did the last sea level lowstand always lead to cross shelf valley formation and source to sink sediment flux 1 it is commonly believed that the efficiency of sediment flux from continents to oceans is maximized during relative sea level rsl lowstands by means of cross shelf valleys that are directly connected to the continental slope and deep marine environment while such conditions have been documented for the last rsl lowstand along several continental margins there is increasing evidence that radically different conditions persisted during the last glacial maximum lgm elsewhere with lowstand shorelines that remained on the continental shelf here we analyze the relationship between the lgm 21 ka shoreline and the shelf edge for the gulf of mexico off the united states and the bay of biscay off france a geophysical model is used to compute shoreline positions corrected for isostatic movements and the shelf edge position is quantified by means of curvature the conditions in the two study areas differed markedly throughout the gulf of mexico study area lgm sea level dropped to a point commonly 40 m below the shelf edge consistent with conventional sequence stratigraphic models while in the bay of biscay the modeled lgm shoreline remained well landward of the shelf edge in places separated by hundreds of kilometers these observations hint at potentially significant implications for 1 the source to sink sediment flux from continents to oceans and its variation in time and space 2 sequence stratigraphic models that predict deep marine sedimentation as being particularly prominent during rsl lowstands and 3 the occurrence of paleovalleys and related features on the continental shelf in addition our findings raise fundamental questions about the mechanics of shelf edge formation

a diagnostic model of summer circulation on the northwest shelf of the east china sea abstract hydrographic data and moored current meter records collected during a cruise of the china u s joint study in august 1981 were used to compute the circulation in the east china sea a steady state linear diagnostic model with a constant vertical eddy viscosity was developed lateral friction was ignored the taiwan warm current plays a dominant role in the survey area both the huanghai warm current and the cyclonic cold water gyre southwest of cheju island are closely related to the taiwan warm current

the calculation of kuroshio current structure in the east china sea early summer 1986 abstract on the basis of hydrographic data and moored current meter records obtained during an early summer cruise may 20 june 23 of 1986 a three dimensional diagnostic calculation of the circulation is performed in the survey area which covers the east china sea continental shelf okinawa trough and an area east of the ryukyu island the kuroshio current condition and structure in the east china sea its branches and their interrelationship as well as the eddies around the kuroshio are discussed when the kuroshio entered the area northeast of taiwan there were two branches the main branch flowed northeastward along the continental slope and the other branch was at the eastern part of the okinawa trough the main axis of the kuroshio followed the continental slope above the 300 m level but moved gradually eastward to the okinawa trough below the 300 m level

the application of sequence stratigraphy to upper carboniferous fluvio deltaic strata of the onshore uk and ireland implications for the southern north sea stratigraphical correlations and fades interpretations of upper carboniferous fluvio deltaic strata have been based traditionally on cyclothems bound by marine flooding surfaces marine bands the recent recognition of major regionally extensive erosional unconformities exxon style sequence boundaries within selected cyclothems questions their validity as units of genetically related strata u sing examples from the carboniferous of the onshore uk and ireland we present sedimentological criteria for the recognition of sequence boundaries placing particular emphasis on the regional context of these surfaces sequence boundaries comprise widespread deeply eroded surfaces at the base of major fluvial sandstone complexes and laterally equivalent palaeosols developed on interfluves at the margins of the fluvial complexes these sequence boundaries define units of genetically related strata sequences which contain other key surfaces of time stratigraphic significance including marine bands and regionally extensive coals the recognition of key surfaces enables the construction of a high resolution stratigraphic framework within which coeval facies relationships can be interpreted sequence boundaries can be correlated between individual basins in the onshore uk by reference to their position in relation to a particular marine band for example the sequence boundary at the base of the farewell rock in the south wales basin can be correlated with that at the base of the rough rock in the pennine basin northern england since both these sandstone bodies are directly overlain by the subcrenatum marine band interbasinal correlations of this nature imply that potential fluvial sandstone reservoirs within major incised valley fills in the upper carboniferous strata of the southern north sea can be predicted by correlation with the onshore uk the stratigraphical framework can be extended and tested using core and well log data particularly spectral gamma ray data which are able to identify key sequence stratigraphic surfaces

volcanic and climatic controls on fluvial style in a high energy system the lower cretaceous matasiete formation golfo san jorge basin argentina abstract the cretaceous chubut group in the golfo san jorge basin patagonia argentina comprises up to 6000 m of continental sediments at the base of the succession an extensive saline alkaline lacustrine unit pozo d 129 fm grades laterally towards the basin margin into the fluvial matasiete fm hauterivian aptian the matasiete fm comprises up to 650 m of siliciclastic and pyroclastic deposits in its type area where three members have been distinguished the following facies associations were identified 1 single fluvial channels 2 multistorey fluvial channels 3 proximal floodplain 4 distal floodplain 5 pyroclastic ash fall and ground surge deposits additional observations in the time equivalent pozo d 129 fm provide evidence for 6 shallow lacustrine and 7 deep lacustrine facies associations the floodplain association contains paleosols with abundant carbonate concretions and fine pyroclastic tuffs paleosols are mostly vertisols characterized by deep desiccation cracks slickensides and carbonate nodules these observations coupled with the occurrence of shallow water oolitic grainstones in the lacustrine pozo d 129 fm indicate a semiarid environment tree trunks up to 1 m in diameter and 15 m long preferentially located near channel margins provide evidence for vegetated riverbanks the exposures of the matasiete formation in the san bernardo fold belt show individual channel belts containing straight meandering and braided channels evidence of changes in fluvial style attributable to base level control has not been observed the most dramatic changes in fluvial architecture which were comparatively short lived were provoked by intermittent pyroclastic deposition on the floodplain the reduced infiltration capacity of the floodplain and the concomitant increase in sediment load increased runoff as well as volume and flashiness of the discharge which favoured the development of shallow multichannel rivers the fluvial system abruptly changed from single ribbon channels to a braided system which notably increased the width thickness ratio of sandbodies

climate and ephemeral stream processes twentieth century geomorphology and alluvial stratigraphy of the little colorado river arizona during the first 40 years of the twentieth century erosion was the dominant geomorphic process affecting the morphology of the little colorado river channel the discharge regimen was one of frequent large floods and high annual discharge that created a wide sandy channel free of vegetation in the 1940s and early 1950s average annual precipitation declined reducing annual discharge to about 57 of that of the preceding period as well as reducing the frequency of large floods the channel adjusted to the new hydrologic regimen by reducing its width parts of the channel were frequently dry and riparian vegetation primarily nonnative salt cedar became established on the higher channel surfaces precipitation and discharge thereafter increased and aggradation by overbank deposition was the primary geomorphic process as indicated by accretion of 2 to 5 m of flood plain alluvium between 1952 and 1978 events of 1980 however suggest that the flood plain has ceased to accrete although climate has not fluctuated the flood plain has probably reached a critical height above the channel beyond which further accretion is unlikely under the existing discharge regimen the recent history of the little colorado broadly suggests that flood plain development was initiated by climatically induced hydrologic fluctuations flood plain deposits in the stratigraphic column of such ephemeral streams may record repeated adjustments to altered hydrologic conditions

architecture of the castissent fluvial sheet sandstones eocene south pyrenees spain the castissent formation represents a phase of strong fluvial progradation within the fluvio deltaic montanyana group probably enhanced by the late ypresian sea level fall the structural setting is characterized by the emplacement of the south pyrenean nappes the major architectural feature of the formation is the superposition of three multilateral and multistorey sheet sandstone complexes a b and c interbedded in finer floodplain deposits and dark grey mudstones of brackish transitional origin the structure of the sheet sandstone complexes is exemplified by the detailed analysis of the lower sheet sandstone complex a 25 m thick 6 km wide and exposed over 25 km of its length three types of channel fill sandstones serve as components 1 lenticular bedded bodies interpreted as braided stream deposits 2 lateral accretion bedded bodies intepreted as meandering stream deposits and 3 ribbons originating from laterally stable and short lived offshoot or crevasse channels by coalescence and or stacking of these channel fill types higher order architectural units a1 a2 a3 have been formed that together build the sheet sandstone complex on the basis of downstream variation in proportion and geometrical relation between the channel fill components three depositional zones have been differentiated within the fluvial system each zone is characterized by specific architectural processes 1 alternation of minor aggradational degradational cycles in the proximal valley 2 generation of new alluvial belts in the intermediate nodal avulsion zone and 3 successive random avulsion processes with development of semipermanent crevasse channels or minor distributaries in the distal distributive zone the sedimentation of the castissent formation was structurally controlled by an interplay of vertical basement movement due to thrust stacking in the hinterland and surficial thrust displacement to the foreland resulting in alternating southward and northward shift of the fluvial system

stratigraphic sequences and their chronostratigraphic correlation abstract the exxon sequence models of posamentier and coworkers incorporate two concepts which i question they suggest that rivers grade to a bayline but evidence from modern major rivers indicates that they do not they also proposed that fluvial sedimentary accomodation space is generated by the seaward shift in equilibrium profiles during sea level fall but this is too simplistic a model based on the use of schematic continental margin configurations which do not incorporate real slope and relief data in most cases a fall in base level leads to deltaic progradation and upstream fluvial incision most coastal plain fluvial wedges result from two processes sea level rise with the drowning and filling of estuaries and active source area tectonism major tectonic events adjacent to foreland basins such as terrane collisions lead to the development of sequences of third order type duration approximately 1 15 m y changes in intraplate stress regimes resulting from changes in regional plate kinematics have a similar episodicity and can be shown to be responsible for some third order cycles on extensional continental margins examination of the chronostratigraphic basis of the mesozoic cenozoic cycle chart of haq and coworkers reveals internal inconsistencies and an unrealistic downplaying of the built in potential for error this chart is not an approved global standard and it should be used with extreme caution

pennsylvanian time scales and cycle periods geochronological results from central europe indicate that the duration of pennsylvanian time is only 19 m y compared to the harland et al and palmer estimates of 34 m y prior calculations of pennsylvanian cycle periods from the midcontinent of north america suggesting a fit with milankovitch orbital parameters may well be in errors as a consequence other mechanisms for possible eustatic sea level changes represented in those cycles are needed calculation of cycle periods of 100 ka or less lack precision in stratigraphic intervals representing ages characterized by error margins of millions of years thus cycle periods may be less reliable as an indicator of global process than previously considered particularly in rocks of paleozoic and early and middle mesozoic age

middle pleistocene to holocene geochronology of the river aguas terrace sequence iberian peninsula fluvial response to mediterranean environmental change abstract our results from the river aguas basin suggest that fluvial archives travertine and slope deposits provide sensitive resolution records of environmental changes during the last 170 kyr from the chronostratigraphic data sets we have established a model of middle and late pleistocene river response for littoral basins on the southern iberian peninsula u th and osl dating indicate the major periods of travertine formation of the alfaix travertine platform which range from 169 to 26 kyr at least four incision events interrupted this aggradation period between 167 and 148 kyr between 148 and 110 kyr around 95 kyr and at 71 kyr aggradation ceased after 26 kyr and incision occurred during ois 2 subsequently the terraces t4a and t4b were deposited osl dating of the t4a channel deposit provides maximum ages of 28 20 and 18 kyr however short climatic events such as the younger dryas produced two more river incision episodes during ois 2 nonetheless for river systems influenced by tectonics climate and sea level changes it is difficult to assess the weight of each controlling factor regarding the three mechanisms of pleistocene river dynamics in middle size catchment areas of the littoral region of southeastern spain our results support the hypothesis that large scale tectonics triggered the general downcutting trend whereas the main aggradation and incision phases occurred during periods of major sea level changes over short time scales the influence of climate variability as documented by pollen records plays a decisive role thus the river responses to the three cyclic mechanisms operate at different time scales although synergetic processes should be considered with respect to the magnitude of abrupt incision aggradation events

a numerical modeling study of the east australian current encircling and overwashing a warm core eddy 1 warm core eddies wces often form in the meanders of western boundary currents wbcs wces are frequently overwashed with less dense waters sourced from the wbc we use the regional ocean modelling system to investigate the ocean state during the overwashing of one such wce in october 2008 in the east australian current eac comparisons of model outputs with satellite sea surface temperature and vertical profiles show that the model provides a realistic simulation of the eddy during the period when the eac encircled and then overwashed the eddy during the encircling stage an eddy with closed circulation persisted at depth in the surface eac water entered from the north encircled the eddy and exited to the east the overwashing stage was initiated by the expulsion of cyclonic vorticity for the following 8 days after the expulsion waters from the eac washed over the top of the eddy transferring heat and anticyclonic vorticity radially inward after approximately one rotation period of overwashing the eddy separated the overwashing creates a two layer system that forms a subsurface maximum velocity at the interface of the two layers analysis of water mass properties eulerian tracer dynamics and lagrangian particle tracks show that the original eddy sinks 10 50 m during the overwashing period overwashing has been observed in many wbcs and occurs in most wces in the western tasman sea

three dimensional numerical modeling of deltaic depositional sequences 2 influence of local controls abstract we investigate the influence of three local controls sediment supply subsidence and physiography on delta development and sequence variability using the three dimensional numerical model of deltaic deposition presented in a companion paper ritchie et al 2004 independently varying a single local control within geologically constrained limits produces marked differences in three dimensional morphology cross sectional stratal geometry and delta evolution during a cycle of sea level change sediment supply strongly influences not only the timing of transgressive and maximum flooding surface development during sea level rise and hence the diachroneity of lowstand transgressive and highstand systems tracts but also the timing of onset of fluvial incision and the characteristics of incised valleys and forced regressive wedges low sediment supply leads to early drowning of forced regressive and lowstand prograding wedges high magnitude transgressions and the late development of maximum flooding surfaces during relative sea level fall low sediment supply results in early initiation of fluvial incision and development of few but major incised valleys that route sediment to elongate forced regressive lobes at their mouths in contrast high sediment supply leads to early onset of normal regression and late transgression during relative sea level rise and numerous poorly developed incised channels and a broad laterally continuous forced regressive apron during relative sea level fall on basin margins with a shelf slope morphology base of slope deepwater deposits may occur at times of sea level highstand due to sediment bypass across the slope during relative sea level fall fluvial incision is enhanced by the relatively steep gradient of the slope leading to the early onset of incision and rapid headward propagation as a result major deep incised valleys develop that capture sediment and feed it directly to thick shelf edge forced regressive and lowstand prograding wedges the greater water depth ahead of the shelf edge and the steep slope gradients result in limited forced and normal regression compared to a ramp setting in contrast to other controls tectonic subsidence or uplift leads to modification of accommodation so that relative sea level change may vary significantly along a basin margin in high subsidence settings relative sea level may continue to rise even at times of high rates of background sea level fall in such settings deltas lack incised valleys forced regressive delta lobes and prominent sequence boundaries furthermore normal regression and even transgression in high subsidence locations can be contemporaneous with forced regression and incised valley development in adjacent lower subsidence locations the results of this sensitivity analysis suggest that systems tracts and their bounding surfaces are likely diachronous along many basin margins and may locally be absent more than one control can produce a similar stratigraphic response making interpretation of controlling processes from the stratigraphic product equivocal the models provide a framework for understanding the stratigraphy of natural basin fills but further research on the interplay between the controls is required in order to understand the climatic tectonic and sea level signals concealed in the stratigraphic record

an experimental study of the effects of base level change on fluvial coastal plain and shelf systems abstract several of the concepts of sequence stratigraphic models were tested by experiments in a large flume using different gradients for successive runs a physical model of a fluvial drainage basin coastal plain continental shelf and continental slope was constructed in all experiments initial gradients of the coastal plain and shelf were identical systematic raising and lowering of the water surface simulated the changes in relative sea level i e base level that are similar to most sequence stratigraphic models base level changes significantly affected the shelf area but they had little effect on the fluvial drainage basin during base level falls fluvio deltaic progradation occurred fluvial aggradation occurred only during periods of base level stillstand or rise because of the slow rate of head ward erosion of incised valleys a significant time gap existed from the time base level first fell below the shelfbreak and the development of a cross shelf bypass valley during this lag time deposition occurred on the exposed shelf to form a fluvial braid plain concurrently channels developed at the shelfbreak and grew by headward erosion at various rates continuous incision and widening of these channels formed valleys these valleys were not linked directly to the main drainage basin unt l ultimately one captured the flow from that drainage at that point other valleys were abandoned and ceased to grow during the subsequent base level rise the single large cross shelf valley filled with coarser sediments while the other valleys partially filled with finer suspended load sediments the main cross shelf valley also supplied coarser sediments to the slope

major controls on architecture sequence stratigraphy and paleosols of middle pleistocene continental sediments qc unit eastern central italy abstract middle pleistocene continental sediments in central italy qc unit record the oldest fluvial accumulation along the uplifting margin of the peri adriatic basin the architecture of the sediment body can be divided into two unconformity bounded fining upward cycles interpreted as genetically related depositional sequences these sequences highlight the systematic adjustment of the fluvial system to changes in the ratio between accommodation space and sediment supply a s ratio and from base to top comprise the following surfaces and stratal components i a regionally correlative sequence boundary resulting from an a s ratio 0 ii a low accommodation systems tract characterized by conglomerate rich amalgamated channel fills and recording an a s ratio 1 and v a mature red argillic paleosol to constrain the climatic signal for paleosols formation the two sequence capping mature paleosols have been investigated the results of these studies suggest that they were developed under humid and warm climatic conditions associated with interglacial phases which have been correlatively attributed to marine oxygen isotope stages 11 and 9

on the periodicity and magnitude of late carboniferous glacio eustatie sea level changes data from sedimentary cycles in basins from northern england the appalachians and midcontinent us afford an insight into periodicities and controls of late carboniferous glacio eustatic sea level changes lithofacies with identifiable palaeobathymetry are used to assess the magnitude of sea level change in the pennine basin of northern england the method yields a minimum value of 42m walsh power spectral analysis is employed to resolve periodicities of about 120ka within the pennine basin of northern england 212 140 and 93 ka within the midcontinent us succession and 109 84 67 63 ka within the appalachian basin within the pennine basin periodicities and magnitudes are found to be independent of their position within the basin thus any tectonism can be assumed to have had a negligible effect on the transgressions a simplified modelled climatic curve is derived from milankovitch parameters and pleistocene 18 o data this is used in a basin fill model that simulates the thermally subsiding pennine basin the resulting distribution of marine deposits is seen to depend upon both the steady regional subsidence and the magnitude and extent of glacio eustatic transgressions

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

estimating carboniferous sea level fluctuations from gondwanan ice extent the magnitude of carboniferous sea level fluctuations is not well known but the estimates are important for constraining cyclothem models in this paper we apply area volume relations developed for quaternary ice sheets to estimate the glacio eustatic component of sea level fluctuations in the carboniferous utilizing the best estimate of gondwanan ice area at the time of its greatest extent we arrive at a figure of 60 15 m for the isostasy corrected glacio eustatic component this value is nearer the lower limit of sea level estimates for cyclothem fluctuations from other sources

longitudinal profile evolution of the rhine meuse system during the last deglaciation interplay of climate change and glacio eustasy fluvial longitudinal profiles reconstructed from abandoned floodplains contain significant evidence about the role of relative sea level vs climatic and tectonic controls on depositional systems two weichselian floodplain surfaces that occur as terraces updip of the hinge zone of the rhine meuse system have recently been mapped beneath the holocene rhine meuse delta the netherlands their vertical offset is several metres in the upstream area and decreases to only 0 4 m in the central part of the delta the older and higher of the two floodplain surfaces is generally assumed to have been formed around the last glacial maximum whereas the younger dates to the younger dryas following a phase of climatically induced fluvial incision during the bolling allerod the downstream convergence of these two floodplain surfaces may be related to the relative rise of sea level forcing the rhine meuse system to become graded to a higher base level during the younger dryas the upper weichselian rhine meuse system then provides an example of a basin marginal fluvial system that responds in terms of its longitudinal profile to the combined effects of upstream control primarily climate change affecting water and sediment flux from the hinterland and downstream control glacio eustatically driven relative sea level change this new evidence may therefore revitalize the presently unfashionable concept of relative sea level control penetrating many hundreds of kilometres inland

tectonic control on the sequence stratigraphy of nonmarine retroarc foreland basin fills insights from the upper jurassic of central utah u s a abstract continental successions of the north american western interior retroarc foreland basin provide an excellent opportunity to evaluate the tectonic controls on nonmarine sequence stratigraphy the transition between the upper jurassic brushy basin member anastomosed fluvial system of the morrison formation and the gravelly braided river deposits of the buckhorn conglomerate has been studied to assess the dispersal of coarse clastics and the development of associated basin wide unconformities in a sequence stratigraphic framework the sharp contact between the two members is interpreted to be conformable based on stratigraphic sedimentologic and petrologic data collected at and near cedar mountain in central utah while a regional mature paleosol at the top of the buckhorn conglomerate indicates the presence of a major sequence boundary these interpretations are combined with paleoflow data and fluvial architectural analysis to reconstruct the evolution of the alluvial equilibrium profiles that controlled deposition of the succession the buckhorn conglomerate is interpreted as an example of a post orogenic deposit on the basis of 1 its tabular geometry 2 distance from the contemporaneous thrust belt 3 shift to transverse paleoflow direction from the preceding brushy basin axial drainage 4 conformable lower contact and 5 presence of an overlying sequence boundary with a westward expanding hiatus eroding the coeval foredeep the onset of a protracted period of low rate of orthogonal convergence between the farallon and north american plates resulted in tectonic quiescence and consequent isostatic rebound of the middle to late jurassic thrust belt and the contiguous contemporaneous foredeep as well as dynamic uplift the ensuing basin wide decrease in subsidence rate induced the progradation of the buckhorn alluvial plain into the morrison back bulge depozone and the subsequent generation of the overlying pedogenic unconformity which separates the deposits of the jurassic flexural event from the overlying sevier tectonostratigraphic unit

modelling holocene stratigraphy and depocentre migration of the volga delta due to caspian sea level change the volga system is sensitive to allogenic control due to its low on and offshore gradient similar to 5 cm km in sequence stratigraphy little attention has been paid to the effects of sea level change in these ramp margin fluvio deltaic settings the high frequency sea level changes of the caspian basin have considerable amplitude up to 18 m over the holocene time span which is usually considered as the lower boundary of fifth order cycles a process response model aquatellus has been used to investigate fluvio deltaic response to sea level fluctuation calibration of the model with measured data over the last century comprising a full 3 m sea level cycle showed plausible progradation and sedimentation rates the numerical modelling showed that sea level changes forced the holocene volga delta to migrate similar to 200 km over the caspian plain leaving only thin laterally extensive deposits the frequent depocentre shifts add a whole new perspective to the ongoing discussion about the impact of sea level changes along the longitudinal profile the periods during which significant deposition occurred coincide with the times that migration distances were relatively low thicker progradational wedges have been deposited at these time intervals at similar to 9000 8000 similar to 7400 6700 similar to 5200 3700 and similar to 2400 900 years bp c 14 dated deposits in the lower delta plain area corroborate the model output remarkably this is both in highstand and lowstand conditions the low gradient makes wave effects insignificant and tides are nonexistent so that the fluvial deposits are hardly reworked and no shoreface facies or maximum flooding surface develop the volga delta response indicates that sequence stratigraphic concepts are not scale independent in low gradient settings and that short term high frequency sea level changes have a far reaching impact on the stratigraphy c 2002 elsevier science b v all rights reserved

late neogene rift basin evolution and its relation to normal fault history and climate change along the southwestern margin of the gerania range central greece abstractthe south to southwest dipping north and south saros normal faults occupy the southeastern margin of the gerania range a major massif of mesozoic limestone and o phi o lite in the eastern gulf of corinth rift cen tral greece the history of the saros faults is constrained by adjacent basin ll sediments and modern drainage patterns older basin ll pliocene lower pleistocene which consists of terrestrial ne sands carbona ceous muds marls and micrite limestones is uplifted on the south saros fault block and onlaps the north saros fault footwall block on its northern side to near its crest suggest ing that it predates major fault activity in contrast younger basin ll middle pleisto cene was deposited and locally deformed during fault activity in a main basin south of the faults and in a perched basin on the south saros fault block main basin deposits consist of alluvial fan fan delta and shallow marine sediments up to 50 m thick whereas perched basin fanglomerates are 5 15 m thick fault scarp retreat and sediment onlap indicate that the faults became inactive late in the history of deposition of the younger basin ll the perched and main basins are currently undergoing incision allowing mod ern sediment to bypass the basins and to be deposited on modern fan deltas and beaches along the gulf of megara coast the absence of knickpoints and upstream deepening of the canyons suggest that a climatically driven increase in catchment runoff was responsible for basin incision although uplift and sea level change may have contributed as well the north and south saros faults each consist of three segments characterized by different strikes the major drainages cross the saros faults at or near segment boundar ies suggesting that the drainages may have initially owed between the tips of isolated fault segments as the segments became linked the antecedent drainages maintained their course and cut deep gorges at the scale of the entire eastern gulf of corinth region however older unlinked faults were aban doned and new faults were created in a gen eral northward and basinward direction the origin of this process remains controversial introduction

evolution of miocene fluvial environments eastern potwar plateau northern pakistan the miocene pliocene siwalik group records changing fluvial environments in the himalayan foreland basin the nagri and dhok pathan formations of this group in the eastern potwar plateau northern pakistan comprise relatively thick tens of metres sandstone bodies and mudstones that contain thinner sandstone bodies metres thick and palaeosols thick sandstone bodies extend for kilometres normal to palaeoflow and are composed of large scale stratasets storeys stacked laterally and vertically adjacent to each other sandstone bodies represent single or superimposed braided channel belts and large scale stratasets represent channel bars and fills channel belts had widths of km bankfull discharges on the order of 103 cumecs and braiding parameter up to about 3 individual channel segments had bankfull widths maximum depths and slopes on the order of 102 m 101 m and 10 4 respectively and sinuosities around 1 1 these rivers are comparable to many of those flowing over the megafans of the modern indo gangetic basin and a similar depositional setting is likely thin sandstone bodies within mudstone sequences extend laterally for on the order of 102 m and have lobe wedge sheet and channel form geometries they represent crevasse splays levees and floodplain channels mudstones are relatively bioturbated disrupted and represent mainly floodbasin and lacustrine deposition mudstones and sandstones are extremely disrupted in places showing evidence of prolonged pedogenesis these mature palaeosols are m thick and extend laterally for km lateral and vertical variations in the nature of their horizons apparently depend mainly on deposition rate the 500 m thick nagri formation has a greater proportion and thicker sandstone bodies than the overlying 700 m thick dhok pathan formation the thick sandstone bodies and their large scale stratasets thicken and coarsen through the nagri formation then thin and fine at the base of the dhok pathan formation compacted deposition rates increase with sandstone proportion 0 53 mm year for nagri 0 24 mm year for dhok pathan and palaeosols are not as well developed where deposition rates are high within both formations there are 100 m scale variations representing on the order of 105 years in the proportion and thickness of thick sandstone bodies and tens of m scale alternations of thick sandstone bodies and mudstone sandstone strata that represent on the order of 104 years formation scale stratal variations extend across the potwar plateau for at least 100 km although they may be diachronous however 100 m and smaller scale variations can only be traced laterally for up to tens of km alluvial architecture models indicate that increases in the proportion and thickness of thick sandstone bodies can be explained by increasing channel belt sizes mainly average deposition rate and avulsion frequency on a megafan comparable in size to modern examples 100 m scale variations in thick sandstone body proportion and thickness could result from regional shifts in the position of major channels possibly associated with fan lobes on a single megafan or with separate megafans however such variations could also be related to local changes in subsidence rate or changes in sediment supply to the megafan system formation scale and 100 m scale stratal variations are probably associated with interelated changes in tectonic uplift sediment supply and basin subsidence increased rates of hinterland uplift sediment supply and basin subsidence recorded by the nagri formation may have resulted in diversion of a relatively large river to the area alternatively changing river sizes and sediment supply rates may be related to climate changes affecting the hinterland possibly linked to tectonic uplift climate during deposition of the siwalik group was monsoonal although the deposits contain no direct evidence for climate change independent evidence indicates global cooling throughout the miocene and the possibility of glacial periods e g around 10 8 ma corresponding to base of nagri formation if the higher himalayas were periodically glaciated a mechanism would exist for varying sediment supply to megafans on time scales of 104 105 years although eustatic sea level changes are related to global climatic change they are not directly related to siwalik stratigraphic changes because the shoreline was many 100 km away during the miocene

late carboniferous cyclothems and alluvial paleovalleys in the sydney basin nova scotia cyclothems are documented for the first time in alluvial to coastal plain strata west phalian d to stephanian of the sydney basin nova scotia well developed cyclothems commence with an extensive carbonaceous lime stone or shale with a restricted marine biota that indicates maximal flooding succeeding gray detrital bay and lake fills with distributary channel deposits are overlain by stacked channel deposits paleovalley fills that mark an abrupt basinward facies shift and a profound change in alluvial style channel fills and red vertisols were deposited on an alluvial plain above the filled valleys and the paleovalley is equated with thick vertisols in adjacent inter fluve areas the cyclothems are capped by gray coastal deposits with economic coals agglutinated foraminifera are present in seat earths beneath the coals which formed as a result of a brief stillstand during transgression red mudstones pass laterally into gray detrital bay fills in regions of greater subsidence associated with faulted basement blocks poorly developed cyclothems are bounded by extensive but split coals and autogenic effects partially obscure allogenic patterns mean cyclothem duration approximates 200 ka

high resolution sequence stratigraphy of an alluvial fan fan delta environment stratigraphic and geodynamic implications an example from the keuper chaunoy sandstones paris basin abstract facies analysis of the chaunoy formation conducted as the first stage of this study reveals that the corresponding fluvial system essentially involved bedload deposition 2 d and 3 d megaripple migration and debris flow deposition such processes are characteristic of alluvial fan depositional environments these alluvial fan deposits pass laterally eastward into a shallow lacustrine environment in stage 2 of the study electrofacies are defined by well log analysis and then matched with sedimentary facies defined by core analysis electrofacies associations and depositional environments are then inferred directly from well logs on this basis six electrofacies characterizing the main sedimentary facies associations and depositional environments within the chaunoy formation are defined channel lag deposits channel infilling lake or flood plain overflow deposits and paleosols stage 3 involves establishing correlations based on high resolution sequence stratigraphy within these continental deposits the procedure consists in analysing high frequency fluctuations in baselevel defined from sedimentological studies and calibrated on well log signatures the correlations show that the top of the chaunoy formation is diachronous the formation is subdivided here into three stratigraphic units from base to top chaunoy i ii and iii this study shows that the degree of preservation of continental deposits varies with stratigraphic cycle genetic sequences and genetic sequence sets are asymmetrical with the baselevel rise being better preserved than the baselevel fall while for minor cycle deposits may be similarly preserved during baselevel rise and fall the sequence stratigraphy pattern of the genetic sequences and the genetic sequence sets can result from climatic and or tectonic factors but their effects are difficult to distinguish at the scale of the minor chaunoy i cycle or the chaunoy ii cycle preservation is similar during the baselevel rise and fall that implies that the chaunoy minor cycles were influenced by load discharge resulting in greater accommodation space which could result from climatic or tectonic fluctuations the chaunoy formation was deposited as part of a major baselevel rise during the carnian liassic cycle during this cycle the paris basin was generally tilted to the northwest producing the intra marnes irisees superieures truncation which seems to have been induced by large scale wavelength tectonic deformation detailed isopach maps of minor baselevel cycles in chaunoy i with inferred depositional environments are used to define the extent of depositional environments and fault activity during baselevel rise and fall during emplacement of the braided alluvial fan and lacustrine deposits of the chaunoy formation fault activity which was confined to the western part of the basin controlled the preservation potential i e the thickness of the deposits and depositional environment profiles within the chaunoy i and ii cycles the increased thickness of the sandstone deposits to the northeast and the onlap at the top of chaunoy i can be explained by local fault activity and by the general tilting of the basin the chaunoy iii sandstones are confined to the western part of the basin and seem to have been controlled by local factors only

fluviodeltaic response to sea level perturbations amplitude and timing of shoreline translation and coastal onlap 1 alluvial river systems respond to changing sea level by adjusting channel length through shoreline translation and coastal onlap offlap at the alluvial basement transition the magnitude and timing of shoreline translation and coastal onlap offlap relative to the driving sea level signal depend on the dynamics of the fluvial system and have important implications for interpreting ancient fluviodeltaic deposits i obtain analytical solutions to a diffusive geometric model of fluviodeltaic response to sea level perturbations that treats the shoreline and alluvial basement transition as moving boundaries fluviodeltaic behavior is most sensitive to the ratio of the period of eustatic cycling to the fluvial response time which varies with the length and water discharge of the fluvial system the square root of this ratio provides a first order estimate of the fraction of the fluvial long profile affected by eustatic forcing the fluviodeltaic system behaves as a low pass filter with respect to eustatic cycling the amplitude of both shoreline translation and coastal onlap offlap increase with increasing cycle period within a relatively narrow bandwidth in which the fluvial response time is comparable to the cycle period only small time lags develop between shoreline response and eustatic forcing the time lag between maximum coastal onlap and maximum sea level increases without bound as the forcing period decreases relative to the fluvial response time model predictions agree with experimental data and differ considerably from the model predictions of pitman 1978 and angevine 1989 which suggest that fluviodeltaic systems are strong high pass filters to sea level cycling

sand body orientation palaeoslope analysis and basin fill implications in the westphalian a c of great britain channel orientation and palaeoflow analyses across the british westphalian carboniferous coalfields show that three main inflow directions dominated the palaeogeography from the mid langsettian to the mid bolsovian in eastern scotland and ne england flow was mainly from the n and ne in the pennine basin of north central england flow was mainly from the w and nw whilst in south wales main flow from the sw was compatible with a westerly system that also branched to give the northerly inflows recorded in the culm basin of southwest england the depositional area included discrete tectonic depocentres notably the pennine basin which was traversed directly and tangentially by major channel belts these basins were essentially incidental to the main channel pathways but sand body characteristics vary according to basin location a new depositional model for the post rift pennine basin is proposed relating sand concentrations and connectivities to the depositional and tectonic setting the description of dominant sw to ne flow across south wales through much of the langsettian and duckmantian in contrast to the centripetal inflows previously proposed implies some similar channel depocentre relationships to those described here for the pennine basin

sedimentology of the rough rock a carboniferous braided river sheet sandstone in northern england the rough rock is a coarse grained fluvial sheet sandstone which outcrops across northern and central england it is interpreted as a braided river sandstone on the basis of sedimentary structures internal erosion and growth surfaces this study reveals that the rough rock represents more than a single phase of deposition and that internal erosion surfaces may indicate anabranch avulsions or more significant river avulsions detailed outcrop profiles are presented to try and distinguish the styles of deposition and the nature of internal bounding surfaces and channel geometry the rough rock formation contains a very large number of first and third order bedding contacts which represent the migration of dunes and channels respectively there are relatively few macroforms and bars preserved the lack of second order surfaces within many outcrops could indicate that bars in the rough rock rivers were very large and therefore cannot be resolved at the outcrop scale similarly the rivers which deposited the rough rock may have had such high width depth ratios that the dip of second order bounding surfaces are too low to be identified the large number of third order bounding surfaces indicates channel stacking which may have occurred in two ways 1 relocation of rivers in the same area over time or 2 anabranch avulsion within a braided river within a hierarchy of channels the problems associated with differentiating between these two mechanisms are discussed 1993 the geological society

calcrete and coal in late carboniferous cyclothems of nova scotia canada climate and sea level changes linked modern tropical peats require continuity of precipitation for accumulation whereas calcretes and calcic vertisols require strongly seasonal conditions the 20 30 m thick cyclothems of the sydney basin nova scotia canada show a systematic alternation of coals and other hydromorphic paleosols with calcretes and calcic vertisols this implies strong variation in seasonality during the duration of a cyclothem estimated at 200 ka in at least one cyclothem calcic paleosols formed on an interfluve adjacent to a paleovalley cut through marine strata suggesting that a more seasonal and probably drier climate prevailed during sea level lowstand the calcic paleosols are estimated to have formed during periods of 10 sup 4 yr possibly indicative of partial control by obliquity and precessional cycles 27 refs 5 figs 1 tab

summer kuroshio intrusion through the luzon strait confirmed from observations and a diagnostic model in summer 2009 abstract based on current measurements recorded at mooring station n2 20 40 441 n 120 38 324 e hydrographic data and argo observations in the period starting from july 2009 a diagnostic model with a modified inverse method is used to study the circulation in the luzon strait ls a number of new circulation features in the ls are found as follows 1 both observed and modeled currents show that the intruded kuroshio flow northwestward through the ls into the south china sea scs in the upper 400 m during july 2009 2 the diagnostic model confirms that the kuroshio is located in the area east of 121 20 e and west of 122 20 e at 20 00 n there is a meso scale cyclonic eddy at both the surface and 1000 m depth in the area west of the kuroshio near 20 00 n the meso scale cyclonic eddy forced the argo float 1 to make the cyclonic trajectory then the argo float 1 went into the area of the western kuroshio the argo float 1 was tracked as the flow moved northwestward into the scs across the ls in july and august 2009 reflecting the northwestward flow at both the surface and 1000 m depth which coincided with modeled currents these results confirm the northwestward kuroshio intrusion into the scs across the ls in summer 2009 for the first time 3 from the dimensional analysis for the equation of stream function it is seen that the joint effect of the baroclinity and relief jebar and the effect are two important mechanisms on the kuroshio intrusion into the scs in this period this summer kuroshio intrusion results from the weaker upstream kuroshio transport in summer 2009 el nino initiating period due to inertia effects and is associated with a weak volume transport across the ls 2 15 106 m3 s 1 westward 4 after comparison of the dynamics of the kuroshio intrusion during october 2008 and summer 2009 it is clear that these were influenced by the seasonal variability due to the monsoon winds and the interannual variation resulting from the weak upstream kuroshio transport affected by the enso due to inertia effects

the sequence stratigraphy of fluvial depositional systems the role of floodplain sediment storage abstract the currently used model for alluvial sequence stratigraphy has been criticised miall 1991 and an alternative model is offered here in this model alluviation mainly takes place during transgressive and not highstand phases when accommodation space allows sediment storage the high capacity for some river systems to store floodplain sediments is a critical consideration the effects of climatic and intrinsic geomorphic changes during fluvial deposition are likely to greatly complicate simple base level controlled sequence models and recognising higher order fourth and fifth order cycles will be particularly difficult

a synthetic stratigraphic model of foreland basin development the processes of erosion and deposition must be included in foreland basin models to predict correctly basin geometry and stratigraphy we present a synthetic stratigraphic model of the development of nonmarine foreland basins that predicts progressive geometry topography and facies patterns in the model steady crustal shortening occurs according to a wedgethickening model erosion and deposition follow a diffusive process and the lithosphere is compensated elastically erosion and deposition are controlled by the transport coefficients r of the diffusion equation for a range of thrust velocities and lithospheric rigidities transport coefficients are of order 102 103 m yr in the mountain belt these values are much higher than those derived from the study of scarp degradation in the sedimentary basin transport coefficients of order 104 m2 yr are appropriate and are compatible with previous studies of fluvial and deltaic deposition rapid thrusting results in a narrow underfilled basin while slow thrusting results in a wide overfilled basin in addition by varying the erosional and depositional transport coefficients while holding other parameters constant we generate both overfilled and underfilled basins these results suggest that changes in the rate of thrust loading the climate or the source rock lithology can create stratigraphic signatures that have been interpreted to record viscoelastic relaxation of the lithosphere clearly to understand either the long term behavior of the lithosphere or to interpret orogenic history from preserved foreland strata the manner in which a basin was filled must be considered we apply the model to the evolution of the modern sub andean foreland and find that an erosional transport coefficient of 3000 m2 yr and a depositional transport coefficient of 20 000 m2 yr successfully predict the observed basin geometry

timing of the last sequence boundary in a fluvial setting near the highstand shoreline insights from optical dating we investigated by means of optical dating the chronostratigraphic nature of the sequence boundary associated with the last glacial in a sandy to gravelly compound paleovalley fill just landward of the highstand shoreline in the rhine meuse delta netherlands laterally extensive fluvial strata deposited during oxygen isotope stage 4 coeval with a major sea level fall unconformably overlie estuarine deposits from stage 5 or fluvial deposits from the penultimate glacial stage 6 these chronostratigraphic relationships differ substantially from widely used models and indicate 1 that sequence boundary formation in this setting was associated with the onset of pronounced sea level fall shortly after 80 ka 2 that the time gap represented by the sequence boundary may be extremely small 10 k y 3 that the age of the sequence boundary may decrease both updip and downdip of the highstand shoreline and 4 that our study does not provide viable diagnostic criteria for a sea level controlled sequence boundary above the falling stage systems tract despite the high frequency high amplitude glacio eustatic regime that might be considered ideal for the formation of an unambiguous unconformity the last sequence boundary in this setting is commonly cryptic

late quaternary sedimentation lower colorado river gulf coastal plain of texas investigations in the lower colorado river valley gulf coastal plain of texas have resulted in the development of a spatially and temporally controlled history of changes in channel and flood plain erosional and depositional processes when combined with paleoclimatic and stratigraphic data from the upper colorado river drainage and the record of glacio eustasy in the gulf of mexico this study permits evaluation of the relative influence of different external controls on channel and flood plain behavior the development of alluvial landforms and the development of alluvial stratigraphic sequences late pleistocene and holocene alluvial deposits of the lower colorado river have been subdivided into allostratigraphic units with chronological control afforded by radiocarbon ages in the bedrock confined valley up to 10 m of late pleistocene 20 000 14 000 yr b p sediments referred to as the eagle lake alloformation ela underlie a terrace at 17 20 m above the present day channel deposition of the ela was followed by bedrock valley incision then deposition of a complex holocene valley fill referred to as the columbus bend alloformation cba columbus bend allomembers 1 and 2 cba 1 and cba 2 underlie a terrace at 12 14 m above the present day channel cba 1 was deposited 12 000 5 000 yr b p whereas cba 2 was deposited 5 000 1 000 yr b p columbus bend allomember 3 cba 3 consists of channel and flood plain deposits that represent the past 600 yr of activity allostratigraphic units within the lower colorado valley correlate with allostratigraphic units in major valley axes of the upper colorado drainage and with records of climatic and environmental change suggesting that alluvial deposits record basinwide responses to climatically controlled changes in discharge regimes and sediment supply basal unconformities for holocene valley fills however appear to be 1 000 2 000 yr younger in the upper colorado drainage than they are in the lower colorado valley this time transgressioe episode of bedrock valley cutting was initiated by climatically controlled reductions in sediment supply but conditioned by limits on rates of up stream propagation of incision through a large drainage basin by contrast unconformities within holocene valley fills document time parallel episodes of flood plain abandonment and soil formation but little additional bedrock valley cutting and indicate decreased flood magnitudes following shifts to drier climatic conditions flood plain morphology and sedimentary facies changed through time in response to changes in climate coupled with a protracted degradation of upland soil mantles which altered the rate at which precipitation was transferred to stream channels as runoff during the late pleistocene through middle holocene runoff was filtered through deep upland soils floods were for the most part less flashy and contained within channel perimeters and flood plains were constructed by lateral migration without significant vertical accretion hence the ela and cba 1 contain few vertical accretion facies exposure of bedrock surfaces during the late holocene resulted in increased flood stages deep overbank flooding and construction of flood plains by vertical accretion hence cba 2 and cba 3 contain thick vertical accretion facies allostratigraphic units and bounding unconformities persist through the bedrock confined valley to the quaternary alluvial plain but stratigraphic architecture changes substantially in the downstream direction as a result of the last glacio eustatic cycle on the alluvial plain late holocene cba 2 and modern cba 3 deposited contemporaneously with the present interglacial highstand onlap and bury the ela and cba 1 which were emplaced during the last full glacial lowstand and the transgression that followed

the application of high resolution sequence stratigraphy to fluvial systems a case study from the upper carboniferous breathitt group eastern kentucky usa the pennsylvanian pikeville hyden and four corners formations of the breathitt group in eastern kentucky usa contain six major facies associations along with a number of subassociations these facies associations are offshore siltstone rhythmically bedded mouthbar heteroliths predominantly fine grained floodplain deposits minor channel fills major distributary channels and major stacked fluvial bodies the stacked fluvial bodies are incised into a variety of open marine and delta plain deposits have widths of several kilometres and exhibit a range of sandy fill types these fluvial complexes are interpreted as incised valley fills parasequences and parasequence sets are not identifiable nonetheless it is possible to identify systems tracts on the basis of sequential position facies associations and systematic changes in architectural style and sediment body geometries the studied portion of the breathitt group comprises stacked 4th order sequences which occur in lowstand transgressive and highstand sequence sets related to the development of a lower frequency base level cycle in the lowstand sequence set incision associated with successive 4th order sequence boundaries has commonly removed all the hst and tst of the underlying sequences such that succeeding 4th order incised valley fills are amalgamated within the transgressive sequence set incision is at a minimum and incised valley fills tend to stack discretely with the maximum amount of fine grained tst and hst between them the highstand sequence set is transitional between the lowstand and transgressive sequence sets in terms of the amount of transgressive and highstand deposits preserved incised valley fills tend to stack discretely

development of longitudinal profiles of alluvial channels in response to base level lowering degradation of alluvial channels in cohesive sediments was studied in 15 m and 20 m long flumes with a slope of 0 01 cm cm degradation was initiated by lowering base level to a fixed position and the development of the longitudinal profile of the channel is analysed through a model formulated as a heat diffusion equation it is based on the equation of sediment continuity combined with an assumption regarding sediment transport namely that sediment discharge is linearly proportional to the channel slope in accordance with the boundary and initial conditions imposed by the experimental setup and procedure the basic equation is amenable to an analytical solution which defines bed elevation at any distance and time as a function of the amount of base level lowering and a diffusion coefficient additional problems arising from bank erosion and channel armouring are also treated successfully within the framework of the same model the results show that in homogeneous alluvial sediments not subject to armouring the ultimate result of base level lowering by a certain amount is degradation all along the channel by the same amount the main impact of erosion is felt in the early stages after initiation of the process and mainly near the mouth the rate of degradation at any station along the channel reaches a peak and then slowly decreases with time and the peak rate is attenuated with distance from the outlet the model permits the prediction of intermediate stages of profile development at any distance from the outlet and at different times

large scale fluvial grade as a nonequilibrium state in linked depositional systems theory and experiment 1 a graded river conveys its sediment load without net aggradation or degradation grade is thought to represent the equilibrium state of a river system subject to steady allogenic forcing we address the concept of grade in linked depositional systems through a combination of mathematical modeling and flume experiments we develop a moving boundary morphodynamic model of fluviodeltaic sedimentation and use it to quantify the conditions necessary for a state of sustained grade in an alluvial deltaic system developing on a uniformly sloping shelf to test our theory we conducted a series of flume experiments in which we constructed laboratory scale fluviodeltaic systems under specific relative sea level histories on large spatiotemporal scales our theoretical and experimental results suggest an alternative view of grade as an intrinsically nonequilibrium state that requires a fall in relative sea level under conditions of stillstand or rise in relative sea level the equilibrium graded profile does not exist and the alluvial river will always aggrade with a steady sediment supply alluvial grade can be sustained if relative sea level falls with a specific square root of time dependence common sequence stratigraphic conceptualizations of alluvial river response to sea level change suggest that rivers aggrade and degrade in response to relative sea level rise and fall respectively we show that rivers can remain aggradational if the rate of sea level fall is sufficiently small the boundary between aggradational and degradational states is the graded state described here that associated with a relative sea level fall that varies with the square root of time

late permian to middle triassic correlations and palaeogeographical reconstructions in south western european basins new sedimentological data from minorca balearic islands spain description of sedimentary sections and interpretations of sequence stratigraphic evolution of permian triassic red beds of minorca allow a new proposal of palaeoenvironment reconstructions the permian sediments mainly correspond to floodplain and pond deposits with sheetflood sand bed rivers environment de 1 within a warm and semi arid climate and the preserved succession forms one complete stratigraphic cycle the retrogradational phase of this cycle is represented by alluvial colluvial deposits grading upwards to environment de 1 and to extensive floodplain and pond deposits the progradational phase is characterized by increasing fluvial influence with palaeocurrent mainly oriented to the sw palaeosol horizons and preservation of a late permian palynoflora the uppermost part of this succession is truncated by a major erosional surface the sediments above this unconformity are characterized by braided river deposits environment de 2 with palaeocurrent oriented to the ssw within the more basal conglomeratic facies and to the wnw in overlying units the absence of extensive floodplain deposits a paucity of evidence for biogenic activity and palaeosols together with the presence of ventifacts indicate an arid climatic setting for the succession this environment evolved from braided rivers palaeocurrents mainly oriented to the se environment de 3 with in situ palaeosols and reworked breccias to fluvial coastal and shallow marine deposits environment de 4 dated as upper anisian to ladinian this succession characterizes a retrogradational trend although the transition between de 2 and de 3 was not observed a switch in palaeocurrent directions may indicate a change in source area a comparison at a regional scale with other peri tethyan basins allows the succession to be placed within a broader palaeoenvironmental and stratigraphic context during late permian to middle triassic during the late permian sedimentation occurred in alluvial playa lake or ponded environments where fluvial systems generally flowed southward except in south eastern france oriented to the ne within these sw european basins such as minorca the late permian succession shows a major retrogradational evolution from fluvial or alluvial fan deposits to extensive lake playa or floodplain deposits and a progradational trend fluvial or alluvial fan deposits the permian triassic transition corresponds to an unconformity overlain by braided river deposits with arid climate indicators aeolian deposits ventifacts and aeolian dune sedimentation at the scale of western europe this arid episode is dated as smithian and the induan age sedimentation deposits seem to be preserved only in the central part of the germanic basin as with all other peri tethyan basins environment de 2 of minorca above the major erosional surface is attributed to the smithian in the upper part of the studied succession braided river deposits indicative of less arid climatic conditions are preserved this succession contains the earliest mesozoic palaeosols dated as anisian by palynomorphs and expresses a vertical evolution from fluvial to open marine depositional environments attributed to the muschelkalk transgression

application of a diffusion erosion model to alluvial channels which degrade due to base level lowering the applicability of a diffusion erosion model that predicts transient longitudinal profiles of degrading alluvial channels has already been demonstrated in laboratory experiments and is here applied to some field examples by fitting simulated longitudinal profiles to measured ones for several streams with discharge 0 04 q5 680 m3s 1 diffusion erosion coefficients k were determined which are well correlated to discharge and drainage area headward knickpoint migration which results from base level lowering was also treated through the diffusion erosion model theoretically the distance of a knickpoint from the mouth of a tributary should be proportional to the square root of the time that elapsed since the base level was lowered field observations are in accordance with these theoretical considerations use of the model is discussed for prediction of erosion and for assessment of the age of alluvial fault scarps crossed by streams

palaeovalleys and protozoan assemblages in a late carboniferous cyclothem sydney basin nova scotia the early stephanian bonar cyclothem of the sydney basin nova scotia contains an erosional surface cut through coastal plain strata with economic coals and distributary channel bodies the erosion surface is interpreted as a palaeovalley 20 m deep and at least 7 km wide that marks a sequence boundary formed during relative fall in sea level the palaeovalley is filled with stacked alluvial channel bodies which become more isolated as the valley fill passes upward into red alluvial plain deposits probably laid down in an anastomosed river system in an adjacent interfluve area calcretes and red vertic palaeosols cap coastal strata assemblage analysis of agglutinated foraminifera and thecamoebians indicates that the palaeovalley was filled with freshwater sediments before an initial marine transgression flooded the alluvial surface and adjacent interfluve valley incision probably reflects glacioeustatic sea level fall however the alluvial nature of the valley deposits suggests that valley filling reflects an abundant sediment supply during lowstand and or transgressive stages and was not a direct consequence of sea level rise during the subsequent transgression phase aggradation was rapid as sediment supply apparently kept pace with rising sea level features of both channel and extra channel facies suggest that seasonality intensified during the transition from coastal plain to palaeovalley and alluvial plain deposition

lower triassic sequence stratigraphy of the western part of the germanic basin west of black forest fluvial system evolution through time and space abstract the aim of this paper is to analyse the fluvial evolution of the lower triassic in the western part of the germanic basin through time and space as well as the impact of the geodynamic and climatic setting on the preservation of fluvial deposits the lower triassic crops out only in the vosges massif and the black forest so well log studies are required to realise sequence stratigraphy correlations and establish comparisons with others parts of the germanic basin in a first step we use well log data analyses to characterise the electrofacies associations in the triassic and then define the well log signatures of each formation in a second step the characterisation and recognition of genetic sequences and their stacking pattern allow us to define seven minor cycles integrated into two major cycles finally the quantification of the lithologies at different stages of basin evolution leads to the reconstruction of paleoenvironmental maps to illustrate facies evolution through space and time a comparison with cycles defined in the germanic basin allows us to propose correlations of the lower triassic on either side of the rhine graben and leads to a discussion of the evolution of fluvial systems through time and space during the scythian the fluvial style is characterised by braided fluvial systems evolving laterally into lake deposits towards the central part of the germanic basin during this stage the basin was a huge depression with very few marine connections in its extreme eastern part the stratigraphic cycles represent rhythmic fluctuations in relative lake level that could be attributed to sediment supply and or lake level variations in an arid setting four minor stratigraphic cycles are observed that are integrated within a single major stratigraphic cycle during the period of the stratigraphic base level rise of the major cycle a maximum of 233 m of sediment would represent a duration of sedimentation in the paris basin of at least 1 8 m y during the period of the stratigraphic base level fall of the major cycle a maximum of 65 m of sediment would have accumulated over 2 5 m y on the western edge of the germanic basin the top of the scythian is marked by a major sedimentary break characterised by a planation surface with preservation of the first paleosols followed by the hardegsen unconformity this unconformity is tectonically deformed leading to the development of a new sedimentation area in the west of the basin the fluvial sedimentation above this discontinuity shows a trend towards enhanced development of floodplain or lacustrine type environments at its western margin with the formation of paleosols the fluvial systems are linked with sabkhas and then with a shallow sea connected to the tethys ocean in this context the stratigraphic cycles are caused by variations in relative sea level and or sediment supply the fluvial deposits are preserved in an exoreic basin

numerical modelling of depositional sequences in half graben rift basins a three dimensional numerical model of sediment transport and deposition in coarse grained deltas is used to investigate the controls on depositional sequence variability in marine half graben extensional basins subject to eustatic sea level change using rates of sea level change sediment supply and fault slip reported from active rift basins the evolution of deltas located in three contrasting structural settings is documented 1 footwall sourced deltas in high subsidence locations near the centre of a lault segment 2 deltas fed by large drainage catchments at fault tips and 3 deltas sourced from drainage catchments on the hangingwall dip slope different es in the three dimensional form and internal stratigraphy of the deltas result from variations in tilting of the hangingwall and the impact of border fault slip rates on accommodation development because subsidence rates near the centre of fault segments are greater than all but the fastest eustatic falls footwall sourced deltas lack sequence boundaries and are characterized by stacked highstand systems tracts high subsidence and steep bathymetry adjacent to the fault result in limited progradation in contrast the lower subsidence rate settings of the fault tip and hangingwall dip slope deltas mean that they are subject to relative sea level fall and associated fluvial incision and forced regression low gradients and tectonic tilting of the hangingwall influence the geometry of these deltas with fault tip deltas preferentially prograding axially along the fault creating elongate delta lobes in contrast broad sheet like delta lobes characterize the hangingwall dip slope deltas the model results suggest that different systems tracts may be coeval over length scales of several kilometres and that key stratal surfaces defining and subdividing depositional sequences may only be of local extent i urthermore the results highlight pitfalls in sequence stratigraphic interpretation and problems in interpreting controlling processes from the preserved stiatigraphic product

sequence stratigraphy of the upper yeadonian of northern england abstract a detailed study of an upper namurian cyclothem is presented the upper yeadonian basin fill of the pennine basin consists of three deltaic sandstones interbedded with mudstones of a variety of facies the cyclothem is a fourth order cycle representing deposition over a period of a few hundred thousand years the results of the study in terms of sediment accumulation patterns are investigated using the exxon sequence stratigraphic model in addition a simple computer model is presented to illustrate idealized pennine sedimentary fill in a one dimensional succession multiple condensed sequences at the base of cyclothems form part of a transgressive systems tract the succeeding fluvio deltaic facies are interpreted as part of a highstand systems tract the latest yeadonian rough rock sandstone is interpreted as a possible lowstand wedge a high resolution relative sea level curve is also presented for the late yeadonian

revised stratigraphic framework of pre westphalian carboniferous petroleum system elements from the outer moray firth to the silverpit basin north sea uk

the circulation in the upper and middle layers of the luzon strait during spring 2002 1 on the basis of current measurements at the mooring station and hydrographic and wind data obtained in the luzon strait during spring 2002 the numerical calculation and comparison of circulation were implemented by the aid of a diagnostic model with a modified inverse method during the observation period the directions of subtidal current at the mooring station are mostly northwestward or northward at depths of 200 and 500 m different from those at a depth of 800 m at depths above 400 m most of the kuroshio bypasses the south china sea scs near the luzon strait however both the observed and modeled results show part of the kuroshio flows westward to intrude into the area around the continental slope south of china and the net westward volume transport across the longitudinal section of 120 33 e is about 0 82 106 m3 s 1 in the upper layers from the sea surface to 400 m level at depths below 400 m the directions of flow east of 120 57 e are mostly eastward and the net eastward volume transport across the longitudinal sections of 121 09 e and 121 15 e both are about 2 4 106 m3 s 1 in the middle layers between 500 m and 1200 m this indicates the scs water with a higher oxygen concentration flows eastward into the eastern side of the luzon strait in the middle layer comparison between the observed and modeled results shows they agree basically with each other

effect of far field slope on morphologic dating of scarplike landforms the principal finding of this paper is that the far field slope has a first order effect on model age determinations of scarplike landforms in weakly consolidated terrains observationally this can be demonstrated in two ways using the lake bonneville and lahontan shoreline scarps as separate and combined data sets use of the reduced scarp slope tan theta sub s minus b where theta sub s is the maximum scarp angle and b is the far field or fan slope instead of tan theta sub s alone as the measure of scarp slope measurably reduces separation between the two data sets induced by different average fan slopes for the two data sets and significantly reduces scatter in the slope offset plot for both the separate and combined data sets theoretically the argument can be put even more strongly at least within the range of linear and nonlinear diffusion models that the authors consider here together with a mathematical transformation of the empirical approach of r c bucknam and r e anderson when one correctly takes into account the far field slope one will basically get the same age determination no matter which of these models one uses conversely without accounting properly for the effect of far field slope one is virtuallymore guaranteed to get an erroneous age determination no matter which model is used less

rapid and widespread response of the lower mississippi river to eustatic forcing during the last glacial interglacial cycle the lower mississippi valley provides an exceptional fi eld example for studying the response of a continental scale alluvial system to upstream and downstream forcing associated with the large orbitally controlled glacialinter glacial cycles of the late quaternary however the lack of a numerical chronology for the widespread pleistocene strata assemblage known as the prairie complex which borders the holocene fl oodplain of the lower mississippi river has so far precluded such an analysis here we apply optically stimulated luminescence osl dating mainly on silt sized quartz from prairie complex strata in total 27 osl ages indicate that the prairie complex consists of multiple allostratigraphic units that formed mainly during marine isotope stages 7 5e and 5a thus the aggradation of the prairie complex is strongly correlated with the sea level highstands of the last two glacialinterglacial cycles fluvial incision during the sea level fall associated with the mis 5a mis 4 transition extended as far inland as 600 km from the present day shoreline testifying to the dominant downstream control of fl stratigraphic architecture in the lower mississippi valley in addition the short reaction time of the lower mississippi river suggests that large fl uvial systems can respond much more rapidly to allogenic forcing than is commonly believed

sediment pore water interactions associated with arsenic and uranium transport from the north cave hills mining region south dakota usa abstract the extent of historical u mining impacts is well documented for the north cave hills region of harding county south dakota usa while previous studies reported watershed sediment and surface water as and u concentrations up to 90 established background concentrations it was unclear whether or how localized changes in sediment redox behavior may influence contaminant remobilization five pore water equilibration samplers peepers were spatially and temporally deployed within the study area to evaluate seasonal solid liquid as and u distributions as a function of sediment depth pore water and solid phase as and u concentrations fe speciation eh and ph were measured to ascertain specific geochemical conditions responsible for as and u remobilization and transport behavior at a mine overburden sedimentation pond adjacent to the mine sites high total aqueous as and u concentrations 4920 and 674 g l respectively were found within surface water during summer sampling however pond dredging prior to autumn sampling resulted in significantly lower aqueous as and u concentrations 579 and 108 g l respectively however both as and u still exceeded regional background concentrations 20 and 18 g l respectively at a wetlands dominated deposition zone approximately 2 km downstream of the sedimentation pond pore water geochemical conditions varied seasonally summer conditions promoted reducing conditions in pore water resulting in active release of as iii to the water column autumn conditions promoted oxidizing conditions decreasing pore water as aspw 5 and increasing upw 10 peak u pore water concentrations 781 g l were 3 5 greater than determined for the surface water 226 g l and approximately 40 background concentrations at the bowman haley reservoir backwaters 45 km downstream from the mine sites as and u pore water concentrations increased significantly between the summer and autumn deployments attributed to increased fe reduction processes geochemical modeling suggests solid phase fe reduction promotes the liberation of pore water as and u via suppressing the formation of thioarsenite intermittent hydrological processes facilitate as and u transport and deposition throughout the watershed while biogeochemical influenced redox changes cycle as and u between pore and surface water within localized environments

relation of sediment load and flood plain formation to climatic variability paria river drainage basin utah and arizona suspended sediment load flow volume and flood characteristics of the paria river were analyzed to determine their relation to climate and flood plain alluviation between 1923 and 1986 flood plain alluviation began about 1940 at a time of decreasing magnitude and frequency of floods in winter summer and fall no floods with stages high enough to inundate the flood plain have occurred since 1980 and thus no flood plain alluviation has occurred since then the decrease in magnitude and frequency of floods appears to have resulted from a decrease in frequency of large storms particularly dissipating tropical cyclones and not from a decrease in annual or seasonal precipitation suspended sediment load is highest in summer and fall whereas flow volume is highest in winter fall shows the greatest interannual variability in suspended sediment load flow volume and flood size because climatic conditions are most variable in fall the relation between sediment load and discharge apparently did not change within the period of sediment sampling 1949 1976 even though the channel elevation and width changed significantly annual suspended sediment loads estimated for periods before and after 1949 1976 show that decrease in suspended sediment load caused by floodplain alluviation in the paria river and other tributaries could have been a significant part of the decrease of suspended sediment load in the colorado river in the early 1940s

uplift driven valley incision and climate controlled river terrace development in the thames valley uk abstract the sequence of terraces of the river thames in southeast england has previously been shown to span the period from the earliest pleistocene to the present this terrace sequence contains biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary large scale fluvial incision resulting in basin wide terrace formation appears to have been concentrated at the warming limbs of the major climatic glacial interglacial cycles when sediment supply was greatly reduced this incision and subsequent valley floor widening created the accommodation space for the later aggradation of the terrace sediments during the following warm cold transitions and during the cold stages when high sediment supply conditions prevailed although the timing of terrace aggradation may be controlled by climate change the progressive valley incision recorded by terrace staircases cannot easily be explained in terms of quaternary climatic change alone and recently developed models suggest that long term incision by the thames has been driven by uplift this paper presents an overview of the available terrace data and tabulates incision amounts and rates between key stratigraphic horizons superimposed upon these broad changes revealed by the complex internal sedimentary architecture of many terrace sediments are the geomorphological system responses to both higher frequency climate driven changes and more localized intrinsic fluvial system adjustments

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

generic types of stratigraphic cycles controlled by eustasy thought experiments imply that stratigraphic cycles controlled directly by eustasy include keep up catch up catch down foreshortened or truncated and give up variants different patterns of thick ness and facies being governed by the interplay of sedimentation rate and accommodation space most examples of these types are in addition base cutout cycles wherever lowstands of sea level dropped below the top of the underlying cycle overall thicknesses of multiple cycles at any locale are controlled ultimately by net subsidence rate accordingly even keep up and catch up cycles can faithfully record full accommodation only where tectonic subsidence during cycle formation paced eustatic fluctuation paradoxically however only condensed cycles that fortuitously compensate for syncycle tectonic subsidence can accurately record the eustatic amplitude as adjusted for water loading

pleistocene geomorphological and sedimentary development of the akaki river catchment northeastern troodos massif in relation to tectonic uplift versus climatic change the uplift of the troodos ophiolite is reflected in the development of the akaki river catchment in the northeast troodos massif four main stages f1 f4 of geomorphological terrace development and related deposits are recognised using satellite imagery and field observations the geomorphological terraces have been tectonically uplifted during the pleistocene so that they dip northwards from the troodos mountains until they merge with the mesaoria plain lithology e g hard diabase versus soft extrusive rock has exerted an important control on the geomorphology of the akaki river channel the f1 terraces and related deposits are well preserved in the lower reaches of the catchment the f2 terraces are more widely preserved but with few preserved deposits the f3 erosional surfaces e g strath terraces and related deposits are widespread up into the higher reaches of the catchment the f4 to recent geomorphological surfaces and deposits are confined to near the modern river channel the f1 to f3 aged deposits each include very high energy mass flow deposits and somewhat lower energy traction flow deposits with minimal sand preservation stages of fluvial aggradation were followed by soil development e g terra rossa the f1 to f4 aged terraces and related deposits mainly formed in response to a combination of very long term tectonic uplift and climatic related change long term and short term tectonic uplift was the dominant driver related to the updoming of the troodos ophiolite especially during the earlier time period f1 and f2 whereas climate related effects appear to have dominated more recently f3 and f4 sedimentary aggradation is likely to have predominated during interglacial periods while interglacial glacial transitions when climate fluctuated are seen as times of increased incision previous correlations of the f1 f4 fluvial deposits with similar deposits elsewhere in cyprus including coastal marine carbonate deposits suggest that the f1 and f2 deposits are likely to be of middle pleistocene age and the f3 f4 deposits of late pleistocene to holocene age