the adiabatic pole to pole overturning circulation abstractthe adiabatic pole to pole cell of the residual overturning circulation roc is studied in a two hemisphere semienclosed basin with a zonally reentrant channel occupying the southernmost eighth of the domain three different models of increasing complexity are used a simple analytically tractable zonally averaged model a coarse resolution numerical model with parameterized eddies and an eddy resolving general circulation model two elements are found to be necessary for the existence of an adiabatic pole to pole cell 1 a thermally indirect wind driven overturning circulation in the zonally reentrant channel analogous to the deacon cell in the antarctic circumpolar current acc region and 2 a set of outcropping isopycnals shared between the channel and the semienclosed region of the northern hemisphere these points are supported by several computations varying the domain geometry the surface buoyancy distribution and the wind forcing all three models give results that are qualitat

a simple kinematic model for crustal deformation along two and three dimensional listric normal faults derived from scaled laboratory experiments abstract we have derived a simple kinematic model of the deformation that results from extension accommodated by movement of a crustal block along two and three dimensional listric fault surfaces the model accurately reproduces deformation observed in a series of scaled analogue models the kinematic model is based on the simple assumption that lines within the hangingwall that are normal to the fault surface before deformation remain so following deformation an additional constraint built into the model is that of incompressibility deformation in the hangingwall block as observed in the laboratory experiments and predicted by the kinematic model is characterized by 1 a key stone structure or crestal collapse graben at some finite distance from the fault tip and 2 pure solid body rotation of the hangingwall head area near the tip of the fault in three dimensions the central region of the model undergoes extension in a direction normal to the direction of imposed displacement in such a way that the direction of dip of the upper surface of the hangingwall is aligned with the direction of extension this result provides quantitative support for the use of dip analysis to infer tectonic transport direction we also show how the distribution of extension within the hangingwall is affected when the constraint of constant displacement along the fault is relaxed

analogue modelling of reverse fault reactivation in strike slip and transpressive regimes application to the giudicarie fault system italian eastern alps abstract sandbox analogue models were used to study the reactivation of a reverse fault in strike slip and transpressive regimes for comparison with the evolution of the giudicarie fault system in the central eastern alps the giudicarie system is interpreted as resulting from late miocene sinistral transpressive reactivation of an older late oligocene reverse fault the old reverse fault was reproduced as a pre cut dilatant surface obtained by pulling a stiff metal wire through the model sand layer the position of the pre existing fault with respect to the base plate fault accommodating the strike slip and transpressive faulting phase controlled the extent and geometry of reactivation the clearest reactivation in a pure strike slip regime was achieved in experiments where the basal strike slip fault was immediately below the pre existing fault plane this strong reactivation involved lateral extrusion and lateral stepping of secondary faults from the basal fault to the pre existing reverse fault in the case of transpression the most spectacular reactivation was achieved for a convergence angle of 10 strongly asymmetric structures developed on either side of the pre cut dilatant zone the analogue experiments reproduced very closely the structural features of the giudicarie fault system supporting a model involving a twofold tectonic evolution for the giudicarie fault system with later reactivation in sinistral transpression of an older reverse fault

vertical averages of rheology of the continental lithosphere relation to thin sheet parameters abstract we calculate vertically averaged rheologies for continental lithosphere subject to biaxial states of stress corresponding to extensional compressional and strike slip regimes we assume that brittle deformation occurs by byerlee s law and that ductile deformation occurs by steady state creep mechanisms under these conditions the vertically averaged rheology may be approximated by a single power law over the range of strain rates from 10 13 to 10 17 s 1 this is true not only when either brittle or ductile behavior dominates the strength of the lithospere but also when the contributions of brittle and ductile behavior are comparable the value of the power law exponent n and the strength of the lithosphere depend on the depth and stress difference at the brittle ductile transition the temperature at the moho and the geothermal gradient in the range of vertically integrated stress between 1012 and 1013 n m 1n reaches a minimum of between 5 and 10 under other circumstancesn increases rapidly as brittle behavior dominates over ductile behavior the strength of the lithosphere depends most strongly on the thermal state of the upper mantle but also is influenced by the stress supported in brittle portions of the lithosphere

motion of the pacific plate relative to eurasia and its potential relation to cenozoic extension along the eastern margin of eurasia extension along the eastern margin of eurasia has been regarded commonly as a far field effect of the india eurasia collision however some aspects of the timing and location of this extension make a link between the collision and extension difficult we suggest that some extensional features commonly interpreted as effects of the collision may be related more simply to changes in plate convergence rates along the eastern plate boundary of eurasia an analysis of the motion of the pacific plate relative to eurasia suggests that the rate of pacific eurasia convergence varied significantly during the tertiary period from a late cretaceous convergence rate of 120 140 mm yr the rate declined substantially during early tertiary time and reached a minimum in eocene time of 30 40 mm yr in oligocene to earliest miocene time the average convergence rate increased moderately to 70 95 mm yr then decreased again to 65 70 mm yr during early to middle miocene time from late miocene to the present the rate of convergence increased to an average of 100 110 mm yr the paleocene through middle miocene episode of relatively slow convergence correlates with a period of widespread extension along the eastern margin of eurasia decreased convergence may have been related to a net reduction in horizontal compressional stress transmitted between the pacific and eurasian plates which resulted in widespread extension adjacent to the margin of eurasia

rifting process of the xihu depression east china sea basin abstract having a maximum depositional depth up to 15 km the ne trending xihu depression is evolved from a deep paleogene continental margin rifting along the present day east china sea continental shelf in this paper we use deep seismic reflection well logging and gravity data to synthesize early rifting process of the depression to study the regional tectonic subsidence history we developed a computer program that performs backstripping and simultaneous inversion for stretching factor initial lithospheric thickness and incipient age of thermal subsidence tectonic subsidence analyses of 40 industrial wells reveal nonuniform stretching preferential crustal extension along the depocenter but preferential mantle extension at the western flank uniform extension may have occurred only somewhere between the central inversion zone and the western margin in the early rifting stage subdued initial subsidence or initial uplift is observed on several wells near the western margin due possibly to flexural isostatic balance the initial mechanical lithospheric thicknesses from subsidence inversion seem to vary from about 55 km to almost 130 km suggesting significant longitudinal segmentation as well as transverse variation in the prerifting lithosphere it is likely that the southern part of the xihu depression was developed initially on a region of relatively thin lithosphere a statement conformable to geological evidences nw se trending deep seismic profiling clearly reveals the deep basement structure of the depression as well as the synrift and postrift sedimentary packages separated by a breakup unconformity crustal layer thicknesses are independently estimated from gravity modeling inversion tectonic subsidence analyses and deep seismic profiling respectively these methods all arrive at very small present day thicknesses of the crustal layer beneath the depocenter of the xihu depression

eastern boundary contribution to the residual and meridional overturning circulations a model of the thermocline linearized around a specified stratification and the barotropic linear winddriven stommel solution is constructed the forcings are both mechanical the surface wind stress and thermodynamical the surface buoyancy boundarycondition the effects of diapycnal diffusivity and of eddy fluxesofbuoyancy parameterizedintermsofthelarge scalebuoyancygradient areincluded theeddyfluxes of buoyancy are especially important near the boundaries where they mediate the transport in and out of the narrow ageostrophic down upwelling layers the dynamics of these narrow layers can be replaced by effective boundary conditions on the geostrophically balanced flow the effective boundary conditions state that the residual flow normal to the effective coast vanishes the separate eulerian and eddy induced components may be nonzero this formulation conserves the total mass and the total buoyancy while permitting an exchangebetweentheeulerianandeddytransportofbuoyancy withinthedown upwellinglayers inturn this exchange allows buoyancy gradients along all solid boundaries including the eastern one a special focus is on the buoyancy along the eastern and western walls since east west buoyancy difference determines the meridional overturning circulation the inclusion of advection of buoyancy by the barotropic flow allows a meaningful distinction between the meridional and the residual overturning circulations while retaining the simplicity of a linear model the residual flow in both meridional and zonal directions reveals how the subsurface buoyancy distribution is established and in particular how the meridional buoyancy gradient is reversed at depth in turn the horizontal buoyancy gradient maintains stacked counterrotating cells in the meridional and residual overturning circulations quantitative scaling arguments are given for each of these cells which show how the buoyancy forcing the wind stress and the diapycnal and eddy diffusivities as well as the other imposed parameters affect the strength of the overturn

normal fault inversion by orthogonal compression sandbox experiments with weak faults abstract linear frictional failure criteria predict that normal faults form dipping around 60 and reverse faults around 30 depending on dry rock properties therefore it is unlikely that normal faults be reactivated as reverse faults unless the stress conditions are favourable or the intrinsic properties of the intact rock or of the precursor fault pf are modified in the present study we focused on friction strength of the pf we used sandbox experiments with an initially embedded weak pf dipping 60 or 70 filled with a thin film of silicone putty that lubricated the weak fault to investigate inversion of high angle pf by orthogonal compression the results show that 1 the pf can be inverted if it is weak during compression even if the angle of dip is as great as 70 2 after inversion initiation the reverse movement on the pf can last for as much as 30 model shortening leading to great amounts of reverse displacement along the pf before the formation of a thrust ahead 3 in models with more than one pf the weakness of the reactivated fault closer to piston was not enough to prevent reactivation of the pf further ahead after an amount of shortening that depended on distance between pfs the viscous material used to weaken the fault is scalable to salt in nature however the great decrease in friction due to lubrication with a viscous material can simulate many other weakening mechanisms observed in nature

what sets the strength of the middepth stratification and overturning circulation in eddying ocean models abstract the processes maintaining stratification in the oceanic middepth between approximately 1000 and 3000 m are explored using an eddy resolving general circulation model composed of a two hemisphere semienclosed basin with a zonal reentrant channel in the southernmost eighth of the domain the middepth region lies below the wind driven main thermocline but above the diffusively driven abyssal ocean here it is argued that middepth stratification is determined primarily in the model s antarctic circumpolar current competition between mean and eddy overturning in the channel leads to steeper isotherms and thus deeper stratification throughout the basin than would exist without the channel isotherms that outcrop only in the channel are nearly horizontal in the semienclosed portion of the domain whereas isotherms that also outcrop in the northern hemisphere deviate from horizontal and are accompanied by geostrophically balanced meridional transport a northern source of deep water water with temp

eastern boundary conditions and weak solutions of the ideal thermocline equations abstract it is argued that the ideal fluid thermocline equations have weak i e nondifferentiable solutions that satisfy no mass flux boundary conditions at the east this conclusion is based on a local analysis of the eastern corner of a subtropical gyre specifically we suppose that the surface density is uniform while the density on the eastern boundary is either uniform but different from that of the surface or else is linearly stratified the surface density is injected into the interior by specified ekman pumping in the absence f dissipation the resulting solution would have a discontinuity is smoothed and becomes an internal boundary layer which separates the light fluid originating at the surface from the denser fluid which abuts the eastern boundary this solution which is of the similarity type illustrates the applicability of solutions of the ideal fluid thermocline problem with discontinuities it is these discontinuities which enable ideal fluid solutions to satisfy eastern boun

sandbox experiments of inverted listric and planar fault systems abstract the kinematic and geometric evolution of basement controlled inversion structures has been analyzed using a plane strain sandbox apparatus the results of two representative scaled analogue models comprising rigid listric and planar detachment faults that both have cut off angles of 60 to the horizontal are described in detail the hangingwall above these detachment geometries was constructed from alternate layers of sand and mica in order to simulate an anisotropic sedimentary sequence in both experiments initial shortening at the onset of inversion was accommodated by bulk strain this was followed by reactivation of the basal detachment together with the main basin controlling planar and listric faults which propagate upwards through the post rift sequence at approximately the same angle as the upper part of the detachment fault i e 60 reactivation of relatively steep intra basinal extensional faults within the cover was restricted to nucleation of reserve faults and thrusts in the region of the tips during approximately the first 10 to 15 contraction this resulted in gently dipping thrusts that propagated upwards through the post rift sequence to produce harpoon shaped structures later in the inversion phase after approximately 15 contraction backthrusts cut through and displaced the original antithetic extensional graben faults producing downward tapering wedge shaped structures at the margins of the basin although deformation in these experiments was limited to purely dip slip displacement the nature of the original extensional faults and their reactivated tip regions resulted in cross sectional geometries that have a marked resemblance to strike slip induced flower structures uplift was asymmetric and centred above the upper part of the main detachment above the listric fault but was more symmetrical and centred above the soling out point of the detachment in the case of the planar fault geometry the results of these experiments show distinct similarities to structures seen on seismic sections form the southern north sea and other inverted sedimentary basins

early cenozoic two phase extension and late cenozoic thermal subsidence and inversion of the bohai basin northern china abstract the bohai basin is one of a family of early cenozoic extensional basins that lie along the eastern margin of asia from russia to vietnam initial extension was probably triggered by subduction roll back of the oceanic pacific plate from the asian continent there were two phases in the bohai basin s rift history the earlier paleocene early eocene phase resulted in the deposition of the kongdian formation and the fourth lowest member of the shahejie formation in a series of elongate half grabens these half grabens have master faults with a nne ssw orientation secondary normal faults are typically clockwise oblique to the master faults indicating a component of dextral transtension deposition was focused in the west and south of the present basin these rocks are mainly alluvial fan and fluvial red beds the architecture of the basin underwent an important change at ca 43 45 ma middle eocene beginning with the deposition of the third member of the shahejie formation in part these sediments were deposited in the same half grabens as the kongdian formation but the bozhong depression in the central part of the basin originated at this time and became the major depocentre the bozhong depression superficially resembles a pull apart basin it formed when continued transtension of the earlier tertiary fault systems to the east and west created an extensional overlap between them during this phase the basin as a whole had a geometry with elements typical of both pull apart and transtensional basins regional extension in many east asian basins ended at the end of the oligocene probably because of the onset of transpression within eastern asia caused by the collision of australia with the philippine sea plate dextral transpression caused minor inversion of some of the earlier normal faults in bohai but as a whole the basin began to subside in a post rift phase of thermal subsidence that has lasted until the present day

analogue models of orogenic wedges controlled by erosion abstract indentation in the upper brittle crust where one plate is stiffer than the other produces vertical extrusion of a doubly vergent orogenic wedge sandbox models of this process show that erosion with or without deposition of the eroded material onto one or both margins significantly changes the internal patterns of orogenic shear and compaction within the orogens erosion decreases the vertical stress and changes the criticality of the orogenic wedge whereas redeposition increases the vertical stress on its margins effective indenters of accreted sand which develop in models without erosion if the rigid indenter face dip is 75 e g 45 or 15 are strongly affected by erosion rapid erosion favors thrusting over compaction and decreases both the size and the relevance of the effective indenters redeposition of eroded material on the margins also expands the lifetime of the active shear as the additional load delays initiation of underlying new shears

the dinevar transtensional pull apart basin nw zagros mountains iran a geological study and comparison to 2d finite element elastic models the dinevar transtensional pull apart basin is a nw se trending basin located in the northwest part of the zagros mountains sanandaj sirjan tectonic zone iran this basin was formed by oblique extension in a strike slip fault system which was controlled by the pre existing sahneh and the mianrahan faults in addition to a field study we constructed a 2d finite element elastic model based on the major fault segments according to the field study various geological structures are formed around the pre existing fault segments including pencil structures with 13 aspect ratio 19 tight to open asymmetric folds oblique normal faults synthetic and antithetic faults normal and reverse fault drags and negative and hybrid type flower structure fe model results show that around the fault step is a zone of displacement gradient that indicates extension transtension within the overlapping zone consequently subsidence is predicted over the releasing fault step the modelled stress distributions within the fault step and around the fault segment tips are asymmetric elastic modelling shows that the mean normal stress within the step is tensional which would impede plastic yield while the region outside the step is characterised by compressive mean normal stress the mean normal stress pattern is characterised by a regional minimum localised inside the extensional step transtension zone and two local maximum and minimum couples formed at the advancing and retreating sides respectively in the fault segment tips the results show that two main subsidence regions depocentres or sub basins form along and in the proximity of the fault segment tips the imposed relative motion is entirely accommodated by creep on the faults which causes plastic strain to accumulate outside the faults mostly localised within the fault step this localised strain between fault segments could initiate connecting faults or reactivate earlier faults generally at high angles relative to the master fault segments as suggested by the stress and strain patterns the rotation and magnitude variation in the stress and strain trajectories reflects heterogeneous deformation in general the dinevar transtensional pull apart basin is characterised by an elongate rhomboidal to trapezoidal shaped geometry the modelled stress distribution and strain localisations within the basin are in general agreement with the locations of fault segments within the dinevar transtensional pull apart basin

trace and rare earth element ree characteristics of mudstones from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin implications for provenance depositional conditions and paleoclimate abstract the interpretation of depositional conditions provenance and paleoclimate provide important information to understand hydrocarbon source rock formation and distribution the concentrations of trace elements and rare earth elements rees of fifty mudstone samples from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin were determined by inductively coupled plasma mass spectrometry icp ms to test the depositional conditions provenance and paleoclimate evidences from the visual comparisons of the simple bivariate plots diagrams and statistical comparisons of the mann whitney rank sum test suggest that there may be a common source for the pinghu formation and huagang formation mudstones sedimentary provenance from bivariate plots diagrams of hf versus la th and la sc versus co th shows that pinghu formation mudstones are mainly composed of mixed felsic basic source and acidic source whereas huagang formation is mainly acidic source additionally the ree vs la yb discrimination diagram shows that the property of the provenance for the pinghu formation mudstones consists sedimentary rock alkaline basalt and a small amount of continent tholeiitic basalts whereas that of the huagang formation is mainly alkaline basalt and sedimentary rock discriminant diagrams consisting of la th sc and th co zr 10 suggest that the mudstones of two formations were deposited in continental island arc and active continental margin tectonic setting redox proxies v ni v v ni and ce indicate that most of the mudstones of two formations were deposited in a relatively dysoxic anoxic condition the cool and humid climate represented by sr cu and rb sr ratios were prevailing in xihu sag during the eocene and oligocene period and the oligocene was cooler than eocene moreover five long term base level cycles siii1 siii5 and four sequence boundaries sb2 sb5 were recognized in the pinghu formation and huagang formation based on the previous research we find that the abnormal surfaces of geochemical parameters such as v ni sr ba u ti v ti ti and ree to some extent agree with sequence boundaries sb2 sb3 sb4 and sb5 in mudstones additionally the increment of ti and ree concentrations and the decrease of sr ba v ni u ti and v ti ratios above the sb4 indicates that terrigenous clast grew significantly and the sea level dropped after late eocene which is related with the late eocene tectonic movement

deformation mechanisms in granitic rocks at shallow crustal levels abstract microstructural observations of naturally faulted granitic gneisses show that feldspar grains are weaker than quartz grains at temperatures below 325 c and at depths of less than 8 10 km feldspar grains sustained most of the deformation by grain scale faulting slip along cleavage controlled fractures and cataclasis fracture of feldspar grains within fault zones promoted their alteration to kaolinite quartz grains also deformed by fracturing and often healed to form quartz porphyroclasts and mosaics in a comminuted matrix of feldspar and kaolinite syntectonic alteration of the feldspar grains may have weakened the fault zones over time and resulted in foliated textures within the fault zones this study of naturally deformed rocks confirms published experimental results on the behavior of granitic rocks at low temperatures and pressures and taken together these data show that the theology of the upper 10 km of the crust is greatly influenced by cataclastic processes in feldspar

dynamics of the atlantic meridional overturning circulation part 2 forcing by winds and buoyancy abstract recently schloesser et al 2012 explored the dynamics of the descending branch of meridional overturning circulations mocs by obtaining analytic solutions to a variable density 2 layer model vlom forced only by a surface buoyancy flux key processes involved are the poleward thickening of the upper layer along the eastern boundary due to kelvin wave adjustments the westward propagation of that coastal structure by rossby waves and their damping by mixing the resulting zonal pressure gradient causes the surface moc branch to converge into the northern basin near the eastern boundary in this paper we extend the schloesser et al 2012 study to include forcing by a zonal wind stress x y much of the paper is devoted to the derivation and analysis of analytic solutions to vlom for validation we also report corresponding numerical solutions to an ocean general circulation model ogcm solutions are obtained in a flat bottom rectangular basin confined to the northern hemisphere the buoyancy forcing relaxes upper ocean density to a prescribed profile y that increases polewards until it becomes as large as the deep ocean density at latitude y2 north of y2 then the ocean is homogeneous a 1 layer system the wind stress x drives subtropical and subpolar gyres and in our standard solution the latter extends north of y2 vertical diffusion is not included in vlom minimized in the ogcm consequently the moc is not closed by upwelling associated with interior diffusion but rather by flow through the southern boundary of the basin into a southern boundary sponge layer in the ogcm and solutions are uniquely determined by specifying the strength of that flow or the thermocline depth along the tropical eastern boundary solutions forced by x and differ markedly from those forced only by because water flows across y2 throughout the interior of the subpolar gyre not just near the eastern boundary in some of our solutions the strength of the moc s descending branch is determined entirely by this wind driven mechanism whereas in others it is also affected by rossby wave damping near the eastern boundary upwelling can occur in the interior of the subpolar gyre and in the western boundary layer providing shortcuts for the overturning circulation consequently there are different rates for the convergence of upper layer water near y 2 m n and the export of deep water south of the subpolar gyre m the latter being a better measure of large scale moc strength when western boundary upwelling occurs in our solutions m is independent of the diapycnal processes in the subpolar ocean

4d analogue modelling of transtensional pull apart basins abstract scaled sandbox models were used to investigate the 4d evolution of pull apart basins formed above underlapping releasing stepovers in both pure strike slip and transtensional basement fault systems serial sectioning and 3d volume reconstruction permitted analysis of the full 3d fault geometries results show that very different pull apart basins are developed in transtension compared to pure strike slip both types of models produced elongate sigmoidal to rhomboidal pull apart systems but the transtensional pull apart basins were significantly wider and uniquely developed a basin margin of en echelon oblique extensional faults dual opposing depocentres formed in the transtensional model whereas a single central depocentre formed in pure strike slip in transtension a distinct narrow graben system formed above the principal displacement zones pdzs cross basin fault systems that linked the offset pdzs formed earlier in the transtensional models sequential model runs to higher pdz displacements allowed the progressive evolution of the fault systems to be evaluated in cross section transtensional pull aparts initiated as asymmetric grabens bounded by planar oblique extensional faults with increasing displacement on the pdzs basin subsidence caused these faults to become concave upwards and lower in dip angle due to fault block collapse towards the interior of the basin in addition strain partitioning caused fault slip to become either predominantly extensional or strike slip the models compare closely with the geometries of natural pull apart basins including the southern dead sea fault system and the vienna basin austria

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

effect of burial history on diagenetic and reservoir forming process of the oligocene sandstone in xihu sag east china sea basin abstract porosity evolution history hydrocarbon charging periods diagenetic and reservoir forming characteristics of low permeability and tight sandstone are presented in this study the interpretation is based on information including thin section scanning electron microscope homogenization temperature of fluid inclusion bulk rock x ray diffraction analysis clay x ray diffraction analysis and stable isotopic composition these sandstones are located in the oligocene e3h formation in the xihu sag east china sea basin east china five diagenetic events in the h3 h4 and h5 members were determined including connate alkaline pore water of the oligocene sandstone meteoric water leaching in late miocene organic acids and co2 acidic fluids in early middle miocene reservoir temperature decrease induced by tectonic uplift and alkaline diagenetic environment from late miocene to present day porosity evolution history of different grain size lithology were evaluated by basin modelling and test data the medium sandstone and coarse sandstone of the h3 member and medium sandstone of the h4 member not reached the tight state in the geologic time the fine sandstone of the h4 member entered the tight state at 12 ma suffered acidic fluids to improve the tight state in late stage and entered the tight state again since 6 5 ma the medium sandstone fine sandstone and siltstone in the h5 member entered the tight state at 13 5ma 16ma and 19ma respectively three hydrocarbon charging periods were determined including 15 5 ma 10 4 ma in the middle miocene 9 6 ma 7 0 ma in the late miocene and 6 2 ma 0 0 ma from the late miocene to present day three diagenetic and reservoir forming patterns were proposed including accumulation without tightness accumulation after tightness improving reservoir quality with acidic fluid accumulation while tightness accumulation after tightness the burial history cannot be ignored in the diagenetic events porosity evolution history and hydrocarbon charging periods of similar low permeability and tight sandstone in sedimentary basins

numerical modeling of late miocene tectonic inversion in the xihu sag east china sea shelf basin china abstract the east china sea shelf basin is an important oil and gas bearing basin in the west pacific continental margin this region was affected by subduction of the pacific plate and the philippine plate in cenozoic and experienced multi stage tectonic inversions this paper presents results from a numerical simulation by finite element method to the xihu sag in the east china sea shelf basin and neighboring areas in an attempt to evaluate the wnw directed compression on the sag during late miocene based on comprehensive structural analysis of a large number of seismic profiles we determine the structural geometry of the sag including the basement of the basin the sedimentary cover and 29 major faults in the xihu sag simulation results show that under continuous wnw directed compression tectonic inversion occurred firstly in the longjing and yuquan tectonic zones in the sag based on quantitative analysis of vertical displacement field of the xihu sag and peripheral areas and its stress intensity evolution we identify a compressional regime in the longjing anticline zone with a gradually propagated uplifting from south to north whereas the propagation of uplifting in the yuquan anticline zone is from north to south the inversion intensity decreases from north to south the formation of the tectonic inversion zone in the xihu sag is not only correlated to the direction of compression and fault patterns in the basin but also closely related to the spatial configuration of fault surfaces of the xihu jilong fault in the xihu sag

analogue models of pull apart basins sandbox analogue models of pull apart basins that developed in sedimentary strata above releasing steps in underlying basement faults are characterized by rhombic basins that are flat bottomed box grabens with a subhorizontal synkinematic basin infill steep to nearly vertical sigmoidal oblique slip and segmented oblique extensional faults are the dominant bounding structures of the pull apart basins cross basin short cut faults link the offset principal displacement zones that are characterized by flower structure development the structural architectures of the physical models compare directly in form and dimensions to natural examples of strike slip pull apart basins

mesozoic basins in eastern china and their bearing on the deconstruction of the north china craton abstract mesozoic basins occur widely in the eastern block and the neighboring area of the north china craton including the bohai bay the jiaolai the hefei and the north yellow sea in the north and the jianghan and the subei south yellow sea basins to the south their spatial temporal framework is the consequence of the indosinian and yanshanian tectonic regimes in eastern china and record the events related to mesozoic deconstruction of the north china craton our results demonstrate that the mesozoic tectonic evolution of the eastern north china craton was related to both sub crustal delamination and intra crustal extrusion or escape tectonics thus we propose that the mechanism of uplift of the yanshanian north china plateau and related lithosphere thinning in the eastern north china craton were related to sub crustal delamination at depth however the different distribution patterns of the basins on both sides of the tan lu fault system as well as the co existence of both compressional and extensional basins in the mesozoic indicate that these were controlled by escape tectonics in different tectonic parts of the crust

cenozoic tectonic jumping and implications for hydrocarbon accumulation in basins in the east asia continental margin abstract tectonic migration is a common geological process of basin formation and evolution however little is known about tectonic migration in the western pacific margins this paper focuses on the representative cenozoic basins of east china and its surrounding seas in the western pacific domain to discuss the phenomenon of tectonic jumping in cenozoic basins based on structural data from the bohai bay basin the south yellow sea basin the east china sea shelf basin and the south china sea continental shelf basin the western pacific active continental margin is the eastern margin of a global convergent system involving the eurasian plate the pacific plate and the indian plate under the combined effects of the india eurasia collision and retrogressive or roll back subduction of the pacific plate the western pacific active continental margin had a wide basin arc trench system which migrated or jumped eastward and further oceanward this migration and jumping is characterized by progressive eastward younging of faulting sedimentation and subsidence within the basins owing to the tectonic migration the geological conditions associated with hydrocarbon and gashydrate accumulation in the cenozoic basins of east china and its adjacent seas also become progressively younger from west to east showing eastward younging in the generation time of reservoirs seals traps accumulations and preservation of hydrocarbon and gashydrate such a spatio temporal distribution of cenozoic hydrocarbon and gashydrate is significant for the oil gas and gashydrate exploration in the east asian continental margin finally this study discusses the mechanism of cenozoic intrabasinal and interbasinal tectonic migration in terms of interplate intraplate and underplating processes the migration or jumping regimes of three separate or interrelated events 1 tectonism magmatism 2 basin formation and 3 hydrocarbon gashydrate accumulation are the combined effects of the late mesozoic extrusion tectonics the cenozoic nw directed crustal extension and the regional far field eastward flow of the western asthenosphere due to the india eurasia plate collision accompanied by eastward jumping and roll back of subduction zones of the pacific plate

eddy driven buoyancy gradients on eastern boundaries and their role in the thermocline abstract it is demonstrated that eddy fluxes of buoyancy at the eastern and western boundaries maintain alongshore buoyancy gradients along the coast eddy fluxes arise near the eastern and western boundaries because on both coasts buoyancy gradients normal to the boundary are strong the eddy fluxes are accompanied by mean vertical flows that take place in narrow boundary layers next to the coast where the geostrophic constraint is broken these ageostrophic cells have a velocity component normal to the coast that balances the geostrophic mean velocity it is shown that the dynamics in these thin ageostrophic boundary layers can be replaced by effective boundary conditions for the interior flow relating the eddy flux of buoyancy at the seaward edge of the boundary layers to the buoyancy gradient along the coast these effective boundary conditions are applied to a model of the thermocline linearized around a mean stratification and a state of rest the linear model parameterizes the eddy fluxes of buoya

intraplate lithosphere deformation and the strength of the lithosphere summary the intraplate deformation of continental lithosphere in response to applied stress has been investigated using a mathematical model which incorporates the elastic ductile and brittle response of lithosphere material ductile deformation is assumed to be controlled in the crust by dislocation creep in quartz and in the mantle by dislocation creep and plasticity in olivine brittle failure is predicted using modified griffith theory a fundamental feature of the model is the redistribution of stress within the lithosphere following stress release by both ductile and brittle deformation this redistribution produces high levels of stress in the middle or lower crust immediately above the elastic ductile or brittle ductile transition lithosphere deformation is shown to be critically dependent on the temperature structure of which surface heat flow is a convenient indicator for higher geothermal gradients the release of stress in the lower lithosphere by ductile deformation is more rapid and complete and results in large stress levels in the upper lithosphere for sufficiently large applied stresses or steep geothermal gradients the stress levels in the upper and middle crust will cause complete fracture of the upper lithosphere whole lithosphere failure wlf then results by continued brittle and ductile deformation causing geologically significant strains the critical value of applied stress required to give wlf has been calculated for both tensional and compressional deformation as a function of surface heat flow the predicted lithosphere bulk strength is then compared with expected levels of intraplate stress arising from plate boundary forces and isostatically compensated loads which are thought to give net stress levels in the continental lithosphere in the range 0 25 to 0 25 kb using these expected maximum stress levels the model predicts significant extensional deformation in regions of moderate heat flow with q c 60mwm e g central europe as well as for areas of high heat flow like the basinand range province significant compressional deformation is predicted for areas of high heat flow with q c 75 mwm 2 but only for restricted conditions of stress combination these results are in good agreement with

are diamond bearing cretaceous kimberlites related to low angle subduction beneath western north america abstract diamond bearing cretaceous kimberlites of western north america were emplaced 1000 1500 km inboard of the farallon plate subduction margin and overlap with the development of the western interior seaway shut down of the sierra nevada arc and the laramide orogeny these events are consistent with a decrease in subduction angle along much of the margin which placed the subducted farallon plate in close proximity to the continental interior at the time of kimberlite magmatism our numerical models demonstrate that low angle subduction can result from high plate convergence velocities and enhanced westward motion of north america further rapid subduction allows hydrous minerals to remain stable within the cool interior of the subducting plate to more than 1200 km from the trench destabilization of these minerals provides a fluid source that can infiltrate the overlying material potentially triggering partial melting and kimberlite lamproite magmatism

reconstructing the meridional overturning circulation from boundary densities and the zonal wind stress numerical models are used to test whether the meridional overturning circulation moc can be reconstructed from boundary densities and the wind stress in idealized model setups without topography the strength as well as the temporal and spatial variability of the moc cell can largely be reproduced from boundary densities and the zonal wind stress with added slopes along the meridional boundaries most of the depth averaged flow is missed and neither strength nor spatial structure of the moc is well reproduced however the temporal evolution of both moc and its estimate are similar in an eddy permitting model with realistic bottom topography the contribution of the depth averaged meridional flow to the moc is captured at some places while it is missed at others nevertheless boundary densities and the zonal wind stress allow the leading modes of the temporal and spatial moc variability to be reproduced on seasonal time scales most of the moc variability is due to the wind stress but changes in the boundary density affect the moc as well on interannual time scales the moc variability largely reflects changes in the boundary density generally the moc reconstructions are accurate when bottom velocities are small an assumption made in the reconstruction approach the results are relevant for estimates of both the modern and the past moc in the real ocean boundary densities can be obtained from measurements of temperature conductivity and pressure in the water column whereas past seawater densities have left their imprint in sea sediments

equilibrium structure and dynamics of the california current system this paper addresses the structure and dynamical mechanisms of regional and mesoscale physical variability in the subtropical northeast pacific ocean using the regional oceanic modeling system roms the model is configured with a u s west coast domain that spans the california current system ccs with a mesoscale horizontal resolution up to as fine as 3 5 km its mean seasonal forcing is by momentum heat and water fluxes at the surface and adaptive nudging to gyre scale fields at the open water boundaries its equilibrium solutions show realistic mean and seasonal states and vigorous mesoscale eddies fronts and filaments the level of eddy kinetic energy eke in the model is comparable to drifter and altimeter estimates in the solutions with sufficiently fine resolution because the model lacks nonseasonal transient forcing the authors conclude that the dominant mesoscale variability in the ccs is intrinsic rather than transiently forced the primary eddy generation mechanism is the baroclinic instability of upwelling alongshore currents there is progressive movement of meanseasonal currents and eddy energy offshore and downward into the oceanic interior in an annually recurrent cycle the associated offshore eddy heat fluxes provide the principal balance against nearshore cooling by mean ekman transport and upwelling the currents are highly nonuniform along the coast with important influences by capes and ridges in both maintaining mean standing eddies and launching transient filaments and fronts

analog modeling of pull apart basins scaled sandbox models have successfully simulated the geometries and progressive evolution of pull apart basins developed in a weak sedimentary cover above right stepping releasing dextral strike slip fault systems in rigid basement synkinematic basin infill was added progressively as the models were deformed vertical and horizontal sectioning of the completed models has allowed the full three dimensional architecture of the pull apart system to be analyzed we present three representative end member experiments 30 underlapping releasing sidestep 90 sharp nonoverlapping releasing sidestep and 150 overlapping releasing sidestep the pull apart basin geometries are typically sigmoidal to rhombic grabens the geometries of which are dependent upon the architecture of the underlying basement fault systems underlapping releasing sidestepping faults offset angles of 30 75 typically form elongate rhomboidal grabens 90 releasing offset sidesteps produce shorter squat rhomboid pull apart basins and overlapping releasing sidesteps 115 150 produce box like grabens with highly kinked basin sidewalls the pull apart basins are bounded by terraced oblique slip extensional sidewall fault systems that link the laterally offset principal displacement zones pdz of the main dextral strike slip faults the sidewall faults show changes in kinematics from dominantly dip slip extension in copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received june 24 1996 revised manuscript received november 20 1996 final acceptance june 10 1997 2fault dynamics project geology department royal holloway university of london egham surrey tw20 oex united kingdom supported by the fault dynamics project sponsored by arco british limited petrobras u k ltd bp exploration conoco u k limited mobil north sea limited and sun oil britain we also acknowledge additional funding from sun oil britain landsat thematic mapper data courtesy of rtz mining and exploration limited south american division jurrian reijs is thanked for field data relating to the salina del fraile pull apart basin chris elders is thanked for reviewing earlier versions of this manuscript and j crowell c morley and k biddle are thanked for constructive reviews of the manuscript the contents of this paper have been

sandbox experiments on basin inversion testing the influence of basin orientation and basin fill analogue modelling experiments using brittle materials are performed to study the inversion of extensional structures asymmetric grabens of two different orientations are first created during a phase of extension and progressively filled they are subsequently shortened in the same direction the aim of our experiments is to determine factors affecting the style of deformation during inversion we specifically investigate variations in thickness and distribution of strong and weak layers constituting the graben fill and in initial basin orientation the main advantage of our experimental set up is that we have a complete control on graben location width infill and orientation before inversion the experiments show that shortening results only in limited reactivation of pre existing normal faults in general forward thrusts and backthrusts cut across normal faults into the footwall of the graben the forward thrusts either propagate parallel to the enveloping surface of faulted blocks or they cut across basin limiting normal faults at various angles the graben fill is mechanically extruded by displacement along forward thrusts that accommodate most of the shortening both pre existing faults and weak graben fill act as zones of weakness during inversion and determine the orientation and location of both backthrusts and forward thrusts the results of our experiments conform well to natural examples of inverted graben structures

cenozoic faulting of the bohai bay basin and its bearing on the destruction of the eastern north china craton abstract the cenozoic bohai bay basin is located at the center of the eastern block of the north china craton the structural architecture of this basin provides important clues on the deep seated lithosphere thinning of the north china craton the cenozoic regional stress field is characterized by nw oriented extension however the various cenozoic structural patterns of normal faulting and related transverse folding in the bohai bay basin are controlled not only by cenozoic stress field but also by strain field and mesozoic basement fault assemblages in this area regionally the cenozoic tectonic features and the dynamic evolution of the eastern north china craton are dominated by two lithosphere penetrating fault systems including the sinistral tan lu fault system and the dextral lan liao fault system to the west of the lan liao fault system cenozoic extensional tectonics includes nne trending listric normal faults that controlled half grabens however between these two fault systems are wnw trending half grabens which show basement involved faulting in the north and overlapping relations between sedimentary cover and basement in the south to the east of the tan lu fault the north yellow sea basin is a wnw trending fault depression with faulting in the south and overlapping relations in the north these structural features are inherited from the mesozoic tectonic framework of this area whose tectonic characteristics were completely controlled by two opposite strike slipping faults the trans extensional or oblique rifting in the paleogene followed by extensional faulting and subsequent subsidence furthermore the culmination of the decratonization of the north china craton was also related to an eastward jump of cenozoic subduction of the pacific plate and the far field effect of eastward extrusion of cenozoic subduction of the indian plate and was not essentially restricted to the early mesozoic processes therefore the cenozoic especially 25 ma marks the time of cessation of the processes that led to lithosphere thinning and destruction of the eastern block of the north china craton

cenozoic tectonic evolution of the east china sea shelf basin and its coupling relationships with the pacific plate subduction abstract the east china sea shelf basin is one of the mesozoic cenozoic basins located in the edge of eastern china continent whose formation and evolution are closely related to the subduction of the pacific plate however the underlying correlations between the tectonic evolution of the east china sea shelf basin and the pacific plate subduction 65 ma to present remain poorly understood in this paper the basin is divided into western and eastern depression groups to further study its tectonic evolution in combination with the characteristics of pacific plate subduction this paper performs a coupling analysis of the basin evolution regarding its migration direction and evolution rate the results of balanced section and deformation rate analyses reveal that the east china sea shelf basin experienced different regional activities during the cenozoic which could be summarized as four geologic periods and three tectonic evolution stages in this interpretation it is recognized that tectonic activity occurred in the western depression group and then shifted to depocenters of the eastern group in contrast the pacific plate subducted westwards beneath the eurasian plate over the same geologic time span surprisingly a slightly negative correlation between the intensity of the tectonic deformation of the east china sea shelf basin and the subduction rate of the pacific plate is demonstrated when the subduction rate is no more than 75 mm a however the basin deformation intensity increases with the plate subduction rate after 75 mm a the results of this work have implications for explaining the major role that the subduction of the pacific plate played in the formation and evolution of the eastern china basins

evaluating the role of syn thrusting sedimentation and interaction with frictional detachment in the structural evolution of the sw tarim basin nw china insights from analogue modeling abstract the structural evolution of the fold and thrust belt in sw tarim basin nw china is poorly understood as the region is covered by thick pliocene quaternary conglomerate which significantly decreases the quality of seismic images we here improve the understanding of the thrust belt evolution with an investigation using analogue modeling on the deformation mechanism based on a case of real geological section in which we focus on the impact of syn thrusting sedimentation on the structural style and evolution the results show that syn thrusting sedimentation significantly increases the distance and rate of foreland propagation resulting in a much broader fold and thrust belt the modeling results also suggest that the fold and thrust belt exhibits different structural patterns under different syn thrusting sedimentary conditions in the case of thick syn thrusting sediments a frictional detachment layer of mudstone acts as decollement and the fold and thrust belt develops a duplex pattern in the hinterland in the case of thin syn thrusting deposits the belt develops a pop up structure with backthrusts in the foreland region which cut through the detachment layer the striking similarity between the model with thick syn thrusting sediments and the real geologic section implies that the overlying thick pliocene quaternary sediments play a major role in shaping the structure pattern in the fold and thrust belt of sw tarim basin

the effect of cover composition on extensional faulting above re activated basement faults results from analogue modelling abstract analogue models were used to investigate differences in deformation between sedimentary cover sequences of contrasting composition above reactivated basement faults during extension two types of model arrangements were used the first represented clastic sediments directly overlying faulted basement and the second represented a basal ductile layer in an overburden overlying the same faulted basement the basement configuration consisted of faults both oblique and orthogonal to the bulk extension direction particular attention was paid to the resulting map view fault patterns in experiments without a basal ductile layer in the overburden grabens only developed in areas directly above basement faults in section cover faults above oblique basement faults curved in profile and in places exhibited reverse movement at shallow depth in experiments involving a ductile layer at the base of the overburden faults developed oblique to both the bulk extension direction and the basement faults the resulting fault pattern was influenced by both bulk extension and basement fault reactivation the results indicate that cover sequences that include thick basal ductile layers above reactivated basement faults are more likely to develop faults with strikes perpendicular to the regional extension direction compared to those without faulting in an overburden lacking a basal ductile sequence is more likely to be directly influenced by the underlying reactivated basement faults

analogue modelling and mechanism of tectonic inversion of the xihu sag east china sea shelf basin abstract the east china sea shelf basin lies between the pacific subduction and indian eurasian collision tectonic domains and records cenozoic tectonic inversion especially in the xihu sag to improve the understanding of the evolution and mechanism of tectonic inversion this paper employs analogue modelling to reproduce the evolutionary process combined with the structural analysis of seismic profile this paper determines the pattern of basement involved faults simulation results show that under the transtension two subsidence centers developed and a number of normal faults assembled in two flower structures when the stress field turned into transpression the geometry and deformation of inversion basin inherited the previous transtensional basin and pre existing faults respectively the geometry and fault patterns in models are well consistent with those observed in the xihu sag which indicates the plausibility of similar deformation controls the formation of the tectonic inversion is related to the variation in stress field caused by the changes in the rates and directions of the subduction of the pacific plate and the collision of the indian plate with eurasian plate

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

sedimentary basin inversion and intra plate shortening abstract sedimentary basin inversion the shortening of formerly extensional basins is accommodated mainly by compressional reactivation of extant faults and fractures across a wide range of scales as such inversion is a large scale manifestation of byerlee friction the dynamic criterion for fault reactivation governing the effective shear strength of the shallow crust basin inversion generates distinctive deformational architecture and it is implicated strongly in sedimentary basin exhumation as a principal source of horizontal stress inversion drives significant sedimentary porosity reduction and resultant fluid flow upper crustal deformation is critically dependent on fluid overpressure i e pore fluid pressures greater than would be calculated from a hydrostatic gradient and perhaps more than in any other tectonic setting overpressures are potentially large during sedimentary basin inversion this review therefore includes discussion of the role of fluid overpressure in inversion and the evidence for it collectively inversion has profound implications good and bad for the prospectivity of many petroliferous sedimentary basins thus recognizing the evidence for basin inversion quantifying its magnitude and understanding the mechanisms that accommodate inversion and other phenomena affected by it have become essential components of the basin analyst s remit

the influence of pre existing thrust faults on normal fault geometry in nature and in experiments relations between normal faults and pre existing thrust faults are classically described in terms of three basic situations normal faults can cross cut thrust faults they can branch out from thrust faults at depth on a de collement level or they can entirely reactivate thrust planes the mechanical aspects of these types of interaction were studied by analogue modelling in which sand simulates the brittle rocks and silicone putty an interlayered de collement the models underwent compression producing thrust faults with variable dips followed by extension three possible ways of interaction are described here a no interaction occurs in the case of low dip thrust faults 32 1 and normal faults are developed independently displaying a listric geometry b branching at depth on the de collement level occurs when dip of the thrust faults reaches 32 1 in this case the dip of the normal faults whose geometry becomes planar decreases with increasing thrust dip we suggest that this change in dip of normal faults depends upon the rotation of stress tensor axes along the pre existing fault zone where a drop in the friction coefficient is likely to occur c reactivation occurs in brittle material when dip of the pre existing fault exceeds 41 1

paleogeography reconstruction of a multi stage modified intra cratonic basin a case study from the jurassic ordos basin western north china craton abstract post depositional modification is commonly found in sedimentary basins particularly in the eastern tethys tectonic domain and is related to special geological settings and evolution processes of the region the chinese continent is composed of numerous small scale blocks that underwent intensive tectonic movements paleogeography reconstruction for a modified basin is fundamental for objectively understanding the basin dynamics and exploration of hydrocarbon sandstone type uranium deposits and other mineral resources as a large scale intra cratonic depression basin in the western part of the north china craton ncc the mesozoic ordos basin underwent multi stage modification as a result only the western part was preserved in this study the paleogeography in bathonian oxfordian ages of the jurassic was reconstructed via integrated approaches including stratigraphic correlation sedimentary facies analysis provenance analysis and fission track analysis the original sedimentary boundary of the ordos basin during this period is approximately outlined we determine that the northern and southern borders reach the cenozoic hetao basin and the cenozoic weihe basin respectively and that the eastern northwestern and southwestern borders lie to the west of taihang mountain at the langshan bayanhot basin kexueshan and to the west of liupan mountain respectively the original sedimentary extent of the ordos basin was almost twice that of the present day residual basin the evolution of this basin in the mesozoic recorded the evolution and destruction processes of the ncc the ncc shows that n s and w e trending compressional setting occurred during the triassic and the jurassic respectively the interactive activities of adjacent tectonic domains played a critical role in subsidence dynamics for the intra cratonic ordos basin this study provides further insights for exploration of hydrocarbon and sandstone type uranium deposits in the ordos basin

seasonal overturning circulation in the red sea 2 winter circulation author posting 0american geophysical union 2014 this article is posted here by permission of american geophysical union for personal use not for redistribution the definitive version was published in journal of geophysical research oceans 119 2014 2263 2289 doi 10 1002 2013jc009331

mesoscale eddy buoyancy flux and eddy induced circulation in eastern boundary currents abstracta dynamical interpretation is made of the mesoscale eddy buoyancy fluxes in the eastern boundary currents off california and peru chile based on regional equilibrium simulations the eddy fluxes are primarily shoreward and upward across a swath several hundred kilometers wide in the upper ocean as such they serve to balance mean offshore air sea heating and coastal upwelling in the stratified interior the eddy fluxes are consistent with the adiabatic hypothesis associated with a mean eddy induced velocity advecting mean buoyancy and tracers furthermore with a suitable gauge choice the horizontal fluxes are almost entirely aligned with the mean horizontal buoyancy gradient consistent with the advective parameterization scheme of gent and mcwilliams the associated diffusivity is surface intensified matching the vertical stratification profile the fluxes span the across shore band of high eddy energy but their alongshore structure is unresolved because of sampling limitations in the sur

basin inversion and contractional reactivation of inherited normal faults a review based on previous and new experimental models abstract compressional inversion of former extensional sedimentary basins is a particularly common phenomenon given that passive margins share the same destiny of being subsequently incorporated into fold and thrust belts during basin inversion pre existing faults may concentrate stress and localise future thrust ramps or may be reactivated recording reversal of movement from extension to reverse this process has attracted attention largely because of its economic implications related to petroleum and ore deposit prospects and seismic hazard assessment since more than two decades analogue modelling has been used to indentify and or test a number of parameters relevant for the inversion process this paper aims therefore to offer a reasoned review of the analogue modelling work done on the subject coupling such previous results with those of a new experimental series inspired to the northern apennines stratigraphy and evolution past models have explored the role of main factors governing fault reactivation susceptibility such as fluid pressure fault weakness fault steepness angle of shortening and sediment loading the new models have addressed the role played by geometry and strength of a basal ductile layer during inversion two sets of sand silicone models were first extended orthogonally at different velocities to produce dissimilar pre inversion internal geometries and then shortened coaxially at different velocities to vary the brittle ductile coupling the experimental results confirm the selectiveness of fault inversion and reveal strong similarities with structural styles of tectonic inversion reported from the northern apennines and various areas worldwide the preferred geological model inferred from this modelling involves contribution of 1 syn inversion rotation of pre existing faults to shallower dip and 2 rotation of principal stress axes which could explain the invariable reactivation of only one of the two oppositely dipping graben bounding faults these factors would thus interact with the other well established parameters controlling the fault reactivation process

basin inversion and fault reactivation in laboratory experiments abstract a series of analogue models have been performed to get insights into the relationships between the reactivation of pre existing normal faults and the orientation of a successive compressive stress field the models were deformed in two phases 1 a first extension phase h 3 generating a graben and 2 a successive compressive phase with the orientation of the shortening direction h 1 trending between 0 and 90 obliquity angle to the faults bounding the graben the deepening of this graben was accompanied by syn tectonic sedimentation that included a basal ductile layer simulating salt in nature overlain by a brittle sand pack the experimental results suggest that the development of compressive structures is strongly controlled by the pre existing normal faults and by the obliquity angle the experiments have invariably shown that the extensional faults were reactivated during shortening whatever the value of the angle whereas strike slip reactivation of major normal faults is favoured by low obliquity angles mostly dip slip reactivation of pre existing structures is instead promoted for high obliquity angles the analysis of model results highlights the important role played by a ductile layer at the base of the basin fill and the obliquity angle in controlling both strain partitioning and brittle ductile decoupling

strength of two phase rocks a model based on fiber loading theory abstract in order to predict the strength of two phase rocks in terms of the component volume fraction the aspect ratio of the strong phase and the strength contrast between the strong and weak phases a simple model is developed according to a fiber loading theory modified for short fiber composites the analytical solution derived from elastic theory is found to hold in good approximation for rocks consisting of power law viscous minerals there is a good agreement between the predicted results and the experiments for two phase aggregates anhydrite halite calcite halite fe ag and clinopyroxene plagioclase the model is compared with several previous different models

oblique half graben inversion of the mesozoic neuquen rift in the malargue fold and thrust belt mendoza argentina new insights from analogue models abstract the malargue fold and thrust belt located in the andean mountains between 34 s and 36 30 s formed in response to contraction during cenozoic times its structural style and geometry was controlled by the mesozoic rift system that formed the neuquen basin in west central argentina the rift architecture in the southern sector of this belt was previously interpreted in terms of the present n s compressive structural trends assuming the inversion of pre existing normal faults with the same orientation here we propose that the nw se trending el manzano liu cullin lineament located in the northern termination of the sierra azul reflects the presence of a half graben master fault in the subsurface this hypothesis is supported by subsurface data a balanced cross section and it is tested using a series of scaled sandbox analogue models we suggest that the lineament responds to a reactivated nw trending half graben fault hidden by the mainly n s trending andean structures the proposed orientation is in agreement with the ne sw extension developed in the neuquen basin during the triassic early jurassic the modeling of the inverted oblique half graben reveals that the strikes of the main structures of inversion related belts may often be independent of the orientation of the previously developed extensional system providing a new perspective for their interpretation

boundary mixing and the dynamics of three dimensional thermohaline circulations boundary mixing is implemented in an ocean general circulation model such that the vertical mixing coefficient ky is nonzero only near side boundaries and in convection regions the model is used in a highly idealized configuration with no wind forcing and very nearly fixed surface density to investigate the three dimensional dynamics of the thermohaline circulation for ky 5 20 3 1024 m2 s21 and lower the meridional overturning strength to great accuracy is proportional to meridional heat transport is proportional to the circulation 2 3 1 2 kk y y patterns resemble those from runs with uniform vertical mixing but vertical motion is entirely confined to the boundary regions near the western boundary there is upwelling everywhere near the eastern boundary there is a consistent pattern of downwelling above upwelling with downwelling reaching deeper at high latitudes this pattern is explained by convection and vertical advective diffusive balance underneath for ky 5 30 3 1024 m2 s21 and higher no steady solutions have been found the meridional overturning oscillates on a timescale of about 25 years a time averaged thermally direct overturning cell is not supported dynamically because convection extends longitudinally across the entire basin and upwelling near the western boundary does not lead to densities higher than at the eastern boundary assuming uniform upwelling in the west level isopycnals near the equator and level isopycnals along the eastern boundary south of the outcropping latitude permits the analytic determination of convection depth at the eastern wall and hence the density difference between the eastern and western walls this difference is at most one quarter the surface density difference between high and low latitudes and agrees in magnitude and latitudinal dependence with the numerical experiments scaling arguments estimate overturning strength as of the order of 10 3 106 m3 s21 and confirm the 2 3 power dependence onky the derivation also gives a dependence of overturning strength with latitude that agrees qualitatively with the numerical results the scaling for the dependence of meridional heat transport on latitude agrees well with the model results scaling for heat transport amplitude agrees less well but correctly predicts a weaker dependence on ky than maximum overturning

mesozoic cenozoic basin inversion and geodynamics in east china a review abstract east china experienced alternating tectonic extension and compression with ambiguous tectonic settings in the mesozoic cenozoic interval long term extensional episodes associated with the subduction retreat of the paleo pacific and pacific slabs have been widely studied the compressional events of which basin inversion is a typical case are less concerned but important in understanding the tectonic evolution and geodynamics in east china we made a systematic study involving tectonics sedimentation apatite fission track and dynamic topography on the mesozoic cenozoic basin inversion in east china four phases of basin inversion were concluded 1 early late cretaceous inversion occurred at 115 100 ma in southeast china and at 100 89 ma in northeast china showing a northward migration due to the diachronous collision of the northward moving okhotomorsk block with east asia 2 the latest cretaceous early paleogene inversion was widely developed throughout east china it is associated with the increasingly younger subducted oceanic crust of the izanagi plate which caused the progressively increasing buoyancy beneath east china and an uplift in dynamic topography cenozoic inversion showed an eastward migration from 3 the western part of each basin at the late paleogene to 4 the eastern part at the neogene due to the subduction retreat of the pacific plate