seasonal ratcheting and softening in clay slopes leading to first time failure centrifuge tests have been carried out on kaolin clay slopes subject to variations in surface rainfall and humidity corresponding at model scale to successive wet and dry seasons in the field these model slopes have been instrumented with miniature high capacity tensiometers and the deformations of their cross sections have been observed by digital photography and analysed by particle image velocimetry sequences of swelling and shrinkage have been seen to be potentially irreversible leading to creep in the form of down slope ratcheting accompanied by progressive regional softening within the zone affected by the seasonal moisture movements ultimately this regional softening has been seen to lead to slope failures in which segments of soil have separated from the mass through the opening of tension cracks and the formation of a localised shear rupture an analysis of the phase of episodic regional softening is presented here based on a spencer limit equilibrium approach these back analyses illu

northern england serpukhovian early namurian farfield responses to southern hemisphere glaciation abstract during the serpukhovian early namurian icehouse conditions were initiated in the southern hemisphere however nearfield evidence is inconsistent glaciation appears to have started in limited areas of eastern australia in the earliest serpukhovian followed by a long interglacial whereas data from south america and tibet suggest glaciation throughout the serpukhovian new farfield data from the woodland throckley and rowlands gill boreholes in northern england allow this inconsistency to be addressed 18 o from well preserved late serpukhovian late pendleian to early arnsbergian woodland brachiopods vary between 3 4 and 6 3 and 13 c varies between 2 0 and 3 2 suggesting a 18 o seawater w value of around 1 8 vsmow and therefore an absence of widespread ice caps the organic carbon 13 c upward increasing trend in the throckley borehole serpukhovian to bashkirian c 24 to c 22 and the rowlands gill borehole serpukhovian c 24 to c 23 suggests large scale burial of organic material probably in burgeoning lycophyte dominated coal forest implying a fall in p co 2 p co 2 reduction appears not to have caused large scale glaciation until the early bashkirian but a scenario of coalescing upland ice caps through the serpukhovian with a background of decreasing p co 2 appears to be similar to the process that initiated cenozoic antarctic glaciation

inverse relation between ice extent and the late paleozoic glacial record of gondwana the late carboniferous earliest permian age estimate 300 280 ma for maximum ice volume during late paleozoic glaciation of gondwana is challenged past estimates assume a direct relation between extent of depositional glacial record and former ice cover this assumption cannot be sustained given that the glacial record is composed predominantly of glacially influenced marine strata that accumulated on the margins of ice covered areas we argue that gondwana ice cover expanded in the early carboniferous in response to polar position availability of moisture from a mediterranean sea and epeirogenic uplift of the gondwana interior in namurian time ca 325 ma gondwana ice cover attained a maximum extent of about 21 10 6 km 2 nearly the area of maximum pleistocene ice cover despite extensive ice cover the depositional record is meager continental glacial deposits are poorly preserved on a regional unconformity thereafter extensional subsidence of intracratonic basins promoted marine flooding fragmentation of the ice cover and the accumulation of thick glacially influenced marine deposits in stephanian asselian time ca 285 ma ice cover had decreased to about 15 10 6 km 2 but glacial marine strata were being deposited and preserved across a very large area of the gondwana supercontinent

pennsylvanian uplands were forested by giant cordaitalean trees the precise timing of when upland terrains first became forested is highly controversial pennsylvanian palynoflora and megaflora transported into marine highstand deposits imply that emergent topographic highs may have supported cordaitalean forests the discovery of a new pennsylvanian bolsovian plant assemblage in southwest newfoundland confirms this hypothesis and allows the architecture of these upland trees to be reconstructed in detail the assemblage includes several hundred calcareously permineralized stumps trunks and branches and represents the remains of shallowly rooted cordaitalean trees that were 48 5 m high when mature the fossils occur in alluvial conglomerates that constitute a 10 km diameter outlier on the margins of the paleoequatorial variscan foreland the paleogeographic setting together with plant taphonomic inferences strongly indicate that these giant trees were transported from nearby upland alluvial plains and deposited in an elevated intermontane basin this interpretation is supported by analysis of rootstock morphology which implies tree growth in thin soils consistent with an alluvial gravel substrate this improved understanding of pennsylvanian upland forests has important implications for geochemical modeling of the global carbon cycle

origin and implications of early diagenetic quartz in the mississippian bowland shale formation craven basin uk abstract silica cementation exerts a key control on the compaction and geotechnical properties of mudstones and by extension the style of hydrocarbon and or mineral systems present in a given sedimentary basin integrated microscopic and bulk geochemical observations demonstrate that siliceous mudstones in the bowland shale formation a target for uk shale gas extraction exhibit abundant dispersed discrete m scale quartz cements and exhibit silica enrichment excess above a local detrital si al threshold of 2 5 dissolution of siliceous radiolarian tests during early diagenesis is identified as the main source of silica opal a required for quartz precipitation either via opal ct or directly to quartz and potentially generated as a product of anoxic marine weathering dissolution of reactive silicates during early diagenesis excess silica correlates with free hydrocarbons s1 normalised to total organic carbon oil saturation index osi we propose early diagenetic quartz precipitation suppressed pore collapse buttress effect retaining the pore space capacity to host oil quartz precipitation was likely catalysed for example via low porewater ph elevated al and or fe oxide content and or abundant labile organic matter juxtaposition of siliceous mudstones and mudstones lacking quartz cement indicates silica was immobile beyond the bed scale thus metre scale siliceous packages likely represent more prospective units within the bowland shale in terms of unconventional hydrocarbons on the basis of early diagenetic biogenic derived quartz cementation leading to improved hydrocarbon storage capacity coupled to enhanced brittleness these findings are relevant for shale oil and shale gas systems specifically where oil retained in pores subsequently cracks to generate gas these findings also suggest the bowland shale is a sub class of black shale defined by the potential to host a relatively large volume of early diagenetic fluids derived from anoxic bottom waters which were potentially s and or metal bearing this is potentially relevant for understanding the genesis of adjacent and related pb zn mineral deposits

global neoproterozoic petroleum systems the emerging potential in north africa the neoproterozoic eon is relatively poorly known from a petroleum perspective despite the existence of producing proven and potential plays in many parts of the world in tectonic climatic and petroleum systems terms the neoproterozoic to early cambrian period can be divided into three distinct phases a tonian to early cryogenian phase prior to about 750 ma dominated by the formation stabilization and initial break up of the supercontinent of rodinia a mid cryogenian to early ediacaran phase c 750 600ma including the major global scale sturtian and marinoan glaciations and a mid ediacaran to early cambrian c post 600ma phase corresponding with the formation and stabilization of the gondwana supercontinent there is increasing evidence that deposition of many mid to late neoproterozoic to early palaeozoic organic rich units was triggered by strong post glacial sea level rise on a global scale following the snowball earth type glaciations coupled with basin development and rifting on a more local scale fieldwork in north africa including the taoudenni basin in mauritania algeria and mali the anti atlas region of morocco and the cyrenaica kufra and murzuk basins in libya has added to the understanding of reservoir source and seal relationships and confirmed the widespread presence of precambrian stromatolitic carbonate units of potential reservoir facies current research on the chronostratigraphy distribution and quality of source rocks controls on reservoir quality and distribution of seals in the precambrian early cambrian hydrocarbon plays through out south america north africa the middle east and the indian subcontinent is documented in this special publication the geological society of london 2009

the prospectivity of a potential shale gas play an example from the southern pennine basin central england uk during the serpukhovian late mississippian stage the pennine basin now underlying much of northern england consisted of a series of interlinked sub basins that developed in response to the crustal extension north of the hercynic orogenic zone for the current study mudstone samples of the morridge formation from two sub basins located in the south eastern part of the pennine basin were collected from the carsington dam reconstruction c3 borehole widmerpool gulf sub basin and the karenight 1 borehole edale gulf sub basin detailed palynological analyses indicate that aside from the dominant often 90 or more heterogeneous amorphous organic matter aom variable abundances of homogeneous aom and phytoclasts are present to complement the palynological dataset a suite of geochemical and mineralogical techniques were applied to evaluate the prospectivity of these potentially important source rocks changes in the carbon isotope composition of the bulk organic fraction 13com suggest that the lower part biozone e2a of carsington dr c3 is markedly more influenced by terrigenous kerogen than the upper part of the core biozones e2a3 e2b1 the karenight 1 core yielded more marine kerogen in the lower part marine bands e1 e2b than the upper part marine band e2b present day rock eval total organic carbon tocpd surpasses 2 in most samples from both cores a proportion suggested by jarvie 2012 that defines prospective shale gas reservoirs however when the pyrolysable component that reflects the generative kerogen fraction is considered very few samples reach this threshold the kerogen typing permits for the first time the calculation of an original hydrogen index hio and original total organic carbon toco for carboniferous mudstones of the pennine basin the most prospective part of carsington dam reconstruction c3 marine bands e2b1 e2a3 has an average toco of 3 2 and an average hio of 465 mg g toco the most prospective part of karenight 1 242 80 251 89 m is characterized by an average toco of 9 3 and an average hio of 504 mg g toco lastly x ray diffraction xrd analysis confirms that the siliceous to argillaceous mudstones contain a highly variable carbonate content the palynological geochemical and mineralogical proxies combined indicate that marine sediments were continuously being deposited throughout the sampled intervals and were punctuated by episodic turbiditic events the terrestrial material originating from the wales brabant high to the south of the pennine basin was principally deposited in the widmerpool gulf with much less terrigenous organic matter reaching the edale gulf as a consequence the prospective intervals are relatively thin decimetre to meter scale and further high resolution characterization of these intervals is required to understand variability in prospectivitiy over these limited intervals

the geology and palynology of lower and middle pennsylvanian strata in the western kentucky coal field abstract the western kentucky coal field is the southern tip of the eastern interior or illinois basin pennsylvanian rocks in this area which include conglomerate sandstone siltstone shale limestone and coal were deposited primarily in coastal deltaic settings at a time when western kentucky was located close to the equator this paper discusses temporal changes in regional sedimentation patterns and coal forming floras of lower and middle pennsylvanian strata in the western kentucky coal field lower pennsylvanian strata of the caseyville formation are characterized by paleovalley filling sedimentation patterns and extabasinal quartz pebbles caseyville formation coals are characteristically thin and discontinuous and were strongly influenced by subsidence within underlying paleovalleys and the dissected lower pennsylvanian paleotopography caseyville coals are commonly dominated by lycospora but can also have variable palynofloras which probably reflects variable edaphic conditions and edge effects within small patchy paleomires tradewater formation strata show increased marine influences and tidal estuarine sedimentation especially in the middle and upper parts coal beds in the lower part of the tradewater typically are thin and discontinuous although some economically important beds are present coals become thicker more abundant and more laterally persistent towards the top of the formation palynologically lower and middle tradewater formation coals are dominated by lycospora but begin to show increased amounts of tree fern spores middle and upper tradewater coals are thicker and more continuous and contain high percentages of tree fern spores in addition cordaite pollen is locally abundant in this interval carbondale and shelburn desmoinesian strata are much more laterally continuous and occur within classic cyclothems that can be traced across the coal field cyclothems have long been interpreted as being eustatically driven and glacio eustacy controlled not only sedimentation but also the formation of desmoinesian paleomires palynologically carbondale and shelburn coals are either dominated by lycospora or have heterogeneous palynofloras palynologic and coal quality data suggest that hydrologic base level may have been the primary control on desmoinesian paleomires rather than paleoclimate as the coals display rheotrophic rather than ombrotrophic characteristics

a water retention model for deformable soils the paper presents an experimental study on water retention behaviour of two reconstituted soils a silty clay speswhite kaolin and a sandy clayey silt barcelona silt and two compacted soils a silty clay speswhite kaolin and a silty sandy gravel adige river embankment these soils were used with the aim of encompassing a wide range of soil types and soil fabrics specimens were subjected to drying and wetting hydraulic paths by removing or adding water under zero total stress and to mechanical wetting paths by compressing specimens at constant water content to investigate a broad range of void ratios the reconstituted sandy clayey silt was initially reconstituted from slurry by applying different consolidation vertical stresses whereas the compacted speswhite kaolin and adige river embankment were compacted to a broad range of water contents and compaction energy on the basis of the experimental data a modification to the van genuchten s model is proposed to account for the effect of voi

onset of late palaeozoic glacio eustasy and the evolving climates of low latitude areas a synthesis of current understanding studies of depth sensitive carbonate successions in the uk indicate that regular orbitally forced glacio eustatic sea level oscillations which characterized the late palaeozoic started abruptly around 330 ma early asbian the gondwanan ice sheet was highly sensitive to orbitally forced variations in solar insolation and the resultant sea level oscillations had an approximate 100 ka periodicity studies of fossil soils and palaeokarst from low latitude settings suggest that pre asbian climates were relatively stable with infrequent changes however climatic changes became increasingly frequent in the asbian and brigantian with regular fluctuations of a sub 100 ka periodicity occurring during glacial lowstand intervals

petrographic classification of sand and sandstone abstract petrographic classifications of sand and sandstone proposed more than half a century ago are still in use although they were formulated at a time when depositional and post depositional sedimentary processes were poorly understood and before the relationships between tectonics and sedimentation could be interpreted in modern plate tectonic terms as a consequence too many scientific articles and technical reports are still encumbered with obsolete concepts graphical tools and ambiguous terminology that make sediment descriptions awkward and misleading a renovation that treasures the legacy of the pioneers is required the descriptive petrographic classification of sand and sandstone proposed in this paper is based on the quasi universally used gazzi dickinson point counting method and simply translates into words ternary compositions of quartz feldspar and lithic fragments without introducing any new names the classic qfl plot is subdivided into 15 fields labelled by adjectives introduced long ago by k a w crook and endorsed by w r dickinson and more recently by g j weltje which reflect relative abundances of the three main framework components provided they exceed 10 qfl according to standard use the less abundant component goes first the more abundant last e g litho feldspatho quartzose composition translates into q f l 10 qfl for lithic rich sand and sandstone information on the prevailing rock fragment type can be added by an additional free adjective e g metamorphiclastic carbonaticlastic as proposed long ago by r v ingersoll for lithic poor feldspatho quartzose and quartzose sand and sandstone further formal subdivisions are proposed based on the q f ratio thus reaching a total of 18 compositional fields overall modern sand known to be derived from different source rocks and found in major world s rivers deserts and deep sea fans fits in the pigeonholes defined by the relative abundance of quartz feldspar and lithic fragments the aim of this classification is to restore directness in sandstone petrology and to avoid ambiguities generated in the past by making reference to badly defined archetypes such as greywacke or arkose thus confusing petrographic composition with subjective considerations about plate tectonic setting texture hydraulic behaviour mechanical durability or chemical durability in the illusion that a classification could be genetic at the same time as descriptive

an assessment of geochemical preparation methods prior to organic carbon concentration and carbon isotope ratio analyses of fine grained sedimentary rocks 1 this study summarizes organic carbon isotope 13c and total organic carbon toc data from a series of tests undertaken to provide an appropriate methodology for pre analysis treatment of mudstones from an upper carboniferous sedimentary succession in order to develop a consistent preparation procedure the main treatments involved removing both inorganic carbonate and hydrocarbons which might be extraneous before 13c and toc analysis the results show that decarbonating using hydrochloric acid causes significant reduction in 13c and total carbon tc of the bulk material due to the removal of inorganic carbonate these changes are most pronounced where soluble calcium carbonate rather than ca mg fe carbonate is present deoiled samples show only slightly higher mean 13c where visible bitumen was extracted from the bulk sample moreover the isotopic signatures of the extracts are closely correlated to those of their respective bulk samples suggesting that small yields of hydrocarbons were generated in situ with no isotopic fractionation in addition further 13c and tc analyses were performed on samples where mixing of oil based drilling mud with brecciated core material had been undertaken brecciated mudstone material did not display distinct isotopic signals compared to the surrounding fine grained material overall we show that the most accurate assessment of bulk organic carbon isotopes and concentration in these samples can be achieved through decarbonating the material prior to measurement via the rinse method however our results support recent findings that pre analysis acid treatments can cause variable and unpredictable errors in 13c and toc values we believe that despite these uncertainties the findings presented here can be applied to paleoenvironmental studies on organic matter contained within sedimentary rocks over a range of geological ages and compositions

carbon isotopes as indicators of dispersal patterns in devonian mississippian shales of the appalachian basin measurement of the carbon isotopic composition of organic matter in about 200 samples from the devonian shale sequence of the eastern united states shows a definite transition from nonmarine values of around 25 through intermediate values in prodelta samples to distal basinal samples with values around 30 5 this trend matches very closely that found for paleocurrents in the sequence from sole markings on turbidite siltstone beds thus the carbon isotopes suggest that the organic matter and hence the enclosing shale had the same dispersal pattern as the silt stones furthermore the steady westward change to more marine values indicates that the cincinnati arch was never sufficiently positive to act as a source of organic matter the nonmarine carbon has an isotopic composition very similar to that of coal and so probably represents woody material the basinal values however are much lighter than modern marine plankton this may be a diagenetic effect or it may reflect a difference in the devonian plankton

the riddle of volcaniclastic sedimentation in ancient deep water basins a discussion abstract sedimentary records of deep water basins are useful tools for understanding how volcanism shapes distal environments furthermore these basins represent uncontaminated places where catastrophic eruptions are clearly preserved for these reasons the study of the depositional records of deep sea realms becomes of primary importance to better understand the temporal incidence and the consequences of catastrophic events that may occur on earth however their inaccessible underwater conditions limit the possibility of deep investigations thus ancient analogues represent the best way to integrate direct observations with detailed sedimentological and petrographic analyses this work introduces concepts derived from the study of three sedimentary sequences that form the oligocene foreland and foredeep deep sea basins of the proto alpine belt each succession is characterized by its volcaniclastic detritus and two of them were deposited during volcanic activity we compare their sedimentological and volcanological characteristics highlighting the main features derived from a volcanically controlled sedimentation we emphasize 1 the importance of stratigraphy and petrography in the identification of criteria to recognize volcanism phases in ancient distal deep water sequences 2 the propensity of volcanism to produce detritus during its life rather than after its death and 3 the fundamental role of pyroclastic density currents in delivering particles from source areas to depositional basins these three points suggest that a deep knowledge of ancient sedimentary records integrates our knowledge on the interaction existing between volcanoes and surrounding environments with a hazard assessment perspective

postglacial denudation of western tibetan plateau margin outpaced by long term exhumation the indus river one of asia s premier rivers drains the western tibetan plateau and the nanga parbat syntaxis these two areas juxtapose some of the lowest and highest topographic relief and commensurate denudation rates in the himalaya tibet orogen respectively yet the spatial pattern of denudation rates upstream of the syntaxis remains largely unclear as does the way in which major rivers drive headward incision into the tibetan plateau we report a new inventory of 10 be based basinwide denudation rates from 33 tributaries flanking the indus river along a 320 km reach across the western tibetan plateau margin we find that denudation rates of up to 110 mm k y 1 in the ladakh and zanskar ranges systematically decrease eastward to 10 mm k y 1 toward the tibetan plateau independent results from bulk petrographic and heavy mineral analyses support this denudation gradient assuming that incision along the indus exerts the base level control on tributary denudation rates our data show a systematic eastward decrease of landscape downwearing reaching its minimum on the tibetan plateau in contrast denudation rates increase rapidly 150 200 km downstream of a distinct knickpoint that marks the tibetan plateau margin in the indus river longitudinal profile we infer that any vigorous headward incision and any accompanying erosional waves into the interior of the plateau mostly concerned reaches well below this plateau margin moreover reported long term 10 6 yr exhumation rates from low temperature chronometry of 0 1 0 75 mm yr 1 consistently exceed our 10 be derived denudation rates with averaging time scales of 10 3 10 4 yr for our denudation data we report postglacial rates of downwearing in a tectonically idle landscape to counterbalance this apparent mismatch denudation rates must have been higher in the quaternary during glacial interglacial intervals

focused erosion at the core of the greater caucasus sediment generation and dispersal from mt elbrus to the caspian sea abstract the highest peaks in europe are found in the central greater caucasus an orogenic belt characterized by extremely active tectonic and sedimentary processes in this rugged mountain region we have investigated sand generation and erosion patterns by using high resolution petrographic and heavy mineral data on river sands complemented by detailed morphometric analysis of 9 major mountain branches of the terek river also presented is an extensive review of sediment transport data available in the russian literature on glacial lake outburst floods and rainfall triggered debris flows which owing to global warming and glacier retreat have afflicted the greater caucasus with increasing frequency in the last 50 years the accurate definition of mineralogical signatures characterizing detritus derived from six end member volcanic metamorphic basement and sedimentary metasedimentary rock units allowed us to calculate the relative contribution of each to the sand load with particular precision for the baksan river draining mt elbrus results clearly indicate that volcanic and basement rocks supply a disproportionate amount of sand relatively to their outcrop area testifying to strongly focused erosion in the high relief axial part of the range river channels here display extreme steepness ksn up to 200 300 and low concavity indices 0 15 0 35 typical of thalwegs shaped by debris flows average erosion rates reach as high as 2 4 mm a which is explained by the frequency of catastrophic mass transport events able to mobilize in one single episode between 106 and 107 tons of detritus corresponding to 10 50 mm of erosion distributed across the catchment upstream on 20 september 2002 the kolka glacier disaster mobilized 2 108 tons of debris corresponding to 400 mm of erosion in the upper genaldon valley to quantify the intrinsic capacity of different bedrock types to generate sand isolated from such a strong focused erosion effect we used the normalized steepness index ksn as a proxy of erosion rate and thus redefined the sand generation index as s g i s a s a a a k s n k s n a more realistic values are thus obtained although far more comprehensive data on sediment load than those presently available are required to discriminate robustly between the effect of focused erosion versus lithological control on sand generation

investigating the record of permian climate change from argillaceous sedimentary rocks oman a standard method for the analysis of carbon isotope composition of bulk organic matter 13 c bulk in palaeoenvironmental and stratigraphic studies of sedimentary basins associated with hydrocarbons is suggested this method includes the removal of interstitial hydrocarbon within the sediments which is shown to have a negative effect on 13 c using the method a 13 c bulk trend c 21 to 24 was found within the lower permian al khlata and lower gharif formations of thuleilat 16 and 42 well sections south oman palaeontological and sedimentological evidence indicates considerable palaeoenvironmental change from a cold climate lowland fern flora and upland primitive conifer flora low in the sequence to a lowland cycad like and upland glossopterid or other gymnospermous flora higher in the sequence the lithologies range from glacial diamictite at the base to calcrete horizons and redbeds at the top it is therefore likely that the 13 c bulk trend is related to palaeoenvironmental change

k o ocr relationships in soil the relationships between k o and ocr are investigated for primary loading unloading reloading conditions the study reviews laboratory data from over 170 different soils and presents an approach common to clays silts and sands simple empirical methods for predicting k o for normally consolidated and overconsolidated soils are evaluated the validity of the methods is supported by statistical analyses on the basis of the findings only the effective stress friction angle o and prior stress history ocr and ocrmax are needed to predict approximate values of k o

organic geochemistry of duckmantian pennsylvanian coals from the ruhr basin western germany abstract the molecular composition of 58 duckmantian ruhr coals and adjacent sedimentary rocks has been analyzed using organic geochemical investigations representing a maturity range from 0 74 to 0 98 vitrinite reflectance in addition eight samples of higher maturity 1 46 to 3 55 vitrinite reflectance were studied for comparison the composition of coals depends primarily on plant input into the peat swamps but also to a large extent on thermal maturity several maturity related parameters have been applied in this study such as mpi dmai and diverse hopanoid based maturity ratios especially diamantane based parameters proved to be excellent for characterizing high rank samples whereas hopane and phenanthrene based parameters are well suited for the lower maturity range various specific biomarkers reflect the composition of the duckmantian coals concerning the floral differences and floral shift during the westphalian the dominating n alkanes hopanes and bicyclic sesquiterpanes show only marginal differences and reveal a quite homogenous floral composition within the six coal seams tetracyclic diterpanes as approved markers for modern as well as paleozoic conifers and pre gymnosperms have been identified in all six coal seams but in low concentration one order of magnitude lower than bicyclic sesquiterpanes a slight increase of the tetracyclic diterpane ent beyerane in the younger seams indicates an increase in abundance of pre gymnosperms cordaites during the duckmantian significantly increased proportions of diverse compounds like bicyclic sesquiterpanes eudesmane or tetracyclic terpanes clearly testify an origin from higher land plants the major part of the duckmantian coal swamps biomass with its vitrinite rich coals originated presumably from barks of arborescent lycopods high concentrations of hopanes mirror the input of bacterial organic matter and a strong microbial reworking of the deposited terrestrial plant organic matter

reduced sediment supply in a fast eroding landscape a multi proxy sediment budget of the upper rhone basin central alps alpine water and sediment supply influence the sediment budget of many important european fluvial systems such as the rhine rhone and po rivers in the light of human induced climate change and landscape modification it becomes increasingly important to understand the mechanisms of sediment production and supply in alpine sediment systems this study aims to investigate the modern sediment budget of the upper rhone basin one of the largest alpine intramontane watersheds located in the central alps of southwestern switzerland major areas of sediment generation are fingerprinted by framework petrography heavy mineral concentrations and bulk geochemistry the relative contributions of the three major sources to the sediment of the trunk rhone river are identified by compositional mixing modelling concentrations of the terrestrial cosmogenic nuclide 10be measured in quartz separated from fluvial sediments provide spatially averaged denudation rates for selected tributary basins results from sediment fingerprinting and mixing modelling suggest that tributaries located in the north and the east of the catchment are generating most of the sediment transported by the rhone river to its primary sedimentary sink in lake geneva despite having some of the highest denudation rates within the basin tributaries located in the southern area of the rhone basin are relatively underrepresented in the sediment budget of the rhone river these tributaries are severely affected by human activities for example through sediment mining as well as water and sediment abstraction in large hydropower reservoirs together these processes reduce the basin wide sediment discharge by about 50 thereby explaining most of the observed compositional pattern in addition there is evidence suggesting that large amounts of glaciogenic sediments are currently supplied by retreating glaciers glaciogenic material with its low 10be concentrations can lead to a significant overestimation of denudation rates and thus limit the applicability of cosmogenic nuclide analysis in such glaciated settings

provenance analysis of the voirons flysch gurnigel nappe haute savoie france stratigraphic and palaeogeographic implications the chablais prealps haute savoie france represent a well preserved accretionary wedge of the western alpine tethys they comprise a stack of sedimentary nappes related to palaeogeographic realms ranging from the ultrahelvetic to the southern penninic the provenance analysis is based on the gazzi dickinson method and on qemscan for heavy minerals the quartzose petrofacies is the most important of the two sources and supplied three of the four formations of the voirons flysch it is similar to the sources that fed the other flyschs from the gurnigel nappe it is characterised by a mature quartz rich assemblage and a heavy mineral population dominated by apatite and the zircon tourmaline rutile mineral group these observations suggest a clastic wedge provenance the feldspathic petrofacies is derived from a feldspar rich source associated with metamorphic clasts and a heavy mineral population dominated by garnet this provenance characterises only one formation of the voirons flysch and is related to the axial belt provenance this provenance analysis shows that the middle eocene to early oligocene voirons flysch was fed by two sources in contrast to the other flyschs of the gurnigel nappe and further suggests that this flysch was not deposited in the piemont ocean but in the valais domain based on the results and comparative provenance analysis with the other flyschs of the gurnigel nappe we propose a generic feeding model which involves the sesia dent blanche nappe the sedimentary nappes incorporated in the accretionary prism and probably the brianconnais basement

depositional controls on mudstone lithofacies in a basinal setting implications for the delivery of sedimentary organic matter deep water mudstones from ancient epicontinental settings are significant repositories for organic matter but the detailed temporal variations of and controls on the abundance and type of organic matter om is little studied using micro petrographic and geochemical data from late mississippian mudstones of the widmerpool gulf uk the processes that delivered fine grained sediment to this basin during a glacioeustatic sea level cycle are interpreted from detailed lithofacies analysis seven primary lithofacies are identified from core which show specific and systematic variations in total organic carbon toc content and bulk carbon isotope composition of organic material 13corg during sea level highstands thin bedded carbonate bearing mudstones are the dominant facies deposited contain up to 6 6 toc average 4 6 1 3 and have mean 13corg of 28 5 0 9 during phases of lower sea level thin bedded silt bearing clay rich mudstones with up to 4 1 toc average 2 3 0 8 mean 13corg 28 2 1 0 were interbedded with more organic lean graded silt bearing mudstones and sand bearing silt rich mudstones average toc 1 7 0 6 derived from turbidity currents the latter mean 13corg 26 2 0 7 are closely linked to significant proportions of terrestrial plant material while some rare plant debris and sand bearing mudstones produced from debris flows have more than 7 0 toc and 13corg 26 0 the 13c values of wood fragments ranged from 27 1 to 24 0 and therefore the 13corg is interpreted as a function of the ratio of marine and terrestrial organic matter more negative values in the carbonate bearing and the clay rich mudstones indicate marine planktonic algae whereas the least negative values reflect greater contribution of terrestrial plant material the data suggest that the marine conditions prevailed and supported marine planktonic algae throughout different sea level stages marine om was delivered to the sea floor by continuous hemipelagic settling whereas terrestrial om was delivered by sediment density flows variations in bioproductivity and dilution by siliciclastics influenced the burial rate of marine om organic rich mudstones preserved in these marine basins are potential hydrocarbon source rocks especially as unconventional shale gas reservoirs detailed microtextural and compositional analysis coupled with rigorous geochemical parameters as used in this study are important for the understanding of the source rock potential of basinal mudstones and of fine grained organic rich sediments in general

geochemical and lithological controls on a potential shale reservoir carboniferous holywell shale wales the holywell shale is part of the carboniferous bowland shale formation identified as the main potential shale gas system in the uk here we report geochemical and petrographic data from five outcrops of the lower and upper holywell shale across northeast wales at outcrop the holywell shale is immature to early oil mature and has total organic carbon toc values ranging between 0 1 and 10 3 wt with a mean of 1 9 wt carbon isotope data clearly differentiate terrestrial and marine organic matter and show that both occur throughout the holywell with terrestrial sources type iii iv dominating the upper holywell and marine sources dominating the lower holywell type ii iii trace element data indicate that bottom waters were oxygenated resulting in poorly preserved organic matter supported by c n and hi data a range of silt and clay rich lithofacies occur which show no relationship to either the amount or type of organic matter we interpret the data in terms of a mixed supply of terrestrial and marine organic matter to marine depositional environments in which there was sufficient hydrodynamic energy to transport fine grained sediment as bed load the resulting mudstones exhibit a range of sedimentary textures with millimetre to centimetre scale silt clay bed forms which show almost no relationship to organic matter type and amount the small scale variability and heterogeneity of both organofacies and lithofacies means that the reservoir quality of the holywell shale is inherently difficult to predict

from static to dynamic provenance analysis sedimentary petrology upgraded abstract the classical approach to sandstone petrology established in the golden years of plate tectonics and based on the axiom that detrital modes of sandstone suites primarily reflect the different tectonic settings of provenance terranes has represented a benchmark for decades the composition of sand and sandstone however simply provides us with a distorted image of the lithological structure of source terranes and gives us little clue whether they are allochthonous or autochthonous orogenic or anorogenic young or old what we may able to see reflected in detrital modes is the nature of source terranes continental arc oceanic and the tectonostratigraphic level reached by erosion in space and time the proposed new approach to the petrology of sand and sandstone 1 starts with a simple classification scheme circulated since the 1960s which is purely descriptive objective and free of ill defined ambiguous terms and 2 focuses on the nature and tectonostratigraphic level of source terranes further steps are essential to upgrade provenance analysis acquiring knowledge from modern settings is needed to properly identify and wherever possible correct for physical and chemical processes introducing environmental and diagenetic bias and thus address nature s complexities with adequate conceptual tools equally important is the integration of multiple techniques ideally including bulk sediment multi mineral and single mineral methods bulk sediment petrography remains the fundamental approach that allows us to capture the most precious source of direct provenance information represented by the mineralogy and texture of rock fragments bulk sediment geochemistry applicable also to silt and clay carried in suspension is a superior method to check for hydraulic sorting chemical weathering and fertility of detrital minerals in different sediment sources detrital geochronology thermochronology and isotope geochemistry reveal the diverse time structures of source rocks and have become necessary complementary techniques in modern provenance analysis inferences on geodynamic processes need independent geological information and come last but if tackled properly they can lead us much farther than the standard label obtained by using triangular diagrams uncritically as if they were infallible oracles

numerical modelling of a centrifuged embankment on soft clay biot coupled consolidation numerical analyses have been applied to a stage constructed embankment on soft clay in the centrifuge in the test the sand embankment was constructed on a clay foundation consisting of an overconsolidated crust overlying a normally consolidated layer measurements were taken of pore pressures dissipation rates and displacements in the foundation clay predictions of these were made using a simple cam clay model for the clay and the cambridge crisp computer program a linear elastic idealization was used for the embankment with some exceptions pore pressures and dissipation rates were very well predicted as were maximum values of both horizontal and vertical displacements however displacement profiles with depth were not so well predicted particular attention is given in the paper to the determination of relevant values of shear modulus g and the difference in behaviour resulting from using constant permeability and permeability varying with void ratio

response of late carboniferous tropical vegetation to transgressive regressive rhythms at joggins nova scotia fossil plant assemblages are described in their sequence stratigraphic context from the upper carboniferous langsettian joggins formation of nova scotia to elucidate ecosystem response to transgressive regressive rhythms results show that rising base level resulted in retrograding submerged coastal mires co dominated by lepidodendron and lepidophloios which were replaced by short lived paralycopodites communities immediately following mire drowning extensive brackish bays existed during early highstand distally fringed by gymnospermous and putative progymnospermous coastal and or upland vegetation late highstand bay filling generated prograding distributary wetlands dominated by flood disturbed lycopsid pteridosperm sphenopsid communities and locally by cordaite mangroves as base level fell well drained alluvial plains were dominated by fire prone cordaite and or sigillaria communities which persisted until the next phase of base level rise this rhythmic ecosystem succession repeatedly occurred on a c 50 200 ka time scale and was probably driven by glacial interglacial climate rhythms

sedimentary process control on carbon isotope composition of sedimentary organic matter in an ancient shallow water shelf succession 1 source and delivery mechanisms of organic matter are rarely considered when interpreting changing 13c through sedimentary successions even though isotope excursions are widely used to identify and correlate global perturbations in the carbon cycle combining detailed sedimentology and geochemistry we demonstrate how organic carbon abundance and 13c values from sedimentary organic matter from carboniferous aged mudstones are influenced by the proportion of terrestrial versus water column derived organic matter silt bearing clay rich shelf mudstones that were deposited by erosive density flows are characterized by 1 8 2 4 organic carbon and high 13c values averaging 22 9 0 3 n 12 typically these mudstones contain significant volumes of terrestrial plant derived material in contrast clay rich lenticular mudstones with a marine macrofauna are the products of the transport of mud fragments eroded from pre existing water rich shelfal muds when shorelines were distant and biological productivity in the water column was high higher organic carbon 2 1 5 2 and lower 13c values averaging 24 3 0 5 n 11 characterize these mudstones and are interpreted to reflect a greater contribution by isotopically more negative amorphous organic matter derived from marine algae differences in 13c between terrestrial and marine organic matter allow the changing proportions from different sources to be tracked through this succession combining 13c values with zirconium measured from whole rock here used as a proxy for detrital silt input provides a novel approach to distinguishing mudstone provenance and ultimately using 13c to identify oil prone organic matter in potential source rocks these results have important implications for using bulk organic matter to identify and characterize global c isotope excursions

changing patterns of pennsylvanian coal swamp vegetation and implications of climatic control on coal occurrence abstract improved regional and interregional stratigraphic correlations of pennsylvanian strata permit comparisons of vegetational changes in euramerican coal swamps the coal swamp vegetation is known directly from in situ coal ball peat deposits from more than 65 coals in the united states and europe interpretations of coal swamp floras on the basis of coal ball peat studies are extended to broader regional and stratigraphic patterns by use of coal palynology objectives of the quantitative analyses of the vegetation in relation to coal are to determine the botanical constituents at the peat stage and their environmental implications for plant growth and peat accumulation morphological and paleoecological analyses provide a basis for deducing freshwater regimes of coal swamps changes in composition of pennsylvanian coal swamp vegetation are quire similar from one paralic coal region to another and show synchrony that is attributable to climate paleobotany and paleogeography of the euramerican province indicate a moist tropical paleoclimate rainfall runoff and evapotranspiration were the variable climatic controls in the distribution of coal swamp vegetation peat accumulation and coal resources in relative terms of climatic wetness the pennsylvanian period is divisible into five intervals which include two relatively drier intervals that developed during the lower middle and middle upper pennsylvanian transitions the climate during early pennsylvanian time was moderately wet and the median in moisture availability early middle pennsylvanian was drier probably seasonally dry wet late middle pennsylvanian was the wettest in the midcontinent early late pennsylvanian was the driest and late late pennsylvanian was probably the wettest in the dunkard basin the five climatic intervals represent a general means of dividing coal resources within each region into groups with similar botanical constituents and environments of peat accumulation regional differences in basinal geology and climate were significant variables but the synchronous control of paleoclimate was of primary importance

pennsylvanian tropical rain forests responded to glacial interglacial rhythms pennsylvanian tropical rain forests flourished during an icehouse climate mode although it is well established that milankovitch band glacial interglacial rhythms caused marked synchronous changes in pennsylvanian tropical climate and sea level little is known of vegetation response to orbital forcing this knowledge gap has now been addressed through sequence stratigraphic analysis of megafloral and palynofloral assemblages within the westphalian d cantabrian sydney mines formation of eastern canada this succession was deposited in a low accommodation setting where sequences can be attributed confidently to glacio eustasy results show that long lived low diversity peat mires dominated by lycopsids were initiated during deglaciation events but were mostly drowned by rising sea level at maximum interglacial conditions only upland coniferopsid forests survived flooding without significant disturbance mid to late interglacial phases witnessed delta plain progradation and establishment of high diversity mineral substrate rain forests containing lycopsids sphenopsids pteridosperms cordaites and tree ferns renewed glaciation resulted in sea level fall paleovalley incision and the onset of climatic aridity glacial vegetation was dominated by cordaites pteridosperms and tree ferns hydrophilic lycopsids and sphenopsids survived in paleovalley refugia findings clearly demonstrate the dynamic nature of pennsylvanian tropical ecosystems and are timely given current debates about the impact of quaternary glacial interglacial rhythms on the biogeography of tropical rain forest

divergence in subduction zones and exhumation of high pressure rocks eocene western alps abstract exhumation of high pressure rocks has long remained a controversial issue in the earth sciences in this article we analyze the tectono metamorphic stratigraphic and plate motion constraints from the western alps region providing new insights on exhumation mechanisms and tectonic evolution during the earliest orogenic stages eocene eclogites of the western alps form a 20 25 km wide belt on the upper plate side of the orogen eclogite belt exposed beneath extensional shear zones at the rear of a lower pressure accretionary wedge units of the eclogite belt show the youngest peak pressure assemblages within the subduction zone and experienced superfast tectonic exhumation since 45 40 ma the role of erosion was negligible during the whole of this stage eocene foreland basins remained starved and the massive arrival of axial belt detritus began well after exhumation was completed tectonic reconstructions based on fixed boundaries exhumation models e g channel flow and or implying fast erosion at the surface e g slab breakoff are thus not consistent with geological evidence in the lack of erosion exhumation through the overburden requires divergence within the subduction zone we demonstrate that this was not attained by rollback of the lower plate europe but was instead attained by nneward motion of the upper plate adria africa away from the western alps trench such motion induced localized extension within the weak portion of the upper plate at the rear of the accretionary wedge and allowed tectonic emplacement of the eclogite belt in the upper crust at rates much faster than subduction rates tectonic exhumation ceased in the oligocene when oblique divergence along the western alps traverse changed into oblique convergence the onset of slow erosional unroofing was synchronously recorded by pressure temperature paths in all major tectonic units of the western alps and by arrival of orogenic detritus in sedimentary basins this work demonstrates that divergence between upper plate and trench is a viable mechanism to exhume large and coherent eclogite units in continental subduction zones our exhumation model can be applied to other eclogite belts showing a similar exhumational record including the western gneiss region the dabie sulu and eastern papua new guinea

sediment recycling at convergent plate margins indo burman ranges and andaman nicobar ridge subduction complexes large enough to be exposed subaerially and become significant sources of terrigenous detritus are formed by tectonic accretion above trenches choked with thick sections of remnant ocean turbidites they thus need to be connected along strike to a major collision zone where huge volumes of orogenic detritus are produced and conveyed via a major fluvio deltaic system to the deep sea in this article we investigate sediment generation and recycling in the archetype of such settings the eastern prolongation of the himalayan collisional system we illustrate the petrographic and heavy mineral suites of modern sands produced all along the indo burman andaman nicobar subduction complex which includes accreted abyssal plain sediments overthrust by ophiolites and unconformably overlain by volcaniclastic forearc strata subduction complex provenance is thus composite and overwhelmingly consists of detritus recycled from largely turbiditic parent rocks recycled clastic provenance with local supply from obducted ultramafic and mafic rocks of forearc lithosphere ophiolite provenance or recycled paleovolcanic to neovolcanic sources volcanic arc provenance in order to specifically investigate the effect of recycling we characterize the diverse detrital signatures of cenozoic sandstones originally deposited during subsequent stages of soft and hard himalayan collision and presently exposed from bangladesh to the andaman islands and discuss the reasons for compositional discrepancies between parent sandstones and their recycled daughter sands long distance multistep and multicyclic sediment transfer along and across convergent plate boundaries follows complex trajectories in space and time which must be resolved whenever we want to obtain a reasonably faithful paleogeographic reconstruction for the recent and less recent geological past

tracking sediment provenance and erosional evolution of the western greater caucasus this article investigates landscape characteristics and sediment composition in the western greater caucasus by using multiple methods at different timescales our ultimate goal is to compare short term versus long term trends in erosional processes and to reconstruct spatio temporal changes in sediment fluxes as controlled by partitioning of crustal shortening and rock uplift in the orogenic belt areas of active recent uplift are assessed by quantitative geomorphological techniques digital elevation model dem analysis of stream profiles and their deviation from equilibrium and compared with regions of rapid exhumation over longer time intervals as previously determined by fission track and cosmogenic nuclide analyses complementary information from petrographic and heavy mineral analyses of modern sands and ancient sandstones is used to evaluate erosion integrated throughout the history of the orogen river catchments displaying the highest relief as shown by channel steepness indices correspond with the areas of most rapid exhumation as outlined by thermochronological data the region of high stream gradients is spatially associated with the highest topography around mount elbrus where sedimentary cover strata have long been completely eroded and river sediments display the highest metamorphic indices and generally high heavy mineral concentrations this study reinforces the suggestion that the bedrock channel network can reveal much of the evolution of tectonically active landscapes and implies that the controls on channel gradient ultimately dictate the topography and the relief along the greater caucasus our integrated datasets obtained during a decade of continuing research display a general agreement and regularity of erosion patterns through time and consistently indicate westward decreasing rates of erosional unroofing from the central part of the range to the black sea 2014 john wiley sons ltd

detrital fingerprints of fossil continental subduction zones axial belt provenance european alps abstract collision orogens such as the alps or the himalayas are generated by plate convergence culminating in attempted subduction of a thinned continental margin massive amounts of metamorphic rocks displaying high pressure parageneses are produced during such relatively brief tectonic events and then rapidly exhumed to form the axial backbone of the new orogen sediment composition provides a fundamental key to identify past events of continental subduction although coupled detrital geochronology techniques are needed to discriminate neometamorphic and paleometamorphic sources of detritus within the austroalpine cretaceous and penninic eocene axial belts of the alps we ideally distinguish three structural levels each characterized by diagnostic detrital fingerprints the shallow level chiefly consists of offscraped remnant ocean turbidites and unmetamorphosed continental margin sediments and mostly produces lithic to quartzolithic sedimentaclastic sands yielding very poor heavy mineral suites inc

stable carbon isotopes as potential sea level indicators in salt marshes north carolina usa we compared the use of 13c values and c n ratios from salt marsh sediments to reconstruct relative sea level rsl with an established approach using foraminifera analysis of bulk organic sediment and plant samples collected along transects at two sites in north carolina usa demonstrates that sediment 13c values can be used to distinguish between spartina alterniflora dominated low marsh c photosynthetic pathway 13c values from 17 6 to 16 1 and juncus roemerianus dominated high marsh c 3 photosynthetic pathway 13c values from 28 2 to 21 8 environments juncus roemerianus plants undergo little decompositional change in 13c average 0 8 although there is a clear difference between spartina alterniflora tissue and bulk organic sediments approximately 4 c n ratios on bulk organic sediment from freshwater upland and salt marsh environments converge during early diagenesis rendering them of little use in reconstructing rsl the utility of 13c values as a sea level indicator is limited by the elevational range of c4 plants making it difficult to recognize salt marsh subenvironments and improve the precision of rsl reconstructions furthermore juncus roemerianus dominated high marsh and freshwater upland sediments cannot be adequately distinguished with 13c values

a mississippian black shale record of redox oscillation in the craven basin uk early diagenetic redox oscillation processes have been rarely recognised in the ancient rock record but potentially exert an important control on mineral authigenesis hydrocarbon prospectivity and supply of metals and or reduced s as part of associated mineral systems the upper unit of the mississippian bowland shale formation is a candidate record of diagenetic redox oscillation processes because it was deposited under a relatively high sediment accumulation rate linked to a large delta system and under dominantly anoxic and intermittently sulphidic bottom water conditions in order to characterise the syngenetic and early diagenetic processes sedimentological and geochemical data were integrated through the upper bowland shale at three sites in the craven basin lancashire uk organic matter om comprises a mixture of type ii ii s ii iii and iii om redox zones are defined by patterns of fe speciation and redox sensitive trace element enrichment and split into two groups sulphidic zones eux an iii an i and an it represent sediments deposited under conditions of at least intermittently active sulphate reduction in bottom waters non sulphidic zones ox rx ox f and ox represent sediments deposited under non sulphidic oxic to ferruginous anoxic bottom waters operation of a shelf to basin reactive fe fehr shuttle moderated by sea level fluctuation and delta proximity controlled the position and stability of redoxclines between zones of fe and sulphate reduction and methanogenesis early diagenetic redoxclines were capable of migration through the shallow sediment column relatively quickly in response to sea level fluctuation preservation of syngenetic and early diagenetic geochemical signals shows redoxclines between fe and sulphate reduction and the upper boundary of sulphate methane transition zone were positioned within decimetres i e 10 s cm of seabed falling sea level and increasing fehr supply is recognised as a switch from zones eux high sea level an iii and ultimately an i and an it low sea level zone an i defines the operation of redox oscillation between zones of fe and sulphate reduction in shallow porewaters associated with enhanced degradation of om and complete dissolution of primary carbonate preservation of om and carbonate in this system was a function of changing bottom and pore water redox processes redox oscillation operated in a siliciclastic prodeltaic environment associated with a relatively high sediment accumulation rate and high loadings of labile organic matter and metal oxides these findings are important for understanding late palaeozoic black shales in the context of hydrocarbon and mineral systems

stable carbon isotopes of amorphous kerogens from phanerozoic sedimentary rocks amorphous kerogens from phanerozoic sedimentary rocks may be divided into two groups on the basis of their 13c values h amorphous kerogens have isotopic values in the range of 24 to 20 per mil and l amorphous kerogens have isotopic values in the range of 35 to 26 per mil the occurrence of amorphous kerogens in the intermediate isotopic range from one rock unit in the data set suggests a weak continuum may exist between these two groups phytoplankton and to a lesser extent zooplankton and bacteria are considered to be the precursors for both kerogen types a plausible explanation for this dichotomy may be found in the source of co2 utilized by phytoplankton which is considered to be controlled by environmental factors h amorphous kerogens are expected to occur in silled basins that are overlain by expansive well circulated deep 500 m water where the prevailing source of carbon in the photic zone is atmospheric derived co2 conversely l amorphous kerogens are expected to occur in restricted basins that are overlain by stratified shallow 200 m water where the prevailing source of carbon in the photic zone may be organic derived co2

modelling seasonal ratcheting and progressive failure in clay slopes a validation seasonal wetting and drying stress cycles can lead to long term deterioration of high plasticity clay slopes through the accumulation of outward and downward deformations leading to plastic strain

grain size dependence of garnet composition revealed by provenance signatures of modern stream sediments from the western hohe tauern austria abstract heavy minerals are valuable indicators about the geological framework in the source area the heavy mineral garnet is one of the most widespread heavy minerals in orogenic sediments and its geochemistry provides important information about metamorphic conditions the application of heavy minerals and garnet geochemistry for sedimentary provenance analysis is tested for modern stream sediments collected along three rivers draining the eclogite zone and adjacent geological source units of the western hohe tauern area in the central eastern european alps for comparison with the stream sediments rock outcrops exposed in this area were also sampled the chosen area is very well investigated and provides an excellent place to constrain the relations between source rocks and sediment in first order drainages the influence of grain size is studied in detail by considering grain size fractions ranging from coarse silt to coarse sand 32 to 1000 m in all grain size fractions the heavy mineral assemblages are characterised to a variable extent by epidote zoisite garnet and green calcic amphibole in the smaller grain size fraction apatite is more frequent whereas in the coarser grain size fractions an increase of green calcic amphibole and garnet can be observed electron microprobe analysis of detrital garnet shows the dominance of almandine rich garnet stream sediments within and downstream of the eclogite zone show an increase of pyrope rich garnets interestingly in all samples grossular rich garnets are more frequent in the smaller grain sizes and pyrope rich garnets are more frequent in the coarser grain sizes this is controlled by the original finer size distribution of grossular in the source rocks rather than being a hydraulic effect the heavy mineral assemblages and garnet geochemical data reflect the geological setting of the study area hence confirming the general strength of these methods in sedimentary provenance analysis however the data underline strong grain size control on sediment composition including single grain compositional variations

cyclic changes in pennsylvanian paleoclimate and effects on floristic dynamics in tropical pangaea abstract wetland floras narrowly define perceptions of pennsylvanian tropical ecosystems the so called coal age such wetlands reflect humid to perhumid climate leading to characterizations of pennsylvanian tropics as everwet swampy these views are biased by the high preservation potential of wetlands sedimentation patterns paleosols and fossil floras indicate the presence of vegetation tolerant of subhumid to dry subhumid perhaps semi arid climate in basins between peat formation times understanding the significance of this seasonally dry vegetation has suffered from conceptual and terminological confusion a clearer view has emerged as models for framing the data have improved basinal floras typical of seasonally dry conditions relatively low soil moisture regimes are well documented but mainly from isolated deposits some of the earliest dominated by primitive pteridosperms flozfern floras occur in clastic rocks between european early pennsylvanian coal beds later early pennsylvanian fern cordaitalean vegetation different from coal floras is preserved in marine goniatite bullions conifers are first suggested by late mississippian potoniesporites pollen about the same time in north america broadleaf foliage lesleya and megalopteris occur in basin margin settings on drought prone limestone substrates the best known xeromorphic floras found between coal beds appear in the middle through late pennsylvanian containing conifers cordaitaleans and pteridosperms the middle pennsylvanian appearances of this flora are mainly allochthonous though parautochthonous occurrences have been reported parautochthonous assemblages are mostly late pennsylvanian the conifer flora became dominant in western and central pangaean equatorial lowlands in earliest permian location of the humid perhumid wetland flora during periods of relative dryness though rarely discussed is as or more perplexing than the spatial location of seasonally dry floras through time wetland plants had few migratory options and possibly survived in small refugia within and outside of basins coupled oscillations in climate sea level and vegetation were driven most likely by glacial interglacial fluctuations perhaps controlled by orbital cyclicity

the alps in the cretaceous a doubly vergent pre collisional orogen current palaeotectonic models see the alps chiefly as a collisional orogen with the southalpine retrobelt developed only as a post collisional feature new structural and geochronological data show instead that the continental margin of africa adria was being structured as a doubly vergent orogen during subduction of alpine tethys in the cretaceous tens of million years before collision with europe subduction is envisaged here to have nucleated in the latest albian cenomanian within the attenuated adriatic margin most continental slivers exhumed as eclogites in the axial part of the cretaceous orogen contain gabbros and relics of ht lp metamorphic rocks indicating inheritance from permian to jurassic rifting cretaceous shortening in the southalpine retrobelt is indicated by several lines of evidence including orogen derived turbidites and syn sedimentary compressional activity since the cenomanian upper cretaceous pseudotachylytes dating major s severging thick skinned thrusts and widespread fold and thrust deformation cut by eocene plutons and dikes

place vs time and vegetational persistence a comparison of four tropical mires from the illinois basin during the height of the pennsylvanian ice age abstract coal balls were collected from four coal beds in the southeastern part of the illinois basin collections were made from the springfield herrin and baker coals in western kentucky and from the danville coal in southwestern indiana these four coal beds are among the principal mineable coals of the illinois basin and belong to the carbondale and shelburn formations of late middle pennsylvanian age vegetational composition was analyzed quantitatively coal ball samples from the springfield herrin and baker are dominated by the lycopsid tree lepidophloios with lesser numbers of psaronius tree ferns medullosan pteridosperms and the lycopsid trees synchysidendron and diaphorodendron this vegetation is similar to that found in the springfield and herrin coals elsewhere in the illinois basin as reported in previous studies the danville coal sample which is considerably smaller than the others is dominated by psaronius with the lycopsids sigillaria and synchysidendron as subdominants coal balls from the springfield coal were collected in zones directly from the coal bed and their zone by zone composition indicates three to four distinct plant assemblages the other coals were analyzed as whole seam random samples averaging the landscape composition of the parent mire environments this analysis indicates that these coals separated from each other by marine and terrestrial clastic deposits have essentially the same floristic composition and thus appear to represent a common species pool that persisted throughout the late middle pennsylvanian despite changes in baselevel and climate attendant the glacial interglacial cyclicity of the pennsylvanian ice age patterns of species abundance and diversity are much the same for the springfield herrin and baker although each coal both in the local area sampled and regionally has its own paleobotanical peculiarities despite minor differences these coals indicate a high degree of recurrence of assemblage and landscape organization the danville departs dramatically from the dominance diversity composition of the older coals presaging patterns of tree fern and sigillaria dominance of late pennsylvanian coals of the eastern united states but nonetheless built on a species pool shared with the older coals

upland ecology of some late carboniferous cordaitalean trees from nova scotia and england abstract permineralised logs and charcoal fragments composed of dadoxylon type wood and derived from cordaitalean trees are described from the upper carboniferous westphalian of nova scotia and england they exclusively occur in sandstone bodies interpreted as the deposits of braided meandering and anastomosing river channels the architecture and ecology of this type of cordaitalean has not yet been satisfactorily described estimates of tree height using an allometric approach suggest that the largest trees attained an approximate height of ca 45 m the absence of true growth rings in the logs indicate that they grew under non seasonal humid tropical conditions however the presence of charred wood fragments implies that droughts of sufficient intensity to permit wildfire did occasionally occur the charcoal fragments are usually associated with incised poorly sorted chaotically bedded channel facies interpreted as flood deposits dramatic increases in runoff and sediment discharge are known to follow the destruction of vegetation in modern wildfire events and the high energy charcoal bearing channel facies described may represent a similar geomorphic response to cordaitalean vegetation fires geomorphic sensitivity to fire is greatest for steeply sloping terrains and it is therefore probable that the cordaitaleans described in this paper occupied upland settings this palaeoecological interpretation is supported by occurrence of the cordaitalean remains in river channel deposits immediately downstream of regions of palaeo upland and by the palynological record the presence of upland forests in late carboniferous times has important implications for numerical modelling of global geochemical cycles

stable carbon isotopes of wood a clue to palaeoclimate abstract detailed stable carbon isotope and molecular investigations were undertaken on a number of archaeological and fossil wood specimens to provide insights into their use as rigorous independent palaeoclimatic and palaeoenvironmental parameters the isotope data revealed large differences amongst the material with the oldest specimens being least depleted in 13 c although natural variation could account for some of the observed differences the isotope values of the archaeological and tertiary specimens are most probably related to the absolute abundance of polysaccharides present and the degree of lignin alteration the molecular data based on pyrolysis of the antarctic cretaceous conifer specimens revealed only transformed lignin with virtually no intact lignin building blocks 2 methoxyphenols preserved and no evidence of polysaccharides this degree of chemical alteration is suggested here to be one of the main causes for the 13 c enriched values of these conifer specimens these results show the importance of combining detailed molecular information on individual wood components with stable carbon isotope data for palaeoclimatic and palaeoenvironmental studies

the land plant δ13c record and plant evolution in the late palaeozoic abstract based on the evaluation of 1323 carbon isotope values for silurian to permian terrestrial organic carbon measured on plant fossils cuticules humic coals and bulk terrestrial organic matter tom we conclude that the temporal trend in 13ctom records variations in the global carbon cycle notably an increase in the fractional burial of light terrestrial organic matter in late palaeozoic sediments 13ctom values suggest that the late palaeozoic po2 peak could have been restricted to a time frame of 40 ma carbon isotope data from four taxonomic groups reveal small differences that could be a consequence of habitat conditions no significant differences in organic carbon isotopic composition in relation to variable climatic conditions are discernible the carbon isotopic composition solely reflects c3 plant metabolism

vegetation ecology of early pennsylvanian alluvial fan and piedmont environments in southern new brunswick canada abstract the vegetation ecology of pennsylvanian upland dryland regions is poorly known despite its evolutionary significance here fossil plant assemblages are described from well drained alluvial fan piedmont deposits in the uppermost boss point and tynemouth creek formations late yeadonian langsettian southern new brunswick beds record the northward building of a large alluvial fan complex over alluvial plain deposits in response to near continuous sourceland uplift proximal alluvial fan environments characterized by sheetfloods and braided streams were dominated by large cordaitalean trees medullosan pteridosperms ferns and calamiteans distal alluvial fan environments where braided stream and levee splay sedimentation predominated were covered by similar vegetation together with lycopsids in localized poorly drained depressions calamitean thickets were particularly widespread in rapidly aggrading settings on the distal fan well drained alluvial plains beyond the fan toe were characterized by axial braided rivers containing cordaitalean trunks transported from proximal settings piedmont vegetation is otherwise poorly resolved all studied plant assemblages are of low to medium diversity and dominated by the remains of a single group cordaitalean seed plants such dominance diversity characteristics together with the presence of charcoal the product of wildfire imply that pennsylvanian upland dryland vegetation experienced water stress and that the seed habit was integral to successful colonization

palaeoecological and possible evolutionary effects of early namurian serpukhovian carboniferous glacioeustatic cyclicity early namurian serpukhovian carboniferous sedimentary cycles in the throckley and rowlands gill boreholes near newcastle upon tyne uk consist of fossiliferous limestones overlain by usually unfossiliferous black mudstone followed by sandstones and often by thin coal seams sedimentological and regional geological evidence suggests that the largest are high amplitude cycles probably of glacioeustatic origin 13 c bulk organic matter delineates marine and non marine conditions because of the large difference between terrestrial and marine 13 c and indicates that full marine salinity was only intermittent and resulted from glacioeustatic marine transgression superimposed on a background of inundation by freshwater from large rivers which killed off the marine biota palynology suggests that plant groups including ferns and putative pteridosperms were affected by changing sea level and that there is a theoretical possibility of connection between cyclicity and the first appearance of walchiacean conifer like monosaccate pollen such as potonieisporites long term terrestrial and marine increasing 13 c organic may reflect the onset of major glaciation in gondwana as there is evidence to suggest that the two are coeval but no specific mechanism can be suggested to link the trends

arborescent lignophytes in the tournaisian vegetation of queensland australia palaeoecological and palaeogeographical significance abstract a middle tournaisian flora comprising several taxa of arborescent lignophytes is documented for the first time in australia it challenges earlier hypotheses considering that the early mississippian vegetation of australia was impoverished and dominated by small to medium sized arborescent lycopsids until the serpukhovian when climatic conditions became favorable to the thriving of the famous lignophyte dominated rhacopteris flora recorded in australia but also south america the present account is based on anatomically preserved fragments of trunks and branches from two localities of queensland in the broken river province and the burdekin basin three taxa are recognized dameria hueberi gen et sp nov the putative progymnosperm species protopitys buchiana goeppert 1850 and a taxon of uncertain affinities characterized by a pitus type of wood but which differs from the latter genus by anatomical traits relative to its primary body the possible occurrence of subtle growth rings in some of the woods from the burdekin basin and the conifer like traits of the dameria wood are interpreted as ecological clues suggesting that these trees may have inhabited drier settings than the wetland habitats generally inferred for the lycopsids this difference in habitats is suggested to explain the rarity of arborescent lignophytes compared to lycopsids in the australian record of plants of early mississippian age the three taxa reported in this paper represent the earliest record of arborescent lignophytes in australia after the global events that affected the vegetation at the devonian carboniferous boundary and the extinction of archaeopteris they show that the successional pattern of arborescent lignophytes around the devonian carboniferous boundary is comparable to that observed in western europe with the evidence of a diversification occurring as early as the middle tournaisian the palaeogeographic and stratigraphic distribution of protopitys and dameria indicates the occurrence of extensive floral exchanges between southern laurussia and north eastern gondwana in the late devonian to mississippian

some measurements of the permeability of kaolin this paper reports an experimental investigation of the vertical and horizontal permeabilities of speswhite kaolin clay the permeabilities were measured using falling head permeability tests a mo

paleoecology of the springfield coal member desmoinesian illinois basin near the leslie cemetery paleochannel southwestern indiana abstract the springfield coal member carbondale group petersburg formation of indiana is split locally in warrick and gibson counties indiana by clastic rocks of the folsomville member carbondale group petersburg formation that represent the leslie cemetery paleochannel part of a large interconnected paleochannel system in the springfield coal bed this study incorporated analysis of miospore and megaspore assemblages coal petrography plant compression fossils and conodonts from the coal and clastic split to document changes in the swamp and its vegetation in response to the activity of the leslie cemetery paleochannel palynological and petrographic data indicate that environmental conditions and vegetation in the lower bench of coal near the leslie cemetery paleochannel were similar to those found in profiles through the coal bed at sites near the larger more extensive galatia paleochannel miospore floras of the high vitrinite lower bench of coal were dominated by tree fern miospores with those of lycopsids ranking second in abundance megaspore assemblages were dominated by lycopsid megaspores near the contacy between the lower bench of coal and clastic split medullosan prepollen increases in abundance and fusain bands are more common which may indicate the occurrence of fire either within or outside the swamp vegetation in the folsomville member and upper bench of coal differ markedly from that of the lower bench of coal plant megafossils from the folsomville member indicate dominance by pteridosperms and or lycopsids and folsomville member miospore assemblages are dominated by lycopsid miospores most typically found in mudstones including lycospora torquifer and higher than normal abundances of granasporites medius in the transition from clastic rocks of the folsomville member to the upper bench of coal miospores of ecotonal lycopsids paralycopodites reach their peak abundance pteridosperms dominate megafossil assemblages and inertinite levels are relatively high at higher levels of the upper bench of coal vitrinite levels are higher and miospore assemblages are dominated by lycopsid miospores typical of coal swamps lycospora granulata l pusilla the presence of conodonts in coalballs in the upper bench of coal and spirorbid worms in the split indicate that the paleoswamp may have received some marine or brackish water influence higher than normal salinity levels may explain the vegetational changes observed in the upper bench of coal near the leslie cemetery paleochannel

stratigraphic imprint of the late palaeozoic ice age in eastern australia a record of alternating glacial and nonglacial climate regime stratigraphic and sedimentological data from new south wales and queensland eastern australia indicate that the late palaeozoic ice age comprised at least eight discrete glacial intervals each 1 8 ma in duration here termed glaciations separated by nonglacial intervals of comparable duration these events spanned an interval from mid carboniferous c 327 ma to the early late permian c 260 ma and illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the late early permian followed by an opposite trend towards the final demise of glaciation in the late permian the alternating glacial nonglacial motif suggests that the late palaeozoic ice age was considerably more dynamic than previously thought these patterns are remarkably consistent with recent interpretations of palaeofloral change eustatic sea level fluctuations and co 2 climate glaciation relationships for this interval of time the detailed record of alternating glacial and nonglacial climate mode disclosed herein may facilitate more closely resolved evaluations of stratigraphic records elsewhere notably in far field ice distal northern hemisphere successions

a conifer dominated palynological assemblage from pennsylvanian late moscovian alluvial drylands in atlantic canada implications for the vegetation of tropical lowlands during glacial phases abstract new research suggests that pennsylvanian coal forests were commonly replaced by conifer dominated vegetation during seasonally dry glacial phases here we describe palynological assemblages from stacked sequences of the middle pennsylvanian late moscovian sydney mines formation of nova scotia canada which lends some support to this hypothesis one critical sample from a widespread redbed succession below the harbour coal is dominated by conifer pollen 55 together with abundant representatives of cordaitaleans other coniferopsids and rare pteridosperms ferns and lepidodendrids it differs markedly from 13 other samples obtained from coals their roof shale limestone and associated channel bodies which are dominated by lepidodendrids marattialean tree ferns cordaitaleans and or calamiteans the latter beds represent coastal wetlands and are attributed to late transgressive and highstand systems tracts whereas the conifer bearing sample represents a dryland alluvial plain and may be attributed to lowstand or earliest transgressive systems tracts three additional samples from grey shale below a sequence boundary late highstand and between a redbed succession and major coal seam early to mid transgressive deposits contain transitional palynofloras with a high proportion of herbaceous gleicheniaceous and sphenopteroid ferns herbaceous lycopsids and sphenophylls interspersed with cordaitaleans and or lepidodendrids the dominance of conifer pollen within the dryland components of well defined sequences which have been linked to relative sea level change promoted by gondwanan glaciation supports the view that pennsylvanian tropical biomes responded to the beat of glacial interglacial cycles

the paleozoic to mesozoic carbon cycle revisited the carbon isotopic composition of terrestrial organic matter 1 two thousand one hundred forty eight carbon isotope values for terrestrial organic matter plant fossils coal bulk terrestrial organic matter provide a proxy record for temporal changes in the global carbon cycle 13ctom 13ccarb and 13cco2 allow a full evaluation of carbon transfer in the atmosphere ocean system as well as between the marine and the terrestrial realm the temporal evolution of 13ctom parallels respective data sets from marine carbonate carbon thus reflecting the linkage between both reservoirs via atmospheric carbon dioxide on the basis of a comparison between measured and predicted isotope records for 13ctom changes in the carbon isotopic fractionation associated with plant metabolism are discernible this contradicts the notion of an invariable carbon isotopic fractionation associated with c3 plant metabolism in light of results from current plant growth experiments these changes are viewed as dependent on the atmospheric o2 co2 hence 13ctom might serve as a proxy signal for atmospheric composition

delayed collapse of cut slopes in stiff clay delayed failure of railway cutting slopes in stiff clays excavated in the nineteenth and early twentieth centuries has been studied for some forty years known failures have generally been deep seated more recently failures have been a problem in the slopes of motorway cuttings and embankments although generally these have been shallow the average operational strength at failure in these slides has been significantly less than the peak strength and progressive failure has been postulated as the probable cause of this progressive failure can now be analysed using advanced numerical techniques a series of coupled finite element analyses have been conducted assuming strain softening soil with properties based on the brown london clay and the results are reported they show that progressive failure is considerable and fully explain the observed field behaviour the delays experienced in the field are also recovered by the analyses progressive failure is generated primarily by the high lateral stresse

paleoclimate controls on stratigraphic repetition of chemical and siliciclastic rocks climate is a primary control on sediment flux from continental sources into sedimentary systems in warm climates siliciclastic input is greatest under highly seasonal rainfall nonseasonal conditions favor formation of end member chemical rocks perennially wet climates are conducive to coal formation whereas dry climates produce carbonates and or evaporites stratigraphic repetition of siliciclastic and chemical rocks therefore appears to be related to paleoclimate cycles as well as to transgressive regressive events and tectonics

evaluation of garnet discrimination diagrams using geochemical data of garnets derived from various host rocks abstract this work is an attempt to evaluate six different garnet discrimination diagrams one binary diagram and five ternary diagrams commonly used by many researchers the mineral chemistry of detrital garnet is a useful tool in sedimentary provenance studies yet there is no clear cut understanding of what garnet type originates from which host lithology several discrimination diagrams exist for garnet showing distinct compositional fields separated by strict boundaries that are thought to reflect specific types of source rocks for this study a large dataset was compiled n 3532 encompassing major element compositions of garnets derived from various host lithologies including metamorphic igneous and mantle derived rocks in order to test the applicability of the various discrimination schemes the dataset contains mineral chemical data collected from the literature complemented with some new data n 530 from garnet bearing metamorphic and ultramafic rocks in austria and norway discrimination of the tested diagrams only works for a small group of garnets derived from mantle rocks granulite facies metasedimentary rocks and felsic igneous rocks for other garnet types the assignment to a certain type of host rock remains ambiguous this is considered insufficient and therefore the evaluated diagrams should be used with great care we further apply compositional biplot analysis to derive some hints towards future perspectives in detrital garnet discrimination