carbonate factories a conundrum in sedimentary geology abstract describing characterizing and interpreting the nearly infinite variety of carbonate rocks are conundrums intricate and difficult problems having only conjectural answers that have occupied geologists for more than two centuries depositional features including components rock textures lithofacies platform types and architecture all vary in space and time as do the results of diagenetic processes on those primary features approaches to the study of carbonate rocks have become progressively more analytical one focus has evolved from efforts to build reference models for specific phanerozoic windows to scrutinize the effect of climate and long term oscillations of the ocean atmosphere system in influencing the mineralogy of carbonate components this paper adds to the ongoing lively debates by attempting to understand changes in the predominant types of carbonate producing organisms during the mesozoic cenozoic while striving to minimize the uniformitarian bias our approach integrates estimates of changes in ca2 concentration in seawater and atmospheric co2 with biological evolution and ecological requirements of characteristic carbonate producing marine communities the underlying rationale for our approach is the fact that co2 is basic to both carbonates and organic matter and that photosynthesis is a fundamental biological process responsible for both primary production of organic matter and providing chemical environments that promote calcification gross photosynthesis and hypercalcification are dependent largely upon sunlight while net primary production and e g subsequent burial of organic matter typically requires sources of new nutrients n p and trace elements our approach plausibly explains the changing character of carbonate production as an evolving response to changing environmental conditions driven by the geotectonic cycle while identifying uncertainties that deserve further research with metazoan consumer diversity reduced by the end permian extinctions excess photosynthesis by phytoplankton and microbial assemblages in surface waters induced by moderately high co2 and temperature during the early mesozoic supported proliferation of non tissular metazoans e g sponges and heterotrophic bacteria at the sea floor metabolic activity by those microbes especially sulfate reduction resulted in abundant biologically induced geochemical carbonate precipitation on and within the sea floor for example with the opening of tethyan seaways during the triassic massive sponge microbe boundstones the benthic automicrite factory formed steep massive and thick progradational slopes and locally mud mounds as tectonic processes created shallow epicontinental seas photosynthesis drove lime mud precipitation in the illuminated zone of the water column the resulting neritic lime mud component of the shallow water carbonate factory became predominant during the jurassic paralleling the increase in atmospheric pco2 while the decreasing importance of the benthic automicrite factory parallels the diversification of calcifying metazoans phytoplankton and zooplankton with atmospheric pco2 declining through the cretaceous the potential habitats for neritic lime mud precipitation declined at the same time peak oceanic ca2 concentrations promoted biotically controlled calcification by the skeletal factory with changes produced by extinctions and turnovers at the cretaceous tertiary boundary adaptations to decreasing ca2 and pco2 coupled with increasing global temperature gradients i e high latitude and deep water cooling and strategies that efficiently linked photosynthesis and calcification promoted successive changes of the dominant skeletal factory through the cenozoic larger benthic foraminifers protist protist symbiosis during the paleogene red algae during the miocene and modern coral reefs metazoan protist symbiosis since late miocene

sedimentary architecture and depositional controls of a pliocene river dominated delta in the semi isolated dacian basin black sea abstract sedimentological facies models for semi isolated basins are less well developed than those for marine environments but are critical for our understanding of both present day and ancient deltaic sediment records in restricted depositional environments this study considers an 835 m thick sedimentary succession of mid pliocene age which accumulated in the dacian basin a former embayment of the black sea detailed sedimentological and palaeontological analyses reveal a regression from distal prodelta deposits with brackish water faunas to delta top deposits with freshwater faunas sediments contain frequent hyperpycnal plumes and an enrichment in terrestrial organic material ichnofossils and in situ brackish and freshwater faunas deltaic progradation created thin sharply based sand bodies formed by multiple terminal distributary channels covering a wide depositional area the system experienced frequent delta lobe switching resulting in numerous thin parasequences parasequences are overlain by erosive reddish oxidized sand beds enriched in broken abraded brackish and freshwater shells these beds were formed after sediment starvation on top of abandoned delta lobes during each flooding event a robust magnetostratigraphic time frame allowed for comparison between the observed sedimentary cyclicity and the amplitude and frequency of astronomical forcing cycles our results indicate that parasequence frequencies are significantly higher than the number of time equivalent astronomical cycles this suggests that delta lobe switching was due to autogenic processes we consider the observed facies architecture typical for a delta prograding on a low gradient slope into a shallow brackish protected semi isolated basin furthermore in the absence of significant wave and tidal influence sediment progradation in such a protected depositional setting shaped a delta strongly river dominated

a coal depositional model for the durham coal measures of ne england the upper carboniferous westphalian coal measures of the durham coalfield were deposited on a broad flat deltaic plain in early westphalian a times a lower delta plain setting prevailed evolving through southward deltaic progradation into an upper delta plain by mid westphalian a detailed facies analysis of large opencast exposures supported by extensive subsurface data has shown that a hierarchy of depositional controls operated across the durham area during westphalian times i on the large scale depositional geometry was controlled by patterns of major delta progradation and switching ii on the medium scale by a combination of structurally and compactionally induced subsidence and iii on the small scale by local sedimentary processes and subsidence patterns these observations form the basis of a coal depositional model for the durham coal measures which predicts that the thickest coals are to be found in upper delta plain domains controlled by compactional subsidence and not underlain by substantial channel sandstones this model may also be applicable to other coalfields of northern england and to ancient delta plain sequences elsewhere in the world

the fluid dynamics of a basaltic magma chamber replenished by influx of hot dense ultrabasic magma this paper describes a fluid dynamical investigation of the influx of hot dense ultrabasic magma into a reservoir containing lighter fractionated basaltic magma this situation is compared with that which develops when hot salty water is introduced under cold fresh water theoretical and empirical models for salt water systems are adapted to develop a model for magmatic systems a feature of the model is that the ultrabasic melt does not immediately mix with the basalt but spreads out over the floor of the chamber forming an independent layer a non turbulent interface forms between this layer and the overlying magma layer across which heat and mass are transferred by the process of molecular diffusion both layers convect vigorously as heat is transferred to the upper layer at a rate which greatly exceeds the heat lost to the surrounding country rock the convection continues until the two layers have almost the same temperature the compositions of the layers remain distinct due to the low diffusivity of mass compared to heat the temperatures of the layers as functions of time and their cooling rate depend on their viscosities their thermal properties the density difference between the layers and their thicknesses for a layer of ultrabasic melt 18 mgo a few tens of metres thick at the base of a basaltic 10 mgo magma chamber a few kilometres thick the temperature of the layers will become nearly identical over a period of between a few months and a few years during this time the turbulent convective velocities in the ultrabasic layer are far larger than the settling velocity of olivines which crystallise within the layer during cooling olivines only settle after the two layers have nearly reached thermal equilibrium at this stage residual basaltic melt segregates as the olivines sediment in the lower layer depending on its density the released basalt can either mix convectively with the overlying basalt layer or can continue as a separate layer the model provides an explanation for large scale cyclic layering in basic and ultrabasic intrusions the model also suggests reasons for the restriction of erupted basaltic liquids to compositions with mgo 10 and the formation of some quench textures in layered igneous rocks

fluvial facies model of the ganga river sediments india abstract the river ganga flows from the northwest to the southeast following the lineaments developed in response to the himalayan tectonics ganga sediments show a large number of facies developments throughout the study area from hardwar to kachhla the active channel deposits are marked by the development of large scale facies in gravel and coarse sand small scale facies comprising fine sand silt and clay are developed in inactive channel deposits and overbank deposits the depositional model shows a progressive decrease in particle size thickness of units and scale of cross bedded sets from the lower to the upper parts of sequences as well as from upstream to downstream the sedimentation of the ganga basin is seasonally and tectonically controlled

some late eocene depositional environments of the coal bearing puget group of western washington state u s a abstract plant bearing sediments of the puget group in the area of detailed study accumulated in large flood basins cutoff meanders and along channel margins in point bars and crevasse splay settings in addition to the plant bearing deposits peat swamp deposits and coarse grained channel deposits are represented by stacked sandstone bodies and thick coal sequences the depositional environments of the fluvial deltaic deposits are distinguished by the presence and distribution of sedimentary structures grain size grain size variability and the densityand layering of organic remains both plant and invertebrate the importance of organic matter distribution in the sediments to differentiation of subenvironments was unexpected and may prove to be a valuable sedimentary characteristics in depositional interpretations within a single basin the sedimentary characterization of environments was made exclusive of the taxonomic composition of the plants preserved and is presented here without paleobotanical interpretation the separation of depositional interpretation from taxonomic identity of the fossil plants allows an independent assessment of the paleoecology of the plants preserved two prominent coal depositional models are discussed and evaluated in light of these data from the puget group it is concluded that peat accumulation in this system can be attributed most easily to a domed peat swamp model

early middle pleistocene sediments at sidestrand northeast norfolk yield the most extensive preglacial cold stage beetle assemblage from britain fluvial sediments cromer forest bed formation at sidestrand northeast norfolk have yielded the most extensive preglacial early middle pleistocene cold arctic stage beetle assemblage known from britain the assemblage is composed of 59 taxa indicating severely cold and continental climatic conditions mutual climatic range reconstructions suggest that the mean temperature of the warmest month july was between 10 c and 13 c and the mean temperature of the coldest months january and february between 17 c and 10 c although the actual palaeotemperatures were probably towards the lower end of these ranges associated pollen and macroflora remains were poorly represented but all are known from other cold stage contexts excavations reveal that this freshwater arctic assemblage occurs within units between two important stratigraphic marker horizons the sidestrand hall member of the cromer forest bed formation and the first lowland glacigenic deposit happisburgh till member in eastern england although the ages of both remain equivocal recent amino acid chronologies of molluscan faunas from the sidestrand hall member indicate a mis 13 age with by inference a mis 12 age for the overlying arctic units with cold beetle fauna and for the happisburgh till member however the arctic units are separated from the two stratigraphic marker horizons by shallow marine deposits wroxham crag formation demonstrating at least two intervening phases of marine transgression and a cold climate marine regression the climatic significance of these marine transgressions and their chronostratigraphic implications are currently uncertain

application of an alluvial architecture model to better understand seepage risk in floodplains abstract the amount and distribution of coarse grained sediment e g sands and gravels relative to fine grained sediment e g clays and silts within a floodplain influences many of the floodplain geotechnical properties including the potential for groundwater seepage seepage is a primary driver of levee and dam failure and understanding its potential is of paramount concern to engineers and resource managers this paper reports the results of a computational modeling study that simulated alluvial floodplain construction using a suite of simple geomorphic process imitating rules a model aggrades a floodplain cross section within an alluvial basin creating floodplain architecture by differentiating between sediment deposited by channel processes sand and sediment deposited by overbank flood processes clay the evolution of two floodplain cross sections of the trinity river near dallas texas is simulated using five different experimental scenarios the study area is the site of large levee rehabilitation projects in which accurate characterization of the geologic environment has significant engineering importance study results predict that scenario components including the alluvial basin width the initial topography of the floodplain base level and the channel aggradation rate significantly affect the fraction of the floodplain width that contains channel deposits by influencing the avulsion frequency of the river during floodplain construction increased avulsion frequency equated to more numerous yet smaller channel deposits the dimensions of the channel deposits predicted by this study are similar to those typically observed in large fully meandering river systems the model devised for this study is relatively simple and can be run in multiple iterations to produce probabilistic outputs such as the likely range of channel deposit widths within a floodplain cross section this type of information is useful to engineers for a host of applications including predicting the data collection density necessary to characterize the geotechnical properties of a project site

deltaic sedimentation in an unstable tectonic environment the lower limestone group lower carboniferous of east fife scotland the lower limestone group which outcrops extensively on the east coast of fife southeast scotland consists of interbedded sandstones siltstones and claystones with occasional coal seams and limestone beds several of the coals have been mined economically in the past the sequence was deposited in a shallow water deltaic setting three facies associations have been distinguished 1 laminated claystones and marine bioclastic limestones which were deposited in prodelta and marine shelf environments 2 crudely coarsening upward sandstone units interpreted as delta front deposits of fluvially dominated though wave influenced shallow water deltas and 3 interbedded clastic sedimentary rocks and coals deposited in delta plain environments the sequence as a whole accumulated by repeated progradation and abandonment of deltaic complexes palaeosol profiles of four types are superbly preserved within the delta plain facies association these are 1 organic soils peats now coal seams 2 gley palaeosols which formed in persistently waterlogged conditions 3 freely drained soils which formed on a quartz sand rich substrate and 4 similar profiles formed by free drainage through variable substrates and involving b horizon accumulation of concretionary iron oxides compound palaeosols are common deposition of the lower limestone group was influenced by the tectonic and volcanic instability of the fife area during visean times frequent seismic events centred on active fault lines caused local uplift of parts of the normally waterlogged delta plain environment allowing the formation of well drained soils peats coals were best developed and least affected by oxidation in an elongate fault bounded zone of enhanced subsidence

dynamics of tethyan carbonate platforms tethyan carbonate platforms are relatively short lived depositional systems which were born developed died and sometime resurrected in a tectonically active area in contrast with pericratonic platforms which are generally huge in size hundreds of kilometers across and show wide facies belts very gentle slopes ramps and transitional boundaries tethyan carbonate platforms are smaller tens of kilometers and have steep slopes generally faulted boundaries and abrupt facies changes it appears clear that the overall control on these two contrasting systems is the geodynamic milieu relatively stable in the first case where eustatic oscillations and long term subsidence are probably the main dictators quite dynamic and aggressive in the second one where carbonate platforms developed through the entire geodynamic spectrum rifting transtension transpression and collision of the wilson cycle primary controls on tethyan carbonate platforms appear to be tectonics most important and eustatic sea level oscillations which determine their emplacement growth and decay their overall shape and architecture are a function of these factors secondary factors affecting tethyan carbonate platform evolution are physiography oceanographic conditions and biology as a function of geologic time especially across the mesozoic tertiary boundary facies and facies distribution and to a lesser extent their shape are controlled by thesemore variables less

large fluvial systems the atane formation a fluvio deltaic example from the upper cretaceous of central west greenland abstract recognition of major river deposits are crucial to the understanding of palaeogeography and basin evolution this paper describes the geometry of 2 30 m thick fluvial sand bodies which occur in upper cretaceous strata deposited in a major river delta in central west greenland the deposits are cyclic and each cycle can be divided into four genetic facies associations which reflect deposition 1 at the delta front 2 on the delta plain 3 in fluvial channels and 4 during transgression of a delta lobe the cyclicity is attributed mainly to autocyclic shifting of delta lobes the study area is very well exposed and an advanced new photogrammetric system was used both for making accurate vertical profiles and for mapping the horizontal extent of individual sand bodies based on horizontal extent internal architecture and relationship to other facies associations the c 100 investigated sand bodies from the fluvial channel association can be divided into two important types distributary channel sand bodies are the dominant type 80 they vary in thickness from 3 m up to as much as 30 m and reflect the migration and infilling of rather narrow distributary channels that existed on a flat vegetated delta plain the relationship with the surrounding sediments as well as faint epsilon cross beds which extend right through the sand bodies indicate that the thicknesses of the sand bodies approximate the bankfull depth of the palaeochannels many small and medium sized sand bodies have very narrow cross sections and show no signs of lateral migration the preserved geometry of these sand bodies consequently represents the original channel morphology the sand bodies show an increasing degree of migration with increasing thickness and the width thickness ratio increases from c 6 for the smaller sand bodies up to c 20 for the largest the distributary channels were only moderately sinuous with an average sinuosity of 1 2 channel mouth complexes are the other type of fluvial sand bodies 20 they are 3 8 m thick and have a large lateral extent with a width thickness ratio of 50 or more they have an erosive base and occur in the top of the coarsening upward sequences made by the delta front association internal bounding surfaces suggest that these sand bodies were generated by lateral amalgamation of many small channel fills in fan shaped sub deltas at the sea ward end of distributary channels the discharge through the distributary channels has been calculated using the manning equation these calculations indicate that the river system which supplied the atane delta was very large and may well have drained most of the presently ice covered interior of greenland

latest mid pennsylvanian tree fern forests in retrograding coastal plain deposits sydney mines formation nova scotia canada a latest mid pennsylvanian early cantabrian tree fern forest is reported from cape breton island nova scotia the fossil forest is rooted below the point aconi coal seam of the sydney mines formation at cranberry head the tree ferns are preserved in the deposits of a coastal plain subject to brackish incursions they were constructed of psaronid type trunks and massive pecopterid fronds and locally intergrew with sigillarian lycopsids neuropterid pteridosperms and calamiteans basal stump diameter measurements including the root mantle range from 12 to 89 cm indicating that the ferns were mostly large forest trees rather than shrubs stump distribution measurements on palaeosols indicate that localized patches of tree fern dominated forest attained densities of c 3850 trees per hectare when scaled up to standard forestry units much denser than typical mid pennsylvanian lycopsid forests tree ferns dominantly grew in aggrading floodbasin settings and a few of the largest trees show evidence for post burial regeneration being approximately coeval with the late mid pennsylvanian extinction event which resulted in tree fern forests rising to dominate tropical lowlands for the first time the cranberry head fossil forests provide insight into community composition and structure during a critical phase of ecosystem reorganization

gplates building a virtual earth through deep time gplates is an open source cross platform plate tectonic geographic information system enabling the interactive manipulation of plate tectonic reconstructions and the visualization of geodata through geological time gplates allows the building of topological plate models representing the mosaic of evolving plate boundary networks through time useful for computing plate velocity fields as surface boundary conditions for mantle convection models and for investigating physical and chemical exchanges of material between the surface and the deep earth along tectonic plate boundaries the ability of gplates to visualize subsurface 3 d scalar fields together with traditional geological surface data enables researchers to analyze their relationships through geological time in a common plate tectonic reference frame to achieve this a hierarchical cube map framework is used for rendering reconstructed surface raster data to support the rendering of subsurface 3 d scalar fields using graphics hardware accelerated ray tracing techniques gplates enables the construction of plate deformation zones regions combining extension compression and shearing that accommodate the relative motion between rigid blocks users can explore how strain rates stretching shortening factors and crustal thickness evolve through space and time and interactively update the kinematics associated with deformation where data sets described by geometries points lines or polygons fall within deformation regions the deformation can be applied to these geometries together these tools allow users to build virtual earth models that quantitatively describe continental assembly fragmentation and dispersal and are interoperable with many other mapping and modeling tools enabling applications in tectonics geodynamics basin evolution orogenesis deep earth resource exploration paleobiology paleoceanography and paleoclimate

effect of ocean gateways on the global ocean circulation in the late oligocene and early miocene 1 we investigate the effect of changes in the tectonic boundary conditions on global ocean circulation patterns using a fully coupled climate model in an idealized setup we compare situations corresponding to the late oligocene the early miocene and present day the model results show the existence of a flow reversal through the panama seaway between the oligocene and miocene this flow reversal is induced by global tectonic changes related to the widening of the southern ocean passages and the closing of the tethys seaway it mainly involves the wind driven ocean circulation in agreement with previous model studies the global thermohaline circulation in the oligocene and miocene simulations is significantly different from the present day conveyor circulation as there is deepwater formation in both the north atlantic and the north pacific oceans in particular in the oligocene simulation the salinity contrast between the atlantic and pacific oceans is reduced because of water mass exchange through the low latitude connections between the two oceans

late pleistocene early holocene paraglacial and fluvial sediment history in the turbio valley semiarid chilean andes abstract the transitional character of climatic conditions confers great relevance to paleoclimate studies in the semiarid region where glacial and holocene geomorphologic records are scarce here we present the paraglacial and fluvial evolution of the turbio valley 30 s using both field observations and 14 c ams chronology two key sites at the uppermost turbio valley show glacial margins which likely formed during the 17 12 ka central andean pluvial event and earlier 37 27 ka episodes associated with glacial advances reported elsewhere in the semiarid andes likewise two episodes of subsequent paraglacial response are identified a first episode corresponds to early holocene fine grained deposits 11 500 7800 cal yr bp extending far downstream 40 km from the glacial margins these deposits and coeval debris cones 11 000 5500 cal yr bp are the result of arid conditions with occasional runoffs that were unable to export sediments along the trunk valley the second episode corresponds to disconformably overlying fluvial gravels extending 70 km downstream from the glacial margin indicative of an increase in the fluvial transport capacity occurring not long after 5500 cal yr bp fluvial transport increase resulted from a late holocene shift to wetter climate conditions representing a forcing factor which enhanced the paraglacial response

high resolution sequence stratigraphy of the late namurian in the widmerpool gulf east midlands uk abstract analysis of facies stacking patterns and stratal surfaces within late namurian deltas of the widmerpool gulf has revealed 10 high frequency fourth order depositional sequences sequence correlation is based on the characteristic marine band fauna of their condensed sections in many instances sequence boundaries are difficult to recognize unless there is clearly demonstrable lowstand incision consequently it is often difficult to separate late highstand from falling stage progradation with any degree of confidence sequence thickness variations and the dominance of particular stratal surfaces and systems tracts were controlled by a longer period third order cycle of relative sea level rise and fall during the marsdenian yeadonian major fluvio deltaic sand bodies in the widmerpool gulf were formed by distributary channel progradation e g chatsworth grit during the late highstand and or falling stage systems tracts and by the filling of incised valleys e g ashover grit and rough rock following marked sea level falls channel belt and valley fill orientation was initially influenced by differential compaction but this influence decreased during the late namurian the recognition of incised valley fills within the late namurian has implications for estimating the magnitudes and periodicities of carboniferous relative sea level change

lacustrine delta deposits and their effects on coal mining in a surface mine in derbyshire england abstract five late carboniferous pennsylvanian coal seams and associated inter seam strata have been examined at lodge house surface mine in the east midlands coalfield of england deposition of these coal seams and their accompanying inter seam intervals occurred in an equatorial fluvio lacustrine environment in an area approximately halfway between the depocentre and the southern margins of the pennine basin controls on the onset of inter seam sedimentation and cessation of peat formation appear to have operated at two scales fourth order glacio eustatic rises exerted the dominant control over formation of peats in laterally extensive mires however fifth order and smaller scale autocyclic mechanisms specifically avulsion are believed to have accompanied splitting of other seams close to but beyond the confines of the mine a study of contrasting lacustrine delta deposits occupying two of the inter seam intervals has enabled proximal distal wave dominated and delta distributary channel sub facies to be recognised the lacustrine deltas prograded rapidly into shallow but extensive freshwater lakes and both delta lobe switching and avulsion of delta distributary channels were important mechanisms the lower lacustrine delta sequence is characterised by mud filled delta distributary channels near the top of the interval the upper sequence is dominated by wave formed structures and massive sandstone delta distributary channels which formed during a period of episodic floods and strong winds lacustrine delta deposits generally create good mining conditions but delta distributary channels can present difficulties in underground mines mud filled delta distributary channels subject to early compaction can give rise to swilleys elongate depressions resulting in thickness changes and undulation of the overlying seam when filled with strong well cemented abrasive sandstone delta distributary channel deposits can be hard to excavate at lodge house the narrow width of the delta distributary channels meant that they were not detected by drilling prior to mining thus outcrop studies should be used to complement subsurface data as they can significantly enhance our understanding of small scale features

a depositional model for the mid westphalian a to late westphalian b coal measures of south wales mid westphalian a to late westphalian b sediments of the south wales coalfield comprise mainly lacustrine raised mire and flood deposits developed in an upper coastal plain environment occasional high sinuosity fine grained channel systems drained the subdued topography of the wales brabant massif to the north and east of the basin low sinuosity channels with lithic coarse grained fills drained a rising source to the south direct marine influence was restricted to a single marine band facies distributions were controlled by 1 local scale 10 2 10 3 m 2 autocyclic sedimentary processes 2 regional scale 10 km 2 synsedimentary fault activity and differential subsidence and 3 basin wide scale 10 2 km 2 response to changes in relative sea level base level changes are recorded by basin wide bivalve horizons up dip or landward extension of marine bands developed in lacustrine mudstones above basin wide coal seams peat accumulation was terminated by a water table rise related to base level rise following flooding re establishment of the clastic supply resulted in the gradual infilling of the basin wide lake to produce coarsening upwards cyclothems or parasequences a eustatic origin for parasequence development is supported by the development of identical facies associations and parasequences in coeval sediments from the pennine and midland valley coalfields

what is a fluvial levee abstract fluvial levees are elevated partitions between channels and floodplains because of their character and position levees may provide critical controls on and insights into geomorphic processes that determine the distribution of water and sediment within river systems few studies have analysed the character distribution sedimentology and processes that form levees in modern depositional environments characterisation of levee deposits from the mississippi river continues to form the basis for most levee interpretations from the rock record this discussion paper assesses the reliability of interpretations of levee deposits in numerous examples from the rock record and their associated inferences for river style this uncertainty reflects the lack of definitive sedimentological attributes for levee deposits their limited preservation potential and the fact that levee identification in the rock record is inhibited by the reliance on geometric descriptors or indirect associations between channel and floodplain facies given these concerns it is suggested that geomorphologists and sedimentologists need to recognise the limitations of our present knowledge of levees and work towards a more systematic understanding of these significant fluvial landforms in the full spectrum of modern and ancient river settings

depositional environments of overbank sedimentation in the lignite bearing grey clays member new evidence from middle miocene deposits of central poland abstract a detailed sedimentological study of polish lignite bearing successions has not previously been undertaken this contribution focuses on the lignite lithotypes and lake and crevasse splay lithofacies that together constitute the grey clays member this lithostratigraphic unit strictly refers to the middle miocene overbank fluvial environments in central poland it mostly consists of the first mid polish lignite seam mpls 1 in the tomislawice lignite opencast mine this lignite seam containing four lithotypes is interbedded by sandy and silty clayey lithofacies the lithotype associations are characteristic of the low lying mires representing fen or open water 2 m lakes in the mire area this is additional evidence of the relatively long lasting and slow sedimentation of these very fine grained clastics from suspension in standing lake water conversely the sandy lithofacies associations representing crevasse splays were deposited suddenly during overbank flooding crevasse splay deposits are typical of initial stages of avulsion and are moderately diverse both texturally and structurally exceptions here are slurry flow deposits that contain rip up clasts of paleosol aggregates these crevasse splay deposits provide the first evidence of the fluvial environments of the mid miocene mires backswamp in central poland and they split the currently exploited lignite seam mpls 1 in the study area thus identification and description of lithofacies and lithotypes and determination of their spatial distribution can contribute to a better understanding of the mire development of which the examined lignite seam arose

magma mixing in mantle xenolith bearing calc alkalic ejecta ichinomegata volcano northeastern japan abstract the latest pleistocene ejecta from the ichinomegata volcano ne japan composed of three maars show a wide compositional variation ranging from basalt 51 sio 2 to dacite 65 sio 2 these have the same phenocryst assemblage of olivine augite hornblende biotite quartz plagioclase and titanomagnetite upper mantle peridotite xenoliths are found not only in basalts but also in andesite whole rock major chemistry and modal compositions indicate that the chemical and modal variations have been caused by the mixing of three magmatic components primitive high alumina basalt sio 2 51 wt mgo 8 5 wt with olivine fo 88 and augite phenocrysts differentiated basaltic andesite sio 2 54 wt mgo 5 wt which has the same but slightly fe rich phenocryst phases as the primitive basalt and porphyritic dacite sio 2 65 wt mgo 2 0 wt with phenocrysts of hornblende biotite quartz plagioclase and titanomagnetite the upper mantle peridotite bearing andesite may not be derived directly from the upper mantle and its peridotite xenoliths may have been carried by the primitive basaltic magma the estimated density for three magmatic end components requires a high flow velocity of basaltic magma and a small volume 5 m 3 of the dacite magma body to facilitate breaking of the stratification in the dacite magma body this is consistent with the retention of peridotite xenoliths in the mixed magma and the preserved disequilibrium petrographic features

analysis of floodplain sedimentation avulsion style and channelized fluvial sandbody distribution in an upper coastal plain reservoir middle jurassic ness formation brent field uk north sea

lignite and carbonate deposition in middle lignite succession of the soma formation soma coalfield western turkey the middle miocene carbonate dominated units that are called the middle lignite succession of the soma formation from the soma coalfield of western turkey were analyzed and two facies associations containing eight facies were determined from the detailed measured sections of the opencast lignite mines the sedimentological stratigraphical and palaeobotanical data and regional geology indicate alluvial and or floodplain shallow freshwater carbonate lakes and lake margin environments including forest mountain swamps in the intramontane basin which was developed on the collision related basement rocks the middle lignite succession displays cyclic depositional nature consisting of alternating fine grained siliciclastic rock lignite and freshwater carbonate rock some diagenetic features and algal laminations structures in carbonate rocks as well as paleosol relics and geological evidence of the lignite forming paludal swampy conditions suggest alternating wet and dry periods in depositional system the lignite deposition occurred in wetlands that formed during deposition of the middle lignite succession in alluvial plain and shallow carbonate lake margins the paleobotanical palynological considerations sedimentological features and depositional setting of the middle lignite succession indicate a seasonal warm and semi arid or dry climate for lignite deposition the subsidence sediment supply seasonal climate topography and pre miocene carbonate basement may suggest main factors for lignite formation and preservation

depositional evolution of miocene coal successions in the soma coalfield western turkey abstract miocene alluvial and fluvial lacustrine deposits comprising three lignite successions lower middle and upper are exposed in the soma coalfield in western anatolia the total thickness of the coal successions is about 900 m and they rest unconformably on mesozoic carbonate and siliciclastic basement rocks several lithofacies are recognised and are arranged into 15 facies assemblages fa1 to fa15 within coal successions the lower coal succession fa1 to fa3 has been interpreted as the deposits of alluvial fan to ephemeral lacustrine and forest lower mire system resulting in a subbituminous coal which averages thickness of 20 m the freshwater carbonate dominated middle coal succession fa4 to fa7 has been interpreted as the deposits of an anastomosed river system including shallow carbonate mudflats to lake and ponds and frequently drying poor forest mires depositing lignitic coal the volcanic influenced upper coal uc succession fa8 to fa15 has been interpreted as the fluvial channel floodplain and allochthonous peat mire deposits fa8 to fa10 associated with a braided river system that was rapidly buried and eroded by volcaniclastic apron deposits fa11 to fa14 and culminated in large carbonate dominated shallow lake deposits fa15 the miocene coal successions were probably deposited in a slowly subsiding and fault controlled karst based paleovalley and lowlands of the intramontane paleomorphology that resulted from the early tertiary collision of the eurasian and anatolian plates

facies and architectural analysis to interpret avulsion style and variability upper cretaceous blackhawk formation wasatch plateau central utah u s a abstract sequence stratigraphic models emphasize the role of external allogenic controls such as relative sea level tectonic subsidence and climate on alluvial to coastal plain stratigraphic architecture at the expense of internal autogenic behaviors such as avulsion these models are tested via sedimentologic analysis of fine grained floodplain deposits and their relationship to channelized fluvial sandbodies in a well exposed alluvial to coastal plain succession developed under progressively increasing distance from the coeval shoreline and an accompanying decrease in the rate of accommodation creation late cretaceous blackhawk formation wasatch plateau central utah u s a the studied alluvial to coastal plain succession contains fourteen lithofacies which are grouped into four associations and eight architectural elements facies associations consist of 1 channelized fluvial sandstone bodies 2 nonchannelized fluvial sandstone and siltstone bodies 3 fine grained floodplain deposits and 4 brackish floodplain deposits paleosols are immature and are classified as entisols inceptisols and histosols integrated analysis of paleosol character facies analysis and architectural element analysis indicates deposition on a rapidly aggrading floodplain that was subject to frequent crevassing and channel belt switching the character relative abundance and vertical stacking of the paleosol types architectural elements and the first three facies associations exhibit little variation stratigraphically from base to top of the blackhawk formation c 250 m or paleogeographically between the northern and southern limits of the outcrop belt c 100 km local stratigraphic architectures record three styles of avulsion representing avulsion by reoccupation avulsion by progradation and avulsion by incision avulsion style displays no consistent pattern with stratigraphic position or paleogeographic location in combination these results suggest that floodplain sedimentation and local stratigraphic architecture are dominated by autogenic avulsion the three observed avulsion mechanisms operated in apparent uniformity over a range of tectonic subsidence rates c 80 700 m ma and distances from the coeval shoreline c 0 100 km

three dimensional distribution of lithofacies bounding surfaces porosity and permeability in a fluvial sandstone gypsy sandstone of northern oklahoma where it was studied at two sites in north central oklahoma the gypsy sandstone of the pennsylvanian vamoosa formation provides significant insights into the controls on reservoir quality in a meandering river deposit at an outcrop site west of tulsa a three dimensional architectural framework based on erosional surfaces allowed the recognition of a channel fill sequence consisting of six channel sand bodies and representing at least three channel belts belts are vertically stacked and are incompletely separated by low permeability flood plain deposits which are locally eroded porosity and permeability are primarily related to depositional facies within channel belts mudclast lags associated with erosion surfaces at the base of channels have the potential to act as vertical permeability baffles between channel sand bodies as do mud draped lateral accretion surfaces within channel sand bodies at a subsurface site 31 km 19 mi to the west of the outcrop site nine wells were drilled and cored through the gypsy interval at this site it was possible to identify and correlate three channel belts comprising amalgamated channel sand bodies although lower level architectural elements could be recognized in cores they could not be correlated with confidence given a 100 m 330 ft well spacing

atmospheric circulation upwelling and organic rich rocks in the mesozoic and cenozoic eras abstract by using the basic principles of atmospheric circulation and analogies from present circulation patterns it is possible to construct qualitative atmospheric circulation models on paleogeographic maps the wind patterns predicted by these models then serve as the basis for predicting the locations of ancient upwelling zones atmospheric circulation and upwelling models for seven geologic stages in the mesozoic and cenozoic were constructed and the distribution of the upwelling zones compared with the distribution of organic rich rocks for all time periods together the correlation was statistically significant when the individual time periods were analyzed separately the following pattern emerged significant correspondence between upwelling zones and organic rich rocks in the triassic middle early cretaceous to late cretaceous and middle paleogene to neogene no significant correspondence was found for the intervening times upwelling does not account for all organic rich rocks so called anoxic oceanic events and transgressions play an important role in their deposition it is suggested that upwelling contributes significantly to the pattern of organic rich rock distribution and is important in determining organic facies

prediction of channel connectivity and fluvial style in the flood basin successions of the upper permian rangal coal measures queensland predicting the presence and connectivity of reservoir quality facies in otherwise mud prone fluvial overbank successions is important because such sand bodies can potentially provide connectivity between larger neighboring sand bodies this article addresses minor channelized fluvial elements crevasse splay and distributary channels and attempts to predict the connectivity between such sand bodies in two interseam packages of the upper permian rangal coal measures of northeastern australia channel body percent as measured in well logs was 2 in the upper aries castor interseam and 17 in the lower castor pollux interseam well spacing were too great to allow accurate correlation of channel bodies the ob river siberia was used as a modern analog to supply planform geometric measurements of splay and distributary channels so that stochastic modeling of channel bodies was possible the resulting models demonstrated that 1 channel body connectivity is more uniform between minor distributary channels than between crevasse splay channels 2 relatively good connectivity is seen in proximal positions in splays but decreases distally from the source as channel elements diverge and 3 connectivity tends to be greater down the axis of splays with more isolated channel bodies occurring at the margins

petrology of selected carbonaceous limestones and shales in late carboniferous coal basins of atlantic canada carbonaceous limestones and shales are associated with coal in late carboniferous alluvial to coastal successions of nova scotia the units are thin 45 km they consist of micrite and or illitic and kaolinitic clay and some contain abundant bivalves ostracodes pyrite up to 11 vol and phosphatic and sideritic nodules trace fossils are scarce to absent the organic material 2 43 toc is characterised as type ii iii and is mainly of terrestrial derivation predominantly vitrinite and sporinite with lamalginite and telalginite as minor constituents vitrinite reflectance measurements indicate immaturity ro 0 5 but are lower than those of associated coals source rock and hydrocarbon recovery potentials are good to very good and the potentials of some units compare favourably with those of alginite rich carboniferous oil shales in adjacent basins the carbonaceous units were deposited in shallow lakes and or interdistributary bays with aerobic to anaerobic bottom waters at times of minimal detrial input

life time of a stratified magma chamber recorded in ultramafic xenoliths from ichinomegata volcano northeastern japan variations in major element chemistry and modal compositions of the mantle xenolith bearing calc alkalic ejecta from ichinomegata volcano are inferred to be due to mixing of three magmatic end members basalt i sio2 51 wt mgo 8 5 wt basalt ii sio2 54 wt mgo 5 wt and dacite sio2 65 wt mgo2 wt ultramafic xenoliths are found in mafic mixtures of dacite basalt i and dacite basalt ii the thermal histories of the xenoliths in both mixtures are compared with each other chemical compositions of olivine and orthopyroxene in xenoliths suggest that xenoliths in basalt i were equilibrated at about 800 c while those in basalt ii were also equilibrated originally at about 800 c but were subsequently annealed at about 1000 c for more than 102 3 years prior to the eruption

palaeochannels stone rolls in coal seams modern analogues from fluvial deposits of the okavango delta botswana southern africa abstract two varieties of fluvial sandstones are associated with coal seams in the permian witbank coalfield of south africa the first comprises lenticular channel fill sandstone minor conglomerate and siltstone encased entirely within the coal seam medium to coarse grained arkosic sandstones are structured by planar cross bedding and fine upwards into carbonaceous siltstone and overlying coal these palaeochannel fill deposits are 5 km wide in proximal basin areas and narrow down palaeoslope to less than 1 km in width the second variety of channel fill consists of medium to coarse grained sandstone which occurs below the floor of the coal seam these deposits form undulating ridges that occur either in sub parallel groups or as isolated shoe string type bodies at the coal floor rock contact both features are referred to as stone rolls in colliery terminology these ancient deposits are compared with active and abandoned fluvial systems from the okavango delta in botswana southern africa active channels are flanked by extensive peat swamps which effectively confine and stabilize the channel margins clastic sedimentation is therefore completely confined to the channels by the vegetation and deposition occurs by vertical aggradation recently abandoned channels in the okavango delta display a variety of well preserved bed forms which alternate with scoured depressions along the thalweg producing an undulating topography to the channel floor these features provide a modern analogue for the stone rolls in the coalfield deposits the subsequent channel abandonment vegetation encroachment and peat formation over the sand bodies would form a coal seam superimposed on the irregular surface provided channel abandonment was followed by subsidence overlying sediment deposition compaction and coalification of the peat although the okavango rivers are narrower and transport finer grained sand than their permian counterparts the mechanism of formation and style of deposition was similar for both systems

the baganuur coal deposit mongolia depositional environments and paleoecology of a lower cretaceous coal bearing intermontane basin in eastern asia abstract the investigations involved geophysical sedimentological palynological chemical and mineralogical studies supported by field based infrared spectrometry the baganuur basin central mongolia is among the rift or pull apart basins which subsided at the boundary between the jurassic and the lower cretaceous in east asia during the berriasian peat accumulation began in the area under study in central mongolia the palynoflora is akin to the siberian palynological province based on the phytoclast assemblages and the ratios of total sulfur content to total organic content marine transgressions into this intermontane basin may be ruled out the coal interseam sediments were laid down prevalently under neutral to slightly alkaline conditions only in some carbonaceous sediments the ph of intrastratal solutions was lowered suboxic to anoxic conditions persisted during almost the entire lower cretaceous period in the baganuur basin based on the distribution of fining and coarsening upward sequences and the organic matter the basin fill has been subdivided into seven depositional units a fluvial swamp b fluvial lacustrine c deltaic fluvial d fluvial e fluvial deltaic lacustrine floodplain f lacustrine deltaic swamp g swamp fluvial a conspicuous change in the fluvial lacustrine regime and an increase in the sediment supply may be observed at the boundary between depositional units b and c a strong uplift triggered the onset of an intensive delta sedimentation lithoclasts heavy minerals e g apatite zircon garnet anatase brookite epidote sphene tourmaline and phyllosilicates e g kaolinite smectite mica chlorite attest to a mixing of detrital material one provenance area was abundant in acidic plutonic rocks as shown by the granitic lithoclasts the other in volcanic rocks which produced the vitroclastic debris deposited as tephra fallout post depositional alteration of the siliciclastic interseam sediments was favored by a distinctive facies association of transmissive and sealing horizons it led to a re deposition of ca u and sr in the siliciclastics post depositional alteration of the organic material converted it into lignite to subbituminous c coal

delta plain coal deposits from the than formation of the early cretaceous saurashtra basin gujarat western india abstract the than formation of the early cretaceous saurashtra basin consists of an interbedded assemblage of sandstone claystone carbonaceous shale and coal facies small scale crossbedded and laminated mudstone siltstone sr lm facies are considered to have formed by down current migration of small scale subaqueous bedforms and overbank deposits of distributary channels the planar and trough crossbedded sandstone lithofacies sp st formed by migration of sand dunes and transverse bars in distributary channels laminated to ripple laminated siltstone f1 facies with or without coaly stringers alternate with fine clastics are suggestive of flood deposits and abandoned interchannel plain of delta distributaries the muddy carbonaceous shale fm facies represents deposition largely in low lying interchannel plains and backswamps peat coal pc facies are interpreted as in situ deposits in quiet water conditions of sedimentation across a lake the integrated results of lithofacies texture and palaeocurrent analysis suggest that than strata were deposited in a prograding major delta distributary complex in lower and upper delta plain environments

quantifying the paleogeographic driver of cretaceous carbonate platform development using paleoecological niche modeling abstract platform carbonates are a major component of the earth system but their spatial extent through geological time is difficult to reconstruct due to the incompleteness of the geological record sampling heterogeneity and their intrinsic complexity here we use coupled ecological niche modeling and deep time general circulation models to predict the occurrence of platform carbonates at the global scale during the cretaceous specifically niche modeling uses fuzzy logic to predict probable occurrence of platform carbonates as a function of sea surface temperature sea surface salinity primary productivity and water depth the first three parameters derive from cretaceous global paleoclimatic simulations using a coupled ocean atmosphere general circulation model while bathymetry is based on paleogeographical reconstructions model predictions are validated with the well documented and abundant geological data from the aptian the methodologies developed for the aptian are subsequently extended to other cretaceous time intervals the results of the niche model accurately predict the geographic distribution of aptian carbonate platforms if a preference for low open marine productivity levels is assumed for the rudist dominated carbonate factories however if a preference for high productivity levels is assumed the modeling results do not match the reported global distribution of aptian carbonate platforms from the early cretaceous into the late cretaceous sea level rose and the continents on average moved into lower latitudes the model predicts a corresponding increase in the extent of the carbonate platforms mainly due to the increasing extent of shallow water environments available to carbonate development these results indicate that long term sea level rise may have been a major factor responsible for the increase in the area of platform carbonates during the cretaceous

the cretaceous pyonghae basin southeast korea sequential development of crevasse splay and avulsion in a terminal alluvial fan abstract the pyonghae basin early cretaceous southeast korea comprises a thick sequence of purplish siltstone with subordinate gravelstone and gravelly sandstone deposited in a terminal alluvial fan environment based on bed geometry and facies assemblage the gravelly sandstone bodies are divided into four types type a deposit consists of disorganized gravel patches and massive sandstone lenticules a few decimetres thick and a few metres wide most likely deposited from overflows type 2 deposit is characterized by crudely stratified and massive sandstone beds up to 2 m thick 20 m wide and comprises lower disorganized gravel layers and upper stratified gravelly sandstone beds forming a fining upward trend it probably represents crevasse channel distributary channel fills type 4 deposit 3 5 m thick 20 m wide consists of stratified cross stratified gravelly sandstone beds which are interpreted as main braided channel fills aggradation of the terminal fan was associated with frequent shift of channels which range from crevasse splay channel type 2 through crevasse channel distributary channel type 3 to main channel type 4 the crevassing or avulsion was preceded by overflows type 1 the avulsion processes in the terminal fan were achieved through stepwise enlargement of crevasse channels which reflect different channel responses to floods of different magnitude and frequence

experimental investigation of camg exchange between olivine orthopyroxene and clinopyroxene potential for geobarometry abstract the distribution of ca and mg among coexisting olivine clinopyroxene and orthopyroxene has been studied in a piston cylinder apparatus in the temperature range 1100 1300 c and pressure range 9 41 kbar ca in olivine decreases with increasing pressure and decreasing temperature the pressure effect is the result of ca going into the higher coordination m2 site in clinopyroxene as pressure is increased for the ca mg exchange reaction between olivine and clinopyroxene v 0 249j bar 1 mole 1 this is sufficient for pressure estimates accurate to 3kbar if temperatures of equilibration are independently known ca mg exchange between olivine and orthopyroxene is not sufficiently pressure dependent to be used as a geobarometer application of the olivine clinopyroxene geobarometer to coarse garnet lherzolites from southern africa gives p t results consistent with a continental geotherm for spinel lherzolites from southwestern united states the geotherm appears to be displaced to higher temperatures indicating oceanic affinities application of the geobarometer to natural systems requires assumptions about activity relationships in clinopyroxene which should be checked by experiment

sequence stratigraphy of coastal alluvial plain westphalian b coal measures in northumberland and the southern north sea abstract westphalian b coastal alluvial plain coal measures of northumberland and the southern north sea are susceptible to stratigraphic base level fluctuations of various magnitudes which create a hierarchy of flooding surfaces 1 high magnitude third order maximum flooding surfaces corresponding to the anthracoceratites vanderbeckei and anthracoceras aegiranum marine bands defining the top and bottom of the succession when vast areas of the westphalian foreland basin were flooded by marine incursions 2 high frequency fluctuations promoting small scale fourth order flooding of the entire or large areas 100 s km 2 of the alluvial plain resulting in deposition of non marine bivalve beds or marine bands depending on their position on the third order base level curve and 3 small scale localised base level rises due to differential compaction and autocyclic switching of minor crevasse splays and distributary channels a regionally extensive third order tectonically induced sequence boundary is also recognised in the southern north sea slightly above the maximum stand in stratigraphic base level recorded by the vanderbeckei marine band this sequence boundary which represents the lowest point on the background eustatic base level curve between the two maximum flooding surfaces is overlain by the multilateral multistorey caister sandstone the lack of significant erosional relief beneath this channel sandstone suggests that accommodation space at this time was being created at a very low rate the succession above the caister sandstone sequence boundary up to the aegiranum marine band maximum flooding surface records an increasing rate of stratigraphic base level rise this equates to a third order transgressive systems tract or sequence set comprising a number of fourth order sequences which change upwards in response to the background low frequency rise the increasing rate of base level rise and increased accommodation space is accompanied by a change in fluvial style to more isolated channels enclosed within floodplain deposits

comparative organic petrology of interlayered sandstones siltstones mudstones and coals in the upper carboniferous ruhr basin northwest germany and their thermal history and methane generation in the coal mining ruhr area upper carboniferous rocks ca 4000 m consist of interlayered sandstones siltstones mudstones and coals they were deposited in a tropical paralic environment where alternating fluvial sedimentation occasional marine ingressions and swamp growth resulted in an irregular cyclic succession the total sedimentary package contains on an average 6 vol of organic matter about 70 vol of the organic matter occurs in coal seams the rest as dispersed organic matter in clastic rocks the organic matter is autochthonous in the coals and allochthonous in associated sandstones and siltstones it consists of about 70 vitrinite 20 inertinite and 10 liptinite the overall maceral group composition is the same for coals and dispersed organic matter this surprising similarity is caused by a nearly exclusive input of land plant derived organic matter to swamps and fluvial systems and a similar degree of preservation highest average liptinite contents of total macerals were found in unrooted mudstones highest average inertinite contents in coarse grained siltstones and highest average vitrinite percentages in sandstones

sand body orientation palaeoslope analysis and basin fill implications in the westphalian a c of great britain channel orientation and palaeoflow analyses across the british westphalian carboniferous coalfields show that three main inflow directions dominated the palaeogeography from the mid langsettian to the mid bolsovian in eastern scotland and ne england flow was mainly from the n and ne in the pennine basin of north central england flow was mainly from the w and nw whilst in south wales main flow from the sw was compatible with a westerly system that also branched to give the northerly inflows recorded in the culm basin of southwest england the depositional area included discrete tectonic depocentres notably the pennine basin which was traversed directly and tangentially by major channel belts these basins were essentially incidental to the main channel pathways but sand body characteristics vary according to basin location a new depositional model for the post rift pennine basin is proposed relating sand concentrations and connectivities to the depositional and tectonic setting the description of dominant sw to ne flow across south wales through much of the langsettian and duckmantian in contrast to the centripetal inflows previously proposed implies some similar channel depocentre relationships to those described here for the pennine basin

paleoreef maps evaluation of a comprehensive database on phanerozoic reefs to get a better understanding of controls on reef development through time we created a comprehensive database on phanerozoic reefs the database currently comprises 2470 reefs and contains information about geographic position paleoposition age reef type dimensions environmental setting paleontological and petrographical features and reservoir quality of each buildup reef data were analyzed in two qualitatively different ways the first type of analysis was by visualization of paleogeographic reef distribution maps five examples late devonian early permian late triassic late jurassic middle miocene are presented to show the potential of paleoreef maps for paleogeographic and paleoclimatological reconstructions the second type of analysis was a numerical processing of coded reef characteristics to realize major trends in reef evolution and properties of reef carbonates the analysis of paleolatitudinal reef distributions through time shows pronounced asymmetries in some time slices probably related to climatic asymmetries rather than controlled by plate tectonic evolution alone the dominance of particular reef builders through time suggests that there are seven cycles of phanerozoic reef development first curves for the phanerozoic distribution of bioerosion in reefs bathymetric setting and debris potential of reefs are presented the observed pattern in the temporal and spatial distribution of reefs with reservoir quality may assist in hydrocarbon exploration statistical tests on the dependencies of reefal reservoir quality suggest that large size high debris potential low paleolatitude high amount of marine aragonite cement and a platform shelf edge setting favor reservoir quality reefal reservoirs are significantly enhanced in times of high evaporite sedimentation elevated burial of organic carbon low oceanic crust production low atmospheric co2 content and cool paleoclimate as well as when they are present in aragonite oceans

carbonate platform facies models various types of carbonate platforms are characterized by distinctive profiles facies and evolutionary sequences ramps may be homoclinal or distally steepened and may have fringing or barrier shoal water complexes of ooid pellet sands or skeletal banks homoclinal ramps pass seaward into deeper water without major break in slope and lack deep water breccias distally steepened ramps may be low energy and characterized by widespread shallow subwave base mud blankets or high energy with coastal beach dune complexes and widespread skeletal sand blankets slope facies may contain abundant breccias of slope derived clasts rimmed shelves have relatively flat tops and marked break in slopes at the high energy shallow shelf edge where they pass into deep water such shelves may be aggraded with peritidal facies extending over much of the shelf or incipiently drowned depending on magnitude of sea level fluctuations they may be accretionary or bypass types that include gullied slope escarpment and high relief erosional forms intrashelf basins occur on some shelves controlling distribution of reservoir and source beds isolated platforms are surrounded by deeper water and may be located on rifted continental margins or on submarine volcanoes most have high relief rimmed margins platforms that have been subjected to rapid sea level rise may be incipiently drowned and characterized by raised rims elevated patch or pinnacle reefs and widespread subwave base carbonate or fine clastic blankets completely drowned shelves develop where the shelf is submerged to subphotic depths terminating shallow water deposition and commonly resulting in blanketing of the shelf by deeper water facies some margins show extensive down to basin faulting that is contemporaneous with carbonate deposition or associated with thick prograding clastic sequences the various types of platforms change in response to variations in sedimentation subsidence or sea level rise and may form distinctive evolutionary sequences the relatively few models presented appear to accommodate most geological examples some of which contain major reservoir facies

seismic facies analysis of westphalian sequences of the southern north sea abstract differing seismic facies are observed from within the westphalian sequences of the southern north sea a review of published synthetic seismograms and seismic data from known coal bearing basins establishes seismic facies types and their relationships similar reflection character is recognized from westphalian sequences in the southern north sea and lithologies confirmed by borehole information probable sand silt or clastic prone upper coal measures westphalian c d stages and coal prone lower and middle coal measures westphalian a b and part c stages can be defined and mapped providing information on the regional distribution of source and reservoir rocks and stratigraphic plays it is suggested that sand prone channel complexes or clastic dominated areas within the mainly a b stages can be recognized and mapped providing information on migration pathways and stratigraphic plays

spatial and temporal distribution of sand containing basin fills in the holocene rhine meuse delta the netherlands the quantitative significance of coarse grained deposits in the overbank realm such as crevasse splay deposits has not been studied at the delta scale or at the holocene timescale such knowledge would be beneficial for understanding and explaining sediment distribution in delta plains this study addresses delta scale distribution of sand containing basin fills and their sand body proportion variability based on eight valleywide cross sections in the holocene rhine meuse delta in the netherlands we found that sand containing basin fills form 7 1 of the fluviodeltaic wedge of which splay deposits are most frequently observed midway between the delta apex and the coast organic clastic lake fills and bay head delta deposits in contrast are limited to the distal delta plain over four successive periods between 9000 and 800 cal yr bp the largest proportions of splay deposits remain at 50 150 km downstream of the upstream shifting delta apex we show that intermediate floodbasin widths between 3 1 and 3 6 km in the holocene rhine meuse delta yield the highest proportions of splay deposits high rates of base level rise and wide floodplains both facilitate the creation of accommodation which in turn provides conditions for peat forming wetlands in which organic clastic lake fills can develop the results show that sand bodies form 26 30 of sand containing basin fills this proportion is shown to be controlled by among other variables channel planform and superelevation of the trunk channel and substrate composition we conclude that potentially large volumes of nonchannel sand bodies exist in distal delta plains they constitute up to 39 of the reservoir volume in the distal rhine meuse delta and yield relatively high connectedness ratios 2011 by the university of chicago all rights reserved

trace fossils in coal bearing sequences in the past decade trace fossils have been recorded extensively from coal bearing sediments differing widely in facies age and location westphalian or stephanian 9coal measures9 in britain europe and eastern canada contain an ichnofauna produced by invertebrates and or vertebrates in upper delta plain sediments this contrasts with the marine related lower delta plain ichnofaunas known from pennsylvanian rocks of the united states and permian gondwana 9coal measures9 of south africa deltaic complexes of middle jurassic age in the north sea basin and upper cretaceous age in north america contain marine trace fossils and dinosaur footprints in coastal coal bearing facies these case histories illustrate the importance of trace fossils both in facies analysis of coal bearing sequences and in recording the presence of animals rarely known as body fossils in such clastic sediments

the silkstone rock westphalian a from the east pennines england implications for sand body genesis the silkstone rock westphalian a langsettian is a major multistorey channel sandstone formed in a delta plain environment with minimal marine influence it occupies up to three interseam intervals in the east pennine coalfield england and exceeds 50 m in thickness and 15 km in width at its maximum development which is larger than many westphalian channel sand bodies the high ash content of coal adjacent to the channel belt indicates that regional peat accumulation took place contemporaneously with the existence of the channel system the major channel system fed a number of minor channels during different interseam intervals and conducted sediment and water into nearby delta plain lakes via lacustrine delta and crevasse splay systems these minor channels which show a range of fills are sub parallel and show lateral offset stacking suggesting that differential compaction was an important control on their location the major channel belt acted as a long lived distributary system that flowed towards the east away from the overall basin depocentre with its position being controlled mainly by deltaic processes

palaeovalleys and protozoan assemblages in a late carboniferous cyclothem sydney basin nova scotia the early stephanian bonar cyclothem of the sydney basin nova scotia contains an erosional surface cut through coastal plain strata with economic coals and distributary channel bodies the erosion surface is interpreted as a palaeovalley 20 m deep and at least 7 km wide that marks a sequence boundary formed during relative fall in sea level the palaeovalley is filled with stacked alluvial channel bodies which become more isolated as the valley fill passes upward into red alluvial plain deposits probably laid down in an anastomosed river system in an adjacent interfluve area calcretes and red vertic palaeosols cap coastal strata assemblage analysis of agglutinated foraminifera and thecamoebians indicates that the palaeovalley was filled with freshwater sediments before an initial marine transgression flooded the alluvial surface and adjacent interfluve valley incision probably reflects glacioeustatic sea level fall however the alluvial nature of the valley deposits suggests that valley filling reflects an abundant sediment supply during lowstand and or transgressive stages and was not a direct consequence of sea level rise during the subsequent transgression phase aggradation was rapid as sediment supply apparently kept pace with rising sea level features of both channel and extra channel facies suggest that seasonality intensified during the transition from coastal plain to palaeovalley and alluvial plain deposition

benthic carbonate factories of the phanerozoic marine carbonate precipitation occurs in three basic modes abiotic or quasi abiotic biotically induced and biotically controlled on a geologic scale these precipitation modes combine to form three carbonate production systems or factories in the benthic environment 1 tropical shallow water factory dominated by biotically controlled mainly photo autotrophic and abiotic precipitates 2 cool water factory dominated by biotically controlled mainly heterotrophic precipitates and 3 mud mound factory dominated by biotically induced mainly microbial and abiotic precipitates sediment accumulations of the factories differ in composition geometry and facies patterns and some of these differences appear prominently in seismic data thus facilitating subsurface prediction the characteristic accumulation of the tropical factory is the flat topped often reef rimmed platform in cool water systems reefs in high energy settings are scarce and hydrodynamic influence dominates producing seaward sloping shelves and deep water sediment drifts often armored by skeletal framework the typical accumulation of the mud mound factory is groups of mounds in deeper water where the mud mound factory expands into shallow water it forms rimmed platforms similar to the tropical factory the tropical factory is most productive the mud mound factory reaches 80 90 and the cool water factory 20 30 of the tropical growth rate the three factories represent end members connected by transitions in space transitions in time are linked to biotic evolution

middle to late holocene paleochannels and migration of the palar river tamil nadu implications of neotectonic activity abstract geomorphic tectonic and sedimentary investigations have been carried out to understand the landscape evolution of the palar river basin southern peninsular india for this purpose satellite data interpretations coupled with field investigations fluvial architecture and optically stimulated luminescence osl dating methods were adopted to infer climatic variations and neotectonic deformation that took place during the mid to late holocene period several paleochannels have been identified in the northern part of the present day palar river the distribution pattern of the palar paleochannels and its present course indicate its migration towards the south leaving behind the old palar river streams as paleochannels significant changes in the morphological characteristics channel width and river pattern in the successive paleochannels reveal evidences of channel movement by avulsion largely controlled by reactivation of pre existing lineaments and intensified ne monsoon based on osl ages two major phases of migration have been identified that occurred between 4 83 ka to 1 88 ka first phase occurred between 3 59 ka to 3 26 ka due to intensified monsoon accompanied with small scale neotectonic activity the second phase took place between 2 42 ka to 1 88 ka which occurred probably due to the rapid upstream avulsion this rapid avulsion is due to the close proximity of mpa and the reactivation of the pre existing lineaments moreover the present palar river basin exhibits evidences of neotectonic activity such as soft sediment deformation structures anomalous drainage deflections and reactivation of lineaments and faults further indicating that the palar river is still draining a tectonically active region thus neotctonics and fluctuations in the intensity of monsoon are largely responsible for sculpting the present landscape

fluvial channel and overbank deposits from the westphalian of the durham coalfield ne england the westphalian upper carboniferous coal measures of the durham coalfield in ne england were deposited in lower and upper delta plain environments distributary channels crossed the plain and were separated by shallow interdistributary lakes and bays detailed observation of three dimensional 3 d opencast surface mine exposures in collaboration with subsurface borehole analysis has revealed the existence of five varieties of channel deposits and two associated overbank facies within the durham coal measures major distributary channels were the major avenues of sediment transport across the coal measures plain were variably sinuous mostly 1 2 km wide and deposited elongate belts of sand mostly up to 5 km wide proximal major crevasse splay channels formed by the breaching of major channel banks during flood events were straight sand filled and up to 400 m wide minor distributary channels formed by the sustained operation of such crevasses varied from straight to highly sinuous and deposited shoestring sand mud belts up to a few hundred metres wide minor crevasse channels generally straight and up to 50 m wide were formed through bank breaching of minor and in a few cases major distributaries distal feeder channels formed down palaeocurrent extensions of minor distributaries which supplied interdistributary minor delta subsystems were generally straight and up to 200 m wide of the two types of channel overbank levee deposits recognized one comprising thinly interbedded fine grained sandstone and siltstone claystone is mostly though not exclusively associated with major distributary channels the other consisting of massive siltstones with regularly spaced thin claystone bands is uniquely developed at the margins of minor distributary channels the lower part of the westphalian a succession in the northern pennines records a change in the depositional environment upwards from a lower to upper delta plain through this transition major channel deposits show evidence of having evolved from being of dominantly low sinuosity to being more variable in morphology channel sedimentation was profoundly influenced by regular possibly seasonal variations in flow stage and sediment load

evolution of lower jurassic coastal plain and fan delta sediments in the beryl embayment north sea coastal plain and fan delta sediments accumulated throughout the sinemurian to late pliensbachian in the beryl embayment area north sea these sediments represent a marginal clastic fringe along the southern extension of the boreal ocean into the northern north sea two informal formations are recognized in these predominantly sandy deposits the lower formation comprises interbedded sandstones siltstones and coals of minor fluvial channel and associated coastal floodbasin marsh lake and sheetflood origin the overlying formation represents a fan delta system possibly generated as a result of footwall uplift and associated erosion this formation is dominated by probable channel sandstones with marine influenced debris flow deposits developed at a number of levels indicating an active coastal fan setting fan sediments are capped by a marine sandstone beds of which interfinger with the overlying offshore siltstones thickness variations are related to major normal faults suggesting at least a limited fault control on the deposition and distribution of facies during a time conventionally regarded as tectonically quiescent in the northern north sea there is no clear evidence for a eustatic control on sedimentation although deposition of post fan delta shallow marine siltstones may have been principally controlled by eustatic sea level rise recording the acme of the early jurassic expansion of boreal waters into the viking graben

short paper a standardized model for tethyan tertiary carbonate ramps low latitude carbonates in massive and clinoform bedded sheets termed ramps occur throughout the tertiary tethyan realm and are characterized by recurring biofacies usually including large foraminifera rhodolithic algae coralgal patch reef and gastropod dominated sequences all can be interpreted broadly within a standardized tertiary carbonate ramp model biota can be used to define precise palaeobathymetric zones which have a predictive utility in palaeoenvironmental modelling especially where data are limited the carbonate ramp model of earlier authors has been elaborated by read 1982 and ramp formation occurs mostly in passive margin and extensional tectonic settings ramps are characterized by slope gradients of less than 1 degree and once established are conservative to change much use has been made of the ramp model for palaeozoic and mesozoic lithofacies modelling in contrast published work on cenozoic ramps is limited however tethyan ramps are particularly widespread and extend tens to hundreds of kilometres along strike and occupy tens of kilometres of slope many studies have dealt with cenozoic ramp associations and sequences e g pedley 1983 reiss hottinger 1984 purser 1973 and have demonstrated the diversity of biotal and sediment detail but without ascribing them to a ramp model biota were quick to adapt to the tertiary environments left vacant after the k t boundary extinction events new genera of foraminifera mollusca bryozoa and echinoder mata rapidly replaced the extinct forms in bursts of innovative opportunism codiacean algae rhodophyta and marine angiosperms were equally adaptive colonizers of the carbonate platforms novel biofacies associations were derived from

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

the table rocks sandstone a fluvial friction dominated lobate mouth bar sandbody in the westphalian b coal measures ne england abstract westphalian b duckmantian alluvial coal measures along the northumberland coast ne england comprise coal capped coarsening upward crevasse splay sequences of shale siltstone and sandstone interbedded with a number of major distributary channel sandbodies including the table rocks sandstone lithofacies architectural analysis and outcrop geometries divide the table rocks sandstone into flaggy sandstone massive sandstone heterolithic and mudstone facies associations each comprising up to 7 lithofacies types the three sandy facies associations are characterised by lenticular bed geometries on different scales producing a hierarchy of lensoid packages and associated bounding surfaces all showing typical offset stacking patterns 1 lenses represent individual lenticular cross bed sets bounded by 1st order surfaces 2 packages of lenses called lens clusters are bounded by 2nd order surfaces and are the basic architectural building block of the sandy facies associations and 3 vertically stacked lens clusters called amalgamated lens clusters bounded by 3rd order surfaces the table rocks sandbody has a laterally extensive irregular lobate subsurface plan geometry it displays a radial palaeocurrent pattern with 180 dispersion and it forms part of a 14 m thick coarsening upward regressive sequence it is interpreted as a composite lobate crevasse splay delta system that prograded into a shallow interdistributary fresh to brackish water lake up to 14 m deep the shallow lake water fluvial input and extensive development of traction structures such as cross bedding and ripple cross lamination suggests a friction dominated delta in which the four facies associations can be interpreted in terms of discrete elements of the mouth bar environment the flaggy sandstone facies association represents the main axial part of the mouth bar system the erosively based massive sandstone facies association major subaqeous distributary channels the lithologically more variable heterolithic facies association the medial mouth bar and the mudstone facies association the distal mouth bar fringe and prodelta within this environmental setting amalgamated lens clusters are interpreted as small discrete mouth bar sand lobes whose offset imbricate stacking pattern reflects channel spacing and bifurcation the rate of channel shifting or shallow depths and lack of accommodation space thus lens clusters are interpreted as discrete growth elements of the mouth bar sand lobes and lenses as individual bedforms making up these growth elements because of the high rate of channel shifting lack of extensive erosion of the mouth bar lobes and deposition of low discharge fines the lobes retained much of their original depositional geometry thereby providing advantageous gradients for offset deposition and stacking of adjacent sand lobes although the delta complex was maintained by frequent crevassing from the feeder channel and by subsidence due to contemporaneous compaction and or local tectonism it was deeply incised on two occasions by subaqeous channels in response to high magnitude floods or falling lake level

late pleistocene fluvial sedimentary facies the dhadhar river basin western india abstract the late pleistocene fluvial succession is exposed as 18 20 m high incised vertical cliffs all along the dhadhar river basin in western india the major fluvial sedimentary facies of the late pleistocene deposits in the dhadhar river basin have preserved evidence of palaeodrainage and could provide an important link between the sub humid narmada basin in the south and the semi arid mahi basin in the north the sedimentary facies documented include overbank fines which are associated with crevasse splays fine grained overbank sediments are interpreted as having formed by sheet flow of sediments over the banks of minor distributary channels during the flood stage the overlying thinly stratified fluvial sands and silts at the top of the exposed sediment succession show a thin cap of aeolian sediments suggesting less intense aeolian activity than that observed in sabarmati mahi and orsang basins though a significant reduction in fluvial activity is suggested during the arid phase of the lgm however the river may still have been perennial assuming that it retained the larger part of the catchment

effects of volatiles on mixing in calc alkaline magma systems the intimate mixing between different magmas of disparate densities characteristic of some calc alkaline magma systems is explained by a new mechanism involving the emplacement of a layer of wet undersaturated mafic magma at the base of a magma chamber containing more differentiated magma turbulent transfer of heat between the mafic magma and the overlying magma leads to crystallization and exsolution of volatiles in the lower layer for an initial water content of a few per cent the bulk density of the mafic magma can become equal to that of the overlying magma causing overturning and intimate mixing of the magmas the mechanism is most probable in the low pressure environment of a high level magma chamber

marine carbonate factories a global model of carbonate platform distribution platform carbonates are a major component of the earth system but their spatial distribution through geological times is difficult to reconstruct due to the incompleteness of geological records sampling heterogeneity and their intrinsic complexity beyond this complexity carbonates are not randomly distributed in the world oceans neither in the modern nor in the past and thus global trends exist in the present review we focus on the understanding of the spatial distribution of carbonate production at a global scale we use a deterministic approach which focuses on discriminating components stratigraphic architectures and environmental features to relate shallow water carbonate production to oceanographic parameters the work is based on extensive literature reviews on carbonate platforms ecological niche modelling coupled with deep time general circulation models is used to calibrate a predictive tool of carbonate factory distribution a carbonate factory function is set up that is based on sea surface oceanographic parameters temperature salinity and primary productivity the model was tested using remote sensing and in situ oceanographic data of modern times while outputs of paleoceanographic models are utilized for lower aptian cretaceous modelling the approach allows determining four neritic carbonate factories that are called the marine biochemical photozoan photo c and heterozoan factories the model finely simulates the global distribution of lower aptian and modern carbonate platforms carbonate factories appear to thrive for specific ranges along the environmental gradient of carbonate saturation this conceptual scheme appears to be able to provide a simple universal model of paleoclimatic zones of shallow water marine carbonates

mining geology of the pond creek seam pikeville formation middle pennsylvanian in part of the eastern kentucky coal field usa abstract the pond creek seam is one of the leading producers of coal in the eastern kentucky coal field the geologic factors that affect mining were investigated in several underground mines and categorized in terms of coal thickness coal quality and roof control the limits of mining and thick coal are defined by splitting along the margin of the coal body within the coal body local thickness variation occurs because of 1 leader coal benches filling narrow elongated depressions 2 rider coal benches coming near to or merging with the main bench 3 overthrust coal benches being included along paleochannel margins 4 cutouts occurring beneath paleochannels and 5 very hard and unusual rock partings occurring along narrow elongated trends in the study area the coal is mostly mined as a compliance product sulfur contents are less than 1 and ash yields are less than 10 local increases in sulfur occur beneath sandstones and are inferred to represent post depositional migration of fluids through porous sands into the coal run of mine quality is also affected by several mine roof conditions and trends of densely concentrated rock partings which lead to increased in and out of seam dilution and overall ash content of the mined coal roof control is largely a function of a heterolithic facies mosaic of coastal estuarine origin regional fracture trends and unloading stress related to varying mine depth beneath the surface lateral variability of roof facies is the rule in most mines the largest falls occur beneath modern valleys and parallel fractures along paleochannel margins within tidally affected stackrock and beneath rider coals shale spalling kettlebottoms and falls within other more isolated facies also occur many of the lithofacies and falls related to bedding weaknesses within or between lithofacies occur along northeast southwest trends which can be projected in advance of mining fracture related falls occur independently of lithofacies trends along northwest southeast trends especially beneath modern valleys where overburden thickness decreases sharply differentiating roof falls related to these trends can aid in predicting roof quality in advance of mining

oligocene and miocene global spatial trends of shallow marine carbonate architecture abstractthe present study provides the baseline status of the spatial distribution of carbonate platforms for the oligo miocene interval the resulting global trend quantitatively shows the decreas

development of a lake in a subsiding basin in front of a saalian ice sheet kleszczow graben central poland abstract relative movements of the substratum in a still active graben in central poland in combination with the n s advance of pleistocene ice masses largely determined the sedimentary conditions in front of the ice sheet during one of the saalian glacial phases the vertical successions and lateral facies transitions that formed under these extreme conditions which may include a forebulge of the ice in the ice front parallel graben show an order that can be logically explained by facies shifts four lithofacies associations with a total of eleven lithofacies have been distinguished they represent a transition from a glaciofluvial to a glaciolacustrine sedimentary environment with an extraglacial anastomosing river a partly submerged alluvial fan a lake both the margin and the central part and a delta slope the completeness of this sequence is probably due to continuous subsidence in the graben area the only interruption of the logical sequence is by a homogeneous mud layer which is explained as a result of reworking of a large volume of lacustrine mud possibly as a result of slope instability but more probably triggered by an earthquake during graben activity