a different perspective on glauconite as a chronometer for geologic time scale studies there are advocates of the use of glauconite as a chronometer for geologic time scale studies who insist that if the geohistory of the sample in question is known in detail one can ascertain before hand that the sample will yield a radiometric result that is accurate in the geological sense examples are presented indicating that while some glauconite samples may yield the correct age within their assigned analytical uncertainties when compared to high temperature minerals others clearly do not and are too young by varying degrees the outright acceptance of published results on glauconite can result in erroneous age estimates of various biostratigraphic levels and stage or epoch boundaries

shelf construction in a foreland basin storm beds shelf sandbodies and shelf slope depositional sequences in the upper cretaceous mesaverde group book cliffs utah the upper cretaceous campanian kenilworth member of the blackhawk formation mesaverde group is part of a series of strand plain sandstones that intertongue with and overstep the shelfal shales of the western interior basin of north america analysis of this section at a combination of small sedimentological and large stratigraphical scales reveals the dynamics of progradation of a shelf slope sequence into a subsiding foreland basin four major lithofacies are present in the upper mancos and kenilworth beds of the book cliffs a lag sandstone and channel fill shale lithofacies constitutes the thin basal transgressive sequence which rests on a marine erosion surface it was deposited in an outer shelf environment shale interbedded sandstone and shale and amalgamated sandstone lithofacies were deposited over the transgressive lag sandstone lithofacies as a wave dominated delta and its flanking strand plains prograded seaward analysis of grain size and primary structures in kenilworth beds indicates that there are four basic strata types which combine to build the observed lithofacies the fine to very fine grained graded strata of the interbedded facies are tempestites deposited out of suspension by alongshelf storm flows geostrophic flows there is no need to call on cross shelf turbidity currents density underflows to explain their presence very fine to fine grained hummocky strata are likewise suspension deposits created by waning storm flows but were deposited under conditions of more intense wave agitation on the middle shoreface cross strata sets in this region are bed load deposits that accumulated on the upper shore face in the surf zone lag strata are multi event bed load deposits that are the product of prolonged storm winnowing they occur on transgressive surfaces while the graded beds are tempestites in the strict sense all four classes of strata are storm deposits the distribution of strata types and their palaeocurrent orientations suggests a model of the kenilworth transport system driven by downwelling coastal storm flows and probably by a northeasterly alongshore pressure gradient the stratification patterns shift systematically from upper shoreface to lower shoreface and inner shelf lithofacies partly because of a reduction in fluid power expenditure with increasing water depth but also because of progressive sorting which resulted in a decrease in grain size in the sediment load delivered to successive downstream environments the kenilworth member and an isolated outlier the hatch mesa lentil constitute a delta prodelta shelf depositional system their rhythmically bedded lenticular sandstone and shale successions are a prodelta shelf facies and may be prodelta plume deposits major upper cretaceous sandstone tongues in the book cliffs are underlain by erosional surfaces like that beneath the blackhawk formation which extend for many tens of kilometres into the mancos shale these surfaces are the boundaries of upper cretaceous depositional sequences the sequences are large scale genetic stratigraphic units they result from the arranging of facies into depositional systems the depositional systems are in turn stacked in repeating arrays which constitute the depositional sequences the anatomy of these foreland basin sequences differs

element localization in archaeological bone using synchrotron radiation x ray fluorescence identification of biogenic uptake abstract trace element analysis related to archaeological bone is viewed as one way to determine levels of element exposure in past populations this area of research is complex because there is the potential for the incorporation of trace elements from the burial environment into archaeological bone we tested the hypothesis that matching the spatial distribution of trace elements within cortical bone with the biological structures would provide evidence of biogenic uptake we examined samples from a non segregated royal british naval cemetery 1793 1822 in antigua west indies a key historical question related to this population was the extent of exposure to lead and the resulting health effects images from conventional light microscopy histological analysis of the bone samples were matched with elemental maps of calcium strontium and lead that were created through the use of synchrotron radiation x ray fluorescence sr xrf biogenic uptake of both strontium and lead was indicated based on the localization of these trace elements within discreet microstructural elements the successful integration of histological information with xrf data is a powerful technique for the interpretation of past biological events through trace elements

eustatic sea level changes interpreted from seismic stratigraphy a critique of the methodology with particular reference to the north sea jurassic record seismic stratigraphic methods for interpreting eustatic sea level change are based on generalized stratigraphic models and chronostratigraphic interpretations that have not been substantiated by publication of the necessary basic supportive data chronostratigraphic correlations of sea level change curves between basins are based partly on circular reasoning onlap and offlap seismic models may not indicate sea level change but flexural subsidence facies shifts or changes in sea level in the opposite direction to that proposed resolution of some of these problems may be achieved by publication of basic data now in confidential industry files the widely acclaimed vail curves should not be used as templates for basin correlation until such data have been provided and such use should be supported by appropriate conventional lithostratigraphic and biostratigraphic documentation from each new basin where such data have been made available as with the north sea jurassic serious questions of interpretation are raised

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

fluvial inertia dominated deltaic deposition in the namurian carboniferous of northern england the namurian upper carboniferous scar house beds of yorkshire northern england are an example of a fluvial dominated deltaic sequence that cannot be adequately described using existing classification schemes for deltas for substantial periods of the scar house delta history inertial processes and hyperpycnal mixing prevailed in the river mouth area due to repeated frequent flooding in the distributary system this generated voluminous density currents which deposited their sandy loads in successively stacked lobes beyond the river mouth bar in the prodelta area the position of a lobe was directly controlled by the position of an active river mouth only during periods of low discharge in the distributary system did homo and hypopycnal mixing take place in these periods frictional and buoyant forces operated and sand was deposited from tractional sheet flow on the mouth bar while mudstone was laid down in the otherwise density current dominated prodelta because of the dominantly hyperpycnal mixing mode the river effluent experienced a low lateral spread causing an elongate delta lobe to form that in geometry can be compared with some recent and ancient bar finger sands important differences exist in terms of dominant depositional processes however most other bar finger sands were controlled by a hypopycnal mixing mode and buoyant forces e g south pass mississippi while the scar house delta was controlled by hyperpycnal mixing and inertial forces this study shows that similar sand body geometries can be generated from different river mouth processes in the future particularly in the field of hydrocarbon exploration there may be a need to classify deltas both in terms of geometry and dominant river mouth processes in that respect the scar house beds represent a fluvial inertia dominated elongate delta

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

devonian carboniferous tectonics and basin deformation in the cabot strait area eastern canada the magdalen basin in the cabot strait bay st george area was a major depocenter for devonian carboniferous sediments in eastern canada structure within the basin is complex and is characterized by northeast and east trending mainly dextral strike slip faults associated with the bend in the appalachian orogenic belt known as the st lawrence promontory under the cabot strait two linear grabens parallel the major fault trends and preserve up to 6 km of devonian carboniferous sedimentary rocks comprising mainly coarse grained terrigenous clastics with a lower carboniferous transgressive episode recorded by marine carbonates evaporites and fine grained clastics several unconformities within the sedimentary succession record deformation associated with movement alo g the regional strike slip faults minor local unconformities are interpreted within the upper horton early visean upper barachois late westphalian and post pennsylvanian successions a major unconformity cuts out most of the namurian and westphalian section in the study area and can be correlated on a regional scale kinematic strain partitioning along the master cabot fault led to the development of doubly vergent compressional structures within a wrench borderland this was complicated by transpressive deformation at a restraining bend in the master fault and by deformation associated with overstepped ends of splays of the regional fault system the magdalen basin probably formed in an early phase of post acadian extension and was later reactivated by regional strike slip faults the presence of thick source and reservoir rocks as well as diverse trapping possibilities and a favorable burial and maturation history indicate that the cabot strait area has good potential for accumulating and preserving petroleum

effects of climate tectonics and sea level changes on rhythmic bedding patterns in the niobrara formation upper cretaceous u s western interior regional correlation of interbedded pelagic hemipelagic limestones and calcareous shales of the fort hays limestone member of the niobrara formation confirms development of at least two levels of cyclicity occurrence of time parallel rhythmically deposited beds that can be correlated over distances exceeding 800 km lends strong support to the hypothesis that these cycles were induced by milankovitch type climatic forcing however visual observation and fourier analysis of variations in shale and limestone thickness demonstrate that the pattern of fort hays cyclicity lacks regional uniformity complications in the cyclic pattern may have resulted from the influence of orbital parameters having differing periodicities additionally departures from simple cyclical patterns resulted from sedimentary effects of the sevier orogeny and from erosional events associated with sea level changes documentation of thickness variations within the regionally persistent fort hays bedding sequence furnishes a basis for fine scale analysis of cretaceous crustal movements within the western interior seaway

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

origin of cratonic basins tectonic subsidence curves show that the illinois michigan and williston basins formed by initial fault controlled mechanical subsidence during rifting and by subsequent thermal subsidence thermal subsidence began around 525 ma in the illinois basin 520 460 ma in the michigan basin and 530 500 ma in the williston basin in the illinois basin a second subsidence episode middle mississippian through early permian was caused by flexural foreland subsidence in response to the alleghanian hercynian orogeny resurgent permian rifting in the illinois basin is inferred because of intrusion of well dated permian alnoites such intrusive rocks are normally associated with rifting processes the process of formation of these cratonic basins remains controversial past workers have suggested mantle phase changes at the base of the crust mechanical subsidence in response to isostatically uncompensated excess mass following igneous intrusions intrusion of mantle plumes into the crust or regional thermal metamorphic events as causes of basin initiation cratonic basins of north america europe africa and south america share common ages of formation around 550 to 500 ma histories of sediment accumulation temporal volume changes of sediment fills and common dates of interregional unconformities their common date of formation suggests initiation of cratonic basins in response to breakup of a late precambrian super continent this supercontinent acted as a heat lens that caused partial melting of the lower crust and upper mantle followed by emplacement of anorogenic granites during extensional tectonics in response to supercontinent breakup intrusion of anorogenic granites and other partially melted intrusive rocks weakened continental lithosphere thus providing a zone of localized regional stretching and permitting formation of cratonic basins almost simultaneously over sites of intrusion of these anorogenic granites and other partially melted intrusive rocks

transgressive regressive cycles and the occurrence of coal in some upper cretaceous strata of utah cenomanian santonian strata contain about 60 of the known cretaceous coal resources of utah the areal and temporal distribution of these resources can be related to the transgressive regressive history of the western shoreline of the interior cretaceous seaway two orders of transgressive regressive cycles the larger of which corresponds to third order cycles of vail et al are deemed important in analyzing the distribution of coal in utah the largest coal fields are associated with extensive vertical stacking of the deposits of what are here termed fourth order cycles at the transgressive and regressive maxima of third order cycles deposits of transgressive and regressive phases of third order cycles contain only minor amounts of coal this genetic relationship may prove useful in predicting areas of important cretaceous coal resources in deeper parts of structural basins in the rocky mountain region

paleogeographic and paleotectonic setting of laramide sedimentary basins in the central rocky mountain region in the rocky mountain region between central montana and central new mexico sedimentologically isolated nonmarine basins were produced by basement deformation during the laramide orogeny within the area formerly occupied by a broad late cretaceous foreland basin in which laterally continuous marine facies had accumulated previously laramide structures of varying trend and scale reflect heterogeneity of crustal strain caused by shear between the continental lithosphere and an underlying subhorizontal slab of subducted oceanic lithosphere laramide basins include perimeter basins along the cratonic periphery of the arcuate laramide province axial basins along a north south intramontane trend and ponded basins located farther west closer to the overthrust belt twelve specific stratigraphic and sedimentologic criteria for the onset duration and termination of laramide deformation allow the chronology of basin development to be inferred independently for each basin maastrichtian initiation of laramide deformation was approximately synchronous throughout the laramide province but termination of laramide deformation was systematically diachronous from north to south between early and late eocene time widespread eocene erosion surfaces truncate syntectonic laramide sequences and are overlain by largely volcanic and volcaniclastic post laramide strata of eocene age in the north and oligocene age in the south fluvial depositional systems draining toward the great plains were dominant in perimeter and axial basins but ponded basins were occupied at times by large lakes that served as regional sediment traps paleocene drainages from ponded basins also led eastward toward the continental interior but partly interconnected lakes that developed within several ponded basins by mid eocene time were either closed hydrologically or else they drained westward into the tyee paleoriver of the pacific northwest

transgressions and regressions a model for the influence of tectonic subsidence deposition and eustasy with application to quaternary and carboniferous examples the position of a coastline in time and space is determined by 1 the vertical displacement and or tilting of the depositional surface 2 the rate of sediment accumulation or erosion across that surface and 3 variation of sea level all three rates of change may vary through time we present computer simulations of coastline movements that illustrate the interaction of the above variables with 1 and 2 held at various defined levels whilst 3 is varied according to the late quaternary glacio eustatic sea level curve the corinth canal section in central greece exposes uplifted late quaternary coastal transgressive cycles each of which may be related to a radiometrically dated c 100 ka duration cycle of sea level change observed stratigraphic sequence geometries are predicted by forward modelling based on the known glacio eustatic history over the last 430 ka milankovitch orbital parameters are calculated for the carboniferous period the obliquity and precession parameters are found to have been significantly shorter than at present a simulation is presented of the effects of sea level changes across low gradient fluvio deltaic environments such as existed in northern england and other parts of the laurentian continental margin during upper carboniferous time

depositional model for understanding geometry of cretaceous coals major coal seams rock springs formation green river basin wyoming the upper cretaceous rock springs formation of the green river basin ranges from marine strata of prodelta origin to marginal marine and nonmarine equivalents of delta front and delta plain fluvial strata coal exploration drill holes measured sections and underground mine data have been analyzed to reconstruct the depositional setting of the rock springs formation extensive sheet sandstones are inferred to be delta front deposits reflecting the cuspate to arcuate geometry of wave dominated deltaic deposits extensive coal deposits up to 22 ft 6 7 m thick that developed on top of delta front sandstones extend for 15 mi 24 1 km along depositional dip and 36 mi 58 km along depositional strike these coal deposits are referred to as type a coal seams coal deposits 1 17 ft 0 3 5 2 m thick that developed in upper delta plain fluvial environments are less than 20 mi 32 2 km in length these deposits are referred to as type b coal seams type c seams are persistent thin coal deposits 1 8 ft 0 3 2 4 m thick developed on top of delta plain fluvial deposits less than 25 mi 40 2 km in length and they mark the delta lobe abandonment phase approximately 15 major coal zones exist in the rock springs formation the geometry of types a b and c reflects a genetic relationship to both deltaic and fluvial units in the marginal marine and nonmarine components of the rock springs formation a model for predicting coal seam thickness and continuity is believed to be applicable to additional exploration in the green river basin and in other cretaceous coal bearing basins in the western interior

cyclic facies architecture as a key to depositional controls in a distal foredeep campanian mesaverde group wyoming usa the mesaverde group consists of a thick wedge of fluvial littoral deltaic and shallow marine clastics shed into the cretaceous western interior seaway of north america the western parts of the seaway lay within the strongly subsiding foredeep of the active sevier fold and thrust belt further to the west the study area is located east of the axis of maximum subsidence and is thus in a favourable position to record competing effects of eustasy sediment supply and thrust load induced subsidence facies and sequence analysis carried out on high quality outcrop and well log data led to the recognition of a complex depositional cycle hierarchy within the typical storm and wave dominated inner shelf shoreface strand plain and delta systems of the mesaverde

thrust loads and foreland basin evolution cretaceous western united states two dimensional modeling of loading during the formation of the idaho wyoming thrust belt shows that regional isostatic compensation by flexure of an elastic lithosphere is sufficient to control the formation of a foreland basin the flexural rigidity of the lithosphere is inferred to have been approximately 1023 nm 1030 dyne cm on the basis of palinspastic comparison of predicted downwarping due to the thrust plate loads to the shape of the sedimentary wedge on the west side of the cretaceous western interior seaway erosion of part of the uplifted thrust plates redistributed the load depositing it farther to the east thereby causing subsidence over a much wider area than could have been accomplished only by the loading by thrust plates paleotopography after major cretaceous thrust events was calculated the resulting mountainous terrain gentle alluvial plain and flat sea floor correspond well with the topography of the modern foreland thrust belt and basin system in the andes of south america and to paleogeographic reconstructions in the western united states thrust belt topography is controlled by the subsurface geometry of the thrust faults particularly the positions of ramp zones and by isostatic subsidence

onlap offlap and the origin of unconformity bounded depositional sequences christie blick n 1991 onlap ofttap and the origin of unconformity bounded depositional sequences mar geol 97 35 56 unconformity bounded depositional sequences represent the fundamental building blocks of sedimentary successions they are typically characterized by onlap at the base and by offlap at the top and they tend to be markedly asymmetrical with onlap accounting for a larger part of any cycle of sedimentation than offlap offlap cannot be attributed solely to erosional truncation but instead implies that sequence boundaries develop over a finite interval of time depositional sequences are commonly associated with a cyclic arrangement of facies but transgressive regressive cycles are out of phase with respect to sequence boundaries which in down dip locations are both overlain and underlain by progradational deposits and hence form during times of regression of the shoreline these observations are used to develop some ideas about the origin of unconformity bounded sequences with reference to the inter related roles of changes in depositional base level and sediment supply in particular it is shown than onlap and offlap are due to lateral migration of a line of critical bypassing defined so as to incorporate the effects of sediment loading and compaction as well as the rate of change of elevation with respect to sea level downward shifts in onlap may be achieved by either an increase in the rate of eustatic fall or a decrease in the rate of tectonic subsidence and it is premature to assume that eustatic and tectonic controls on sea level may be distinguished solely on the basis of the frequency of depositional cyclicity small shifts in the position of onlap can also be produced by changes in sediment supply and more attention needs to be paid to the influence of sediment supply in the development of minor boundaries unconformities related to eustatic fluctuations are thought to correspond approximately to times of relatively rapid sea level fall inflection points but questions remain about the existence of possible leads and lags of up to cycle and hence about the degree to which sequence boundaries of eustatic origin may vary in age both within a given basin and from one basin to another

ammonite correlation of the uppermost campanian of western europe the u s gulf coast atlantic seaboard and western interior and the numerical age of the base of the maastrichtian

cretaceous rhythmic bedding sequences a plausible link between orbital variations and climate abstract simple oscillation cycles have been recognized in cretaceous pelagic sequences as a marked periodicity in carbonate and or organic carbon content the estimated periodicities of these cycles resemble milankovitch type variations in orbital elements however during warm geologic periods the nature of the link between orbital variations and the sedimentary record has been problematic climate model studies show that the intensity of continental margin precipitation in specific low latitude regions is a function of land sea thermal contrast which is sensitive to orbital variations cretaceous climate model simulations are characterized by regions of intense precipitation the locations of which are controlled by geographic configuration in particular in the model simulation the northern margin of the tethys ocean has all the climatic characteristics necessary to exhibit a sensitivity to orbital variations detailed studies of the biota sedimentology and geochemistry of the bedding rhythms in greenhorn cyclothem in the western interior seaway of north america are best interpreted in terms of variations in precipitation runoff and stable stratification of the seaway combined the geologic and model studies support a link between orbital periodicities variations of intense precipitation associated with specific paleogeographic situations and cretaceous bedding patterns this hypothesis has important implications for the sensitivity of the atmosphere hydrosphere lithosphere system to external forcing

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

tectonic subsidence flexure and global changes of sea level tectonic models for the evolution of passive continental margins predict that following rifting sediments should progressively onlap basement at the edge of a margin as the lithosphere cools and increases its flexural rigidity with age the pattern of modelled onlap is strikingly similar to that used by vail and colleagues to estimate sea level rise through geological time this similarity suggests that major portions of stratigraphical sequences at margins may have a tectonic rather than eustatic control the patterns of onlap used by vail and colleagues may be widespread however because several widely separated passive margins rifted at similar times but they are unlikely to be worldwide

coherence of surf zone and shelf current flow on the texas u s a coastal margin implications for interpretation of paleo current measurements in ancient coastal sequences abstract measurements from the texas coastal margin a microtidal fetch limited wind dominated shallow sea reveal a strong correlation in timing and direction of surf zone and shelf flow during both fairweather and storm events coherence of current motion is statistically significant at many frequencies cycle lengths and is highest during storm events the lack of a significant lag between surf zone and shelf flow indicates that both respond rapidly to changes in the magnitude and direction of the wind field the alongshelf component of the wind stress is a major force in generating currents both on the shelf and in the surf zone as exhibited by comparison of numerical predictions and observed velocities during the 140 day study period current flow was mainly directed alongshelf to the northeast and southwest driven by southerly fairweather and northerly storm winds respectively however the threshold for generation and migration of megaripple bedforms in upper shoreface bar troughs was exceeded only during storm events when surf zone flow was oriented to the southwest along the coast this observation coupled with the knowledge that storm generated bedforms have the highest preservation potential imply that multi event traction bedding in upper shoreface bar troughs of analogous ancient environments will be dominated by unimodal alongshore current orientations large scale bedforms which respond to this time averaged flow on the shelf are expected to display a similar unimodal alongshelf orientation with a low angle deviation toward the offshore direction careful study of paleo current measurements in a well documented ancient shelf to shoreline sequence in the cretaceous of new mexico reflects this similarity in transport kinematics

development of tectonic cyclothems in rift pull apart and foreland basins sedimentary response to episodic tectonism the thickest part of asymmetric rift pull apart and foreland basin fills commonly consists of large scale hundreds to thousands of metres thick tectonically generated cyclothems of fine grained marine lacustrine or longitudinal fluvial deposits and coarse grained transverse braid plain or alluvial fan deposits the appearance of coarse clastics in these basin fills is typically noted as the time of tectonically rejuvenated source area uplift based on the conceptual tie between relief and coarse grain size and on the application of the davis theory of landform development we propose the opposite interpretation that the commencement of fine grained sedimentation above coarse grained deposits in a tectonic cyclothem is the best indicator of renewed tectonic activity this reinterpretation is more consistent with 1 modern examples 2 the consideration of source area and sedimentary basin geomorphology 3 the disparity between the reaction rates of the various environments to subsidence 4 the disparity between the rates of tectonic uplift and erosion and 5 the controls on elastic wedge progradation in our model extensive coarse grained clastic wedge progradation is an indicator of tectonically quiescent phases

stratigraphic simulation of sedimentary basins concepts and calibration a two dimensional stratigraphic simulation program based on semiempirical algorithms has been successfully applied to clastic carbonate and mixed clastic carbonate depositional regimes the program may be used to predict reservoir distribution to constrain interpretations of well and seismic data to test exploration scenarios in frontier basins and to evaluate the fundamental controls on basin stratigraphy applications to seismic and well log data sets from main pass u s gulf coast offshore sarawak malaysia and the baltimore canyon u s east coast demonstrate that the program simulates stratigraphy on a basin wide scale as well as on the scale of individual prospects the main pass section is an offlapping sequence of neogene clastics the model simulates 17 m y of geologic history at a 200 000 yr resolution and reproduces gross basin geometry major sequence boundaries depth and location of nearshore marine sands intervals of sediment bypass into deep water shelf margin positions and paleobathymetry three neogene carbonate buildups of central luconia offshore sarawak malaysia were simulated using a sea level history optimized to reproduce the carbonate growth anatomy the model reproduced observed seismic reflection geometries and transgressive aggradational progradational retrogradational and subaerial exposure phases the program has also simulated jurassic pleistocene basin and stratigraphic sequence geometries and mixed clastic carbonate facies distribution along a 300 km regional dip line of the baltimore canyon trough modeled features of interest include a progradational middle jurassic carbonate margin punctuated by clastic deposition during sea level lowstands and a late jurassic early cretaceous aggradational carbonate margin culminating in the development and subsequent drowning of isolated carbonate buildups simulated bathymetries facies relations and subaerial exposure surfaces for the early cretaceous aggradation margin are consistent with detailed petrographic paleontologic and seismic stratigraphic interpretations