the effect of clay minerals on diasterane sterane ratios to examine the effect of clay minerals on diasterane sterane ratios the mineral compositions of three sample sets of sedimentary rocks displaying a wide range of diasterane sterane ratios were analysed quantitatively diasterane sterane ratios do not to correlate with clay content but depend on the amount of clay relative to the amount of organic matter clay toc ratios this correlation may explain the high diasterane sterane ratios in crude oils and extracts derived from certain carbonate source rocks based on the concentrations of regular and rearranged steroids in the sample sets it is proposed that diasterenes are partly reduced to diasteranes and partly degraded during diagenesis in a ratio largely determined by the availability of clay minerals it is suggested that the hydrogen atoms required for reduction of the diasterenes originate from the water in the interlayers of clay minerals

palinspastic reconstruction and topographic evolution of the eastern alps during late tertiary tectonic extrusion this paper presents a new palinspastic restoration of the eastern alps for neogene time and an attempt to reconstruct the neogene palaeogeology palaeotopography and palaeohydrography in connection with the structural evolution the eastern alps underwent radical horizontal displacement during the neogene due to large strike slip systems and formation of structural windows our palinspastic reconstruction considers a the rearrangement of tectonic units dismembered during tectonic extrusion b the tectonic denudation driven by displacement of the crystalline blocks c geochronological arguments and d the sedimentary record of the syn extrusion basins the rearrangement of tectonic blocks results in a remarkably good fit of highly dismembered zones both in crystalline and sedimentary areas and shows the pre miocene unstretched pattern of the eastern alps reduced to 65 of its present day e w elongation using this structural frame and considering the sedimentary record a set of palaeogeologic and palaeotopographic sketch maps with the palaeo river systems is presented for three time slices pre syn and post extension situation in late oligocene and early miocene times the western eastern alps were already mountainous whereas the eastern part of the orogen formed lowlands or hilly areas enhanced block movement in the course of the extrusion process around the early middle miocene boundary led to the formation of intramontane sedimentary basins and a fault induced reorientation of the drainage pattern which forms the basis of the modern river system in the area east of the tauern window this region where pre miocene land surfaces are preserved probably became a mountainous area not before late miocene time and never reached the elevations of the areas further west

organic matter rich shales of china abstract organic matter rich shales are the main target rocks for unconventional oil and gas exploration and development across the world in china shale gas geological resources are estimated as approximately 110 1012 m3 with recoverable gas reserves of ca 20 1012 m3 recoverable shale oil reserves are estimated as ca 5 109 t a total 35 important organic matter rich shale units have been recognized from mesoproterozoic to cenozoic strata across the entire china these shales are categorized according to their origin under marine marine nonmarine transitional and lacustrine conditions shales of marine origin with ca 9 1012 m3 recoverable resources dominate china s potential in terms of total volume of organic carbon currently the most favorable marine shales for oil and gas exploration are found in the sichuan basin within the lower cambrian qiongzhusi formation and in the wufeng longmaxi formations of uppermost ordovician through lower silurian a fortuitous combination of of sea level variations of paleo productivity of tectonic activity causing development and migration of partially closed deep basin depocenters and of sediment accumulation rates controlled the extensive deposition and distribution of organic matter rich shales in these wufeng and longmaxi formations organic matter rich shales in marine nonmarine transitional facies associated with coal measures occur in north china within the carboniferous and permian and in south china within the permian these carboniferous permian organic matter rich shales are important source rocks for the gas fields in the ordos and sichuan basins abundant organic rich shales are also widely distributed within coal bearing clastics and coal measure shales of fluvial lacustrine and swamp facies in upper triassic to middle jurassic successions of many basins lacustrine organic rich shales were deposited during the permian through neogene in various freshwater to saline lake settings lacustrine organic matter rich shales are the main oil source rocks in the songliao bohai bay ordos and junggar basins lacustrine algae contributed to the rain of organic matter and the preservation of organic matter and distribution of organic rich shale was controlled by lake currents water depth and oxygen poor conditions with enhanced preservation when buried by turbidity currents algal blooms were partly induced by trace nutrients from volcanic ash falls in all of these lacustrine basins seawater intrusion into the freshwater lake of the songliao basin promoted some episodes of black shales saline lacustrine basins such as middle permian junggar basin contain organic rich dolomite mudstone that mainly formed during hot climate conditions when the lakes had high salinity and stratified water columns that deprived the bottom waters of oxygen thereby preserving massive amounts of organic matter laminated calcite rich mudstone in the saline lacustrine settings formed in more brackish waters under stable warm conditions and weak biological activity the modeling of the factors controlling the distribution of organic matter rich shales within china s basins is important for the exploration and development of unconventional oil and gas resources

the western mediterranean extensional basins and the alpine orogen the western mediterranean late oligocene miocene basins alboran valencia and provencal basins are a coherent system of interrelated troughs in all basins normal faults and thermal subsidence migrated toward the east progressively moving to the miocene to pleistocene algerian and tyrrhenian basins all those troughs appear elements of the back arc opening related to the eastward roll back of the w directed apennines maghrebides subduction zone similarly to western pacific back arc settings these late oligocene early miocene basins nucleated both within the betic cordillera e g alboran sea and in its foreland valencia and provencal troughs the n40 70 direction of grabens is oblique to the coexisting n60 80 trending orogen and shows its structural independence from the orogenic roots thus as the extension cross cuts the orogen and developed also well outside the thrust belt front the westernmost basins of the mediterranean had to develop independently from the alps betics orogen therefore the alboran extension considered a classic example of a basin generated by the collapse of an orogen cannot be ascribed to the detachment or annihilation of the lithospheric root in contrast with the eastward migrating extensional basins the betic balearic thrust front was migrating westward producing interference or inversion structures

the barnett shale compositional fractionation associated with intraformational petroleum migration retention and expulsion abstract the marathon 1 mesquite well was drilled in hamilton county texas targeting the barnett shale with late oil window maturity combining a large suite of petrologic and high resolution organic geochemical analyses on 120 core samples we have been able to document qualitatively and quantitatively the effects of petroleum retention within and expulsion from five intervals within the barnett shale lithological heterogeneities control the composition and amount of retained fluids the sorption of oil by solid organic matter is important in all intervals applying empirical formulas we have been able to demonstrate not only that retention is primarily controlled by total organic carbon toc but also that the live or labile component rather than dead or inert carbon constitutes the most active sorptive sites additional retention in the micropores provided by biogenic microcrystalline quartz sponge spicules accounts for the sweet spot defined by an oil crossover in the 9 14 m 30 ft thick second interval the fluorescing oil occurring in the axial chamber of the sponge spicules and that sorbed on organic particles are together enriched in saturated hydrocarbons whereas the dispersed oil from the adjacent interval 3 is depleted in this compound class mass balance calculations reveal that short distance migration of petroleum into this reservoir interval second fractionates the generated oil into a higher quality oil by preferential retention in the order polar compounds aromatic hydrocarbons saturated hydrocarbons within the underlying organic matter and clay rich third interval source unit furthermore molecular fractionation i e a preferential expulsion of lower molecular weight hydrocarbons n alkanes could be calculated an additional practical result for source rock assessment is that corrected s2 petroleum generated by pyrolysis and toc values should be calculated by combining rock eval pyrolysis data on whole rocks and rocks following soxhlet extraction using parameters based on unextracted rock only the expulsion of petroleum is systematically overestimated and the degree of kerogen conversion is therefore concomitantly underestimated

lateral extrusion in the eastern alps part 1 boundary conditions and experiments scaled for gravity lateral extrusion encompasses extensional collapse gravitational spreading away from a topographic high in an orogenic belt and tectonic escape plane strain horizontal motion of wedges driven by forces applied to their boundaries in the eastern alps it resulted from 1 an overall northerly compression apulia against eurasia 2 a strong foreland bohemian massif 3 lack of constraint along a lateral boundary carpathian region and 4 a previously thickened gravitationally unstable thermally weakened crust eastern alpine orogenic belt six indentation experiments reproduce lateral extrusion at lithospheric scale the models have two to four lithospheric layers with a mohr coulomb rheology for the upper and a viscous rheology for the lower crust the lithosphere rests upon a low viscosity asthenosphere a broad indenter a narrow deformable area and a weakly constrained eastern margin fullfill as closely as possible conditions in the eastern alps indentation produces both thickening in front of the indenter and escape of triangular wedges lateral variations in crustal thickness become attenuated by gravitational spreading the overall fault pattern includes domains of reverse strike slip oblique normal and pure normal faults strike slip faults in conjugate sets develop serially the narrow width of the deformable area and the strength of the foreland determine the angles between the sets gravitational spreading produces a rhombohedral pattern of oblique and pure normal faults along the unconstrained margin opposite the unconstrained margin the indenter front shows thrusts and folds intersecting with the conjugate strike slip sets a triangular indenter favors spreading high velocity of indentation favors escape high confinement limits lateral motion inhibits spreading and favors thickening lateral extrusion in the eastern alps is best modeled by 1 a weak lateral confinement 2 a broad and straight indenter 3 a narrow width of the deformable area and 4 a rigid foreland crustal thickening lateral escape and gravitational spreading all contribute to the overall deformation

extension in compressional orogenic belts the eastern alps extension in the eastern alps encompasses the following 1 extension accompanying simple shear crustal stacking subhorizontal stretching occurs along flat lying foliations and regionally consistent stretching lineations with associated high strains on a local scale stretching results from extrusion of ductile sediments squeezed between rigid basement blocks basement blocks during thrust sheet imbrication the overall geometric effect is crustal thickening 2 classical extensional tectonics extension first occurs as a consequence of accretion and underthrusting of continental and oceanic material and represents gravitational adjustment of an unstable orogenic wedge extension then occurs as a consequence of terminal continental collision and is accommodated by lateral extrusion of crustal of crustal blocks the overall geometric effect is crustal thinning extension is generally oriented subparallel to the strike of the orogen

organic petrology of source rocks history and state of the art abstract the development of organic source rock petrology depended on the methods applied a procedure derived from coal petrology is the study of polished sections of the untreated rock under incident light this method combined with the fluorescence techniques is best suited to characterize and identify the discrete organic matter macerals and permits the most reliabble maturity measurements on the basis of vitrinite reflectance and of various fluorescence parameters another common method treats the rock with acids and studies strew slides of organic matter concentrates this destroys the natural texture of the rock and often some of the individual macerals as well but on the other hand it allows recognition of extremely fine particles which are not resolvable in polished sections maturity studies based on maceral colour changes as observed in strew slides are rapid and practical although they are rather subjective the relative merits of the various methods are discussed the individual organic constituents as seen in the whole rock and in organic matter concentrates are described and illustrated in two colour plates some classification systems are compared in tabular form finally the history of microscopic observations and measurements with respect to the generation of petroleum like substances in coal is briefly reviewed

geochemical correlation of windalia oil and extracts of winning group cretaceous potential source rocks barrow subbasin western australia windalia oil is a commercial accumulation in a cretaceous reservoir at barrow island western australia a chemical correlation study has been made between this oil and hydrocarbons extracted from 37 cretaceous sedimentary rock samples from different stratigraphic levels in seven wells on and around barrow island seven established correlation parameters and one new parameter have been applied to establish oil source rock relations the new parameter is the ratio of pristane heptadecane to phytane octadecane the influence of maturation on several correlation parameters has been investigated by pyrolyzing source rocks at 300 c for varying times the changes observed in these experiments have been used to infer the effects which maturation processes have on the co relation parameters to assess the overall degree of correlation between source rock extracts and oil each method has been assigned a weighting which reflects its power as a correlation technique an overall correlation score was obtained for each potential source rock by totaling the contributions from the eight individual methods it appears likely that the windalia oil had its source within the winning group of sedimentary rocks the most probable source formations being the middle shale of the windalia sandstone member the muderong shale and the windalia radiolarite several mechanisms of formation of windalia oil from these source beds are possible

reconstructing the alps carpathians dinarides as a key to understanding switches in subduction polarity slab gaps and surface motion palinspastic map reconstructions and plate motion studies reveal that switches in subduction polarity and the opening of slab gaps beneath the alps and dinarides were triggered by slab tearing and involved widespread intracrustal and crust mantle decoupling during adria europe collision in particular the switch from south directed european subduction to north directed wrong way adriatic subduction beneath the eastern alps was preconditioned by two slab tearing events that were continuous in cenozoic time 1 late eocene to early oligocene rupturing of the oppositely dipping european and adriatic slabs these ruptures nucleated along a trench trench transfer fault connecting the alps and dinarides 2 oligocene to miocene steepening and tearing of the remaining european slab under the eastern alps and western carpathians while subduction of european lithosphere continued beneath the western and central alps following the first event post late eocene nw motion of the adriatic plate with respect to europe opened a gap along the alps dinarides transfer fault which was filled with upwelling asthenosphere the resulting thermal erosion of the lithosphere led to the present slab gap beneath the northern dinarides this upwelling also weakened the upper plate of the easternmost part of the alpine orogen and induced widespread crust mantle decoupling thus facilitating pannonian extension and roll back subduction of the carpathian oceanic embayment the second slab tearing event triggered uplift and peneplainization in the eastern alps while opening a second slab gap still present between the eastern and central alps that was partly filled by northward counterclockwise subduction of previously unsubducted adriatic continental lithosphere in miocene time adriatic subduction thus jumped westward from the dinarides into the heart of the alpine orogen where northward indentation and wedging of adriatic crust led to rapid exhumation and orogen parallel escape of decoupled eastern alpine crust toward the pannonian basin the plate reconstructions presented here suggest that miocene subduction and indentation of adriatic lithosphere in the eastern alps were driven primarily by the northward push of the african plate and possibly enhanced by neutral buoyancy of the slab itself which included dense lower crust of the adriatic continental margin

a study of the 2006 and 2007 earthquake sequence of pisco peru with insar and teleseismic data 1 we combine interferometric synthetic aperture radar insar and teleseismic body waves to study the largest earthquake mw 8 1 in a sequence of events on the subduction megathrust near pisco peru our analysis includes some of the first insar data from the alos satellite and wide swath data from the envisat satellite the teleseismic data indicate the slip maximum occurred 60 90 seconds after the mainshock started the insar data constrain the main slip patch to be about 70 km from the hypocenter suggesting an extremely low rupture velocity 1 5 km s or long slip rise time no large earthquake has occurred in the 2007 rupture area since at least 1746 and possibly 1687 suggesting significant aseismic deformation in the area the slip deficit apparently cannot be filled with rapid after slip in addition the area where the nazca ridge is subducting appears to be either a seismic gap or a persistent area of aseismic slip

diamondoid hydrocarbon ratios novel maturity indices for highly mature crude oils abstract diamondoid hydrocarbons have been identified in oil and source rock samples from the tarim yinggehai qiongdongnan and other chinese basins two diamondoid hydrocarbon ratios have been used as novel high maturity indices to evaluate the maturation and evolution of crude oils and condensates in these chinese basins the two ratios 1 ma 1 ma 2 ma mai methyl adamantane index and 4 md 1 md 3 md 4 md mdi methyl diamantane index were found to increase with increasing vitrinite reflectance the initial values for the ratios are ca 50 and 30 respectively diamondoid hydrocarbons are products of rearrangement of polycyclic hydrocarbons and their ratios are found to be affected by organic input to a minor extent based on this study crude oils from the tarim basin are generally believed to be very mature ro 1 1 the cambrian ordovician source beds are the major source rocks of crude oils and natural gases in this basin condensates from the tarim yinggehai and qiongdongnan basins have higher maturities equivalent to ro values of 1 6 2 0 gases and condensates from the yinggehai and qiongdongnan basins are generated mainly from tertiary source rocks below 4000 5000 m

multistage accretion and exhumation of the continental crust ivrea crustal section italy and switzerland the ivrea crustal section exposes in map view all levels of the southern alpine continental crust from ultramafic mafic and felsic granulite facies rocks of the deep crust ivrea verbano zone through medium grade basement rocks strona ceneri zone and val colla zone to unmetamorphosed permo mesozoic sediments the oldest part of the crustal section is preserved in the medium grade basement units which are interpreted to be the overprinted remains of an ordovician 440 480 ma magmatic arc or forearc complex during variscan subduction this arc was technically underplated by a carboniferous accretion subduction complex 320 355 ma containing metasediments and slivers of rheic oceanic crust presently found in the ivrea verbano zone during the late stages of variscan convergence 290 320 ma lithospheric delamination triggered magmatic underplating and lead to polyphase deformation under amphibolite to granulite facies conditions this was broadly coeval with extensional exhumation and erosion of the variscan overprinted ordovician crust presently exposed in the strona ceneri and val colla zones post variscan transtensional tectonics 270 290 ma were associated with renewed magmatic underplating mylonitic shearing and incipient exhumation of the lower crust in the ivrea verbano zone this coincided with the formation of elongate basins filled with volcanoclastic sediments in the upper crust early mesozoic tethyan rifting of the southern alpine crust 180 230 ma reduced crustal thickness to 10 km or less in the lower crust most of this thinning was accommodated by granulite to retrograde greenschist facies mylonitic shearing the lower crust was exhumed along a large noncoaxial mylonitic shear zone that was linked to asymmetrical rift basins in the upper crust the composite structure resulting from this complex evolution is probably typical of thinned late variscan continental crust on the passive margins of western europe alpine faulting and folding 20 50 ma fragmented the crustal section the originally deepest levels of the crustal section in the ivrea verbano zone as well as some segments of the basement cover contact were steepened whereas other parts of the crustal section particularly the strona ceneri zone underwent only minor to moderate alpine rotation

precise maturity assessment over a broad dynamic range using polycyclic and heterocyclic aromatic compounds abstract the construction and reliable application of maturation indices is extremely important in deep earth exploration yet predicting levels of maturation on a molecular level especially at overmature stages is still a major challenge here we report robust broad ranging and precise maturity parameters that were developed using a continuous core of thermally overmature lacustrine deposits shahezi fm from the deep songke 2 well sk 2 songliao basin china augmented by shallow cores of lower maturity marine deposits posidonia shale from the hils syncline germany the novel indices presented here are based on the general process of thermally induced cyclization aromatization and aliphatic chain cracking of hundreds to thousands of compounds during maturation the newly developed parameters with an extremely broad dynamic range extending from catagenesis and into metagenesis vitrinite reflectances ro range from 0 9 to 2 2 are based on polycyclic and heterocyclic aromatic compounds measured using fourier transform ion cyclotron resonance mass spectrometry ft icr ms the high coefficient of correlations between the new maturity parameters with ro and tmax demonstrate their utility for assessing precisely the thermal maturity of overmature shales

cenozoic granitoids in the dinarides of southern serbia age of intrusion isotope geochemistry exhumation history and significance for the geodynamic evolution of the balkan peninsula two age groups were determined for the cenozoic granitoids in the dinarides of southern serbia by high precision single grain u pb dating of thermally annealed and chemically abraded zircons 1 oligocene ages kopaonik drenje eljin ranging from 31 7 to 30 6 ma 2 miocene ages golija and polumir at 20 58 20 17 and 18 06 17 74 ma respectively apatite fission track central ages modelling combined with zircon central ages and additionally local structural observations constrain the subsequent exhumation history of the magmatic rocks they indicate rapid cooling from above 300 c to ca 80 c between 16 and 10 ma for both age groups induced by extensional exhumation of the plutons located in the footwall of core complexes hence miocene magmatism and core complex formation not only affected the pannonian basin but also a part of the mountainous areas of the internal dinarides based on an extensive set of existing age data combined with our own analyses we propose a geodynamical model for the balkan peninsula the late eocene to oligocene magmatism which affects the adria derived lower plate units of the internal dinarides was caused by delamination of the adriatic mantle from the overlying crust associated with post collisional convergence that propagated outward into the external dinarides miocene magmatism on the other hand is associated with core complex formation along the southern margin of the pannonian basin probably associated with the w directed subduction of the european lithosphere beneath the carpathians and interfering with ongoing dinaridic hellenic back arc extension

on the causes and modes of exhumation and lateral growth of the alps 1 a compilation of the apatite and zircon fission track ages of the alpine chain points to markedly different patterns of cooling and exhumation of the eastern alps compared to the central and western alps the site of exhumation and shortening in the western alps migrated outward whereas it was more stationary in the eastern alps where it created a narrower metamorphic belt a correlation of these observations to the deep structure of the orogen suggests that north directed lower crustal wedging induces northward propagation of the deformation and exhumation front in the middle and upper crust of the central and western alps the absence of such lower crustal wedges in the eastern alps does not induce a similar shift of deformation but rather a long term localization of shortening and exhumation in one and the same area namely the axial zone of the orogen a critical review of the temporal correlations between inferred changes in the erosional efficiency of the alps and tectonic phases points to a negative correlation and hence no erosional control on the shifts of the deformation front of the alps therefore we conclude that changes in the deep structure and rheology of the orogen instead of changes in its erosional efficiency exerted the prime control on the lateral growth of the alps

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

crustal scale geometry and kinematics of late orogenic extension in the central aegean cyclades and ewia island abstract the aegean continental domain is known to be the site of widespread back arc extension since at least the middle miocene overprinting structures related to the mesozoic cenozoic hellenic orogeny features attributed to early thrusting include the overall ductile deformation within two broad belts that have suffered hp lt metamorphism across the aegean this study summarizes the results of a structural study in the central aegean area cyclades and evvia island examining in particular the relationship between ductile and brittle deformation on a regional scale extension appears to be responsible for most of the ductile deformation within hp rock units that have experienced penetrative greenschist facies and higher grade metamorphic overprinting on each island studied progressive extensional deformation has occurred through the development of a major normal sense detachment zone down to depths of about 18 25 km the geometry of the extensional system on the scale of the central aegean is described taking into account the characteristic features of the regional scale ductile strain field at least two probably three subparallel major north dipping detachment zones are identified trending nw se in the northwestern cyclades and e w in the southeastern cyclades both with initial dips estimated at around 30 45 the present geometry of the extensional system implies that these detachment zones and related metamorphic core complexes interfere with each other two main evolutionary models are considered which can account for such a kinematic link between parallel detachment zones structural data favour the sequential development of synthetic major detachments zones in a direction opposite to the sense of dip of the detachments early oligocene lower miocene detachment type extension in the area studied is related to a late orogenic post thickening back arc setting

new paleocene eocene paleomagnetic results from the foreland of the southern alps confirm decoupling of stable adria from the african plate abstract from the undeformed foreland of the southern alps paleocene through early miocene rocks mostly biostratigraphically well dated sediments with sub horizontal bed attitude were collected for a paleomagnetic study from 23 geographically distributed localities the samples were subjected to standard paleomagnetic measurements and evaluation while the miocene samples are unstable most of the older localities yielded statistically well defined paleomagnetic directions these are interpreted as primary for the compact marls supported by positive between locality tilt and reversal tests this large group of localities is characterized by ccw rotated declinations with respect to the present north combined with paleomagnetic directions of corresponding age from stable istria these allow definition of the apw for stable adria for the 61 6 33 9 ma interval which is significantly displaced from the coeval segment of the african apw due to the decoupling of the former to the latter by a moderate ccw rotation this post eocene final separation exact age is not constrained directly but estimated as end of miocene was preceded by a small cw rotation of adria with respect to africa suggested by unchanged orientation of the former across the cretaceous paleocene boundary while the latter continued its ccw rotation

late cretaceous intra oceanic magmatism in the internal dinarides northern bosnia and herzegovina implications for the collision of the adriatic and european plates abstract the kozara mountains of northern bosnia and hercegovina form part of the internal dinarides and host two tectonically juxtaposed ophiolitic successions of different age the southern part of the kozara mountains exposes the western vardar ophiolitic unit which was obducted onto the adriatic margin in the late jurassic the northern part exposes a bimodal igneous succession that was thrust onto the western vardar ophiolitic unit during the latest cretaceous to early paleogene this bimodal igneous succession comprises isotropic gabbros doleritic dikes basaltic pillow lavas and rhyolites pelagic limestones intercalated with pillow lavas yielded a campanian globotruncanid association consistent with concordant u pb ages on zircons from dolerites and rhyolites of 81 39 0 11 and 81 6 0 12 ma respectively chondrite normalised rare earth element patterns of the bimodal igneous rocks show enrichment of lree over hree primitive mantle normalised multi element diagrams do not reveal significant depletion of hfse the end t and initial 87sr 86sr isotopic values range from 4 4 to 6 3 and from 0 70346 to 0 70507 respectively suggesting an intraoceanic origin the bimodal igneous succession is unconformably overlain by maastrichtian to paleocene siliciclastics that contain abundant ophiolitic detritus suggesting reworking of the campanian magmatics an eocene turbiditic sandstone succession unconformably covers both the western vardar ophiolitic unit and the late cretaceous bimodal igneous successions these observations suggest that the adriatic plate and the europe derived tisza and dacia mega units were still separated by a deep basin floored by oceanic lithosphere until the campanian and that its closure did not occur before the maastrichtian to earliest paleogene this late cretaceous oceanic domain probably represented a remnant of the vardar ocean or alternatively the alpine tethys possibly the traces of both oceanic domains were connected in the area

sedimentary record and tectonic implications of mesozoic rifting in southeast mongolia the east gobi basin of mongolia is a poorly described late jurassic early cretaceous extensional province that holds great importance for reconstructions of mesozoic tectonics and paleogeography of eastern asia extension is especially well recorded in the structure and stratigraphy of the unegt and zuunbayan subbasins southwest of saynshand mongolia where outcrop and subsurface relationships permit recognition of prerift synrift and postrift mesozoic stratigraphic megasequences within the synrift megasequence three sequences developed in response to climatic and rift related structural controls on sedimentation where best exposed along the northern margin of the unegt subbasin each of the synrift sequences is bounded by unconformities and generally fines upward from basal alluvial and fluvial conglomerate to fluvial and lacustrine sandstone and mudstone resedimented ashes and basalt flows punctuate the synrift megasequence rifting began in the unegt subbasin prior to 155 ma with coarse alluvial filling of local fault depressions subsidence generally outstripped sediment supply and fresh to saline lacustrine environments expanding southward with time dominated the unegt zuunbayan landscape for much of latest jurassic early cretaceous time episodic faulting and volcanism characterized the basin system for the balance of the early cretaceous a brief period of compressional and or transpressional basin inversion occurred at the end of the early cretaceous prior to deposition of a widespread upper cretaceous overlap sequence the driver s of late jurassic early cretaceous extension remain uncertain because southeast mongolia occupied an intraplate position by the beginning of the cretaceous extension in the east gobi basin was coeval with collapse and extension of early mesozoic contractional orogenic belts along the northern and southern borders of mongolia and probably was a linked phenomenon strike slip faulting associated with collisions on the southern asian and mongol okhotsk margins likely also played a role in late mesozoic deformation of the east gobi region perhaps partitioning the gobi from apparently coeval large magnitude contractional deformation in the yinshan yanshan orogenic belt south of the study area in inner mongolia

biomarker maturity parameters the role of generation and thermal degradation abstract the effects of burial maturation upon seven molecular maturity parameters and the concentrations of individual biomarkers employed in these parameters have been studied in a well in the barents sea the depth interval between 1400 and 3000 m comprises homogenous eocene claystones with effectively uniform organic carbon content 0 4 0 6 and kerogen type hi of 100 200 mg hc g toc the quantitative biomarker data thus contain minimal interference from organic facies hydrocarbon expulsion effects and the presence of migrated hydrocarbons bulk geochemical data define the hydrocarbon generation threshold or oil window at around 2300 m molecular maturity parameters proceed to equilibrium and in some cases demonstrate inversion at high maturity these molecular changes are associated with major changes in biomarker concentrations the hopane 22 s c 31 hopane and 20 s c 29 sterane parameters proceed as a result of the balance between the relative rates of generation and thermal degradation of the different isomers increased concentrations of the individual isomers are interpreted to be the result of biomarker generation from the kerogen mainly and other macromolecular polar fractions the c 29 sterane parameter and the three parameters involving rearranged hopanes ts 29ts and diahopane operate at higher maturity levels and proceed as a result of the relative rates of thermal degradation of the compound pairs isomerisation in the bitumen may also influence the operation of the parameters involving stereoisomers but must be a relatively minor contribution

geometry of the pamir hindu kush intermediate depth earthquake zone from local seismic data 1 we present new seismicity images based on a two year seismic deployment in the pamir and sw tien shan a total of 9532 earthquakes were detected located and rigorously assessed in a multistage automatic procedure utilizing state of the art picking algorithms waveform cross correlation and multi event relocation the obtained catalog provides new information on crustal seismicity and reveals the geometry and internal structure of the pamir hindu kush intermediate depth seismic zone with improved detail and resolution the relocated seismicity clearly defines at least two distinct planes one beneath the pamir and the other beneath the hindu kush separated by a gap across which strike and dip directions change abruptly the pamir seismic zone forms a thin approximately 10 km width curviplanar arc that strikes east west and dips south at its eastern end and then progressively turns by 90 to reach a north south strike and a due eastward dip at its southwestern termination pamir deep seismicity outlines several streaks at depths between 70 and 240 km with the deepest events occurring at its southwestern end intermediate depth earthquakes are clearly separated from shallow crustal seismicity which is confined to the uppermost 20 25 km the hindu kush seismic zone extends from 40 to 250 km depth and generally strikes east west yet bends northeast toward the pamir at its eastern end it may be divided vertically into upper and lower parts separated by a gap at approximately 150 km depth in the upper part events form a plane that is 15 25 km thick in cross section and dips sub vertically north to northwest seismic activity is more virile in the lower part where several distinct clusters form a complex pattern of sub parallel planes the observed geometry could be reconciled either with a model of two sided subduction of eurasian and previously underthrusted indian continental lithosphere or by a purely eurasian origin of both pamir and hindu kush seismic zones which necessitates a contortion and oversteepening of the latter