validating novel boundary conditions for three dimensional mechanics based restoration an extensional sandbox model example geomechanical restoration methods are dependent on boundary conditions to ensure geological consistency of the restored model in terms of geometry and strain classical restoration boundary conditions such as flattening a datum horizon may lead to inconsistent displacement and strain fields we restore a laboratory structural sandbox model with known deformation history to develop guidelines for definition of boundary conditions that produce improved results from geomechanical restorations the sandbox model has a basal silicone layer includes synkinematic deposition and is characterized by structures analogous to those found in suprasalt extensional environments the deformed geometry is interpreted from three dimensional tomography imaging and a time series of cross section tomography images provides a benchmark to quantify restoration error and inform boundary conditions we confirm that imposing a lateral displacement equal and opposite to far field tectonic shortening or extension provides a more accurate restoration however the amount of displacement may not be known in real cases we therefore test several established methods using only the unrestored geometries to assess the amount of shortening that should be used to guide geomechanical restorations an accurate estimation is provided by the area depth method and potentially by a dilatation analysis additionally novel fault compliance boundary conditions produce improved results in the vicinity of crossing and branching faults application of similar methods should produce improved restoration of natural geologic structures

locating and quantifying geological uncertainty in three dimensional models analysis of the gippsland basin southeastern australia abstract geological three dimensional 3d models are constructed to reliably represent a given geological target the reliability of a model is heavily dependent on the input data and is sensitive to uncertainty this study examines the uncertainty introduced by geological orientation data by producing a suite of implicit 3d models generated from orientation measurements subjected to uncertainty simulations the resulting uncertainty associated with different regions of the geological model can be located quantified and visualised providing a useful method to assess model reliability the method is tested on a natural geological setting in the gippsland basin southeastern australia where modelled geological surfaces are assessed for uncertainty the concept of stratigraphic variability is introduced and analysis of the input data is performed using two uncertainty visualisation methods uncertainty visualisation through stratigraphic variability is designed to convey the complex concept of 3d model uncertainty to the geoscientist in an effective manner uncertainty analysis determined that additional seismic information provides an effective means of constraining modelled geology and reducing uncertainty in regions proximal to the seismic sections improvements to the reliability of high uncertainty regions achieved using information gathered from uncertainty visualisations are quantified in a comparative case study uncertainty in specific model locations is identified and attributed to possible disagreements between seismic and isopach data further improvements to and additional sources of data for the model are proposed based on this information finally a method of introducing stratigraphic variability values as geological constraints for geophysical inversion is presented

uncertainty estimation for a geological model of the sandstone greenstone belt western australia insights from integrated geological and geophysical inversion in a bayesian inference framework

working in complex areas new restoration workflow based on quality control 2d and 3d restorations when working in complex areas the explorationist needs to construct 3d models and to check their coherency coherence can be analyzed on the current geometry but could also be quantified through restoration to achieve this restoration i e the search for an initial geometry with a realistic deformation pathway between the initial and the final geometries appropriate tools are necessary these include classical cross section balancing surface unfolding and volumetric restoration in this paper we will describe a workflow to do quantitative structural geology in complex areas this includes the construction and quality control of the surfacic model the line balancing the cross section surface and multi surface restoration and the volumic restoration in addition to the quality control of the geometries the restoration allows us to compute strain tensors this can be done in the three types of restoration and visualized through ellipses and ellipsoids resp 2d and 3d that represent the main strain or stress vectors we shall discuss the relationship between these strain tensors and the expected fracture network in density as in direction

three dimensional model and late stage warping of the plattengneis shear zone in the eastern alps abstract the plattengneis shear zone is a 250 600 m thick flat lying cretaceous eclogite facies mylonitic shear zone with north over south transport direction that is exposed over almost 1000 km2 in the koralpe region along the eastern margin of the alps although the shear zone is one of the largest in the alps its role in the eoalpine metamorphic evolution and the subsequent exhumation of the region remain enigmatic and its large scale geometry is not well understood the outcrop pattern suggests that the shear zone is made up of a single sheet that is folded into a series of open syn and antiforms with wavelengths of about 10 km eclogite bodies occur above within and below the shear zone and there is no metamorphic grade change across the shear zone in the south the fold axes strike east west and plunge shallowly to the east in the north the fold axes are oriented in north south direction and form a dome shaped structure of the shear zone total shortening during this late stage warping event was of the order of 5 indirect evidence constrains this folding event to have occurred between 80 and 50 ma and the fold geometry implies that the final exhumation in the koralpe occurred somewhat later than further north interestingly the shear zone appears to strike out of the topography in the south and dip into the topography in the north so that north of the shear zone only hanging wall rocks are exposed and south of it only foot wall rocks possibilities for the geometric relationship of the plattengneis shear zone with the surrounding south dipping detachments are discussed

geological modelling from field data and geological knowledge part ii modelling validation using gravity and magnetic data inversion the analysis of multiple data sets is required to select a realistic 3d geological model among an infinite number of possibilities an inverse method that aims at describing the 3d geometry of geological objects is presented the method takes into account the geology and the physical properties of rocks while respecting the topological properties of an a priori model the a priori model is built from the geological data set and its geometry is largely dependent upon assumptions about inaccessible geology at depth this method referred to as total litho inversion is a generalized 3d inversion that results in quantifying the lithology and the distribution of rock property in a probabilistic way its application is demonstrated through i a simple synthetic case and ii the relative distribution characterization of granites and diorites in an orogenic domain

method and analysis for the upscaling of structural data abstract 3d geological models are created to integrate a set of input measurements into a single geological model there are many problems with this approach as there is uncertainty in all stages of the modelling process from initial data collection to the approach used in the modelling scheme itself to calculate the geological model this study looks at the uncertainty inherent in geological models due to data density and introduces a novel method to upscale geological data that optimises the information in the initial dataset this method also provides the ability for the dominant trend of a geological dataset to be determined at different scales by using self organizing maps som s to examine the different metrics used to quantify a geological model we allow for a larger range of metrics to be used compared to traditional statistical methods due to the som s ability to deal with incomplete datasets the classification of the models into clusters based on the geological metrics using k means clustering provides a useful insight into the models that are most similar and models that are statistical outliers our approach is guided and can be calculated on any input dataset of this type to determine the effect that data density will have on a resultant model these models are all statistical derivations that represent simplifications and different scales of the initial dataset and can be used to interrogate the scale of observations

quantifying stratigraphic uncertainties by stochastic simulation techniques based on markov random field abstract stratigraphic or lithological uncertainty refers to the uncertainty of boundaries between different soil layers and lithological units which has received increasing attention in geotechnical engineering in this paper an effective stochastic geological modeling framework is proposed based on markov random field theory which is conditional on site investigation data such as observations of soil types from ground surface borehole logs and strata orientation from geophysical tests the proposed modeling method is capable of accounting for the inherent heterogeneous and anisotropic characteristics of geological structure in this method two modeling approaches are introduced to simulate subsurface geological structures to accommodate different confidence levels on geological structure type i e layered vs others the sensitivity analysis for two modeling approaches is conducted to reveal the influence of mesh density and the model parameter on the simulation results illustrative examples using borehole data are presented to elucidate the ability to quantify the geological structure uncertainty furthermore the applicability of two modeling approaches and the behavior of the proposed model under different model parameters are discussed in detail finally bayesian inferential framework is introduced to allow for the estimation of the posterior distribution of model parameter when additional or subsequent borehole information becomes available practical guidance of using the proposed stochastic geological modeling technique for engineering practice is given

structural data constraints for implicit modeling of folds a recent method for modeling folds uses a fold frame with coordinates based on the structural geology of folds fold axis direction fold axial surface and extension direction the fold geometry can be characterised by rotating the fold frame by the pitch of the fold axis in the axial surface and the angle between the folded foliation and the axial surface these rotation angles can be expressed as 1d functions of the fold frame coordinates in this contribution we present methods for extracting and automatically modeling the fold geometries from structural data the fold rotation angles used for characterising the fold geometry can be calculated locally from structural observations the fold rotation angles incorporate the structural geology of the fold and allow for individual structural measurements to be viewed in the context of the folded structure to filter out the effects of later folding the fold rotation angles are plotted against the coordinates of the fold frame using these plots the geometry of the folds can be interpolated directly from structural data where we use a combination of radial basis function and harmonic analysis to interpolate and extrapolate the fold geometry this contribution addresses a major limitation in existing methods where the fold geometry was not constrained from structural data we present two case studies a proof of concept synthetic model of a non cylindrical fold and an outcrop of an asymmetrical fold within the lachlan fold belt at cape conran victoria australia

integrated 3d geophysical and geological modelling of the hercynian suture zone in the champtoceaux area south brittany france this paper combines geological knowledge and geophysical imagery at the crustal scale to model the 3d geometry of a segment of the hercynian suture zone of western europe in the champtoceaux area brittany france the champtoceaux complex consists of a stack of metamorphic nappes of gneisses and micaschists with eclogite bearing units the exhumation of the complex during early carboniferous times was accompanied by deformation during regional dextral strike slip associated with a major hercynian shear zone the south armorican shear zone sasz dextral shearing produced a km scale antiformal structure with a steeply dipping axial plane and a steeply eastward plunging axis armor 2 deep seismic profile shows that the regional structure was cut by a set of faults with northward thrusting components based on the seismic constraint direct 2d crustal scale modelling was performed throughout the champtoceaux fold on seven radial gravity profiles also using geological data and density measurements from field and drill hole samples the 3d integration of the cross sections the digitised geological map and the structural information foliation dips insure the geometrical and topological consistency of all sources of data the 2d information is interpolated to the whole 3d space using a geostatistical analysis finally the 3d gravity contribution of the resulting model is computed taking into account densities for each modelled geological body and compared to the bouguer anomaly the final 3d model is thus compatible with the seismic and gravity data as well as with geological data main geological results derived from the modelling are i the overall 3d geometry of the south dipping thrust system interpreted on the seismic profile emphasises northward thrusting and folding of the champtoceaux complex which was coeval with strike slip along the south armorican shear zone ii the gravity modelling suggests the presence of a relatively dense body below the champtoceaux complex that could be interpreted as a result of relative uplift of midcrustal material during thrusting along the e w trending wrench thrust system iii the northern limb of the champtoceaux anticline is a relatively shallow feature and iv vigneux synkinematic granitic body is a laccolith sheared and rooted along the southern branch of the sasz and spreads away from the strike slip zone within weak country rocks d 2004 elsevier b v all rights reserved

ore shoots in folded and fractured rocks insights from 3d modelling of the fosterville gold deposit victoria australia abstract at the fosterville gold deposit high concentrations of visible and refractory gold are hosted in arrays of quartz and quartz carbonate veins they are distributed in elongate zones to form south plunging ore shoots within a folded and fractured turbidite sequence here we distinguish the influence of faults versus folds at fosterville by assessing the deposit scale structural framework and hydrothermal fluid flow using a combination of 3d implicit modelling structural analysis and 3d fault slip dilation tendency analyses gold assay and bedding trend data from a large drillhole dataset were spatially interpolated and used to analyse and measure the orientation of ore bodies and folded host rocks field measurements of fold axis orientations were compared to bedding measurements in oriented drillcore bingham axial analysis of bedding trends and orientation data from a 3d implicit model both field and drill core structural data show that ore shoots at fosterville do not parallel the first order gently 10 south plunging folds instead the orientation of the ore shoots is coincident with an intersection lineation between steeply west dipping bedding parallel faults and moderately dipping linkage faults that obliquely cut across the main structural grain resulting in ore shoot plunges larger than 20 slip and dilation tendencies suggest that linkage faults had a higher likelihood of activity in the inferred far field stress regimes at the time of mineralisation relative to other structures at fosterville these linkage faults are therefore interpreted to have been preferential fluid flux conduits in the system despite appearing to be subordinate structures at the scale of the deposit this new structural model for fosterville highlights that fluid flow and ore shoot formation are strongly controlled by obliquely oriented structures that are unlike the main structural grain of first order folds and faults

uncertainty reduction through geologically conditioned petrophysical constraints in joint inversion abstractwe have developed a joint geophysical inversion workflow that aims to improve subsurface imaging and decrease uncertainty by integrating petrophysical constraints and geologic data in this framework probabilistic geologic modeling is used as a source of information to condition the petrophysical constraints spatially and to derive starting models the workflow then uses petrophysical measurements to constrain the values retrieved by geophysical joint inversion the different sources of constraints are integrated into a least squares framework to capture and integrate information related to geophysical petrophysical and geologic data this allows us to quantify the posterior state of knowledge and to calculate posterior statistical indicators to test this workflow using geologic field data we have generated a set of geologic models which we used to derive a probabilistic geologic model in this synthetic case study we found that the integration of geologic information and petrophysical con

a 3d geological model for the ruiz tolima volcanic massif colombia assessment of geological uncertainty using a stochastic approach based on bezier curve design abstract the ruiz tolima volcanic massif rtvm is an active volcanic complex in the northern andes and understanding its geological structure is critical for hazard mitigation and guiding future geothermal exploration however the sparsity of data available to constrain the interpretation of this volcanic system hinders the application of standard 3d modelling techniques furthermore some features related to the volcanic system are not entirely understood such as the connectivity between the plutons present in its basement i e manizales stock el bosque batholith we have developed a methodology where two independent working hypotheses were formulated and modelled independently i e a case where both plutons constitute distinct bodies and an alternative case where they form one single batholith a monte carlo approach was used to characterise the geological uncertainty in each case bezier curve design was used to represent geological contacts on input cross sections systematic variations in the control points of these curves allows us to generate multiple realisations of geological interfaces resulting in stochastic models that were grouped into suites used to apply quantitative estimators of uncertainty this process results in a geological representation based on fuzzy logic and in maps of model uncertainty distribution the results are consistent with expected regions of high uncertainty near under constrained geological contacts while the non unique nature of the conceptual model indicates that the dominant source of uncertainty in the area is the nature of the batholith structure

stochastic fracture generation accounting for the stratification orientation in a folded environment based on an implicit geological model article i nfo this paper presents a new approach in generating stochastic discrete fracture networks the particularity of the approach isthatitallows us tosimulate thetheoreticalfamiliesoffractures thatare expected ina foldedenviron ment the approach produces fractures that are consistent with the local stratigraphic orientation the fractures are modeled as simplerectangular planarobjects whenthey are modeled they arerotatedaccordingtothe local stratigraphic orientation as the stratigraphy is modeled using an implicit approach we use the gradient of this geological potential field to retrieve the information about the geological orientation the fracture number and size are following user defined probability density functions 2015 elsevier b v all rights reserved

geodiversity exploration of 3d geological model space abstract the process of building a 3d model necessitates the reconciliation of field observations geophysical interpretation geological data uncertainty and the prevailing tectonic evolution hypotheses and interpretations uncertainty is compounded when clustered data points collected at local scales are statistically upscaled to one or two points for use in regional models interpretation is required to interpolate between sparse field data points using ambiguous geophysical data in covered terranes it becomes clear that multiple interpretations are possible during model construction the various interpretations are considered as potential natural representatives but pragmatism typically dictates that just a single interpretation is offered by the modelling process uncertainties are introduced into the 3d model during construction from a variety of sources and through data set optimisation that produces a single model practices such as these are likely to result in a model that does not adequately represent the target geology a set of geometrical geodiversity metrics are used to analyse a 3d model of the gippsland basin southeastern australia after perturbing geological input data via uncertainty simulation the resulting sets of perturbed geological observations are used to calculate a suite of geological 3d models that display a range of geological architectures the concept of biodiversity has been adapted for the geosciences to quantify geometric variability or geodiversity between models in order to understand the effect uncertainty has models geometry various geometrical relationships depth volume contact surface area curvature and geological complexity are used to describe the range of possibilities exhibited throughout the model suite end member models geodiversity metrics are classified in a similar manner to taxonomic descriptions further analysis of the model suite is performed using principal component analysis pca to determine important geometrical characteristics the configuration of the model space is determined through identifying outlier model examples which potentially represent undiscovered model species

structure of reunion island indian ocean inferred from the interpretation of gravity anomalies abstract reunion is a volcanic edifice whose origin is related to a hot spot in the indian ocean only 3 of its volume is emergent many geological and geophysical studies were carried out on reunion island during the 1980 s but few of them allow study of the internal structure of the edifice several gravity surveys have been carried out on the island since 1976 and we have compiled the available data set the lack of data on the western side of the island led us to conduct a regional survey in 1993 to obtain a more homogeneous distribution of the stations computation of bouguer anomalies for different correction densities accounts for the variable density of the rocks constituting the edifice and provides a distribution of gravity anomalies interpreted as dense bodies of intrusive rocks inside the edifice two very large intrusive complexes can be unambiguously recognised one beneath piton des neiges and one beneath the grand brule area both have been penetrated by geothermal exploration drill holes and the first is also known from outcrop observations 2 5d simple models were constructed to reveal the geometry and extent of the buried intrusives they are deeply rooted extending several kilometres below sea level and extensive 20 25 km long and 10 13 km wide for the piton des neiges complex 12 15 km long and some kilometres wide for the grand brule complex the development of such complexes implies that the activity of the two volcanic centres was long lasting and remained stable while the volcanoes were growing the grand brule complex has been interpreted as relics of an old volcano named alizes volcano the interpretation of the gravity maps suggests the presence of a ridge of dense rocks to the north of the axis joining the centres of piton des neiges and piton de la fournaise volcanoes by analogy with the other structures 2 5d models show that this structure would culminate between 0 and 1 km below sea level and be 15 km wide this complex induces a maximum anomaly in takamaka valley and we thus propose to name it takamaka volcano no geological evidence of the nature of these dense rocks is available but the ridge coincides with structures revealed by magnetic and seismic data interpretation of the bouguer anomaly maps suggests that the inner gravity structure of piton de la fournaise is not characterised by the presence of a voluminous dense body but probably by more restricted concentrations of dense rocks some structures can be recognised along the present ne and se rift zones and in the previous central part of piton de la fournaise to the west of the present summit the recent eastward migration of the centre of activity of piton de la fournaise accounts for the lack of a large positive anomaly beneath the active craters

gravity modellings of the cadomian active margin of northern brittany abstract the geometrical relationships existing between the saint brieuc saint malo and guingamp units which form the cadomian active margin of northern brittany have been determined by gravity analyses and 2 5d modelling correlated with other geophysical magnetic seismic etc and geological observations automatic structural analyses were performed before modelling to identify lateral gravity discontinuities averaged density measurements were used for 2 5d gravity modelling along six profiles across the arcuate geological and gravity shape of the cadomian basement this study allowed the third dimension to be obtained through correlating each profile with its neighbours we propose that orthogneiss formations equivalent to the port morvan orthogneiss constitute the saint brieuc upper crustal unit below the lanvollon formation 2 5d gravity modelling outlines downward geological differences in the western and eastern parts of the ploufragan complex as previously indicated by surface mapping these results stress the necessity for distinguishing between the guingamp and saint malo units

stratigraphy and volcanic facies architecture of the torres syncline southern brazil and its role in understanding the parana etendeka continental flood basalt province abstract the torres syncline is a large structure that constitutes the eastmost outcrop of the parana etendeka cfb in south american side and this work focuses the stratigraphy and facies architecture of the volcanic pile in the syncline the volcanic sequence along the study area permits the division of three regions main valley intermediate zone and south hinge each of them with distinct stratigraphy which probably reflects the structural evolution of the syncline the stratigraphy of the torres syncline is composed by 1 botucatu palaeoerg 2 basic volcanic episode i 3 basic volcanic episode ii 4 acidic volcanic i 5 basic volcanic episode iii and 6 acidic volcanic episode ii the five volcanic episodes recognized in study area can be related to five volcanic facies architecture compound braided tabular classic tabular lobate escoriaceous dome field acidic lavas and tabular flows acidic lavas the basic episode i is composed by pahoehoe flows with a compound braided facies architecture that covered the botucatu palaeoerg the basic episode ii is a tabular classic facies architecture predominantly composed by simple flows 10 20 m thick reaching the total thickness of 500 m in main valley the acidic episode i is exposed in main valley and south hinge and is composed by acidic lavas forming lava dome field facies architecture with a thickness of 150 m the basic episode iii is predominantly constituted by a flows with tabular lobate escoriaceous facies architecture the acidic episode ii is constituted by tabular flow volcanic facies acidic flows and outcrops all along the study area the torres syncline constitute the eastmost on shore exposures of the parana etendeka cfb in south american side and detailed stratigraphic volcanological and structural studies in these area coupled with correlation with huab basin nw namibia africa will aim the understanding of the gondwana breakup process and the early stages of the south atlantic margin opening

building 3d solid models of sedimentary stratigraphic systems from borehole data an automatic method and case studies abstract 3d solid models of geological structures are particularly useful to practical geological analysis and engineering design the main difficulty raised by 3d geological modeling of sedimentary system is determining the geological genesis and geometrical boundaries of missing strata for the lack of the comprehensive mechanism to handle missing strata it is difficult to construct spatial geometric shapes of complicated strata with a desired accuracy in 3d utilizing the existing modeling methods this situation limits the reliability and the practicality of the computer models in order to construct the discontinuous geological surfaces induced by missing strata an adapted and automatic approach for generating 3d solid models of sedimentary stratigraphic systems from borehole data called the borehole surface solid method is presented the method first utilizes the topologic dimidiate data structure to discretize borehole data into a series of scatter points then interpolates the initial elevations of the top and bottom surfaces for each stratum and automatically deduces the genesis of the missing strata subsequently according to different geological genesis surfaces intersecting elevations adjusting and consistency processing are performed automatically on the missing strata s surfaces and their control surfaces and finally the solid model filled with 3d blocks or triangular prism meshes is built the borehole surface solid method has higher automaticity and stronger adaptability and overcomes limitations of the existing modeling methods two concrete examples of using this method to shanghai s construction projects show that the resulting models are natural geologically reasonable and close to the actual stratigraphic distribution in addition during the implementing process the geological laws such as the different genesis controlling the spatial geometry of the missing strata are converted skillfully into modeling rules that can be identified and programmed automatically by modelers and this is helpful to promote further study on 3d modeling techniques for complex geological structures

3d geometrical modelling of post foliation deformations in metamorphic terrains syros cyclades greece superposed to ductile syn metamorphic deformations post foliation deformations affect metamorphic units during their exhumation understanding the role of such deformations in the structuration of metamorphic units is key for understanding the tectonic evolution of convergence zones we characterize post foliations deformations using 3d modelling which is a first order tool to describe complex geological structures but a challenging task where based only on surface data we propose a modelling procedure that combines fast draft models interpolation of orientation data with more complex ones where the structural context is better understood implicit modelling allowing us to build a 3d geometrical model of syros island blueschists cyclades based on field data with our approach the 3d model is able to capture the complex present day geometry of the island mainly controlled by the su perposition of three types of post metamorphic deformations affecting the original metamorphic pile i a top to south ramp flat extensional system that dominates the overall island structure ii large scale folding of the metamorphic units associated with ramp flat extensional system and iii steeply dipping normal faults trending dominantly nnw sse and ew the 3d surfaces produced by this method match outcrop data are geologically consistent and provide reasonable estimates of geological structures in poorly constrained areas

a multidisciplinary study of a syntectonic pluton close to a major lithospheric scale fault relationships between the montmarault granitic massif and the sillon houiller fault in the variscan french massif central 2 gravity aeromagnetic investigations and 3 d geologic modeling 1 new gravity and aeromagnetic investigations have been carried out to understand the emplacement mechanisms of a granitic pluton and the relationships with a nearby lithospheric scale fault this paper concerns the second part of a methodological multidisciplinary study and complements previous geochronologic and anisotropy of magnetic susceptibility ams studies on the same pluton in the northern part of the variscan french massif central fmc the montmarault massif crops out along the sillon houiller fault shf bouguer and aeromagnetic anomaly maps imply thickening of the pluton along the shf and suggest laccolitic spreading northwestward on the basis of petrophysical measurements direct two dimensional 2 d joint gravity and magnetic modeling has been performed along 10 cross sections in order to quantitatively constrain the 3 d pluton geometry and its relationships with surrounding geologic units these geophysical cross sections new structural information field and ams measurements and petrophysical data have been integrated into a regional 3 d geological and geophysical model altogether the results obtained from geochronology petromagnetic fabrics part 1 gravity and aeromagnetic investigations as well as 3 d modeling part 2 demonstrate that the montmarault pluton was emplaced during the namurian period along the shf our results further show that at that time in response to a nw se regional extension if the shf existed it behaved as a normal fault mylonites attesting for synmagmatic normal motion on the northeastern part of the montmarault pluton strengthen this tectonic scenario during the late carboniferous the fmc experienced ne sw extension along the shf by 80 km of brittle left lateral wrench offset this second tectonic event is well recorded in the stephanian coal basins which were formed along nw se listric brittle faults and constrain the present day shape of the montmarault pluton

quantifying structural uncertainty on fault networks using a marked point process within a bayesian framework abstract faults are one of the building blocks for subsurface modeling studies incomplete observations of subsurface fault networks lead to uncertainty pertaining to location geometry and existence of faults in practice gaps in incomplete fault network observations are filled based on tectonic knowledge and interpreter s intuition pertaining to fault relationships modeling fault network uncertainty with realistic models that represent tectonic knowledge is still a challenge although methods that address specific sources of fault network uncertainty and complexities of fault modeling exists a unifying framework is still lacking in this paper we propose a rigorous approach to quantify fault network uncertainty fault pattern and intensity information are expressed by means of a marked point process marked strauss point process fault network information is constrained to fault surface observations complete or partial within a bayesian framework a structural prior model is defined to quantitatively express fault patterns geometries and relationships within the bayesian framework structural relationships between faults in particular fault abutting relations are represented with a level set based approach a markov chain monte carlo sampler is used to sample posterior fault network realizations that reflect tectonic knowledge and honor fault observations we apply the methodology to a field study from nankai trough kumano basin the target for uncertainty quantification is a deep site with attenuated seismic data with only partially visible faults and many faults missing from the survey or interpretation a structural prior model is built from shallow analog sites that are believed to have undergone similar tectonics compared to the site of study fault network uncertainty for the field is quantified with fault network realizations that are conditioned to structural rules tectonic information and partially observed fault surfaces we show the proposed methodology generates realistic fault network models conditioned to data and a conceptual model of the underlying tectonics

explicit implicit integrated 3 d geological modelling approach a case study of the xianyan demolition volcano fujian china abstract explicit interactive modelling and implicit interpolation modelling are the two classic three dimensional 3 d modelling approaches for reconstructing 3 d geological structures from sparse data the limitations of using a single method appear when performing complex regional modelling containing various types of geological structures however due to the complication of spatial geometry computation the integration and coupling of explicit and implicit modelling approaches and modelling results remain difficult and unresolved in this paper we propose an explicit implicit integrated 3 d geological modelling approach for the geometric fusion of different types of complex geological structure models first suitable methods were chosen to model different types of structures for example a hermite radial basis function hrbf based implicit method was used to model general strata faults and folds from geological boundaries and attitudes in a regional geological map explicit approaches such as the skinning method and the free form surface were used to model local detailed structures such as quaternary deposits monoclinic strata and multi layer volcanic edifices from section constrained data finally the explicit models were resampled and converted to implicit models and were coupled with the implicit models leading to the integrated regional modelling of various types of geological structures the validity of the proposed method was tested using the geological map of the xianyan demolition volcano in fujian the results demonstrate that the proposed explicit implicit integrated 3 d geological modelling approach is efficient and effective and this approach provides a probable solution for coupling and integrating multiple modelling methods and geological models for an area containing complex geological structures the 3 d model established using this method can directly reflect the geomorphic features and volcanic passage facies of the xianyan demolition volcano moreover the simulation of radioactive fractures around the center of the volcano can also help to accurately determine the volcano type

quartz latite rheoignimbrite flows of the etendeka formation north western namibia the etendeka formation of north western namibia consists of a sequence of interbedded quartz latites and tholeiitic basalts and forms part of the karoo igneous province in southern africa the age of the etendeka formation is approximately 130 135 ma the quartz latites make up a significant proportion of the stratigraphic succession 25 of the total stratigraphic thickness and form as much as 60 of the outcrop area in the southern etendeka apart from some systematic differences between pitchstones and devitrified quartz latite largely explained by alteration processes individual quartz latite units exhibit remarkably uniform compositions with no significant vertical or lateral variation geochemistry can be used as a primary criterion for the correlation of major quartz latite units over much of the southern etendeka area enabling the reconstruction of the etendeka formation stratigraphy in this region individual quartz latite units occur as voluminous 400 2600 km3 widespread up to 8800 km2 sheet like deposits typically between 40 and 300 m thick each unit consists of basal main and upper zones the main zone generally constitutes over 70 of the thickness of the unit and typically consists of texturally featureless devitrified quartz latite in contrast the basal and upper zones of the flow are characterised by flow banding pitchstone lenses and breccia with rare occurrences of pyroclastic textures the quartz latites are sparsely porphyritic 10 phenocrysts with glassy or devitrified groundmass textures the phenocrysts consist of plagioclase pyroxene titanomagnetite and rare ilmenite pyroxene geothermometry indicates high 1000 1100 c temperatures of crystallisation which coupled with the absence or primary hydrous phases indicates that the quartz latites were relatively hot h2o undersaturated magmas the quartz latites display features common to both rhyolite lavas and ignimbrites and are clearly the products of an unusual eruption style the local preservation of pyroclastic textures and the broad areal extent of these units lead to the conclusion that the quartz latites are high temperature rheomorphic ignimbrites i e rheoignimbrites a combination of high eruption temperature and relatively low viscosity helps to explain the often completely welded and homogeneous textures observed in most quartz latite outcrops in the etendeka area

3d implicit modeling of the sishen mine new resolution of the geometry and origin of fe mineralization the sishen deposit is one of the largest iron ore concentrations in current production hematite mineralization occurs along a strike length of 14 km with a width of 3 2 km and a maximum vertical extent of 400 m below the original surface the 986 mt reserve incorporates a suite of individual orebodies beneath a locally preserved tectonized unconformity with a wide range of geometries depths and orientations fully constrained implicit 3d modeling of the entire mining volume 70 km3 was undertaken to the original pre mining topography the model incorporates 5287 mapping points and 21 000 drillholes and provides exceptional insight into the original configuration of ore and its relationship to contacts unconformities and structures in the enclosing country rock the bulk of ore occurs to the west of a strike extensive partially inverted normal fault sloep fault within an asymmetrical synclinal structure on its western flank this linear n s distribution of deep thick ore is punctuated by palaeosinkholes wherein base of ore dips of greater than 45 are concentrically arranged localized ore volumes also occur along faults and in fault bounded downthrown blocks to the north of nw se and ne sw trending strike slip faults that show relatively minor uplift to the south probably due to the lomanian namaqua natal orogeny the revised model demonstrates the proximity of ore to a tectonized unconformity and highlights the structural control on ore volumes implying that fe mineralization at sishen cannot be exclusively attributed to supergene enrichment and concentric palaeosinkhole formation

regional dome evolution and its control on ore grade distribution insights from 3d implicit modelling of the navachab gold deposit namibia abstract we introduce a novel approach to analyse and assess the structural framework of ore deposits that fully integrates 3d implicit modelling in data rich environments with field observations we apply this approach to the early palaeozoic navachab gold deposit which is located in the damara orogenic belt namibia compared to traditional modelling methods 3d implicit modelling reduces user based modelling bias by generating open or closed surfaces from geochemical lithological or structural data without manual digitisation and linkage of sections or level plans instead a mathematically defined spatial interpolation is used to generate 3d models that show trends and patterns that are embedded in large drillhole datasets in our 3d implicit model of the navachab gold deposit distinctive high grade mineralisation trends were identified and directly related to structures observed in the field the 3d implicit model and field data suggest that auriferous semi massive sulphide ore shoots formed near the inflection line of the steep limb of a regional scale dome where shear strain reached peak values during fold amplification this setting generated efficient conduits and traps for hydrothermal fluids and associated mineralisation that led to the formation of the main ore shoots in the deposit both bedding parallel and highly discordant sets of auriferous quartz sulphide veins are interpreted to have formed during the later lock up stage of the regional scale dome additionally pegmatite dykes crosscut and remobilise gold mineralisation at the deposit scale and appear to be related to a younger joint set we propose that kilometre scale active folding is an important deformation mechanism that influences the spatial distribution and orientation of mineralisation in ore deposits by forming structures traps and pathways for fluids at different preferred sites and orientations we also propose that areas that experience high shear strain located along the inflection lines of folds can act as preferred sites for syn deformational hydrothermal mineralisation and should be targeted for regional scale exploration in fold and thrust belts our research also suggests that examination of existing drillhole datasets using 3d implicit modelling is a powerful tool for spatial analysis of mineralisation patterns when combined with fieldwork this approach has the potential to improve structural understanding of a variety of ore deposits

structural model creation the impact of data type and creative space on geological reasoning and interpretation the authors would like to thank participants in the interpretation exercises bond was funded by midland valley exploration and a scottish executive score award whilst collecting the cohort 1 interpretation dataset midland valley exploration s move software was used to create the geological model and borehole dataset fiji image j software was used to create figure 5a and c ion gxt are thanked for creation of the synthetic seismic image dataset

towards incorporating uncertainty of structural data in 3d geological inversion abstract all geological models are subject to several kinds of uncertainty these can be classified into three different types data imprecision and quality inherent randomness and incomplete knowledge with our approach we address uncertainties introduced by input data quality in complex three dimensional 3d models of subsurface structures geological models as input data we consider parameters of geological structures i e formation and fault boundary points and orientation measurements our method consists of five steps construction of an initial geological model with an implicit potential field method assignment of probability distributions to data positions and orientation measurements simulation of several input data sets construction of several model realisations based on these simulated data sets and finally the visualisation and analysis of the uncertainties we test our approach in two generic models a simple graben setting and a complex dome structure the first model shows that our approach can evaluate uncertainties from different structures and their interaction furthermore it indicates that the final uncertainty of the model is not simply the sum of all input data uncertainties but complex interactions exist the second example demonstrates that our approach can handle full three dimensional settings with overturned surfaces results of the uncertainty simulation can be visualised and analysed in several ways ranging from borehole histograms to uncertainty maps for complex 3d visualisation and analysis we use indicator functions when we apply these we can treat the visualisation of uncertainties in complex settings in a self consistent manner with our simulation method it is possible to analyse and visualise the uncertainties directly introduced by imprecision in the input data our approach is intuitive and straight forward and suitable in both simple and complex geological settings it enables detailed insights into the model quality even for the non expert in cases where a geological model is the basis for geophysical simulation it opens up the way to geological data driven ensemble modelling and inversion

integration of uncertain subsurface information into multiple reservoir simulation models successful appraisal and development of oil and gas fields requires the integration of uncertain subsurface information into multiple reservoir simulation models this information includes seismic data various types of well data and geologic concepts over the past five years a workflow has been developed by various organizations in conjunction with bhp billiton petroleum this distinctive approach focuses first on building mesoscale reservoir models that can be constrained by seismic data typically with a resolution up to the stratigraphic seismic loop scale see prather et al 2000 then introducing the finer scale geologic concepts and well data needed for reservoir simulation models stratigraphic first and second order subseismic scale where each order is about a factor of three in size via a downscaling step that honors mesoscale model constraints uncertainty and correlations of the well and seismic measurements are always taken into account in fact they are necessary to be able to combine the various measurements bayesian probabilistic techniques are used extensively in this process the result is an ensemble of reservoir simulation models consistent with all subsurface information

three dimensional geological modelling and multivariate statistical analysis of water chemistry data to analyse and visualise aquifer structure and groundwater composition in the wairau plain marlborough district new zealand summary concerns regarding groundwater contamination with nitrate and the long term sustainability of groundwater resources have prompted the development of a multi layered three dimensional 3d geological model to characterise the aquifer geometry of the wairau plain marlborough district new zealand the 3d geological model which consists of eight litho stratigraphic units has been subsequently used to synthesise hydrogeological and hydrogeochemical data for different aquifers in an approach that aims to demonstrate how integration of water chemistry data within the physical framework of a 3d geological model can help to better understand and conceptualise groundwater systems in complex geological settings multivariate statistical techniques e g principal component analysis and hierarchical cluster analysis were applied to groundwater chemistry data to identify hydrochemical facies which are characteristic of distinct evolutionary pathways and a common hydrologic history of groundwaters principal component analysis on hydrochemical data demonstrated that natural water rock interactions redox potential and human agricultural impact are the key controls of groundwater quality in the wairau plain hierarchical cluster analysis revealed distinct hydrochemical water quality groups in the wairau plain groundwater system visualisation of the results of the multivariate statistical analyses and distribution of groundwater nitrate concentrations in the context of aquifer lithology highlighted the link between groundwater chemistry and the lithology of host aquifers the methodology followed in this study can be applied in a variety of hydrogeological settings to synthesise geological hydrogeological and hydrochemical data and present them in a format readily understood by a wide range of stakeholders this enables a more efficient communication of the results of scientific studies to the wider community

mesozoic intraplate deformation in the southern part of the central european basin results from large scale 3d modelling abstract the central european basin is an intracontinental basin that initially formed due to long lasting thermal subsidence accompanied with several tectonic phases of extension during mesozoic times locally thick evaporites were incorporated in the deformation and led to the formation of detached structures salt pillows and diapirs at the end of the late cretaceous the formation of sub basins and half grabens became interrupted by a short term event of contraction especially along the northern and southern edges of the basin lithospheric shortening resulted in basin inversion and the uplift of large basement blocks hence the present day s structural framework shows a complex pattern of kinematically and chronologically variable structures herein we unravelled these structures for the altmark region in northern saxony anhalt central germany we used regional depth maps reflection seismics and borehole data analysed by use of large scale subsurface mapping and 3d modelling techniques to completely re evaluate the structures in the late palaeozoic to cenozoic sedimentary basin succession our results show a high variability of tectonic structures narrow and distributed in parts reactivated normal fault zones huge inverted basins thin skinned thrust faults detachment folds and large basement thrusts the style of deformation significantly changed during the region s evolution this is indicated by particular structural kinematic thermal and rheological conditions which existed for the individual phases of basin formation and inversion and probably persist until today

3d volumetric modelling of cadomian terranes northern brittany france an automatic method using voronoi diagrams abstract an automatic method based on the use of voronoi diagrams is proposed for the 3d volumetric reconstruction of geological objects it enables volumes to be constructed starting from the combined use of geological maps and cross sections defined in multiple directions and can also take into account incomplete information on geological interfaces and faults the method is suitable for global modelling of a set of geological objects it gives a consistent 3d volumic partition of space according to geological information contained in the maps and the cross sections the method is described and applied to modelling the main domains of the cadomian collisional orogenic belt of panafrican age in northern brittany france thanks to the contrasting densities of the main units involved in the collisional process the gravimetric effect of the volumic model can be calculated its comparison with the observed anomaly allows us to discuss the validity of the geological model although some improvements appear to be necessary it is concluded that the method can make geological modelling more efficient through providing the possibility of rapidly testing many hypotheses

constraints of deep crustal structures on large deposits in the cloncurry district australia evidence from spatial analysis abstract deep structures are commonly recognized as critical factors for controlling the formation of large hydrothermal deposits it is of great importance for the metallogenic studies to quantitatively describe the spatial associations of deep structures with mineral deposits in the cloncurry district of the mt isa province australia many large deposits have been discovered and district scale deep structures have also been recognized from the magnetic gravity seismic and magnetotelluric data in this paper we delineate the 3d configuration of the deep structures by 3d geometric modeling and gaussian curvature analysis and quantify spatial associations of the deep structures with the large deposits by the weights of evidence method the results demonstrate that the configuration of deep structures has a positive spatial constraint on the distribution of deposits many deposits are located close to the high curvature portion of the deep structures according to this rule there are some potential target areas where curvature of the deep structural surfaces is high but no deposits have been discovered such results can be used to identify targets with potential for finding undiscovered deposits

structural control of geothermal reservoirs in extensional tectonic settings an example from the upper rhine graben abstract in extensional tectonic settings major structural elements such as graben boundary faults are typically oriented subparallel to the maximum horizontal stress component shmax they are often structurally accompanied by transfer zones that trend subparallel to the extension direction in the upper rhine graben such transfer faults are typically characterized by strike slip or oblique slip kinematics a major re orientation of the regional stress field by up to 90 of the upper rhine graben in the early miocene led to the present day normal and strike slip faulting regimes in the north and south of the upper rhine graben respectively and a transition zone in between consequently conditions for fault frictional failure changed significantly moreover it has been observed during tracer and stimulation experiments that such transfer faults may be of major importance for the hydraulic field of geothermal reservoirs under the present stress condition especially when located between production and injection well in this context we have investigated slip and dilation tendencies ts and td of major structural elements at reservoir scale for two representative geothermal sites bruchsal germany and riehen switzerland located close to the eastern main boundary fault of the upper rhine graben we have evaluated the quality and uncertainty range of both tendencies with respect to potential variation in shmax orientation despite significant differences in orientation of the structures and the stress regimes the resulting variation of ts and td reveal major similarities concerning the reactivation potential of both the graben parallel structures and the transfer faults the conditions of criticality for tensile failure and non criticality for shear failure suggest that transfer faults are most likely naturally permeable structures with low stimulation potential this is in agreement with the absence of both immediate tracer recovery and seismicity in the studied geothermal sites

three dimensional geometry and tectonostratigraphy of the pennine zone central alps switzerland and northern italy abstract continental collision during alpine orogenesis entailed a polyphase deformation history d1 d5 in the pennine zone of the central alps the regional tectonostratigraphy was basically developed during d1 and d2 characterised by isoclinal typically north closing recumbent anticlines separated by pinched in synclines on the scale of tens of kilometres later deformation phases d3 and d4 warped the stack into wavy to open folds exhumation of this zone resulted locally in later vertical shortening and folding of already steep fabrics d5 three dimensional models of the nappe pile were constructed based on geostatistical assessment of the regional foliation field and considering the abundant structural field data these models indicate the existence of five principal tectonostratigraphic levels developed during d1 and thus equivalent to nappe units s str the gotthard the leventina antigorio the maggia simano and probably the monte leone as well as the composite lepontine series lebendun soja and adula cima lunga levels all these tectonic units formed part of the passive continental margin of europe prior to the onset of the alpine orogenesis individual isoclinal post nappe folds reflect relative displacements on the order of 40 km or more the most prominent d2 post nappe structure is the wandfluhhorn fold structurally equivalent to the northern closure of the leventina lucomagno antiform the lebendun and monte leone folds are of similar magnitudes and also affect the whole nappe pile whereas the smaller mogno and molare synforms only refold the maggia simano nappe internally principal d3 and d4 structures are the tight mergoscia synform directly north of the insubric fault between bellinzona and locarno southern steep belt the maggia steep zone forming the steep western limb of the campo tencia synform and subdividing the lepontine dome into the simplon and ticino subdomes the chiera synform steepening the dominant foliation in the north northern steep belt and the vanzone and claro antiforms steepening the dominant foliation in the south southern steep belt the current geometry of the northern and southern steep belts reflects an interplay between d4 and d3 involving both fold interference and reactivation tightening

glacial dynamics in southernmost south america during marine isotope stage 5e to the younger dryas chron a brief review with a focus on cosmogenic nuclide measurements the timing of major glacial changes between marine isotope stage mis 5e and the younger dryas chron yd in southern south america is reviewed focus is placed on studies that use cosmogenic nuclide measurements however other dated records and modelling results are also discussed to provide the broader glacial geological context limits on the state of glacial geologic knowledge are examined and suggestions are made as to how some of these can be addressed in future studies studies show that on the east side of the andes at lago buenos aires 45 s there is evidence indicating that following a mis 6 glaciation ice was less extensive during mis 4 than mis 2 in contrast on the west side of the andes in the chilean lake district area mis 4 ice may have been more extensive than during mis 2 although patagonia experienced an mis 2 glaciation broadly in phase with that in other areas around the globe there are differences in glacial histories between areas on millennial timescales climate reversals are evident in many records between ca 17 and 10 ka the timing of such lateglacial activity which included less extensive advances than during the local last glacial maximum lgm varies somewhat between areas this could be due to the relative influence of middle to high latitude climatic regimes at present chronological uncertainties prevent confident assignment of cosmogenic ages for glacial events at the millennial timescale and defining associated climate variability between different study areas copyright 2008 john wiley sons ltd