stress strain and strength characteristics of silt clay transition soils abstractthe influence of nonplastic silt content on the stress strain volume change and strength characteristics of anisotropic silt clay transition soils is investigated a series of one dimensional compression tests isotropic compression tests and undrained and drained triaxial tests on three soils of similar base clay but different nonplastic silt contents are performed on cross anisotropic specimens prepared from consolidation of slurries tests with major loading directions both parallel and perpendicular to the specimens axis of deposition are performed it is observed that the tested silt clay soils are less compressible with increasing silt content during one dimensional and isotropic compression tests during drained and undrained triaxial tests the normally consolidated soils at the same consolidation stress show larger values of stiffness and drained and undrained shear strengths with increasing silt content the silt clay soils also show larger pore pressure changes during undrained tria

practical estimation of compression behavior of clayey silty sands using equivalent void ratio concept abstractclayey silty sands are widespread as naturally sedimentary soils such as marine deposits in estuaries and offshore locations they belong to a unique class of gap graded soils featuring a d

insights into the crustal scale dynamics of a doubly vergent orogen from a quantitative analysis of its forelands a case study of the eastern pyrenees this study was funded by the anr france pyramid research project the french norwegian foundation 13 06 pyr fftp sedimentary basin and north pyrenean foreland fold and thrust belt formation supported study visits to the university of bergen norway collaboration with csic barcelona spain was funded by the project alpimed pie csic 201530e082

strain partitioning in a pluton during emplacement in transpressional regime the example of the neouvielle granite pyrenees this microstructural and anisotropy of magnetic susceptibility study of the internal structures of the hercynian neouvielle granite pluton 100 km2 provides new data indicating that the pluton was emplaced during the main hercynian tectonic event recognized in the pyrenees it also provides new data about the later alpine deformation localized along narrow mylonitic bands these bands acted as reverse faults and have not rotated the hercynian structures that define the main part of the pluton the pluton is composed of two structural domains the northern half of the pluton displays a beak shape in map view with subhorizontal e w trending lineations of magmatic origin the southern half is semi circular and displays rather steeply northward plunging lineations corresponding to magmatic and high temperature ht solid state microstructures these features are associated with magma deformation during emplacement magma deformation corresponds in the northern half of the pluton to an e w strike slip deformation recognized in the enveloping pelitic metasediments of carboniferous age and in the southern half of the pluton to southward overthrusting recognized in the enveloping quartzites of devonian age juxtaposition in a single granite body of transcurrent and compressive domains is viewed as a strain partitioning in the magma this strain partitioning is linked to both the transpressive character of the main regional deformation event and the rheological contrast between the pelitic country rocks and quartzose country rocks

factors controlling late cenozoic continental margin growth from the ebro delta to the western mediterranean deep sea abstract the ebro continental margin sedimentation system originated with a messinian fluvial system this system eroded both a major subaerial canyon cutting the margin southeastward from the present ebro delta and an axial valley that drained northeastward down valencia trough post messinian submergence of this topography and the pliocene regime of high sea levels resulted in a marine hemipelagic drape over the margin late pliocene to pleistocene glacial climatic cycles drainagebasin deforestation and sea level lowstands combined to increase sediment supply cause the margin to prograde and create a regime of lowstand sediment gravity flows in the deeper margin the depositional patterns of regressive transgressive and highstand sea level regimes suggest that location of the sediment source near the present ebro delta throughout the late cenozoic southward current advection of sediment and greater subsidence in the southern margin combined to cause generally asymmetric progradation of the margin to the southeast thicker less stable deposits filling the messinian subaerial canyon underwent multiple retrograde failures eroded wide gullied canyons and formed unchanneled base of slope sediment aprons in the central margin area other margin areas to the north and south developed a series of channel levee complexes on the basin floor the formation of valencia valley over the messinian subaerial valley and earlier faults led to draining of about 20 of the ebro pleistocene sediment from channel levee complexes through the valley to prograde valencia fan as much as 500 km northeast of the margin thus the ebro margin has two growth directions mainly southeastward during higher sea levels and eastward to northeastward during lower sea levels the northeastward draining of turbidity currents has produced unusually thin and widely dispersed turbidite systems compared to those on ponded basin floors during the past few centuries man s impact has exceeded natural controls on ebro margin growth deforestation of the drainage basin more than doubled the normal holocene sediment supply and construction of dams then reduced the supply by 95 this reduction of the past 50 years has caused erosion of the delta and contamination of bottom sediment because normal holocene sediment discharge is not available to prograde the delta or help dilute pollutants

organic geochemistry of the carapita formation and terrestrial crude oils in the maturin subbasin eastern venezuelan basin abstract geochemical characteristics of the organic matter in the thick shaly sequence of the carapita formation lower miocene were analyzed in five exploratory wells drilled in the maturin subbasin eastern venezuela the study also includes crude oils from well one analyzed to establish their origins and possible sources the quantity and quality of organic matter in the carapita formation toc h c hi oi and kerogen type indicate vertical variation shales of the carapita formation increase in source rock potential from top to bottom this suggests two facies with different hydrocarbon potential maturity parameters t max 428 446 c r o 0 35 0 73 indicate that the upper section is immature and the lower section is mature thus the lower section is sufficiently mature to generate oil matoil modeling in well one shows that the lower section of the carapita formation began to generate oil in late miocene time 6 4 m a at a depth of about 15 900 ft 4846 m geochemical characteristics of oils from well one indicate generation from a source with abundant higher land plant input these are the first terrestrial crude oils of this type found in the fold thrust belts of the maturin subbassin gc ms analyses of saturated hydrocarbon fractions suggest a possible correlation with the terrestrial organic matter in the carapita formation

relationship between petroleum composition and depositional environment of petroleum source rocks crude oils of nonmarine source can be distinguished from those of marine shale source and from oils originating in marine carbonate sequences by using a battery of geochemical parameters as demonstrated with a sample suite of nearly 40 oils a novel parameter based on the presence of c30 steranes in the oil was found to be a definitive indication of a contribution to the source from marine derived organic matter a second novel parameter based on monoaromatized steroid distributions was effective in helping to distinguish nonmarine from marine crudes and can be used to gauge relative amounts of higher plant input to oils within a given basin sterane distributions were similarly useful for detecting higher plant input but were less effective than monoaromatize steroid distributions for making marine versus nonmarine distinctions concentrations of high molecular weight paraffin can also be effective nonmarine indicators but are influenced by maturation and biodegradation processes certain algal derived nonmarine oils may show little high molecular weight paraffin response oils from carbonate sources with a few exceptions can be distinguished by having low pristane phytane ratios low carbon preference indexes and high sulfur contents gammacerane indexes and carbon isotope ratios of the whole crude are not effective in distinguishing these types of environmental differences on a global basis

evaluation of common practice empirical procedures for residual friction angle of soils hawaiian amorphous material rich colluvial soil case study the residual strength of soils has received considerable attention after skempton suggested that the stability of reactivated landslides may be governed by residual strength in this respect numerous studies have been conducted to determine the factors affecting the residual strength of soils specifically research effort was focused on determining correlations between the residual friction angle of soils and soil indexes such as atterberg limits and clay fraction some of these researchers suggested that strong correlations exist with soil indexes other researchers claimed that there is no correlation between the soil index and the residual friction of soils thus there is a need to clarify whether there is a correlation between residual friction angle and soil index properties in this effort we describe general properties of landslides in hawaii with an emphasis on an active landslide followed by evaluating correlations between the residual strength and soil indexes the results of this study show that the existing empirical correlations for soil index properties and residual friction angle predict poorly the residual friction angle of colluvial soils that rich in amorphous materials however the results also show that a strong correlation between ll and pi and residual friction angle may exist depending on the soil mineral type

evidence for mesozoic shear along the western kunlun and altyn tagh fault northern tibet china the strike slip faults of north tibet accommodate part of the cenozoic convergence between india and asia along the karakax valley south of yecheng and near the xidatan trough south of golmud the active traces of the altyn tagh and kunlun faults follow narrow belts of metamorphic rocks the deformation recorded in those mylonites is sinistral strike slip rb sr and 40ar 39ar ages of deformation from syntectonic fabrics formed at 350 400 c 120 ma argon loss suggests that deformation was associated to a 250 300 c thermal pulse that lasted 5 20 ma after the onset of movement unroofing occurred much later around 25 ma when sudden cooling suggests a component of thrusting or more likely normal faulting the cretaceous shear may be related to collision between the qiantang and the lhasa blocks the karakax and xidatan shear zones may have formed a unique continuous boundary in the cretaceous which was later reused by the tertiary strike slip faults leading to potentially calculable offsets along the altyn tagh fault

the main variscan deformation event in the pyrenees new data from the structural study of the bielsa granite abstract a structural and magnetic fabric study of the bielsa granite axial zone of the pyrenees provides new data indicating that this pluton was emplaced during the main variscan event recognized in the pyrenees we argue that the later post triassic deformation was localized along mylonitic bands reactivating earlier variscan shear bands the bielsa granite intrudes cambro ordovician metasediments at its northern border and the pluton is unconformably overlain by sediments triassic in age to the south and east the main structures in the igneous body are magmatic foliations and lineations defined by feldspar phenocrysts and biotite and dextral shear bands with dominant wnw ese trends the wnw ese striking magmatic foliations have variable dips and the magmatic lineation a subhorizontal wnw ese trend the zonation of low field magnetic susceptibility coarsely related to mineral content indicates a layer arrangement of rock types with more basic compositions at the northern border the magnetic ellipsoids are prolate along a wnw ese central band and oblate at the pluton borders where flattening is more important all these data allow us to interpret the bielsa intrusion as being caused by coeval nne shortening and dextral shear the presence of shear bands indicates that strain localization under dextral transpression continued during late variscan times

a chlorine disinfectant for excess argon released from k felsspar during step heating abstract the release of excess 40 ar 40 ar e from virtually all alkali feldspars at low temperatures 40 ar 39 ar step heating experiments obscures potentially valuable age and thermal history information we report a method that takes advantage of the differential release of 40 ar e between contiguous isothermal heating steps due to the decrepitation of fluid inclusions and which permits derivation of a correction for the contaminating argon differences in age and cl k between successive temperature pairs commonly yield a single well correlated array on a 40 ar k versus cl k plot that identifies the cl correlated composition of 40 ar e 40 ar e cl affecting that sample eighteen of the twenty k feldspar samples we have measured yield a single 40 ar e cl component that varies from 1 1 10 3 to 4 2 10 6 making possible recovery of otherwise unobtainable thermochronological information the upper bound on the 40 ar e cl distribution of 10 3 may reflect ar saturation of pore fluids or the maximum duration between deuteric alteration and cooling below ar closure in k feldspar

thermochronology of lower cretaceous source rocks in the idaho wyoming thrust belt lower cretaceous organic rich source rocks that are thermally mature to postmature crop out on the absaroka darby and prospect plates in linear belts that run parallel to the trace of the thrusts in the idaho wyoming portion of the idaho wyoming utah thrust belt although the common assumption is that burial by thrust plates and the synorogenic sediments derived from them have been responsible for thermal maturation of the organic rich strata commercial amounts of hydrocarbons have not been found in structural traps in this portion of the thrust belt in a companion paper burtner and nigrini demonstrated that gravity driven fluid flow in the idaho wyoming portion of the thrust belt was responsible for moving large amounts of heat from the depths of the early cretaceous foreland basin eastward toward the stable platform in this paper we demonstrate through the application of organic maturation indicators and a new refinement of the apatite fission track technique that this process heated lower cretaceous organic rich source rocks to temperatures sufficient to generate hydrocarbons hydrocarbon generation and migration occurred prior to the development of the thrusts that are often assumed to have played a major role in the generation and entrapment of hydrocarbons in this portion of the thrust belt

analysis of the experimental compressibility of deep water marine sediments from the gulf of guinea abstract this study strives to analyze the compressibility of deep water marine sediments originating from the gulf of guinea our approach is multi scaled and on the macroscopic level based on two equations which link the overburden effective stress with the liquidity index the biarez favre equation on the one hand and the burland equation on the other hand after calculation of the icl expression as a function of the i l parameter on the local level the evolution of the microstructures is analysed and compared with gog remoulded clay two additional observation techniques have been used the scanning electron microscope and the mercury intrusion porosimetry

thermochronology constraints for the propagation sequence of the south pyrenean basement thrust system france spain 1 in this work we combined apatite fission track and biotite k feldspar 40ar 39ar ages with tectonic data in the west central part of the axial zone of the pyrenees we discuss the exhumation ages and rates of the neouvielle bordere louron and bielsa variscan granites and their relationships with the timing and sequence of south vergent basement thrusting within the pyrenean orogenic prism the 40ar 39ar ages on k feldspars from the neouvielle massif sample nv7 seem to indicate tectonic movements on the eaux chaudes thrust during the early middle eocene fission track results suggest that the exhumation of the neouvielle massif occurred around 35 ma and exhumation of the bordere louron massif around 32 ma in relation to thrusting on the gavarnie thrust the bielsa massif was exhumed from around 19 ma by out of sequence movements on the bielsa thrust we thus show that whereas most of the pyrenean basement thrust faults here the eaux chaudes gavarnie and guarga thrusts were active in sequence toward the southern foreland from the early eocene to the earliest miocene some of them here the bielsa thrust were activated out of sequence in the hinterland later than the generally accepted aquitanian age for the end of the pyrenean compression finally the apatite fission track modeling indicate a last cooling episode starting around 5 ma which is most certainly related to the pliocene reexcavation of the southern and northern flanks of the pyrenees

the neoproterozoic brasiliano orogeny in northeast brazil 40ar39ar and petrostructural data from ceara abstract the borborema province in ne brazil comprises paleoproterozoic basement and its proterozoic cover that experienced a complex tectonometamorphic history during the brasiliano pan african orogeny in ceara four major domains separated by continental scale steeply dipping dextral shear zones have been identified 40 ar 39 ar step heating of mineral separates and laser probe fusion of single grains have been used in conjunction with petro structural observations to delineate the cooling tectonic history of these domains to the north of the senador pompeu shear zone spsz amphibole and biotite pairs from low pressure granulite belts exposed along the granja shear zone and spsz record plateau ages in the range 575 560 ma corresponding to cooling rates close to 20 c m y 40 ar 39 ar laser probe muscovite dates from the chaval augen gneiss point to a similar age for shearing responsible for the exhumation and fast cooling of the granulite belts a muscovite biotite pair from the central ceara high pressure nappes lying between the shear zones documents a lower cooling rate in the interval 534 525 ma related to the decompression and uplift of previously deelly buried rocks to the south of the spsz only moderate crustal thickening occurred within the various schist belts a distinct cooling pattern is indicated for these belts and the western patos shear zone attesting to a different crustal development 40 ar 39 ar dates of amphibole phlogopite muscovite and biotite range from 550 to 522 ma recording a postmetamorphic cooling rate of 6 9 c m y slower cooling rates of 3 4 c m y between amphibole and biotite closure ages in the range 540 500 ma are reported for the eastern part of the palos shear zone system the diachronous cooling recorded along this shear zone is interpreted to reflect the variations in thickness of the high temperature mylonitic belts earlier more rapid cooling occurred where the belts are narrow in the west late slower cooling occurred in wider zones to the east these thermochronological data reveal an age and cooling rate distribution at the scale of the borborema province that provides new constraints on the development of the brasiliano orogeny between 580 and 500 ma

evolution of a turbiditic foreland basin and analogy with an accretionary prism example of the eocene south pyrenean basin the south pyrenean tertiary basin was an east west trending foreland trough which developed from early eocene to miocene times in a north south trending compressive regime a turbiditic series of lower and middle eocene age hecho group enables us to define the typical features of the tectono sedimentary evolution of the basin 1 slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders 2 the southern basin border evidenced by the onlap of the turbidites onto slope and shelf deposits migrated progressively southwards in time and 3 the deformation pattern is characterized in the meso cenozoic sediments by a complex thrust fold system of thin skinned tectonics style its specific geometry and kinematics were influenced by the pre deformation geometry onlap this thrust fold system is related to south directed basement nappes and its front advanced progressively southwards in time from this data we infer an evolutionary model for this highly mobile basin it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south directed crustal accretionary prism as the nappes advanced the basin migrated progressively southwards in the foreland direction as for the actual basin evolution many analogies with accretionary prism trench systems of active margins exist

geotechnical characterization and facies change detection of the bogacay coastal plain antalya turkey soils the bogacay plain is well known tourist site in turkey which is famous for its wide beaches however almost 60 of the area is now occupied by buildings and some of the high rise buildings suffer from foundation settlement and tilting soils of the plain are of lagoonal origin all of the facies which are typical of the lagoonal environment are present in the geological profile because of variation in grain size and development of a weathered crust the fine grained soils of the central lagoon environment are highly variable with regard to their engineering properties the compression indices of clays range from 0 25 to 0 55 and correlate relatively well with initial void ratio liquid limit and moisture content over consolidation ratio varies between 1 4 and 10 and decreases from the surface down to the base of the weathered crust zone the undrained shear strength of clays decreases with depth for the first 6 m this behaviour is because of apparent overconsolidation in the weathered crust zone sedimentary facies and their boundaries can be detected using cpt data moreover for profiling and facies boundary detection spt and seismic sounding are not as effective as cpt

dating the northern deposits of the ebro foreland basin implications for the kinematics of the sw pyrenean front abstract dating the sedimentary infill of the northern margin of the ebro foreland basin informs about the orogen basin evolution a magnetostratigraphic section of 5 km thick combines new magnetostratigraphic results from the syntectonic alluvial uncastillo fm upper oligocene lower miocene 1 km thick the fuencalderas section with previous 3 3 km thick and new 0 7 km thick magnetostratigraphic data from the underlying fluvial campodarbe fm luesia and san marzal sections eocene oligocene this composite section allows dating the entire basin infill in this sector therefore bracketing the timing of the deformation in the southern margin of the pyrenees after considering previous kinematic studies deformation recorded by the continental deposits spans from syn gavarnie nappe activity broto and fiscal basement thrust sheets from 31 3 to 24 55 ma rupelian chattian oligocene to the syn guarga thrust activity from 24 55 to 21 2 ma chattian aquitanian oligocene miocene the accumulation rates vary from ca 22 to ca 39 cm kyr between the genetic stratigraphic units in the uncastillo fm through the section these rates are close to those of the underlying deposits of the campodarbe fm average of ca 36 cm kyr deformation for the latest pyrenean front syn guarga thrust is younger than previously assigned in 5 4 1 5 and 1 1 myr of the beginning of the punta comun thrust sheet from 29 4 ma to 24 ma lower riglos thrust sheet system from 24 to 22 5 ma and the upper riglos thrust system 22 5 to 21 4 ma respectively other significant changes in accumulation rate and its derivative also indicate variations in the tectonic activity ca 33 and 28 ma

properties and behaviour of hong kong marine deposits with different clay contents large scale marine reclamation has taken place on soft hong kong marine deposits hkmd more and more reclamation is to be undertaken due to the rapid development of infrastructures and housing pr

the anso transect of the southern pyrenees basement and cover thrust geometries a balanced geological section through the western central pyrenees allows the alpine geometry of hercynian basement to be determined this shows marked differences with other transects of the southern part of the chain basement involved thrust sheets do not form an antiformal stack but are imbricated and define steps separated by frontal culmination limbs basement thrusts propagate upwards and have formed distinct thrust systems in the cover in this transect the north pyrenean zone is bounded to the south by gently dipping thrusts of large displacement and the axial zone massif at its western termination area is a flat topped culmination caused by a single thrust fault the gavarnie thrust this thrust emerges to the south in the interior of the syntectonic jaca basin the geometry of which is also controlled by underlying basement thrusts various generations of structures can be correlated with distinct episodes of syntectonic sedimentation a sequential restoration of the section illustrates how successive foreland sedimentary wedges were generated and progressively involved in deformation tectonic shortening is 48 km almost half of that estimated further to the east for the southern pyrenees the structure deduced at the ecors pyrenees seismic section cannot be translated to this transect

nucleation of ductile shear zones in a granodiorite under greenschist facies conditions neouvielle massif pyrenees france abstract the problem of ductile shear zone nucleation under greenschist facies conditions is approached from the example of small scale shear zones developed in the neouvielle granodioritic pluton pyrenees france by means of field and microstructural observations and chemical analyses these shear zones are not related to pre existing fractures and exhibit networks of numerous conjugate fairly parallel and regularly spaced centimetre scale brittle ductile shear zones involving diffuse localization mechanisms although the mode of deformation depends on the minerals present deformation in the shear zones is basically controlled by hydration processes hydration and consequent fluid controlled alteration and deformation are related to fluid migration towards developing cracks all these cracks are extensional and formed on the scale of at most a few grains and frequently single grains a comparison of chemical compositions of undeformed and sheared granodiorite shows that the shear zones can be interpreted as isochemical and isovolumetric systems we propose a sequence of mechanisms by which the nucleation of a small scale brittle ductile shear zones spreading out within a granodioritic rock may occur in these mechanisms shear zone nucleation occurs independently of pre existing fractures and results from the heterogeneous character of the polymineralic rock in the studied granodiorite the mineral heterogeneities favour focusing of locally derived fluids by processes involving grain scale hydraulic fracturing fluid focusing generates instabilities by local softening and subsequently shear zone nucleation

organic geochemistry of an anoxic cycle a case history from the oligocene section hungary total organic carbon extractable organic matter sulfur content kerogen type and saturated hydrocarbons have been determined in 25 core samples from an approximately 100 m thick section of the oligocene tard clay near budapest the tard clay records a five million year long anoxic cycle initiated by isolation of the sea development of a positive water balance and resulting density stratification and terminated by the re opening of access to the sea the lower non and moderately laminated shales record the build up of anoxia they contain 0 5 5 0 of organic carbon and type iii kerogen their saturated hydrocarbon fractions show high abundance of phyllocladanes biomarkers characterising coniferae derived organic matter the overlying moderately and strongly laminated sediments containing 1 5 5 0 organic carbon a predominance of hopanes over the n alkanes and type ii kerogen show the imprint of increased planktonic productivity the nutrients needed for this high productivity were liberated by alteration processes of contemporaneous volcanic glass the upper part of the strongly laminated shales containing a maximum of 2 organic carbon and type iii kerogen deposited after the termination of volcanic ash falls records a drop of planktonic productivity at the top of the tard clay the weak lamination and the low content 1 of organic carbon signifies the end of the bottom water oxygen depletion due to the destruction of density stratification of the water column

hydrocarbon systems of northeastern venezuela plate through molecular scale analysis of the genesis and evolution of the eastern venezuela basin abstract the prolific oil bearing basins of eastern venezuela developed through an unusual confluence of atlantic caribbean and pacific plate tectonic events mesozoic rifting and passive margin development created ideal conditions for the deposition of world class hydrocarbon source rocks in the cenozoic transpressive west to east movement of the caribbean plate along the northern margin of venezuela led to the maturation of those source rocks in several extended pulses directly attributable to regional tectonic events the combination of these elements with well developed structural and stratigraphic fairways resulted in remarkably efficient migration of large volumes of oil and gas which accumulated along the flanks of thick sedimentary depocenters at least four proven and potential hydrocarbon source rocks contribute to oil and gas accumulations cretaceous oil prone marine source rocks and miocene oil and gas prone paralic source rocks are well documented we used reservoired oils seeps organic rich rocks and fluid inclusions to identify probable jurassic hypersaline lacustrine and albian carbonate source rocks hydrocarbon maturation began during the early miocene in the present day serrania del interior as the caribbean plate moved eastward relative to south america large volumes of hydrocarbons expelled during this period were lost due to lack of effective traps and seals by the middle miocene however when source rocks from the more recent foredeeps began to mature reservoir migration pathways and topseal were in place rapid tectonically driven burial created the opportunity for unusually efficient migration and trapping of these later expelled hydrocarbons the generally eastward migration of broad depocenters across venezuela was supplemented by local tectonically induced subsidence these subsidence patterns and later migration resulted in the mixing of hydrocarbons from different source rocks and in a complex map pattern of variable oil quality that was further modified by biodegradation late gas migration water washing and subsequent burial the integration of plate tectonic reconstructions with the history of source rock deposition and maturation provides significant insights into the genesis evolution alteration and demise of eastern venezuela hydrocarbon systems we used this analysis to identify additional play potential associated with probable jurassic and albian hydrocarbon source rocks often overlooked in discussions of venezuela the results suggest that oils associated with likely jurassic source rocks originated in restricted rift controlled depressions lying at high angles to the eventual margins of the south atlantic and that albian oils are likely related to carbonate deposition along these margins post continental break up in terms of tectonic history the inferred mesozoic rift system is the eastern continuation of the espino graben whose remnant structures underlie both the serrania del interior and the gulf of paria where thick evaporite sections have been penetrated the pattern of basin structure and associated mesozoic deposition as depicted in the model has important implications for the mesozoic paleogeography of northern south america and africa cuba and the yucatan and associated new play potential

syntectonic burial and post tectonic exhumation of the southern pyrenees foreland fold thrust belt in the oligocene to earliest miocene the entire southern pyrenean foreland fold and thrust belt was backfilled and buried in up to 3 km of syntectonic continental conglomerates from the range9s own erosional debris then starting in the mid to late miocene the pyrenees were exhumed by erosional excavation to their present relief a model is proposed for this unusual development whereby late eocene oligocene tectonic uplift of the margins of the ebro basin raised local base level and blocked normal dispersal of erosional debris to adjacent oceans thus causing the basin to fill then backfill northwards across the entire southern flank of the pyrenees subsequent miocene rifting of the catalan mediterranean margin and the messinian salinity crisis lowered base level allowing the ebro river to cut headward capture the ebro basin and re excavate the pyrenees

origin of the highly elevated pyrenean peneplain 1 peneplanation of mountain ranges is generally considered the result of long term erosional processes that smooth relief and lower elevation near sea level therefore peneplain remnants at high elevation in mountain ranges are used to infer posttectonic surface uplift such an interpretation has been proposed for the pyrenees where high elevation low relief erosional surfaces rose up to more than 2000 m because the pyrenean foreland basins are filled with very thick continental deposits which have buried the early jagged landscape we challenge this hypothesis by pointing out that relief applanation does not necessarily require elevation lowering we propose an alternative interpretation in which piedmont aggradation of detrital sediment that comes from erosion of the high chain induces the rise of the base level of the range therefore reducing strongly the erosive efficiency of the drainage system and resulting in the progressive smoothing of the relief such a process allows a high elevation low relief erosional surface to develop at the scale of the range in the pyrenees occurrence of high elevation low relief erosional surface remnants does not imply a posttectonic uplift but is instead due to the dissection of the initial miocene high elevation low relief surface by the recent drainage system the erosive activity of which has been enhanced by global climate change from the late pliocene onward

potential role of event driven sediment transport on sediment accumulation in the cariaco basin venezuela abstract a sediment density flow was observed in the eastern cariaco basin during september 2008 evidence suggests that this flow was likely triggered by a magnitude 5 2 earthquake that occurred on august 11 2008 with an epicenter located at 10 51 n 64 17 w off the city of cumana venezuela elevated suspended sediments near the bottom were observed at the mouth of the manzanares canyon 90 g m 2 over a depth of 165 m and decreased to 11 g m 2 over a depth of 40 m 42 km away from the canyon s mouth at the cariaco ocean time series site the sediment flux associated with this single event was 10 of the total annual sediment flux that typically reaches the cariaco basin deep seafloor carbon to nitrogen ratios and isotope composition confirm that most of the organic matter transferred by the sediment flow was of continental origin c n ratios of 17 67 13c of 27 04 and 15n of 6 83 our observations contribute to the growing body of evidence that suggests that submarine canyons are rapid efficient sediment conduits of particles from shallow to deep waters and that they should be included in efforts to constrain estimates of sediment and terrestrially derived carbon transport from the continental shelves to the deep ocean

thick skinned tectonics and basement involved fold thrust belts insights from selected cenozoic orogens defining the structural style of fold thrust belts and understanding the controlling factors are necessary steps towards prediction of their long term and short term dynamics including seismic hazard and to assess their potential in terms of hydrocarbon exploration while the thin skinned structural style has long been a fashionable view for outer parts of orogens worldwide a wealth of new geological and geophysical studies has pointed out that a description in terms of thick skinned deformation is in many cases more appropriate this paper aims at providing a review of what we know about basement involved shortening in foreland fold thrust belts on the basis of the examination of selected cenozoic orogens after describing how structural interpretations of fold thrust belts have evolved through time this paper addresses how and the extent to which basement tectonics influence their geometry and their kinematics and emphasizes the key control exerted by lithosphere rheology including structural and thermal inheritance and local regional boundary conditions on the occurrence of thick skinned tectonics in the outer parts of orogens

fluid pressure and salinity variations in shear zone related veins central pyrenees france implications for the fault valve model abstract fluid inclusion microthermometry data is presented from quartz veins associated with high angle reverse shear zones cutting the neouvielle massif in the central french pyrenees a complex series of veins were formed during both normal and reverse movement on brittle faults within the shear zone brittle structures developed contemporaneously with quasi plastic deformation in the shear zones fluid inclusion data are presented from a variety of vein types and shows that a wide variation in fluid density and salinity is present in the fault system these variations occur both within individual veins and between different vein types temperatures at the time of vein filling are constrained to be in the range 310 360 c by chlorite microthermometry the variation in homogenisation temperature is too large to be accounted for by variations in the fluid temperature and is interpreted to reflect variations in fluid pressure between lithostatic 500 mpa and hydrostatic 200 mpa values at the time of quartz growth in the veins the shear zones carry modest displacements and may not themselves have been seismogenic a model is presented in which fluid pressure variations and stress cycling within the steeply dipping shear zones is controlled by the seismogenic cycle on large underlying thrust structures the model predicts that the highest maximum trapping pressures should occur in fluid inclusions from low angle veins formed in a high pfluid compressional regime immediately before earthquake rupture lower maximum pressures are expected in steep veins related to extension and normal fault movement across the shear zones immediately after rupture the fluid inclusion data support this model when maximum trapping pressures are considered but the majority of inclusions in all vein types formed at pressures well below lithostatic values this suggests that the dominant factor causing quartz precipitation was the sudden pressure drop immediately after earthquake rupture regardless of vein type

geotechnical properties of pusan clays the nakdong river plain is one of the few areas in korea where soft clays have been deposited although many site investigations related to large scale reclamation works have been carried out over the past 10 years soil profiles still need to be better characterized the pusan clays at this location constitute an interesting topic for researchers both in and outside korea due to their geological complexity unusually great thickness very low overconsolidation ocr values large consolidation settlement and the effects of artesian pressure this paper represents the first comprehensive review of pusan clays and collates extensive existing and new geotechnical data these data are then analyzed within the frameworks of both classical and new developments in soft clay engineering to address the problems mentioned above key words pusan soft clay intrinsic compression geotechnical properties

some aspects of the compressibility behaviour of a clayey sand the intrinsic behaviour of a residual clayey sand derived from sandstone was investigated in one dimensional compression the data show some interesting differences when compared with other published data in that no unique normal compression line can be identified although the compressibility on first loading is similar to that for many sandy materials at states on their normal compression lines the locations of the compression curves were found to be a function of the initial voids ratio and there was no convergence at higher stresses tests on a model clay sand mixture indicated that this behaviour is common to gap graded clayey sands key words sands compressibility oedometer tests

asymmetric growth of the pyrenees revealed through measurement and modeling of orogenic fluxes orogenic asymmetry is ubiquitous in terms of topography structure and metamorphism but the relative influences of climate and tectonics in determining such asymmetry remain contentious this study demonstrates that for the case of the european pyrenees orogenic asymmetry is not defined by inherited structural asymmetry nor by orographic asymmetry of precipitation but is the simple consequence of the inherent tectonic growth of a doubly vergent orogen the pyrenees record approximately 60 myr of upper crustal accretion erosion and sedimentation that developed from late cretaceous to early miocene times approximately 165 km of plate convergence was accommodated by four phases of orogenic growth that can be summarized in terms of their generic orogenic development as follows 1 early inversion of passive margin extensional faults initiating the pro wedge 2 growth by a combination of frontal accretion and underplating to the pro wedge symmetrical and steady record of erosion and foreland basin sedimentation 3 cessation of pro wedge frontal accretion with propagation of the retro wedge deformation front 4 accelerated growth of pro wedge antiformal stack induced by underplating accelerated erosion over antiformal stack and increase in sediment discharge to pro foreland basin stabilization of outer pro wedge by sediment blanketing discrete element model experiments are used to explore the natural tendency of the system towards asymmetry model output demonstrates that during active frontal accretion to the pro wedge of an orogen the maxima in erosional denudation is offset towards the pro wedge relative to the maximum depths of exhumation this asymmetry is fundamentally driven by the progressive reduction in advection velocities of material within the orogen from the pro wedge into the retro wedge hence for an efficient erosional regime a dynamic coupling between erosion and structural uplift of the pro wedge will reduce activity of the retro wedge and hence drive asymmetry in terms of low temperature thermochronometry erosion and sedimentation the models also demonstrate the tendency for pro wedge growth through frontal accretion to slow however the cessation of frontal accretion as recorded by the south pyrenean thrust belt phases 3 and 4 requires additional forcing it is proposed that the thick wedge top sedimentation recorded at this time increased taper angles and hence stabilized the wedge accretionary influx into the orogen at this time was accomplished through underplating these processes governing asymmetry do not require a spatially variable climate or a laterally heterogeneous underthrust plate

interplay between tectonics climate and fluvial transport during the cenozoic evolution of the ebro basin ne iberia 1 three dimensional modeling that integrates fluvial sediment transport crustal scale tectonic deformation and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the ebro sedimentary basin ne iberia the ebro basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the pyrenees the iberian range and the catalan coastal range in the late oligocene the catalan coastal range underwent extension leading to the formation of the valencia trough nw mediterranean but the ebro basin remained closed for nearly 15 myr more before the ebro river cut through the remnants of the topographic barrier this drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill here we investigate the processes controlling these major drainage changes the modeling results constrained by a large data set on the tectonic and transport evolution of the area predict a closed phase characterized by a large lake in the central eastern ebro basin dry climatic conditions probably lowered the lake level and contributed together with rift flank uplift to prolong this endorheic basin stage the age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8 5 ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions sea level changes in the mediterranean had no major impact in the large scale drainage evolution of the ebro basin index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 3210 mathematical geophysics modeling 3344 meteorology and atmospheric dynamics paleoclimatology 8102 tectonophysics continental contractional orogenic belts keywords pyrenees drainage evolution lake sediment budget erosion flexure

vanadium nickel and sulfur in crude oils and source rocks and their relationship with biomarkers implications for the origin of crude oils in venezuelan basins abstract this work presents a study of vanadium nickel and sulfur concentrations and biomarkers in a suite of crude oils and source rocks from three venezuelan basins maracaibo and eastern basins and barinas sub basin crude oils range from unaltered to altered by biodegradation and source rocks are characterized by having different kerogen types type ii iii or iv and maturity levels early mature to post mature vanadium nickel and sulfur concentrations v ni or v v ni and saturate biomarkers were used to classify the oils and source rocks based on inferred paleo redox environment lithology and maturity of the source rock oils are classified into five groups based on v ni ratios they appear to be related to variations in the paleo redox environment from suboxic dysoxic to anoxic suboxic of source rocks with variable lithological composition and organic matter input regardless of their maturity or biodegradation level these five groups are also classified based on biomarkers related to maturity organic matter type paleo redox environment and source rock lithology in source rocks vanadium nickel and sulfur concentrations together with v ni or v v ni ratios provide information about the paleo redox environment and are related to lithology regardless of their maturity these results also indicate variable paleo redox conditions during the sedimentation of venezuelan source rocks all this suggests that while the main source rocks in venezuelan basins are well established there are still uncertainties regarding their lateral and vertical variations in organic and inorganic facies and paleo redox conditions the presence of other source rocks contributing to the accumulation of hydrocarbons in the venezuela basins is also a possibility

crustal structure and orogenic material budget in the west central pyrenees surface and subsurface data are combined to construct a crustal scale cross section of the western central pyrenees france and spain at the boundary between the european and iberian plates the position of moho reflections in the ecors arzacq reflection profile suggests a tectonic wedge of european crust and upper mantle had indented the iberian plate at lower crustal levels the european wedge is overlain by an upper iberian wedge thus constituting a double stacked wedge geometry the upper wedge was delaminated and deformed giving rise to the pyrenean orogenic prism manifested as a bivergent fan in upper crustal levels the underthrust lower iberian plate has been imaged to depths of 55 60 km but crustal budget considerations based on a palinspastic reconstruction require that this continental root subducted to depths up to 90 km total orogenic contraction calculated from surface structures is about 75 80 km which was accomplished between the latest cretaceous and the early miocene at an averaged rate of 1 2 mm yr consistent with these moderate values exhumation of the orogen is much less than in the more shortened eastern parts of the range paleozoic basement and preorogenic mesozoic rocks are little eroded and much of the exhumation involved cannibalization of early foreland basins which once covered the entire poorly emergent orogen at this transect this resulted in a continuous process of sediment recycling and coupled with a considerable lateral arrival of material a bulk negative erosion sedimentation budget