sediment dispersal and quantitative stratigraphic architecture across an ancient shelf two large 200 to 300 km near continuous outcrop transects and extensive well log data ca 2800 wells allow analysis of sedimentological characteristics and stratigraphic architecture across a large area ca 60 000 km2 of the latest santonian to middle campanian shelf along the western margin of the western interior seaway in eastern utah and western colorado usa genetically linked depositional systems are mapped at high chronostratigraphic resolution ca 0 1 to 0 5 ma within their sequence stratigraphic context in the lower part of the studied interval sediment was dispersed via wave dominated deltaic systems with a compound clinoform geomorphology in which an inner wave dominated shoreface clinoform was separated by a muddy subaqueous topset from an outer clinoform containing sand poor gravity flow deposits these strata are characterized by relatively steep net regressive shoreline trajectories 0 1 with concave landward geometries narrow nearshore belts of storm reworked sandstones 2 to 22 km wide offshore mudstone belts 250 km and relatively high sediment accumulation rates ca 0 27 mm year 1 the middle and upper parts of the studied interval also contain wave dominated shorefaces but coeval offshore mudstones enclose abundant isolated tide influenced sandstones that were transported sub parallel to the regional palaeoshoreline by basinal hydrodynamic tidal circulation these strata are characterized by relatively shallow net regressive shoreline trajectories 190 km and relatively low sediment accumulation rates ca 0 11 mm year 1 the change in shelfal sediment dispersal and stratigraphic architecture from i compound clinoform deltas characterized by across shelf sediment transport to ii wave dominated shorelines with isolated tide influenced sandbodies characterized by along shelf sediment transport is interpreted as reflecting increased interaction with the hydrodynamic regime in the seaway as successive shelfal depositional systems advanced out of a sheltered embayment utah bight this advance was driven by a decreasing tectonic subsidence rate which also suppressed autogenic controls on stratigraphic architecture

tectonic control of nested sequence architecture in the castlegate sandstone upper cretaceous book cliffs utah abstract the castlegate sandstone at its type section price canyon near price utah encompasses a single stratigraphic sequence spanning approximately 5 m y it includes a sandstone member corresponding to a lowstand systems tract consisting of braided fluvial sheet sandstones and a mudstone member in which shales are more abundant and some evidence of tidal influence is present this is the transgressive to highstand systems tract from near trail canyon eastward the mudstone member passes laterally into the sego sandstone and neslen formation a succession of at least six higher frequency sequences of fluvial estuarine origin the buck tongue a marine shale unit separating the castlegate sandstone and the sego sandstone east of green river is erosionally truncated below the sego sand tone northwest of trail canyon we suggest that the origin of the sequences is related to flexural loading and intraplate stress on two time scales eustasy cannot be ruled out but there is no independent evidence for this process the main 5 m y sequence reflects regional tectonism with the sandstone member developing at a time of slow subsidence and the mudstone member reflecting a higher long term subsidence rate the higher order sequences nested within the third order sequence east of trail canyon are interpreted as a basinal response to episodes of crustal shortening on a 105 yr time scale this study amplifies the model of posamentier and allen 1993a in which ramp type foreland basins are divided into areas of rapid and slow subsidence zones a and b we postulate that these zones migrated asinward and landward in response to variations in long term subsidence rate an effect not predicted in the original model and can be mapped by reference to the distribution of type 1 sequence boundaries in the higher order sequences differences in sequence architecture east and west of trail canyon may have been amplified by differences in crustal rheology the sequence architecture changes at the boundary of the underlying paleozoic paradox basin a zone of nw se oriented folds faults and salt diapirs which we suspect were reactivated by cretaceous tectonism the high frequency sequences are within the area of the paradox basin an area that may have been more prone to vertical structural movements in response to intraplate stresses incipient uplift of laramide structures may also have modified fluvial patterns and controlled the orientation of incised valleys on several of the sequence boundaries

accommodation and sediment supply controls on clastic parasequences a meta analysis this study combines data from many published case studies to undertake a quantitative characterization of clastic parasequences with the aim to determine how accommodation sediment supply and autogenic sediment storage dynamics are recorded in their sedimentary architecture and stacking patterns results of this study are used to critically evaluate the validity of paradigms and models that are routinely used to explain and predict trends in the anatomy and arrangement of parasequences data on 957 parasequences from 62 case studies of clastic shallow water successions were coded in a relational database which includes outcrop and subsurface datasets of ancient and quaternary examples these units cover the preserved records of both river dominated deltas and wave dominated coasts representing shoreline transits over a breadth of timescales likely of both local and regional extent the role of extant accommodation rates of creation of accommodation and rates of sediment supply in determining parasequence architecture is assessed through analysis of relationships between i proxies of these variables at different scales rates of aggradation and progradation facies belt shoreline trajectories systems tract type parasequence set stacking patterns parasequence progradation angle and stratigraphic rise size of feeder rivers and ii parameters that describe the geometry and stacking style of parasequences and associated shallow water sand bodies statistical analyses of database outputs indicate which proxies of accommodation sediment supply and accommodation sediment supply ratio are significant as predictors of parasequence architecture and allow for interpretations of the importance of allogenic and autogenic factors the principal results of this study reveal the following i parasequence thickness varies as a function of water depth accommodation generation and erosional truncation and these variations are also reflected across types of systems tracts and parasequence sets ii the dip length of parasequence sand bodies demonstrates scaling with measures of accommodation sediment supply ratio at multiple scales partly in relation to the possible effect of sediment supply on progradation rates iii in systems tracts stratigraphic trends in parasequence stacking due to autogenic mechanisms or to acceleration or deceleration in relative sea level fluctuations are not revealed quantitatively iv some association is seen between the abundance of deltaic or river dominated parasequences and progradational stacking v positive but modest correlation is observed between measures of river system size and the dip length of shallow marine parasequence sand bodies the resulting insights can be applied to guide sequence stratigraphic interpretations of the rock record and the characterization of sub seismic stratigraphic architectures of subsurface successions

high resolution facies analyses of mudstones implications for paleoenvironmental and sequence stratigraphic interpretations of offshore ancient mud dominated successions abstract the extent of lithofacies variability in fine grained sedimentary rocks is very poorly known in comparison to that present in coarser grained clastic and carbonate successions the absence of this information means that sediments present on continental shelves are rarely considered as integrated systems because fine grained facies such as shales are mostly excluded from sophisticated regional facies models to shed light upon lithofacies and grain size in shale dominated successions so that they can be incorporated into shelf wide depositional models the blackhawk formation of the mancos shale campanian age exposed in the book cliffs utah was investigated using combined field whole rock geochemical optical and electron optical methods these sediments show systematic grain size variations are intensely bioturbated and composed predominantly of detrital clays mainly dioctahedral micas quartz and feldspar with minor pyrite and organic matter they are organized into very thin 10 mm upward fining genetic beds they exhibit both systematic lateral 103 m scale and vertical 10 2 to 100 m scales lithofacies variability preferentially cemented units occur close to sequence boundaries unconformities these cemented units typically contain a very different detrital assemblage including significant quantities of chlorite from the rest of the succession and are located close to levels where there are marked stacking pattern discontinuities overall lithofacies variability is interpreted in terms of deposition occurring on an oxic continental shelf with the coarser grained facies being deposited in proximal settings offshore transition zone in contrast to the finer grained units that were deposited in more distal environments offshore zone storms are interpreted to have been the dominant mechanism dispersing the sediment once deposited the surface layers of the sediment were intensely reworked by burrowing organisms preferential preservation of ichnogenera from mid and lower tiers suggest that the depositional environment was energetic and erosion commonly removed the surface sediment layers prior to deposition of thin 10 2 m storm beds the larger scale 100 m upward coarsening units that are composed of stacked beds are interpreted to be parasequences preferential cementation at levels where large scale stacking patterns change is interpreted to occur at horizons where there were breaks in sediment accumulation and bacterial metabolic processes were able to supply sufficient solutes to fill uncompacted pore space with cement the presence of a very different detrital assemblage in these units suggests that winnowing occurred despite their relatively innocuous appearance in the field these surfaces are likely to be significant bypass surfaces over which sediment was delivered to the deeper parts of the basin during times of relative lowstand of sea level

confluence scours versus incised valleys examples from the cretaceous ferron notom delta southeastern utah u s a abstract confluence scours in braided rivers occur where channel threads join together producing erosional relief that may be considerably deeper than average channel depth based on studies of the continental scale ganges brahmaputra river system it has been observed that the maximum depth of confluence scours by autocyclic processes may reach up to four to five times the average depth of the incoming channels considering the possibility of such massive scours in an ancient fluvial system it was argued that allogenically produced incised valleys at sequence boundaries should only be properly defined in ancient systems if the erosional relief is more than five times average channel depth based on cross sectional geometries a number of confluence scour fills were interpreted on well exposed fluvial outcrops in a cretaceous age compound incised valley system in the notom delta complex of the ferron sandstone member utah cross sectional observations from outcrops and comparisons with modern rivers reveal that confluence scours have diagnostic fill facies single set of large steep foresets and do not produce multistory sand bodies a confluence scour fill produces a single story body in which a fifth order scour is filled with unit bar foresets which in turn are overlain by a fourth order surface capped by compound bar deposits the story thickness in the confluence scour does not represent the average channel depth because confluence scours allow preservation of the deepest parts of channels as well as fully preserved abnormally thick stories therefore we argue that interpretation of incised valleys in the ancient system associated with a sequence boundary should not be based on the depth of the erosional surface versus the number of average preserved channel stories rather it should be defined by the erosional relief that is significantly deeper than the thickest fully preserved stories which in a braided stream are likely to represent confluence scour fills

cyclic stacking pattern architecture and facies of the turbidite lobes in the macigno sandstones formation chattian aquitanian northern apennines italy abstract this study presents a detailed facies analysis of an 800 m thick stratigraphic succession in the basinal turbidites of the macigno sandstones formation msf recording the first foredeep in the northern apennines italy this stratigraphic succession shows an evident stacking pattern that besides the basal part 200 m thick dominated by fine grained and thin beds is characterized by seven magnificently exposed sandstone lobes from 90 to 19 m thick separated by well developed fine grained interlobe deposits thanks to the detailed facies analysis not only a well defined architectural hierarchy has been identified but a facies scheme has also been proposed whereby cyclic recurring of three facies associations has in turn been identified each facies association records a well determined evolutionary stage of lobe development where an early depositional stage of the lobe building phase is followed by a flow impact and bypass stage recording flow decelerations and hydraulic jumps induced by the morphology created by the underlying depositional lobe the latter phase promotes a switching and channel feeder avulsion that heralds the third phase of abandonment with the deposition of fine grained interlobes the facies stacking pattern and the evolutionary model of the msf also supported by other similar field and experimental works are intended as a contribution to the understanding of intrinsic autogenic mechanisms at the basis of sand rich depositional lobe development

a test of analog based tools for quantitative prediction of large scale fluvial architecture outcrop analogs are routinely used to constrain models of subsurface fluvial sedimentary architecture built through stochastic modeling or interwell sand body correlations correlability models are analog based quantitative templates for guiding the well to well correlation of sand bodies whereas indicator variograms used as input to reservoir models can be parameterized from data collected from analogs using existing empirical relationships this study tests the value and limitations of adopting analog informed correlability models and indicator variogram models and assesses the effect and significance of analog choice in subsurface workflows for characterizing fluvial reservoirs a 3 2 km 2 mi long architectural panel based on a virtual outcrop from the cretaceous blackhawk formation wasatch plateau utah has been used to test the methodologies vertical dummy wells have been constructed across the panel and the intervening fluvial architecture has been predicted using correlability models and sequential indicator simulations the correlability and indicator variogram models employed to predict the outcrop architecture have been compiled using information drawn from an architectural database these models relate to 1 analogs that partially match with the blackhawk formation in terms of depositional setting and 2 empirical relationships relating statistics on depositional element geometries and spatial relations to net to gross ratio based on data from multiple fluvial systems of a variety of forms the forecasting methods are assessed by quantifying the mismatch between predicted architecture and outcrop observations in terms of the correlability of channel complexes and static connectivity of channel deposits results highlight the effectiveness of correlability models as a check for the geologic realism of correlation panels and the value of analog informed indicator variograms as a valid alternative to variogram model parameterization through geostatistical analysis of well data this work has application in the definition of best practice use of analogs in subsurface workflows it provides insight into the typical degree of realism of analog based predictions of reservoir architecture as well as the effect of analog choice and draws attention to associated pitfalls

studies of stress and displacement distribution and the evolution law during rock failure process based on acoustic emission and microseismic monitoring abstract the evolutions of stress and deformation inside of rock is highly important in studies of the rock failure mechanism but is difficult to obtain via the traditional stress measurement methods due to limited measuring points thus studies of the stress and displacement evolution within rock were conducted based on acoustic emission ae monitoring in laboratory experiments the differences in the distributions and evolution characteristics of the stress field and deformation field before caving in a deep stope were also examined based on in situ microseismic ms monitoring the results show that the distributions of micro cracks apparent stress and deformation inside the rock are highly consistent and can reflect the spatial temporal evolution characteristics of the stress field and deformation field within the rock the accumulated apparent volume is more accurately than the strain to reflect the changes in inelastic deformation inside the rock based on in situ ms monitoring ms activities were found to be closely related to blasting disturbances during the caving process before a caving of the deep stope the distributions of stress and displacement showed obvious differences reflecting the loosening process of the rock mass the non uniformity and the differences in the stress and deformation can deepen the understanding of the rock mass failure process

recommendations for a uniform chronostratigraphic designation system for phanerozoic depositional sequences many published sequence stratigraphic frameworks lack a systematic and consistent designation for both depositional sequences and key surfaces despite the original goal to provide a fully integrated stratigraphic architecture including diagnostic age information based on a system in use for more than 10 yr at exxonmobil we recommend methodologies for a chronostratigraphic designation system cds using more uniform and robust sequence stratigraphic designations after objectively defining important physical stratigraphic surfaces biostratigraphic and other age constraining information is used to designate surfaces and the packages of rocks they bound this leads to the establishment of a sequence chronostratigraphic framework for a local area of investigation outcrop section field region or basin only after demonstrating clear well documented ties to phanerozoic global coastal onlaps or cycle charts are these sequences and associated surfaces considered as global entities and designated as such higher frequency sequences and surfaces are also accommodated in this cds alternative designations for areas with limited or poor quality chronostratigraphic information are also discussed the cds has proven to have great use in all phanerozoic strata different tectonic settings and depositional environments especially when chronostratigraphic age constraints are robust we have used this system at regional and basinal scales in many geographic locations to help reduce uncertainty in identifying and correlating reservoirs sources and seal rocks predicting the local distribution and quality of reservoirs as well as seals within a producing field and near field wildcats is also facilitated by this system this system has demonstrated use in the correlation of outcrop sections within a basin or between basins rigorous use of the cds proposed here will permit meaningful regional and or interbasinal correlation that is difficult to carry out with the diverse systems currently in use this uniform designation scheme will also facilitate communication within a company and between institutions as well as among academic investigators

no change in fluvial style across a sequence boundary cretaceous blackhawk and castlegate formations of central utah u s a nonmarine sequence stratigraphic models are based largely on studies of fluvial units in the cretaceous western interior of north america including the blackhawk and castlegate formations of central utah these models suggest that fluvial units should show a transition from mudstone prone isolated meander belt deposits of the transgressive and highstand systems tract into amalgamated braided stream sandstones of the lowstand systems tract these mudstone rich fluvial strata are largely assumed rather than documented to represent the deposits of isolated meander belt deposits despite recent work that suggests that there is no simple relationship between the proportion of preserved floodplain mud and fluvial style there are numerous studies documenting the braided character of the sandstone rich castlegate formation but there are no corresponding studies that document the internal fluvial facies architecture within the blackhawk formation to support the interpretation that the blackhawk comprises the deposits of a meandering stream system we test the validity of the sequence stratigraphic model by comparing dimensions and styles of associated bar and channel deposits as well as cross stratal thicknesses between the blackhawk and castlegate formations along salina canyon in utah data compiled from 24 measured sections and 6 photomosaics show that the blackhawk formation comprises isolated sandy channel belt sheet sandstones 5 8 m thick contained within thick floodplain mudstones whereas the castlegate formation consists of about 80 m of amalgamated sandy channel belt sheets 4 7 m thick with only minor mudstone the average height of cross sets is 13 cm in the castlegate formation and 14 cm in the blackhawk formation and formative dune height is estimated to be 38 cm for the castlegate formation and 45 cm for the blackhawk formation average bar accretion thicknesses are 2 m in both the blackhawk and castlegate formations corresponding water depths are estimated to be 2 5 4 1 m for the blackhawk and 2 3 3 8 m for the castlegate the correlation of master bedding planes in the blackhawk formation shows overlapping lens shaped bar deposits and channel fills bar tops appear to dip in several directions indicating both lateral and downstream accretion of mid channel braid bars while there is some indication that castlegate rivers were slightly shallower the differences do not suggest a major change in fluvial style across the sequence boundary both are braided the lack of change in scale of channels also is not compatible with a hypothesized increase in aridity between the blackhawk and the castlegate the difference in fluvial architecture between the two formations is interpreted to reflect changes in accommodation that were likely tectonic in origin this supports that idea that preservation of thick successions of fine grained overbank material is not a function of the plan view channel geometry

sediment supply dominated stratal architectures in a regressively stacked succession of shoreline sand bodies campanian desert member to lower castlegate sandstone interval book cliffs utah colorado usa

environmental signal propagation in sedimentary systems across timescales abstract earth surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales the geomorphic and stratigraphic products of this source to sink sediment transfer record signals of external environmental forcings as well as internal or autogenic dynamics of the sedimentary system here we evaluate environmental signal propagation across sediment routing systems with emphasis on sediment supply qs as the carrier of up system forcings we review experimental numerical and natural examples of source to sink sediment routing and signal propagation during three timescales 1 historic which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries 2 centuries to several millions of years referred to as intermediate timescale and 3 deep time we discuss issues related to autogenic dynamics of sediment transport transient storage and release that can introduce noise lags and or completely mask signals of external environmental forcings we provide a set of conceptual and practical tools for evaluating sediment supply within a source to sink context which can inform interpretations of signals from the sedimentary record these tools include stratigraphic and sediment routing system characterization sediment budgets geochronology detrital mineral analysis e g thermochronology comparative analog approaches and modeling techniques to measure calculate or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment routing systems

stratigraphy and depositional setting of slurry and contained reflected beds in the marnoso arenacea formation langhian serravallian northern apennines italy this work presents the stratigraphy and facies analysis of an interval of about 2500 m in the langhian and serravallian stratigraphic succession of the foredeep turbidites of the marnoso arenacea formation a high resolution stratigraphic analysis was performed by measuring seven stratigraphic logs between the sillaro and marecchia lines 60 km apart for a total thickness of about 6700 m the data suggest that the stratigraphy and depositional setting of the studied interval was influenced by syndepositional structural deformations the studied stratigraphic succession has been subdivided into five informal stratigraphic units on the basis of how structurally controlled topographic highs and depocentres a consequence of thrust propagation change over time these physiographic changes of the foredeep basin have also been reconstructed through the progressive appearance and disappearance of thrust related mass transport complexes and of five bed types interpreted as being related to structurally controlled basin morphology apart from bouma like type 4 beds type 1 tripartite beds characterized by an internal slurry unit tend to increase especially in structurally controlled stratigraphic units where intrabasinal topographic highs and depocentres with slope changes favour both mud erosion and decelerations type 2 beds with an internal slump type chaotic unit characterize the basal boundary of structurally controlled stratigraphic units and are interpreted as indicating tectonic uplift type 3 beds are contained reflected beds that indicate different degrees of basin confinement while type 5 are thin and fine grained beds deposited by dilute reflected turbulent flows able to rise up the topographic highs the vertical and lateral distribution of these beds has been used to understand the synsedimentary structural control of the studied stratigraphic succession represented in the marnoso arenacea formation by subtle topographic highs and depocentres created by thrust propagation folds and emplacements of large mass transport complexes

autogenic erosional surfaces in fluvio deltaic stratigraphy from floods avulsions and backwater hydrodynamics erosional surfaces set the architecture of fluvio deltaic stratigraphy and they have classically been interpreted in terms of changes in boundary conditions such as climate tectonics and base level allogenic forces intrinsic dynamics of sedimentary systems autogenic dynamics can also create a rich stratigraphic architecture and a major knowledge gap exists in parsing the relative roles of autogenic versus allogenic processes emerging theoretical and experimental work suggests that backwater hydrodynamics play an important role in driving transient channel incision in river deltas even those experiencing net aggradation here we identify and quantify two autogenic mechanisms that produce broad erosional surfaces in fluvio deltaic stratigraphy namely floods and avulsions using a simple mass balance model for single threaded delta channel systems we show that flood induced scours begin near the shoreline and avulsion induced scours begin at the avulsion site and both propagate upstream over a distance that scales with the backwater length bed slope and bed grain size we also develop scaling relationships for the maximum scour depths arising from these mechanisms which are functions of characteristic flow depth and formative flood variability we test our theoretical predictions using a flume experiment of river delta evolution governed by persistent backwater hydrodynamics under constant relative sea level results indicate that autogenic dynamics of backwater mediated deltas under conditions of constant base level can result in stratigraphic surfaces and shoreline trajectories similar to those often interpreted to represent multiple sea level cycles our work provides a quantitative framework to decouple autogenic and allogenic controls on erosional surfaces preserved in fluvio deltaic stratigraphy

high resolution linkage of channel coastal plain and shallow marine facies belts desert member to lower castlegate sandstone stratigraphic interval book cliffs utah colorado usa

analysis of fluvial architecture in the blackhawk formation wasatch plateau utah u s a using large 3d photorealistic models abstract there are numerous allocyclic and autocyclic factors which influence fluvial sandbody geometry unraveling the relative importance of such factors is challenging because fluvial systems can migrate and avulse across significant distances on the floodplain so that collecting datasets that cover a large enough area with sufficient detail is difficult this problem has been addressed by acquiring an oblique helicopter mounted lidar survey over 16 km of exposed sections from cretaceous coastal plain deposits cropping out in the wasatch plateau of east central utah the exposures of the blackhawk formation occur in steep cliffs which are continuous for several tens of kilometers and have been previously inaccessible for study the recorded lidar data were used to build detailed photorealistic models virtual outcrops from which quantitative dimensional data on fluvial architectural elements mostly sandstone channel bodies were collected those channelized bodies show significant variation in width and thickness 26 of the sandbodies were identified as being multistory channel bodies with a thickness of 9 1 m 4 67 m 1 and a width of 142 6 m 180 7 m which are significantly larger than the measured single story sandbodies 5 9 m and 96 9 m respectively 50 of all sandbodies have aspect ratios smaller 13 1 and the highest values reach 78 1 the spatial constraint of the 397 fluvial sandbodies enabled the recognition of a series of vertical trends within the dataset these trends include a subtle upward increase in width and thickness of both the mean and maximum values this is coupled with a general upward decrease in the number of sandbodies and results in a broadly constant channel to overbank ratio a clear correlation between wider channels with increased distance to the shoreline could also be documented these observations can be explained by considering the entire blackhawk formation as the deposits of a large distributive fluvial system in this model the key control on channel architecture is the distance to the shoreline contrasting with previous interpretations of the blackhawk depositional system in which the rate of accommodation creation in the coastal plain was thought to be the key control on channel geometry and stacking patterns

complex fluvial response to low gradients at maximum regression a genetic link between smooth sequence boundary morphology and architecture of overlying sheet sandstone abstract the mesa rica sandstone is an extensive fluvial sandstone sheet that is separated from underlying marine strata throughout northeastern new mexico by a regionally smooth and laterally continuous sequence bounding unconformity the mesa rica sandstone consists mostly of channel fill elements with lesser proportions of lateral accretion elements and almost everywhere is of the same thickness as the largest channel fills this broad sandstone sheet reflects deposition on a coastal plain by frequent avulsion and minor lateral migration of straight and low sinuosity streams under nearly stable base level conditions which are here attributed to rapid progradation of the adjacent mesa rica deltaic shoreline relative to change in relative sea level during maximum kiowa skull creek regressi n rapid deltaic shoreline progradation under such conditions caused seaward extension and gradient reduction in the adjacent mesa rica coastal plain overextension and resultant loss of power in mesa rica rivers crossing this coastal plain forced both stream straightening and storage of nontransportable coarser sediment in coastal plain channels because base level was stable mesa rica channels could aggrade only minimally and were forced to spread excess sediments mostly laterally by avulsion frequent avulsion and minor lateral migration of mesa rica channels under these conditions caused both regional scouring of a smooth sequence bounding unconformity and deposition of a sheet sandstone with minimal channel stacking the mesa rica sandstone and the sequence boundary that underlies it represent a distinctive genetic association of single story fluvial sheet sandstone and smooth sequence boundary morphology that is probably not unique to the lower cretaceous of northeastern new mexico such unincised sequence boundaries are also implied in conceptual models and flume experiments of previous authors

practical problems in the application of the sequence stratigraphic method and key surfaces integrating observations from ancient fluvial deltaic wedges with quaternary and modelling studies sequence stratigraphy solved the basic problem that genetically related but different lithofacies were routinely assigned to different lithostratigraphic units defined by arbitrary vertical and horizontal cutoffs stratigraphically important stratal relationships and especially stratal terminations for example lapout can be observed in seismic data and can be documented in continuous outcrops such as in the deserts of the western interior of north america and in closely spaced well log data sets in sparse data sets interpolation of lapout patterns introduces uncertainty in correlation and designation of sequences and systems tracts and their associated surfaces diachroneity of fluvial terrace deposits is documented using detailed facies architectural studies and calls into question the assumed chronostratigraphic significance of many so called sequence boundaries identified in the rocks of the cretaceous interior seaway of north america sequence boundaries formed during prolonged sea level falls may be less chronostratigraphically significant than transgressive surfaces formed during rapid rises as a consequence flooding surfaces are theoretically more significant and also have greater utility as allostratigraphic boundaries although they may also exhibit diachroneity tectonic unconformities produce differential lithospheric deformation which results in angular unconformities although the angle of discordance may be very small in the cretaceous interior seaway of north america such unconformities may be expressed by marine erosion in distal basin settings regional isochronous bentonites provide useful marker beds that clearly illustrate angular discordance in the fluvial realm such tectonic discontinuities may be indicated by changes in palaeocurrent orientations as well as by provenance changes although sequence stratigraphy provides a powerful methodology and theoretical framework for correlating and understanding the evolution of stratigraphic successions in the context of changing accommodation allostratigraphy remains the only accepted scheme for the formal naming of stratigraphic units based on bounding discontinuities whatever type of sequence stratigraphy or allostratigraphy is preferred in all cases it is key to recognize that sequence stratigraphy at its heart is the re ordering correlation and sometimes renaming of stratigraphic units on the basis of bounding discontinuities and their correlative surfaces as opposed to the arbitrary lithofacies oriented approach using broad facies zones for example shazam lines or arbitrary cutoffs such as is used in traditional lithostratigraphy

reappraisal of the sequence boundary in time and space case and considerations for an su subaerial unconformity that is not a sediment bypass surface a time barrier or an unconformity abstract the sequence bounding unconformity bears the key defining traits of being a surface separating younger from older strata along which there is evidence of subaerial erosional truncation or subaerial exposure with a significant hiatus indicated van wagoner et al 1988 this subaerial component of sequence boundaries subaerial unconformity su is also broadly considered to form as a topographic surface of sediment bypass carved during relative sea level fall and buried by backfilling during relative sea level rise accordingly the su is commonly presumed to record an approximate time barrier which separates older from younger strata along its full length in this paper we show that regional composite scour rcs surfaces that are traditionally mapped as an integral component of the su were never a single subaerial topographic surface characterized by sediment bypass are not unconformities do not record an effective time barrier and form diachronously at the channel belt scale over the entire fall to rise of a base level cycle these rcs surfaces and by inference the su surfaces they comprise thus do not fully fit key defining characteristics embodied in the conceptual sequence boundary flume observations and field data show that the rcs is buried by fluvial sediment simultaneously as it is scoured accordingly the rcs is perennially covered with stored sediment during formation is only exposed as a subaerial topographic surface at the local place and time where it is undergoing active growth and forms over the duration of local marine drainage during a relative sea level cycle this cut and cover model differs greatly from more established bypass models which assume that the rcs was roughly sediment free and subaerially exposed for long durations of incision during regression and thus preserves a significant depositional hiatus upon later burial instead the rcs may commonly and locally record a hiatus more typical of a facies bounding diastem without a lacuna significantly greater than that of surfaces within the strata it binds fragments of fluvial strata may commonly and sporadically be preserved above the rcs that are older than underlying marine units overrun by this surface consequently the rcs is not an effective time barrier lateral planation by migrating and avulsing channels as the rcs expands laterally after nucleation can place younger fluvial strata over much older units which means that this surface is also composite and highly diachronous laterally at the scale of channel belts the cut and cover model has additional implications not captured by the bypass model first significant sediments may be stored within fluvial strata above the rcs during regression that are not available for contemporary falling stage and lowstand marine shorelines this can result in marine sediment starvation particularly of the sand fraction and in extreme cases can result in sand autodetachment and an absence of regressive marine reservoir sandstones second cutting of the rcs co generates a suprafluvial surface above the covering fluvial strata during regression that may be used as a mappable proxy for the conceptual maximum regressive surface mrs the mrs may be raised above this surface locally by low accommodation aggradation during lowstand normal regression but in either case preserves an approximate time line where not reworked during later transgression third valley development across the rcs does not exclusively form by landward knickpoint growth and may include complexly formed and potentially cross cutting buffer valleys su valley incision can be divided into four modes which include denudation structural buttress and buffer valley components which may work together locally and tend to have variable importance along the shore to hinterland profile although the rcs is not a good rock proxy for the conceptual sequence boundary it remains a very mappable surface which may separate facies of potentially very different origin and reservoir quality the rcs is also inseparable from the su and typically the only terrestrial erosional surface of extent in most short duration sequences its nullification as a sequence boundary would mean abandonment of depositional sequence stratigraphy as a correlation and interpretive tool within these sections an alternative to abandonment of the su as a sequence boundary is to loosen the definition of a sequence boundary to a discrete surface of erosional truncation carved landward of contemporary shorelines that is traceable beyond the scale of a single valley or comparable local system and its correlative surfaces of conformity and or non deposition and continue its use as before

quantitative reconstruction of cross sectional dimensions and hydrological parameters of gravelly fluvial channels developed in a forearc basin setting under a temperate climatic condition central japan abstract reconstructions of the dimensions and hydrological features of ancient fluvial channels such as bankfull depth bankfull width and water discharges have used empirical equations developed from compiled data sets mainly from modern meandering rivers in various tectonic and climatic settings however the application of the proposed empirical equations to an ancient fluvial succession should be carefully examined with respect to the tectonic and climatic settings of the objective deposits in this study we developed empirical relationships among the mean bankfull channel depth bankfull channel depth drainage area bankfull channel width mean discharge and bankfull discharge using data from 24 observation sites of modern gravelly rivers in the kanto region central japan some of the equations among these parameters are different from those proposed by previous studies the discrepancies are considered to reflect tectonic and climatic settings of the present river systems which are characterized by relatively steeper valley slope active supply of volcaniclastic sediments and seasonal precipitation in the kanto region the empirical relationships derived from the present study can be applied to modern and ancient gravelly fluvial channels with multiple and alternate bars developed in convergent margin settings under a temperate climatic condition the developed empirical equations were applied to a transgressive gravelly fluvial succession of the paleogene iwaki formation northeast japan as a case study stratigraphic thicknesses of bar deposits were used for estimation of the bankfull channel depth in addition some other geomorphological and hydrological parameters were calculated using the empirical equations developed by the present study the results indicate that the iwaki formation fluvial deposits were formed by a fluvial system that was represented by the dimensions and discharges of channels similar to those of the middle to lower reaches of the modern kuji river northern kanto region in addition no distinct temporal changes in paleochannel dimensions and discharges were observed in an overall transgressive iwaki formation fluvial system this implies that a rise in relative sea level did not affect the paleochannel dimensions within a sequence stratigraphic framework

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

tectonic control on facies distribution of the camp rice and palomas formations pliocene pleistocene in the southern rio grande rift the pliocene pleistocene camp rice and palomas formations in the rio grande rift of southern new mexico provide an excellent test of the role of basin symmetry in the distribution of piedmont and axial fluvial facies in the asymmetrical palomas and northern mesilla basins the axial fluvial facies is characterized by multistory channel sands and sandstones and is concentrated near the locus of maximum subsidence within a few kilometers of the footwall scarp fanglomerate derived from the footwall uplift extends only a few kilometers or less from the footwall scarp whereas alluvial fan and alluvial flat conglomerate sand and mudstone deposited on the hanging wall dip slope occupy a much wider outcrop belt in the symmetrical hatch rincon basin the axial fluvial facies extends to within a few kilometers of both the northern and southern basin margins and has a much higher percentage of fine grained overbank deposits some of which contain calcareous paleosols in all three basins a tongue of fanglomerate as much as 30 m thick prograded over the axial fluvial facies near the end of camp rice and palomas deposition the distribution of facies of the camp rice and palomas formations supports previously published models that predict a two stage history of asymmetrically subsiding basins during tectonically active periods axial river channels preferentially avulse into the topographically lowest area of the alluvial plain which is directly above the axis of maximum subsidence during the postorogenic stage when erosion rate exceeds subsidence rate coarse transverse dispersed sediment progrades toward the center of the basin

tectonic control on coarse grained foreland basin sequences an example from the cordilleran foreland basin utah newly released reflection seismic and borehole data combined with sedimentological provenance and biostratigraphic data from upper cretaceous paleocene strata in the proximal part of the cordilleran foreland basin system in utah establish the nature of tectonic controls on stratigraphic sequences in the proximal to distal foreland basin during campanian time coarse grained sand and gravel were derived from the internally shortening charleston nebo salient of the sevier thrust belt a rapid regional campanian progradational event in the distal foreland basin 200 km from the thrust belt in 8 m y can be tied directly to active thrust generated growth structures and an influx of quartzose detritus derived from the charleston nebo salient eustatic sea level variation exerted a minimal role in sequence progradation

flow depth scaling in alluvial architecture and nonmarine sequence stratigraphy example from the castlegate sandstone central utah u s a changes in the proximity and arrangement of channel belt sandstone bodies in the rock record and associated unconformities in alluvial successions i e alluvial architecture and nonmarine sequence stratigraphy are often interpreted to reflect changes in basin boundary conditions including subsidence and sea level such interpretations do not often consider how the size of a depositional system influences alluvial architecture and sequence stratigraphy we investigate how paleoflow depth scaling affects fluvial stratigraphic interpretations using the castlegate sandstone campanian at its type section in central utah as an example using lidar imaging channel preservation and paleoflow depths are estimated from bar clinoforms throughout the unit and these data are compared to scour spacing scour continuity and mudstone content within the study interval within the castlegate sandstone bar clinoforms are routinely close to fully preserved i e rollover of the upper part of the bar is present and an overall increase in paleoflow depth up section is coincident with changes in other alluvial architecture characteristics including increases in scour surface spacing and mudstone abundance up section this suggests that alluvial architecture commonly ascribed to changes in accommodation may result primarily from changes in the scale and style of fluvial deposition rather than accommodation limited reworking and amalgamation additionally although sequence boundaries have previously been identified in the section no scour surfaces deeper or more extensive than what could be produced autogenically by large rivers typical of the castlegate system were found in the study interval this study demonstrates that estimates of paleoriver depth can enhance studies of alluvial architecture and provide a more robust basis for correlating and interpreting fluvial deposits

sedimentology and stratigraphic architecture of the late permian betts creek beds queensland australia abstract the late permian betts creek beds form a succession of coal bearing alluvial coastal plain sediments in a basin marginal setting within the northeastern galilee basin queensland australia the unit is 50 60 m in thickness at porcupine creek national park where outcrop is laterally continuous for several kilometers eight facies have been identified within the formation and can be grouped into 2 facies associations a channel deposits and b floodbasin deposits the channel association consists of conglomerate a1 and trough cross bedded multistorey sandstone facies a2 both interpreted as deposits of low sinuosity river systems tidally influenced fluvial channels a3 interbedded sandstone and siltstone a4 interpreted as the abandonment fill of the alluvial systems and diamictite a5 interpreted as debris flows the floodbasin facies association is composed of sandy siltstone b1 proximal distal floodbasin carbonaceous siltstone b2 mire and bioturbated siltstone b3 estuarine facies the overall sediment body architecture can be resolved into 6 unconformity bounded cycles interpreted as sequences in the genetic sense which are sheet like in geometry and in general consist of amalgamated multistorey multilateral braided fluvial deposits at the base overlain by extensive sheet like overbank mudstones carbonaceous shales and coals sea level change is interpreted as the primary control on the sequence architecture of the formation while the internal stratigraphic architecture however varies between sequences and is a function of a combination of sea level tectonic and autogenic controls

rethinking the incised valley fill paradigm for campanian book cliffs strata utah colorado u s a evidence for discrete parasequence scale shoreface incised channel fills

re evaluating the sedimentology and sequence stratigraphy of classic book cliffs outcrops at tusher and thompson canyons eastern utah usa applications to correlation modelling and prediction in similar nearshore terrestrial to shallow marine subsurface settings worldwide abstract the campanian book cliffs strata of eastern utah and western colorado has been used to develop test and refine sedimentological and stratigraphic ideas and models over the years including the principles and concepts of sequence stratigraphy book cliffs data sets are often used as outcrop analogues for similar subsurface settings worldwide thousands of geologists have visited the book cliffs including the archetypal desert member to lower castlegate sandstone outcrops at tusher and thompson canyons which are the focus of this study these localities regularly serve as representative field stops for teaching sequence stratigraphy recent work has begun to cast doubt on certain aspects of the conventional sequence stratigraphic interpretation of the desert castlegate interval hence re evaluation of these classic outcrops is warranted a progradational stack of shallow marine to nearshore terrestrial facies are observed at tusher canyon from bottom to top these include shelf mudstones lower shoreface to inner shelf heterolithics foreshore to upper shoreface sandstones cut by distributary and tidal estuarine channels coal bearing coastal plain mudstones with single storey fluvial sandstones amalgamated multi storey fluvial channel fills and a capping coastal plain mudstone package overlain by the marine mudstones of the buck tongue of the mancos shale a similar progradationally stacked facies succession is observed 30 km basinwards at thompson canyon with the exception of the proximal amalgamated fluvial sandstone package which is absent five of eleven desert member parasequences d1 to d5 are noted at tusher canyon while all eleven desert parasequences d1 to d11 and two of six castlegate parasequences c1 and c2 are identified at thompson canyon although parasequences and their flooding surfaces can be correlated between tusher and thompson canyons the discrete shoreface incised channels are only restricted to the proximal portions of each parasequence these channels mostly cut foreshore shoreface sandstones and are not continuously correlatable between tusher and thompson canyons re examination of these desert castlegate outcrops exemplifies the misfit with the conventional sequence stratigraphic model specifically the miscorrelation of the d5 and d11 shoreface incised channels over 60 m of deposits separate the d5 and d11 horizons along 30 km of dip oriented outcrop between tusher and thompson canyons contrary to earlier interpretations the shoreface incised channels in the desert castlegate are not nested within larger incised valley fills an alternative model showing temporal and spatial linkage between the nearshore terrestrial and laterally adjoining shallow marine facies is the best fit with the desert castlegate field observations selecting the appropriate correlation style has significant implications for the prediction of sand body continuity connectivity and distribution especially applications to subsurface data sets where visualization is limited and correlation uncertainties are high

extensive carbonate cementation of fluvial sandstones an integrated outcrop and petrographic analysis from the upper cretaceous book cliffs utah abstract extensive large scale pervasive cementation in the form of cement bodies within fluvial strata has rarely been documented although fluvial strata commonly act as important hydrocarbon reservoirs as well as groundwater aquifers here we present outcrop petrographic and geochemical data for pervasive ferroan dolomite cement bodies up to 250 m in size from upper cretaceous desert member and castlegate sandstone fluvial strata exposed in the book cliffs in utah these cement bodies are present with coastal plain fluvial strata within both the desert and castlegate lowstand sandstones and are most abundant in the thin distal fluvial strata cement bodies are almost entirely absent in updip thicker fluvial strata petrographic observations suggest a predominantly early diagenetic timing to the mildly ferroan dolomite with a component of later burial origin 13 c values for the cement 4 8 to 5 7 v pdb suggest a marine derived source for the earliest phase with a burial organic matter source for later cement 18 o data 6 3 to 11 8 v pdb suggest precipitation from freshwater dominated fluids it is proposed here that dolomite was derived from leaching of detrital dolomite under lowstand coals and cementation took place in coastal aquifers experiencing mixed meteoric marine fluids as a result of base level fluctuations this data presented here shows that large cement bodies can be an important component within fluvial sandstones with a potentially significant impact upon both reservoir quality and fluid flow within reservoirs especially at the marine non marine interface

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

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

the castlegate sandstone of the book cliffs utah sequence stratigraphy paleogeography and tectonic controls abstract earlier stratigraphic work had predicted that at the type section of the castlegate formation the castle gate near price utah the unit consists of two sequences separated by a sequence boundary representing approximately one million years of unrecorded time although the type section is well exposed it consists of a monotonous succession of braided fluvial sandstones and no obvious boundary can be identified using facies criteria this is a good example of a cryptic sequence boundary petrographic data indicate however a significant change in detrital composition 20 m above the base of the section at a through going erosion surface that is therefore interpreted as the sequence boundary revised sequence correlations together with other petrographic data and regional paleocurrent patterns provide the basis for a model of the paleogeographic evolution of the area rocks assigned to the castlegate sandstone comprise two or possibly three sequences formed at times of slow regional subsidence erosional sequence boundaries and tilts in paleoslope between each sequence record thrust loading and unloading of the basin and the growing influence of intrabasinal upwarps movement of which was beginning to be affected by laramide movements toward the end of castlegate sedimentation

facies architecture of asymmetrical branching distributary channels cretaceous ferron sandstone utah usa distributary channel systems are an important component of deltaic systems but details of their branching pattern stream order internal variability and relation with adjacent levee bay and bayhead delta are rather poorly documented in ancient examples photomosaic and measured sections collected along a gooseneck shaped canyon in southern utah allow direct mapping of the branching pattern of an ancient distributary system the main channel belt is ca 250 m wide and narrows to ca 200 m downstream of the branching point a subordinate channel belt ca 80 m wide branches off of the main channel forming a distinctly asymmetrical branching pattern water discharge in the main channel is estimated to be 85 to 170 m3 sec 1 comparison with palaeodischarge estimates of trunk rivers mapped in previous studies suggests that the branching documented in this study probably is a fourth order split the distributary channels are characterized by a u shaped geometry filled with medium grained cross bedded sandstone and are dominated by lateral accretion suggesting limited lateral migration and moderate sinuosity tidally influenced facies and limited trace fossils indicate direct marine influence the distributary channels erode into adjacent levee and underlying heterolithic bay fill deposits and the marine influence suggests that they were deposited on a lower delta plain rather than on a non marine floodplain the subordinate channel fed a bayhead delta suggesting that it was formed by a partial avulsion rather than bifurcation around a mouth bar as is more characteristic of terminal distributary channels channel floor drapes bar accretion drapes and abandoned channel fills within the sandstone channel belts represent the most important heterogeneity from the perspective of reservoir characterization

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

sequence architecture within a low accommodation setting an example from the permian of the galilee and bowen basins queensland australia the coal bearing upper permian betts creek beds bcb of the northeastern intracratonic galilee basin in north central queensland australia record sedimentation within an alluvial coastal plain in a low accommodation basin margin setting six third order depositional sequences are preserved within the bcb and are characterized by a sequence architecture that is overall relatively thin 15 m 49 ft condensed and top truncated sequences have a lowstand systems tract composed of extensive braided fluvial sheet sandstones a transgressive systems tract characterized by tidally influenced fluvial sheet sandstones and bioturbated estuarine mudrocks and a highstand systems tract composed of coastal plain mudrocks and coals sequences can be correlated throughout the entire galilee basin and related to the lithostratigraphy established in the adjacent bowen basin a foreland basin to the east the overall late permian fill is considered a second order sequence the stacking patterns show an overall retrogradational to progradational architecture suggestive of relatively low accommodation space sequences show an extremely laterally continuous geometry 1000 km 600 mi and are relatively uniform in thickness sequences do not show evidence of onlap toplap or erosional truncation but instead are thin in areas of low accommodation and expand into areas of higher accommodation that these third order sequences can be traced across basins with differing tectonic regimes together with the persistent sheetlike nature of the sequences suggests that tectonic effects on the sequence architecture were minimal the basin fill covers a time interval during which two glacial events occurred in the final stages of the late paleozoic ice age suggesting that changes in glacioeustasy may have been the dominant controls on the sequence architecture of the late permian succession in the galilee basin of northeastern australia

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

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

channel planform as a non controlling factor in fluvial sedimentology the case of the squamish river floodplain british columbia abstract channel planform styles demonstrate a continuum of variability whereas end member situations may exhibit diagnostic sedimentologic characteristics non end member situations may be exceedingly difficult to reliably differentiate the relevance of channel planform based sedimentologic differentiation of fluvial depositional units has been questioned for some time e g jackson 1978 bridge 1985 brierley 1989a despite reservations outlined in these papers facies models and interpretations of depositional suites in the rock record continue to be applied in terms of channel planform style this paper describes a test of this principle in one particular depositional setting the squamish river in southwestern british columbia is a high energy gravel based river in a fjord setting in a 20 km reach this river displays a distinct downstream gradation in channel planform type from braided through wandering gravel bed to meandering assemblages of bedform scale facies units on bar surfaces in this river do not differ by planform type brierley 1989a rather facies associations relate directly to the pattern of morphostratigraphic units on bar surfaces brierley 1991a when analysed in floodplain exposures sediment sequences which are equivalent to morphostratigraphic units are termed elements these elements are defined in terms of their geometry bounding surface and sediment characteristics detailed analysis of floodplain deposits in the braided wandering gravel bed and meandering reaches of the squamish river demonstrates that just as assemblages of bedform scale facies cannot be differentiated by planform style neither can assemblages of floodplain elements indeed for the squamish river the type character and spatial association of these elements cannot be differentiated reliably at the channel planform scale this indicates the limited relevance of planform differentiation of sedimentary environments under transitional planform situations such as those of high energy gravel bed rivers in confined valleys in such situations sediment inventory at the element scale provides greater insight into mechanisms of floodplain evolution than can be provided by interpretation at either the channel bedform or channel planform scales

no evidence for an unconformity at the base of the lower castlegate sandstone in the campanian book cliffs utah colorado united states implications for sequence stratigraphic models regional high resolution correlations of the campanian desert member of the blackhawk formation to the lower castlegate sandstone interval book cliffs utah colorado show no evidence for a single through going unconformity separating the amalgamated channel sandstones of the castlegate from the underlying blackhawk formation coastal plain deposits this is a facies contact which interfingers both laterally and vertically channel incisions are discrete and mostly confined to individual parasequences they do not coalesce landwards into gigantic valleys as shown in the conventional model but are restricted to the proximal shoreface and are rarely traceable for more than a few kilometers landwards time lines extend uninterupted from the shallow marine into the neighbouring coastal plain deposits connecting flooding surfaces with coals shoreface sandstones emerge from the adjacent coastal plain this has significant implications for modelling in similar clastic settings worldwide conventional sequence stratigraphic models of fluviodeltaic systems show radically different stacking patterns compared to those of the high resolution model presented herein each model carries a significantly different prediction regarding the three dimensional distribution and architecture of reservoir and nonreservoir bodies in a fluviodeltaic system hydrocarbon exploration and development activities such as optimally locating seismic surveys and or drilling locations could be impacted if the wrong model is applied as such it is recommended that fluviodeltaic systems worldwide should be critically re examined in the light of the high resolution sequence stratigraphic model presented herein

quantitative analysis of the dimensions and distribution of channelized fluvial sandbodies within a large outcrop dataset upper cretaceous blackhawk formation wasatch plateau central utah u s a abstract conceptual and quantitative models of fluvial stratigraphy typically argue that alluvial architecture is driven by a combination of allogenic processes e g tectonic subsidence sea level sediment supply and autogenic behaviors e g avulsion we test these models via analysis of a large c 200 m thick by 100 km depositional strike extent alluvial to coastal plain succession that records shoreline progradation in response to decreasing tectonic subsidence late cretaceous blackhawk formation wasatch plateau central utah u s a oblique aerial photographs and architectural panels of six nearly linear nearly vertical cliff face windows were used to characterize the dimensions apparent widths thicknesses and spatial distributions of channelized fluvial sandbodies two statistical measures raster based lacunarity and point based l function are used to investigate whether the distribution of channelized sandbodies show significant regularity randomness or clustering over 490 channelized fluvial sandbodies are identified in the six cliff face windows from base to top of the blackhawk formation sandbodies broadly increase in width and decrease in overall abundance per unit area clustering of sandbodies occurs relatively frequently in lower coastal plain strata 50 km from the coeval shoreline a strong negative correlation between lacunarity and stratigraphic position is also observed such that a wider range and greater variety of spatial gaps occurs between sandbodies in lower coastal plain strata relative to upper coastal plain and alluvial strata comparison with numerical modeling studies of fluvial stratigraphic architecture implies the predominance of an avulsion generated pattern of sandbody distribution that includes an element of compensational stacking on the upper coastal plain and alluvial plain for a range of distances from the coeval shoreline c 40 130 km and tectonic subsidence rates c 40 700 m myr on the lower coastal plain 50 km from the coeval shoreline localized clustering of channelized sandbodies is interpreted to have formed by avulsion of deltaic distributary channels downstream of delta apex avulsion nodes possibly modulated by low amplitude 30 m sea level fluctuations

mass balance constraints on stratigraphic interpretation of linked alluvial coastal shelfal deposits from source to sink example from cretaceous western interior basin utah and colorado u s a abstract experimental work suggests that the rate of upstream to downstream loss of sediment from an active depositional system to permanent storage exerts a fundamental control on stratigraphic architecture this rate of sediment mass loss is determined by the spatial distribution of tectonic subsidence and rate of sediment supply the character of input sediment grain size distribution and composition is the third parameter that affects stratigraphic architecture we apply this concept in a mass balance framework to linked alluvial coastal shelfal deposits of the upper cretaceous castlegate sandstone blackhawk formation star point sandstone and mancos shale western interior basin utah and colorado usa facies partitioning and sediment budgets are estimated for eight stratigraphic intervals in order to compare temporal dynamics of the sediment routing system from erosional source to depositional sink mapping of each stratigraphic interval and its constituent segments from upsystem to downsystem was achieved along a representative dip oriented 2d cross section over a distance of c 350 km using extensive outcrop exposure and densely spaced subsurface wells the cross section provides time averaged estimates of the spatial distribution of deposition grain size data show that there is limited downsystem fining of any particular facies within the castlegate sandstone but that the proportion of facies changes systematically downsystem to accommodate an overall fining trend therefore it is reasonable as a first approximation to use facies proportions as a textural replacement for grain size sediment supply characteristics for each of the eight stratigraphic intervals are constrained by total facies proportions in each interval for each stratigraphic interval we assess the level of interaction between alluvial and coastal to shelfal segments of the routing system comparison of the downsystem mass balance characteristics of the eight stratigraphic intervals suggests that there were depositional gains and losses of shallow marine shale in the five youngest intervals which can be attributed to along strike sediment transport this result is consistent with increased interaction through time with vigorous wave and tide driven circulation in the seaway as the sediment routing system advanced out of a sheltered embayment in response to decreasing tectonic subsidence in the youngest stratigraphic interval the upstream unconformable base of the castlegate sandstone is marked by a pronounced increase in the sand to gravel grade mass fraction of the fluvially supplied depositional volume this marked increase can be attributed to hinterland unroofing and or cannibalization of wedge top basins leading to import of coarse grained sediment into the castlegate fluvial system our results demonstrate the value of analyzing downsystem sediment loss i e downsystem mass extraction within a mass balance framework as a simple and practical tool to quantify the relationship between accommodation and sediment supply and thus to decode past external forcing mechanisms from stratigraphic architecture

braided rivers perspectives and problems progress towards a fuller understanding of the dynamics and deposits of braided rivers demands an interdisciplinary approach to a host of unresolved problems although many advances have been made within recent years in interpreting the mechanics of flow transport of sediment and sedimentary architecture of braided rivers many key issues remain to be addressed in particular several areas demand attention the mechanisms of braid bar initiation confluence diffluence dynamics the nature of sedimentary facies over a range of grain sizes and the influence of flow stage and aggradational regime upon the depositional architecture over a range of channel scales this paper focuses upon these issues and highlights several areas of fruitful future interdisciplinary collaboration 1993 the geological society

sedimentary structures exposed in bar tops in the brahmaputra river bangladesh the brahmaputra river is one of the world s largest sand bed braided rivers with a channel belt up to 15 km wide a mean channel depth of 5 m and maximum scour depths of up to 40 m the recorded discharge varies by around 60 000 cumecs every year following the annual monsoon producing dramatic stage fluctuations with the water level falling between 7 and 8 m from bankfull to low flow stage in the dry season large areas of bar top and channel bed are exposed and low flow channels cut natural sections through bar tops exposing the internal stratification elements of upstream downstream and lateral accretion are identified although the high width depth ratio of channels up to 500 1 results in extremely low depositional dips on bed bounding surfaces within the accretionary elements vertical and lateral changes in sedimentary structures are ubiquitous and varied but some patterns can be discerned channel deposits are dominated by sinuous crested dunes and trough cross stratification upper stage plane bed lamination often with a very low angle depositional dip has been observed in beds up to 4 m thick and is generally found at the base of the exposed bar top sections trough cross stratification in bar tops occurs in sets from 0 1 m to 3 m thick with rapid vertical and lateral changes in set thickness very large sets of trough cross stratification 3 m thick do not occur in the bar top sections current ripple lamination is most abundant on the tops of bars with very high rates of climb associated with high rates of sediment deposition from these observations a generalised vertical sequence of bar top origin might include trough cross stratification overlain by upper stage plane bed lamination isolated sets of trough cross stratification truncated and capped by current ripple lamination this sequence which is considered to represent the deposits of a single flood may occur within the upstream downstream or lateral accretion elements however it should be noted that vertical and lateral changes in facies are extremely abundant with many changes in sedimentary structures and reactivation surfaces within each depositional episode

reevaluating dune scaling relations abstract in sand bedded rivers dunes dominate sediment transport and flow resistance dunes are also commonly preserved in fluvial deposits as cross stratified units that record their size shape and migration rates prediction of dune dimensions is therefore important for forecasting modern river channel dynamics as well as reconstructing past fluvial environments on earth and other planets predictions are often made by assuming that the formative flow depth h sets dune dimensions with height scaling as 1 6h and length as 5h yet there is a suite of other scaling relations that link dune dimensions to other variables like grain size transport stage and froude number here we present a new compilation of flow and dune dimension data to evaluate scaling relations the data reveal approximately two orders of magnitude variation in dune height and length at any given flow depth dune heights in shallow flows 2 5 m are often more symmetric have lower lee angles are relatively shorter in height than 1 6h and have a wider range of observed heights for a given depth none of the scaling relations predict the observations exceptionally well likely because of natural variability in dune dimensions and because they do not explicitly account for the apparent scaling break that occurs at 2 5 m we propose new simple depth scaling relations with added statistical uncertainty for the prediction of dune height and length from flow depth as well as flow depth from dune height we conclude that shallow and deep flow dunes exhibit different scaling due to a change in the dominant process controls as dunes get larger

quantitative characterization of architecture elements and their response to base level change in a sandy braided fluvial system at a mountain front abstract the rockcave member of the yungang formation middle jurassic in the datong basin china is a multistory sandstone that is interpreted as a sandy braided fluvial deposit based on grain size lithofacies and architectural elements the depositional setting was the mountain front of the datong basin which was tens of kilometers from the shoreline of a lacustrine basin during the middle jurassic the concept of base level is used to analyze the architectural elements of the braided system obtained from photographic mosaics and high resolution measurement of six outcrop sections from yungang rock cave grain size lithology and bounding surfaces together with scale and dimension parameters of the sedimentary structures in various architectural elements were used to quantitatively characterize each group of architectural elements and stratigraphic units width thickness values of trough crossbeds were found to be a fundamental component of the hydrodynamic regimes during base level rise the braided fluvial system developed large scale channel units bar units and overbank fills the relatively high proportion of bar units and overbank fills reflect processes operating during positive accommodation however during base level fall there are a high proportion of small scale channel units that reflect incision dominated processes such as channels with low w t values for trough crossbeds and less common overbank fines

possible climate variability in the lower old red sandstone conigar pit sandstone member early devonian south wales uk abstract the early devonian conigar pit sandstone member cpsm of the freshwater west formation lower old red sandstone lochkovian age at freshwater west in south wales comprises a heterolithic predominantly alluvial suite mudstones fine to coarse grained sandstones conglomerates with varying depositional architecture a number of discrete facies associations are observed the fine grained inclined and non inclined heterolithic association is dominant within the cpsm it represents dryland sinuous channelized flow ihs bedsets and unconfined flow non inclined bedsets at terminal and intermediate floodouts deposited under semi arid conditions mudstones were deposited in two distinct environments associated with this semi arid river system laminated and burrowed reddish brown mudstones were deposited in shallow semi permanent lakes or pools on the floodplain massive mudstones were deposited as within channel muddy braid bars with sedimentary structures being lost during subsequent compaction the mudstones exhibit vertisol pedogenesis reflecting the seasonal wetting and drying associated with the semi arid climate periods of intense desiccation are indicated by deep desiccation cracks and associated rubbly surfaces possible though unproven tidal conditions influenced a small percentage of the heterolithic channels at freshwater west the extent of these channels is uncertain the coarser grained multi storey sandstone association was deposited by low sinuosity rivers with a fluctuating but perennial discharge associated with these laterally extensive sandbodies was a high water table with surface ponding wetlands that enabled the preservation of plant detritus during high discharge events flow expanded over the contemporaneous floodplain depositing the sheet sandstone association within splay complexes the interpretation that perennial discharge may have been triggered by basin wide climate change challenges the long held view that the lower ors climate was continuously semi arid in nature the spatial temporal extent of this climate change is uncertain as it is possible that the multi storey sandbodies were deposited by allogenic rivers draining a distant possibly uplifted source area a decrease in the observed frequency and maturity of vertisol profiles and a corresponding increase in multi storey sandbodies upward through the succession may reflect a long term episodic pattern of climate change

perspectives on the sequence stratigraphy of continental strata this report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 nuna conference in banff canada to date sequence stratigraphic concepts have been applied mainly to the marine realm but unconformity bounded units have long been recognized in nonmarine strata successful application of sequence stratigraphic concepts to continental strata requires careful consideration of controls on base level and sediment supply as with shallow marine environments relative sea level can be considered as the stratigraphic as well as the geomorphic base level for coastal nonmarine settings farther inland stratigraphic base level which determines accommodation space is more complex and takes various forms such as the graded profile for fluvial strata groundwater tables for some eolian strata and lake level for some intermontane sediments sediment supply is also generally a more complex variable for nonmarine environments than in the marine realm because of the proximity to the source area the influence of climate and tectonism on sediment supply can clearly be seen in many continental sediments the fact that the major controls of climate tectonism and eustasy are somewhat interdependent and that a change in one parameter will most likely be reflected in others is also more readily apparent in continental strata although in its infancy sequence stratigraphic concepts have been applied to a wide variety of continental settings in attempts to explain variations in facies architecture of particular interest are studies that have linked fluvial architecture on coastal plains to variations in relative sea level as indicated by coeval marine strata and studies of lacustrine environments that show marked variation in facies between highstand and lowstand deposits the application of sequence stratigraphy to continental strata will likely result in the development of better correlation techniques and models that better predict the location and nature of fluvial and eolian reservoirs

relationships between discharge parameters and cross sectional channel dimensions of rivers in an active margin influenced by tropical climate the case of modern fluvial systems in the indonesian islands abstract the present study investigates 1 the relationships between discharge parameters and bankfull channel width wb based on statistical analyses of hydrological data obtained from 649 sites at rivers on the indonesian islands of java sumatra and kalimantan and 2 the relationship between depth parameters and wb using channel cross sections obtained from 86 sites at rivers on these three large islands these analyses are used to describe geomorphological and hydrological features of fluvial systems developed in a convergent margin under the influence of a low latitude tropical climate the relationship between mean discharge qmean and wb shows distinct variation within the indonesian rivers and reflects regional variations in annual rainfall of a tropical climate the relationship between bankfull discharge qb and wb shows only minor variations across the three islands regardless of bed and bank material types the qb wb relationship in the indonesian rivers has a pattern similar to that of fluvial systems in europe and the north american continent which are influenced by mid and high latitude climates minor regional variation in the qb wb relationship regardless of the tectonic and climatic settings suggests that the development of fluvial morphology is controlled mainly by flood related episodic discharge in contrast the empirical equations between maximum channel depth db and wb and between mean channel depth dm and wb show distinct regional variations not only within the indonesian fluvial systems but also in fluvial systems of europe and the north american continent these regional variations are thought to reflect the fact that db wb and dm wb relationships are controlled by the tectonic and climatic settings of a drainage basin and factors such as the interrelationships between precipitation vegetation and slope consequently selection of an appropriate dm wb or db wb equation combined with an appropriate qb wb equation permits us to reconstruct spatial and temporal variations in hydrological features in both modern and ancient fluvial systems more precisely than applying previously proposed equations to fluvial systems formed in active margin and low latitude climatic settings

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

towards a sequence stratigraphic solution set for autogenic processes and allogenic controls upper cretaceous strata book cliffs utah usa upper cretaceous strata exposed in the book cliffs of east central utah are widely used as an archetype for the sequence stratigraphy of marginal marine and shallow marine deposits their stratal architectures are classically interpreted in terms of accommodation controls that were external to the sediment routing system allogenic and that forced the formation of flooding surfaces sequence boundaries and parasequence and parasequence set stacking patterns processes internal to the sediment routing system autogenic and allogenic sediment supply controls provide alternatives that can plausibly explain aspects of the stratal architecture including the following 1 switching of wave dominated delta lobes expressed by the internal architecture of parasequences 2 river avulsion expressed by the internal architecture of multistorey fluvial sandbodies and related deposits 3 avulsion generated clustering of fluvial sandbodies in delta plain strata 4 autoretreat owing to increasing sediment storage on the delta plain as it lengthened during progradation expressed by progradational to aggradational stacking of parasequences 5 sediment supply control on the stacking of and sediment grain size fractionation within parasequence sets the various potential allogenic controls and autogenic processes are combined to form a sequence stratigraphic solution set this approach avoids anchoring of sequence stratigraphic interpretations on a specific control and acknowledges the non unique origin of stratal architectures

relationships of bankfull channel width and discharge parameters for modern fluvial systems in the japanese islands abstract the relationships between the bankfull channel width and the mean bankfull and maximum discharges of japanese rivers were examined using the hydrological and geomorphological data from 368 sites the relationships between the bankfull channel width and the mean and bankfull discharges do not show any distinct regional variations in contrast the relationship between the maximum discharge and the bankfull channel width shows regional variations and the lower and higher maximum discharges relative to bankfull channel widths are documented in the fluvial systems in hokkaido and southwest japan respectively these variations are interpreted to reflect regional variations in precipitation intensity during the rainy season and the magnitude and frequency of typhoon related flooding the relationship between the bankfull channel width and the bankfull discharge can be described by an empirical equation similar to that described from modern fluvial systems on the european and american continents consequently this empirical equation may have wider applicability for the estimation of hydrological features of modern and ancient fluvial systems not only in active margin settings influenced by mid latitude temperate climates but also in passive continental margins and continental interior basins

high resolution correlation of the upper cretaceous stratigraphy between the book cliffs and the western henry mountains syncline utah u s a abstract exposures of upper cretaceous strata in the book cliffs have played a key role in the formulation of modern sequence stratigraphic concepts and yet correlations with time equivalent strata in nearby regions remain uncertain resulting in an incomplete understanding of regional paleogeography this study presents detailed high resolution correlations of the upper cretaceous stratigraphy between the book cliffs the wasatch plateau and the western henry mountains syncline in utah with emphasis on the campanian interval two newly acquired measured vertical sections at coal canyon near green river in the book cliffs and blind trail in the henry mountains inform the correlations which also incorporate the substantial body of previous research correlations are further constrained by vertical and lateral facies stacking patterns and changes in sediment dispersal directions at discrete stratigraphic horizons derived from paleocurrent measurements much of the campanian succession can be characterized as a single low frequency third order depositional sequence within which are nested numerous high frequency sequences while it is not possible to correlate every high frequency sequence recognized in individual outcrop areas we define four intervals numbered 1 4 in ascending stratigraphic order that we correlate across the entire region interval 1 basal campanian is represented by initially deltaic and later wave dominated shoreface strata of the star point sandstone and equivalent basal muley canyon sandstone interval 2 lower campanian comprises coastal plain facies passing eastward into shallow marine strata of the lower blackhawk formation and equivalent muley canyon sandstone interval 3 lower to mid middle campanian comprises a thick aggradational stack of coastal plain fluvial strata that pass eastward into coastal and shallow marine facies blackhawk formation and equivalent masuk formation interval 4 overlying a major facies dislocation third order sequence boundary comprises amalgamated sheet fluvial deposits of the lower castlegate sandstone and equivalent tarantula mesa sandstone during the early to middle campanian the northern wasatch plateau and western henry mountains regions were along depositional strike with respect to one another the book cliffs near green river were located obliquely down depositional dip from the western henry mountains region during the campanian these new correlations and the improved understanding of paleogeography that derive from them have the potential to inform basin scale stratigraphic interpretations to a greater extent than has been hitherto possible

estimation of source to sink mass balance by a fulcrum approach using channel paleohydrologic parameters of the cretaceous dunvegan formation canada abstract trunk rivers transport the bulk of the sediment in a source to sink s2s system and total mass passing through any cross section i e fulcrum of a trunk river over geologic time should allow matching of source area sediment delivery budgets to downstream sediment volumes deposited in the basin we analyze the paleohydrology of ancient trunk channels and link downstream deltaic strata of allomember e of the cretaceous dunvegan alloformation in the western canadian sedimentary basin to test the total mass balance fulcrum approach bankfull channel depth and width grain size paleoslope velocity and discharge are derived from outcrop core and well logs some parameter estimates use multiple methods providing a range of values and serve as a cross check of independent methods estimates of annual flood frequency and paleodischarge associated with long term geologic time estimates are derived from chronostratigraphic analysis and allow calculation of cumulative sediment discharge isopach maps are used to measure sink area sediment volumes the results indicate that the trunk river of allomember e was 10 15 m deep and 150 250 m wide carried fine to medium grained 200 microns sand and flowed over a low gradient paleoslope of 4 1 6 1 10 5 annual total sediment discharge is estimated to have ranged from 5 4 to 12 106 m3 within 25 000 years the river is estimated to have transported 135 307 km3 of sediment into the basin this is consistent with the 130 km3 of sediment mapped in the study area however the upper range estimate of sediment delivered into the sink is 2 5 times the measured sediment volume in the map area which if accurate suggests significant sediment escape this supports the hypothesis that in dunvegan time mud was widely dispersed southward along the alberta foreland basin by geostrophic currents associated with storm processes and counterclockwise oceanic gyres in the cretaceous seaway

fourth order nonmarine to marine sequences middle castlegate formation book cliffs utah the lower part of the campanian castlegate formation one of the best known fluvial sheet sands of the western interior seaway combines with an overlying finer grained unit middle member of the castlegate formation to form an unconformity bounded third order stratigraphic sequence 3 m y duration this sequence contains a mappable muddy zone along the western book cliffs of utah now mapped as contiguous with the open marine parts of the succession buck tongue sego sandstone anchor mine tongue to the east the correlation within the middle castlegate has been refined and the nature of the link between tidally influenced fluvial strata in the west and marine strata in the east has been remapped five high frequency stratigraphic sequences all within the upper part of the larger third order sequence forming a thickness to 160 m have been mapped in the price area southeastward into the time equivalent marine succession near green river individual sequences probably 0 5 m y duration reflecting transgressive to regressive estuary infilling have an internal architecture in which fluvial and tidally influenced distributary channel belts pass up into muddy central basin sedimentary units to bayhead delta deposits and in some places up to more fluvial channel belts the key to the mapping of individual sequences is recognition of the muddy brackish water interval developed during maximum transgression of the time equivalent shoreline the two most proximal marine influenced sequences 2 and 3 are probably broadly time equivalent with the buck and anchor mine tongues to the east the analysis here contrary to recent suggestions shows that the marine sequences in the eastern book cliffs can be traced far into the time equivalent western fluvio estuarine succession

facies to sandbody scale heterogeneity in a tight gas fluvial reservoir analog blackhawk formation wasatch plateau utah usa abstract using photomosaics and measured sections this outcrop study characterizes facies to sandbody scale heterogeneity in the fluvial and coastal plain deposits of the blackhawk formation of the wasatch plateau utah usa as an outcrop analog for the fluvial tight gas reservoirs of the adjacent greater western rocky mountain basins as well as for conventional fluvial reservoirs elsewhere analysis on eight contiguous vertical cliff faces comprising both depositional dip and strike oriented segments provides field validation and calibration of the entire range of fluvial heterogeneity where 1 large scale heterogeneity 10 s of m vertically and 100 s of m laterally is associated with stacking of channelized fluvial sandbodies encased within coastal plain fines 2 intermediate scale heterogeneity 1 s of m vertically and 10 s of m laterally is related to type and distribution of architectural elements like bar accretion and crevasse splay units within individual sandbodies and 3 small scale heterogeneity 10 s of cm vertically and 1 s of m laterally is attributed to facies spatial variability within individual architectural elements at a reservoir scale 6 km strike transect impact of these heterogeneities has resulted in potential stratigraphic compartmentalization in varied patterns and scales within and among three zones which have similar lateral extents distinct vertical or lateral compartmentalization contrasting net to gross pattern width constraint by either large or intermediate scale heterogeneity disparity in communication between principal reservoir compartments by intermediate scale heterogeneity and reservoir quality segregation to barrier styles rendered by small scale heterogeneity are documented in an array of trends these intriguing trends are challenging to correlate across the reservoir scale dataset contributing to multiple analogous exploration and production uncertainties for improved tight gas exploration and production strategy of the western rocky mountain basins study results were also used in developing potential predictive tools 1 thickness threshold of individual channelized sandbody favoring multiple well intersection 2 aspect ratio in performing probabilistic sandbody width estimation and 3 prediction of sandbody amalgamation using underlying coal thickness