the oligocene succession in the eastern north sea basin development and depositional systems the oligocene sedimentary succession in the eastern north sea is revised and re interpreted by applying new state of the art reflection seismic data integrated with new bio and sr stratigraphy data from three key wells in the study area the oligocene succession in the eastern north sea is divided into four transgressive regressive t r sequences characterized by non accretional and or aggradational transgressive systems tracts and prograding regressive systems tracts detailed studies of three wells including biostratigraphy and sr analysis constrain the age relationships between the t r sequences internal clinoform geometry indicates that the sediments were sourced from the present southern norwegian mainland to the north of the depositional area the direction of progradation shifted from being se directed in the earliest rupelian early oligocene to s and sw directed during chattian time late oligocene rapid basin subsidence is indicated by the development of non accretionary transgressive systems tracts with subsequent progradation into water depths of hundreds of metres the creation of accommodation space was out of phase relative to eustatic sea level changes and mainly controlled by regional scale differential vertical movements where uplift and exposure of landmasses of the hinterland southern norway occurred concurrently with basin subsidence halokinesis had an intra basinal influence on the main sediment transport direction but probably did not contribute much in creation of accommodation space

why does salt start to move abstract this paper concerns mechanisms of salt and ductile shale movement it investigates salt flow due to differential loading folding of the overburden during compression and drag by a moving overburden the approach is to compare the salt flux caused by these processes to that generated by buoyancy it is demonstrated that overburden folding and drag by the overburden can under commonly encountered conditions result in greater amounts of salt movement than that produced by buoyancy or differential loading these conclusions apply during the early stages of salt anticline salt pillow and salt roller formation but not during the later stages of salt diapir and salt wall growth when buoyancy dominates the quantitative significance of these alternatives to buoyancy is determined by considering an elastic plate overlying a viscous fluid this is the simplest mathematical model that can reproduce the processes considered the model shows that 1 under certain conditions these mechanisms produce more salt movement than buoyancy differential loading dominates when the surface slopes become more than a small fraction of the slope of the salt top overburden buckling dominates if the in plane stress exceeds a critical value drag dominates when the salt layer is thinner than a few hundred metres 2 the strength of the overburden inhibits formation of salt diapirs even those due to buoyancy on wavelengths less than about 12 km

a model for low amplitude detachment folding and syntectonic stratigraphy based on the conservation of mass equation abstract this paper presents a model for the structural evolution of low strain detachment folds in which rock is treated as an incompressible deformable material and its kinematics is governed by the continuity equation the model also considers the following boundary conditions i the vertical flux across the core of the fold is described by a cosine function ii the horizontal flux due to transport along a basal detachment remains constant with depth and iii the depth of the detachment remains fixed upon finding analytical expressions for the velocity field of this deformation process a model for the accumulation of growth strata and the degradation of the topography created by folding is then derived these processes are approximated by means of the transport diffusion equation solutions of these two models are in excellent agreement with geometric and stratigraphic relations documented in fold and thrust belts and analog experiments moreover the model indicates that fold growth in this class of structures is a self affine process a compilation of detachment folds around the world indicates that these structures share a common profile moreover fold amplitude and wavelength of these folds are scaled by different amounts confirming this result the stratigraphy obtained with the growth strata model exhibits the typical thinning and truncation of timelines toward the core of the anticline cross cutting relations often observed in seismic cross sections and field data

heat flow distribution in southeast asia with consideration of volcanic heat abstract as of 1995 in southeast asia from 15 s to 25 n and from 90 to 160 e 2539 heat flow measurements are available despite a recent increase in the number of measurements still important data gaps exist in the region especially around the volcanic regions so far the contribution of heat flux from active volcanoes has largely been overlooked in regional heat flow maps because of uncertainties surrounding it we have tried to estimate the volcanic heat in this region with the assumption that these volcanoes emit a similar amount of heat as those in northeast honshu japan where heat flow studies and seismic tomography enable us to estimate that as a first approximation a volcano can be represented by 140 mw m 2 of heat flow a heat flow map including volcanic heat estimated in this way makes the heat flow in the sunda arc and the philippines where conventional heat flow data are scarce much higher than on a map without the volcanic heat

misr based passive optical bathymetry from orbit with few cm level of accuracy on the salar de uyuni bolivia abstract we demonstrate that under ideal circumstances passive optical measurements can yield surface water depth estimates with an accuracy of a few centimeters our target area is the salar de uyuni in bolivia it is a large active salt flat or playa which is maintained as an almost perfectly level and highly reflective surface by annual flooding to a mean depth of 30 50 cm we use misr data to estimate spatial and temporal variations in water depth during the waning portion of the 2001 flooding cycle we use a single icesat laser altimetry profile to calibrate our water depth model though the salt surface is probably the smoothest surface of its size on earth with less that 30 cm rms height variations over an area of nearly 104 km2 it is not completely featureless topography there includes a peripheral depression or moat around the edge of the salt and several sets of prominent parallel ridges with 5 km wavelength and 30 cm amplitude the process by which these features form is still not well characterized

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

overburden deformation related to the pre piercement development of salt structures in the north sea the nature of the stress regime imposed on a clastic overburden by a developing salt structure changes with time these changes are directly related to the evolving morphology of the salt structure in a sequence of events which is now quite well understood the stress pattern produced by initial almost purely vertical uplift changes rapidly into a more complex pattern as the flanks of the rising salt mass collapse progressively with flow of salt towards the crestal zone the two main stress elements involved derive from extension within the superincumbent overburden produced by the salt uplift and the effects of gravity that exercise an increasingly important influence as the structure develops vertically other factors also affecting the form taken by the overburden deformation are outlined the discussion is illustrated with examples of migrated seismic data

new results on the resistivity structure of merapi volcano indonesia derived from three dimensional restricted inversion of long offset transient electromagnetic data three long offset transient electromagnetic lotem surveys werecarried out at the active volcano merapi in central java indonesia during the years 1998 2000 and 2001 the measurements focused on the general resistivity structure of the volcanic edifice at depths of 0 5 2 km and the further investigation of a southside anomaly the measurements were insufficient for a full 3d inversion scheme which could enable the imaging of finely discretized resistivity distributions therefore a stable damped least squares joint inversion approach is used to optimize 3d models with a limited number of parameters the mode ls feature the realistic simulation of topography a layered background structure and additional coarse 3d blocks representing conductivity anomalies twenty eight lotem transients comprising both horizontal and vertical components of the magnetic induction time derivative were analyzed in view of the few unknowns we were able to achieve reasonable data fits the inversion results indicate an upwelling conductor below the summit suggesting hydrothermal activity in the central volcanic complex a shallow conductor due to a magma filled chamber at depths down to 1 km below the summit suggested by earlier seismic studies is not indicated by the inversion results in conjunction with an anomalous density model derived from arecent gravity study our inversion results provide information about the southern geological structure resulting from a major sector collapse during the middle merapi period the density model allows to assess a porosity range andthus an estimated vertical salinity profile to explain the high conductivities on a larger scale extending beyond the foothills of merapi

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

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

viscosity ratio estimates from natural rayleigh taylor instabilities the geometry of natural gravity driven overturns potentially contains information on viscosity ratios of the material involved irregularities at the interface between two superposed horizontal fluid layers tend to amplify and grow with time with a regular wavelength if the top iayer is more dense published formulas woidt for such rayleigh taylor r t instabilities have been used to construct graphs which can constrain the effective viscosity ratio at the onset of the overturn only the initial thicknesses of the two layers and the final wavelength of the structures need be known the theory is based on an infinite two layer system of newtonian fluids between rigid boundaries with no slip or free slip at contacts geological examples included are soft sediment dewatering on the scale of decimetres in northern norway an unusual instability between basalt and sand in australia of hundreds of metres salt diapirism of kilometres in germany and the persian gulf and granitic diapirism from northern sweden of tens of kilometres viscosity ratios in the order of 1 10 are found for soft sediments with the top layer as the more viscous ratios inferred from patterns of salt diapirs are very large with the overburden approximately 103 105 times more viscous than the salt the viscosities of granites are indicated as lower than their overburden and with ratios of 103

structural evolution timing and tectonic style of the sole pit inversion abstract the nw se oriented sole pit high located in the western half of the southern north sea basin is the result of three different structural processes initiated during the late palaeozoic basin subsidence probably related to late hercynian pull apart movements led to continuous sedimentation from the permian to the middle jurassic mid jurassic doming of its eastern flank followed by erosion transtensional movements and differential subsidence until the early cretaceous reflect the mid and late kimmerian crustal distension and fragmentation of the north sea rift basinwide inversion occurred between the turonian and the campanian and was repeated in the oligocene resulting in a total uplift of some 1500 m the present structural style is represented by a complex network of transpressional and transtensional faults at permian rotliegend levels which are thought to represent the upward termination of a series of wrench induced flower structures with a right lateral sense of displacement these faults are detached by zechstein and triassic salt from more orderly transtensional faults systems at shallower levels in areas where salt is absent late kimmerian normal faults became reactivated in a reverse sense during inversion however the relationship of these shallow mappable tectonic components to the deeper pre permian structure of the sole pit high and to the underlying crustal configuration remains speculative

geometry and growth kinematics of salt pillows in the southern north sea abstract low amplitude salt pillow structures can potentially reveal important details of the physical behaviour of salt and overburden from their growth histories this is because the initial characteristic wavelengths are likely to be preserved beds are more easily traceable across the tops of the structures and original salt thicknesses can be accurately estimated for these reasons a detailed analysis of depth converted seismic data was undertaken to gain insight into the formation growth and spatial distribution of salt pillows in the southern north sea basin around quadrant 44 this area contains a permian zechstein salt interval which has undergone widespread halokinesis to the pillow stage since triassic times but with the main movement during the tertiary perhaps due to inversion the wavelength of the pillows decreases northwards from over 24 to 1 km and estimated original salt thickness also decreases northwards from 1300 to 800 m and there is a strong positive relationship between salt thickness and pillow wavelength pillows appear to be spaced at a characteristic wavelength as they are not directly related to faults and the wavelength varies smoothly through the area however there is a strong alignment of some pillows parallel with the underlying nw se fault trend suggesting that their axis of elongation was controlled by faulting average vertical growth rates of the pillows vary from 40 m ma in the north to less than 10 m ma in the central part of the area measured over vertical distances up to 1250 m most of the growth occurred in the tertiary although a few pillows initiated in the triassic in the north of the area the northern pillows appear to have slowed or even stopped growing during the jurassic and cretaceous and then restarted in the tertiary assuming rayleigh taylor instability controlled the initial pillow wavelengths and using the calculated original salt overburden thicknesses ratios the viscosity ratio between the overburden and the salt can be estimated across the area and was found to vary from 6000 to less than 100 the pillows which moved earliest had the lowest inferred viscosity ratios which is probably because the sediments were less lithified at the time of movement

tertiary tectonic and magmatic evolution of western sulawesi and the makassar strait indonesia evidence for a miocene continent continent collision

an investigation of the relationship between the geology of indonesian sedimentary basins and heat flow density abstract geothermal data collected from 929 wells drilled by oil companies in 20 tertiary basins of indonesia have been related to the geology and tectonics of the area it is found that the thermal conductivity increases with the depth of burial and degree of compaction in both transgressive and regressive sediments but decreases with increases in impurities and heterogeneous grain sizes the temperature gradient is controlled mainly by the depth and temperature of a heat source beneath a basin very high heat flow densities 125 mw m 2 found in central sumatra south sumatra salawati basin and bintuni basin may be caused by relatively shallow magmatic diapirism

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

high heat flow effects on a coalbed methane reservoir east kalimantan borneo indonesia abstract the balikpapan formation miocene age in sangatta east kalimantan is thick 1500 m containing abundant coal seams that range in thickness from less than a meter to over 5 m coal seams are distributed throughout the section and may represent 5 to 7 of the total formation thickness measured gas contents range from

evolution of salt structures east texas diapir province part 1 sedimentary record of halokinesis post aptian post 112 ma strata in the east texas basin were strongly influenced by halokinesis and therefore record the evolution of associated salt structures dome induced changes in patterns of sandstone distribution depositional facies and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion salt domes in the east texas basin exhibit three stages of growth pillow diapir and post diapir each of which affected surrounding strata differently pillow growth caused broad uplift of strata over the crest of the pillows the resulting topographic swell influenced depositional trends and was susceptible to erosion fluvial channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs lower cretaceous reefs on topographic saddles between secondary peripheral sinks now host major oil production at fairway field post diapir crestal uplifts and peripheral subsidence affected smaller areas than did equivalent processes during pillow or diapir stages documented facies variations over and around domes at different stages of growth enable prediction of subtle facies controlled hydrocarbon traps facies controlled traps are likely to be the only undiscovered ones remaining in mature petroliferous basins such as the east texas basin

how will we recognize buried impact craters in terrestrial sedimentary basins criteria that are deemed critical for recognition of terrestrial impact craters include features from hand specimens such as shock metamorphic structures although these criteria have been selected because they are unique physical products of bolide impact strict adherence to these criteria means that we cannot positively identify buried astroblemes that are tomographically imaged on three dimensional seismic data but are undrilled because many of earth9s deeply buried structures may never be drilled because of prohibitive cost and lack of commercial incentive a large proportion of as yet undiscovered terrestrial astroblemes including the best preserved examples may remain unclassified and be excluded from impact structure research a framework for the identification of impact structures imaged on three dimensional seismic data is proposed on the basis of geometrical criteria plus additional image quality and preservation criteria that assign a level of confidence to the assessment

exploring the continental shelf for low geological risk nuclear waste repository sites using petroleum industry databases a uk case study abstract site selection for deep disposal of intermediate and high level radioactive waste in the uk to date has not taken full advantage of oil industry databases that cover offshore areas the shallow water area of the uk continental shelf is twice that of the onshore area and due to variations in regional geology many geological settings occur that are not found onshore the geology and hydrogeology of the uk continental shelf contrast in many respects with that of onshore areas the geology of the north sea in particular is constrained by over 3000 deep 2 km exploration wells 50 000 km 2 of 3d seismic data and several million line kilometres of 2d seismic data vastly more than the coverage of data constraining the deep geology onshore combined with detailed studies of oil and gas fields this data has led to a greater technical understanding of many aspects of offshore geology relative to that onshore these data represent an original investment of 20bn by oil and gas companies but are now in the public domain these databases are used here to compare onshore and offshore settings in terms of criteria such as structural geology fault activity and uplift subsidence clear differences emerge such as risk of seismicity exhumation and the variety of hydrogeological systems the distribution and geometry of candidate repository sites throughout the north sea salt structures shale basins sealed sandstone reservoirs and basement highs are illustrated several lines of petroleum related research have yielded lessons that may be useful in assessing deep repository locations such as migration of hydrocarbons through shale seals the exceptional combination of seismic data and well control means that offshore areas on the continental shelf and the north sea in particular can now be thoroughly explored in this context and contribute candidate sites into a nationwide portfolio of deep geological disposal options in the event of site selection being pursued in the uk an example framework for this process is presented here

synthesis of salt tectonics in the southern north sea uk abstract a structural model encompassing the southern north sea basin west of the central graben has been developed this model consists of a rift system affecting the post salt section around the basin margin and a large area of detached compressional buckle folds within the basin this pattern is initially a response to gravity sliding of the post salt section on the salt within the basin during the late triassic to late jurassic a close relationship between the location and trend of the peripheral graben system and basement structures in the pre salt is noted pre jurassic extension across the peripheral graben systems was balanced by the sum of fault heaves at the pre salt rotliegend level and shortening across salt cored buckle folds in the post salt section salt pillows and swells passively infilled the cores of these gravity induced buckle folds cretaceous and tertiary inversion involved basin tilt and renewed movement on basin bounding basement faults notably reverse movements did not propagate from basement structures up into the peripheral graben systems the post salt sedimentary section experienced gravity spreading in response to inversion related uplift resulting in syn inversion extensional faulting in the sole pit high where the mesozoic section was thickest this extension combined with a loss of fault heave in the pre salt section was balanced by amplification of salt cored buckle folds in the centre of the basin in the context of the model described here salt pillows represent passive infill of thin skinned compressional buckle folds which later amplified during thick skinned basement shortening crestal collapse of such folds occurs via normal faulting accompanied by reactive diapirism such reactive diapirs establish conduits through which salt may leak leading to pillow deflation and ultimately conduit preservation as a salt wall flanked by rim synclines in areas where the buckle folds were emergent the salt structures described here are related to cover folds and faults which in turn reflect episodes of basin extension tilting and inversion hence individual salt structures can be said to be only remotely connected with regional intraplate stresses

evolution of the nw margin of the north permian basin uk north sea mapping of depositional zones within the zechstein supergroup using semi regional 2d and 3dseismic data constrains the geological evolution of the northwestern margin of the north permian basinin uk offshore quadrants 14 15 19 20 and 21 four depositional zones are identified on the basis of mappable seismic facies which are assumed to vary with halite content well control characterizes the most reflective seismic facies as an interbedded carbonate and anhydrite shelf succession which grades laterally through clastic rich sequences to the least reflective a thick halite basinal equivalent the trendsof the depositional zones illustrate the geometry of the north permian basin and may have been locally controlled by basement lineaments within the north permian basin a n s trending axis devil s hole high characterized by thick reflective facies separates the central north sea from the forth approaches basin basement fault blocks control facies type and thickness along the northwest margin of the north permian basin in the moray firth area permian tilt of the zechstein shelf related to regional flexure played a role in precipitating gravity driven tectonics within the seismically reflective facies on the east flank of the devil s hole high this permian phase of salt tectonics resulted in numerous intra zechstein structures which can be interpreted as rafted and folded zones of interbedded halite carbonate sulphate and clastics the rafts initially slid downdip towards the main halite basin then their evolution became dominated by differential subsidence of the interbeds which forced salt layers into adjacent passive diapirs this episode predates deposition of the triassic smith bank shales which rest upon the zechstein with local angular unconformity the spatial distribution of zechstein facies influenced the tectonostratigraphy of the triassic jurassic and cretaceous systems boundaries between zechstein facies correspond to the limit of triassic halokinesis on the west central shelf and the limit of detachment of jurassic and lower cretaceous thin skinned tectonics in moray firth half graben

a 1 5d model of the steady state thermal structure of detachment folds abstract we present a 1 5d steady state model of thermal perturbations in the core of detachment anticlines the model incorporates the effects of heat conduction advection by folding radiogenic sources and conversion of work into heat by viscous dissipation we work out analytical solutions of model s equations for heat flow and temperature field for the case of low amplitude detachment folds growing in a thick homogeneous stratigraphy our analytical solutions for the simplest case of no heat sources show that detachment folds develop a thermal boundary layer conduction of heat dominates inside the layer whereas advection of heat by folding prevails outside the boundary layer we also find that heat flow in a growing detachment fold decays exponentially with the square of the thickness of the detached stratigraphic section when heat sources are included into the problem we find that radiogenic heat generates thermal anomalies at the crest of the anticlines whereas viscous dissipation produces thermal anomalies at the core of the detachment fold we analyze three cases of geological interest detachment folds growing in evaporitic sequences marine carbonates and shaley sediments for a typical uplift rate of 2 mm yr conduction dominates in the first class of rocks viscous dissipation dominates in folds growing in limestone due to its high viscosity advection and the generation of heat by radiogenic isotopes dominate the growth of detachment folds in shale additionally the cooling histories of lagrangian particles embedded in the fold for the last two cases are analyzed the core of the fold is characterized by rapid cooling whereas the limbs cool at slower rates than the core thus the development of detachment anticlines may either accelerate maturation of source rocks and expand the maturation window or halt it by removing source rocks from the generating window

evolution of salt structures east texas diapir province part 2 patterns and rates of halokinesis the effects of salt mobilization on aptian and younger post 112 ma strata in the east texas basin can be used to illustrate patterns of dome growth through time and to estimate rates and amounts of salt movement pre aptian domes grew in three areas around the margin of the diapir province apparently in pre aptian depocenters maximum dome growth along the basin axis coincided with maximum regional sedimentation there during the middle cretaceous aptian albian and cenomanian in the late cretaceous the sites of maximum diapirism migrated to the periphery of the diapir province diapirism began after pillows were erosionally breached leading to salt extrusion and formation of peripheral sinks the duration of pillow and diapir stages of growth was subequal ranging from 10 to 30 ma post diapiric stage of growth continued for more than 112 ma in some cases diapirs grew fastest in the early cretaceous when peak growth rates ranged from 150 to 530 m ma 490 to 1 740 ft ma declining in the early tertiary to 10 to 60 m ma 30 to 200 ft ma assuming steady state conditions over periods of 1 to 17 ma strain rates for the rise of the east texas diapirs averaged 6 7 10 16 sec peak gross rate of growth averaged 2 3 10 15 sec similar to slow orogenic rates the evolution of east texas salt domes essentially ended in the early tertiary with uplift rates less than 30 m ma 100 ft ma

geological interpretation and numerical modelling of salt movement in the barbastro balaguer anticline southern pyrenees abstract the barbastro balaguer salt anticline located in the south pyrenean foreland basin was characterised with seismic reflection profiles and well logs interpretation to be the result of a combination of thrusting buoyancy and differential loading mechanisms these mechanisms were responsible for the formation and the evolution of the structure from the late oligocene to the present seismic reflection interpretation indicates that alpine compressional tectonics played the major role in the early stages of the formation of the anticline a numerical model based on the finite difference involving thrusting buoyancy and differential loading mechanisms was developed and applied to the modelling of the development of the salt structure the results of our modelling suggest that buoyancy and differential loading have played an important role in the subsequent growth of the barbastro balaguer anticline

mantle structure and seismotectonics of the sunda and banda arcs abstract we have examined the mantle structure and seismotectonic features of the sunda and banda arcs indonesia based on the p wave tomographic images focal mechanism solutions gravity anomaly and heat flow data on the basis of slab morphology and seismicity we can divide the arcs into three parts the western sunda eastern sunda and banda arc the slab like tomographic image penetrates to a depth of about 500 km below the western sunda arc where seismicity does not exceed a depth of 250 km in the eastern sunda arc where a seismic gap exists between 300 and 500 km depths the slab appears to be continuous and to penetrate into the lower mantle beneath the banda arc with seismicity down to a depth of about 650 km the slab dips gently and does not appear to penetrate into the lower mantle the positive gravity anomaly shows a systematic pattern namely the anomaly along the eastern sunda arc is larger than that in the western sunda and the banda arcs along the back arc side of the sunda and banda arcs the heat flow decreases from the west to the east seismic strain release from the shallow earthquakes calculated from the cmt solutions show the strain axes to be oblique to the structural trends the cmt solutions show that the eastern sunda arc is characterized by normal earthquakes along the trench and back arc thrusting earthquakes north of the volcanic line in the western sunda and the eastern sunda arcs earthquakes of the down dip extension type dominate the slab down to a depth of 200 km while down dip compression earthquakes occur below 500 km depth in the banda arc deep earthquakes show down dip extension to a depth of 500 km below this depth the state of stress is not clearly defined