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

drainage development and sediment supply within rifts examples from the sperchios basin central greece drainage systems juxtaposed with modern depositional environments within the sperchios rift allow detailed analysis of the relationships between drainage catchments sediment supply and alluvial fan fan delta geometries prominent footwall escarpments within the rift are created by e w trending normal faults and variations in the topography of these escarpments are related to fault segmentation and bedrock lithology drainage catchments within the rift are classified on the basis of morphology area bedrock lithology and relationship to fault geometries five drainage domains can be identified within the sperchios rift i footwall ii hanging wall iii transfer zone iv axial and v karst domains bedrock lithology has a major control on the size of catchments in all drainage domains in addition topographic lows associated with transfer zones along the border fault are sites of major drainage catchments and act as conduits for sediment supply to the rift variations in drainage catchments the resultant sediment supply and accommodation development along the rift produce a range of stratigraphic architectures along fault segments low sediment supply and high subsidence rates lead to aggradational sequence sets whereas progradational sequence sets develop at transfer zones where rates of sedimentation are high and the rate of subsidence is low

accommodation and supply a dual control on stratigraphic sequences abstract it is widely accepted that both eustatic and tectonically controlled regional changes of sea level have contributed to the record of stratigraphic sequences i suggest that environmental change be added as a third autonomous control sedimentologic principles clearly indicate that sequences and their systems tracts are controlled by the interplay of two rates the rate of change in accommodation space available for sedimentation and the rate of sediment supply sea level has direct control on accommodation but its influence on sediment supply is remote and easily overshadowed by environmental factors for instance the record of the most recent sea level rise is a transgressive systems tract where supply is low it is a prograding highstand systems tract in deltas where the supply is high examples of sequence boundaries generated by changes in sediment supply include tectonically driven shifts in sediment input into basins changes in ocean currents pulsating supply from failure of submarine slopes and drowning of carbonate platforms by environmental stress furthermore the stratigraphic sequences in fluviatile continental basins are physically removed from sea level induced changes in accommodation and must have formed by changes in the rate and pattern of supply subaerial exposure of marine sediments at the sequence boundary is a most important criterion for recognizing sea level cycles as opposed to supply cycles other criteria include downstepping of shelf breaks and characteristic patterns in the spacing of time lines within sequences some third order cycles ca 0 5 3 ma duration meet these criteria others do not cycle stacking patterns and the shifting facies belts on cratons indicate that many second and third order cycles lack pronounced exposure unconformities and represent gradual changes superimposed on more rapid shorter oscillations seismic data yield poor images of these gradational changes because they lack resolution seismic models of outcrops show that near the limits of resolution the seismic tool tends to portray rapid changes in facies and bed thickness i e lateral variations in supply as unconformities seismic unconformities do not necessarily correspond to unconformities in outcrop the succession of stratigraphic sequences is best considered a composite record of sea level and environmental change separating the various controls requires carefully planned experiments work on the oxygen isotope curve another proxy for sea level has set an example in this respect

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

interaction of an antecedent fluvial system with early normal fault growth implications for syn rift stratigraphy western corinth rift greece continental overfilled conditions during rift initiation are conventionally explained as due to low creation of accommodation compared with sediment supply alternatively sediment supply can be relatively high from the onset of rifting due to an antecedent drainage system the alluvial lower group of the western plio pleistocene corinth rift is used to investigate the interac tion of fluvial sedimentation with early rifting this rift was obliquely super imposed on the hellenide mountain belt from which it inherited a significant palaeorelief detailed sedimentary logging and mapping of the well exposed syn rift succession document the facies distributions palaeocurrents and stratigraphic architecture magnetostratigraphy and bios tratigraphy are used to date and correlate the alluvial succession across and between fault blocks from 3 2 to 1 8 ma a transverse low sinuosity braided river system flowed north north east to east across east west striking active fault blocks 4 to 7 km in width deposits evolved downstream from coarse alluvial conglomerates to fine grained lacustrine deposits over 15 to 30 km the length scale of facies belts is much greater than and thus not directly controlled by the width of the fault blocks at its termination the distribu tive river system built small stacked deltas into a shallow lake margin the presence of a major antecedent drainage system is supported by i a single major sediment entry point ii persistence of a main channel belt axis iii downstream fining at the scale of the rift basin the zones of maximum sub sidence on individual faults are aligned with the persistent fluvial axis sug gesting that sediment supply influenced normal fault growth instead of low accommodation rate during the early rift phase this study proposes that facies progradation can be controlled by continuous and high sediment sup ply from antecedent rivers

sedimentation and tectonic geomorphology adjacent to major active and inactive normal faults southern greece the active psatha skinos normal fault is uplifting a contrasting variety of lithologies in its footwall including mesozoic limestones ophiolitic peridotites and poorly consolidated plio pleistocene sediments of the inactive megara basin in the latter basin linear marginal uplands border the sedimentary fill and are interpreted as degraded and segmented scarp lines which exhibit features such as facetted spurs drainage domains are defined as groups of drainage basins sharing a common tectono geological substrate contrasting domains in the footwall of the active fault have given rise to spectacular differences in drainage basin growth and form in the uplifting footwall raised coastal terrace levels are present at about 10 and 40 m the latter have yielded corals dated at between 90 126 ka and have enabled us to calculate uplift and erosional rates extrapolation of these rates indicate that some 350 m of footwall relief has been produced over approximately 1 ma most of the sediment eroded from the uplifting footwall is presumed to have been re sedimented into the alkyonides gulf basin plain during this time the prominent footwall unconformity so produced forms a fine modern analogue to features seen in ancient syn rift tilt blocks such as the viking graben footwall uplift has also backtilted the former depositional surface of the megara basin and caused reversal of flow in its axial drainage domain a variety of depositional environments are documented in the subsiding hangingwall to the coastal fault including syn quake talus cones alluvial fans intra fan marshes and swamps truncated fans transgressive barriers and spits

quaternary rate of folding of the ventura avenue anticline western transverse ranges southern california upper quaternary terraces of the ventura river california are uplifted tilted and folded over the ventura avenue anticline rates of uplift and tilting have decreased since inception of the structure over the past 200 ka assuming that the chronology based on amino acid racemization 14c dates and soils correlation is approximately correct then the minimum possible average rate of uplift in the axial region of the fold has decreased from 14 mm yr to 2 mm yr during the past 200 ka interval rates of uplift for the periods 200 ka to 80 or 105 ka 80 or 105 ka to 30 ka and 30 ka to present are respectively about 20 mm yr 9 mm yr and 5 mm yr the rate of tilting shows a similar trend decreasing from 5 8 urad yr 2 5 urad yr and 1 2 urad yr for the same time intervals respectively based on the mechanics of flexural slip folds in stratified sedimentary rocks these data suggest that the rootless ventura avenue anticline is a fold that has been shortening at a relatively constant rate of about 9 mm yr since its inception

denudation vertical crustal movements and sedimentary basin infill denudation and vertical crustal movements are linked through the isostatic equation for conservation of lithospheric mass recent empirical results from a wide range of sources are presented on the rates of these processes denudation alone can cause non tectonic isostatic surface uplift of the right magnitude predicted by theory a case is made following ahnert for a single linear relationship although with much scatter between denudation rate and mean drainage basin relief for large basins some recent determinations of denudational time constants have neglected to include tectonic and isostatic terms which oppose the reduction of relief by denudation application of diffusional transport models to determine the rate of sediment deposition are severely limited by inherent one dimensionality and neglect of suspended and washload contributions basin infill sequences may be used to determine past sediment transfer coefficients from a hinterland but problems arise in the apportionment of the various hinterland fluxes that occur in real world three dimensional basins sediment yields in smaller half graben and growth fold basins must reflect the magnitude of drainage basins and the complex local controls upon sediment yields examples are given from extensional basins in the western usa and greece the length of tectonic relief produced in tilt blocks and growth folds will control the area of drainage basin developed through the fractal form of hack s law and hence the magnitude of deposition in sedimentary basins adjoining tectonic uplands

the geometrical evolution of normal fault systems abstract the purpose of this paper is to examine the kinematic behaviour of normal fault systems and see what general conditions govern their geometrical evolution we pay particular attention to seismological and surface data from regions of present day active normal faulting as the instantaneous three dimensional geometry at the time of fault movement is better known in active regions than in areas where the faults are now static most normal faults are concave upward or listric this shape can be produced by geometric constraints either because the faults reactivate curved thrusts or because they must be curved to accommodate rotations another effect which will produce curved faults is the variation of rheology with depth brittle failure at shallow depths produces less fault rotation than does distributed creep in the lower part of the crust an important geometric feature of normal faulting is the uplift of the footwall the amount of such uplift is related not only to the elastic properties of the lithosphere but also to the throw and dip of the fault a striking feature of active normal faults is that they occur in groups in which all the faults dip in the same direction this behaviour arises because the faults cannot intersect if they do one must cease to be active the rotation which such fault systems produce reduces the dip of the faults until a new steeply dipping fault is formed once a new fault cuts pre existing faults the earlier faults become locked and a new set of faults must propagate rapidly across the whole region involved many of these geometric constraints also apply to thrust faulting

normal fault control on bedrock channel incision and sediment supply insights from numerical modeling 1 the evolution of footwall drainage basins sediment supply and hanging wall stratigraphy in rift basins is investigated using a coupled numerical model of detachment limited stream network evolution and coarse grained fan delta deposition the response of bedrock channel networks to repeated footwall uplift events leads to increasing sediment supply over tens of thousands of years as the networks initiate and then expand followed by relatively constant sediment supply as the stream networks reach their maximum spatial extent the distinct time lag between the onset of tectonic activity and attainment of maximum sediment supply leads to stratigraphies that are initially aggradational and then progradational much of the variation in sediment supply is the product of the complex response and reorganization of the stream networks to faulting related perturbations and is not directly related to specific faulting events increasing fault displacement drives the system toward a new steady state with a higher sediment supply but is initially expressed as a retrogradation as sediment supply lags behind increased displacement the converse is true for a decrease in fault displacement which is initially expressed as progradation continual stochastic variation in recurrence interval leads to a system that does not achieve a steady state and as a result exhibits continual variation in sediment supply the model results emphasize the local tectonic controls on stratigraphic architectures developed within extensional basins and the complex manner in which stream network growth and response to tectonic activity can be expressed in the stratigraphic record

impacts of small scale faults on continental to coastal plain deposition evidence from the realgrunnen subgroup in the goliat field southwest barents sea norway abstract in this study we synthesise sedimentological fault and amplitude versus angle ava analysis and propose that the fruholmen and tubaen formations realgrunnen subgroup are syn kinematic deposits that record a previously undocumented early phase of mesozoic rifting on the troms finnmark fault complex and within the hammerfest basin the realgrunnen subgroup hosts one of two triassic reservoirs currently being produced in the goliat field here the subgroup sits unconformably on top of the storfjorden subgroup carnian snadd formation away from the goliat field which is characterised by a periclinal anticline the realgrunnen subgroup also comprises the lower middle jurassic nordmela and sto formations sedimentological analysis of six exploration wells reveals that the fruholmen formation was deposited in a prodelta to delta plain environment where tide influenced and fluvial dominated distributary channels are represented by clay siltstones and very fine grained sandstones the overlying tubaen formation is characterised by medium to very coarse grained deposits locally conglomeratic and represents a widespread braid plain with localised alluvial fans displacement profiles of faults and along fault thickness variations demonstrate that an immature fault system was active during deposition of the realgrunnen subgroup a series of unconnected fault segments hosted isolated sub basins and erosional catchment areas in their hanging and footwalls respectively an ava attribute map generated from a 10 ms interval of the uppermost part of the subgroup reveals gross sand prone depositional bodies i e individual and amalgamated channels some of which show meandering geometries ox bow lakes and alluvial fans sand bodies frequently show elongate geometries parallel to faults indicative of syn depositional fault related subsidence driving mechanisms responsible for the norian to rhaetian event may relate to contemporaneous rejuvenation of the fennoscandian hinterland development of the novaya zemlya fold and thrust belt and or the early cimmerian tectonic phase in northern europe

holocene palaeoenvironmental changes in agia paraskevi prehistoric settlement lamia central greece abstract holocene palaeoenvironmental changes in the area of the prehistoric settlement of megali vrysi close to the village of agia paraskevi in central greece 5 km east of lamia city were investigated the area is situated in the low flat alluvial plain on the outskirts of sperchios valley that is bordered nnw to ene by a rocky hilly ridge of the othrys mountain foothills 5 5 km away from the present coastline the megali vrysi site is considered to be an important mediterranean prehistoric commercial centre reconstruction of the palaeoenvironmental changes of the broader area adds new information concerning the general palaeogeographical setting of the settlement multidisciplinary research involved a detailed geomorphological survey combined with stratigraphical palaeontological and geophysical studies the penetrated strata differentiated into 4 units from top to bottom the first represents the archaeological strata the second consists of the freshwater marshy sediments while the third is the transition layer between the second and the deeper fourth group of marine lagoonal sediments the holocene stratigraphy data was combined with the 14 c ams dating results and showed a marine palaeoenvironment 5500 bc gradually having shifted to a coastal lagoonal one 3500 bc and finally changed to a freshwater marshy environment 2500 bc the comparison between ages and depths of the relative sea level points allowed the estimation of the sea level rise rate for the agia paraskevi area which is considerably lower than the one proposed for the aegean sea in the same time period this considerable offset is attributed to the intensive tectonic uplift of the study area due to the tectonic deformation of the sperchios valley and this is probably why the prehistoric coastal settlement remained on the surface and unaffected from the sea transgression for more than 7000 yrs during holocene

tectono sedimentary evolution and hydrocarbon reservoirs in the early cretaceous tanan depression tamtsag basin mongolia abstract the responses of depositional patterns to extensional faulting during the rift cycle are discussed in this article based on an integrated analysis of 3d seismic reflections wire logs and cores from the early cretaceous tanan depression in the tamtsag basin mongolia the synrift succession comprises four third order sequences sq1 4 a four stage fault evolution is defined including early synrift sq1 initial isolate faults early synrift sq2 rapid fault propagation climax synrift sq3 maximum fault relief and late synrift sq4 minor fault activity stages the initial isolated fault stage is defined by separated and small sized half grabens associated with short dispersal alluvium in contrast the rapid fault propagation stage is characterised by much longer dispersal systems of fan delta deposits as rifting progressed a considerable increase in the basin subsidence occurred and the maximum fault displacement led to a dustpan basin geometry the coalescence of depocentres and extensive deep water deposits the observed both sediment starvation and balanced filled patterns in sq3 indicate that caution must be exercised when attempting to correlate reservoirs and source rocks since variations in basin filled patterns would be enhanced by the displacement localisation on several major faults during the significant basin formation during the early period of the climax synrift stage footwall sourced systems were prominent but drainages in prior relay zone sites were mostly decayed or submerged in response to the subsequent degradation of the footwall sources axial sourced braided deltaic systems became more important during the later period an abrupt decrease of faulting at the end of the rift cycle gave a rise to an increased sediment supply and long dispersal axially sourced systems in the tanan depression petroleum exploration shows that fan delta front sandstones in sq2 are the most prospective hydrocarbon reservoirs whereas the nearshore and offshore sub lacustrine fan deposits in sq3 have proved to be secondary potential oil bearing reservoirs this study indicates that sediment dispersal patterns would be significantly re organised by the differential faulting displacement patterns and varied sediment potentials during the different synrift stages the rapid fault propagation allowed the fault arrays to reach their nearly maximum length during the early period of the basin evolution while the displacement remained almost constant this fault growth pattern tends to establish large scale topographic lows including overlapped transfer zones and hanging dip slope hence major drainage catchments and long dispersal depositional systems of sand rich deposits are facilitated during this early fault propagation stage which may be a key aspect for the tectono sedimentary evolution in rift basins in addition the fault and sedimentary relationships defined here may be used as a model when studying less data rich rift basins elsewhere

tectonic geomorphology of the easternmost extension of the gulf of corinth beotia central greece the easternmost sector of the gulf of corinth the beotia area in central greece is an area with active normal faults located between the two major rift structures of central greece the gulf of corinth and the north gulf of evia these active normal faults include wnw to e w and ne to ene trending faults affect the landscape and generate basin and range topography within the beotia we study four normal fault zones and drainage basin geometry in the easternmost sector of the gulf of corinth to document the impact of active tectonics on the landscape evolution fault and drainage geometry are investigated based on detailed field mapping and high resolution digital elevation models tectonic geomorphic analysis using several parameters of active tectonics provides information concerning the relative tectonic activity and fault growth in order to detect areas of lateral stream migration that could indicate recent tectonic activity the transverse topographic symmetry factor and the asymmetry factor are used to analyse drainage basin geometry in six large drainage basins and a drainage domain covering the study area our results show that vertical motions and tilting associated with normal faulting influence the drainage geometry and its development values of stream gradient indices sl are relatively high close to the fault traces of the studied fault zones suggesting high activity mountain front sinuosity smf mean values along the fault zones ranges from 1 08 to 1 26 valley floor width to valley height ratios vf mean values along the studied fault zones range between 0 5 and 1 6 drainage basin shape bs mean values along the fault zones range from 1 08 to 3 54 all these geomorphic parameters and geomorphological data suggest that the analyzed normal faults are highly active lateral fault growth was likely produced by primarily eastward propagation with the wnw to e w trending faults being the relatively more active structures

geodetic determination of tectonic deformation in central greece from 1900 to 1988 the global positioning system has been used to measure the relative displacements of fifteen monuments in a hundred year old triangulation network spanning part of the aegean extensional basin these displacements reflect the tectonic deformation of the region over the past century showing more than one metre of north south extension across the network the crust in this region appears to contain a few slowly deforming blocks separated by more rapidly deforming zones

a multi proxy approach to reconstructing sedimentary environments from the sperchios delta greece this paper presents an integrated approach to assess holocene environmental changes in the sperchios delta sperchios rift central greece a multidisciplinary study was carried out applying established analytical methods as well as exploring new techniques to detect past environmental conditions in a fluvio deltaic depositional system a series of six deep boreholes up to 50 m long and four shallow cores up to 6 m long from across the delta plain were studied in detail sedimentary facies were defined by changes in grain size and macro and microfaunal composition variability in mineral magnetic composition documented by changes in bulk magnetic susceptibility and 77k 293k and remanence parameters s 300 and arm sirm ratios as well as down core elemental variations obtained by scanning micro x ray fluorescence xrf provide constraints on the depositional changes related to the evolution of the sperchios delta correlations between elemental data derived by xrf analyses and grain siz

geological and geomorphological evidence of recent coastal uplift along a major hellenic normal fault system the kamena vourla fault zone nw evoikos gulf greece the active normal faulting region of central greece has been the focus of intense study due to its relatively high rates of tectonic deformation and the frequent occurrence of damaging moderate magnitude earthquakes the structure of central greece is dominated by a series of roughly wnw ese trending extensional faults which have created a series of half grabens the most prominent of which are the gulf of corinth and the evoikos gulf of these two structures the evoikos gulf and particularly its northern part remains poorly understood in terms of its geodynamic structure and tectonic significance here we use exposed coastal sediment sequences and coastal geomorphological indicators to examine the pattern of historical sea level change in the northern evoikos gulf specifically in the hangingwall of the prominent kamena vourla fault system to better constrain recent coastal elevational changes and tectonic activity in this area in particular we describe and analyse a series of exposed coastal sections which contain recent 1 m above contemporary high water level these deposits occur in the hangingwall of the prominent arkitsa normal fault strand and indicate a local uplift rate possibly exceeding 1 mm year significantly greater than long term regional uplift rates the pattern of uplift of these coastal sections is most consistent with recent coseismic uplift on an offshore shore parallel fault strand north of arkitsa

the depositional evolution of diapir and fault bounded rift basins examples from the lusitanian basin of west iberia new data on the evolution of rift basins is presented after analysing the late jurassic stratigraphy of the central lusitanian basin west iberia well outcrop and regional 2d seismic reflection profiles are used to investigate the differences in stratigraphic signature between diapir and fault bounded sub basins during the late jurassic syn rift phase surface rupturing in fault bounded sub basins resulted in the formation of tectonic scarps from which footwall derived gravity flows were sourced in contrast the diapir bounded bombarral alcobaca sub basin evolved as a distal bowl shaped depocentre with an axis located up to 10 km away from its basin margins low gradient marginal slopes developed in the bombarral alcobaca sub basin during the late jurassic rifting while growing salt pillows limited the vertical propagation of basement normal faults differences in tectonic evolution basin physiography and sediment input are the main factors responsible for the distinct sedimentary evolutions recorded in the study area 1 transverse footwall derived sediment fans predominant in fault bounded regions give place to axial southwards prograding fluvial to shallow marine units in the diapir bounded sub basins 2 growing salt pillows absent in the fault bounded sub basins formed barriers to and limited the development of transverse drainage systems

the ochil fault and the kincardine basin key structures in the tectonic evolution of the midland valley of scotland the ochil fault one of the most prominent tectonic features in the midland valley of scotland juxtaposes lower devonian volcanic rocks against late westphalian strata implying a possible vertical displacement of up to 4 km the kincardine basin in its hanging wall although actively subsiding during the greater part of the silesian trends generally n s perpendicular to the ochil fault and its silesian sedimentary record shows little sign of tectonic control by that fault it is proposed that the ochil fault was initiated possibly as a sinistral strike slip feature in the devonian but acted as a sidewall fault during the early evolution of the kincardine basin attributed to extension on a hypothetical pre brigantian fault along the bo9ness line on the east side of the basin until late namurian times when active extension ceased both faults were probably buried during late namurian and westphalian times reactivation of the ochil fault during end carboniferous n s extension dated by quartz dolerite emplacement was responsible for probably at least 2 km displacement including the presently visible footwall uplift it is suggested that the hanging wall may have contained a permian basin now removed