ridges are interpreted as produced by high level back thrusts nucleating at

late orogenic carboniferous extensions in the variscan french massif central the variscan french massif central experienced two successive stages of extension from middle carboniferous to early permian in the northern massif central the first stage began in the late visean immediately after nappe stacking and is well recorded by namurian westphalian synkinematic plutonism the middle carboniferous leucogranites widespread in the nw massif central limousin and sioule area were emplaced within a crust extending along a ne sw direction at the same time the hanging wall or gueret extensional allochton moved toward the se several examples of the synextensional plutonism are also recognized in central limousin saint mathieu dome la porcherie and cornil leucogranites these examples illustrate the relationship between granite emplacement and crustal scale deformation characterized by nw se stretching and ne sw shortening in the central and southern massif central cevennes ch taigneraie and margeride areas plutonism is dominantly granodioritic and exhibits the same structural features nw se maximum stretching and overturning to the se middle carboniferous namurian westphalian extension was parallel to the variscan belt both in the massif central and southern armorican area this extensional regime was active from the late visean in the north while compression dominated in the southernmost domains montagne noire and pyrenees the second extensional stage occurred from late carboniferous to early permian this event was responsible for the opening of intramontane coal basins brittle deformation in the upper crust and ductile normal faulting localized on the margin of cordierite granite migmatite domes data from the coal basins show that the half graben is the dominant structural style except for basins located along submeridianal left lateral faults which have pull apart geometries late carboniferous extension occurred along the ne sw direction the ne sw maximum stretching direction can be found in the whole massif central but is more developed in the eastern part the extensional direction is transverse to the general trend of the belt and top to the ne shearing is dominant correlations of these two extension directions with neighboring variscan massifs are discussed

orientation and origin of ridges in the lunae palus coprates region of mars numerous wrinkle ridges similar in appearance to lunar mare ridges occur on volcanic plains units surrounding the tharsis region of mars where they are oriented circumferential to the center of the plateau by analogy with lunar mare ridges and from morphologic evidence such as the smooth slopes of arches these features are interpreted to result primarily from compressional folding of the volcanic plains although the uppermost ridge may represent faulting of the near surface materials east of the tharsis region ridges are best developed in the lunae palus and coprates quadrangles where they can be used to indicate the degree of compressional stress occurring there comparison of ridge orientations in these quadrangles to a tharsis center at 1 n 122 w indicates that more than 60 of the total length of ridges is orthogonal to a normal from this center non orthogonal ridges are seen to have general northerly orientations after removal of the tharsis orthogonal population trends of graben in surrounding terrain indicate that non orthogonal ridges are not greatly affected by regional scale structures comparison of the frequency of orthogonal and non orthogonal ridges further suggests that loading due to the tharsis plateau was effective in producing compressional features as far as 4000 km from the center of the load additional sources for compressional stress are necessary to account for ridge systems at greater distances from the tharsis plateau

resurfacing of the martian highlands in the amenthes and tyrrhena region the southern cratered highlands of mars contain a large population of flat floored rimless craters which have previously been interpreted to have formed by aeolian mantling or flood volcanism neither of these geologic processes accurately explains the observed morphology or the crater statistics geologic mapping in the amenthes and tyrrhena region indicates that craters with this morphology occur on undulating intercrater materials near the dichotomy boundary and on more rugged materials farther into the highlands containing numerous ancient valley networks cumulative size frequency distribution curves indicate ages of n 5 790 early to middle noachian and n 5 540 middle noachian for the cratered plateau and cratered highland materials respectively opposite the observed stratigraphic relations for crater diameters 16 km the population of impact craters is consistent with stratigraphy but the population of smaller craters in the region indicates the importance of resultacing superposed fresh craters indicate a resultacing event that ceased at n 5 200 250 late noachian to early hesperian crater counts divided into 5 o latitudinal bins show an increase in the number of craters between the 8 and 50 km diameter range with increasing northerly latitudes suggesting that the resurfacing was not a single event statistical modelling of an erosive event capable of removing the continuous ejecta deposits from the craters eroding them to reduce the apparent diameter and simultaneously burying smaller eroded craters explains both the morphology of the flat floored rimless craters and their population distribution matching the slope of the modelled curves with that of the cratered highland materials suggests that up to 1400 m of erosion may have taken place in the highlands some of this eroded material probably remained locally burying the smaller craters later stripping of this material indicated by exposed layering and inverted topography has exhumed the smaller craters in the cratered plateau material resulting in the apparent age discrepancy determined from crater counts up to 1 0 km of material may have been removed by this later erosive event to explain the low density of ancient valley networks in the cratered plateau materials