growth faults and fault related structures of prograding terrigenous clastic continental margins abstract growth faults are the structural manifestation of the inherent tensional stress regime that is focused at the upwardly convex margin of a prograding continental platform extension and faulting may be triggered by either gravitational gliding or spreading extensional faulting results in both lateral translation and subsidence of the down faulted sediment mass consequently outer platform and upper slope facies are expanded and disproportionately preserved relative to paralic or deep water facies specific growth fault geometries and patterns are related in part to the depositional history and style of the prograding margin unusually continuous and low angle master faults are proposed to result from a history of rapid progradation of a deltaic depocenter onto an older retrograditional slope growth fault zones function as major conduits for large scale circulation of both ground waters and hydrocarbon fluids within the sedimentary prism

mio pliocene to pleistocene paleotopographic evolution of brittany france from a sequence stratigraphic analysis relative influence of tectonics and climate the mio pliocene in western europe is a period of major climatic and tectonic change with important topographic consequences the aim of this paper is to reconstruct these topographic changes based on sedimentological analysis and sequence stratigraphy for the armorican massif western france and to discuss their significance the mio pliocene sands of the armorican massif red sands are mainly preserved in paleovalleys and are characterized by extensive fluvial sheetflood deposits with low preservation and by pass facies this sedimentological study shows that the red sands correspond to three main sedimentary environments fluvial alluvial fan low sinuosity rivers and braided rivers estuarine and some rare open marine deposits marine bioclastic sands faluns of french authors two orders of sequences have been correlated across brittany with one or two minor a s cycles comprised within the retrogradational trend of a major cycle the unconformity at the base of the lower cycle is more marked than the unconformity observed at the top which corresponds to a re incision of the paleovalley network a comparison of the results of the sequence stratigraphy analysis with eustatic variations and tectonic events during the mio pliocene allows 1 to discuss their influence on the evolution of the armorican massif and 2 to compare the stratigraphic record with other west european basins the unconformity observed at the base of the first minor cycle may be attributed to serravallian tortonian tectonic activity and or eustatic fall and the unconformity of the second minor cycle may be attributed to late tortonian early messinian tectonic activity the earlier unconformity is coeval with the development of a smooth paleovalley network compared to the jagged present day relief a single episode of mio pliocene deformation recorded in brittany may be dated as zanclean thus explaining the lack of the maximum flooding surface except in isolated areas from this study five paleogeographic maps were drawn up also indicating paleocurrent directions three maps for the lower cycle tortonian retrogradational trend late tortonian to early messinian maximum flooding surface and messinian progradational trend and two for the upper cycle pliocene retrogradational trend and piacenzian maximum flooding surface these maps show 1 the variations of paleocurrent directions during the mio pliocene 2 the extent of estuarine environments during the maximum flooding intervals and 3 a paleodrainage watershed oriented nnw sse following the regional quessoy nort sur erdre fault during the retrogradational trend of the upper cycle and possibly during the progradational trend of the lower cycle the present day morphology of the armorican massif is characterized by 1 incised

do seismic reflections necessarily have chronostratigraphic significance many seismic reflections from within sedimentary successions are thought to be generated along stratal surfaces because those surfaces are laterally continuous and have marked acoustic impedance contrasts as stratal surfaces are isochronous those reflections are then also taken as being chronostratigraphically significant in contrast seismic reflections are thought not to be generated along the boundaries of lithostratigraphic units because those boundaries are discontinuous and gradational nevertheless synthetic seismic analysis shows that seismic reflections should in many circumstances be expected to follow lithostratigraphic unit boundaries not stratal surfaces as these lithostratigraphic unit boundaries will generally be diachronous seismic reflections from within sedimentary successions should evidently not be treated as necessarily having chronostratigraphic significance

lacustrine paleoshoreline determination under established sequence stratigraphic framework and its controls on sand bodies and hydrocarbon accumulations abstract the lacustrine palaeoshoreline is the intersection between lake level and ancient land in geological time and it marks the boundary between onshore deposits and subaqueous deposits identifying lacustrine paleoshorelines is the process of reconstructing past depositional environments the study establishes the sequence stratigraphic framework of the ordos yanchang formation based on a comprehensive analysis of seismic and well log data the hierarchical lithological cycles is determined through fourier transform and band pass filtering analysis of gramma ray data subsequently the lacustrine paleoshoreline is determined using the shoreline hierarchical control method under the established sequence stratigraphic framework with additional evidence from cores well logs and cutting and seismic sections lacustrine paleoshorelines has controlling effects on the sand bodies and hydrocarbon accumulations for one thing different types of paleoshoreline control the genesis of sand bodies and the location of paleoshoreline in sag basin controls sand body distribution furthermore the migration of lacustrine paleoshoreline in sag basin indicates stacking patterns of sand bodies and hydrocarbon accumulations

coal facies studies in spain this work is a synthesis of the distribution of the main coal basins and sub basins in spain as well as the research carried out on their coal facies the coal fields are distributed through the paleozoic mainly pennsylvanian mesozoic cretaceous and cenozoic times peats also exist in the southeast spain granada area although these types of deposits are not included in this review spanish coal basins are both of a paralic and intramontane type and the coal rank is highly variable from lignite in the case of the younger coal seams to anthracite for those of carboniferous age

depositional architecture of growth fault related wave dominated shelf edge deltas of the oligocene frio formation in corpus christi bay texas abstract growth faults within the frio formation define six subbasins on the south texas shelf and add to the complexity of the sediment dispersal along the shelf margin these growth faults influenced sediment pathways controlled sediment partition and provided increased accommodation for deltaic depocenters rollover and thickening of sediments occur on the downthrown side of growth faults with offsets of at least 150 m and up to 750 m growth strata are indicated by intervals that thicken landward by several tens of meters from anticline crests individual 4th order 100 500 ky regressive cycles expand about five to seven times across growth faults expansion ratios as great as 10 are observed the shelf edge is associated with the largest displacement expansion ratios and thickness of prograding deltaic sequences sedimentary structures and trace fossil associations identified in cores from nueces encinal and red fish bay subbasins indicate deposition on a wave dominated deltaic shoreline the cores exhibit highly bioturbated muddy sandstones alternating with decimeter thick clean sandstones with hummocky cross stratification alternation of fair weather wave deposits with sandy storm beds in two successive fault zones suggests that all subbasins developed under similar conditions during growth fault development high sediment supply conditions favored accumulation of thicker sediments on the downthrown sides of the faults wave dominance of deltas on the outer shelves in the growth compartments suggest that building of the upper slope rather lowers slope margin and decreases the likelihood of the presence of sandy deep water fans correlation of about 700 well logs integrated with seismic data provided the areal distribution and relative timing of sediment filling of the growth faulted compartments to unravel the evolution of higher order fourth and fifth sequences affected by these growth faults core data were used to recognize depositional environments to calibrate lithology to well logs and to characterize seismic amplitude anomalies within this shoreface succession the clean sandy storm beds will make attractive hydrocarbon reservoirs especially on the crest of rollover anticlines in downthrown compartments these sandstone bodies pinch out seaward into open marine shelf mudstones and are sealed by overlying shelf mudstones deposited during transgressive episodes

varying discharge controls on timescales of autogenic storage and release processes in fluvio deltaic environments tank experiments 1 changes in external forcing have traditionally been the main areas of interest in understanding sedimentary records while in most stratigraphic interpretation autogenic behavior has been thought of as a noise generator this study aims to investigate autogenic processes in a fluvio deltaic system under a range of discharge conditions and to show that autogenic processes generate distinct signatures rather than random noise a matrix of nine different experiments is presented here to systematically evaluate the effects of sediment and water discharge variations on the timescale of fluvial autogenic processes temporary sediment storage regularly occurs by backfilling of sediment in the fluvio deltaic channels followed by a period of strong channelization that releases the stored sediment these storage and release processes cycle along with changes in the fluvial slope and planform pattern of the flow here we propose that the autogenic behavior of deltaic progradation has a distinct timescale that is controlled by sediment and water discharges an increase in sediment discharge primarily reduces the autogenic timescale as higher sediment supply fills the channels faster in contrast the high sediment discharge causes a morphologic feedback by increasing the magnitude of fluvial slope change between the storage and release events and increasing the size of the temporary sediment storage termed the fluvial envelope this works against the sediment discharge control as the autogenic timescale is increased increasing the water discharge increases the autogenic timescale by improving the fluvial organization toward a strongly channelized system changes in autogenic timescale due to variations in the sediment and water discharges are nonlinear for different sediment to water discharge ratios as the ratio decreases the fluvial system is better organized and the timescale is more linearly related to the change in sediment discharge as the ratio increases deltas develop poorly organized fluvial systems and the associated timescales converge even with different sediment discharges the results presented here provide enhanced interpretation of sedimentary records by better decoupling of autogenic signatures from allogenic products developed across a wide range of discharge conditions

the stratigraphic record of prebreakup geodynamics evidence from the barrow delta offshore northwest australia the structural and stratigraphic evolution of rift basins and passive margins has been widely studied with many analyses demonstrating that delta systems can provide important records of postrift geodynamic processes however the apparent lack of ancient synbreakup delta systems and the paucity of seismic imaging across continent ocean boundaries mean that the transition from continental rifting to oceanic spreading remains poorly understood the early cretaceous barrow group of the north carnarvon basin offshore nw australia was a major deltaic system that formed during the latter stages of continental rifting and represents a rich sedimentary archive documenting uplift subsidence and erosion of the margin we use a regional database of 2 d and 3 d seismic and well data to constrain the internal architecture of the barrow group our results highlight three major depocenters the exmouth and barrow subbasins and southern exmouth plateau overcompaction of pre cretaceous sedimentary rocks in the south carnarvon basin and pervasive reworking of permian and triassic palynomorphs in the offshore barrow group suggests that the onshore south carnarvon basin originally contained a thicker sedimentary succession which was uplifted and eroded prior to breakup backstripping of sedimentary successions encountered in wells in the exmouth plateau depocenter indicates that anomalously rapid tectonic subsidence 0 24 mm yr 1 accommodated barrow group deposition despite evidence for minimal contemporaneous upper crustal extension our results suggest that classic models of uniform extension cannot account for the observations of uplift and subsidence in the north carnarvon basin and may indicate a period of depth dependent extension or dynamic topography preceding breakup

statistical evaluation of elemental concentrations in shallow marine deposits cretaceous lusitanian basin abstract the elemental geochemistry of ancient shallow marine carbonates represents an often underexplored archive of paleoenvironmental change and diagenetic pathways complex multi parameter datasets from a lithologically heterogeneous sedimentary succession in the southern part of the lusitanian basin ericeira portugal are presented and interpreted the section comprises marly carbonate and sandstone rich coastal marine deposits of early albian to early cenomanian age principal component analysis of bulk elemental abundance ca mg sr fe and mn lead to define four geochemical clusters based on common elemental attributes siliciclastics and dolomitized limestones facies yield evidence for significant diagenetic alteration but still preserve information on paleoshoreline position mixed carbonate siliciclastics and limestone facies bear evidence for relative sea level position and relevant paleoclimatic information in their elemental record accordingly mid albian mixed carbonate siliciclastic deposits present variable degrees of continental influx specifically a sharp increase of fe and mn concentrations in relation to continental input is in agreement with periods of enhanced hydrological cycling and increased weathering on adjacent emerged lands the progressive transition towards more marine conditions is accompanied by higher ca and sr content and represented by limestone facies corresponding to a higher sea level position during late albian to early cenomanian times moreover this facies records a trend towards warmer and more arid conditions early diagenetic stabilization and or dissolution of aragonite into low mg calcite can account for major elemental variations including higher sr content strongly coupled with ca content along with lower mg fe and mn concentrations data shown here provide solid evidence that the statistical analysis of the elemental record of ancient marine deposits when combined with conventional sedimentology and thin section petrography allow for elaborate conclusions on their depositional environment and diagenetic pathways cored wells and facies specific reservoir properties can be addressed by these methodologies able to detect and quantify changes in patterns both industry and academy can therefore benefit from approaching such a complex interplay

potential health impacts of burning coal beds and waste banks uncontrolled release of pollutants from burning coal beds and waste banks presents potential environmental and human health hazards on a global scale the emissions of large volumes of greenhouse gases from burning coal beds may contribute to climate change that alters ecosystems and patterns of disease occurrence on regional and local scales the emissions from burning coal beds and waste banks of acidic gases particulates organic compounds and trace elements can contribute to a range of respiratory and other human health problems although there are few published reports of health problems caused by these emissions the potential for problems can be significant in india large numbers of people have been displaced from their homes because of health problems caused by emissions from burning coal beds volatile elements such as arsenic fluorine mercury and selenium are commonly enriched in coal deposits burning coal beds can volatilize these elements which then can be inhaled or adsorbed on crops and foods taken up by livestock or bioaccumulated in birds and fish some of these elements can condense on dust particles that can be inhaled or ingested in addition selenium arsenic lead tin bismuth fluorine and other elements condense where the hot gaseous emissions come in contact with ambient air forming mats of concentrated efflorescent minerals on the surface of the ground these mats can be leached by rainwater and washed into local water bodies providing other potential routes of exposure although there are little data linking burning coal beds and waste banks to known health problems a possibly analogous situation exists in rural china where mineralized coal burned in a residential environment has caused widespread and severe health problems such as fluorosis and arseniasis

on shelf lower miocene oakville sediment dispersal patterns within a three dimensional sequence stratigraphic architectural framework and implications for deep water reservoirs in the central coastal area of texas through integrating three dimensional seismic and wireline log pattern data we found that the sequence stratigraphic architecture of the lower miocene oakville formation along the central part of the texas gulf coast reveals four third order sequences the lower two containing lowstand lst transgressive tst and highstand systems tracts hst and the upper two appearing to contain only tst and hst these sequences average 1 2 m y in duration the lowstand incised valley fill sandstones are massive as thick as 420 ft 73 m on wireline logs seismic stratal slices demonstrate that the incised valleys are dip oriented and more than 20 mi 32 km wide strata reflections within the incised valleys onlap the sides of the valley the third order tst comprise backstepping high frequency sequences seismic stratal slices and wireline log patterns within the tst suggest deltaic sediment dispersal patterns that appear reworked third order hst comprise aggradational to progradational high frequency sequences and seismic stratal slices and wireline log patterns indicate a variety of depositional environments that we interpreted as deltaic shoreface coastal plain and interdistributary the hst is significantly truncated by the overlying sequence boundary sandstone rich incised valley fills suggest that large amounts of sediment may have been transported through these channels and may have supplied lowstand deposits and associated reservoirs seaward of the previous shelf edge

experimental measurement of the relative importance of controls on shoreline migration abstract shoreline position in sedimentary rocks is a sensitive recorder of the interplay of several controlling factors the most important of these are thought to be the stratigraphic trinity eustatic sea level subsidence and sediment supply in ancient rock sequences it is generally difficult to disentangle the effects of these variables here we analyze the relative influence of sea level subsidence sediment supply and other controlling variables on shoreline migration in an experimental basin equipped with a subsiding floor the experiment used a linear hinge type subsidence profile for which the rate was kept constant in time constant overall sediment supply and base level variation on two time scales that were first applied separately and then superimposed although base level was the only controlling variable that was externally varied in time the base level changes induced changes in other variables indirectly e g by changing the partitioning of sediment between the fluvial and offshore segments of the system we examine the relative importance of measured direct and indirect changes in all the governing variables through the use of a moving boundary equation for shoreline migration when measured values are used for all the variables in the equation shoreline migration rate throughout the run can be predicted with a maximum r2 of 0 92 starting with this optimal prediction of the observed shoreline behavior we successively replace variables in the equation with their run averaged values degrading the prediction the relative loss of prediction accuracy as each variable is replaced is a measure of the importance of that variable in accounting for the observed shoreline migration by this measure base level is the most important variable followed in turn by sediment supply to the foreset geometry of the foreset and the average subsidence rate over the foreset from the shoreline migration equation we also derive a quantitative version of the a s ratio often applied in sequence stratigraphy the new formulation reduces to a form comparable to the traditional descriptive a s ratio if changes in foreset slope gain or loss of sediment to the fluvial system and spatial variation in subsidence rate are all negligible

shoreline autoretreat substantiated in flume experiments abstract under conditions of constant sediment supply s to the basin and a steady rate of rise a in relative sea level the autoretreat theory predicts that shorelines can retreat landwards at a relatively early stage of delta growth and attain an autobreak state after which the existing subaqueous slope begins to be starved of sediment and thereby lose its clear delta front configuration a numerical model based on this theory further suggests that shoreline migration depends on the inclination of basin s basement slope and subaqueous depositional slope and to a lesser degree on the inclination of subaerial depositional slope two dimensional flume experiments in which a miniature delta is subject to steady forcing a const 0 s const 0 were conducted to test the expectations of the autoretreat theory the experiments consisted of two different series of runs one was of modulation associated with a narrow range of the ratio of water discharge to sediment discharge q s the other was of q s modulation with kept nearly constant the q s ratio was mostly responsible for changes in but also affected to some extent all experimental runs substantiated the landward turnaround feature of shoreline accretion i e autoretreat and the geometrical break of the delta front shape during its retreat phase i e autobreak the obtained shoreline trajectories hold their geometrical patterns even after they were nondimensionalized in terms of the s a ratio a key hypothesis confirmed in the experiments is that a and s can never balance each other both of the experimental series brought some systematic change of shoreline trajectories but the variations of shoreline trajectory due to modulation were much more striking than those related to q s even these contrasting results are consistent with the numerical predictions the present experimental results support the applicability of the autoretreat concept to natural environments and help clarify the processes governing the regression and transgression of a shoreline on a constructional margin

sequence paleogeography and coal accumulation of the early middle jurassic in central qilian mountain belt muli basin qinghai province northwestern china the muli basin in the qinghai province located at the northeastern margin of the tibetan plateau is a jurassic coal bearing basin and is an important area for coal production in china recent explorations have revealed the presence of unconventional types of gases such as coalbed methane and gas hydrates we have investigated the sedimentology sequence stratigraphy and lithofacies paleogeography of this basin based on data from outcrop and borehole sections the coal bearing strata include the lower jurassic reshui and the middle jurassic muli and jiangcang formations lithofacies including conglomerates sandstones mudstones and coal were identified and have been interpreted to be formed in environments ranging from braided fluvial braided fluvial delta to lacustrine the preferred sites of coal accumulation are the interdistributary bays of lower delta plain and upper delta plain environments three types of sequence boundaries are recognized including regional unconformities between the lower jurassic and underlying triassic the basal surface of incised valley fills of thick bedded sandstones in the muli and jiangcang formations and the surfaces that mark abrupt depositional facies shifts four third order sequences were subdivided namely s1 s2 s3 and s4 in ascending order which correspond to the reshui formation the muli formation the lower member of the jiangcang formation and the upper member of the jiangcang formation respectively each sequence consists of a lowstand systems tract a transgressive systems tract tst and a highstand systems tract a series of sequence specific basin wide paleogeographic maps have been constructed based on contour maps of several lithological parameters including stratal thickness sandstone to mudstone ratio and mudstone thickness from s1 to s4 the muli basin experienced an evolution from a braided fluvial system to braided fluvial delta then to a lacustrine system showing a gradual deepening process thick coal seams with thickness greater than 3 5 m 11 5 ft were primarily developed in the delta plain environment where the rate of peat accumulation can be easily balanced by the rate of accommodation generation a five stage coal accumulation model has been summarized and the major coal seams mainly developed in the early and late tst of sequences s1 and s2

comprehensive characterization of anthracite fly ash from a thermo electric power plant and its potential environmental impact abstract anthracite fly ash from a deactivated portuguese thermo electric power plant has been characterized to assess its relationship to the mineral matter in typical feed coal and the potential environmental impacts that might be caused by ash disposal several different aspects of the ash were characterized including the petrographic and mineralogical composition as well as the chemical composition of both the ash samples and their water leachates petrographic analysis demonstrates that the fly ash consists predominantly of glass followed by char and crystalline mineral particles sem edx studies were used to complement this approach revealing a mixture of different inorganic phases and unburnt organic matter quantitative xrd analysis further showed that amorphous material or glass is the main constituent 60 70 followed by mullite quartz and traces of maghemite small proportions of kaolinite and illite also occur in some of the fly ash samples according to their chemical composition the fly ashes would be classified as sialic and are within the range of values shown by other european fly ash samples relatively low concentrations of elements in leachates from the fly ash could be due to enclosure of most of the elements within the amorphous material together possibly with mobilization of some of the material e g adsorbed ions from the ashes with storage the fly ash leachates developed very acidic ph values between 2 5 and 2 8 under test conditions attributed to the low cao content and the co firing with fuel oil

depositional systems and sequence stratigraphy of mesozoic lacustrine rift basins in ne china a case study of the wulan hua sag in the southern erlian basin abstract the deltaic and lacustrine sediments respectively in the syn and post rift stages are recorded during the cretaceous at the wulan hua sag erlian basin inner mongolia in this study the mesozoic depositional system and sequence stratigraphic framework are recognized in the wulan hua sag using core well log and seismic data five sedimentary facies have been identified including fan delta braided delta shallow lacustrine deep lacustrine and sublacustrine fan during cretaceous at the wulan hua sag one first order sequence msq1 three second order sequences ssq1 ssq2 and ssq3 and five third order sequences sq1 sq2 sq3 sq4 and sq5 are classified by subaerial unconformities along the basin margins and correlative conformities in the central part of the basin during the depositional period of sq1 sq2 and sq3 the depocenter controlled by lake level fluctuations migrated from southern to northern part companying with multiple to single provenance supplies the characteristics of sedimentary facies and sequence stratigraphy in the wulan hua sag are commonly controlled by faults provenance and depocenters the development of the third order sequences is dominated by tectonism and sediment supplies as well as lake level changes driven by climate the favorable targets for hydrocarbon located in the lowstand system tract of sq1 sq2 and sq3 at the southern parts of the wulan hua sag

apatite fission track analysis of oligocene strata in south texas u s a testing annealing models analysis of apatite fission track data from forty seven surface and subsurface samples of fine grained sandstone to pebbly conglomerate from the oligocene catahoula gueydan frio and vicksburg formations documents the response of fission track ages and track length distributions to simple post depositional thermal histories characterized by monotonic heating data from outcrop samples document that the apatite component was derived from source areas characterized by rapid cooling through the temperature range from 120 to 50 c during the early tertiary the apatite population is characterized by a log normal chlorine distribution mean 0 3 wt 0 3 wt consisting predominantly of low cl apatites 80 is 0 5 wt mean track lengths from core samples decrease systematically with increasing depth and temperature the decrease in apatite fission track ages with increasing depth and temperature is less systematic due to the scatter in inherited ages at the time of deposition no tracks were observed in apatite from samples at temperatures above 130 c mean track lengths for the south texas data agree well with those for a similar data set from the otway basin southeastern australia for present day temperatures of 70 c at higher temperatures mean lengths are 1 to 9 m longer than those observed from the otway basin this discrepancy is interpreted to reflect up to 40 ma longer residence times at maximum burial temperatures for the otway basin samples standard deviations about mean lengths are also lower than observed in the otway basin study consistent with the wider variation of cl contents mean 0 8 wt 0 7 wt that characterize apatite from the otway basin recently published apatite fission track annealing models predict significantly different mean track length vs present day temperature profiles for thermal histories believed to be representative of those experienced by sampled south texas strata because of the large uncertainties attributed to present day temperatures 10 c the predicted mean length vs temperature trends for these models essentially fall within or on the uncertainty envelope for the observed trend residuals of predicted minus observed mean lengths suggest that the previously published carlson composite parameter model using an initial mean length of 15 8 m instead of 16 5 m or the crowley et al model for track length reduction down to 11 m provide the best estimates of mean track length reduction over geologic time scales for near end member f apatite populations

petrography and mineralogy of self burning coal wastes from anthracite mining in the el bierzo coalfield nw spain abstract coal fires burning around the world over many years have been responsible for the loss of natural resources and also for negative environmental and human health impacts study of self burning coal wastes based on organic petrology mineralogy and geochemistry allows the evaluation of factors responsible for the combustion process and can also be used to assess the changes that are taking place in thermally affected materials the main goal of this study is to characterize the materials from the arroyo galladas arroyo mourin and fabero coal waste piles which resulted from coal mining in the el bierzo coalfield nw spain samples of coal and of unburned and burned or burning coal waste material were studied by optical microscopy and x ray powder diffraction xrd the results demonstrate that some of the organic matter has preserved its characteristics but other organic material shows signs of thermal alteration such as cracks devolatilization vacuoles dark reaction rims plasticized edges and increased or decreased vitrinite reflectance the resistance of the unaltered organic matter to thermal effects is attributed to the coalification process previously undergone by these coals the mineralogical composition of the samples indicates that newly formed minerals are present in the burned or burning material including mullite cristobalite cordierite hematite jarosite sanidine anorthite sulfur pyrite rozenite coquimbite tschermigite boussingaultite and amorphous material the formation of these minerals is attributed to combustion at maximum temperatures of at least 1100 c in the fabero coal waste pile and lower temperatures in the arroyo galladas coal waste pile and to interaction of gases released by combustion with the solid particles the waters and the atmosphere in and around the waste piles

formation of high frequency sequences and their bounding surfaces case study of the eocene yegua formation texas gulf coast usa abstract short term variations in accommodation and sediment supply on the continental shelf cause imbalances within longer term dynamic equilibrium conditions these imbalances result in the deposition of high frequency sequences the eocene yegua formation of the texas gulf coast is made up of six such sequences which have average durations of 0 8 million years or less they formed in response to distinct variations in the rate and quantity of sediment supply increases and decreases in the average grain size carried into the basin relative sea level position and the capacity of basinal energy regimes to transport and rework sediments each sequence may be characterized by the mix of particular regime conditions which were dominant during its deposition if the rate of sediment supply and the average grain size were more significant factors than the rate of relative sea level change and the capacity for basinal transport then the sequence was supply dominated and was characterized by fluvio deltaic deposition progradation of parasequences and river mouth bypassing onto the shelf and slope if instead relative sea level rise and basinal transport were the dominant factors the sequence was accommodation dominated and was characterized by estuarine and wave dominated deposition retrogradation of parasequences and shoreface bypassing onto the shelf when the accommodation and supply factors were in equilibrium sequences containing both fluvial and estuarine deposits characterized by aggradational parasequence stacking were deposited no two consecutive sequences in the yegua were dominated by the same mix of regime conditions therefore the sequence boundaries are important indicators of changes in regime conditions all of the boundaries are highly correlatable well constrained regional marine flooding surfaces flooding of the shelf thus apparently either causes or occurs as a result of a readjustment between sediment supply and accommodation continuous readjustments between these factors result in long term equilibrium conditions

the cenozoic lower rhine basin rifting sedimentation and cyclic stratigraphy in the cenozoic the lower rhine basin formed as a rift at the southeastern terminus of the dutch german central graben while the rhenish massif was uplifted the study focusses on the marginal marine and fluvial fill of the lower rhine basin a basin model is developed support for this study was given by extensive industry outcrop and well data by new stratigraphical and sedimentological observations the ingression and subsequent regression of the cenozoic north sea is analysed using the concept of base level cyclicity as the geohistory of the basin was complex a subsidence curve is constructed furthermore an attempt is made to trace the simultaneous uplift of the rhenish massif

depositional settings and history of the lower miocene fleming group refugio county texas as defined using seismic geomorphology abstract a study of the lower miocene fleming group in refugio county texas from 3 d seismic and wireline log data documents continuous strandplain and associated lower coastal plain fluvial systems along a wave dominated shoreline this study delineates and characterizes through the interpretation of seismic attributes and seismic geomorphology maps from 15 horizons three principal styles of stratal patterns 1 parallel and subparallel strike continuous sets of beach ridge and swale deposits within a strandplain system that prograded at least 12 km 2 sinuous channel belts in a coeval mixed load meanderbelt system and 3 acoustically dim nearly featureless seismic attribute patterns that record homogenous and topographically subdued shallow marine mudstones associated with transgressive marine deposits and flooding surfaces holocene depositional analogs for these lower miocene sandy strandplain deposits include the nayarit coastline in mexico whereas the lower coastal plain between galveston and corpus christi texas serves as an appropriate analog for mixed load meanderbelt systems the lower miocene coastline in refugio county consists of a regressive phase that was punctuated by two transgressive phases these episodes of marine transgression correspond to the anahuac formation and the marginulina a shale respectively succeeding events record complex amalgamated beach ridge deposits and coeval fluvial channel systems that exhibit patterns of channel migration erosion incision and downdip fusion of channel belts this study concludes that potential reservoir geometries and architectures in the lower miocene succession are much more complex than previously inferred the result of rapidly fluctuating and evolving strike fed shoreline systems and contemporaneous fluvial dip dispersal systems some manifested by shore parallel trends confined in swales improved reservoir development strategies in this prolific hydrocarbon bearing play should be guided by distribution of sandy depositional elements and the paleogeographic setting

the spi lake formation of the central hearne domain western churchill province canada an axial intracratonic continental tholeiite trough above the cogenetic kaminak dyke swarm the spi group is a package of plagioclase porphyritic amygdaloidal basalt flows and sandstone spi lake formation conformably overlain by coarse conglomerate and sandstone old boot formation these unconformably overlie the kaminak lake segment of the central hearne supracrustal belt western churchill province the spi group developed in a small isolated basin 8 km2 and is older than the paleoproterozoic hurwitz group our data demonstrate that the basalts of the spi lake formation are genetically related to the ca 2450 ma kaminak dyke swarm a speculation previously promoted by some workers based on field characteristics alone they are continental tholeiites with large ion lithophile and light rare earth element enriched multielement profiles with prominent high field strength element troughs the 143nd 144nd compositions overlap the contemporaneous chondritic bulk earth data all of these are features we infer to have resulted from mixing of melts from dominantly depleted mid ocean ridge basal

abstract lower claiborne regional stratigraphic architecture southeast texas to east central louisiana abstract the lower claiborne section and its units discussed and illustrated here of lutetian age middle eocene figure 1 are recognized as a series of marine shelf marginal marine and deltaic strandline deposits regional closely spaced well log cross sections extending for almost 500 miles from south texas to eastern louisiana updip of the claiborne shelf margins clearly show the regional stratigraphic architecture along depositional strike from southeast central texas through east central louisiana ewing 1994 ewing and vincent 1997 the obvious internal forms when viewing the lower claiborne at such great scale are large very low angle sigmoidal clinoform sets delineated by regional flooding surfaces see figure 2 below the flooding surfaces fs are depicted as the flat to sigmoidal lines seen in that cross sectional diagram major fs s shown by heavier lines lesser fs s by thin and or dashed lines these large downlaps are roughly oriented from nw to se across coastal texas and into central louisiana demonstrating the time transgressive nature of the entire lower claiborne the downlaps proceed from oldest to youngest coming from west to east contrast with perkins and hobday 1980 and fisher 1964 basin analysis and subsurface exploration rely on the identification of genetic units or sequences because they are time bounded units which unite all of the co occurring processes and their resulting deposits genetic stratigraphic units are defined and bounded by key flooding surfaces which approximate time lines genetic sequences of galloway 1989a b these units combining progradational and transgressive elements have the advantage of being bounded by surfaces which on the shelf at least are continuous are easy to recognize have associated biozonations and are verifiably correlatable on well logs unconformities which may be detectable in up dip positions in these dynamic basin margin settings are for all practical purposes difficult to impossible to find in the down dip conformable portions of these units and for simplicity s sake are not shown on the accompanying cross section fig 2

depositional tectonic and eustatic controls on hydrocarbon distribution in divergent margin basins cenozoic gulf of mexico case history abstract the evolution of continental margins and related distribution of hydrocarbon reservoirs in divergent margin basins reflects the primary interaction between sediment supply and process regime within the basin and secondary modifications by sea level change and structural history cenozoic sequences of the northwestern gulf coast basin contain numerous highly explored hydrocarbon fairways that reflect typical productive styles resulting from progressively reduced influences of tectonic events in the north american plate and progressively increased influences of eustasy most paleogene and lower neogene sequences record moderate to high rates of sediment supply locally enhanced load or salt induced subsidence and infrequent relatively low amplitude eustatic change accommodation space was created by crustal loading and gravity driven continental margin extension or salt evacuation along with progradation into the deep water gulf shorezone deposits are sand rich because slow or limited eustatic shoreline shift promoted effective reworking and shelfal storage of coastal facies progradational depocenters were characterized by large long lived wave reworked shelf edge delta systems sands were largely stored close to the delta front and flanking shorezone systems prolonged periods of aggradation and retrogradation preserved thick vertically stacked parasequences of deltaic and interdeltaic barrier strandplain facies hydrocarbons accumulated in multiple superimposed reservoirs primarily in mixed structurally and depositionally defined plays in contrast upper neogene and quaternary sequences are products of frequent high amplitude eustatic cycles rapid subsidence and locally very high rates of sedimentation accommodation space was created by load induced subsidence modified by salt evacuation and intermittent relative rises in sea level shorezone deposits are heterolithic because rapid subsidence and frequent eustatic shoreline shifts prevented extensive reworking progradational episodes were characterized by mud rich river dominated shelf edge deltas of moderate size rapid lowering of sea level promoted gravity remobilization of deltaic sediments and deposition of sand rich lobes that created broad structurally and bathymetrically complex submarine fans and slope aprons some sand rich submarine fan lobes extend more than 160 km basinward from the paleoshelf margin in contrast strike reworking and sand storage on the shelf were minor combination structural and stratigraphic traps define most upper neogene and quaternary hydrocarbon plays correlating observed patterns of cenozoic basin fill with contemporaneous plate interactions and eustatic fluctuations reveals the relative control of these variables on rates of sediment supply characteristics of depositional sequences and styles of basin fill deformation

impact of eustatic amplitude variations on shelf morphology sediment dispersal and sequence stratigraphic interpretation icehouse versus greenhouse systems the pliocene pleistocene icehouse stratigraphic record is characterized by distinct sediment distribution patterns and chronostratigraphic relationships resulting from high frequency high amplitude changes in sea level these modern relationships are often used as a template for sequence stratigraphic interpretation and for predicting sediment distribution in ancient greenhouse systems deposited at times when sea level fluctuations are known to have been different from the most recent period of geologic time numerical modeling suggests that the depth of the shelf rollover and thereby also shelf accommodation rapidly adapts to changes in eustatic amplitude along passive constructional sedimentary margins lower amplitudes and perhaps also lower frequencies during greenhouse periods would allow across shelf delta progradation and sediment delivery to the slope and basin floor during both third and fourth order highstands care should therefore be taken when extrapolating stratigraphic models between icehouse and greenhouse systems

high frequency 4th order sequence stratigraphy of early miocene deltaic shorelines offshore texas and louisiana abstract well logs and 3d seismic reflection data are integrated to image lower miocene depocenters of the upper texas and westernmost louisiana coastal and offshore areas although previously interpreted at a large scale 3rd order cycles the detailed stratigraphy and depositional history of the early miocene succession has not been fully developed the upper lower miocene interval from robulus l mfs10 to amphistegina b mfs9 has been further subdivided into five 4th order cycles each 200 300 m thick to provide finer scale stratigraphic detail and interpretation of depositional environments results of the finer scale correlations are presented in a series of sandstone percent maps overall the maps display a strike elongate sub parallel to the present day coastline orientation for the sandstone bodies which thin to the southeast basinward net sandstone thickness is relatively low in older cycles and increases in younger cycles suggesting an overall progradation of the deltaic system into the mapped area through time continued marine regression and southward movement of the shoreline are also confirmed by seismic amplitude maps after a major transgression associated with robulus l deltaic progradation occurred under rising sea level conditions deltaic sediments prograded southward and sandstone brought to the upper texas coast was distributed laterally by longshore currents to form strandplain coast lines maximum regression occurred during the interval mfs9 2 to mfs9 3 when a deltaic depocenter formed offshore texas in east high island area however sandstone thickness progressively decreased laterally to the east offshore louisiana where more shale was present and marine processes reworked deltaic derived sandstones into shore parallel bars there was a clear retreat of the shoreline during the youngest cycle marking the beginning of transgression associated with amphistegina b detailed stratigraphic interpretation at a 4th order scale shows more variability in the dominant shoreline processes during early miocene than previously thought recognition of sedimentary systems variability at a 4th order scale is critical for improved hydrocarbon exploration and in understanding potential future co2 storage in the area

modern uparching of the gulf coastal plain a broad doming of the gulf coastal plain between jackson mississippi and new orleans louisiana is indicated by leveling surveys carried out in 1934 1959 1964 and 1969 the progressive arching over a distance of 275 km attains a maximum average rate of 3 4 0 5 mm yr relative to jackson additional leveling in the area indicates that the observed pattern of movement could be elongate with its major axis parallel to the coast the observed uplift is consistent at least in sign with longer term trends indicated by deformed terraces in mississippi and louisiana oil gas and water withdrawal mechanisms as well as systematic leveling errors appear inadequate to explain the wavelength and magnitude of the observed elevation changes the pattern of uplift resembles that which might be expected from flexure due to sedimentary loading at the mouth of the mississippi delta simple models of flexure of a thin elastic plate overlying a viscous half space caused by sediment loading during the holocene do predict rates similar to those evidenced by leveling if relatively low mantle viscosities 3 l019 pa s 1 pa s 10 poise are used these observations may represent direct measurements of ongoing dynamic flexure at a passive continental margin

distribution and origin of minerals in high rank coals of the south walker creek area bowen basin australia the coals of the south walker creek area in the northern bowen basin with a vitrinite reflectance rvmax of 1 7 to 1 95 are among the highest rank coals currently mined in australia x ray diffraction studies have identified an unusual mineral variation through the vertical sequence with kaolinite rich assemblages typical of other australian coals at the top and bottom of the seam section and an illite chlorite assemblage resembling a metamorphic association in the middle calcite and ankerite are also abundant in parts of the vertical sequence diaspore is abundant in the middle section of the seam in some areas and paragonite dickite or nacrite occurs in some locations as well the distribution of the non carbonate mineral assemblages cross cuts the seam stratigraphy and appears to be primarily controlled by faults and other structural features integration of the mineral distribution with optical and electron microscope data on the coal and non coal bands chemical data from coal ash analysis and information from x ray micro tomography suggests that the illite chlorite and diaspore bearing assemblages resulted from hydrothermal effects associated with fluid migration through the middle part of the coal seam this is further confirmed by the development of metamorphic textures in a tonstein band also altered to illite and chlorite in the illite rich part of the seam section in contrast to a tonstein with more normal sedimentary textures and a kaolinite composition in the kaolinite rich upper part of the seam detailed studies of cleat mineralisation suggest that fluids rich in ca mg and al were introduced relatively early in the seam s post depositional history associated with heat flow sufficient to alter the minerals in the coal and tonstein in the affected part of the seam section the relatively uniform vitrinite reflectance profile observed through the seam section may indicate that the coal was already of high rank before the fluids were introduced or that any localised heat effects on the organic matter associated with the changes in clay mineralogy were overprinted by subsequent wider ranging rank advance processes

genetic stratigraphic sequences in basin analysis ii application to northwest gulf of mexico cenozoic basin the northwest gulf of mexico cenozoic sedimentary wedge illustrates the application of genetic stratigraphic sequence analysis and documents several general conclusions 1 sequences defined by regional marine flooding are the principal genetic stratigraphic units of the basin fill continental margins are characterized by repetitive episodes of basin margin offlap punctuated by periods of transgression and marine flooding of the depositional platform 2 continental margin outbuilding is concentrated at one or more shelf edge deltaic depocenters separated by interdeltaic bights depocenters remain fixed during a depositional episode but commonly relocate during transgression and flooding 3 a distinct syndepositional structural style in prograding continental margins results in sporadic uplift of a basin fringing peripheral bulge and accentuates preservation of shelf margin facies along zones of extensional normal faulting and enhanced subsidence 4 genetic stratigraphic sequences commonly reflect an evolving interplay among two or even three variables for example early cenozoic gulf sequences are most closely related to tectonic events of the intraplate source terrane which in turn affect rate and location of sediment supply and basin margin response to loading late cenozoic sequences more closely reflect proposed eustatic cycles

southern gulf of mexico wilcox source to sink investigating and predicting paleogene wilcox reservoirs in eastern mexico deep water areas source to sink analyses show that northern gulf of mexico gom wilcox group siliciclastic deep water systems are linked to transport of sediments from the laramide tectonic belt into the deep basin less is known however about southern gom sedimentation new drilling and discoveries in the mexican deep water have generated considerable interest since the opening of mexico to international exploration to investigate paleogene deposition in mexico s offshore areas a three phased approach was employed 1 seismic mapping of deep water depocenters 2 regional stratigraphic analysis of potential basin entry points and 3 prediction of submarine fan dimensions using empirical scaling relationships isochore and structural mapping of the wilcox depocenters used available well and seismic data potential basin entry points were identified by evaluation of wilcox fluvial deltaic systems and tectonic elements empirical scaling relationships previously established between fluvial and deep water segments provide first order predictions of submarine fan dimensions paleogene wilcox source to sink systems of the greater gom basin change north to south as a function of varied tectonics and sedimentary accommodation the united states sector was a passive margin continental scale drainage systems fed a broad gently dipping shelf by contrast the southern gom basin was a tectonically active margin smaller scale fluvial systems sourced from the hidalgoan uplands flowed directly into foreland basins located on the slope results presented here indicate that several systems rimming the southern gom were able to effectively transfer sediment from the mountain belt into the basin regional observations and semiquantitative predictions of fan dimensions provide a context for future detailed work based on new well and seismic information

construction of a palaeogene tide dominated shelf influence of top chalk topography and sediment supply wessex basin uk palaeogene siliciclastic sediments reading and london clay formations in the wessex basin record an upward change through four tidally influenced deposition systems the lowest reading formation was deposited in estuarine and coastal plain environments the overlying london clay records discrete upward changes from deltaic to mixed tidal flat to tidal sandsheet bagshot sands erosional topography on the top chalk surface had an important control on deposition 1 topographic lows controlled the initial sites of marine flooding and sedimentation 2 lows would have acted as conduits for sediment delivery 3 lows created additional accommodation by the compaction of thick mud fills 4 lows may have formed preferential sites for delta growth as topography was reduced by sediment infill depositional units tended toward more sheet like geometries heavy minerals reveal that an upward progradational aggradational trend and the development of more sand rich facies are related to a change in provenance toward sand rich cornubian sources

timing of deformation in overthrust belt and foreland of idaho wyoming and utah a review of the timing and displacement evidence of the major structures of the western wyoming overthrust belt and foreland shows there is a progression in thrust displacement apparent duration of motion and palinspastic position of thrust traces from west to east those toward the west moved farther for an apparently longer period of time and are more widely spaced in their restored positions than those toward the east however average thrust velocities are all on the order of 0 5 0 5 cm yr 0 2 in yr foreland events are in part synchronous with thrust belt events and had an effect on them although dating precision varies widely on major normal faults present evidence does not contradict the generally held view that all normal faults postdate the youngest thrusting

high frequency miocene sequence stratigraphy offshore louisiana cycle framework and influence on production distribution in a mature shelf province the regressive miocene succession of offshore louisiana comprises 10 third order sequences and no fewer than 58 fourth order sequences which average approximately 1 1 and 0 19 m y in duration respectively comparable to durations measured in the gulf coast basin and basins worldwide upper lower to middle miocene distal third order sequences comprise mostly lowstand prograding wedge slope fan and basin floor fan deposits in contrast middle to upper miocene medial sequences record progressively more landward systems tracts 1 the lateral transition between on shelf incised valley fills and the proximal parts of basinward thickening lowstand prograding wedges and 2 cyclic on shelf highstand and transgressive systems tracts upper miocene inner shelf and marginal marine systems tracts and more abundant incised valleys dominate the thinner proximal third order sequences this genetic framework has a major influence on hydrocarbon distribution although a strong structural trapping component is present in the fields more than 90 of cumulative production originates where fourth order systems tracts stack to form third order lowstand systems tracts in all 10 third order sequences the development of a high frequency sequence framework for the prolific miocene succession and the discovery that hydrocarbons are pooled within the miocene third order lowstand systems tracts yield a focused model for the development of abundant undiscovered miocene reserves in the mature northern gulf of mexico shelf province

a tectonic redefinition of the southern rocky mountains abstract the southern rocky mountains of the western united states physiographically defined and described by n m fenneman nearly 60 yrs ago are tectonically redefined and extended they are shown to constitute the crestal range of a mammoth continental arch like feature here named the alvarado ridge its axis trends south from casper wyoming at least as far south as el paso texas beyond which the ridge begins to lose morphological identity maximum elevations along the crest of the ridge exceed 4 2 km the summit ranges are bordered on either side by gently sloping rises that extend outward for at least 1300 km falling to elevations of less than 400 m modest rift structures along the ridge axis continue beyond the southern terminus of the mountains before playing out a major sediment filled axial graben exists over the southern two thirds of the ridge but equivalent parts of it farther north were stripped of their neogene fill by erosion in the headwaters areas of the colorado and north platte rivers the maximum elevation of earlier laramide mountains in this area has been estimated to have been no more than 2 km in colorado half that of the present range related topography was nearly obliterated by erosion prior to late eocene time lateral stream planation produced a southeast sloping major late eocene erosion surface across the region that had what was probably an isostatically adjusted average maximum elevation of less than 900 m present day elevations and relief on the ridge crest are the result of steep crestal normal faulting pronounced block uplift and regional arching with extensional strain limited to an axial corridor less than 200 km wide this episode of mountain building began in middle miocene time 17 to 12 ma culminating in latest miocene and early pliocene time between 7 and 4 ma ago debris from the newly elevated range the southern rocky mountains sensu lato was shed along the full length of the neogene alvarado ridge down parts of both rises as well as into its medial graben the uplifted and tilted east rise the great plains ramp has an extensive aggradational cover that spread eastward to distances of 700 km and more in middle miocene to earliest pliocene time its fluviatile lacustrine and eolian sediments are undergoing dissection today but a sufficient portion remains to define the unmodified profile of the east rise as well as the original length of the ridge it is coincidentally similar in configuration and scale to the west rise of the mid atlantic ridge the topography of the crestal mountain ranges on both structures is also remarkably similar the southern rocky mountains are as high as the alps but are not the product of lithospheric compression and crustal thickening rather they reflect profound epeirogenic uplift driven by lithospheric thinning and accompanied by extensional strain and differential vertical jostling along the crest of the ridge

presenting meso cenozoic seismic sequential stratigraphy of the offshore indus basin pakistan abstract preserved deformed depositional sequences along passive continental margins are important repositories of natural resources as well as key laboratories for understanding rift drift tectonics with better post signal processing schemes interpretation techniques and potential data imaging sedimentary basins along these margins has reached unique levels of refinement this in turn has led to considerable improvement in unfolding the complex tectono sedimentary history since rifting to basin development in this paper deep reflection seismic coupled with well data and biostratigraphic information have been used to decipher the third order depositional sequences of meso cenozoic succession in western parts of the indian plate passive continental margin offshore indus basin as pioneer research based on morpho tectonic considerations the depositional sequences are divided into syn rift passive margin and post rift stages deformed by steeply dipping normal faults using the principles of classic sequence stratigraphy five third order mappable depositional sequences have been recognized on seismic records that are controlled by regional tectonics and sea level fluctuations coupled with sedimentation type and rates in the region the associated system tracts were recognized and mapped based on genetic reflection terminations on seismic profiles and log motifs and constraint surfaces include sequence boundaries sbs maximum flooding surfaces mfss and transgressive surfaces tss the depositional systems encompass lowstand system tracts lsts transgressive system tracts tsts and highstand system tracts hsts the lsts are composed of shallowing upward lowstand deltas or terraces prograding in the basin ward direction while pinches out landward at preceding depositional shoreline breaks the sand units of tsts are interpreted as shoreface sands deposited in the shelfal part during rising sea levels and hsts are characterized by coarsening and shallowing upward intervals with both fluvial and laterally prograding deltaic deposits a hydrocarbon entrapment model is proposed suggesting an interesting petroleum trap based on the entire course of this research valuable recommendations have been made for answering past exploration failures and future efforts such studies can be applied to worldwide passive margins dominated by third order sequences with complex sediments tectonic interplay

the cretaceous paleogene k p boundary at brazos texas sequence stratigraphy depositional events and the chicxulub impact abstract two cores from brazos texas spanning the cretaceous paleogene k p boundary are investigated by a multidisciplinary approach aiming at unraveling environmental changes and sequence stratigraphic setting in addition the sedimentology of the k p event deposit and its correlation with the k p boundary is studied foraminifera and nannofossil stratigraphy indicates that both cores include a latest maastrichtian zone cf1 cf2 and earliest danian p0 p and p1a shale sequence with a sandy and chicxulub ejecta bearing event deposit at the k p boundary a hiatus of unknown duration may be present by the unconformable base of the event deposit planktic foraminifera as well as calcareous nannofossil abundance and diversity both decline abruptly above the event deposit k p mass extinction whereas benthic foraminifera show a pronounced faunal change but no mass extinction mineralogical and geochemical proxies suggest that except for the sandwiched k p event deposit no facies change took place across the k p boundary and no evidence for adverse an or dysoxic sedimentary conditions following the chicxulub impact was observed therefore the interval bracketing the k p event deposit is considered as highstand systems tract increased coarse detritus input and low planktic benthic p b foraminifera ratios during the earliest paleocene p0 and p both suggest an increased coastal proximity or relative sea level lowering although the k p mass extinction of planktic foraminifera might have influenced the p b ratios as well consequently the sandy shales of the early paleocene are considered as late regressive highstand or as lowstand deposit during p1a shales assigned as transgressive systems tract overlie a pyrite and glauconite rich bioturbated transgressive surface or type 2 sequence boundary the smectite dominated clay assemblage with minor illite kaolinite and chlorite indicates semiarid humid climates with no obvious shifts across the k p boundary the magnetic susceptibility signature during the maastrichtian reveals a subtle cyclic or rhythmic pattern whereas a high amplitude cyclic pattern is present during the early danian the k p event deposit shows a succession of high energetic debris flows and turbidites derived from multiple source areas followed by a period of decreasing current energy deposition was likely triggered by multiple tsunami or tempestites followed by a prolonged period of reworking and settling the chicxulub ejecta at the base of the k p event deposit consists of mg rich smectite as well as fe mg rich chlorite spherules their mineralogical composition points to target rocks of mafic to intermediate composition presumably situated in the northwestern sector of the chicxulub impact structure besides these silicic phases the most prominent ejecta components are limestone clasts accretionary carbonate clasts and microspar suggesting that the texas area received ejecta also from shallow carbonate rich lithologies at the impact site on the yucatan carbonate platform the excellent correlation of chicxulub ejecta at brazos with ejecta found in the k p boundary layer worldwide along with the associated mass extinction provides no evidence that chicxulub predated the k p boundary and allows for unequivocal positioning of the k p boundary at the event deposit

high resolution sequence stratigraphy of an alluvial fan fan delta environment stratigraphic and geodynamic implications an example from the keuper chaunoy sandstones paris basin abstract facies analysis of the chaunoy formation conducted as the first stage of this study reveals that the corresponding fluvial system essentially involved bedload deposition 2 d and 3 d megaripple migration and debris flow deposition such processes are characteristic of alluvial fan depositional environments these alluvial fan deposits pass laterally eastward into a shallow lacustrine environment in stage 2 of the study electrofacies are defined by well log analysis and then matched with sedimentary facies defined by core analysis electrofacies associations and depositional environments are then inferred directly from well logs on this basis six electrofacies characterizing the main sedimentary facies associations and depositional environments within the chaunoy formation are defined channel lag deposits channel infilling lake or flood plain overflow deposits and paleosols stage 3 involves establishing correlations based on high resolution sequence stratigraphy within these continental deposits the procedure consists in analysing high frequency fluctuations in baselevel defined from sedimentological studies and calibrated on well log signatures the correlations show that the top of the chaunoy formation is diachronous the formation is subdivided here into three stratigraphic units from base to top chaunoy i ii and iii this study shows that the degree of preservation of continental deposits varies with stratigraphic cycle genetic sequences and genetic sequence sets are asymmetrical with the baselevel rise being better preserved than the baselevel fall while for minor cycle deposits may be similarly preserved during baselevel rise and fall the sequence stratigraphy pattern of the genetic sequences and the genetic sequence sets can result from climatic and or tectonic factors but their effects are difficult to distinguish at the scale of the minor chaunoy i cycle or the chaunoy ii cycle preservation is similar during the baselevel rise and fall that implies that the chaunoy minor cycles were influenced by load discharge resulting in greater accommodation space which could result from climatic or tectonic fluctuations the chaunoy formation was deposited as part of a major baselevel rise during the carnian liassic cycle during this cycle the paris basin was generally tilted to the northwest producing the intra marnes irisees superieures truncation which seems to have been induced by large scale wavelength tectonic deformation detailed isopach maps of minor baselevel cycles in chaunoy i with inferred depositional environments are used to define the extent of depositional environments and fault activity during baselevel rise and fall during emplacement of the braided alluvial fan and lacustrine deposits of the chaunoy formation fault activity which was confined to the western part of the basin controlled the preservation potential i e the thickness of the deposits and depositional environment profiles within the chaunoy i and ii cycles the increased thickness of the sandstone deposits to the northeast and the onlap at the top of chaunoy i can be explained by local fault activity and by the general tilting of the basin the chaunoy iii sandstones are confined to the western part of the basin and seem to have been controlled by local factors only

a record of appalachian denudation in postrift mesozoic and cenozoic sedimentary deposits of the u s middle atlantic continental margin abstract the complex interplay between source terrain uplift basin subsidence paleoclimatic shifts and sea level change left an extensive sedimentary record in the contiguous offshore basins of the u s middle atlantic margin salisbury embayment baltimore canyon trough and hatteras basin isopach maps of 23 postrift lower jurassic to quaternary a allostratigraphic units coupled with a revised stratigraphic framework reveal that tectonism by regulating sediment supply accumulation rate dominated the interplay of forcing mechanisms tectonic pulses are evidenced by abruptly accelerated sediment accumulation marked latitudinal shifts in the location of depocenters and regional changes in lithofacies relatively rapid tectonic subsidence during the early and middle jurassic history of the basins may have enhanced sediment accumulation rates beginning in the late jurassic however subsidence rates decreased significantly though occasional short pulses of subsidence may have effected relative sea level rises sea level change heavily influenced the distribution and redistribution of sediments one they reached the basins and paleoclimate regulated the relative abundance of carbonates and evaporites in the basins we conclude that source terrains of the central appalachian highlands were tectonically uplifted intensely weathered and rapidly eroded three times since the late triassic 1 early to middle jurassic aalenian to callovian 2 mid early cretaceous barremian and 3 late cenozoic middle miocene intervals of tectonic quiescence following these three tectonic pulses provided conditions suitable for the formation of regional erosion surfaces geomorphic features commonly reported to characterize the central appalachian highlands this series of three irregularly spaced tectonic quiescent cycles does not however match the traditional four cycle concept of post triassic appalachian peneplanation

foraminiferal sequence biostratigraphy and seismic stratigraphy of a tectonically active margin the yakataga formation northeastern gulf of alaska abstract upper miocene through recent glacial marine deposits of the yakataga formation which underlie the northern gulf of alaska continental shelf are the focus of an integrated study to understand the depositional and climatic history of the upper cenozoic gulf of alaska biostratigraphic lithologie and multichannel seismic data were integrated in a sequence stratigraphic analysis of the yakataga continental margin a paleontologically based approach to sequence stratigraphy known as sequence biostratigraphy was used to define eight seismic stratigraphic sequences on this tectonically active glaciated continental margin foraminifera provide information on the age paleoenvironments and paleoclimates of strata within these eight sequences lithologic evidence is used to infer the presence and influence of tidewater glaciers the three oldest sequences arbitrarily labeled brown red and orange early pliocene mid pliocene late pliocene respectively were deposited in mainly outer neritic through upper bathyal environments planktic foraminiferal assemblages show that sea surface temperatures during deposition of these sequences were mainly cool temperate in the gulf of alaska at this time yet benthic assemblages indicate cold bottom waters and dropstones indicate glacial marine sedimentation during the late pliocene the five youngest sequences labeled yellow green aqua blue violet which are pleistocene to recent in age were deposited in deeper environments on average upper bathyal to middle bathyal than the older sequences glacial marine sedimentation was common during deposition of these sequences abundant dropstones and foraminiferal assemblages indicate both cold sea surface and bottom water temperatures

oligocene miocene alluvial sedimentation in the northern ebro basin ne spain tectonic control and palaeogeographical evolution abstract the oligocene early miocene rocks cropping out in the northern ebro basin central sector comprise conglomerates at the margin of the basin gradually passing into sandstones and mudstones towards more central areas these rocks belong to the peraltilla and sarinena formations and originated in both small monogenic conglomerate alluvial fans that fed from the south pyrenean sierras directly and large polygenic conglomerate fans which drained more internal areas of the pyrenees their lithological textural and geometrical features in combination with sedimentary structures reveal the existence of several lithofacies associations whose lateral and vertical relationships and distribution throughout time have been used to establish the main features for each type of depositional system near the margin of the basin the tertiary series is folded and thrusted and several unconformities can be identified three tecto sedimentary units t3 to t5 have been characterised for the whole area at the margin they are bounded by angular or syntectonic unconformities in more central areas their correlative conformities can be registered as changes from coarsening to fining upward general trends or as sudden shifts in the vertical trend fining upward trends are related to onlaps and record the retrogradational stages of the alluvial fans in contrast coarsening upward trends record the progradation of the fans stratigraphic and sedimentological studies permit to establish the palaeogeographical evolution of the area during oligocene and early miocene times also it can be demonstrated that during periods of tectonic activity in the pyrenees the alluvial fans prograded whereas during the stages of relative tectonic inactivity the fans retrograded

stable seafloor conditions sea level and food supply during the latest maastrichtian at brazos river texas abstract the cretaceous paleogene k pg boundary extinction event is inextricably linked to the chicxulub impact environmental changes like sea level changes and changes in food supply prior to or after the impact could however have contributed to the biotic turnover in this study benthic foraminifera from two cores from the brazos river area in texas are quantitatively analyzed in order to reconstruct environmental changes across the k pg boundary cluster analysis as well as non metric multidimensional scaling reveals three distinct benthic foraminiferal assemblages an upper maastrichtian assemblage a post impact assemblage and a lower danian assemblage the rather uniform upper maastrichtian assemblage at brazos river composed of e g clavulinoides midwayensis gavelinella dumblei cibicidoides harperi gyroidinoides aequilateralis and bulimina kickapooensis indicates a stable paleodepth of about 75 100 m up to the k pg boundary food supply indicators such as percentage buliminaceae and foraminiferal numbers suggest a relatively low and stable food supply during this interval environmental disruption caused by the chicxulub impact led to the settlement of a typical pioneer assemblage characterized by endobenthic morphotypes such as ammobaculites spp and pseudouvigerina naheolensis during the early danian the typical midway type benthic foraminiferal shelf fauna e g alabamina midwayensis anomalinoides acutus gyroidinoides subangulatus praebulimina carseyae and cibicidoides alleni developed indicating a paleodepth of 75 100 m no clear water depth changes can be derived from the benthic foraminiferal record during this interval although the sedimentary record suggests a shallowing followed by a transgressive pulse in zone p1a food supply indicators suggest a lower food supply in the early danian than during the upper maastrichtian because of the stability of the late maastrichtian environment we conclude that environmental disruption caused by the impact was most likely the principal cause of the benthic foraminiferal turnover across the k pg boundary observed at brazos river

depositional cycles and evolution of the paleogene wilcox strata gulf of mexico basin texas the wilcox group is one of the major thick clastic successions of the tertiary gulf coast the wilcox is conventionally subdivided into lower middle and upper parts detailed correlation of more than 700 well logs has identified two depositional cycles of the wilcox strata each of which is represented by four parasequence sets or high frequency genetic stratigraphic sequences two depositional cycles bounded by maximum flooding events were characterized by depocenter shifting shelf margin progradation and depositional system evolution and lasted several million years the sedimentary record of two depositional cycles documents two aspects of these cycles one aspect is that the shelf margin alternated between periods of active outbuilding and periods of relative stability or minor retrogradation another aspect of the cycle is that depositional system evolution displays a progression from progradation to aggradation to retrogressive transgression the time spans of these two cycles are 3 6 m y and 7 5 m y respectively based on the haq time scale each of the two depositional cycles generally corresponds to a pulse of laramide tectonism deposition of two cycles may also reflect a eustatic sea level overprint

coal basins in the cantabrian mountains northwestern spain abstract the cantabrian mountains containing about 70 of the total coals of the country and 95 of the anthracitic and bituminous resources is the most important coal mining district of spain coal bearing successions are late carboniferous in age and their deposition took place in a syn orogenic context during the hercynian activity mainly in three different time successive locations foreland basins intrathrust basins and intramontane fault controlled basins foreland deposition occurred in strongly asymmetrical basins located ahead of thrust sheets units intrathrust basins resulted from folding and tightening of these units during or after their emplacement intramontane and fault controlled basins were developed along lineaments with strike slip movements and as a result of fold and fault reactivation peat mires in foreland and intrathrust coal basins mainly occupied broad areas on abandoned delta and fan delta lobes coals in intramontane and fault controlled basins were related with alluvial fan and lacustrine environments coal ranks vary from high volatile bituminous coals to anthracite depending on the structural location of the coalfields hydrothermal activity seems to be the most important factor in coal evolution

oligocene climate changes controlling forced regression in the eastern north sea abstract in this paper we investigate the early oligocene rupelian high angle clinoform complex from the western part of the norwegian danish basin the study consists of an integrated analysis of 3d seismics petrophysical well logs and micropaleontological data a series of erosional features and geometry of prograding units e g the high angle clinoform complex interpreted as a forced regressive unit is identified the proposed depositional model accounts for lithological variations climate induced sea level fluctuation and depositional environment the characteristic high angle clinoform complex has been estimated to be of late rupelian age paleoenvironmental reconstruction of the unit based on dinocyst analysis suggests that the deposition of the succession took place in submarine conditions presence of a cold water dinoflagellate svalbardella within the unit containing high angle clinoforms suggests that the unit was deposited during one of the oligocene glacial maxima the most probably the oi2 cooling event

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

tectono sequence stratigraphic analysis of the lower cretaceous abu gabra formation in the fula sub basin muglad basin southern sudan abstract the fula sub basin of the muglad basin of southern sudan is an active fault bounded basin with an area of approximately 3300 km 2 the lower cretaceous abu gabra formation formed during the first of three rifting cycles it can be subdivided into five 3rd order sequences named sqa sqe from bottom to top indicating five stages of tectonostratigraphy and tectonosedimentary evolution the spatial distribution and temporal evolution of clastic depositional systems are described in this paper based on integrated analysis of seismic core and well logging data in the abu gabra formation of the fula sub basin a variety of depositional systems are recognized namely fan delta braided delta delta sublacustrine fan and lacustrine system the fula sub basin has undergone a complex and phased rifting evolution and a high abundance of transfer zones developed causing the resulting distribution and architecture of both the sequence and depositional system to be controlled by various types of transfer zones the following three types of sequence architectures from northern to southern part of the fula sub basin have been identified simple dustpan shaped sequence architecture in the north transfer zone sequence stratigraphic architecture in the middle and graben shaped sequence architecture in the south the sequence architecture is under the control of the large scale central transfer zone and nine models are built to study the effect of at least three categories of small scale transfer zones on the depositional systems in the fula sub basin the small scale transfer zones play significant roles in basin fill primarily in controlling of the positions of deposit input points this study provides valuable insights into tectonic control of depositional systems and sequence architectures in a continental rift basin such as the fula sub basin

seismic stratigraphic interpretation of megasequence and sequence framework in the upper cambrian through devonian formations in the central part of the darling basin western new south wales australia abstract upper cambrian through devonian formations in the central part of the darling basin western new south wales were investigated using seismic data complemented by well and outcrop information detailed seismic stratigraphic interpretation of four main second order seismic megasequence buildups in the central northern blantyre and southern pondie range sub basins shows that they are constructed of seventeen principal third order seismic sequences the four seismic megasequences are characterized as follows seismic megasequence a corresponds to the upper cambrian through middle ordovician strata and is equivalent to the scropes range formation or mutawintji group seismic megasequence b corresponds to uppermost silurian through lower devonian strata and is equivalent to the winduck interval seismic megasequence c corresponds to upper lower devonian through lower middle devonian strata and is equivalent to the snake cave interval and seismic megasequence d corresponds to upper middle devonian through upper devonian strata and is equivalent to the ravendale interval five regional seismic stratigraphic boundaries have been identified in the three seismic sections to show the continuity of the upper cambrian through devonian formations throughout the central northern blantyre and southern pondie range sub basins all seismic stratigraphic boundaries are based on good continuous markers with strong amplitudes throughout the whole sub basins detailed sedimentological analysis was applied using lithologic samples wireline log and limited biostratigraphic information to aid in the development of a paleodepositional environment for the upper cambrian through devonian sequence which displays ten different sedimentary facies successions seismic facies analysis was also applied to some of the seismic lines comparing well log observation with reflection configuration and other seismic characteristics for the upper cambrian through devonian successions the seismic facies patterns show continuous semicontinuous and discontinuous reflections with moderate amplitude and high to moderate frequency the sedimentary sequence from the well data can also be recognized in the seismic lines with features such as subparallel to divergent high amplitude reflections parallel to subparallel medium to low amplitude reflectors with high amplitude and high continuity reflections sediment waves with hummocky clinoforms and sometimes high angle clinoforms indicating fluvial channels complex and shallow channel fill complex as a result a sequence stratigraphic framework was constructed successfully consisting of nine seismic sequences six of these contain three systems tracts lowstand transgressive to highstand and two sequence surfaces transgressive surface and marine flooding surface another seismic sequence is composed of two systems tracts a transgressive systems tract and a highstand systems tract separated by a maximum flooding surface the other two within the blantyre 1 well and the pondie range 1 well consist of one stratal pattern that has a highstand systems tract capped by a seismic sequence boundary

bob west field extending upper wilcox production in south texas discovered in 1990 near the southern limit of the upper wilcox gas producing trend in south texas bob west field is the largest pool to date in this trend with probable reserves of up to 1 tcf the field produces from seven major sandstone packages comprising 27 individual reservoirs and distributed over 3500 productive acres the sandstones represent either fluvial deltaic deposits or delta margin barrier bar and strand plain sediments porosities range up to 20 but permeabilities are low commonly less than 1 5 md artificial stimulation is therefore required to establish commercial rates of production bob west lies on a faulted anticline between two major growth fault structures with several stages of structural development evident such development has directly affected sandstone thickness rates of production are higher at bob west than at other upper wilcox fields due to commingling of zones large scale fracture treatments and directional drilling discovery at bob west has significant implications for renewed exploration in this part of the upper wilcox gas trend

sequence stratigraphic interpretations from palynofacies dinocyst and lithological data of upper eocene lower oligocene strata in southern mississippi and alabama u s gulf coast abstract this paper presents new information on the sequence stratigraphy of the upper eocene lower oligocene strata in southern mississippi and alabama based on palynological and lithological data from five sections by integrating lithological characteristics with palynofacies assemblages several dinocyst paleoecological groups the deflandrea group and the abundance of reworked dinocysts in samples paleobathymetric curves were reconstructed and used to revise the sequence stratigraphy of the area we identified a maximum flooding surface in the middle of the shubuta clay formation in southern mississippi and dated it as latest eocene in southern alabama the eocene oligocene boundary was placed within a condensed section representing about 0 19 ma and it coincided with the shubuta clay vicksburg group contact this condensed section is equivalent to the accumulation of the upper shubuta and red bluff formations in southern mississippi the forest hill mint spring contact which has been interpreted as a sequence boundary that merged with a transgressive surface does not correlate with the tejas a ta 4 3 4 4 sequence boundary of haq et al 1988 the pachuta marl and lower shubuta clay formations are constituents of a late eocene transgressive systems tract in southern mississippi but this systems tract extended to the shubuta clay vicksburg group contact in southern alabama the overlying early oligocene highstand systems tract consisted of the upper shubuta in mississippi and the red bluff bumpnose forest hill formations a thin sandstone in the mint spring was interpreted as a deposit of a possible lowstand systems tract above the sequence boundary in one southern mississippi section in general the mint spring marl and marianna limestone constituted a transgressive systems tract

the relationship between glacio eustatic parasequences and a third order sequence in the kakegawa group central japan abstract the plio pleistocene kakegawa group central japan consists of a third order depositional sequence 2 6 1 0 ma the northwestern part of the kakegawa sequence consists of up to 500 m of alluvial shoreface shelf slope and submarine channel facies it contains at least sixteen upward shallowing cycles parasequences the deposition of which was affected by high frequency eustatic sea level cycles the lower part of the sequence is characterized by a retrogradational parasequence set which formed a transgressive systems tract 2 2 1 75 ma followed by a progradational parasequence set comprising a highstand systems tract 1 75 1 4 ma subsidence analysis and evaluation of changes in the shelf sedimentation rate estimated from cross sections suggest that formation of the third order sequence was controlled by tectonic subsidence and variation in the sedimentation rate rapid subsidence and a high rate of sedimentation during 2 2 2 0 ma resulted in deposition of the lower part of the transgressive systems tract characterized by thick backstepping successions the rate of subsidence decreased in the period 2 0 1 75 ma the sedimentation rate also decreased due to a high rate of sediment bypassing however subsidence was still the dominant factor leading to the formation of thin backstepping successions the 1 75 1 4 ma progradational succession resulted from a combination of a low rate of subsidence and moderate sedimentation the progradational units become thicker basinward owing to faster subsidence in the basin center the maximum flooding surface was formed around 1 75 ma even though subsidence was slow at this time

autostratigraphy a framework norm for genetic stratigraphy abstract autostratigraphy is the stratigraphy generated by large scale autogenic processes and needs to be heeded because of a current overreliance on allogenic controls in sequence stratigraphy key principles of autostratigraphy emerging from the theory of autoretreat and a new understanding of alluvial grade derive from the non equilibrium stratigraphic response i e the general lack of equilibrium configuration of depositional systems the non equilibrium behavior of fluvial deltas during times t of steady dynamic forcing leads to variable stratigraphic response that is the inevitable result of length d and time scaling particular to the depositional system rather than necessarily reflecting any sudden or unsteady change in the rate of allogenic forcing some abrupt breaks in the stratigraphic record are not necessarily associated with changes in allogenic conditions but can result from purely autogenic processes of the system when t is comparable to or longer than 1 the depositional system takes the non equilibrium large scale autogenic response 2 the superposition of autogenic and allogenic components of the forcing is prominently nonlinear and thus 3 sequence stratigraphic models that have been built on the assumption of equilibrium response are incorrect autostratigraphic analysis makes it possible to detect and identify complex autogenic responses and unsteady allogenic events in the stratigraphic record by quantifying a temporal change in the magnitude of d autostratigraphy thus functions as a norm for genetic stratigraphy

the cuyama strike slip basin california u s a an exemplar of contrasting syntectonic and post tectonic strata abstract miocene strata in the cuyama basin of southern california exemplify syntectonic and post tectonic stratigraphic development in a strike slip basin integrated seismic well log and outcrop data provide a detailed portrayal of the seismic stratigraphy and sedimentary facies in the previously unstudied middle and upper miocene sequences results show sharp contrast among syntectonic and post tectonic strata from composition and texture of sediments to lateral distribution and thickness of facies seven post tectonic sequences were mapped across the basin sequences contain eolian to fluvial terrestrial facies wave and tide dominated nearshore facies biosiliceous dolomitic and phosphatic outer shelf and slope mudstones and shale rich submarine fans in basinal environments authigenic dolomites and phosphates are pervasive in outer shelf and slope facies and indicate the possibility of restricted sediment supply post tectonic sequences are thin but laterally continuous and they exhibit little depositional asymmetry minor erosion is distributed equally among regressive and transgressive relative sea level changes asynchronous changes in tectonism sediment supply and eustatic sea level change created dramatic differences among syntectonic and post tectonic sequences interbasinal tectonic quiescence led to the abrupt end of stratigraphic mismatches and the accumulation of sediment during brief episodic periods multiple points of progradation persisted through several million years of post tectonic basin development and highlight the importance of extrabasinal sediment supply to the development of all sequences the eventual loss of most accommodation space promoted the importance of eustatic sea level change and reduced the prominence of asymmetric facies and abrupt lateral facies changes

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

quantification of mineral matter in the argonne premium coals using interactive rietveld based x ray diffraction abstract the mineral matter in the eight reference north american coal samples of the argonne premium coal series has been investigated on a quantitative basis using x ray diffraction xrd techniques x ray diffraction data obtained from electronic low temperature oxygen plasma ash lta residues from ashes produced by heating the coals in air at 370 c and also from the raw coals themselves were evaluated using an interactive data processing system siroquant based on rietveld interpretation methods the results from the three types of material lta 370 c ash and raw coal were compared for each sample this allowed the components present in the raw coals in crystalline form to be recognised separately from mineral artifacts produced particularly in the low rank coals from interaction of organically associated elements ca s etc during the two ashing processes after the allowance for the production of any artifacts the quantitative mineral assemblages identified from xrd of the raw coals were found to be consistent even for coals having a relatively low ash percentage around 5 with the results obtained from the respective mineral concentrates prepared by the ashing methods the effects of heating the coal to 370 c could also be distinguished relative to the raw coal or the lta through changes in components such as pyrite and the clay minerals although some areas of uncertainty exist particularly with magnesium in the low rank coals the calculated chemical compositions of the coal ash derived from the mineral mixtures identified for each coal were also found to be consistent with the results of direct chemical analysis of the respective coal ash materials

sedimentation and tectonism in the laramide tornillo basin of west texas abstract the tornillo basin of west texas and adjacent mexico is the southernmost laramide age intermontane basin in the north american cordillera the basin is bounded on the west by the chihuahua tectonic belt a southern extension of the cordilleran fold and thrust belt and on the east by the marathon uplift a laramide style basement cored uplift sedimentological evidence indicates that tectonism began in this region during late cretaceous time ca 70 ma and ended during middle eocene time ca 50 ma the basin experienced two major pulses of fluvial sedimentation the first during middle to late maastrichtian time and the second during late paleocene to early eocene time high sedimentation rates during these periods correspond to the influx of coarse extra basinal detritus high mudstone content in the basin alluvium and thick tabular fluvial sand bodies these episodes probably reflect pulses of tectonism a lull in sedimentation during early paleocene time resulted in a thin sequence of alluvium with very high mudstone content thin lenticular fluvial sand bodies and well developed paleosols the basin experienced left lateral transpressive deformation during the second phase of tectonism the sedimentary sequence in the tornillo basin is compatible with the two phase model of laramide tectonism developed for the central and southern rocky mountains

seismic structure gravity anomalies and flexure of the amazon continental margin ne brazil 1 seismic and gravity data have been used to determine the structure of the sediments crust and upper mantle that underlie the amazon continental margin offshore ne brazil seismic reflection profile data reveal a major unconformity at 7 s two way travel time twtt which we interpret as marking the onset of the transcontinental amazon river and the formation of the amazon deep sea fan system in the late miocene seismic refraction data show mean sediment velocities that decrease by 1 5 km s 1 in a seaward direction we attribute this decrease to facies changes associated with sediment progradation and the development of topset foreset and bottomset beds seismic refraction data show that the sediments are underlain by oceanic crust that has a similar velocity structure compared to elsewhere in the atlantic ocean but is unusually thin 4 2 km we attribute the thin crust to either slow seafloor spreading or a limited magma supply during the initial rifting of south america and africa in the early cretaceous the seismic data have been used to construct a new sediment thickness grid that together with gravity anomaly data suggests the amazon fan loaded lithosphere with an unusually high flexural strength while a high strength lithosphere explains the overall depth of the seismic moho there are discrepancies of up to 2 km beneath the upper fan where the modeled flexed moho is shallower than the seismic moho and beneath the middle fan where it is deeper gravity and seismic modeling suggest these discrepancies are caused by lateral changes in subcrustal density such that the mantle underlying the upper fan is denser than it is beneath the middle fan we attribute these lateral density differences to proximity to the ceara rise which is believed to have formed during the late cretaceous in a mid ocean ridge setting fan loading of a relatively strong dense and hence cold lithosphere predicts stress orientations that are consistent with borehole breakout data and the location and height of the gurupe arch onshore despite its proximity to leaky transform faults the margin that underlies the amazon fan appears to be of nonvolcanic origin the main differences with other nonvolcanic margins such as west iberia and newfoundland are a greater sediment accumulation a narrower zone of transitional crust and a lack of any evidence for extreme extension and mantle serpentinization

review and update of the applications of organic petrology part 2 geological and multidisciplinary applications abstract the present paper is focused on organic petrology applied to unconventional and multidisciplinary investigations and is the second part of a two part review that describes the geological applications and uses of this branch of earth sciences therefore this paper reviews the use of organic petrology in investigations of i ore genesis when organic matter occurs associated with mineralization ii the behavior of organic matter in coal fires self heating and self combustion iii environmental and anthropogenic impacts associated with the management and industrial utilization of coal iv archeology and the nature and geographical provenance of objects of organic nature such as jet amber other artifacts and coal from archeological sites and v forensic science connected with criminal behavior or disasters this second part of the review outlines the most recent research and applications of organic petrology in those fields

long periodic variations in the earth s obliquity and their relation to third order eustatic cycles and late neogene glaciations abstract evolutive spectra of four high resolution climatic proxy records reveal that the spectral power in the obliquity frequency band increases during five well defined intervals in the last 5 3 million years these intervals correspond to periods of high amplitude variations in the tilt obliquity of the earth s axis connected with a 1 2 myr cycle and to sea level lowstands of third order eustatic cycles in the haq et al 1987 curve this implies that the development of major plio pleistocene glaciations proceeded episodically and that third order cycles are glacio eustatically controlled in at least two of these intervals sinistrally coiled neogloboquadrinids entered the mediterranean at times of glacial periods one interval starts around 2 8 ma and is characterized by the first occurrence of n atlantica s another interval begins at the plio pleistocene boundary around 1 8 ma and is characterized by the common occurrence of sinistrally coiled n pachyderma also during the late miocene third order cycles correlate well with the 1 2 myr cycle of obliquity a significant drop in the third order eustatic curve starting at the tortonian messinian boundary for instance coincides with a period of high amplitude variations in the obliquity time series connected with the 1 2 myr cycle

rapid cenozoic subsidence in the gulf of mexico resulting from hess rise conjugate subduction enigmatic surface deflections occurred in north america starting from the cretaceous including the continental scale drainage reorganization and the long wavelength subsidence in the western interior seaway these surface undulations cannot be simply explained by sea level change or flexure loading coinciding with the large scale surface deflection the gulf of mexico gom has an immense paleocene sediment deposition probably caused by tectonic subsidence increasing evidence indicates a distinct seismic anomaly localized in the mantle below the gom with geodynamic models we show that the hess rise conjugate coincides with the position of the seismic anomaly the basalt eclogite transition in the hess conjugate can lead to a localized dynamic subsidence in the gom which is superimposed on the broad surface deflection caused by the farallon slab the hess conjugate transformed to eclogite could tilt the surface southward in the u s and help frame the gom as a main depocenter in the cenozoic

the late cretaceous to holocene sequence stratigraphy of a sheared passive upper continental margin northern kwazulu natal south africa abstract high resolution single channel seismic data reveal seven seismic units a g from the narrow and steep upper portions of the sheared passive continental margin of northern kwazulu natal several characteristic internal geometries are evident onlapping sheet like unit c aggradational progradational unit a and facies d3 and progradational unit b facies d1 2 and facies g1 on the basis of internal geometry and bounding unconformities lowstand units b facies d3 and lowermost unit g possible transgressive unit c highstand upper unit g and falling stage facies d1 and d2 systems tracts are delineated units e and f are not reconcilable due to acoustic opacity overall five incompletely preserved sequences are observed sequence one comprises unit a of suspected middle maastrichtian age separated from the overlying sequence by a subaerial unconformity surface sb1 units b and c form sequence two and span the late cretaceous late maastrichtian to mid late palaeocene two major hiatuses ensued angus and jimmy until mid pliocene times when unit d was deposited during shelf margin advance linked to hinterland uplift these falling stage systems tract deposits are separated from latest pliocene early pleistocene lowstand shelf edge deltaic deposits by a subaerial unconformity marking the deposition of sequence four facies d3 the age of unit e is uncertain unit f represents a series of shorelines formed during oxygen isotope stage ois 5a to 2 on the regressive and transgressive limbs preceding and following the last glacial maximum lgm the final partial sequence preserved is comprised of unit g formed during the ois 2 transgression to present mean sea level and subsequent development of the contemporary highstand wedge in terms of stratigraphic architecture this study shows an evolution from a ramp style margin with a poorly defined shelf break to that of a shelf break profile with a narrow and steep shelf in this respect the narrowness of this shelf cannot be accounted for by the inheritance of shearing effects rather the stratigraphic architecture reflects a period of slow and protracted subsidence with strong sediment dispersal later punctuated by hinterland uplift this formed the late pliocene shelf margin clinoforms of unit d and established the shelf break position at the offlap break of this wedge the resulting narrow shelf may play a significant role in the preservation of later sequences particularly in light of the continued uplift of the margin causing off shelf sediment bypass where tst and hst sequences may not be preserved this is reflected in the isolated preservation of shoreline and shallow marine deposits of the pleistocene units e and f

shelf edge delta and reef development on a mixed siliciclastic carbonate margin central great barrier reef the great barrier reef gbr is the world s largest extant mixed silicilastic carbonate margin previous research on the great barrier reef has suggested that the extensive barrier reef system may act as an impermeable barrier and limit the development of delta systems during lowstands but sufficient geophysical data to support this hypothesis are lacking we use dense sparker seismic and sub bottom profiler data to better understand the structure of a large lobe shaped feature 10 km 10 km on the shelf edge of the central gbr and the interactions between siliciclastic and carbonate sedimentary systems interpreted sparker seismic contains prograding clinoforms and suggest that the lobe shaped feature was a river dominated shelf edge delta a delta on the shelf edge implies that the presence of an exposed barrier reef was not a major impediment to deposition and that other adjacent lobe shaped features are also deltaic deposits the shelf edge deltas were deposited onto a broad upper slope terrace that allowed continued progradation and limited incision when sea level fell below the shelf edge delta foresets are commonly colonized by coral reefs but the spatial and temporal relationship between reefs and some deltaic units remains unclear the presence of multiple shelf edge deltas that link to previously mapped burdekin river paleo channels indicates a complex history of sedimentation with the burdekin river delta migrating up to 100 km along the gbr margin during the late quaternary regional bathymetric data suggest that large modern or recent shelf edge deltas are rare on the gbr and that there was a broad range of sedimentary processes operating along the margin of the gbr during periods of low sea level

shelf fed turbidite system model and its application to the oligocene deposits of the campos basin brazil despite the large number of models involving the genesis and sedimentary facies of deep water sandstones none of these models adequately explain the origin and evolution of the extremely clean widespread over 6000 km2 predominantly massive thick over 150 m blanket like sandstones deposited in the deep water environment of the campos basin during the oligocene consequently to explain this sandstone i propose a shelf fed turbidite system model which is strongly based on the campos basin data set the basic framework necessary for the development of a shelf fed turbidite system includes 1 deposition of a large volume of clastics during the buildup of a shelf sand rich unit which later constitutes the main source of sediment for the system 2 localized tectonic pulses that modify the outer shelf declivity and trigger mass flows and 3 a relative fall of sea level which causes the subaqueous exposure of the shelf sediments to reworking in a shallow high energy marine environment these three basic elements are equally important for shelf fed turbidite system development but relative sea level position controls the development of the progradational aggradational and retrogradational depositional phases within the system submarine canyons commonly are scoured during al three phases on the outer shelf and lower slope environments the shelf fed turbidite system model may apply to other sedimentary basins principally to those of the atlantic continental margins that have a thick evaporite sublayer halokinesis can provide the necessary room for the shelf sedimentary unit buildup the tectonic pulses that trigger the flows and even localized relative sea level oscillations that can accelerate or abort any one of the depositional phases of the system

linked sequence stratigraphy and tectonics in the sichuan continental foreland basin upper triassic xujiahe formation southwest china abstract intracontinental subduction of the south china block below the north china block in the late triassic resulted in formation of the transpressional sichuan foreland basin on the south china block the upper triassic xujiahe formation was deposited in this basin and consists of an eastward tapering wedge of predominantly continental siliciclastic sedimentary rocks that are up to 3 5 km thick in the western foredeep depocenter and thin onto the forebulge and into backbulge depocenters five facies associations a e make up the xujiahe formation and these are interpreted respectively as alluvial fan transverse and longitudinal braided river meandering river overbank or shallow lacustrine and deltaic deposits this study establishes a sequence stratigraphic framework for the xujiahe formation which is subdivided into four sequences sq1 2 3 and 4 sequence boundaries are recognized on the basis of facies tract dislocations and associated fluvial rejuvenation and incision and systems tracts are identified based on their constituent facies associations and changes in architectural style and sediment body geometries typical sequences consist of early to late transgressive systems tract deposits related to a progressive increase in accommodation and represented by facies associations a b and c that grade upwards into facies association d regionally extensive and vertically stacked coal seams define maximum accommodation and are overlain by early highstand systems tract deposits represented by facies associations d e and c late highstand systems tract deposits are rare because of erosion below sequence boundaries sequence development in the xujiahe formation is attributed to active and quiescent phases of thrust loading events and is closely related to the tectonic evolution of the basin the sichuan basin experienced three periods of thrust loading and lithospheric flexure sq1 lower sq2 and sq3 two periods of stress relaxation and basin widening upper sq 2 and sq3 and one phase of isostatic rebound sq4 paleogeographic reconstruction of the sichuan basin in the late triassic indicates that the longmen mountains to the west consisting of metamorphic sedimentary and pre neoproterozoic basement granitoid rocks was the major source of sediment to the foredeep depocenter subordinate sediment sources were the xuefeng mountains to the east to backbulge depocenters and the micang mountains to the northwest during the late history of the basin this study has demonstrated the viability of sequence stratigraphic analysis in continental successions in a foreland basin and the influence of thrust loading on sequence development

prograding muddy shelves in the paleogene wilcox deltas south texas gulf coast abstract core facies analysis integrated with subsurface well log correlations and seismic horizon mapping document two thick mudstone dominated deltaic successions in the wilcox group along the south texas gulf coast meters to tens of meter thick upper slope to outer shelf mudstones form units that lie at the base of upward coarsening successions which are interpreted as fluvial or storm wave dominated shelf deltas the muddy character of the deposits is observed in cores and inferred from well logs whereas the larger depositional architecture is interpreted from well log correlations and seismic data physical sedimentary structures described from a lower wilcox core reflect deposition on a mud dominated prodelta controlled by hyperpycnal processes normally and inversely graded beds are present indicating sustained flows that waxed and waned upward coarsening facies successions contain current ripples organic matter and siderite cemented bands low trace fossil abundance and low diversity which suggest deposition in a fluvial prodelta to shelf environment centimeter thick interbeds of normal and inversely graded mudstones siltstones and very fine grained sandstones with low intensities of bioturbation reflect the high physical and chemical stresses of hyperpycnal environments heterolithic stratification with lenticular wavy and flaser bedding indicates some tidal influence on the other hand cores of the middle wilcox reflect deposition on a muddy wave storm dominated shelf bioturbation intensities tend to be high with unstressed fully marine ichnological suites pervasively bioturbated sandy mudstones and muddy sandstones with cruziana ichnofacies wavy parallel and low angle lamination and structureless sandstones with ophiomorpha record deposition in a wave influenced prodelta to shelf environment hyperpycnal flows associated with river floods might have transported mud across the shelf to the outer shelf where prevailing wave and storm conditions facilitated suspension and transport of mud beyond the shelf edge previous studies have shown that wilcox delta sandstones are largely trapped on the shelf by contemporaneous growth faults however this paper illustrates that at times the wilcox shelf margin prograded through mud accretion

evolution of fluvial style in the siwalik group in the foothills of the nepal himalaya abstract middle miocene to pleistocene fluvial sediments of the siwalik churia group are widely distributed in the southern frontal area of the himalaya the succession is about 6 km thick and was derived from denudation of the himalayan orogen the siwalik group in nepal is well exposed in the surai khola area western nepal and the hetauda bakiya khola area central nepal the group is separated into northern and southern belts by the central churia thrust cct eight facies associations fa1 to fa8 are recognized in the siwalik group in these areas they are interpreted as the deposits of fine grained meandering flood flow dominated fine grained meandering sandy meandering deep sandy braided comparatively shallow sandy braided anastomosed gravelly braided and debris flow dominated braided systems respectively fa6 fa7 and fa8 occur only in the southern belt in each area the sedimentary succession generally coarsens upwards the accumulation of these facies associations related to the paleomagnetic time frame indicates that flooding increased dramatically from about 10 5 to 9 5 ma and fluvial style changed from meandering to braided between 9 0 and 6 5 ma a gravelly fluvial system prevailed after 3 0 to 2 5 ma the evolution of these fluvial styles is intimately related to the uplift of the himalaya and associated thrust movements and consequent effects on atmospheric circulation and precipitation by comparison with the characteristics of the submarine bengal fan deposits it is apparent that an increase in flood flow is strongly influenced by increased precipitation due to onset and intensification of monsoon climate the sandy braided system was mainly induced by regional tectonic uplift and the gravelly fluvial system may have been formed due to regional thrust movements along the himalaya frontal area

assessment of undiscovered conventional oil and gas resources onshore claiborne group united states part of the northern gulf of mexico basin the middle eocene claiborne group was assessed for undiscovered conventional hydrocarbon resources using established u s geological survey assessment methodology this work was conducted as part of a 2007 assessment of paleogene neogene strata of the northern gulf of mexico basin including the united states onshore and state waters dubiel et al 2007 the assessed area is within the upper jurassic cretaceous tertiary composite total petroleum system which was defined for the assessment source rocks for claiborne oil accumulations are interpreted to be organic rich downdip shaley facies of the wilcox group and the sparta sand of the claiborne group gas accumulations may have originated from multiple sources including the jurassic smackover formation and the haynesville and bossier shales the cretaceous eagle ford and pearsall formations and the paleogene wilcox group and sparta sand hydrocarbon generation in the basin started prior to deposition of claiborne sediments and is currently ongoing primary reservoir sandstones in the claiborne group include from oldest to youngest the queen city sand cook mountain formation sparta sand yegua formation and the laterally equivalent cockfield formation a geologic model supported by spatial analysis of petroleum geology data including discovered reservoir depths thicknesses temperatures porosities permeabilities and pressures was used to divide the claiborne group into seven assessment units aus with three distinctive structural and depositional settings the three structural and depositional settings are 1 stable shelf 2 expanded fault zone and 3 slope and basin floor the seven aus are 1 lower claiborne stable shelf gas and oil 2 lower claiborne expanded fault zone gas 3 lower claiborne slope and basin floor gas 4 lower claiborne cane river 5 upper claiborne stable shelf gas and oil 6 upper claiborne expanded fault zone gas and 7 upper claiborne slope and basin floor gas based on monte carlo simulation of justified input parameters the total estimated mean undiscovered conventional hydrocarbon resources in the seven aus combined are 52 million bbl of oil 19 145 tcf of natural gas and 1 205 billion bbl of natural gas liquids this article describes the conceptual geologic model used to define the seven claiborne aus the characteristics of each au and the justification behind the input parameters used to estimate undiscovered resources for each au the great bulk of undiscovered hydrocarbon resources are predicted to be nonassociated gas and natural gas liquids contained in deep mostly 12 000 ft 3658 m present day drilling depths overpressured structurally complex outer shelf or slope and basin floor claiborne reservoirs the continuing development of these downdip objectives is expected to be the primary focus of exploration activity for the onshore middle eocene gulf coast in the coming decades

the role of the sediment load in sequence stratigraphy the influence of flexural isostasy and compaction simplified physically based models are utilized in order to examine the effects of sea level sedimentation tectonic subsidence isostatic compensation and compaction on development of unconformities unconformities divide volumes of relatively conformable sediments defining the time and spatial extent of sedimentary sequences the model parameters are varied both individually and in concert in order to isolate their contributions to sequence architecture these models reveal the importance of sedimentation and subsidence rates as well as sea level amplitude and rate in determining the type and extent of sequence boundary formed sedimentation and subsidence rate can vary significantly within and between margins producing different sequence boundaries given an identical eustatic sea level fall it is shown that sea level amplitude plays an important role in determining which systems tracts are present and sequence boundary timing for type 1 sequences and that sea level rate controls the same attributes in type 2 sequences isostatic compensation and compaction which have been described as secondary effects are shown to have considerable influence on sequence architecture these two processes due to isostatic response to sediment loading and sediment self loading initiate feedback by enhancing and partitioning accommodation space these additional effects invalidate application of the equilibrium point as a guide to where and how all accommodation space is created the manner in which flexure distributes accommodation space is a function of lithospheric rigidities higher rigidities partition space laterally producing wide shelves which favor type 1 sequence boundaries whereas lower rigidities partition space vertically forming narrow shelves which favor type 2 sequence boundaries compaction generates a net landward shift of the shelf edge and favors type 2 sequence development both isostatic compensation and compaction introduce time delays in sequence development one consequence of compaction is to rotate sedimentary packages generating growth and leakage of anticlinal structures as fluids are driven from the underlying section this process has important implications for hydrocarbon migration in compaction dominated systems such as the gulf of mexico margin