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

from quantitative 3d seismic stratigraphy to sequence stratigraphy insights into the vertical and lateral variability of shelf margin depositional systems at different stratigraphic orders abstract a major challenge in sequence stratigraphy is objectively identifying stratigraphic surfaces and sequences across multiple scales of observation identification is commonly dependent on the resolution of the data used i e seismic vs well data its dimension i e 1d vs 2d vs 3d or the criteria chosen to select sequence boundaries through shelf edge trajectory analysis the clinothem i e highest order seismic sequence identified on seismic data can constitute the elementary building block of an observation based and data driven quantitative workflow to develop sequence stratigraphic frameworks across different orders and ranks of hierarchy here we use high quality 3d seismic data to interpret a late tithonian early cretaceous shelf margin the lower barrow group lbg developed in the northern carnarvon basin on the north west shelf of australia based on full volume seismic interpretation techniques that integrate the 3d variability of the data when identifying seismic unconformities a high resolution seismic stratigraphic framework was built 73 interpreted clinothems with an average time duration of 63 000 yrs the computation of high frequency shelf edge trajectory angle tse curves on selected seismic cross sections is used to objectively pick sequence stratigraphic surfaces based on the accommodation succession method thereby highlighting small changes in trajectory and proposing a method reproducible by interpreters based on the same quantitative data within the d lobispinosum interval 142 3 140 9 ma the definition of stratigraphic sequences and composite stratigraphic sequences through this workflow is used to discriminate the controls at high and low temporal frequency on the vertical and lateral variability which is here quantified of this shelf slope basin system the results show that the high frequency interplay between short term glacio eustasy i e milankovitch eccentricity cycles of 100 000 yrs and sediment supply locus of fluvial input along the margin impacted the three dimensional stratigraphic architecture of the lbg in contrast tectonic subsidence had a significant impact on the stratigraphic architecture of the lbg within the main depocentre at lower temporal frequency by overprinting the eustatic signal and accelerating decelerating the rates of accommodation creation however identification of long term glacio eustatic milankovitch cycles 400 000 yrs outside the main depocentre where the rates of accommodation creation due to rift related subsidence are moderate also suggests low frequency eustatic control therefore the vertical and lateral variability of the lbg results from variations in sediment supply and subsidence regime under local i e process regime currents regional i e tectonics and global i e eustasy climate forcing parameters interplaying across timescales in contrast to standard sequence stratigraphic workflows that are based on model dependent choices to select sequence boundaries quantitative 3d seismic stratigraphy constitutes an improved method to interpret 3d seismic data in shelf margin depositional systems within a sequence stratigraphic framework which provides an observation based and model independent tool allowing the definition of stratigraphic sequences with results that are reproducible across multiple stratigraphers this work highlights the need for developing new sequence stratigraphic tools and methods that integrate the 4d variability of depositional systems and moves beyond the two dimensionality inherent to current sequence stratigraphic methods quantitative 3d seismic stratigraphy represents a first step towards the creation of 3d sequence stratigraphic workflows that could improve the prediction of stratigraphic patterns and facies relationships source reservoir seal distribution across shelf margins

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

impact of relative sea level and rapid climate changes on the architecture and lithofacies of the holocene rhone subaqueous delta western mediterranean sea abstract the modern rhone delta in the gulf of lions nw mediterranean is a typical wave dominated delta that developed after the stabilization of relative sea level following the last deglacial sea level rise similar to most other deltas worldwide it displays several stacked parasequences and lobes that reflect the complex interaction between accommodation sediment supply and autogenic processes on the architecture of a wave dominated delta the interpretation of a large set of newly acquired very high resolution seismic and sedimentological data well constrained by 14c dates provides a refined three dimensional image of the detailed architecture seismic bounding surfaces sedimentary facies of the rhone subaqueous delta and allows us to propose a scenario for delta evolution during the last deglaciation and holocene the subaqueous delta consists of parasequence like depositional wedges a few metres to 20 30 m in thickness these wedges first back stepped inland toward the nw in response to combined global sea level rise and overall westward oceanic circulation at a time when sediment supply could not keep pace with rapid absolute eustatic sea level rise at the younger dryas preboreal transition more rapid sea level rise led to the formation of a major flooding surface equivalent to a wave ravinement surface after stabilization of global sea level in the mid holocene accommodation became the leading factor in controlling delta architecture an eastward shift of depocentres occurred probably favoured by higher subsidence rate within the thick messinian rhone valley fill the transition between transgressive backstepping geometry and regressive prograding geometry para sequences resulted in creation of a maximum flooding surface mfs that differs from a classical mfs described in the literature it consists of a coarse grained interval incorporating reworked shoreface material within a silty clay matrix this distinct lithofacies results from condensation erosion which appears as an important process even within supply dominated deltaic systems due to avulsion of distributaries the age of the mfs varies along strike between ca 7 8 and 5 6 kyr cal bp in relation to the position of depocentres and climatically controlled sediment supply the last rapid climate change of the holocene the little ice age 1250 1850 ad had a distinct stratigraphic influence on the architecture and lithofacies of the rhone subaqueous delta through the progradation of two deltaic lobes in response to changes in sediment supply linked to rapid climate changes and to anthropic factors the rhone delta evolved from wave dominated to fluvial dominated and then wave dominated again

novel 3d sequence stratigraphic numerical model for syn rift basins analysing architectural responses to eustasy sedimentation and tectonics syn rift clastic sedimentary systems preserve a complicated stratigraphic architecture that records the interplay of tectonics eustatic sea level and storage and routing of sediments previous conceptual models describe and explain changes in depositional stacking patterns along a fault segment however stacking patterns and the nature of key stratigraphic surfaces is challenging to predict accurately with conventional sequence stratigraphic models that do not consider the three dimensional interplay of subsidence sedimentation and eustasy we present a novel geometric 3d sequence stratigraphic model syn strat which applies temporally and spatially variable fault scale tectonic constraints to stratigraphic forward modelling as well as allowing flexibility in the other controls in time and space syn strat generates a 3d graphical surface that represents accommodation although the model has the capacity to model footwall variation here we present model results from the hangingwall of a normal fault with temporal and spatial dip and strike predictions made of stacking patterns and systems tracts for a given set of controls sensitivity tests are tied to the depositional architecture of field based examples from the loreto basin gulf of california and alkyonides basin gulf of corinth here the relative influence of major sedimentary controls different subsidence histories varying sedimentation distribution including along strike variation in stacking patterns are assessed and demonstrate the potential of syn strat for reducing subsurface uncertainties by resolving multiple scenarios in addition the model demonstrates the nature of diachroneity of key stratigraphic surfaces that can arise in syn rift settings which could be represented by a bypass surface sequence boundary or reservoir seal maximum flooding surface in the rock record enabling a quantitative assessment of these surfaces is critical for prospect analysis in hangingwall half graben fills where these surfaces are heavily relied upon for well correlations that are used for hydrocarbon volume and production rate predictions

facies architecture and sequence stratigraphy of fine grained lacustrine deltas along the eastern margin of late pleistocene lake bonneville northern utah and southern idaho this study documents the effects of changing lake level limnostasy tectonics sediment yield and basin physiography on the facies architecture sequence stratigraphy and reservoir quality of three fine grained deltas deposited along the eastern margin of late pleistocene lake bonneville analysis of facies architecture indicates that the weber and spanish fork deltas were strongly wave modified because they were situated along openly exposed portions of the shoreline the bear river delta nestled in a relatively isolated northeast arm of the lake records both fluvial and wave processes these fine grained deltas were fed by low gradient rivers that drained large regions that were sparsely glaciated whereas other contemporaneous coarse grained gilbert deltas were fed by steep gradient rivers that drained local source areas that were strongly influenced by glaciers limnostasy tectonics and sediment yield were similar for all three fine grained deltas implying that the most influential forcing parameter on sequence stratigraphy is basin physiography basin physiography specifically ramp length and accommodation most strongly controlled the external and internal geometry of the lowstand systems tract of each delta potential hydrocarbon reservoir quality e g grain size and sorting is largely a product of drainage basin size and stream gradient relative differences in ramp lengths seemed to determine thickness and lateral continuity of delta front deposits relative differences in accommodation appeared to determine the internal geometry of the delta front deposits especially in the lowstand systems tract these deltas can serve as analogs for lacustrine exploration and production where many forcing parameters typically are unknown

arsenic and lead concentrations in the pond creek and fire clay coal beds eastern kentucky coal field abstract the middle pennsylvanian breathitt formation westphalian b pond creek and fire clay coal beds are the 2 largest producing coal beds in eastern kentucky single channel samples from 22 localities in the pond creek coal bed were obtained from active coal mines in pike and martin countries kentucky and a total of 18 fire clay coal bed channel samples were collected from localities in the central portion of the coal field the overall objective of this study was to investigate the concentration and distribution of potentially hazardous elements in the fire clay and pond creek coal beds with particular emphasis on as and pb 2 elements that are included in the 1990 clean air act amendments as potential air toxics the 2 coals are discussed individually as the depositional histories are distinct the fire clay coal bed having more sites where relatively high s lithologies are encountered in an effort to characterize these coals 40 whole channel samples excluding 1 cm partings were analyzed for major minor and trace elements by x ray fluorescence and proton induced x ray emission spectroscopy previously analyzed samples were added to provide additional geographic coverage and lithotype samples from one site were analyzed in order to provide detail of vertical elemental trends the as and pb levels in the fire clay coal bed tend to be higher than in the pond creek coal bed one whole channel sample of the fire clay coal bed contains 1156 ppm as ash basis with a single lithotype containing 4000 ppm as ash basis most of the as and pb appears to be associated with pyrite which potentially can be removed in beneficiation particularly coarser pyrite disseminated finer pyrite may not be completely removable by cleaning in the examination of pyrite conducted in this study it does not appear that significant concentration of as or pb occurs in the finer pyrite forms the biggest potential problem of as or pb enriched pyrite is therefore one of refuse disposal

sediment supply as a control on the variability of sequences an example from the late namurian of northern england currently variations in accommodation space are seen as the major control on facies stacking patterns and stratal geometries this paper emphasizes the importance of the sediment supply variable through the use of a regional stratal surface based interpretation of the late namurian stratigraphy of northern england late highstand palaeogeographies and stacking pattern variations highlight spatial and temporal variations in sediment supply which promote the contemporaneous development of prograda tional aggradational and retrogradational stacking patterns this questions the derivation of relative sea level curves from specific stacking patterns and highlights the potential for miscorrelation in areas with major sediment supply variations

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

the geochemistry of environmentally important trace elements in uk coals with special reference to the parkgate coal in the yorkshire nottinghamshire coalfield uk abstract the parkgate coal of langsettian age in the yorkshire nottinghamshire coalfield is typical of many coals in the uk in that it has a high sulphur s content detailed information on the distribution of the forms of s both laterally and vertically through the seam was known from previous investigations in the present work 38 interval samples from five measured sections of the coal were comprehensively analysed for major minor and trace elements and the significance of the relationships established using both raw and centered log transformed data the major elements are used to quantify the variations in the inorganic and organic coal components and determine the trace element associations pyrite contains nearly all of the hg as se tl and pb and is also the major source of the mo ni cd and sb the clays contain the following elements in decreasing order of association rb cs li ga u cr v sc y bi cu nb sn te and th nearly all of the rb is present in the clay fraction whereas for elements such as v cu and u a significant amount is thought to be present in the organic matter based on the k vs trace element regression equations only ge and possibly be would appear to have a dominant organic source the trace element concentrations are calculated for pyrite the clay fraction and organic matter for pyrite it is noted that concentrations agree with published data from the yorkshire nottinghamshire coalfield and also that tl concentrations median of 0 33 ppm in the pyrite are greater than either hg or cd unlike these elements tl has attracted less attention and possibly more information is needed on its anthropogenic distribution and impacts on man and the environment a seawater source is thought to be responsible for the high concentrations of s cl and the non detrital trace elements in the parkgate coal indicative of the seawater control is the th u ratio which expresses the detrital to non detrital element contributions using other elements similar ratios can be calculated which in combination offer greater interpretative value

effects of adjacent fault systems on drainage patterns and evolution of uplifted rift shoulders the lower cretaceous in the loppa high southwestern barents sea abstract sedimentological models for rift shoulders have poorly documented the effect of adjacent fault systems on drainage patterns in this study we investigate the loppa high an ancient tilted rift shoulder located in the southwestern barents sea we use seismic and well data sedimentological log descriptions and biostratigraphic information to understand the drainage patterns and the early cretaceous geological history of the loppa high this study provides an example of how the drainage systems in low gradient flanks of a rift shoulder can be modified and confined by normal faults occurring almost orthogonal to the main fault system these orthogonal faults might have acted as preferential sediment routes thus potential deposits of the main drainage systems directed to the low gradient flank are found almost exclusively associated with grabens formed due to these orthogonal faults the early cretaceous evolution of the loppa high is summarized as follow 1 during the boreal berriasian volgian to early barremian the asterias and the bjornoyrenna fault complexes were active diachronous shallow to eventually deep marine fans and incised valleys were developed along the southern and western flanks of the loppa high 2 late barremian aptian fault activity is interpreted along the ringvassoy loppa fault complex a second generation of incised valleys and their related shallow marine fans were formed in the western flank of the loppa high and 3 during late aptian early albian the loppa high and the hammerfest basin were tilted eastwards the latter event triggered a switch in depocenter location and development of shelf margin clinoforms downlapping in close proximity to the eastern flank of the high

three dimensional numerical modeling of coarse grained clastic deposition in sedimentary basins a three dimensional numerical model of clastic deposition in sedimentary basins is used to investigate the development of coarse grained deltas in response to relative sea level changes the model incorporates fully three dimensional sediment delivery and deposition together with incised channel formation and slope failure a combined random walk steepest descent algorithm is used to simulate sediment delivery from a drainage basin outlet to the depositional shoreline together with a nonlinear three dimensional diffusion equation for modeling slope dependent sediment erosion transport and deposition when sediment channels transport pathways are out of a specified grade advective erosion occurs thereby increasing the total sediment supply delivered to the basin multiple sediment sources into a basin can be simulated together with tectonic subsidence and eustatic sea level changes the model results presented display many of the key features observed in both modern and ancient coarse grained deltas during periods of slowly changing and high relative sea level highstands a broad delta front progrades approximately radially away from the sediment source conversely incised channels are developed during rapid falls of relative sea level leading to localized deposition of deltaic lobes at the mouths of these channels the incised channels initiate at the exposed delta front and propagate backward toward the sediment source the rate of growth of incised channels is shown to be an important control on delta morphology sediment distribution and lowstand lobe size and location lobes are particularly well developed during periods of slowly changing low relative sea level lowstands periods of rapid rise of relative sea level lead to flooding and infilling of incised channel systems and a rapid landward shift in deposition transgressions incised channels and delta lobes are best developed in a model where tectonic subsidence is similar to that expected for hanging wall sourced deltas in extensional half graben settings in contrast both channels and lobes are less well developed in a model where tectonic subsidence is similar to that expected for footwall sourced deltas in such settings many of the features developed in the models are by their nature three dimensional and two dimensional analysis of the model results can lead to erroneous interpretations of the causes of along strike variability these aspects of sequence variability have important implications for the application of the sequence stratigraphic methodology to many sedimentary basins

two dimensional stratigraphic forward modeling reconstructing high relief clinoforms in the northern taranaki basin clinoforms the basic large scale architectural form within which sediments are stored and eventually fed down depositional dip in clastic wedges exist in many shapes and sizes understanding how they form evolve and degrade is critical to understanding how transport mechanisms affect the shelf margin and sediment partitioning and distribution and their implications on the presence of a working petroleum system the neogene stratigraphic succession of the taranaki basin in new zealand contains clinoform packages that display a variety of architectures well imaged on seismic data quantitative characterization of this interval was performed to unravel the processes by which clinoforms evolve under the influence of tectonic and isostatic driven subsidence sea level change and sediment supply fluctuations nine different clinoform packages were identified on the basis of changes in their seismic stratigraphic characteristics two dimensional stratigraphic forward modeling was used to conduct a sensitivity analysis and determine the relative importance of different geologic controls on their genesis our results show that during the early to late pliocene clinoform architectures were influenced by the opening of a back arc rifting structure in the taranaki basin northern graben which controlled sediment redistribution and partitioning at the same time a drop in global sea level allowed sediment bypass to distal parts of the basin during the late pliocene changes in the australian pacific subduction zone forced rapid uplifting of the southern alps generating a significant increase in sediment supply model simulations suggest that clinoform architectures during the late pliocene were controlled by this increase in sediment supply and associated loading

cretaceous and tertiary inversion in the bjornoyrenna fault complex south western barents sea a system of half flower like structures folds reverse faults and footwall cut offs is observed adjacent to the bjornoyrenna fault complex in the south western barents sea although the bjornoyrenna fault complex itself is principally an extensional feature with its period of maximum extensional activity in the early cretaceous these structures suggest that the subsidence along the fault complex was interrupted in the hauterivian aptian by left lateral transtension and in the late cretaceous early tertiary by head on inversion both these episodes caused relatively intense deformation and seem to have regional significance consequently the events need to be seen in relation to the plate tectonic development of the south western barents sea

strike variability of clastic depositional systems does it matter for sequence stratigraphic analysis current sequence stratigraphic models are two dimensional in nature and predict variability in depositional dip sections strike and dip variability of sediment supply to clastic depositional systems causes significant changes to sequence architecture so that contrasting yet coeval stacking patterns result these changes ultimately affect prediction potential based on fixed systems tract stacking patterns and relation to relative sea level curves identification of key surfaces in sequences rather than stacking patterns is the most reliable indicator of relative sea level history

three dimensional stratigraphic evolution of the miocene baltimore canyon region implications for eustatic interpretations and the systems tract model a seismic stratigraphic analysis of miocene deposits in the baltimore canyon region offshore new jersey reveals tremendous threedimensional complexity and challenges traditional approaches to sequence stratigraphic interpretation individual sequences vary dramatically in along strike thickness revealing the locations of the sediment sources within sequences the lowstand wedge thins dramatically along strike tens to hundreds of meters and is interpreted to record variable paleobathymetry along strike as indicated by sequence thickness distributions shelf break positions lithologic composition and stratigraphic relationships sequences record sediment migration and progradation across the basin through time as a result of these depositional complexities relative sea level curves interpreted from parallel dip lines vary in magnitude and amplitude across the basin development of neogene stratal patterns within the baltimore canyon region has been closely linked to glacioeustatic change our reconstructions of delta switching and progradation emphasize that miocene stratal patterns were greatly influenced by autocyclic depositional processes

shelf edge deltas along structurally complex margins a case study from eastern offshore trinidad a 15 000 km2 5792 mi2 three dimensional seismic data survey that covers the shelf slope transition of the eastern offshore trinidad continental margin reveals the geometry and depositional history of the last maximum glacial lowstand shelf margin succession despite the lack of well information at these shallow depths the quality and continuity of the seismic data allow us to pursue a detailed seismic stratigraphic interpretation of the last lowstand margin succession the basin fill stratal architecture of the studied stratigraphic interval shows a great deal of lateral and vertical variability along the continental margin during the pleistocene to holocene three geomorphological elements controlled the character of the accommodation within the basin and were crucial in transporting delivering and storing sediment supply from shelf to slope areas 1 the columbus sedimentary pathway on the shelf 2 bypass zones in the shelf break region and 3 deep water depocenters the location and geometry of these geomorphological elements within the basin are clearly controlled by underlying structures transpressional to the north and gravity driven to the south migration of the paleo orinoco delta system across the shelf was also a key factor in defining the stratigraphic geometries that are observed within the shelf break development of shelf edge versus outer shelf deltaic systems on the continental margin was controlled by the nature of sediment supply at specific times as well as by the availability of accommodation although to a lesser extent to relative sea level fluctuations the interpretation also showed that for time equivalent units parts of the shelf edge region could develop as an erosional margin sediment bypass zones whereas other parts of the shelf edge could behave as an accretionary margin sediment accumulation the sequence stratigraphic interpretation that was attempted in this work also demonstrated that the characteristics of systems tracts can abruptly change along strike in the shelf edge region for time equivalent units these changes can be misleading if a genetic interpretation is pursued only on the basis of the definition of system tracts in the shelf edge region without the consideration of a complete regional framework

controls on clastic sequence geometries in a shallow marine transtensional basin the bohemian cretaceous basin czech republic the bohemian cretaceous basin combines features of a shallow water mostly 100 m epicontinental seaway formed during a global transgression with those of a tectonically active transtensional setting the basin formed under a greenhouse climate and was affected by strong axial currents dense well log coverage combined with locally high quality exposures and biostratigraphic control make it possible to examine in three dimensions the geometries of genetic sequences and interpret their controlling variables sand dominated deltas formed sequences at several spatial scales that reflect nested transgressive regressive cycles with durations ranging from tens of thousands of years to millions of years progradation directions and distances thicknesses and internal geometry of the individual sequences were controlled primarily by intrabasinal faulting basin scale changes in subsidence rate eustatic fluctuations and localized bathymetric changes due to successive filling of the basin along strike change in sediment input from different parts of the source area and a short lived uplift of a secondary clastic source provided additional controls on the sequence geometry efficient hypopycnal transport combined with redeposition of fine clastics in shallow water promoted development of steep slopes of sand dominated deltas while preventing downlap of muddy clinoforms most of the suspended load became deposited downcurrent in subhorizontal or gently dipping bottomsets long term accommodation rates were low during the early to middle turonian with minor intrabasinal faulting but became accelerated in the late turonian and early coniacian this acceleration was caused at least partly by increased subsidence rate accompanied by structural partitioning of the depocentre and partly compensated by increased sediment input indicating increased uplift rates in the western sudetic island source area this event probably reflected an increase in the regional strain rate in central europe the succession of two major flooding events in the early turonian and late early coniacian separated by a low accommodation interval in the middle turonian shows a close similarity to published estimates of long term eustatic curves however the eustatic component of accommodation rate in the bohemian late turonian and coniacian is difficult to separate from accelerated subsidence in several cases evidence for short term 100 kyr scale forced regressions independent of basinal structural activity suggests small scale eustatic falls at rates which as presently understood cannot be explained other than by a glacio eustatic mechanism

depositional systems and sequence stratigraphy of coarse grained deltas in a shallow marine strike slip setting the bohemian cretaceous basin czech republic deposits of coarse grained gilbert type deltas showing varying degrees of reworking of foresets by basinal currents were identified in middle turonian to early coniacian sandstones of the bohemian cretaceous basin the progradation of the deltaic packages earlier interpreted as large scale subaqueous dunes shelf ridges or subaqueous fault scarp accumulation terraces was controlled by high and low frequency relative sea level changes in a relatively slowly subsiding intracontinental strike slip basin end member types of the bohemian cretaceous coarse grained deltas are deep water deltas characterized by thick 50 80 m foreset packages with steep 10 30 foresets and shallow water deltas which deposited thin 15 m packages with foresets typically between 4 and 10 the differences in thickness and foreset slope angle were controlled predominantly by the accommodation available during progradation the depositional regime of the deltas was governed by i the fluvial input of abundant sand bedload with a minor proportion of gravel ii gravity flows most probably caused by liquefaction of the upper part of the unstable foreset slope and iii migration of sandy bedforms on the foreset slopes the bedform migration was driven by unidirectional currents of possible tidal origin individual foreset packages represent systems tracts or parts of systems tracts of depositional sequences a variety of stacking patterns of high frequency sequences exists in the basin caused by low frequency relative sea level changes as well as by local changes in sediment input because of generally low subsidence rates fluvial or beach topset strata were not preserved in the cases studied the absence of preserved fluvial facies which has been one of the main arguments against the fluvio deltaic origin of the sandstone bodies is explained by erosion of the topsets during transgression and their reworking into coarse grained lags of regional extent covering ravinement surfaces

tectonic development and hydrocarbon potential offshore troms northern norway four years of exploration activity offshore troms has resulted in four gas discoveries with total resources of 170 109 cu m 6 000 109 cu ft recoverable gas shows of heavy waxy oil are present in most wells recent regional studies on structural evolution and organic geochemistry suggest that in parts of the area where exploration activities have been concentrated so far the oil prone source rock has not been mature enough to expel the generated oil in other parts all potential source rocks became overmature 100 million years ago because of extreme subsidence during the early cretaceous the regional studies clea ly demonstrate the close relationship between the structural evolution and the hydrocarbon potential of the region the different regional structural elements are individual provinces with respect to hydrocarbon potential the remaining hydrocarbon potential within tromsoflaket is fair end page 615

how much systems tract scale three dimensional stratigraphic variability is present in sequence stratigraphy an answer from the middle miocene pearl river mouth basin prior sequence stratigraphic methods mainly employed two dimensional 2 d stacking patterns to reconstruct stratigraphic frameworks the future of sequence stratigraphy will pay more attention to systems tracts scale and three dimensional 3 d stratigraphic variability using 1 2 104 km2 4 63 103 mi2 3 d seismic data tied to regional 2 d seismic lines and 21 boreholes the present study examines systems tract scale and 3 d stratigraphic variability of the 14 8 13 8 ma pearl river shelf margin to deep water sedimentary prisms the studied prisms were divided into four main systems tracts namely highstand systems tract hst falling stage systems tract fsst lowstand systems tract lst and transgressive systems tract tst each systems tract is represented by a given clinoformal architecture and stacking pattern 1 clinothem sets with aggradation to progradation are hst 2 clinothem sets with progradation to degradation pd are fsst 3 clinothem sets with progradation to aggradation pa are lst and 4 clinothem sets with retrogradation are tst lst or hst in addition pearl river fsst and lst display downdip stratigraphic variabilities which are regionally manifested in at least three ways 1 shelf edge deltas linked downdip to basin floor fans 2 shelf edge deltas linked downdip without fans and 3 basin floor fans linked updip that lack deltas in along strike orientation the pearl river fsst could exhibit low angle progradation not just pd stacking the lst could present retrogradational stacking not just pa stacking therefore the physical position of a systems tract is reemphasized in terms of assigning a given systems tract the concepts of three systems tracts are then revised for chronostratigraphic significance the lst is the lowermost systems tract of a sequence presenting a normal regression of the shoreline as its diagnostic characteristic and including contemporaneous stratigraphic units laterally the hst is the upper systems tract of a sequence providing a normal regression of the shoreline as its diagnostic characteristic and including contemporaneous stratigraphic units laterally the tst is the middle systems tract of a sequence generating a backstep of the shoreline and excluding contemporaneous onlapping units of both the lst and hst laterally the fsst has not been revised because fsst may be a supply independent feature

arsenic bearing pyrite and marcasite in the fire clay coal bed middle pennsylvanian breathitt formation eastern kentucky abstract arsenic concentrations determined on 11 lithotype samples from the middle pennsylvanian breathitt group fire clay coal bed leslie county ky range from 1 to 418 ppm whole coal basis the 11 lithotype samples which vary in thickness from 4 to 18 cm were sampled from a continuous 1 38 m channel sample and were selected based on megascopic appearance vitrain rich versus attrital rich a lithotype that contains 418 ppm as is located near the top of the coal bed and is composed of 10 5 cm of bright clarain bands containing fusain that within short distances grade laterally into fe sulfide bands to determine the mode of occurrence of as in this lithotype the coal was examined with scanning electron microscopy and analyzed by energy dispersive x ray fluorescence massive framboidal cell filling cell wall replacement and radiating forms of fe sulfide were observed in the high as lithotype many of the radiating fe sulfide forms and one of the cell wall replacements contained as examination of the grains with optical light microscopy shows that the majority of radiating morphologies are pyrite the remainder are marcasite selected fe sulfide grains were also analyzed by electron microprobe microscopy arsenic concentrations within individual grains range from 0 0 wt to approximately 3 5 wt on the basis of morphology these fe sulfides are presumed to be of syngenetic origin and would probably be removed from the coal during physical coal cleaning thus eliminating a potential source of as from the coal combustion process however because the grains are radiating and have high surface area dissolution and release of as could occur if the pyrite is oxidized in refuse ponds

building up or out disparate sequence architectures along an active rift margin corinth rift greece early pleistocene synrift deltas developed along the southern corinth rift margin were deposited in a single dominantly lacustrine depocenter and were subject to the same climate related base level and sediment supply cyclicity two synrift deltas just 50 km apart show markedly different sequence geometry and evolution related to their location along the evolving border fault in the west strongly aggradational fan deltas 600 m thick 2 4 km radius deposited in the immediate hanging wall of the active border fault comprise stacked 30 100 m thick stratal units bounded by flooding surfaces each unit evolves from aggradational to progradational with no evidence for abrupt subaerial exposure or fluvial incision in contrast in the central rift the border fault propagated upward into an already deep lacustrine environment locating rift margin deltas 15 km into the footwall the deltas here have a radius of 9 km and comprise northward downstepping and offlapping units 50 200 m thick that unconformably overlie older synrift sediments and are themselves incised the key factors driving the marked variation in sequence stratigraphic architecture are 1 differential uplift and subsidence related to position with respect to the border fault system and 2 inherited topography that influenced shoreline position and offshore bathymetry our work illustrates that stratal units and their bounding surfaces may have only local 10 km extent highlighting the uncertainty involved in assigning chronostratigraphic significance to systems tracts and in calculating base level changes from stratigraphy where marked spatial variations in uplift and subsidence occur

temporal significance of sequence boundaries abstract this paper analyses the temporal significance of stratigraphic surfaces bounding the marine portions of the depositional sequence genetic stratigraphic sequence and transgressive regressive sequence these bounding surfaces known as the correlative conformity c c maximum flooding surface mfs and conformable transgressive surface cts respectively may either be defined on the basis of stratal stacking patterns which we call type a surfaces or on the basis of water depth changes and relative sea level changes which we call type b surfaces the type a mfs and cts are time lines in a depositional dip section corresponding to the turnaround points from shoreline transgression to regression and vice versa they separate prograding coarsening upward from retrograding fining upward geometries with a timing determined by the interplay between the rates of sedimentation and relative sea level rise in the shoreline area the timing of type a mfs and cts is not affected by the offshore variations in sedimentation and subsidence rates but it is only controlled by the shoreline movements and the associated facies shifts the type a c c separates rapidly prograding and offlapping forced regressive strata from the overlying lower rate prograding and aggrading normal regressive strata this surface is diachronous younger basinward with the rate of offshore sediment transport the timing of the type a c c in the shoreline area corresponds to the end of relative sea level fall but it develops under relative sea level rise conditions offshore the timing of the type b mfs and cts depends on the offshore variations in the sedimentation and subsidence rates these surfaces defined on the basis of bathymetric changes become younger and older seaward respectively tending to merge together offshore the type b c c marks the end of relative sea level fall in any point along a depositional dip section it is diachronous older basinward as its timing depends on the offshore variations in subsidence rates the diachroneity of type b surfaces reaches a quarter of the period of the highest frequency variable whichever that is among the eustasy tectonics or sedimentation controls types a and b surfaces merge together in the shoreline area but they become temporally divergent offshore deepening upward and shallowing upward facies should not be confused with transgressive and regressive systems tracts the latter are strictly controlled by the shoreline movements which determine the direction of facies shifts and the stratal stacking patterns

anatomy of rapid margin progradation three dimensional geometries of miocene clinoforms new jersey margin documentation of along strike variations in the morphologies of continental margin clinoforms is essential for understanding mechanisms of progradation one of the fundamental relationships between depositional processes and preserved stratigraphy maps based on a grid of commercial multichannel seismic data offshore new jersey extending more than 70 km along strike and approximately 50 km downdip reveal the three dimensional morphology and evolution of four buried surfaces correlated with middle upper miocene sequence boundaries calibrated by drilling on the adjacent continental slope miocene clinoform breakpoints are not depositional analogs of the modern shelf edge they are linear to gently arcuate breakpoint and slope trends indicate a systematic southward displacement of depocenters over about 5 6 m y progradation responded to point fluvial sediment sources but efficient along strike sediment dispersal muted their influence canyons are absent on three of four clinoform slopes the fourth slope has one v shaped canyon and a broad erosional area possible slope failure planar floored canyons also occur albeit rarely seaward of clinoform toes apparently v shaped and planar floored canyons previously ascribed to downslope erosion vs slope failure headward erosion respectively can coexist the accretionary northern slope of little bahama bank is a possible morphologic analog by analogy with pleistocene shelf slope geometries an absence of canyons breaching clinoform breakpoints suggests that rivers did not discharge at paleoshelf edges indicating that sea level lowstands postulated for the middle upper miocene did not expose breakpoints reconstruction of breakpoint paleoelevations supports this conclusion for three of the four mapped surfaces suggesting that elevations of some miocene lowstands on the global sea level curve are too high by up to 60 m

the decay of the barents ice sheet as documented in nordic seas ice rafted debris abstract a large marine based ice sheet that covered the barents sea and svalbard during the height of the weichselian glaciation began to disintegrate at 15 ka the decay produced enormous quantities of icebergs that drifted parallel to the norwegian continental margin southward and northwestward into the fram strait this drifttrack is reflected by a trace of ice rafted clastic sedimentary rocks from the bottom of the barents sea in deep sea sediments of the norwegian sea and the fram strait the petrographic composition of ice rafted lithic particles dropstones 0 5 mm in late quaternary 20 ka recent deep sea sediments of the norwegian greenland sea was analyzed in order to determine the source areas of the dropstones the dropstone provenance was deciphered from the regional distribution of some precisely defined lithotypes during the maximum glaciation between 20 and 15 ka the norwegian sea received crystalline rocks primarily from western norway but also from svalbard and the northwestern british isles the greenland sea was supplied with clay silt and sandstones from central and northern east greenland and rocks from circum arctic areas at 15 ka a dramatic shift in provenance from crystalline rocks to clastic sedimentary rocks is recorded in the dropstone composition of the northern and eastern norwegian sea this impulse was the ultimate result of the deterioration of the barents ice sheet the dispersal area of clastic rock fragments reaches from the barents shelf between 72 and 76 n and 15 and 20 e to the voring plateau eastern norwegian sea at 67 n and 5 e the main direction of iceberg drift was to the south and southeast after an initial period of only 500 years duration and extremely high dropstone deposition rates the influx from the barents shelf ceased and gradually changed into the modern surface current system

quantitative sequence stratigraphy sequence stratigraphy based on wire line logs cores and outcrops is entering its fourth decade of mainstream usage in industry and academia the technique has proved to be an invaluable tool for improving stratigraphic analyses in both clastic and carbonate settings here we present a simple quantitative technique to support sequence stratigraphic interpretations in clastic shallow marine systems the technique uses two pieces of data that are readily available from every subsurface field or outcrop study 1 parasequence thickness t and 2 parasequence sandstone fraction sf the key assumptions are that parasequence thickness can be used as a proxy for accommodation at the time of deposition and parasequence sandstone fraction can be used as a proxy for sediment supply this means that quantitative proxies for rates of accommodation development and sediment supply can be acquired from wire line logs cores and outcrop data vertical trends in parasequence thickness divided by sandstone fraction t sf approximate trends expected in systems tracts for changes in ratios of rate of accommodation development to rate of sediment supply the technique termed tsf analysis can also be applied at lower order sequence and composite sequence scales it provides a quantitative and objective methodology for determining rank and order of sequence stratigraphic surfaces and units absolute t sf values can be used to determine shoreline stacked shoreline and shelf margin trajectories four case studies are presented which demonstrate the robustness of the technique across a range of different data sets implications and potential future applications of tsf analyses are discussed

evolution of shelf margin clinoforms and deep water fans during the middle eocene in the sorvestsnaget basin southwest barents sea interpretation of seismic data from the sorvestsnaget basin southwest barents sea demonstrates gradual middle eocene basin infilling from the north generated by southward prograding shelf margin clinoforms the basin experienced continued accommodation development during the middle eocene because of differential subsidence caused by the onset of early eocene sea floor spreading in the norwegian greenland sea faulting salt movement and different tectonic activity between the sorvestsnaget basin and veslemoy high during this time the margin shows transformation from an initially high relief margin to a progradation in the final stage the early stage of progradation is characterized by the establishment of generally oblique clinoform shifts creating a flat shelf edge trajectory that implies a gentle falling or stable relative sea level and low accommodation to sediment supply ratio 1 in the topsets during the early stage of basin development the high relief margin narrow shelf stable or falling relative sea level seismicity and presumably high sedimentation rate caused accumulation of thick and areally extensive deep water fans seismic scale sandstone injections deform the fans a fully prograding margin developed when the shelf to basin profile lowered apparently because of increased subsidence of the northern part this stage of the basin development is generally characterized by the presence of sigmoid clinoform shifts creating an ascending shelf edge trajectory that is implying steady or rising relative sea level with an accommodation to sediment supply ratio of greater than 1 implying sand accumulation on the shelf this study suggests that some volume of sand was transported into the deep water during relative sea level rise considering the narrow shelf and inferred high rates of sediment supply

nearshore along strike variability is the concept of the systems tract unhinged sequence stratigraphic models assume that nearshore strata have relatively consistent and laterally persistent stacking at the systems tract scale and therefore may not fully describe the three dimensional stratigraphic architecture in areas displaying marked nearshore along strike variability a stratigraphic model of nearshore deposits is presented that corrects for this assumption by explaining variations in along strike stratal geometries in terms of a systematic change in the orientation of a shoreline trend or clinoform rollover a scenario comparable to deflection around a hinge the model defines hinge zones that are both fixed and moving with respect to time and was created from outcrop well log and seismic reflection data model end members predict contemporaneous progradational aggradational and retrogradational stacking bounded by surfaces displaying significant along strike changes in architecture implying that sequence stratigraphic surfaces can be diachronous we advocate examining the impact of stratigraphic variations parallel to depositional strike by testing for the presence of uniform versus differential progradation phenomena responsible for creating unhinged and hinged nearshore depositional systems respectively understanding these differences will improve subsurface predictions and provide a more complete understanding of the stratigraphic evolution of sedimentary basins

sedimentary response to a tectonically induced sea level fall in a shallow back arc basin the mulichinco formation lower cretaceous neuquen basin argentina this study examines the sedimentary response to a tectonically driven relative sea level fall that occurred in the neuquen basin west central argentina during the late early valanginian early cretaceous at this time the basin lay behind the emergent andean magmatic arc to the west following the relative sea level fall sedimentation was limited to the central part of the neuquen basin with the deposition of a predominantly clastic continental to shallow marine wedge on top of basinal black shales this lowstand wedge is called the mulichinco formation and consists of a third order sequence that lasted about 2 myr and contains high frequency lowstand transgressive and highstand deposits significant variations in facies depositional architecture and internal organization of the sequence occur along depositional strike these variations are attributed mainly to tectonic and topographic controls upon sediment flux basin gradient fault tilting and shifting of the depocentre through time these controls were ultimately related to asymmetrically distributed tectonic activity that was greater towards the magmatic arc in the west the superposition of fluvial deposits directly upon offshore facies provides unequivocal evidence for a sequence boundary at the base of the mulichinco formation however the mulichinco sequence boundary is marked by shallow low erosional relief and widespread fluvial deposition the surface lacks prominent valleys traditionally associated with sequence boundaries this non erosive sequence boundary geometry is attributed to the ramp type geometry of the basin and or rapid uplift that limited stratigraphic adjustment to base level fall significant along strike facies changes and a low relief sequence boundary are attributes that may be common in tectonically active semi enclosed basins e g shallow back arc basins foreland basins

seismic interpretation and characterization of anhydrite caprocks in the tromso basin sw barents sea abstract the origin of anhydrite caprocks found in many evaporite basins is currently under debate existing models in the literature for anhydrite formation include rotated stratigraphic layering rotated crestal caprock and diagenetic anhydrite in this work we interpret high quality 2d seismic reflection data to understand the processes associated with anhydrite caprock formation our study focuses on anhydrite caprock formation in the tromso basin which represents one of several underexplored salt basins in the arctic we use well log data and seismic stratigraphic as well as seismic attribute analyses to characterize the anhydrite layers associated with salt diapirs our results reveal that the anhydrite layers are high amplitude reflections at the crests which are often found close to the seabed and lateral caprocks on the flanks of salt diapirs a third class of anhydrite layers is folded faulted and boudinaged intrasalt stringers encased by the salt diapirs lateral caprocks in the tromso basin are formed in response to rotated crestal caprock failure the crestal caprocks are secondary in origin occur at shallow depths and are formed as insoluble residues from the dissolution of halite by the ingress of basinal fluids into the tops of diapirs anhydrite stringers or floaters originate from tectonic related multi dimensional salt flow salt diapirs in the tromso basin are associated with varied anhydrite caprocks their formation cannot be fully explained using a single model our work demonstrates from seismic reflection data the occurrence of caprock events that formed progressively on the flanks of salt diapirs due to local folding

three dimensional numerical modeling of deltaic depositional sequences 1 influence of the rate and magnitude of sea level change abstract a three dimensional numerical model of deltaic deposition is used to investigate the influence of sea level changes on delta development and sequence variability results illustrate the three dimensional morphology of key stratal surfaces and architecture of stratal units systems tracts and highlight the importance of the rate and magnitude of sea level change in controlling the evolution of deltaic depositional sequences high rates of sea level fall lead to the development of a limited number of major incised channels that focus sediment supply to a few elongate finger like forced regressive lobes separated by large areas of nondeposition in contrast low rates of sea level fall cause only minor channel incision which occurs late during sea level fall as a result sediment is supplied more uniformly to the delta front leading to an attached laterally continuous forced regressive apron during lowstand and subsequent sea level rise the delta morphology and internal geometry are strongly controlled by the rate of rise high rates lead to i poorly developed lowstand wedges that are drowned early ii high magnitude transgressions and iii the late development of maximum flooding surfaces the stratigraphy developed during sea level rise is also strongly influenced by the incised valley system created during the preceding sea level fall if deep major valleys developed that captured most of the sediment supply the resultant stratigraphy has well developed lowstand wedges that are flooded relatively late during sea level rise even within a single delta systems tracts and key stratal surfaces show three dimensional variability and two dimensional sections often lack significant elements of the stratigraphy as a result analysis of two dimensional sections can often lead to miscorrelation and erroneous interpretations of the controlling processes

fault kinematics and localised inversion within the troms finnmark fault complex sw barents sea abstract the areas bounding the troms finnmark fault complex are affected by complex tectonic evolution in this work the history of fault growth reactivation and inversion of major faults in the troms finnmark fault complex and the ringvassoy loppa fault complex is interpreted from three dimensional seismic data structural maps and fault displacement plots our results reveal eight normal faults bounding rotated fault blocks in the troms finnmark fault complex both the throw depth and displacement distance plots show that the faults exhibit complex configurations of lateral and vertical segmentation with varied profiles some of the faults were reactivated by dip linkages during the late jurassic and exhibit polycyclic fault growth including radial syn sedimentary and hybrid propagation localised positive inversion is the main mechanism of fault reactivation occurring at the troms finnmark fault complex the observed structural styles include folds associated with extensional faults folded growth wedges and inverted depocentres localised inversion was intermittent with rifting during the middle jurassic early cretaceous at the boundaries of the troms finnmark fault complex to the finnmark platform additionally tectonic inversion was more intense at the boundaries of the two fault complexes affecting middle triassic to early cretaceous strata our study shows that localised folding is either a product of compressional forces or of lateral movements in the troms finnmark fault complex regional stresses due to the uplift in the loppa high and halokinesis in the tromso basin are likely additional causes of inversion in the troms finnmark fault complex

reciprocal stratigraphy of the campanian paleocene western interior of north america abstract the claggett bearpaw and cannonball successions campanian paleocene of the western interior foreland system were deposited during a series of regional second and third order transgressions and regressions locally modulated by fourth and lower order cycles the reciprocal flexural behaviour of the foreland lithosphere in response to orogenic cycles of loading and unloading results in out of phase sequences on opposite sides of the basin which defines the concept of reciprocal stratigraphies the proximal and distal regions of the basin are separated by a few kilometre wide hinge zone of proximal to distal facies change with the mid point taken as a stratigraphic hinge line which defines the boundary between coeval marine transgressive and regressive systems tracts or between nonmarine sequences and correlative sequence boundaries hinge lines have been mapped in alberta saskatchewan montana and wyoming for consecutive time slices during the campanian paleocene interval areally the hinge line traces a semielliptical pattern outlining the region of maximum foreland basin subsidence it migrated at 10 km ma to the north in response to late cretaceous paleocene orogenic dextral transpression the hinge line also migrated eastward during the campanian and maastrichtian in response to thrust sheet advance and westward during the paleocene in response to the redistribution of orogenic load associated with a transition from transpression to transtension possibly accompanied by a visco elastic deepening and narrowing of the foredeep

tectonic control of facies architecture in falling stage deposits in a forearc basin upper miocene senhata formation boso peninsula japan abstract the upper miocene senhata formation is the infill of the middle miocene middle pliocene forearc basin that developed in response to the north ward to northwestward subduction of the philippine sea plate beneath the eurasia plate at the sagami trough the formation has been affected by anticlinal and synclinal deformation and provides an opportunity for analyzing three dimensional variations in thickness stacking patterns and bounding surface features of component lithofacies associations the lower part of the formation consists mainly of shoreface and shelf deposits and indicate falling stage deposits that are overlain by transgressive shoreface and shelf deposits of the upper senhata formation with the contact defined as a wave ravinement surface forced regressive shoreface to shelf deposits of the lower senhata formation are characterized by an erosional basal surface of a type 1 sequence boundary and lateral change to multiply stacked thicker regressive deposits with a gradational basal contact with the underlying shelf and upper slope deposits indicating progradational and aggradational stacking of shoreface and shelf deposits which are interpreted to be equivalent to the shelf margin systems tract of a type 2 sequence the erosional sequence boundary at the base of forced regressive deposits coincides laterally with a transgressive surface of erosion to the northwestern upslope area where the forced regressive deposits are absent the lateral variation in the falling stage regressive deposits of the lower senhata formation is interpreted to indicate that falling stage and lowstand stage deposits of types 1 and 2 sequences are largely contemporaneous and their development is controlled by spatial variation in the rate of basin subsidence in both depositional dip and depositional strike directions

coalesced delta front sheet like sandstone bodies from highly avulsive distributary channels the low accommodation mesa rica sandstone dakota group new mexico u s a