characteristics features and compaction of plant tissues traced from permineralized peat to coal in pennsylvanian coals desmoinesian from the illinois basin abstract plant tissues were traced from coal balls to coal to identify and distinguish their characteristic structures in coal and to determine compaction ratios for specific tissues comparison of average cell sizes of lycopod aerial periderm in coal ball peat and coal gave compaction ratios ranging from 7 1 to 19 1 some of this compaction took place by three dimensional contraction of the periderm so that the shapes of the cells in cross section were not greatly changed compaction ratios of other tissues ranged from 3 1 to 60 1 tissues traced into vitrinite include lycopod stem periderm stigmaria periderm diaphorodendron cortex myeloxylon pennsylvanioxylon wood and bark marattialean fern leaves psaronius outer roots and stigmaria rootlets tissues traced into fusinite or semifusinite include lycopod stem periderm myeloxylon and psaronius inner roots cordaitean leaves cordaianthus and marattialean fructifications were identified in coal and coal balls from the same layer the coal balls were from the herrin springfield and houchin creek coal members of the carbondale formation desmoinesian series pennsylvanian system and an unnamed coal in indiana equivalent to the murphysboro coal member in illinois staunton formation desmoinesian series pennsylvanian system thin sections and etched polished blocks were characterized by light and sem microscopy

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

groundwater controls on biogeomorphic succession and river channel morphodynamics biogeomorphic succession describes feedbacks between vegetation succession and fluvial processes that at the decadal timescale lead to a transition from bare river deposited sediment to fully developed riparian forest where the rate of stabilization by biogeomorphic succession is greater than the rate of ecological disturbance by fluvial processes a river is likely to evolve into less dynamic states while river research has frequently considered the physical dimensions of morphodynamics less is known about physical controls on succession rates and how these impact stream morphodynamics here we test the hypothesis that groundwater dynamics influence morphodynamics via the rate of biogeomorphic succession we applied historic imagery analysis in combination with dendroecological methods for willows growing on young gravelly fluvial landforms along a steep groundwater depth gradient we determined the following floodplain morphodynamics and plant encroachment at the decadal scale pioneer willow growth rates and their relationships to hydrological variables willow growth rates were correlated with moisture availability groundwater discharge and precipitation variability in the downwelling reach while little correlation was found in the upwelling reach after a reduction in ecological disturbance frequency data suggest that where groundwater is upwelling biogeomorphic succession is fast the engineering effect of vegetation is quickly established and hence channel stability increased and active channel width reduces where groundwater is downwelling deeper and more variable biogeomorphic succession is slower the engineering effect is reduced and a wider active width is maintained thus groundwater is an important control on biogeomorphic feedbacks intensity and through the stabilizing effect of vegetation may drive long term river channel morphodynamics

fireball passes and nothing burns the role of thermal radiation in the cretaceous tertiary event evidence from the charcoal record of north america high soot contents have been reported in cretaceous tertiary k t sedimentary rocks leading to the suggestion that the amount of thermal power delivered from the chicxulub impact was sufficient to have ignited wildfires soot cannot be used to indicate fire location however as soot from one large fire could spread globally sources other than biomass burning could also yield soot charcoal in nonmarine sedimentary rocks here quantified in situ in polished blocks provides a unique tool to record the distribution of wildfires and therefore assess the extent of any thermal radiation associated with the impact at chicxulub the k t and lowermost tertiary sedimentary rocks of six nonmarine sequences colorado to saskatchewan contain no charcoal or below background levels of charcoal and a significant quantity of noncharred organic materials revealing that there was no distinctive wildfire across the north american continent related to the k t event this finding indicates that the k t impact cannot have delivered a peak irradiance of 95 kw m 2 of thermal power to the atmosphere and 19 kw m 2 to the ground therefore the thermal power delivered from the impact to north america did not have the destructive potential previously predicted high amounts of thermal radiation were not responsible for the environmental perturbations or extinctions associated with the k t event

petrological recognition of bituminous inertinite enriched coals of the lower silesian coal basin central sudetes sw poland abstract upper carboniferous bituminous coals of the lower silesian coal basin occur in three main coal bearing regions the walbrzych region in the n the nowa ruda region in the se and the slupiec region in the sse in contrast to the walbrzych region coals representing acler formation from the nowa ruda and slupiec regions display elevated up to 39 0 mmf inertinite abundances these coals were analyzed petrographically to determine what factors may have caused such inertinite enriched coal formation and how these factors may have influenced the surrounding palaeoenvironment the results of microscopic analyses show high amounts of vitrinite relatively high content of inertinite low quantities of liptinite and low to high abundances of minerals values of random vitrinite reflectance are fairly constant average 1 07 and 1 19 in the slupiec and nowa ruda regions respectively and designate these coals as a medium volatile bituminous the reflectance of inertinite varies significantly from 1 58 to 4 90 this parameter has been used as a basis for further wildfire studies the values of inertinite reflectance and studies of its distribution and morphology imply occurrence of diversified types of wildfires ground surface and crown fires though surface fires distinctly prevailed estimated temperatures ranging from 405 c to 615 c the evidences for ground and crown fires are scarce and suggest just occasional episodes of such wildfires or may indicate transport of charred material from another source area domination of microscopic charcoal may suggest transport by wind but other transportation pathways e g by water cannot be excluded negative correlation of inertinite macerals and inorganic matter in some parts of studied profiles may reflect impact of wildfire on local erosional depositional system where increased share of mineral matter may suggest post fire clastic dominated input due to enhanced soil erosion

channel erosion along the carmel river monterey county california historic maps photographs and channel cross sections show that the channel of the carmel river underwent massive bank erosion channel migration and aggradation in a major flood in 1911 then narrowed and incised by 1939 the channel was stable until 1978 and 1980 when bank erosion affected some reaches but not others the narrowing and incision were in response to a lack of major floods after 1914 and construction in 1921 of a dam that cut off sediment supply from the most actively eroding half of the basin localized erosion in 1978 and 1980 occurred during low magnitude events along reaches whose bank strength had been reduced by devegetation these events illustrate that the stability of a fluvial system can be disrupted either by application of a large erosive force in a high magnitude event the 1911 flood or in a low magnitude event by reducing the resistance to erosion bank devegetation the carmel river is a potentially unstable system its discharge and slope characteristics place it near the threshold between meandering and braided on the lower carmel the presence of bank vegetation can make the difference between a narrow stable meandering channel and a wide shifting channel with braided reaches

observations and experiments on the origin and formation of inertinite group macerals the inertinite group macerals include fusinite semifusinite inertodetrinite macrinite micrinite and funginite and secretinite which together replace sclerotinite the macrolithotype fusain comprises fusinite and semifusinite and is now widely accepted as charcoal formed by wildfire activity however alternative origins for fusinite and semifusinite are still claimed this paper considers the use of the terms pyrofusinite degradofusinite rank fusinite and primary fusinite misleading while the definitions of the terms funginite and secretinite are also considered problematic observations made on modern wildfire derived and volcanogenic charcoal assemblages using reflectance and scanning electron microscopy together with experimental charcoalification studies demonstrate that most if not all inertinite macerals have acquired their optical and physical characteristics through the action of elevated temperatures the criteria for the identification of charcoals produced by wildfire and volcanic activity are outlined and the role of the petrographic nomenclature system is discussed

first report of cisuralian early permian charcoal layers within a coal bed from baode north china with reference to global wildfire distribution abstract fossil charcoal is reported for the first time from a cisuralian coal bed of the shanxi formation in the qiaotou section baode shanxi north china based on anatomical characteristics these charcoal fragments consist of coniferous or cordaitalean xylem unidentified primary xylem and cordaitalean and possible fern leaves these charcoal fragments represent the evidence of palaeowildfire taking place in tropical peat swamps during the cisuralian in cathaysia the palaeowildfire is most likely to be a surface fire and burning litter and shrubby vegetation fire frequency for this early permian peat swamp might have been on the order of 176 294 588 1429 years close to modern values compared with modern analogues the north china block during the cisuralian was probably wet in general but could be occasionally seasonally dry for short time intervals previous charcoal and inertinite records moreover indicate that palaeowildfires were globally common during the cisuralian overall more wildfire evidence was found in the artinskian kungurian than the asselian sakmarian except in the euramerican realm probably due to more suitable regional climate vegetation to fuel fires and taphonomic circumstances

early paleogene wildfires in peat forming environments at schoningen germany wildfire activity in early paleogene greenhouse conditions can be used as an analogue to gauge the effect of future warming trends on wildfire in the current climate system inertinite fossil charcoal in coal from 11 autochthonous early paleogene lignite seams from the schoningen mine germany was quantified using macerations in situ pillars and industry standard crushed samples a new three transect method was developed to quantify in situ charcoal the combination of in situ pillars and crushed samples accounts for temporal and spatial variation in charcoal through a stratigraphically oriented pillar whilst maintaining comparability with industry standards and previous work charcoal occurs as a range of randomly distributed particle sizes indicating that fires were burning locally in the schoningen peat forming environment and in the surrounding areas but according to petrological data not in an episodic or periodic pattern although charcoal abundance is low relative to previous high fire worlds such as the cretaceous three quantitative and semi quantitative methods show increased wildfire activity relative to the modern world in the warmest parts of the early paleogene as atmospheric oxygen levels stabilised to modern values and precipitation and humidity became the main control on wildfire increased rainfall followed by drier intervals would have created an environment rich in dry fuel in which wildfires could easily propagate if humidity was low enough in the later part of the early eocene ypresian charcoal abundance fell to levels similar to those found in modern peats this indicates that the transition to the modern low fire world occurred within the early eocene earlier than previous records suggest

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

charcoal in the silurian as evidence for the earliest wildfire rare basal pridoli plant fossils which resemble the rhyniophytoid hollandophyton colliculum and have exceptional three dimensional cellular anatomy are preserved as charcoal as such these fossils from ludford lane in the welsh borders are evidence of the earliest recorded wildfire and are the first documented from before the devonian the fossils represent the charred remains of a low growing low diversity in situ rhyniophytoid or cryptospore bearing plant vegetation charred during a low temperature fire

permian phytogeographic patterns and climate data model comparisons abstract the most recent global icehouse hothouse climate transition in earth history began during the permian warmer polar conditions relative to today then persisted through the mesozoic and into the cenozoic we focus here on two permian stages the sakmarian 285 280 ma and the wordian 267 264 ma also known as the kazanian integrating floral with lithological data to determine their climates globally these stages postdate the permo carboniferous glaciation but retain a moderately steep equator to pole gradient judging by the level of floral and faunal differentiation floral data provide a particularly useful means of interpreting terrestrial paleoclimates often revealing information about climate gradations between dry and wet end member lithological indicators such as evaporites and coals we applied multivariate statistical analyses to the permian floral data to calibrate the nature of floral and geographical transitions as an aid to climate interpretation we then classified sakma

discussion on the concepts in paleoenvironmental reconstruction from coal macerals and petrographic indices abstract organic facies analyses quantify the coal constituents and plot various associations to discriminate the paleoenvironment for coal bearing successions this allows the relation of coal composition to mire ecosystems or environments coal petrographic models are used extensively to reconstruct the nature of ancient peat forming environments many authors proposed relations between specific maceral assemblages and or micro lithotypes and peat forming environments the key controlling factors which affect peat environment include hydrogeology redox ph vegetation type clastic influx sedimentation and peat accumulation rate etc recent advancements in coal maceral study and organic petrology reveal the pros and cons of the available indices and models the main reasons for the failure of the petrographic models are oversimplification of the effects of humification on tissue preservation vs destruction the use of post diagenetic processes e g geochemical gelification in determining depositional environments changes in petrographic composition related to floral evolution geological age rank increase and compaction lack of distinction between different inertinite maceral in some models here the widely used petrographic indices and models are reviewed based on the observations of several workers and the applicability and concepts of paleo environmental reconstruction are discussed a multi disciplinary approach including petrography palynology chemistry etc has been recommended which is more logical and scientific than the exclusive use of petrographic composition for paleoenvironmental interpretation

the record of triassic charcoal and other evidence for palaeo wildfires signal for atmospheric oxygen levels taphonomic biases or lack of fuel abstract as wildfires are today important sources of disturbance in many terrestrial ecosystems it is of great interest to understand how different environmental parameters and fire activity interacted during past periods of the earth history fossil charcoal inertinites and pyrogenic polycyclic aromatic hydrocarbons pahs represent the only direct evidence for the occurrence of such palaeo wildfires in the present study a review of published data together with new data on the occurrence of fossil charcoal for the permian and the triassic is presented for a long time it has been speculated that an assumed lack of evidence for palaeo wildfires during the triassic should be explained by a large drop in atmospheric oxygen concentration following or during the end permian mass extinction event preventing the occurrence of wildfires however evidence for palaeo wildfires is relatively common in many middle and late triassic strata whereas such evidence is almost totally lacking from early triassic sediments the interpretation of this charcoal gap or depression is difficult as many factors e g atmospheric oxygen concentration taphonomical biases lack of sediments suitable for the preservation of macroscopic charcoal lack of fuel and ignorance of scientists may have influenced not only the production but also the preservation and recovery of evidence for palaeo wildfires during this period thus it is not clear whether this early triassic charcoal gap can also be seen as evidence for an assumed wildfire gap or not without any doubt further investigations on the early triassic record of charcoal and other evidence for palaeo wildfires will be necessary before this problem can be solved in fact it can be expected that the number of published records of early triassic evidence for palaeo wildfires will increase in the future as more and more scientist working on sediments of this age may become aware of the interest in fires from this time this will certainly make it possible to give a much better picture of the temporal and regional distribution of wildfires during this period in the future

hypautochthonous allochthonous coal deposition in the permian south african witbank basin no 2 seam a combined approach using sedimentology coal petrology and palaeontology abstract a suite of techniques including coal petrology micropalynology mesofossil analysis and macroscopic appearance has been used to examine the early permian south african witbank basin no 2 seam from a sample locality near ogies this coal appears to be similar in its palynological and petrographic composition to other coals of this interval from this basin however its accumulation appears to have been largely hypautochthonous or allochthonous evidenced by erosive contacts small scale cross laminations and fine lenticular bodies being recognised within the coal seam profile this ex situ deposition probably in part relates to frequent wildfire activity which may have promoted subsequent run off and erosion and led to the numerous mineral rich horizons observed in the sample seam profile in addition to the sedimentological characters described above the petrology of the seam and its mesofossils most particularly megaspores from a lycopsid parent vegetation indicate saturated peat forming conditions however examination of charred mesofossil fragments indicates periods of low humidity and even drying of the peat itself rendering it liable to combustion these contradictory characters may indicate seasonality and suggest a coldness of the climate at least for part of the year that could account for the retardation of peat decay during these drier intervals these characters can be reconciled with deposition during an interglacial phase as the dwyka glaciation terminates as has previously been proposed for the witbank basin no 2 seam

experiments in waterlogging and sedimentology of charcoal results and implications abstract fossil charcoal has a sporadic occurrence in sedimentary rocks since devonian time it is moderately common as a component of the organic material found in a wide variety of facies but there are also some notable concentrations which occur locally these occurrences have considerable palaeobotanical and palaeoecological value because the process of charring may result in excellent preservation of plant tissue if assemblages of charred material are to be used to interpret palaeoenvironments it is important to understand the behaviour of charcoal during transport from the site of the fire charcoal is an unusual sedimentary material because most fresh material floats but with prolonged immersion becomes waterlogged and sinks we carried out a series of waterlogging experiments on uncharred material and charcoal from a range of different plant types and tissues these show considerable variations in the rates of waterlogging of different charred and uncharred plant tissues and it is suggested that buoyancy contrasts are likely to result in separation during transport and deposition furthermore experiments in a flume tank have shown that the process of deposition of charcoal in sand is controlled by the rate of migration of bedforms which is in turn determined by depth flow velocity and sediment supply allochthonous assemblages of charred and uncharred plant debris will most probably be biased and not fully representative of the contemporaneous plants or vegetation the presence of charcoal concentrations may be used as an aid in interpreting palaeohydraulic conditions

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

particle motion and the theory of charcoal analysis source area transport deposition and sampling principles from particle motion physics were applied to recurring problems of the interpretation of stratigraphic charcoal data 1 fires within catchments of lakes often produce no record in fossil charcoal curves and 2 periods characterized by no local fire e g 20th century fire suppression often display as much charcoal as times when local fire was frequent quantitative theory on source area transport deposition and sampling of charcoal shows the relationship between particle sizes counted by alternative methods of charcoal analysis pollen slides for particles 5 80 m in diameter petrographic thin sections for particles 50 10 000 m diameter and charcoal diagrams the relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods charcoal recorded on pollen slides is of a size that is difficult to lift but once entrained it remains in suspension thin section charcoal is lifted at relatively low wind velocities but it is not suspended at normal surface wind speeds thermal buoyancy during fire lofts charcoal above the forest canopy depending on particle size and wind speed pollen slide charcoal sizes are underrepresented near the fire because they remain in suspension and are preferentially exported from the burn area thin section charcoal is convected to lower heights on average and is deposited nearby following fire thin section charcoal is redistributed locally by wind and thus may enter lakes because of cohesive forces and aerodynamics more pollen slide charcoal remains on the ground and less enters lakes source areas for pollen slide charcoal are subcontinental to global and diagrams of pollen slide charcoal are biased toward nonlocal charcoal they can be used to interpret importance of fire for broad spatial and temporal scales thin section charcoal represents the catchment fire regime simulation models that generate charcoal during fire mix sediments and then sample at specified intervals indicate that 1 in the absence of sediment mixing the pollen slide method should consistently resolve individual fires that occur with an expectation of 30 50 yr 2 unless samples are continuous neither method will produce useful estimates of fire frequency and 3 even a modest amount of sediment mixing will obscure the signal

petrologic and stable isotopic study of the walloon coal measures surat basin queensland peat accumulation under changing climate and base level abstract the late jurassic walloon subgroup recently dated as oxfordian is a productive subbituminous coal seam gas source in the surat basin and can be subdivided from bottom to top into the taroom coal measures the tangalooma sandstone the lower and upper juandah coal measures which have different coal character the lower taroom coals are commonly thick associated with sandstones and interpreted to form as base level is rising creating sodden anoxic conditions for peat accumulation the middle tangalooma to lower juandah contains fewer and thinner coals and transitions upwards from a sandstone to siltstone dominated sequence responding to inundation with the development of floodplain lakes the strata then coarsen upward in both grain size and coal thickness in the upper juandah coal measures which may be eroded by an overlying unit the springbok sandstone this unconformable surface is basin wide and depending on age can be tied into global changes in climate and base level existing models for peat growth under changing base level and the variability in terms of the conditions of peat formation through time as well as throughout the basin are tested environment of peat deposition and changes therein are investigated by petrographic analysis of the walloon coals coupled with high resolution lithotype logging of core and organic stable carbon isotope analysis fine microlayering and abundance of root suberinite telo and detrovitrinite indicate precursory peat formation in a mostly herbaceous marsh to fen environment in which bigger trees are either infrequent or absent except for the lower seams of the taroom coal measures and the upper seams of the lower juandah coal measures where bright bands are thicker 10 mm and more frequent no extended periods of dehydration oxidation stable carbon isotopes of coal show a distinct positive shift in the lower juandah coal measures that sets in well before the increased inertinite content in the upper juandah coal measures the enrichment in 13 c could be linked to a change in climate during the high stand depositional cycle marking the onset of late stage falling where base level begins to drop later creating exposures and water stress a shift to a less humid climate in the upper juandah coal measures could have favoured the conditions for desiccation mouldering and bush fires which is reflected in the coal s maceral composition the surat basin 13 c isotope trend follows the global trend found in marine carbonate samples from the same age interval that corroborates increasing enrichment towards the top of the coal measures approximately middle oxfordian followed by a shift to more negative compositions which corresponds to the onset of the springbok sandstone deposition on an unconformable surface

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

relationships between charcoal particles in air and sediments in west central siberia production and size of charred particles determine transport and deposition in lakes lack of such data is a principal obstacle to interpretation of past fire from charcoal profiles our two part a

fluvial geomorphology wood and river landscapes the influence of trees and dead wood on river dynamics has long been overlooked recent work suggests that large wood pieces can stabilize the land surface contributing to a large wood cycle that profoundly affects floodplain morphology and ecology

deposition in the kuznetsk basin siberia insights into the permian triassic transition and the mesozoic evolution of central asia abstract this paper describes the permian mesozoic stratigraphy of the kuznetsk basin southern siberia which is adjacent to the vast and hydrocarbon rich west siberian basin and on the edge of the siberian flood basalts the basin fill is permian to cretaceous in age and is dominated by non marine siliciclastics up to 7 km thick palaeocurrent indicators show dominant flow to the north northeast during the permian to jurassic fourteen lithofacies are grouped in three facies associations fluvial channel belt overbank and floodplain floodplain pond coal bearing permian siliciclastics are interpreted as meandering river deposits in a foreland basin with subsidence generated by thrust sheet loading from at least three basin margins these sediments pass abruptly but conformably upwards into coal barren sandstones and conglomerates and siltstones interpreted as braided river deposits two basalt flows occur within the coal barren succession a recently published precise ar ar age of 250 3 0 7 ma for the lower of these basalts

the timing and extent of the eruption of the siberian traps large igneous province implications for the end permian environmental crisis we present new high precision 40ar 39ar ages on feldspar and biotite separates to establish the age duration and extent of the larger siberian traps volcanic province samples include basalts and gabbros from noril sk the lower tunguska area on the siberian craton the taimyr peninsula the kuznetsk basin vorkuta in the polar urals and from chelyabinsk in the southern urals most of the ages except for those from chelyabinsk are indistinguishable from those found at noril sk cessation of activity at noril sk is constrained by a 40ar 39ar age of 250 3 1 1 ma for the uppermost kumginsky suite the new 40ar 39ar data confirm that the bulk of siberian volcanism occurred at 250 ma during a period of less than 2 ma extending over an area of up to 5 million km2 the resolution of the data allows us to confidently conclude that the main stage of volcanism either immediately predates or is synchronous with the end permian mass extinction further strengthening an association between volcanism and the end permian crisis a sanidine age of 249 25 0 14 ma from bed 28 tuff at the global section and stratotype at meishan china allows us to bracket the p tr boundary to 0 58 0 21 myr and enables a direct comparison between the 40ar 39ar age of the traps and the permo triassic boundary section younger ages 243 ma obtained for basalts from chelyabinsk indicate that volcanism in at least the southern part of the province continued into the triassic

investigations of fusain transition fossils from the lower carboniferous comparisons with modern partially charred wood plant fossils showing vitrinite semifusinite fusinite transitions and permineralised semifusinite transitions were collected from lower carboniferous locations within the british isles several were obtained from east kirkton quarry bathgate scotland and one fusinite semifusinite vitrinite semifusinite fusinite transition fossil was collected at muckros head county donegal ireland the muckros head fossil was found in a limestone sea cliff face where it had been weathered proud of the rock matrix thus enabling a detailed examination and interpretation of the macroscopic appearance of the specimen the distinctive sandwich like cross section of the fossil is interpreted as being caused by the burial and coalification of a partially charred plant stem with recent exposure and weathering resulting in the loss of its shattered edges under s e m and reflected light microscopy non permineralised transition fossils are seen to grade from structureless vitrinite into compressed and bogen structured semifusinite and occasionally continue through to structured uncompressed fusinite with corresponding increases in reflectance these gradations parallel the reflectances seen in modern partially charred stems stable carbon isotopic analysis of the transition fossils c13 17 19 0 to 19 26 0 22 46 0 to 24 54 0 24 47 0 24 47 0 to 26 20 0 show a significant difference between the vitrinite and semifusinite fusinite with the semifusinite fusinite isotopically heavier the various techniques employed to investigate these transition fossils all indicate that they represent coalified partially charred stems correlation of the properties and characteristics of the semifusinite fusinite in transition fossils with the properties and characteristics of isolated semifusinite and fusinite fragments collected from rocks of the lower carboniferous through to the tertiary supports the view that most of these isolated fragments also represent fossil charred wood and charcoal

phanerozoic concentrations of atmospheric oxygen reconstructed from sedimentary charcoal varying concentrations of atmospheric oxygen have affected the development of animals and the role of wildfire in ecosystems reconstructions of past oxygen concentrations from fossil charcoal constrain atmospheric oxygenation over the past 400 million years variations of the earth s atmospheric oxygen concentration po2 are thought to be closely tied to the evolution of life with strong feedbacks between uni and multicellular life and oxygen1 2 on the geologic timescale po2 is regulated by the burial of organic carbon and sulphur as well as by weathering3 reconstructions of atmospheric o2 for the past 400 million years have therefore been based on geochemical models of carbon and sulphur cycling4 5 6 however these reconstructions vary widely4 5 6 7 8 9 10 particularly for the mesozoic and early cenozoic eras here we show that the abundance of charcoal in mire settings is controlled by po2 and use this proxy to reconstruct the concentration of atmospheric oxygen for the past 400 million years we estimate that po2 was continuously above 26 during the carboniferous and permian periods and that it declined abruptly around the time of the permian triassic mass extinction during the triassic and jurassic periods po2 fluctuated cyclically with amplitudes up to 10 and a frequency of 20 30 million years atmospheric oxygen concentrations have declined steadily from the middle of the cretaceous period to present day values of about 21 we conclude however that variation in po2 was not the main driver of the loss of faunal diversity during the permo triassic and triassic jurassic mass extinction events

macrinite forms in pennsylvanian coals abstract fungi are not as evident in pennsylvanian coals as in younger mesozoic or cenozoic coals however macerals formed through the interaction of fungi with woody and herbaceous precursors do occur one example of this is in some forms of the maceral macrinite this study analyzes macrinite forms from geographically distinct pennsylvanian coals the macrinite observed in this study is characterized by the presence of inclusions of other detrital macerals indicative of ingestion and excretion similar to that documented in macrinite of younger coals this suggests that while not all ecologic niches in the pennsylvanian were filled in the same manner as in younger settings similar processes implying similar types of interactions between fungi bacteria and fauna were producing similar products

testing the integrity of fine spatial resolution palaeoecological records microcharcoal data from near duplicate peat profiles from the north york moors uk microcharcoal data which cover the millennium preceding the ulmus decline from near replicate peat profiles 30 cm apart are presented from north gill an intensively studied upland spring head site in north east england with an established detailed palaeoecological record the ulmus decline at this site has been consistently dated to ca 4700 14c years bp the microcharcoal records from these two very closely adjacent points which must have had virtually identical microcharcoal source areas are assessed for their degrees of similarity and variability at 1 cm vertical sampling intervals in an investigation which parallels a previous comparative pollen study of the two profiles the major trends and frequency peaks and troughs of the twin microcharcoal curves were found to correspond well suggesting that microcharcoal records from small peat mires within forested catchments have fine spatial integrity are reproducible and can be interpreted securely as reliable records of fire history in their small source areas much variation occurred at the level of individual spectra within coeval zones which must record the same fire history and ecology however producing differently shaped microcharcoal curves while the record of major trends will be accurate therefore too precise an interpretation of microcharcoal data at this temporal scale may not be justified micro spatial variations in frequencies of fungal spores associated with local burning are also presented and evaluated

climate and local geomorphic interactions drive patterns of riparian forest decline along a mediterranean basin river abstract dynamic fluvial processes strongly influence ecological communities and ecosystem health in riverine and riparian ecosystems particularly in drought prone regions in these systems there is a need to develop tools to measure impacts from local and regional hydrogeomorphic changes on the key biological and physical processes that sustain riparian ecosystem health and potential recovery we used dendrochronology of populus nigra a riparian tree that is vulnerable to changes in local hydrology to analyze ecosystem response following channel incision due to gravel mining along the drome river a mediterranean basin stream in southern france we cored 55 trees at seven floodplain sites measured ring widths and calculated basal area growth to compare the severity and timing of local growth decline along the river current basal area increment bai growth per tree ranged almost 10 fold among sites 7 7 1 3 to 63 9 15 2 cm 2 year 1 mean se and these differences were significant mean bai was correlated positively with the proportion of healthy trees at a site and negatively with proportion of dead canopy area regime shift analysis of the tree ring series indicates that tree growth declined significantly at four sites since 1978 coincident with documented channel incision in addition patterns of low growth and crown dieback are consistent with stress due to reduced water supply the most impaired sites were not directly adjacent to local mining pits visible on aerial photographs nor did the sequence of growth regime shifts suggest a pattern of channel incision progressing from these areas the initiation of site growth declines was most typically associated with drought years and the most impaired sites were spatially distributed to suggest the influence of local bedrock controls on soil depth climate in the drome basin and in the mediterranean region is trending significantly toward hotter growing seasons with a decrease in summer river discharge and this will increase both chronic and acute water shortage for riparian trees this study shows that drought prone riparian forests are vulnerable to hydrogeomorphological changes but the severity of impacts is conditioned by interactions between drivers at different scales including regional climate variability reach based geomorphic alteration and local lithological controls

active width of gravel bed braided rivers previous analyses have identified the active width of braided rivers the bed area over which bed load flux and short term morphological change occurs as an important element of braiding dynamics and predictions of bed load flux here we compare theoretical predictions of active width in gravel bed braided rivers with observations from sunwapta river and from a generic physical model of gravel braided rivers to provide general observations of the variation in active width and to develop an understanding of the causes of variation bed topography was surveyed daily along a 150 m reach of the pro glacial sunwapta river for a total of four weeks during summer when flow was above threshold for morphological activity in the laboratory detailed digital elevation models dems were derived from photogrammetric survey at regular intervals during a constant discharge run from the field and flume observations there is considerable local and circumstantial variation in active width but also a general trend in average active width with increasing discharge there is also a clear relationship of active width with active braiding index number of active branches in the braided channel network and with dimensionless stream power which appears to be consistent across the range of data from field and physical models thus there is a link between active width and the river morphology and dynamics and the possibility of a general relationship for estimating active width from channel pattern properties or reach scale stream power values from which approximate bedload flux calculations may be made the analysis also raises questions about differences between hydraulically based numerical model computations of instantaneous active width and observation of time integrated morphological active width understanding these differences can give insight into the nature of bedload transport in braided rivers and the relationship to morphological processes of braiding copyright 2011 john wiley sons ltd

fire history and the global charcoal database a new tool for hypothesis testing and data exploration version 1 of the global charcoal database is now available for regional fire history reconstructions data exploration hypothesis testing and evaluation of coupled climate vegetation fire model simulations the charcoal database contains over 400 radiocarbon dated records that document changes in charcoal abundance during the late quaternary the aim of this public database is to stimulate cross disciplinary research in fire sciences targeted at an increased understanding of the controls and impacts of natural and anthropogenic fire regimes on centennial to orbital timescales we describe here the data standardization techniques for comparing multiple types of sedimentary charcoal records version 1 of the global charcoal database has been used to characterize global and regional patterns in fire activity since the last glacial maximum recent studies using the charcoal database have explored the relation between climate and fire during periods of rapid climate change including evidence of fire activity during the younger dryas chronozone and during the past two millennia

the burning of gondwana permian fires on the southern continent a palaeobotanical approach abstract fossil charcoal has widely been accepted as a direct indicator for the occurrence of palaeo wildfires in upper palaeozoic sediments of euramerica and cathaysia records of these remains are relatively common and regionally and stratigraphically more or less homogeneously distributed in terrestrial sequences on the other hand just a few records have been published for the permian of gondwana and only recently has it been demonstrated that macroscopic charcoals are also common here most permian macroscopic charcoal from gondwana is gymnospermous and has been reported from coal bearing strata macroscopic charcoal occurrences are spread out in different sequences and also in distinct stratigraphic intervals in the permian e g parana basin sakmarian artinskian of brazil karoo basin artinskian of south africa damodar basin lopingian of india and dead sea area changhsingian of jordan they range from peri glacial post glacial to warm temperate climatic systems throughout the permian macro and micro charcoal occurrences are compared to inertinite incidences to support the pyrogenic origin for these coal macerals and to provide an up to date overview on the known evidences of permian wildfires on gondwana in space and time

evaluating the extent to which wildfire history can be interpreted from inertinite distribution in coal pillars an example from the late permian kuznetsk basin russia abstract inertinite charcoal distributions in two randomly sampled in situ coal pillars seams 78 and 88 from the late permian kuznetsk basin siberia were analysed using petrographic techniques to determine palaeowildfire histories fire occurrence type and return interval in situ coal pillars are judged to be essential for this type of research as they retain information on the original inertinite distribution and maceral clast size ranges which can never be obtained from the crushed coals typically used for petrographic analysis the seams represent an ombrotrophic mire seam 78 and mire with mire lake seam 88 depositional settings but both environments show the same pattern of fire history charcoal is present in all lithotype units in both pillars both pillars contain episodic charcoal horizons representing local surface fires within the peat forming environment interspersed with frequent regional background fire events as shown by small scattered inertinite this paper presents an approach to calculating fire return intervals fri in these coal pillars by removing the thickness of less compactable charcoal horizons before calculating original duration of peat formation this is achieved by using a range of peat accumulation rates and peat to coal compaction ratios resultant mean fri ranges from 7 years extremes 0 5 to 143 years for a lithotype unit containing 4 horizons to 70 years extremes 5 to 1550 years for a lithotype unit with 2 horizons the mid range values both suggest shorter fire return intervals than seen in modern peat forming environments

some semifusinite in coal may form during diagenesis not wildfires abstract semifusinite can be an important component of coals and has previously been interpreted to represent partially charred material produced in palaeowildfires low reflecting semifusinite is well known for its chemically reactive properties good burning behaviour and for its reflectance to increase with coal rank yet when inertinite in coal and sediments is used to interpret palaeowildfire history the diagenetic history of the basin is rarely considered here we sought to explore whether the low temperature heating that would occur during diagenesis over geological timescales is sufficient to produce semifusinite considering the interpretation that semifusinite represents partially charred material we reheated thermally degraded but not charred wood at 100 c and 200 c for 24 h through prolonged heating at low temperatures the previously thermally altered but non charred wood increased in reflectance to such an extent that it would be classified as semifusinite this finding suggests that not all semifusinite necessarily has a wildfire origin and calls into question its utility in interpreting palaeowildfire activity

does hydrological connectivity improve modelling of coarse sediment delivery in upland environments modelling the delivery of landslide generated sediment to channel networks is challenging due to uncertainty in the magnitude frequency distribution of failures connected to the channel network here we investigate a simplified treatment of hydrological connectivity as a means for improving identification of coarse sediment delivery to upland rivers sediment generation from hillslopes and channel banks and its delivery to the channel network are modelled based on a modified form of shalstab coupled to a network index version of topmodel the network index treatment has two important hydrological effects a it only allows saturated areas to connect to the hydrological network when there is full saturation along the associated flow path and 2 overland flow associated with unconnected but saturated zones is assumed to remain within the catchment and to contribute to a reduction in the catchment averaged saturation deficit we use this hydrological treatment to restrict sediment delivery to situations where there is surface hydrological connection i e saturation along the complete flow path that connects failure areas to the drainage network this represents an extreme restriction on the possibility of connected failure as it does not allow for failed material to connect if failures are associated with partial saturation or where delivery involves runout across areas where hydrological connection is not maintained the impact of this restriction is assessed by comparing model predictions with field mapping of connected failures and data from continuously recording coarse sediment sensors for two storm events the hydrological connection requirement restricted connected failures to zones closer to the drainage network and resulted in a better level of agreement with the field mapped failures simulations suggested that in the study catchment the majority of sediment inputs occur from hydrologically connected areas close to the channel network during moderate sized rainstorms that occur relatively frequently 2007 elsevier b v all rights reserved

coal petrology and the origin of coal macerals a way ahead the development of coal petrology and the establishment of a nomenclatural system have proved of major use both for the industrial utilization of coal and for the development of a broad understanding of coal formation and diagenesis the development over the past 30 years however of nomenclature that includes aspects of plant origin and process is a retrograde step e g pyrofusinite degradofusinite and funginite equally problematic is the use of prescriptive formulae to indicate coal origins this paper reviews some of the problems involved with coal petrology as it is usually practiced in addition new advances in organic geochemical techniques have led to a fuller understanding of the relationship of plants and coal macerals recent research on the origin of coal macerals is presented and there is a discussion of the problems and challenges facing coal petrologists a holistic approach to studies of the origin of coal and coal macerals which includes not only petrographic but also chemical and biological studies is advocated d 2002 elsevier science b v all rights reserved

channel pattern and river floodplain dynamics in forested mountain river systems channel pattern effectively stratifies the dynamics of rivers and floodplains in forested mountain river systems of the pacific northwest usa straight channels are least dynamic with relatively slow floodplain turnover and floodplains dominated by old surfaces braided channels are most dynamic with floodplain turnover as low as 25 years and predominantly young floodplain surfaces island braided and meandering channels have intermediate dynamics with moderately frequent disturbances erosion of floodplain patches maintaining a mix of old and young surfaces return intervals for the erosion of floodplains increase in the order of braided island braided meandering and straight 8 33 60 and 89 years respectively a threshold for the lateral migration of a channel occurs at a bankfull width of 15 20 m the most likely mechanism underlying this threshold is that larger channels are deep enough to erode below the rooting zone of bank vegetation above this threshold channels not confined between valley walls exhibit channel patterns distinguishable by slope and discharge and slope discharge domains can be used to predict channel patterns meandering and braided patterns are most consistently identified by the model and prediction errors are largely associated with indistinct transitions among channel patterns that are adjacent in plots of slope against discharge locations of straight channels are difficult to identify accurately with the current model the predicted spatial distribution of channel patterns reflects a downstream decline in channel slope which is likely correlated with a declining ratio of bed load to suspended load ecological theory suggests that biological diversity should be highest where the intermediate disturbance regime of island braided channels sustains high diversity of habitat and successional states through time

stable channels with mobile gravel beds regime type equations for mobile gravel bed rivers are presented based on data obtained from 62 stable gravel bed river reaches in the united kingdom multiple regression techniques are applied to derive equations relating reach average and riffle values of width mean and maximum depth slope velocity sinuosity and riffle spacing to bankfull discharge bed and bank material characteristics valley slope bank vegetation type and an independent estimate of bankfull bed load transport rates although discharge has a dominant control on channel geometry these equations indicate that bed load discharge also has a significant influence particularly with regard to channel slope bank vegetation has a major control on width and velocity while depth velocity and slope are storngly affected by bed material size reasons for these results are considered in terms of the physical processes controlling channel adjustment the application of these regime equations is discussed and particular consideration is given to the design of sinuous channels with a pool riffle bed topograph

episodic fire runoff and deposition at the palaeocene eocene boundary qualitative and quantitative coal petrological analyses have been undertaken on the laminated lignite at the base of the cobham lignite bed from scalers hill kent england the maximum negative carbon isotope excursion which marks the beginning of the palaeocene eocene thermal maximum petm occurs near the top of the laminated lignite the lignite contains inertinite a petrographic term used to describe charcoal the laminated lignite has inertinite rich and inertinite poor layers indicative of episodic fires and post fire erosion charcoal clasts are derived from living or recently senesced plants and are dominated by the leaf stalks of herbaceous ferns and wood fragments from flowering plants the charcoal assemblage reflects a low diversity flora possibly adapted to disturbance by fire derived from a source vegetation subjected to seasonal surface wildfires the environmental conditions leading up to and across the onset of the petm are therefore interpreted as incorporating a persistent fire regime with episodic wildfires followed by rainfall and runoff events abundant charcoal indicates near modern oxygen levels whereas the absence of charred peat in this area calls into question previous suggestions that burning of palaeocene peats might have contributed to the short lived negative carbon isotope excursion at the palaeocene eocene boundary

organic matter processing and soil evolution in a braided river system traditionally braided river research has considered flow sediment transport processes and recently vegetation dynamics in relation to river morphodynamics however if considering the development of woody vegetated patches over a time scale of decades we must consider the extent to which soil forming processes particularly related to soil organic matter impact the alluvial geomorphic vegetation system here we quantify the soil organic matter processing humification that occurs on young alluvial landforms we sampled different geomorphic units ranging from the active river channel to established river terraces in a wandering braided river system for each geomorphic unit soil pits were used to sample sediment soil layers that were analysed in terms of grain size 2 mm and organic matter quantity and quality rock eval method a principal components analysis was used to identify patterns in the dataset results suggest that during the succession from bare river gravels to a terrace soil there is a transition from small amounts of external organic matter supply provided by sedimentation processes e g organic matter transported in suspension and deposited on bars to large amounts of autogenic in situ organic matter production due to plant colonisation this appears to change the time scale and pathways of alluvial succession bio geomorphic succession however this process is complicated by the ongoing possibility of local sedimentation which can serve to isolate surface layers via aggradation from the exogenic supply and erosion which tends to create fresh deposits upon which organic matter processing must re start the result is a complex pattern of organic matter states as well as a general lack of any clear chronosequence within the active river corridor this state reflects the continual battle between deposition events that can isolate organic matter from the surface erosion events that can destroy accumulating organic matter and the early ecosystem processes necessary to assist the co evolution of soil and vegetation a key question emerges over the extent to which the fresh organic matter deposited in the active zone is capable of significantly transforming the local geochemical environment sufficiently to accelerate soil development

the topographic signature of vegetation development along a braided river results of a combined analysis of airborne lidar color air photographs and ground measurements 1 this paper combines archived remotely sensed data airborne lidar and digital color air photographs with nonsynchronous ground observations including observations of topographic form and vegetation cover and growth to test the hypothesis that colonization of exposed river sediments by riparian trees has an impact on channel form and to quantify any impact that is identified this is achieved along a 21 km reach of the braided gravel bed tagliamento river in northeast italy where the width of the braided corridor typically exceeds 800 m lidar data are analyzed to extract a 2 m resolution digital evolution model dem and determine riparian vegetation extent height and structure within the active corridor aerial photographs are used to map the topography of the submerged parts of the corridor these data are divided into 1 km length subreaches which possess strong contrasts in vegetation height and extent joint analysis of vegetation and morphological properties of these subreaches reveals significant associations between vegetation properties and reach morphology residuals from a gamma function fitted to the topographic data for each subreach show a good fit with poorly vegetated reaches but a weakening fit with increasing vegetation cover largely as a result of the appearance of secondary peaks in the elevation frequency distribution associated with the heavily vegetated areas furthermore the overall skewness and kurtosis of the elevation frequency distribution within each of the subreaches are both significantly correlated with vegetation extent height median elevation and growth rate indicating a clear topographic signature of vegetation development along this braided river that reflects sediment accumulation within and around the vegetated patches

fire frequency and forest structure at a dry site between ad 440 and 1110 based on charcoal and pollen records from a laminated lake sediment in eastern finland the fire history of a dry boreal forest site in eastern finland before settlement in the area was studied by means of charcoal and pollen analysis of annually laminated lake sediments the average estimated local fire interval of 70 80 years corresponds to values quoted in a few earlier finnish studies based on annually laminated lake sediments from more mesic sites the fire interval is longer than expected from dendrochronological results obtained for dry sites in fennoscandian forests suggesting human influence during the periods studied by the dendrochronological method the high representation of picea pollen preceding the period of slash and burn cultivation at this and some other dry sites suggests a mixed coniferous forest structure at dry forest sites before significant human influence the charcoal influx reflected estimated climatic shifts suggesting that the fires increased during the warmer climatic periods a small test comparing charcoal records on pollen slides with thin sections was inc

physical modelling of the combined effect of vegetation and wood on river morphology abstract the research reported in this paper employs flume experiments to investigate the potential effects of living vegetation and large wood on river morphology specifically aiming to explore how different wood input and vegetation scenarios impact channel patterns and dynamics we used a mobile bed laboratory flume divided into three parallel channels 1 7 m wide 10 m long and filled with uniform sand to reproduce braided networks subject to a series of cycles of flooding wood input and vegetation growth temporal evolution of river configuration in terms of the braiding index vegetation establishment and erosion and wood deposition amount and pattern was recorded in a series of vertical images the experiments reproduced many forms and processes that have been observed in the field from scattered logs in unvegetated dynamic braided channels to large wood jams associated with river bars and bends in vegetated stable single thread rivers results showed that the inclusion of vegetation in the experiments changes wood dynamics in terms of the quantity that is stored and the depositional patterns that develop vegetated banks increased channel stability reducing lateral erosion and the number of active channels this promoted the formation of stable wood jams where logs accumulated continuously at the same locations during subsequent floods reinforcing their effect on river morphology the feasibility of studying these processes in a controlled environment opens new possibilities for disentangling the complex linkages in the biogeomorphological evolution of the fluvial system and thus for promoting improved scientific understanding

riparian vegetation and island formation along the gravel bed fiume tagliamento italy after more than 300 years of river management scientific knowledge of european river systems has evolved with limited empirical knowledge of truly natural systems in particular little is known of the mechanisms supporting the evolution and maintenance of islands and secondary channels the dynamic gravel bed fiume tagliamento italy provides an opportunity to acquire baseline data from a river where the level of direct engineering intervention along the main stem is remarkably small against a background of a strong alpine to mediterranean climatic and hydrological gradient this paper explores relationships between topography sediment and vegetation at eight sites along the active zone of the tagliamento a conceptual model of island development is proposed which integrates the interactions between large woody debris and vegetation geomorphic features sediment calibre and hydrological regime islands may develop on bare gravel sites or be dissected from the floodplain by channel avulsion depositional and erosional processes result in different island types and developmental stages differences in the apparent trajectories of island development are identified for each of the eight study sites along the river the management implications of the model and associated observations of the role of riparian vegetation in island development are considered in particular the potential impacts of woody debris removal riparian tree management regulation of river flow and sediment regimes and changes in riparian tree species distribution are discussed

macrinite and funginite forms in cretaceous menefee formation anthracite cerrillos coalfield new mexico abstract inertinite macerals in the anthracite rank campanian menefee formation coal from the cerrillos coalfield santa fe county new mexico show a range of forms consistent with forms found in lower rank mesozoic and younger coals in particular funginite is recognized in these anthracites as is macrinite and fusinite formed following microbial degradation the macrinite in the menefee coal has forms that are consistent with fungal and or bacterial degradation of wood followed by the ingestion of the latter material by insects or other animals the regurgitation or excretion of the partially digested material and the coprophagous recycling of the latter product

particle size evidence for source areas of charcoal accumulation in late holocene sediments of eastern north american lakes abstract two methods of analyzing charcoal in sediment reveal changes in charcoal accumulation across temperate eastern north america during the last several hundred years in one method the analyst counts mostly small particles that reflect regional emissions in the other the analyst counts only larger particles derived mostly from such local sources as catchment fires we used these methods to compare charcoal accumulation at 14 lakes from the prairie forest border in minnesota to eastern maine the two methods gave concordant accumulation rates for sediments of pre 1850 age at each of 4 lakes analyzed by both methods this concordance is consistent with the interpretation that pre 1850 emissions were controlled by broad scale factors such as climatically controlled regional differences in fuels and moisture since 1900 large particles decreased greatly and small particles decreased slightly in minnesota and wisconsin by contrast in the northeast the large particle accumulation has remained at the low values measured in pre 1900 sediments at most sites while small particles increased everywhere east of central new york and pennsylvania the observed patterns suggest that 1 large particles primarily reflect local fires that were common in the midwest before fire suppression became effective 2 large particles were rare in the northeast especially before extensive land clearance 3 small particles reflect regional combustion that increased in the northeast after extensive use of fire for land clearance and wood burning for industrial purposes of the 19th century and 4 small particles remain abundant in the midwest long after effective fire suppression probably because these well dispersed small particles have a large source area that extends beyond the local wildfires that account for large particles before european settlement

a paleoclimatic and paleoatmospheric record from peatlands accumulating during the cretaceous paleogene boundary event western interior basin canada petrological and 13 c analyses were undertaken on contiguous specimens of coal and intercalated minor organic rich clastic sediments collected from coal seams spanning the cretaceous paleogene boundary in the alberta and saskatchewan portions of the western interior basin the generally high smectite content of the coal suggests that the original mires were largely small disconnected and rheotrophic readily receiving abundant waterborne detrital clastic material of largely volcanic origin nevertheless using the distinctive claystone that marks the cretaceous paleogene boundary as a regional datum it is possible to correlate cycles in the vitrinite and inertinite composition of the coals over 500 km estimates of peat accumulation rates suggest that the cycles in vitrinite and inertinite composition represent regional cyclic fluctuations in wildfire and oxidation of the peatlands and overlying canopy at a frequency of hundreds to thousands of years the likely causes of these fluctuations were cyclic regional scale changes in temperature the cretaceous paleogene boundary event occurred early during a phase of gradually increasing temperature and or decreasing rainfall but peak wildfire and desiccation of peat occurred up to 14 000 yr later than the cretaceous paleogene boundary and the mires did not experience significant water stress in the immediate aftermath of the extinction event a persistent 1 5 3 0 negative 13 c excursion occurs across the cretaceous paleogene boundary but it cannot be readily separated from four further negative excursions later in the earliest danian the negative carbon isotope excursion linked to the cretaceous paleogene boundary began a few hundred years before the event itself and recovery occurred within 21 k y and possibly in as little as just a few thousand years consistent with recently calibrated shallow marine 13 c records hence the atmospheric and surface ocean carbon pools were coupled at this time the absence of evidence for catastrophic change in the climatic regime at the time of the cretaceous paleogene extinction in these mires supports the notion that the negative shift in atmospheric 13 c was brought about by changes in the 13 c composition of the surface ocean this is consistent with the greater magnitude of extinction experienced by marine fauna relative to the terrestrial realm

a cellular model of braided rivers a broad sheet of water flowing over non cohesive sediment typically breaks up into a network of interconnected channels called a braided stream fig 1 the dynamics of such networks are complex channels migrate laterally split rejoin and develop bars with the flow shifting unpredictably from one part of the network to another many processes are known to operate in a braided river1 3 but it is unclear which of these are essential to explain the observed dynamics we describe here a simple deterministic numerical model of water flow over a cohesionless bed that captures the main spatial and temporal features of real braided rivers the patterns arise from local scour and deposition caused by a nonlinear dependence of bedload sediment flux on water discharge although the morphology of the resulting network depends in detail on the sediment transport rule used in the model our results suggest that the only factors essential for braiding are bedload sediment transport and laterally unconstrained free surface flow

when do plants modify fluvial processes plant hydraulic interactions under variable flow and sediment supply rates flow and sediment regimes shape alluvial river channels yet the influence of these abiotic drivers can be strongly mediated by biotic factors such as the size and density of riparian vegetation we present results from an experiment designed to identify when plants control fluvial processes and to investigate the sensitivity of fluvial processes to changes in plant characteristics versus changes in flow rate or sediment supply live seedlings of two species with distinct morphologies tamarisk tamarix spp and cottonwood populus fremontii were placed in different configurations in a mobile sand bed flume we measured the hydraulic and sediment flux responses of the channel at different flow rates and sediment supply conditions representing equilibrium sediment supply transport rate and deficit sediment supply transport rate we found that the hydraulic and sediment flux responses during sediment equilibrium represented a balance between abiotic and biotic factors and was sensitive to increasing flow rates and plant species and configuration species specific traits controlled the hydraulic response compared to cottonwood which has a more tree like morphology the shrubby morphology of tamarisk resulted in less pronation and greater reductions in near bed velocities reynolds stress and sediment flux rates under sediment deficit conditions on the other hand abiotic factors dampened the effect of variations in plant characteristics on the hydraulic response we identified scenarios for which the highest stem density patch independent of abiotic factors dominated the fluvial response these results provide insight into how and when plants influence fluvial processes in natural systems

the nature and influence of fire in carboniferous ecosystems fusain occurs widely in carboniferous coals and sediments it is now recognised to represent charcoal and be the product of wildfire the occurrence of fire is partly constrained by atmospheric oxygen levels availability and nature of fuel and by aspects of climate rainfall and seasonability in particular the majority of fires in the carboniferous were probably started by lightning strikes or by volcanic activity experiments on the charring of modern plants has shown that the reflectance of charcoal and hence fusain is directly related to temperature of formation different fire types may yield fusain assemblages of differing reflectance spectrums but it may be significant that many modern charcoal assemblages yield only semifusinites as seen by reflectance microscopy the significance of these findings is assessed in relation to the use of fusinites and semifusinites as depositional indicators as interpreted from coal petrology fires may have a dramatic effect on ecosystems not only causing changes in vegetational succession but also severe erosion can occur following a major fire which can be traced in depositional systems in this paper we document three major carboniferous sedimentary systems affected by fire clastic sedimentary systems using extensive fusain deposits in mid lower carboniferous near shore sediments in donegal ireland volcanic systems using late early carboniferous volcaniclastic sequences in the midland valley of scotland and coal and coal bearing sequences in the upper carboniferous westphalian b of the pennine basin england in the later settings the influence of fire in peat formation and succession is assessed in addition data on the vegetational composition of charcoal assemblages is considered it is concluded that fire plays a major role in many carboniferous ecosystems

classification of oil shales coals and other organic rich rocks abstract oil shales are a complex group of rocks which were deposited in a wide range of sedimentary environments and have a wide range of largely alginite dominated maceral assemblages a system of classifying oil shales and sapropelic coals is based on relative abundances of macerals classification of oil shales has applications to the commercial development of oil shale deposits and to the classification of petroleum source rocks

experimental characterization of vegetation uprooting by flow we investigate vegetation uprooting by flow for avena sativa seedlings with stem to sediment size ratio close to unity and vanishing obstacle induced scouring by inducing parallel riverbed erosion within an experimental flume we measure the time to uprooting in relation to root anchoring and flow drag forces we link the erosion rate to the uprooting timescales for seedlings with varying mean root length we show that the process of continuous erosion leading to uprooting resembles that of mechanical fatigue where system collapsing occurs after a given exposure time by this analogy we also highlight the nonlinear role of the residual root anchoring versus the flow drag acting on the canopy when uprooting occurs as a generalization we propose a framework to extend our results to time dependent erosion rates which typically occur for real river hydrographs finally we discuss how the characteristic timescale of plant uprooting by flow erosion suggests that vegetation survival is conditioned by multiple erosion events and their interarrival time

reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors a review of complementary approaches abstract until recently one way relationships between flow dynamics geomorphology and plant ecology were considered dominantly when studying the functioning of river systems whereby fluvial landforms and hydrogeomorphic processes drive the evolution of riparian plant communities however biological communities may significantly control geomorphic processes and have strong impacts on landform dynamics in order to fully identify the processes linked to river dynamics changes in time and space of fluvial landforms and associated plant communities conceptual multidisciplinary progress is clearly needed to understand the mutual interactions and feedbacks between fluvial landforms and vegetation community dynamics this paper presents a detailed literature review of fluvial geomorphology riparian plant ecology and hydraulic engineering knowledge the historical and recent development of ecological plant succession theory toward the integration of hydrogeomorphic disturbances is discussed as well as the integration of vegetation within geomorphology as a significant landform control factor incorporating both hydrogeomorphic controls on riparian vegetation dynamics and mechanical impacts of vegetation structures on flow properties and sediment dynamics recent progress in ecology hydraulic engineering and fluvial geomorphology emphasises interdependence between biological and physical forms and processes based on this literature review a fluvial biogeomorphic succession concept is proposed to link fluvial landform and riparian vegetation community evolution within a bi directional model the succession of fluvial landforms and associated vegetation communities is composed of four main critical phases that represent a shift in the relative dominance of hydrogeomorphic and ecological processes as a response to biostabilisation and passive bioconstruction processes the positive feedbacks associated with this shift lead to the development of characteristic biogeomorphic structures such as vegetated banks islands or floodplains which are moderated by the biogeomorphic functional roles of ecosystem engineers that induce or reinforce the positive feedbacks this fluvial biogeomorphic succession concept relates the natural darwinian selection and ecological succession theories to fluvial geomorphology

populus nigra l establishment and fluvial landform construction biogeomorphic dynamics within a channelized river populations of the riparian pioneer species populus nigra l which establish on alluvial bars within river channels modulate sediment dynamics and fluvial landforms dense cohorts of p nigra have colonized gravel point bars along the channelized river garonne france during the last 20 years and have enhanced the vertical lateral and longitudinal development of the bars for this period the geomorphic characteristics of two wooded point bars on this laterally stable river are closely linked to the spatial distribution and intensity of establishment and resistance of different cohorts of p nigra furthermore p nigra colonization dynamics were controlled by engineer effects of this same species this relationship is illustrated by a significant correlation between key geomorphic and biological variables measured in situ and characterized with a set of four aerial photographs taken between 2000 and 2010 the development of wooded point bars which are discrete biogeomorphic units over the studied period appear to result from a specific biogeomorphic positive feedback of matter aggregation and vegetation establishment related to sediment trapping and stabilization by pioneer engineer plants we propose a conceptual model of biogeomorphic unit construction for channelized lateral stable rivers we consider the resultant biogeomorphic units as functional from an ecological point of view because p nigra enhances at the cohort scale i its own inherent capacity to resist hydrogeomorphic disturbances and ii its resilience capacity as a result of successful colonization especially downstream of mature poplar stands

floodplain response to varied flows in a large coastal plain river abstract the natural flood pulse maintains river floodplain ecosystems through the exchange of freshwater resources between the main stem and floodplain habitats few prior studies have quantified the relationship between flows and floodplain response including estimating inundation area floodwater volumes and slough connectivity floodplain modeling typically uses the flow stage height relationship at river gauge stations in this study we compared a relative elevation model rem and the hydrologic engineering center river analysis system hec ras 1d model using events from 2015 and 2016 covering a range of flows from the 1st to the 99th percentile for the apalachicola river florida because digital elevation models dem from lidar light detection and ranging data lack details of riverbed topography we compared a lidar alone and lidar sonar combined dem to assess their differences estimates from the rem and hec ras models were compared to maps based on landsat imagery derived water and vegetation indices in this river we found a non linear relationship between the inundated area and flow increasing markedly through the 90th flow percentile after which increases are minimal inundated areas from both rem and hec ras models were similar for all selected flow levels except at the 74th percentile 708 m3 s flow at which the rem produced 11 higher inundated area than hec ras near the median flows major sloughs were fully connected with backswamps and low lying patches being inundated at the higher flows only a few anthropogenic features were exposed floodplain inundation estimates from landsat performed poorly detecting 9 with the modified normalized difference water index mndwi and 41 with the open water likelihood index owl these estimates were much lower than the hec ras model 96 flooded largely because the satellite is unable to penetrate dense forests and examine the floodplain surface and the landsat pixel size is twice the width of floodplain sloughs the lidar sonar combined dem produced a higher floodwater volume estimate with the hec ras model than using lidar alone the difference of 1 368 000 m3 at the 1st percentile 142 m3 s and 2 825 000 m3 at the 89th percentile 1133 m3 s demonstrate the limitation of using a lidar alone dem which cannot penetrate the water surface and the importance of surveying floodplains using sonar modeling results under predict historical wetting of the floodplain because corps dredging made the main channel approximately 13 wider from its historical width in 1941 further in the past few decades droughts and low flows have become more common because of varied upstream water uses resulting in less inundation than in the past frequent high flows are required to maintain river floodplain connectivity floodplain forests and other hydroecological functions in the apalachicola river floodplain our findings present a basis to assess the legacy of past and ongoing disturbances inform potential policy decisions for water and floodplain management and provide a baseline for further research

impacts of flow regulation on geomorphic adjustment and riparian vegetation succession along an anabranching reach of the upper yellow river abstract closure of longyangxia dam in 1986 the uppermost large dam along the trunk stream of the upper yellow river in western china permanently altered the flow regime in guide reach an anabranching section of river located 41 km downstream of the dam two smaller hydropower structures nina and laxiwa dams were constructed between longyangxia dam and guide in 2003 and 2009 respectively but they had a minor influence on the flow regime this study uses the indicators of hydrologic alteration model satellite imagery and field analyses to assess how the magnitude and duration of changes to the flow regime impacted upon geomorphic adjustments and riparian vegetation succession from 1987 to 2015 flow impoundment resulted in near instantaneous reduction in the width of the active channel zone human activities have manipulated the additional floodplain areas created by these changes aggregation of mid channel bars into larger compound features decreased channel multiplicity negligible bed incision likely reflects local supply of sediment from tributary sources downstream of the dam significant correlations are shown between changes to the balance between channel depositional and erosional processes induced by flow regulation and the functional composition of vegetation succession patterns maintenance of a higher water table for longer periods of time is inferred to have altered mutual interactions between hydrogeomorphic processes and riparian vegetation in this semi arid setting

charcoal fragments in surface samples following a fire and the implications for interpretation of subfossil charcoal data abstract following an uncontrolled fire in an area of heathland in sw england surface samples were taken from selected positions charcoal concentrations charcoal pollen ratio and size class frequencies were measured and the data from burned unburned and forest areas are compared charcoal concentrations show distinct variability between closely spaced samples but despite this differences are shown between the burned and unburned areas selected size classes are suggested as being appropriate for distinguishing between burned and unburned areas in palaeoecological studies while in need of replication these data should provide a basis for further studies of this type

dynamic single thread channels maintained by the interaction of flow and vegetation most rivers on earth today flow as a single channel in some cases with occasional islands and follow a more or less sinuous course however single thread channels have proven difficult to reproduce and study experimentally experimental self formed channels tend to widen and subdivide leading to a braided pattern cohesive sediment has been the main mechanism studied for stabilizing banks and producing a single thread channel we show how laboratory experiments using vegetation to stabilize banks can organize the flow and convert the planform morphology from braided to single thread our experimental strategy a repeated cycle of short periods of high water discharge alternating with longer periods of low discharge accompanied by plant seeding and growth leads to the evolution of a dynamic self maintaining single thread channel with well defined banks and floodplain by eliminating weak flow paths the vegetation corrals the water into a single dominant channel until the reduction in total wetted width leads to a new self organized state in which the flow removes vegetated area as fast as it is produced the new channel is deeper and has a broader distribution of depths than the braided one with channel size adjusted to carry almost all the flood flow the resulting system maintains a dynamic steady state via similar mechanisms to those that operate in meandering channels in the field specifically erosion at the outside of bends bend growth and bar development our methodology provides a basis for experimental development of self sustaining high amplitude meanders and has applications for river management and basic research purposes

sn polymetallic greisen type deposits associated with late stage rapakivi granites brazil fluid inclusion and stable isotope characteristics tin polymetallic greisen type deposits in the itu rapakivi province and rondonia tin province brazil are associated with late stage rapakivi fluorine rich peraluminous alkali feldspar granites these granites contain topaz and or muscovite or zinnwaldite and have geochemical characteristics comparable to the low p sub type topaz bearing granites stockworks and veins are common in oriente novo rondonia tin province and correas itu rapakivi province deposits but in the santa barbara deposit rondonia tin province a preserved cupola with associated bed like greisen is predominant the contrasting mineralization styles reflect different depths of formation spatial relationship to tin granites and different wall rock fluid proportions the deposits contain a similar rare metal suite that includes sn fw fta fnb and base metal suite zn cu pb is present only in correas deposit the early fluid inclusions of the correas and oriente novo deposits are 1 low to moderate salinity 0 19 wt nacl eq co2 bearing aqueous fluids homogenizing at 245 450 8c and 2 aqueous solutions with low co2 low to moderate salinity 0 14 wt nacl eq which homogenize between 100 and 340 8c in the santa barbara deposit the early inclusions are represented by 1 low salinity 5 12 wt nacl eq aqueous fluids with variable co2 contents homogenizing at 340 to 390 8c and 2 low salinity 0 3 wt nacl eq aqueous fluid inclusions which homogenize at 320 380 8c cassiterite wolframite columbite tantalite scheelite and sulfide assemblages accompany these fluids the late fluid in the oriente novo and correas deposit was a low salinity 0 6 wt nacl eq co2 free aqueous solution which homogenizes at 100 260 8c and characterizes the sulfide fluorite sericite association in the correas deposit the late fluid in the santa barbara deposit has lower salinity 0 3 wt nacl eq and characterizes the late barren quartz muscovite and kaolinite veins oxygen isotope thermometry coupled with fluid inclusion data suggest hydrothermal activity at 240 450 8c and 1 0 2 6 kbar fluid pressure at correas and oriente novo the hydrogen isotope composition of breccia greisen stockwork and vein fluids

quantifying the source area of macroscopic charcoal with a particle dispersal model abstract to aid interpreting the source area of charcoal in lake sediment records we compare charcoal deposition from an experimental fire to predictions from a particle dispersal model this provides both a theoretical framework for understanding how lake sediments reflect fire history and a foundation for simulating sediment charcoal records the dispersal model captures the two dimensional patterns in the empirical data predicted vs observed r2 0 67 p