generation of gas and oil from coal and other terrestrial organic matter abstract late carboniferous permian sedimentary rocks contain the world s largest coal reserves which have generated and released gas but little if any oil in comparison organic matter deposited in lacustrine fluvial deltaic or brackish water sediments has sourced large quantities of waxy oils in countries such as china australia the u s a argentina venezuela and indonesia plus gas and condensate in deltas worldwide why is more oil coming from land derived organic matter disseminated in sediments than from the carboniferous permian coal beds which also are land deposits the answer appears to be in the hydrogen content and the ease of migration when organic matter and coals have high hydrogen contents relative to carbon they can form oil when the hydrogen is low mainly gas is formed most of the world s coal is low in hydrogen whereas much of the terrestrial organic matter disseminated in sediments is higher in hydrogen so it forms more oil also both gas and oil are adsorbed on coal more strongly than on the disseminated kerogen of sedimentary rocks this makes migration of oil out of the coal more difficult compared to migration from conventional shale source rocks

biomarker distributions in australian oils predominantly derived from terrigenous source material oils found in many australian sedimentary basins contain a relatively high input of terrigenous organic source material a study of a large number of these oils has permitted a number of biomarker distributions to be determined that appear to be characteristic for oils derived from terrigenous source material these features include the presence of sesquiterpanes absence of tricyclic terpanes relatively high concentrations of a c24 tetracyclic terpane predominance of c29 steranes presence of two unidentified c27 and c30 terpanes and virtual absence of 18 h oleanane the latter observation is significant since it appears that 18 h oleanane appears only in oils of tertiary age derived from terrigenous source material an attempt has also been made to compare the results for the australian oils with published results for oils derived from terrigenous source material in other parts of the world the number of reports in the literature for these oils is fairly limited but it appears that some of the observations for the australian oils can be extended to them this study is an initial attempt to devise a classification scheme that can be used to determine the origin of an oil unambiguously from biomarker parameters in order for this approach to be successful a relatively large number of biomarker parameters need to be assigned as characteristic of a particular type of source material

seismic images of the grenville orogen in ontario in 1990 lithoprobe acquired 240 km of seismic reflection data across parts of the central gneiss belt cgb and the central metasedimentary belt cmb within the western grenville province of southern ontario interpretation of these data in conjunction with geological constraints provided by bedrock mapping supports a model of northwest directed thrusting and crustal shortening for the grenville orogen within the cgb the parry sound shear zone is imaged as a 3 km wide zone of reflections dipping southeastward at 20 25 and soling at depths 7 km in the north and 3 km in the south beneath parry sound domain parry sound domain and the immediately adjacent domains are underlain by a gently southeast dipping reflective zone at 4 5 12 0 km depth interpreted as a detachment surface likely associated with the central britt shear zone this zone may have accommodated northwesterly transport of parry sound southern britt and northwestern rosseau domains over britt domain during grenvillian thrusting wit

geochemical and petrographic characterization of humic coals considered as possible oil source rocks abstract recently several groups of authors have argued that coals should be considered as possible source rocks for oil as well as being source rocks for gas the present study was undertaken with the objective of evaluating the various methods of characterization of maturation levels and oil potentials of coals from within the oil window it was found that the degree of maturation of a coal could not be specified exactly no matter what parameter describing coal rank was used this lack of precision obviously makes it difficult to compare coals especially from the point of view of their petroleum potential which varies during the course of coalification furthermore quantitative evalution of the oil potential of coals is difficult particularly the present day petrographic concept of exinite does not seem very well adapted to this quantitative evaluation differences in oil potential might in fact be better explained by the relative proportions of the various vitrinite macerals which are present rather than by the proportion of exinite in the coal

carbonate xenoliths hosted by the mesoproterozoic siddanpalli kimberlite cluster eastern dharwar craton implications for the geodynamic evolution of southern india and its diamond and uranium metallogenesis a number of limestone and metasomatised carbonate xenoliths occur in the 1 090 ma siddanpalli kimberlite cluster raichur kimberlite field eastern dharwar craton southern india these xenoliths are inferred to have been derived from the carbonate horizons of the kurnool palnad and bhima proterozoic basins and provide evidence for a connection between these basins in the geological past a revised mesoproterozoic age is proposed for the bhima and kurnool palnad basins based on this kimberlite association and is in agreement with similar proposals made recently for the chattisgarh and upper vindhyan sediments in central india the observed bhima kurnool interbasinal uplift may have been caused by 1 extension or plume related mafic alkaline magmatism that included the emplacement of the southern indian kimberlites at 1 1 ga 2 mantle plume related doming of the peninsular india during the cretaceous or 3 quaternary differential uplift in this region it is not possible with the currently available geological information to constrain the exact timing of this uplift the deep erosion of primary diamond sources in the raichur kimberlite field in the upper reaches of the krishna river caused by this uplift could be the elusive source of the alluvial diamonds of the krishna valley mesoproterozoic sedimentary basins can host world class unconformity type uranium deposits in light of its inferred mesoproterozoic age a more detailed stratigraphic and metallogenic analysis of the kurnool basin is suggested for uranium exploration

a laser 40ar 39ar study of minerals across the grenville front investigation of reproducible excess ar patterns 40ar 39ar ages have been determined on single grains of biotite and amphibole from rocks on a 40 km traverse across the grenville front gf in the temagami area ontario minerals in the vicinity of the gf contain excess ar in varying amounts characterized by both anomalously high integrated and plateau ages the excess ar in biotite varies with distance from the gf such that the overall age distribution along the gf forms an asymmetric wave like pattern an argonami with two age maxima one on either side of the gf the integrated age maxima are 2 34 ga for biotite and 3 21 ga for amphibole located 6 and 0 2 km north of the gf respectively whereas maxima are 1 33 ga for biotite and 1 50 ga for amphibole 7 km south of the gf this wave like pattern of apparent ages shows a remarkable similarity with that seen in an earlier k ar study across the gf at chibougamau quebec and also with a small scale pattern of excess ar associated with the emplacement of a dyke variations in the magnitude of excess a

neoarchean trondhjemitic and tonalitic orthogneisses identified within the northern grenville province in ontario by precise upb dating and petrologic studies abstract integrated field petrologic and geochronological studies reveal the presence of heretofore unrecognized neoarchean trondhjemitic and tonalitic orthogneisses north and northwest of lake nipissing in the northern grenville province of ontario the high al type trondhjemitic orthogneiss termed warren trondhjemite forms several intrusions with a total exposed area of 300 km 2 the tonalitic orthogneiss including the tilden tonalite forms a discontinuous zone of intrusions about 20 km long and up to 1 6 km wide both trondhjemitic and tonalitic orthogneisses are geochemically distinct from paragneiss that forms the country rocks precise u pb zircon and titanite dating of the warren trondhjemite at six locations and of the tilden tonalite at one location indicates that the former was emplaced at 2679 2 ma whereas the latter was intruded at 2669 4 ma a 996 to 975 ma metamorphism shown by the lower intercept ages of concordia plots of all samples caused partial pb loss from primary neoarchean zircons and titanites and also induced new growth of zircons in a local pegmatitic patch and of titanite in orthogneisses intrusive relationships between the orthogneiss and the country rock paragneiss indicate that the paragneiss is also archean in age the orthogneiss and the paragneiss together constitute an archean crustal sequence southeast of the grenville front boundary fault within the ontario segment of the grenville province this archean sequence resembles the pontiac subprovince of the superior province in western quebec in several important ways including the dominance of compositionally similar metasediments comparable depositional ages of the metasediments and contemporaneous granitoid plutonism at about 2680 to 2670 ma differences also exist between the two for example the major granitoids in the pontiac subprovince are generally more k rich

coal as a source rock for oil a review the geological debate about whether and to what extent humic coals have sourced oil is likely to continue for some time despite some important advances in our knowledge of the processes involved it is clear that not only liptinites but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification some liptinites especially alginite cutinite and suberinite contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are therefore more oil prone it is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed review of the distribution of oil prone coals in time and space reveals that most are jurassic tertiary with key examples from australia new zealand and indonesia methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals results are not entirely consistent among the different approaches and there is much overlap in the ranges of degradation but it seems probable that in the natural environment vitrinites begin to generate early followed by labile liptinites such as suberinite then cutinite sporinite and finally alginite petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro techniques especially fluorescence and infrared ir spectroscopy or bulk techniques such as elemental analysis and 13c nmr spectroscopy the latter three techniques enable a measure of the polymethylene component of the coal which now appears to be one of the best available approaches for determining petroleum potential no method of experimental simulation of petroleum generation from coals is without criticism and comparative results are highly variable however hydrous pyrolysis confined pyrolysis and forms of open system hydrous pyrolysis approach acceptable simulations whether and to what degree generated liquid hydrocarbons are expelled has long been the central problem in oil from coal studies the structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained recent studies show the pores are not interconnected combined with a dynamic model of pore generation it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries the main reason for poor expulsion is the adsorption of oil on the organic macromolecule which may be overcome 1 if coals are thin and interbedded with clastic sediments or 2 if the coals are very hydrogen rich and generate large quantities of oil the existence of oil in vitrinite is attested to by solvent extractions fluorescence properties and by microscopic observations of oil and bitumen experimental simulation of expulsion of oil from coals has only recently been attempted the relative timing of release of generated co2 and ch4 could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear as it is universally agreed that dispersed organic matter dom in some shales readily generates and expels petroleum it is curious that few consistent geochemical differences have been found between coal macerals and dom in interbedded shales unambiguous evidence of expulsion from coals is limited and in particular only a few commercial oil discoveries can be confidently correlated to coals these include upper cretaceous fruitland formation coals in the usa from which oil is produced new zealand tertiary coals and middle jurassic coals from the danish north sea it is likely that coals have at least contributed to significant oil discoveries in the gippsland basin australia in the turpan basin china and in the kutei and ardjuna basins in indonesia but this remains unproven early reports that early jurassic coals in mid norway were a major source of the reservoired oils have been shown to be inaccurate none of the proposed rules of thumb for generation or expulsion of petroleum from coals seem particularly robust decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information the assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain

main oil generating macerals for coal derived oil a case study from the jurassic coal bearing turpan basin nw china abstract this paper examines the geochemical characteristics of pyrolysates from macerals such as the alginite sporinite cutinite collotelinite and collodetrinite isolated from jurassic coals and investigates their relative contributions to oil potential in respect to the jurassic coal measures in the turpan and other basins of northwest china the alginite pyrolysate has the lightest carbon isotopic composition followed by the sporinite and cutinite while the collotelinite and collodetrinite pyrolysates show comparatively heavy carbon isotopic compositions pyrolysates from the alginite sporinite and cutinite demonstrate much lower pr ph ratios than those from the collotelinite and collodetrinite regarding the distributions of regular biomarkers such as steranes and hopanes the alginite pyrolysate is comparatively rich in c 27 steranes followed by pyrolysates from the sporinite and cutinite whereas pyrolysates from the collotelinite and collodetrinite contain little or undetectable c 27 steranes furthermore the pyrolysates from different kinds of macerals have remarkably different gammacerane concentrations the gammacerane concentrations in pyrolysates from the alginite and cutinite are higher than that from the sporinite though these macerals were separated from the same coal whereas the collotelinite and collodetrinite pyrolysates have almost no gammacerane the experimental results suggest that liptinite content in one given coal e g alginite sporinite and cutinite controls the biomarker distributions in the coal derived oils mass balance calculations of carbon isotopic compositions from the maceral pyrolysates show that the carbon isotopic composition of liquid hydrocarbons generated by organic matter in mudstone is very similar to that of most of the oils in the jurassic coal bearing basins of northwest china while liquids from coal are much heavier than that of the oils this indicates that the mudstone is likely to be the major source rocks of the oils and coals likely to be the subordinate source rocks mass balance calculation based on the maceral contents and hydrocarbon generative potential suggests that liptinites in mudstone in the jurassic coal measures of the turpan basin generate about 70 of oils while the vitrinites produce about 30 of the oils therefore the hydrogen rich liptinites alginite sporinite and cutinite are the main oil generating macerals while vitrinites collotelinite and collodetrinite are secondary oil generating macerals in the jurassic coal bearing turpan basin and other jurassic basins of northwest china

the petroleum geochemistry of canadian beaufort tertiary non marine oils abstract molecular isotopic and elemental data for a set of 28 paleogene and 3 cretaceous oils from the mackenzie delta and offshore canadian beaufort sea have been evaluated the depositional environment and organic matter characteristics of the source units for these oils have been predicted the paleogene oils of the canadian beaufort are molecularly distinctive and clearly contain a major land plant component oleanane and the 17 h and 17 h 24 28 bisnorlupanes are present as well as the following compound types 24 norlupanes and possibly higher homologues de a lupane noroleanenes norursene dehydroabietane 28 30 bisnorhopanes several molecular and isotopic characteristics are useful in assessing and ordering the extent of biodegradation and thermal maturation of these oils the cretaceous oils are separately sourced from the paleogene oils the latter oils comprise two distinct land plant derived genetic families distinguished by the presence absence of 24 28 bisnorlupanes 24 norursene 24 norlupane and 24 noroleanenes the kugmallit richards family contains each of these compound types and is considered to originate from the eocene richards formation in contrast lupanoids and noroleanenes are absent in oils of the reindeer moose channel family the occurrence of 28 30 bisnorhopane and or oleanane in these oils suggests a paleocene origin although these source rock predictions are supported by the available data they must be considered speculative until detailed molecular isotopic and elemental compositional data are available regionally for potential source rocks of the eocene and paleocene source units in the canadian beaufort

petrology and petrogenesis of mesoproterozoic lamproites from the ramadugu field nw margin of the cuddapah basin eastern dharwar craton southern india abstract petrography mineral chemistry and major and trace element data are presented for the newly discovered mesoproterozoic 1 33 1 43 ga lamproites from the ramadugu field rlf at the nw margin of the paleo mesoproterozoic cuddapah basin in the eastern dharwar craton edc southern india rlf lamproites are emplaced as dykes have a nw se trend and their petrography reveal the effects of low temperature alteration however their textural features mineralogy and geochemistry are closely similar to other well characterised lamproites worldwide including examples from the eastern dharwar craton leucite hills west kimberley smoky butte and labrador the rlf magmas have undergone varying degrees of olivine clinopyroxene fractionation yet their compatible and incompatible trace element concentrations are sufficiently high to signal a primitive character incompatible element ratios suggest limited contamination by continental crust geochemical evidence indicates the derivation of rlf magmas from metasomatised harzburgite within the garnet stability field rare earth element inversion modelling further highlights substantial involvement of the sub continental lithospheric mantle in their genesis the rlf lamproites are geochemically similar to the well known extension related ultrapotassic lavas from eastern virunga and western anatolia and exclude an affinity with orogenic lamproites such as those from the mediterranean region bulk rock geochemical models recently developed to infer diamond potential reveals that rlf lamproites are non prospective lamproites of the rlf together with those from the krishna lamproite field and cuddapah basin are interpreted as an expression of extensional events in the eastern dharwar craton possibly related to the break up of the supercontinent of columbia between 1 5 and 1 3 ga

a regional paleomagnetic study of lithotectonic domains in the central gneiss belt grenville province ontario abstract we have made a regional paleomagnetic study of lithotectonic domains in the central gneiss belt of the grenville province in ontario along ten n s and e w traverses up to 200 km in length although originally intended to clarify the tectonic mechanism by which these exotic terranes were assembled and welded to the archean superior craton during the 1150 ma grenvillian orogeny we actually learned much more about the timing of post orogenic uplift of the various domains around 1000 900 ma as they stabilized and became part of the rodinia supercontinent the normal n and reverse r natural remanent magnetizations nrms of all domains as well as those of reactivated regions flanking the grenville front gf the superior grenville boundary to the north and south have paleomagnetic poles falling on the 980 920 ma 40ar 39ar calibrated portion of the grenville apparent polar wander track for laurentia there is a general tendency for paleopoles to young with increasing distance of domains from the gf implying that more southerly domains were uplifted and magnetized later but two of the domains do not fit this pattern previously reported younging trends away from the gf based on k ar thermochron maps and paleomagnetic zone poles are untrustworthy because of hydrothermal alteration which causes chemical remagnetization and anomalously old k ar ages near the gf another trend in our data is a regular increase in the r n ratio with increasing distance south of the gf in the reactivated zones flanking the gf nrms are overwhelmingly of n polarity whereas well away from the gf r n is close to 50 50 also nrm intensities and susceptibility values increase 100 fold away from the gf peaking 10 km south of the front with a pulse like pattern similar to that documented in anomalously high 40ar 39ar dates in the same region both the magnetic and ar ar results are likely due to a wave of hydrothermal alteration and remagnetization during which fluids were driven away from the gf since the remagnetized nrm near the gf has approximately the same direction as nrms in domains away from the gf hydrothermal activity along fault systems south of the gf must have continued until 1000 ma long after the collisional orogeny itself

petrographic changes induced by artificial coalification of peat comparison of two planar facies rhizophora and cladium from the everglades mangrove complex of florida and a domed facies cyrilla from the okefenokee swamp of georgia abstract petrographic changes during coalification of three peat samples were investigated by artificial coalification experiments using a semi open reactor system compressions of from 83 to 88 produced dark brown to black shiny flattened pellets exhibiting microscopic banding overall amounts of compression inversely correlated with the framework to matrix ratios f m although certain tissue fragments remained relatively uncompressed due to the presence of tanniniferous cell fillings and also hypothetically to the presence of colorless plant secretions or gelified wall materials that were present in the cells but only recognizable after a change in color during coalification the most distinct microscopic banding longest and widest bands developed in samples of the dome formed peat facies which had the highest framework to matrix ratios of any type and the greatest contents of surface litter composing the framework i e highest s n ratio the planar root dominated rhizophora facies showed the greatest change in microbanding character during coalification in that the numerous lens like bands produced by the compressed roots were very distinct at the 60 2100 psi 121 4 kg cm 2 stage but nearly disappeared at the 175 5000 psi 289 1 kg cm 2 stage this is explained as a result of differences in rates of coalification of the different telinitic precursors in the roots multilinear vitrinization and could explain why roots are significant components of many modern peats and ancient coal ball concretions but are difficult to recognize in bituminous coals similarly separation of cuticles from leaves in modern peat forming environments due to irreversible shriveling and subsequent enhanced microbiological decay partially explains why leaf remains are also difficult to recognize in most coals even those with abundant cutinites microcracks developed in all pellets with dominant orientations of cracks being either perpendicular to induced banding or horizontal to it minute vertical microcracks interpreted as dewatering features were observed primarily in gelinitic bands especially in the most fire prone cladium coal facies but these rarely extended into juxtaposed microlithotypes as did most of the larger vertical cracks horizontal cracks tended to form at microband boundaries almost all humotelinitic and humocollinitic precursors showed some changes in color during artificial coalification with humotelinites exhibiting less or slower changes than humocolinites or humodetrinites finer grained matrix material additionally nearly all dark brown degraded tissues in the peats became dark orange or red during coalification but many of these tissue masses were observed to contain significant amounts of minute inertinite derived from microorganisms pseudomicrinite that only became prominent after coalification and subsequent change in color of surrounding macerals fusinite precursors were only found in the fire prone cladium facies and although the coalified doming generated cyrilla facies exhibited evidence of significant drying events i e occasional bands or parts of bands containing significant pseudomicrinites macrinites and sclerotinites it was dominated by huminitic vitrinitic components liptinites were most common in the coalified dome formed cyrilla facies and displayed a slight qualitative increase in red green fluorescence during coalification and some possible flow of components into nearby cracks changes in mean random reflectance of huminitic macerals although still requiring more data and only measured to the 60 c 2100 psi 121 4 kg cm 2 level indicated increasing directions of change during artificial coalification with humocollinitic macerals progressing from an average of about 0 21 to 0 32 and humotelinitic macerals which consistently had lower inherent reflectances in the peats progressing from 0 15 to 0 25 the above petrographic results along with previously reported chemical results all suggest that the methods that we have used in these experiments have produced changes that might reasonably be expected to occur during natural coalification despite the fact that we have speeded up the process although more work needs to be done to verify and refine these results and to establish a correlation between these artificial coalification steps and true coalification the new observations and conclusions from these studies might still be helpful in constructing models to predict or interpret coal seam characteristics and to establish the timing and release potential of gaseous or liquid hydrocarbons from coals

marine influence helps preserve the oil potential of coaly source rocks eocene mangahewa formation taranaki basin new zealand abstract many cretaceous cenozoic coaly source rocks in australasian and southeast asian basins were deposited in coastal plain environments yet the effect of early diagenetic marine influence on their oil potential is not well understood an integrated organic geochemical and petrographic study of humic coals from the eocene mangahewa formation taranaki basin new zealand was undertaken with coals predominantly from raised mire petrofacies with subordinate proportions from planar mires the total s content of 0 63 4 4 dry ash free indicated very slight to strong degrees of marine influence other than minor addition of inferred mangrove derived suberinite and associated liptodetrinite the degree of marine influence had no obvious effect on maceral or plant tissue abundance however hydrogen index hi values were up to ca 150 109 mg hc g toc higher and total c 6 oil potential up to ca 140 43 mg g toc higher among the more strongly marine influenced coals correlation of organic s with solvent extract parameters pristane phytane c 27 c 29 diasteranes steranes c 29 steranes hopanes c 35 c 35 c 34 homohopanes and oleanane index suggested that inundation of brackish water into the early diagenetic peat forming environment enhanced the bio resistance of higher plant and other lipids through sulfurization thereby helping to preserve more of the inherent h content and total oil potential of the original peat biomass conversely marine influence had only a minor effect on the capacity of mangahewa coals to generate paraffinic oil total n c 6 and non volatile n c 15 paraffinic oil potentials were instead controlled primarily by the abundance of leaf derived cutinite and associated liptodetrinite this in turn was dependent on the type of peat mire facies with planar mire facies having better potential for preservation of leaf litter than raised mire facies because of their generally higher groundwater level marine influence is nonetheless beneficial for paraffinic oil charge from coaly source rock sequences in that the associated higher his enhance the efficiency and quantum of paraffinic oil expulsion through increased saturation of the coal pore system

early proterozoic melt generation processes beneath the intra cratonic cuddapah basin southern india early proterozoic tholeiitic lavas and sills were emplaced during the initial phase of extension of the intra cratonic cuddapah basin southern india ar 40 ar 39 laser fusion determinations on phlogopite mica from the tadpatri fm mafic ultramafic sill complex constrain the age of the initial phase of extension and volcanism in the basin at 1 9 ga despite their early proterozoic age the igneous rocks are unmetamorphosed undeformed and remarkably fresh they exhibit a wide range in mgo contents 4 28 wt and have undergone varying degrees of accumulation or crystal fractionation variable la nb ratios 1 2 3 7 and epsilon nd values 1 to 10 suggest that some but not all of the mafic rocks have been affected by crustal contamination this appears to have taken place in magma chambers at similar to9 kbar i e the base of the continental crust forward modelling of major and trace elements fe and nd and inverse modelling of rare earth elements suggest that the primary cuddapah melts were generated by similar to10 15 partial melting of a lherzolite mantle source this corresponds to a mantle potential temperature of similar to1500degreesc the thickness of the mechanical boundary layer predicted by the geochemical modelling is 70 km with a minimum initial lithospheric thickness of 120 kin this corresponds to a stretching factor of 1 6 1 8 richter s 1988 secular cooling model for the earth predicts that at 1 9 ga the ambient mantle had a potential temperature of similar to1500degreesc i e similar to200degreesc hotter than phanerozoic mantle if the cooling model is correct then proterozoic lithospheric stretching and mantle melting beneath the intra cratonic cuddapah basin could have been caused by passive rather than active rifting

relative sea level changes recorded by paralic liptinite enriched coal facies cycles middle jurassic muslingebjerg formation hochstetter forland northeast greenland abstract the middle jurassic muslingebjerg formation of hochstetter forland northeast greenland consists of a succession of shallow marine sandstones encasing four coal seams formed in low lying coastal mires the seams are up to 3 45 m thick and contain coal facies cycles with high liptinite contents up to 70 vol the cycles generally start with huminite rich bright or banded coal and end with dull coal or clayey coal coaly claystone the dull coals are characterized by a high proportion of liptinite commonly resinite and often mineral matter liptodetrinite resinite and cutinite dominate the liptinite maceral group similarity in the relative proportions of the liptinite macerals in the bright and dull coals and the general association of bright coal and dull coal with a high resinite concentration suggest that the dull coals represent a residue after selective removal of ligno cellulosic tissues in the precursor peat of primarily the bright lithotype the clayey coal coaly claystone lithotypes have high contents of mineral matter and commonly contain alginite and pyrite occurrence of pyrite in levels with high diasterane c 27 c 29 ratios and sometimes also alginite in the clayey coal coaly claystone lithotypes indicates a marine influence during flooding of the mires this suggests a causal link between base level rise in the coastal mires and relative sea level rise accommodation space available for thick peat accumulations was governed by overall relative sea level rise and the dulling upward cycles record outpacing of peat accumulation due to accelerated rise in base level relative sea level the muslingebjerg formation consists of four depositional sequences beginning with a thick coal seam resting on a sequence boundary peat accumulation reflects onset of base level rise in the coastal area and the coals represent the lower part of the transgressive systems tract the overlying shoreface sandstones form the upper part of the transgressive systems tract and a progradational highstand systems tract alternatively the two lower seams in the succession may form a transgressive regressive couplet separated by a lagoonal sandstone split in this case a sequence boundary occurs at the top of the upper regressive seam the dulling upward cycles within the coal seams represent parasequences or possibly higher order sequences minimum age estimates suggest that they accumulated over 4000 11000 yr

unusual biological marker geochemistry of oils and possible source rocks offshore beaufort mackenzie delta canada abstract tertiary oils and source rocks from the offshore beaufort mackenzie delta have been examined for their biological marker content the triterpane and sterane distributions suggest a predominant land plant contribution to the oils the oils range in maturity from extremely immature to moderately mature 18 h oleanne is a major triterpane of the oils together with probable bisnorlupanes and an excellent correlation is observed in the concentration of these components in individual oils an excellent correlation is also observed between the concentration of bisnorlupanes and oil maturity based on sterna and triterpane maturation parameters suggesting that the decrease in relative concentration of these components with increasing maturity is a result of progressive dilution by hydrocarbons generated by the cracking of kerogen only one formation in cores taken from the delta has been found to contain bisnorlupanes and were present they are the dominant hydrocarbons of the branched cyclic fraction

petroleum source rock assessment in non marine sequences pyrolysis and petrographic analysis of australian coals and carbonaceous shales a series of australian coals and terrestrial sediments ranging in age from permian through tertiary have been analyzed to assess their petroleum source character and the suitability of various techniques for assessment of source rock potential in non marine sequences the procedures used include organic petrography rock eval pyrolysis elemental analysis and quantitative pyrolysis gas chromatography the latter procedure was used to assess the potential yield of paraffins which is critical to the assessment of most non marine source rocks principal components analysis was used to assist in the analysis of the data although the petroleum potential of the samples follows the broad trends in petrographic composition established for australian coals i e relative proportions of vitrinite inertinite and liptinite there is much variation which cannot be explained petrographically at the maceral group level further pyrolytic hydrocarbon yield is not related to overall elemental composition below an atomic h c ratio of 1 0 the yield of phenols in flash pyrolysis is related to depositional setting as well as degree of maturation the yield and carbon number distribution of normal hydrocarbons in flash pyrolysis varied widely depending on the age nature and amount of liptinite macerals particularly in samples with hydrogen indices below 300 liptinite poor 10 samples may yield significant amounts of hydrocarbons but typically they have a low wax content sporinite rich and liptodetrinite rich samples give lower yields of normal hydrocarbons these are predominantly of lower molecular weight suberinite and to a lesser extent cutinite are associated with high yields of waxy normal hydrocarbons but some samples with high yields did not contain large amounts of these maceral the correlation of tmax to vitrinite reflectance varies with petrographic composition the results have implications for the way source rock analyses are conducted and interpreted in non marine sequences

new tectonic divisions of the grenville province southeast canadian shield on the basis of geological geophysical and geochronological data the grenville province has been divided into three first order longitudinal belts the parautochthonous belt pb allochthonous polycyclic belt apb and allochthonous monocyclic belt amb these are set apart by three first order tectonic boundaries the grenville front gf allochthon boundary thrust abt and monocyclic belt boundary zone mbbz the belts are subdivided into terranes based on internal lithological character the gf separates the archean to proterozoic foreland northwest of the orogen from reworked equivalents to the southeast continuous at the scale of the orogen its main characteristic is that of a crustal scale contraction fault the pb although less clearly identified along the length of the orogen in most places represents upgraded and tectonically reworked rocks of the adjacent foreland the boundary between the pb and the apb to the southeast the abt is most clearly delineated in the eastern half of the province it is the locus of major crustal delamination along which high grade mostly middle proterozoic polycyclic terranes were tectonically transported northwest toward and onto the pb the amb comprises two separate areas underlain by the wakeham supergroup and what is currently known as the grenville supergroup respectively its basal contact the mbbz is a decollement zone of variable kinematic significance between older polycyclic rocks and tectonically overlying monocyclic rocks this first order zonation implies a tectonic polarity to the grenville province superimposed on which are second order features evident from contrasting tectonic styles and radiometric ages these characteristics are consistent with a diachronous or oblique collisional model for the grenville orogen

the biogeochemistry of ellesmere lake u k i source correlation of leaf wax inputs to the sedimentary lipid record abstract analyses of the free lipid distributions from ellesmere lake sediments taken from two depths and comparison with leaf wax lipid distributions from six deciduous tree species around the lake were made in order to assess lipid sources close correlations of aliphatic lipid distributions in the carbon number range c 20 c 50 were seen c 28 and c 29 sterols were observed in both sediment and leaf waxes but c 27 sterols were only present in the sediments and were thus assigned a nonleaf wax source unsaturated steroidal ketones were observed both in the sediment and in certain leaf waxes and were assigned specific sources alkan 2 ones were not present in the leaf waxes but were present in the sediment samples with an almost identical distribution to the sediment n alkanes indicating a microbially mediated source c 20 c 30 n aldehydes which have not previously been widely reported in free lipid distributions of freshwater lacustrine sediments were prominent in the surface sediment and in the leaf waxes examined

detrital mineral age radiogenic isotopic stratigraphy and tectonic significance of the cuddapah basin india abstract the cuddapah basin is one of a series of proterozoic basins that overlie the cratons of india that due to limited geochronological and provenance constraints have remained subject to speculation as to their time of deposition sediment source locations and tectonic geodynamic significance here we present 21 new stratigraphically constrained u pb detrital zircon samples from all the main depositional units within the cuddapah basin these data are supported by hf isotopic data from 12 of these samples that also encompass the stratigraphic range and detrital muscovite 40ar 39ar data from a sample of the srisailam formation taken together the data demonstrate that the papaghni and lower chitravati groups were sourced from the dharwar craton in what is interpreted to be a rift basin that evolved into a passive margin the nallamalai group is here constrained to be deposited between 1659 22 ma and 1590 ma it was sourced from the coeval krishna orogen to the east and was deposited in its foreland basin nallamalai group detrital zircon u pb and hf isotope values directly overlap with similar data from the ongole domain metasedimentary rocks depositional age constraints on the srisailam formation are permissive with it being coeval with the nallamalai group and it was possibly deposited within the same basin the kurnool group saw a return to dharwar craton derived provenance and is constrained to being neoproterozoic it may represent deposition in a long wavelength basin forelandward of the tonian eastern ghats orogeny detrital zircons from the gandikota formation which is traditionally considered a part of the chitravati group constrain it to being deposited after 1181 29 ma more than 700 ma after the lower chitravati group it is possible that the gandikota formation is correlative with the kurnool group the new data suggest that the nallamalai group correlates temporally and tectonically with the somanpalli group of the pranhita godavari valley basin which is tightly constrained to being deposited at 1620 ma these syn orogenic foreland basin deposits firmly link the se india proterozoic basins to their orogenic hinterland with their discovery filling a missing link in the tectonic development of the region

seismic images of a grenvillian terrane boundary a series of gently dipping reflection zones extending to mid crustal depths is recorded by seismic data from lakes ontario and erie these prominent reflection zones define a broad complex of southeast dipping ductile thrust faults in the interior of the grenville orogen one major reflection zone provides the first image of a proposed grenvillian suture the listric boundary zone between allochthonous terranes of the central gneiss and central metasedimentary belts curvilinear bands of reflections that may represent ramp folds and ramp anticlines that originally formed in a deep crustal scale duplex abut several faults vertical stacking of some curvilinear features suggests coeval or later out of sequence faulting of imbricated and folded thrust sheets grenvillian structure reflections are overlain by a thin wedge shaped package of shallow dipping reflections that probably originates from sediments deposited in a local half graben developed during a period of post grenville extension this is the first seismic evidence for such extension in this region which could have occurred during terminal collapse of the grenville orogen or could have marked the beginning of pre appalachian continental rifting

petroleum generation and migration from talang akar coals and shales offshore n w java indonesia abstract the oligocene talang akar formation is the major source for petroleum oil and gas in the ardjuna sub basin source rock quality varies within the deltaic to marginal marine complex with coals deposited on the lower delta plain being distinctly oil prone whereas the surrounding delta plain shales are largely gas prone shales and drifted coals laid down in marine influenced interdistributary bay environments show increasingly oil prone characteristics possibly due to preferential transport of hydrogen rich plant components to more distal setting molecular characteristics of the coals and shales are similar with higher plant angiosperm biomarkers and their aromatic derivatives occuring widely kinetic studies of hydrocarbon generation and stimulated maturation experiments using hydrous pyrolysis indicate that the delta plain coals are the major source for crude oils in the basin with a secondary but minor contribution from marine influenced interdistributary bay shales delta plain shales are interpreted to expel gaseous products only the stratigraphic and spatial location of oil and gas fields were examined with respect to their position relative to oil and gas generating source rocks the field distribution could not be explained in terms of source rock geochemistry alone and phase behavior of petroleum during secondary migration was shown to exert an important influence on the distribution of oil and gas deposits in the basin

crustal structure of the grenville front and adjacent terranes under the auspices of the great lakes international multidisciplinary program on crustal evolution approximately 320 km of deep seismic reflection data were collected in lake huron along a profile that extends east from the manitoulin terrane across the grenville front to the interior of the grenville orogen the manitoulin terrane is characterized by a series of gently east dipping reflections at about 20 km depth that separate a highly reflective lower crustal layer from a markedly less reflective upper layer imaged by strong reflections at the western end of a spectacular band of moderately east dipping reflections the grenville front clearly truncates manitoulin terrane structures to the west these data are interpreted in terms of a speculative two stage model involving 1 creation of a major decollement during northward collision of an allochthonous terrane with the southern superior cratonic margin 1 83 1 89 ga penokean orogeny and 2 northwest directed stacking of microterranes at the southeastern margin of the craton followed by crust penetrating ductile imbrication under high pressure high temperature conditions leading to the ramping of deeply buried rocks to the near surface 1 0 1 3 ga grenvillian orogeny

a stable carbon isotope and biological marker study of polish bituminous coals and carbonaceous shales abstract biological marker and carbon isotopic compositions of coals and carbonaceous shales from the upper carboniferous strata of the upper silesian uscb lower silesian lscb and lublin lcb coal basins were determined to assess depositional conditions and sources of the organic matter n alkane sterane and isoprenoid distribution and carbon isotope ratios are consistent with an origin from higher plants in some cases pristane phytane pr ph ratios of carbonaceous shales roof and floor shales are 29 stereoisomers typical but not conclusive of higher plant origin carbonaceous shales exhibit a wider range of sterane composition suggesting local significant input of algal organic matter significant amounts of benzohopanes and gammacerane are present in some coals although benzohopanes are present at least in small amounts in samples from many different environments they have been reported to occur most commonly in marine environments the present study seems to provide the first example where benzohopanes have been reported in significant amounts in terrestrial organic matter gammacerane is abundant in rocks or sediments deposited in carbonate or highly saline marine environments the finding of high gammacerane concentrations in the coals expands the depositional settings in which it has been observed and questions its utility as an independent indicator of hypersaline carbonate environments stable carbon isotope composition of coals and type iii kerogen in carbonaceous shales as well as correlation of stable carbon isotope composition of saturated and aromatic hydrocarbons in carbonaceous shales from both the uscb and the lscb indicate terrigenous origin bitumens are always co genetic with associated coals and kerogens isotopic data reveal that sofer s genetic classification of oils is not applicable to organic matter in coals

the cuddapah salient a tectonic model for the cuddapah basin india based on landsat image interpretation abstract analysis of geologic geophysical data and lineaments derived from landsat image interpretation has revealed a pattern of tectonic inheritance of archean structural elements by the folded and thrusted eastern margin of the middle late proterozoic cuddapah basin in india a structural pattern set by deep crustal faults in the archean and intracratonic basin fabric is apparent in both sedimentary and tectonic trends in the basin the lineaments represent broad zones of en echelon and parallel alignments that appear to have nucleated on deep crustal faults which were reactivated as structural uplifts lateral and frontal ramps and transverse tear faults the major zones recognized are the northeast trending veldruti guntur lateral ramp to the north and the northwest trending cuddapah nellore transverse tear fault to the south east west directed compression during the eastern ghats latest proterozoic orogeny was apparently confined within these converging lineament zones that effectively buttressed the west verging thrust fronts block uplift along the ne trending veldruti guntur lateral ramp acted as a boundary to east to west thrust translation the northeastern ends of folds and thrusts were pinned down with relative displacement being clockwise and greater increasing to the southwest the lack of a lateral ramp or basement buttress to the south resulted in the development of the left lateral cuddapah nellore transverse tear fault steep imbricate thrust ramps in the foreland resisted further movement westward the resulting convex to the west arcuate nallamalai and vellikonda thrust fronts broadly paralleled by the east coast gravity high anomaly kaila and bhatia 1981 is herein named the cuddapah salient

inversion of calcite twin data paleostress reconstruction and multiphase weak deformation in cratonic interior evidence from the proterozoic cuddapah basin india abstract paleostress orientations from mechanically twinned calcite in carbonate rocks and veins in the neighborhood of large faults were investigated to comment on the nature of weak upper crustal stresses affecting sedimentary successions within the proterozoic cuddapah basin india application of turner s p b t method and spang s numerical dynamic analysis on cuddapah samples provided paleostress orientations comparable to those derived from fault slip inversion results from the neighborhood of e w faults cutting through the paleoproterozoic papaghni and chitravati groups and the neoproterozoic kurnool group in the western cuddapah basin reveal existence of multiple deformation events 1 ne sw 3 in strike slip to extensional regime along with an additional event having nw se 3 for lower cuddapah samples 2 compressional transpressional event with ese wnw or nne ssw 1 mainly from younger kurnool samples integrating results from calcite twin data inversion fault slip analysis and regional geology we propose that late mesoproterozoic crustal extension led to initial opening of the kurnool sub basin subsequently influenced by weak compressional deformation the dynamic analysis of calcite twins thus constrains the stress regimes influencing basin initiation in the southern indian cratonic interior and subsequent basin inversion in relation to craton margin mobile belts and plausible global tectonic events in the proterozoic

extent of grenvillian remanence components in rocks of the southern province early aphebian gowganda sedimentary rocks and intruding nipissing diabase sills were sampled for paleomagnetic study at 88 sites 500 cores 1000 specimens along two 42 km long profiles extending north from the grenville front into the cobalt plate of the southern structural province in the river valley lake temagami area of ontario after af demagnetization a postfolding pre nipissing 2200 ma remanence was found in eight of the 37 gowganda sediment sites that were 2 km north of the front giving a pole at 109 w 63 n dp 10 dm 19 the nippissing diabase from 2 km north of the front retains a stable antiparallel prefolding n1 remanence direction in 22 of 40 sites giving a pole position of 85 w 17 s dp 6 dm 10 these south and down remanence directions found in the southern portion of the plate contrast with the antiparallel north and up directions found in the northern portion thereby indicating the occurrence of either two nearly cogenetic nipissing intrusive events or

a ramm study of thermal maturity of dispersed organic matter in marine source rocks abstract the raman maturity method ramm is a non graphical technique for thermal maturity determination based on the multi linear regression analysis of parameters derived from carbon raman spectra of humic macerals it is calibrated against vitrinite reflectance with a suite of australian mostly permian coals in a previous communication an equation to cover the range 0 4 1 2 equivalent vitrinite reflectance was derived in this report we extend the range with a second equation for the range 1 0 2 5 and validate its use by testing a series of australian permian and german carboniferous coals the special features of the technique are that it is equally applicable to vitrinite and inertinite it corrects internally for the suppression of vitrinite reflectance effect grains as small as 5 m are suitable and it does not require well depth information to be available the technique has been applied to two wells cape range 2 and dampier 1 from the rift margin of the north west shelf of australia both wells intersect large thicknesses of fine grained marine jurassic and cretaceous sediments including the major source rock formation of the carnarvon basin there are no terrestrial sediments for control there is good agreement between ramm and vr results for vr 1 2 for cape range 2 however within the oil window in both wells ramm results indicate the vitrinites in many of the samples have reflectance suppression to such a degree that the vr results would be misleading or useless for maturity modeling it is likely that this problem which is well documented for marine influenced coals to some degree affects organic matter in marine source rocks worldwide

depositional environments and oil potential of jurassic cretaceous source rocks within the seychelles microcontinent abstract the seychelles microcontinent became isolated between the somali mascarene and arabian basins of the indian ocean as a result of the mesozoic fragmentation of gondwana major rifting events occurred during the triassic middle jurassic and late cretaceous cenomanian santonian and maastrichtian during which shaly source rock facies accumulated in principally marginal marine deltaic environments between these times post rift passive margin deposition de wit et al 1988 hin restricted to open marine environments produced shaly source rocks during late middle jurassic early cretaceous campanian maastrichtian and paleocene times recent geochemical analysis of cuttings from the seagull shoals l well has identified an oil prone liptinitic type ii coaly shale de wit et al 1988 hin early middle jurassic abandoned deltaic deposits this coaly source rock is regionally developed having also been identified in the majunga and morondava basins of madagascar oil prone type ii organic matter has also been identified in the owen bank a 1 well de wit et al 1988 hin restricted marine shales of late middle jurassic age these shales are part of a thick post rift source rock sequence that extends into the early cretaeous and is in part correlative de wit et al 1988 h the proven late jurassic uarandab shale of somalia analysis of campanian marine shales from reith bank 1 well identified significant dilution of total organic carbon content in composite compared to picked well cuttings samples this finding supports a published inference that these post rift shales have source rock potential the very limited drilling of the various jurassic cretaceous source rock sequences in seychelles only three penetrations all de wit et al 1988 hin a 13 km radius indicates that they span the entire maturity window and that some have generated hydrocarbons however the petroleum system associated de wit et al 1988 h the triassic early cretaceous rift drift sequence has been tested only by three invalid wells at the western extremity of the seychelles plateau whilst that associated de wit et al 1988 h the late cretaceous rift drift sequence remains untested 1998 elsevier science ltd all rights reserved

isolation of early paleohelikian remanence in grenville anorthosites of the french river area ontario specimens were collected at 19 sites from precambrian anorthosites in the french river region of the grenville province af and thermal step demagnetization analyses indicate the presence of four components a b c and d after bulk af and thermal demagnetization at 550 650 and 670 c conventional two tiered statistical analysis reveals only the presence of the b component for the collection point density contour plots isolate objectively all four components vector subtraction shows that the a component survives up to 40 10 mt or 300 100 c and resides in magnetite its pole position of 45 w 26 n p 9 m 10 is consistent with it being a grenvillian orogenic metamorphic overprint acquired 975 ma ago at the same time as the k ar dates were reset the b component survives up to 100 mt and resides both in magnetite up to 585 c and in hematite up to 670 c its pole position of 26 w 13 s p 1 m 2 is 30 off the pre 1000 ma portions of the apw path but falls directly on the 172

shrimp u pb zircon provenance of the sullavai group of pranhita godavari basin and bairenkonda quartzite of cuddapah basin with implications for the southern indian proterozoic tectonic architecture abstract proterozoic basins in cratonic india referred to as purana basins cover about 20 of the archean basement of the subcontinent although the stratigraphy of most of these basins has been well established it is only recently that radiometric age constraints have been obtained for some of the sedimentary sequences this study provides new data for two of the purana basins in southern india using shrimp u pb analysis of detrital zircons for the pranhita godavari basin an age limit of 709 ma is provided for the age of deposition of the sullavai group this prolongs the duration of proterozoic sedimentation to approximately one billion years ca 1700 709 ma and establishes the venkatpur sandstones of sullavai group as the youngest purana basin succession identified in india so far a major zircon provenance age peak at about 1000 ma and zircon ages between 800 and 750 ma are correlated with major tectonothermal events in the eastern ghats mobile belt egmb and intrusion of granites and associated pegmatites at that time the main provenance area of the venkatpur sandstones is interpreted to be the egmb with subordinate supply of sediments from the eastern dharwar craton it is suggested that portions of the egmb must have been an integral part of peninsular india at the time of deposition of these sediments for the cuddapah basin new u pb detrital zircon age constraints are provided for the nallamalai group sediments bairenkonda quartzites within the nallamalai fold belt the youngest population of which yielded an age of ca 1550 ma this age is similar to the emplacement age of the vinukonda granite 1589 4 4 ma in the nellore schist belt this suggests that the nellore schist belt was a source region for the bairenkonda quartzites and that deposition continued until at least 1550 ma a high precision archean age ca 3366 ma for a detrital zircon grain indicates the presence of paleoarchean components within the sediment source region provided that paleoarchean rocks are as yet unknown from the largely juvenile neoarchean eastern dharwar craton there exists a possibility that the nallamalai group was sourced from the ongole domain of the egmb

deformation pattern of the nw terrane boundary of the eastern ghats mobile belt india a tectonic model and correlation with antarctica abstract thrusts interspersed with lateral ramp and wrench structures mark the join between proterozoic eastern ghats mobile belt and archaean cratons of the eastern india the join referred to as terrane boundary shear zone exhibits an arcuate geometry at the nw margin of the eastern ghats where the mobile belt shows the presence of northwesterly verging nappes based on this the area has been described to represent the salient part of a fold thrust belt juxtaposition of the granulites over the low grade craton is largely attributed to thrusting along the terrane boundary shear zone as the folds are disoriented and the granulites are retrograded along the thrusts the terrane boundary shear zone is interpreted to be a retrograde shear zone the shear zone hosts a number of synkinematic alkali intrusive rocks that constrain the age of thrusting to 1 4 ga in the correlative framework of gondwanaland the terrane boundary shear zone is very likely to be contiguous with the rayner napier boundary of antarctica

new constraints from zircon monazite and uraninite dating on the commencement of sedimentation in the cuddapah basin india the cuddapah basin in southern india consisting of the palnad srisailam kurnool and papaghni sub basins contains unmetamorphosed and undeformed sediments deposited during a long span of time in the proterozoic in the absence of robust age constraints there is considerable confusion regarding the relative timing of sedimentation in these sub basins in this study u pb isotopic dating of zircon and u th pb total dating of monazite and uraninite from the gritty quartzite that supposedly belongs to the formation banganapalle quartzite have been used to constrain the beginning of sedimentation in the palnad sub basin magmatic and detrital zircons recording an age of 2 53 ga indicate that the sediments were derived from the granitic basement or similar sources and were deposited after 2 53 ga hydrothermally altered zircons both in the basement and the cover provide concordant ages of 2 32 and 2 12 ga and date two major hydrothermal events thus the gritty quartzite must have been deposited sometime between 2 53 and 2 12 ga and represents the earliest sediments in the cuddapah basin monazite and uraninite give a wide spectrum of ages between 2 5 ga and 150 ma which indicates several pulses of hydrothermal activity over a considerable time span both in the basement granite and the overlying quartzite the new age constraints suggest that the gritty quartzite may be stratigraphically equivalent to the gulcheru quartzite that is the oldest unit in the cuddapah basin and that a sedimentary erosional hiatus exists above it

the purana basins of southern cratonic province of india a case for mesoproterozoic fossil rifts abstract since its cratonization in the palaeoproterozoic southern peninsular india witnessed the development of a number of large intracratonic sedimentary basins traditionally referred to as purana basins spanning in age from late palaeoproterozoic through neoproterozoic the localization of these intracratonic basins namely pranhita godavari pg chattisgarh and cuddapah basins is apparently controlled by pre existing sutures and or weak zones the pg basin and the cuddapah basin host unconformity bound thick sediment dominated successions attesting to several cycles of fluvial shallow marine to shelf slope basin sedimentation deposition was punctuated by block uplifts resulting in local hiatuses and or volcanic upheavals leading to intercalation of thin but persistent basaltic flows and acid tuffs and ignimbrites basin margin deep faults apparently played a role in the facies distribution in these basins based on these features we propose that these basins initiated as continental rifts which however never opened up into a full fledged ocean basin but links with open seaway are evident from frequent occurrence of deposits representing tidal and storm influence particularly in upper part of the chattisgarh succession spatial distribution of facies and sediment thickness in the cuddapah and pg basins suggest that an open seaway existed to the east of the south indian cratonic province during the mesoproterozoic while similar criteria point to the existence of an open seaway north of the chattisgarh basin development history including nature of inversion suggest that the southern cratonic province of india existed as a single large continental mass since the mesoproterozoic in spite of episodes of supercontinent build up and fragmentation involving india and east gondwana during the proterozoic

assessment of hydrocarbon source rock potential of polish bituminous coals and carbonaceous shales abstract we analyzed 40 coal samples and 45 carbonaceous shale samples of varying thermal maturity vitrinite reflectance 0 59 to 4 28 from the upper carboniferous coal bearing strata of the upper silesian lower silesian and lublin basins poland to evaluate their potential for generation and expulsion of gaseous and liquid hydrocarbons we evaluated source rock potential based on rock eval pyrolysis yield elemental composition atomic h c and o c and solvent extraction yields of bitumen an attempt was made to relate maceral composition to these source rock parameters and to composition of the organic matter and likely biological precursors a few carbonaceous shale samples contain sufficient generation potential pyrolysis assay and elemental composition to be considered potential source rocks although the extractable hydrocarbon and bitumen yields are lower than those reported in previous studies for effective type iii source rocks most samples analysed contain insufficient capacity for generation of hydrocarbons to reach thresholds required for expulsion primary migration to occur in view of these findings it is improbable that any of the coals or carbonaceous shales at the sites sampled in our study would be capable of expelling commercial amounts of oil inasmuch as a few samples contained sufficient generation capacity to be considered potential source rocks it is possible that some locations or stratigraphic zones within the coals and shales could have favourable potential but could not be clearly delimited with the number of samples analysed in our study because of their high heteroatomic content and high amount of asphaltenes the bitumens contained in the coals are less capable of generating hydrocarbons even under optimal thermal conditions than their counterpart bitumens in the shales which have a lower heteroatomic content

stratigraphic and structural development of the precambrian cuddapah basin s e india abstract the present work recognizes a subdivision of the cuddapah basin into 3 separate main units of deposition some of the earlier correlations proved to be untenable for practical reasons king s widely used stratigraphy is retained where possible in a revised form we recognise the cuddapah group 2000 1490 1450 ma nallamalai group 1490 1450 1090 870 ma and the kurnool group 1090 870 500 ma on the basis of surface geology mapping and photo interpretation we discern 5 tectonic zones the boundaries of these zones coincide with deep crustal faults encountered in a deep seismic sounding survey three phases of tectonic activity are 1 1 crustal movements resulting in broad folds affecting the cuddaph rocks exposed in the western area followed by 2 2 folding of the nallamalai rocks east of the rudravaram line and 3 3 later folding and metamorphism in the eastern tectonic zones structural sections allow an interpretation of an eastward continuation of the cuddapah basin rocks into the highly metamorphosed series underlying the eastern ghats complex a colour geological map and sections are included

mineralogy of the tk1 and tk4 kimberlites in the timmasamudram cluster wajrakarur kimberlite field india implications for lamproite magmatism in a field of kimberlites and ultramafic lamprophyres abstract a mineralogical study of the hypabyssal facies late cretaceous macrocrystic pulse of tk1 intrusion and the mesoproterozoic aphanitic pulse of tk4 intrusion in the wajrakarur kimberlite field of southern india shows that the rocks contain macrocrysts of forsteritic olivine phenocrysts and microphenocrysts of al na poor diopside and phlogopite set in a groundmass mainly of al na poor diopside and phlogopite other groundmass minerals are spinel perovskite and fluorapatite in tk1 and spinel titanite chlorite calcite and gittinsite in tk4 k richterite and perovskite occur only as inclusions in phlogopite and titanite respectively in tk4 late stage deuteric phases include pyrite and barite in tk1 and strontianite chalcopyrite galena and pentlandite in tk4 diopside microphenocrysts in tk4 exhibit oscillatory zoning with characteristics of diffusion controlled magmatic growth tk1 spinels show magmatic trend 2 that evolves from magnesiochromite and culminates in titaniferous magnetite whereas tk4 spinels are less evolved with magnesiochromite composition only tk1 phlogopites show a simple compositional trend that is typical of lamproite micas while four distinct growth zones are observed in tk4 phlogopites with the following compositional characteristics zone i high cr 2 o 3 and tio 2 and low bao zone ii low cr 2 o 3 zone iii low tio 2 and high bao zone iv low bao forsterite contents and trace element concentrations reveal two xenocrystic core populations and one magmatic rim population for tk1 olivines mineralogically both tk1 and tk4 are classified as diopside phlogopite lamproites rather than archetypal kimberlites the two lamproites are considered to have formed from the same parent magma but crystallised under distinct oxygen fugacity conditions with elevated content of fe 3 in phlogopite spinel and perovskite tk1 appears to have crystallised in a relatively high oxygen fugacity environment multiple growth generations of phlogopite spinel and fluorapatite in tk4 indicate a complex evolutionary history of the magma close spatial and temporal associations of mesoproterozoic kimberlites and lamproites in southern india can possibly be explained by a unifying model which accounts for the generation of diverse magmas from a range of geochemical resevoirs in a continental rift setting

tertiary deltaic and lacustrine organic facies comparison of biomarker and kerogen distributions abstract biological marker and kerogen compositional data in tertiary deltaic and lacustrine settings were compared and contrasted the two settings are represented by a coals and organic carbon rich shales in a ick deltaic sequence from the far east constituting three distinct organic facies and b humic coals and spropelic oil shales in a restricted intermontane freshwater lacustrine sequence from western montana u s a constituting two distinct organic facies wedistinguish the organic facies in each depositional setting by systematic differences in gross compound class distributions kerogen and infrared spectral characteristics molecular character of pyrolyzates sterane carbon number distribution and sterane hopane ratios the kerogens of the three deltaic organic facies are characterized by varying quantities of vitrinite resinite sporinite cutinite and fluorescent amorphinite triterpane distributions reveal numerous terrigenous compounds including oleanane oleanenes and unidentified c 30 presumably resin derived components the two organic facies of the freshwater lacustrine setting are distinguishedased upon either a vitrinite or an alganite fluorescent amorphinite predominance in the kerogen numerous characteristics facies related markers are also present including dehydroabietane land plant resins and 4 methylsteranes perhaps from freshwater dinoflagellate input the available molecular and petrographic data are evaluated and characteristics are proposed for distinguishing five organic facies of these two depositional settings the successful simultaneous use of molecular geochemistry and organic petrography in this study provides a format for refining the organic facies concept

determining the petroleum generating potential of coal using organic geochemistry and organic petrology abstract the ardjuna basin of northwest java is typical of many tertiary basins in that it contains high wax crude oil pyrolysis gas chromatography revealed that potential precursors of long chain waxy paraffins are present in coals of the talang akar formation and are most abundant in those that are rich in matrix liptinite conversely it was not possible to estimate waxy oil generating potential using rock eval because pyrolysates from talang akar coal are mainly comprised of naphthenic and aromatic compounds these being derived from resinite and fluorescing vitrinite because of a controlling influence by the abundance of these macerals changes in hydrogen index could not be used to assess maturity resinite and related macerals might play an especially important role in petroleum expulsion as evidenced by their high genetic potential and hence inherent capability of saturating the source rock pore system it is speculated that their maturation products while not constituting typical crude oil might pervade the coal fabric deactivate adsorptive sites and hence facilitate the expulsion of waxy oil that is generated from matrix liptinite

proterozoic evolution of eastern dharwar and bastar cratons india an overview of the intracratonic basins craton margins and mobile belts abstract based on critical analysis of stratigraphic succesions in the proterozoic intracratonic basins geochronological data and possible connections or disconnections with adjacent fold belts and craton margin mobile belts an overview of the proterozoic evolution of the eastern dharwar and bastar cratons in india is presented the chattisgarh and cuddapah basins in these cratons with archean nuclei host sedimentary successions ranging in age from the paleoproterozoic to the ediacaran period and representing several silicilastic and carbonate cycles the proterozoic successions of the pranhita godavari valley pgv basin along the dharwar bastar join record multiple rifting since late neoarchean suturing of the two cratons we postulate a first order stratigraphic correlation across the cratons and their join and discuss how major sea level fluctuations coupled with regional tectonic events shaped the development of unconformity bound successions adjoining fold belts and the mobile belts with supposed global tectonic connections the oldest paleoproterozoic intracratonic sedimentation is preserved in the cuddapah and pgv basins while sedimentation in the bastar craton is largely mesoproterozoic the fluviodeltaic to shallow marine neoproterozoic sedimentation followed emplacement of end mesoproterozoic kimberlites and lamproites indicating thermal rejuvenation of the indian continental crust the allochthonus nallamalai fold belt in eastern cuddapah basin and the early mesoproterozoic fold belt in pgv basin point to craton margin crustal convergences which punctuated the paleoproterozoic sedimentation widespread development of carbonate bearing sequences in the mesoproterozoic to neoproterozoic successions point to peneplanation of the cratons and stable platformal sedimentation the neoproterozoic sedimentation was terminated following the docking of the eastern ghats belt to the eastern margin of the dharwar bastar ensemble and possible final tectonic hiccups in the central indian tectonic zone bordering the bastar craton the available data and their analysis rule out any foreland basin type connection between the eastern ghats belt and cratonic sedimentation in bastar and eastern dharwar

neoarchean suprasubduction zone arc magmatism in southern india geochemistry zircon u pb geochronology and hf isotopes of the sittampundi anorthosite complex abstract the sittampundi anorthosite complex sac in southern india is one of the well exposed archean layered anorthosite gabbro ultramafic rock associations here we present high precision geochemical data for the various units of sac coupled with zircon u pb geochronology and hf isotopic data for the anorthosite the zircon ages define two populations the older yield a concordia age of 2541 13 ma which is interpreted as the best estimate of the magmatic crystallization age for the sittampundi anorthosite a high grade metamorphic event at 2461 15 ma is suggested by the upper intercept age of the younger zircon population a neoproterozoic event at 715 180 ma resulted in pb loss from some of the metamorphic zircons the magmatic age of the anorthosite correlates well with the timing of crystallization of the arc related 2530 ma magmatic charnockites in the adjacent salem block while the metamorphic age is synchronous with the regional metamorphic event the geochemical data suggest that the rocks were derived from a depleted mantle source sub arc mantle metasomatism of slab derived fluids and subsequent partial melting produced hydrous aluminous basalt magma the magma fractionated at depth to produce a variety of high alumina basalt compositions from which the anorthositic complex with its chromite rich and amphibole rich layers formed as cumulates within the magma chamber of a supra subduction zone arc the coherent initial176hf 177hf ratios and positive ehf values 1 7 4 5 of the magmatic zircons in the anorthosite are consistent with derivation of a rather homogeneous juvenile parent magma from a depleted mantle source our study further confirms that the southern part of the dharwar craton was an active convergent margin during the neoarchean with the generation and emplacement of suprasubduction zone arc magmas which played a significant role in continental growth

alkaline magmatism along the southeastern margin of the indian shield implications for regional geodynamics and constraints on craton eastern ghats belt suturing abstract deformed alkaline complexes at the contact between the eastern ghats belt egb and the archaean cratons in southeastern india mark the location of a collisional suture superimposing an earlier mesoproterozoic 1 5 1 3 ga rift this article offers a plausible geodynamic model explaining the alkaline magmatism and its relationship to regional crustal evolution the mesoproterozoic rift can be correlated to the breakup of the supercontinent columbia and may have opened an ocean between eastern india and east antarctica where the sedimentary sequences of the eastern ghats province egp were deposited between 1 4 and 1 2 ga inversion of the rift basin during the late mesoproterozoic 1 0 ga led to the collision of eastern india with east antarctica during rodinia assembly the collision formed the grenvillian egp rayner complex orogen where the egp sediments and the rocks of the rayner complex were deformed metamorphosed and migmatized at granulite facies condition the mesoproterozoic rifting and grenvillian basin closure may thus represent a wilson cycle related to the breakup of columbia and the assembly of rodinia the craton egb suture was subsequently modified significantly during pan african tectonism 0 5 0 6 ga when the egb granulites were thrust westward over the cratonic foreland along a number of amphibolite facies shear zones at the contact the shearing deformed and metamorphosed the cratonic margin and the alkaline complexes it hosts the thrust stacking in many places has the craton boundary and the alkaline rocks in the footwall and the egb granulites in the hanging wall the continuity of the pan african shear fabric across the craton granulite contact and the lack of grenvillian ages from the alkaline and other craton margin rocks in such regions give the apparent impression that the two crustal segments amalgamated during pan african tectonism and not during the earlier grenvillian collision geodynamic constraints however indicate that this was unlikely and the inconsistency arises because the present crustal geometry exposes only the eroded pan african thrust contact between the craton and the egb and not the original grenvillian suture which may be lying unexposed under the granulite thrust sheets

precise u pb ages for grenvillian and pre grenvillian thrusting of proterozoic and archean metamorphic assemblages in the grenville front tectonic zone canada while the position of the grenville front is placed at a structural feature associated with the onset of high grade rocks when approached from the north the time of first metamorphism in these rocks is in general pre grenvillian and highly variable at killarney amphibolite to granulite grade rocks were metamorphosed lineated and foliated to their present front parallel configuration mainly by 1453 6 ma north of north bay amphibolite grade migmatites have been subjected to a pre 2650 ma metamorphism granulite grade gneisses south of the grenville front near val d or record a 2640 ma metamorphic event south of chibougamau mafic enclaves in tonalite south of the front were converted to migmatitic amphibolite at about 2680 to 2690 ma in central labrador a 1650 ma foliated granite is present south of the grenville front and at least some of the banding is this old at the atlantic coast granulite facies metamorphism in front parallel gneisses predates a 1790 1662 ma deformation in contrast each of these areas shares a near common age of second metamorphism that is variable in degree and accompanies nw directed thrusting or crustal loading near killarney on georgian bay titanite records an episode of 977 2 ma partial resetting the degree of which increases with distance into the grenville province here grenvillian deformation where present is manifest as feldspar porphyroclastic fabric with strong se plunging lineations near north bay archean pegmatites in the grenville front zone were similarly deformed at 988 10 ma and strongly rodded ductile amphibolite underwent late melting to produce postlineation tonalite in which new zircon tips grew at 987 2 ma a 991 4 ma cooling age for titanite in this melt is analytically identical to the zircon growth age hence rapid cooling occurred south of chibougamau new zircons grew in high pressure coronite in response to tectonic loading at 995 6 ma and in central labrador melt pods that developed in 1650 granites in response to thrusting record a zircon new growth age of 995 2 ma titanite in the granitic host rock has an analytically identical age of 992 4 ma again indicating rapid cooling this second event is recorded by 28 titanite and zircon analyses for samples up to 225 km apart that record a 1651 5 ma to 988 5 ma two age mixing line grenville resetting at about 1037 19 ma in the grenville front zone on the labrador coast is indicated but major thrusting is pre 1662 ma u pb isotopic results indicate that the grenville front zone is characterized along its length by partially reset u pb systems high pressure assemblages local melting and rapid cooling crustal loading and shearing with lead loss related to mechanically induced recrystallization and local heat that was rapidly terminated by rebound and cooling are required