the mesozoic and tertiary basins of the bohemian massif and their evolution abstract the bohemian massif is a major positive element within the structural framework of the alpine carpathian foreland its basement became consolidated during the variscan orogeny crustal thicknesses range between 32 5 km and 40 km during the late carboniferous and early permian the bohemian massif became dissected by a conjugate system of wrench faults which controlled the accumulation of a continental coal bearing series late permian red beds were deposited on intramontane topographic depressions in triassic to mid jurassic times the bohemian massif formed a high from which clastics were shed into adjacent basins during the late jurassic and late cretaceous it became transected by nw se trending sedimentary basins the sub hercynian and laramide phases of foreland compression resulted in deformation and uplift of the bohemian massif the eger graben a 350 km long volcanotectonic zone cutting across the bohemian massif in an ene wsw direction came into evidence during the oligocene and is at present inactive the crust of the bohemian massif forms the autochthonous substratum of the outer carpathians which are paralleled by the neogene carpathian foredeep the neogene intramontane neo autochthonous vienna basin is superimposed on the alpine carpathian nappe systems and developed under a tensional setting

the hydrology of piermont marsh a reference for tidal marsh restoration in the hudson river estuary new york abstract the topography hydroperiod water table and selected edaphic characteristics are described for piermont marsh an irregularly flooded tidal marsh in the hudson river estuary new york usa despite variations in microtopography overall the marsh is flat and although the observations were conducted at a high point in the estuary s 18 6 year metonic cycle its surface was only inundated 10 12 times a month observations of spatial differences in the saturated hydraulic conductivity and surface infiltration rates are also discussed edge portions of the marsh are characterized by a slightly higher more uniform more structured less organic and less hydrologically conductive substrate than found in the marsh interior preferential flow is facilitated by macropores in the creekbank wall the water table is close to the marsh surface for a lesser percentage of the lunar month in the marsh edge when compared to the interior where it is almost always within 10 cm of the surface the extent to which the spatial variability of these hydrologic characteristics determines the marsh s ability to provide various ecosystem services is also discussed and the implications of these observations on tidal marsh restoration efforts briefly presented

changes in optical properties chemistry and micropore and mesopore characteristics of bituminous coal at the contact with dikes in the illinois basin abstract changes in high volatile bituminous coal pennsylvanian near contacts with two volcanic intrusions in illinois were investigated with respect to optical properties coal chemistry and coal pore structure vitrinite reflectance ro increases from 0 62 to 5 03 within a distance of 5 5 m from the larger dike and from 0 63 to 3 71 within 3 3 m from the small dike elemental chemistry of the coal shows distinct reductions in hydrogen and nitrogen content close to the intrusions no trend was observed for total sulfur content but decreases in sulfate content towards the dikes indicate thermochemical sulfate reduction tsr contact metamorphism has a dramatic effect on coal porosity and microporosity in particular around the large dike the micropore volume after a slight initial increase progressively decreases from 0 0417 cm3 g in coal situated 4 7 m from the intrusive contact to 0 0126 cm3 g at the contact strongly decreasing mesopore and micropore volumes in the altered zone together with frequent cleat and fracture filling by calcite indicate deteriorating conditions for both coalbed gas sorption and gas transmissibility

laterally varying structure and kinematics of the molasse fold and thrust belt of the central eastern alps implications for exploration the molasse deposits of the central eastern alps are partly incorporated into a fold and thrust belt that recently has come into exploration focus the structural style and timing of deformation varies significantly alongstrike regional three dimensional seismic and well data interpretation indicate three different structural segments from east to west 1 the sierning imbricates have a decollement close to the base of the molasse sequence and consist of varying numbers of thrust sheets alongstrike early miocene shortening of the molasse is at least 6 2 km 3 9 mi overthrusting of the internal penninic and helvetic wedge since the oligocene accommodated at least 25 km 15 5 mi of additional shortening 2 the regau segment is dominated by one to two small thrust sheets above a shallow detachment this segment is dominated by overthrusting of the alpine wedge 3 the perwang imbricates consist of an oligocene wedge with complex deformed thrust sheets above a detachment horizon in upper cretaceous marls minimum shortening in the imbricates is 18 5 km 11 5 mi with overthrusting 33 3 km 20 7 mi all shortening estimates have an uncertainty of approximately 20 to 35 the laterally varying thrust belt architecture results from predeformational conditions e g sediment thickness mechanical stratigraphy and basement dip in the sierning imbricates hydrocarbon trap definition and charge issues are exploration risks in the regau segment exploration is focused on the subthrust play the perwang imbricates have hydrocarbon shows but no economic discoveries charge and seal issues are the main risks the petroleum systems in the context of the structural evolution are not yet fully understood

tectonostratigraphy of the north alpine foreland basin correlation of tertiary depositional cycles and orogenic phases abstract tectonostratigraphic analysis of the depositional history of the north alpine foreland basin indicates that temporal relationships exist between short term events in the foredeep and the adjacent alpine orogen the foredeep can be divided stratigraphically into an alpine foredeep thanetian bartonian pre molasse basin latest bartonian earliest rupelian and molasse basin rupelian tortonian their general and tectonostratigraphic development includes time significant cycle sets and so called cenozoic rift and foredeep crf sequences which are apparently correlative to both foreland and orogen deformation events as well as to changes in global sea level individual basin fill sequences and consequently general stratigraphic and palaeogeographical aspects of the evolving basin system are thus found to be frequently defined by contemporaneous widely distributed tectonics and eustasy successive dominant depositional states underfilled steady state and overfilled episodes and facies flysch molasse are correlated with different concurrently progressing phases of the convergence and subduction history of the european and apulian plates

the extent of lateral water movement in the sediments of a new england salt marsh models of depth averaged hydraulic head are used with data from a water balance study in a new england salt marsh to describe horizontal pore water water fluxes near a creek bank three hydrologically distinct regions are identified in the sediment in the marsh studied semidiurnal tides may drive an oscillating horizontal flux in the narrow region within about 2 5 m of the creek bank farther than 15 m from the creek there is essentially no horizontal water movement in the region between 2 5 and 15 m drainage to the creek is driven by alternating periods of surface flooding and nonflooding due to the spring neap variation in tidal amplitudes there is little or no input of fresh groundwater to the marsh sediment at this site the spatial extent of the drained region depends on the duration of the nonflooded period the morphology of the sediment surface and the ratio of hydraulic conductivity to specific storage of the sediment

brittle deformation events at the western border of the bohemian massif germany investigations of brittle deformation structures present within the crystalline rocks of the bavarian oberpfalz reveal a complex late to post variscan crustal evolution upper carboniferous mainly westphalian granites were emplaced into semibrittle to brittle rocks of the zev zone of erbendorf vohenstraus and the egz erbendorf greenschist unit respectively from both the alignment of the granites and the direction of granite related tension gashes a north east south west extension must be assumed for the period of magmatic activities apart from the granite intrusions rapid crustal uplift about 1 5 km my led to an increase in the geothermal gradient from 40 c km late variscan post granitic the increased geothermal gradient persisted during the succeeding reverse faulting which results from late carboniferous probably stephanian east west and northeast south west compression although not evidenced directly in the area considered strike slip faults seem to have played an important part during the late variscan crustal evolution particularly in the early permian the strike slip events indicate further crustal shortening and indentation under north south compression a similar indentation was present in cretaceous time after a weak phase of early cretaceous reverse faulting which results from north south compression strike slip faults formed under north west south east and north south compression all these faults in particular the strike slip faults seem to be related to the cretaceous and lowermost tertiary convergence of the alpine carpathian orogeny a late stage of crustal extension characterized by a radial stress tensor 2 3 is indicated through high angle normal faults which probably formed during the subsidence of the adjacent neogene eger graben

fluxes of water and solute in a coastal wetland sediment 2 effect of macropores on solute exchange with surface water abstract we investigated interactions between sediment physical structure and solute transport in an intertidal coastal wetland two distinct pore size classes in the sediment were identified macropores had effective diameters greater than 100 m and a normalized volume of 5 matrix pores had effective diameters smaller than 100 m and were the volumetrically dominant pore size class 95 we found that infiltration and evaporation driven water fluxes were segregated between macropores and matrix pores respectively which had the effect of enhancing diffusive effluxes of chloride from the sediment to surface water chloride was highly concentrated relative to seawater in matrix porewater but was comparatively dilute in macropores concentration differences in pore size classes declined with depth until indistinguishable below 10 cm the segregated chloride distribution can be explained if recharge to the sediment occurred by downward infiltration in macropores and discharge occurred by an upward flux in matrix pores to satisfy evapotranspiration without disturbance by the downward infiltration flux in macropores upward advection of chloride in matrix pores and evapoconcentration increased chloride concentrations in matrix pores to a level well above the concentration in seawater the resulting high concentrations of chloride in matrix pores induced a large diffusive efflux of chloride into surface water that was sufficient to balance new input of chloride by infiltration of seawater in macropores 0 085 mmol cl cm 2 day transport models that were constrained by water balance measurements at the field site explained both the exponential form of the vertical distribution of chloride in matrix pores and the rate of change in storage of chloride in sediment porewater over a 1 month period we conclude that segregation of water and solute fluxes in two pore size classes strongly influences sediment salinity of coastal wetlands which has direct bearing on primary productivity of dominant vegetation and on exchange of dissolved nutrients and contaminants between intertidal wetlands and open water

inversion tectonics along the western margin of the bohemian massif abstract the block faulted southwestern margin of the bohemian massif is superimposed on a permo carboniferous graben major faults of which became repeatedly reactivated during the mesozoic and cenozoic inversion of sedimentary basins associated with this fault system occurred during the early cretaceous and again during the latest cretaceous early cenozoic

the dip of the foreland monocline in the alps and apennines the foreland monocline dips underneath thrust belts and accretionary wedges both in oceanic and continental subduction zones we present new data on the dip of the monocline in the frontal part of two orogens the alps and the apennines there is an overall difference between the dip of the relative monoclines and there is also a strong lateral variation along both arcs in the alps the regional dip varies between 0 in the remote foreland to an average of 2 3 at the front of the thrust belt below the foredeep to about 5 beneath the external thrust sheets within 40 km from the leading edge of the accretionary wedge the regional dip of the monocline in the apennines has an average of 4 5 at the front of the thrust belt below the foredeep to about 10 beneath the external thrust sheets within 40 km from the leading edge of the accretionary wedge there are areas where the dip exceeds 20 the apennines though topographically lower than the alps present higher monocline dips and a deeper foredeep moreover there are variations in the dip of the monocline moving along the strike of the two belts the low values coincide with permian mesozoic inherited horsts whereas the steeper values correspond to basinal areas and they usually match the salients of the thrust belt front within the salients the distance between thrust ramps increases therefore there are two orders of mean values of the dip of the foreland monocline the first at the orogen scale more than 1000 km wavelength the second at the regional scale 100 200 km wavelength within the single orogen lateral variations in the lithospheric buoyancy due to the inherited mesozoic stretching may explain the second order variations in foreland dip but not the first order mean values which seem to be more sensitive to the geographic polarity of the subduction rather than to the lithospheric composition which is rather similar in the alpine and in the central northern apennines slabs

tectonic and climatic control of paleogene sedimentation in the rhenodanubian flysch basin eastern alps austria abstract the paleocene to lowermost eocene formations of the rhenodanubian flysch were deposited in an abyssal environment at the continental rise to the south of the european plate the pattern of paleocurrents indicates a number of small distributary systems for the turbiditic material that entered the basin from the north and was deflected to the east and to the west heavy mineral assemblages in the turbidites suggest the erosion of medium grade metasediments in the danian and the progressive erosion of underlying metamorphic magmatic rocks in the thanetian and ypresian the most obvious sedimentary event is the breakdown in turbidite sedimentation during the late danian to the early thanetian remarkably this starvation of turbidites is associated with high values of chlorite in the clay mineral assemblages of interturbidite shales indicating increased mechanical erosion of the adjoining land areas tectonic uplift of these areas and associated block faulting and tilting is assumed to be responsible for this increase in erosion as well as for the synchronous cutting off of the basin from the source area of the turbidites this tectonic activity is related to the onset of the collision of the european and the adriatic plates a second major event documented in the paleogene record is the change from a predominantly siliciclastic system to a carbonate system in the latest thanetian associated with the global negative carbon isotope excursion cie in the upper part of calcareous nannozone np9 calcareous mudturbidites become the prevailing rock type eutrophication of surface waters is indicated by acmes of diatoms radiolaria and dinoflagellates at the level of the cie together with slightly increased values of kaolinite in the clay mineral assemblages of interturbidite shales this can be interpreted as a result of increased continental run off due to high precipitation rates in a humid climate the top of the increased kaolinite input is poorly constrained because of a very high input of smectite due to volcanic activity in sub zone np10a this igneous activity is assigned to the opening of the northern atlantic ocean and has no geodynamic relevance for the rhenodanubian basin

late cretaceous and cenozoic intra plate compressional deformations in the alpine foreland a geodynamic model abstract the mesozoic grabens and wrench induced troughs of western and central europe developed in response to triassic early cretaceous intra plate tensional stresses which affected the arctic north atlantic and the tethys borderlands during the rifting phase preceding the opening of the respective oceans this resulted in the fragmentation of the continental crust of the alpine foreland during the late cretaceous and tertiary alpine orogeny collision related compressive stresses exerted on the foreland induced the reactivation of these fracture systems causing the inversion of mesozoic grabens and the uplifting of major basement blocks at distances up to 1300 km to the north of the present alpine deformation front the structural style of these inverted basins and basement uplifts is indicative of compressional and transpressional deformations the total amount of crustal shortening associated with these deformations is unlikely to exceed a few tens of kilometres these displacements require a coupling between the foreland and the orogen at the alpine a subduction zones and within the foreland a decoupling at intra crustal levels between the crust and mantle and or at deeper lithospheric levels the example of the alpine foreland indicates that compressive stresses inducing major deformations can be transmitted from a collisional plate boundary through continental lithosphere over distances of up to 1300 km circumstantial evidence suggests that collision related compressive stresses not large enough to give rise to significant deformations can be transmitted through continental lithosphere over even greater distances

mesozoic and early tertiary evolution of the alpine foreland in upper austria and salzburg austria abstract the cenozoic molasse basin of upper austria and salzburg is part of the alpine foredeep its substratum is formed by the crystalline basement of the bohemian massif and its mesozoic sedimentary cover this autochthonous complex extends for a considerable but unquantifiable distance beneath the alpine nappes the area occupied by upper austria and salzburg started to subside during the middle jurassic and by late jurassic time it was covered by an extensive carbonate platform early cretaceous wrench deformations related to rifting activity in northwestern europe were accompanied by a major erosional phase during the late cretaceous 750 to 1000 m of shallow marine shales and elastics accumulated in the area whereby the clastic influx from the bohemian massif increased during the late senonian at the transition from the cretaceous to the tertiary dextral transpressional deformation induced partial basin inversion this deformation phase may be related to the collision of the north european craton with the alpine orogenic system following an erosional phase during the palaeocene and early eocene the area subsided again and became part of the alpine foredeep

source rock characteristics of the lower cretaceous abu gabra formation in the muglad basin sudan and its relevance to oil generation studies organic rich shale and claystone are present within the lower cretaceous abu gabra formation of the muglad basin representing excellent oil source rocks the source rock potential of abu gabra organicrich whole rock samples from two oilfields in the muglad basin was investigated using bulk and quantitative pyrolysis techniques the analytical program included toc pyrolysis sra pyrolysis gc bulk kinetics elemental analysis and kerogen microscopy the results were used to characterize the kerogen composition and type of petroleum generated from these abu gabra organic rich sediments to clarify the structural variability of the organic matter in the abu gabra source rock the investigated abu gabra organic rich sediments proved to contain excellent quality lacustrine kerogens the samples have moderate to high hydrogen index hi values 267e837 mg hc g rock consistent with predominantly oil prone types i and ii kerogen with a minor contribution of type iieiii kerogens this is supported by the abundant liptinitic materials i e lipid rich structured algae structureless amorphous alginite and sporinite and high atomic hydrogen to carbon h c ratio however pyrolysis gc analysis proved that all the investigated abu gabra samples contain homogeneous type i kerogen that produces mainly waxy oil bulk kinetic experiments on these samples indicate that the source rock facies derived from a homogenous organic matter spans an extremely narrow distribution of activation energy ea ranges from 49 kcal mol to 51 kcal mol the magnitude order of frequency factors a also show a narrow distribution range from 10

the minimal response to contact metamorphism by the devonian buchan caves limestone buchan rift victoria australia abstract a 2 2 m thick late eocene dike that intruded the devonian buchan caves limestone near murrindal victoria has produced a narrow contact aureole only centimeters wide in the adjacent host rock mean solid bitumen reflectance ranges from about 2 4 to 2 7 and shows little change up to 6 m away from the dike contact carbon and oxygen isotope values also show little change except at the dike contact the most detectable response of the rock to contact metamorphism is the proportion of solid bitumen grains with finely granular mosaic structure increase towards the dike also under cathodoluminescence cl excitation the host rock is initially observed to be recrystallized to a uniform bright orange color by 1 cm away from the contact however cl shows preservation of sharp boundaries in finely zoned burial cements a regional study of thermal maturation and a geothermometer based on solid bitumen reflectance indicate paleotemperatures near 200 c were widespread in the buchan rift during peak burial near the time of the devonian tabberabberan deformation the lack of response of the buchan caves limestone to contact metamorphism is attributed to 1 prior heating to near 200 c and 2 the fact that the dike intruded into cool near surface low porosity rocks which may have been in the vadose zone

temperature effects on kerogen and on molecular and isotopic composition of organic matter in pierre shale near an igneous dike abstract a suite of siltstone samples from the upper cretaceous pierre shale from the contact zone of a 130 cm thick igneous dike near wolcott colorado u s a was taken from the contact to 170 cm from the dike to study the effects of temperature on the organic matter the sampled bedding interval was about 10 cm thick so variation in lithology and type of organic matter is minimal vitrinite reflectance values r 0 increase from 0 4 far from the dike to 3 3 near the dike contact geochemical measurements show systematic thermal effects analogous to those often observed for catagenesis and metagenesis in the depth range of 1 4 km within a sedimentary basin the h c ratio of kerogen and the hydrogen index rock eval decrease most rapidly in the 0 6 1 7 r 0 range in which the transformation ratio rock eval increases from 0 1 to 0 3 based on extraction of c 15 compounds the main increase of hydrocarbons and total extractable organic matter occurs between 0 6 and 1 0 reflectance the saturated aromatic hydrocarbon ratio increases almost twofold in this range of maturity however the pristane phytane ratio is essentially constant through the hydrocarbon generation zone but decreases slightly at high levels of thermal alteration r 0 1 2 the 13 c values for aromatic and saturated hydrocarbons are about 27 and 29 respectively and are constant to about 1 0 r 0 then both become heavier by about 2 at higher r 0 values

evolution of the molasse basin germany switzerland abstract in the molasse basin 500 1000 m thick mesozoic sediments overlie the variscan basement and locally permo carboniferous grabens containing a largely unknown thickness of clastic sediments the vindelician basement high extended southwestward from the bohemian massif and separated the southern part of the german basin from the tethys shelf triassic early and middle jurassic sediments progressively transgressed over this high which became fully inundated during the late jurassic following a temporary regression sedimentation resumed in the early cretaceous and after another hiatus in the late aptian to campanian during the latest cretaceous to earliest tertiary the area of southern germany became uplifted resulting in a progressive northwestward truncation of cretaceous strata and the late jurassic carbonates at the same time the bohemian massif became upthrusted along northwest striking wrench faults similar faults controlled the upthrusting of the landshut neuoetting high over which some 1 000 m of mesozoic sediments were eroded these wrench and thrust tectonics are part of an extensive compressional deformation in central europe that is supposed to be caused by the latest cretaceous earliest tertiary collision of the adriatic african and european plates during the alpine orogeny the area subsided again during the late eocene and developed into the molasse basin proper in which oligocene to miocene elastics reach a thickness of some 5 000 m near the alpine thrust front subduction and flexuring of the foreland caused numerous essentially basin parallel synthetic and antithetic normal faults the latter form the primary traps for oil and gas accumulations in the molasse basin

how contact metamorphism can trigger global climate changes modeling gas generation around igneous sills in sedimentary basins abstract large volumes of greenhouse gases such as ch4 and co2 form by contact metamorphism of organic rich sediments in aureoles around sill intrusions in sedimentary basins thermogenic gas generation and dehydration reactions in shale are treated numerically in order to quantify basin scale devolatilization we show that aureole thicknesses defined as the zone of elevated metamorphism relative to the background level vary within 30 250 of the sill thickness depending on the temperature of the host rock and intrusion besides the sill thickness in shales with total organic carbon content of 5 wt ch4 is the dominant volatile 85 135 kg m3 generated through organic cracking relative to h2o generation from dehydration reactions 30 110 kg m3 even using conservative estimates of melt volumes extrapolation of our results to the scale of sill complexes in a sedimentary basin indicates that devolatilization can have generated 2700 16200 gt ch4 in the karoo basin south africa and 600 3500 gt ch4 in the voring and more basins offshore norway the generation of volatiles is occurring on a time scale of 10 1000 years within an aureole of a single sill which makes the rate of sill emplacement the time constraining factor on a basin scale this study demonstrates that thousands of gigatons of potent greenhouse gases like methane can be generated during emplacement of large igneous provinces in sedimentary basins

basement involved reactivation in foreland fold and thrust belts the alpine carpathian junction austria the late eocene early miocene alpine carpathian fold and thrust belt ftb lies in the transition between the eastern alps and the western carpathians se of the bohemian crystalline massif our study shows the involvement of crystalline basement from the former european jurassic continental margin in two distinct events a first extensional event coeval with eggerian karpatian c 28 16 ma thin skinned thrusting reactivated the rift basement fault array and resulted from the large degree of lower plate bending promoted by high lateral gradients of lithospheric strength and slab pull forces slab break off during the final stages of collision around karpatian times c 17 16 ma promoted large wavelength uplift and an excessive topographic load this load was reduced by broadening the orogenic wedge through the reactivation of the lower plate deep detachment beneath and ahead of the thin skinned thrust front with the accompanying positive inversion of the basement fault array and ultimately by the collapse of the hinterland summits enhanced by transtensional faulting although this work specifically deals with the involvement of the basement in the alpine carpathian junction the main conclusions are of general interest to the understanding of orogenic systems

contact metamorphic devolatilization of shales in the karoo basin south africa and the effects of multiple sill intrusions abstract quantification of fluid generation during contact metamorphism of shale is important for the understanding of metamorphic processes fluid flow in sedimentary basins and perturbations of the global carbon cycle in this study we provide geochemical and numerical analyses from the organic rich ecca group in the karoo basin south africa which was affected by contact metamorphism from multiple sill intrusions in the early jurassic organic matter was efficiently converted to hydrocarbons during contact metamorphism and complete loss of organic carbon in the innermost aureole is common mineral dehydration reactions are evident from the occurrence of metamorphic minerals like biotite and loss of the clay fraction towards the intrusive contact we have developed a numerical model in order to quantify fluid production from both inorganic and organic reactions during contact metamorphism the modelling results are constrained by data from two case studies in the karoo basin in order to obtain reliable estimates of the carbon loss from metamorphism of shale we show that single thin 15 m thick sills have a gas production potential of several gigatons of methane ch4 if emplaced over a 1000 km2 area furthermore the vertical spacing between simultaneously emplaced sills has an important influence on the gas generation potential when two sills are emplaced with a vertical spacing of 7 times the intrusion thickness the total ch4 generation is up to 35 more than for two separate sills data and modelling from five sills emplaced within the ecca group show hydrocarbon generation throughout the organic rich section with total carbon loss next to the sills this has implications for the fluid production and metamorphism in volcanic basins where multiple sills are common

two dimensional flow response to tidal fluctuation in a heterogeneous aquifer aquitard system in alluvial coastal aquifers finer sediments are preferentially deposited along the downstream direction so the hydraulic conductivity is generally heterogeneous and changes with distance from the coastline to investigate the influence of aquifer heterogeneity on seawater groundwater interaction a new two dimensional model characterising groundwater flow in an aquifer aquitard system was developed assuming that the hydraulic conductivity of the aquifer linearly increases with the distance from the coastline along the inland direction a closed form analytical solution was derived using the separation of variables method comparing the new solution with the numerical solution by comsol multiphysics sweden based on the finite element method one can see that the new solution agreed with the numerical solution very well except at the early time we found that both aquitard leakance and the heterogeneity factor b could result in the propagation bias the propagation bias represents the inconsistency between the theoretical calculation and the observed strong attenuation and small time lag between the head and tide fluctuations the attenuation decreased with perpendicular distance from the coastline x axis whereas the time lag increased with distance along the x axis the relationship between the time lag and the distance along the x axis seemed to be linear when b was 0 001 m 1 whereas it obeyed a power function when b was greater than 0 01 m 1 copyright 2014 john wiley sons ltd

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

thermal alteration of cretaceous black shale by diabase intrusions in the eastern atlantic ii effects on bitumen and kerogen abstract the thermal effects of three one major and two minor miocene diabase intrusions on cretaceous black shales from dsdp site 41 368 have been analyzed a concentration gradient was observed especially for the hydrocarbons decreasing towards the major intrusion and between the three sills the thermally altered samples in the proximity of and between the sills contained elemental sulfur and an excess of thermally derived pristane over phytane whereas the unaltered sediments contained no elemental sulfur and more phytane than pristane a maximum yield of the extractable hydrocarbons was observed at a depth of 7 m below the major sill two classes of molecular markers were present in this bitumen suite the first was sesqui di and triterpenoids and steranes which could be correlated with both terrigenous and autochthonous sources they were geologically mature and showed no significant changes due to the thermal stress the second class was found in the altered samples which contained only polynuclear aromatic hydrocarbons with low alkyl substitution and sulfur and oxygen heterocyclic aromatic compounds these compounds were derived from pyrolytic reactions during the thermal event kerogen was isolated from all of these samples but only traces of humic substances were present the h c n c 13 c 34 s and d all exhibit the expected effects of thermal stress the kerogen becomes more aromatized and richer in 13c 34s and d in the proximity of and between the sills maturation trends were also measured by the vitrinite reflectance and electron spin resonance where the thermal stress could be correlated with an elevated country rock temperature and an increased degree of aromaticity the effects of in situ thermal stress on the organic rich shales resulted in the generation and expulsion of petroliferous material from the vicinity of the sills

seismic stratigraphy of late oligocene puchkirchen formation of upper austria a semi regional study of the late oligocene puchkirchen formation deep water clastics of the molasse basin has increased our understanding of the depositional facies patterns thereby improving our ability to seismically recognize potential stratigraphic and structural stratigraphic hydrocarbon traps

mesozoic and tertiary evolution of the alpine carpathian foreland in eastern austria abstract the bohemian massif partly covered by mesozoic sediments extends southward some 50 km under the alpine carpathian nappe complex a major basement spur devoid of mesozoic sediments and referred to as the south bohemian basement spur separates the jurassic cretaceous upper austrian basin from the lower austrian basin the latter came into evidence during the middle jurassic under a tensional setting late jurassic shelf carbonates and basinal shales were deposited under a tectonically quiet regime early cretaceous uplift of the south bohemian basement spur induced the truncation of jurassic strata along its margins transgressive late cretaceous elastics overlap the truncated jurassic series and locally onlap on basement upper austria latest cretaceous to paleocene foreland deformations may have caused a renewed uplift of the south bohemian basement spur the eocene to late miocene evolution of the molasse foredeep went hand in hand with the emplacement of the alpine carpathian nappe system differential movements between the eastern alpine nappes and the carpathian nappes combined with tensional stresses in the basement caused the subsidence of the vienna basin

the effects and implication of tides and rainfall on the circulation of water within salt marsh sediments the response of the water table of an intertidal salt marsh in nw england has been investigated during neap tides water seeps upward from the underlying sand silt clay interface this effect continues as the marsh is overtopped during spring tides but is then dwarfed by penetration of water downward from the surface under typical conditions the delay between high water in the river and maximum apparent water level for the marsh becomes less as the spring tide cycle maximum is approached lags also appear smaller during summer probably mainly due to desiccation cracks precipitation effects are only important when rainfall is significant in quantity and coincides with low water during neap tides

the late and post variscan tectonic evolution of the western border fault zone of the bohemian massif wbz paleostress analysis and evaluation of the stratigraphic unconformities reveal an extremely polyphase development of one of the most prominent fault zones of central europe usually known as the franconian line fl because the fl is just one fault zone although it is the most important fault zone within a complex fault system a more appropriate term is used herein western border fault zone of the bohemian massif wbz the reconstruction of the paleostress history was carried out by analysing sequences of individual strain increments that belong to the same stratigraphic units e g late variscan granites tertiary basalts a succession of at least 15 paleostress directions and tectonic regimes have been determined since late variscan time

influence of the geologic and geomorphologic characteristics and of crab burrows on the interrelation between surface water and groundwater in an estuarine coastal wetland the interrelation between surface water and groundwater in intertidal flats is often studied through mathematical models in many cases these models need to be supported by an integral analysis of the geologic geomorphologic hydrologic and biological characteristics of the environment that are to be obtained from field surveys the marshy environment of the river ajo in the samborombon bay wetland argentina is a typical example of an estuarine coastal zone geologic and geomorphologic surveys were carried out as well as measurements of surface water and groundwater level changes as a response of the aquifer to tidal forcing the banks of the river ajo are either scarped with storm flats or mildly sloped with intertidal flats and numerous crab burrows sediments are mainly silty clayey with low permeability and lie over silty sandy layers at the erosion scarps the tidal wave enters the aquifer as a sub horizontal flow through the pore space of the sediments the tidal range in the aquifer depends on the lithological characteristics of the sediments and on the side changes of their hydraulic conductivity the rise of the water table at high water and its subsequent fall are nearly sinusoidal with a period similar to that of the tide at the river at the intertidal flats instead the tidal wave enters the aquifer mainly as a sub vertical flow through the crab burrows as the crab burrows are not interconnected they are not distinct pathways for preferential flow therefore the groundwater flux into the river is very slow during low water and the recovery of the water table takes a long time the tidal influence upon the water table on both kinds of banks affects only a narrow strip of the aquifer not only are the characteristics of the marshy environment of the river ajo representative of most of the samborombon bay wetland they can also be extended to other similar coastal wetlands to help preserve these invaluable environments

balancing lateral orogenic float of the eastern alps abstract oligocene to miocene post collisional shortening between the adriatic and european plates was compensated by frontal thrusting onto the molasse foreland basin and by contemporaneous lateral wedging of the austroalpine upper plate balancing of the upper plate shortening by horizontal retrodeformation of lateral escaping and extruding wedges of the austroalpine lid enables an evaluation of the total post collisional deformation of the hangingwall plate quantification of the north south shortening and east west extension of the upper plate is derived from displacement data of major faults that dissect the austroalpine wedges indentation of the south alpine unit corresponds to 64 km north south shortening and a minimum of 120 km of east west extension lateral wedging affected the eastern alps east of the giudicarie fault west of the giudicarie fault north south shortening was compensated by 50 to 80 km of backthrusting in the lombardian thrust system of the southern alps the main structures that bound the escaping wedges to the north are the inntal fault system ca 50 km sinistral offset the konigsee lammertal traunsee klt fault 10 km and the salzach ennstal mariazell puchberg semp fault system 60 km these faults as well as a number of minor faults with displacements less than 10 km root in the basal detachment of the alps the thin skinned nature of lateral escape related structures north of the semp line is documented by industry reflection seismic lines crossing the northern calcareous alps nca and the frontal thrust of the eastern alps complex triangle zones with passive roof backthrusts of middle miocene molasse sediments formed in front of the laterally escaping wedges of the northern eastern alps the aim of this paper is a semiquantitative reconstruction of the upper plate of the eastern alps most of the data is published elsewhere

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago