detrital carbonate peaks on the labrador shelf a 13 7 ka template for freshwater forcing from the hudson strait outlet of the laurentide ice sheet into the subpolar gyre abstract the laurentide ice sheet lis was a large dynamic ice sheet in the early holocene the glacial events through hudson strait leading to its eventual demise are recorded in the well dated labrador shelf core md99 2236 from the cartwright saddle we develop a detailed history of the timing of ice sheet discharge events from the hudson strait outlet of the lis during the holocene using high resolution detrital carbonate ice rafted detritus ird 18o and sediment color data eight detrital carbonate peaks dcps associated with ird peaks and light oxygen isotope events punctuate the md99 2236 record between 11 5 and 8 0 ka we use the stratigraphy of the dcps developed from md99 2236 to select the appropriate r to calibrate the ages of recorded glacial events in hudson bay and hudson strait such that they match the dcps in md99 2236 we associate the eight dcps with h0 gold cove advance noble inlet advance initial retreat of the hudson strait ice stream hsis from hudson strait opening of the tyrrell sea and drainage of glacial lakes agassiz and ojibway the opening of foxe channel and retreat of glacial ice from foxe basin are represented by a shoulder in the carbonate data r of 350 years applied to the radiocarbon ages constraining glacial events h0 through the opening of the tyrell sea provided the best match with the md99 2236 dcps r values and ages from the literature are used for the younger events a very close age match was achieved between the 8 2 ka cold event in the greenland ice cores dcp7 8 15 ka bp and the drainage of glacial lakes agassiz and ojibway our stratigraphic comparison between the dcps in md99 2236 and the calibrated ages of hudson strait bay deglacial events shows that the retreat of the hsis the opening of the tyrell sea and the catastrophic drainage of glacial lakes agassiz and ojibway at 8 2 ka are separate events that have been combined in previous estimates of the timing of the 8 2 ka event from marine records sw iceland shelf core md99 2256 documents freshwater entrainment into the subpolar gyre from the hudson strait outlet via the labrador north atlantic and irminger currents the timing of freshwater release from the lis hudson strait outlet in md99 2236 matches evidence for freshwater forcing and lis icebergs carrying foreign minerals to the sw iceland shelf between 11 5 and 8 2 ka the congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the lis through hudson strait into the subpolar gyre and provides specific time periods when pulses of lis freshwater were present to influence climate

factors controlling high yield coalbed methane vertical wells in the fanzhuang block southern qinshui basin abstract whether a coalbed methane cbm well achieves high yield is controlled by various factors structural and hydrological control models of cbm productivity in vertical wells were built using a combined investigation of basic tectonic settings and hydrological conditions as well as drainage parameters of the coal reservoir in the fanzhuang block southern qinshui basin this study indicates that gas water production differs significantly among wells with different structural settings or hydrogeological conditions low and unstable gas production rates in individual wells are the primary problem for the cbm development in the fanzhuang block the impacts of some geologic and engineering factors on gas production were analyzed and estimated based on comparative analysis quantitative analysis and gray system theory the results indicate that the critical reservoir ratio crr liquid column height lch and gas content are the most important factors in determining well productivity followed by the equivalent drainage radius edr the volume of frac sand and the decline rate of working fluid levels during initial production high yield wells in the fanzhuang block always have the following conditions gas content 20 m 3 t burial depth of 500 700 m crr 0 7 lch 400 m volume of frac sand 40 m 3 edr of 30 60 m and a decline rate of working fluid level lower than 2 m day during the initial production stage

variations in melt layer frequency in the gisp2 ice core implications for holocene summer temperatures in central greenland the rare melt features in the gisp2 central greenland deep ice core have decreased in frequency over the most recent 7000 years calibration of this change in melt frequency against modern spatial variation of melt frequency and temperature in central greenland and against modern temporal variability of temperatures in central greenland indicates that mean mid summer temperatures have cooled over the most recent 7000 years probably by slightly more than l c if variability of summer temperatures has not changed comparison to grip isotopic records from central greenland and to the melt record from the agassiz ice cap arctic canada suggests some seasonal and regional coherence for this cooling signal as well as for a cold event about 8000 8500 bp

geological and hydrological controls on water coproduced with coalbed methane in liulin eastern ordos basin china significant amounts of water are currently being extracted from coalbed methane cbm wells in permian carboniferous coal in the liulin area of the eastern ordos basin china waters coproduced with cbm have common chemical characteristics that can be an important exploration tool because they relate to the coal depositional environment and hydrodynamic maturation of groundwater and can be used to guide cbm development strategies the cbm production targets of the no 3 and 4 coal seams from sandstone in the shanxi formation and no 8 9 and 10 coal seams in the karst of the taiyuan formation were deposited in fluvial deltaic and epicontinental sea environments respectively this paper combines cbm geology hydrogeology cbm recovery and laboratory data to define mechanisms of cbm preservation including the important influence of groundwater relevant indices include fluid inclusions as an indicator of the hydraulic connection between the coal seam reservoir and the overlaying strata and the ensemble characteristics of total dissolved solids tds contents of water water production rates and reservoir temperatures as an indication of the current hydraulic connection the tds contents of waters from the no 3 and 4 and no 9 and 10 coal seams are double those from the subjacent karst no 8 coal seam indicating the important control of fast flow in karst low salinity fluid inclusions from the roof of the subjacent karst no 8 coal seam also indicate an enduring hydraulic connection with overlaying strata during its burial history relatively low current temperatures in the no 8 subjacent karst coal seam also infer a strong hydraulic connection and active flow regime deuterium concentrations are elevated in the mudstone bounded no 9 and 10 coal seams further confirming low rates of fluid transmission the gas contents of coal seams from the taiyuan formation are higher than those from the sandstone bounded coal seams in shanxi formation also correlating with low rates of water transmission and low permeability conceptual models for these fluvial deltaic and epicontinental sea environments that are consistent with geology gas content and gas and water production rate histories are of gas pressure sealing for the shanxi formation and hydrostatic pressure sealing for the taiyuan formation these results confirm the important controls of hydrogeological conditions on the preservation of cbm and the utility of hydrogeological indicators in prospecting for cbm

storage filters upland suspended sediment signals delivered from watersheds climate change tectonics and humans create long and short term temporal variations in the supply of suspended sediment to rivers these signals generated in upland erosional areas are filtered by alluvial storage before reaching the basin outlet we quantified this filter using a random walk model driven by sediment budget data a power law distributed probability density function pdf to determine how long sediment remains stored and a constant downstream drift velocity during transport of 157 km yr for 25 km of transport few particles are stored and the median travel time is 0 2 yr for 1000 km of transport nearly all particles are stored and the median travel time is 2 5 m y both travel time distributions are power laws the 1000 km travel time distribution was then used to filter sinusoidal input signals with periods of 10 yr and 10 4 yr the 10 yr signal is delayed by 12 5 times its input period damped by a factor of 380 and is output as a power law the 10 4 yr signal is delayed by 0 15 times its input period damped by a factor of 3 and the output signal retains its sinusoidal input form but with a power law tail delivery time scales for these two signals are controlled by storage in channel transport time is insignificant and low frequency signals are transmitted with greater fidelity than high frequency signals these signal modifications are essential to consider when evaluating watershed restoration schemes designed to control sediment loading and where source area geomorphic processes are inferred from the geologic record

modeling framework for sediment deposition storage and evacuation in the floodplain of a meandering river theory 1 a theory for the movement of suspendible sediment through the floodplain of a simple actively migrating river is developed the floodplain is represented as a series of sediment storage reservoirs each incorporating multiple bends of a river independent models for floodplain sediment deposition and for subsequent removal of sediment by lateral channel migration allow the volume of sediment stored in the floodplain and the associated average floodplain elevation to change over time and down the valley at a given quasi steady discharge deposition depends on a simple one dimensional partition between channel and floodplain discharge and on suspended sediment concentration one size class which varies along the reach depending on lateral supply and floodplain history sediment supply is specified at the upstream end of the reach using a suspended sediment rating curve long term average overbank deposition rates are approximated by weighting multiple steady state solutions using a flow duration curve the channel bed elevation of the system is assumed to be fixed and tributaries are handled using simple lateral source terms the interaction between the submodels is such that under constant boundary conditions the channel evolves toward a state of geomorphic equilibrium where the volume of sediment added to the floodplain by overbank deposition just balances the volume removed by channel migration the model is easily adapted to track conservative suspended sediment tracer material concentration as such material moves through the channel floodplain system

lake agassiz outburst age and routing by labrador current and the 8 2 cal ka cold event abstract catastrophic drainage of glacial lake agassiz impounded by the laurentide ice sheet lis into hudson bay and strait is widely thought to have caused the 8 2 cal ka cold event though the path of its drainage in the north atlantic is poorly known analysis and compilation of 10 sediment cores from 8 sites distributed on the eastern canadian continental shelf and upper slope south of hudson strait revealed distinct beds with elevated detrital carbonate dc concentrations known by their distinct composition to originate from erosion of carbonate bedrock and carbonate rich glacial sediments in the hudson bay hudson strait region at all but one site radiocarbon ages bracketing and within the thickest and most widespread of these beds are coeval with the age constraints for the agassiz floods in hudson strait and southeastern hudson bay the dc distribution and concentration of this bed are consistent with southward transport in the labrador current transfer function analysis of dinoflagellate assemblage data from cores on the central labrador shelf in hudson bay and on the northeast newfoundland shelf reveal that early holocene seasonal ice cover was 5 6 months longer than at present requiring the application of a 200 year reduction to the radiocarbon age constraints on the lake agassiz outburst floods the age of the floods is reduced to about 8 33 cal ka 7 5 14 c ka from the previous determination of 8 47 cal ka 7 7 14 c ka with a similar reduction in their error ranges to 8 04 8 49 cal ka from 8 16 8 74 cal ka based on present current routing the agassiz floodwaters and icebergs are inferred to have travelled south in the labrador current and to have possibly become incorporated into the north atlantic current and transported to the nordic seas there the freshwater additions would have lessened deepwater production with a concomitant reduction in northward heat transport in the upper limb of the atlantic meridional overturning circulation thereby contributing to the 8 2 cal ka cold event variation in the calcite and dolomite content of the agassiz dc bed two salinity reductions during agassiz bed deposition and low level shorelines of lakes agassiz and ojibway suggest that more than one outburst was delivered during the final agassiz drainage the 8 2 cal ka cold event registered in greenland was coeval with a second or later flood which possibly accompanied the final collapse of the lis in hudson bay

the holocene labrador current changing linkages to atmospheric and oceanographic forcing factors the role of labrador current lc in providing freshwater to the north atlantic and hence modulating the atlantic meridional overturning circulation amoc has been debated with very few data this study provides the first data on the relative speed of the lc for the past 9 2 ka using mean size of the sortable silt of sediments as a proxy from a mid shelf basin in the western labrador sea lc speed progressively intensified from 9 2 5 ka during which two meltwater events had minor influence the lc was fastest between 5 ka and 3 1 ka and gradually weakened after 3 1 ka the mean size of the sortable silt data shows overall co variations with similar existing data from deep water areas of the greater north atlantic suggesting an overarching link that modulates changes in both the near surface and deep north atlantic a dynamical link between the lc and amoc vigor is hypothesized in which high meltwater discharge in the labrador sea oriented the subpolar gyre spg more north south meridional weakening the spg and thus decelerating the upper limb of the amoc conversely reduction in lc transport during the late holocene due to the greater export of sea ice oriented the spg more east west

modeling long term contamination in river systems from historical metal mining heavy metal contamination of sediments within river systems is a major environmental problem around the world deposited as a by product of metal mining contaminated sediments are persistent and widespread frequently affecting large areas of floodplains which makes precise assessments of contamination levels and patterns difficult this paper describes findings from a new generic catchment sediment model called tracer which uses historical mining records to accurately predict present day and future levels and patterns of contamination this model provides detailed views of the extent of contami nation and demonstrates how contaminated sediments form into hot spots which in turn become secondary sources of pollution the exceptional longevity of the contamina tion is also revealed 70 of the deposited contaminants remain within the river system for 200 yr after mine closure simulations of the impact of future climate changes in northern england show that increased flood magnitudes are likely to decrease surface contamination through dilution by cleaner sediment from hillslopes unaffected by mining activity

steady state reach scale theory for radioactive tracer concentration in a simple channel floodplain system 1 a steady state analytical model is presented for reach scale variation in the concentration of a decaying radioactive tracer associated with sediment particles that regularly pass through an off channel floodplain the floodplain is represented as a series of well mixed sediment reservoirs that continually exchange sediment with the channel the model allows for tributary input and valley wide aggradation or degradation tracer concentration depends on the upstream boundary concentration the tracer and sediment load floodplain geometry and the rates of in floodplain tracer production and or decay the theory predicts relatively modest down channel change in the concentration of long lived isotopes but implies that significant change may occur for 1 tracers with a short enough half life such as 14c or 2 floodplains with sediment residence times that are large enough for cosmogenic production or meteoric fallout to increase tracer concentration in the down valley direction the profiles are shown to be strongly dependent on the grain size distributions of both the sediment load and the floodplain the results imply that down channel 14c profiles have the potential to constrain holocene bed material loads in systems with sufficient storage the theory concisely describes the general importance of a floodplain for modifying in situ produced cosmogenic tracer concentration and can also characterize floodplain importance for fallout radioisotopes i e 10be 210pb or 7be or organic 14c

modeling framework for sediment deposition storage and evacuation in the floodplain of a meandering river application to the clark fork river montana 1 a theory for the evolution of a river floodplain and the associated movement of tracer sediment is applied to the case of the upper clark fork river montana whose floodplain is contaminated with tailings derived from historical mining activities deposition of mine tailings raised the elevation of the floodplain which now contributes contaminated sediment to the channel the theory is capable of reproducing the basic aspects of the system s evolution including aggradation of the floodplain during the mining era and subsequent net supply of sediment from floodplain to channel after the cessation of mine input results indicate that the natural removal of tailings from the floodplain could take thousands of years a period longer than is required for the channel to simply rework the tailings the self stabilizing nature of the model results in an evolution toward a new postmine steady state with tailings eventually almost entirely removed from the system

sediment reservoirs at mountain stream confluences dynamics and effects of tributaries dominated by debris flow and fluvial processes radiocarbon age estimates n 68 from bank terrace riser and in channel materials sampled from random locations near two channel confluences a debris flow dominated tributary to cedar creek and a fluvially dominated tributary to golden ridge creek in the oregon coast range are proxies for sediment transit times through tributary and mainstem sediment reservoirs separated from one another by incised bedrock risers geomorphic volumetric stratigraphic and sedimentologic data aided reservoir characterizations inferred transit time distributions for tributary deposits are right skewed and heavy tailed indicating preferential evacuation of younger deposits the debris flow fan is much larger than fluvial terraces on the other tributary but mean transit times in both reservoirs are similar 1370 2240 yr and 1660 2130 yr for fan and terrace deposits respectively whereas tributary deposits are much larger than mainstem deposits at both sites mainstem deposits adjacent to the fan have a relatively short mean transit time of 442 491 yr but mean transit time in mainstem deposits adjacent to the fluvial terrace is much greater 3870 6720 yr reservoir flux estimates indicate that most 60 of the debris flow fan tributary9s sediment yield enters fan storage but only a small part 3 of the fluvial tributary9s yield enters storage at the confluence debris flows from the debris flow fan tributary apparently promote both greater storage of mainstem sediments and more rapid unbiased evacuation of mainstem deposits whereas old mainstem deposits adjacent to the fluvial tributary have a much greater probability of preservation

a decadal scale holocene sea surface temperature record from the subpolar north atlantic constructed using diatoms and statistics and its relation to other climate parameters 1 a sediment core from reykjanes ridge has been studied at 10 to 50 year time resolution to document variability of holocene surface water conditions in the western north atlantic and to evaluate effects of holocene ice rafting episodes diatom assemblages are converted to quantitative sea surface temperatures sst using three different transfer functions spectral and scale space methods are also applied on the records to explore variability at different timescales diatom assemblage and sst records clearly show that decaying remnants of the laurentide ice sheet strongly influenced early holocene climate in the western north atlantic this overrode the predominance of milankovitch forcing which played a key role in the development of holocene climate in the eastern north atlantic and nordic seas superimposed on general holocene climate change is high frequency sst variability on the order of 1 3 c the record also documents climatic oscillations with 600 to 1000 1500 and 2500 year periodicities with a time dependent dominance of different periodicities through the holocene a clear change in variability occurred about 5 ka bp the sst record also provides evidence for holocene cooling events hce that in some cases correlate to documented southward intrusions of ice into the north atlantic

floodplain storage of mine tailings in the belle fourche river system a sediment budget approach arsenic contaminated mine tailings that were discharged into whitewood creek at lead south dakota from 1876 to 1978 were deposited along the floodplains of whitewood creek and the belle fourche river the resulting arsenic contaminated floodplain deposit consists mostly of overbank sediments and filled abandoned meanders along white wood creek and overbank and point bar sediments along the belle fourche river arsenic concentrations of the contaminated sediments indicate the degree of dilution of mine tailings by uncontaminated alluvium about 13 per cent of the 110 106 mg of mine tailings that were discharged at lead were deposited along the whitewood creek floodplain deposition of mine tailings near the mouth of whitewood creek was augmented by an engineered structure about 29 per cent of the mine tailings delivered by whitewood creek were deposited along the belle fourche river floodplain about 60 per cent of that sediment is contained in overbank deposits deposition along a segment of the belle fourche river was augmented by rapid channel migration the proportions of contaminated sediment stored along whitewood creek and the belle fourche river are consistent with sediment storage along the floodplains of perennial streams in other similar sized watersheds

the effects of stress and fracturing on permeability of coal abstract this paper examines the changes in structure and permeability of coal under the stress conditions experienced around longwall faces the effect of fracturing on permeability of coal is discussed and the stress permeability relationship for fractured coal is compared with that of non fractured coal an empirical relationship between stress and permeability for coal is derived from the experimental data which relates the stress permeability behaviour of coal to its rank through the compressibility of the coal itself

development and response of a coupled catchment fan system under changing tectonic and climatic forcing sediment fans are a potentially useful and underexploited recorder of earth s climatic and tectonic history but historical observations have led to conflicting views on the importance of tectonic climatic and lithologic variables in controlling fan morphology and deposition a one dimensional model of a sediment fan and its associated catchment is used to explore the sensitivity of such simple sediment routing systems to perturbations in fault slip and precipitation rates a transport limited catchment is coupled to a fan whose surface slope is set by the balance between catchment sediment efflux and the available tectonically generated basin accommodation rock uplift rate is spatially variable across the model space increasing the fault slip rate or decreasing the precipitation rate leads to an increase in fan slope temporary back stepping of the fan toe and a pronounced angular unconformity conversely a decrease in slip rate or an increase in precipitation rate results in a decrease in fan slope and progradation and eventual stabilization of the fan toe once perturbed the system evolves toward a new equilibrium state with time constants of 0 5 to 2 myr these response times are insensitive to slip rate but are strongly dependent on precipitation rate variations in fan slope are well described by a dimensionless parameter that expresses equilibrium slope as a function of slip rate precipitation rate system size and catchment lithology this parameter holds promise as a predictive tool in inverting the morphology of natural fans for environmental variables

sediment storage and evacuation in headwater valleys at the transition between debris flow and fluvial processes sediment from landscape disturbance often enters temporary storage in valleys and evacuates over longer times which in steeplands are poorly delimited we hypothesize that across process transitions e g debris fl ow versus fl uvial transport distributions of sediment transit times also change we use fi eld surveys and extensive radiocarbon dating to assess the distribution of transit residence times through the proxy measurement of ages of bank deposits in two mainstem reaches of a 2 23 km 2 watershed in the oregon coast range in the downstream reach debris fans impound fl uvial deposits debris fl ow fi ne fl uvial and coarse fl uvial deposits compose nearly equal parts of the valley fi ll and fl uvial erosion evacuates deposits transit times have a sample mean of 1 22 10 3 14 c yr and an exponential distribution indicating uniform probability of evacuation from storage in the upstream reach valleyspanning debris jams impound debris fl ow deposits composing 95 of the valley fi ll which is routinely scoured by debris fl ows transit times have a sample mean of 4 43 10 2 14 c yr and if 100 14 c yr a power law distribution indicating preferential evacuation of younger deposits and retention of older deposits in both reaches most sediment has short transit times 600 14 c yr but signifi cant volumes remain for millennia less than 20 of basin wide denudation passes through these reservoirs but the latter are still signifi cant buffers between hillslope disturbance and downstream aquatic habitat especially for coarse sediment

numerical model of sediment pulses and sediment supply disturbances in mountain rivers sediment pulses in rivers can result from many mechanisms including landslides entering from side slopes and debris flows entering from tributaries artificial sediment pulses can be caused by the removal of a dam this paper presents a numerical model for the simulation of gravel bedload transport and sediment pulse evolution in mountain rivers a combination of the backwater and quasi normal flow formulations is used to calculate flow parameters gravel bedload transport is calculated with the surface based bedload equation of parker in 1990 the exner equation of sediment continuity is used to express the mass balance at different grain size groups and lithologies as well as the abrasion of gravel the river is assumed to have no geological controls such as bedrock outcrops and immobile boulder pavements the results of nine numerical experiments designed to study various key parameters relevant to the evolution of sediment pulses are reported here results of the numerical runs indicate that the evol

a network based framework for identifying potential synchronizations and amplifications of sediment delivery in river basins long term prediction of environmental response to natural and anthropogenic disturbances in a basin becomes highly uncertain using physically based distributed models particularly when transport time scales range from tens to thousands of years such as for sediment yet such predictions are needed as changes in one part of a basin now might adversely affect other parts of the basin in years to come in this paper we propose a simplified network based predictive framework of sedimentological response in a basin which incorporates network topology channel characteristics and transport process dynamics to perform a nonlinear process based scaling of the river network width function to a time response function we develop the process scaling formulation for transport of mud sand and gravel using simplifying assumptions including neglecting long term storage and apply the methodology to the minnesota river basin we identify a robust bimodal distribution of the sedimentological response for sand of the basin which we attribute to specific source areas and identify a resonant frequency of sediment supply where the disturbance of one area followed by the disturbance of another area after a certain period of time may result in amplification of the effects of sediment inputs which would be otherwise difficult to predict we perform a sensitivity analysis to test the robustness of the proposed formulation to model parameter uncertainty and use observations of suspended sediment at several stations in the basin to diagnose the model the proposed framework has identified an important vulnerability of the minnesota river basin to spatial and temporal structuring of sediment delivery

current status and geological conditions for the applicability of cbm drilling technologies in china a review abstract coalbed methane cbm drilling technology is critical in achieving efficient cbm development the geological conditions for cbm development in china are complex including special terrain high rank coal areas deep coal seams multiple superposed coal seams and coal measure gas symbiosis areas steeply inclined coal seam areas and tectonic coal seam areas therefore it is critical to apply the optimum drilling technology in each different area this paper first reviews the current cbm drilling technologies and gas production behaviors in china it is found that although vertical wells and cluster well groups are common well types for cbm development in china u v and l shaped horizontal wells and multilateral horizontal wells have been favored for cbm development in recent years the paper then discusses the applicability of different well types to geological conditions and proposes a modification method for well design in various geologic conditions this method uses the coal structure ro in situ stress and ratio of critical desorption pressure to the reservoir pressure as the main inputs

channel response to sediment wave propagation and movement redwood creek california usa redwood creek north coastal californa usa has experienced dramatic changes in channel confguation since the 1950s a series of large floods in 1955 1964 1972 and 1975 combined with the advent of widespread commercial timber harvest and road building resulted in extensive erosion in the basin and contributed high sediment loads to redwood creek since 1975 no peak flows have exceeded a 5 year recurrence interval twenty years of cross sectional survey data document the downstream movement of a sediment wave in the lower 26 km of this gravel bedded river at a rate of 800 to 1600 m a i durng this period of moderately low flows higher transit rates are associated with reaches of higher unit stream power the wave was initially deposited at a site with an abrupt decrease in channel gradient and increase in channel width the amplitude of the wave has attenuated more than i m as it moved downstream and the duration of the wave increased from eight years upstream to more than 20 years downstream channel aggradation and subsequent degradation have been accommodated across the entire channel bed channel width has not decreased significantly after initial channel widening from large 25 year recurrence interval floods three sets of longitudinal surveys of the streambed showed the highest increase in pool depths and frequency in a degrading reach but even the aggrading reach exhbited some pool development through time the aggraded channel bed switched from functioning as a sediment sink to a significant sediment source as the channel adjusted to high sediment loads from 1980 to 1990 sediment eroded from temporary channel storage represented about 25 per cent ofthe total sediment load and 95 per cent of the bedload exported from the basin

suspended sediment and contaminant routing with alluvial storage new theory and applications abstract in large watersheds sediment storage imposes geologic timescales on the downstream movement of suspended sediment and associated contaminants modeling these processes requires temporal and spatial averaging a task often accomplished using concepts derived from reservoir theory where residence times and age and storage time distributions of stored sediment are treated as constants even though all of these quantities should be time variable under conditions of unsteady sediment transport here concepts from reservoir theory are replaced by deposition and erosion laws to develop a parsimonious quantitative framework for watershed scale routing of sediment and contaminants that explicitly accounts for time dependent alluvial storage solution of the new equations combined with appropriate initial and boundary conditions predicts the age and storage time distributions of stored sediment the sediment residence time the mass of stored sediment and the variations in all of these quantities through time model calibration is illustrated by reinterpreting previously published data from the little missouri river in north dakota to create a 3 dimensional chronostratigraphic model of stored sediment supplemented by observations of contemporary patterns of erosion model parameters from the little missouri river are then used to demonstrate that approximately 750 yr will be required to remove arsenic contaminated alluvium supplied by a century of mine tailings discharges to a 112 km reach of the belle fourche river in south dakota the new approach described here requires very modest computing resources to simulate long timescales across large watersheds and the fidelity of storage parameters which ultimately control the timing of sediment delivery is supported by site specific stratigraphic observations and sediment dating

physical and chemical characteristics of a metal contaminated overbank deposit west central south dakota u s a a metal contaminated overbank deposit in west central south dakota resulted from the discharge of a large volume of mine tailings into a river system between the late 1800s and 1977 the deposit along the belle fourche river is typically up to 2 m thick and extends about 90 m away from the channel along the insides of meander bends the sediments contain above background levels of copper iron manganese zinc and particularly arsenic which is commonly two orders of magnitude above background level in the contaminated sediments carbonate minerals in the deposit limit the desorption of arsenic by preventing acid formation arsenic concentrations provide a measure of the dilution of mine tailings by uncontaminated sediment the arsenic appears to have been transported and deposited as arsenopyrite but is now at least partially associated with iron oxides and hydroxides within individual samples arsenic concentration has an inverse relation with grain size that results from the more efficient accumulation of arsenic on the greater surface area of the smaller particles arsenic concentration is inversely related to the sample weight percent finer than 16 m however as a consequence of the dilution of the contaminated sediments by uncontaminated sediment with a finer grain size distribution dilution by uncontaminated sediment from tributaries cause arsenic concentrations to decrease by a factor of 3 along 100 km of floodplain an influx at high streamflow of uncontaminated sediment from terraces and the premining floodplain as well as from tributaries causes arsenic concentrations in parts of the contaminated deposit that are farthest away from the channel to be two to three times less than arsenic concentrations in overbank sediment that is immediately adjacent to the channel

transformation of tectonic and climatic signals from source to sedimentary archive sedimentary rocks reflect past tectonic and climatic events numerical simulations suggest that changes in precipitation and in the rate of tectonic uplift affect the grain size and the distribution of sediments deposited downstream

variable gas content saturation and accumulation characteristics of weibei coalbed methane pilot production field in the southeastern ordos basin china using diverse geologic and geophysical data from recent exploration and development and experimental results of analysis of gas content gas capacity and gas composition this article discusses how geologic structural and hydrological factors determine the heterogeneous distribution of gas in the weibei coalbed methane cbm field the coal rank of the pennsylvanian no 5 coal seam is mainly low volatile bituminous and semianthracite the total gas content is 2 69 to 16 15 m3 t 95 00 570 33 scf t and gas saturation is 26 0 to 93 2 burial coalification followed by tectonically driven hydrothermal activity controls not only thermal maturity but also the quality and quantity of thermogenic gas generated from the coal gas composition indicates that the cbm is dry and of dominantly thermogenic origin the thermogenic gases have been altered by fractionation that may be related to subsurface water movement in the southern part of the study area three gas accumulation models are identified 1 gas diffusion and long distance migration of thermogenic gases to no flow boundaries for sorption and minor conventional trapping 2 hydrodynamic trapping of gas in structural lows and 3 gas loss by hydrodynamic flushing the first two models are applicable for the formation of two cbm enrichment areas in blocks b3 and b4 whereas the last model explains extremely low gas content and gas saturation in block b5 the variable gas content saturation and accumulation characteristics are mainly controlled by these gas accumulation models

incision and morphologic evolution of an alluvial channel recovering from hydraulic mining sediment hydraulic gold mining in the sierra nevada california produced such a large volume of sediment from 1853 to 1884 that channels could not carry a substantial proportion of the delivered sediment the lower bear river aggraded as much as 5 m and underwent a major avulsion during the 1870s channel morphology continues to respond to these changes more than 100 years after the cessation of most hydraulic mining textures of mine tailings and older alluvium are contrasted and channel incision and channel shape changes from 1930 to 1985 are documented unlike the yuba and sacramento rivers the lower bear river had not returned to pre mining base levels by 1950 as sediment loads decreased nor were incision rates or morphological change governed by reduced sediment loads below dams built in 1928 and in the mid 1960s channel stability was due to resistance of a cohesive stratum on the channel bed an episode of channel down cutting was instigated by a moderately large flood in december 1955 that pierced the cohesive layer and was sustained through the 1970s by moderate magnitude floods the 1955 flood did not directly erode large volumes of sediment but it destabilized the channel allowing smaller floods to erode the channel at an accelerated rate episodic channel bed incision is contrasted to progressive morphologic changes cross section shape narrowed and deepened steadily from 1930 through the mid 1970s as the channel was superimposed onto cohesive older alluvium progressive deepening set up a positive feedback that ensured the ultimate penetration of the paved bed channel morphologic readjustment from the avulsion thus was both progressive and episodic

stochastic model for the long term transport of stored sediment in a river channel we develop a stochastic model for the transport of stored sediment down a river channel the model is based on probabilities of transition of particles among four different sediment storage reservoirs called active often mobilized semiactive inactive and stable hardly ever mobilized the probabilities are derived from computed sediment residence times two aspects of sediment storage are investigated flushing times of sediment out of a storage reservoir and changes in the quantity of sediment stored in different reservoirs due to seasonal sediment transport into and out of a reach we apply the model to redwood creek a gravel bed river in northern california although the redwood creek data set is incomplete the application serves as an example of the sorts of analyses that can be done with the method the application also provides insights into the sediment storage process sediment flushing times are highly dependent on the degree of interaction of the stable reservoir with the more mobile sediment reservoirs the most infrequent and highest intensity storm events which mobilize the stable reservoir are responsible for the long term shifts in sediment storage turnover times of channel sediment in all but the stable reservoir are on the order of 750 years suggesting this is all the time needed for thorough interchange between these sediment compartments and cycling of most sediment particles from the initial reservoir to the ocean finally the markov model has adequately characterized sediment storage changes in redwood creek for 1947 1982 especially for the active reservoir the model replicates field observation of the passage of a slug of sediment through the active reservoir of the middle reach of redwood creek in the 18 years following a major storm in 1964 that introduced large quantities of landslide debris to the channel

how plausible are high frequency sediment supply driven cycles in the stratigraphic record abstract this paper is an attempt to quantify the plausible time scales of clastic sediment supply variations at the entrance of sedimentary basins our approach is based on the sedimentary system concept which simplifies natural systems by dividing them into three zones of dominant processes the erosion the transfer and the sedimentation subsystems we examine recent results from geomorphology which show that frequent climate changes can induce high frequency sediment flux variations at the outlet of the source area we put forward the crucial role of the transfer subsystem which conveys sediment from the erosion zone to the basin by applying a diffusive model to a number of worldwide rivers we extend from large 1000 km to intermediate 300 km rivers the previous finding that the transfer subsystem acts as a buffer for short periods sediment pulses tens to hundreds of kiloyears this implies that high frequency stratigraphic cycles in clastic accumulations fed by large drainage systems are unlikely to reflect sediment supply cycles of tens to hundreds of thousands of years of periodicities

influence of flow variability on floodplain formation and destruction little missouri river north dakota resolving observations of channel change into separate planimetric measurements of floodplain formation and destruction reveals distinct relations between these processes and the flow regime we analyzed a time sequence of eight bottomland images from 1939 to 2003 along the little missouri river north dakota to relate geomorphic floodplain change to flow along this largely unregulated river at the decadal scale floodplain formation and destruction varied independently destruction was strongly positively correlated with the magnitude of infrequent high flows that recur every 5 10 yr whereas floodplain formation was negatively correlated with the magnitude of frequent low flows exceeded 80 of the time at the century scale however a climatically induced decrease in peak flows has reduced the destruction rate limiting the area made available for floodplain formation the rate of destruction was not uniform across the floodplain younger surfaces were consistently destroyed at a higher rate than older surfaces suggesting that throughput of contaminants would have occurred more rapidly than predicted by models that assume uniform residence time of sediment across the floodplain maps of floodplain ages produced by analysis of sequential floodplain images are similar to maps of forest ages produced through dendrochronology confirming the assumption of dendrogeomorphic studies that riparian tree establishment in this system is limited to recent channel locations

characteristics of natural fractures in the upper paleozoic coal bearing strata in the southern qinshui basin china implications for coalbed methane cbm development abstract natural fractures as the effective storage space and fluid flow pathway of hydrocarbons play a critical role in the exploration and development of unconventional gas resources in the coal bearing strata in the present study to reveal the effects of natural fractures on coalbed methane cbm preservation and development the types origins and development characteristics of natural fractures in the upper paleozoic permian shanxi formation in the southern qinshui basin were systematically described and analyzed based on outcrops cores borehole image logs thin sections and sem four types of natural fractures have been identified in the shanxi formation according to their geologic origins including the endogenic fractures cleats and exogenous fractures in the no 3 coal seam and tectonic fractures and diagenetic fractures in its roof and floor tectonic fractures can be further divided into small faults intraformational shear fractures intraformational open fractures and slip fractures while diagenetic fractures are mainly bed parallel fractures the statistical results show that the development and distribution characteristics of those types of fractures are significantly different which are mainly influenced by lithology layer thickness and geological structure further natural fractures with different types and distributions show different influences on cbm preservation and well productivity exogenous fractures can effectively improve the seepage capability of coal reservoirs and are conducive to cbm wells productivity whereas endogenic fractures have less contributions to coal permeability due to their poor effectiveness the intraformational open fractures in the fold axis zones and intraformational shear fractures and small faults in the fault zones are generally excessive developed those fractures may result in gas dissipation and external water supplement which have negative effects on cbm preservation and production however moderate developed intraformational shear fractures in the sandstone roof can favorably affect the pressure reduction of coal reservoir and improve the recovery potential of unconventional gas resources these investigations may serve as a geological basis for unconventional gas exploration and development of the upper paleozoic coal bearing strata in the southern qinshui basin

preliminary evaluation of the coalbed methane production potential and its geological controls in the weibei coalfield southeastern ordos basin china article i nfo the coalbed methane cbm geology resource and production potential in the weibei coalfield southeastern ordos basin are studied based on geological surveys and laboratory measurements the results showed that coal rank varies both laterally and vertically and changes from volatile bituminous coals in the margin to anthracites towards the basin 1 6 2 5 ro coals are composed of 60 85 vitrinite 15 40 inertinite and a trace amount of minerals methane isothermal adsorption measurements of 20 coal samples revealed that the maximum adsorption capacity on a dry and ash free basis of coals which are affected by coal rank coal maceral coal lithotype and especially to the moisture content varies from 13 91 to 29 54 m 3 t estimated gas contents range from 0 to 15 m

dynamic variation effects of coal permeability during the coalbed methane development process in the qinshui basin china abstract the commercial exploitation of coalbed methane cbm has been achieved in the qinshui basin china however the productivity of wells varies greatly because of their different geological settings and production rules and the permeability damage to coal reservoirs caused during the development process is one of the most important factors affecting productivity in this study the patterns of permeability variation in coal seam no 3 and their influence on cbm recovery were analyzed and the degree of permeability damage caused by different factors was calculated the results show that the burial depth the bottom hole pressure and the dewatering rate affected the effective stress imposed on the coal reservoir which further induced changes in permeability and productivity the elastic modulus of the coal body reflects its ability to withstand compression the greater the elastic modulus is the less the permeability decreases when the pressure drops from 7 05 mpa to 0 20 mpa the relatively low elastic modulus of coal seam no 3 can cause a 10 decrease in permeability coals at different burial depths have different formation pressures and elastic moduli causing different levels of permeability damage during the development process calculations indicate that the absolute permeability will decrease by 5 5 and 14 3 at depths of 500 m and 1000 m respectively if the bottom hole pressure drops too fast or the dewatering rate is too high there will be a strong stress response resulting in decreasing permeability and productivity this study found that in high productivity wells a larger pressure drop approximately 0 022 mpa d and stroke 3 0 min are favorable in the early drainage period but a smaller pressure drop 0 002 mpa d and stroke 0 4 min should be applied when the gas peak appears

residence times and alluvial architecture of a sediment superslug in response to different flow regimes abstract a superslug was deposited in a basin in the colorado front range mountains as a consequence of an extreme flood following a wildfire disturbance in 1996 the subsequent evolution of this superslug was measured by repeat topographic surveys 31 surveys from 1996 through 2014 of 18 cross sections approximately uniformly spaced over 1500 m immediately above the basin outlet these surveys allowed the identification within the superslug of chronostratigraphic units deposited and eroded by different geomorphic processes in response to different flow regimes over the time period of the study the superslug went through aggradation incision and stabilization phases that were controlled by a shift in geomorphic processes from generally short duration episodic large magnitude floods that deposited new chronostratigraphic units to long duration processes that eroded units these phases were not contemporaneous at each channel cross section which resulted in a complex response that preserved different chronostratigraphic units at each channel cross section having in general two dominant types of alluvial architecture laminar and fragmented age and transit time distributions for these two alluvial architectures evolved with time since the extreme flood because of the complex shape of the distributions they were best modeled by two parameter weibull functions the weibull scale parameter approximated the median age of the distributions and the weibull shape parameter generally had a linear relation that increased with time since the extreme flood additional results indicated that deposition of new chronostratigraphic units can be represented by a power law frequency distribution and that the erosion of units decreases with depth of burial to a limiting depth these relations can be used to model other situations with different flow regimes where vertical aggradation and incision are dominant processes to predict the residence time of possible contaminated sediment stored in channels or on floodplains and to provide insight into the interpretation of recent or ancient fluvial deposits

in situ stress pore pressure and stress dependent permeability in the southern qinshui basin this study focuses on the in situ stress pore pressure and permeability in the southern qinshui basin one of largest coalbed methane basins in china well tests show that permeability in this basin is higher than other coalbed methane reservoirs this is because it is located in an extensional basin where the normal faulting stress regime is dominated this in situ stress regime is advantageous to keep coal cleats open hydraulic fracturing tests indicate that the fracture gradient or minimum horizontal stress is much lower than the shales in the gulf of mexico and other oil basins the minimum horizontal stress model is proposed with consideration of the stress coefficient based on the uniaxial strain method this model provides a fairly good prediction on the minimum stress permeability data show that the effective stress dependent permeability is pronounced in the coalbed methane reservoir this is significant for the dual porosity and dual permeability coal reservoirs which consist of coal porous matrices and cleats the reason is that a rapid increase in effective stress can induce the closure of cleats which may cause a permanent loss of permeability in the cleats this reduces the connectivity between the cleats and coal matrices hence the coal matrices cannot deliver gas pressure to the cleats for supporting the cleat space therefore slowing down the effective stress change during production e g slowing reservoir drawdown can decelerate the permeability reduction this is particularly important for the reservoir in which the pore pressure is not significantly overpressured such that in the southern qinshui basin

elastic and shear moduli of coal measure rocks derived from basic well logs using fractal statistics and radial basis functions abstract gamma ray density sonic and core logs obtained from two boreholes drilled over a longwall panel in southwestern sw pennsylvania were analyzed for formation boundaries log derived porosities and densities and for rock elastic properties from sonic transit times gamma ray gr and density logs dl were analyzed using univariate statistical techniques and fractal statistics for similarity and ordering of the log data in depth a fourier transformation with low pass filter was used as a noise elimination filtering technique from the original logs filtered data was tested using basic univariate and fractal statistics rescaled range r s and power spectrum ps analysis to compare the information characteristics of the filtered logs with the original data the randomness of log data in depth was analyzed for fractional gaussian noise fgn or fractional brownian motion fbm character a new prediction technique using radial basis function rbf networks was developed to calculate shear and young s moduli of the formations when sonic logs are not available for this approach the filtered logs were used as input to an rbf based upon a combination of supervised and unsupervised learning the network was trained and tested using rock elastic properties calculated from the sonic log of one of the boreholes the network was used to predict the elastic and shear moduli of the coal measure rocks over a longwall coal mine in sw pennsylvania this approach demonstrated that it could be used for prediction of elastic and shear moduli of coal measure rocks with reasonable accuracy

evolution of a landslide induced sediment wave in the navarro river california a streamside landslide delivered 60 000 m3 of mixed size sediment to the navarro river a sinuous gravel bed channel drainage area 535 km2 at the end of the annual high runoff period in spring 1995 the deposit formed a 9 m high dam that partially breached within several hours but recessional flows entrained little material until the following high runoff season the landslide afforded the opportunity to measure the evolution of a sediment wave from its inception to near obliteration and particularly to test relative tendencies for translation and dispersion of a sediment wave in a natural gravel bed channel this study represents a simple case the wave originated from a single input the preexisting channel was relatively uniform and resistant banks prevented adjustments in width we surveyed channel topography over a 1 5 4 5 km reach centered on the landslide dam each year from 1995 to 1999 and we sampled bed material downstream of the dam in 1995 and 1997 landslide material was coarser than ambient bed material but all sizes were mobilized by subsequent peak flows abrasion of weathered and fractured graywacke sandstone landslide material was roughly an order of magnitude greater than the ambient river gravel the sediment wave dispersed and mostly disappeared within a few years with no measurable translation sediment filled the reservoir created by the eroding landslide dam until throughput of bed load was restored in 1998 the stationary wave crest eroded until in 1999 it was 1 m higher e mail dsutherl fs fed us than the preslide elevation as the wave profile flattened its detectable leading edge extended downstream from 620 m in 1995 to 1600 m in 1997 downstream advance of the wave was associated with coarsening of bed material the sediment wave created a longitudinal disturbance in sediment transport by using the dam as a reference datum of zero bed load transport we computed longitudinal variations in annual bed load and suspended sediment transport rates in 100 m increments downstream of the dam these longitudinal variations were controlled by scour and fill of the bed and by abrasion of bed load particles bed load transport rates in the first and second years after the landslide increased in the landslide vicinity and then decreased downstream as sediment deposited behind the advancing leading edge of the wave the location of peak bed load transport rate advanced from the first year 400 m to the second 800 m we used a physically based one dimensional model cui et al 2002b to hindcast annual changes in transversely averaged bed elevation over the study reach agreement between measured and predicted bed elevations was very good this result supports our conclusion that once emplaced sediment waves in gravel bed rivers tend to disperse with little or no translation

simulation study on evolution of coalbed methane reservoir in qinshui basin china a dynamic equilibrium model has been proposed to describe the coalbed methane concentration dissipation evolution process in coal including its generation storage and migration the model developed with a computational program has been applied to the qinshui basin china which allows to evaluate features of coal seam of the basin including coal quality and burial palaeo geothermal field and coal organic material maturation evolution history the simulation study was focused on coalbed methane concentration dissipation evolution history of the upper and lower main coal seams in the basin the results indicate that the whole evolution process can be divided into three stages at the first stage i e the primary concentration stage gas generation quantity and gas content were lower and only weak diffusion took place the second stage can be called the active concentration dissipation stage during this period coal organic material was matured at a higher rate generating a large amount of gas because of abnormal high palaeo geothermal field in the middle and late yanshan epoch as a result gas content in coal reservoir was higher and gas could be lost in different ways including diffusion cap outburst and permeation the third stage can be defined as the absolute dissipation stage at which coal organic material no longer generates gas meanwhile much gas was lost mainly by diffusion and partly by permeation simulation results further show that although the high gas generation led to active dissipation in the coal reservoir there still remains comparatively high gas content on the south and north ends of the qinshui basin due to the preserving geological conditions this suggests that these regions are favorable for coalbed methane exploitation which has been confirmed by recent geological exploitations in qinshui basin c 2007 published by elsevier b v

production characteristics and the key factors in high rank coalbed methane fields a case study on the fanzhuang block southern qinshui basin china abstract the temporal and spatial production characteristics of coalbed methane cbm wells in the fanzhuang block of the southern qinshui basin the first commercial cbm producing basin in china were studied to determine the dominant factors the study indicates that gas production differs significantly in different wells adjacent to or located in different tectonic areas in combination with the production characteristics in the temporal and spatial variations the impact of seven factors burial depth thickness of coal gas content porosity permeability effect of fracturing structural setting and hydrogeological conditions on the gas production was analyzed based on bivariate correlation analysis and gray system theory which are suitable for solving the complex interrelationships between multiple factors and variables the results indicate that hydraulic fracturing is an effective guarantee of high production cbm wells in the first several months during a high rank cbm field development however the effect of hydraulic fracturing on enhancing the gas production of cbm wells decreases with time because the initial reservoir permeability lower than the hydraulic fracture permeability limits the adsorption diffusion and flow of cbm this limitation inevitably leads to a slow gas production rate when the adsorbed cbm from the initial reservoir becomes the main gas source instead of the fracturing affected zone gas content and permeability are two key factors that dominate cbm well productivity because they perform elementary roles in controlling the volume of gas sources and conductivity respectively the structural setting and hydrogeological condition are also two important factors that dominate cbm well productivity because they can influence the spatial distribution of permeability and gas content as well as other factors such as aquifers

holocene multidecadal to millennial scale variations in iceland scotland overflow and their relationship to climate the nordic seas overflows are an important part of the atlantic thermohaline circulation while there is growing evidence that the overflow of dense water changed on orbital time scales during the holocene less is known about the variability on shorter time scales beyond the instrumental record here we reconstruct the relative changes in flow strength of iceland scotland overflow water isow the eastern branch of the overflows on multidecadal millennial time scales the reconstruction is based on mean sortable silt ss from a sediment core on the gardar drift 60 19 n 23 58 w 2081 m our ss record reveals that the main variance in isow vigor occurred on millennial time scales 1 2 kyr with particularly prominent fluctuations after 8 kyr superimposed on the millennial variability there were multidecadal centennial flow speed fluctuations during the early holocene 10 9 kyr and one prominent minimum at 0 9 kyr we find a broad agreement between reconstructed isow and regional north atlantic climate where a strong weak isow is generally associated with warm cold climate we further identify the possible contribution of anomalous heat and freshwater forcing respectively related to reconstructed overflow variability we infer that ocean poleward heat transport can explain the relationship between regional climate and isow during the middle to late holocene whereas freshwater input provides a possible explanation for the reduced overflow during early holocene 8 10 kyr

neotectonic effects on sinuosity and channel migration belle fourche river western south dakota short term instability in the behaviour of a small meandering alluvial channel is identified from the relation between sinuosity and either floodplain slope or channel slope within 17 reaches along an 81 kilometre section of the belle fourche river in western south dakota in reaches 1 to 4 and 11 to 17 the channel is relatively stable and sinuosity varies inversely with channel slope in reaches 5 to 10 sinuosity is positively related to floodplain slope sinuosity increases markedly in reaches 5 6 and 7 which are immediately downstream from a discontinuity in the long profile of the floodplain in association with an increase in floodplain slope immediately upstream from the discontinuity bankfull channel depth and sinuosity decrease and the area of the floodplain reworked by meander migration between 1939 and 1981 increases in association with a decrease in floodplain slope channel behaviour in reaches 5 to 10 is best explained as a consequence of neotectonic activity as indicated by changes in elevation recorded along geodetic survey lines that cross lineaments that may delimit the eastern boundary of the black hills uplift sinuosity acts as a barometer of the effects of neotectonic activity on alluvial channels initial indications of channel and floodplain instability due to neotectonic activity may be derived from evidence of anomalously active channel migration as documented from photographic or topographic sources

unsteady sediment transport law and prediction of aggradation parameters a general law for unsteady sediment transport in the form of a differential equation has been established this law has been tested against the sediment transport rates obtained in the laboratory during aggradation arising from an increase in sediment supply over and above the equilibrium sediment transport capacity of the channel using the law expressions for predicting the maximum depth of aggradation and length of aggradation under the above stated boundary conditions have been obtained the agreement between values of the parameters computed from these expressions when compared with the values observed in the laboratory and with the values obtained from the numerical model of gessler is very good

provenance of sediment in the labrador current a record of hinterland glaciation over the past 125 ka the labrador current flows southward along the continental margin off eastern canada and is the principal source of sediment to the outer continental margin areas where ice sheets did not cross the continental shelf we present multi proxy mineralogical and geochemical records based principally on x ray diffraction and x ray fluorescence for core 2011031 059 from northern flemish cap to determine changes in supply and hence to reconstruct provenance evolution during the last glacial cycle the calcite to dolomite ratios in heinrich layers ranged from 2 to 4 suggesting carbonate layers derived from hudson strait as early as marine isotope stage mis 5a d mineral abundance shows three time dependent predominant sediment sources other than in heinrich layers i baffin bay shelves and adjacent land in mis 5 and 1 with high ca sr kaolinite and feldspars and low clay minerals and calcite dolomite ratios ii labrador in mis 3 with low clays and grey color and iii north east newfoundland shelf in mis 2 and 4 with higher concentrations of clay minerals red sandstones and transition elements these results allow a reconstruction of principal ice streams supplying the north west atlantic over the last full glacial cycle

evaluation of coal texture distributions in the southern qinshui basin north china investigation by a multiple geophysical logging method abstract coal texture is indicative of coal mechanical strength which is important not only for evaluating coalbed methane cbm reservoir permeability but also for evaluating the possibility of coal and gas outbursts in underground coal mining this paper begins with a foundation of a geophysical logging based coal texture evaluation method that compares the digital logging data with the results from 108 coring samples then the method was applied to the analyses of coal textures in 39 cbm wells the results of which are discussed in terms of the vertical distribution of coal textures in the study area finally a ternary diagram based on thickness proportions of coal textures was used to identify reservoir compartments in the zhengzhuang field of the southern qinshui basin the results show that undeformed coals are easily distinguished from cataclastic and granulated coals because of the high den and gr of undeformed coals meanwhile cataclastic coal has lower response values of ac and lld than granulated coal which can be used in identifying cataclastic from granulated coal a multiple geophysical logging method combining the log data of den gr ac and lld was provided for predication of the coal textures in the zhengzhuang field the predicated results show that the coal seam can be vertically divided into three to eight sub layers with a typical interbedded pattern of undeformed and cataclastic coals on the upper and lower parts and granulated coal in the middle at a relatively large thickness the study area is divided into four major regions and 11 sub regions based on the classification of coal texture types the undeformed coal dominated region is located in the southwestern part of the study area indicating a low permeability in the coal reservoir the granulated coal dominated region is mainly in the northern and eastern parts of the study area and has resulted from deep burial and multi period structural activities the cataclastic coal dominated region is in the middle of the study area the coal reservoir in this region is possibly the most favorable for cbm production

stochastic forcing of sediment routing and storage in channel networks the stochastic field of sediment supply to the channel network of a drainage basin depends on the large scale interactions among climatically driven processes such as forest fire and rainstorms topography channel network topology and basin scale during infrequent periods of intense erosion large volumes of colluvium are concentrated in parts of a channel network particularly near tributary junctions the rivers carry bed material and wash load downstream from these storage sites at different rates the bed material travels slowly creating transient patterns of sediment transport sediment storage and channel morphology along the channel network as the concentrations of bed material migrate along the network their waveforms can undergo changes by diffusion interference at tributary junctions and loss of mass through temporary sediment storage in fans and terraces and through particle abrasion which converts bed material to wash load we investigated how these processes might influence the sediment mass balance in channels of third and higher order in a 215 km 2 drainage basin within the oregon coast range over a simulated 3000 year period with a climate typical of the late holocene we used field measurements and a simulation model to illustrate interactions between the major controls on large scale processes functioning over long periods of time in complex drainage basins

the 8200 year b p event in the slope water system western subpolar north atlantic 1 stable isotope trace metal alkenone paleothermometry and radiocarbon methods have been applied to sediment cores in the western subpolar north atlantic between hudson strait and cape hatteras to reveal the history of climate in that region over the past 11 kyr we focus on cores from the laurentian fan which is known to have rapid and continuous accumulation of hemipelagic sediment although results among our various proxy data are not always in agreement the weight of the evidence alkenone sea surface temperature sst 18o and abundance of globigerinoides ruber indicates a continual cooling of surface waters over laurentian fan from about 18 c in the early holocene to about 8 c today alternatively mg ca data on planktonic foraminifera indicate no systematic change in holocene sst the inferred long term decrease in sst was probably driven by decreasing seasonality of northern hemisphere insolation two series of proxy data show the gradual cooling was interrupted by a two step cold pulse that began 8500 years ago and lasted about 700 years although this event is associated with the final deglaciation of hudson bay there is no 18o minimum anywhere in the labrador sea yet there is some evidence for it as far south as cape hatteras finally although the 8200 year b p event has been implicated in decreasing north atlantic ventilation and hence widespread temperature depression on land and at sea we find inconsistent evidence for a change at that time in deep ocean nutrient content at 4 km water depth