facies and architectural element analysis of a meandering fluvial succession the permian warchha sandstone salt range pakistan abstract the 30 to 155 m thick early permian artinskian warchha sandstone of the salt range pakistan is a conglomerate sandstone and claystone succession within which seven lithofacies types gt st sp sr sh fl and fm occur in a predictable order as repeated fining upward cycles common sedimentary structures in the conglomerates and sandstones include planar and trough cross bedding planar lamination soft sediment deformed bedding compound cosets of strata with low angle inclined bounding surfaces and lags of imbricated pebbles structures in the finer grained facies include desiccation cracks raindrop imprints caliche nodules and bioturbation groups of associated facies are arranged into nine distinct architectural elements channels gravel bars sandy bedforms downstream and laterally accreting barforms sand sheets crevasse splays levees floodplain units and shallow lakes which is consistent with a fluvial origin for the succession the types of architectural elements present and their relationship to each other demonstrate that the warchha sandstone preserves a record of a meandering river system that drained the northern margin of gondwanaland the dominance of fine grained floodplain facies over gravel grade channel base facies and the widespread occurrence of large scale lateral accretion elements supports the interpretation of a high sinuosity meandering fluvial system in which channel bodies accumulated via the lateral accretion of point bars but in which the active channels covered only a small part of a broad floodplain at any time instant although the regional and temporal distribution of these deposits is complex in broad terms the lower part is dominated by stacked multistorey channel bodies whereas single storey channel elements isolated in abundant fine grained floodplain deposits dominate the middle and upper parts of the formation

events of sediment deformation and mass failure in upper cretaceous estuarine deposits cameta basin northern brazil as evidence for seismic activity abstract event beds recording late cretaceous synsedimentary seismicity occur in the cameta subbasin northern brazil the deposits consist of nearly 40 m of kaolinized fluvio estuarine deposits the lower fluvial tidal influenced complex which carries a high quality commercial kaolin includes genetically related channel fill floodplain crevasse splay and mud plug deposits the upper estuarine deposits contain trace fossils indicating marine influenced settings thalassinoides ophiomorpha teichichnus diplocraterion skolithos cylindrichnus rhizocorallium and planolites and include heterolithic sandy and bioturbated units interpreted as tidal flat storm overwash and low energy estuarine bay deposits respectively in the upper portion of the estuarine lithosomes four successive events events 1 4 of synsedimentary brittle and ductile deformation and large scale sediment failure anomalous in estuarine settings were recognized and attributed to earthquakes event 1 is recorded by heterolithic and bioturbated deposits with vertical to subvertical fractures that disappear into underlying undeformed deposits event 2 is recorded by thin sharply bounded sections composed of heterolithic mudstone and very fine grained sandstone that shows convolute folds and pillow like structures event 3 is documented by intraformational conglomerate and breccia and minor mudstones and sandstones with abundant trace fossils skolithos and thalassinoides event 4 is characterized by vertical to subvertical fractures and faults with homogenized sandstone intrusions along their planes mostly developed in the upper parts of the deposits corresponding to event 3 a detailed analysis of facies relationships combined with consistent orientations of brittle deformation structures and the regional tectonics of the cameta subbasin suggests earthquakes as the triggering mechanism for sediment deformation and large scale mass failure

formation of scalloped cross bedding without unsteady flows abstract scalloped cross bedding compound cross bedding with internal bounding surfaces that cyclically scoop into the previously deposited foresets and into the sediment below the set is a common and distinctive structure in eolian fluvial tidal and nearshore marine sands scalloped cross bedding in shallow marine deposits previously has been interpreted to be produced by cyclic flows such as neap spring tidal flows which are known to cause cyclic fluctuations in the depth of scour in the troughs of migrating bedforms but scalloped cross bedding also originates by a process that does not require fluctuating flow migration of small bedforms across the lee slopes or along the troughs of larger bedforms intersections of the troughs of the two sets of bedforms form topographicall low scour pits and cyclic passage of these scour pits through the outcrop plane the plane that later becomes an outcrop surface causes the lower set boundary to rise and fall scalloped cross bedding formed by fluctuating flow superficially resembles that formed by superimposed or intersecting bedforms but as illustrated in three dimensional computer plots the two kinds of structures commonly can be distinguished by directional properties of the bedding scallops deposited by alongslope migrating superimposed bedforms have cross bed and bounding surface dip patterns that lack bilateral symmetry and have cross bed dips that are asymmetrically distributed relative to bounding surface dips scallops with dip patterns that are bilaterally symmetrical and with cross bed dips that are symmetrically distributed relative to the bounding surface dips can be produced either by fluctuating flow or by downslope or upslope migration of superimposed bedforms an example of nearshore marine scalloped cross bedding of pleistocene age was examined in detail in a coastal terrace of monterey bay california the three dimensional structure and directional properties of the bedding suggest that the deposit was produced by a series of small bedforms migrating offshore down a rip channel that was bounded on one side by a migrating oblique bar

variations in natural levee morphology in anastomosed channel flood plain complexes abstract natural levees are common features of alluvial river systems yet their origin and evolution are poorly understood in this paper we present morphologic and sedimentologic data from two anastomosed rivers and offer a hypothesis of natural levee growth in these systems based on mechanisms of sediment transport in settings where floodbasins fill at the same rate as the channel levees form by turbulent diffusion of suspended sediment away from a high velocity thread into a floodbasin of relatively stagnant water the theory of diffusive transport suggests that these levees should be narrow steep and display abrupt decreases in grain size due to rapid decreases in carrying capacity with distance into the floodbasin in environments where an appreciable water surface slope is maintained between the main channel and the floodbasin levees form by advection of sediment out of the channel and into the floodbasin advective transport theory indicates that these levees should be broad and gently sloped with grain sizes gradually decreasing away from the main channel natural levees occurring in the anastomosed reach of the upper columbia river in se british columbia display significantly different morphology from levees in the cumberland marshes region of the lower saskatchewan river in east central saskatchewan at the upper columbia site the rise in stage of the floodbasin water nearly keeps up with that of the channel water because of good communication between channel and floodbasins through crevasses this inhibits the establishment of a water surface slope and the bulk of the escaping sediment is deposited close to the channel in contrast the cumberland marshes region is characterized by wide and volumetrically large floodbasins these conditions keep floodbasin water surface elevations relatively low and maintain an appreciable elevation head between the channel and its floodbasin fostering levee growth by advective transport

petrography and provenance of the early permian fluvial warchha sandstone salt range pakistan abstract the warchha sandstone of the salt range of pakistan is a continental succession that accumulated as part of a meandering fluvial system during early permian times several fining upward depositional cycles are developed each of which is composed of conglomerate cross bedded sandstone and in their upper parts bioturbated siltstone and claystone units with distinctive desiccation cracks and carbonate concretions clast lithologies are mainly of plutonic and low grade metamorphic origin with an additional minor sedimentary component textural properties of the sandstone are fine to coarse grained poorly to moderately sorted sub angular to sub rounded and with generally loose packing based on modal analyses the sandstone is dominantly a feldspathoquartzose arkose to sub arkose detrital constituents are mainly composed of monocrystalline quartz feldspars more k feldspar than plagioclase and various types of lithic clasts xrd and sem studies indicate that kaolinite is the dominant clay mineral and that it occurs as both allogenic and authigenic forms however illite illite smectite mixed layer smectite and chlorite are also recognised in both pores and fractures much of the kaolinite was likely derived by the severe chemical weathering of previously deposited basement rocks under the influence of a hot and humid climate transported residual clays deposited as part of the matrix of the warchha sandstone show coherent links with the sandstone petrofacies thereby indicating the same likely origin illite smectite and chlorite mainly occur as detrital minerals and as alteration products of weathered acidic igneous and metamorphic rocks based primarily on fabric relationship the sequence of cement formation in the warchha sandstone is clay generally kaolinite iron oxide calcareous and siliceous material before iron rich illite and occasional mixed layer smectite illite and rare chlorite both petrographic analysis and field characteristics of the sandstone indicate that the source areas were characterised by uplift of a moderate to high relief continental block that was weathered under the influence of hot and humid climatic conditions the rocks weathered from the source areas included primary granites and gneisses together with metamorphic basement rocks and minor amounts of sedimentary rocks regional palaeogeographic reconstructions indicate that much of the warchha sandstone detritus was derived from the aravalli and malani ranges and surrounding areas of the indian craton to the south and southeast before being transported to and deposited within the salt range region under the influence of a semi arid to arid climatic regime

floodplain development based on selective preservation of sediments squamish river british columbia abstract in the conventional model of floodplain sediment accumulation mechanisms of floodplain growth are differentiated into lateral and vertical accretion processes in which within channel deposits are capped by overbank deposits in the high energy gravel based squamish river sediments laid down on bar surfaces are composed of trough and planar crossbedded coarse sands these sequences contrast incongruously with adjacent floodplain deposits which are composed in large part of vertically accreted fine sands atop coarse alluvial gravels using element analysis it is inferred that bar platform sediments are stripped away by chute channels which are subsequently infilled with lower energy deposits from this a model of floodplain growth based on selective preservation of bar platform sands and prefrential preservation of vertically accreted deposits is proposed this mechanism of sediment replacement occurs independent of channel planform type

effects of peat on the shapes of alluvial channels examples from the cumberland marshes saskatchewan canada abstract an avulsion of the lower saskatchewan river in the 1870s inundated a large segment of peat covered floodplain that subsequently has become aggraded with a broad 500 km 2 belt of alluvium deposited by the redirected flow routing of water and sediment discharge through the avulsion affected area has been accomplished mainly by networks of sandy bedded anastomosed channels that have formed evolved and abandoned as the alluvial belt prograded down the floodplain slope these processes continue today though at a much reduced rate new channels formed by crevassing and basinward extension of distributaries are initially small and shallow with bottom elevations situated within the avulsive alluvium but above the pre avulsion peat floodplain surface subsequent enlargement and downcutting of many of these channels eventually uncovers the underlying peat layer whose resistance to erosion exerts significant influence on cross sectional shape and further channel development peat floored channels tend to have rectangular cross sections high ratios of average to maximum depth d d max and a large range of width to depth ratios if the channel continues to enlarge the peat layer eventually becomes breached commonly leading to temporarily irregular cross sections caused by localized scouring at the breach sites eventually the peat layer is completely eroded from the channel floor by undercutting and slumping after which channel shape becomes governed mainly by other perimeter characteristics channels unaffected by peat either before the peat layer is encountered during early channel development or after it is entirely removed tend to have low width depth ratios and a large range of d d max values

large scale facies sequences in alluvial overbank environments abstract gradational coarsening upwards or fining upwards sequences order of meters thick in overbank environments can be produced by progressive crevasse splay levee progradation or abandonment while the channel belt remains unchanged in position in contrast meter scale facies sequences related to periodic channel bell avulsion may show relatively abrupt changes in facies and paleocurrent direction simulation models suggest that the number of such avulsion related facies changes in any overbank sequence bounded above and below by channel belt deposits is on the order of 1 to 10 this is confirmed using an ancient example in this example the average thickness of each avulsion bounded overbank facies sequence was 3 m assuming an average recurrence interval for avulsions of about 1 000 ye rs the mean overbank deposition rate was about 3 mm per year

high resolution seismic tomography across the 1980 ms 6 9 southern italy earthquake fault scarp 1 a high resolution multi fold wide angle seismic survey carried out across the irpinia fault southern italy yields new information about the shallow structure of this normal fault that was reactivated in 1980 the fault zone is imaged to a depth of about 60 m by using a non linear tomographic technique that is specially designed to image strongly heterogeneous media results confirm the location of the fault as previously inferred by a trench excavated in soft soils and clearly delineates a 30 35 m step in the bedrock this single step is indicative of a narrow fault zone which corresponds upward to warped soils exposed in the trench thus demonstrating that the near surface warping is directly related to a brittle faulting in the bedrock assuming that the vertical slip rate yielded by paleoseismic data 0 25 0 35 mm yr has been constant since the fault s inception the latter should date back to about 100 140 kys ago such a young age may explain why the irpinia fault is not associated with evident large scale geomorphic indicators of its activity

magnitude and timing of peat to coal compaction the peat to coal transition is commonly assumed to be accompanied by compaction that decreases the thickness of the organic deposit to values of 10 or less of the original peat thickness decompaction modeling using such values for coal seams in contact with penecontemporaneous channel sandstones leads to impossible depositional geometries for the sandstones which have a final thickness that is 90 of their original thickness similarly decompaction modeling of the fragments of organic material within channel lags using the assumed large peat compaction value results in the destruction of the associated sedimentary structures such as trough cross beds dinosaur tracks in the roofs of coal mines show a shallow depth of penetration and a preservation of foot morphology that is not possible unless the peat the animals walked upon was very firm these data confirm the macroscopic observations from coal balls that the compaction associated with the peat to coal transformation is minimal equally important the data also show that most of the compaction occurs essentially at the surface and not at the depths where coalification takes place

what is a fluvial levee abstract fluvial levees are elevated partitions between channels and floodplains because of their character and position levees may provide critical controls on and insights into geomorphic processes that determine the distribution of water and sediment within river systems few studies have analysed the character distribution sedimentology and processes that form levees in modern depositional environments characterisation of levee deposits from the mississippi river continues to form the basis for most levee interpretations from the rock record this discussion paper assesses the reliability of interpretations of levee deposits in numerous examples from the rock record and their associated inferences for river style this uncertainty reflects the lack of definitive sedimentological attributes for levee deposits their limited preservation potential and the fact that levee identification in the rock record is inhibited by the reliance on geometric descriptors or indirect associations between channel and floodplain facies given these concerns it is suggested that geomorphologists and sedimentologists need to recognise the limitations of our present knowledge of levees and work towards a more systematic understanding of these significant fluvial landforms in the full spectrum of modern and ancient river settings

distal alluvial deposits in a foreland basin setting the lower freshwater molasse lower miocene switzerland sedimentology architecture and palaeosols the lower freshwater molasse untere susswasser molasse crops out over a wide area of the swiss molasse basin coarse grained alluvial fan conglomerates dominate in proximal basin areas along the alpine front these conglomerates pass northwards into sandstones and mudstones of an extensive northeastward draining meandering river system which ran parallel to the basin axis sedimentological study of outcrops quarry exposures and boreholes in the basal miocene aquitanian has permitted detailed facies analysis of this distal alluvial sequence the distal aquitanian is made up of distinct architectural elements characterized by their geometries and sedimentary structures each may be assigned to a particular depositional setting meander belt levees crevasse channels and splays overbank fines and palaeosols and lacustrine meander belt sandstones were deposited in mixed load channels with a dominant bedload component sandstones commonly comprise amalgamated and locally stacked ribbon bodies 2 15 m thick and 150 1500 m wide interbedded rippled laminated and mottled fine grained levee sandstones and siltstones form lenticular packages up to 3 m thick and 30 100 m across small scale crevasse channel sandstones 2 4 m thick and 5 10 m across pass laterally into metre scale medium to fine grained crevasse sandstone sheets rare laminated lacustrine siltstones occur only in the north east part of the basin floodplain mudstones and marls make up the remainder of the succession these display a variety of pedogenic features recording cyclical palaeosol development palaeosols show strong variations in morphology and maturity both laterally across the floodplain and downstream along the basin axis reflecting local variation in aggradation rate associated with proximity to alluvial channel courses as well as regional variation in subsidence and floodplain drainage analysis of the organization and distribution of the various sediment bodies permits reconstruction of the fluvial system and allows development of a model for the sedimentary architecture of the lower freshwater molasse in the study area integration of palaeosol studies into a well defined architectural framework assists recognition of areal facies belts and may aid location of sand prone sequences in the subsurface

sedimentology and geomorphology of overbank flows on meandering river floodplains abstract along floodplains there occurs an ordered sequence of geomorphic events during floods the following sequence occurs for individual flood events 1 the rise of floodwater and of groundwater 2 the inundation of the floodplain 3a adjustments of the overbank flow pattern to the floodplain environment 3b the flood peak 4 the initial fall of floodwaters and changes in the overbank flow pattern 5 a gradual cessation of the overbank flow 6a infiltration evaporation and a wave like motion of stagnant water and 6b postflood transformation under subaerial conditions field observations support this model for meandering rivers in the polish lowland

anomalous clastic wedge development during the sevier laramide transition north american cordilleran foreland basin usa new high resolution regional correlation and isopach maps provide evidence that 1 laramide style deformation began as early as ca 77 ma in central utah and 2 rapid 208 km m y 1 and extensive 400 km progradation of a clastic wedge was facilitated by reduced subsidence during the transition from sevier to laramide style deformation this study defi nes three campanian alluvialto marine clastic wedges that traversed 200 400 km eastward across the utah colorado segment of the cordilleran foreland basin wedges a and c are thicker successions with rising trajectory shoreline stacking patterns blackhawk formation and lower castlegate sandstone bluecastle tongue and rollins sandstone that refl ect relatively slow overall progradation 50 81 km m y 1 of narrow 10 20 km wide wave dominated shorelines in contrast wedge b consists of lower volume successions with a fl at to falling shoreline stacking pattern middle castlegate sandstone sego sandstone neslen formation corcoran and cozzette members of the iles formation that suggests rapid progradation 208 km m y 1 of embayed 60 80 km wide mixed energy wave and tide infl uenced shore lines wedges a and c prograded 200 250 km in more than 3 m y whereas wedge b prograded 340 400 km in 2 m y 170 km m y 1 the anomalously extensive wedge b is unique in the utah colorado segment because of its long extent rapid progradation rate dominance of tidally infl uenced facies long transit transgressions regressions and low accommodation nested sequence architecture stratigraphic relationships indicate development of wedge b coeval with both sevier and laramide style deformation in utah assuming a constant sediment supply the extensive 300 400 km sheet like amalgamated wedge wedge b may have been caused by 1 reduced subsidence driven by a fl exural interference pattern whereby two short wavelength 200 km fl exural profi les are superimposed during the uplift of both basement cored and thin skinned thrust belt 2 an increase in or eastward migration of dynamic subsidence during tectonic transitions associated with slab fl attening or rollback i e long wavelength fl exure or 3 reduced subsidence due to short wavelength fl exural interference augmented by the reduction or migration of long wavelength fl

crevasse splays from the rapidly aggrading sand bed braided niobrara river nebraska effect of base level rise base level rise of 2 35 m on the niobrara river has resulted in aggradation of the channel belt and a recent avulsion overbank areas have become flooded by rising groundwaters and more than eight crevasse splays have formed between 1993 and 1997 two crevasse splays situated on the west and east sides of the niobrara have been studied using ground penetrating radar gpr shallow boreholes and topographic surveys the vibracores and gpr profiles provide a nearly three dimensional view of the architecture of crevasse splay deposits the east splay was initiated in the winter of 1993 94 and has expanded to cover an area 200 m by 1000 m with sediment up to 2 5 m thick the west splay which was initiated by the opening of a crevasse channel through a levee in the autumn of 1995 covers an area 150 m by 250 m with up to 1 2 m of sand deposited in a single year the niobrara splays are sand dominated and characterized by bedload deposition within channels 5 30 m wide and 0 5 2 m deep with the development of slipfaces where splays prograde into standing bodies of water sedimentary structures in cores include horizontal lamination ripple lamination and sets of cross stratification there is a slight tendency for splays to coarsen up but individual beds within the splays often fine up the abundance of crevasse splays on the niobrara river contrasts with other braided river floodplains in the niobrara crevasse splay formation followed aggradation within the channel belt which occurred in response to base level rise the link between crevasse splays channel aggradation and base level rise has important implications for the interpretation of ancient braided river and floodplain sequences it is suggested that crevasse splay deposits should be an important component of aggrading fluvial sediments and hence should be preserved within the rock record in this case the aggradation and crevassing have been tied to a rise in base level elevation and it is suggested that similar deposits should be preserved where braided rivers are affected by base level rise for instance during transgression and filling of palaeovalleys

contrasting development patterns of crevasse channel deposits in cretaceous alluvial successions korea abstract the eumsung and pyonghae basins both of cretaceous age in korea comprise a thick alluvial sequence of conglomerate sandstone and purplish siltstone laterally impersistent gravelly sandstone beds can be classified into two types based on bed geometry internal structure and occurrence a vertically stacked sheetlike bodies facies 1 and b migratory ribbon shaped bodies facies 2 facies 1 is characterized by symmetrical channel geometry with a large ratio of width to thickness of sandstone beds which are mostly stratified and bounded by relatively distinct lower and upper boundaries they are frequently found in aggradational style facies 2 shows asymmetric geometry with a relatively small ratio of width to thickness of sandstone beds it comprises massive cross stratified units bounded by sharp basal contacts and gradational upper boundaries which resulted from laterally shifting mode both types represent crevasse distributary channels developed in floodplain environments facies 1 is suggestive of gradual migration of crevasse distributary channels under the conditions of overall aggradation whereas facies 2 represents discrete abrupt diversion of crevasse channels these features are due to differences in floodplain gradients paleohydrology and trunk channel behaviour

massive sandstone facies in the hawkesbury sandstone a triassic fluvial deposit near sydney australia abstract massive sandstone is a common facies in the hawkesbury sandstone a triassic formation attributed to deposition by a large braided river the massive sandstone occurs as sheets and in elongate depressions trending perpendicular to the paleoslope as indicated by the unidirectional mean orientation of abundant cross strata some of the depressions filled with massive sandstone also contain angular mudstone intraclasts up to several meters in length massive sandstone is also associated with deformed cross strata formed by progressive loss of lamination during mass movement down foreset slopes foreset failure is attributed to liquefaction due to falling water level or to collapse of adjacent mud banks the latter mechanism resulted in rapid loading of bedform foresets and introduce large mudclasts into the massive sand sand and mudclasts accumulated in transverse scours at the foot of the foreset slopes but also travelled along the scours or spilled out to form massive sheet sands the abundance of massive sandstone in the hawkesbury sandstone is attributed to deposition in a large river in which flood stage bedforms were probably up to 15 m high because of the size of the bedforms large volumes of liquefied sand were generated when foreset slopes failed

spatial and temporal evolution of an avulsion on the taquari river distributive fluvial system from satellite image analysis avulsion processes have been observed and analyzed using field based studies however they have rarely been analyzed through use of satellite imagery even though such an approach allows documentation of spatial and temporal variations of the resulting deposits in order to document changes that are occurring at the caronal avulsion on the taquari river brazil a time series of landsat imagery from 1985 to present 2010 was compiled as of july 2010 the imagery shows that the avulsion is not yet complete with discharge being routed to both the parent channel and the avulsion channel in the floodbasin the avulsion was initiated as flow was diverted from the parent channel to the floodbasin through two small crevasses allowing the development and evolution of splays with a single splay stabilizing only since 1999 the avulsion area is marked by the growth of new splays the formation of an avulsion belt and progradation of avulsion deposits into the floodbasin the parent channel downstream of the avulsion site has experienced decreasing width through time associated with the higher volumes of water and sediment being captured by the avulsion channel because this avulsion is not yet complete we expect more morphological changes to occur as the avulsion belt evolves into the primary channel rapid sedimentation caused by this avulsion and the 24 year time series of imagery that captured this change allowed us to construct a 3d block representing the evolution of depositional environments associated with avulsion using time in the vertical dimension thus we could represent the evolution of geomorphological patterns including floodbasin proximal levee distal levee and channel deposits and project their distributions through time this block of evolving sedimentary settings can be used as a guide for future sedimentologic studies by offering visual clues regarding the way which depositional systems track avulsion initiated changes

overbank sand deposition in relation to transport volumes during large magnitude floods in the dutch sand bed rhine river system using aerial photographs and field measurements sandy overbank deposits formed by the large magnitude floods of 1993 94 and 1995 were quantified along two branches of the dutch rhine river system the waal 1993 94 and 1995 and the ijssel 1995 these deposits were laid down intermittently all along the length of these rivers on the top and landward slope of the natural levees and covered about 4 per cent of the embanked floodplain on the waal and about 1 per cent on the ijssel the overbanks and transport mechanism is basically convective by nature the spatial variability of overbank sedimentation points to the important role played by helicoidal currents in determining overbank deposition the presence of embankments and training works appears to influence the sand transport to and morphological development of the floodplains along the dutch rhine river system overbank deposition volumes about equal present estimates of sand transport during a large magnitude flood it appears that studies on sand transport in the dutch rhine carried out so far underestimate sand transport during floods 1998 john wiley sons ltd

pre vegetation fluvial floodplains and channel belts in the late neoproterozoic cambrian santa barbara group southern brazil abstract one key element to the understanding of the dynamics of pre vegetation fluvial systems is the reconstruction of processes operating on their floodplains given that in modern systems channel banks and floodplains are the environments most affected by plant colonization notwithstanding few pre vegetation floodplains have been described and major questions regarding their most basic characteristics are still unresolved in order to address these questions detailed analysis of coeval channel belt fluvial floodplain and alluvial fan deposits from the santa barbara group late neoproterozoic to early cambrian southern brazil was performed while floodplain facies resemble ephemeral stream deposits being coarser grained than modern floodplains and marked by the stacking of flood event cycles channel belt deposits show composite bars which do not present conclusive evidence for high water discharge variation the floodplain deposits show particular features common to other pre vegetation fluvial systems such as better preserved small scale structures lack of bioturbation and abundance of cross laminated sandstones while other features differ from previous depositional models namely abundant mudcracks and evidence of soil formation the lateral variation of depositional systems recorded in the santa barbara group shows contrasting signatures of water discharge variation in sand dominated coeval environments and offers an example of the relation between different alluvial environments before the evolution of land plants

classification of paleosols despite increased interest in paleosols during the past decade no satisfactory classification is in current use presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope the classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes organic matter content horizonation redox conditions in situ mineral alteration illuviation of insoluble minerals compounds and accumulation of soluble minerals the most prominent of these six features processes provides the key to classifying a paleosol into one of nine orders four of the order names are borrowed from soil taxonomy histosol spodosol oxisol vertisol whereas the other five order names are presented here for the first time calcisol gypsisol gleysol argillisol protosol the orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol the classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology

processes facies and architecture of fluvial distributary system deposits abstract there is evidence from the stratigraphic record of examples of fluvial deposits that were the products of deposition from river systems which had decreasing discharge down flow and transitions from proximal channelised to distal unconfined flow these deposits form fan shaped bodies several tens of kilometres in radius and their stratigraphic architecture is aggradational with no evidence of deep incision driven by base level fall the fluvial systems that generated these deposits formed under conditions for which there is no complete analogue today an endorheic basin with a relatively arid climate adjacent to an uplifted area with higher precipitation a conceptual model for fluvial systems of this type has therefore been built on the basis of outcrop examples and a consideration of the controls on sedimentation proximal areas are characterised by amalgamated coarse pebbly and sandy channel deposits with little preservation of overbank facies channel dimensions are generally smaller in the medial areas but sizes are variable deposits are of braided meandering and simple channels which show varying degrees of lateral migration the channel fills may be mud or sand with overbank flow processes playing an important role in filling channels abandoned on the floodplain after avulsion the proportion of overbank deposits increases distally with sheets of sand deposited as lateral and terminal splays by unconfined flow interconnection of sandstone bodies is poor in the distal areas because channel fill bodies are sparse small and are not deeply incised the radial pattern of the sediment body forms by the repeated avulsion of channels active channels build up lobes on the alluvial plain and rivers switch position to follow courses on lower lying areas the term fluvial distributary system is here used to describe a river system which has a downstream decrease in discharge and has a distal zone which is characterised either by terminal splays on to a dry alluvial plain or a lake delta during periods of lake highstand

anatomy and dimensions of fluvial crevasse splay deposits examples from the cretaceous castlegate sandstone and neslen formation utah u s a abstract crevasse splay deposits form a volumetrically significant component of many fluvial overbank successions up to 90 in some successions yet the relationships between the morphological form of accumulated splay bodies and their internal facies composition remains poorly documented from ancient successions this work quantifies lithofacies distributions and dimensions of exhumed crevasse splay architectural elements in the campanian castlegate sandstone and neslen formation mesaverde group utah usa to develop a depositional model fluvial crevasse splay bodies thin from 2 1 m average to 0 8 m average and fine from a coarsest recorded grain size of lower fine sand to fine silt away from major trunk channel bodies internally the preserved deposits of splays comprise laterally and vertically variable sandstone and siltstone facies associations proximal parts are dominated by sharp and erosional based sandstone prone units which may be structureless or may comprise primary current lineation on beds and erosional gutter casts medial parts comprise sets of climbing ripple strata and small scale deformed beds distal parts comprise sets of lower stage plane beds and complex styles of lateral grading into fine grained floodbasin siltstones and coals lithofacies arrangements are used to establish the following i recognition criteria for crevasse splay elements ii criteria for the differentiation between distal parts of crevasse splay bodies and floodplain fines and iii empirical relationships with which to establish the extent ca 500 m long by 1000 m wide and overall semi elliptical planform shape of crevasse splay bodies these relationships have been established by high resolution stratigraphic correlation and palaeocurrent analysis to identify outcrop orientation with respect to splay orientation this permits lateral changes in crevasse splay facies architecture to be resolved facies models describing the sedimentology and architecture of crevasse splay deposits preserved in floodplain successions serve as tools for determining both distance from and direction to major trunk channel sandbodies

sediment infilling and wetland formation dynamics in an active crevasse splay of the mississippi river delta abstract crevasse splay environments provide a mesocosm for evaluating wetland formation and maintenance processes on a decadal time scale site elevation water levels vertical accretion elevation change shallow subsidence and plant biomass were measured at five habitats along an elevation gradient to evaluate wetland formation and development in brant pass splay an active crevasse splay of the balize delta of the mississippi river the processes of vertical development vertical accretion elevation change and shallow subsidence were measured with the surface elevation table marker horizon method there were three distinct stages to the accrual of elevation capital and wetland formation in the splay sediment infilling vegetative colonization and development of a mature wetland community accretion elevation gain and shallow subsidence all decreased by an order of magnitude from the open water lowest elevation to the forest highest elevation habitats vegetative colonization occurred within the first growing season following emergence of the mud surface an explosively high rate of below ground production quickly stabilized the loosely consolidated sub aerial sediments after emergent vegetation colonization vertical development slowed and maintenance of marsh elevation was driven both by sediment trapping by the vegetation and accumulation of plant organic matter in the soil continued vertical development and survival of the marsh then depended on the health and productivity of the plant community the process of delta wetland formation is both complex and nonlinear determining the dynamics of wetland formation will help in understanding the processes driving the past building of the delta and in developing models for restoring degraded wetlands in the mississippi river delta and other deltas around the world

sequential architecture in a fluvial succession sequence stratigraphy in the upper cretaceous mesaverde group prince canyon utah abstract five unconformity bounded sequences have been documented within a 1300 m thick succession of predominantly fluvial upper cretaceous and lower tertiary deposits in the price canyon area of the westernmost part of the book cliffs east central utah u s a this area experienced major tectonically induced changes in the paleogeography during deposition the earliest fluvial deposits in the study area were formed in a relatively simple foreland basin setting in front of the sevier orogenic belt and contain more marine influence than previously recorded following a gradual termination of thrusting sedimentation became increasingly controlled by uplift of the san rafael swell to the southeast our studies suggest that the fluvial systems in the upper part of the succession alternated bet een being confined within a valley open towards the north and being more directly eastward flowing on the basis of the observed sequences an idealized model of alluvial sequences whose internal architecture can be related to a fall rise fall cycle of the stratigraphic base level has been established upward or downward changes in the position of this base level dictate the creation and destruction of accommodation on the alluvial plain and therefore exert a direct control on the sequential architecture and sandstone body geometry of fluvial successions in our model the basal sequence boundary is overlain by an amalgamated fluvial sandstone sheet the sheet is succeeded by a fining upward more mudstone rich level with more isolated sandstone bodies and this level may culminate in a marine or lacustrine transgression the upper part of the sequence may show a coarsening upward trend heralding the next phase of base level fall and sequence boundary generation use of the suggested model has the potential to refine existing lithostratigraphic schemes and given the higher resolution and more detailed correlation may significantly improve paleogeographic reconstructions and aid in prediction of potentially hydrocarbon bearing reservoirs a revised and refined lithostratigraphy has been established on the basis of alluvial sequence analysis the lower half of the succession forms the youngest part of a major eastward prograding clastic tongue the mesaverde group and is campanian we divide this part into the blackhawk castlegate and price river formations the rest of the succession is maastrichtian to paleocene and is referred to the north horn formation this formation was deposited in an intermontane setting

depositional patterns following the 1870s avulsion of the saskatchewan river cumberland marshes saskatchewan canada abstract the avulsion of the saskatchewan river cumberland marshes east central saskatchewan canada has resulted in new floodplain deposition over an area of more than 500 km2 since beginning in the 1870s the avulsion deposits are predominantly fine grained and could be otherwise classifiable as overbank sediments in alluvial floodplains presumed to be supplied by intermittent flooding of dominant master channels the north angling and cadotte channels are older pre existing channels that were intercepted and appropriated by the expanding avulsion following annexation of the north angling channel stable cohesive banks inhibited channel enlargement and crevassing forcing the increasing discharges to be accommodated by overbank flow and in the process enhancing new levee aggradation these levee deposits coarsen upward and thin downstream as a result of greater competence and higher proximal deposition rates brought on by the larger flows in contrast the cadotte channel responded to increasing discharges by levee breaching giving rise to splay progradation and floodbasin filling the cadotte splay complex formed from the avulsively annexed cadotte channel represents a small but typical area of the avulsion belt facies characteristics and interrelationships examined from auger borings and vibracores are presented to illustrate patterns of deposition and floodplain development avulsive flooding initially raised local water surface elevations deepening small existing lakes and creating new shallow 1 2 m deep lakes on the floodplain surface deposition began when levees of the cadotte channel were breached allowing water and coarser sediment to spread as sheet like flows while finer sediment was carried and deposited farther into the basin later as the proximal splay sheets coalesced and grew basinward flows became channelized and progradation of mouth bars into marshes and shallow lakes together with deposition of interchannel fines became dominant forming coarsening upward sequences further floodplain aggradation developed by overbank flooding when splay channels became stabilized and bordered by levees gradual abandonment was accompanied by deposition of organic rich fine grained sediment on top of the progradational sequences throughout the avulsion the north angling channel has stood as an older alluvial ridge separating two broad areas of avulsive deposition its recent levee deposits now grade basinward into these new floodplain sediments composed of thicker heterogeneous predominantly upward coarsening and rapidly deposited facies of the avulsion

architecture and origin of an amalgamated fluvial sheet sand lower castlegate formation book cliffs utah abstract amalgamated fluvial sheet sandstones in the stratigraphic record are often interpreted as the deposits of braided rivers alluvial sequence stratigraphic models show these sheet sandstones overlying sequence boundaries and deposited during low rates of base level rise and fall since sequence stratigraphic models rely on the balance between creation destruction of accommodation and sediment supply is the sheet like nature of these units controlled by channel style by aggradation rates tied to base level changes or a combination of both the lower member of the castlegate formation in the book cliffs of eastern utah u s a was selected to answer these questions regarding the origin and architecture of amalgamated sheet sandstones the lower castlegate is 60 m thick and is underlain by a regional sequence boundary delineation of the alluvial architecture utilized a combination of outcrop photography measured sections and paleochannel dimension estimation at two outcrops in the type area architectural components within the outcrops were defined and include 1 basal thalweg fill units 2 inclined sandy or heterolithic barform deposits and 3 overbank siltstone and mudstone thalweg fill units represent deposition in the topographically lowest part of the channel and are preferentially preserved thalweg units exist as single units or as a composite of multiple thalweg units overlying thalweg units inclined barform deposits are in places preserved and genetically linked to an underlying thalweg fill unit bar accretion directions when combined with paleocurrent indicators show that lateral downstream and upstream accretion all occur in the lower castlegate overbank deposits are rarely preserved but where present they typically overlie bar deposits the architectural components stack to form a threefold cyclic hierarchy of 1 channel bar systems 2 12 m thick 2 channel belts 2 16 m thick and 3 stacked channel belt complexes 17 40 m thick complete channel bar systems are rarely preserved and occur locally as a succession of multiple stacked thalweg fill units the lack of barforms within a composite thalweg unit suggests that channel migration is the dominant process controlling preservation within channel bar systems possibly associated with a component of local avulsion channel belts are composed of stacked channel bar systems capped by a barform the barform is preserved due to a regional avulsion moving the active channel to another location within the floodplain isolating it from potential reworking stacked channel belt complexes are characterized by alternations of thalweg dominated and barform dominated channel belts the mechanism responsible for deposition at the stacked channel belt complex scale may be creation destruction of accommodation associated with base level changes paleochannel reconstructions show that channel flow depths using bar and underlying thalweg thickness were up to 7 6 m channel depth estimates utilizing a cross bed set thickness of 26 cm averaged 4 6 7 7 m these values were used to calculate channel widths which were estimated at 143 365 m up to a maximum of approximately 1 km regional paleoflow within the lower castlegate was dominantly southeast directed the architectural components paleochannel characteristics and paleocurrent data suggest the lower castlegate member was deposited in low to intermediate sinuosity rivers influenced by autocyclic processes at smaller scales and allocyclic processes at the larger outcrop scale

reservoir and aquifer characterization of fluvial architectural elements stubensandstein upper triassic southwest germany this paper aims at a quantitative sedimentological and petrophysical characterization of a terminal alluvial plain system exemplified by the stubensandstein south german keuper basin the study follows the outcrop analogue approach where information derived from outcrops is collected in order to enhance interpretation of comparable subsurface successions quantitative data on sandbody geometries porosities and permeabilities are presented in order to constrain modelling of subsurface sandbodies and permeability barriers for sedimentological characterization the method of architectural element analysis miall a d 1996 the geology of fluvial deposits springer berlin was used and modified to include poroperm facies a special photo technique with a precise theodolite survey was developed to create optically corrected photomosaics for outcrop wall maps from up to 20 000 m2 large outcrops nine architectural elements have been classified and quantified bedload mixed load and suspended load channel fills are separated the petrophysical characterization of the architectural elements integrated porosity and permeability measurements of core plugs with gamma ray measurements along representative sections it could be demonstrated that certain architectural elements show a characteristic poroperm facies four scales of sedimentary cycles have been recognized in the stubensandstein cyclic sedimentation causes changing lithofacies patterns within the architectural elements depending on their position in the sedimentary cycle stratigraphic position exerts only some paleogeographic position exerts significant influence on porosity and permeability of the sandbodies the highest poroperm values were found in proximal areas of the alluvial plain and in middle parts within sedimentary macrocycles the strong internal heterogeneity on the alluvial plain system is important for its reservoir and aquifer characteristics compartments of bedload channel sandstones in medial positions of a stratigraphic cycle represent very good reservoirs or aquifers the seals or aquicludes are formed by extensive floodplain claystones lacustrine sediments paleosols and suspended load deposits strongly cemented zones of sandstones represent aquitards

crevasse splay morphodynamics in a dryland river terminus rio colorado in salar de uyuni bolivia high resolution satellite imagery in combination with field investigation enables the analysis of splay morphological developments in time and space at the low gradient terminus of the modern rio colorado dryland river system in the salar de uyuni bolivia two sets 2004 2005 2010 2011 of satellite images are used to visualize splay morphological developments and three types of crevasse splays are identified based on temporal changes 1 new crevasse splays ncs refers to those splays that are not observed in the first set of images but can be observed on the second sets of images 2 changing crevasse splays ccs representing those splays that are found on the first set of images but their geometry has changed between two satellite observation periods and 3 inactive crevasse splays ics referred to those splays that are found on the first set of images but on the second set of images they remain the same or are partially overlapped by adjacent expanding crevasse splays the density or frequency of these three types of crevasse splays has no correlation with the distance to the starting point of the river or the local slope the cross sectional area of the studied river steadily decreases downstream and frequency analysis shows a downstream increase in the number of crevasse splays and suggests an exponential relationship with the river cross sectional area development of crevasse splays is often attributed to topographic lows between adjacent crevasse splays and they fill in the depression by compensational stacking e g li et al 2014 these amalgamated splays are capable of forming a large area of sheet sands and potentially provide an analogue for thin bedded hydrocarbon reservoirs

sequence stratigraphy and marine to nonmarine facies architecture of foreland basin strata book cliffs utah u s a the desert member of the blackhawk formation and the castlegate sandstone in the book cliffs of utah and colorado were analyzed to develop a model of sequence stratigraphy and facies architecture in foreland basins stratal architecture of these rocks is controlled by two regionally extensive surfaces of incision and subaerial exposure interpreted as major sequence boundaries and at least six surfaces of incision and subaerial exposure with more limited lateral extent interpreted as minor sequence boundaries each sequence boundary is a regionally correlatable single surface major sequence boundaries can be traced from marine into proximal alluvial plain environments sequence boundaries have different physical expressions depending upon where in the basin they are observed strata beneath sequence boundaries are unrelated to strata above and time lines cannot be carried across these boundaries flooding surfaces called parasequence or parasequence set boundaries also exert an important control on facies architecture based on parasequence stacking patterns position of sequence boundaries and facies associations the desert member and castlegate sandstone have been divided into sequences with durations of 200 000 to 300 000 yr there are an order of magnitude more sequences in this interval than are predicted by the global sea level chart of haq et al 1988 the major sequences have been divided into the following systems tracts or sequence sets 1 grassy highstand sequence set below the desert sequence boundary named for the grassy member of the blackhawk formation 2 desert lowstand transgressive and highstand systems tracts between the desert and castlegate sequence boundaries 3 castlegate lowstand sequence set resting on the castlegate sequence boundary and 4 castlegate transgressive systems tract parasequence stacking patterns suggest that the grassy highstand sequence set and the desert highstand systems tract were deposited during a relative rise in baselevel the grassy highstand sequence set is punctuated by minor relative falls in baselevel both of these stratal units contain thick

practical characterization of eolian reservoirs for development nugget sandstone utah wyoming thrust belt abstract the jurassic eolian nugget sandstone of the utah wyoming thrust belt is a texturally heterogeneous formation with anisotropic reservoir inherited primarily from the depositional environment original reservoir quality has been reduced somewhat by cementation and slightly enhanced by dissolution low permeability gouge filled micro faults compartmentalize the formation whereas intermittently open fractures provide effective permeability paths locally where productive the nugget sandstone ranges from approximately 800 to 1050 ft 244 320 m thick at subsurface depths of 7500 to 15 000 ft 2286 4572 m porosity ranges from several percent to 25 and permeability covers five orders of magnitude from hundredths of millidarcies to darcies some nugget reservoirs are fully charged with hydrocarbons different stratification types have unique depositional textures primary and diagenetic mineralogies and deformational fabrics resulting in characteristic porosity permeability permeability directionality and pore geometry attributes such characteristics can be determined from core analysis mercury injection nuclear magnetic resonance conventional log dipmeter and production data nugget dune deposits good reservoir facies primarily consist of grainflow and wind ripple cross strata the former of which have the better reservoir quality and the lesser heterogeneity in bedding texture high permeability facies are commonly affected by local quartz and nodular carbonate cementation chlorite and lesser illite precipitation and minor framework and cement dissolution gouge filled micro faults are the predominant deformational overprint interdune sand sheet and other water associated deposits poor reservoir facies are characterized by low angle wind ripple laminae and more irregular bedding some of which is associated with damp or wet conditions water associated nugget stratification generally contains the finest grained depositional textures and has the poorest reservoir properties these non dune facies contain intergranular micritic carbonate and illite precipitates and are most affected by compaction and pressure solution phenomena open types of fractures are somewhat more likely in this lower permeability rock depositional models incorporating dune morphologies facies distribution permeability directionality and theoretical concepts regarding dune migration through time are useful in delineating correlative intervals most likely to have continuity and potential communication of reservoir properties stratigraphic models can be adapted for reservoir simulation studies and also can be utilized in solving structural resolution problems if correlatable vertical sequences and relatively consistent cross strata orientations exist

characterizing avulsion stratigraphy in ancient alluvial deposits guidelines for identifying ancient avulsion deposits were set forth by kraus and wells kraus m j wells t m 1999 recognizing avulsion deposits in the ancient stratigraphical record in smith n d rogers j eds fluvial sedimentology vi special publication of the international association of sedimentologists vol 28 pp 251 268 building on the study by smith et al smith n d cross t a dufficy j p clough s r 1989 anatomy of an avulsion sedimentology 36 1 23 of the modern saskatchewan river system cumberland marshes central canada and serve to characterize avulsion depositional sequences in the ancient willwood and fort union formations paleogene bighorn basin nw wyoming usa we recognize however that the model is not universally applicable to avulsion dominated successions specifically systems which lack defining heterolithic avulsion deposits set forth by kraus and wells kraus m j wells t m 1999 recognizing avulsion deposits in the ancient stratigraphical record in smith n d rogers j eds fluvial sedimentology vi special publication of the international association of sedimentologists vol 28 pp 251 268 observations in several fluvial intervals suggest that the avulsion stratigraphy outlined by kraus and wells kraus m j wells t m 1999 recognizing avulsion deposits in the ancient stratigraphical record in smith n d rogers j eds fluvial sedimentology vi special publication of the international association of sedimentologists vol 28 pp 251 268 represents one category of avulsion stratigraphy found in the rock record but does not capture the nature of avulsion deposits everywhere based on observations using measured sections outcrop photo panels and aerial photographs in the willwood formation eocene wyoming and ferris formation cretaceous paleogene wyoming we present two end member categories of avulsion stratigraphy in ancient deposits stratigraphically abrupt when a main paleochannel is stratigraphically juxtaposed directly atop floodplain overbank deposits and stratigraphically transitional where crevasse splays and other non floodplain overbank deposits stratigraphically precede a main paleochannel this characterization provides a broader more inclusive way to recognize and describe avulsion stratigraphy in ancient deposits and may be an important factor to consider when modeling connectivity in fluvial reservoirs furthermore our observations show that one type of avulsion channel stratigraphy may prevail over another within an ancient basin suggesting that system wide factors such as splay proneness or avulsion style i e aggradational incisional etc slingerland r smith n d 2004 river avulsions and their deposits annual review of earth and planetary sciences 32 257 285 may be primary controls on the type of avulsion stratigraphy deposited and preserved in ancient basin fills

landsat imagery based visualization of the geomorphological development at the terminus of a dryland river system abstract in this remote sensing based study we present the analysis of the geomorphological development at the low gradient terminus of the modern rio colorado dryland river system in the endorheic altiplano basin bolivia changes in the river morphology occur after short periods of catastrophic peak discharge which result in the expansion of existing crevasse splays formation of new crevasse splays and in river path avulsion episodic peak discharge events in the study area were pinpointed and quantified by combining daily precipitation records from gauging stations in the vicinity with catchment area analysis from aster global dem gdem remote sensing data a time series of landsat imagery for the period 1975 2001 was then used to analyze the river morphology changes after major peak discharge events compensational stacking of crevasse splays in combination with river avulsion produced a thin but aerially extensive connected sand sheet at the terminus of the fluvial system