diagenesis associated with cooling during burial an example from lower cretaceous reservoir sandstones sirt basin libya fluid inclusions in quartz and dolomite cements were used to determine temperature timing origin and function of fluids in the diagenetic evolution of the lower cretaceous upper sarir sandstone sirt basin libya transmitted light backscattered electron and scanning electron microscope sem cathodoluminescence analyses were carried out to determine the paragenesis in quartz overgrowths fluid inclusions along the grain overgrowth boundary yield homogenization temperatures from 130 to 141 degreesc and salinities between seawater and freshwater aqueous fluid inclusions in later quartz overgrowths have homogenization temperatures from 114 to 129 degreesc and salinities between 18 and 21 wt nacl equivalent fluid inclusions in dolomite have variable homogenization temperatures 120 141 degreesc and high salinities 20 22 wt nacl equivalent this trend in homogenization temperatures of fluid inclusions is interpreted as the result of quartz cement precipitation in the presence of hot low salinity connate fluids connected with an increased heat flow related to regional rifting later quartz overgrowths precipitated during regional cooling concurrent with the end of the rifting and after invasion of saline fluids possibly brought in from adjacent areas or refluxed downward during or after times of evaporite deposition this diagenetic history linked to a decreasing heat flow could be common in other aborted rift basins which are important targets for oil exploration

diagenesis and formation water chemistry of triassic reservoir sandstones from southern tunisia the fluvial triassic reservoir subarkoses and arkoses 2409 5 2519 45 m of the el borma oilfield southern tunisia were subjected to cementation by haematite anatase infiltrated clays kaolinite and k feldspar at shallow burial depths from meteoric waters subsequently basinal brines controlled the diagenetic evolution of the sandstones and resulted initially in the precipitation of quartz overgrowths magnesian siderite minor ferroan magnesite and anhydrite the enrichment of siderite in 12c isotope 13cpdb 14 5 to 9 results from derivation of carbon from the thermal decarboxylation of organic matter during further burial the precipitation of dickite and pervasive transformation of kaolinite into dickite occurred followed by the formation of microcrystalline k feldspar and quartz chlorite and illite prior to the emplacement of oil present day formation waters are na ca cl brines evolved by the evaporation of seawater and water mineral interaction and are in equilibrium with the deep burial 3 1 km minerals these waters are suggested to be derived from the underlying silurian and devonian dolomitic mudstones

regional geology and petroleum systems of the illizi berkine area of the algerian saharan platform an overview abstract the berkine and illizi basins are palaeozoic mesozoic intraplate depressions that preserve an over 7000 m thick sedimentary rock record and contain world class petroleum systems with over 39 bboe eur hydrocarbon reserves regional seismic transects and a wealth of well data are used to review the tectonostratigraphic evolution of the area the gondwana palaeozoic and tethys mesozoic supercycles make up the bulk of the phanerozoic succession these 1st order cycles record extensional basin formation followed by a protracted period of overall net subsidence and conclude with basin inversion and regional uplift during the hercynian and alpine orogenies respectively structural styles were dictated by transpressional or transtensional reactivation of mostly nne oriented basement structural grain of late proterozoic ea cambrian pan african age and vertical movement of long wavelength regional highs and lows local tectonism is considered to be the far field effect of plate tectonic processes that affected the north african plate boundaries such as the caledonian and hercynian orogenies the opening of the tethys and atlantic oceans and the alpine orogeny these were accompanied by localised thermal mantle processes regional unconformities subdivide the gondwana and tethys supercycles into eight and seven megasequences respectively these regional units often record 2nd order transgressive regressive cycles that constrain the mapping of reservoir seal pairs and of main source rock intervals the lower palaeozoic megasequences are characterised by sand rich laterally extensive coarse grained fluvial and shallow marine reservoirs interbedded with thin and widespread marine shales they were mostly deposited in shorelines of shallow epeiric seas and continental braided river systems or during the late ordovician in a short lived continental glacial system third order sequences display ramp style geometries with largely parallel to low angle sigmoidal stratal patterns early mesozoic sedimentation followed the late palaeozoic uplift and peneplanation in the form of hinterland sequences containing fluvial and alluvial sandstones and playa lake mudstones and evaporites interbedded with thin lacustrine or shallow marine shales and dolomites the prolific petroleum systems that evolved within these series are associated with the early silurian and late devonian world class source rocks and numerous paleozoic and triassic reservoirs this regional review provides a renewed comprehensive insight into the geological evolution of the area that can help guide local exploration efforts but also serves as a model for exploration in other intracratonic basins of the world

active fault related folding in the epicentral area of the december 25 1222 io ix mcs brescia earthquake northern italy seismotectonic implications abstract a dense grid of petroleum industry seismic reflection profiles coupled with field mapping exploratory trenching and geomorphic and structural analysis are used to characterize the quaternary growth history of the capriano del colle fault system one of several inferred active buried thrusts that extend across the po plain in northern italy shortening is characterized here by a deeply buried south vergent forethrust and an associated north vergent backthrust whose upward propagation is expressed by fault propagation folding near the surface structural interpretation based on seismic data suggests that strain is accommodated at very shallow levels by secondary flexural slip thrusts and reverse faults developed on synclinal flanks that emanate from active axial surfaces analysis of syntectonic growth strata document maximum rates of dip slip of 3 45 0 66 mm yr 1 6 myr 1 2 myr and 0 47 0 22 mm yr during a more recent time period 0 89 myr present a quarry excavation at capriano del colle allows a preliminary paleoseismologic analysis of coseismic surface faulting and liquefaction exposed near the core of an active mid pleistocene to holocene anticline these features are interpreted to be generated during strong local earthquakes consistent with the environmental effects and ground motions of an event similar to the december 25 1222 brescia earthquake io ix mcs this indicates for the first time that compressive folds and blind thrusts in the po plain are currently accommodating slow rates of modern contraction in an active zone of the southern alps that extends from lake garda to varese we thus argue that earthquakes similar to the december 25 1222 brescia event are likely to occur in this region and pose a direct threat to such a densely populated and developed area

paleosols and associated channel belt sand bodies from a continuously subsiding late quaternary system po basin italy new insights into continental sequence stratigraphy previous sequence stratigraphic work has emphasized the key role of paleosols and associated sand dominated fluvial bodies as key features for interpreting alluvial architecture the temporal resolution of the ancient record is however insufficient to fully explain the complex relationship between soil formation and the evolution of fluvial systems under changing sea level and climate conditions in this paper we present a detailed record of paleosol channel belt relationships reconstructed from the subsurface of a rapidly subsiding region po plain italy that spans almost all of the last glacial interglacial cycle 120 k y the studied succession preserves a systematic bipartite zonation into a thick paleosol bearing segment close to the basin margin and a sand dominated interval with vertically amalgamated channel belts in an axial position individual paleosols are weakly developed and represent key stratigraphic markers that can be traced basinwide into adjacent essentially contemporaneous unconfined channel belt deposits unlike conventional models of late quaternary alluvial coastal plain systems no persistent incised valley was established in the po system during the last glacial interglacial cycle continuous accommodation was the key depositional control on alluvial stratigraphy during the prolonged 90 k y phase of late pleistocene sea level fall which led to the deposition of a thick dominantly aggradational alluvial succession the development of shallowly incised short lived valley systems took place only at the transition to glacial stages associated with substantial sea level drop marine oxygen isotope stage mis 3 2 transition and possibly mis 5 4 transition this study shows that in rapidly subsiding settings with high rates of sedimentation incised valley systems may be replaced by aggradationally stacked essentially nonincised fluvial bodies in these cases overbank packages bounded by immature paleosols represent the most likely alternative to the highly weathered interfluve paleosol predicted by classic sequence stratigraphic models fourth order sequence boundaries and lower rank erosional surfaces may be easily confused at the 100 k y scale and transgressive surfaces defining the onset of retrogradation may become the most readily identifiable sequence stratigraphic surfaces

regional trends in water chemistry smackover formation southwest arkansas geochemical and physical controls we present results on regional geochemical analyses of formation waters from jurassic carbonate strata of the upper smackover formation from the southwest arkansas shelf gulf coast basin these formation waters have been noted in earlier studies for their exceptional salinities and abnormally br rich composition our detailed and regionally extensive database shows that chemical heterogeneities occur on a relatively small scale and have spatial relations to faults which may act as pathways for fluid migration from deeper and hotter portions of the stratigraphic section one of the most pronounced heterogeneities in water chemistry is an h 2 s rich anomaly in the center of the shelf enrichments in h 2 s are accompanied by large increases in alkali elements li k and b and b which could be produced by higher temperature diagenesis of clay minerals and feldspars in deeper seated siliciclastic strata bromide enrichments in all smackover formation waters are apparent from relations between br and cl contents as well as br and divalent cation carpenter function values as suggested by earlier studies of these waters evaporatively concentrated seawater expelled from associated thick monomineralic evaporite sections may be an important source of br cl and na whereas ca mg and sr concentrations have been modified by carbonate mineral recrystallization and dolomitization mineral equilibria exert significant controls on concentrations of ca mg sr and so 4 in these brines br enrichment likely was produced by halite recrystallization in fluids already enriched in br from seawater evaporation elevated cl br ratios occur in regional association with lower salinity water near t e south arkansas fault system consistent with halite dissolution during meteoric water recharge thus despite relatively uniform reservoir lithology and simple structural setting processes on small spatial scales have resulted in significant heterogeneity in water chemistry within a small area of the gulf coast sedimentary basin although movement of fluids along these fault systems is not demonstrated in our study the regional trends in geochemistry are strongly suggestive of their important role in controlling chemical heterogeneities in smackover formation waters

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

br cl na systematics in illinois basin fluids constraints on fluid origin and evolution the authors present here bromide chloride and sodium data for fluids from reservoirs of ordovician through pennsylvania age in the illinois basic which suggest that remnant marine fluids contribute significantly to fluid cl budgets cl br and nabr ratios for ordovician through devonian formation fluids are relatively uniform and near those for seawater despite greater than a factor of ten range in cl concentration in contrast fluids from mississippian and pennsylvanian reservoirs separated from older reservoirs by the new albany shale group have more variable fluid cl br and na br ratios most of which are significantly greater then those of seawater the 1 1 stoichiometry of cl and na increases for mississippian and pennsylvanian formation fluids is consistent with halite dissolution nevertheless br systematics and mass balance considerations indicate that he overall cl budget of illinois basin formation fluids appears to be more significantly influenced by the contribution from subaerially evaporated seawater than by halite dissolution

remobilization of deep basin brine during exhumation of the illizi basin algeria abstract understanding the processes that drive fluid flow in sedimentary basins has important implications for models of metallic ore and petroleum migration and accumulation in the subsurface potential drive mechanisms include gravity driven flow compaction driven flow and density driven convection in this study we demonstrate that the brine hosted in ordovician sandstone in the illizi basin in algeria is genetically linked to triassic liassic evaporites deposited 400 km to the north in the berkine basin this observation confirms that long distance lateral brine migration has occurred within the basin in the past we assess the hydrogeologic record preserved in aqueous fluid inclusions within the ordovician sandstone document a marked increase in formation water salinity during cooling and exhumation and evaluate the drive mechanisms for late stage remobilization of deep brines within the basin it is hypothesized that the release of overpressure during exhumation of the illizi basin may have been a critical contributor to updip fluid flux this model could be applicable to other exhumed basins worldwide

reservoir compartmentalization get it before it gets you abstract this paper examines the impact of compartmentalization on oil recovery the importance of identifying it during field appraisal and methods to evaluate it using fluid data the impact on recovery factor is highlighted using a global database of oil field recovery factors as a function of reservoir complexity and compartmentalization and emphasized in two case studies the effect of compartmentalization on oil recovery demonstrates the benefit in characterizing compartmentalization correctly during appraisal so that the field can be developed in an optimal manner early characterization of field compartmentalization requires making maximum use of available fluid data during appraisal when interpreting fluid data to identify compartmentalization it is critical to take into account the different time scales for various fluid signals pressure contacts density composition to equilibrate and to be able to extrapolate to field production time scales this is essential to avoid false negatives compartments assumed absent due to homogeneous fluid properties when in fact fluids would have equilibrated even in the presence of compartments false positives where fluid differences are interpreted as evidence of compartments when in fact there has not been sufficient time for equilibration to occur and to resolve apparently conflicting data some fluid indicators are at equilibrium others are not rigorous simulation of fluid equilibration is a complex multiphase multidimensional process and is generally reserved for specialist in depth studies however order of magnitude evaluations can be made using analytical solutions in minutes allowing many what if scenarios to be considered and uncertainty to be assessed analytical solutions for estimating the time required for spatially varying fluid properties to revert to steady state distributions are reviewed all these mixing processes are shown to be diffusive in character an effective diffusion coefficient for each process can be calculated from the reservoir rock and fluid properties for an isothermal system the different time scales and distances for each fluid property variation to attain equilibrium can be compared on a single graph where the time elapsed since fluid perturbation is known analytical solutions can be used to estimate the degree of compartmentalization e g permeability of barriers these solutions lend themselves to the development of simple practical compartment assessment tools for industry practitioners

fluid flow in sedimentary basins abstract the pore waters in sedimentary basins are ultimately derived from sea water meteoric water mineral bound water or from the underlying basement geochemically these waters initially have different signatures however the pore water compositions are easily altered by reactions with minerals or by mixing with other fluids meteoric water is driven downwards into sedimentary basins by the gravitational potential which approximately corresponds to the elevation of the ground water table above the sea or lake level it is difficult to model such flow however because the permeability on a large scale is almost impossible to represent realistically the continuity of confined sandstone and limestone aquifers plays an important role in determining the flux of meteoric water received by rocks in different parts of the basin but this is again difficult to predict pore water flow driven by compaction typically has velocities several orders of magnitude lower than what is commonly found in meteoric water flow regimes the average rate of upwards flow is lower than the rate of subsidence and the difference is the rate of incorporation of sea water in the topmost layer at the sea floor the salinity of formation water provides important constraints on fluid flow in sedimentary basins in the north sea basin and the gulf coast basin these types of data indicate that vertical mixing by compaction driven flow and convection is limited compaction driven flow obeys darcy s law but there are complex interdependencies between pressure permeability and compaction given the low compressibility of water the flow which can result from pressure release alone is very limited except on a local scale along permeable faults and fractures the main flow of pore water during burial is driven by compaction which is a slow process even when overpressure is released abruptly with a resulting increase in the net effective stress in the case of high permeability faults the flow into the fault from low permeability sedimentary rocks at depth may be rate limiting the displacement of pore water in adjacent sediments near the top of the faults may also slow down fluid flow on fractures that do not reach the sea floor modelling of fluid flow in sedimentary basins should be based on permeability distributions which are mostly determined by primary facies diagenesis and the tectonic history of the basin extensional tectonics produce a predominantly vertical fracture network which may serve as conduits for pore water flowing deep into the crust upward flow of hot fluids in basement fractures must have a high velocity in order to produce large thermal anomalies concentrations of dissolved components precipitate at the surface and form deposits of quartz and ore minerals if basement fractures are overlain by a thick sequence of soft sediments the rate of flow on the fractures will be reduced because of the low permeability in the sedimentary cover and conductive heat transport will dominate flow of water at high enough velocities to bring hot water to the surface and produce hot springs is most likely to occur in fractured basements rocks or well cemented sedimentary rocks concentrated precipitation of dissolved components will occur near the surface where the rate of cooling is highest also sediment hosted ores precipitated from flow of hot water on fractures are therefore likely to form before accumulation of thick overlying sedimentary sequences

late cretaceous cenozoic tectonic sedimentary evolution and u enrichment in the southern songliao basin abstract late cretaceous cenozoic tectonic sedimentary evolution is fundamental to u uranium migration and u enrichment in the southern songliao basin northeast china to establish the genetic connection between tectonic sedimentary evolution and u enrichment this paper presents a mineralogical study apatite fission track aft analysis and sem cl analysis of quartz grains two stages of mineralization were proposed including the u pre enrichment stage during the late cretaceous and the ore forming stage during the cenozoic based on the density plots of the aft ages paleoclimate studies and sem cl analysis of quartz grains it is inferred that the u pre enrichment was closely related to the rapid uplift of the great xing an range and the zhangguangcai range and the o2 rich atmosphere during 97 90 ma in the southern songliao basin the o2 rich atmosphere increased u mobility and led to the formation of red beds during the late cretaceous which widely developed u pre enrichment in the basins of northeast china the mineralogical study reveals that the qianjiadian uranium deposit developed in two stages the diagenetic process experienced the transition from early alkaline to late acidic conditions to promote the stage i mineralization u pre enrichment the dominant occurrence spaces for u were the dissolution pores of quartz tightly packed with calcite cement u enrichment during alkaline ambient conditions was mainly via adsorption with the increase of the buried depth the early alkaline diagenesis returned to acidic conditions due to the abundant organic material u vi was reduced to pitchblende due to the reducing capacity of the organic matter om stage ii ore forming stage mineralization was strictly related to the hydrocarbon re concentration according to the thermal history study of the cc1 and q2 boreholes the southern songliao basin experienced four episodes of rapid uplift during the cenozoic at 83 80 ma 68 52 ma 33 23 ma and 8 ma respectively the cenozoic uplifts led to hydrocarbon migration at 65 ma 23 ma and present the re concentration of hydrocarbon prompted the u mineralization in the qianjiadian uranium deposit in the southern songliao basin during the stable period of tectonic movements the reducing conditions caused by hydrocarbons promoted u mineralization the dominant spaces of coffinite were intergranular dissolved pores formed during the transformation from the feldspar to the kaolinite under acidic conditions the post rift phase and structural inversion phase directly controlled the u pre enrichment stage and the ore forming stage respectively overall the tectonic sedimentary evolution played an important role in controlling the u leaching from granites the dominant occurrence spaces and u recycling

erosion driven uplift of the modern central alps abstract we present a compilation of data of modern tectono geomorphic processes in the central european alps which suggest that observed rock uplift is a response to climate driven denudation this interpretation is predominantly based on the recent quantification of basin averaged late holocene denudation rates that are so similar to the pattern and rates of rock uplift rates as determined by geodetic leveling furthermore a gps data based synthesis of adriatic microplate kinematics suggests that the central alps are currently not in a state of active convergence finally we illustrate that the central alps have acted as a closed system for holocene redistribution of sediment in which the peri alpine lakes have operated as a sink for the erosional products of the inner central alps while various hypotheses have been put forward to explain central alpine rock uplift e g lithospheric forcing by convergence mantle processes or ice melting we show with an elastic model of lithospheric deformation that the correlation between erosion and rock uplift rates reflects a positive feedback between denudation and the associated isostatic response to unloading thus erosion does not passively respond to advection of crustal material as might be the case in actively converging orogens rather we suggest that the geomorphic response of the alpine topography to glacial and fluvial erosion and the resulting disequilibrium for modern channelized and associated hillslope processes explains much of the pattern of modern denudation and hence rock uplift therefore in a non convergent orogen such as the central european alps the observed vertical rock uplift is primarily a consequence of passive unloading due to erosion

physical and chemical controls on the composition of waters in sedimentary basins abstract the composition of subsurface waters is determined not only by diagenetic reactions but also by physical processes of fluid convection and hydrodynamic dispersion the south west louisiana gulf coast provides an instructive field example of the net effects of diagenetic reaction and solute transport on pore water compositions in a regional siliciclastic sequence most formation waters here have compositions totally unlike the compositions of the connate meteoric and marine fluids that were buried with their host sediments at the time of deposition dissolved chloride has been generated by the subsurface dissolution of salt domes and has been pervasively transported by fluid flow throughout most of the upper 3 km of the sedimentary section the simultaneous systematic variation in dissolved na k mg ca and alkalinity with chloride in these waters supports the hypothesis that metastable thermodynamic buffering by silicate carbonate mineral assemblages is a first order control on fluid compositions the chemical potential of chloride or alternatively total anionic charge appears to be a master variable which ranks in importance with such other variables as pressure and temperature in driving diagenesis in this region this variable is controlled largely by physical processes of advection and dispersion in the upper 3 km of the section and by dehydration reactions in deeper mudstone dominated sediments where the composition of the fluid is largely rock buffered the ultimate origin of the fluid and its pathway of chemical evolution may be obscured at least in terms of major solute composition non buffered components such as cl and br or isotopic compositions are more likely to retain information on original end member fluid compositions and reaction pathways

origin distribution and movement of brine in the permian basin u s a a model for displacement of connate brine na cl halite ca cl and gypsum ca cl brines with salinities from 45 to 300 g l are identified and mapped in four hydrostratigraphic units in the permian basin area beneath western texas and oklahoma and eastern new mexico providing spatial and lithologic constraints on the interpretation of the origin and movement of brine na cl brine is derived from meteoric water as young as 5 10 ma that dissolved anhydrite and halite whereas ca cl brine is interpreted to be ancient modified connate permian brine that now is mixing with and being displaced by the na cl brine displacement fronts appear as broad mixing zones with no significant salinity gradients evolution of ca cl brine composition from ideal evaporated sea water is attributed to dolomitization and syndepositional recycling of halite and bittern salts by intermittent influx of fresh water and sea water halite ca cl brine in the evaporite section in the northern part of the basin differs from gypsum ca cl brine in the south central part in salinity and na cl ratio and reflects segregation between halite and gypsum precipitating lagoons during the permian ca cl brine moved downward through the evaporite section into the underlying lower permian and pennsylvanian marine section that is now the deep basin brine aquifer mixing there withmore pre existing sea water buoyancy driven convection of brine dominated local flow for most of basin history with regional advection governed by topographically related forces dominant only for the past 5 to 10 ma 71 refs 11 figs less

salinity variations in north sea formation waters implications for large scale fluid movements abstract sodium chloride is the major salt dissolved in formation waters even at a considerable distance away from any evaporites chloride anions are not consumed to any significant extent by diagenetic reactions outside the salt deposits chloride ions are therefore preserved in the pore waters and the distribution of pore water salinities in sedimentary basins may help to constrain pore water flow and the transport of dissolved species of silica and carbonate minerals in the north sea basin and haltenbanken mid norway salinity gradients can be inferred from formation water samples measurements of pore water salinity from wireline logs are less accurate than formation water samples but have the advantage that a much larger database can be obtained data from 150 wells in the north sea and haltenbanken show that the salinities measured from well logs range from 20000 to 300000 ppm in the southern part of the norwegian north sea and haltenbanken there is a clear trend towards higher salinities with greater burial depth there is a pronounced salinity increase in the 500 m of section closest to the evaporites in the northern north sea where underlying evaporites are not known there is only a slight increase in the measured salinities with depth there are however no measurements of high salinity pore water 100000 ppm at depths shallower than 2200 m this pattern of salinity distribution in the pore water precludes large scale convection of the pore water during diagenesis it also indicates limited compaction driven flow log derived salinity data from the north sea suggest that the pore waters in upper jurassic and tertiary reservoirs are generally more saline than those of middle and lower jurassic reservoirs at the same depth the constraints on pore water flow that can be deduced from salinity variations puts severe limitations on the mechanisms of transport of dissolved solids in sedimentary basins and thus also on aspects of diagenetic models

14c activity and global carbon cycle changes over the past 50 000 years a series of 14c measurements in ocean drilling program cores from the tropical cariaco basin which have been correlated to the annual layer counted chronology for the greenland ice sheet project 2 gisp2 ice core provides a high resolution calibration of the radiocarbon time scale back to 50 000 years before the present independent radiometric dating of events correlated to gisp2 suggests that the calibration is accurate reconstructed 14c activities varied substantially during the last glacial period including sharp peaks synchronous with the laschamp and mono lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14c production rate together with plausible changes in deep ocean ventilation and the global carbon cycle during glaciation

correlations of cave levels stream terraces and planation surfaces along the river mur timing of landscape evolution along the eastern margin of the alps the transition zone of the eastern alps to the pannonian basin provides one of the best sources of information on landscape evolution of the eastern alpine mountain range the region was non glaciated during the entire pleistocene thus direct influence of glacial carving as a landscape forming process can be excluded and relics of landforms are preserved that date back to at least the late neogene in this study we provide a correlation between various planation surfaces across the orogen basin transition in particular we use stream terraces planation surfaces and cave levels that cover a vertical spread of some 700 m our correlation is used to show that both sides of the transition zone uplifted together starting at least about 5 ma ago for our correlation we use recently published terrestrial cosmogenic nuclide tcn burial ages from cave sediments new optically stimulated luminescence osl ages of a stream terrace and u th ages from speleothems minimum age constraints of cave levels from burial ages of cave sediments covering the last 4 ma are used to place age constraints on surface features by parallelizing cave levels with planation surfaces the osl results for the top section of the type locality of the helfbrunn terrace suggest an early wurm development 80 5 3 7 to 68 7 4 0 ka the terrace origin as a penultimate gravel deposit in classical alpine terminology riss is therefore questioned u series speleothem ages from caves nearby indicate formation during marine isotope stages mis 5c and 5a which are both interstadial warm periods as osl ages from the terrace also show a time of deposition during mis 5a ending at the mis 5 4 transition this supports the idea of temperate climatic conditions at the time of deposition in general tectonic activity is interpreted to be the main driving force for the formation and evolution of these landforms whilst climate change is suggested to be of minor importance obvious hiatuses in miocene to pleistocene sediments are related to ongoing erosion and re excavation of an uplifting and rejuvenating landscape

petroleum inclusions in sedimentary basins systematics analytical methods and applications abstract fluid dynamics in sedimentary basins is of tremendous interest both from a scientific and an economic point of view integration between fluid inclusion and present day fluid data provides the time aspect necessary for reconstruction of fluid flow paths and can be used for mapping fluid dynamics both on a regional basin scale or on the more local scale of petroleum reservoirs this paper presents a review of analytical and modelling methods for petroleum in fluid inclusions essentially four types of data for petroleum inclusions can be established through analysis and modelling 1 textures which give indirect information of the time aspect 2 fluid composition 3 fluid properties and 4 pressure temperature of trapping during the last decade development of analytical methods for determination of inclusion fluid compositions has taken place traditional correlation studies for characterisation of maturity and source facies may now therefore include fluid inclusion data the development has also been directed towards an improved understanding of the physical properties of petroleum inclusions although these methods are in their early stages concerning precision and accuracy data necessary for fluid flow modelling such as fluid densities viscosities pressure and temperature can be estimated

controls on reservoir quality in exhumed basins an example from the ordovician sandstone illizi basin algeria abstract petroleum exploration in many north african intracratonic basins targets early paleozoic sandstones as the primary reservoir objective these sandstones are often characterized by highly variable reservoir quality 0 0001 1000 md and the ability to predict and selectively target areas of enhanced porosity and permeability is crucial to unlock the hydrocarbon potential the objective of this study is to characterize the primary controls on reservoir quality in an ordovician field in the illizi basin of algeria through detailed core and petrographic analysis and establish if variations in thermal history across the field have a material impact on reservoir quality the best reservoir quality is observed in facies where primary intergranular porosity has been preserved in fine to coarse grained quartzarenites with less than 1 fibrous illite these lithologies are most commonly found within the high energy tidally reworked post glacial facies sandstones of the uppermost ordovician succession observed differences in quartz cement volume within compositionally and texturally similar samples from the southern and northern parts of the field are interpreted to reflect variations in thermal exposure due to deeper burial this interpretation is supported by field wide numerical modelling of sandstone diagenesis this study indicates that subtle variations in thermal history can have a material impact on the spatial trends in reservoir permeability thermal history therefore is an important consideration in reservoir quality studies in exhumed basins where variations in present day burial depth will be a poor guide for evaluating reservoir quality risk across a basin or play

grain size of fluvial deposits and late quaternary climate a case study in the po river valley italy by stacking the grain size data interpreted from many logs of borings down to 200 m deep in a sector of the po river valley we have obtained a curve of the clay silt fraction vs depth that matches the oxygen isotope curve of paleotemperatures for the late quaternary contour maps and plots for selected subzones show that the northern half of the study area is characterized by this correlation whereas the southern part adds only a random low amplitude noise to the curve the suggested dependence of grain size of fluvial deposits on climate in a part of the study area would provide an indirect way to date these not otherwise datable sediments allowing an evaluation of the sedimentation rates and of the total subsidence since the last interglacial

palaeoenvironmental and climatic inferences from the late early pleistocene lacustrine deposits in the eastern tiberino basin central italy within the neogene quaternary evolution of the mediterranean intermountain basins the eastern tiberino basin provides new multifaceted chronological biostratigraphic palaeoecological and palaeoenvironmental information appreciably improving the knowledge of palaeoenvironmental and climate conditions during the middle late matuyama chron late early pleistocene shallow to relatively deep lacustrine deposits and alluvial plain deposits magnetostratigraphically calibrated hold malacofaunas ostracofaunas and carpological remains as well as a pollen record palaeocarpological remains widely originated from the local azonal vegetation of waterlogged environments nonetheless some taxa show transitional morphology between possibly extinct pliocene pleistocene forms and living taxa the pollen record highlights a conifer dominated forest phase indicating a temperate wet interglacial period well aligned inside the schemes for the same latitudinal band the abundance of tree taxa currently absent from the italian peninsula points to pre jaramillo late early pleistocene biostratigraphical characters here compared to other sections from central italy and contributes to a better definition of modes and timing of their disappearance in southern europe malacofaunas and ostracods still with late early pleistocene features together with charophyte mark repeated fluctuations in energy temperature and chemical composition of water the overall record identifies an incipient diachronous cooling trend for the first time recognized in southern europe

subsurface magnetostratigraphy of pleistocene sediments from the po plain italy constraints on rates of sedimentation and rock uplift we used facies analysis to reconstruct the pleistocene sedimentary evolution of seven cores from the central northern po plain italy the cores record an overall regressive sequence consisting of shallow water marine and fl uvial deltaic deposits overlain by fully continental sediments we used magnetostratigraphy to date marine and fl uvial deltaic sediments to the early pleistocene and continental sediments to the middle late pleistocene sediment accumulation rates were 30 40 cm k y in the early pleistocene whereas relevant unconformities and or an overall reduction in sediment accumulation rates characterized the middle late pleistocene a simple airy compensation model was applied to restore actual sediments elevations to elevations at times of deposition expressed in meters above current sea level the correlation of isostatically corrected sedimentary facies to a sea level curve obtained from classic oxygen isotope studies shows that an event of rock uplift on the order of 70 120 m occurred in the middle late pleistocene literature studies of vegetational cyclicity used in conjunction with the sea level curve allowed us to link sedimentary facies to climate variability we propose that the onset of fully and persistently continental sedimentation occurred in response to the waxing of the fi rst major pleistocene glaciation in the alps currently correlated to marine isotope stage 22 at ca 0 87 ma and that the episode of uplift occurred at least in part as a consequence of erosion and crustal rebound of the alpine chain triggered by pleistocene glacialinterglacial cycles

vegetation change in a climatic cycle of early pleistocene age in the leffe basin northern italy abstract the plio pleistocene deposits of the leffe basin in the lombardian pre alps in italy first investigated in quarry and lignite mine shafts by lona in 1950 were recently cored the pollen record of part of this core reveals a sequence of four climatic cycles one of them which is about 1 6 ma old and particularly characteristic is discussed here a long interglacial stage can be identified by the dominance of pollen of deciduous trees of temperate climate it clearly shows a forest succession of a mixed oak forest of dry temperate climate followed by a strong development of a juglandaceae assemblage rich in arcto tertiary elements some of them indicating a wet climate in particular the carya peaks appear to be linked to a warm temperate 14 16 c mean annual temperature humid maritime climate with a long growth season if we compare them with modern and fossil analogs this stage is followed by a cooling leading to a long phase of wet coniferous forest this forest succession is subsequently interrupted by a brief period of open vegetation indicating a drier and colder continental climate followed by a new vegetational cycle the climate evolution is discussed in comparison with other recent pollen successions of uppermost pliocene age in the mediterranean area the cycle described is estimated to have lasted about 30 ka the entire leffe lacustrine succession records eight climatic cycles of moderate amplitude we suggest that this cyclicity has been induced by obliquity forcing correlation of the cold phases with the major glacial events of the southern alps as proposed by venzo 1950 and lona 1950 is excluded

a stalactite record of four relative sea level highstands during the middle pleistocene transition ice sheet and sea level fluctuations during the early and middle pleistocene are as yet poorly understood a stalactite from a karst cave in north west sicily italy provides the first evidence of four marine inundations that correspond to relative sea level highstands at the time of the middle pleistocene transition the speleothem is located 97 m above mean sea level as result of quaternary uplift its section reveals three marine hiatuses and a coral overgrowth that fixes the age of final marine ingression at 1 124 0 2 thus making this speleothem the oldest stalactite with marine hiatuses ever studied to date scleractinian coral species witness light limited conditions and water depth of 20 50 m integrating the coral constrained depth with the geologically constrained uplift rate and an ensemble of rsl scenarios we find that the age of the last marine ingression most likely coincides with marine isotope stage 35 on the basis of a probabilistic assessment our findings are consistent with a significant antarctic ice sheet retreat

petroleum generation and accumulation in the berkine basin eastern algeria the berkine ghadames basin is regarded as an important hydrocarbon play in eastern algeria an evaluation of organic source facies the application of petroleum geochemistry and an extensive basin modeling study were carried out to improve the understanding of the petroleum charge of the basin geochemical data indicate that the llandoverian wenlockian and the frasnian hot shales are the most important oil prone source rocks for the known hydrocarbon accumulations in the basin maturity data reflect the late cretaceous tertiary burial and are consistent with a 60 63 mw m2 heat flow in the vicinity of the anticlines and 50 mw m2 heat flow farther away from the folded area a two dimensional basin modeling study revealed the importance of poorly constrained parameters such as the amount and rate of hercynian erosion on hydrocarbon generation and trapping efficiencies the model shows that a cretaceous tertiary petroleum generation and emplacement for both source rocks can better explain the different gas and oil fields than can an earlier hercynian event the faults related to the triassic jurassic rifting are most certainly permeable and can be considered as major migration pathways for petroleum in contrast the overpressure that developed along the el biod hassi messaoud axis in the ordovician reservoirs was probably caused by the low permeability of the faults bounding the anticlines that therefore prohibited any lateral or vertical fluid movements the model also indicates two petroleum systems that have triassic reservoirs 1 a frasnian sourced system that is confined to the central part of the basin and 2 a llandoverian wenlockian sourced system in the western part of the basin migration into paleozoic reservoirs was followed by dismigration into overlying triassic traps after the cretaceous compressive movements

dynamic ray tracing in an anisotropic medium abstract we derive a dynamic ray tracing system for seismic waves in an anisotropic medium it consists of ten equations and can be solved numerically for isotropic media it does not reduce to the drt systems derived by other authors

a new active tectonic model for the construction of the northern apennines mountain front near bologna italy 1 we integrate existing and new geologic data retreating trench extension and accretion tectonics retreat project particularly on the origin growth and activity of the mountain front at bologna italy into a new model that explains apennine orogenesis in the context of a slab rollback upper plate retreat process the bologna mountain front is an actively growing structure driving rock uplift 1 mm year cored by a midcrustal flat ramp structure that accommodates ongoing shortening driven by adria subduction at a rate of 2 5 mm year the data we use are assembled from river terraces and associated pleistocene growth strata geodesy including releveling surveys reinterpretation of published reflection lines and a new high resolution reflection line these data constrain a simple trishear model that inverts for blind thrust ramp depth dip and slip apennine extension is recognized both in the foreland as high angle normal faults and modest stretching in the carapace of the growing mountain front and in the hinterland with larger normal faults that accomplish some crustal thinning as the upper plate retreats this coevolution of extension and shortening shares some notable characteristics with other basement involved collisional orogens including the early tertiary laramide orogeny in the american west and the oligocene to miocene evolution of the alps we propose a possible relationship between underplating and the development of the po as a sag basin as a quaternary phenomenon that may also apply to past periods of apennine deformation tortonian continued shortening on the structure beneath the bologna mountain front represents by far the most important and underappreciated seismogenic source in the front of the northern apennines

hydrogeophysical imaging of alluvial aquifers electrostratigraphic units in the quaternary po alluvial plain italy the integration of surface geological and geomorphological information with borehole point data and geophysical e g geoelectrical images of the subsurface yields spatially consistent representations of alluvial aquifers heterogeneity at different scales from depositional systems to basin fills such an approach requires a conceptual framework to match the stratigraphic units with their evidence from ground based dc resistivity methods to effectively fill the gaps between sparse borehole data and to obtain valid representations of sedimentary heterogeneities such an approach is applied to characterize two sites of the quaternary aquifers of the central po plain italy which represent 1 the middle upper pleistocene braided to meandering river depositional systems sitting on southalpine crust and 2 their down current counterparts where they are involved by the latest uplift and deformation due to the tectonic activity of the apennine frontal thrusts electrical resistivity was considered as a proxy of the litho textural properties of hydrofacies and their major hierarchical association at depth and was interpreted in accordance with the depth decreasing resolution of ground based resistivity methods thus it was possible to identify the geophysical signature of hydrostratigraphic units through electrostratigraphic units i e sedimentary volumes identified by resistivity contrasts that spatially preserve the vertical polarity hydrostratigraphy and electrostratigraphy were then joined together through a site specific relationship between electrical resistivity and hydraulic conductivity which takes into account the prevailing process of current conduction the litho textural properties of hydrofacies and the groundwater electrical conductivity at the scales of aquifer systems and complexes this approach permitted to establish the conceptual framework to match hydrostratigraphy electrostratigraphy average hydrodynamic properties and distribution of heterogeneities

crustal uplift in the alps why the drainage pattern matters introductionmountain belts grow by accretion ofupper crustal material into the orogen icwedge fig 1 materialenteringthewedge gets deformed uplifted andexhumed basedontheoreticalmodels willett et al 1993 concluded thatorogensadoptadistinctgeometrywitha low tapered pro wedge facing thesubduction plate and a high taperedretro side this geometry establishesbecauseorogenstendtobeonthevergeof gravitational failure davis et al 1983 according to these models thevelocity eld of the crust and hence the exhumation path of rock particles depends on erosion at the surface e g horton 1999 consequently anychanges in erosion rates potentiallyresult in a modi cation of the patternof strain rates of surface erosion however depend on climate exposedlithologies the size of the catchmentarea thegeometriccon gurationofthedrainage basin and rates of crustaluplift tucker and slingerland 1996 although the impact of these para meters on surface erosion has beenstudied extensively using numericalmodels tucker and slingerland 1997 ku hni and p ffner 2001 schlu neggeret al 2001 verylittleattentionhas been paid to the in uence of thedrainage geometry on the spatial pat tern of erosion and on strain the central swiss alps provide anexample where the present daydrainage geometry reveals a distinctpattern that is characterized by largeorogen parallel dispersal systems therhone and rhine rivers fig 2a that drain the core of the alps and smaller orogen normal rivers according to the conceptual modelsoutlined above it is reasonable tospeculate that the asymmetry of thealpine drainage pattern is likely toin uence the pattern of crustal up lift speci cally the highest rates ofstrain release are expected in therhone and rhine valleys becausethe large drainage basins of theserivers are likely to result in enhancederosional potentials this hypothesiswill be tested in the following chap ters this present paper evaluates thepotential controls of the asymmetriccon guration of the alpine drainagepattern on possible variations oferosional potential as well as onpresent day and glacial sedimentyield this information is then rela ted to the published pattern ofcrustal uplift allowing possible pos itive feedback between surface ero sion and lithospheric forcing to beidenti ed the intention is not todiscard other processes as possiblecontrols on the pattern of crustaluplift e g exural rebound afterremoval of the pleistocene ice sheet kahle et al 1997 but rather topropose an alternative model thatmight enrich the range of possibleinterpretations pattern of crustal upliftand seismic activityfigure 2 a displays the recent verti cal movements of the swiss alpscomputed for rst order levellingbenchmarks relative to the benchmarkat aarburg gubler et al 1981 kahleet al 1997 the geodetic data wascollected repeatedly between c 1905and 1990 measured uplift is inter preted in terms of crustal upliftbecause benchmarks have not experi enced erosion i e they record theshort term velocity eld of upper most crustal levels the data indicatea considerable increase of crustaluplift rates from the foreland tothe rear of the alps where currentrates of 1 mm yr

insights on the opening of the galerian mammal migration pathway from magnetostratigraphy of the pleistocene marine continental transition in the arda river section northern italy abstract we investigated the magnetostratigraphy of the arda river section northern italy where the transition from marine to continental sedimentation occurring in the po river basin during the pleistocene is registered four magnetic polarity reversals were used to construct an age model of sedimentation aided by marine biostratigraphy and tied to a standard 18o curve from the literature the section spans from the olduvai subchron 1 94 1 78 ma across the jaramillo subchron 1 07 0 99 ma up to the brunhes matuyama boundary 0 78 ma the onset of continental deposition occurred during marine isotope stage mis 30 at 1 04 ma an association of villafranchian and early galerian mammals including sus strozzii and ursus dolinensis has been found in the continental sediments dated to mis 29 27 0 99 ma above follows a prominent fluvial conglomerate attributed to the first major lowstand of the pleistocene culminating with mis 22 at 0 9 ma during the late early pleistocene climate turnover ept these and other data from the literature are used to reconstruct the onset of continental deposition in the greater po basin and shed light on the opening of the migration pathway that brought far traveled galerian mammal immigrants to enter europe for the first time during the ept

long period amplification in deep alluvial basins and consequences for site specific probabilistic seismic hazard analysis an example from the po plain northern italy this study deals with the impact of deep soil discontinuities on ground motion amplification in the po alluvial basin northern italy and consequently on long period probabilistic seismic hazard analysis estimates the focus is on castelleone where a seismic station of the italian national seismic network has been deployed since 2009 to define a detailed shear wave velocity v s profile extensive active and passive geophysical surveys were carried out the active measurements included seismic profiles examined through standard refraction techniques and multichannel analysis of surface waves the passive methods included ambient vibration measurements in both single and array configurations in particular three microtremor arrays with increasing apertures were performed to capture the experimental dispersion curve down to 0 2 hz the horizontal to vertical spectral ratio hvsr showed two main peaks at 0 17 and 0 70 hz a joint inversion of the experimental phase velocity dispersion and hvsr curves was performed to obtain the v s profile the data show two main discontinuities at 160 and 1350 m in depth according to the italian and european seismic codes the shallow v s discontinuity can be ascribed to the seismic bedrock i e v s 800 m s whereas the deeper one is observed at the transition between pliocene quaternary deposits and miocene marls preliminary site specific seismic hazard analysis in terms of displacement response spectra for periods up to 10 s shows that neglecting the effects of the deeper discontinuity implies underestimation in hazard estimates of up to about 49 for mean return period mrp of 475 years and about 57 for mrp of 2475 years with possible consequences regarding the design of very tall buildings and large bridges

continental depositional systems of the quaternary of the po plain northern italy abstract the po plain is a molasse foredeep bounded by two mountain chains apennines and alps apenninic thrusting is still active whereas the alpine one ended by early pliocene times the continental deposits form a veneer at the surface and form the topset of a prograding complex the po river divides the plain into two sectors with different sedimentary facies and body geometries to the south the alluvial fan and plain deposits are small embedded in clays and show elongate shapes to the north sedimentary bodies are laterally extensive tabular and with minor amounts of fine grained sediments this difference could be due to a different climatic conditions during quaternary ice ages on the two sides of the basin b different structural settings in the two sectors of the basin that produce a higher subsidence rate to the south c different lithologies in the source areas i e alps and apennines

ghadames basin southern tunisia a reappraisal of triassic reservoirs and future prospectivity recent discoveries of oil and gas in triassic reservoirs of the ghadames basin eastern algeria suggest that similar potential exists to the east in the southern tunisian part of the province for decades southern tunisia has remained an underexplored part of the basin in large part owing to older geological interpretations that focus on paleozoic reservoirs and to limitations in seismic data quality resulting from statics problems that have rendered trap identification inaccurate or tenuous new analyses of previously and recently acquired geological and geochemical data as well as improvements in seismic data acquisition and processing have begun to reverse older notions regarding limited hydrocarbon presence in southern tunisia log correlations indicate that productive sand rich intervals of the major triassic reservoir in the region the trias argilo greseux inferieur tagi can be correlated over large distances suggesting significant continuity into lightly drilled and undrilled areas analyses of geochemical data reveal a more complex multistage history of hydrocarbon maturation and migration than previously believed much greater volumes of petroleum have been generated and a larger variety of traps have been created than can be accounted for by older interpretations where added to the use of new field and processing parameters for seismic surveys these factors have together led to important upgraded evaluations of basin potential in southern tunisia

quaternary erosion induced isostatic rebound in the western alps the high elevation and deep incision of the alps have traditionally been used as an argument for recent tectonic activity that has elevated the belt and increased erosion rates normal faulting and horizontal extension however dominate current tectonic activity and isostatic compensation of thinning crust should lead not to increased but to decreased mean elevations here we test the idea that enhanced quaternary erosion of the alps and isostatic compensation of the mass removed can account for the distribution of present day geodetically measured rates of vertical movement in the western alps using geophysical relief and kuhlemann s estimated average erosion rate for the alps we quantify the spatial distribution of erosion and the volume of eroded rock respectively from these we obtain a map of rock eroded within a given time span the calculated isostatic response of the alpine lithosphere to erosional unloading for a variety of values of the flexural rigidity of the alpine lithosphere reaches a maximum of 500 m since 1 ma in the inner swiss alps and vertical movement extends across the entire belt including peri alpine basins assuming a steady erosion rate since 1 ma this rebound accounts for half of the measured vertical motion of 1 1 mm yr in the southern valais thus a significant fraction 50 of the present day vertical movement results from the isostatic response to enhanced erosion during plio quaternary time

modeling subsurface flow in sedimentary basins groundwater flows that arise in sedimentary basins from the effects of topographic relief buoyant convection sediment compaction erosional unloading and combinations of these driving forces can be described using quantitative modeling techniques models can be constructed to consider the effects of heat and solute transport petroleum migration and the chemical interaction of water and rocks the accuracy of model predictions however is limited by the difficulty of predicting hydrologic properties of sediments on regional dimensions estimating past conditions such as topographic relief and knowledge of how physical and chemical processes interact over gelogic time scales progress in basin modeling will accelerate as hydrologic research efforts are better integrated with those of other specialities such as sedimentology rock mechanics and geochemistry

late neogene erosion of the alps a climate driver as with many mountain belts globally the alps have seen a large increase in sediment yield in the late neogene the hypothesis that this increase results from climate change impacts on erosion rate over the past 5 ma is testable given the extensive work completed in the alps sediment budgets thermochronology based cooling rates and estimates of modern rock uplift and erosion in the western alps are reviewed to search for correlation in space and time that might fingerprint climatic events major increases in sediment yield are apparent starting in the late messinian 5 5 mya and accelerating toward the present day this suggests the occurrence of a series of climatic changes that increased erosion rates even as tectonic processes appear to have slowed or stopped at present tight correlations in time are difficult to establish and there remain open questions about the role of tectonics in the coupled system

fluid expulsion from overpressured basins implications for pb zn mineralisation and dolomitisation of the east midlands platform northern england abstract our understanding of burial diagenesis within carbonates is often limited by poor constraints on available fluid volumes and geochemistry however regional stratigraphic and burial history data are often readily available using these data to develop numerical models which couple sedimentological and hydrological basin evolution we estimate the volumes and geochemistry of fluids that were available to drive dolomitisation and pb ore genesis within the carboniferous derbyshire platform of northern england current conceptual models of these processes invoke tectonic release of burial induced overpressure developed within adjacent dinantian basins as a drive for reactive fluid flow to the platform our simulations show that compaction driven flow may lead to a supply of fluids that is more complex in its temporal evolution than may be expected spatial variations in the rate of fluid expulsion from different sediments lead to a staggered delivery of fluids from different sources rapid fluid expulsion within deeper sediments leads to a downwards decreasing pressure gradient that subsequently draws down fluid from within overlying sediments thus early fluid supply to the platform is sourced from the deep basins while later fluid supply descends from above the platform as well as from the sides we suggest that such a flow development may have important implications for the relative timing and distribution of a sequence of diagenetic products within the platform this hypothesis is tested using volume estimates from our simulations we conclude that although this staggered fluid supply model may be applicable generically it appears that it is only valid for explaining mineralisation in the derbyshire platform fluid volumes supplied to the platform are insufficient to explain dolomitisation our simulations are supported by a sensitivity analysis that identifies that compaction driven flow in this system is strongly controlled by the rate of burial and sediment permeabilities within the compacting basins

na cl br systematics of mineralizing brines in mississippi valley type deposits new and published analyses of fluid inclusion leachates from mississippi valley type mvt deposits can be divided into two groups on the basis of na br and cl br ratios mvt leachates from the illinois kentucky and cincinnati arch districts and from cubic galena in the viburnum trend have na br and cl br ratios that extend to values significantly above that of seawater which are characteristic of evaporite dissolution brines mvt leachates from polaris and octahedral galena in the viburnum trend have na br and cl br ratios that plot below seawater and along the compositional trend formed by evaporation solubility volume constraints require that brines formed by seawater evaporation had high dissolved metal contents preliminary correlation of leachate compositions allows delineation of two brine provinces in the midcontinent united states 1 an early high br province found only in southeastern missouri and 2 a later low br province of probable permian age that extended from the cincinnati arch to the tri state district these observations along with na cl br data for modern brines from the illinois basin argue against models for single stage midcontinent mvt brine flow based on recharge from late paleozoic arkoma foreland basins to the south

variable fault tip propagation rates affected by near surface lithology and implications for fault displacement hazard assessment abstract the fabric of reverse fault zones close to the surface is usually partitioned in between a narrow discrete rupture zone and a more distributed one where folding is predominant this makes quite challenging the adoption of proper setbacks in surface rupture hazard studies for critical facilities or microzoning some of the parameters controlling fault zone fabric are related to mechanics of near surface geology lithology overburden thickness cohesion and water content whose interaction is complex and only partially understood nevertheless these can be seldom measured or derived kinematic models conversely express such an interaction of complex variables as simple synthetic parameters such as the amount of upward propagation of the fault tip for unit of slip usually referred to as the p s ratio propagation on slip here we discuss results on the trishear kinematic inverse modeling of a contractional fault propagation fold at monte netto hill capriano del colle n italy observing a two stage fault and fold growth evolution marked by a significant shift in the p s parameter at this site exceptional sequence of exposures due to ca 10 years of quarry excavations allowed to obtain a series of cross sections across the fault zone we use this detailed high resolution example as a natural analogue for more general large scale surface ruptures involving a thick alluvial cover a very common setting for the siting of critical facilities during the early stage of displacement the fault cut through clast supported fluvial gravels with a high propagation rate p s 7 and a discrete rupture width then during the latest movements of the thrust fault tip propagation slowed down to p s 2 9 as the fault started cutting through several stacked bodies of clays and silty clays pedogenized aeolian silts and overbank deposits causing a pronounced folding of the layers over a wider deformation zone these results strongly suggest that lithological changes in the underlying shallow stratigraphy common in an alluvial plain depositional setting would significantly affect the potential for surface faulting across the same tectonic structure with relevant implications in the fault displacement hazard assessment

an electrostratigraphic cross section across the central po plain bearings on subsurface geology and hydrostratigraphy a 72 km long n s cross section was surveyed with direct current resistivity soundings through the quaternary clastic infill of the apennine foredeep in the po plain of lombardy northern italy the aims are 1 to test the potential of dc resistivity methods at the regional scale 2 to draw the electrostratigraphic picture of the basin fill down to the pre quaternary substratum 3 to refine and test the methodology and concepts of hierarchic electrostratigraphy at the basin scale 4 to contribute to characterize the regional hydrostratigraphy of a relevant hydrogeological basin 163 resistivity versus depth profiles with a maximum investigation depth of 450 m were obtained from vertical electrical soundings to draw the electrostratigraphic cross section the polarity of the resistivity contrast across resistivity interfaces i e resistive over conductive layers or vice versa was considered and the discontinuities were correlated according to the persisting pattern from north to south doing so the hierarchic assemblage of four major electrostratigraphic boundaries and the five intervening groups of electrostratigraphic units esus was established the resulting picture was compared to the available subsurface reconstructions from the literature using the 1 d borehole data only to check the geophysical image at some random sample sites the results show that the electrostratigraphic picture captures the geological and hydrostratigraphic complexity of the subsurface of the basin comparing well with the available direct subsurface geological and hydrostratigraphic reconstructions at the regional scale of the cross section two hierarchic orders of esus and correlative boundaries could be drawn first order groups and second order individual esus while the lowermost third order rank the electrolayer is recognized at the single ves sites only

fluid inclusions in sedimentary and diagenetic systems abstract some of the major problems in sedimentary geology can be solved by using fluid inclusions in sedimentary and diagenetic minerals important fluids in the sedimentary realm include atmospheric gases fresh water of meteoric origin lake water seawater mixed water evaporated water formation waters deep in basins oil and natural gas preserving a record of the distribution and composition of these fluids from the past should contribute significantly to studies of paleoclimate and global change research is essential for improving understanding of diagenetic systems and provides useful information in petroleum geology applications of fluid inclusions to sedimentary systems are not without their complexities some fluid inclusions exposed to natural conditions of increasing temperature may be altered by thermal reequilibration which results in stretching or leakage and refilling of some fluid inclusions similarly overheating in the laboratory can also cause reequilibration of fluid inclusions so fluid inclusions from the sedimentary realm must be handled carefully and protected from overheating natural overheating of fluid inclusions must be evaluated through analysis of the most finely discriminated events of fluid inclusion entrapment fluid inclusion assemblages fia consistency in homogenization temperatures within a fluid inclusion assemblage consisting of variably sized and shaped inclusions is the hallmark of a data set that has not been altered through thermal reequilibration in contrast fluid inclusion assemblages yielding variable data may have been altered through thermal reequilibration if a fluid inclusion assemblage has not been altered by thermal reequilibration its fluid inclusions may be useful as geothermometers for low and high temperature systems or useful as geobarometers applicable throughout the sedimentary realm if a fluid inclusion assemblage has been altered partially by thermal reequilibration techniques for distinguishing between altered and unaltered fluid inclusions may be applied in studies of global change fluid inclusions can be used as sensitive indicators of paleotemperature of surface environments fluid inclusions also preserve microsamples of ancient seawater and atmosphere the analysis of which could figure prominently into discussions of past changes in chemistry of the atmosphere and oceans in petroleum geology fluid inclusions have proven to be useful indicators of migration pathways of hydrocarbons they can delineate the evolution of the chemistry of hydrocarbons and they remain important in understanding the thermal history of basins and relating fluid migration events to evolution of reservoir systems in studies of diagenesis fluid inclusions can be the most definitive record most diagenetic systems are closely linked to temperature and salinity of the fluid thus fluid inclusions are sensitive indicators of diagenetic environments

reconstructing the palaeoenvironments of the early pleistocene mammal faunas from the pollen preserved on fossil bones abstract we carried out a systematic investigation on the pollen content of sediment adhering to skeletal elements of large mammals which originate from the long lacustrine record of leffe early pleistocene of the italian alps three local faunas were discovered during mining activities along the intermediate part spanning from 1 5 to 0 95 ma of the basin succession the excellent pollen preservation allowed testing the reproducibility of the pollen signal from single skeletons a clear palaeoenvironmental patterning consistent with the ecological preferences of the considered mammal species emerged from the canonical correspondence analysis of pollen types diagnostic for vegetation communities edaphic factors related to seasonal river activity changes and to the development of swamp forests in the riverbanks are significantly associated to the occurrences of hippopotamus cf antiquus whereas finds of mammuthus meridionalis belong to fully forested landscapes dominated by conifer or mixed forests of oceanic warm to cool temperate climate rhinoceros habitats include variable forest cover under different climate states distinct cool temperate partially open vegetation could be recognized for large deer included cervalces cf carnutorum a palynostratigraphic correlation between individual spectra and a reference palynostratigraphic record allowed assignment of many fossil remains to a precise stratigraphic position this procedure also shown that the leffe local faunas include specimens accumulated under different environmental and climate states as a consequence of high frequency climate changes characterizing the late villafranchian early pleistocene

teleseisms as estimators of experimental long period site amplification application to the po plain italy for the 2011 mw 9 0 tohoku oki japan earthquake abstract this study focuses on the evaluation of teleseisms as estimators of long period seismic site amplification in correspondence to large alluvial basins using the recordings of the 11 march 2011 m w 9 0 tohoku oki japan earthquake the site response at low frequency of the po plain italy was investigated the interdistances among the analyzed sites compared to the travel paths of the tohoku oki waveforms with respect to the target area allowed us to investigate the reliability of the standard spectral ratio ssr technique applied to teleseismic recordings the results are presented as directional ssrs calculated considering 2 min of p s and rayleigh lr waves filtered from 0 025 to 1 0 hz considering the horizontal components at frequency from 0 04 to 0 3 hz the po plain stations show amplification factors up to 20 and 16 detected for the s and lr phases respectively in some cases the amplified ground motion appeared to be affected by polarization phenomena in particular in the north south direction moving from the center to the edge of the basin the lr wave amplification remarkably decreases in particular for frequencies between 0 1 and 0 3 hz this was not observed for the s wave amplification factors 10 were also detected for the vertical component with increasing resonance periods moving from p to lr waves comparing ssrs with the single station horizontal to vertical spectral ratios the latter case shows that the vertical amplifications lead to the partial masking of the actual response of a site in particular for frequencies 0 15 hz finally the relative p wave amplitudes were also investigated the results of the spectral analysis and the correlation between the relative p wave amplitudes and the geometry of the bedrock suggest that the proposed approach is appropriate for the investigation of long period seismic site response in similar settings

late quaternary sequence stratigraphy as a tool for groundwater exploration lessons from the po river basin northern italy sequence stratigraphy typically used for hydrocarbon exploration in ancient strata can be applied to late quaternary successions to decipher complex spatial relations among their aquifers late pleistocene holocene strata of the po basin were investigated using a sequence stratigraphic approach to produce a high resolution model for guiding groundwater exploitation because facies tend to be diachronous across depositional basins facies analysis was done within the conformable intervals of strata revealed by sequence stratigraphy to accurately interpret and map coeval lateral facies relations volumetric assessments sand distribution mapping hydraulic characterization of facies and spatial variations of hydraulic parameters revealed two aquifer systems the lowstand systems tract lst and the highstand systems tract hst vertically separated by an aquitard the transgressive systems tract tst the lst aquifer consists of amalgamated fluvial sands average transmissivity 3 5 e 3 m2 s 37 7 e 3 ft2 s with considerable width 25 km 16 mi preferentially elongated downstream the widespread tst aquitard is dominated volumetrically 57 by low permeability estuarine deposits the hst aquifer average transmissivity 5 4 e 5 m2 s 58 1 e 5 ft2 s is 5 10 km 3 6 mi wide elongated parallel to the modern shoreline sequence stratigraphic analysis at the parasequence scale revealed an almost unprecedented level of detailed insight into aquifer or aquiclude dimensions and the complex distribution of hydraulic parameters in the subsurface showing that similar facies have different permeabilities depending on systems tract in contrast lithostratigraphic mapping obscures subsurface connectivity and directional trends and has minimal predictive power away from control these insights should be useful for guiding correlation and mapping of the deep subsurface and for hydrocarbon reservoir modelers

characterization of pore pressure fracture pressure shear failure and its implications for drilling wellbore stability and completion design a case study from the takouazet field illizi basin algeria abstract this work presents the assessment of overburden stress pore pressure and fracture pressure distribution in the paleozoic stratigraphic units in the takouazet field eastern illizi basin algeria we studied a vertical exploration well where significant hydrocarbon discoveries have been established in devonian and ordovician sandstone reservoirs overburden stress interpreted from density log has an average 1 07 psi ft 24204 04 pa m gradient pore pressure derived from sonic log reveals that hydrostatic conditions prevail in devonian and ordovician units whereas abnormal pore pressure with a maximum 0 66 psi ft 14929 60 pa m gradient was recorded against the marine silurian shale fracture pressure was modeled using effective stress ratio models as well as a poisson s ratio based approach rock property based fracture pressure estimate is more sensitive to lithological variations and hence this estimate was used for determining safe drilling mud window and casing placements the estimated pore pressure and fracture pressure were calibrated with direct downhole formation pressure measurements and leakoff test lot measurements respectively shear failure using mohr coulomb rock failure criterion detected the minimum allowable mud pressure to avoid wellbore instability issues and the result was validated with caliper log observations it indicated that solid production from the reservoir is very likely during initial production from the reservoir and a solid control mechanism has been suggested also widening of breakouts and deteriorating wellbore interpreted from time lapse formation imaging logs strongly suggest against open hole completion based on interpreted pressure gradients and image log analyses optimum drilling mud and casing design and completion policies were recommended for safe and successful operational planning

stratigraphic evidence of a middle pleistocene climate driven flexural uplift in the alps 1 this interdisciplinary study on the subsurface stratigraphy of the po plain northern italy brings new evidence in support of a climate driven erosional unloading of the alps since the middle pleistocene a newly acquired high resolution seismic profile and a critical review of industrial seismic lines were integrated with sedimentologic observations on four magnetostratigraphically dated continental cores to reconstruct a three sequence evolution of the pleistocene clastic infill in the northern po basin during the first sequence ps1 1 4 0 87 ma characterized by sedimentation rates of 34 cm kyr outpacing regional subsidence meandering river systems prograded over the basin passing downstream to a cyclothemic shelfal succession the second sequence ps2 0 87 0 45 ma heralded by a regional unconformity r surface correlated to the onset of the major pleistocene glaciations was characterized by widespread continental sedimentation of generally distal braidplain the third sequence ps3 0 45 ma to present marked at the base by another regional unconformity y surface is characterized by proximal braided fluvial deposition under combined conditions of confinement erosion and bypass we interpret the ps3 sequence as deposited under the effects of a flexural uplift of the northern po plain during the middle pleistocene starting at 0 45 ma in response to the long term erosional unloading of the alps triggered by the waxing and waning of alpine glaciers since the late early pleistocene global cooling 0 9 ma according to our modeling erosion on a relatively limited area of the alpine mountain chain ranging from 1 3 to 1 7 mm yr in the axial sector to 0 1 0 3 mm yr at the margins has been able to trigger rock uplift over a wider area including the proximal peripheral basins

surface uplift uplift of rocks and exhumation of rocks uplift of the surface of mountain belts requires forces that are comparable in magnitude to those associated with plate motion and therefore determination of rates of surface uplift could provide important information on the dynamics of mountain ranges rates of uplift of the surfaces of mountain ranges have not however been quantified sufficiently well that they provide useful constraints on those processes many reports off surface uplift in mountain ranges are based on mistaking exhumation of rocks or uplift of rocks for surface uplift and provide no information whatsoever on the rates of surface uplift

progressive offset and surface deformation along a seismogenic blind thrust in the po plain foredeep southern alps northern italy here we present for the first time in the po plain foredeep northern italy the middle to late pleistocene growth history of an outcropping secondary fold and related faults whose progressive deformation over an intermediate time window 105 years is driven by an underlying seismogenic blind thrust we trenched and logged an outcropping decametric secondary anticline related to a deeper blind compressional structure which deforms fluvial sediments and an overlying loess paleosol sequence folded units were dated using radiocarbon and optically stimulated luminescence methods to the late pleistocene holocene and tentatively correlated with glacial interglacial phases occurring during the time interval from marine isotope stage 6 to the present a multistep retrodeformation of the fold allowed us to calculate uplift rates for this secondary and shallow anticline varying between 0 02 and 0 1 mm yr since circa 200 kyr trishear forward deformation modeling of the fold indicates that the amplification of the observed fold could be caused by two shallow thrusts formed through a break backward activation this generated a decametric surface fold whose most recent growth was associated with bending moment normal faulting in the crestal and forelimb region our observations demonstrate that near surface compressive tectonics can be caused by blind thrusting via a complex array of fault and folds upward strain propagation and generation of shallow low angle thrust and related folding seem to be mainly due to secondary fold related faulting according to an out of syncline thrusting mechanism

the evaporation path of seawater and the coprecipitation of br and k with halite brines and salt were sampled at the morton bahamas solar salt production facility on great inagua island in the bahamas the brines were analyzed by ion chromatography to define more precisely than heretofore the evaporation path of seawater to the end of the halite facies at inagua calcium carbonate begins to precipitate at a brine concentration factor of 1 8 times that of seawater gypsum begins to precipitate at a brine concentration of 3 8 times seawater and halite at a concentration factor of 10 6 three of the most concentrated brines from inagua 40 times seawater were evaporated further in the laboratory magnesium sulfate first precipitated at brine concentrations about 70 times those of seawater and potassium bearing phases began to precipitate for these brines at concentrations greater than 90 times those of seawater the distribution of coefficients of br and k between brines and halite were determined by combining analytical data for the inagua brines with measurements of the br and k content of halites from inagua and of halite which had precipitated from inagua brines during storage the observed average value of dbr is 0 032 in good agreement with some of the previous measurements the measured values of dk are highly variable 0 001 to 0 021 dk for halite precipitated early in the halite facies is in the vicinity of 0 015

climate induced rebound and exhumation of the european alps foreland basins record the regional isostatic compensation of mountain belts during periods of crustal thickening they subside and when erosion unloads the mass of the mountains the basins rebound and are eroded in order to evaluate this mechanism for rebound it is critical that the timing and magnitude of erosion are documented we present data estimating the timing and magnitude of late orogenic or postorogenic erosion in the north alpine foreland basin of switzerland mineral cooling ages demonstrate that the basin underwent 1 3 km of erosion soon after 5 ma this erosion coincided with a decline in structural deformation in the swiss alps and a doubling of sediment accu mulation rates in surrounding depocenters we propose that accelerated erosional un roofing of the swiss alps triggered isostatic rebound and erosion of the foreland basin after 5 ma a projection of the isostatic rebound of the basin into the mountains suggests that at least 6 5 km of erosion should have occurred in the high topography of the aar massif accelerated erosion in the swiss alps at that time is explained by an increase in atmospheric moisture driven by an intensification of the atlantic gulf stream at 4 6 ma consequently we propose that the changing erosional capacity of the climate triggered late orogenic to postorogenic mass reduction and isostatic rebound of the swiss alps and their neighboring foreland basin

constraining burial history and petroleum charge in exhumed basins new insights from the illizi basin algeria intracratonic sag basins commonly have relatively simple tectonic histories however later tectonic activity involving exhumation can make reconstructing the burial history a challenging task this is important because the relative timing of hydrocarbon generation and trap formation can be a key factor in risk assessment if trap formation postdates peak hydrocarbon generation exploration plays are typically downgraded mechanisms for charge in such exhumed basins are critical factors for understanding exploration risk this study uses data collected from an ordovician gas condensate field in the illizi basin of algeria to document the charging of a trap formed or modified during exhumation of the basin following maximum burial integrated analysis of sonic compaction data thermal history indicators and stratigraphic well data was used to constrain the burial and thermal history of the region hydrocarbon generation in the lower silurian source rock is interpreted to have occurred during the carboniferous prior to hercynian exhumation and during the late cretaceous early eocene maximum burial prior to eocene exhumation structural reconstructions indicate that the field was initially located on the southern flank of a long lived intrabasinal paleozoic paleohigh the large low relief structural closure that defines the present day accumulation formed as a result of northward tilting of the illizi basin during eocene uplift of the hoggar massif the study demonstrates that the timing of trap formation at the ordovician field postdates the main local hydrocarbon generation events within the basin suggesting that alternative hydrocarbon charge mechanisms are required this study indicates considerable potential to charge updip traps on the flanks of exhumed petroliferous basins via redistribution of the preexisting hydrocarbons within the basin

microspectrofluorimetric and microthermometric evidence for variability in hydrocarbon fluid inclusions in quartz overgrowths implications for inclusion trapping in the alwyn north field north sea abstract hydrocarbon inclusions trapped in quartz cement from alwyn north field sandstones of well 3 9a 6 north sea have been analyzed using microthermometric and microspectrofluorimetric methods they are two phased with consistent gas oil ratios and mainly occur along the detrital grain overgrowth boundary their homogenization temperatures vary from 60 to 129 c with a great variability within a single fluid inclusion assemblage up to 40 c the fluorescence colour of the hydrocarbon inclusions has been characterized using a microspectrofluorimeter which allows the analysis of very small inclusions 1 7 m with good reproducibility hydrocarbon inclusions display large variations in their fluorescence colour converted in chromaticity coordinates even within a single fluid inclusion assemblage moreover they are concentrically distributed within the detrital grain overgrowth interface according to the relationship between api gravity and fluorescence colour established with reference to crude oils from alwyn north field this observation is interpreted as representing compositional variations such compositional variability in a single fluid inclusion assemblage could result from either the progressive entrapment of oils in which api gravity evolves through time and or the fractionation of hydrocarbons at the time of trapping

variable late neogene exhumation of the central european alps low temperature thermochronology from the aar massif switzerland and the lepontine dome italy 1 several recent studies proposed an important increase in exhumation rate in the western european alps since circa 5 4 ma in order to assess potential spatial differences in exhumation histories we present new apatite fission track aft and apatite u th he ahe ages from the central aar massif guttannen area switzerland and the western lepontine dome formazza area italy internal u th zoning in apatites explains alpha ejection corrected ahe ages that are older than the corresponding aft ages in this study a qualitative interpretation of aft and ahe age elevation relationships suggests a two phase 9 7 and 5 3 ma exhumation scenario affecting the central alps with a stronger expression of the pliocene signal in the formazza area however a quantitative evaluation of exhumation scenarios using the 3 d heat equation solver pecube highlights the existence of several other likely scenarios casting doubt on the validity of a qualitative interpretation of the age elevation relationships in formazza scenarios suggested by quantitative modeling include continuous denudation at a rate of 750 m ma and a one step exhumation rate change from 300 to 1000 m ma at 5 ma in guttannen they include continuous denudation at a rate of 400 m ma with valley deepening and two periods of higher exhumation rate increasing from 300 to 700 m ma repeatedly at 9 7 and at 5 3 ma contingent upon further flexural isostatic modeling the magnitude of exhumation recorded in the axial region of the alps since circa 5 ma does not appear sufficient to solely explain the denudation recorded in the north alpine foreland basin

increase in late neogene denudation of the european alps confirmed by analysis of a fission track thermochronology database abstract a sharp increase in deposited sediment volume since pliocene times has been observed worldwide and in particular around the european alps this phenomenon has been linked to a rise in denudation rates controlled by an increase of either climatic or tectonic forcing observation of in situ cooling histories for orogens is critical to assess the reality of the inferred increase in denudation rates and to determine whether this phenomenon is widespread or localized at active tectonic structures we exploit the unique density of fission track ages in the western european alps to reconstruct cooling isoage surfaces and to estimate exhumation rates on the orogen scale between 13 5 and 2 5 ma our novel technique is based on the association of isoage contours with age elevation relationships it uses map view interpolation enabling a spatio temporal analysis of exhumation rates over the entire western alps the resulting exhumation histories reconstructed for eight areas of the western alps display strong similarities in timing and rates with orogen wide average denudation rates inferred from sediment volumes this consistency validates the use of both techniques for the study of an orogen characterized by strong relief and high recent exhumation rates we conclude that exhumation rates in the western alps have increased more than twofold since late miocene times this increase may have been locally modulated by the distinct response of different tectonic units

age of mammuthus trogontherii from kostolac serbia and the entry of megaherbivores into europe during the late matuyama climate revolution abstract at the drmno open pit coal mine near kostolac in serbia a nearly complete skeleton of mammuthus trogontherii nicknamed vika was discovered in a fluvial deposit overlain by a loess paleosol sequence where a second paleontological level named nosak with remains of m trogontherii was found we studied the magnetostratigraphy of the kostolac sedimentary sequence and found that the vika layer dates to 0 8 ma shortly before the brunhes matuyama boundary in addition according to our age model and previously reported optically stimulated luminescence and electron spin resonance dates the nosak fossils have an estimated age of 0 19 ma and lived during the earliest part of marine isotope stage 6 it appears therefore that at kostolac m trogontherii is preserved both at its earliest occurrence at 0 8 ma and close to its latest occurrence at 0 19 ma and may well have been present in between albeit not yet found we speculate that megaherbivores such as m trogontherii entered europe along a conjunct danube po river migration conduit connecting western asia levant with central southern europe where vast and exploitable ecosystems particularly suited for steppe or savanna adapted megaherbivores from asia and africa developed during the late early pleistocene climate revolution at around 0 8 ma

exhumation charge the last gasp of a petroleum source rock and implications for unconventional shale resources petroleum oil and gas forms from the bacterial or thermal breakdown of kerogen during progressive burial in sedimentary basins during times of petroleum generation kerogens in organic rich source rocks expel petroleum to form a fluid phase in the pore system capable of migrating under hydrodynamic and buoyancy forces to ultimately escape to the surface or accumulate within petroleum traps in the subsurface the relative timing of petroleum charge and trap formation is a vital component in the accumulation of petroleum deposits exhumed basins have been historically viewed as higher risk targets for conventional petroleum exploration because of inter alia the switch off of petroleum generation in the source rock at the commencement of cooling during exhumation however even at the switch off point the source rock may retain a significant volume of petroleum sorbed in kerogen and within its pore system herein we demonstrate that if the source rock is exhumed to shallower depths after peak burial pore pressure reduction and the associated volumetric expansion of the petroleum particularly of the gaseous phase in the pore system will result in the discharge of additional petroleum into the adjacent carrier bed or reservoir formations because most onshore sedimentary basins are characterized by major exhumation events at some point in their history this represents an additional and underappreciated mechanism for a late stage petroleum charge in exhumed sedimentary basins the modeling also indicates that both the initial pre exhumation total gas storage capacity and the exhumation gas charge are likely to be volumetrically more significant for gas bearing source rocks that have been exposed to higher initial pressures and lower thermal gradients the concepts presented here also have implications for petroleum resources retained within unconventional shale reservoirs because high graded shale plays may be associated with systems where the magnitude or rate of relative overpressure dissipation has limited exhumation charge from the unconventional to conventional reservoirs within the basin

modelling of thermal convection in sedimentary basins and its relevance to diagenetic reactions abstract mathematical calculations of thermal convection have been carried out using a porous three player model to simulate pore water flow in a sedimentary basin with layers of different permeabilities the calculated flow lines demonstrate that even very thin layers eg around salt domes and igneous or hydrothermal intrusions analyses of formation waters from sedimentary basins like the north sea often show evidence of a crude stratification of the pore water with respect to salinity and isotopic composition this is evidence suggesting that large scale convection or other types of mixing does not take place and positive salinity depth gradient may help to physically stabilize the formation water the fact that many of the shallow reservoir rocks from the north sea have formation water with low salinity and negative 18 o values suggest that this is modified meteoric water and that migration of petroleum from deeper parts of the basin occurred as a separate phase along restricted migration pathways and was not associated with a high flux of pore water in the absence of thermal convection the total pore water flux through sandstones will be rather small except locally where we may have focused compactional flow through small cross sections diagenetic reactions will therefore normally be relatively isochemical during deeper burial

origin and evolution of formation waters from oil fields on the norwegian shelf abstract stable isotopes of h and o and chemical analyses of formation waters from upper triassic jurassic clastic reservoirs and cretaceous carbonate reservoirs offshore norway are employed to interpret the origin and evolution of these waters in both types of reservoir the formation waters become progressively enriched in total dissolved solids and the heavy isotope of o with increasing depth whereas deuterium varies erratically between 20 and 40 smow bromine analyses and stable isotope data indicate that the formation waters are mixtures of a brine end member formed by evaporation of sea water beyond the point of halite saturation and meteoric water the chemical and isotopic composition of the formation waters and general geological considerations suggest that the brines originated as connate waters in permian evaporites and were later expelled into overlying strata there is a disequilibrium stable isotope distribution between the bulk chalk formations and the formation waters and only minor diagenetic modification of the formation waters appears to have taken place in these reservoirs the formation waters from the clastic reservoirs on the other hand are modified by diagenetic reactions