boundary fault linkage and its effect on upper jurassic to lower cretaceous sedimentation in the gudian half graben songliao basin northeastern china abstract the songliao basin northeastern china is one of the few ultra large petroleum basins in the world fault superposition linkage and stratigraphic architecture have produced a complicated basin evolutionary history in this study we report the boundary fault linkage and associated upper jurassic and lower cretaceous stratigraphic record using 3d seismic reflection data and well data our results show that the geometry of the boundary gudian fault was originally controlled by six shorter fault segments which grew and were linked during a syn rift stage then frictionally weakened and inverted in a post rift stage this boundary fault has variably controlled coeval syn rift sedimentation fault segments in the middle section controlled the development of the limited but thickest huoshiling and the first member of shahezi formations in the early syn rift stage ca 150 133 9 ma later that control gradually weakened and vanished on succeeding the second member of shahezi and yingcheng formations in the late syn rift stage ca 133 9 105 ma the processes and the diverse syn rift sedimentation response to gudian fault growth and linkage have further implications for graben evolution and can guide hydrocarbon exploration in the songliao basin this study will help elucidate the different controls of boundary fault linkage on associated sedimentation as well as rift basins development in eastern china and similar areas throughout the world

palinspastic reconstruction and topographic evolution of the eastern alps during late tertiary tectonic extrusion this paper presents a new palinspastic restoration of the eastern alps for neogene time and an attempt to reconstruct the neogene palaeogeology palaeotopography and palaeohydrography in connection with the structural evolution the eastern alps underwent radical horizontal displacement during the neogene due to large strike slip systems and formation of structural windows our palinspastic reconstruction considers a the rearrangement of tectonic units dismembered during tectonic extrusion b the tectonic denudation driven by displacement of the crystalline blocks c geochronological arguments and d the sedimentary record of the syn extrusion basins the rearrangement of tectonic blocks results in a remarkably good fit of highly dismembered zones both in crystalline and sedimentary areas and shows the pre miocene unstretched pattern of the eastern alps reduced to 65 of its present day e w elongation using this structural frame and considering the sedimentary record a set of palaeogeologic and palaeotopographic sketch maps with the palaeo river systems is presented for three time slices pre syn and post extension situation in late oligocene and early miocene times the western eastern alps were already mountainous whereas the eastern part of the orogen formed lowlands or hilly areas enhanced block movement in the course of the extrusion process around the early middle miocene boundary led to the formation of intramontane sedimentary basins and a fault induced reorientation of the drainage pattern which forms the basis of the modern river system in the area east of the tauern window this region where pre miocene land surfaces are preserved probably became a mountainous area not before late miocene time and never reached the elevations of the areas further west

origin dimensions and distribution of remobilized carbonate deposits in a tectonically active zone eocene thebes formation sinai egypt abstract determination of the distribution and mechanism for carbonate dominated mass transport sediments is often compromised by the scale and access to exposures consequently many studies lack the resolution to capture the heterogeneity and dimensions of mass transport deposits this study documents the size shape and stratal assemblage of remobilized carbonates in the eocene thebes formation in the hammam faraun fault block hffb of western sinai revealing the complexities of carbonate mass transport deposits at sub seismic scale present day pseudo three dimensional exposure of the thebes formation in a large fault block formed during the opening of the gulf of suez allowed for lateral and down dip measurement of slope and basinal facies in the field and from photos remobilized facies were digitized in the photos and evaluated using image analysis software a technique with a wide range of applications to outcrop studies of sedimentary architecture debris flow deposits in the lower section of the thebes formation comprises clasts with differing fossil assemblages a relative sea level rise at the start of upper thebes formation deposition resulted in basinal sediments comprising periodic incursions of high density turbidite grainstones encased within a background of planktonic foraminiferal wackestones foraminiferal assemblages of remobilized facies imply multiple sources on the carbonate platform demonstrating the effect of short lived tectonism on slope instability and deposition of mass transport deposits the results of the study confirm that tectonism associated with the syrian arc fold belt which altered the style of basin sedimentation between egypt and syria persisted into the eocene at least as far south as wadi araba in the western desert and hammam faraun in sinai in addition the shape size and extent of the two dominant remobilized facies debris flows and grainstone turbidites are influenced by their mud rich versus grainy compositions

possible evidence for variation in magnitude for marsquakes from fallen boulder populations grjota valles mars following observations of mobilized boulder trail populations from cerberus fossae mars that have been interpreted as possible evidence of large magnitude marsquakes rupturing for distances of 207 km along exposed active faults additional boulder trail populations were measured along shorter faults within the region of grjota valles 50 150 km length to test the hypotheses that 1 these faults are also candidate locations for marsquakes and 2 that marsquake magnitude might be smaller limited by fault dimensions available for rupture for a region containing two en echelon graben boulder trail data define two anomalies with maxima in a boulder trails per kilometer and b maximum width of boulder trails one that is 116 km in length along strike and the other 70 km in length along strike values for the maxima are 45 trails per km and 5 m mean trail width for the 70 km long anomaly and 115 trails per km with 5 3 m mean trail width for the 116 km long anomaly above background values measured elsewhere along these faults of zero trails per kilometer with zero boulder trail widths if combined with published data from cerberus fossae with a 207 km long anomaly in boulder trails per km 125 trails per km maxima and maximum mean boulder trail width 8 5 m maximum trail width the 3 datasets suggest correlations between the a along strike length of boulder trail anomalies b boulder trails per km and c maximum boulder trail width if interpreted as due to single marsquakes and if the dimensions of these anomalies are a proxy for rupture length when combined one interpretation of this is that boulders have been mobilized by marsquakes and that the marsquake magnitude is proportional to the along strike length of the anomalies in other words the data suggest that marsquake magnitude if that is the cause of the anomalies is limited by fault length as expected for terrestrial seismically active faults such findings suggest that the martian surface may have been shaken in the very recent past by large magnitude marsquakes we discuss this in terms of the seismicity of mars

the onaman prospect ontario an unusual occurrence of cu bearing au mineralization in a shear zone the onaman prospect is an unusual example of mesothermal gold mineralization in which native gold electrum and minor chalcopyrite are disseminated in metavolcaniclastic rocks in shear zones or concentrated in felsite dikes that intrude the metavolcaniclastic rocks mineralization was contemporaneous with carbonatization and involved early replacement of iron bearing minerals in the wall rock by ankerite and pyrite and later replacement of pyrite by arsenopyrite pyrrhotite chalcopyrite electrum and native gold oxygen isotope ratios of ankerite suggest a metamorphic origin for the fluid and carbon isotope ratios are similar to those of large mesothermal gold deposits in the superior province for which a mantle origin has been proposed sulfur isotope ratios correlate positively with gold grades and may reflect decreasing f o2 during mineralization a model is proposed in which deformation of the volcanic pile led to the formation of a shear zone and created dilational zones allowing dike intrusion metamorphic fluids rose along the shear zones and the dikes pyritization of the host rock was the major control on gold and chalcopyrite deposition reducing a h 2 s and destabilizing the bisulfide complexes of au and cu the onaman occurrences provide an uncommon example of a mesothermal system in which ph was relatively low and the correspondingly low solubility of copper allowed the fluid to saturate with and deposit chalcopyrite in most other mesothermal gold systems copper is too soluble to saturate the fluid with a copper mineral and is therefore flushed through the system

rhyolite geochemical signatures and association with volcanogenic massive sulfide deposits examples from the abitibi belt canada the relationship between rhyolite geochemistry and volcanogenic massive sulfide vms mineralization has been proposed as an exploration tool to discriminate prospective felsic volcanic centers the most widely used classification discriminates between four types of rhyolite fi fii fiiia and fiiib the fi rhyolites are calc alkaline with strongly fractionated ree patterns and strongly negative ta and nb anomalies they are usually considered barren unless associated with fii or fiii felsic volcanic rocks the fii rhyolites are calc alkaline to transitional with moderately fractionated ree patterns and moderate ta and nb anomalies they range from barren to having a high potential to host vms mineralization the fiiia and fiiib rhyolites are tholeiitic and show weakly fractionated ree patterns and weak to absent nb and ta anomalies they have the highest potential to host vms mineralization the fiiib rhyolites are high temperature rhyolites with flat ree patterns and no ta or nb anomalies the abitibi greenstone belt especially in quebec is well known for its abundant and diverse vms deposits representative samples of vms associated rhyolites within and outside of mining districts including the classic noranda vms district were analyzed for major and trace elements to validate their proposed favorability for hosting vms deposits results indicate that all of the rhyolite types are prospective but mineralization may differ from the classic noranda type vms deposit the fi type rhyolites appear to be particularly associated with gold rich vms deposits such as the world class laronde deposit and are more prospective for cu au replacement and vein type deposits the fii type rhyolites account for about 70 percent of rhyolites in the abitibi belt although considered less prospective some districts dominated by fii rhyolites such as val d or and selbaie have collectively produced in excess of 100 million metric tons mt of ore deposits in these districts mainly consist of sulfide veins and disseminated ore with low cu and zn grades and are associated with abundant and highly vesicular volcaniclastic rocks that display a compositional continuum from andesite to rhyolite other weakly mineralized fii districts e g hunter mine gemini turgeon are characterized instead by bimodal flow dome sequences the fiiia type rhyolites occur mainly in the noranda district and form flow dome complexes in bimodal sequences with associated noranda type vms mineralization in small felsic centers joutel normetal chibougamau quevillon that show a volcanic evolution from fiiia to fii to fi affinities vms deposits are directly associated with fiiia rhyolites thus demonstrating the usefulness of rhyolite geochemistry for exploration in these areas the fiiib rhyolites are rare in the abitibi belt with most occurring in the matagami district where they are associated with zn cu vms deposits based on this analysis we suggest that a combination of rhyolite geochemistry volcanic facies and style of the mineralization may be more meaningfully applied in exploration than rhyolite type alone particularly in the case of fi and fii rhyolites

evolution from sea floor related to sulfide rich quartz vein type gold mineralization during deep submarine volcanic construction the geant dormant gold mine archean abitibi belt canada the geant dormant sleeping giant mine is a vein type gold deposit that contrasts with archean shear related mesothermal deposits in the preductile deformation timing of the quartz gold bearing veins and in their high sulfide content gold mineralization is centered about a felsic complex that intrudes a volcano sedimentary succession composed of mafic sills interbedded pelagic sediments and mafic pillowed and felsic lavas the felsic complex includes a dacitic subvolcanic dome and a swarm of polyphase plagioclase porphyritic and quartz and plagioclase porphyritic dikes all felsic rocks are cogenetic and have calc alkalic affinity zr y nearly equal 12 whereas all mafic rocks including postmineralization dikes are cogenetic and tholeiitic zr y nearly equal 2 5 strata were built from two different volcanic sources a proximal felsic and a distal mafic one in a deep submarine setting 3 150 m three successive mineralizing events are recognized 1 a sea floor related gold poor event characterized by sericite chlorite and quartz alteration with disseminations and stringers of gold bearing pyrrhotite and chalcopyrite affecting rocks of paleo sea floor origin 2 an autometasomatic event affecting only the dacitic dome expressed by chloritization and dissemination of auriferous pyrite and 3 quartz sulfide vein style gold mineralization with only weak chlorite sericite or no altered selvages the gold bearing vein network was formed during the last stage of a four stage volcanogenic hydrothermal system as indicated by the parallelism between volcanic and hydrothermal evolutionary patterns at stage 1 diffuse sea floor related hydrothermal fluids altered and mineralized lavas and fe rich sediments stage 2 involves the sealing of the hydrothermal system by injection of a 1 km thick stack of impermeable mafic sills during stage 3 the mineralizing system was reactivated by the emplacement of the dacitic dome stage 4 involves injection of quartz and plagioclase porphyritic dikes along active synvolcanic faults these dikes served as conduits for the ascension of mineralizing fluids through the volcanic pile gold and related quartz and sulfides precipitated in open fractures developed mainly in mafic rocks near these dikes vein formation is a consequence of the specific two source volcanic pile the exogenic voluminous mafic sills disturbed the evolution of a volcanogenic hydrothermal system related to the felsic center renewed felsic activity generated fractures for vein formation enhanced by pressurization of mineralizing fluids at near lithostatic pressure within the impermeable host sequence gold enrichment from stage 1 to stage 4 is consistent with the proposed evolution and most likely related to boiling of the mineralizing fluids during vein formation

extension during continental convergence in the eastern alps the influence of orogen scale strike slip faults in the miocene the european eastern alps extruded laterally along orogen scale strike slip faults due to both extensional gravitational collapse and compressional tectonic forcing horizontal extension is most prominently evidenced by detachments east and west of the tauern window it is commonly explained by a retreating slab beneath the carpathian arc hundreds of kilometers east of the orogen horizontal compression is shown by north south shortening in the tauern window and the entire eastern alps in response to the convergence of the adriatic plate with europe it is interesting that analogue and numerical models for the eastern alps designed to describe the east directed lateral extrusion have failed to explain the extensional regime in the region of the tauern window using a numerical model for plan view deformation that considers internal faults we show here that orogen scale strike slip faults are mechanically required to cause extension during plate convergence in the miocene eastern alps we test the idea by coupling this model with a landscape evolution model and by comparing modeled and observed drainage system geometries

the influence of pre existing structure on the growth of syn sedimentary normal faults in a deltaic setting niger delta abstract three dimensional seismic reflection data from the western niger delta were used to investigate the segmentation and linkage of a syn sedimentary normal fault array and to estimate the influence of a pre existing normal fault on the geometry and growth of younger faults the nucleation growth and linkage of a regional seaward dipping deltaic fault system were analyzed on reflectivity time horizon slices and vertical seismic sections in the deep subsurface a master fault that consists of two segments northwestern nw and southeastern se grew through time into a single fault by lateral tip propagation reaching a final length of about 15 km after attaining this length displacement along the fault system developed non uniformly through time the analysis of the hanging wall sediments of the deep seated master fault shows two different processes of vertical linkage above the nw and se segment the se segment links vertically to several younger faults contemporaneously with displacement accumulation on the master fault in contrast fault linkage above the nw segment occurred only after an interval of master fault inactivity connecting the deep seated structure upwards to a single syn sedimentary normal fault the observed differences in fault development suggest that although multi segment deltaic faults form single fault systems after segment linkage individual pre linkage characteristics can be preserved supporting a possibly diverse upward growth and connection to younger faults in the overburden the geological interpretations presented highlight the influence of large deep rooted structures on the development location and geometry of shallow deltaic faults documenting the influence of an older structural grain on delta tectonics

orogen parallel strike slip faults bordering metamorphic core complexes the salzach enns fault zone in the eastern alps austria abstract the approximately ene trending salzach enns fault eastern alps contributed to late stage exhumation of the tauern metamorphic core complex in response to oblique convergence of european and adriatic plates six stages of kinematic evolution with early ductile and later brittle deformational structures were recognized as follows 1 initial ductile deformation is represented by a combination of sinistral shear dominated noncoaxial strain and coaxial strain 2 early brittle sinistral strike slip is combined with a pure shear deformation and represents roughly n s contraction it is followed by 3 sinistral strike slip and 4 ca n s extension due to normal slip striations 5 subsequent n s compression resulted in counterclockwise rotation of the maximum principal stress from ne to nw and led to final dextral strike slip displacements along the salzach enns fault the exhumation of the tauern window was accommodated by dip slip on the fault plane at shallow levels and coaxial flattening at deeper structural levels brittle sinistral faults at shallow structural levels produced a larger amount of strike slip displacement than ductile shear zones at the deeper structural levels which is explained as a scissors like movement and which resulted in the eastward tilting of the tauern window

exploration and assessment of the geothermal resources in the hammam faraun hot spring sinai peninsula egypt abstract the tectonic position of egypt in the northeastern corner of the african continent suggests that it may possess significant geothermal resources especially along its eastern margin the most promising areas for geothermal development in the northwest red sea gulf of suez rift system are located where the eastern shore of the gulf of suez is characterized by superficial thermal manifestations including a cluster of hot springs with varied temperatures magnetotelluric and gravity reconnaissance surveys were carried out over the geothermal region of hammam faraun to determine the subsurface electric resistivity and the densities that are related to rock units these surveys were conducted along profiles one dimensional 1d and two dimensional 2d inversion model techniques were applied on the mt data integrating the 2d inversion of gravity data the objectives of these surveys were to determine and parameterize the subsurface source of the hammam faraun hot spring and to determine the origin of this spring based on this data a conceptual model and numerical simulation were made of the geothermal area of hammam faraun the numerical simulation succeeded in determining the characteristics of the heat sources beneath the hammam faraun hot spring and showed that the hot spring originates from a high heat flow and deep ground water circulation in the subsurface reservoir that are controlled by faults these studies were followed by an assessment of the geothermal potential for electric generation from the hammam faraun hot spring the value of the estimated potential is 28 34 mw as the reservoir is assumed to be only 500 m thick this value would be enough for the desalination of water for both human and agricultural consumption

lateral extrusion in the eastern alps part 1 boundary conditions and experiments scaled for gravity lateral extrusion encompasses extensional collapse gravitational spreading away from a topographic high in an orogenic belt and tectonic escape plane strain horizontal motion of wedges driven by forces applied to their boundaries in the eastern alps it resulted from 1 an overall northerly compression apulia against eurasia 2 a strong foreland bohemian massif 3 lack of constraint along a lateral boundary carpathian region and 4 a previously thickened gravitationally unstable thermally weakened crust eastern alpine orogenic belt six indentation experiments reproduce lateral extrusion at lithospheric scale the models have two to four lithospheric layers with a mohr coulomb rheology for the upper and a viscous rheology for the lower crust the lithosphere rests upon a low viscosity asthenosphere a broad indenter a narrow deformable area and a weakly constrained eastern margin fullfill as closely as possible conditions in the eastern alps indentation produces both thickening in front of the indenter and escape of triangular wedges lateral variations in crustal thickness become attenuated by gravitational spreading the overall fault pattern includes domains of reverse strike slip oblique normal and pure normal faults strike slip faults in conjugate sets develop serially the narrow width of the deformable area and the strength of the foreland determine the angles between the sets gravitational spreading produces a rhombohedral pattern of oblique and pure normal faults along the unconstrained margin opposite the unconstrained margin the indenter front shows thrusts and folds intersecting with the conjugate strike slip sets a triangular indenter favors spreading high velocity of indentation favors escape high confinement limits lateral motion inhibits spreading and favors thickening lateral extrusion in the eastern alps is best modeled by 1 a weak lateral confinement 2 a broad and straight indenter 3 a narrow width of the deformable area and 4 a rigid foreland crustal thickening lateral escape and gravitational spreading all contribute to the overall deformation

sedimentology of rift climax deep water systems lower rudeis formation hammam faraun fault block suez rift egypt abstract in most marine rift basins subsidence outpaces sedimentation during rift climax times typically this results in sediment starved hangingwall depocentres dominated by deep marine mudstones with subordinate local development of coarser clastics in the immediate hangingwall derived from restricted catchments on the immediate footwall scarp to highlight the spatial variability of rift climax facies and the controls upon them we have investigated the detailed three dimensional geometry and facies relationships of the extremely well exposed miocene rift climax lower rudeis formation in the immediate hangingwall to the thal fault zone suez rift egypt detailed sedimentological analyses allows the lower rudeis formation to be divided into two contemporaneous depositional systems 1 a laterally continuous slope system comprising hangingwall restricted interpretation of individual facies facies relationships and their spatial variability indicate that deposition in the immediate hangingwall to the thal fault occurred via a range of submarine concentrated density flows surge like turbidity flows mass wasting and hemipelagic processes major controls on the spatial variability and stratigraphic architecture of the depositional systems identified reflect the influence of the steep footwall physiography accommodation and drainage evolution associated with the growth of the thal fault the under filled nature of the hangingwall depocentre combined with the steep footwall gradient result in a steep fault controlled basin margin characterised by either slope bypass or erosion with limited coastal plain or shelf area sediment supply to the slope apron deposits is controlled in part by the evolution and size of small footwall drainage catchments in contrast the localized submarine fan is interpreted to have been fed by a larger antecedent drainage network the structural style of the immediate footwall is also believed to exert a control on facies development and stratigraphic evolution in particular fault scarp degradation is enhanced by fault propagation folding which creates basinward dipping bedding planes in the pre rift footwall strata that large pre rift blocks slide on

continental collision with finite indenter strength 2 european eastern alps 1 comparison of the results of a thin viscous sheet model with the velocity field determined by gps stations in the alpine pannonian realm shows that the adriatic plate is only slightly stronger than the eastern alps the observed velocity field is best approximated with a newtonian fluid however this scenario must be fairly recent as the overall geometry of the orogen can only be reproduced if the rheology contrast was about 1 10 before the late miocene the boundary conditions for this model are tested against the orientation of the intraplate stress field and are robust for argand numbers between 1 and 5 we conclude that the convergence rate between the adriatic and european plates must have slowed since the miocene and that the present day eastward extrusion of the eastern alps is largely due to lateral escape and only to a minor degree due to gravitational collapse scaled viscosities of the eastern alps are on the order of 1023 pa s

extension in compressional orogenic belts the eastern alps extension in the eastern alps encompasses the following 1 extension accompanying simple shear crustal stacking subhorizontal stretching occurs along flat lying foliations and regionally consistent stretching lineations with associated high strains on a local scale stretching results from extrusion of ductile sediments squeezed between rigid basement blocks basement blocks during thrust sheet imbrication the overall geometric effect is crustal thickening 2 classical extensional tectonics extension first occurs as a consequence of accretion and underthrusting of continental and oceanic material and represents gravitational adjustment of an unstable orogenic wedge extension then occurs as a consequence of terminal continental collision and is accommodated by lateral extrusion of crustal of crustal blocks the overall geometric effect is crustal thinning extension is generally oriented subparallel to the strike of the orogen

channel profiles around himalayan river anticlines constraints on their formation from digital elevation model analysis 1 we present a comparison between measured and numerically modeled channel profiles of rivers in two important drainage basins of central nepal the kali gandaki and the arun drainage basins modeled channel profiles are based on a simple stream power approach using best fit exponents defining the nonlinearities in the relative contributions of local channel gradient and water flux to erosion rate our analysis of the stream power in the whole river network confirms the work of other authors that a 50 to 80 km wide zone roughly corresponding to the high himalayan topography is subjected to rapid rock uplift we suggest a model where the uplift of this zone is driven by erosion and isostatic response so that centers of maximum uplift are located within the main channels of the north south draining rivers we also suggest that the rate of uplift slows down with increasing distance to the main channels such a spatial distribution of the uplift leads ultimately to the formation of river anticlines as observed along all major himalayan rivers we propose that the formation of river anticlines along south draining himalayan rivers was accelerated by a sudden increase of the drainage area and discharge when the rivers captured orogen parallel drainages on the north side of the range this may follow successive headward cutting into the tibetan plateau the model is confirmed by differences between main channels and east west running tributaries time dependent numerical models predict that capture events cause strongly elevated erosion rates in the main channel

sequence stratigraphy in active extensional basins implications for the interpretation of ancient basin fills abstract systematic variations in sequences their component units and their stacking patterns exist within rift basins these variations can be related to displacement gradients associated with the large scale 12 50 km segmentation of normal fault zones which control accommodation sediment supply and basin physiography sediment supply is also strongly influenced by the nature of pre rift drainage networks and variations in bedrock lithology high rates of hangingwall subsidence close to the centre of normal fault segments may cancel out the effects of glacio eustatic sea level fall so that accommodation development is normally characterized by the continual addition of new space the resulting sequences lack type 1 sequence boundaries and lowstand systems tracts and stack into aggradational sequence sets the adjacent footwall is subject to uplift which may lead to subaerial exposure and incision generating a composite type 1 sequence boundary away from the fault zone and near segment boundaries slip rates are much lower and hence relative sea level change is dominated by eustasy here falls in relative sea level are important resulting in type 1 sequences sequence stacking patterns reflect not only eustasy and local fault controlled subsidence but also the interaction of these with adjacent uplifting footwalls and or regional uplift tectonic influence on sequence development will be more pronounced during greenhouse times than icehouse times

relay ramp forms and normal fault linkages canyonlands national park utah fieldwork within a series of mesoscale grabens in southeast utah has revealed a particularly well exposed system of interlinked extensional faults a series of down faulted grabens are developed within a 460 m thick brittle layer of upper paleozoic sandstone and shale which overlies a ductile layer with a high gypsum content all the major grabens consist of two or more overlapping elements which are composed of fault segments these segments may be hard linked fault surfaces are joined or soft linked fault surfaces are isolated but linked by ductile strain of the rock volume between them in map view relay structures are defined as zones connecting the footwalls and hanging walls of overlapping fault segments representing soft linkage of fault segments in the canyonlands grabens the transfer of displacement between soft linked fault segments is characterized by well de fined dipping relay ramps commonly rotated and extended to accommodate the ductile strain between the overlapping fault segments relay ramps develop as ephemeral structures eventually becoming breached by hard linkage of the fault segments breakdown of ramps by breaching is part of the process of fault growth by segment linkage within the canyonlands graben system four orders of segmentation are present this may be a consequence of different scales of mechanical heterogeneity but evidence from the canyonlands grabens and elsewhere points to a fundamental process of discontinuous fault growth by segment linkage

normal fault growth and fault related folding in a salt influenced rift basin south viking graben offshore norway abstract three dimensional seismic data were analysed to reconstruct the structural and stratigraphical development of a salt influenced rift basin and thus gain an understanding of the relationships between normal fault growth salt tectonics and the evolution of syn rift depocentres the sleipner basin south viking graben northern north sea is ca 30 km long by 8 km wide and is bound to the east by a major extensional fault zone sleipner fault zone two types of fault related fold are identified within the basin 1 a fault parallel monocline interpreted as an extensional forced fold which formed through the upward propagation of the sleipner fault zone through ductile evaporites of the zechstein supergroup and 2 three fault perpendicular salt cored anticlines that compartmentalise the basin into four sub basins and are related to displacement gradients along strike of the sleipner fault zone detailed seismic stratigraphic analysis of pre and syn rift stratal units reveals a complex interplay between fault growth and salt movement which strongly controlled the evolution of syn rift depocentres during the early syn rift a series of depocentres separated along strike by the fault perpendicular folds were offset into the axis of the basin ca 3 4 5 km to the west of the sleipner fault zone by the fault propagation fold later in the rift event the influence of the fault perpendicular folds depleted resulting in a larger interconnected depocentre that shifted into the immediate hangingwall of the fault as the surface of the fault propagation fold was breached the results of this study have implications for normal fault growth and sedimentary depocentre development in salt influenced rift basins and contribute to the general understanding of the controls on salt migration

growth and linkage of the east tanka fault zone suez rift structural style and syn rift stratigraphic response abstract an integrated tectono stratigraphic analysis of the east tanka fault zone suez rift indicates fault growth by linkage of initially isolated fault segments that is consistent with fault growth models based on displacement length d l scaling laws during the initial 2 4 ma of rifting the east tanka fault zone was composed of two en echelon fault segments c 1 1 5 km long separated by a hanging wall intrabasin high that controlled the geometry of depocentres filled with continental deposits alluvial fan conglomerates were fed through the region between the two fault segments and form a discrete coarse grained body preserved in the immediate hanging wall of the fault zone subsequent stratigraphic patterns indicate that the two faults hard linked to form a single fault zone c 3 5 km long hard linkage of the segments resulted in migration of the zone of maximum displacement and subsidence into the zone of linkage uplift due to the migration of activity caused modification of drainage in the footwall of the fault zone that terminated the growth of the alluvial fan this study demonstrates the need to integrate structural and stratigraphic data when attempting to reconstruct the temporal and spatial evolution of normal fault zones additionally the fault dynamics illustrated have implications for tectono stratigraphic models of rift basins and syn rift stratigraphic evolution

endorheic exorheic transitions of the rio grande and east african rifts this research was supported by nsf ear 1516680 and spanish government project mite cgl2014 59516

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

fault propagation folding in extensional settings examples of structural style and synrift sedimentary response from the suez rift sinai egypt field data from the oligocene miocene gulf of suez rift demonstrate that coeval growth faults folds and transfer zones exerted a major control on synrift stratigraphic sequence development growth folds in the suez rift are related to steeply dipping normal faults that propagated upward resulting in broad upward widening monoclines in overlying strata folding during fault propagation was accommodated by layer parallel slip and detachment along mudstone horizons as well as by normal and rare reverse secondary faults that propagated away from the master fault the eventual propagation of the master fault through to the surface left the steep limb of the monocline and most of the secondary faults in the hanging wall this evolving structural style exerted a marked control on the geometry and stacking patterns of coeval synrift sediments synrift sediments display onlap and intraformational unconformities toward the growth monoclines and buried faults whereas they diverge into broadly synclinal expanded sections away from the growth monocline continued movement across buried faults resulted in the progressive rotation of the monoclinal limb and associated synrift sediments each successively younger sequence dipping basinward at a shallower angle than the previous one the resulting synrift geometries differ significantly from stratal geometries normally anticipated adjacent to normal faults along strike variations in facies stacking patterns are also commonly associated with decreasing displacement across faults and associated folds toward low relief transfer zones data from other rift basins indicate that fault propagation folds are not unique to the gulf of suez

geology alteration and origin of archean au ag cu mineralization associated with the synvolcanic chibougamau pluton the brosman prospect abitibi greenstone belt canada the au ag cu brosman prospect is located in the line lake area on the northern limb of the chibougamau anticline in the northeast part of the archean abitibi greenstone belt this prospect comprises a broad n s subvertical mineralized envelope formed in a synvolcanic fault related environment this envelope is at least 300 m long up to 30 m wide and is known to a depth of 950 m where it remains open it exhibits two contrasting mineralized zones that are representative of the varying styles of mineralization in the area the auriferous zone consists of both ubiquitous pyrite disseminations and au bearing silicate sulfide veins in strongly fractured intrusive effusive and volcaniclastic rocks showing propylitic and chloritic alteration assemblages the polymetallic zone on the other hand is characterized by discrete cu ag au rich magnetite sulfide veins and lesser pyrite disseminations within distal propylitic and proximal potassic to sodic alteration zones the polymetallic zone is hosted by a chaotic assemblage of gabbro and tuff bodies interpreted as a talus megabreccia several lines of evidence including the spatial distribution pattern and nature of the alteration and mineralization assemblages metal associations mass balance calculations pyrite composition and crosscutting relationships are indicative of a preregional deformation synvolcanic origin for the hydrothermal activity crosscutting relationships alteration characteristics as well as whole rock and la icp ms pyrite analyses reveal two stages of hydrothermal alteration and mineralization stage i consists of both ubiquitous disseminated pyrite found in the polymetallic and auriferous zones and contemporaneous magnetite sulfide veins restricted to the polymetallic zone stage ii is restricted to the auriferous zone and corresponds to au bearing silicate sulfide veins with characteristic vein halo chloritic alteration overprinting stage i alteration and mineralization this hydrothermal activity is interpreted to have occurred concurrently with the development of the fertile deeper magmatic hydrothermal system related to the chibougamau pluton stage i hydrothermal activity related to the early build up of the volcanic sequence formed a continuum of mineralization from discrete massive magnetite sulfide veins to ubiquitous pyrite disseminations in a submarine talus megabreccia generated along synvolcanic faults afterward a late au rich contribution to the hydrothermal fluids possibly related to intermediate to felsic magmatism the 2707 6 1 4 ma line lake stock produced stage ii silicate sulfide veins overprinting mineralization and alteration in favorably oriented and sustainably permeable fracture zones of the auriferous zone overall this study suggests that the brosman prospect is a rare example of archean polymetallic mineralization produced by a shallow subaqueous epithermal style subsystem developed in a broader fertile magmatic hydrothermal arc setting

structural geology and 4d evolution of a half graben new digital outcrop modelling techniques applied to the nukhul half graben suez rift egypt abstract lidar based digital outcrop mapping in conjunction with a new surface modelling approach specifically designed to deal with outcrop datasets is used to examine the evolution of a half graben scale normal fault array in the suez rift syn rift deposition in the nukhul half graben was controlled by the graben bounding nukhul fault the fault can be divided into four segments based on the strike of the fault the morphology of hangingwall strata and the variation in throw along strike the segments of the fault became geometrically linked within the first 2 5 m y of rifting as evidenced by the presence of early syn rift abu zenima formation strata at the segment linkage points fault perpendicular folds in the hangingwall related to along strike variations in throw associated with precursor fault segments persist for a further 1 8 m y after linkage of the segments suggesting that the fault remains kinematically segmented we suggest this occurs because of sudden changes in fault strike at the segment linkage points that inhibit earthquake rupture propagation or because displacement is geometrically inhibited at fault linkage points where the orientation of the intersection line of the segments is significantly different from the orientation of the slip vector on the fault system length throw plots and throw contour patterns for minor faults show that some faults initiated in pre rift strata whereas late east striking faults initiated in the syn rift basin fill the late initiating faults are spatially associated with the east striking baba markha fault which was active throughout the rift history but developed as a transfer fault between major block bounding fault systems around 6 7 ma after rift initiation

a coastal aquifer study using magnetotelluric and gravity methods in abo zenema egypt magnetotelluric mt soundings and gravity methods were employed to study the deep freshwater aquifer in the area north of abo zenema city on the eastern side of the gulf of suez egypt seven mt sites and 48 gravity stations were surveyed along northeast southwest profiles as close as possible to a line perpendicular to the coast of the gulf of suez the mt survey was conducted using high and low frequencies to investigate shallow and deep areas respectively one dimensional inversion was conducted using a heuristic inversion scheme of the bostick algorithm the mt data were also inverted with a 2 d smooth model inversion routine using the nonlinear conjugate gradient method to infer variation in vertical and lateral resistivity inside the earth a 100 ohm m homogeneous half space initial model was used to invert the te mode data only then the inverted model obtained from the te mode data was used as an initial model for inversion of the tm mode data the inverted model thus obtained from the tm mode data inversion was used as an initial model for the inversion of the joint te and tm responses two dimensional 2 d forward modeling of the gravity data was conducted using the 2 d polygon method of talwani s algorithm for an arbitrarily shaped body and was based on the subsurface information from the mt survey and the available information about the geological structure of the study area this method enabled us to obtain the basement structure of the coastal aquifer in the study area the results from the analysis and the interpretation of mt and gravity data were used to detect and delineate the groundwater coastal aquifer in the study area

episodic growth of normal faults as recorded by syntectonic sediments july oil field suez rift egypt the july oil field is a major normal fault bounded structural block in the suez rift basin egypt it is adjacent to a major structural transfer zone which has controlled sediment influx to the rift basin center for the past 20 m y the lower to middle miocene upper rudeis formation part of the synrift stratigraphic sequence records deformation of the july structural block the formation contains abrupt lateral changes in thickness and facies which record earlier phases of fault movement and deformation in the july field area that do not conform to the present day structural configuration the upper rudeis formation was deposited as turbidites in a submarine fan system sourced from the western rift shoulder it was deposited over and around bathymetric highs created by coeval fault displacement in the july field area by studying thickness and facies patterns we have determined that the present day main bounding fault to the july block consisted of a series of unlinked fault segments which linked after upper rudeis deposition a subsidiary fault west of the block exerted the most control on thickness patterns not the present day main bounding fault thus commonly used models of deposition in active half grabens are difficult to apply at july field

controls of sedimentation in the malawi rift valley central africa abstract the malawi rift is the southermost classic rift valley trough in the cenozoic african rift valley system much of its floor is flooded by lake malawi which is approximately 570 km long 60 km across and up to 500 m deep this rift basin is a potentially useful analogue of many economically important ancient sedimentary troughs rift valley structures are extremely important in controlling both the distribution of sediments in the basin as a whole and also details of sedimentation on a local scale on the basin wide scale an important association between the type of rift boundary structure and amount of rift floor subsidence is recognised this association appears to apply to several section of the african rift system pre rift topography is major control on the position of major rivers and their deltas or turbidite fans along the basin margin the area of pre rift drainage network captured in the course of rift movements is a significant factor in the hydrologic budget of the basin climate is however the dominant control on the hydrologic budget and at present the basin is flooded to overflow level prevailing winds are important in beach ridge and back beach aeolian dune development climatic conditions produce thermal stratification of the lake with an oxic epilimnion down to 250 m depth overlying an anoxic hypolimnion the oxic bottom waters in the shallower parts of the lake appear to promote iron precipitation in the sediments

fault growth and propagation during incipient continental rifting insights from a combined aeromagnetic and shuttle radar topography mission digital elevation model investigation of the okavango rift zone northwest botswana 1 digital elevation models dem extracted from the shuttle radar topography mission srtm data and high resolution aeromagnetic data are used to characterize the growth and propagation of faults associated with the early stages of continental extension in the okavango rift zone orz northwest botswana significant differences in the height of fault scarps and the throws across the faults in the basement indicate extended fault histories accompanied by sediment accumulation within the rift graben faults in the center of the rift either lack topographic expressions or are interpreted to have become inactive or have large throws and small scarp heights indicating waning activity faults on the outer margins of the rift exhibit either 1 large throws or significant scarp heights and are considered older and active or 2 throws and scarp heights that are in closer agreement and are considered young and active fault linkages between major fault systems through a process of fault piracy have combined to establish an immature border fault for the orz thus in addition to growing in length by along axis linkage of segments the rift is also growing in width by transferring motion to younger faults along the outer margins while abandoning older faults in the middle finally utilization of preexisting zones of weakness allowed the development of very long faults 100 km at a very early stage of continental rifting explaining the apparent paradox between the fault length versus throw for this young rift this study clearly demonstrates that the integration of the srtm dem and aeromagnetic data provides a 3 d view of the faults and fault systems providing new insight into fault growth and propagation during the nascent stages of continental rifting

the role of trace fossil ichnofabric analysis in the development of depositional models for the upper jurassic fulmar formation of the kittiwake field quadrant 21 ukcs

characterization of the monument hill fault system and implications for the active tectonics of the red rock valley southwestern montana new geologic mapping morphologic fault scarp modeling and geomorphic metrics in the red rock valley southwestern montana help characterize the quaternary history of the virtually unstudied monument hill fault and tectonics of the youthful and seismically active red rock graben two generations of pleistocene surface ruptures are preserved along the monument hill fault similarity in rupture ages along multiple strands determined from offset alluvial surfaces and morphologic modeling suggest earthquake clusters at 22e32 ka and possibly 160 ka quaternary activity along the monument hill fault is also reflected in elongate drainage basins and channel profiles with anomalously steep reaches coincident with mapped faults an anticlinal accommodation zone at kidd accommodates a change in fault polarity between the en echelon monument hill and red rock faults and a northward decrease in extension within the red rock graben the unique rupture histories of the monument hill and red rock faults however suggest the systems are not seismogenically linked and that the accommodation zone serves as a rupture barrier the geometry interconnectivity and kinematics of faults in the red rock valley may represent a snapshot of the early stages of extension applicable to the evolution of other northern basin and range grabens 2007 elsevier ltd all rights reserved

fault linkage in continental rifts structure and evolution of a large relay ramp in zavarotny lake baikal russia abstract the internal structure of a large 10 40 km relay ramp has been described between two border faults of the baikal rift zone the relay ramp which is located partly onshore and partly offshore has been investigated using a dense grid of high resolution seismic profiles and a digital terrain model containing topographic as well as bathymetric data the structure of the relay ramp in zavarotny is characterised by the development of secondary faults striking approximately parallel to the main faults in combination with this breaching occurred through the development of a new connecting fault the breaching in zavarotny has not lead to the destruction of the relay ramp but a clear further evolution has been observed e g a similar morphology of the lake floor and the basement inside the relay ramp as well as the development of a second connecting fault the strike direction of the secondary faults in the relay ramp has likely been influenced by the pre existing basement fabric in the area

using the aster global dem to derive empirical relationships among triangular facet slope facet height and slip rates along active normal faults abstract the advent of global dems provided a uniform elevation dataset for studying geomorphic parameters in a variety of settings in this paper aster dem data 30 m pixel size are used to derive empirical relationships between triangular facet attributes and slip rates along active normal faults we sampled 232 triangular facets along 10 normal faults in greece and bulgaria that slip with rates from 0 1 mm yr up to 1 3 mm yr the studied normal faults accumulate quaternary tectonic strain in well known extensional provinces such as central greece crete and sw bulgaria the normal fault footwalls analyzed herein have been developed under similar long term climatic conditions it is suggested that two key geometrical features of the youngest generation of triangular facets slope angle and height can provide useful metrics to assess rates of deformation when seismological and geodetic data are lacking or not found in sufficient quantity to make reasonable assessments our derived empirical relation between slip rate and facet slope angle is y 0 057 x 1 where y is the fault slip rate mm yr and x is the facet slope angle degrees with an r 2 0 728 it is envisaged that our analysis may be helpful in assessing seismic hazard along normal faults with similar facet characteristics in other extensional settings

throw rate variations within linkage zones during the growth of normal faults case studies from the western volcanic zone iceland abstract this work investigates how throw rates vary within fault bends and sites of fault linkage during the process of normal fault growth in the western volcanic zone iceland through detailed field mapping and field measurements of fault throws normal faults are mapped and along strike throw profiles are constructed in order to understand how the throw rates relate with the local fault geometry along faults at different stages of linkage the results show that throw rates increase within linkage zones and propagating fault bends independently from the stage of maturity of the fault bend this implies that 1 the relationship between the local fault geometry and the along strike distribution of throw rate is driven by the deeper part of the fault where established fault bends start propagating to the surface 2 faults grow first by linkage and coalescence of separate faults and then by accumulation of slip on the resultant fault in agreement with models of fault growth by linkage and coalescence 3 incipient fault bends can produce uncertainty associated with palaeoseismological results if fault bends remain unrecognised moreover this work demonstrates that existing models showing increased co seismic and throw rates within fault bends and sites of fault linkage found in continental extensional settings are valid in a geodynamic context of a mid oceanic rifts

segmentation and increasing activity in the neogene quaternary teruel basin rift spain revealed by morphotectonic approach abstract the nnw sse trending teruel basin rift is the largest late miocene quaternary extensional intracontinental structure located within the central eastern iberian chain spain the structural and morphotectonic study carried out in the central northern part of this half graben basin north of teruel city has allowed us to analyse rift segmentation deformation partitioning and rift evolution results are based on vertical displacement calculations fault throw and bending of the main border and intrabasin fault zones we use two geomorfological stratigraphical markers the intramiocene erosion surface ies 11 2 ma and the fundamental erosion surface fes 3 5 ma while the first marker reveals rift initiation under an e w extension the late marker records vertical displacements associated to a second late pliocene quaternary rifting stage characterized by a nearly multidirectional extension regime with prevailing ene wsw trending o3 despite the along axis rift segmentation into three structural domains northern central and southern and the distribution of deformation among border and intrabasin faults in the central and southern domains a consistent average slip rate post ies of 0 09 mm a has been calculated on distinct transects across the basin suggesting a homogeneous crustal scale extension process in the region the results also reveal that slip rates during the late pliocene quaternary 0 12 0 16 mm a are higher than the late miocene early pliocene 0 05 0 07 mm a slip rate increase is caused by i a westward propagation of deformation from the valencia through and ii a change in the regional stress field both enhanced by crustal doming affecting central eastern iberia as well as progressive fault linkage throw vs distance graphs suggest that the main faults are in a transient stage towards coalescence less advanced within the southern domain regional late pliocene quaternary uplift concomitant with increasing slip rates in the teruel basin rift has caused the basin to rise so that synrift sedimentation only took place in rapidly subsiding residual basins until the region became exorheic and the basin was incised by the present day fluvial network

identifying rift zones on volcanoes an example from la reunion island indian ocean we describe a methodology for identifying complex rift zones on recent or active volcanoes where structures hidden by recent deposits and logistical conditions might prevent carrying out detailed fieldwork la reunion island was chosen as a test site we used georeferenced topographic maps aerial photos and digital terrain models to perform a statistical analysis of several morphometric parameters of pyroclastic cones this provides a great deal of geometric information that can help in distinguishing the localisation and orientation of buried magma feeding fractures which constitute the surface expression of rift zones it also allowed the construction of a complete gis database of the pyroclastic cones la reunion is a perfect example where past and active volcanic rift zones are mostly expressed by clusters of monogenic centres the data has been validated in the field and compared and integrated with the distribution and geometry of dyke swarms results show the presence of several main and secondary rift segments of different ages locations and orientations whose origin is discussed considering regional tectonics local geomorphology and volcano deformation

linked sequence stratigraphic and structural evolution of propagating normal faults two distinct phases in the structural evolution of normal faults can be identified in the miocene gulf of suez rift 1 an initial growth fold stage when the fault is a buried structure and 2 a subsequent surface faulting stage during the growth fold stage strata thin and become truncated toward the fault zone and are rotated and diverge away from the buried fault into growth synclines in contrast once the fault breaks surface strata form a divergent wedge which is rotated and thickens into the fault the two tectono stratigraphic styles also occur contemporaneously along the length of a single fault segment growth folding characterizes deformation around the ends of fault segments where the fault is blind whereas the center of fault segments are characterized by surface faulting these observations suggest that marked along strike variation in stratal surfaces and facies stacking patterns will occur in depositional sequences in areas of normal faulting

patterns of displacement along large normal faults implications for basin evolution and fault propagation based on examples from east africa seismic reflection data across six boundary faults from east africa have revealed information about the way boundary faults develop with respect to the synkinematic basin fill previous models of basin fill assume that lateral fault propagation and deposition occur simultaneously which gives rise to along axis onlap of the basin fill onto the prerift basement propagating basin model seismic reflection data from boundary faults in east africa show only rare evidence for along axis broadening of the basins instead the basin margins appear to be fixed from a very early stage in the basin history nonpropagating basin model depocenters shift not by gradual lateral propagation but by abrupt changes in location such observations indicate that boundary fault propagation to near maximum length occurs rapidly during the very early stages of rifting probably by linkage of numerous small faults displacement then builds following the b value earthquake model along the fault during basin development out of phase with the main propagation phase mature fault systems may have experienced several phases of jumps in fault length or the location of fault activity major boundary faults exhibit three basic patterns of evolution these patterns of evolution can have many variants and include 1 simple displacement where maximum displacement is approximately at the center of the fault and decreases gradually toward the fault tips 2 variable along strike displacement that incorporates linkage of in line or en echelon relatively large displacement faults of similar age leaving transverse anticlines and synclines and 3 asymmetric propagation where one tip of a fault remains more or less fixed while the other tip propagates a relatively long distance asymmetric propagation can occur smoothly and gradually or alternatively there can be a jump in the location of the fault and a new fault of different age can form along strike from the older fault eventually the new fault propagates and links with the older fault segment reactivating the older fault to some extent addition ally long lived faults may be composites of fault types 1 3

sedimentology and sequence stratigraphy of early syn rift tidal sediments the nukhul formation suez rift egypt abstract facies and tectono stratigraphic models for the tidally influenced miocene nukhul formation are presented based on outcrop data from hammam faraun fault block suez rift egypt deposits of the nukhul formation are attributed to two linked depositional settings offshore to shoreface and estuary settings and were deposited during initial stages of rifting in hanging wall depocenters of early formed propagating fault segments the offshore to shoreface deposits consist of variably bioturbated mudstones that pass gradationally upward to bioturbated bioclastic sandstones the more landward estuary deposits can be separated into a tripartite division of estuary mouth estuary funnel with bayhead delta and upper estuary channel deposits estuarine processes generated a complex intercalation of lithologies with both gradational and sharp facies transitions in the estuary deposits tidal ravinement surfaces are typically characterized by mudstones of the estuary funnel association below passing abruptly up to erosionally based estuary mouth sandstones maximum flooding surfaces are expressed by an abrupt erosional contact separating estuary mouth sandstones below and estuary funnel mudstones above stratigraphic development was strongly influenced by the evolving early rift structure depocenters were narrow 2 5 km wide and elongate 10 km long parallel to the strike of normal fault segments the shoreface shoal prevented wave energy in the estuary and increased the relative influence of tidal currents the elongate fault controlled geometry of the depocenters confined the bayhead delta and further enhanced tidal influence stratal geometry reflects deformation associated with low relief growth folds and surface breaking faults that together formed part of an evolving fault array this basin configuration and associated nukhul stratigraphy is markedly different to tectono stratigraphic models for crustal scale tilted fault blocks that are applicable from late stages of rifting

fault related folds and along dip segmentation of breaching faults syn diagenetic deformation in the south western sirt basin libya field examples of fault related folds were observed in the south western margin of the sirt basin south central libya single or paired conjugate monoclines drape synclines special drag faults can be put in a geometric and evolutionary model which describes the propagation of basement faults to overlying sediments at the first stage of evolution the propagating normal or oblique slip faults show segmentation along dip direction fault segments are separated by continuous moderately to strongly bended horizons which show different degrees of diagenesis than surrounding intervals fault related folding and faulting was coeval with lithification of certain carbonate levels their gradual cementation increased the rigidity of layers promoting discrete faulting and breaching of fault related folds however folding can be maintained up to the extent when layer dip approaches the dip of the propagating fault zone this type of deformation can be characteristic for sequences consisted of lithified carbonates sandwiched between thicker marl shale intervals

growth and linkage of a segmented normal fault zone the late jurassic murchison statfjord north fault northern north sea abstract the structure of the 25 km long northeastern portion of the murchison statfjord north fault zone and adjacent syn rift stratigraphy are integrated to reconstruct the temporal and spatial evolution during c 30 5 myr of late jurassic north sea rifting based on a structural analysis d d data alone approximately 14 precursor fault strands are identified incorporation of stratigraphic data shows that only six of these strands were important in controlling stratal architecture and distribution three main stages in the evolution of the fault zone are recorded in the syn rift stratigraphy and are biostratigraphically constrained these are 1 following initiation of rifting six isolated fault strands developed each 9 km long fault segments separated by a 2 km wide relay ramp that controlled the stratigraphy for at least the following c 10 5 myr and 3 the two fault segments hard linked forming a single continuous fault trace during the final c 7 myr of rifting the results of this study reveal the necessity to adopt an integrated structural and stratigraphic approach when reconstructing the evolution of normal fault zones the results may also help to further constrain models of fault evolution

structural and stratigraphic development of the newark extensional basin eastern north america evidence for the growth of the basin and its bounding structures the newark basin is a half graben bounded on its northwestern margin by a system of mostly normal slip faults many of which are reactivated paleozoic thrust faults and were active at least sporadically during the deposition of the entire basin fill as a result of along strike variations in displacement on the border fault system subsidence increased from the lateral edges toward the center of the basin and from the hinged margin toward the border fault system some intrabasinal faults also formed during the deposition of units currently preserved in their hanging walls along strike variations in the density of intrabasinal faults probably reflect changes in the dip angle of the border fault system variations in the amount of extension accommodated on these intrabasinal faults resulted in the formation of a transfer fault along strike variations in fault displacement probably produced the transverse folds in the hanging walls immediately adjacent to border faults and major intrabasinal normal faults some folds formed syndepositionally progressively younger strata onlap basement rocks along the hinged margin of the basin and younger splays of the border fault system propagated into the footwall the basin therefore grew deeper wider and longer through time

synvolcanic gold mineralization within a deformation zone the chevrier deposit chibougamau abitibi subprovince canada the chevrier gold deposit is located in the northeastern part of the abitibi subprovince within the chevrier volcanic centre cvc this calc alkaline volcanic centre evolved from mafic to felsic in a submarine environment and the chevrier deposit is spatially associated with the uppermost unit composed mostly of massive dacite to rhyolite dated at 2730 ma the chevrier deposit is divided in two zones the north zone is composed of high grade discordant quartz carbonate veins and disseminated pyrite mostly within melanocratic gabbro dykes whereas the south zone is within a low grade concordant pyrite envelope associated with quartz carbonate pyrite veinlets both zones are highly deformed and show strong carbonate sericite and chlorite alterations although these zones share many characteristics with orogenic deposits the crosscutting of the chevrier deposit by structures associated with the major deformation events suggests that mineralization was prior to these events furthermore felsic dykes associated with the formation of the cvc crosscut auriferous veins and zones therefore suggesting a synvolcanic timing for the gold mineralization characteristics of the zones such as similar vein composition and alteration mineral assemblages and location within the volcanic pile suggest that they are part of a single hydrothermal event where the south zone represents the shallower part of the deposit the chevrier deposit is classified as a noncarbonate hosted stockwork and disseminated deposit and shows many similarities with strata bound gold deposits of the andacollo mining district of chile dating of mineralization at the chevrier deposit indicates that the emplacement of gold occurred more than 25 ma before the onset of the orogeny affecting this part of the abitibi subprovince it also illustrates how synvolcanic mineralization can be misinterpreted as an orogenic deposit without the presence of crosscutting relationships with dykes faults or other structures

evolution of a major segmented normal fault during multiphase rifting the origin of plan view zigzag geometry abstract this case study addresses fault reactivation and linkage between distinct extensional episodes with variable stretching direction using 2 d and 3 d seismic re ection data we demonstrate how the vesterdjupet fault zone one of the basin bounding normal fault zones of the lofoten margin north norway evolved over c 150 myr as part of the north atlantic rift this fault zone is composed of nne ssw and ne sw striking segments that exhibit a zigzag geometry the structure formed during late jurassic and early cretaceous rifting from selective reactivation and linkage of triassic faults a rotation of the overall stress field has previously been invoked to have taken place between the triassic and jurassic rift episodes along the lofoten margin a comparison to recent physical analogue models of non coaxial extension reveals that this suggested change in least principal stress for the lofoten margin may best explain the zigzag style linkage of the triassic faults although alternative models cannot be ruled out this study underlines the prediction from physical models that the location and orientation of early phase normal faults can play a pivotal role in the evolution of subsequent faults systems in multi rift systems

indentation model of the eastern alps and the origin of the tauern window a lithospheric model scaled for density and viscosity was shortened obliquely in front of an indenter whose shape and orientation match those of the south alpine indenter deformation was initially localized into subparallel sets of conjugate transpressive thrusts these structures evolved into folds which were strongly amplified and converged closer together during ongoing shortening finally forming a series of tight antiforms at the same time this tightly folded structure locally accommodated significant orogen parallel extension attaining 100 in front of the leading edge of the indenter but only 15 on the scale of the entire model the internal architecture and fault pattern of the model in map view are very similar to those of the tauern window in the eastern alps emphasizing the importance of localization of folding and shortening rather than orogen parallel extension for its formation

fault growth and linkage implications for tectonosedimentary evolution in the chezhen basin of bohai bay eastern china the chezhen basin has highly representative structural features of the jiyang depression bohai bay area the structural geometry and the boundary fault linkage exert a strong influence on basin development and depositional environment based on structural analysis at least six early fault segments are identified in the northern boundary of the chezhen basin these fault segments are important in controlling stratal architecture and distribution the antecedent structures controlled subbasin initiation and development the cenozoic rift initiated in the early eocene with the development of six isolated fault segments associated with deposition of the es4 member during the deposition of the lower es3 member these six fault segments quickly linked and formed the present architecture frame fault linkage has not resulted in a redistribution of displacement with the expansion of the chezhen basin the depocenters of the upper strata were kept in nearly the same sites until the early miocene then the activity of the chengnan fault ceased fault linkage is a significant event in basin evolution and its process may be very rapid however the fault linkage exerted considerable control on sedimentation and evolution of the basin this study demonstrates that it is necessary to integrate structural and stratigraphic data to reconstruct the temporal and spatial evolution of normal fault zones

fault growth by linkage observations and implications from analogue models abstract using time sequence analyses of extensional fault models we demonstrate the pivotal role played by fault segmentation in the accumulation of displacement and length during the growth of faults experiments are described in which incremental steps during the development of individual faults have been reconstructed from time lapse photographs taken during model deformation these records confirm the composite segment hierarchy of fault structure a pattern that is frequently recognised in many natural arrays they reveal the progressive enlargement of individual faults to be the product of a repetitive cycle of tip line propagation overlap and linkage between nearest neighbours by contrasting the displacement patterns of successive increments during growth convincing evidence is also presented to suggest that individual segments of faults may remain kinematically independent once they are physically linked this behaviour is shown to be responsible for the characteristic saw tooth patterns often recognised in strike parallel fault displacement profiles such patterns are believed to arise where relict segment boundaries remain preserved as asperities to slip so that displacement is confined to discrete parts of a fault plane surface growth in this way also causes the maximum displacement d and surface length l of faults to continually change by different proportions incremental displacement records presented here corroborate field evidence which shows that linkage between fault segments during growth is responsible for a significant component of the spread of values often recorded in d versus l compilations finally we speculate that linkage between fault segments also accounts for transient irregularities recorded in the frequency distribution of the fault length populations of each model

petrogenesis of the rambler rhyolite formation controls on the ming vms deposit and geodynamic implications for the taconic seaway newfoundland appalachians canada the ming cu zn ag au volcanogenic massive sulfide vms deposit is hosted by the upper cambrian lower ordovician rambler rhyolite formation which consists of a folded northeast plunging felsic dome complex developed in the uppermost segment of the obducted supra subduction baie verte oceanic tract in the north central newfoundland appalachians the deposit is overlain by interstratified mafic volcanic flows and volcaniclastic rocks of the snooks arm group the upper 1 km of the rambler rhyolite formation consists of a coherent felsic lithofacies at its base overlain by a quartz bearing volcaniclastic dominated lithofacies units 1 2 and 1 3 geochemically these rocks are light rare earth element lree and large ion lithophile element lile enriched la yb pn 4 20 th 2 58 4 05 ppm and high field strength element hfse depleted y 5 64 6 59 ppm rhyodacite with calk alkalic affinities th yb 2 zr y 7 the last pulse of felsic volcanism unit 1 3 is intimately associated with the massive sulfide lenses and has fi and fii type rhyolite signatures high la yb ratios commonly attributed to deep 30 km crustal melting the end t values of the rhyolites range from 2 5 to 1 3 indicating the rocks were influenced by crustal material a 10 percent batch partial melt of a garnet amphibole metamorphosed normal mid oceanic ridge basalt n morb and island arc tholeiite iat crustal material can generate a melt similar to the felsic rocks hosting the ming deposit however the iat reproduces much better the absolute abundances of lile th sr hfse nb zr y and middle rare earth elements mree of the felsic rocks it is interpreted that the felsic melt came from melting of a subducted slab with iat affinity thus explaining the depth of melt generation and fi fii signatures of the felsic rocks moreover the slab derived siliceous melt may also have contributed magmatophile elements for example ag au se te sn sb hg into the hydrothermal system once it had reached near surface depths and may explain the epithermal suite element enrichment in the ming deposit this study shows that strongly fractionated felsic volcanic rocks associated with boninites such as those associated with the ming vms deposit can be important hosts for precious metal enriched vms and may be as prospective as tholeiitic felsic volcanic sequences for example fiii fiv type rhyolite low la yb ratios the base of the snooks arm group is comprised of spatially restricted sulfide bearing mafic breccia overlain by a regionally extensive sedimentary sequence end t 3 1 to 5 5 which is in turn overlain by interstratified high mg basalt end t 1 6 th enriched back arc basin basalt babb enriched mid oceanic ridge basalt e morb end t 6 6 and lree enriched low ti tholeiitic tuffs end t 0 5 four generations of mafic to intermediate dikes and sills cross cut the rambler rhyolite formation and share similar geochemical characteristics to the extrusive rocks of the snooks arm group suggesting comagmatic relationships the combination of variations in nb yb th yb and end t values within and between units suggest melts derived from depleted to enriched mantle material with melts synchronously generated by both slab metasomatized mantle wedge and upwelling back arc asthenosphere

style and sequence of deformation during extensional fault propagation folding examples from the hammam faraun and el qaa fault blocks suez rift egypt kilometre scale fault parallel folds are identified adjacent to normal faults in the oligo miocene suez rift egypt and are interpreted to have formed in response to fault propagation folding above upward propagating blind faults the geometry scale and distribution of secondary structures within the folds and their cross cutting relationships with the master faults allow the style and sequence of deformation during fault propagation folding to be established and suggest that during the initial stages of folding the proto footwall underwent extension which was accommodated by layer parallel slip in encasing mudstone horizons and linked normal faulting and block rotation in carbonate and sandstone units the proto hanging wall also contains dominantly extensional normal faults although locally where the master fault had a convex into the footwall map view trace reverse faulting and fracturing occurred secondary structures adjacent to the master fault were not all active simultaneously but initiated and died at different stages during the evolution of the fault propagation fold the results of this study confirm many key predictions of numerical and physical analogue models but also highlight several important controls on the evolution of fault propagation folds in extensional settings which existing models cannot capture such as the influence of the map view trace of the propagating fault and lateral variations in cover stratigraphy lithology and strength on the style and magnitude of secondary deformation

lithospheric memory and stress field controls on polyphase deformation of the pannonian basin carpathian system abstract the pannonian basin carpathian system displays pronounced lateral variation in lithopsheric structure and sedimentary basin configuration the tectonic history of the system is characterised by a polyphase history with late miocene extension in the pannonian basin and simultaneously occurring compression in the carpathian arc pre existing structures play a key role in subsequent basin reactivation explaining anomalous features in subsidence characteristics and inferred thinning factors the area exhibits a relatively high level of neotectonic activity imaged by high resolution seismic data intraplate seismicity and stress indicator data major parts of the system have experienced a rapid late neogene uplift and erosion amounting up to several kilometres in the romanian carpathians a major part of the present basin configuration previously primarily attributed to basin formation mechanisms such as stretching in the pannonian basin and lithospheric flexure in the carpathians appears to be strongly affected by recent deformation postdating basin formation of the pannonian basin and the carpathian foredeep these findings affect modelling predictions of basin subsidence sediment sourcing thermal evolution and hydrodynamic regime with implications for hydrocarbon play concepts in the area

the link between tectonics and sedimentation in asymmetric extensional basins inferences from the study of the sarajevo zenica basin abstract the coupled tectonic and depositional history of extensional basins is usually described in terms of stratigraphic sequences linked with the activity of normal faults this depositional kinematic interplay is less understood in basins bounded by major extensional detachments or normal fault systems associated with significant exhumation of footwalls of particular interest is the link between tectonics and sedimentation during the migration of normal faulting in time and space across the basin one area where such coupled depositional kinematic history can be optimally studied is the late oligocene miocene sarajevo zenica basin located in the dinarides mountains of bosnia and herzegovina this intra montane basin recorded oligocene pliocene sedimentation in an endemic and isolated lake environment we use field kinematic and sedimentological mapping in outcrops correlated with existing local and regional studies to derive a high resolution evolutionary model of the basin the novel results demonstrate a close correlation between moments of normal faulting and high order sedimentological cycles while the overall extensional basin was filled by a largely uni directional sediment supply from the neighbouring mountain chain the migration in time and space of listric ne dipping normal faults was associated with a gradual shift of the sedimentological environment transgressive regressive cycles reflect sequential displacements on normal faults and their footwall exhumation defining a new sedimentological model for such basins this early middle miocene extension affected the central part of the dinarides and was associated with the larger opening of the neighbouring pannonian basin the extension was preceded and followed by two phases of contraction the oligocene early miocene thrusting took place during the final stages of the dinarides collision while the post middle miocene contraction is correlated with the regional indentation of the adriatic continental unit this latter phase inverted the extensional basin by reactivating the inherited basal listric detachment

depositional gaps in abitibi greenstone belt stratigraphy a key to exploration for syngenetic mineralization models of greenstone belt development are crucial for exploration allochthonous models predict belts to be a collage of unrelated fragments whereas autochthonous models allow for prediction of syngenetic mineral deposits within specific stratigraphic intervals superior province greenstone belts consist of mainly volcanic units unconformably overlain by largely sedimentary timiskaming style assemblages and field and geochronological data indicate that the abitibi greenstone belt developed autochthonously we describe major revisions to stratigraphy of the abitibi greenstone belt and the implications of an autochthonous development of the volcanic stratigraphy for exploration for syngenetic mineralization the abitibi greenstone belt is subdivided into seven discrete volcanic stratigraphic episodes on the basis of groupings of numerous u pb zircon ages of pre 2750 2750 to 2735 2734 to 2724 2723 to 2720 2719 to 2711 2710 to 2704 and 2704 to 2695 ma we present revised lithotectonic and or stratigraphic nomenclature using these time intervals including 1 isotopic inheritance in younger episodes which indicates that the older episodes 2750 2735 and 2734 2724 ma had greater extent than is presently seen 2 dikes feeding younger volcanic episodes 2706 ma cutting older volcanic units 2734 2724 ma and 3 2710 to 2704 ma mafic to ultramafic sills intruding the 2719 to 2711 ma episode changes to the nomenclature include the identification of pre 2750 ma volcanic episode supracrustal fragments in the northern and southern abitibi greenstone belt and subdivision of the 2719 to 2711 ma 2710 to 2704 ma and 2704 to 2695 ma episodes into lower and upper parts we present the results of this lithostratigraphic subdivision as the first geochronologically constrained stratigraphic and or lithotectonic map of the abitibi greenstone belt many of the volcanic episodes are intercalated with and capped by a relatively thin sedimentary interface zone dominated by chemical sedimentary rocks stratigraphic and geochronological analysis of these zones indicates discontinuous deposition with localized gaps of 2 to 27 m y between volcanic episodes the zones consist of up to 200 m of iron formation chert breccia heterolithic debris flows of volcanic provenance sandstone and or argillite and conglomerate modeling of the time required for deposition of the volcanic units based on rates of magma production in modern arc and plume environments is on the order of 103 to 104 years whereas the time interval between basalt rhyolite cycles is 106 years the sedimentary interface zones are therefore interpreted as condensed sections zones with very low rates of sedimentation in a basinal setting or zones with negligible rates of sedimentation marked by silicification of existing rock types the sedimentary interface zones are therefore considered submarine correlative conformities disconformities or unconformities separating the equivalent of group level stratigraphic and lithotectonic units the unconformity bounded stratigraphic model provides a new regional to deposit scale interpretive model for use in exploration for syngenetic mineralization

sedimentary architecture during carboniferous rift initiation the arid billefjorden trough svalbard analysis of the sedimentary architecture of the early billefjorden trough an exceptionally well exposed carboniferous half graben located in svalbard arctic norway allows detailed reconstruction of fault development and basin geometry sedimentary facies distribution reveals facies variability in an early synrift fill when an array of meso scale intra basinal faults segmented the basin into rotated blocks with differential subsidence growth of these faults into larger systems impacted the distribution of accommodation space and the drainage pattern expressed in fluvial and deltaic sandstone dominated units an axially back stepping character of the early synrift facies associations stages 1 3 is reflected in aggrading homogenous facies types of continental depositional stage 1 which evolved into back stepping facies belts of deltaic to nearshore depositional environment stages 2 and 3 due to the opening of a connection to the sea the drainage pattern and accommodation distribution in the early synrift deposits reflect a relatively symmetrical basin that predates a later prominent half graben configuration of the basin supplementary material figures presenting lithostratigraphic columns of the well data supplementary material 1 location of logs in ragnardalen supplementary material 2 and geological map used in figure 2b supplementary material 3 are available at https doi org 10 6084 m9 figshare c 4293077

normal fault growth displacement localisation and the evolution of normal fault populations the hammam faraun fault block suez rift egypt abstract fault segment linkage migration of the locus of fault activity and displacement localisation were important processes controlling the late oligocene recent evolution of the normal fault population of the hammam faraun fault block suez rift initial fault activity was distributed across the fault block on fault segments that had attained their final length within 1 2 my of rifting these initial segments then either grew by increasing displacement and linked to form longer segmented fault zones or died during a rift initiation phase that lasted 6 8 my following this rift initiation phase displacement became localised onto 25 km long border fault zones bounding the fault block and many of the early high displacement intra block fault zones died following displacement localisation onto the major faults bounding the fault block the locus of maximum displacement continued to migrate with post middle miocene displacement focused on the western margin of the fault block this migration of fault activity between major crustal scale normal faults can be viewed in terms of strain localisation at the rift scale the results from this study question conventional fault growth models based on final displacement distributions and highlight the sequential nature of faulting on major normal faults bounding domino style tilted fault blocks

overlapping faults intrabasin highs and the growth of normal faults normal fault systems bounding extensional basins are typically adjoined by a series of subbasins separated by intrabasin highs the strata within these basins form syndepositional anticlines and synclines whose axes are transverse to the strike of the main bounding fault one possible explanation for these intrabasin highs is that they result from persistent along strike deficits in fault displacement such deficits are incompatible with scaling relationships observed between fault displacement and length based on large populations of faults we present data from active normal faults within the basin and range province and from inactive normal faults of the newark basin of eastern north america demonstrating a clear correlation between the along strike position of overlapping splay faults and the location of intrabasin highs as well as syndepositional transverse folds summed displacements for all faults within an intrabasin high are comparable to the displacements on faults bounding flanking subbasins o

the role of fault interaction and linkage in controlling synrift stratigraphic sequences late jurassic statfjord east area northern north sea examination of well constrained three dimensional seismic data demonstrates the role of fault interaction and linkage in controlling the nature of synrift sequences on the hanging wall of the statfjord east fault a typical late jurassic structure in the northern north sea brent province al though now a single fault the statfjord east fault originally consisted of several en echelon segments each of which defined individual subbasins structural and stratigraphic evidence both along and across fault strike indicates that the fault resulted from segment propagation interaction and linkage facies architecture thickness variations and the internal character of synrift formations are temporally and spatially related to the subbasin geometry variations in displacement along the fault segments exhibit characteristics of interacting en echelon faults including anomalous displacement gradients in regions of segment overlap we attribute the observed shifts in depocenters to local enhancement of displacement rates resulting from the interaction of neighboring fault segments the results have far reaching consequences for synrift plays in the northern north sea because they imply that only from the perspective of fault growth and linkage can the late jurassic structure and stratigraphy be fully understood

kinematic modelling of extensional fault propagation folding abstract many studies have shown that in extensional basins discrete faulting at depth is commonly linked to more distributed deformation in particular folding at higher levels such extensional fault propagation folds are particularly common where there is a distinct mechanical contrast between faulted basement and sedimentary cover outcrop and analogue modelling studies indicate that such folds form as upward widening zones of distributed deformation monoclines above discrete faults at depth with increasing displacement strain the folds are cut by faults as they propagate upwards into the cover to date however there has been little investigation into the kinematics of linked basement faulting and extensional fault propagation folding here we present a two dimensional kinematic model of linked basement faulting and fault propagation folding which is based upon trishear the model allows investigation of the influence of shear zone geometry and the rate of fault propagation upon the style of folds and the strains associated with them the evolution of linked basement faulting and folding predicted by the model is compared in detail to that observed in an analogue model the kinematic model reproduces well many of the features seen both in the analogue model and reported from outcrop and seismic studies

influence of normal fault growth and linkage on the evolution of a rift basin a case from the gaoyou depression of the subei basin eastern china abstract it is widely acknowledged that the growth and linkage of a boundary fault affects the evolution of the accompanying sedimentary basin and exerts a strong influence on its sedimentary characteristics in this study we attempt to discuss the evolution of a boundary fault and rift basin by using seismic interpretation incremental fault throw and growth rate distance g d profile which are more suitable parameters than the expansion index in rift basins where footwall strata are missing because of erosion or a depositional hiatus therefore the gaoyou depression is taken as an example the gaoyou depression is the largest hydrocarbon bearing depression in the subei basin which is a representative rift basin in eastern china the depression is bounded to the south by the jiangdu wubao fault zone which includes the zhen 1 wu 1 zhen 2 and wu 2 faults using high resolution three dimensional seismic data the zhen 1 wu 1 fault can be subdivided into four segments based on its g d profile the shaobo fanchuan liuwushe and liulu segments growth rates indicate that the zhen 1 wu 1 fault and the zhen 2 and wu 2 faults developed successively from the late cretaceous to the miocene during rifting of the gaoyou depression and that development of the zhen 2 and wu 2 faults was controlled by the zhen 1 wu 1 fault the four segments of the zhen 1 wu 1 fault were linked with each other by the time the zhen 2 and wu 2 faults formed in the late paleocene an evolution model of the gaoyou depression is set up in this study integrating the fault activity with previous sedimentological studies we suggest that the evolution of the gaoyou depression was controlled by the jiangdu wubao fault zone rather than by a single fault successive slip of the zhen 1 wu 1 fault and the zhen 2 and wu 2 faults caused subsidence and migration of the depocenters this study presents a case investigation of the effects of boundary faults on rift basins in eastern china

volcanogenic related origin of sulfide rich quartz veins evidence from o and s isotopes at the geant dormant gold mine abitibi belt canada the geant dormant gold mine is a sulfide rich quartz vein gold deposit hosted by a volcano sedimentary sequence and an associated felsic endogenous dome and dikes the auriferous quartz sulfide veins were preceded by two synvolcanic gold bearing mineralizing events early sulfidic seafloor related and later disseminated pyrite in the felsic dome this deposit differs from classical archean auriferous quartz vein deposits by the low carbonate and high sulfide contents of the veins and by their formation prior to ductile penetrative deformation the 18o values of quartz associated with seafloor related auriferous sulfides average 11 9 0 6 n 3 the seafloor hydrothermal fluids had a 18o value of 3 2 calculated at 250 c the oxygen isotope composition of quartz and chlorite from veins average 12 5 0 3 n 20 and 5 9 1 1 n 4 respectively assuming oxygen isotope equilibrium between quartz and chlorite the veins formed at a temperature of 275 c which is consistent with the calculated temperature of 269 10 c from chlorite chemistry the gold bearing fluids had a 18o value of 4 7 calculated at 275 c the 34s values of sulfides from the three gold events range from 0 6 to 2 8 n 32 and are close to magmatic values sulfur isotope geothermometry constrains the sulfide precipitation in the gold bearing veins at a temperature of 350 c the similarity of the isotope data the calculated 18o of the mineralizing fluids and the likely seawater fluid source suggest that the three mineralizing events are genetically related to a volcanogenic hydrothermal system the high value of the auriferous fluids 18o 4 7 is attributed to a significant magmatic fluid contribution to the evolved seawater dominated convective hydrothermal system the two stage filling of veins at increasing temperature from quartz chlorite 275 c to sulfides 350 c may reflect the progressive maturation of volcanogenic hydrothermal systems these results together with field and geochemical data suggest that formation of gold rich volcanogenic systems require specific conditions that comprise a magmatic fluid contribution and gold from arc related felsic rocks coeval with the mineralizing events this study shows that some auriferous quartz vein orebodies in archean terranes are formed in volcanogenic rather than mesothermal systems

early synrift reservoir development on the flanks of extensional forced folds a seismic scale outcrop analog from the hadahid fault system suez rift egypt forced folds typically develop above the tips of propagating normal faults in rifts that contain thick prerift salt or mudstone sequences this structural style is associated with the deposition of wedge shaped synrift deposits that thin and onlap toward monoclinal growth folds overlying the vertically restricted fault tips subtle stratigraphic traps may develop on the flanks of these folds although because of limited seismic resolution and sparse well data the architecture thickness and distribution of these early synrift reservoirs are difficult to predict to improve our understanding of early synrift reservoir development on the flanks of forced folds we focus on seismic scale outcrop analogs along the hadahid fault system suez rift egypt our data indicate that forced folding dominated during early rifting and that the onset of folding was diachronous along strike fluvial systems incised the rotating monocline limbs leading to the formation of valley like erosional relief along the base synrift unconformity reservoir prone fluvial facies are only locally developed along the forced fold flank with their distribution related to the degree of sediment bypass downdip into the adjacent basin early synrift relief not filled by fluvial strata was backfilled by transgressive tidally influenced reservoir prone facies with carbonates being locally developed in areas of low clastic sediment supply further extension and fault tip propagation led to amplification of the forced folds and deposition of shallow marine to shelf parasequences that became thinner toward the growing folds although displaying greater strike continuity than the underlying fluvial or tidal reservoirs shoreface sandstone reservoirs amalgamate onto the flanks of the forced folds and may be absent toward the fold crest this seismic scale outcrop analog helps us better understand the subseismic stratigraphic architecture and facies distributions of early synrift reservoirs on the flanks of extensional forced folds observations from this and other well exposed outcrop analogs should help reduce subsurface uncertainty and risk when exploring for hitherto under explored subtle early synrift stratigraphic traps

experimental models of extensional forced folds we have used single layer and multilayer clay models to study the development of forced folds above normal faults our modeling results show that the deformation patterns associated with extensional forced folding depend on the dip of the underlying normal fault and the presence of layer parallel detachments in single layer clay models extensional forced folds are upward widening monoclines anticlinal axial surfaces dip in the same direction as underlying master normal faults and synclinal axial surfaces dip in the opposite direction of master normal faults most secondary faults are upward steepening normal faults if master normal faults are steeply dipping however many secondary normal faults become high angle reverse faults at shallow depths the propagation and linkage of secondary faults into through going normal faults terminates the development of extensional forced folds more folding occurs prior to fault linkage if the master normal fault is steeply dipping rather than gently dipping most dipping beds and secondary faults are preserved in the hanging walls of the through oing normal faults in multilayer clay models with layer parallel detachments extensional forced folds are also upward widening monoclines slip on the lowest detachment laterally transfers extension induced by normal faulting and forced folding from the master normal fault to the detachment edge slip on overlying detachments accommodates minor thickness changes associated with upward widening of the fold secondary faults include low angle normal faults near the anticlinal axial surface minor thrust faults near the synclinal axial surface and high angle normal faults above the detachment edge the model predicted deformation patterns are similar to those of extensional forced folds from the gulf of suez and offshore norway this similarity suggests that our modeling results apply to extensional forced folds and can provide guidelines for interpreting field well and seismic data

are the alps collapsing abstract orogenic collapse is a process that transfers gravitational potential energy from regions of high potential energy to regions of lower potential energy this transfer is classically considered to be accomplished by extension in the orogenic core and by synchronous shortening in foreland regions of the orogen not all extensional features in collisional mountain belts need however reflect orogenic collapse normal faulting thrust faulting and strike slip faulting are all active in different parts of the alps today and reflect complex local responses to ongoing europe adria convergence the western alps is the only area today where extension and shortening radial to orogen trend occur synchronously and where orogenic collapse may be an important process elsewhere in the alps normal faults are oriented at a high angle to orogen trend and were primarily active in oligocene and miocene time most present day activity in the central and eastern alps is on strike slip faults that are accommodati

tectonic sedimentology sediment systems deciphering global to local tectonics tectonic sedimentology has broad appeal because it can be applied at many time and length scales such as sedimentary consequences of changing rates of plate creation at mid ocean ridges continent continent collisions plateaux uplift active plate margins extensional rift tectonics and the birth growth and death of individual folds and faults tectonic sedimentology deals with the direct influence of neotectonics on sedimentation and basin development and with the inverse problem of reconstructing the order and development of palaeotectonic structures this review attempts to show how the scope and importance of the subject has developed over the last decade and is divided into five themes i at the largest tectonic scale constraints on mid ocean ridge activity and continent continent collisions come from a precise chemical analyses of fluid inclusions in marine halite deposits dating back to ca 550 ma b sr isotopic ratios of marine phanerozoic calcitic fossils and c chemical composition of archaean and proterozoic banded iron formations ii at regional scales constraints on the timing and extent of continental plateau uplift incision and cratonic tilting are given by a palaeoaltimetry estimates from oxygen isotope depletion in carbonate palaeosols b radiometric dating of palaeowater table speleothems and c preferential river migration iii at basin scales catchment processes are emphasized as key controls on sediment flux from tectonic uplands to sedimentary basins the inadequacy of sediment transport algorithms based on tractive stress and flow power to describe erosion incision and sediment transport during the most formative catchment hydrological events is emphasized iv rates of basin scale fault and fold growth displacement death and basement uplift are provided by application of facies analysis and sequence stratigraphy to accurately dated sediments in sedimentary basins v the effects of changing climate and varying basin base level in modifying tectonic influences on erosion and sedimentation are examined in such cases experimental and numerical modelling using multi variate parameters of subsidence rate sediment supply and sea level change can shed light on the problem future developments will undoubtedly improve such models hopefully establishing full linkage and feedback between sediment water supply and changing climate within an overall tectonic framework that may itself be changing

3d seismic analysis of the structure and evolution of a salt influenced normal fault zone a test of competing fault growth models abstract in this paper we determine the structure and evolution of a normal fault system by applying qualitative and quantitative fault analysis techniques to a 3d seismic reflection dataset from the suez rift egypt our analysis indicates that the october fault zone is composed of two fault systems that are locally decoupled across a salt bearing interval of late miocene messinian age the sub salt system offsets pre rift crystalline basement and was active during the late oligocene early middle miocene it is composed of four planar nw se striking segments that are hard linked by n s striking segments and up to 2 km of displacement occurs at top basement suggesting that this fault system nucleated at or more likely below this structural level the supra salt system was active during the pliocene holocene and is composed of four nw se striking listric fault segments which are soft linked by unbreached relay zones segments in the supra salt fault system nucleated within pliocene strata and have maximum throws of up to 482 m locally the segments of the supra salt fault system breach the messinian salt to hard link downwards with the underlying sub salt fault system thus forming the upper part of a fault zone composed of i a single amalgamated fault system below the salt and ii a fault system composed of multiple soft linked segments above the salt analysis of throw distance t x and throw depth t z plots for the supra salt fault system isopach maps of the associated growth strata and backstripping of intervening relay zones indicates that these faults rapidly established their lengths during the early stages of their slip history the fault tips were then effectively pinned and the faults accumulated displacement via predominantly downward propagation we interpret that the october fault zone had the following evolutionary trend i growth of the sub salt fault system during the oligocene to early middle miocene ii cessation of activity on the sub salt fault system during the middle miocene to early pliocene iii stretching of the sub and supra salt intervals during pliocene regional extension which resulted in mild reactivation of the sub salt fault system and nucleation of the segmented supra salt fault system which at this time was geometrically decoupled from the sub salt fault system and iv pliocene to holocene growth of the supra salt fault system by downwards vertical tip line propagation which resulted in downward breaching of the salt and dip linkage with the sub salt fault system the structure of the october fault zone and the rapid establishment of supra salt fault lengths are compatible with the predictions of the coherent fault model although we note that individual segments in the supra salt array grew in accordance with the isolated fault model our study thereby indicates that both coherent and isolated fault models may be applicable to the growth of kilometre scale basin bounding faults furthermore we highlight the role that fault reactivation and dip linkage in mechanically layered sequences can play in controlling the three dimensional geometry of normal faults

seismic stratigraphy of camamu basin northeastern brazil the camamu basin is located at the northeastern brazilian coastline and has significant hydrocarbon potential in both shallow and deep water settings however despite an already operating productive gas field the basin is not well known herein a regional stratigraphic interpretation of the rift the transitional and the drift megasequences is reported based on a data set of 152 post stacked 2d seismic lines 1 3d seismic cube and 34 wells with eletro logs the study revealed that the rift megasequence is much more complex than previously thought in the southern region of the camamu basin five rift sequences were mapped while in the northern region in the area of the regional tectonic lineament known as the salvador transcurrent zone stz seven rift sequences were recognized this difference suggests a tectonic control during the rifting process because the northern region is intensely affected by shear stress induced by transcurrent tectonics of the stz during the crustal breakup for the post rift or transitional phase associated with thermal subsidence installed after the rift as well as for the drift succession the tectonic control exerted by salvador s transcurrent zone is not detectable and the tectono sedimentary evolution of the basin follows the general pattern of the brazilian marginal basins

stratigraphic control on laterally persistent cementation book cliffs utah field data from the upper cretaceous blackhawk formation in the book clitfs utah colorado demonstrate the presence of laterally extensive carbonate cements beneath major marine flooding surfaces the occurrence of firmgrounds compaction around concretions and high minus cement porosities indicate that cementation occurred during early diagenesis it is proposed that the early cementation associated with these marine flooding surfaces occurred as a result of reduced sediment accumulation rates or non depositional hiatuses linked to abrupt deepening during marine flooding these reduced sediment accumulation rates extended sediment residence time within early diagenetic zones leading to enhanced early cementation in shallow marine sandstones and mudstones