burial and degradation of organic carbon in louisiana shelf slope sediments abstract the primary focus of this paper is to better understand carbon burial on the louisiana continental margin using spatial scales that covered various shelf depositional areas far field and near field sediment and organic carbon inputs relative to river mouth proximity and covering a variety of sedimentation rates box cores samples were collected in july 2003 cores were collected along two depositional transects extending westward and southward from the southwest pass sw pass a key difference between the two transects sampled in this study was the greater occurrence of mobile muds derived from spillover from shallower regions along the westward 50 m isobaths the dominant mechanism for mixing in the surface active zone saz on the inner louisiana shelf was due to physical not biological forces burial efficiencies for organic carbon 57 2 91 5 and total nitrogen 44 2 86 9 ranged widely across all shelf stations lower burial efficiencies for bulk organic carbon total nitrogen and pigment biomarkers were associated with mobile muds west of southwest pass chlorophyll a concentrations were significantly higher than pheopigments at depth at the mississippi river and southwest pass stations making up 40 4 and 77 4 of total pigment concentrations in the saz and 46 2 and 63 2 in the accumulation zone az respectively these results are in agreement with earlier plant pigment studies which showed that a large fraction of the phytodetritus delivered to the inner shelf was derived from coastal and river diatoms the amount of lignin preserved with depth decreased with increasing residence time in the saz and diagenetic zone dz along the canyon transect but not along the western transect trends for lignin concentration followed previously identified surface sediment trends indicating overall lower burial of refractory terrestrial material at depth with greater distance offshore

keys and pitfalls in mesoscale fault analysis and paleostress reconstructions the use of angelier s methods whereas most of the stress inversion methods using fault slip data only minimize the angle between the measured striation and a computed shear stress to find the best fitting reduced stress tensor angelier 1990 proposed an alternative method named invd that also takes into account the relative shear stress magnitude which allows the fault to move using artificial datasets and particular fault geometries we compare this method with one of the classical methods based on the minimization of the shear slip angles r4dt angelier 1984 and we show that in most cases the new method has improved the quality of the results furthermore as proposed by angelier we point out that the quality of the stress inversion primarily depends on the quality of the field data we give advice and warn about some pitfalls concerning determination of sense of slip on fault planes recognition of successive faulting events and their chronology drawer or wedge faults stress permutations faults in vertical bedding we also argue that in case of tilted sequences fault diagrams should not be presented without bedding planes but we show that stress inversions when realized with caution and with the correct method can havemuch more applications than reconstructing stress fields like for determining the paleo horizontal the nature and the sense of motion of large faults the chronology and age of large structures

deposition and modification of a flood layer on the northern california shelf lessons from and about the fate of terrestrial particulate organic carbon the 1995 flood of the eel river in northern california provided an opportunity to follow the short term history of riverine particulate matter on a continental shelf particulate organic carbon including both vascular plant debris and soil carbon was utilized as a tracer of the distribution and modification of the shelf flood deposit these components were sorted during initial emplacement of the deposit both in the river plume and in the benthic boundary layer during the 8 months following the flood lateral transport shallow burial and bioturbation contributed to spatial changes in the amount and character of carbon in the flood deposit study of the deposit suggests that this and previous flood layers may be preserved in the shelf and upper slope stratigraphic record as clay rich beds with relatively high carbon to nitrogen ratios and more negative 13c values than background non flood sediment concentrations of vascular plant debris are locally characteristic of such layers and may serve as distinctive stratigraphic markers investigation of organic carbon in the 1995 flood layer on the eel river shelf provides insight into the fate of terrestrial particulate carbon on continental margins in general flooding of the eel river and of similar river systems draining mountainous terrains introduces large quantities of terrestrial carbon to the marine environment and may favor the preservation of both terrestrial and marine carbon the abundant woody vascular plant debris discharged during floods is especially likely to survive oxidation and sulfate reduction in the shallower zones of the seabed this study reveals the dominant role that physical and biological processes may play in attenuating the terrestrial organic carbon signal on shelves over monthly to yearly time scales

the effects of a lateral variation in lithospheric strength on foredeep evolution implications for the east carpathian foredeep abstract lateral variations in lithospheric strength have been adopted often in flexural modeling both 2d and 3d to better fit the observed basement deflections typically supported by gravity data this approach provides essentially a snap shot of the role of lithosphere strength in determining the present day geometry in contrast we investigate and quantify the effects of a lateral change in lithospheric strength on the evolution of the foredeep in front of an advancing orogen transitions in lithospheric strength are common in the foreland of orogens and show large variations in the width of the transition zone and the strength difference former passive margins for instance will display strength changes distributed over several tens to hundreds of kilometers other transitions may originate from juxtaposition or accretion of pieces of lithosphere with different properties and may be characterized by a much smaller width than former passive margins in our modeling a constant load representing an advancing orogenic belt is displaced towards and across a transition from a weak to a strong plate in a 2d elastic thin plate model the effect of different transition widths and strength contrasts on foredeep geometry and bending stress is investigated interference of flexural wavelengths across the transition affects foredeep geometry by causing rapid basin widening oscillation of the bulge and volume increase the bending stresses are found to concentrate and amplify around the strength transition large transition gradients i e large strength contrast or small transition width cause the highest rates of change basin widening caused by the orogenic load advancing towards the transition between the east european craton and the moesian platform appears to control the sarmatian transgression over the east carpathian foreland in romania

life cycle of the east carpathian orogen erosion history of a doubly vergent critical wedge assessed by fission track thermochronology apatite fission track b t thermochronology applied to the east carpathian fold and thrust belt in romania constrains the interaction between the erosion history and the tectonic evo lution of the orogen the long lived constant asymmetric topography of the orogen and the erosion pattern as inferred from apatite ft data are in agreement with the style of evolution predicted by doubly vergent critical coulomb wedge models during the miocene up to 4 km of erosion took place over the actively deforming orogen and the erosion patterns forms a mirrored image of the subsurface deforming wedge the erosion products are deposited in flanking molasse basins which subsided contemporaneously due to the growing topographic weight of the wedge deformation of the wedge was presumably active from the early to late miocene but apatite ft ages between 14 and 9 ma and track length modeling predict an acceleration of erosion rates 0 5 0 3 mm yr ini tially in the middle to late miocene 3 2 ma the onset of erosion coincides with the last phase of convergence and a climax in the deformation history these features are interpreted to have been caused by underplating of the european continental margin convergence ceased before the pliocene according to the activity of thrust faults during the pliocene and quaternary up to 2 km of overburden was removed by erosion leading to isostatic rock uplift of the entire region the use of apatite fission track minimum ages supports the general idea that the orogen has a di achronous evolution from north to south the orogen in the southern bend zone has a more juve nile tectonic character and the main erosion phase took place during the pliocene and quaternary 5 0 ma the integrated approach of large scale morphology and fission track analysis confirms the applicability of the theoretical coulomb wedge mechanics to a natural compressive fold and thrust belt the study complements the geometric features of the orogenic wedge with quantified erosion histories and illustrates the effects of orogen evolution on vertical movements in the entire convergent setting

evolution of the transport direction of the carpathian belt during its collision with the east european platform the evolution of the carpathians is in its final stage with intermediate seismic activity 70 200 km mw 4 7 7 localized beneath its southeastern salient vrancea zone our analysis in the transition area between south carpathians and east carpathians reveals that the termination of convergence is characterized by a clockwise rotation of the carpathian belt transport direction using structural maps and cross sections we show that this change of convergence direction had several structural consequences including 1 the pliocene quaternary activation of out of sequence structures in the southern east carpathians and 2 the creation of dextral strike slip faults bounding the mobile belt to the west in the south carpathians our fracture analysis in syntectonic deposits allows us to distinguish and stratigraphically date two fanning stress patterns corresponding to the two last transport directions of the carpathian system 1 a burdigalian to early tortonian stress field with compression directions rotating along with the carpathian curved orogenic belt but with transpression nw se compression and a low strain partitioning along east trending internal strike slip faults in the south carpathians and 2 a late tortonian to pleistocene rotated and smaller radial stress pattern with n s compression in the south carpathians the rotation of the convergence direction is interpreted as the result of the miocene migration and progressive collision of the carpathian system with the thick crust of the nw trending tornquist teisseyre line and its prolongation in romania the area able to subduct determined by thickness of crust entering the subduction zone was progressively restricted to a foreland corner in front of the southeastern carpathians the progressive collision forced the convergence to slow down and rotate from eastward to southeastward in late miocene the dobrogea hills in front of the latest migrating system may represent the late neogene ne sw flexural bulge of the subducting foreland panel this clockwise rotation of the transport direction can be compared with the clockwise rotation that occurred in other subduction systems tyrrhenian subduction caribbean subduction etc which were controlled by the location of oceanic versus continental crust in front of the orogenic belt

xenon isotopes in archean and proterozoic insoluble organic matter a robust indicator of syngenecity abstract insoluble organic materials kerogens isolated from ancient sedimentary rocks provide unique insights into the evolution of early life however establishing whether these kerogens are indeed syngenetic with the deposition of associated sedimentary host rocks or contain contribution from episodes of secondary deposition is not straightforward novel geochemical criterions are therefore required to test the syngenetic origin of archean organic materials on the one hand the occurrence of mass independent fractionation of sulphur isotopes mif s provides a tool to test the archean origin of ancient sedimentary rocks determining the isotope composition of sulphur within kerogens whilst limiting the contribution from associated minerals e g nano pyrites is however challenging on the other hand the xe isotope composition of the archean atmosphere has been shown to present enrichments in the light isotopes relative to its modern composition together with a mono isotopic deficit in 129xe given that the isotopic composition of atmospheric xe evolved through time by mass dependent fractionation mdf until 2 5 to 2 0 ga the degree of mdf of xe isotopes trapped in kerogens could provide a time stamp for the last chemical equilibration between organic matter and the atmosphere however the extent to which geological processes could affect the signature of xe trapped in ancient kerogen remains unclear in this contribution we present new ar kr and xe isotopic data for four kerogens isolated from 3 4 to 1 8 gy old cherts and confirm that xe isotopes from the archean atmosphere can be retained within kerogens however new xe derived model ages are lower than expected from the ages of host rocks indicating that initially trapped xe components were at least partially lost and or mixed together with some xe carried out by younger generations of organic materials therefore complicating the xe based dating method whilst non null 33s values and 129xe deficits relative to modern atmosphere constitute reliable imprints from the archean atmosphere using xe isotopes to provide information on the syngenetic origin of ancient organic matter appears to be a promising but not unequivocal tool that calls for further analytical development

dynamics of the polish and eastern slovakian parts of the carpathian accretionary wedge insights from palaeostress analyses the arcuate outer carpathian accretionary wedge formed in front of the east alpine carpathian pannonian alcapa megablock during the eocene sarmatian the wedge accreted sediments of the subducting remnants of the carpathian flysch basin a large oceanic tract left in front of the alpine orogen the palaeostress data for the orogenic hinterland particularly the data related to the early miocene extension that was expanding towards the ne combined with coeval subduction related volcanism that was expanding towards the ne indicate that the uneven roll back of the subduction zone was the main mechanism controlling the development of the northern west carpathian arc the palaeostress data for the tertiary accretionary wedge from the same time period are characterized by outward fanning 1 trajectories that changed gradually during the wedge development in contrast the palaeostress data for the hinterland are characterized by preferred directional stress events that changed abruptly during the wedge development these palaeostress results are in accordance with the behaviour of the wedge and the hinterland as the wedge behaved as a weak continuum and the hinterland behaved as a block mosaic with weak boundaries the fault traces of the northern west carpathian arc converge to both ends of the arc and suggest that the pre existing basin was the factor that controlled the arc location these fault trace patterns are asymmetric indicating a slightly oblique overall convergence in a ne sw direction in accordance with this convergence the palaeostress data for the accretionary wedge indicate that the western part of the wedge which is characterized by nw se oriented maximum principal compressional stress 1 was undergoing sinistral transpression meanwhile the eastern part which is characterized by ne sw oriented 1 was undergoing compression apparently the dynamics of the accretionary wedge was further influenced by the shape of an elongated ne sw trending alcapa megablock which was located behind the wedge and advanced in the direction of the general early miocene convergence during the most pronounced stages of the wedge development this megablock served as the local indenter as its strength surpassed that of the accretionary wedge located to its front further dynamic complexities were added because of the complex shape of the magura unit which was located in the most proximal portion of the wedge and was stronger than the units in front of it wedge outcrops indicate that the large scale shortening which is characterized by the development of detachments and ramps was preceded by an initial layer parallel shortening this is indicated by scaly fabrics and minor reverse faults that rotated into locked positions during the later accretion several outcrops with a wedge detachment fault indicate that there was a relatively low amount of friction during its development the decollement zone is several hundred metres thick and shows evidence of transient fluid flow that was driven by pressure gradients this is documented by frequent hydrofracturing sandstone dykes and fibrous veins that opened against the weight of the whole wedge all of which indicate cycles of higher pore fluid pressures that lowered the basal friction

diffusive separation of noble gases and noble gas abundance patterns in sedimentary rocks the mechanisms responsible for noble gas concentrations abundance patterns and strong retentivity in sedimentary lithologies remain poorly explained diffusion controlled fractionation of noble gases is modeled and examined as an explanation for the absolute and relative abundances of noble gases observed in sediments since the physical properties of the noble gases are strong functions of atomic mass the individual diffusion coefficients adsorption coefficients and atomic radii combine to impede heavy noble gas xe diffusion relative to light noble gas ne diffusion filling of lithic grains half spaces by diffusive processes thus produces ne enrichments in the early and middle stages of the filling process with f ne values similar to that observed in volcanic glasses emptying lithic grains half spaces produces a xe enriched residual in the late but not final stages of the process producing f xe values similar to that observed in shales exotic but unexceptional shales that exhibit both f ne and f xe enrichments can be produced by incomplete emptying followed by incomplete filling this mechanism is consistent with literature reported noble gas abundance patterns but may still require a separate mechanism for strong retention a system of labyrinths with constrictions and or c si nanotubes when combined with simple adsorption can result in stronger diffusive separation and non steady state enrichments that persist for longer times enhanced adsorption to multiple c atoms inside c nanotubes as well as dangling functional groups closing the ends of nanotubes can provide potential mechanisms for strong retention we need new methods of examining noble gases in rocks to determine the role and function of angstrom scale structures in both the diffusive enrichment process and the strong retention process for noble gas abundances in terrestrial rocks

neogene kinematics of the transylvanian basin romania the transylvanian basin is a major sedimentary basin located in the eastern part of the european alpine orogenic system it has a sedimentary fill more than 5 km up to 8 km in some small areas thick of upper cretaceous to upper miocene deposits it represents the main gas producing province in romania and central eastern europe in this article we analyze seismic lines and structural data from the basin as well as from its northern eastern and southeastern borders these data indicate a tectonic origin for the neogene structures from the transylvanian basin these structures include 1 northeast and southwest dipping thrust faults and 2 east northeast and west northwest striking strike slip faults having normal or reverse slip secondary structures such as salt diapirs and folds are related to these faults structural data from the basin and its border indicate a neogene overall compressional transpressional regime having maximum principal stress oriented north to northeast daniel ciulavu received a diploma in geology and geophysics at the university of bucharest in 1989 and his ph d in geology at the vrije universiteit amsterdam netherlands in 1999 he worked two years for geasol s a romania in hydrogeology coal and alluvial gold exploration since 1991 he has been on the staff of the university of bucharest where he teaches the courses on structural geology in the department of geophysics and kinematic analysis for master s students corneliu dinu received a diploma in geology in 1966 and his ph d in 1976 at the university of bucharest romania after graduation he worked as field geologist for prospectiuni s a romania since 1970 he has been on the staff of the university of bucharest where he is professor of structural geology and basin analysis since 1990 he has served as the dean of sciences at the faculty of geology and geophysics university of bucharest alexandru szakacs received a diploma in geology in 1974 and his ph d in 2000 at the university of bucharest romania he is senior geologist at the romanian institute of geology he has 25 years of experience in studying the neogene volcanism of the carpathian pannonian area he has also worked on the neogene volcanism of the cordillera betica spain dorin dordea received a diploma in geology in 1974 at the university of cluj romania his field of activity is remote sensing he has worked in several areas in africa and romania since 1999 he has served as the chief geologist of prospectiuni s a bucharest romania he is now working on the application of remote sensing in mining exploration

tertiary tectonic evolution of the external south carpathians and the adjacent moesian platform romania depth interpreted seismic sections of the getic depression foredeep paleostress indicator data and analysis of outcrop to regional scale structures are integrated to derive the tectonic evolution of the south carpathians moesian platform area following late cretaceous and older orogenic phases the south carpathians moesian platform area underwent strike slip deformation with ne sw oriented compression and nw se tension in paleogene to early burdigalian times tensional deformation is recorded which led to the opening of wsw ene to e w trending extensional basins in the late burdigalian ne sw oriented contraction took over causing the oblique inversion of preexisting extensional structures during sarmatian times nw se and slightly younger n s trending compression caused the activation of mainly nw se dextral strike slip faults and in the frontal areas south directed thrusting the nw se direction of extension determined for paleogene to early burdigalian times is hardly compatible with presently accepted models of substantially continuous dextral wrenching between the intra carpathians units to the north of the south carpathians and the moesian platform to the south in contrast we have demonstrated dextral transpressive to transtensional movements within an e w trending corridor from the late burdigalian to late sarmatian which are compatible with available models

from pull apart to the rifting process the formation of the pannonian basin abstract during the middle and the late miocene intra carpathian basins have developed south and west of the carpathian arc these basins are bounded by normal faults and connected by conjugate shear zones sinistral strike slip fault systems trend ne sw whereas dextral ones trend nw se by means of geometrical analyses of fault system and paleostress tensor determinations it has been possible to consistently reconstruct the succession of tectonic events in the hungarian mountains the two main stages in the structural development of the intra carpathian basins are 1 1 the initiation of pull apart basins along conjugate shear zones in a n s compressional and e w extensional regime and 2 2 the development of these basins in a tectonic regime characterized by a dominant e w trending extension

the atmospheric inventory of xenon and noble gases in shales the plastic bag experiment noble gases in five shales have been examined in the traditional protocol for trapped gas analysis and also in a new protocol in which the shales are sealed in air prior to analysis the second protocol eliminates the possibility of gas loss in the preanalysis laboratory vacuum exposure characteristic of the traditional protocol this experiment is designed to further test the shale hypothesis which stipulates that atmospheric noble gases occur in the same proportions as planetary gases in meteorites and that the factor of approximately 23 deficiency of air xe relative to planetary xe is made up by xe stored in shales or other sedimentary rocks previously available data do not support this hypothesis but could be criticized as possibly seriously underestimating shale xe contents because of experimental limitations the procedure used in this study circumvents these limitations and the results still do not support the shale hypothesis from these results it appears quite unlikely that sedimentary rocks can account for the hypothesized missing xe and unless some other atmospheric reservoir can be found to contain it it correspondingly appears that the best working hypothesis is that atmospheric noble gases are simply not planetary if so either the chemical history of the earth must account for preferential storage of xe in the earth s interior or solar nebula process responsible for noble gas incorporation in solids were significantly different for meteorites and the earth

from orientation to magnitudes in paleostress determinations using fault slip data abstract determinations of reduced stress tensors using fault slip data yield the orientation of principal stress axes and the ratio of the differences between principal stress magnitudes the use of rupture and friction laws allows determination of the two remaining unknowns that is the reconstruction of the complete stress tensor taking into account the depth of overburden brings an additional constraint the method is applied and discussed in the case of the hoover dam site western u s a where large data sets and rock mechanics information are available differences between intact sample and rock mass properties account for apparent disagreements between paleostress levels determined in similar tectonic environments pore pressure plays an important role where information about pore pressure is absent zero and hydrostatic pore pressure cases should be considered as limits

composition and provenance of terrigenous organic matter transported along submarine canyons in the gulf of lion nw mediterranean sea abstract previous projects in the gulf of lion have investigated the path of terrigenous material in the rhone deltaic system the continental shelf and the nearby canyon heads this study focuses on the slope region of the gulf of lion to further describe particulate exchanges with ocean s interior through submarine canyons and atmospheric inputs nine sediment traps were deployed from the heads to the mouths of lacaze duthiers and cap de creus submarine canyons and on the southern open slope from october 2005 to october 2006 sediment trap samples were analyzed by cuo oxidation to investigate spatial and temporal variability in the yields and compositional characteristics of terrigenous biomarkers such as lignin derived phenols and cutin acids sediment trap data show that the dense shelf water cascading event that took place in the months of winter 2006 january february and march had a profound impact on particle fluxes in both canyons this event was responsible for the majority of lignin phenol 55 4 and cutin acid 42 8 inputs to submarine canyons with lignin compositions similar to those measured along the mid and outer continental shelf which is consistent with the resuspension and lateral transfer of unconsolidated shelf sediment to the canyons the highest lithogenic normalized lignin derived phenols contents in sediment trap samples were found during late spring and summer at all stations i e 193 46 g vp g 1 lithogenic at deep slope station when river flow wave energy and total particle fluxes were relatively low during this period lignin compositions were characterized by elevated cinnamyl to vanillyl phenol ratios 3 at almost all stations high p coumaric to ferulic acid ratios 3 and high yields of cutin acids relative to vanillyl phenols 1 all trends that are consistent with high pollen inputs our results suggest marked differences in the sources and transport processes responsible for terrigenous material export along submarine canyons mainly consisting of fluvial and shelf sediments during winter and atmospheric dust inputs during spring and summer

sedimentary organic matter preservation a test for selective degradation under oxic conditions the authors report here a test of the hypothesis that the extent of organic matter preservation in continental margin sediments is controlled by the average period accumulating particles reside in oxic porewater immediately beneath the water sediment interface oxygen penetration depths organic element compositions and mineral surface areas were determined for 16 sediment cores collected along an offshore transect across the washington continental shelf slope and adjacent cascadia basin individual amino acid sugar and pollen distributions were analyzed for a 11 to 12 cm horizon from each core and sup 14 c based sediment accumulation rates and stable carbon isotope compositions were determined from depth profiles within a subset of six cores from representative sites sediment accumulation rates decreased and dissolved o sub 2 penetration depths increased offshore along the sampling transect as a result oxygen exposure times oet increased seaward from decades mid shelf and upper slope to more than a thousand years outer cascadia basin organic contents and compositions were essentially constant within individual sediment cores but varied consistently with location in particular organic carbon surface area ratios decreased progressively offshore and with increasing oet three independent compositional parameters demonstrated that the remnant organic matter in farther offshore sediments is more degraded both concentrationmore and compositional patterns indicated that sedimentary organic matter exhibits a distinct and reproducible oxic effect oet helps integrate and explain organic matter preservation in accumulating continental margin sediments and hence provides a useful tool for assessing transfer of organic matter from the biosphere to the geosphere less

multiple atmospheric noble gas components in hydrocarbon reservoirs a study of the northwest shelf delaware basin se new mexico the northwest shelf of the delaware basin se new mexico is the site of several large and productive oil and gas fields the most productive reservoirs are located in the late pennsylvanian morrow and early permian abo formations production from the latter more important play is predominately from fluvial abo red beds of the pecos slope field the oxidizing conditions implied by the reddish color of the formation require an external hydrocarbon source to test the existing migration model for the region and constrain the location of potential hydrocarbon sources we measured the elemental and isotopic composition of noble gases produced along with the hydrocarbons we found the hydrocarbons to be highly enriched in radiogenic 4he 40 ar and nucleogenic 21 ne f 4he 44 000 250 000 40ar 36ar 400 3145 21ne 22ne 0 044 0 071 the greatest enrichments occur in the pecos slope gas fields the hydrocarbons also contain three independent nonradiogenic noble gas components each with an atmospheric isotopic composition one component is most likely air saturated water asw the second component is enriched in the heavy noble gases f 130xe 8 5 and is derived from the hydrocarbon sources the third component is enriched in ne f 20ne 0 8 that we believe is degassed from sources within the reservoirs this component is correlated with but decoupled from the dominant source of radiogenic 4he and 40 ar very high concentrations of 4he up to 1 by volume in the pecos slope reservoirs require a source external to the reservoirs such as the underlying precambrian basement granites and sedimentary equivalents structural buckles cutting through the pecos field may act as high flux vertical pathways for the radiogenic 4he if the hydrocarbons in the pecos slope fields have migrated northward from the deeper delaware basin as suggested by compositional trends then perhaps the buckles also play an important role in the distribution and filling of the pecos slope reservoirs

sources and distribution of terrigenous organic matter delivered by the atchafalaya river to sediments in the northern gulf of mexico abstract suspended sediments ss from the atchafalaya river ar and the mississippi river and surficial sediment samples from seven shallow cross shelf transects west of the ar in the northern gulf of mexico were examined using elemental oc c n isotopic 13c 14c and terrigenous biomarker analyses the organic matter om delivered by the ar is isotopically enriched 24 5 and relatively degraded suggesting that soil derived om with a c4 signature is the predominant om source for these ss the shelf sediments display oc values that generally decrease seaward within each transect and westward parallel to the coastline a strong terrigenous c n 29 signal is observed in sediments deposited close to the mouth of the river but values along the remainder of the shelf fall within a narrow range 8 13 with no apparent offshore trends depleted stable carbon isotope 13c values typical of c3 plant debris 27 are found near the river mouth and become more enriched 22 to 21 offshore the spatial distribution of lignin in shelf sediments mirrors that of oc with high lignin yields found inshore relative to that found offshore water depth 10 m the isotopic and biomarker data indicate that at least two types of terrigenous om are deposited within the study area relatively undegraded c3 plant debris is deposited close to the mouth of the ar whereas more degraded isotopically enriched soil derived om appears to be deposited along the remainder of the shelf an important input from marine carbon is found at the stations offshore from the 10 m isobath quantification of the terrigenous component of sedimentary om is complicated by the heterogeneous composition of the terrigenous end member a three end member mixing model is therefore required to more accurately evaluate the sources of om deposited in the study area the results of the mixing calculation indicate that terrigenous om soil derived om and vascular plant debris accounts for 79 of the om deposited as inshore sediments and 66 of om deposited as offshore sediments importantly the abundance of terrigenous om is 40 higher in inshore sediments and nearly 85 higher in offshore sediments than indicated by a two end member mixing model such a result highlights the need to reevaluate the inputs and cycling of soil derived om in the coastal ocean

129i and 36cl in dilute hydrocarbon waters marine cosmogenic in situ and anthropogenic sources abstract the long lived halogen radioisotopes 129 i and 36 cl provide valuable information regarding the source of fluids in hydrocarbon systems and in localized areas where infiltration of younger meteoric water has occurred despite the utility of these two isotopes in providing time signatures for fluid end members considerable uncertainty remains regarding the interpretation of intermediate age waters in hydrologic systems these waters are likely the result of the combination of two or more halogen sources at some time in the past each with its own characteristic concentration and isotopic composition in order to unravel the evolution of these intermediate age waters the effect that infiltration of meteoric water has on the isotopic composition of older formation waters is modeled also evaluated is the effect that the timing of dilution has on 129 i and 36 cl signatures observed in the present specifically the hypothesis that halogen isotopic signatures imparted by the mixing of brine and meteoric waters early in the development of a sedimentary basin are quantitatively different from those imparted by the mixing of old brines with recent meteoric waters the modeled results are compared to previously published isotopic data from production wells in the fruitland formation coalbed methane system portions of the basin preserve enough of the original brine source to retain 129 i i ratios roughly recording the age of deposition of organic matter 73 76 ma even where some degree of dilution by meteoric water has occurred however the 129 i signatures of waters that presently contain less than 10 of the original formation water component indicate that mixing has occurred within the past 10 ma consistent with recently published 4 he data both 36 cl concentrations and 36 cl cl ratios show that waters containing more than 10 formation water are all in secular equilibrium with the host formation coals in contrast waters with less than 1 of the original formation water s cl content all have 36 cl cl ratios which are greater than secular equilibrium values indicating the migration of meteoric water into the coal formation more recently than 2 ma although 36 cl signatures in the fruitland formation are not significantly affected by anthropogenic input 129 i i ratios in a subset of samples that retain less than 1 of the initial formation water component suggest input of anthropogenic 129 i during the past 50 a

sedimentation accretion and subsidence in marshes of barataria basin louisiana1 vertical accretion and sediment accumulation rates were determined from the distribution of 137cs in cores collected from freshwater intermediate brackish and salt marshes in the barataria basin louisiana vertical accretion rates vary from about 1 3 cm yr l in levee areas to 0 7 in backmarshes mineral sediment content of the marsh soil profile decreased with distance from the coast however vertical accretion rates were about equivalent in areas of the same type autochthonous organic matter appears to be an important factor defining the process and rate of vertical accretion especially in the freshwater marshes except in natural levee areas marsh accretion rates are less than subsidence measured by water level data however this alone cannot account for observed land loss patterns in the basin area

cretaceous to miocene thrusting and wrenching along the central south carpathians due to a corner effect during collision and orocline formation field studies in the romanian south carpathians longitude 22 5 to 24 2 e and latitude 45 2 to 45 6 n demonstrate 1 cretaceous top to ne shearing parallel to the present strike of the thrust system connected with coaxial flattening within the generally northwest dipping foliation 2 paleogene ductile brittle dextral wrenching e w compression 1 87 15 and basin formation petrosani basin along the cerna jiu fault system 3 large scale miocene dextral wrenching along the northern margin of moesia 1 143 16 and 4 probably pliocene early pleistocene n s compression 1 205 25 we discuss the tectonics of the south carpathians stressing the corner effect of the moesian foreland promontory during convergence and formation of the carpathian orocline up to the late early cretaceous subduction of oceanic crust was active between europe moesia on one side and east carpathia rhodopia on the other side collision and intracontinental deformation occurred during the late early and late cretaceous the pinning of the thrust front at the western tip of moesia and the foreland recess north of it caused superposition of thrusting and wrenching during collision and lateral translation tangential stretching during orocline formation and spreading into the recess further convergence during the early tertiary resulted in dislocation of the previously welded east carpathian rhodopian and moesian fragments along the cerna jiu fault system and the further northeast translation of the western segment the intramontane petrosani basin opened as a northeasterly propagating transient pull apart structure along the cerna jiu fault system which acquired a curved northwesterly convex transtensional trace due to the shape of the moesian promontory tightening of the carpathian orocline and or rearrangement of the microplate geometry during the formation of the pannonian basin system led to large scale dextral wrenching along the northern margin of moesia pliocene n s compression reflects final shortening in the carpathian system before ongoing convergence between europe and africa was transferred to the mediterranean rotation of material lines around the moesian corner is corroborated by paleomagnetic studies

tertiary tectonic evolution of the external east carpathians romania abstract paleostress calculation and analysis of mesoscopic structures are integrated with depth interpreted geological profiles based on seismic studies and well correlation to derive a tertiary tectonic model for the east carpathians following early miocene and older orogenic phases the first tectonic event that affected the studied area is characterised by a wsw ene oriented shortening of middle miocene late burdigalian in age resulting deformations induced ene ward thrusting of tarcau and marginal units as well as the internal part of the subcarpathian nappe a second shortening event with an e w to wsw ene contraction direction took place in the late miocene sarmatian characterised by further foreland thrusting of the subcarpathian nappe and out of sequence deformation in the tarcau and marginal folds nappes along strike differences in deformation mechanisms are controlled by the friction coefficients along the main detachment layers by the lateral variations in the wedge thickness and by the involvement in the northern part of the thrusting system of the thick competent east european platform tear faulting occurred in both tectonic events the main resulting structure being the triangle zone developed south of the trotus valley the latest miocene latest sarmatian early pliocene is characterised by a strike slip stress field with nne ssw compression and wnw ese tension axis left lateral faults being dominant the last deformation which affected the studied area is characterised by nnw sse shortening during the pliocene major deformations taking place mainly in the sw most bending zone

middle pleistocene to holocene fluvial terrace development and uplift driven valley incision in the se carpathians romania abstract this study reveals that in the se carpathians terrace development and fluvial incision during the middle pleistocene holocene are predominantly controlled by tectonic uplift as shown by terrace distributions and uplift amounts and rates the work focuses on a transect from the internal nappes and brasov intramontane basin western domain to the external nappes and focsani foredeep basin eastern domain new infrared stimulated luminescence ages were obtained and minimum terrace formation ages were determined to derive fluvial incision rates and thereby to constrain tectonic uplift in the eastern domain non uniform terrace distributions in adjacent sub parallel more active punta and less active usi a rivers and an eastward migrated fluvial incision from the orogen to the foredeep basin indicate tectonic uplift as dominant control on terrace development strath terraces in the western and eastern domains indicate repeated events of vertical fluvial incision and lateral erosion during the early middle pleistocene and late middle pleistocene holocene respectively these events imply successive recurrent disturbances of equilibrium conditions due to pulses of increased tectonic uplift fill terraces in the western domain show that initial aggradation periods were followed by uplift driven vertical incision during the late middle late pleistocene as fill terraces show a wide spread development climatic change and complex response cannot be excluded as contributing factors synchronous to terrace development loess deposition periods during the late middle late pleistocene and latest pleistocene and intercalated episodes of palaeosol formation during the late pleistocene imply comparable climatic conditions across the se carpathians dominant strath terraces of the eastern domain indicate stronger fluvial incision 240 m since the late middle pleistocene whereas older strath and younger dominant fill terraces of the western domain designate a lower amount 90 m since the early middle pleistocene middle pleistocene holocene fluvial incision rates document higher tectonic uplift in the external nappes and lower towards the western intramontane and eastern foredeep basins

xe in amorphous silica a new thermometer in geothermal systems we measured noble gases in amorphous silica of geothermal origin these samples were formed by precipitation from geothermal water in neutral ph and by the leaching of rocks in acid hot springs the concentration of 132xe has a negative correlation with the temperature of geothermal water although 36ar and 84kr show no such correlation the relationship between 132xe content a 10 8cm stp g and temperature t c is approximated by the equation a 4 5 10 3 t 0 50 the obtained equation should be useful for estimating the silica forming temperature that cannot be easily measured by other methods

identifying and quantifying natural co2 sequestration processes over geological timescales the jackson dome co2 deposit usa co2 sources sinks and migration mechanisms in natural co2 gas fields provide critical analogues for developing the safe application of anthropogenic co2 sequestration technologies here we use noble gas and carbon isotopes together with other gases to identify and quantify the origin transport and trapping mechanisms of co2 in the late cretaceous jackson dome co2 gas deposit 98 75 to 99 38 co2 located in central mississippi usa and producing from 5000 m it is one of the deepest commercial co2 gas fields in the world 10 gas samples from producing wells were determined for their noble gas chemical and stable carbon isotope composition he 3 he 4 ratios range between 4 27r a and 5 01r a where r a is the atmospheric value of 1 4 x 10 6 indicating a strong mantle signature similar to co2 deposits worldwide co2 he 3 decreases with increasing groundwater derived ne 20 and he 4 we model several different processes that could account for the jackson dome data and conclude that similar to other co2 dominated deposits a groundwater gas stripping and re dissolution ggs r process best accounts for observed ne 20 ar 36 kr 84 ar 36 co2 he 3 delta c 13 co2 he 4 ne 20 and ar 36 in this context crustal and magmatic co2 components contribute 57 and 43 respectively changes in co2 he 3 across the field show that groundwater contact is responsible for up to 75 loss of original emplaced co2 delta c 13 co2 variance limits the degree of precipitation to be less than 27 with the remaining co2 loss being accounted for by dissolution only a higher degree of dissolution gas loss and evidence for water contact at the reservoir crest compared to the reservoir flanks is used to argue that co2 in this system has not undergone subsequent loss to either dissolution or precipitation since shortly after reservoir filling at over 60 ma c 2012 elsevier ltd all rights reserved

late neogene low angle thrusting on the northwestern margin of the south carpathians poiana rusca west romania abstract mineral exploration drillholes and geoelectric prospecting provide for the first time evidence for thrusting of the south carpathian paleozoic basement over northerly adjacent middle miocene sediments investigations were carried out in two locations 30 km apart along the northern margin of the poiana rusca mountains romania southwestern carpathians drill holes in both locations encountered weakly consolidated middle miocene clay sand and fine gravel below paleozoic low grade metamorphic rocks intersections from various drill holes demonstrate the presence of low angle thrusting kinematic indicators are so far lacking but with a thrust direction oriented roughly normal to strike of the poiana rusca mountains minimum displacement is 1 1 4 km in northwestern or northern direction respectively thrusting occurred most likely during the late miocene pliocene whereafter quaternary regional uplift dissected the thrust plane in the tectonic framework of neogene dextral translation of the tisza dacia block against the southerly adjacent moesian platform transtension appears responsible for middle miocene basin formation along the northern margin of the poiana rusca region proceeding collision of the tisza dacia block with the east european craton introduced stronger impingement of the tisza dacia block against the moesian platform leading to a late miocene pliocene transpressional regime in which the northern poiana rusca basement was thrust over its adjacent middle miocene sediments

the transylvania basin transfer zone between coeval extending and contracting regions inferences on the relative importance of slab pull and rift push in arc back arc regions 1 structural analysis and paleostress fault slip inversion of the transylvanian basin and its border regions with the surrounding east and south carpathians and the pannonian basin e g the apuseni mountains reveal at least two distinct tectonic phases for the neogene evolution for the eastern part of the pannonian basin system our main focus is on the role of the transylvanian basin and its border regions in the neogene as a transition zone between the extending pannonian basin and the converging east and south carpathians the results provide constraints on the mechanisms responsible for as well the formation of the transylvanian basin itself as on the relation between the basin formational processes operating in the pannonian basin and the contractional history of the east and south carpathian mountain belt in the middle miocene 17 14 12 myr the transylvanian basin underwent e w extension coeval with the first and major phase of overall e w extension affecting the pannonian basin and with submarine accretionary wedge tectonics in the east carpathian arc in the late miocene to early pliocene 12 8 6 myr the transylvanian basin experienced a strong pulse of e w oriented shortening coeval with the climax of compression in the east carpathians and a second rift phase affecting the pannonian basin continued contractional deformation affected the transylvanian basin during the pliocene and pleistocene with compression directions shifting to ese wnw directions

glacial to holocene terrigenous organic matter input to sediments from orca basin gulf of mexico a combined optical and biomarker approach in this study we assessed changes in the contribution of terrigenous organic matter om to the gulf of mexico over the course of the last deglaciation the last 25 kyr to this end we combined optical kerogen analyses with bulk sedimentary biomarker and compound specific carbon isotope analyses samples were obtained from core md02 2550 from orca basin 2249 m water depth at 26 56 77n 91 20 74w with temporal resolution ranging from multi decadal to millennial scale depending on the proxy all proxies confirmed larger terrigenous input during glacial times compared to the holocene in addition the kerogen analyses suggest that much of the glacial om is reworked at least 50 of spores and pollen grains and 40 of dinoflagellate cysts the holocene sediments in contrast contain mainly marine om which is exceptionally well preserved during the deglaciation terrigenous input was generally high due to large meltwater fluxes whereby discrepancies between different proxies call for additional influences such as the change in distance to the river mouth local productivity changes and hydrodynamic particle sorting it is possible that kerogen particles and the terrigenous biomarkers studied here represent distinct pools of land derived om with inputs varying independently

neon excess in pumice volcanological implications abstract we measured the noble gas abundance and ne and ar isotopic compositions in pumice samples from japan and the eolian islands italy the goal was to give clues on the mechanism of air incorporation into pumice and its relationship with eruption processes the samples contain large excesses of atmospheric ne over ar with 20 ne 36 ar ratios up to 600 times the atmospheric ratio this excess is produced by the preferential diffusion of ne over ar in pumice vesicles during volcanic eruptions the 20 ne 36 ar ratios measured in pumice reflect the initial quenching temperature the cooling rate of the eruption column and the bubble s wall thickness the final ne amount is likely to be proportional to the volume of preserved vesicles in pumice calculations indicate that the fraction of isolated vesicles are less than 10 of the total suggesting that a few amount of gas is preserved in pumice after deposition

understanding salt in orogenic settings the evolution of ideas in the romanian carpathians the romanian carpathians are of global importance in salt tectonics because they host the type locality for the term diapir although there are several historical reviews of worldwide salt tectonics important aspects of how diapirism has been described and defined in the romanian carpathians are missing in these works many of these publications are difficult to access and most are written in romanian german french or polish this paper aims to present in detail the original ideas and to describe the historical development of these concepts we focus particularly on the work of the outstanding romanian geologist ludovic mrazec who defined the folds with piercing core and coined the term diapir

salt tectonics in the bend zone segment of the carpathian fold and thrust belt romania the carpathian bend zone is part of the eastern romanian carpathians the stratigraphic profile contains two levels of salt lower miocene lower burdigalian and middle miocene badenian the studied segment of the fold belt was deformed during the middle miocene badenian to middle sarmatian phase and during the late miocene to present wallachian phase during this latter phase the lower burdigalian salt was remobilized and reached the surface on several locations piercing through 2 3 km thick post tectonic deposits the salt outcrops and contractional structures now form a 30 km long ne sw lineament at the surface this contribution proposes kinematic models for the lower burdigalian salt movement during both tectonic phases the lineament was a detachment fold in the middle miocene phase thickened burdigalian salt and oligocene s l duplex filled the core of the detachment fold the detachment fold was subsequently peneplained with the burdigalian salt exposed on the paleo surface that locally redeposited during the badenian the wallachian evolution is less clear and we propose two viable kinematic models it is possible that the salt rise kept up with sedimentation and halokinetic sequences formed at the salt sediment interface alternatively the area was reactivated in a thin skinned right lateral strike slip manner with local pull apart basins 1 2 km across providing space for salt plugs currently available data do not allow us to pick a preferred model for the kinematics during the wallachian phase both kinematic models are novel and are in contrast with earlier ideas

architecture of the south eastern carpathians nappes and focsani basin romania from 2d ray tracing of densely spaced refraction data abstract a velocity model of the upper crust maximum depth 10 15 km of the earthquake prone vrancea area romania from 2d forward ray tracing of densely spaced refraction data is presented the model is derived from more than 11 000 travel times recorded at stations 100 m apart picked from 42 shot gathers along a 140 km line crossing the south eastern carpathian bending zone and the adjacent deep foreland focsani basin the model refines basement structure beneath the south eastern carpathian nappe stack and focsani basin and documents reverse faults on which crystalline rocks or highly metamorphosed mesozoic sedimentary cover of the crystalline basement have been elevated to depths as little as 3 5 4 km with a vertical displacement of at least 2 2 5 km beneath the external carpathian nappes in the vrancea zone fault systems flower structures and normal faults associated with the overall tectonic subsidence of the foreland basin are also inferred some of the basement fault systems appear to be recently active since they involve overlying young tertiary quaternary sedimentary layers and may be associated with intracrustal earthquakes recorded in the area

subsidence analysis and tectonic evolution of the external carpathian moesian platform region during neogene times abstract the miocene pliocene subsidence of the tectonic platforms in the romanian carpathians foreland is analysed using standard 1d backstripping techniques for individual wells combined in two regional sections and six contour maps the subsidence patterns were integrated together with previous paleostress and kinematic studies in order to derive the tertiary kinematics of the buried faults in the carpathians lower plate the study revealed accelerated subsidence during the early miocene in the western part of the moesian platform getic depression in direct relationship with the opening of a wsw ene trending extensional basin the largest subsidence recorded in the front of the carpathians took place during the late miocene due to final e ward emplacement of the thrust sheets the late miocene subsidence showed anomalous high values between the intramoesian and trotus faults as a result of the orogenic collision with the east european platform northward and acceleration of the subduction process in the se carpathians corner further pliocene subsidence continued only in the latter region the depocenter being shifted southward near the junction with the south carpathians foreland

architecture of the focsani depression a 13 km deep basin in the carpathians bend zone romania 1 in front of the se carpathians bend a very deep basin focsani depression developed in miocene to recent times an important part of its subsidence occurred after the main stages of thrusting in the carpathians apparently the basin lies in the wrong place and evolved in the wrong time in this study we constrain its architecture and evolution by analyzing a large database consisting of more than 1000 km two dimensional seismic lines and more than 60 wells around 13 km thick badenian to quaternary 16 5 myr sediments were deposited in the central part of the focsani depression during the badenian 16 5 13 myr the foreland south of trotus fault underwent ne sw directed extension and nw trending basins opened in the eastern moesian platform a nw se oriented area of subsidence stretched from the transylvania basin through the focsani depression to the se of the moesian platform while thrusting was going on in the east european scythian platform east carpathians and getic depression starting with the sarmatian 13 10 myr the focsani depression depocenter moved out of the carpathian belt coeval with the exhumation of the south and the east carpathians north of the trotus fault the basin became wider and was tilted toward the belt tilting was accompanied by dextral shearing mainly along the intramoesian and peceneaga camena faults after sarmatian times subsidence occurred practically only sse of trotus fault during meotian pontian 10 5 myr subsidence slowed down stronger pliocene quaternary subsidence is coeval with normal faulting and shearing in moesian platform the western margin of the focsani depression was then tilted eastward coeval with the exhumation of the bend zone and opening of the intramontane basins in the inner part of the belt

air xe enrichments in elk hills oil field gases role of water in migration and storage hydrocarbons from the elk hills naval petroleum reserve npr 1 bakersfield ca are enriched in heavy noble gases the 132xe 36ar ratios are as high as 576 times the ratio in air and represent the largest relative xe enrichments ever observed in terrestrial fluids the xe isotopic composition is indistinguishable from air we show that these samples cannot be explained by equilibration of oil with air saturated water and secondary enrichment via a rayleigh distillation gas stripping process based on laboratory studies of others with potential petroleum source rocks we believe the source of this enriched heavy noble gas component was adsorbed air initially trapped in on the source rocks that was expelled and mixed with the hydrocarbons during expulsion and primary migration kr and xe enrichments decrease with increasing 36ar concentration we propose a model in which an initial kr xe enriched hydrocarbon becomes diluted with noble gases extracted from air saturated groundwater during expulsion migration and storage the model generates an integrated water hydrocarbon ratio for the production fluid which indicates a minimal role for water in hydrocarbon expulsion and migration the results are interpreted to provide time geometrical constraints on the mechanisms by which hydrocarbons can migrate as a separate phase

terrestrial plant biopolymers in marine sediments the vascular land plant biopolymers lignin and cutin were surveyed in the surface sediments of coastal and open ocean waters by controlled alkaline cuo oxidation reaction two contrasting oceanic regimes were studied the northwest mediterranean nwm sea which receives significant particulate terrigenous debris through riverine discharge and the northeast atlantic nea ocean with poorly characterised terrestrial carbon inputs in the nwm products of lignin and cutin co occurred at all stations elevated levels ca 0 5 3 0 mg lignin phenols 100 mg organic carbon ca 0 01 0 09 mg cutin acids 100 mg organic carbon were observed for near shore deltaic and shelf sediments the influence of terrestrial land plant inputs extended across the shelf and through the slope to the abyssal plain providing molecular evidence for advective offshore transfer of terrestrial carbon mass balance estimates for the basin suggest riverine inputs account for the majority of surface sedimentary lignin cutin most of which 90 is deposited on the shelf products of cuo oxidation of lignin and cutin were also detected in nea surface sediments at levels comparable to those observed for the nwm continental slope and were detectable at low concentrations ca 0 5 gg 1 in the sediments of the abyssal plains 4 000 m depth while atmospheric deposition of lignin cutin derived material cannot be discounted in this open ocean system lateral advective transfer of enriched shelf sediments is inferred as a possible transport process a progressive enrichment in cutin derived material relative to lignin was observed offshore with evidence of an increase in the degree of oxidative alteration of lignin residues to account for these observations preferential offshore transport of finer and more degraded material is proposed nonspecific oxidation products dominated the gas chromatograms of nea sediments which appear to originate from marine sources of sedimentary organic carbon preliminary mass balance calculations applied to the global ocean margin suggest riverine sources of both particulate lignin and cutin are important and that most 95 deposition of recognisable land plant biopolymers occurs in shelf seas

post cretaceous to recent stress fields in the se moesian platform bulgaria abstract the reconstruction of the stress fields in the se moesian platform in bulgaria has been made by means of earthquake fault plane solutions tectonic fracture and fold patterns and physical electrical anisotropy in rocks restricted stratigraphically from the early cretaceous up to the late pliocene the philosophy of the study is that the recognition of the older stress fields for a given area can be successful if the characteristics of the youngest ones are known the contemporary stress field is discussed using the fault plane solutions from earthquakes and the kinematics of the activated faults the reconstruction of the post pliocene paleo stress field was made by studies of conjugate shear joints systems in upper pliocene limestones measurements of elements of tectonic fractures were also performed in situ on more than 60 outcrops of rocks aged from aptian to pliocene a limited number of sites were studied for electrical anisotropy using the azimuthal vertical electrical sounding method a more complete study of the tectonic meso and micro structures has been performed on the sarmatian sediments in the se moesian platform this study includes a description of the discovered folds brittle tectonic analysis and reconstruction of the post sarmatian paleo stress field as a result it was deduced that the compression after the early cretaceous period is ne sw directed the direction of compression since sarmatian to early quaternary was nw se a clockwise rotation of the main stress axes was established for a number of sites the contemporary contraction is directed also nw se according to the fault plane solutions determined for crustal earthquakes in the region this result is tested using the data from the gps measurement recently performed in this part of the balkan peninsula it could be suggested that there has been a clockwise rotation of the stress field due to the evolution of curved fold thrust belt in the south eastern carpathians and the collision of the balkanides with the moesian platform

kinematics of an arcuate fold thrust belt the southern eastern carpathians romania abstract flysch and molasse nappes of the eastern carpathians strike mainly n s and were folded and imbricated since the late early cretaceous boundaries of stratigraphic and structural units and calculated fold trend axes from the southern part of the eastern carpathians indicate a curvature of the orogen by 80 kinematic data from fault slip analysis of all nappe systems exposed in the arc document an overall nw se contraction nappes of the external moldavides nappe complex underwent deformation since the late cretaceous peaking in the miocene and exhibit fanning subhorizontal contraction axes from e w in the n striking part of the eastern carpathians through wnw ese and nw se in the northern part of the arc to nnw sse in its southwestern part geometric relations between faults and folds indicate that this fan pattern reflects an extended interval and was contemporaneous to nappe stacking and subsequent continental collision statistical analysis reveals correlation between orientation of the fanning kinematic axes and the structural trend where fanning of subhorizontal contraction axes is systematically smaller than change of strike of fold thrust structures orogen parallel extension in the tarcau nappe of the moldavides nappe complex is estimated to be 20 this low value of orogen parallel extension indicates a primary arc in contrast to bending of a previously straight fold thrust belt low orogen parallel extension and the observed pattern of structural and kinematic axes can be simulated in sand wedge indentation models where the indenter moves oblique to its margins in these models thrust traces and fold axes are curved around the arc but are parallel to the margins of the indenter away from the corner area the movement directions of the thrust faults in the models are deflected from normal to fault strike towards the movement direction of the indenter leading to fanning contraction directions similar to those observed in the eastern carpathian arc thus the main controlling factors on arc formation were the plate margin geometry i e the shape of the upper plate and the movement direction of the upper plate relative to the orientation of its margins the influence of the geometry of the continental margin in the lower plate was mainly by imposing constraints on the movement direction of the upper plate

the nature and significance of sand intrusions in a hydrocarbon rich fold and thrust belt eastern carpathians bend zone romania sand intrusions are commonly associated with hydrocarbon bearing clastic reservoirs and they can host a significant part of the reserves they modify the depositional sandbody architecture and can have an impact on the petroleum system elements their significance and complex architecture is difficult to assess in the subsurface due to limited resolution of seismic or core data outcrop analogues are key to better understand these complex reservoirs in the eastern carpathians bend zone the oligocene and lower miocene succession offer spectacular exposures of deep water siliciclastic rocks modified by remobilization and sand intrusion processes these rocks are also present in producing fields in this area sills can be as thick as the depositional sandstones c 4 m and sill dominated outcrops can provide a net gross net sandstone to shale ratio of about 35 50 we quantified their architecture in a study of the timing and mechanism of emplacement their relationship to regional tectonics and their impact on reservoir connectivity the intrusions are interpreted to be syn tectonic related to the major mid miocene compression in this part of the carpathian mountain belt the intrusions lead to a large increase in vertical and horizontal connectivity our results will help to improve reservoir characterization and production in these reservoirs

3 d upper crustal tomographic structure across the vrancea seismic zone romania abstract the vrancea99 and vrancea2001 seismic refraction experiments are part of a multidisciplinary project to study the eastern carpathians in romania the objectives of these studies are intended to disclose a more detailed picture of the crustal and upper mantle structures above the seismically active vrancea region in this paper we provide additional constraints for the upper crustal structures of the area the 1999 campaign consisted of a 320 km long n s profile and a 70 km long e w profile the intersecting 2001 profile extended in e w direction from the hungarian border to the black sea in order to enhance the model resolution first arrival data from local crustal earthquakes were also included this configuration allowed for the first time to derive a 3 d velocity model for the upper crust of the romanian carpathian orogen within a 115 235 km wide region centred over the vrancea seismic zone the 3 d model reveals lateral velocity variations which were not visible on the in line interpretations it allows us to distinguish between foreland platform areas foreland basins and the carpathian orogen clear velocity differences between the foreland basins south and southeast of the eastern carpathians and the focsani basin further north indicate different pre miocene sedimentary compositions and geological evolutions of these foreland platforms the involved moesian and scythian platforms are separated by the trotus fault system which is observed as a velocity discontinuity an upper crustal high velocity zone above the northern vrancea seismic zone could also be identified this high velocity zone is explained by a middle pliocene to pleistocene e w oriented out of sequence thrust of the crystalline basement below the decollement of the flysch nappes

basin scale natural gas source migration and trapping traced by noble gases and major elements the pakistan indus basin he ne and ar concentrations he and ar isotopic ratios carbon isotopic ratios and chemical compositions of hydrocarbon gases were measured in natural gas samples from gas producing wells in the indus basin pakistan where no oil has ever been found 3he 4he ratios are in the range 0 01 0 06 ra ra is the atmospheric value of 1 38 10 6 indicating the absence of mantle derived helium despite the trias extension 40ar 36ar ratios range from 296 to 800 consistent with variable additions of radiogenic argon to atmospheric groundwater derived argon rare gas concentrations show large variations from 6 10 5 to 1 10 3 mol mol for 4he and from 3 10 7 to 3 10 5 mol mol for 36ar in general 36ar concentrations are high compared to literature data for natural gas co2 and n2 concentrations are variable ranging up to 70 and 20 respectively mantle derived he is not observed therefore co2 and n2 are not mantle derived either hydrocarbon gas maturity is high but accumulation efficiency is small suggesting that early produced hydrocarbons including oil were lost as well as mantle helium this is consistent with the generally late pliocene trap formation and explains the high n2 concentrations since n2 is the final species generated at the end of organic matter maturation based on 13c data co2 originates from carbonate decomposition very elevated 20ne 36ar ratios are found reaching a maximum of 1 3 compared to 0 1 0 2 for air saturated water and 0 5 for air and these high values are related to the lowest rare gas concentrations we suggest that this highly fractionated signature is the trace of the past presence of oil in the basin and appeared in groundwater we propose a model where oil water contact is followed by gas water contact both with rayleigh distillation for rare gas abundance ratios thereby generating the fractionated 20ne 36ar signature in groundwater first and transferring it to gas later assuming the gas water contact occurred shallower than present reservoir depths this model explains the generally high 36ar concentrations and low ch4 36ar ratios compared to other studies on younger basins it thus provides a historical perspective on fluid transfer in a sedimentary basin where a gas accumulation may have been buried to greater depth since formation rare gas and major element data point to mixing between two gas pulses produced successively the very co2 n2 rich gases are terminal products of organic matter maturation which have been trapped after important migration this gas was followed by a more typical thermogenic gas which mixed with it

phosphorus distribution c n p ratios and δ13coc in arctic temperate and tropical coastal sediments tools for characterizing bulk sedimentary organic matter abstract onshore offshore trends in phosphorus p organic carbon oc and total nitrogen tn concentration p distribution elemental organic c n p ratios and stable carbon isotopic composition of oc 13 c oc of surficial sediments are presented from three river dominated coastal regimes the mackenzie river beaufort shelf in the canadian arctic the mississippi delta and louisiana shelf in the temperate gulf of mexico and the tropical amazon shelf these parameters measured in surficial sediments from the three sites are used to assess changes in the importance of terrestrial and marine organic matter sources to sediments as a function of distance from the locus of riverine discharge trends in elemental ratio data from the arctic transect and a portion of the gulf of mexico transects can be explained in terms of a two end member mixture of terrestrial and marine phytodetritus in the arctic transect covariation of organic c p ratios with 13 c oc is consistent with a two end member mixture of terrestrial and marine organic matter a similar relationship between c p ratios and 13 c oc is not evident in gulf of mexico or amazon shelf sediments at these sites the two end member model fails to explain the data adequately the most striking feature of the onshore offshore trends in elemental oc op and oc tn ratios is the occurrence of low ratios in sediments from deep water stations in the gulf of mexico and all stations on the amazon shelf resulting from p and n enrichments exceeding the redfield ratio for marine plankton three explanations are discussed to account for these low ratios 1 the dominance of refractory op and on compounds in the residuum of degraded organic matter 2 differential sorption of op and n compounds regardless of lability on the surfaces of the fine grained sediments characteristic of these sites and 3 a dominance of bacterial biomass or components derived from bacterial biomass elemental ratios and 13 c oc signatures indicate that differential sorption may be most important in the deep water gulf of mexico sites in contrast elemental ratios and 13 c oc on the amazon shelf are most consistent with a sedimentary organic matter pool dominated by bacterial biomass or derivative substances

2 5d seismic velocity modelling in the south eastern romanian carpathians orogen and its foreland 2 5 d seismic velocity modelling in the south easter romainan carpathians orogen and its foreland

terrestrial organic carbon contributions to sediments on the washington margin elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the columbia river basin and the washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments the biomarkers include an homologous series of long chain n alkanes derived from the surface waxes of higher plants phenolic and hydroxyalkanoic compounds produced by cuo oxidation of two major vascular plant biopolymers lignin and cutin all marine sediments including samples collected from the most remote sites in cascadia basin showed organic geochemical evidence for the presence of terrestrial organic carbon using endmember values for the various biomarkers determined empirically by two independent means we estimate that the terrestrial contribution to the washington margin is 60 for shelf sediments 30 for slope sediments and decreases further to 15 in basin sediments results from the same geochemical measurements made with depth in gravity core 6705 7 from cascadia seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the washington margin can be applied to the study of sediments depositing in this region since the last glacial period

neogene quaternary tectonic evolution of the leeward antilles islands aruba bonaire curacao from fault kinematic analysis aruba bonaire and curacao are islands aligned along the crest of a 200 km long segment of the east west trending leeward antilles ridge within the broad caribbean south america plate boundary zone presently characterized by east west right lateral strike slip motion the crust of the leeward antilles ridge represents the western segment of the cretaceous early cenozoic great arc of the caribbean which obliquely collided with the continental margin of northern south america in early cenozoic time following the collision the ridge was affected by folding and was segmented by oblique northwest striking normal faults that have produced steep sided northwest trending elongate islands and narrow shelves separated by deepwater sediment filled and fault controlled basins in this paper we present the first fault slip observations on the neogene carbonate rocks that cover large areas of all three islands our main objective is to quantify the timing and nature of neogene to quaternary phases of faulting and folding that have affected the structure and topography of this area including offshore sedimentary basins that are being explored for their petroleum potential these data constrain three fault phases that have affected aruba bonaire and curacao and likely the adjacent offshore areas 1 nw se directed late paleogene compression 2 middle miocene syndepositional nnw sse to nne ssw extension that produced deep rift basins transverse to the east west trending leeward antilles ridge and 3 pliocene quaternary nne trending compression that produced nw se trending anticlines present on aruba curacao and bonaire islands our new observations that include detailed relationships between striated fault planes paleostress tensors and bedding planes show that prominent bedding dips of neogene limestone on aruba bonaire and curacao were produced by regional tectonic shortening across the entire leeward antilles ridge rather than by localized syndepositional effects as proposed by previous workers we interpret pliocene quaternary nne directed shortening effects on the leeward antilles ridge as the result of northeastward extrusion or tectonic escape of continental areas of western venezuela combined with southeastward shallow subduction of the caribbean plate beneath the ridge

piggyback basin development and thrust belt evolution structural and palaeostress analyses of plio quaternary basins in the southern apennines abstract in southern italy structural analysis of the intramontane pliocene quaternary terrigenous basins of sant arcangelo and ofanto shows that they are piggyback basins the recent uplift of the southern apennines provides good conditions for carrying out detailed studies of palaeostresses in relation to structure and sediment accumulation in such piggyback basins we demonstrate that in the pleistocene sant arcangelo marine basin a single n70 compression induced a complex pattern of folds and strike slip faults in contrast the older pliocene ofanto basin reveals a polyphase history characterized by successive tilts and palaeostresses according to different compressions in both basins compressional stresses are syn depositional the geometry of the sedimentary infill of these basins provides information on the thrusting activity in terms of location geometry and age we point out that in addition to sedimentary and structural studies including interpretation of seismic reflection data palaeostress analyses provide a valuable tool for deciphering development and evolution of compressional basins in a fold and thrust belt

paleostress characterization of the wallachian phase in its type area southeastern carpathians romania abstract the wallachian phase is defined in the east carpathians a convex to the east mountain belt in romania as a tectonic event occurring between pliocene and quaternary times this event formed folds and minor thrusts structures that are usually located in internal parts of the somewhat older fold and thrust belt structure this location contrasts with the location one would predict from their recent age and contrasts with the older cretaceous middle tortonian piggyback thrust mode of propagation in the southeastern carpathians this late overstep sequence of thrusting resulted from a modification in the stress field our data indicate that the direction of compression changed from nw se to n s during middle tortonian time this is further supported by stratigraphic dating of structures and thereby paleostresses indicating that the wallachian episode was not a brief event at the pliocene quaternary boundary but lasted from middle tortonian to early pleistocene

large scale deformation in a locked collisional boundary interplay between subsidence and uplift intraplate stress and inherited lithospheric structure in the late stage of the se carpathians evolution 1 the interplay between slab dynamics and intraplate stresses in postcollisional times creates large near surface deformation particularly in highly bent orogens with significant lateral variations in mechanical properties this deformation is expressed through abnormal foredeep geometries and contrasting patterns of vertical movements intraplate folding is often the controlling mechanism particularly when the orogenic belt is locked the study of these tectonic processes in the se carpathians indicates a generalized subsidence period during latest miocene pliocene times driven by the slab pull and an intraplate folding due to an overall quaternary inversion the latter accommodates 5 km ese ward movement of this area with respect to the neighboring units which creates complicated three dimensional deformation patterns potentially driven at a larger scale by the interaction between the adriatic indentor and the entire carpathians system the lithospheric anisotropy inherited from the subduction times concentrates strain and induces large scale deformation far away from the active plate margins this anisotropy is dynamic because of deep mantle processes related to the subducted slab during postcollisional times such as thermal reequilibration or increase in slab dip

from nappe stacking to out of sequence postcollisional deformations cretaceous to quaternary exhumation history of the se carpathians assessed by low temperature thermochronology 1 apatite fission track aft and u th he ahe thermochronology have been combined to constrain the exhumation history of the se carpathians cooling ages generally decrease from cretaceous for the internal basement nappes aft ages to miocene quaternary aft and ahe respectively for the external sedimentary wedge the aft and ahe data show a paleogene age cluster which confirms a suspected but never demonstrated tectonic event the new data furthermore suggest that the se carpathians have been affected by a middle miocene exhumation phase related to continental collision which occurred at rates of 0 8 mm yr similar to the one previously inferred for the east carpathians the se carpathian tectonic evolution however is overprinted by two younger exhumation events in the pliocene pleistocene the first exhumation phase latest miocene early pliocene occurred at high exhumation rates 1 7 mm yr and is interpreted as a tectonic event and or associated with a sea level drop in the paratethys basins during the messinian low stand the youngest recorded tectonic phase suggests rapid pleistocene exhumation 1 6 mm yr and is interpreted to represent crustal scale shortening different in mechanics from collisional processes the data suggest that the se carpathians did not develop as a typical double vergent orogenic wedge instead exhumation was related to a foreland vergent sequence of nappe stacking during collision and was subsequently followed by a large out of sequence shortening event truncating the already locked collisional boundary

evolution of the stress fields in the carpatho pannonian area during the neogene abstract observations of microtectonic faults in and around the pannonian basin suggest that the tertiary evolution of the area was controlled by large scale strike slip fault activity statistical analysis of the fault pattern for different localities makes it possible to separate several conjugate sets of strike slip faults and related dilatational and compressive structures these stress fields have a distinct rotation pattern with time inversion of fault data suggests a characteristic rotation of the principal stress axes with time some rigid body rotations are indicated by paleomagnetic data there are basically three contrasting mechanisms to explain this observation 1 1 appropriate rotation of the regional e g european stress field 2 2 rotation of larger tectonic units e g microcontinents under a stable regional stress field and 3 3 coherent rotation of smaller detached continental blocks under a stable regional stress field our model for the neogene tectonic evolution of the pannonian area combines these mechanisms moderate microcontinent rotation may have occurred during the paleogene early miocene in the early middle miocene the microcontinents were dissected by a system of strike slip and normal faults created by a n s compressive e w extensive stress field gravity spreading of the pannonian units and block rotation within bounding strike slip faults are suggested to explain rotated magnetic directions and fault patterns in the late neogene clockwise rotation of the general stress field by at least 40 is thought to be responsible for the reactivations of older strike slip faults and for the creation of new sets this change in the orientation of the stress field is related to the eastward and then southward shift of the carpathian subduction activity

the danube river inception evidence for a 4 ma continental scale river born from segmented paratethys basins before reaching the black sea the danube river passes through a string of para tethyan vienna pannonian and western and eastern dacian basins the key question is when and how did the danube river became a continental scale river with a drainage similar to present new data presented here show that the late miocene deep water strata in the black sea have a significant sediment source and depositional style change at about 4 ma however the presence of active miocene basins within the danube catchment raises questions about the timing of danube river inception and whether the upstream palaeogeography would have allowed or disallowed delivery of large sediment volumes to the deep water black sea stratigraphic analyses in the pannonian and dacian basins reveal a phase of coeval sedimentary fill of the basins along the danube at about 4 ma this multi basin observation points to a concurrent basin fill model rather than the basin fill and spill or messinian type lowstand models previously proposed for danube inception this article is protected by copyright all rights reserved

sedimentary basins formed and carried piggyback on active thrust sheets small sedimentary basins that formed on the apennine southern margin of the po basin complex northern italy have been studied using borehole and seismic reflection information and their evolution can be dated using the largely marine biostratigraphy of the miocene to quaternary sediments these studies show that the basins formed and were filled while being carried on moving thrust sheets and they are therefore named piggyback basins each of these basins corresponds to the active phase of a different thrust front ramp on the pyrenean northern margin of the ebro basin complex northern spain similar piggyback basins formed between eocene and mid miocene time they have since been uplifted and eroded and may therefore be studied in outcrop in northern spain much of the basin fill sediment was deposited in nonmarine environments

lateral and vertical distributions of living benthic foraminifera off the douro river western iberian margin impact of the organic matter quality abstract in this study we assess the impact of the quantity and quality of the organic matter on the distribution of live benthic foraminifera on a cross margin transect off the douro river western iberian margin surface sediments from five stations ranging from 50 to 2000 m water depth were collected in march 2011 at the end of the period of maximal river runoff in order to better evaluate the importance of terrestrial input living stained benthic foraminiferal assemblages 150 m and environmental parameters grain size total organic carbon toc total nitrogen tn c n ratio 13 c toc pigments and amino acids were investigated organic matter amounts follow the sediment grain size pattern with higher concentration in fine sediments and seem to control faunal density except at the shallowest station where toc is low and faunal density high at this coastal site a massive sandy deposit is identified and associated with very low faunal diversity labile organic matter is richest at the shelf stations where benthic foraminifera standing stocks are high this is particularly evident on the douro mud patch where both density and diversity are high foraminiferal faunas living at the shelf stations are dominated by species e g nonion scaphum ammonia beccari i bulimina aculeata and eggerella scabra characteristic of the rich trophic conditions with organic matter of mixed estuarine and marine origin very low total standing stocks on the upper slope are associated with coarse sediments probably resulting from intense bottom currents at this depth resulting in poor trophic conditions deeper environments are characterized by species e g hoeglundina elegans uvigerina mediterranea and reophax scorpiurus indicative of fairly abundant but low quality organic matter finally the faunal differences between the shelf stations may reflect different successional stages an early stage at 50 m water depth where unstable conditions are observed with faunas dominated by opportunistic species and a more mature fauna in the mud patch where more stable conditions prevail

disentangling marine soil and plant organic carbon contributions to continental margin sediments a multi proxy approach in a 20 000 year sediment record from the congo deep sea fan abstract a 20 kyr long sediment sequence from the congo deep sea fan core geob 6518 1 one of the world s largest deep sea river fans has been analysed for bulk and molecular proxies in order to reconstruct the marine soil and plant organic carbon oc contributions to these sediments since the last glacial maximum the bulk proxies applied c n ratio and 13 c org ranged from 10 to 12 5 and from 24 5 to 21 vpdb respectively as molecular proxies concentrations of marine derived alkenones and terrestrial derived odd numbered n alkanes were used which varied between 0 2 and 4 g g dry weight sediment in addition the branched vs isoprenoid tetraether bit index a proxy for soil organic matter input was used which varied from 0 3 to 0 5 in this core application of binary mixing models based on the different individual proxies showed estimates for terrestrial oc input varying by up to 50 due to the heterogeneous nature of the oc application of a three end member mixing model using the 13 c org content the c n ratio and the bit index enabled the distinction of soil and plant organic matter as separate contributors to the sedimentary oc pool the results show that marine oc accounts for 20 to 40 of the total oc present in the deep sea fan sediments over the last 20 kyr and that soil oc accounts for about half 45 on average of the oc present this suggests that soil oc represents the majority of the terrestrial oc delivered to the fan sediments accumulation rates of the plant and soil oc fractions over the last 20 kyr varied by a factor of up to 5 and are strongly related to sediment accumulation rates they showed an increase starting at ca 17 kyr bp a decline during the younger dryas peak values during the early holocene and lower values in the late holocene this pattern matches with reconstructions of past central african humidity and congo river discharge from the same core and revealed that central african precipitation patterns exert a dominant control on terrestrial oc deposition in the congo deep sea fan marine oc accumulation rates are only weakly related to sediment accumulation rates and vary only little over time compared to the terrigenous fractions these variations are likely a result of enhanced preservation during times of higher sedimentation rates and of relative small fluctuations in primary production due to wind driven upwelling

radiocarbon age offsets in an arctic lake reveal the long term response of permafrost carbon to climate change continued warming of the arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon oc thereby accentuating global warming however it is unclear if recent warming has raised the current rates of permafrost oc release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing here we use a time series of radiocarbon age offsets 14c between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost oc release over the last 14 500 years the lake traps and archives oc imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age offsets today the age offset 2 ka thousand of calibrated years before a d 1950 and the depositional rate of ancient oc from the watershed into the lake are relatively low and similar to those during the younger dryas cold interval occurring 12 9 11 7 ka in contrast age offsets were higher 3 0 5 0 ka when summer air temperatures were warmer than present during the holocene thermal maximum 11 7 9 0 ka and bolling allerod periods 14 5 12 9 ka during these warm times permafrost thaw contributed to ancient oc depositional rates that were 10 times greater than today although permafrost oc was vulnerable to climate warming in the past we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release as a result the temperature threshold to trigger widespread permafrost oc release is higher than during previous warming events

late miocene quaternary volcanism tectonics and drainage system evolution in the east carpathians romania abstract middle miocene sarmatian convergence created the fold and thrust belt of the eastern carpathians of romania which subsequently experienced post collisional crustal deformation combined with calc alkaline and alkalic basaltic volcanism in late miocene quaternary time this deformation led to the rise of the c limani gurghiu harghita volcanic mountains and to the subsidence of the n s oriented intramontane borsec bilbor gheorgheni ciuc and brasov pull apart basins and the e oriented monocline related f g ras basin the regional drainage network is the composite of 1 older e se and s flowing rivers which cross the carpathians radiate towards the foreland and were probably established during the middle miocene sarmatian collision event 2 a more recent drainage system related to the contemporaneous development of the volcanoes and intramontaneous basins which generally drains westward into the transylvanian basin since late miocene time and has been capturing the older river system the older river drainage system has also been modified by late pliocene quaternary folding thrusting and monoclinal tilting along the pericarpathian orogenic front and by reactivated transverse high angle basement faults which cross the eastern carpathian foreland

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

late pliocene quaternary tectonics in the frontal part of the se carpathians insights from tectonic geomorphology abstract the romanian east carpathians display large scale heterogeneities along the mountain belt unusual foredeep geometries significant post collisional and neotectonic activity and major variations in topography mostly developed in the aftermath of late miocene sarmatian 11 ma subduction underthrusting and continental collision between the east european scythian moesian foreland and the inner carpathians tisza dacia unit in particular the se corner of the arcuate orogenic belt represents the place of still active large scale differential vertical movements between the uplifting mountain chain and the subsiding focsani foredeep basin in this key area we have analysed the configuration of the present day landforms and the drainage patterns in order to quantify the amplitude timing and kinematics of these post collisional late pliocene quaternary vertical movements a river network is incising in the upstream a high topography consisting of the external carpathians nappes and the pliocene lower pleistocene sediments of the foreland further eastwards in the downstream this network is cross cutting a low topography consisting of the middle pleistocene holocene sediments of the foreland geological observations and well preserved geomorphic features demonstrate a complex succession of geological structures the late pliocene holocene tectonic evolution is generally characterised by coeval uplift in the mountain chain and subsidence in the foreland at a more detailed scale these vertical movements took place in pulses of accelerated motion with laterally variable amplitude both in space and in time after a first late pliocene uplifting period subsidence took place during the earliest pleistocene resulting in a basal quaternary unconformity this was followed by two quantifiable periods of increased uplift which affected the studied area at the transition between the carpathians orogen and the focsani foreland basin in the late early pleistocene and the late middle to late pleistocene both large scale deformation events affected the western focsani basin flank tilting the entire structure with 9 during the late early pleistocene and uplifted it as a block during the early late pleistocene the late early pleistocene tilting resulted in 750 m uplift near the frontal monocline and by extrapolation in a presumed 3000 m uplift near the central parts of the carpathians the late middle to late pleistocene cumulative uplift reaches 250 m and correlates with a contemporaneous progradation of the uplifted areas towards the focsani basin the uplifting events are separated by a second quaternary unconformity on the whole the late pliocene quaternary evolution of the carpathians orogen focsani basin structure indicate large scale differential uplift during the latest stages of a continuous post collisional orogenic evolution

dynamic modeling of the transition from passive to active rifting application to the pannonian basin we examine a number of first order features of pannonian basin evolution in terms of the feedback relation between passive far field induced extension and active raleigh taylor instable upwelling of the astheno sphere we show that active mantle upwelling following a phase of passive extension are viable mechanisms ex plaining the pannonian basin formation the dynamic interplay between far field driven passive extension and active thinning of the mantle lithosphere by convective upwelling beneath the rift zone is modeled using ther momechanical finite element methods our modeling results predict a first phase of passive lithospheric thin ning which is followed by a second phase of late synrift to postrift active mantle lithosphere thinning due to buoyancy induced flow beneath the rift zone we argue that the pattern of coeval extension in the thinning re gion and compression in the flanking regions may be explained by the buoyancy forces due to lithosphere thinning it is demonstrated that timescales of and stresses generated by both processes are comparable the model appears also to explain the occurrence of late shallow mantle related decompression melts in the pannonian region and late regional doming

paleostress field reconstruction and revised tectonic history of the donbas fold and thrust belt ukraine and russia 1 in the wnw ese donbas fold belt df inversion of 3500 microtectonic data collected at 135 sites in proterozoic devonian carboniferous and cretaceous competent rocks allowed reconstruction of 123 local stress states accordingly four successive paleostress fields reveal the tectonic evolution of the df at the numerous sites that have been affected by polyphase tectonics the chronology between local paleostress states also paleostress fields was established using classical criteria crosscutting striae pre or post folding stress states stratigraphic control the oldest event is an extensional stress field with nne ssw 3 it corresponds to the rifting phases that generated the basin in devonian times and its early visean reactivation later the df was affected by a transtension with nw se 3 characterizing early permian tectonism including the development of the main anticline of the df and the pronounced uplift of its southern margin and ukrainian shield two paleostress fields characterize the cretaceous paleocene inversion of the df which was accompanied by folding and thrusting both are compressional in type but differ by the trend of 1 which was first nw se and subsequently n s the discrete paleostress history of the df allows a revised interpretation of its tectonic evolution with significant implications for understanding the geodynamic evolution of the southern margin of the east european craton

vertical movements in and around the south east carpathian foredeep lithospheric memory and stress field control a 10 km thick basin formed in tertiary to quaternary times in front and overlapping with the south east carpathians the focs depression is part of this system and overlies the vrancea seismogenetic volume thought to correspond to the remnants of the continental slab subducted beneath the carpathians slab detachment and its lateral migration are considered to control vertical movements in the area we present the first complete analysis of subsidence patterns in the depression and derive a substantially different picture the strongest subsidence is sarmatian in age coeval with the main nappe emplacement events subsequently subsidence did not stop and persisted until present times despite cessation of thrusting the main depocen

interplay of tectonics and neogene post collisional magmatism in the intracarpathian region abstract distribution of the neogene calc alkaline magmatism of the carpathian arc is directly related in space and time to the kinematics of the two major terranes of the intracarpathian area alcapa tisia getia along the south eastern border of the european plate in the west carpathians and adjacent areas the volcanic activity occurred between 20 11 ma with large volumes of both acidic and intermediate rocks generally distributed randomly sometimes transversally to the orogenic belt and as rare small occurrences along the flysch belt in the east carpathians the volcanic rocks are distributed along the northern margin of the zemplin block the north easternmost part of the alcapa and eastward along the front of the getic block at the contact with european plate between tokaj slanske vihorlat up to northern calimani mountains the magmatism occurred between 14 9 ma and along the calimani harghita chain between 9 0 2 ma the calc alkaline magmatic rocks of the apuseni mountains are located in the interior of the tisia block and occurred between 14 9 ma the generation of the calc alkaline magmatism is considered here as the result of complex interplay between plate roll back and lithospheric detachment tectonic processes and the break off of the subducted plate mostly in a post collisional setting 1 the magmatites of the western carpathians and the pannonian basin were generated in direct relation to subduction roll back processes over the downgoing slab during the period of lateral extrusion and back arc extension in this area characterized by maximum crustal shortening we can infer further delamination processes to explain the generation of magmas 2 the magmatic rocks from the northern sector of the east carpathians tokaj slanske vihorlat up to the northern calimani mountains resulted after subduction roll back processes and an almost simultaneous break off of the descending plate all along the arc segment during main clockwise rotation of the intracarpathian terranes 3 in the eastern sector of the east carpathians calimani up to harghita mountains the magmatic rocks were generated through partial melting of the subducted slab followed by gradual break off of the subducted plate along strike north to south 4 the apuseni mts magmatic activity resulted in transtensional tectonic regime by decompressional melting of lithospheric mantle during the translation and rotation of tisia getia block

problems of the pannonian median massif and the plate tectonic concept contributions based on the distribution of late paleozoic early mesozoic isopic zones after a short historical review of conceptions about the pannonian median massif or tisia the distribution of middle upper carboniferous and lower triassic liassic facies is briefly examined on the two sides of the zagreb zemplin line dividing into two main segments the basement of the carpathian basin it shows on the one hand that the igal bukk zone igal bukk eugeosyncline ofwein 1969 thought to establish a connection between the nw dinarides and the dinaric type bukkium is only a tectonic zone and could never have been a paleogeographical unit on the other hand the northern marginal part of tisia mecsek bihor crystalline belt and its sedimentary cover dank b it was rather part of the northern northeastern marginal complex of tethys therefore allochthonous models suggesting largerscale horizontal movements give a much more plausible explanation the style of late hercynian development and the distribution of lower triassic liassic facies zones suggest that tisia was part of the northern northeastern shelf of the tethys until the end of the liassic in accordance with the opinion ofbleahu then split off and was wedged in by horizontal movements between the nw dinarides and the dinaric type bukkium by the end of the jurassic beginning of the cretaceous

carbon isotope geochemistry of the santa clara river the santa clara river is a prototypical small mountainous river with a headwater height greater than 1000 m and a basin area smaller than 10 000 m 2 although individual small mountainous rivers export trivial amounts of sediment and carbon to the ocean as a group these rivers may export a major fraction as much as 50 of the total global river sediment flux milliman and syvitski 1992 making their geochemistry relevant the study of the ocean s carbon cycle in addition many small rivers export sediment in a few high flux events causing massive sporadic discharge of carbon onto coastal shelves discharge conditions very different from those of large rivers this class of rivers is an end member of the river ocean carbon exchange system opposite the earth s largest river the amazon the carbon mass and isotopic properties of the santa clara river are significantly different from previously studied large rivers during the 1997 1998 winter all santa clara carbon pools were old with flux weighted average l4c values of 428 76 for particulate organic carbon 73 31 for dissolved organic carbon and 644 58 for black carbon the age of exported carbon is primarily due to the deep erosion of old soils and not to inclusion of fossil fuel carbon additionally the 13c signatures of exported carbon pools were high relative to terrestrial carbon bearing a signature quite similar to marine carbon average particulate organic carbon poc 13c 22 2 0 8 the santa clara s estuary is small and drains onto the narrow eastern pacific coastal margin exporting this old soil organic matter directly into the ocean if the santa clara export patterns are representative of this class of rivers they may be a significant source of refractory terrestrial carbon to the ocean

sources and distribution of organic matter in a river dominated estuary winyah bay sc usa abstract the sources and distribution of organic matter om in surface waters and sediments from winyah bay south carolina usa were investigated using a variety of analytical techniques including elemental stable isotope and organic biomarker analyses several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range the dissolved organic carbon doc concentrations of surface waters ranged from 7 mg l 1 in the lower bay stations closest to the ocean to 20 mg l 1 in the river and upper bay samples there was a general linear relationship between doc concentrations and salinity in three of the four sampling periods in contrast particulate organic carbon poc concentrations were significantly lower 0 1 3 mg l 1 and showed no relationship with salinity the high molecular weight dissolved om hmw dom isolated from selected water samples collected along the bay displayed atomic carbon nitrogen ratios c n a and stable carbon isotopic compositions of organic carbon 13coc that ranged from 10 to 30 and from 28 to 25 respectively combined such compositions indicate that in most hmw dom samples the majority of the om originates from terrigenous sources with smaller contributions from riverine and estuarine phytoplankton in contrast the c n a ratios of particulate om pom samples varied significantly among the collection periods ranging from low values of 5 to high values of 20 overall the trends in c n a ratios indicated that algal sources of pom were most important during the early and late summer whereas terrigenous sources dominated in the winter and early spring in winyah bay bottom sediments the concentrations of the mineral associated om were positively correlated with sediment surface area the c n a ratios and 13coc compositions of the bulk sedimentary om ranged from 5 to 45 and from 28 to 23 respectively these compositions were consistent with predominant contributions of terrigenous sources and lesser but significant inputs of freshwater estuarine and marine phytoplankton the highest terrigenous contents were found in sediments from the river and upper bay sites with smaller contributions to the lower parts of the estuary the yields of lignin derived cuo oxidation products from winyah bay sediments indicated that the terrigenous om in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil om based on the lignin phenol compositions most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region a few samples displayed lignin compositions that suggested a more significant contribution from marsh c3 grasses however there was no evidence of inputs of spartina alterniflora a c4 grass remains from the salt marshes that surround the lower sections of winyah bay

the noble gas geochemistry of natural co2 gas reservoirs from the colorado plateau and rocky mountain provinces usa identification of the source of co2 in natural reservoirs and development of physical models to account for the migration and interaction of this co2 with the groundwater is essential for developing a quantitative understanding of the long term storage potential of co2 in the subsurface we present the results of 57 noble gas determinations in co2 rich fields 82 from three natural reservoirs to the east of the colorado plateau uplift province usa bravo dome nm sheep mountain co and mccallum dome co and from two reservoirs from within the uplift area st john s dome az and mcelmo dome co we demonstrate that all fields have co2 3he ratios consistent with a dominantly magmatic source the most recent volcanics in the province date from 8 to 10 ka and are associated with the bravo dome field the oldest magmatic activity dates from 42 to 70 ma and is associated with the mcelmo dome field located in the tectonically stable centre of the colorado plateau co2 can be stored within the subsurface on a millennia timescale the manner and extent of contact of the co2 phase with the groundwater system is a critical parameter in using these systems as natural analogues for geological storage of anthropogenic co2 we show that coherent fractionation of groundwater 20ne 36ar with crustal radiogenic noble gases 4he 21ne 40ar is explained by a two stage re dissolution model stage 1 magmatic co2 injection into the groundwater system strips dissolved air derived noble gases asw and accumulated crustal radiogenic noble gas by co2 water phase partitioning the co2 containing the groundwater stripped gases provides the first reservoir fluid charge subsequent charges of co2 provide no more asw or crustal noble gases and serve only to dilute the original asw and crustal noble gas rich co2 reservoir scale preservation of concentration gradients in asw derived noble gases thus provide co2 filling direction this is seen in the bravo dome and st john s dome fields stage 2 the noble gases re dissolve into any available gas stripped groundwater this is modeled as a rayleigh distillation process and enables us to quantify for each sample 1 the volume of groundwater originally stripped on reservoir filling and 2 the volume of groundwater involved in subsequent interaction the original water volume that is gas stripped varies from as low as 0 0005 cm3 groundwater cm3 gas stp in one bravo dome sample to 2 56 cm3 groundwater cm3 gas stp in a st john s dome sample subsequent gas groundwater equilibration varies within all fields each showing a similar range from zero to 100 cm3 water cm3 gas at reservoir pressure and temperature

the syn and post collisional evolution of the romanian carpathian foredeep new constraints from anisotropy of magnetic susceptibility and paleostress analyses abstract the first results of anisotropy of the magnetic susceptibility ams data from the romanian carpathian foredeep reveal compression directions generally perpendicular to the highly bended carpathian orogenic arc the distribution of the present day stress field in the pannonian carpathian region reflects pre imposed plate boundaries that were established during late miocene collision analysis of the ams along the eastern and southern carpathian foredeep at the contacts of the orogenic nappe pile the lower plate and the overlying sedimentary rocks indicates that two factors are critical for the distribution of the stress field during and after collision i e 1 the inherited highly bended plate geometry and 2 the quaternary deformation that lead to differential vertical and horizontal movements in the se carpathians the ams analysis was successfully used in the weakly deformed mio pliocene sedimentary rocks from the carpathian foredeep revealing information about the deformation history of the soft non competent rocks where the poor preservation of traditional kinematic indicators e g faults and folds is difficult

neogene kinematic development of the east carpathian bend area central romania abstract kinematic analysis of fault slip data from the junction of the eastern and southern carpathian fold thrust belt documents distinct movement patterns associated with successive phases of neogene deformation early to middle miocene deformation achieved ese to se shortening accommodated by nearly orthogonal to oblique sinistral thrusting in the eastern carpathians and oblique dextral thrusting in the southern carpathians following late miocene burial of the thrust front beneath foreland sediments the kinematic framework changed to one of sinistral escape of material from the eastern carpathians which drove minor nne ssw shortening in the southern carpathians the kinematic data indicate progressive clockwise rotation of the shortening direction until 11 ma which is consistent with clockwise rotation of the tisza dacia block as it converged with the european moesian platform

the geochemistry of river particulates from the continental usa major elements river particulates have been collected from twenty three rivers from throughout the continental usa the rivers drain mostly large basins basin areas range from 2 1 x 10 3 to 2970 x 10 3 km2 composed of mixed lithologies and spanning a wide range of climatic conditions as evidenced by a large variation in air and ground water temperatures precipitation and runoff suspended particulates have been analyzed for organic and inorganic carbon as well as the major elements al fe mn k si ca mg and na also determined were suspended sediment loads at the time of sampling particle surface areas and grain size distributions five year average river water chemistry and suspended sediment concentrations obtained from usgs water supply reports are also included as supporting information particle chemistry systematically varies with rates of runoff with high runoff rivers transporting the most heavily altered particulates and low runoff rivers carrying the least altered degrees of alteration are indicated by the extent to which the refractory nonmobile elements al and fe are concentrated into the particulates and the extent to which the most easily weathered elements na ca and mg have been leached overall the susceptibility of elements towards leaching is consistent with numerous previous descriptions of element mobility on weathering a simple predictive model has been developed to explore and explain the observed trends between particle composition and river runoff thus the elemental composition of riverine particulates may be given by the expression pcoi propi tm dcoi ss where pcoi is the concentration of element i as the oxide in a riverine particulate propi is the proportion of i as the oxide in unweathered rock dcoi is the dissolved concentration of i as the equivalent oxide tm is the total rock derived mass dissolved in river water and ss is suspended sediment concentration to utilize this equation a model was first developed to predict the concentration of river solutes with the input of temperature precipitation and a limited number of weathering parameters combining this solute model with the above predictive equation for particle composition it was discovered that the observed trends between particle composition and runoff require the special circumstance of decreasing ss with increasing runoff hence the composition of river particulates depends both on the climate parameters of runoff and temperature as they control dissolved river chemistry and the nonclimate parameters including elevation relief tectonics and basin area that control the ss load of rivers

seismic crustal structure between the transylvanian basin and the black sea romania abstract in order to study the lithospheric structure in romania a 450 km long wnw ese trending seismic refraction project was carried out in august september 2001 it runs from the transylvanian basin across the east carpathian orogen and the vrancea seismic region to the foreland areas with the very deep neogene focsani basin and the north dobrogea orogen on the black sea a total of ten shots with charge sizes 300 1500 kg were recorded by over 700 geophones the data quality of the experiment was variable depending primarily on charge size but also on local geological conditions the data interpretation indicates a multi layered structure with variable thicknesses and velocities the sedimentary stack comprises up to 7 layers with seismic velocities of 2 0 5 9 km s it reaches a maximum thickness of about 22 km within the focsani basin area the sedimentary succession is composed of 1 the carpathian nappe pile 2 the post collisional neogene transylvanian basin which covers the local late cretaceous to paleogene tarnava basin 3 the neogene focsani basin in the foredeep area which covers autochthonous mesozoic and palaeozoic sedimentary rocks as well as a probably permo triassic graben structure of the moesian platform and 4 the palaeozoic and mesozoic rocks of the north dobrogea orogen the underlying crystalline crust shows considerable thickness variations in total as well as in its individual subdivisions which correlate well with the tisza dacia moesian and north dobrogea crustal blocks the lateral velocity structure of these blocks along the seismic line remains constant with about 6 0 km s along the basement top and 7 0 km s above the moho the tisza dacia block is about 33 to 37 km thick and shows low velocity zones in its uppermost 15 km which are presumably due to basement thrusts imbricated with sedimentary successions related to the carpathian orogen the crystalline crust of moesia does not exceed 25 km and is covered by up to 22 km of sedimentary rocks the north dobrogea crust reaches a thickness of about 44 km and is probably composed of thick eastern european crust overthrusted by a thin 1 2 km thick wedge of the north dobrogea orogen

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control

sources and transport of land derived particulate and dissolved organic matter in the gulf of mexico texas shelf slope the use of ligninphenols and loliolides as biomarkers the fate and transport of terrestrial organic matter across the continental margin in the gulf of mexico was studied in 1992 and 1993 using chemical biomarkers lignin phenols were utilized as biomarkers for terrestrial inputs and indicated that much of the terrestrial organic matter inputs were deposited on the shelf break and slope the lignin phenol concentrations normalized to carbon in poc hmw doc and sediments in slope waters were considerably higher than at other open ocean sites studied previously the dominant mechanism for transport of terrestrially derived poc and hmw doc across the shelf and slope was hypothesized to be advection of riverine and estuarine discharges through benthic nepheloid layers based on loliolide concentrations in the water column we believe that lateral transport of these materials at the shelf break through extensions of benthic nepheloid layers may have been an important mechanism for the injection of terrestrially derived organic matter into deep slope waters