a numerical dynamic model for the norwegian danish basin abstract a 2d numerical dynamic model for the late palaeozoic and mesozoic formation and evolution of the norwegian danish basin ndb is presented this basin developed in the eastern part of the northern permian basin within the system of northwest european sedimentary basins the basin forming processes are modelled in a lithospheric plane strain model along a 400 km profile across the basin layered rheology is used with elasto plastic behaviour in the brittle parts and elasto viscous behaviour at higher temperatures and pressures the mechanical equations of equilibrium and the heat equation are solved by the finite element technique the model contains two tectonic events basin initiation in late carboniferous and early permian times is modelled by combined lithospheric heating and lithospheric extension additional lithospheric extension however less pronounced and taking place over a longer period is introduced during the triassic isostatic effects associated with lithospheric extension combined with thermal contraction and sediment loading accounts for up to 6 km of sediments of which 2 3 km are of triassic age the model shows a generally good agreement with observations in terms of basin geometry sediment layer thicknesses stratigraphy crustal thickness and heat flow in the central parts of the basin the model implies a crustal thinning factor of about 1 5 from 35 km to about 23 km close to that observed in seismic data

a critical reappraisal of preconsolidation pressure interpretations using the oedometer test over the past 70 years a number of methods have been proposed for the interpretation of the characteristic vertical effective yield stress or preconsolidation pressure of compressible soils as defined using the standard oedometer test the concept of the preconsolidation pressure has been extraordinarily useful in geotechnical engineering for analysing and predicting settlement behaviour and for normalizing other engineering parameters for comparative purposes defining this characteristic stress however is often problematic and relies heavily on graphical techniques that are subject to some uncertainty particularly when using semi log plots for this purpose this paper illustrates fundamental difficulties with the interpretation of oedometer test and presents an alternative technique for defining unambiguous values of the vertical effective yield stress

structural development of the fennoscandian border zone offshore denmark abstract the hans 1 saeby 1 and terne 1 wells are located within the danish part of the fennoscandian border zone and provide significant new data pertaining to the evolution of this important tectonic belt all three wells encountered palaeozoic and mesozoic rocks the cambrian to lower silurian deposits can be closely correlated to sections known from bornholm and scania and tectonic activity within the fennoscandian border zone cannot be verified during this time interval the thick upper silurian shales were probably deposited in a rapidly subsiding foreland basin marginal to the speculative caledonian deformation front which lies south of the ringkobing fyn high a major hiatus comprises the devonian and early carboniferous upper carboniferous sediments were deposited before a phase of rifting upper carboniferous intrusive and extrusive volcanic rocks suggest tectonic activities heralding the rifting phase extensive block faulting occurred in the border zone during the rotliegende and more than 650 m of reworked volcanic rocks were deposited in an alluvial fan environment syndepositional erosion created a major unconformity before the deposition of post rift zechstein sediments during the mesozoic the fennoscandian border zone was divided into two zones the sorgenfrei tornquist zone to the west and the skagerrak kattegat platform to the east the sorgenfrei tornquist zone continued to experience tectonic activity in triassic and middle jurassic times the zone has experienced an uplift of 1700 2000 m during late cretaceous to early tertiary inversion tectonics and the late tertiary uplift of fennoscandia

evolution of paleostress fields and brittle deformation of the tornquist zone in scania sweden during permo mesozoic and cenozoic times abstract the nw se oriented sorgenfrei tornquist zone stz has been thoroughly studied during the last 25 years especially by means of well data and seismic profiles we present the results of a first brittle tectonic analysis based on about 850 dykes veins and minor fault slip data measured in the field in scania including paleostress reconstruction we discuss the relationships between normal and strike slip faulting in scania since the permian extension to the late cretaceous tertiary structural inversions our paleostress determinations reveal six successive or coeval main stress states in the evolution of scania since the permian two stress states correspond to normal faulting with ne sw and nw se extensions one stress state is mainly of reverse type with ne sw compression and three stress states are strike slip in type with nnw sse wnw ese and nne ssw directions of compression the ne sw extension partly corresponds to the late carboniferous permian important extensional period dated by dykes and fault mineralisations however extension existed along a similar direction during the mesozoic it has been locally observed until within the danian a perpendicular nw se extension reveals the occurrence of stress permutations the nnw sse strike slip episode is also expected to belong to the late carboniferous permian episode and is interpreted in terms of right lateral wrench faulting along stz oriented faults the inversion process has been characterised by reverse and strike slip faulting related to the ne sw compressional stress state this study highlights the importance of extensional tectonics in northwest europe since the end of the palaeozoic until the end of the cretaceous the importance and role of wrench faulting in the tectonic evolution of the sorgenfrei tornquist zone are discussed

the mechanical relationship between strike slip faults and salt diapirs in the zagros fold thrust belt analogue models are used to study the mechanical relationship between basement strike slip faults and salt diapirs displacement along a strike slip fault in 1 g models resulted in extension along pre existing jogs and the formation of oblique extensional faults where reactive diapirs were triggered in some models in the centrifuge models prescribed cuts simulating pre existing structures were reactivated during simple shear deformation of the models resulting in formation of pull apart basins which were intruded by diapirs the models show that because of the low ratio of salt to overburden thickness in the zagros 0 15 0 35 it is unlikely that diapirs have formed solely if at all as a result of movement along basement strike slip faults two mechanisms are suggested first pre kinematic thin overburden and continuous movement along a releasing bend in the cover units may have triggered some of the diapirs in the zagros which were later downbuilt to their current geometry by additional sedimentation second movement along the strike slip faults e g the kazerun and mangarak faults induced oblique movement along nw se zagros structures folds or thrusts resulting in the formation of pull apart basins where diapirs were eventually intruded fault plane solution of shallow earthquakes supports the second scenario which is also in agreement with previous interpretations that some of the salt diapirs associated with basement faults are younger than zagros shortening and young southwestwards

the effect of decollement dip on geometry and kinematics of model accretionary wedges we conducted a series of sand box models shortened asymmetrically above a frictional plastic decollement to study the influence of amount and sense of the decollement dip on the geometry and kinematics of accretionary wedges model results illustrate that the amount and direction of decollement dip strongly influence the geometry and mode of deformation of the resulting wedge in general for models having similar decollement frictional parameters the resulting wedge is steeper grows higher and is shorter when shortened above a decollement that dips toward the hinterland at 42 bulk shortening the length height ratio of wedges formed above a 5 dipping decollement was equal to 2 4 whereas this ratio was equal to 3 for wedges shortened above a horizontal decollement moreover models with a hinterland dipping decollement undergo larger amounts of layer parallel compaction lpc and area loss than models shortened above a non dipping decollement the effect of decollement dip on wedge deformation is most pronounced when basal friction is relatively high b 0 55 whereas its effect is less significant in models where the basal decollement has a lower friction b 0 37 model results also show that increasing basal slope has a similar effect to that of increasing basal friction the wedge grows taller and its critical taper steepens

paleostress field reconstruction in the oslo region abstract the geodynamic history of a region is archived in its geologic record which in turn may reflect deformation patterns that causally can be related to certain configurations of paleostresses in the oslo region the exposed geological record ranges from precambrian high grade metamorphic rocks through cambro silurian sedimentary rocks to permo carboniferous sedimentary and magmatic rocks the latter being related to the development of the oslo rift system we investigate the kinematics of outcrop scale faults to derive the diversity of paleostress states responsible for the observed strain for this purpose we combine different graphical and numerical approaches to separate heterogeneous fault slip data sets and estimate the associated reduced stress tensors a reduced stress tensor consists of the directions of the three principal stress axes with 1 2 3 and the ratio of principal stress differences r 2 3 1 3 the present study gives evidence for three major regional paleostress fields that affected the oslo region a compressional stress field with a nw se directed maximum compression 1 has been identified as a caledonian imprint the most prominent regional stress field however is tensional characterised by a wnw ese directed minimum compression 3 and related to the permo carboniferous rifting later the area was affected by a wrench regime with a roughly n s directed 1 and a maximum age of permian whereas the absolute timing of this stress field is unclear due to the lack of exposed rocks younger than permian for a large number of estimated stress states none of the principal axes are sub vertical these oblique paleostresses cannot be integrated into a common regional stress field but rather correspond to local effects of intense magmatic activity during the permo carboniferous phase of rifting the present study tends to show that the oslo region remained unaffected by major tectonic activity for much of the mesozoic and cenozoic which is when the central european basin system to the south experienced several phases of intense deformation

the oslo rift its evolution on the basis of geological and geophysical observations abstract the formation and evolution of the oslo rift have puzzled geoscientists for more than a century we have reexamined this problem in view of recent detailed geophysical information bearing on crust and lithosphere structures in the general rift area for example the rift contours closely correlate with a moho elevation of 3 5 km the crustal thinning partly predates the rifting and apparently the same is the case for lithospheric deformations cambro silurian sediments are found mainly within the present day rift and this implies rifting contemporaneous with uplift the southern rift segment the skagerrak graben appears to be somewhat different from the northern segment the oslo graben with relatively less magmatism and larger subsidence crustal laminae are found inside and especially outside the rift area including sub moho dipping reflectors whose origin is attributed to magmatic intrusions and or stretching the strength of the lithosphere increases northwards with increasing thicknesses of both the brittle crust and the lithosphere a variety of continental rifting mechanisms has been examined in view of the observational data at hand basically a passive rifting mechanism is presumed with dominant east west tensional stresses albeit we are unable to be specific on driving forces the model presented in this paper reflects concepts introduced by dunbar and sawyer 1988 and neugebauer 1983 on preweakening of the crust and lithosphere and diapirism as a transport mechanism the essential elements of the model are 1 1 the area in question was preferential for rifting in view of previous crust and lithosphere deformations from late precambrian to silurian times 2 2 lithosphere stretching is needed for creating favorable conditions for diapirism 3 3 the shield strength increases rapidly towards the northern part of the rift preventing further migration

comparison of the paleoclimatic significance of higher land plant biomarker concentrations and pollen data a case study of lake sediments from the holsteinian interglacial abstract a sediment core from the dethlingen paleolake holsteinian interglacial northern germany was subjected to integrated organic geochemical and palynological paleobotanical analyses in order to reconstruct past environmental conditions the fractionated lipid extracts were investigated using gas chromatography mass spectrometry gc ms and gc combustion isotopic ratio ms ring a aromatized pentacyclic triterpenoids most likely glutinane derivatives were the only higher plant derived pentacyclic triterpenoids found the saturated ring a degraded triterpenoid des a lupane was the most abundant aliphatic hydrocarbon throughout the core based on published pollen data which imply the strong presence of betula and alnus around the paleolake the des a lupane would be expected to originate mainly from lupane type precursors synthesized by betulaceae the carbon isotopic composition of des a lupane varied from 28 2 to 30 6 and no significant trend or isotopic shift was observed however the discrepancy between the variation in pollen data and biomarker concentration i e quasi absence of diterpenoids in the core argues for a scenario in which the two proxies represent different components of the vegetation in the catchment area of the paleolake

detailed stratigraphic subdivision and regional correlation of the southern danish triassic succession this paper provides a regional log based lithostratigraphic correlation of the danish triassic deposits with deposits known from the southern north sea basin including the northwest german and dutch onshore areas a new lithostratigraphic nomenclature mainly adapted from the dutch nomenclature is suggested for the danish area south of the ringkobing fyn high replacing the previously used nomenclature the new nomenclature comprises the lower triassic bunter shale and bunter sandstone formations the lower to middle triassic rot and muschelkalk formations and the uppermost middle triassic and upper triassic keuper and sleen formations in total 22 members are also defined from the southern north sea into the southern danish area this main marine southern facies province is separated from a continental northern facies province by the northern flank of the ringkobing fyn high trend units of the southern province only crossed the central and western part of the ringkobing fyn high during the rot and the muschelkalk transgressions whereas the basin north of the eastern part of the high was influenced by the southern facies province during the early to early late triassic

characteristics and deformation mechanism of salt related structures in the western kuqa depression tarim basin insights from scaled sandbox modeling abstract three scaled analog sandbox models are constructed to simulate the evolution of thick skinned shortening on broad and narrow salt basins these models simulate the evolution of the cenozoic salt salt related structures in the westernmost kuqa salt bearing depression quele area tarim basin the formation mechanism and the controlling factors of structural deformation in this area are investigated and discussed systematically model results show that the variable depositional width of the salt basin has a major controlling influence on the differential structural deformation in different longitudinal segmentations from east broad to west narrow in the western kuqa depression quele area model results also demonstrate that the early salt structure salt diapir has an important controlling role on the subsequent compressional structural deformation the pre existing thin overburden quele diapir which acts as a stress concentration zone during the subsequent shortening is deformed to the quele salt nappe on the basis of the model results it is suggested that the formation of the long distance quele allochthonous salt sheet is related with the pre existing quele diapir which displaces up paralleling the hanging wall and flows to the surface during the subsequent shortening

physical explanation of the formation and evolution of inversion zones and marginal troughs inversion zones are elongate structures some tens of kilometers wide and up to hundreds of kilometers long that have deformed in response to compression and produced topography inversion zones in the alpine foreland are mainly associated with mesozoic grabens and troughs and although very important in the geologic picture the conditions of their formation and evolution and their regional geologic significance are not entirely understood the internal structure of inversion zones is variable and depends on details in the pre inversion setting the inversion inducing stress field and the sedimentary fill however on a larger scale most inversion zones share certain principal observational features which sample the physical structure and the rheologic properties of the lithosphere and thereby provide an opportunity to test hypotheses of lithospheric rheology and dynamics the quantitative model presented in this paper explains how inversion zones and the associated marginal troughs are related to lithospheric zones of differential shortening and regional isostatic compensation of the induced topography

petrographical and organic geochemical study of the kovin lignite deposit serbia abstract the origin of the organic matter om and the characteristics of the depositional environment of lignites from the upper miocene kovin deposit hosting three coal seams of serbia were evaluated based on petrographic data bulk organic geochemical parameters biomarker analysis and stable isotope geochemistry 13c of individual biomarkers samples were collected from four boreholes gd 601 and gd 603 the a field and kb 79 and kb 91 the b field representing different parts of coal seams i ii and iii investigated lignites are typical humic coals the om of lignites is derived from woody vegetation and herbaceous peat forming plants with prevalence of the former in most samples peat forming vegetation is characterized by abundant decay resistant gymnosperm coniferous plants followed by a low amount of angiosperms lignite forming plants mostly belonged to the gymnosperm families cupressaceae taxodiaceae phyllocladaceae and pinaceae slight input of ferns fungi and aquatic macrophyta to lignite om is also evident distributions of hopanoids and isotopic compositions of these biomarkers reflect the activity of various microbial populations represented by methanotrophic chemoautotrophic and heterotrophic bacteria during diagenesis prominent c28 28 30 bisnorneohop 13 18 ene was observed for the first time in the lignite extracts according to the 13c value it was probably derived from chemoautotrophic bacteria c28 28 30 bisnorneohop 13 18 ene could be one of the possible precursors of a series of orphan aromatic hopanoids bearing an ethyl group at c 21 via progressive aromatization peatification proceeded in a fresh water environment under variable redox conditions from anoxic to slightly oxic all three coal seams are heterogeneous the lower parts of the coal seams represent a topogenous fresh water peat mire with open water areas which was subjected to inundations the upper parts of coal seams represent a wet forest swamp with relatively stable conditions despite the observed variations in all three coal seams the mean values of petrographic and organic geochemical parameters suggest general increasing of wetness and establishment of more stable conditions from seam iii to seam i maceral and biomarker data indicate that rapid flooding of the bogs stopped peat growth in all three coal seams relatively frequent variations in all three coal seams followed by repetition of lignite characteristics depict well the pronounced seasonality e g short term cycles of the climate during late miocene in investigated area

the post triassic evolution of the sorgenfrei tornquist zone results from thermo mechanical modelling abstract the sorgenfrei tornquist zone stz is part of the fennoscandian border zone separating the danish basin from the fennoscandian shield the stz as a structural element is of palaeozoic origin and represents the north westerly segment of the tornquist teisseyre zone which separates the younger west european crust from the older east european platform and extends from the black sea to the eastern north sea area the stz was reactivated in triassic jurassic extension and late cretaceous and paleogene compression this paper investigates the regional geological consequences of the reactivations by quantitative modelling along a profile across the stz in the danish area the numerical model invokes elastic viscous and plastic deformations of the lithosphere as well as surface processes governed by erosion sedimentation and lateral transport under the influence of eustatic sea level variations and regional isostatic compensation surface processes and lithospheric mechanics are coupled through thermal blanketing effects and loading the results in general address the regional geological consequences of the existence of intracontinental zones of structural weakness more specifically the results show that the late cretaceous and paleogene chalk depocentres in the danish basin are a direct consequence of the inversion of the stz and that the stz inversion together with falling sea level in cenozoic time are amongst the principal controlling factors in the geological evolution in the eastern north sea area

the tectonic evolution of the fennoscandian border zone in denmark abstract the fennoscandian border zone is a complex tectonic zone defining the border between the stable fennoscandian baltic shield and the metastable danish basin and polish trough it forms the northwestern part of the tornquist teisseyre lineament one of the major european tectonic sutures intricate tectonic movements took place within the fennoscandian border zone from early paleozoic to recent time it is postulated that its evolution was dominated during the early palaeozoic by tensional tectonics and during the late paleozoic by dextral wrench movements the latter led to the development of curvilinear faults and the subsidence of pull apart basins transtensional stresses governing the triassic to early cretaceous evolution of the fennoscandian border zone induced the differential subsidence of rift basins during the late cretaceous and early cenozoic dextral transpressional stresses induced the partial inversion of mesozoic basins associated with the fennoscandian border zone this is reflected by the uplift of a major anticlinorium over which cretaceous strata became progressively truncated whilst adjacent areas developed into late cretaceous early tertiary depocentres basin inversion diminishes to the northwest along the fennoscandian border zone and disappears in the skagerrak area

evolution and timing of salt diapirism in the iranian sector of the persian gulf abstract the iranian sector of the persian gulf is affected by more than 30 large diapiric structures triggered by the mobilization of the infracambrian hormuz complex an evaporite rich unit that overlies precambrian basement at the base of the sedimentary succession nineteen non piercing diapirs without any appreciable salt intrusion into the upper succession were studied in detail and retro deformed by the decompaction and unfolding of 13 seismic horizons that were identified by the interpretation of a dense grid of 2d seismic lines and calibrated by well data salt uplift had begun by the early palaeozoic and persists to the present day with major pulses of intensity during the middle triassic cenomanian late oligocene and post middle miocene the structural reconstructions and the analysis of the progressive deformation of the study diapirs do not show any link between diapiric uplift and local tectonic structures and no clear correlation with the regional geodynamic events acting at the boundary of the arabian plate on the contrary the salt uplift seems strongly influenced by the differential rate of sedimentation that affected the whole study basin more than 40 000 km 2 with a coefficient of correlation between the salt uplift rate and the differential rate of sedimentation expressed by the standard deviation of the sedimentation rate calculated over the entire basin of 0 95 this downbuilding mechanism of diapiric growth is apparently induced by differential sedimentation over long distances several tens of kilometers showing that the flow of salt affected the whole basin and not just the areas around the single diapiric structures

effect of basal friction on surface and volumetric strain in models of convergent settings measured by laser scanner abstract this paper uses measurements by a high accuracy laser scanner to investigate the role of basal friction on surface and volumetric strains in sandbox models simulating fold thrust belts and accretionary wedges we monitor progressive deformation wedge growth and strain distribution in three models with similar initial boundary conditions but with different basal frictions our analyses show that in addition to influencing the kinematics and geometry of model wedges basal friction also governs both the surface and volumetric strains of the wedge after 16 3 bulk shortening the volume decreased 5 0 5 9 5 0 5 and 12 5 0 5 in the models shortened above low intermediate and high friction decollements respectively applied to nature our model results suggest that more compaction and penetrative strain is expected in convergent settings with a high friction decollement than those shortened above a low friction decollement or a weak basal bed like the salt formation under parts of the zagros fold thrust belt this volume decrease probably reduces the porosity in the deformed lithologies

molecular stable carbon isotope compositions of alkylphenanthrenes in coals and marine shales related to source and maturity abstract phenanthrene phe and methylphenanthrenes mps extracted from coaly shale and coal samples containing terrestrial organic matter are compared with the same compounds from marine shales in terms of yields and 13 c values at marginally to fully mature stages of thermal evolution the shales derived from four boreholes in the hils half graben area northwestern germany were shown to be representative of a greater number of samples from the same sites the 13 c values of extractable phe and mps are less negative in the terrestrial 24 3 to 26 0 than in the marine 28 8 to 30 5 samples since these values are unrelated to mean vitrinite reflectance r r values in the range of 0 5 0 9 it appears that the stable carbon isotope composition of phe and mps is controlled by organic matter type rather than maturity

a drying upward aeolian system of the bohdasin formation early triassic sudetes of ne czech republic record of seasonality and long term palaeoclimate change abstract the record of aeolian processes was studied in early triassic sandstones of the upper part of the bohdasin formation ne bohemia an isolated erosional relict of a triassic fluvial aeolian succession in the sudetes block of the bohemian massif central europe the aeolian system exposed in the dev t k i quarry near cerven kostelec provides a significant addition to the generally poorly preserved record of early triassic palaeoclimate and palaeowind regime in central europe two mutually interbedded facies occur in the aeolian succession 1 dune facies comprising cross strata that show interdune reactivation and superimposition bounding surfaces and 2 interdune facies formed by horizontally stratified commonly mud draped sandstones which display a number of indicators of damp to wet conditions and fluctuations in water table the succession of the dev t k i sandstones is interpreted as a record of migration and climb of dunes with intervening interdune flats which replaced an underlying fluvial system it is likely that a coeval fluvial system existed near the dev t k i dune field providing available sand in dry periods and flooding in wet periods dominant palaeowind directions are southwestward and northward in present day coordinates repeated reversals of palaeowind direction interpreted as seasonal are recorded in changes in the internal structure of the cross strata reworking and reactivation in the dune migration direction at least some episodes of dune reworking occurred simultaneously with episodes of water table rise a drying upward trend in the aeolian succession is interpreted from evidence for increased availability of sand through time the upward transition from a braided fluvial to a wet drying upward aeolian system within the bohdasin formation represents a shift toward maximum aridity of the palaeoenvironment which marks also the peak arid conditions in the long term palaeoclimatic evolution of the carboniferous triassic succession of the sudetes region and correlates with the establishment of aeolian settings in other regions of central europe during the early triassic the record of changing palaeowind directions documented in several cases to have been coupled with episodes of rapid rise in water table is taken as evidence for pronounced climatic seasonality and brings additional support to the models predicting strong monsoonal circulation during the early triassic affecting particularly the eastern subequatorial coast of pangaea and adjoining regions

estimating the ocr in uniform cohesive soil with cone penetrometer tests considering soil structure and index properties a basic empirical approach to estimate the preconsolidation stress and overconsolidation ratio ocr in uniform cohesive soils using the cone penetration and piezocone tests uses a correlation fact

paleoenvironmental reconstruction of the coal and oil shale bearing interval in the lower cretaceous muling formation laoheishan basin northeast china abstract the laoheishan basin in northeast china has been filled with lower cretaceous coal and oil shale bearing sediments the basin fill includes from base to top alluvial conglomerate lower member of muling formation fan delta sediments interbedded with coal and oil prone mudstone denominated as oil shale layers in the upper member of muling formation and volcaniclastic rocks dongshan formation in the present study the maturity of organic matter oil shale quality and paleoenvironment of the coal and oil shale accumulation are investigated based on macro and micropetrographic data proximate and ultimate analyses bulk geochemical parameters biomarkers analysis and stable isotope geochemistry in the laoheishan basin both coal and oil shale layers are derived from land plant organic matter this contrast the oil shale of this basin from oil shale coal intercalations in fault related basins in which oil shale has been found to be of algal origin the coal is sub bituminous in rank hydrogen rich and oil prone the oil shale is of low medium grade and the relatively low oil yield may relate to the abundant resinite and sporinite because of their lower generation potential compared with alginite accumulation of the high ash coal commenced in low lying mire drowned during frequent floodings subsequently high ash low sulfur coal was deposited in a stable low lying mire under oxic conditions and limited bacterial activity afterwards the mire was drowned and formed a freshwater dysoxic to oxic shallow lake in which oil shale layers accumulated finally the depositional environment returned to low lying mire but probably with a brackish influence as indicated by elevated sulfur contents in the uppermost samples petrography and biomarker based proxies indicate that gymnosperms dominated the paleovegetation of the mire accompanied by variable amounts of herbaceous plants such as ferns

aliphatic and diterpenoid hydrocarbons and their individual carbon isotope compositions in coals from the liaohe basin china abundant tricyclic diterpanes i e pimarane dehydroabietane and simonellite and tetracyclic diterpanes e g phyllocladane were detected in coal samples from the third member of the shahejie formation lower eogene liaohe basin china gas chromatography isotope ratio mass spectrometry gc irms analyses show that the carbon isotopic composition of terrigenous tricyclic and tetracyclic diterpenoid hydrocarbons are about 4 6 enriched in 13c compared to n alkanes in the same samples in addition the pimaranes and phyllocladane have comparatively narrow stable carbon isotopic compositions among the different samples with a slightly wider range in 13c compositions for the abietanes i e abietane dehydroabietane and simonellite the n alkanes and triterpenoids reflect the 13c compositions of higher plant wax

paleoenvironment of the eocene coal seam in the fushun basin ne china implications from petrography and organic geochemistry abstract the fushun basin in northeast china is a strike slip basin filled with coal bearing eocene sediments the basin fill includes from base to top volcaniclastic rocks a 20 to 145 m thick coal seam lower eocene guchengzi formation and lacustrine oil shale up to 300 m thick jijuntun formation the sub bituminous coal of the guchengzi formation famous for the amber inclusions is exploited in the largest opencast coal and oil shale mine in asia in the present contribution the depositional environment and the thermal history of the guchengzi formation are investigated based on macro and micropetrographic data bulk geochemical parameters biomarker analysis stable isotope geochemistry and vitrinite reflectance measurements according to our interpretation accumulation of the low sulfur coal commenced in a low lying mire near a shallow lake subsequently low ash coal was deposited either in a low lying mire protected from clastic influx or in a raised mire finally high subsidence rates typical for strike slip basins caused the flooding of the mire and terminated peat accumulation pristane phytane ratios suggest a gradual change from oxic to less oxic conditions during the drowning phase of the seam organic rich shales accumulated in the newly formed freshwater lake and resulted in the deposition of the overlying oil shale bearing jijuntun formation the coal is rich in liptinite macerals especially sporinite gymnosperms dominated the paleovegetation of the mire something that is also reflected by the frequent occurrence of resinite and amber and their biomarker composition the coal reached the sub bituminous or even the high volatile bituminous stage despite the limited burial depth simple 1d models suggest that this is a result of high heat flow rather than of deep burial and erosion the hydrogen rich coal is oil prone

the influence of lateral spreading on settlements beneath a fill the discrepancy between calculated consolidation settlements and measured settlements under a 3 8 m high section of an earth embankment is investigated in this paper a conventional one dimensional analysis underestimated the observed settlement by 40 a two dimensional finite element analysis was carried out to assess the effects of lateral spreading on vertical movements and the results were in close agreement with the measured values key words case history consolidation finite element analysis settlement

palaeozoic structures at the margin of the baltic shield revealed by new and reprocessed marine reflection seismic data from kattegat south west scandinavia abstract this study focuses on the late palaeozoic tectonic evolution and deformation of the sw border of the baltic shield scandinavia new and reprocessed seismic data are used to show a fault controlled structural depression in the skagerrak kattegat platform skp located between the baltic shield and the sorgenfrei tornquist zone stz the depression is characterised by a material with unusual seismic structures which are undulating to conical have a lateral width of about 5 km and a height of more than 1 km they are truncated at their top by the top pre zechstein unconformity and they occur above top lower palaeozoic the stratigraphic interval where the undulating structures occur is characterised by unusually high seismic velocities a plausible tectonic setting for the undulating structures is found in the tectonic and volcanic events during the late carboniferous early permian correlation of seismic and drilling data suggests that the faults controlling the sw border of the baltic shield are of at least two generations the borglum fault and the saeby fault are interpreted to be of silurian age and the faults of the skp of late carboniferous early permian age a proposed erosional phase in devonian or early carboniferous time removed lower palaeozoic rocks from the skp before the deposition of late carboniferous sediments such an erosional phase may explain the well established devonian and early carboniferous hiatus in kattegat and surrounding areas the seismic data display key features from late carboniferous and early permian times in an area where such structures have survived subsequent erosion and deformation

paleozoic paleo cover of the southern part of the fennoscandian shield fission track constraints abstract granitic intrusions older than 1200 ma from an area west of lake vanern south sweden show fission track ages of 680 50 ma 2 late precambrian for sphene and 220 10 ma late triassic for apatite the samples were taken at the present post glacial erosion surface which is close to the sub cambrian peneplain the c 680 ma sphene fission track ages are thought to be related to the uplift of the area which led to the establishment of this erosion surface at c 600 ma ago the much younger apatite fission track ages and the confined spontaneous track length distributions along with regional stratigraphic constraints suggest that the basement was subsequently buried under 3 4 km of paleozoic supracrustals this induced in the basement a rise in temperature which obliterated the older apatite fission tracks but not those in sphene which has a higher closure temperature at the beginning of the mesozoic the area was uplifted again the cover rocks were removed and the basement rocks cooled slowly below the temperature range of fission track annealing in apatite

rheological and physical characteristics of crustal scaled materials for centrifuge analogue modelling abstract we characterize a set of analogue materials used for centrifuge analogue modelling simulating deformation at different levels in the crust simultaneously specifically we improve the rheological characterization in the linear viscoelastic region of materials for the lower and middle crust and cohesive synthetic sands without petroleum binding agents for the upper crust viscoelastic materials used in centrifuge analogue modelling demonstrate complex dynamic behaviour so viscosity alone is insufficient to determine if a material will be an effective analogue two series of experiments were conducted using an oscillating bi conical plate rheometer to measure the storage and loss moduli and complex viscosities of several modelling clays and silicone putties tested materials exhibited viscoelastic and shear thinning behaviour the silicone putties and some modelling clays demonstrated viscous dominant behaviour and reached newtonian plateaus at strain rates 2 s 1 while other modelling clays demonstrated elastic dominant power law relationships based on these results the elastic dominant modelling clay is recommended as an analogue for basement cratons inherently cohesive synthetic sands produce fine detailed fault and fracture patterns and developed thrust strike slip and extensional faults in simple centrifuge test models these synthetic sands are recommended as analogues for the brittle upper crust these new results increase the accuracy of scaling analogue models to prototype additionally with the characterization of three new materials we propose a complete lithospheric profile of analogue materials for centrifuge modelling allowing future studies to replicate a broader range of crustal deformation behaviours

high resolution sequence stratigraphy from piezocone tests an example from the late quaternary deposits of the southeastern po plain abstract cone penetration tests are traditionally regarded as a major tool for geotechnical investigations this study based upon interpretation of 234 cone penetration tests with pore pressure measurements piezocone tests or cptu carried out in the late quaternary deposits of the southeastern po plain shows how cptu tests can also be used for sedimentological purposes including detailed facies characterization subsurface stratigraphic correlations and identification of the key surfaces for sequence stratigraphic interpretation the late quaternary depositional history of the southeastern po plain reconstructed on the basis of data from seventeen continuously cored boreholes includes 1 alluvial plain development during the late quaternary lowstand and the early stages of transgression 2 formation of a rapidly migrating barrier lagoon system during the late transgressive phases 8800 6000 y bp 3 construction and progradation of a wave dominated delta ancient po delta during the following sea level highstand 6000 800 y bp and 4 development of the present day alluvial plain following the delta lobe abandonment in the 13th century a d local execution of cptu tests in coincidence with drilling sites enables the calibration of borehole data with piezocone penetration profiles lithofacies characterization is based upon estimation of three major parameters corrected cone resistance q t sleeve friction f s and pore water pressure u plotting of q t versus the ratio of cone friction to cone bearing fr is adopted as the major tool for sediment texture classification eight major facies associations for the southeastern po plain are identified these are for decreasing q t values 1 fluvial channel sands 2 beach ridge sands 3 transgressive barrier sands 4 crevasse sands and silts 5 levee silts and sands 6 floodplain silts and clays 7 prodelta clays and 8 marsh clays and peats cptu profile interpretation also provides the basis for the identification of the three major key surfaces within the late quaternary 4th order depositional sequence 1 the transgressive surface ts marking the boundary between the locally pedogenized stiff pleistocene alluvial clays and the overlying holocene transgressive paralic deposits has a distinctive pore pressure response with very low u values and is characterized by a sharp downward increase in f s which is paralleled by a moderate increase in q t 2 the ravinement surface rs corresponding to the boundary between fine grained back barrier deposits and the overlying transgressive barrier sands is invariably marked by a sharp upward increase in q t and decrease in fr 3 the maximum flooding surface mfs which is not clearly recognizable on the sole basis of core data is identified within shallow marine prodelta clays in combination with minor peaks of q t which have been interpreted to reflect a laterally extensive fossil lag with transition in proximal areas to sand shell rich layers simplicity speed and comparatively low costs of cptu tests imply that an extensive use of this method when used in conjunction with core programs can be a very attractive alternative to economically less convenient methods for the geological mapping of alluvial coastal plain areas consisting of non gravel deposits

intermediate decollement activation in response to the basal friction variation and its effect on folding style in the zagros fold thrust belt an analogue modeling approach although the role of various basal and intermediate decollement levels on structural style is well documented individually in many folded terrains the interaction between basal and intermediate de

carbon isotopic composition of individual biomarkers in gilsonites utah abstract carbon isotopic compositions of saturated hydrocarbon aromatic hydrocarbon nso resin and asphaltene fractions of vein forming gilsonites cowboy bonanza independence wagonhound and harrison veins in the ne uinta basin utah are all similar and isotopically resemble mahogany zone shale extracts of the green river formation 13 c 29 to 31 individual molecular fossils in the gilsonites show a wider variability in compositions indicative of their paleoecological origins within the eocene uinta greater green river paleolake system carbon isotopic compositions of c28 and c29 steranes 13 c 25 to 32 pristance and phytane 33 to 34 and perhydro carotene carotane 13 c 33 2 suggest that organisms producing these compounds grew near the lake surface the c33 carotenoid lexane is isotopically identical to the c40 carotenoid carotane supporting a common c40 carotenoid precursor two groups of hopanes can be differentiated in the gilsonites based on carbon isotopic compositions c29 c31 and c32 hopanes and moretanes 40 9 to 44 3 consistent with a source from midwater bacteria and c30 hopanes and moretanes 51 0 and 60 5 for which the strong 13c depletion suggests at least partial derivation from methylotrophs the isotopic signatures of these molecular fossils suggest the source beds of the gilsonites were deposited in a stratified paleolake system with a depositional environment similar to that which formed the mahogany zone shales of the piceance creek basin algal biomarkers in the gilsonites are isotopically uniform throughout the area of the gilsonite vein occurrence 1500 km3 and resemble those in the mahogany zone shale in the piceance creek basin over 50 km to the east this remarkable lateral uniformity suggests that very similar photic zone water conditions existed across the entire uinta piceance creek paleolake system at the time of deposition of the gilsonite source bed mahogany zone shale sterane isotopic compositions are effective for the genetic correlation of the solid bitumens immature oils in contrast the carbon isotopic compositions of the bacterial biomarkers in the gilsonites vary significantly suggesting that conditions in deeper waters of the paleolake system were more variable carbon isotopic signatures of individual hopane biomarkers in the green river formation appear to be valuable for identifying different source facies characteristics within the same paleolake depositional system

analogue and numerical modelling of salt supply to a diapiric structure rising above an active basement fault salt diapirs preferably rise above basement faults in extensional basins a series of analogue and numerical models were developed in order to assess the supply of salt from the footwall and hanging wall to a diapir and to study the influence of basin inversion on the diapir development the modelling scenario was based on the klodawa salt structure evolution central poland the experiments show that the ductile material derived from the footwall constitutes the dominant portion of the diapir developed due to model extension and this material occurs both in the footwall and hanging wall parts of the diapir shortening of the analogue models resulted in thinning of the diapir and shifting its stem onto the footwall ductile material become redistributed inside the diapir however footwall material still prevails in the diapir structure results from the numerical models show that the magnitude of the basement fault governs the amount of salt supply to a diapir across the fault and that there is a differential salt supply from the hanging wall and footwall with time

is there evidence for a substantial contribution of prokaryotic biomass to organic carbon in phanerozoic carbonaceous sediments the role of prokaryotes bacteria and archaea in producing biomass and reworking settling and buried organic matter is of paramount importance since it exerts a major impact on the composition of sedimentary organic matter and ultimately petroleum this key role of prokaryotes in combination with a biomarker fingerprint often dominated by prokaryotic molecular fossils e g hopanoids has led to the assumption that prokaryotic biomass is a substantial source for organic carbon in carbonaceous sediments however biosynthesising and reworking organic matter does not necessarily imply sourcing organic matter by the prokaryotes and the abundance of biomarkers does not always reflect relative contributions to sedimentary organic matter in this paper the existing evidence for a substantial prokaryotic biomass contribution to sedimentary organic carbon oc is critically evaluated this shows that despite the often prominent presence of prokaryotic biomarkers in sediments evidence for a substantial prokaryotic contribution to sedimentary oc is generally lacking this is demonstrated by i the application of the carbon isotopic mass balance principle in various sedimentary settings ii an alternative explanation for the proposed dominant role of heterotrophic reworking in the oxford clay iii a summary of the effects of bacterial oxidation in organic matter rich turbidites and iv recent data showing that the evidence for recalcitrant carbon in prokaryotes is scant although these observations do not rule out substantial contributions of prokaryotic carbon to oc in phanerozoic carbonaceous sediments this remains to be demonstrated and the final answer awaits the development of new technologies to full characterise sedimentary oc

changes in the trophic state of lake erie discordance between molecular δ13c and bulk δ13c sedimentary records abstract prior to 1980 anthropogenic phosporus p loadings resulted in increased algal productivity and the deterioration of water quality within lake erie we measured c and n elemental compositions geolipid concentrations and 13 c values for bulk organic material and individual alkanes in samples taken from a 40 cm sediment core from the eastern basin of lake erie to infer recent trends in primary productivity and diagenesis the predominance of autochthonous algal derived c throughout the core is evidenced by low c n values 9 10 and the persistent abundance of n c 15 to n c 17 alkanes throughout the core the 13 c values of bulk organic c from lake erie vary between 25 9 and 24 9 with a maximum corresponding to the period of elevated historical p loading within lake erie 13 c values of short chained algal derived alkanes n c 18 are lower approximately 1 0 than their terrestrial derived homologs n c 25 down core variations in the 13 c composition of algal derived short chained alkanes do not exhibit the same trend as that observed for bulk organic c down core variation in 13 c values of individual alkanes likely reflect multiple diagenetic effects including kinetic fractionation effects variations in the relative contributions of isotopically unique n alkanes to the sediments and or temporal changes in 13 c enrichments of n alkanes associated with a single source high sedimentation rates characteristic of this core emphasize temporal variations in molecular 13 c values that might not otherwise be observed whereas 13 c data for bulk sedimentary organic c appear to reflect variation in trophic state the isotopic record for algal derived n alkanes e g n c 17 and pristane from lake erie must be considered from the perspective of molecular transformations

carbon isotope variability of triassic amber as compared with wood and leaves southern alps italy abstract the carbon isotope signatures of carnian late triassic amber drops from rifugio dibona southern alps italy were studied and compared with that of other middle early late triassic fossil plant remains namely wood and leaves amber wood and leaf carbon isotope data are highly variable within the same beds 13camber values vary by up to 5 4 and are enriched by 2 5 with respect to associated wood 13cwood and 13cleaf ranges are narrower than that of amber 2 3 and the isotopic offset within each bed is similar over time the high triassic amber carbon isotope variability is similar to that of recent resin despite the high variability 13cwood and 13cleaf illustrate a middle early late triassic secular positive trend that is similar to that of marine 13cinorg data and must record the carbon isotope evolution of the ocean atmosphere system

aliphatic and aromatic hydrocarbons in candiota coal samples novel series of bicyclic compounds abstract aliphatic and aromatic fractions obtained from nine samples taken from two different seams of five boreholes in the candiota coalfield lower permian were analysed by gas chromatography mass spectrometry the occurrence of the tetracyclic diterpenoids 16 h phyllocladane and ent 16 h kaurane among the aliphatic hydrocarbons and the tricyclic diterpenoids simonellite and retene in the aromatic hydrocarbon concentrates suggest an important input from conifers to the sedimentary biomass this may explain the origin of a novel series of saturated and aromatic bicyclic compounds detected in the extracts which may be structurally related to the same precursor possibly a conifer resin derived tricyclic diterpenoid

the structural styles and formation mechanism of salt structures in the southern precaspian basin insights from seismic data and analog modeling abstract using the seismic profiles and analog modeling this paper addresses the salt structures in the m and b blocks in the southern precaspian basin the salt structural features the formation mechanism and the controlling factors of structural deformation are investigated and discussed systematically the interpretation of the seismic profiles shows that typical salt related structures include salt wall flip flop salt diapir salt roller salt pillow dome salt weld salt withdrawal minibasin and drag structure or drape fold in addition model results demonstrate that the gravity spreading driven by progradation and aggradation is probably the primary factor in controlling the formation of the salt structures in the research area due to the differential loading driven by progradation passive salt diapir developed near the progradational front followed by the formation of intrasalt withdrawal minibasin bounded by two salt diapirs and secondary reactive triangle salt diapir or salt pillow might form within the intrasalt withdrawal minibasin model results also indicate that the pattern of the subsalt basement has important influence on the formation and evolution of salt structures salt diapirs primarily developed along the margin of the subsalt uplift basement where high shear deformation was induced by differential sedimentary loading between the uplift area and the slope area

triassic and jurassic structural development along the tornquist zone denmark abstract in the danish area the old crustal weakness zone the tornquist zone was repeatedly reactivated during the triassic and jurassic early cretaceous causing minor dextral movements along the major boundary faults these tectonic events were minor as compared to the tectonic events of the late carboniferous early permian and the late cretaceous early tertiary although a dynamic structural and stratigraphical analysis indicate that the zone was highly active compared to the surrounding areas during the middle to late permian the area was exposed to erosion and became a peneplane a regional triassic subsidence produces seismic onlap towards the northeast where the youngest triassic sediment is found supercropping the precambrian basement during mainly the early triassic several of the major early permian faults became reactivated probably with dextral strike slip along the borglum fault the jurassic early cretaceous subsidence became restricted primarily to the area between the two main faults in the tornquist zone the grena helsingborg fault and the borglum fault this restricted basin development indicates a change in the regional stress field that seems to have come into existence during the transition between the triassic and the jurassic the subsidence in the middle jurassic and the late jurassic early cretaceous follows the early jurassic pattern with local subsidence in the tornquist zone but even more restricted to the zone the subsidence seems to have decreased in the middle jurassic hereafter subsidence increased again during late jurassic early cretaceous times a set of small faults were generated during the mesozoic internally in the tornquist zone this fault pattern indicates a broad transfer of strike slip oblique slip motion from the grena helsingborg fault to the borglum fault

salt as a 3d element in structural modeling example from the central european basin system abstract based on a well constrained 3d structural model of the central european basin system 3d modeling has been carried out to understand the regional scale regularities between movements of the upper permian zechstein salt and the major post permian tectonic events the 3d reconstruction of the paleo thickness of upper permian salt at the end of the permian period demonstrates that areas of thickened upper permian salt correlate with the present day distribution of the largest salt structures within the central european basin system this spatial correlation implies that the distribution of salt thickness at the end of deposition partially controlled the structural style of the basin during post permian phases of salt tectonics moreover the results of 3d salt redistribution for post permian times indicate that the initiation of salt movements took place in the triassic the triassic extensional events triggered several phases of salt movements within the coeval depocenters of the central european basin system such as the glueckstadt graben the horn graben the norwegian danish basin the fjerritslev trough and the himmerland graben and the polish basin during the late jurassic early cretaceous extensional transtensional tectonic event the strongest salt movement occurred within the central graben the lower saxony basin and the pompeckj block the intensity of the late jurassic early cretaceous phase of salt tectonics is essentially declining from the marginal areas of the central european basin system towards the horn graben the glueckstadt graben and adjacent areas the late early cretaceous early late cretaceous is characterized by tectonic quiescence without strong salt movements over the entire study area the next regional phase of salt movements was triggered by late cretaceous early cenozoic inversion involving almost the entire central european basin system in terms of renewed salt movements inversion related thick skinned salt tectonics is observed along the nw se trending elbe fault system and the teisseyre tornquist zone where strongest compressional deformations were localized on the contrary a thin skinned character of salt movements was prevailing within the largest part of the north german basin post inversion cenozoic subsidence was also accompanied by salt activity related either to diapiric rise due to regional shortening and or to local roughly e w directed extension the cenozoic phase of salt movements was especially prominent within the marginal troughs of the glueckstadt graben

salt tectonics in the norwegian danish basin a study is presented of salt tectonics in a 28 000 km2 area in the norwegian danish basin of the north sea the basin is mainly of permian to early jurassic age and contains sediments which locally reach 8 km in thickness zechstein upper permian salt occurs widely in the basin and has given rise to widespread and intense salt tectonics using seismic reflection sections with a total length of 14 000 km as well as borehole data 86 salt structures have been mapped within the study area the floor of the basin that is the base of the zechstein salt and the faults affecting this floor have also been mapped it is therefore possible to investigate the association of faults and salt structures and hence to ascertain to what extent faulting of the basin floor may have initiated salt movement various lines of investigation and reasoning have been developed to arrive at an estimate of the number of structures for which salt movement is likely to have been initiated by faulting of the basin floor it is found that only for a limited number of salt structures probably about five out of a total of 86 structures the salt movement is likely to have been initiated by faulting the very large majority of the salt structures originated independent of faulting the mechanism responsible for the initiation of salt movement in this majority has also been studied it is found that these salt structures can be divided into two groups one group comprises about 37 salt structures which are randomly distributed nearly all of them are situated where the present basin floor is relatively flat and at its deepest they are thought to be the result of classical halokinesis that is the autonomous upward movement under the influence of gravity of mobile salt at locations where the sedimentary overburden at the time of initial movement was locally less heavy a second group comprises about 43 individual structures which are aligned along nine so called trend lines it is first shown that these trend lines are independent of faults and fault trends in the basin floor the origin of these trends is then discussed by considering two alternative hypotheses for the mechanism responsible for the initiation of salt movement along these trend lines the first hypothesis assumes that salt ridges in the subsurface are initially pushed up by a prograding sedimentary overburden the second hypothesis assumes that initial ridges of mobilized salt are formed along a palaeo depth contour which migrates up the flank of the subsiding basin both hypotheses assume that the salt ridges thus formed can subsequently develop into individual salt structures which produce the observed pattern of trend lines a critical analysis of these two alternative hypotheses leads to the conclusion that the second one involving the concept of a palaeo depth contour which migrates up flank is the more acceptable the mechanism involved may be characterized as a special type of halokinesis namely as halokinesis constrained to operate along a line

carbon isotopic compositions of 28 30 bisnorhopanes and other biological markers in a monterey crude oil abstract an immature tar like oil api 3 13 c 23 6 vs pdb from the miocene monterey formation offshore california was selected for a study of carbon isotopic signatures of individual biomarkers the three principal stereoisomers of 28 30 bisnorhopane c 28 have within analytical precision identical carbon isotopic compositions average 13 c 32 3 0 4 and are considerably depleted in 13 c compared to the whole oil these 28 30 bisnorhopanes bnh differ isotopically from c 29 and c 30 17 h hopanes 25 8 and 26 1 and c 31 c 35 extended hopanes 13 c 27 7 and suggest different precursors for the c 28 hopanes than for c 29 c 35 hopanes the relative depletion of bnh of almost 9 compared to the isotopic composition of the whole oil suggests that these hopanes derive from chemoautotrophic bacteria possibly not yet identified h 2 s oxidizers which utilize 13 c depleted substrates the c 29 and c 30 hopanes are within analytical precision isotopically identical 26 and similar to algal derived compounds e g c 27 steranes 25 9 which is consistent with a cyanobacterial source for these hopanes an archaebacterial biomarker 1 1 biphytane 13 c 25 5 likely derived from methanogens is also isotopically similar to c 27 sterane norpristane pristane and phytane liberated by desulfurization of the aromatic and polar maltene fractions show isotopic compositions similar to the same isoprenoids in the free lipids of the bitumen total range from 24 5 to 27 5 this isotopic similarity supports a common origin for the free and sulfur bound forms of these isoprenoids this origin could be algal and or archaebacterial lipids which both show isotopic compositions within the range of the c 18 c 20 isoprenoids like other marine derived organic matter this monterey oil does not show the strong 13 c depletion typical for methylotroph derived compounds characteristically found in organic matter of lacustrine origin this may indicate fundamental differences of methane recycling processes in marine sulfate dominated as compared to lacustrine environments

late cretaceous intraplate thrusting in central europe effect of africa iberia europe convergence not alpine collision a well established event of intraplate basin inversion and basement thrusting affected central europe in late cretaceous time it is widely accepted to have resulted from the collision of the alpine orogen with europe s margin at that time an early alpine orogen located on the leading edge of the adria microplate still lay far southeast of its present day position and had entered a phase of extension after a first orogenic event characterized by w to nw directed thrusting this configuration is not likely to have induced ssw nne directed thrusting and folding in the future european foreland that was still separated from the alpine wedge by a strip of oceanic lithosphere by contrast the onset of intraplate contraction coincides with an important change in relative motion between the european and african plates at ca 90 ma africa s sse directed sinistral transform motion relative to europe changed to ne directed convergence this agrees well with the timing and kinematics of intraplate thrusting in central europe structures of similar age and kinematics occurring in southern france spain and north africa suggest that the late cretaceous pulse of contraction was caused by pinching west central europe s thin lithosphere between baltica and africa only since the onset of n directed thrusting in the alps in paleocene or eocene time are the kinematics of the alps and their european foreland compatible indicating that mechanical coupling between africa europe and the adria microplate had been achieved

experiments on faulting in a two layer cover sequence overlying a reactivated basement fault with oblique slip abstract two series of experiments were undertaken to investigate the development of faults in a cover sequence overlying a reactivated basement fault with oblique slip the experiments represent physical models properly scaled to account for gravitational forces brittle behaviour of the upper cover and ductile behaviour of evaporites in the lower cover models were made with a coulomb layer sand overlying a newtonian ductile layer silicone putty in each series the thickness of the silicone layer was varied from each experiment to the next in all normal wrench experiments a domain of faults appeared in the brittle layer vertical offsets were mostly of normal sense but some reverse faults occurred in experiments with thick silicone layers the thicker the silicone the wider the fault domain the deformation zone was in all cases limited to the faulted domain in the reverse wrench experiments discrete reverse riedel faults appeared without a silicone layer as the silicone layer became thicker the importance of the reverse faults diminished with the thickest layer of silicone 3 cm no faults appeared in the overburden but a monoclinal flexure accommodated the dip slip component in the presence of silicone the deformation zone was not limited to a faulted domain and the strike slip component was accommodated by a bulk shearing of the overburden in the uplifted compartment these experiments demonstrate that in basins deformed in oblique slip mode any deformation that is localized along discrete faults at the basement level becomes distributed over a much wider zone of overburden when this overlies an interval of evaporites

linking changes in tectonic style with magmatism in northern europe during the late carboniferous to latest permian abstract early carboniferous to permian magmatism associated with rifting within the northern foreland of the variscan orogen was widespread across europe during the long period of magmatic activity the regional tectonic setting changed across the region from early carboniferous extension and basin formation to a rifting wrenching style of deformation in the late carboniferous stephanian to early permian wrenching and faulting were accompanied by widespread voluminous and episodic magmatic extrusion intrusion and underplating this was followed by thermal relaxation and the development of the northern and southern permian basins in later permian times thermal relaxation was punctuated by a permo triassic phase of extension and graben formation 40ar 39ar ar step heating dating for mineral separates and whole rock samples of magmatic rocks from southern scandinavia oslo graben and south sweden and rugen north germany provides further radiometric evidence for three of the proposed periods of magmatic activity in the region latest carboniferous to earliest permian ages c 300 310 ma were obtained for volcanic rocks in the oslo graben and dolerite sills and dykes in south sweden and north germany this phase can be time correlated with magmatic activity that occurred throughout europe during large scale dextral wrenching that followed the variscan orogeny a second phase of alkaline intrusions is confined to the oslo graben and related to caldera collapse around c 275 ma the third permo triassic phase c 250 ma is considered to be related to a new tectonic cycle involving extension that triggered minor melting of enriched fertile mantle

salt structures and hydrocarbon accumulations in the tarim basin northwest china the tarim basin is one of the most important hydrocabon bearing evaporite basins in china four salt bearing sequences the middle and lower cambrian the mississippian the paleogene and the neogene have various thickness and areal distribution they are important detachment layers and intensely affect the structural deformation in the basin the kuqa depression is a subordinate structural unit with abundant salt structures in the tarim basin salt overthrusts salt pillows salt anticlines salt diapirs and salt withdrawal basins are predominant in the depression contraction that resulted from orogeny played a key function on the formation of salt structures growth strata reveal that intense salt structural deformation in the kuqa depression occurred during the himalayan movement from oligocene to holocene with early structural deformation in the north and late deformation in the south growth sequences also record at least two phases of salt tectonism in the yingmaili tahe and tazhong areas low amplitude salt pillows are the most common salt structures and these structures are commonly accompanied by thrust faults the faulting and uplifting of basement blocks controlled the location of salt structures the differences in the geometries of salt structures in different regions show that the thickness of the salt sequences has an important influence on the development of salt cored detachment folds and related thrust faults in the tarim basin salt sequences and salt structures in the tarim basin are closely linked to hydrocarbon accumulations oil and gas fields have been discovered in the subsalt intrasalt and suprasalt strata salt deformation has created numerous potential traps and salt sequences have provided a good seal for the preservation of hydrocarbon accumulations large and small scale faults related with salt structures have also given favorable migration pathways for oil and gas when interpreting seismic profiles special attention needs to be paid to the clastic and carbonate interbeds within the salt sequences because they may lead to incorrect structural interpretation in the tarim basin the subsalt anticlinal traps are good targets for hydrocarbon exploration

fault associated salt flow and mass movement it has been suggested by model studies that swell formation may occur in a mobile layer subjected to faulting where the fault throw is less than the mobile layer thickness in such a case in the real earth differential overburden loading due to deposition or erosion at a later stage will cause a mobile layer e g salt rock to flow from the region of higher to the region of lower load stress via the fault zone resulting in swell formation on the upthrow side of the fault two different examples of this effect are illustrated in marine seismic sections from the north sea associated with one of these examples are seismic events which appear to indicate mass movement of sediment down the fault scarp prior to the deposition of the main body of zechstein halite at this location

formation and inversion of salt detached ramp syncline basins results from analog modeling and application to the columbrets basin western mediterranean abstract the widespread extensional deformation that took place during jurassic to cretaceous times in western europe and the north atlantic margin resulted in the formation of several rift systems some of the resulting basins associated with these rifts show broad synclines detached on pre or syn kinematic permian or triassic salts and are filled by thick sedimentary successions the development of these salt detached ramp syncline basins has been associated to the extensional motion of ramp flat extensional sub salt faults the shape and kinematics of such faults have usually been established using the architecture of syn kinematic units and by assuming complete coupling of the hanging wall rocks therefore there are fault interpretations that do not consider the role played by the deep salt layers which clearly act as an effective detachment decoupling sub and supra salt deformations moreover the complexity of these scenarios further increases due to some of these basins which during latest cretaceous and cenozoic times were partially inverted and were often incorporated into fold and thrust belts based on analog models and using the mesozoic columbrets basin western mediterranean as a case study the aim of this research is to decipher the influence of the ramp flat extensional fault during the syncline development and the interaction with a pre kinematic salt and to infer how salt detached ramp syncline basins are subsequently inverted to achieve this goal we carried out an experimental program consisting of eight different sandbox models our results show that the main structure formed at the end of the extension is a salt detached ramp syncline and that its geometry not only depends on the dip and length of the fault panels but also on the fault displacement and salt thickness the inversion of these salt detached ramp synclines resulted in a major thick skinned fault bend anticline with minor thin skinned contractional structures

palaeozoic structural development along the tornquist zone kattegat area denmark abstract the interpretation of newly released commercial 2d reflection seismic data in the kattegat area denmark has provided us with a better understanding of the palaeozoic tectonic processes along the tornquist fault zone a base palaeozoic time structure map a lower palaeozoic twt isopach map a true lower palaeozoic twt isopach map an upper carboniferous lower permian syn rift twt isopach map a top pre zechstein time structure map and a zechstein combined twt isopach and palaeogeography map have been generated the uniform lower palaeozoic sequence thickness in the kattegat both inside and outside the tornquist zone indicates only minor lateral movements if any whereas the extensive upper silurian sequence increasing in thickness to the north indicates a relatively fast regional subsidence the base palaeozoic time structure map and the late palaeozoic syn rift isopach map show a clear late palaeozoic extension in the area the syn rift isopach map in combination with the time equivalent opening of the skagerrak graben at right angles to the tornquist zone in the kattegat indicates that this extensional tectonic event had a dextral slip component measurements on internal extensional faults in the tornquist zone give a minimum right lateral displacement of 10 4 km the footwall blocks were deeply eroded during the early permian rifting and at zechstein times the area became a peneplane the tornquist zone was later exposed to several tectonic phases where dextral slip played a role indicated by the push up and pull down structures caused by restraining and releasing bends of the borglum fault the dextral displacement along the borglum fault since the beginning of the permian is in the order of 5 7 km based on the displacement of a lower palaeozoic local depocentre early permian depocentres and faults which gives a total amount of right lateral displacement since the early palaeozoic in the order of 15 20 km the continuously repeated tectonic episodes along the tornquist zone throughout most of the phanerozoic show that the zone was easily reactivated implying deep seated basement faults the tornquist zone can be seen as a buffer zone between continental blocks whenever changes in the regional stress field are induced

unusual carbon isotope compositions of biomarker hydrocarbons in a permian tasmanite abstract the permian oil shale sample of this study is from a deposit in tasmania in which the only recognizable structures are large thick walled unicellular specimens of the green alga tasmanites the fossils are so densely packed that this shale is termed tasmanite the carbon isotopic composition of bulk kerogen carbon c 13 c org 16 6 vs pdb is unusually enriched in 13 c compared to marine permian organic carbon 25 to 30 this 13 c enrichment suggests specific environmental conditions co 2 draw down and or physiological specialties cell size and growth rate of tasmanites which in modern environments are known to cause 13 c enrichment in marine phytoplankton isotope signatures of extractable organic species unlike in normal immature oil shales are considerably enriched in 13 c compared to the kerogen the bitumen 10 9 is composed predominantly of extended saturated c 18 c 25 tricyclic terpane hydrocarbons 9 9 to 12 2 total range with an average of 10 8 these tricyclics are not only found as free lipids in the extract but also in pyrolysates with similar isotopic signatures and are therefore likely biosynthesis products of tasmanites the monoaromatic and diaromatic tricyclic terpane hydrocarbons c 17 c 19 have similar isotopic signatures 9 3 to 12 8 total range with an average of 10 6 two monoaromatic tetracyclic hydrocarbons c 23 and c 24 a quantitatively minor but biogenetically interesting group average at 10 2 in contrast pristane and phytane as well as n alkanes 18 to 22 are depleted in 13 c compared to kerogen carbon the isotopic similarity of all the cyclic terpanes in this sample together with their occurrence in the free lipids and kerogen suggests that they have a common origin and are biosynthesis products of the marine unicellular green algae tasmanites the tetracyclic terpanes therefore are not des a oleananes derived from land plants but are possibly monoaromatic des a gammaceranes or other des a triterpenoids derived from marine sources the unusual enrichment in 13 c in the cyclic hydrocarbons is hypothesized to result from the special growth conditions of the algae isoprenoids and n alkanes are also likely biosynthesis products of tasmanites possibly during the spore formation stage when physiological and environmental conditions were different than during planktonic biosynthesis

transformations and correlations among some clay parameters the global database this study compiles a large database of 10 clay parameters labeled as clay 10 7490 from 251 studies covering clay data from 30 regions or countries worldwide hence the range of data covered by

abundant tetracyclic terpenoids in a middle devonian foliated cuticular liptobiolite coal from northwestern china cuticular liptobiolite coal defined by its dominant cutinite is rare and only known in a few regions of the world an occurrence of this type of coal found in the devonian of the hefeng basin xinjiang northwestern china is described for the first time by organic petrography and biomarker analysis the cuticular liptobiolite has distinct sheet like layers and thus splits easily into leafy laminae which are segregated during weathering forming a so called paper coal it is comprised dominantly of cutinites 75 vol on a mineral free basis with minor vitrinites 20 lycopsids are suggested to be the dominant coal forming plants the aliphatic fractions of these samples contain only small amounts of n alkanes and common biomarkers such as steranes and hopanes tetracyclic diterpanes cnh2n 6 with mainly beyerane and atisane skeletons are the dominant constituents the abundant tetracyclic diterpanes present in this and other devonian cuticle rich coals indicate that their parent natural product precursors occurred abundantly in the early vascular land plants of the devonian i e lycopsid and psilopsid species it seems that these early land plants secreted massive amounts of resins from their vascular tissues coating their cuticle surfaces to protect against water evaporation massive cuticle accumulation in the middle devonian likely resulted from a simple assemblage of unique early land plants

decoupled extensional faulting and forced folding in the southern part of the roer valley graben belgium abstract during late oligocene incipient rifting the southern part of the roer valley graben was characterized by normal faulting and forced folding of its paleogene pre rift strata the 2d seismic data used in this study shows that these faults and forced folds were geometrically decoupled from faults or fault zones in the underlying triassic and older strata geometric decoupling consistently took place in an interval that comprises latest triassic to early jurassic soft claystones on top of triassic alternations of evaporites and claystones layers this mechanically weak interval probably inhibited the upward propagation of re activated underlying faults resulting in the formation of the observed forced folds monoclines in the overlying paleogene pre rift strata strain from the sub detachment faults was distributed along the mechanically weak interval towards detachment edges leading to the consistent presence of faults in the footwall domain of the supra detachment monoclines the mechanically weak interval was thereby able to maintain the kinematic coherency between geometrically decoupled under and overlying deformation throughout late oligocene rifting

late cretaceous early tertiary tectonic evolution of the central european basin system cebs constraints from numerical modelling abstract the results obtained from a suite of spherical thin sheet finite element model calculations on the late cretaceous early tertiary tectonic evolution of the area of the central european basin system cebs are presented and discussed the calculations incorporate the effects of variations in lithospheric structures and compositions and changes in the imposed boundary conditions the impact of lateral contrasts such as pre existing weak domains is quantified through a thermo mechanical model for the entire cebs the obtained predictions have been constrained by comparisons with more recent observed field data and resemble the present day dynamics and kinematics a trial and error reconstruction of the development through time of the dynamic of the alpine orogeny as well as of the early atlantic extension have been considered in order to investigate the role of boundary forces in the late cretaceous early tertiary tectonic evolution of the cebs the observed evolution of subsidence depocentres and areas of uplift for the cebs during this time span has been reconstructed the results are in agreement with previous studies which have related the large scale late cretaceous early tertiary inversion within the cebs to long wavelength intra plate compressive stresses exerted mainly by the alpine thrust the models show that lateral heterogeneities have to be considered in order to model more local features such as the observed differential response of adjacent areas to the large scale stress regime this indicates that both intra plate tectonic forces and rheological structural contrasts must be taken into account to reconcile the style of intra plate deformation and to model the evolution through time of complex basin systems

the effect of gravitational compaction on estimation of vertical salt structure growth abstract the growth history of salt structures is reflected in the variation of the present thickness of the overlying and surrounding sediments in relation to the regional normal a method for estimating the growth history of salt structures in the pillow and post diapiric phase including the effect of differential syn and post depositional compaction is described the assumption that stratigraphic thinning and established structural relief is a result of vertical salt movement alone is inadequate a quantification of the true vertical movement of the salt crest necessitates a correction for compaction and differential basement subsidence the on structure thickness is compared to the regional normal for the time stratigraphic interval under consideration on the basis of the dominant porosity reducing process the minimum and maximum net growth can be calculated the true net growth is assumed to be contained within these limits probably closest to the minimum net growth two shallow salt diapirs in the danish basin exemplify the relationship between the observed stratigraphic thinning and structural relief and the differential compaction differential basement subsidence and vertical growth of the salt surface the average minimum and maximum net growth of the salt surface at the batum and mors salt diapirs in the post diapiric phase are calculated the minimum and maximum net growth values for the batum salt diapir are 731 m and 1303 m respectively and for the mors salt diapir 276 m and 996 m respectively thus emphasizing the importance of including the effect of compaction in the calculations of salt structure net growth the implications for storage of hydrocarbons radioactive and chemical wastes as well as for petroleum exploration are emphasized

insights into the origin of perylene from isotopic analyses of sediments from saanich inlet british columbia perylene is an abundant and common polycyclic aromatic hydrocarbon in sedimentary settings yet its origin remains puzzling we have investigated the relation of perylene to the amount and type of organic matter in the sediments of saanich inlet a coastal marine anoxic basin organic matter is predominantly marine in origin but the proportions of marine and land derived components have varied perylene concentrations generally increase with sediment depth relative to toc which indicates continued formation of this compound by microbially mediated diagenesis perylene 13c values range between 27 7 and 23 6 whereas toc 13c values vary narrowly from 21 7 to 21 2 over the same sediment depth interval the variation in isotopic difference suggests that perylene originates from more than one precursor material both aquatic and continental organic matter different microbial processes or some combination of these possibilities

rim syncline volume estimation and salt diapirism quantitative studies of salt structures are based on the assumption of a simple relationship between excess sediment volumes and the volumetric growth of salt structures this assumption is inadequate and instead this article shows how the excess volume relates to the volume swept out by the deforming sediment surface and the moving salt sediment interface the use of this new basis for volume reckoning is demonstrated and its implications for waste disposal hydrocarbon exploration and tectonic subsidence studies are emphasized

submarine salt glacier of northern tunisia a case of triassic salt mobility in north african cretaceous passive margin stratigraphical sedimentological and structural data and a bouguer gravity map of medjez el bab meb in northern tunisia are used to illustrate a cretaceous example of salt extrusion on a passive continental margin located just south of the teboursouk thrust front a preferential decollement surface used by the continuous tertiary shortening in this area the meb structure is a simple n40 e box anticline removing the two tertiary foldings eocene and miocene leads to the exposure of the original feature of a simple submarine salt glacier the triassic salt rocks appear as an albian interstratified body between two cretaceous series with stratigraphic normal polarity suggesting a bedding parallel extrusion at the sediment water interface of the triassic salt in cretaceous times the formation of such salt extrusions are associated with extensional faulting probably both in the cover and basement the presence of a slope and basinwards salt flow this scenario is similar to the allochthonous salt described in other salt provinces characterizing passive margins

salt flow and diapirism related to extension at crustal scale abstract the analysis of the structure and history of salt diapirs in large ancient evaporitic basins such as the southeastern north sea basin suggests that diapirism is controlled by crustal scale extension laboratory experiments on small scale models designed to simulate configurations comparable to the southeastern north sea basin show that diapirs which grow in a sedimentary cover during basement extension can develop close to basement normal faults or at a significant distance from them if the displacement on the basement faults is transfered horizontally along the salt layer for given values of salt viscosity strain rate and friction coefficient in brittle rocks the pattern of salt diapirism in a particular area depends on the ratio of cover thickness to salt thickness as well as the absolute thicknesses of cover and salt layers the experiments give criteria for identifying different types of diapirs and provide models of horizontal flow in a salt layer undergoing extension and diapir development some dynamic implications of the experiments are applied to the southeastern north sea basin

balancing sub and supra salt strain in salt influenced rifts implications for extension estimates the structural style of salt influenced rifts may differ from those formed in predominantly brittle crust salt can decouple sub and supra salt strain causing sub salt faults to be geometrically decoupled from but kinematically coupled to and responsible for supra salt forced folding salt influenced rifts thus contain more folds than their brittle counterparts an observation often ignored in extension estimates fundamental to determining whether sub and supra salt structures are kinematically coherent and the relative contributions of thin i e gravity driven and thick skinned i e whole plate stretching deformation to accommodating rift related strain is our ability to measure extension at both structural levels we here use published physical models of salt influenced extension to show that line length estimates yield more accurate values of sub and supra salt extension compared to fault heave before applying these methods to seismic data from the halten terrace offshore norway we show that given the abundance of ductile deformation in salt influenced rifts significant amounts of extension may be ignored leading to the erroneous interpretations of thin skinned gravity gliding if a system is kinematically coherent supra salt structures can help predict the occurrence and kinematics of sub salt faults that may be poorly imaged and otherwise poorly constrained

comparison of field consolidation with laboratory and in situ tests settlement calculations for an earth embankment resting on soft compressible fraser river delta sediments were made from laboratory consolidation tests and in situ tests using a piezocone and a flat dilatometer the calculated values were compared with measured settlements there was rather good agreement among the three methods of calculation but the actual settlement was about 60 greater than the average calculated value calculated rates of settlement are also compared with observed values key words consolidation settlements piezocone dilatometer in situ tests constrained modulus pore water pressure settlement rate

the horn graben and its relationship to the oslo graben and the danish basin abstract the tectonic development of the horn graben the danish basin and the oslo graben are compared with special emphasis on the timing of their initiation the comparison is based on seismic interpretation and is supported by analysis of tectonic subsidence devonian and carboniferous sedimentary strata and rotliegende volcanics constitutes the pre rift succession in the horn graben in the central part of the graben it rests unconformably on precambrian possibly dalslandian basement to the south on caledonian metamorphic basement whereas lower palaeozoics occur to the north the distribution of these pre devonian assemblages suggests initial early devonian uplift of the ringkobing fyn high as the lower palaeozoic sediments are believed to have covered the high originally further uplift appears to have taken place in the early permian a subdivision of the horn graben into a northern and a southern segment are recognized the rifting was apparently heralded only in the southern segment in the rotliegende and the main rifting phase did not start before the triassic subsidence modelling shows that the thermal anomaly created by rifting of the horn graben was less significant than in the danish basin and resulted in much less post rift thermal subsidence the reduced thermal anomaly may account for an earlier consolidation of the crust thereby rendering the area resistant to late cretaceous early tertiary inversion tectonism the oslo graben was tectonically active during late carboniferous to early permian times and essentially became inactive during triassic times when the main tectonism of the horn graben occurred subsidence modelling shows that the danish basin south of the fjerritslev trough was tectonically active mainly during the zechstein whereas the rapid triassic subsidence is modelled to be caused by phase transformations as indicated by the minor amount of basement attached faulting based on the differing subsidence patterns it is concluded that the three basins did not develop simultaneously and that they are not genetically related

danish basin subsidence by triassic rifting on a lithosphere cooling background i report here the first quantitative study of the entire post palaeozoic subsidence history in the ensemble of north west european sedimentary basins data obtained from wells suggests that the late permian through mesozoic subsidence of the danish basin is a result of lithosphere wide cooling following an igneous event of late carboniferous to early permian age this cooling subsidence was superposed by major triassic rifting and minor mid jurassic uplift both events apparently not having significant thermal consequences the danish basin did not experience the late jurassic to early cretaceous rifting and subsequent cooling which were so important in the development of the central north sea rifts this result suggests that a reappraisal of north sea tectonics should look for pre jurassic subsidence

displacement fields and finite strains in a sandbox model simulating a fold thrust belt this thesis uses geodetic satellite data to measure present day crustal deformation in the zagros fold thrust belt sw iran geodetic type measurements are also used in down scaled models that simulate the surface deformations seen in convergent settings like the zagros fold thrust belt global positioning system gps measurements of three surveys between 1998 and 2001 indicate 9 3 mm yr and 5 3 mm yr shortening across the se and nw zagros respectively gps results show that in addition to the different rates and directions of shortening on either side of the ns trending kazerun fault local along belt extension occurs to the east differential sar interferograms of ers1 2 images between 1992 and 1999 detect 8 4 mm yr uplift rate across a newly recognized fault in sw qeshm island this can be attributed to a steep imbricate thrust that may still represent the local zagros deformation front the salt diapirs in the zagros rise from a source layer that acts as a low frictional decollement that decouples the deformation of the cover sediments from their basement in the eastern zagros whereas the cover to the west deforms above a high friction decollement physical models were prepared to simulate cover deformation in the zagros by shortening a sand pack above adjacent high and low frictional decollements represented by a ductile layer the strain distributions differed above the two types of decollements it was more heterogeneous above the salt where local extension in the shortening direction was dominant a separate work also investigated systematically the role of basal friction on cover deformation in convergent settings accurate height measurements of the model surface by laser scanner indicated a deformation front more distal than usual particularly in the low basal frictional models the volume reduction in our shortened sand models correlated directly with their basal friction

dike filled extensional structures in cenozoic deposits of the kleszczow graben central poland abstract the origin and development of the cenozoic kleszczow graben were strongly influenced by a pre existing fault pattern within the permian mesozoic bedrock dike filled fractures penetrating neogene quaternary deposits analysed in the opencast belchatow browncoal mine follow extensional structural patterns parallel to the axes of the local anticlinal forms established or rejuvenated in the quaternary these structures are particularly well developed along the fold crests the spacing and structural features of the fractures and normal faults are explained in terms of the tensile stress operating in beds subjected to folding the main localities of the quaternary folds precisely align with segments of two deep seated reverse faults the kleszczow kodr b fault and the gomunice piaski fault both are nw se orientated dislocations along a hinge zone of the laramide ekinsko anticline subcropping the cenozoic graben infill in the open mine the origin of the quaternary folds as fault overlying folds is attributed to a young block uplift on the ekinsko anticline area which is well recorded by a strong reduction in thickness of the cenozoic sediments the quaternary succession is reduced in thickness twice as much as the neogene the successive stages of quaternary reactivation of the ekinsko anticline during the cromerian through the late saalian with diminishing intensity are believed to be correlatable with the sequence of glacial rebound events coupled with mobility of the deep rooted fault zone

influence of basement faults on the development of salt structures in the danish basin scaled centrifuged models based on interpreted seismic profiles were used to simulate the salt structures in the danish basin the models consisted of a viscous layer simulating rock salt overlain by layers of cohesive sand that mimic brittle failure in natural overburdens model results support the hypothesis that basement faults trigger the growth of many salt diapirs in the danish basin in plan view model diapirs are localized as buoyant walls along faults in the overburden which collapsed due to basement fault movement with further burial single diapirs rose from these buoyant walls some of the diapirs surfaced through the faulted overburden a few were trapped beneath the competent cretaceous units and others were starved due to lack of supply from below in section model diapirs were asymmetric and were rooted on the tip of the faults or located on the rotated footwall blocks model diapirs not located over faults were triggered by differential loading and collapsing of overburden layers due to basement block rotation models show that the presence of fewer salt structures in the northern than the southern part of the basin is due to differential subsidence and flow of buoyant material from north to south where they rise diapirically in the model the pressure due to loading by overburden layers changed from 1 3 102 pa in the south to 2 3 102 pa in the northern part of the basin in general the model results illustrate that basement faults influence diapirs by accumulating buoyant material in half grabens and introducing a slope and steps at the base of the buoyant layer weakening its overburden and causing differential loading and compaction the spreading overhangs of salt diapirs beneath the cretaceous chalk in the danish basin would seal any potential pre cretaceous reservoir rocks

estimating coefficient of consolidation from piezocone tests data have been reviewed from sites in europe and north and south america as well as published data from south africa the review has concentrated on dissipation data from piezocone tests cptu to

organic geochemistry and coal petrology of tertiary brown coal in the zhoujing mine baise basin south china 4 biomarker sources inferred from stable carbon isotope compositions of individual compounds abstract carbon isotopic compositions of extractable compounds derived from higher land plants are within 2 0 00 of the bulk coal 13 c 27 0 0 00 from baise basin this data suggests that either similar species contributed these compounds or that the plants from which this coal was formed imposed similar biosynthetic fractionations the terpenoid hydrocarbons form two isotopically distinct groups the diterpenoids 13 c 25 0 1 4 0 00 and the sesquiterpenoids 13 c 25 9 1 5 0 00 are on 1 2 0 00 enriched in 13c compared to the bulk coal whereas the oleanane ursane lupane derivatives 13 c 29 0 0 8 0 00 are on average 1 2 0 00 depleted in 13c compared to the bulk coal the n alkanes ranging from c15 to c35 have a mean 13c value of 32 4 0 6 0 00 whereby averages for the c17 c22 and c23 c33n alkanes do not significantly differ from the overall average hopane derivatives in this coal extract are depleted in 13c compared to the bulk coal by 8 34 0 00 suggesting that bacterial cycling of methane played a role during formation of this coal

growth of normal faults in multilayer sequences a 3d seismic case study from the egersund basin norwegian north sea abstract we investigate the structural style and evolution of a salt influenced extensional fault array in the egersund basin norwegian north sea through analysis of 3d reflection seismic and well data analysis of fault geometry morphology throw distribution and syn kinematic strata reveal an intricate but systematic style of displacement and growth suggesting an evolution of 1 initial syn sedimentary fault growth contemporaneous with salt mobilization initiated during the late triassic 2 cessation of fault activity and burial of the stagnant fault tips and 3 subsequent nucleation of new faults in the cover above contemporaneous salt re mobilization initiated during the late cretaceous with downward propagation and linkage with faults stage 3 was apparently largely controlled by salt mobilization in response to basin inversion as reactivated faults are located where the underlying salt is thick while the non reactivated faults are found where salt is depleted based on the 3d throw analyses we conclude that a combination of basement faulting and salt re mobilization is the driving mechanisms behind fault activation and reactivation even though the sub and supra salt faults are mainly geometrically decoupled through the salt a kinematic coupling must have existed as sub salt faults still affected nucleation and localization of the cover faults

work as a criterion for determining in situ and yield stresses in clays discussion this is a discussion of a paper by the same title which appeared in vol 24 canadian geotechnical journal pp 549 564 the authors of the original paper are d e becker j h a crooks k been and m g jefferies

the influence of mechanically weak layers in controlling fault kinematics and graben configurations examples from analog experiments and the norwegian continental margin fault systems in extensional basins commonly display geometries that vary with depth reflecting depth and lithology dependent mechanical strength using an experimental approach we investigate this relationship by deploying physical analog models with stratified sequences consisting of brittle ductile sand silicone polymer sequences subject to single and polyphase deformation the experiments were used as analogs for a sandstone sequence interlayered by beds of evaporates or overpressured or unconsolidated mudstone in nature the latter being representative of decollement horizons experiments series 1 s1 using homogeneous and stratified quartz and feldspar sand produced asymmetric composite single grabens with diverse fault frequencies and fault styles for the graben margin faults for the mechanically stratified experiments with one decollement level series 2 contrasting graben configurations were produced in that the lowermost sequence was characterized by graben geometries of similar type to that of the s1 experiments whereas the sequence above the decollement was characterized by large fault blocks delineated by steepened or oversteepened faults the experiments with two decollements series 3 were displayed similarly but included graben geometries that widened upward with each level being characterized by independent fault systems the results can be used to explain strata bound fault patterns and depth dependent extension as seen in several places along the norwegian continental margin and elsewhere

des a lupane in an east african lake sedimentary record as a new proxy for the stable carbon isotopic composition of c3 plants we studied the high resolution and well dated 25 000 year sedimentary record of lake challa a deep tropical crater lake in equatorial east africa to explore new proxies for paleoenvironmental and paleohydrological change sedimentary biomarker analysis revealed the presence of des a triterpenoids with oleanane ursane and lupane carbon skeletons microbial degradation products of angiosperm plant triterpenoids their increased influx from 16 000 years ago corresponds with previously documented changes in the terrestrial vegetation of the lake challa basin during postglacial warming in particular the relative increase in c3 c4 plant ratio inferred from the stable carbon isotopic signature 13c of sedimentary n alkanes derived from plant leaf waxes in contrast to this n alkane 13c signature the 13c of des a lupane maintains a constant value of 27 4 1 1 across the glacial interglacial transition since des a lupane is derived from c3 plants its 13c signature is here proposed to represent a novel and independent proxy for the time variable carbon isotopic composition of local terrestrial c3 plants which can improve estimates of the c3 c4 plant ratio based on two end member mixing models of n alkane 13c values