3d stratigraphic forward modelling for analysis and prediction of carbonate platform stratigraphies in exploration and production abstract stratigraphic forward modelling sfm has been used to answer important questions in stratigraphic analysis this has been demonstrated through generic modelling of synthetic data and numerous two dimensional 2d real data case studies but the method has rarely been used to further our understanding of specific real three dimensional 3d carbonate data sets by quantitative comparison this paper applies carbonate 3d a sfm program to a hydrocarbon reservoir and outcropping carbonate platforms at both exploration and production scales we show the value of sfm in the exploration and production of hydrocarbons through predicting facies distributions and stratigraphic geometries between wells and by analysing and answering fundamental questions about the formation of specific carbonate strata first the model is tested using the 3d outcrops of a miocene attached carbonate platform at nijar se spain where 78 of mapped facies are matched in the simulations second sfm of an 80 000 km 2 jurassic ramp in ne spain exploration scale predicts new facies in areas without data leads to an improved understanding of ramp evolution modification of the interpreted sea level curve and re interpretation of the main sediment transport direction application to the isolated platform reservoir judy creek devonian canada exemplifies the advantages of applying sfm at reservoir scale the simulations yield information on platform geometries and facies distributions an improved understanding of the factors that control platform evolution and propose a revised sea level history wider applications of sfm in exploration include assessment of the possibilities and probabilities of facies distributions and evaluation and ranking of different interpretations of platform evolution at the reservoir scale facies probability distributions and layer geometries derived from sfm can serve as input into static reservoir models to guide geostatistical simulations

a model for carbonate to terrigenous clastic sequences the development of carbonate sequences that grade toward a source region into terrigenous clastic sediment is poorly understood in both carbonate and terrigenous clastic regimes environments of rapid sedimentation have comparable rates of deposition 102 to 102 5 cm 1 000 yr slowest continuous rates are also comparable 100 5 to 101 cm 1 000 yr because of the inhibiting effect of terrigenous deposition on carbonate skeletal production the slowest rates in a transect tend to occur where mixed lithologies are deposited midway between coarse clastic and pure carbonate sediments this leads to a bimodal distribution of rapid depositional rates and invariably to the development of a basin in the intervening area to develop a model we combine concepts of depositional rate with knowledge of the middle ordovician carbonate to terrigenous clastic sequence of the southern appalachians deposition began on a shallow water ramp sloping gently eastward but everywhere within the photic zone an episode of tectonic subsidence differentiated this ramp into a shallow shelf on the northwest and a deep starved basin on the southeast separated by a linear shelf margin with organic build ups subsequent development of the sequence consisted of the filling of the deep basin first with pelagites then with turbidites during which the carbonate shelf was isolated from terrigenous deposition once the basin filled terrigenous deposition began to affect the shelf inhibition of carbonate deposition near the shelf edge led to formation of successively smaller basins within the old shelf area after the initial pulse of tectonic subsidence deposition of the sequence can be explained by sediment loading subsidence thus the ordovician sequence coupled with the concept of bimodal distribution of sedimentation rates in carbonate to terrigenous clastic facies patterns allows development of a model for basins adjacent to active tectonic lands five model stages are derived by application of calculated deposition rates and sediment loading along a transect away from the terrigenous source these stages are 1 an initial carbonate ramp stage followed by 2 a carbonate shelf starved deep basin stage 3 a carbonate shelf turbidite basin terrigenous shelf stage 4 a carbonate shelf narrowed and shallowed basin broad terrigenous shelf stage and finally 5 a stage in which the initial basin is filled a subsequent starved basin forms on the old carbonate shelf and a new carbonate shelf margin forms a few to tens of kilometres farther from the terrigenous source the model should be useful in predicting depositional facies in analogous basins

combining a computer simulation and eustatic events to date seismic sequence boundaries a case study of the neogene of the bahamas abstract this paper demonstrates that the principles of seismic sequence stratigraphy and the techniques of computer simulation can be combined to date the sedimentary section as an example it uses the neogene section of the western shelf of the straits of andros in the bahamas to this end type i second order seismic sequence boundaries were identified on a seismic cross section from the region these were used as brackets to correlate enclosed third order events with an eustatic sea level curve the interpreted section was then reproduced using a computer simulation program the simulation successfully reproduced the onlapping geometries of the shelf margin identified on the seismic section the early neogene fill of the straits of andros is assumed to have had an uncomplicated and uniform tectonic setting this simplified the inputs to the simulation which focused on capturing the sedimentary response to the eustatic changes inputs included a constant rate of subsidence of 0 009 m ka a uniform linearly increasing rate of carbonate accumulation from 28 5 ma to 11 5 ma and the sea level cycle chart of haq et al 1987 updated for the neogene with the absolute ages provided by berggren et al 1995 the subsequent graphical output shows a good match to the interpreted seismic this suggests that the amplitude and ages of the sea level changes as shown in the eustatic chart can be used to date the sequence boundaries for the neogene of the straits of andros it also establishes that for areas of known subsidence simulation techniques can be used to date seismic sections where biostratigraphic data are poor

cyclicity and paleoenvironmental dynamics rocknest platform northwest canada the superbly exposed rocknest formation northwest territories canada contains 140 to 160 shallowing upward cycles 1 to 15 m thick that contain distinctive marker beds and can be correlated for 200 km parallel to strike and 120 km perpendicular to strike cycles are grouped according to cycle base lithology which reflects paleogeographic position on the platform shale based cycles of the distal inner shelf pass westward into dolosiltite based cycles then into tufa based cycles of the shoal complex and then into grainstone based cycles of the outer shelf cycles are bounded by erosional surfaces that become less pronounced away from the shoal complex cycles formed in response to small asymmetric rapid rise slow fall eustatic oscillations in sea level 10 m during sea level rise rapid transgression and submergence of tidal flats occurred along the eastern margin of the shoal complex followed by eastward expansion of the shoal complex and slow progradation of tidal flats over lagoonal facies during sea level fall a glacio eustatic model for cyclicity accounts for the data favoring asymmetric eustatic sea level oscillations subaerial exposure and vadose diagenesis of platform during sea level falls arrested progradation and incomplete shoaling of many cycles and cycle periods of 20 000 to 100 000 yr 18 000 to 30 000 yr for rocknest inner shelf slopes ranged from 8 cm km average at high sea level stand to 2 cm km average at low sea level stand tidal flat progradation rates were 7 to 9 km 1 000 yr interaction of inner shelf slope sea level fall rate and sedimentation rate generates complete condensed or expanded cycle profiles one dimensional computer modeling reveals that sedimentation rates of shoal complex facies were 250 cm 1 000 yr that lag times in sedimentation following transgression may have ranged from zero on the shoal complex to 2 000 yr on the distal inner shelf and that subtidal sedimentation rates may have ranged from 80 cm 1 000 yr for the proximal inner shelf to 20 cm 1 000 yr for the distal inner shelf

synthetic stratigraphy of carbonate platform and basin systems a forward numerical model of the carbonate platform and basin depositional system aids in understanding the roles played by different variables in controlling the growth patterns of carbonate platforms and thus their internal facies architecture the numerical model simulates the two dimensional development of a carbonate platform and adjacent basin by successively calculating and depositing discrete sediment budgets generated over short time periods 10 sup 4 yr and displaying the results in synthetic cross sections through the carbonate buildup a series of model experiments shows that the effect of changing the eustatic sea level is largely dependent on the rate of subsidence in general sea level fluctuations tend to restrict progradation of the platform by producing periods of exposure of the platform top that decrease the overall sediment budget available for deposition on the marginal slope either increasing the amplitude or decreasing the period of the sea level cycle also restricts progradation which suggests that the higher order short period sea level cycles that are evident in the rock record may play an important role in controlling the cross sectional geometry of carbonate platforms forward models such as the one presented here may provide a basis for creating an inverse model that could be used tomore closely constrain the variables such as sediment production rate subsidence and sea level history that led to the cross sectional geometry observed in the field or in a seismic section less

miocene rifting of fuerteventura canary islands 1 the older geological units of the volcanic island of fuerteventura canary islands i e the so called basal complex and the lower part of the subaerial volcanic rocks show abundant structures indicative of a long lived period of miocene tectonic activity these structures include faults dike swarms kilometer scale folds tilted sequences and fissural and central volcanic edifices a detailed structural study based on geological mapping and the use of fault slip inversion techniques and statistical analysis of dike orientation has allowed the identification of three separated miocene deformation phases m d1 m d2 and m d3 the average extension directions determined for these phases are nw se nne ssw and ene wsw respectively a model of oceanic lithosphere rifting is proposed to account for this deformation history a buoyant anomalous sublithosphere mantle triggered the extension in the lithosphere beneath fuerteventura isolating it during the early and middle miocene from the plate scale collision regime predominant in the nw corner of the african plate

influence of water and sediment supply on the long term evolution of alluvial fans and deltas statistical characterization of basin filling sedimentation patterns 1 the temporal and spatial variability of sedimentation resulting from sediment storage and release and the lateral mobility of sediment transporting flows imparts fundamental patterns into the stratigraphic record recent studies show that paleoenvironmental allogenic signals preserved in stratigraphy may be contaminated by internally generated autogenic sedimentation patterns however it is unclear how the magnitude of autogenic dynamics is related to allogenic forcings utilizing statistical methods we quantify basin filling trends in three laboratory experiments where input water and sediment flux were varied we use the compensation index and compensation time scale to estimate the strength of compensation defined here as the tendency to fill topographic lows faster than would result from random deposit stacking and to estimate the time scales over which autogenic processes operate in the experiments topography of channelized deltas formed by noncohesive sediment was monitored in a basin experiencing temporally and spatially uniform relative subsidence each experiment resulted in construction of a stratigraphic package in excess of 25 channel depths thick we find that compensation strength in the experiments is not influenced by absolute magnitudes of water and sediment flux but does increase as a function of the ratio of water to sediment flux a compensation time scale defined as the maximum depth of a system s channels divided by the long term deposition rate accurately defines the maximum time scale at which autogenic dynamics occur in all experiments when applied to field scale systems we predict that autogenic dynamics occur out to time scales between 5 and 150 kyr

intraplate stresses a new tectonic mechanism for fluctuations of relative sea level stress variations in the lithosphere of a few hundred bars can explain the major part of the seismostratigraphic record at passive margins and intracratonic basins however to induce apparent sea level fluctuations with magnitudes greater than 50 m changes in stress level of more than 1 kbar are required these must be related to major reorganizations at convergent plate boundaries fragmentation of plates or collision processes specific rapid falls in the vail et al curves can be associated quantitatively with particular plate tectonic reorganizations of lithospheric stress fields the seismostratigraphic record may provide a new source of information on paleo stress fields to be correlated with results of independent numerical modeling of intraplate stresses

thermal subsidence and compaction in sedimentary basins application to baltimore canyon trough cooling with the subsidence of continental crust is likely to be an important mechanism for the formation of sedimentary basins if the lithosphere was initially very thin and sedimentation continued to fill the basin to the original depth of basement a similarity solution is possible in this paper the similarity solution is extended to include sediment compaction and a depth dependent thermal conductivity the similarity solution is also used to determine the thermal evolution and petroleum potential of sedimentary basins experience with similarity solutions in many branches of applied physics indicates that they commonly give good results even when the required assumptions are rather poor approximations an empirical subsidence relation valid for older basins is al o extended to include sediment compaction these results are applied to the evolution of the baltimore canyon trough on the outer continental margin of the eastern united states as given by the cost b 2 well good agreement is obtained with both the subsidence record and the present thermal gradient it is predicted that optimal thermal conditions for the conversion of kerogens to petroleum occur between depths of 4 and 6 km

computer simulation of the influence of basin physiography on condensed section deposition and maximum flooding abstract sequence stratigraphic analysis commonly involves the correlation of condensed sections which are widely used as chronostratigraphic markers condensed sections represent periods of very slow deposition due to sediment starvation and have generally been equated with the maximum flooding surface which is most commonly inferred to occur at sometime between the maximum rate of relative base level rise and the highest point of relative base level however similar sediment starvation can be produced by a rapid landward shift in the shoreline over large distances during the early stages of a base level rise over a very low gradient surface condensed section deposition therefore does not always correspond to a period between the maximum rate of relative base level rise and the highest point of relative base level but can be initiated earlier than the maximum rate of relative base level rise or conclude after the highest point of relative base level the initial timing and the duration of condensed section deposition is therefore influenced by basin physiography basin physiography can also contribute to a diachronous maximum flooding horizon lying at different levels throughout a basin because the rate of change in accommodation during fluctuating base level is partially dependent on the slope of the basin surface these principles are illustrated in the paper by computer simulations

out of our depth on the impossibility of fathoming eustasy from the stratigraphic record the evolution of a sedimentary basin s gross morphology depends upon 1 basement movement 2 sediment accumulation and compaction and 3 variations of eustasy with time thus if an accurate history of eustasy could be derived it would aid in our understanding of basin stratigraphy and help in the prediction of sediment geometry from described areas techniques which attempt to determine the magnitude of eustatic sea level excursions include the measurement of 1 the amount of sedimentary onlap onto the continental margins with and without the use of hypsometric curves 2 the thickness of marine sedimentary cycles and the elevation and distance between indicators of old strandlines 3 the perturbations on individual thermo tectonic subsidence curves and stacked crustal subsidence curves 4 the variations in deep ocean oxygen isotopes found in sediments and 5 the size of variables used in graphical and numerical simulations of basin fill in terms of tectonic behavior rates of sediment accumulation and eustasy which invert the problem to date a combination of the use of relative sea level charts derived from sediment onlap of the continental margin with dimensioning by oxygen isotopes responding to glacial events offers the best potential for relative tectono eustatic sea level curves but even this method can not produce a unique solution for absolute eustatic variations mathematical modelling shows that at best it is possible to obtain only the sum of tectonic basement subsidence and sea level variations from the above methods and at worst not even that simple a combination thus every proposed scheme to measure eustatic sea level excursions assumes some behavior for two of the three underlying processes tectonic movement of the basement sedimentary accumulation and eustatic sea level each scheme then determines the third process relative to the assumed model behavior of the other two it would seem that like king canute we cannot command the sea though we can still use undifferentiated relative tectono eustatic sea level curves to generate a family of solutions which are the product of a variety of absolute sea level curves and tectonic models each solution has then to be assessed in terms of geologic setting and the hypotheses it generates

stress in the indo australian plate cloetingh s and wortel r 1986 stress in the ind austr ian plate in b johnson and a w bally editors intraplate deformation characteristics processes and causes tectonophysics 132 49 67 we modelled the state of stress in the indo australian plate in order to investigate quantitatively variations observed in tectonic style the numerical procedure incorporates the dependence of slab pull and ridge push on the age of the oceanic lithosphere estimates are presented for the average net resistive forces at the himalayan collision zone the suction force acting on the overriding indo australian plate segment at the tonga kermadec trench and the drag at the base of the lithosphere our modelhng shows a concen ation of compressive stresses of the order of 3 5 lcbar in the ninetyeast ridge area the effects of the compressive resistance associated with himalayan collision and subduction of young lithosphere off the northern part of the sunda arc are focused in this region the stress field as calculated gives a consistent explanation for the observed concentration of seismic activity stein and okal 1978 and significant deformation in the oceanic crust weissel et al 1980 mcadoo and sandwell 1985 in the area the calculated stress field in the area adjacent to the southeast and central india ridges is characterized by tension parallel to the spreading axis this explains the concentration of near ridge normal faulting seismicity with t axes subparaile1 to the spreading ridge in the indian ocean as recently observed by bergman et al 1984 and wiens and stein 1984 the regional stress field along the strike of the sunda arc varies from compression seaward of and parallel to the sumatra trench segment to tension perpendicular to the java flores segment this explains the selective occurrence of well developed grabens seaward off the java flores segment of the trench observed by hilde 1983 our modelling shows that the observed rotation of the stress field denham et al 1979 in the australian continent is mainly the consequence of its geographic position relative to the surrounding trench segments and the variations of the forces acting on the down going slab in each of these the state of compression in west and central australia is induced by the action of resistive forces at the himalayan and banda arc collision zones the joint occurrence of high levels of compression in the plate s interior and normal faulting seismicity in the near ridge areas is a transient feature unique to the present dynamic situation of the indo australian plate

stratigraphic architecture of an experimental basin with interacting drainages abstract the stratigraphic architecture of intracontinental rift basins is defined by a dynamic relationship between depositional processes associated with the basin floor and flanking tributary streams the resulting depositional belts are sensitive to a variety of factors including basin geometry subsidence rate and sediment discharge the experimental earthscape run in 2006 xes06 examined the development of fluvial morphology and alluvial architecture as a function of subsidence and sediment flux in an experimental basin based on the form of a simple half graben sediments from tributary drainages were introduced into the axial stream through toe cutting and realignment of transverse drainage courses to parallel the prevailing axial flow direction transverse sediment contributions to the axial stream were almost equally apportioned over a wide range of sediment discharges tested in the experiments sediment tracers showed a larger contribution of footwall derived sediment into the axial belt probably due to more frequent and aggressive toe cutting by axial streams changes in the axial transverse deposit boundary to external forcing by subsidence and sediment discharge and relatively rapid intrastage stabilization of the depositional belts resembles the large scale self organization observed in moving boundaries that define the morphology of fluviodeltaic systems basin sedimentation was matched to subsidence in order to maintain a constant base level which made the location and width of the axial belt sensitive to the relative sediment fluxes from the transverse systems rather than the axis of maximum subsidence the asymmetrical subsidence pattern and the transverse fan morphology influenced the preservation of sedimentary sequences stage bounding stratigraphic lacunae were well preserved in the hanging wall succession providing a reliable record of basin development

sequence stratigraphy of experimental strata under known conditions of differential subsidence and variable base level sequence stratigraphy has been applied from reservoir to continental scales providing a scale independent model for predicting the spatial arrangement of depositional elements we examine experimental strata deposited in the experimental earthscape facility at st anthony falls laboratory focusing on stratigraphic surfaces defined by discordant contact geometries surfaces analogous to those delineated in the original work on seismic sequence stratigraphy in this controlled setting we directly evaluate critical sequence stratigraphic issues such as stratigraphic horizon development and time significance as well as the internal geometry and migration of the bounded strata against the known boundary conditions and depositional history four key stratigraphic disconformities defined by marine downlap marine onlap fluvial erosion and fluvial onlap are mapped and vary greatly in their relative degree of time transgression marine onlap and downlap contacts closely parallel topographic surfaces time surfaces and prior to burial approximate the instantaneous offshore topography these stratal bounding surfaces are also robust stratigraphic signals of relative base level fall and rise respectively marine onlap surfaces are of special interest they tend to be the best preserved discordance where widespread allogenic based onlap surfaces subdivide otherwise amalgamated depositional cycles amidst cryptic stacks of marine foresets however local autogenic based marine onlap discordances are present throughout the fill a critical distinguishing feature of allogenic onlap is the greater lateral persistence of the discordance surfaces defined by subaerial erosional truncation and fluvial onlap do not have geomorphic equivalence because channel processes continually modify the surface as the stratigraphic horizons are forming hence they are strongly time transgressive last the stacking arrangement of the preserved bounded strata is found to be a good time averaged representation of the mass balance history

simulation of carbonate depositional response to nutrient supply sunlight temperature salinity oxygen sea level and tectonism abstract this simulation is designed to reduce risk in predicting carbonate depositional facies and geometry in terms of the quantitative controls listed in the title the simulation reproduces the general 2 d geometric response of carbonates independent of facies type to variations in 1 eustatic sea level movement 2 movement of the substrate caused by compaction isostacy and tectonism and 3 variations in rates of accumulation in response to changes in nutrient supply sunlight salinity temperature and oxygen content it reproduces the three major geometric carbonate exploration plays sheet carbonates build ups of the shelf slope and basin and the break in slope clinoforms it tracks these plays as they accumulate through a series of iterative time steps determining the effects of stresses induced when the carbonates 1 keep pace with relative sea level change 2 start up slowly but catch up with sea level change and 3 drown

on a tectonic mechanism for regional sealevel variations abstract no satisfactory tectonic explanations have yet been offered for the apparent sealevel fluctuations of about 1 cm 1000 years and a magnitude of up to a few hundred meters that have been proposed by vail et al 1 we propose a mechanism that does appear to be able to explain these changes if horizontal stresses of the order of a few kilobars occur in the lithosphere and if changes in these stress fields occur on geological time scales the proposed model is one of an interaction between these stresses and the deflections of the lithosphere caused by sedimentary loading apparent sealevel changes of up to 100 m can be produced at the flanks of the sedimentary basins by this interaction the mechanism is most effective for young margins that are subject to rapid sediment loading by its nature the tectonic model can explain contemporaneous fluctuations in apparent sealevel in neighbouring depositional environments in principle it implies the possibility of regional correlations in different basinal settings

forward modeling of bank margin carbonate diagenesis we have applied forward modeling to investigate deposition and early diagenesis resulting from the interaction of high frequency glacioeustatic sea level fluctuation with bank margin carbonates in a subsiding basin the model output yields lithologies predicted by the static model but the relation of these lithologies to any particular subaerial exposure surface is obscured by the complexity of glacioeustatic sea level history the geologic history of our synthetic stratigraphic sequences could not be unraveled by traditional stratigraphic and sedimentologic study methods forward modeling is the preferred approach to analysis of carbonate sequences

synthetic coral reef terraces and variations of quaternary sea level abstract coral reef terraces on tectonically elevated coasts provide important data on variations of sea level in this paper a systematic approach is presented for the construction of synthetic reef terraces idealized reef terraces are generated assuming a constant rate of tectonic uplift and a harmonic variation of sea level with amplitudehwo and period it is further assumed that coral terraces grow only during periods of relative sea level rise the behavior is governed by the parameter u 2 hwo if u 1 no reef terraces form if 0 217

computer models of carbonate platform cycles driven by subsidence and eustasy six computer simulations of cycles developed on carbonate platforms were generated using maps a basic program four simulations employed a flat platform and sinusoidal sea level oscillations with heights ranging from 0 02 to 20 m but a constant 25 ka period superimposed over a constant relative sea level rise of 0 05 m ka the lower height oscillations might reasonably model variable subsidence rates whereas the higher oscillations model glacioeustatic sea level changes metre thick cycles were generated in all cases two simulations involved variations in periods of sinusoidal sea level variations and subsidence rates on a tilting platform the thicknesses of cycles generated are a function of both period of sea level oscillation and subsidence rate in geologic applications either the period of sea level oscillations or the subsidence rate needs to be known to determine the other we suggest that two end member models need to be considered for interpreting carbonate platform cycles 1 constant subsidence with variable sea level 2 constant sea level with variable subsidence combinations of these two end members are likely

post messinian evolution of the southeastern levant basin based on two dimensional stratigraphic simulation abstract the evolution of the southeastern levant basin following the messinian salinity crisis was interpreted using observations derived from seismic sections and well data and from output of a two dimensional forward stratigraphic simulation program sedpak the working assumption was that the thick evaporitic messinian sequence was generated in a shallow water albeit a topographically deep basin the sea level dropped at least 800 m below its present level and may have been as low as 1300 m the latter value representing the reconstructed depth of the top messinian in the deep part of the basin the top of the evaporitic sequence in that part of the basin was virtually horizontal at the end of the messinian crisis and thus may be used as a regional datum subsidence rates measured for the shelf and coastal plain of israel indicate a reduction of these rates for the pleistocene when compared to the pliocene during the pleistocene subsidence rates for the base slope increased and dictated the modern physiography of the margin earlier in the middle to late pliocene small scale salt movements occurred in the deep basin producing the fragmented and irregular shape of the m horizon the seismic event marking the top of the evaporitic sequence and deforming the overlying pliocene section the simulated rate of sediment supply indicates a constant increase over time for the pliocene and the pleistocene probably in response to an increased influx of nile derived along shelf sediment transport

the simulation of the sedimentary fill of basins an interactive computer simulation which erects models of sedimentary geometries by filling in a two dimensional basin from both sides with a combination of clastic sediment and or in situ and transported carbonate sediments is described the simulation program is implemented in c using graphical plotting functions data entry including the initial basin configuration the local tectonic behavior the sea level curves the amount and source direction of clastic sediment and the growth rates of carbonates as a function of water depth is performed interactively geometries of clastic and carbonate sediments evolve through time and respond to tectonic movement eustasy and sedimentation clastic modeling includes sedimentary bypass and erosion and sedimentation in alluvial and coastal plains marine shelf basin slope and basin floor settings carbonate modeling includes progradation the development of hard grounds downslope aprons keep up catch up back step and drowned reef settings as well as lagoonal and epeiric settings also included in the model are extensional vertical faulting of the basin sediment compaction and isostatic response to sediment loading sediment geometries are plotted on a graphics terminal as they are computed so the user can immediately view the results based on these observations parameters can be changed and the program rerun until the user is satisfied with the resultant geometry this paper includes output showing the simulation s sensitivity to eustatic sea level variations and variations in sedimentation and subsidence rates also shown are outputs demonstrating the modeling of some examples from the geologic section in the permian basin of west texas and the upper permian of the sichuan basin

use of fischer plots to define third order sea level curves in ordovician peritidal cyclic carbonates appalachians fischer plots in which cumulative cycle thickness corrected for linear subsidence is plotted against time were originally used in the study of triassic peritidal sequences to define short duration departures in relative sea level in the milankovitch range 104 to 105 yr however they also provide a means of assessing magnitude of third order 1 to 10 m y fluctuations in sea level which on the basis of their regional correlatability we ascribe to eustatic events

recent developments in quantitative stratigraphy abstract during the past 10 years about 150 scientists in 25 countries have collaborated under the auspices of the international geological correlation programme project no 148 evaluation and development of quantitative stratigraphical correlation techniques this paper reviews mathematical methods of stratigraphical correlation mainly in biostratigraphy but also in chronostratigraphy and lithostratigraphy sequencing methods treat the relative order of stratigraphic events such as the highest occurrences of fossil taxa as observed in many sections intervals between successive events in an ordered sequence can be estimated and the results expressed in linear time if a subgroup of the stratigraphical events can be dated recently such methods have been used to develop a new deep water benthic foraminiferal zonation for the cenozoic strata of the central and viking grabens north sea several regional hiatuses of 2 to 5 m y in duration can be recognized and matched to changes in sea level the same methods have been used for automated isochron contouring with error bars in depth or time units in cenozoic and cretaceous basins off eastern canada such information may be used for automated basin history analysis time successive assemblages of fossils can be established by using multivariate methods applied to co occurrences of events or by the method of unitary associations in conjunction with graph theory on the overlap of stratigraphical ranges other methods for stratigraphical correlation reviewed in this paper include the composite standard method and estimation of the age of chronostratigraphical boundaries using maximum likelihood and cubic spline interpolations attractions of quantitative stratigraphy are the use of rigorous methodology which highlights many properties of the data the ability to handle large and complex data bases in an objective manner and statistical evaluation of the uncertainty in the results generally little conceptual orientation is required in order to use these methods and thereby gain more information from a particular dataset

testing a seismic interpretation of great bahama bank with a computer simulation sixty million years of carbonate deposition were simulated to test an interpretation of platform development based on seismic data and limited well control from northwestern great bahama bank seismic profiles of the northwestern great bahama bank document the lateral growth potential of isolated platforms that were welded together by progradation to form the modern bank the mechanism we proposed responsible for an evolution from aggradation to progradation was sediment overproduction on the platform the excess of which was transported offbank and which caused a decrease in accommodation space on the marginal slope progradation occurred in pulses that were interpreted to be the result of third order sea level fluctuations to evaluate the proposed mechanism 15 input p rameters were used to model the platform evolution the simulation program which uses empirical relationships to model basin fill successfully reproduced the geometries seen on the seismic lines indicating that the proposed interplay of mechanisms could have built the observed platform architecture the simulation demonstrated in particular that in a setting like the bahamas a basin must be substantially filled before progradation can take place and that sea level changes can drive the pulses of progradation this implies that laterally stacked sequences often contain the record of sea level changes and therefore have potential use in sequence stratigraphy the simulation can also be used to estimate the quantitative importance of individual factors controlling aggradation and progradation in the bahamas we show how close the balance between aggradation and progradation is and how small changes in the rate of subsidence or accumulation can cause immediate switches from aggradation to progradation in particular we show that the rate of subsidence exerts the major control on the timing of progradation more so than basin width carbonate production rates similar to modern rates were required to produce the necessary sediment input for progradation which suggests that carbonate production has been consistently high since the early tertiary repeated exposure and erosion however have decreased the overall accumulation rate the simula ion also suggests that the asymmetric progradation in the bahamas was only possible where there were extreme differences between windward and leeward conditions with a maximum sediment input of 10 from the windward side

synthetic cyclic stratigraphy abstract there are many examples of cyclic stratigraphy in the sedimentary record in some cases this stratigraphy is attributed to periodic variations in sea level in this paper a harmonic variation in sea level is superimposed on a constant velocity of tectonic subsidence in order to generate synthetic cyclic stratigraphy maximum rates of sedimentation and erosion are considered the age dependence and water depth of the resulting cyclic stratigraphy is determined the results are compared with cyclic sedimentation in the pennsylvanian age sediments in northwestern kansas spatial variations of synthetic cyclic stratigraphy can be used to generate synthetic seismic stratigraphy

sedimentology and mechanism of a lacustrine syn rift fan delta system a case study of the paleogene gaobei slope belt bohai bay basin china abstract fan delta systems have long been studied as a kind of good hydrocarbon reservoirs although many models have been raised according to their local conditions there still exists some controversies regarding the formations of the ones developed in continental syn rift settings taking paleogene es32 3 of gaobei slope belt as an example this paper conducted a comprehensive geological study and a forward depositional modeling the results show that the sediment within the study area came mainly from the northeastern baigezhuang uplift and the northwestern xinanzhuang uplift over a short distance the sedimentary system is characterized by subaerial debris flow subaerial braided channels subaqueous distributary channels front sand bars and front sand sheets furthermore the study area is a balance filled basin that experienced a 3rd order normal regression followed by a transgression during the development of the study interval the results also show that a stable subsidence rate with small magnitude climate changes would be a plausible explain for the entire sequence of the fan delta system in the study area the tectonic subsidence was indeed the dominant driving force to a continental syn rift fan delta system although the climate sediment supply or lake level might bring some lower order e g 4th and 5th order superimpositions this paper proposed a likely model for fan deltas developed in continental syn rift settings which is expected to gain some insights into the forming mechanism and provide some supports for the reservoir characterization of similar and correlative sedimentary systems

sedimentary controls on the sequence stratigraphic architecture in intra cratonic basins an example from the lower permian shanxi formation ordos basin northern china intra cratonic basins are characterized by stable tectonic regimes closed depositional systems finite sizes of receiving basins and extremely low morphological gradients this paper examines the effect of sediment accumulation on the sequence stratigraphic architecture and quantitatively evaluates its controls on the development of intra cratonic sedimentary sequences using numerical modelling a well documented intra cratonic sedimentary sequence the lower permian shanxi formation in the ordos basin northern china was used to illustrate a sequence stratigraphic model developed for intra cratonic sedimentary basins the studied sequence is characterized by a typical backstepping or source ward retrogradation a 2 d simulation software sedpak and a 3 d simulation software sedsim were used to model the intra cratonic sequence the modelling results indicated that sediment accumulation alone can produce the classical retrogradational stratigraphic stacking patterns the sediment accumulation can 1 increase the retrogradational range of the original retrogradational stacking sequences 2 change an original aggradational stacking sequence to a retrogradational stacking one and 3 decrease the progradational range of an original progradational stacking sequence or 4 even change an original progradational stacking sequence to a retrogradational stacking sequence understanding the relationship between the sediment accumulation and the stratigraphic development in an intra cratonic basin is essential for interpreting the sequence stratigraphic framework and stacking patterns and for predicting the distribution of potential reservoir sand bodies within such basins this work enriches the classic sequence stratigraphic models by providing a new model for intra continental basins and offers new insight on hydrocarbon exploration in intra cratonic basins

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

unravelling the conundrum of river response to rising sea level from laboratory to field part i laboratory experiments the most recent deglaciation resulted in a global sea level rise of some 120 m over approximately 12 000 years in this part i of two parts a moving boundary numerical model is developed to predict the response of rivers to this rise the model was motivated by experiments at small scale which have identified two modes describing the transgression of a river mouth autoretreat without abandonment of the river delta no sediment starvation at the topset foreset break and sediment starved autoretreat with abandonment of the delta in the latter case transgression is far more rapid and its effects are felt much further upstream of the river mouth the moving boundary numerical model is checked against experiments the generally favourable results of the check motivate adaptation of the model to describe the response of the much larger fly strickland river system papua new guinea to holocene sea level rise this is done in the companion paper part ii

refining the radiocarbon time scale the annually formed layers of sediment from lake suigetsu have the potential to reveal information about environmental change in japan over the past 50 000 years with chronological precision as good as or better than the greenland ice cores 1 such precision is invaluable for synchronizing records and evaluating leads and lags in the global climate system perhaps even more important the fragile leaves and seeds hidden within these layers see the figure provide a record of past atmospheric concentration of 14c the radioactive isotope of carbon as reported by bronk ramsey et al on page 370 of this issue 2 this record stretches back over the full length of the radiocarbon age scale the results are invaluable for improving the accuracy with which radiocarbon dates can be converted to the calendar time scale

depth dependent sedimentation and the flexural edge effect in epeiric seas measuring water depth relative to the lithosphere s flexural wavelength in sediments deposited within about 300 km of shore downlap is an expected consequence of the lithospheric flexure associated with the edge of sediment and water loads at an epeiric sea s shoreline for loose carbonate sediments in a typical slowly transgressing epeiric sea the dependence of sediment accumulation rate ds dt on water depth h tends to magnify the otherwise subtle downlap making it more practical to determine the dimensions of the water load from the dimensions of the preserved sediment load synthetic stratigraphies for a steadily transgressing sea in which ds dt h the form of depth dependence previously demonstrated for the eastern north american middle ordovician sea reveal downlap of a certain form and scale as the signature of near parity between sediment and water loads in the nearshore zone the k bentonite outlined internal geometry of middle ordovician strata that lap onto the wisconsin arch shows this signature comparison of the paleontologically quantified relative bathy

climatically driven sedimentary cycles in the late miocene sediments of the pannonian basin hungary abstract by detailed cycle analysis of marginal mostly delta plain facies successions of pannonian sediments the frequency of water level changes of the late miocene pannonian lake hungary can be identified cycle analysis is presented with the object of defining the orbital record preserved in the strata we use the bed thickness as input data for our cycle analysis statistical analysis revealed a slow upward increase of both the frequency and thickness of sand beds in the boreholes resulting from infilling of the lake by a basinward migration of the marginal facies cycles of different order were detected in the sediments the higher order cycles are very close to or are equivalent with the milankovitch climatic cycles 19 ka caused by precession 50 ka caused by obliquity and 400 ka is the longer period of eccentricity the longer 1 m y cycle is very poorly developed here it is probably the analogue of the 3rd order global climatic cycle cycle analysis suggests that one of the main controlling factors of the water level changes of the pannonian lake was high frequency climatic oscillations the long term climatic changes only had a faint impact on the sediments the record of the 3rd order water level changes is very subtle our results show that the water level changes followed the rhythm of that of the eustatic changes but being asynchronous to them i e at high sea level stage the pannonian lake level was low and vice versa