dynamic relations for the deposition of sediment on floodplains and point bars of a freely meandering river abstract fluvial features such as floodplains and point bars are built by sediment deposition and sculpted by erosion long term measurements 38 yr of the cross section topography of active floodplains and point bars along the freely meandering powder river in southeastern montana usa mean daily discharge of 12 5 m3 s 1 were used to develop dynamic relations between annual sediment deposition and peak flood discharge five floodplain sections and five point bar sections were selected from 24 cross sections along a 90 km study reach at each cross section the sediment deposition volume per unit streamwise distance was computed as the difference between two topographic surveys made in consecutive years snowmelt floods were found to be the dominant annual process however other processes such as flash floods ice breakup floods and autumnal floods were important episodically the dynamic relations were linear for both fluvial features the snowmelt deposition discharge relations showed in general that point bars were about two times more efficient at trapping sediment than floodplains each relation had a discharge threshold that must be exceeded before sediment was deposited although these discharge thresholds for floodplains and point bars had essentially the same mean value 69 and 71 m3 s 1 respectively they represented different processes thresholds for other rivers will probably differ from those for powder river because of different channel geometry and sediment characteristics

carbon mass balance isotopic tracers of biogenic methane and the role of acetate in coal beds powder river basin usa abstract a multi isotope c h o investigation of biogenic gas 13c ch4 13c co2 d ch4 and coal bed waters d 18o 13c dic 13c acetate was conducted along a 25 km basinward sampling transect in the powder river basin prb in wyoming and montana usa to address inconsistencies among isotope fingerprinting techniques and to apply mass balance isotope modeling to biogenic coalbed methane cbm results include the first published compound specific 13c acetate values from a natural biogenic cbm system providing new constraints on acetate s role in biogenic ch4 generation coal bed water chemistry is anoxic and dominated by na and hco3 with high alkalinity concentrations 14 8 33 0 meq l the deep basin interior environment contains sulfate free na hco3 dominated waters exhibiting signs of methanogenesis ch4 and co2 generally become 13c enriched from the shallow basin edge to the deep basin interior 13c ch4 78 2 to 56 2 and 13c co2 24 7 to 4 7 also compound specific 13c acetate is more positive in the basin interior compared to the basin edge setting range 34 3 to 15 1 using a steady state mass balance isotope model the observed variations in 13c ch4 and 13c co2 can be explained in terms of the favorability of methanogenesis fch4 relative to heterotrophic bacterially mediated non methanogenic pathways such as bacterial sulfate reduction which compete with methanogenesis for substrates at the basin interior fch4 exceeds 0 4 approaching its inferred limiting value hypothesized from the oxidation state of low molecular weight compounds detected in prb formation waters therefore methanogenesis is likely a dominant biogeochemical pathway consuming substrates in the deeper coal beds the basinward shift toward 13c enriched acetate broadly indicates linkage between acetate ch4 and co2 and likely records acetate synthesis effects modified by methanogenic fractionation these results suggest that acetate plays a role in methanogenesis in prb coal beds not necessarily a dominant role while other c isotope and microbial evidence suggests that hydrogenotrophic methanogenesis is also a significant methane producing pathway the results of this study broadly suggest multiple viable methanogenic pathways and c cycling that affects acetate a more complex view of coal bed geochemistry than implied by traditional c and h isotope fingerprinting of accumulated products ch4 co2 and coexisting water

new mineral occurrences and mineralization processes wuda coal fire gas vents of inner mongolia five unique mineral assemblages that include the sulfates millosevichite alunogen anhydrite tschermigite coquimbite voltaite and godovikovite as well as the halide salammoniac and an unidentified phase according to x ray diffraction and eds data were found as encrustations on quartzofeldspathic sand and sandstone adjacent to coal fire gas vents associated with underground coal fires in the wuda coalfield of inner mongolia the mineral assemblage of alunogen coquimbite voltaite and the unidentified phase collected from the same gas vent is documented for the first time coquimbite also occurs as rosettes secondarily nucleated on a cryptocrystalline mass of alunogen coquimbite voltaite and the unidentified phase during storage in a sealed container at room temperature field observations analyses of vent gases sem images and mineral compositions suggest that the sulfates millosevichite alunogen coquimbite voltaite godovikovite and the unidentified phase crystallized in response to a complex sequence of processes that include condensation hydrothermal alteration crystallization from solution fluctuating vent temperatures boiling and dehydration reactions whereas the halide salammoniac crystallized during the sublimation of coal fire gas tschermigite and anhydrite formed by the reaction of coal fire gas with quartzofeldspathic rock or by hydrothermal alteration of this rock and crystallization from an acid rich aqueous solution variations in the mineral assemblages found at five gas vents are possibly due to differences in coal bed chemistry exchange reactions involving coal fire gas and the composition of sediment rock and aqueous solutions prior to the exhalation of gas at the surface as well as the temperature and cooling rate at a vent few studies have addressed the interaction of coal fire gas with sediment rock and aqueous solutions and the subsequent mineralization processes coal fires present opportunities for discovering rare and new mineral occurrences these minerals have potentially important environmental significance and may be vectors for the transmission of toxins coal fires also provide insight for the recognition in the geologic record of preserved mineral assemblages that are diagnostic of ancient fires

clinker deposits powder river basin wyoming and montana a new source of high fidelity paleomagnetic data for the quaternary clinker rock baked and fused by in situ burning of underlying coal posesses a thermoremanent and or thermochemical magnetization that resides in magnetite hematite and goethite data from individual sites imply that clinker may provide a high resolution recording of the geomagnetic field e g within site virtual geomagnetic pole angular standard deviations are usually less than 10 but this is dependent on its thermal history and the time over which magnetic phases formed data from 17 sites in the powder river basin 13 normal polarity 4 reverse yield a mean of decl 348 incl 62 95 5 k 42 and a corresponding pole position of 81 lat 158 long with a virtual geomagnetic pole angular standard deviation of 17 3 the mechanism of clinker formation the wide geographic distribution and the range of available fission track ages suggest that clinker may contain a nearly complete geomagnetic field record for much of the quaternary

influence of soil cover on reducing the environmental impact of spontaneous coal combustion in coal waste gobs a review and new experimental data abstract the process of spontaneous combustion of coal and coal waste gobs including emitted gases condensation of inorganic and organic species in vents and leachable potential are examined in this study which encompasses a literature review and new experimental data furthermore the potential environmental benefits of cover soil reclamation for reduction of atmospheric and water leachable pollutant emissions are also considered the datong district shanxi province is one of the most important coal production areas in china the resulting large accumulations of mining waste are susceptible to spontaneous combustion three coal gangue dumps in the datong region subjected to a range of reclamation conditions were investigated to assess the influence on coal fires coal coal gangue and condensates from gaseous emissions were characterized in terms of chemical composition particle morphology mineralogy and leaching potential the condensates include tar like deposits elemental sulfur gypsum anhydrite ammonium and hg salts and a broad array of al k fe sulfates the latter may give rise to strongly acidic leachates with high metal loads which may pose a serious threat to the environment these findings led to the development of a proposed condensation sequence model for coal gangue fires the presence and distribution of organic compounds in the condensates deposited at vents were used as geothermometers in support of the proposed condensation model additionally the present study has also explored some feasible remediation measures it was found that covering these coal waste dumps with a layer of compacted soils appears to be an excellent cost effective method to reduce spontaneous combustion scavenge pollutants from gaseous emissions and minimize risks associated with the leaching of readily soluble salts condensed on the surface

quantitative clay mineralogy as provenance indicator for recent muds in the southern north sea abstract the origin of recent mud deposits as well as the coastal turbidity maximum in the french belgian dutch nearshore area of the southern north sea is still under debate in the literature some models favor the erosion of the cretaceous chalk cliffs along the english channel and subsequent ne ward directed transport other models focus on the erosion of eocene to earliest oligocene and pleistocene to holocene clays outcropping on the seafloor off the belgian coast in order to validate these hypotheses the detailed qualitative and quantitative clay mineral composition of these sediments was used as a provenance indicator by comparing the clay mineral composition of the mud deposits and the associated suspended particulate matter spm with the composition of potential nearby and more remote sources such as the present day marine environment estuaries and rivers coastal erosion areas and the geological substratum the origin of the mud deposits and the spm could be traced results showed that only the clay composition of the scheldt estuary coincides with those of the mud deposits and the coastal turbidity maximum and that all other potential sources could be excluded our data suggest that the clay mineral composition of the mud deposits has a similar composition since at least about 100 000 years indicating that these deposits originate from a paleo scheldt river rather than from the recent river system as the present day scheldt estuary is not source of fine grained sediments the present day spm in the belgian dutch nearshore area originates mainly from the erosion and resuspension of the existing mud deposits situated in the belgian nearshore this study demonstrates the value and suitability of quantitative bulk and clay mineralogy techniques in sediment provenance studies and highlights the importance of incorporating the recent geological history in hydrodynamic studies of sedimentary basins

palaeogeography europe cut adrift the floor of the english channel provides evidence for two catastrophic floods arising from the drainage of huge glacial lakes in the area of the southern north sea these megafloods made britain what it is today britain became geographically isolated from continental europe when high interglacial seas flooded the shallow english channel and north sea shelf areas but a tenuous link remained the weald artois chalk ridge between southeast england and northwest france just how this isthmus was breached making britain an island has been a matter of conjecture a new bathymetric map of the sea floor may solve the mystery it reveals a large bedrock floored valley containing landforms including grooves and streamlined islands consistent with a megaflood event caused when a rock dam at the dover strait breached draining a large pro glacial lake in the north sea basin

instruments for particle size and settling velocity observations in sediment transport in this paper we describe two sensors for measurement of particle size distribution and settling velocity distribution these measurements are critical to the correct estimation of the true sediment concentration in the field as well as to evaluating models for transport rates of sediments a multi angle measurement of laser scattering is made and inverted to obtain the particle size distribution since small angle scattering is relatively insensitive to particle composition the size distribution measurements are robust and do not require particle refractive index it is shown that with a knowledge of the size distribution true particulate volume concentration can be obtained unaffected in calibration by changes in particle size distribution the data from bottom boundary layer experiments using the instrument show the presence of temporal variability in size distribution associated with the strength of forcing of the boundary layer the importance of these observations lies in the implication that historical data acquired with single parameter optical or other sensors needs to be revisited in the second instrument analyzing the observation of size distributions during settling in a settling column produces settling velocity estimates in this case the history of concentration of each size class is examined to determine the settling velocity without invoking any assumptions of settling regime settling velocity data from a field experiment off the new jersey coast fit the model wf na 0 45 10 23 a 1 2 n

spontaneous combustion of the upper paleocene cerrejon formation coal and generation of clinker in la guajira peninsula caribbean region of colombia abstract clinker referred here as red and brick looking burnt rocks found interbedded in the upper paleocene cerrejon formation is the result of spontaneous and natural combustion of coal seams in the recent geologic past these rocks have been mapped measured and characterized in the cerrejon coal mine at la guajira peninsula colombia these burnt rocks usually outcrop in irregular patterns as almost tabular bodies up to 100 m thick thinning and pinching out below ground surface to depths up to 448 m mapping revealed that clinker is usually found near deformed zones either faults or tight folds timing of spontaneous combustion seems to predate folding and faulting but seems to postdate the development of the cerrejon thrust fault and alluvial fan proceeding from the perija range clinker covers an area of around 2 9 10 6 m 2 with a volume of approximately 1 4 10 8 m 3 the calculation of the amount of heat released through coal burning indicates that complete combustion of 6 4 mt of 26 4 10 6 j kg coal would yield 17 10 13 j

nanominerals and ultrafine particles from coal fires from santa catarina south brazil abstract coal mining in santa catarina south brazil impacted the environment by means of a large number of coal waste piles emplaced over the old mine sites and the adjacent areas of the criciuma urussanga and sideropolis poor disposal of coal cleaning rejects represents significant environmental concerns due to their potential influence on soils and river sediments as well as on the surface and groundwater in the surroundings of these zones in this research advanced analytical techniques were performed to provide an improved understanding of the complex processes related with sulfide rich coal waste oxidation spontaneous combustion sequences of mineral formation and the transport mechanisms of hazardous elements by neoformed soluble nanominerals and ultrafine particles the results showed the presence of massive amorphous si al fe ti zr oxy hydroxides and fe hydr oxides with goethite and hematite with various degrees of crystallinity containing hazardous elements such as cr hf hg mo ni se pb th u zr and others several of the neoformed nanominerals found in the burned coal rejects are the same as those commonly associated with coal mine drainage in which oxidation of sulfides plays an important role to environment and human health this is the first brazilian coal spontaneous combustion research

the effect of different second phase particle regimes on grain growth in two phase aggregates insights from in situ rock analogue experiments the aim of the study was to investigate the effect of rigid second phases on grain growth of a matrix phase for this purpose variable mixtures of norcamphor as the matrix phase with glass beads 0 08 0 51 volume fraction as second phase were used to perform see through rock analogue experiments under static conditions at constant temperatures 50 c irrespective of the second phase content grain size evolution of all mixtures can be subdivided into a stage of continuous grain growth a transient stage and a stage of a finally stabilized grain size on the grain scale the second phases affect the migrating grain boundaries either by pinning by single particles by multiple particles or even by particle clusters summed up over the entire aggregate these pinning regimes affect the average bulk grain size of the matrix grains such that the changes in matrix grain size directly correlate with the amount of second phases their dispersion and their degree of clustering in this way the matrix grain size decreases with increasing second phase content which can be expressed as a zener relationship originating from the modification of an ordinary grain growth law a new mathematical expression is defined which allows the calculation of changes in the matrix grain size as a function of different second phase volume fractions and particle sizes such models will be helpful in the future to predict microstructural changes in polymineralic rocks at depth

formation of the zeebrugge coastal turbidity maximum the role of uncertainty in near bed exchange processes abstract despite availability of a large amount of observational data and modelling studies the mechanisms maintaining the turbidity maximum in the belgian dutch coastal zone around the port of zeebrugge belgium are insufficiently understood in order to better understand the dynamics of this turbidity maximum we examine the role of baroclinic salinity and sediment induced processes and local sediment sources on the formation and persistence of the turbidity maximum through two different numerical model approaches one model approach allows erosion of the highly compacted muddy seabed serving as a sediment source in line with observations of bed level change over several decades the other approach reduces the exchange between the bed and the water column to mimic the formation of highly concentrated near bed suspensions with concentrations of several g l observed around the port of zeebrugge both model approaches are calibrated to various sources of available data in situ sediment concentration observations satellite image bed level changes mud content and dredging data which they reproduce comparably well however reducing the water bed exchange strengthens sediment convergence in the turbidity maximum whereas the sediment source leads to sediment export with the available data it is difficult to determine which of the approaches is more realistic apparently the lack of knowledge on near bed exchange processes introduces an important source of uncertainty which cannot be adequately addressed with currently available observations this work therefore shows that more quantitative knowledge on water bed exchange processes in turbid marine environments is needed it is further hypothesized that the large scale erosion of the muddy seabed following the extension the port of zeebrugge in the early 1980 s brought such a large amount of sediment in suspension 50 100 million ton that sediment convergence was strengthened this increasing sediment convergence introduces a positive feedback mechanism that maintains sediment in the turbidity maximum or even strengthens it the high sediment concentrations observed today may therefore be a long term effect of port construction carried out decades earlier

burning of coal waste piles from douro coalfield portugal petrological geochemical and mineralogical characterization abstract in the douro coalfield anthracites were exploited for decades 1795 1994 besides many small mines douro coalfield had two principal mining areas s pedro da cova and pejao coal mining activities cause several impacts on the environment one of which is the amount of discard or waste which was disposed of all over douro coalfield resulting in one of the most significant and severe impacts on the environment over 20 waste piles exist in the old mining areas geographically dispersed and three of them are presently burning their ignition was caused by forest fires during the summer of 2005 samples from the burning and unburned zones of the waste piles were studied as were the gas from vents and the minerals resulting after combustion geochemical processes and mineralogical transformations in the burning coal waste pile were investigated microscopic analyses of the samples identified some particular aspects related with combustion oxidation of pyrite the presence of iron oxides organic particles with cracks and rims with lowered suppressed rr devolatilization vacuoles and some char structures the occurrence of vitreous glassy material as well as fe al spinels in the burning coal waste provide evidences that the combustion temperature could have reached values above 1000 c due to combustion and as expected the samples studied reported high ash yields samples taken from the burning zones reported an increase of as cr li nb ni pb rb sr and lree concentrations and a decrease in zr and hree concentrations enrichment in cs li and rb was noted when comparing with the geochemical composition of black shales and world coals composition that is related with the contribution of granitic rocks in the sediments that originated the main lithologies of the douro coalfield carbonaceous shale and lithic arenites cluster analyses r type and q type were performed to understand the trend between the unburned and burning samples and it seems that some chemical variations are responsible for this separation elemental sulphur and salammoniac ammonium salt are the coal fire gas minerals neoformed on the surface of piles near the burning zones they were identified by different techniques mainly sem edx xrd and ftir relatively high concentrations of several aromatic compounds were detected in the gas collected at the studied areas as well as aliphatic hydrocarbons the highest concentrations of aromatic hydrocarbons were measured in gas samples from s pedro da cova waste pile the exposure to hazardous compounds present in the gas is a serious risk to human health and the environment

geologic history of natural coal bed fires powder river basin usa abstract coal bed fires ignited by natural processes have baked and fused overlying sediments to form clinker a hard red or varicolored rock through much of the northern great plains of the united states usa the gently dipping coal beds in the region burn when regional downwasting brings them above the local water table the resulting clinker forms a rim along the exposed edge of the coal bed in an ongoing process through geologic time the resistant clinker is left capping buttes and ridges after the softer unbaked strata erode away clinker outcrops cover more than 4100 km2 in the powder river basin prb which lies in wyoming wy and montana mt the clinker in place records tens of billions of tons of coal that have burned releasing gases into the atmosphere the amount of clinker that has eroded away was at least an order of magnitude greater than the clinker that remains in place fission track and uranium thorium helium ages of detrital zircon crystals in clinker and paleomagnetic ages of clinker show that coal beds have burned naturally during at least the past 4 million years ma the oldest in place clinker that has been dated collected from a high isolated clinker capped ridge has a fission track age of 2 8 0 6 ma evidence of erosion and downcutting is also preserved by clinker clasts in gravel terraces one clinker boulder in a terrace 360 m above the yellowstone river has a fission track age of 4 0 0 7 ma coal bed fires are caused by lightning wildfires spontaneous combustion or human activity on coal outcrops and in mines miners government agencies and ranchers have extinguished thousands of coal bed fires but natural ignition continues where fresh coal has access to air at any given time hundreds of fires mostly small are burning in the powder river basin the total amount of coal burned by natural fires in the last 2 ma is one to two orders of magnitude greater than the total amount of coal removed by mining in the past century however current annual rates of coal mining are three to four orders of magnitude greater than estimated prehistoric annual rates of coal consumption by natural fires

clay minerals and sr nd isotopes of the sediments along the western margin of india and their implication for sediment provenance mineralogy and sr nd isotopic composition of the 2 m fraction of the holocene and late pleistocene sediments from 12 gravity cores collected along the western margin of india were used to delineate the provenance and understand the response of isotopes with respect to the source rock composition holocene sediments show distinct clay mineral associations representing three major sources illite chlorite rich sediments from the indus smectite dominated sediments from the deccan traps and kaolinite and smectite enriched sediments from gneissic rocks the mixing of indus derived sediment with the deccan traps derived sediment or the deccan traps derived sediment with gneissic rock derived sediment occurs in the deeper water cores sr isotopes are very sensitive to weathering and laterization weathering does not influence nd isotopes the 87sr 86sr ratios of the holocene sediments in shallow water cores are higher and fluctuated widely than those in deeper water cores nd correlates well with the clay mineral associations indicating source rock composition or mixing of source sediments kaolinite enriched sediments coupled with high sr ratios and low nd on the sw margin of india suggest intense chemical weathering in the hinterland the influence of the sediment from the ganges brahmaputra transported by the bay of bengal waters during the ne monsoon surface current or sw monsoon underwater current on the composition of the sediments of the sw indian margin is insignificant the late pleistocene sediments reflect a decrease of hydrolytic processes resulting in decrease of smectite and sr isotopic ratio clay minerals and nd values suggest that the provenance and transport pathways of the late pleistocene sediments are the same as those of the holocene for each region

empirical evidence of climate s role in rocky mountain landscape evolution 1 climate may be the dominant factor affecting landscape evolution during the late cenozoic but models that connect climate and landscape evolution cannot be tested without precise ages of landforms zircon u th he ages of clinker metamorphosed rock formed by burning of underlying coal seams provide constraints on the spatial and temporal patterns of quaternary erosion in the powder river basin of wyoming and montana the age distribution of 86 sites shows two temporal patterns 1 a bias toward younger ages because of erosion of older clinker and 2 periodic occurrence of coal fires likely corresponding with particular climatic regimes statistical t tests of the ages and spectral analyses of the age probability density function indicate that these episodes of frequent coal fires most likely correspond with times of high eccentricity in earth s orbit possibly driven by increased seasonality in the region causing increased erosion rates and coal exhumation correlation of ages with interglacial time periods is weaker the correlations between climate and coal fires improve when only samples greater than 50 km from the front of the bighorn range the site of the nearest alpine glaciation are compared together these results indicate that the interaction between upstream glaciation and downstream erosion is likely not the dominant control on quaternary landscape evolution in the powder river basin particularly since 0 5 ma instead incision rates are likely controlled by the response of streams to climate shifts within the basin itself possibly changes in local precipitation rates or frequency magnitude distributions with no discernable lag time between climate changes and landscape responses clinker ages are consistent with numerical models in which stream erosion is driven by fluctuations in stream power on thousand year timescales within the basins possibly as a result of changing precipitation patterns and is driven by regional rock uplift on million year timescales

historic and paleomagnetic secular variation and the earth s core dynamo process this paper attempts to summarize briefly the recent and ongoing efforts of the geomagnetism and paleomagnetism community to understand both the earth s magnetic field secular variation and its implications for the core dynamo process secular variation is defined in this paper as the general spatio temporal variation of the field secular change will refer to the first time derivative of the spatial field strict geomagnetic definition of secular variation we will emphasize here the long term 10 year or longer behavior of the historic secular variation hsv for this is the variation that is comparable with the paleomagnetic secular variation psv two important related topics the 1969 1970 geomagnetic jerk in secular acceleration and the spatial geomagnetic field components due to crustal or mantle sources are treated more fully in other reviews

fluvial evolution of the rhine during the last interglacial glacial cycle in the southern north sea basin a review and look forward this paper presents the current state of knowledge on the evolution and depositional history of the river rhine in the southern part of the north sea basin during the upper middle and late pleistocene and its response to climate change sea level oscillation and glacio isostasy the study focuses on the development of the eemian interglacial lower delta in the central netherlands and its relation to records of climate and sea level rise and uses the saalian and weichselian pre and postdating periods to place its development in context the rhine fluvial system fills the gradually subsiding north sea basin but its development has strongly been affected by the saalian glaciation and its remaining topography ice pushed ridges originating off the limit of maximum glaciation basically divided the central netherlands into two sedimentary depocentres a central depocentre within the former ice limit and a southern depocentre south of it the sedimentary record of the central depocentre including an incised valley fill shows a 20 40m thick stacked sequence consisting of three units the incised valley fill consists of a late saalian to early eemian age lower fluvial unit and a weichselian age upper fluvial unit both composed of coarse grained channel deposits sandwiched in between is a 5 15m thick record composed of fine grained fluvial and estuarine tidal floodbasin and shallow marine deposits it is of eemian interglacial and early weichselian age and comprises transgressive and highstand deposits that show the drowning of a fluvial system inland parts transformed from fluvial to deltaic and estuarine environments and the most downstream parts transformed to a shallow marine embayment preservation of these units occurred despite considerable sea level fall and climate controlled erosion taking place in the last glacial preservation potential was increased by the fact that the rhine system avulsed away to the southern depocentre halfway the weichselian pleniglacial consequently the infill of the southern depocentre is of an entire different nature and last interglacial transgressive or highstand units are hardly preserved because of glaciation and resulting depocentre configuration the netherlands in nw europe thus offers a very good opportunity to study the transgressive interglacial lower deltaic records and falling stage preservation thereof both key elements for understanding sedimentary development over full 100 ky glacial interglacial cycles of climate and base level change 2014 elsevier ltd and inqua

risk assessment of underground coal fire development at regional scale abstract underground coal combustion is a phenomenon known worldwide coal fire monitoring and risk assessment provide important input data for the delineation of coal fire zones and planning of extinguishing activities at present research on coal fire risk focuses mainly on the probability assessment of spontaneous combustion at micro scale based on laboratory investigations of coal molecular structure and composition and their impact on the combustion process coal fire risk assessment at a larger scale such as for mines relies on geological factors and aspects of mining engineering and mine management these scales however are insufficient when considering extinguishing activities in larger areas in order to fill these gaps we studied risk assessment of underground coal fire development ucfd at a regional scale the factors impacting on coal fire development were analyzed under three different aspects coal composition and structure which can influence the direction of underground coal combustion topography and geology which determine the burning environment and climatic conditions and human activities which trigger combustion processes based on this analysis a regional underground coal fire risk assessment ucf ra index system was established it is predicated on the assumption that all indices contribute equally to coal fire risk data layers of 1 km 1 km spatial resolution for each index were calculated and overlaid xinjiang uygur autonomous region was selected as a validation area in view of local conditions and the availability of relevant data the index system was modified the applied method however remained unchanged assessment results are generally satisfying and can be used for monitoring and extinguishing of underground coal fires ucfs in xinjiang

microfabric study on the deformational and thermal history of the alpi apuane marbles carrara marbles italy marbles from different geometrical and structural positions within the alpi apuane metamorphic complex show a large variability in microfabric types as indicated by microstructure c axis orientation and temperature analysis statically recrystallized samples showing a granoblastic microstructure and polygonal grain boundaries are characterized by a grain size variation from east to west from 80 100 m to 250 300 m this is correlated with an equilibration calcite dolomite temperature from 360 380 c to 420 430 c two kinds of dynamically recrystallized microstructures have been investigated a first one exhibiting coarse grains 150 200 m with lobate grain boundaries and a strong shape preferred orientation and a second one characterized by a smaller grain size 40 50 m and predominantly straight grain boundaries these microstructural types associated with localized post thermal peak shear zones and meter to kilometer scale folds are interpreted as related to high strain and high temperature crystal plastic deformation mechanisms dislocation creep associated with predominant grain boundary migration type b1 or subgrain rotation recrystallization type b2 these differences in dynamically recrystallized microstructures are related to equilibration temperatures higher in type b1 390 c than in type b2 370 340 c we have been able to relate the development of the different microfabric types to the successive stages of deformation of the alpi apuane metamorphic complex

environmental characterization of burnt coal gangue banks at yangquan shanxi province china the environmental characteristics of coal gangue dumps in yangquan shanxi province china were investigated the amounts of coal gangue are very high in this coal region given the large coal production as a result widespread spontaneous coal gangue combustion gives rise to serious environmental problems coal gangue including bulk gangue and specific lithologies such as coal kaolinite rich material sandstone carbonate minerals and sulfide mineralizations fired coal gangue and condensate products from gas vents were fully characterized with respect to mineralogy chemistry and leaching potential the mineral paragenesis of the fired coal gangue cristobalite mullite hematite trydimite cordierite showed that the combustion temperature could reach 1200 c this was also corroborated by laboratory calcination tests during this combustion some elements such as c cl f s n as cd hg pb sn ge and se are emitted into the atmosphere however condensation processes accounted for the partial trapping of gaseous emissions of as s n hg and se thus condensate mineralizations of elemental sulfur and ammonium salts enriched in se as and other trace elements are frequent in the gas vents the leaching potential of trace elements in the fresh coal gangue was relatively low but the leaching of weathered coal gangue and the gas vents condensates could give rise to environmental problems as these materials produce acidic leachates and yield relatively high leachable levels of a number of elements

changes in coastal zone processes at a high sea level stand a late holocene example from belgium this paper presents the results of an investigation of late holocene deposits on the belgian coastal plain the upper clastic deposits overlying the uppermost intercalated peat bed were studied on the basis of lithology radiocarbon dates and foraminiferal assemblages to determine why silting up phases or peat beds are lacking and to establish the evolution of the sedimentary environments as well as the age of the deposits two contrasting sites in quite different locations and showing a different stratigraphy were studied it appears that the coastal evolution was not gradual and continuous but characterised by short periods with high energy conditions alternating with long periods where low energy conditions and little sedimentation prevailed the evolution is determined mainly by tidal channel activity at about 3400 cal yr bp the peat was eroded in narrow zones by the main tidal channels and this until the landward limit of the plain the peat was only partly flooded and mudflats fringed the channels with time new tributaries formed and the channel network progressively enlarged the channels were rapidly filled followed by a period of little sedimentation which lasted at least until 1400 1200 cal yr bp the following channel activity is characterised by lateral sedimentation rather than vertical erosion together with increased sediment reworking the mechanisms of coastal change in the late holocene might be similar over the entire plain but the timing of the changes is certainly not copyright 2002 john wiley sons ltd

analysis of coal fire dynamics in the wuda syncline impacted by fire fighting activities based on in situ observations and landsat 8 remote sensing data abstract coal fires are a global catastrophe for valuable coal resources the environment human health and safety fire fighting activities are the approach to limit these catastrophic influences and to extinguish active coal fires the wuda syncline in inner mongolia is one of the biggest coalfields suffering from coal fires in china and is one of the coalfire areas globally which has been analyzed most comprehensively massive fire fighting activities have been undertaken to quench coal fires in the wuda syncline particularly activities such as blasting and excavation have accelerated since the year 2010 influence of fire fighting activities on coal fire dynamics is a significant topic but has rarely been reported yet although airborne and spaceborne earth observation data holds the potential to monitor extinguishing activities this data is rarely applied for this purpose airborne thermal scanner data is cost intensive to fly and spaceborne landsat 7 scanner system with a thermal band at 60 m spatial resolution in 2003 led to a limited exploitation of this valuable data source just recently landsat 8 satellite data with a thermal infrared band of 100 m spatial resolution is available since early 2013 and is able to fill this gap we conducted in depth in situ surveys on coal fires and fire fighting activities in the wuda syncline in may 2014 after visiting the wuda coalfield in 2012 we integrated our in situ observations and thermal anomalies extracted from both landsat 8 and landsat 7 slc on acquired before the scanner failure satellite data using an automated moving window thermal anomaly extractor regional anomaly extractor rae and analyzed coal fire dynamics impacted by fire fighting activities and the state of coal fires in the wuda syncline results show that after over 4 years of efforts to fight against coal fires in the wuda syncline the nos 1 7 no 9 no 12 and no 13 coal fire zones are extinct however the no 8 no 10 no 11 and no 14 no 18 coal fire zones are still active and furthermore three novel coal fire zones have evolved in the light of in situ surveys in the wuda coalfield these active and newly developed coal fires are mainly attributed to extinguishing related activities such as the blasting and excavation in fire affected areas which lead to the exposure of pure coal seams weathered coal pillars and coal waste piles to the outside air the contact of this coal and coal remnants with oxygen triggers spontaneous combustion of coal and further develops to coal fires additionally time series analyses of extracted thermal anomalies suggest that coal fires propagate eastward according with the dip direction of coal seams in the wuda coalfield the regional thermal anomaly extraction tool rae can delineate thermal anomalies with a high accuracy which is confirmed by our in situ surveys this paper is the first investigation on dozens of landsat satellite images to evaluate the state of coal fires within one year which is more accurate compared to previous approaches analyzing merely one or several satellite images to assess the state of coal fires during one year period

a new terrestrial plant rich fossil lagerstatte from the middle cenomanian late cretaceous of the apennine carbonate platform magliano vetere southern italy depositional and palaeoenvironmental settings abstract we describe a new terrestrial plant rich fossil lagerstatte discovered at magliano vetere campania region s italy in the middle cenomanian of the apennine carbonate platform the deposit 1 42 m thick is made up of a thin bedded interlayering of evenly laminated dolomicrites lenticular dolorudites and carbonaceous seams which contain well preserved remains of terrestrial plants yielding cuticles and minor fishes this study focuses on plant remains to provide systematical taphonomical and palaeoenvironmental considerations nevertheless a preliminary analysis carried out on fossil fishes has led to the identification of pycnodontids and teleosts the fossil lagerstatte retains sterile foliage bearing shoots with epidermal features belonging to the genus frenelopsis of the extinct conifer family of the cheirolepidiaceae plant remains possibly represent a stable biotope as floral composition displays no variation along the deposit nevertheless episodes of harsh environmental conditions occurred as demonstrated by a fish mortality event and ca sulphate evaporite precipitation taphonomical considerations and sedimentological evidence from the encasing sediments suggest a parautochthonous deposition of fossil plants in a supratidal intertidal mudflat including a salt marsh that was characterised by a restricted sea water circulation deposition of primary dolomite and episodical wildfires the presence of xeromorphic features in frenelopsis from magliano vetere could represent an adaptation to haline environment which was subjected to microtephra supply from a distant orogenic volcanism the facies evolution of the studied fossil lagerstatte records a rapid regressive and a following slower transgressive trend and constitutes the lowermost portion of a 20 m thick interval characterised by several dolomitic plattenkalk up to 1 50 m thick which are separated by cyclically stacked peritidal limestones we infer that 1 the 20 m thick plattenkalk bearing interval represents a sequence boundary zone in the stratigraphical record of the middle cenomanian apcp 2 frenelopsis thrived at the verge of an arid semiarid climatical phase during a major pulse of relative sea level fall

large strain deformation and strain partitioning in polyphase rocks dislocation creep of olivine magnesiowustite aggregates aggregates composed of olivine and magnesiowustite have been deformed to large strains at high pressure and temperature to investigate stress and strain partitioning phase segregation and possible localization of deformation in a polyphase material samples with 20 vol of natural olivine and 80 vol of mg0 7fe0 3 o were synthesized and deformed in a gas medium torsion apparatus at temperatures of 1127 c and 1250 c a confining pressure of 300 mpa and constant angular displacement rates equivalent to constant shear strain rates of 1 3 3 10 4 s 1 the samples deformed homogeneously to total shear strains of up to 15 during constant strain rate measurements the flow stress remained approximately stable at 1250 c while it progressively decreased after the initial yield stress at the lower temperature mechanical data microstructures and textures indicate that both phases were deforming in the dislocation creep regime the weaker component magnesiowustite controlled the rheological behavior of the bulk material and accommodated most of the strain deformation and dynamic recrystallization lead to grain refinement and to textures that were not previously observed in pure magnesiowustite and may have developed due to the presence of the second phase at 1127 c olivine grains behaved as semi rigid inclusions rotating in a viscous matrix at 1250 c some olivine grains remained largely undeformed while deformation and recrystallization of other grains oriented for a slip on 010 resulted in a weak foliation and a texture typical for pure dry olivine aggregates both a slip and c slip on 010 were activated in olivine even though the nominal stresses were up to 2 orders of magnitude lower than those needed to activate these slip systems in pure olivine at the same conditions

influence of groundwater flowpaths residence times and nutrients on the extent of microbial methanogenesis in coal beds powder river basin usa water and natural gas samples were collected from coalbed methane wells and a surface coal mine in the powder river basin prb and analyzed for solute chemistry isotopes and gas composition to test hypotheses about the timing and source of recharge importance of nutrient influx and extent of microbial methanogenesis in coalbeds recharge to the wyodak anderson coal zone in the central portions of the prb appears to be from the southern basin margin based on 18o h2o values and hydraulic gradients coal zones along the eastern margin near the coal outcrop represent mixing between surface water and deeper circulating groundwater coalbeds along the northwestern basin margin may contain high elevation recharge from the bighorn mountains with flow patterns likely affected by local faults detectable 14c 0 39 to 4 13 pmc in coal waters throughout the prb indicates they were recharged 50 000 bp correlation of d ch4 and d h2o values suggests that methane has accumulated since the late pleistocene nutrient concentrations c n and p species are low throughout the prb and do not correlate to groundwater flowpaths or methanogenic pathways nutrients may be sourced from in situ leaching of coals carbon isotope values of ch4 and co2 likely indicate the extent of methanogenesis i e early versus late stage rather than the dominant metabolic pathway i e acetate fermentation versus co2 reduction coal gasses from the northwestern margin of the basin are isotopically depleted and suggest early stage methanogenesis where the reactant carbon reservoir has not been significantly fractionated due to relatively rapid groundwater flow coal gasses from the central basin and southeastern margin are isotopically enriched and suggest late stage methanogenesis where the reactant carbon reservoir has been significantly depleted likely due to longer groundwater residence times

grain coarsening maps for polymineralic carbonate mylonites a calibration based on data from different helvetic nappes switzerland abstract microstructures of carbonate mylonites with 0 40 vol second phase particles from different helvetic nappes switzerland have been analyzed while the mean calcite grain size dcc increases with temperature t second phases pin calcite grain boundaries two types of second phases can be distinguished small second phases included in calcite grains and larger second phases at calcite grain boundaries both coarsening with volume fraction and t these trends are controlled by an interaction of different processes during deformation including diffusion dynamic recrystallization grain growth and pinning in terms of dcc t dependencies the microstructures of the investigated nappes are similar the relationship between dcc and t differs for high t and low t these observations can be explained by a change in the simultaneous activity of dominant mechanisms e g diffusion and dislocation creep as a function of t and second phase content in contrast the relation log dp 1 t dp second phase grain size is linear with constant slope for all nappes indicating that growth processes of second phases are identical despite differences in fluid activity and strain rate between individual nappes the microstructural relationships of dcc second phases and t remain similar therefore grain coarsening maps of second phase and recrystallization controlled calcite aggregates are a representative tool to predict deformation conditions and mechanisms for other shear zones developed under similar physical conditions

looking back at the centralia coal fire a synopsis of its present status abstract centralia is in the anthracite region of eastern pennsylvania the town is part of the western middle field a large synclinorium in columbia and schuylkill counties residents of centralia set fire to a garbage dump in 1962 and in the process ignited the buck mountain coal bed fractured and moderately dipping strata at the site permitted air to circulate into the subsurface thereby promoting combustion and making it difficult to extinguish the centralia fire as the fire advanced during the 1960s 1970s and early 1980s it did so along four fronts however the fire appears to be advancing on only two fronts today the pennsylvania department of environmental protection is currently monitoring the fire fire associated with the first or cemetery front is advancing approximately 20 m year although attempts were made to fight the fire they were unsuccessful for logistical and monetary reasons most residents of centralia relocated with the assistance of funds approved by the u s congress and disbursed by the state of pennsylvania the inexperience of community leaders in working with state bureaucracy contributed to the difficulties of fighting the fire

differences in grain growth of calcite a field based modeling approach normal grain growth of calcite was investigated by combining grain size analysis of calcite across the contact aureole of the adamello pluton and grain growth modeling based on a thermal model of the surroundings of the pluton in an unbiased model system i e location dependent variations in temperature time path 2 3 and 1 3 of grain growth occurs during pro and retrograde metamorphism at all locations respectively in contrast to this idealized situation in the field example three groups can be distinguished which are characterized by variations in their grain size versus temperature relationships group i occurs at low temperatures and the grain size remains constant because nano scale second phase particles of organic origin inhibit grain growth in the calcite aggregates under these conditions in the presence of an aqueous fluid these second phases decay at a temperature of about 350 c enabling the onset of grain growth in calcite in the following growth period fluid enhanced group ii and slower group iii growth occurs for group ii a continuous and intense grain size increase with t is typical while the grain growth decreases with t for group iii none of the observed trends correlate with experimentally based grain growth kinetics probably due to differences between nature and experiment which have not yet been investigated e g porosity second phases therefore grain growth modeling was used to iteratively improve the correlation between measured and modeled grain sizes by optimizing activation energy q pre exponential factor k0 and grain size exponent n for n 2 q of 350 kj mol k0 of 1 7 1021 mns 1 and q of 35 kj mol k0 of 2 5 10 5 mns 1 were obtained for group ii and iii respectively with respect to future work field data based grain growth modeling might be a promising tool for investigating the influences of secondary effects like porosity and second phases on grain growth in nature and to unravel differences between nature and experiment

reaction induced nucleation and growth v grain coarsening in contact metamorphic impure carbonates the understanding of the evolution of microstructures in a metamorphic rock requires insights into the nucleation and growth history of individual grains as well as the coarsening processes of the entire aggregate these two processes are compared in impure carbonates from the contact metamorphic aureole of the adamello pluton n italy as a function of increasing distance from the pluton contact the investigated samples have peak metamorphic temperatures ranging from the stability field of diopside tremolite down to diagenetic conditions all samples consist of calcite as the dominant matrix phase but additionally contain variable amounts of other minerals the so called second phases these second phases are mostly silicate minerals and can be described in a kcmashc system k2o cao mgo al2o3 sio2 h2o co2 but with variable k mg ratios the modelled and observed metamorphic evolution of these samples are combined with the quantification of the microstructures i e mean grain sizes and crystal size distributions growth of the matrix phase and second phases strongly depends on each other owing to coupled grain coarsening the matrix phase is controlled by the interparticle distances between the second phases while the second phases need the matrix grain boundary network for mass transfer processes during both grain coarsening and mineral reactions interestingly similar final mean grain sizes of primary second phase and second phases newly formed by nucleation are observed although the latter formed later but at higher temperatures moreover different kinetic processes attributed to different driving forces for growth of the newly nucleated grains in comparison with coarsening processes of the pre existing phases must have been involved chemically induced driving forces of grain growth during reactions are orders of magnitudes larger compared to surface energy allowing new reaction products subjected to fast growth rates to attain similar grain sizes as phases which underwent long term grain coarsening in contrast observed variations in grain size of the same mineral in samples with a similar t t history indicate that transport properties depend not only on the growth and coarsening kinetics of the second phases but also on the microstructure of the dominant matrix phase during coupled grain coarsening resulting microstructural phenomena such as overgrowth and therefore preservation of former stable minerals by the matrix phase may provide new constraints on the temporal variation of microstructures and provide a unique source for the interpretation of the evolution of metamorphic microstructures

composition of clays along the continental shelf off israel contribution of the nile versus local sources the eastern mediterranean sedimentary regime is dominated by sediment transport from the nile river and its delta but recent studies have also suggested a certain contribution of clay fraction from streams to the continental shelf and slope off israel in the present study we focused on clay fraction deposition along the inner 40 1000 m water depth shelf of israel in order to substantiate and quantify its different sources for this purpose detailed xrd mineralogical determinations as well as chemical compositions of the clay 2 m fraction of marine and continental sediments were used the clay mineral composition of israeli stream sediments is variable with no distinct spatial or temporal trend but within a limited assemblage this clay assemblage is made up of illite smectite is phases 70 90 kaolinite 5 25 and illite 10 and is similar to that of the nile however it is clearly distinguished by the type of the is phases which are derived mainly from mesozoic outcrops and recent sediments soils and are less expandable than those of the nile which are derived mainly from weathered basalt the nile derived component is depleted in the marine clay fraction along the israel coast evidenced by a decrease of is expandability and the fe2o3 al2o3 ratio and an increase in the k2o al2o3 mgo al2o3 and cao al2o3 ratios the depletion is well pronounced north of tel aviv where the largest coastal plain stream flows to the sea a northward increase of carbonates in the clay fraction and particularly of the bioskeletal component is indicated by the ratios of mgo and sr to cao the contribution of the local streams to the shallow shelf marine clay fraction is estimated to be about 50 a minor contribution of desert dust is identified by the relative increase in kaolinite in the marine sediments south of tel aviv

grain coarsening in contact metamorphic carbonates effects of second phase particles fluid flow and thermal perturbations under contact metamorphic conditions carbonate rocks in the direct vicinity of the adamello pluton reflect a temperature induced grain coarsening despite this large scale trend a considerable grain size scatter occurs on the outcrop scale indicating local influence of second order effects such as thermal perturbations fluid flow and second phase particles second phase particles whose sizes range from nano to the micron scale induce the most pronounced data scatter resulting in grain sizes too small by up to a factor of 10 compared with theoretical grain growth in a pure system such values are restricted to relatively impure samples consisting of up to 10 vol micron scale second phase particles or to samples containing a large number of nano scale particles the obtained data set suggests that the second phases induce a temperature controlled reduction on calcite grain growth the mean calcite grain size can therefore be expressed in the form d 1 4 c2 eq rt dp fp m where c2 is a constant q is an activation energy t the temperature and m the exponent of the ratio dp fp i e of the average size of the second phases divided by their volume fraction however more data are needed to obtain reliable values for c2 and q besides variations in the average grain size the presence of second phase particles generates crystal size distribution csd shapes characterized by lognormal distributions which differ from the gaussian type distributions of the pure samples in contrast fluid enhanced grain growth does not change the shape of the csds but due to enhanced transport properties the average grain sizes increase by a factor of 2 and the variance of the distribution increases stable d18o and d13c isotope ratios in fluid affected zones only deviate slightly from the host rock values suggesting low fluid rock ratios grain growth modelling indicates that the fluid induced grain size variations can develop within several ka as inferred from a combination of thermal and grain growth modelling dykes with widths of up to 1 m have only a restricted influence on grain size deviations smaller than a factor of 1 1 to summarize considerable grain size variations of up to one order of magnitude can locally result from second order effects such effects require special attention when comparing experimentally derived grain growth kinetics with field studies

composition and origin of clay minerals in holocene sediments from the south eastern north sea the distribution of clay minerals varies systematically in sediments from holocene core material taken along a profile from the east frisian coast to the doggerbank the proportion of illite increases with distance from the coast at the expense of kaolinite whereas slight variations are seen in smectite and chlorite abundances the chemical composition changes and the k rb ratio and k ar isotopic age of illite increase seawards this trend results from progressive mixing processes of riverine detritus with pleistocene fluvioglacial material reworked during the holocene transgression however the clay fluvial flux only became dominant during the decreasing rate of sea level rise in the late holocene especially near the shore for example modern sediments in tidal flats contain 75 of river borne holocene supplied clay detritus whereas this amount is only 10 in modern marine sediments at the doggerbank

mercury emissions from dynamic monitoring holes of underground coal fires in the wuda coalfield inner mongolia china abstract the wuda coalfield inner mongolia china is one of the largest coalfields suffering from coal fires in china and has experienced fires for 50 years with the aim of observing the active state of underground coal seam fires to protect the main roadways of the coal mine 44 drill holes were drilled in five fire areas of the suhaitu coal mine to monitor gas emissions a lumexra 915 portable mercury analyzer was used to measure mercury concentrations in the exhaust gas the drill holes exhibited high gaseous mercury concentrations with an average of 4165 ng m 3 34 62 513 ng m 3 n 1584 which was 45 times higher than that measured in the near surface atmosphere around the drill holes this finding indicates that the mercury emissions originate from underground coal fires furthermore mercury concentration has a positive correlation with co content and gas temperature implying that mercury has the potential to act as a supplementary coal fire index gases to monitor the prevailing underground coal fire in north china on the basis of traditional indicators whether it can perform satisfactorily in practical applications requires further comprehensive study

fluxes of clay minerals in the south china sea abstract in order to assess dominant settling processes that change the composition of the detrital clay fraction during transport from neighboring estuaries to a deep sea basin we studied relative clay mineral abundances and absolute clay mineral fluxes of clay sized sinking particulate matter collected by eight sediment trap systems deployed from shallow to deep water depth in the south china sea this is the first basin wide study on recent sedimentation processes in the western pacific marginal seas annual averages of relative clay mineral abundances at the shallow traps are temporally more variable and regionally more diverse resembling those of surrounding drainage basins in contrast higher fluxes of material reach the deeper traps their characteristics trend temporally and spatially towards uniformity and are enriched with smectite in the entire deep basin sinking particulate matter that reaches the shallow traps spends less time in pelagic transport and is affected by monsoonal current reversals the enrichment in smectite in the deeper traps is a result of longer duration in transport at low velocities which may increase the effect of differential settling during transport the trend is caused by lateral advection driven by the cyclonic deep circulation and this is considered as the main transport process in the northern and central deep basin the high fluxes in the south western deep basin could be the result of laterally advected re suspended sediments from the neighboring shelves the effects on the composition of the detrital clay fraction caused by oceanographic control which indirectly include those by differential settling mask the climatic signal from surrounding drainage basins in the deep basin sediments this strongly affects the interpretation of the clay mineralogical record in sediments deposited under recent conditions in the south china sea deep basin

sedimentology and stratigraphy of a tidal sand bank in the southern north sea abstract a set of 125 vibrocores collected on the basis of a dense grid of high and very high resolution seismic coverage over a tidal sand bank the middelkerke bank provides a unique opportunity to reconstruct the stratigraphy and sedimentary facies succession of such a large tidal sand body five sedimentary facies are distinguished they range from clay to pebble and display various types of bedding and lithologies corresponding to different depositional environments a succession of four late quaternary units are defined on the basis of the stratigraphic framework given by the seismic grid the first unit represents the infill of a palaeovalley system by tidally influenced sedimentary facies it is followed by extensive and thick lagoonal or sub tidal deposits the third unit reveals the development of a landward prograding storm dominated sand bar this unit is dominated by clean fine sand the last unit corresponds to the present day tidal sand bank it shows the typical offshore tidal sand bank facies cross bedded sand prograding in an offshore direction like other banks located in a more offshore position the middelkerke bank is a composite bank incorporating facies which do not occur in classic tidal sand banks

microfabrics in carbonate mylonites along a large scale shear zone helvetic alps abstract carbonate mylonites with varying proportions of second phase minerals were collected at positions of increasing metamorphic grade along the basal thrust of the morcles nappe helvetic nappes switzerland variations of temperature stress and strain rate changes in chemistry of solid and fluid phases and differing degrees of strain localization and annealing were tracked by measuring the shapes mean sizes and size distributions of both matrix and second phase grains as well as crystal preferred orientation cpo of the matrix field structures suggest that strain rate was constant along the fault the mean and distribution of the calcite grain sizes were affected most profoundly by temperature increased temperature presumably accompanied by decreased stress correlated with larger mean sizes and wider size distributions at a given location the matrix grains in mylonites with more second phase particles are on average smaller have narrower size distributions and have more elongate shapes for example mylonites with 50 vol of second phases have matrix grain sizes half that of pure mylonites changes in calcite chemistry and the presence of synkinematic fluids seemed to influence microfabric only weakly temporal variations in conditions such as exhumation induced cooling apparently provoke changes in temperature stress and strain rate along the nappe these changes result in further strain localization during retrograde conditions and cause the grain size to be reduced by an additional 50 the matrix cpo strengthens with increasing temperature or strain but weakens and rotates with increasing second phase content these fabric changes suggest differing rates of grain growth grain size reduction and development of cpo owing to variations in the deformation conditions and perhaps mechanisms to interpret natural mylonite structures or to extrapolate mechanical data to natural situations requires careful characterization of the microfabric and in particular second phase minerals

archaeo and paleosecular variation and long term asymmetries of the geomagnetic field this report summarizes progress made during the last four years in i obtaining records of the geomagnetic secular variation using paleomagnetic techniques ii analysis and modelling of the secular variation and iii the study of asymmetries in the time averaged field seen both as departures from the geocentric axial dipole model and as statistical differences between polarity states

fine sediment mineralogy as a tracer of latest quaternary sediment delivery to a dynamic continental margin pandora trough gulf of papua papua new guinea abstract sediment cores and geophysical data from the shelf and slope in the pandora trough and gulf of papua gop papua new guinea northern coral sea have been studied to evaluate timing pathways and sources of sediment delivery to a muddy shelf slope depositional system that developed during the late quaternary marine transgression cores were analyzed for 14 c geochronology clay and bulk mineralogy grain size sedimentary fabric and physical properties observations reveal a shelf edge depocenter and adjacent middle to upper slope sediment wedge that each developed at different times from different sedimentary sources despite close proximity along a down slope gradient clay mineralogy of modern shelf sediments reveals strong longitudinal gradients that appear related to fluvial source composition similar gradients in source composition reveal heterogeneous and shifting sediment sources to the shelf and slope through time from the bolling allerod interstadial 14 5 12 5 kyr bp and the younger dryas 12 5 11 5 kyr bp fluvial sediments accumulated in a muddy inner shelf forming a shelf edge depocenter core mv 41 with high kaolinite chlorite values that are indicative of a local volcanic source consistent with the geology of the nearby lakekamu and vailala river catchments shelf edge sediment accumulation decreased from the time of meltwater pulse 1b mwp 1b to the present due to shelf flooding and inshore trapping of sediment during mwp 1b and possibly earlier sediment transport west of mv 41 was steered obliquely offshore to the northern pandora trough continental margin upper middle slope mv 46 and mv 49 this transport has persisted nearly to the present and has allowed for the development of a holocene upper middle slope sediment wedge cores mv 46 and mv 49 that differs strongly in clay composition and so source from the adjacent up slope shelf edge depocenter mv 41 slope deposits have intermediate illite smectite values similar to the central gop which differ from the very low illite smectite values at mv 41 such heterogeneous dispersal patterns oblique to seabed gradient are likely due to complex interactions of shelf processes with dynamic shelf morphology along the flooding gop shelf rather than a response solely due to rising sea level and down slope transport

paleomagnetic and rock magnetic study of combustion metamorphic rocks in israel paleomagnetic and rock magnetic studies were combined with the mineralogy and metamorphic petrology of a sequence of combustion metamorphic cm rocks in israel samples from 12 sites from the three major outcrops of the hatrurim formation mottled zone were analyzed these are originally cretaceous bituminous chalks and marls which have undergone spontaneous combustion during the late neogene the analyses included natural remanent magnetization nrm intensity alternating field af and thermal demagnetization and isothermal remanent magnetization irm measurements mineralogical phases were identified by x ray diffraction and electron microprobe all metamorphosed rocks have a nrm intensity far above normal sedimentary rocks this increase in intensity is observed even in rocks where no mineralogical indications of metamorphism are observed the major contributors to the rock magnetism in these rocks are maghemite hematite and rare magnesioferrite the magnetic properties were acquired during the burning process as a consequence of oxidation of fe sulfides the in situ direction of the mean magnetic vector is dec 8 2 inc 49 2 k 40 and 95 5 2 whereas the stratigraphically corrected mean is dec 25 1 inc 46 9 k 26 and 95 6 5 the stratigraphic mean direction is in accordance with the pliocene expected field direction for this area as derived from stable africa poles therefore combustion must postdate tectonic tilt or vertical axis rotation associated with late cretaceous major folding and faulting and rifting associated with the dead sea transform normal and reverse polarity and paleosecular variation indicate that combustion at the different sites was not simultaneous

effect of mica on the grain size of dynamically recrystallized quartz in a quartz muscovite mylonite abstract quartz ribbons in a quartz muscovite mylonite from the sunchang shear zone of south korea show a variation in the average size 25 107 m of dynamically recrystallized quartz depending on the fraction and dispersion of muscovite within the ribbons micas within the quartz ribbons occur both inside quartz grains and along their boundaries having a strong preferred orientation with the basal planes parallel to the mylonitic foliation micas or mica aggregates inside the quartz show a size range of 1 25 m whereas those along the quartz grain boundaries range from 2 to 98 m the average quartz grain size d calculated from three dimensional grain size distribution decreases drastically with increasing mica volume fraction f m up to f m 3 in the ribbons and further increases in the mica fractions above 3 result in only a little decrease with some fluctuation in the quartz grain size generating the equation of d 20 11 ln f m 9 64 with almost the same fraction of mica however the quartz ribbons with dispersed mica show a smaller quartz grain size than those with clustered mica indicating the importance of dispersion as well as fraction of second phase particles to the grain size of dynamically recrystallized quartz quartz c axes tend to have a random orientation with an f m 3 presumably due to the greater contribution to the total deformation of grain boundary sliding for quartz with a smaller grain size d

on the role of grain topology in dynamic grain growth 2d microstructural modeling abstract microstructural modification processes like dynamic recrystallization and grain growth can have a major effect on the transient and semi steady state flow behaviour of deforming materials work on metals and ceramics suggests that deformation enhanced changes in grain topology and the corresponding increase in fraction of non hexagonal grains called cellular defect fraction can promote grain growth during deformation the present study tests this hypothesis by investigating the evolution of the cellular defect fraction during deformation accompanied by grain growth of aggregates with distributed grain sizes for this purpose we made use of the elle 2d microstructural modeling package we simulated and quantified microstructural evolution under conditions where both surface energy driven grain boundary migration gbm and homogeneous deformation or grain size sensitive gss straining were allowed to occur the simulations show that contemporaneous gbm and simple geometrical straining of grain aggregates with distributed grain size and coordination number lead to extra grain neighbor switching an increase in defect fraction and enhanced grain growth an increase in defect fraction was also found in a selected set of natural calcite mylonites that with increasing temperature show an increase in grain size and contribution of gss creep analysis of defect fraction thus appears to be a good microstructural tool to establish whether or not a material has experienced normal static defect fraction 0 7 or dynamic grain growth defect fraction 0 8

clay mineral evolution in the central okinawa trough since 28 ka implications for sediment provenance and paleoenvironmental change abstract the okinawa trough is a natural laboratory for the study of later quaternary land ocean interaction and paleoenvironmental changes in this study we reconstruct the evolution of clay mineral assemblages in core dgks9604 retrieved from the central okinawa trough illite dominates the clay mineral compositions with average contents above 60 clay mineral evolution since 28 ka is closely related to changes in sediment provenance and paleoenvironment sea level rise and the strength of the kuroshio current control the dispersal and deposition of clays on the east china sea shelf and in the okinawa trough and thus determine the clay mineral compositions in the core sediments during the late last glacial period 28 0 14 0 ka the paleo changjiang river mouth was situated at the shelf edge close to the central okinawa trough and thus together with the outer shelf supplied large volumes of terrigenous sediments directly into the trough from 14 0 to 8 4 ka influence from the changjiang decreased while the mid outer shelf of the east china sea became the dominant sediment source to the central okinawa trough as sea level rose and the changjiang river mouth migrated west strong sediment reworking and erosion at the shelf edge at 15 13 ka significantly increased the lateral transport of fine grained shelf sediments to the central okinawa trough since ca 8 4 ka clays from taiwan have dominated the sediment flux to the site coinciding with the re entry of the kuroshio current into the trough the increasing influence of the changjiang sourced sediments since 1 5 ka was probably related to the weakening of the kuroshio current and or a higher river flux

how human activities affect the fine sediment distribution in the dutch coastal zone seabed abstract the fine sediment distribution in the seabed is an important indicator for the ecological functioning of shallow coastal seas in this paper we investigate the processes and conditions that determine the fine sediment distribution in the dutch coastal zone surficial seabed while also assessing the response of the system to human interventions an extensive sediment dataset collected in the dutch coastal zone from 2006 to 2014 is presented these data are used to map the distribution of fines in the seabed of the dcz at unique spatiotemporal scales for the entire dutch coastal zone the distribution of fines generally agrees well with previous studies the recent extension of the port of rotterdam the maasvlakte 2 reclamation was found to locally change the distribution of fines in the sand mining pit and directly south of the reclamation fines percentages in the seabed increased by more than 10 we developed a conceptual framework to analyse the distribution of fines and how it is affected by human interventions three components are distinguished within this framework 1 sources of fines 2 transport pathways and 3 accumulation potential these components are determined both qualitatively and quantitatively based on high resolution bathymetric and hydrodynamic model data the distinction between the three components makes it possible to unravel the contributions of different human interventions to the changes in the fines distribution in the case of maasvlakte 2 the local increase of fines percentage in the seabed could thus be attributed to a temporary additional source of fines and enhanced accumulation potential the high spatiotemporal resolution of the new sediment dataset proved crucial to enable development and testing of the framework to evaluate the impact of large engineering works on the spatial distribution of fines

detrital fine grained sediment contribution from taiwan to the northern south china sea and its relation to regional ocean circulation article i nfo results of clay mineralogy in 140 samples collected in major rivers and lakes in southwestern taiwan and on the seafloor off taiwan in the northeastern south china sea scs combined with clay mineral records of the pearl river drainage basin rivers in luzon and the south china shelf and slope are used to semi quantitatively evaluate the detrital fine grained sediment contribution of taiwan to the northern scs the clay mineral assemblage of the taiwan sourced sediments consists dominantly of illite average 56 and chlorite 41 with very scarce kaolinite and smectite their respective distribution from the rivers and lakes to the seafloor off taiwan does not show obvious basin wide differences linear correlations of illite chemistry index with illite crystallinity and of illite crystallinity with kaolinite present two end members of provenances the pearl river and taiwan for the south china shelf and slope assuming that kaolinite in the northern scs is provided completely from the pearl river the contribution of taiwan in clay minerals is evaluated as 29 to the south china shelf and 23 to the south china slope respectively accordingly the contribution of the pearl river to the south china shelf and slope is 52 and 31 respectively the luzon arc accounts for the rest of clay mineral components for the northern scs mainly by providing smectite the bashi strait crossed branches of the southward deep north pacific deep water and the northward surface kuroshio current in the western pacific may transport taiwan sourced suspended sediments westwards to the northern scs

grain coarsening in polymineralic contact metamorphic carbonate rocks the role of different physical interactions during coarsening abstract the microstructural evolution of polymineralic contact metamorphic calcite marbles adamello contact aureole with variable volume fractions of second phase minerals were quantitatively analyzed in terms of changes in grain size and nearest neighbor relations as well as the volume fractions dispersion and occurrences of the second phases as a function of changing metamorphic conditions in all samples the calcite grain size is controlled by pinning of grain boundaries by second phases which can be expressed by the zener parameter z i e the ratio between size and volume fraction of the second phases with increasing peak metamorphic temperature both the sizes of matrix grains and second phases increase in dependence on the second phase volume fraction two distinct coarsening trends are revealed trend i with coupled grain coarsening limited by the growth of the second phases is either characterized by large sized or a large number of closely spaced second phase particles and results finally in a dramatic increase in the calcite grain size with z trend ii is manifest by matrix controlled grain growth which is retarded by the presence of single second phase particles that are located on calcite grain boundaries it is supported by grain boundary pinning induced by triple junctions and the calcite grain size increases moderately with z the two different grain coarsening trends manifest the transition between relatively pure polymineralic aggregates trend ii and microstructures with considerable second phase volume fractions of up to 0 5 the variations might be of general validity for any polymineralic rock which undergoes grain coarsening during metamorphism the new findings are important for a better understanding of the initiation of strain localization based on the activation of grain size dependent deformation mechanisms

clay mineral distribution in surface sediments of the northeastern south china sea and surrounding fluvial drainage basins source and transport clay mineralogy of surface samples throughout the northeastern south china sea scs and surrounding fluvial drainage basins has been investigated to reveal source and transport of detrital fine grained sediments three characteristic end members in clay mineral compositions were observed from three major provenances respectively major kaolinite and moderate illite and chlorite from the pearl river predominant illite and chlorite from taiwan and principal smectite from the luzon arc system the transport of four clay mineral species in the northeastern scs is influenced by various mechanisms smectite derived from the luzon arc system is transported mainly by surface current with significant influence of the kuroshio intrusion illite and chlorite from taiwan are mainly carried by deep water current while kaolinite from the pearl river is affected obviously by the westward guangdong coastal current and longshore current a westerly tongue shaped distribution of high contents of illite and chlorite mainly from taiwan on the eastern shelf may result from the westward guangdong coastal current during the winter the results suggest that clay mineral assemblages in the northeastern scs are mainly controlled by provenance supply and current transport and their downcore records do not bear contemporaneous paleoclimatic features the implication of clay minerals for proxies of the late quaternary east asian monsoon evolution is realized through both the provenance supply and current transport processes c 2010 elsevier b v all rights reserved

varied pathways of river borne clay minerals in a near shore marine region a case study of sediments from the elbe and weser rivers and the se north sea abstract the the results outline significant systematic changes in the proportions of clay minerals in the k rb ratios the k ar data and in the heavy metal contents at the fluvial estuarine transition and towards the marine environment these changes result from a progressive mixing of suspended fluvial material with reworked pleistocene sediments at the bottom of the north sea near shore the proportion of reworked pleistocene sediment amounts only 20 30 the mixture is distributed within a 100 km wide zone mainly by currents parallel to the coast it is also transported during flood tide into the estuaries where it is mixed further with suspended fluvial material the k rb ratios and k ar dates obtained from illite prove to be particularly useful for modeling the mixing of the clay minerals as well as their distribution patterns and origin

evolution of a polymineralic mantle shear zone and the role of second phases in the localization of deformation 1 the influence of second phases e g pyroxenes on olivine grain size was studied by quantitative microfabric analyses of samples of the hilti massif mantle shear zone semail ophiolite oman the microstructures range from porphyroclastic tectonites to ultramylonites from outside to the center of the shear zone starting at conditions of ridge related flow they formed under continuous cooling leading to progressive strain localization the dependence of the average olivine grain size on the second phase content can be split into a second phase controlled and a dynamic recrystallization controlled field in the former the olivine grain size is related to the ratio between the second phase grain size and volume fraction zener parameter in the latter dynamic recrystallization manifested by a balance between grain growth and grain size reduction processes yields a stable olivine grain size in both fields the average olivine and second phase grain size decreases with decreasing temperature combining the microstructural information with deformation mechanism maps suggests that the porphyroclastic tectonites 1100 c and mylonites 800 c formed under the predominance of dislocation creep since olivine rich layers are intercalated with layer parallel polymineralic bands in the mylonites nearly equiviscous conditions can be assumed in the ultramylonites diffusion creep represents the major deformation mechanism in the polymineralic layers it is this switch in deformation mechanism from dislocation creep to diffusion creep that forces strain to localize in the fine grained polymineralic domains at low temperatures 700 c underlining the role of the second phases on strain localization in cooling mantle rocks

orbital control climate seasonality and landscape evolution in the quaternary rocky mountains abstract while climate has long been implicated in the extensive erosion of eocene through miocene aged basin fills in the rocky mountains lack of precise high temporal density datasets of landform ages has made it difficult to detail the mechanisms by which climate increased relief a dense dataset of u th he dates from the powder river basin wyoming and montana usa indicates correspondence between elevated exhumation and peaks in orbital eccentricity here we use an atmospheric general circulation model to investigate the potential role of eccentricity in enhancing erosion in the rocky mountains we find that with high orbital eccentricity 0 05767 elevated seasonality the moving vernal equinox of perihelion mvelp 270 results in 10 100 more summer precipitation and surface runoff than low seasonality mvelp 90 under low orbital eccentricity 0 0034 precipitation and runoff changes across a precession cycle are negligible these results suggest that elevated eccentricity could indeed be associated with more intense summer precipitation and runoff which could then drive higher landscape erosion rates this finding could explain the occurrence of 100 kyr cyclicity in powder river basin landform ages and provides a clear non glacial link between climate variability and landscape evolution in the rocky mountains in this and other low to mid latitude sedimentary basins runoff volume and not glacier dynamics may be the variable that exerts primary control on landscape evolution

the effect of second phase particles on stable grain size in regionally metamorphosed polyphase calcite marbles samples of the calcite rich shelburne marble collected at the pfizer quarry in adams massachusetts show an order of magnitude variation in grain size calcite grain size ranges from 94 to 1101 m because these calcite marbles share the same pressure temperature and strain histories some other factor must be responsible for the grain size variation grain size appears to be controlled by the concentration of impurity or second phase particles large calcite grain size occurs where the volume fraction of second phase particles is low and grain size decreases as second phase volume fraction increases the relationship between calcite grain size d second phase grain size d and second phase volume fraction f can be described by the power law d d 1 4 f 0 36 a result that is consistent with models based upon short term hours or days laboratory experiments with metals and ceramics and computer simulations of grain growth grain growth appears to be greatly restricted by as little as a few per cent of second phase particles with a transition from highly restricted to almost unrestricted grain growth occurring at 5 volume of second phase particles these results indicate that second phase particles exercise an important control on grain size and can effectively inhibit grain growth in metamorphic rocks the behaviour of second phases in short term laboratory experiments may closely approximate the behaviour of second phases in grain growth lasting several orders of magnitude longer in the metamorphic environment

climate control on quaternary coal fires and landscape evolution powder river basin wyoming and montana late cenozoic stream incision and basin excavation have strongly influenced the modern rocky mountain landscape but constraints on the timing and rates of erosion are limited the geology of the powder river basin provides an unusually good opportunity to address spatial and temporal patterns of stream incision numerous coal seams in the paleocene fort union and eocene wasatch formations within the basin have burned during late cenozoic incision as coal was exposed to dry and oxygen rich near surface conditions the topography of this region is dominated by hills capped with clinker sedimentary rocks metamorphosed by burning of underlying coal beds we use u th he ages of clinker to determine times of relatively rapid erosion with the assumption that coal must be near earth s surface to burn ages of 55 in situ samples range from 0 007 to 1 1 ma clinker preferentially formed during times in which eccentricity of the earth s orbit was high times that typically but not always correlate with interglacial periods our data therefore suggest that rates of landscape evolution in this region are affected by climate fluctuations because the clinker ages correlate better with eccentricity time series than with an oxygen isotope record of global ice volume we hypothesize thatmore variations in solar insolation modulated by eccentricity have a larger impact on rates of landscape evolution in this region than do glacial interglacial cycles less